Research Journal of Aleppo University - جامعة حلب ... · Dr. Ibrahim Raheb Dr. Gassan Daood...

Research Journal

of

Aleppo University

Basic Science Series

A Periodical Issued by University of Aleppo

Vol. 98 - 2014

ISSN 2227-9210

All rights reserved .No part of this publication may be

reproduced,stored in a retrieval system or transmitted in any

form without the prior written permission of the publisher .

Basic Science Series

Chairman of the Editorial Prof. Dr. Kamal Khoudary

Vice president for scientific research and high studies affairs

Editor in Chief Prof. Dr. Nawar Kadan

Editorial Board

Dr. Hesham Bawadekji Dr. Saad Antakli

Dr. Samer Bashmaf Dr. Mahmoud Amin

Dr Walid Al said Dr Ahmed Kumary

Dr. Zakria Nout

PRODUCTION Eng.Rama Mulki

The view expressed in this issue are those of the authors and do not necessarily

reflect the views of the Editorial Board or the Policies of the University of Aleppo

proof reading Aisha Moussa (Engish) Bakry Eko (Arabic)

5

Contents Dr. Ibrahim Raheb

Dr. Gassan Daood

Hussam Alrekad

Catalytic Cracking of Plastic Wastes

over Sulfated Syrian Natural Zeolite

7

Dr. Fatima Srouji

Sami Orfali

Poling Process Impact on the

Pyroelectric Properties of PZT

19

Dr. Fatima Srouji

Farouk Al Jasem

Optical Properties of CdTe QDs

Synthesized by Chemical Method and

Enhanced by Microwave Irradiation

31

Dr. Walied Hawaleh

Dr. Salah Al Haj Omar

M. Yahia Masri

Studying the Effect of Fineness on the

Thermal Treatment of Syrian

Petroleum Coke to Reduce the Sulfur

Content

47

Dr. Nizar Essa

Dr. Faiza Al atrash

Waleed Mlook

Screening, Identification and Partial

Characterization of Pullulanase

Enzyme from Local Bacterial Strain

49

Dr. Sabah Blaj

Dr. Leka Hoppo

Dr. Abeer Alyosef

Eman Almosa

A Study of Immunological and

Hematological Findings in Systemic

Lupus Erythematosus (SLE) Patients in

Aleppo

51

Dr. Abdel Aleem Bello Dr. Zaher S. Tahan Dr. Firas Haj Zein Yasmin Alshihabi

Antibacterial Activity of Salvia

officinalis against Some Pathogenic

Bacteria Isolated from Tonsillitis and

Pharyngitis Patients

53

Dr. Saleh El-Kadri

Dr. Ani Tersakian

Ahmad Alabboud

Synhesis of Some Push-Pull Alkenes

Containing Two Carbonyl Groups:

Ketene Dimethyl Dithio Acetal Type

55

Dr. Saja Abou Ghaloon A Comparative Study of the Structure

of Pancreas in the Two Species Clarias

gariepinus (syriacus) and Clarias salurus

Living in the Orontes and Euphrates

Rivers

57

Dr. Said Sabbagh

Murhaf Al-Sayed Ali A Comparative Study of Ball Point Pens

Writing Ink Using Techniques of XRF,

UV-VIS, FT-IR

59

Dr. M. Karman

N. Al Ghanom

Studies of XRD, FT-IR and Surface

Areas of Pure MoO3, WO3 and the

Mixed Oxide System Mo-W-O

61

Dr. Emad Asad

Dr. Farouk Kandil

M. Hasan Derbas

Synthesis and Characterization of

Nd:YAG Nanopowder via Polymer

DTPA Metal Chelated Complexes

63

Dr. Said Abdul Nour

Mouna Kurma

Study of the Structural Properties in

Polyacrylonitrile - anionic Surfactant

Systems

65

6

Dr. Anwar Batal

H. Aldeen KASSIR

Linear Waves Propagation in a Dusty

Plasma for Tails of Halley's Comet

67

Dr. M. Hasan

Dr. M. Saleh Hammami

Layla Al Sharif

A Study of the Effect of Adding Zinc

Metal on Physical Properties of Lead-

free Solders Ternary (Sn88 Sb10 Cu2)

Prepared in Rapid Solidification

69

Dr. Nehad Yosef

Faten Kang

Isolating and Identifying of Lactic Acid

Bacteria (LAB) from Fermented Milk

Products (Yoghurt and Traditional

White Cheese)

71

Dr. Said SABBAGH Analysis of Al khalas Date Bio-Physical

and Chemical Characteristics

Sterilized by Irradiation to Substitute

Fumigation Gases and Thermal

Treatments

73

Dr. Hala Wattar Global Optical Potential for Deuteron

Scattering at Energies from 10 to 180

MeV

75

Dr. Walid Al Said

Dr. Abdel Aleem Bello

Oula Darwish

Study of Leaf Epidermis and

Palynology in Two Varieties Related to

Silybum marianum (Asteraceae) in

North Aleppo

77

Dr. Adel Hamo

Dr. Hala Wattar

Eyman Al-hamdan

Advanced Study of Neutrino

Oscillation Phenomenon in Vacuum in

Quantum Fields Theory Framework

79

Dr. Mahmoud Karrom

Dr. Fadia Nashed

M. Salim Alibrahim

A Taxonomical Study on Species of

Helicidae (Gastropoda: Mollusca) in

Aleppo & Edlib Governorates

81

Dr. Adel Hamo A Study of the Time-dependent

Oscillation Systems Using the Creation

and Annihilation Operators

83

Dr. Walid Hawale

Shaghik Taghlian

The Study of Some of the Physical

Properties of the Glazed Layer

Prepared from Local Raw Materials

85

Dr. Tariq Zarouri

Hadeel Fakas Albeed

Studying of Some Thermal and

Electrical Properties of the Lead

Compounds PbS and PbTe

Precipitated in Chemical Solution

Method

87

Dr Ahmed Kumary

Dr. Hachem Alhussein

Omama Alloush

Studying the Effect of the Pomegranates

(Juice, Arils) on HbA1c Level, Serum

Fasting Glucose and Liver Enzymes in

Type II Diabetes Patients

89

R.J.of Aleppo Univ. Basic Science Series No.98 2014

6

Catalytic Cracking of Plastic Wastes over Sulfated

Syrian Natural Zeolite Ibrahim Raheb*, Gassan Daood

**, Hussam Alrekad

***

*Dept. of Chemistry, Faculty of Science, Tishreen University

**Doctor in Banias Refinery

** * Postgraduate Student (PhD). , Dept. of Chemistry, Faculty of Science, Tishreen

University

Abstract

In this paper, catalytic cracking of plastic wastes (PW) over

sulfated and non-sulfated natural zeolite in a batch reactor at 475,500

and 525oC was carried out. Thermal pyrolysis was also performed on

the same conditions. The best results were obtained at 475oC and

500oC for catalytic cracking. Non-sulfated zeolite showed high acidity

and the presence of sulfate ions led to higher acidity.

Catalytic process showed high conversion of PW, low content

of solid residues and direct effect on the reaction time in comparison

with thermal pyrolysis. On the other hand, sulfate ions affected the

content of the products, where the liquid product decreased and the gas

product increased.

Distribution of the liquid fraction showed a low content of light

hydrocarbons for a thermal pyrolysis, while the catalytic pyrolysis

showed a higher content of light hydrocarbons; that made it more

valuable especially when sulfated zeolite was used.

Keywords; catalytic cracking, plastic waste, natural zeolite, polymer

pyrolysis, super acid, impregnation.

Received 25 / 5 /2014

Accepted 14 / 9 /2014

Dr. Raheb Dr. Daood & Rekad

7

1. Introduction Polymers are used in almost all fields of both economy and

daily life. Every year their worldwide production grows together with

the increase in their consumption and the amount of waste. Plastic

waste management policies are based on energy recovery of

elimination processes. A major amount of annually produced plastic is

land filled or incinerated [1,2]. Mechanical recycling aims at the

recovery and reuse of the plastic material contained in the waste,

although it is strongly limited by the low quality of the recycled

plastics due to the presence of different polymers additives and

impurities. Thermal degradation requires high temperatures and

usually leads to wide product distribution with poor economic value

[3].

Chemical recycling has emerged in the last years as a

potentially interesting alternative for the management of plastic wastes

and conversion into a variety of useful products mainly as raw

chemicals or as fuels. In contrast, catalytic degradation allows the

plastic cracking to be performed at lower temperature, while the

product distribution can be controlled by a right selection of the

catalyst type being used. In the case of the HDPE (High density

polyethylene) catalytic cracking, a number of acid porous solids, such

as amorphous silica-alumina, zeolites and ordered mesoporous

materials, Al-MCM-41, have been used as catalysts. ZSM-5 zeolite

directs the catalytic cracking towards light products [4,5,6]. Many

kinds of sulfate supported-materials have a strong acidity and attract

much attention because of their ability to catalyze many reactions such

as cracking, alkylation and isomerization. Sulphated zirconia

incorporating Fe and Mn has been shown to be highly active for butane

isomerization [7].

On the other hand, many metal sulfates generate fairly large

amounts of acid sites of moderate or strong strength on their surfaces

when they are calcined at 400-700 oC. The acidic property of metal

sulfate often gives high selectivity of diversified reaction such as

hydration, polymerization, alkylation, cracking and isomerization [8].

2. Experimental 2-1. Catalyst Preparation

Syrian natural zeolite from Om'ozon area was used. Zeolite was

crushed and sieved into many fractions. We used the fraction which

has (0.1-0.37 mm). The sample was washed with distilled water,


8

filtrated and dried at 110oC for 24h and named (Z). The catalysts

containing various sulfate ions were prepared by adding an aqueous

solution of ammonium sulfate (NH4)2SO4 to the sample Z powder by

impregnation method, at room temperature for 24h, then dried at 110

oC and calcined at 600

oC for 8h in air. These series of catalysts are

denoted by their weight percentage of 2

4

SO for example

ZSOx /2

4

indicates the catalyst containing x.wt% of 2

4

SO , where

x = 5,10,15 and 20.

2-2.Characterization The amount of acidic sites and the distribution of these sites

were determined by NH3-temperatue programmed desorption (TPD).

Measurements were carried out on a labsys instrument (TG-DTA

,France). Prior to TPD studies the sample was outgassed at 200oC for

2h; after outgassing, the sample was saturated with ammonia gas at

25oC for 24h and subsequently flushed with N2 at 100

oC for 1h to

remove the physisorbed ammonia. The total acidity of the samples was

determined by desorption of NH3 as a function of temperature, by

increasing the temperature up to 500oC with a heating rate of

15oC/min.

2-3. Activity Studies

The pyrolytic reactor and its accessories used in the present

study were manufactured locally. Thermal and catalytic cracking

experiments were accomplished at atmospheric pressure in a batch

type reactor as shown in Fig.1. The reactor consists of pyrix glass tube

(leng. 20cm, and diam.2 cm), and is provided with glass tube which

has allowed the exit of the products. The reactor was placed in the

vertical furnace and the heating process was achieved by controlled

temperature unit. The plastic waste (PW) used in this study is the

plastic waste bags of polyethylene LDPE (Low density poly ethylene),

HDPE and polypropylene. PW was shredded to 2×3 mm size. The

mixture of plastic and catalyst (with ratio P/C =3) was charged in the

bottom of the reactor. The furnace was heated to the reaction

temperature (475, 500 and 525oC) with heating rate of 30

oC/min.


01

Fig.1. Schematic experimental setup

After the temperature reached the reaction temperature, the

reactor (containing PW and catalyst) was placed in the furnace and

maintained 4h for thermal pyrolysis and 2.30h for catalytic pyrolysis.

The liquid products were condensed and accumulated in ice trap. The

amount of solids (product in the reactor after cracking) and liquids

obtained in each experiment was weighed and the pyrolysis yield was

calculated. The results of the pyrolysis yields which are presented in

this paper are the mean value of at least three pyrolysis runs carried out

in the same conditions. The mass of all products (gas, liquid, solid

residues) was measured in grams and then converted into mass in

percentage. The relation between product yield with different

(temperature, and amount of 2

4

SO ) was also studied. The yield of

liquid product was calculated as the mass of the collected liquid

divided by the mass of the initial amount of polymer and then the

fraction of original polymer converted to liquid products. The solid

residues (coke) yield was calculated by dividing the mass of coke by

original mass of polymer. Gas yield was calculated by the difference

[(100-(yield of liquid + yield of solid)]. The selectivity to liquid

products was calculated as the mass of liquid divided by the mass of

reacted polymer. The boiling point distribution of each liquid fraction

was used to represent the liquid product distribution.


00

2. Results and Discussion The characterization of prepared samples (surface area, XRD,

FTIR, TG-DTA) was presented in a previous paper [9].

3-1. Acidic Properties

It is an established fact in the literature of surface acid studies that

ammonia is an excellent probe molecule for testing the acidic

properties of solid catalysts. The small size of NH3 molecule and its

basic property allow us to detect the acidic sites which are located in

the narrow pores of the solids [10]. The ammonia –TPD profiles of Z

and ZSOx /2

4

samples are shown in Fig.2 and the corresponding

total acidity results are presented in Table 1. Table 1. Total acidity of the prepared samples

Catalyst Total acidity, µmol/g

Z 108.8

5-SO42-

/Z 149.3

10-SO42-

/Z 162.9

15-SO42-

/Z 212.6

20-SO42-

/Z 251.6

As can be noted from TPD profiles in all samples, the acid

sites are distributed in three temperature regions. Desorption peaks

were observed at 150-250oC, 250-350

oC and 350-450

oC and the

maxima were located at 150oC, 300

oC and 400

oC respectively. These

peaks are normally attributed to NH3 chemisorbed on weak, moderate

and strong acid sites, respectively [11]. Among all prepared catalysts,

the sample Z without SO42-

ions has the lowest amount of acid sites. It

is observed that the weaker acid sites (maximum ~ 150oC) are

increased with increasing of SO42-

content, while the amount of

moderate and strong acid sites is increased slightly.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 100 200 300 400 500

T ,0C

Lo

s m

as

(NH

3)%

Z

5-SO4/Z

10-SO4/Z

15-SO42-/Z

20-SO42-/Z

5-SO42-/ Z

10-SO42-/Z

15-SO42-/Z

20-SO42-/Z

Fig.2. Ammonia TPD analysis of the prepared catalysts


01

The NH3-TPD profile of the samples indicates that sulfate

groups can enhance the total acidity, when adsorbed on the zeolite tuff.

In addition, sulfate species themselves are Lewis acid sites, or they

generate Lewis acid sites on the oxide surface by attracting electrons

[12,13].

These Lewis acid sites increase the Bronsted acid strength of

the surface hydroxyl groups present on the surface. Furthermore, the

chemical states of the sulfate groups sometimes determine the acidity

of the oxide surface. The strong ability of the sulphate complex to

accommodate electrons from a basic molecule such as ammonia is a

driving force to generate super acidic properties [7]. Calcination at

higher temperature leads to change the ionic to covalent character with

S=O bond order close to 1,5, which is responsible for generating strong

acidic active centres on the oxide structures. The position of ammonia

desorption peak corresponding to the super-acidic sites is influenced

by the nature of the mixed oxides [14].

3-2. Catalytic Activity

It is interesting to examine how the catalytic activity of

prepared acid catalysts depends on the acidic properties. The catalytic

activities for cracking plastic waste were measured and the results

were illustrated as a function of the reaction temperature and content of

sulfate, using the mass ratio of polymer/catalyst (P/C=3). The pyrolysis

yields obtained in the thermal and catalytic experiments at different

temperatures were shown in Table 2 and Fig.3. The liquid fraction was

the main product in all cases, reaching almost 93 wt% when catalyst Z

was used, followed by gases. The effects of temperature were studied

without catalyst addition (thermal pyrolysis). The reaction was carried

out at 475,500, and 525oC Tabl.2 and Fig.3.

The results show that the products of pyrolysis were liquid, gas,

and solid residue. At 475oC the yield of liquid was 64.1 wt%, the

average yield of gas was 7.1 wt% and the average yield of solid

residue was 28.8 wt%. When temperature was increased to 500oC, the

yield of liquid, gas and solid residue was 76, 7.3, and 16.7 wt%,

respectively. At 525oC, the yield of liquid, gas and solid residue was

78, 10.4 and 11.6 wt%, respectively.

The use of prepared catalysts (zeolite and sulfated zeolite) in

the cracking process of PW leads to changes in the yield of products.

The results show that the yield of the liquid gases was increased and

the solid residue decreased strongly. At 475oC the amount of liquid

and gas was 93, and 5.3 wt% in the presence of non sulfated zeolite Z,


02

while in the case of the sulfated zeolite, the yield of the liquid

decreased from 90.1 wt% to 86.8 wt% when the loaded sulphate

increased from 5 to 20 wt%. On the contrary the yield of the gases

increased from 5.8 to 13 wt%, Table.2 and Fig.3.

At 500oC, the similar behaviour was noticed. At 525

oC the yields of

the liquid were 93.2 to 90.9 wt %, i.e higher than the yield at 475oC

and 500oC, whereas the yield of the gas was less, i.e 4.9-7.7 wt %. The

catalytic cracking of PW by sulphated Z leads to a decrease in the

amount of solid residue to minimum values.

The reaction time varied. For thermal pyrolysis the reaction time was

215, 95 and 63 min at 475, 500 and 525oC respectively. At 475

oC the

reaction time of catalytic pyrolysis decreased from 147 min when non

sulfated zeolite was used to 80 min in the case of 20-SO42-

/Z. This

trend was observed for catalytic cracking at 500oC and 525

oC.

However, the reaction time was decreased with raising the reaction

temperature, see Table.2. Table 2. Product yield of PW degradation, and reaction time

at different temperatures

thermal Z 5-SO42-

/Z 10-SO42-

/Z 15-SO42-

/Z 20-SO42-

/Z

475oC

liquid wt% 64.1 93 90.1 86.9 87 86.8

gas wt% 7.1 5.3 9.3 12.7 12.1 13

Solid wt% 28.8 1.7 0.6 0.4 0.9 0.2

react time, min 215 147 134 122 85 80

500oC

liquid wt% 76 91.2 89.5 89 84.2 83.5

gas wt% 7.3 6.3 10 10.7 15.6 16.5

solid wt% 16.7 2.5 0.3 0.3 0.2 0.1

react time, min 95 81 77 65 58 48

525oC

Liquid wt% 78 93.2 93 92.6 90.9 91.4

gas wt% 10.4 4.9 6.2 6.9 6.8 7.7

solid wt% 11.6 1.8 0.8 0.5 0.5 0.9

react time, min 63 50 46 45 43 40


03

Fig.3. Product yield of PW degradation at different temperatures


04

The obtained results in certain condition in this work show a

low total yield of products (liquid + gas) in the case of thermal

pyrolysis of PW and high solid residues and long reaction time. While

the catalytic cracking of the same PW using sulfated and non sulfated

zeolite leads to high yield of products (liquid + gas), low solid residues

and short reaction time. The sample Z contains high acidity and this

acidity increased with an increase of sulfate ions Table 1. This is in

agreement with literature, as loading the metal oxides with sulfate ions

was found to enhance the acidic properties of the oxides. [12, 13].

On the other hand, the presence of sulfate ions stabilizes the

structure of the oxides, and the sulfated samples display a smaller

crystalline size and increase the amounts of tetragonal phase in

contrast with the corresponding non-sulfated samples [12].

As a consequence, higher conversion of PW was obtained with

catalysts than in the thermal pyrolysis. This is a well known effect

which has been reported before by other researcher groups [2,15]. The

higher conversion is attributed to both the textural properties of the

zeolite and the presence of Bronsted and Lewis acid sites in this

catalysts. In order to obtain more information about the liquid

products, we compared the liquid products at 475,500 and 525oC in the

thermal and catalytic pyrolysis, for non-sulfate Z and 20-SO42-

/Z were

used. Liquid products, received as a result of pyrolysis process, have

been distilled in the average of temperatures to 4 fractions according to

the boiling point. The distribution of the liquid fractions after

distillation was presented in Table.3. and Fig.4.

At 475oC the thermal pyrolysis gives a liquid product that

consists of light fraction 4.8 wt% on the average of temperature up to

130oC and the medium fraction ~20 wt% on the range of temperature

130-220oC and 220-340

oC, and the heavy fraction was 72.5 wt% at

temperature >340oC. While in the catalytic process by non-sulfated

zeolite, we found that the light, medium and heavy fractions were 16,

40.8, and 43.2 wt% respectively. When the sulfated zeolite (20-SO42-

/Z) was used, the order of the light, medium and heavy fractions was

30.2, 41.8 and 28wt%. These results showed that the presence of

catalyst in pyrolysis process leads to high content of light and medium

liquid fractions and low content of heavy fraction in comparison with

thermal pyrolysis.

At 500oC for thermal pyrolysis the light and medium fractions

were increased but the heavy fractions were decreased, while for

catalytic pyrolysis the main difference was in the case of the (20-SO42-


05

/Z) where the medium fraction was increased and heavy fraction was

decreased in comparison with the results at 474oC. At 525

oC the

picture was different especially in the case of catalytic process, where

the heavy fraction was increased. This can be attributed to the short

connecting time between PW and catalyst due to the high speed of the

vaporous PW at 525oC.

Table.3. Liquid fraction distribution (v/v)% produced

after cracking of PW

475oC 500

oC 525

oC

thermal Z

20-SO

42- /Z

thermal Z

20-SO

42- /Z

thermal Z

20-SO

42- /Z

<130oC 4.8 16 30 6.9 16.2 30.1 7.9 15.5 20

130-220oC 9 19.2 21.5 11.9 19.8 24 13.6 18.3 18.1

220-340oC 13.7 21.6 20.5 17.8 22.1 23.5 20 20.6 19.6

>340oC 72.5 43.2 28 63.4 41.9 22.6 58.5 58.5 42.3

Fig.4. Liquid fraction distribution (v/v)% produced

after cracking of PW

4. Conclusion

A new solid super acid catalyst was prepared x-SO42-

/Z.

Catalysts were prepared by impregnating of Syrian natural zeolite,

with ammonium sulfate solutions. Sulfation of natural zeolite resulted

into significant change in the acidic properties. The ammonia TPD

experiments showed that sulfation of catalyst (natural zeolite) can lead

to the formation of more super-acidic sites in the catalyst than in

unprompted zeolite.


06

Prepared catalyst showed better results in the pyrolysis of plastic

wastes since high conversion of the samples can be obtained compared

with thermal pyrolysis. When the catalyst is used the conversion is

higher than 99 wt%, and the liquid fractions are the main product,

higher than 83 wt%. The increasing of sulfate ions leads to a decrease

in the content of liquid and to an increase of gas products. The

composition of liquid fraction resulting from thermal and pyrolysis of

PW was different. Presence of sulfate ions leads to higher light fraction

~30 wt% and lower heavy fraction at 475oC and 500

oC. The liquid

fraction can be used as an alternative to fossil fuel or as a source of

valuable chemicals, while the gaseous fraction could be used for power

generation for the process itself. Solid residues are lower than 1 wt% in

the catalytic process.

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R.J.of Aleppo Univ. Basic Science Series No. 98 2014

19

Poling Process Impact on the Pyroelectric Properties of

PZT Fatima Srouji, Sami Orfali

*

Dept. of Physics, Faculty of Science, Aleppo University

*Postgraduate Student (MSc.)

Abstract Crystalline nanostructured (PZT) with atomic ratio of the

Pb:Zr:Ti of 1:0.53:0.47 was synthesized by a chemical method starting

from Lead, Titanium and Zirconium salts and using low temperature

synthesis path which is supposed to compose a nanostructured PZT.

Using XRF, a qualitative analysis had been carried out to investigate

that the samples contain Lead, Titanium and Zirconium. The samples

were pressed as pellets then sintered at 11000C. Using a high voltage

generator, a poling process was achieved at (0.5 - 1.5) KV/mm at room

temperature. Using AC measurements, a relative permittivity including

real and imaginary parts in a function of frequency in the range (20

Hz-3 kHz) for unpoled samples at room temperature was measured in

order to investigate the polarization processes. The relative permittivity

and loss factor for poled samples were studied in a function of fre-

quency where the poling process results in increasing the relative per-

mittivity and decreasing the loss factor. The relative permittivity and

loss factor were also studied in a function of temperature at fixed fre-

quency. It is noticed that the relative permittivity increases with tem-

perature up to many thousands times. Hysteresis loop was plot to show

the ferroelectric property of the material. Pyroelectric current was

measured in order to calculate the pyroelectric coefficient of the mate-

rial which exhibits high increasing with temperature after 4000C.

Received 4/8/2014

Accepted 21/9/2014

Dr. Srouji. Orfali

20

1. Introduction Lead Zirconate Titanate, Pb (ZrxTi1-x)O3 (PZT) ceramics are an

important class of piezoelectric, pyroelectric and ferroelectric materi-

als.[1] Due to their excellent dielectric, piezoelectric and electro- optic

properties, they find a variety of applications in high energy capacitors,

non-volatile memories (FRAM), ultrasonic sensors, infrared detectors

and electro optic devices[2-4]. PZT alloys belong to the family of ce-

ramics, which are alloys of lead oxide, zirconium oxide, and titanium

oxide (PbO, ZrO2, and TiO2). The familiar Perovskite structure appears

in PZT alloys because there are equal numbers of divalent (Pb2+

) and

tetravalent (Zr4+

and Ti4+

) cations. PZT alloys are in fact the alloys of

two components: PbZrO3 and PbTiO3. Thus, by controlling the compo-

sition and microstructure of the PZT alloys, it is possible to adapt their

properties to suit particular applications [5]. The general chemical

formula of our samples is PbZr1-xTixO3, with x=0.47, due to the peculi-

arities of PZT; in the transition zone in between the two structures (x=

0.53), it is called morphotropic phase boundary (MPB), which has high

relative and piezoelectric coefficients [6]. Polycrystalline ferroelectric

materials (ceramics) may be brought into a polar state by applying a

strong electric field (10-100 kV/cm), usually at elevated temperatures.

This process, called poling, can reorient domains within individual

grains along those directions that are permissible by the crystal sym-

metry and that lie as close as possible to the direction of the field. A

poled polycrystalline ferroelectric exhibits piezoelectric and pyroelec-

tric properties, even if many domain walls are still present. After the

removal of the poling field, a ferroelectric material possesses macro-

scopic polarization, called spontaneous polarization PS [7,8]. In this

paper, chemical method is used to synthesize PZT at low sintering

temperature. XRF is used to detect the composition. High voltage

source was used to pole the samples. AC electrical measurements were

used to study the electrical properties and DC measurements were cur-

ried out to study the pyroelectric properties. Hysteresis loop was plot

of the material using high voltage supplier.

2. Materials

Lead Nitrate (PbNO3), Titanium tetrachloride (TiCl4), Zirconi-

um oxychloride octahydrate (ZrOCl2.8H2O), analytical grade, ammo-

nia, ethylene glycol, distilled water, and Nitric acid were used for

chemical preparation.


21

3. Experimental 3.1. Preparation of PZT

The Low-Temperature Synthesis path followed by auto-

combustion process was adapted in this paper [2]. Lead Nitrate

(PbNO3), Titanium tetrachloride (TiCl4), Zirconium oxychloride oc-

tahydrate (ZrOCl2.8H2O), and analytical grade were used as starting

materials. Titanium tetrachloride (TiCl4) and Zirconium oxychloride

octahydrate (ZrOCl2.8H2O) were solved in distilled water at low tem-

perature (about 20C) then a stoichiometric amount of ammonia was

added to form a Precipitate of TiO (OH)2 and ZrO(OH)2. Nitric acid

was added to the two solutions until the complete solution yielded

TiO(NO3)2 and ZrO(NO3)2 solutions, then they were added to the

Pb(NO3)2 solution with an appropriate amount of ethylene glycol

which plays two roles, one as a chelating agent and the other is to pro-

vide the fuel for the auto combustion process. The atomic ratio of the

Pb:Zr:Ti of solution which was 1:0.53:0.47 with 2% excess of lead was

introduced to compensate the evaporated amount during sintering pro-

cess. After PZT, precursor sol was obtained; the mixture was heated

under 1000C until the gel formation. Then the gel was calcinated at

5000C. The formed powder was milled by a ceramic mortar, pressed

under 5 ton/cm2 as disks of 10mm diameter and 1mm thickness. The

sintering was at 11000C for 4h with temperature changes rate of

5oC/min. Then an XRF test was carried on the samples to investigate

the compositional characterization. The disks were polished and

washed by alcohol. In addition, an air-dry silver paste was applied to

the samples surfaces as electrodes, to ensure a good electrical contact

and introduce them for further characterization.

4. Results and Discussion 4.1. Qualitative Analysis

Using XRF device, Unisantis® type Si-PIN with molybdenum

(Mo) target operated at 50kV and 1mA, XRF spectrum was taken for

the samples. Fig. 1 reveals the existence of the three elements (Lead,

Zirconium and Titanium). Oxygen element was unable to be detected

because it is out of the resolution of the device.

Dr. Srouji. Orfali

22

Fig.1. XRF spectrum for PZT sample

This method gives a formation of the major tetragonal Perov-

skite phase [2].

4.2.Electrical Measurements

4.2.1 Electrical Characterization for Unpoled Samples

The real and the imaginary parts of the relative permittivity and

the loss factor tgδ were measured using LCR meter from MICRO-

TEST type 6379 in the range of frequency (20Hz-3 kHz) at room tem-

perature. As shown in fig. 2, the real part of dielectric permittivity de-

creases sharply with increased frequency at range (20Hz-100Hz), then

it decreases slightly at higher frequency.

Fig.2 Real part of relative permittivity in a function of frequency in the range of

(a: 20-210 Hz, b: 20-3000 Hz) at room temperature.


23

Fig.3 The imaginary part of the relative permittivity in a function of frequency

at room temperature.

Theoretically, this manner can be explained as follows: at fre-

quencies below 1 KHz, the four polarization mechanisms (electronic,

ionic, orientational and space charge polarization) act. These polariza-

tions involving the movements of charges either by orientation (i.e.,

orientational polarization) or through the migration of charge carriers

(i.e., hopping or space charge polarization) belong to the relaxation

regime, because during the polarization or depolarization processes, a

relaxation phenomenon occurs due to the time required for the charge

carriers to overcome the inertia arising from the surrounding medium

in order to proceed in their movement. Whereas at frequencies increas-

es above 1 KHz, the only active polarization mechanisms are associat-

ed with vibrations of electrons (i.e., electronic or optical polarization)

or with vibrations of atoms or ions (i.e., atomic or ionic polarization).

This behavior belongs to the resonance regime, because at certain fre-

quencies a resonance will occur when the frequency of the excitation

field is close to the natural frequency of the vibration or oscillation

system, where the real part of relative permittivity is theoretically giv-

en by Debye equation [9]:

Where and

are the low- and high–frequency values of ,

respectively. is the relaxation time. Fig. 3 shows the imaginary part

of relative permittivity εr'' in function of frequency measured by LCR

meter. It is similar to the relative permittivity variation with frequency.

The values of εr'' decrease hundreds times before 1 KHz. That

can explained by Koop’s model which states that at low frequency,

grain boundaries are responsible for the high resistivity, and charges

0.00E+00

2.00E+00

4.00E+00

6.00E+00

8.00E+00

1.00E+01

0 1000 2000 3000 4000

ε r''

f(Hz)

Dr. Srouji. Orfali

24

need relatively high energy to hop between grains whereas at high fre-

quency, grains are the responsible areas for conductivity and its resis-

tivity is low [10]. So considering the hopping conductivity, the loss

factor can be theoretically given by the following equation [9]:

(

) ( )

(

)

Where ζ is the conductivity.

Figure 4. shows relative permittivity at different temperatures.

It is clear that the curves have the same shapes at higher degrees which

indicates that the same polarization process occurs at temperatures be-

low Curie point.

Fig.4 Relative permittivity in a function of frequency at different temperature

(25, 350, 550)0C

4.2.2 Poling the Sample

For optimal poling, an electric field is slightly higher than EC

(coercive field). The field should be applied at least for the switching

time of the domains at room temperature [8]. A poled polycrystalline

ferroelectric exhibits piezoelectric and pyroelectric properties, even if

many domain walls are still present. After the removal of the poling

field, a ferroelectric material possesses macroscopic polarization,

called spontaneous polarization PS. A small chamber was made to con-

tain the sample. The chamber was made of Teflon and provided with

terminals and thermocouple, as shown schematically in fig. 5.


25

Fig 5. Schematic diagram for designed chamber.

Samples were submitted to an electrical field (1500V/mm,

1000V/mm and 500V/mm) under atmospheric conditions for half an

hour.

3.2.2 Electrical Characterization for Poled Samples

After poling process application, relative permittivity and die-

lectric loss were measured. Fig. (6,7) represent the dielectric constant

and dielectric loss factor as a function of frequency after poling with

different poling electric fields.

Fig.6 Relative permittivity variations with frequency at different poling field.

To illustrate the poling process effect on relative permittivity of

material, a vertical line is drawn at 1500Hz frequency. Table 1. lists

the values of intersections points. Table 1.

Poling

field(KV/mm)

0 0.5 1 1.5

Relative per-

mittivity

54 81 108 162

Poled samples show significant enhancement of the relative

permittivity with increasing the strength of the poling electric field.

Dr. Srouji. Orfali

26

Contrarily, the dielectric loss slightly decreased with increasing poling

field especially at low frequencies. Table 2. lists the intersection points

of the vertical line drawn at 1000 Hz frequency. This can be interpret-

ed by the formation of domains walls due to the poling process which

limits the conductivity resulting in the decrease of the dielectric loss

[16].

Fig.7 Dielectric loss factor as a function of frequency after poling with different

poling electric fields.

Table 2.

Poling

field(KV/mm)

0.5 1 1.5

Dielectric loss 0.596 0.513 0.394

3.2.3 Hysteresis Loop

As the pyroelectrics are a subgroup of the ferroelectrics, pyroe-

lectric materials exhibit ferroelectric properties. The most important

characteristic of ferroelectricity is the polarization reversal (switching)

with an electric field. One consequence of this switching is the occur-

rence of the ferroelectric hysteresis loop. The hysteresis loop can be

observed experimentally by using different techniques. We used the

Sawyer-Tower setup [17].

A home-made Sawyer-Tower circuit, as schematically repre-

sented in Figure 8, with manually changed electric field with frequency

of about 0.5Hz and an electric field amplitude of 500V/mm was used.


27

Fig.8 schematic diagram of Sawyer-Tower circuit, where C is the sample capaci-

tance and C0=1µF>>C the reference capacitance.

Figure 9 shows the hysteresis loop of the material. It is clear that

there is a delay between the applied voltage and reference capacitor

voltage, and that is due to the time required for the domains wall to

move according to the electric field.

Fig 9. Hysteresis loop of prepared material.

3.3 Pyroelectric Measurements

By changing the samples temperatures gradually up to 550°C

at about 5°C/min rate, the temperature dependence of the dielectric pa-

rameters at 1 kHz for the 1.5 kV/mm poled sample and the non-poled

sample was measured. Fig 10 shows the relative permittivity changing

with temperature. It exhibits relatively constant value up to 300°C at

which the dipoles begin to align each other. The poling field shows

significant increase of the dielectric constant, where many domains are

already formed by mean of the poling field. As the relative permittivity

does not decrease within the used temperature range, Curie tempera-

ture of the material is not less than 550°C.

-200

-100

0

100

200

-400 -200 0 200 400

v o(v

olt

)

V (volt)

hysteresis loop

Dr. Srouji. Orfali

28

Fig 10. The relative permittivity variation in function of temperature for un-

poled sample and 1.5kV/mm poled sample.

The pyroelectric current was measured using KEITHLEY

6517B electrometer then the pyroelectric coefficient p was calculated

using the following relation [9,11]:

(

)

Where A is the sample area, IPyro pyroelectic current, and

(

) is the heating rate with time. Fig.11 shows the pyroe-

lectric coefficient p changing with temperature; it shows nonlinear var-

iation with temperature. As shown, the pyroelectric coefficient exhibits

low increasing with T in range of (200-400°C) and high increasing af-

ter T=400°C.

Fig 11. Pyroelectric coefficient variation in function of temperature.

4. Conclusions

Dielectric constant values decrease sharply with increased fre-

quency in the range of (20Hz-100KHz), then the dielectric con-

stant decreases slightly in the range of (1KHz-3KHz).

The same polarization process occurs at temperature below Tc.

0

5000

10000

0 200 400 600ε r

T0C

Unpoled sample

1.5 kV/mm poled sample

0

100

200

300

400

500

600

700

0 200 400 600pyr

oel

ectr

ic c

oef

fici

ien

t (μ

C/c

m2 .

0 C)

T0C


29

Ferroelectric property of PZT material includes a hysteresis

loop.

Poling process increases the relative permittivity of the sam-

ples.

Poling process decreases the dielectric loss of the material es-

pecially at frequencies below 1 KHz.

The pyroelectric coefficient exhibits high increasing with tem-

perature after 4000C.

References [1] Haertling, G. H. 1999 - Ferroelectric ceramic. History and tech-

nology. J. Am. Ceram. Soc. 82, 797–818.

[2] Gajbhiye N. S.; Pandey P. K.; Smitha P. 2007 - “Low-

Temperature Synthesis of Nanostructured PZT for Dielectric

Studies” Synthesis and Reactivity in Inorganic, Metal-Organic, and

Nano-Metal Chemistry, 37:431–435.

[3]Kim, K.; Lee, S. 2006 - Integration of lead zirconium titanate

thin films for high density ferroelectric random access memory.

J. Appl. Phys. 100, 51604–51611.

[4] Yamashita, K.; Chansomphou, L.; Murakami, H.; Okuyama, M.

2004 - Ultrasonic micro array sensors using piezoelectric thin

films and resonant frequency tuning. Sensors Actuators. 114,

147–153.

[5] Jaffe B.; Cook W.R.; Jaffe H. 1971 - Piezoelectric Ceramics, (Ac-

ademic Press, New York).

[6] Noheda B.; Cox D. E.; Shirane G.; Gonzalo J. A.; Cross L. E.; Park

S-E. 1999 - A monoclinic ferroelectric phase in the Pb(Zr1-xTix)

O3 solid solution, Appl. Phys. Lett. 74, 2059.

[7] Dragan Damjanovic. 2006 - Hysteresis in Piezoelectric and Fer-

roelectric Materials. The Science of Hysteresis, Volume 3; I.

Mayergoyz and G.Bertotti (Eds.); Elsevier.

[8] Kamel T. M. “Poling and switching of pzt ceramics” doctorate of

philosophy essay 2007.

[9] Kwan Chi Kao. 2004 - Dielectric phenomena in solids, book,

ISBN 0-12-396561-6, Elsevier Academic Press, pp.-86-98.

[10] Koops C. G. 1951 - Phys. Rev. 83 (121).

[11] IRE standards on piezoelectric crystals, 1949, Proc. IRE,

37,PP.1378-1395, 1949.

Dr. Srouji. Orfali

30

[12] IRE strandards on piezoelectric crystals-the piezoelectric vi-

brator: definitions and methods of measurement, 1957”, Proc.

IRE, 45, PP. 353-358, 1957.

[13]Shining Zhu, Bei Jiang .; Wenwu Cao. Characterization of pie-

zoelectric materials using ultrasonic and resonant Techniques” SP1E Vol. 3341

[14] Mason W. P. 1950 - Piezoelectric Crystals and Their Applica-

tion to Ultrasonics. New York: Van Nostrand.

[15] Kuwata J.; Uchino K.; Nomura S. 1982 - Jpn. J. Appl. Phys. 21,

1298. [IEEE Standard on piezoelectricity. ANSI/IEEE Std. 176-

1987.

[16] J.Wu and C.Chen, J.Mater.Sci, 23, 4157, (1988).

[17] C. B. Sawyer and C. H. Tower, “Rochelle salt as a dielectric”

Physical Review, vol. 35, pp. 269–275, February 1930


13

Optical Properties of CdTe QDs Synthesized by

Chemical Method and Enhanced by Microwave

Irradiation

Fatima Srouji, Farouk Al Jasem*



Abstract CdTe quantum dots in aqueous phase were prepared by

chemical method enhanced by microwave irradiations. The influence

of capping with Thiol component (3- Mercaptopropionic acid) and

organic component (Polyvinylpyrrolidone) on the stability of the

quantum dots, absorption and Photoluminescence (PL) spectra, was

studied. The influence of microwave irradiations on the quantum dots

stability and reducing of surface defect was also studied. The

preparation parameters (synthesis temperature, PH value of CdTe

precursor solution and the Cd+2

/Te-2

ratio) were studied. It was found

that CdTe Quantum dots in the aqueous phase capped with thiol

(MPA) have high stability and photoluminescence compared with

quantum dots in the aqueous phase capped with PVP (organic). Using

microwaves leads to accelerating the growth of quantum dots; it results

in reducing the interaction energy and detracting the surface defects.

Received 30/6/2014

Accepted 23/10/2014

Dr. Srouji & Al jasem

13

1. Introduction Colloidal semiconductor nanocrystals (also known as quantum

dots, QDs) are generally known as II–VI and III–V semiconductors,

which strongly exhibit size dependent on optical and electrical

properties [1]. Bulk CdTe is transparent in the infrared wavelength,

from its bandgap energy, which is approximately 1.44eV at 300K (i.e.

860 nm) to its wavelength, greater than 20 μm, which is already in the

infrared region. It has been presented that if the size of the bulk CdTe

material shrinks to nanometer scale, normally 2 to 5 nm, the bandgap

energy of the material will increase, due to quantum confinement

effect, which means that the fluorescence peak will shift towards the

infrared region or visible range. This will open a wide gate of

application for this magical semiconductor material to be used in

several areas. CdTe quantum dots are also highly luminescent

nanoparticles with quantum yield up to 80% if the parameters through

the synthesis process are carefully manipulated [1-3]. The synthesis in

aqueous phase is an alternative method for preparation of QDs. A

series of thiol-stabilized QDs, such as CdS [2], CdSe [3] and CdTe [4–

5] could be prepared in aqueous solution. Compared with organic

phase synthesis, aqueous synthesis exhibits good reproducibility, low

toxicity, and low price; the products have especially excellent water-

solubility, stability and biological compatibility [5]. Using microwave

electromagnetic irradiation to synthesize QDs is recently widely used

because it can provide rate and yield enhancements [6]. These benefits

can be explained by dielectric heating in which polar materials are

heated preferentially because they absorb microwaves more strongly.

Depending on the relative polarity difference between the solvent and

precursor molecules, one can rapidly grows QDs by heating precursors

directly or by heating the solvent to form a traditional thermal bath.

Furthermore, dielectric heating differs from convective heating in that

the entire volume is heated uniformly, thereby reducing thermal

gradient effects and hence providing more control over the size

distribution (i.e., optical properties) of the QDs [6]. Therefore, with

careful selection of the reaction system (precursors, passivating

ligands, solvent, etc.) and microwave parameters (temperature, time,

power, etc.), one can potentially achieve superior control of the

nucleation and growth processes to generate high-quality QDs [7].


11

2. Experimental and Result 2.1 Materials

Cadmium chloride monohydrate (CdCl2.H2O, 98%,

HIMEDIA), Sodium tellurrite (Na2TeO3, 98%, BDH), Tri-sodium

citrate dehydrate (C6H5O7Na3.2H2O, 98%, HIMEDIA), 3-

Mercaptopropionic acid (C3H6O2S, 98%, IT USA), Sodium

borohydride powder (NaBH4, Scharlau), Polyvinylpyrrolidone (PVP)

and a modified domestic MW oven (900 Watt, 2.45 GHz).

UV-vis absorption spectra were obtained using a V630 UV-vis

spectrophotometer (Jasco). Photoluminescence (PL) spectra were

recorded with an F-2700 fluorescence spectrophotometer (Hitachi).

2.2. Synthesis of CdTe QDs

2.2.1 Synthesis of CdTe QDs Capped with MPA (Thiol) 4 mL of cadmium chloride solution (CdCl2, 0.04 mol/L) were

diluted to 42 mL with deionized water, and then trisodium citrate

dihydrate (100 mg), Na2TeO3 (0.01 mol/L, 4 mL), MPA (119 mg), and

NaBH4 (50 mg) were added successively under magnetic stirring. The

molar ratio of Cd2+

/MPA/Te-2

was 1:7:0.25. The resulting CdTe

precursor was put into a flask (250 mL). CdTe QDs were prepared at

temperature (120 °C) under microwave irradiation (900 W) for 10 min.

The mixture was allowed to cool to lower than 50 °C, then samples

were stored in the dark at low temperature.

Figures (1 and 2) show absorption and fluorescence spectra of

CdTe QDs aqueous in water capped with MPA (thiol) measured during

different times after preparation. It is clear from figs. (1 and 2) that

CdTe QDs synthesized by irradiation microwave have high stability

and photoluminescence (PL) in aqueous phase. The band gap of CdTe

QDs was determind to be (2.64 ev) and the radius of CdTe QDs

prepared in aqueous phase was 1.75 nm, which was calculated using

Barus equation [8]:

(

)

Where of CdTe is 1.49 eV, of CdTe is 0.098 ,

of CdTe is 0.11 and is 10.3 (

, are the effective

masses of electron and hole, respectively. is free electron mass and

is vacuum dielectric constant). By inserting these values into the

above equation it becomes:


13

√

Where D (nm): is the diameter of CdTe QD , λ (nm) is

wavelength according to a peak absorption of QD

Fig.1: Absorption spectra of CdTe QDs aqueous in water capped with MPA

(thiol) after different aging intervals, where (a) is immediately after

preparation, (b) after one day, (c) after 4 days, (d) after one week.

Fig.2: fluorescence spectra of CdTe QDs aqueous in water capped with MPA

(thiol), where the excitation wavelength =461nm and the emission wavelength

=503nm.

2.3.2. Synthesis of CdTe QDs Capped with PVP

4 mL of cadmium chloride solution (CdCl2, 0.04 mol/L) were

diluted to 42 mL with deionized water, and then trisodium citrate

dihydrate (100 mg), Na2TeO3 (0.01 mol/L, 4 mL), PVP (100 mg), and

NaBH4 (50 mg) were added successively under magnetic stirring to

the first solution. The molar ratio of Cd2+

/PVP/Te-2

was 1:7:0.25. The

resulting CdTe precursor was divided into two parts:

Measurements were conducted on the first one without

exposing it to microwave irradiation; the second was put into a flask

with a volume of 250 mL. These series of CdTe QDs were irradiated in


13

microwaves at power (900W) until their temperature reached 1200C

for 5min. Then the mixture was allowed to cool lower 500C.

Figure (3) shows absorption spectrum of the prepared CdTe

QDs capped with PVP in the precursor solution after different aging

intervals, where (a) is immediately after preparation, (b) after half an

hour, (c) after 4 days, (e) after one week.

Fig.3 Absorption spectra of CdTe QDs capped with PVP after different aging

intervals, where (a) is immediately after preparation, (b) after half an hour, (c)

after 1.5h, (d) after 14.5 h, (e) after 24h.

The figure shows that the quantum dots capped with PVP in the

precursor solution are unstable and change with the time, and indicates

that the peak of absorption shifts toward the red, which means that the

prepared quantum dots have unstable size. Figure (4) shows the photoluminescence spectrum (PL) of the

prepared CdTe QDs, where the PL of this sample is very poor due to

the presence of large surface defects that lead to poor QY.

Fig.4 Photoluminescence spectrum of CdTe QDs capped with PVP immediately

after preparation, where the excitation wavelength λ=400 nm and the emission

wavelength λ=565nm.


13

Figures (5 and 6) represent the relationship between QDs radii

and aging time; the same for energy gaps.

Fig.5 QDs radius variations with time.

Fig.6 Band gap of QDs variations with time.

It is clear from figures 5 and 6 that a large increase in the radii

of quantum dots for these samples takes place within the first 24 hours.

Then it becomes almost stable. Whereas the ∆Eg decreases largely

within the first 24 hours and then becomes stable. This can be

explained by the following: after the microwave irradiation for 5min

and at 1200C temperature, the CdTe QDs become more stable in size

but the photoluminescence stays low. This is because the

electromagnetic waves result in increasing the molecules polarization

and this, in turn, increases the coupling force between the PVP

molecules and the CdTe QDs, hence increasing the stability of CdTe

QDs size. The electromagnetic waves also work in reducing the

reaction energy of Cd2+

and Te2-

ions which accelerates the occurrence

of reactions and changes CdTe QDs size with time.

1.62

1.64

1.66

1.68

1.7

1.72

1.74

1.76

0 50 100 150 200

Rad

ius

(nm

)

Time (Hour)

1.1

1.15

1.2

1.25

1.3

1.35

0 50 100 150 200

∆E

g (

ev)

Time (Hour)


13

Table (1) Aging times, wavelength peak of absorption spectra, energy gaps and

radius of CdTe QDs.

Time (hour)

Wavelength

peak of

absorption

spectra (nm)

Eg nano (ev)

∆Eg (ev) R (nm)

0 444 2.792 1.302 1.63

0.5 450 2.755 1.265 1.66

1.5 458 2.707 1.217 1.69

14.5 468 2.649 1.159 1.74

24 470 2.638 1.148 1.75

168 471 2.632 1.142 1.75

After Irradiation of CdTe QDs using microwave for 5 min at

120ᵒC temperature, CdTe QDs become more stable in size but still

have poor photoluminescence (PL), as shown in figures (7 and 8).

Fig.7 Absorption spectra of CdTe QDs capped with PVP after aging for (a=0,

b=13, c=23) hours.

Fig.8 Florescence spectra of CdTe QDs capped with PVP, where excitation

wavelength (400nm) and emission wavelength (465nm).


13

Fig.9 Variation of QDs radii with aging time.

Fig.10 Variation of QDs band gaps with aging time.

Figures (9,10) show the variation of the radius and the energy

gap with time, where the radius increases with time due to increased

growth of quantum dots and the corresponding change in the band gap,

and these changes are very small. Table (2) shows the aging time of the samples, the length of wave crest

absorption, energy gap, variety of band gap with time, and radius of CdTe QDs.

R (nm)

∆Eg (ev)

Egnano (ev)

Wavelength

peak of

absorption

spectra (nm)

Time (hour)

2.006 0.885 2.375 522 0

2.018 0.876 2.366 524 13

2.029 0.867 2.357 526 23

2.3.3 Influence of Some Parameters on the Properties of CdTe QDs

Capped with MPA 1.2.2 Temperatures

CdTe QDs prepared by the method mentioned in section )2.3.1)

were irradiated under (900 W) microwave irradiation for (5 min) and at

2.005

2.01

2.015

2.02

2.025

2.03

2.035

0 5 10 15 20 25

Rad

ius

(nm

)

Time (Hour)

0.865

0.87

0.875

0.88

0.885

0.89

0 5 10 15 20 25

∆E

g (

ev)

Time (Hour)


13

temperatures (A = 60, B = 80, C = 100 ᵒC). The last sample was heated

from room temperature to 120 ᵒC (line D).

Figures (11 and 12) show the absorption and photoluminescence

spectra of the samples prepared at different temperatures. As shown in

Figure (11), absorption peaks shift toward the red because of the

increase of the QDs size; this is due to the increase in the growth rate

of these dots with temperature. These figures also show an increase in

the intensity of the optical absorption and luminescence with

temperature. That is due to the reduction of surface defects in the

prepared QDs. While the quantum dots prepared at low temperatures

exhibit low intensity absorption and luminescence caused by the large

number of defects on the surface, generated owing to the slow growth

of QDs. The sample (D) showed the best result for the intensity of the

optical absorption and luminescence, so we can say that the

temperatures between 100ᵒC and 120ᵒC are the ideal temperatures to

achieve optimal synthesis of quantum dots.

Fig.11 Absorption spectra of CdTe QDs capped with MPA at different reaction

temperature (A=60 ᵒC, B=80 ᵒC, C=100 ᵒC, D=120 ᵒC).

Fig.12 luminescence spectra of CdTe QDs capped with MPA at different

reaction temperature.

Figures (13 and 14) represent quantum dots radii and the band

gap variations with preparation temperature. They reveal that the

0

200

400

600

800

450 500 550 600 650

Inte

nsi

ty

Wavelength (nm)

60 C 80 C 100 C 120 C


34

radius of the quantum dots increases almost linearly for temperatures

between 60 ᵒC and 100 ᵒC, then becomes quasi-steady for temperatures

between 100 ᵒC and 102 ᵒC. Similarly, the band gap changes contrary

to radii.

Fig.13: Variation of QDs radii with aging time.

Fig14: Variation of QDs band gaps with aging time.

Table (3): Temperature synthesis, the wavelength of absorption peaks, the

energy gap, the gap energy change, and radii quantum dots.

R(nm) ∆Eg (ev) Enano(ev)

Wavelength peak of

absorption spectra

(nm)

t C

1.52 1.498 2.988 415 60

1.63 1.315 2.805 442 80

1.71 1.194 2.684 462 100

1.69 1.217 2.707 458 120

1.2.3. PH

Following the method of preparation in section (2.3.1) and

before adding Sodium borohydride (NaBH4) to the result solution, the

value of pH was controlled by adding sodium hydroxide (NaOH 0.1

mol/L) in different pH values.

1.5

1.55

1.6

1.65

1.7

1.75

50 70 90 110 130

Rad

ius

(nm

)

t ˚C

1

1.1

1.2

1.3

1.4

1.5

1.6

50 70 90 110 130

∆E

g (

ev)

t ͦ C


33

It was found that the samples with pH values (a: PH=4.52, b:

PH=5.12, c: PH=5.28, d: PH=6.8, e: PH=9.3) give better absorption

values as shown in Figure (15).

Fig.15 Absorption spectra of CdTe QDs synthesized at different PH values of

solution (a: PH=4.52, b: PH=5.12, c: PH=5.28, d: PH=6.8, e: PH=9.3).

Figures (15 and 16) show that the intensities of the optical

absorption and luminescence reach the highest values for pH= 6.8 (line

d). Thus, fluorescence intensity and the highest emission peak of the

CdTe QDs were strongly influenced by the pH value of the precursor

solution.

Fig.16 Fluorescence spectra of CdTe QDs synthesized at different PH values of

solution (a: PH=4.52, b: PH=5.12, c: PH=5.28, d: PH=6.8).

0

10

20

30

40

50

60

425 475 525 575 625 675

Inte

nsi

ty

Wavelength (nm)

a b c d


33

Fig.17 radius of QDs with time.

Fig18 band gap variations of QDs with time.

Table (4) temperature synthesis, wavelength peaks of absorption, energy gap

and radii quantum dots.

PH

Wavelength

peak of

absorption

spectra (nm)

Enano (ev) ∆Eg (ev) R (nm)

3.1 575 2.156 0.667 2.35

4.52 451 2.749 1.259 1.66

5.12 433 2.863 1.373 1.59

5.28 431 2.877 1.387 1.58

5.58 441 2.811 1.321 1.62

6.8 480 2.583 1.093 1.79

Figures (17 and 18) represent quantum dots radii and the band

gap variations with PH. These curves show that the energy gap

increases with the pH value increase until the value 5.5. After returning

to decrease, they become almost stable for pH values between 7 and 9.

From the above behavior, it is noticed that the pH values have a

significant influence on the properties of quantum dots (radii,

wavelength and intensities of absorption and luminescence).

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2 4 6 8 10

Rad

ius

(nm

)

PH

0.4

0.6

0.8

1

1.2

1.4

1.6

0 2 4 6 8 10

∆E

g (

ev)

PH


31

1.2.4 Ratio of Cd+2

/Te-2

CdTe QDs prepared by the method mentioned in section )2.3.1)

were irradiated under (900 W) for 5 min and sample temperatures were

allowed to rise from room temperature to 120 ᵒC. The ratio of Cd+2

/

MPA/ Te-2

have been changed as follows: Table (5) The ratio of Cd

+2/Te

-2 in the prepared samples

sample a b c d e f g

Ratio of

Cd+2

/MPA/ Te-2

0.25/7/

0.25

0.5/7/

0.25

0.75/7/

0.25

1/7/

0.25

1/7/

0.0625

1/7/

0.125

1/7/

0.1875

Figures (9, 10) show the peaks of absorption and fluorescence

spectra of samples synthesized with different ratios of Cd+2

and Te-2

.

The figures show the effect of the cadmium ratio on surface defects of

the QDs synthesized in the solution, where the increasing in ratio of

Cd+2

results in an enhancement of the surface of QDs and a decrease in

the surface defects. These defects are less than that in the samples of

the ratio Cd+2

/MPA/Te-2

: 1/7/0.25.

Fig.19 Absorption spectra of CdTe QDs synthesized at different ratio Cd

+2/Te

-2

of solution.

It is obvious from the figure (19) that the intensity of the

photoluminescence is the largest for this ratio.

Fig.20 Photoluminescence spectra of CdTe QDs synthesized at different ratio

Cd+2/Te-2 of solution.


33

Figures 21, 22 show radii and band gap variations of the QDs

for ratio of Cd+2

/Te-2

. From these curves it is noted that the best

samples are corresponding to a ratio of Cd+2

/Te-2

that equals (2:4:8).

Fig.21 Radii of QDs variations with time.

Fig.22 Band gap variations of QDs with time.

Table (6) Temperature synthesis, wavelength peaks of absorption, energy gap,

the gap energy change and radii quantum dots.

Cd+2

/Te-2

Wavelength

peak of

absorption

spectra (nm)

Enano(ev) ∆Eg (ev) R (nm)

1 469 2.661 1.171 1.74

2 404 2.719 1.229 1.48

3 441 2.737 1.247 1.62

4 431 2.877 1.387 1.58

5.33 453 2.644 1.154 1.67

8 456 3.069 1.579 1.68

16 466 2.811 1.321 1.73

Conclusion

A chemical method for CdTe Quantum dots enhanced with

microwave irradiation is a fast, easy, and cheap way for CdTe

1.45

1.5

1.55

1.6

1.65

1.7

1.75

1.8

0 5 10 15 20

Rad

ius

(nm

)

ratio of Cd+2/Te-2

1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

0 5 10 15 20

∆Eg

(e

v)

ratio of Cd+2/Te-2


33

Quantum dots preparation and gives Quantum dots with different sizes

and good structure.

CdTe Quantum dots in the aqueous phase capped with thiol

(MPA) have high stability and photoluminescence compared with

quantum dots in the aqueous phase capped with PVP (organic). Using

microwave in the preparation of quantum dots increases the stability of

the quantum dots and improves the optical character, absorption and

photoluminescence. In addition, CdTe Quantum dots in the aqueous

phase capped with (PVP) have more stability than those prepared

without microwave irradiations. Using the microwaves leads to

accelerating the growth of quantum dots; it results in reducing the

interaction energy and detracting the surface defects.

The various parameters of preparation (temperature, pH and

ratio of Cd+2

/Te-2

) have strong influences on the physical properties of

QDs; therefore, these parameters can be adjusted during the synthesis

process, according to required applications of prepared quantum dots.

References [1] L.E. Brus, Electronic wave functions in semiconductor clusters:

experiment and theory, J. Phys. Chem., 1986, 90 (12), pp 2555–

2560

[2] T. Vossmeyer, L. Katsikas, M. Giersig, I.G. Popovic, K. Diesner,

A. Chemseddine, A. Eychmu¨ ller, H. Weller, CdS Nanoclusters:

Synthesis, Characterization, Size Dependent Oscillator

Strength, Temperature Shift of the Excitonic Transition

Energy, and Reversible Absorbance Shift, J. Phys. Chem.

1994,98, 7665-7673

[3] A.L. Rogach, A. Kornowski, M.Y. Gao, A. Eychmu¨ller, H.

Weller, Synthesis and Characterization of a Size Series of.

Extremely Small thiol-stabilized CdSe Nanocrystals, J. Phys. Chem. 1999; 103:3065–3069

[4] A.L. Rogach, L. Katsikas, A. Kornowski, D. Su, A. Eychmu¨ller,

H. Weller, Ber. Bunsen-Ges. Synthesis and Characterization of

Thiol-Stabilized CdTe Nanocrystals Phys. Chem. 100 (1996)

1772.

[5] N. Gaponik, D.V. Talapin, A.L. Rogach, K. Hoppe, E.V.

Shevchenko, A. Kornowski, A. Eychmu¨ller, H. Weller, Thiol-

Capping of CdTe Nanocrystals: An Alternative to

Organometallic Synthetic Routes, J. Phys. Chem.

B, 2002, 106 (29), pp 7177–7185


33

[6] Gerbec, J. A.; Magana, D.; Washington, A.; Strouse, G. R. J. Am.

Direct Synthesis of Aqueous CdSe/ZnS-Based Quantum Dots

Using Microwave Irradiation, Chem. Soc. 2005, 127, 15791.

[7] William Schumacher, Amber Nagy, W. James Waldman, and

Prabir K. Dutta, Direct Synthesis of Aqueous CdSe/ZnS-Based

Quantum Dots Using Microwave Irradiation, Chemistry and

Pathology. 2009

[8]: A.El Moussaouy, D. Bria, A. Nougaoui. 2006. Thermal effect on

bound exciton inCdTe/Cd1-xZnxTe cylindrical quantum dots.

Solar Energy Materials & Solar Cells 90: 1403–1412.

Res. J of Aleppo Univ. Basic Science Series No.98 2014

74

Studying the Effect of Fineness on the Thermal

Treatment of Syrian Petroleum Coke to Reduce the

Sulfur Content

Walied Hawaleh*, Salah Al Haj Omar**, Mohammad Yahia Masri

***

*Dept. of Chemistry, Faculty of Science, University of Aleppo

**Dept. of Basic Science, Faculty of Mechanical Engineering, University of Aleppo

***Postgraduate Student (PhD), Dept. of Chemistry, Faculty of Science, University

of Aleppo

Abstract

In this research we studied the effect of fineness on the thermal

treatment of Syrian petroleum coke in order to define the favorable

fineness to reduce the sulfur content in lower temperature and time.

The samples of petroleum coke were crushed to different granular size,

from less than 90µm to more than 5mm, then we made physical and

chemical analysis for each sample to know the distribution of sulfur in

each sample. We found that the amount of sulfur is increased by the

increase of fineness. We measured the moisture, ash and volatile

content as well as the caloric value for each sample.

It was concluded that the ability of sulfur removing from

petroleum coke is by increasing treatment temperature up to 1200°C

and time of treatment to 2 hours. The best sulfur removal was with the

granular size between (710-1250µm). This sample is fit with ash and

volatile matter content within the allowed value according to ASTM

specifications.

Keywords: Syrian petroleum coke, Thermal treatment, Fineness effect, sulfur

content.

Received 15/6/2014

Accepted 25/8/2014

R.J. of Aleppo Univ. Basic Science Series No. 98 2014

49

Screening, Identification and Partial Characterization

of Pullulanase Enzyme from Local Bacterial Strain

Nizar Essa, Faiza Al atrash, Waleed Mlook* Dept. of Botany, Faculty of Science, Damascus University

* Postgraduate Student (MSc.)

Abstract

Fifty bacterial isolates, isolated from various local soils (19),

baking wastes (14) and food wastes (19) were screened to detect

pullulanase, by using pullulan as a sole carbon source according to

solid plate assay. Results showed that 17 strains (34 %) had the

ability to produce pullulanase in assay plate as evidenced by clear

hydrolization zones formed around the colonies. Seven strains

which presented considerable pullulytic activity with degradation

efficiency more than 1.5 were chosen, and the pullulanase activity

in poor broth was studied for each one. P8 isolate which had the

biggest degradation efficiency (2.88) showed high activity of the

enzyme (0.549 unit/ml) in broth medium. Based on morphological

and biochemical characteristics, P8 strain was identified as Bacillus

cereus. This isolate showed high activity to produce pullulanase at

50°C and pH 6.0. It was concluded that there is an ability to

produce locally pullulanase which can be used for some

manufacturing purposes. Keywords: Pullulanase, Pullulan, Bacillus.

Received 6/7/4104

Accepted 45/8/ 4104

Res. J. of Aleppo Univ. Basic Science Series No.98 2014

51

A Study of Immunological and Hematological Findings

in Systemic Lupus Erythematosus (SLE) Patients in

Aleppo Sabah Blaj*, Leka Hoppo*, Abeer Alyosef**, Eman Almosa***

* Dept. of Zoology, Faculty of Science, University of Aleppo

**Dept. of Laboratory Medicine, Faculty of Medicine, University of Aleppo ***Postgraduate Student (MSc.) Dept. of Zoology, Faculty of Science, University of

Aleppo

Abstract

The research aimed to study some Immunological and

Hematological findings in SLE patients in Aleppo. The recent study

examined 27 blood samples from Systemic lupus Erythematosus (SLE)

patients of both sexes, who fulfilled four or more of the classification

criteria of American College of Rheumatology (ACR, 1997). We

investigated the presence of Anti-nuclear antibodies (ANA) and double

stranded DNA antibodies (anti-ds-DNA). The positive was %85.18,

and %70.37, respectively. Elevated C-reactive protein (CRP), Low

complement C3, and Elevated immunoglobulin IgG in SLE patients

were found in 40.74%, 48.04%, and 37.04%, respectively. Blood tests

had been done for patients; the most common feature is Anemia, with

66.66%, Leucopenia and Thrombocytopenia were found in 11.11%,

and 18.5% , respectively.

Key words: Systemic lupus erythematosus (SLE), American College

of Rheumatology (ACR), antinuclear antibody (ANA), double stranded

DNA (dsDNA), Complement C3, C-reactive protein (CRP),

immunoglobulin G (IgG).

Received 20/7/2014

Accepted 25/8/2014

Res. J. of Aleppo Uni. Basic Science Series. No. 98 2014

35

Antibacterial Activity of Salvia officinalis against Some

Pathogenic Bacteria Isolated from Tonsillitis and

Pharyngitis Patients

Abdel Aleem Bello٭, Zaher Samman Tahan٭, Firas Haj Zein٭٭, Yasmin Alshihabi٭٭٭

Dept. of Botany, Faculty of Science ٭

Dept. of Otolaryngology, Faculty of Medicine٭٭

Postgraduate Student (MSc.) Dept. of Botany, Faculty of Science, University of ٭٭٭

Aleppo

Abstract

Salvia officinalis has a valuable medicinal importance; it is

used in traditional medicine for the treatment of Pharyngitis and

Tonsillitis. Leaves and aerial parts of Salvia officinalis were extracted

with Petroleum ether, chloroform, ethanol and water. The yield of

extracts was determined. The activity of extracts against bacteria

isolated from tonsillitis and pharyngitis patients was determined by

using Agar Well Diffusion Method, then the Minimal Inhibitory

Concentration (MIC) was determined.

The results showed that most of the examined extracts have

antibacterial activity. The most active extract against Gram positive

bacteria was chloroform extract of aerial parts, where zone of

Inhibition was 34.67 mm for Staphylococcus hominis. The most active

extract against Gram negative bacteria was Petroleum ether extract of

aerial parts, where zone of Inhibition was 19.67 mm for Klebsiella

pneumoniae. Gram positive bacteria were more sensitive to plant

extracts than Gram negative bacteria.

The results showed that plant extracts with examined

concentrations were more active than some standard therapeutic

antibiotics.

Keywords: Antibacterial activity, Plant extracts, Salvia officinalis,

Pharyngitis, Tonsillitis.

Received 14 /7/2014

Accepted 26 /8/2014

Res. J. of Aleppo Univ. Basic Sciences Series No.98 1024

55

Synhesis of Some Push-Pull Alkenes Containing Two

Carbonyl Groups: Ketene Dimethyl Dithio Acetal Type

Saleh El-Kadri, Ani Tersakian, Ahmad Alabboud* Dept. of Chemistry, Faculty of Science, University of Aleppo


Abstract

Starting from compounds containing acidic hydrogens which

are: Acetyl acetone, methyl aceto acetate, dimethyl malonate and ethyl

aceto acetate, we have synthesized some ketene dimethyl dithioacetal

compounds which belong to push – pull alkenes family according to

dithiocarboxylation general reaction in the presence of carbon disulfide

in two alkaline systems K2CO3/DMF and KOH/CH3CN. The

synthesized compounds structures have been approved by infrared

spectroscopy (IR) and mass spectrometry (GC/MS).

Keywords: push-pull alkenes, ketene dithio acetal, active methylene compounds.

Received 08/04/2014

Accepted 28/08/2014

R . J . of .Aleppo Univ. Basic Sciences Series No. 89 2041

75

A Comparative Study of the Structure of Pancreas in the

Two Species Clarias gariepinus (syriacus) and Clarias

salurus Living in the Orontes and Euphrates Rivers

Saja Abou Ghaloon

Dept. of Zoology, Faculty of Science, University of Aleppo

Abstract The research showed a difference in the prevalence,

correlation and thickness of the pancreas in the two Species, Clarias gariepinus (syriacus) and Clarias salurus especially with liver and

great portal vein. The researcher observed an overlap between the

pancreas and liver tissue in Clarias gariepinus (syriacus) without a

barrier of connective tissue between them, constituting pancreatic

liver, unlike the Clarias salurus where a connective capsule separating

the pancreas and liver was observed. The histological structure of

Pancreas in Clarias gariepinus (conjoined with follicle biliary, bile

ducts and blood vessels) interfered with serosa, and the situs exocrine

cells took the shape of sling cells. Also the cell takes Pear shape and is

linked with a thin layer of connective tissue; its tip top is free in

cavities connected with each other. While it takes the alveolar shape in

the Clarias salurus surrounded by connective tissue. The islets of

Langerhans are spread in both species in the central part of the gland

while they are absent in the areas of overlap with other organs. They

take in Clarias gariepinus (syriacus) the form of large vesicles with

irregular boundaries surrounded by thin connective capsule, but in the

Clarias salurus, they are smaller with regular borders surrounded by

thick connective capsule. Two different types of cells in the islets of

Langerhans in both species were distinguished, pyramid-shaped acidic

cells with basic nucleus positioning, and a basic cell with unclear

membrane and central nucleus positioning.

Keywords: Clarias gariepinus (syriacus), Clarias salurus, Pancreas,

islets of Langerhans. Received 6 /7/2014

Accepted 2 /9/2014


95

A Comparative Study of Ball Point Pens Writing Ink

Using Techniques of XRF, UV-VIS, FT-IR

Said Sabbagh, Murhaf Al-Sayed Ali * Dept. of Physics, Faculty of Science, University of Aleppo

*Postgraduate Student (MSc)

Abstract

The purpose of this study was to evaluate, for legal

examinations, the possibility to discriminate among many samples of

ball point pen inks, provided from various manufacturers by using non-

destructive analysis techniques, such as: Fourier Transform Infrared

Spectroscopy (FT-IR), Ultra Violet – Visible (UV-VIS) Spectroscopy,

and Fluorescence X-ray Spectroscopy (XRF). It also aimed to examine

the ability of each technique to develop the devices of physics.

For analysis of UV-VIS spectra, two ways were used:

complementary color analysis, and color analysis using CIE L* a

* b

*

program. XRF and CIE L* a

* b

* program were successful in

discriminating ballpoint pen inks of different bands, while FT-IR

analysis revealed that each brand could be discriminated by looking

for the pattern of each spectrum.

This work suggests carrying out multiple analyses of unknown

and complex components of writing inks.

Keywords: Ball Point Pens, FT-IR Spectroscopy, UV-VIS Spectroscopy,

XRF Spectroscopy, Complementary Color, CIE L* a

* b

* Program, Writing

Inks.

Received 20/7 /2014

Accepted 2/9 /2014

Res. J. of .Aleppo Univ. Basic Science Series No. 89 2014

16

Studies of XRD, FT-IR and Surface Areas of Pure MoO3,

WO3 and the Mixed Oxide System Mo-W-O

M. Karman, N. Al Ghanom

*

Dept. of Chemistry, Faculty of Science, University of Aleppo

* Postgraduate Student (PhD)

Abstract

Pure MoO3, WO3 and a mixed oxide system Mo-W-O were

prepared by mechanical mixing method, then calcined at 500oC and

600oC. The XRD pattern of the pure MoO3 and mixed oxides system

shows peaks only due to MoO3 with an orthorhombic structure. On the

other hand, the pattern of the catalysts contains 15, 35 wt%. WO3

shows new peaks which can be assigned to formation of a new phase.

The FT- IR spectra of all the prepared samples show characteristic

bands referring to presence of MoO3 and not showing any bands

referring to presence of WO3. The surface areas of all the prepared

samples were determined by adsorption of MB from organic solution

and were found (0.84 - 4.45 m2/g) in case of catalysts calcined at 500

oC and (1.49– 3.47 m

2/g) in case of catalysts calcined at 600

oC.

Keywords: MoO3 - WO3 - surface area.

Received 66/9/4162

Accepted / 4/8/4162


63

Synthesis and Characterization of Nd:YAG Nanopowder

via Polymer DTPA Metal Chelated Complexes

Emad Asad*، Farouk Kandil** ،Mohammad Hasan Derbas *** *Dept. of Chemistry and Institute for Laser Research and Applications, Damascus

University

**Institute for Laser Research and Applications, Damascus University

***Postgraduate Student (PhD.) Dept. of Chemistry, Faculty of Science, Damascus

University

Abstract

High transparency ceramic was prepared from Neodymium,

Aluminum and yttrium Nd: YAG nanopowder. This procedure

included preparation of diethylentriaminepentaacetic (DTPA) followed

by polymerization with ethylene glycol. The produced polymer was

used in forming chelated complexes with elements of YAG. The

formed complexes were calcinated at 600, 700 and 950oC and sintering

followed by product under vacuum. The prepared powder was

characterized by SEM, ZETA potential, XRD and DTA to make sure

of distribution homogeneity of YAG elements (components)

(Y2O3.Al2O3) in crystalline net. The studies showed that the prepared

polymer produced from DTPA with ethylene glycol can bond with

Al3+

,Y3+

, Nd3+

along its chains by chelating, which gives good

homogenous powder. The results showed possibility of development of

proposed method to give good homogeneity and to graft YAG crystal

by Nd with concentration more than 5%.

Keywords: NdYAG, nano-powders, DTPA, DTPA/metal.

Received 6/7/4104

Accepted 7/9/4104

Res. J. of Aleppo Univ. Basic Science Series No. 4104 89

56

Study of the Structural Properties in Polyacrylonitrile -

anionic Surfactant Systems

Said Abdul Nour, Mouna Kurma*

Dept. of Chemistry, Faculty of Science, University of Aleppo


Abstract

Viscosity and specific electrical conductivity are studied in N,

and N- dimetheylformamide (DMF) medium in the presence and

absence of anionic surfactant of Sodium Dodecylbenzene Sulfonate

(SDBS). Critical Micelle Concentration (CMC) of SDBS is determined

in DMF. We find that the leading force for the process of micelle

formation is the decrease of Enthalpy. Thermal and structural

properties of PAN are studied by differential thermal analysis and

scanning electron microscopy, respectively.

Keywords: Polyacrylonitrile, Fiber, mechanical properties, surfactants.

Received 4/9/4104

Accepted 9/8/4104

Res. J. of Aleppo Univ. Basic Science Series No. 98 2014

76

Linear Waves Propagation in a Dusty Plasma for Tails of

Halley's Comet Anwar Batal, Houssam Aldeen KASSIR

*

Dept. of Physics, Faculty of Science, University of Aleppo

*Postgraduate Student (PhD)

Abstract

The oblique propagation of the dust-acoustic and the dust-

cyclotron waves in a warm magnetized collisionless (dust-ion) plasma

which is present in some space environments is studied. A linear

dispersion relation which takes into account the effects of dust

streaming and the effects of warm dust grains is derived. It is observed

that the presence of dust streaming causes frequency shift known as the

Doppler frequency shift, and assuming that the dust grain is warm (i.e.

non-zero pressure) leads to generalizing the thermal speed of the dust

(the modified dust-acoustic speed). The implications of these results to

the dust regions (tails) of Halley's comet are applied and discussed.

Keywords: Dusty Plasma, Complex plasma, magnetized (dust-ion)

plasmas, oblique propagation, dust-acoustic wave, dust-cyclotron

wave.

Received 4/8/2014

Accepted 8/9/2014

Res. J. of .Aleppo Univ. Basic Sciences Series No 98 2014

69

A Study of the Effect of Adding Zinc Metal on Physical

Properties of Lead-free Solders Ternary (Sn88 Sb10 Cu2)

Prepared in Rapid Solidification

M. Hasan, M. Saleh Hammami, Layla Al Sharif * Dept. of Physics, Faculty of Science, University of Aleppo


Abstract

The objective of the work is to prepare ternary alloys (Sn88 Sb10

Cu2) using the technique of rapid cooling, and study the impact of

addition of zinc for improving their characteristics. The addition was in

a ratio of 2% from the weight of formation of Quaternary alloys. The

research also aimed to study the physical and mechanical changes by

this addition on ternary alloys, in order to use them as welding

mixtures in electronic devices for their physical and industrial

properties which are better than solder alloys containing lead.

The results showed that the exact composition of ternary alloys

(Sn88Sb10 Cu2) is characterized by intermetallic compounds (SbSn),

(Cu3Sn(, which are small particles of microns. In the case of

Quaternary alloys (Sn86 Sb10 Cu2 Zn2), additional components of the

intermetallic compounds (Cu6Sn5) appeared and attention was

attracted to the role of the intermetallic compounds and their influence

on the apparent properties of the prepared alloys.

Received 21 /7/2014

Accepted 9 /9 /2014

Res. J. of Aleppo Univ. Basic Science Series. No. 98 2014

17

Isolating and Identifying of Lactic Acid Bacteria (LAB)

from Fermented Milk Products

(Yoghurt and Traditional White Cheese) Nehad Yosef, Faten Kang ٭

Dept. of Botany, Faculty of Science, University of Aleppo

Postgraduate Student (PhD) ٭

Abstract

A total of (109) isolates of lactic acid bacteria (LAB) were isolated

from (16) samples of yoghurt and (14) samples of Traditional White

Cheese, collected from different small workshops of Aleppo city. Two

culture media were used: MRS and M17 following Spreader Plates

method. By studying the Morphological Biochemical and

physiological characteristics of these displayed isolates, (56) isolates

isolated from Cheese, were identified as Enterococcus (48.2%),

Lactobacillus (17.86%), Streptococcus (16.1%), Lactococcus (8.92%),

and Leuconostoc (8.92%). While the isolates of yogurt (53 isolates)

were identified as Enterococcus (49.06%), Lactobacillus (35.85%),

Streptococcus (9.43 %), and Leuconostoc (5.66 %). Enterococcus spp.

was the Dominant genus in both samples.

Keywords: Lactic Acid Bacteria, Yoghurt, Traditional White Cheese.

Received 13 /8/2014

Accepted 9/9 / 2014

Res. J. of .Aleppo Univ. Basic Science Series No 98 2014

37

Analysis of Al khalas Date Bio-Physical and Chemical

Characteristics Sterilized by Irradiation to Substitute

Fumigation Gases and Thermal Treatments Said SABBAGH


Abstract Al-khalas Date products, treated with gamma radiation, have

been examined to get rid of the most important bio-pollutants in stored

products. Date-products have been exposed to gamma radiation (0.5-

1.5) kGy. The irradiation effect on physical and chemical

characteristics like color, taste, moisture, protein, sugars and ascorbic

acid has been studied.

The safe dose for international marketing and export sterilized

Date products was suggested to be 1.5 kGy because there are different

types of micro-organisms and different sensitivity to radiation. The

suggested dose necessary to eliminate them all (or most resistant to

radiation) was 1.5 kGy. This result agrees with the results of previous

researches that recommended the dose of 1 kGy and allowed an upper

dose of 0.5 kGy addition.

Keywords: Date Irradiation, Food Irradiation, Food Safety, bio Characteristics,

Sterilization.

Received 1/7/2014

Accepted 14/9/2014

R.J. of Aleppo Univ. Basic Science Series No.98 2014

57

Global Optical Potential for Deuteron Scattering at

Energies from 10 to 180 MeV Hala Wattar


Abstract

The Phenomenological optical potential (potential calculated

avec semiemirical formula) was used to describe the interaction

between two nuclei (scattering reaction and absorbtion reaction). This

potential depends on the energy of the project nucleus and mass, and

charge of the target nucleus.

In this article, we calculated the optical model potential and

geometry parameters for elastic deuteron scattering on nuclei 232

Th,208

Pb, 186

W,140

Ce, 116

Sn , 90

Zr , 70

Ge, 50

V, 32

S, 16

O

with energy10 180E MeV and Wood-Saxon form being used.

From the values of these optical potentials, we calculated the

differential cross sections of the elastic scattering of deuteron, which

agree with the experimental differential cross sections, that affirm the

success of potential formula used in this work in describing the

nuclear reactions. Keywords: Phenomenological Optical potential; Deuteron-nucleus nucleaire

potential; Saxon-Wood potentials; differential cross sections; reaction cross

sections.

Received 2/7/2014

Accepted 17/9/2014

Res. J. of .Aleppo Univ. Basic Sciences Series No.98 . 2014

77

Study of Leaf Epidermis and Palynology in Two

Varieties Related to Silybum marianum (Asteraceae)

in North Aleppo

Walid Al Said, Abdel Aleem Bello, Oula Darwish* Dept. of Botany, Faculty of Science, University of Aleppo


Abstract

Silybum marianum (L.) Gaertn is the only Species distributed

in north Aleppo. It includes two varieties: Silybum marianum var.

marianum with violet flowers, and Silybum marianum var. albiflora with white flowers.

Stomata and trichomes were presented on the adaxial and

abaxial of leaf surface in both varieties. Stomatal types are Anisocytic

and Anomocytic. Trichomes type is non-glandular branched

multicellular uniseriate.

The shape of pollen grains in both varieties is Spheroidal

because of the ratio of polar axis (P) /equatorial diameter (E) =1.

Aperture type of pollen grains is Tricolporate, where they have three

colpi with a pore in each of them. Sculpturing is Echinate in both

varieties. Key words: Silybum marianum, Anisocytic, Anomocytic, Spheroidal, Tricolporate,

Echinate.

Received 25 /06/2014

Accepted 18/09/2014


97

Advanced Study of Neutrino Oscillation Phenomenon in

Vacuum in Quantum Fields Theory Framework Adel Hamo, Hala Wattar, Eyman Al-hamdan* Dept. of Physics, Faculty of Science, University of Aleppo

*Postgraduate Student (MSc)

Abstract

In this study a developed way to study neutrino oscillation

phenomenon in vacuum in quantum fields theory framework was

presented. The probability of neutrino oscillation was calculated

depending on Feynman diagrams which describe the processes of

production, propagation and detection as single process where the

interaction particles in source and detector are represented by external

wave packets, as the dispersion effect was inserted onto wave

functions associated with the propagated neutrinos from source to

detector by using asymptotic expansion method.

Keywords: Neutrino oscillation, Feynman diagrams, external wave packets,

dispersion, asymptotic expansion.

Received 26 /6/2014

Accepted 21 /9/2014

Basic Science Series No. 98 2014 R. J. of Aleppo Univ.

18

A Taxonomical Study on Species of Helicidae

(Gastropoda: Mollusca) in Aleppo & Edlib Governorates Mahmoud Karrom, Fadia Nashed

Mohammad Salim Alibrahim* Dept. of Zoology, Faculty of Science, University of Aleppo


Abstract Terrestrial snail species occupies an important position in

Helicidae mollusks. Terrestrial snails however have not received the

attention and study, which took place on the peers of aquatic snails.

Based on this, we aimed to study the biodiversity of some species in

the Syrian environment under two objectives: first, to start directing

the spotlight on this group, and second, to contribute to the building

map of livestock biodiversity and the environment in Syria. Samples were collected from the northern region in Syria

between 2012-2013, and lines were set for taxonomic study, returning

to the following global taxonomic keys: Bofill & Haas, 1921; Kerny &

Cameron, 1979; Godan, 1983; Dindal, 1990.

Samples followed subfamily Helicinae, with six genera, each with one

or more species as follows:

The genus Helix with two species H. pomatia L. and H.

Engaddensis (Bourguigant).

The genus Cepaea with one species C. hortensis Muller.

The genus Eobania with one species E. vermiculata Muller.

The genus Theba with one species T. pisana Muller.

The genus Levantina with one species L. spiriplana (Oliver).

The genus Monacha with three species M. cantiana (Montagu), M.

cartusiana Muller and M. syriaca (Ehrenberg). Received 21/7/2014

Accepted 28/9/2014

Res. J. of Aleppo Univ. Basic Science Series No.98 / 2014

38

A Study of the Time-dependent Oscillation Systems

Using the Creation and Annihilation Operators Adel Hamo


Abstract

Different possibilities for the treatment of Time-dependent

Oscillation Systems (harmonic oscillators) were discussed. Then an

electrical LC circuit connected on sequence with a variable with time

voltage generator as a time dependent harmonic oscillator was studied

mechanically. The annihilation and creation operators to define the

wave function that describes the system were used, and their energy

matrix was calculated.

Considering that this oscillator is incitement (transference of

squeezing), a system with two coupled oscillators was studied using

special transformations by decoupling the system as uncoupled system.

Keywords: Harmonic Oscillator, Time Dependent Hamiltonian,

Annihilation Operators, Creation Operators, Coupled Systems.

Accepted 27/8/2014

Received 28/9/2014

Res. J. of Aleppo Univ. Basic Sciences Series No. 98 2014

58

The Study of Some of the Physical Properties of the

Glazed Layer Prepared from Local Raw Materials

Walid Hawale, Shaghik Taghlian*

Dept of Chemistry, Faculty of Science , University of Aleppo


Abstract

The glazed layer is the most important layer in a ceramic,

which is considered one of the most common industrial products due to

its wide usage. It can also be used in various products, such as

abrasives, thermoceramics, tiles, ceramic walls etc.

The glazed layer consists of Silica as the main material and

Alumina as an adjuvant (auxiliary material) to form the glazed layer,

which is obtained from fusing the raw materials (quartz- kaoline-

feldspar- dolomite..), and due to the high melting temperature of silica

some flux materials are added to lower it, such as sodium carbonate

and potassium carbonate.

Since Syria is rich in mineral ores and different types of clay,

we suggested using the raw materials in manufacturing the glazed

layer as a substitute for the imported material, thus we would invest

our raw materials in local industries and save the importing expenses.

Received 7/9/2014

Accepted 12/10/2014

Res. J. of Aleppo Uni. Basic Science Series. No. 98 2014

78

Studying of Some Thermal and Electrical Properties of

the Lead Compounds PbS and PbTe Precipitated in

Chemical Solution Method Tariq Zarouri, Hadeel Fakas Albeed *



Abstract PbS and PbTe were prepared using the chemical bath

deposition technique at room temperatures.

Seebeck coefficient was measured for lead compounds (PbS-

PbTe), the values of which ranged between (0.07-0.12) mVk-1

for

PbTe and (0.02-0.09) mVk-1

for PbS. It has good values which are

useful in electro thermic devices used in power generation.

The effect of the presence of impurity on Seebeck coefficient

and the effect of samples thickness were studied.

From dc measurement, I-V characteristic of the resistivity,

activation energy, and power factor was calculated. From Seebeck

coefficient, the type of semiconductor was found to be P-type.

Received 3/7/2014

Accepted 13/10/2014


89

Studying the Effect of the Pomegranates (Juice, Arils) on

HbA1c Level, Serum Fasting Glucose and Liver Enzymes

in Type II Diabetes Patients Ahmed Kumary*, Hachem Alhussein**, Omama Alloush***

*Dept. of Zoology, Faculty of Science, University of Aleppo

**Dept. of Internal Medicine, Faculty of Medicine, University of Aleppo

***Postgraduate Student (MSc.) Dept. of Zoology, Faculty of Science, University of

Aleppo

Abstract The aim of this study is to investigate the effect of each of

pomegranate juice and pomegranate arils on glycated hemoglobin,

serum fasting glucose and liver enzymes (AST, ALT) levels in type II

diabetic patients treated by oral hypoglycaemic drugs.

This experimental study was performed on 60 diabetic

patients, from national diabetes program, ministry of health, Syria.

We concluded that patients treated by oral hypoglycaemic drug

and pomegranate (juice and arils) diet revealed lower serum levels of

glycated hemoglobin, fasting glucose and liver enzymes (AST, ALT)

than the control. On the other hand, when comparing between

pomegranate forms, patients treated by oral hypoglycaemic drug and

only pomegranate arils diet revealed lower serum levels of glycated

hemoglobin, fasting glucose and liver enzymes (AST, ALT) than those

treated by oral hypoglycaemic drug and only pomegranate juice diet.

Statistical analyses in this study illustrated significant positive

correlation between glycated hemoglobin and serum fasting glucose

which means that glycated hemoglobin is an important indicator which

reflects the average of 3 months of serum fasting glucose

concentration.

Keywords: pomegranate, Type 2 Diabetes, oral hypoglycaemic drug, glycated

hemoglobin, serum fasting glucose, liver enzymes.

Received 20/8/2014

Accepted 13/10/2014

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