jou rn al h om ep age: www.elsev ier .com/ locate /apsusc
Full Length Article
Preparation of magnetic Ni-P amorphous alloy microspheres and theircatalytic performance towards thermal decomposition of ammoniumperchlorate
Yi Denga, Yuanyi Yangc, Liya Ged, Weizhong Yangb,∗, Kenan Xiea,∗
a School of Chemical Engineering, Sichuan University, Chengdu 610065, Chinab School of Materials Science and Engineering, Sichuan University, Chengdu 610065, Chinac Department of Materials Engineering, Sichuan College of Architectural Technology, Deyang 618000, Chinad Zerowaste Asia Pte. Ltd., Singapore 637616, Singapore
a r t i c l e i n f o
Article history:Received 11 May 2017Received in revised form 4 July 2017Accepted 4 July 2017Available online 8 July 2017
In this work, a series of amorphous Ni-P alloys with diverse microspheric structures and magnetic proper-ties were successfully prepared through a facile aqueous solution reduction using sodium hypophosphiteas reducing agent with the assistance of polyvinylpyrrolidone (PVP). Scanning electron microscopy (SEM),transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy(XPS), and laser particle size analysis were used to investigate the structure of Ni-P alloy particles,which demonstrated that the as-prepared alloys possessed spherical morphologies and tunable com-positions. We investigated the effects of the synthesis conditions including reaction temperature, initialNi2+ concentration, pH value, and surfactant type on the morphologies and chemical constitutes of Ni-P alloy particles. Compared with other microsphere counterparts (ferromagnetism), the spherical Ni-Palloy powders with diameter of about 500 nm exhibited apparent paramagnetism. In addition, the cat-alytic performance of the products on the thermal decomposition of ammonium perchlorate (AP) wasfurther investigated via thermogravimetric analysis (TG) and differential scanning calorimetry (DSC).These Ni-P noncrystalline alloy particles with different magnetic properties and good catalytic activitieswould broaden the technological and industrial applications of Ni-P alloys in petrochemical reaction, softmagnetic devices, and burning rate catalysts.
Amorphous alloys, also known as noncrystalline alloys ormetallic glasses, structurally deviate from their crystalline coun-terparts in the arrangement of the constituting atoms. They displayunique short-range ordered arrangement (analogous to atomicclusters) but long-range disordered topological structure, whichendow amorphous alloys isotropic and homogeneous structuredevoid of structural characteristics of crystalline materials includ-ing dislocations, grain boundaries, and stacking faults [1–3]. Thesestructural peculiarities contribute to their distinct chemical andphysical properties, like soft magnetism, structural homogene-ity, and high concentration of coordinatively unsaturated sitespromising as crucial catalytic materials in multitudinous applica-
∗ Corresponding authors at: School of Chemical Engineering, Sichuan University,No. 24 South Section 1, Yihuan Road, Wuhou District, Chengdu 610065, China
tion fields such as energy conversion, petrochemical reaction, andenvironmental remediation [4,5]. Among these amorphous alloys,noncrystalline Ni-P alloys have attracted growing interest becauseof their combined advantages of favorable corrosion resistance,magneto-caloric effect, lithium intercalation behavior, and highcatalytic activity [6,7]. If the Ni-P alloy was fabricated to ultrafinepowders, the catalytic capability, magnetic property and other rel-evant performances would be further enhanced because ultrafinepowders possess both the surface effect and small-size effect.
The synthesis and properties of amorphous Ni-X (X = P, B, S)materials become a hot and well-studied subject extending backdecades. A wide variety of hierarchical architectures for amor-phous Ni-X alloy ultrafine powders such as solid spheres [8], hollowspheres [9,10], mesoporous textures [11,12], microchains [13,14],and rod-like shapes [15,16] have been successfully fabricated viadifferent approaches including rapid quenching method [17,18],wet chemical reductive procedure [19], microemulsion approach[15], polymer stabilization [20], and sonochemical technique [21].In terms of the preparation of amorphous alloys, the two most
262 Y. Deng et al. / Applied Surface Science 425 (2017) 261–271
frequently adopted approaches are the rapid quenching methodand the chemical reduction method. The rapid quenching method,nevertheless, relies on a cooling rate of at least 105–106 K s−1 inan inert atmosphere or in vacuo, and it is technologically morechallenging and costly for large-scale production. Thus, the wetchemical reduction approach becomes more prevalent owing to itswell-known inherent advantages, such as simplicity of operation,low energy consumption, low expenditure, and better control oversize and shape. Accordingly, it has been well-developed to fabri-cate plentiful types of hierarchical micro-/nano-structures [1,8,10].The chemical reduction method involves the reduction of Ni saltwith reductants such as borohydride (BH4
−) or hypophosphite(H2PO2
−) usually in an aqueous solution, producing Ni-B or Ni-Pamorphous alloy powders [19,22]. Because of their structural pecu-liarities and appealing catalytic activities, the amorphous Ni-P alloypowders have been employed to catalyze a wide range of reactionsfrom non-selective to selective hydrogenation, hydrogenolysis, anddehydroheteroatom as well as heterogeneous catalysis of compos-ite propellants in solid fueled rockets [1,23–25].
Ammonium perchlorate (AP) is widely used as an oxidizerin energetic composites, and it has become one of the mostparamount raw materials in propellant formulations [26,27]. Itsthermal decomposition process significantly influences the com-bustion behavior of the solid propellant. The catalytic activitiesof some catalysts in the thermal decomposition of AP have beenreported, and it was found that ultrafine powders (for instance Ni[28], !-Fe2O3 [23], MnO2 nanorods [29], and Cu/Fe hydrotalcitepowders [30] etc.) dramatically accelerate the process of low- andhigh-temperature thermal decomposition of AP through differentreaction mechanisms, which are momentous for the practical appli-cation of AP in solid propellants and explosives. However, it is anarduous challenge to synthesize smooth-faced and monodispersedNi-P amorphous alloy particles with good sphere-like morphol-ogy. In addition to its great potential catalytic activity, Ni-P alloyalso inherits the magnetic properties from Ni metals. However,the long-range disordered arrangement can influence the exchangeinteraction of Ni–Ni atoms, resulting in unique magnetic action, dif-fering from that of ferromagnetic Ni, therefore, they are extensivelyapplied as soft magnetic materials [31]. Moreover, initial Ni2+ con-centration, Ni/P ratio, pH value, and surfactant strongly affect thecomposition and structure of the amorphous Ni-P alloy, thus pro-viding abundant possibilities for the manipulation of the magneticperformance. Herein, based on these considerations, we applieda chemical reduction strategy to prepare a series of Ni-P spheri-cal structures with sodium hypophosphite (NaH2PO2) as reducingagent and polyvinylpyrrolidone (PVP) as assistant in high yield.The main novelties and aims of the present study are (1) to pre-pare and characterize the foregoing Ni-P alloy ultrafine powders;(2) to assess their magnetic performances with diverse micro-spheric structures for the first time; (3) to investigate the catalyticactivity towards thermal decomposition of AP. The as-preparedamorphous Ni-P ultrafine products with smooth face and good dis-persion exhibited an interesting paramagnetism action and goodcatalytic activity on thermal decomposition of AP, which couldbode good applications for magnetic elements/sensors and efficientcombustion catalysts in the future.
disulfonic acid sodium salt (NNO, C21H14Na2O6S2), and Tween-80(C24H44O64) were purchased from Chengdu KeLong Reagent. Allaqueous solutions were prepared with de-ionized water (D.I.water).
2.2. Preparation of amorphous Ni-P alloy microspheres
0.15 mol/L of NiSO4·6H2O with 2 wt/v% PVP as surfactant wasput into a glass bottle of 100 mL capacity, and completely dis-solved in 50 mL of D.I. water. The pH of the solution was thenadjusted to the range of 11–12 using NaOH solution (0.1 mol/L).Subsequently, 0.45 mol/L of NaH2PO2 solution worked as P pre-cursor and reductant was added dropwise into the above solutionfor reduction of Ni2+. Crystal growth occurred when kept at 90 ◦Cfor 1 h with continuous stirring. After reaction, the black precipi-tate was centrifuged from the solution, and ultrasonically washedwith D.I. water and ethanol several times, until the supernatantbecame neutral in pH. To investigate the formation of Ni-P alloymicrospheres, a series of controlled experiments were carried outby altering the reaction temperature, initial Ni2+ concentration, pHvalue, and the type and concentration of surfactant including PVP,NNO, and Tween-80, respectively, keeping other synthetic param-eters and procedures the same as those of quintessential reaction.The specific synthetic condition of each sample was listed in Table 1.The chemical reaction process for preparation of Ni-P alloy powdersinvolved multiple steps as the following [32]:
H2PO2− + H2O → 2H+ + HPO−3 + 2H− (1)
Ni2+ + 2H− → Ni+2H+ (2)
H2PO−2 +H− → H2+OH−+P (3)
H2PO−2 +H2O → H2PO−
3 +H2 (4)
3H2PO−2 → H2PO−
3 +H2O+2OH−+2P (5)
2.3. Sample characterization
The crystalline phase of the as-obtained powders was exam-ined by X-ray diffraction analysis (XRD, X’Pert PRO, Netherlands)using Cu target as radiation source (" = 0.15406 nm). The diffrac-tion angles (2#) were set between 20◦ and 90◦, incremented witha scan step size of 0.03◦/s.
X-ray photoelectron spectroscopy (XPS, XSAM800, UK) wasemployed to identify the surface chemical constituent and elemen-tal state of microspheric Ni-P alloys.
The morphological structure and elemental analysis of theseNi-P alloy microspheres were characterized by a field emis-sion scanning electron microscope (FE-SEM, JSM-7500FBX-MAX50,JEOL, Japan). The suspensions of the alloys powders were depositedon Si wafers for SEM observation.
Transmission electron microscopy (TEM) images, and selectedarea electron diffraction (SAED) patterns were taken on a JEM-100CX TEM (JEOL, Japan). Samples for TEM imaging were preparedby placing a drop of the aged Ni-P suspensions (the suspensionswere diluted in D.I. water and dispersed by ultrasonic waves beforeuse) onto carbon coated copper grids, and dried in air.
The particle size distributions were measured by a laser particlesize analyzer (Chengdu Jingxin, JL-6000).
The specific surface area of samples was measured by BETnitrogen adsorption-desorption on a TristarII 3020 gas adsorptionanalyzer (Micromeritics Instrument, USA).
The Ni content in the solution after reaction was determinedby complexometric titration with EDTA, using murexide (Chengdu
libo
快速淬火法和化学还原法。
libo
Y. Deng et al. / Applied Surface Science 425 (2017) 261–271 263
Table 1Synthesizing conditions for preparing Ni-P alloys with PVP, NNO, and Tween-80 as surfactants.
Sample name NiSO4 (mol/L) NaH2PO2 (mol/L) pH value Dispersant (2 wt/v%)
KeLong Reagent) as indicator. The conversion ratio of Ni ions atdifferent temperatures was expressed as follows:
Conversionratio = (C0 − C)/C0
where C0 is the initial Ni2+ concentration (i.e. 0.15 mol/L), and Cdenotes the residual Ni2+ concentration at different temperatures.Six parallel specimens at each temperature point were tested toprovide the average and standard deviation values.
2.4. Magnetic assessment
The magnetic properties, such as coercivity (Hc), remanent mag-netization (Mr), and saturation magnetization (Ms) for sampleswere conducted at room temperature using a vibrating samplemagnetometer (VSM, SQUID MPMS XL-7, USA) with a maximummagnetic field of 5 kOe. The pure metallic Ni nanoparticles wereprepared as a control via chemical reduction of Ni2+ with hydrazinehydrate as reductant in aqueous solution.
2.5. Catalytic activity measurement
The homogeneous mixture of product (Ni-P(P11-P-3) particlesor pure Ni powders) and AP was used for thermal analysis, andthe mass ratios of product to AP was 1:45. The total masses were6.5 mg for both samples with and without Ni-based powders. Ther-mal decomposition characteristics of samples were determinedby a TG analyzer combined with DSC measurement (Netzsch STA,Germany) in a N2 gas atmosphere over the range 25–600 ◦C. Thephase transition of the Ni-P powders during the thermal decompo-sition was analyzed by XRD.
Besides, the durability tests of the Ni-P alloy powder for APdecomposition was carried out in a quartz tube reactor. 0.45 mgcatalyst was fixed in the middle of the tube reactor with plugs ofquartz wool, and 20 mg/min AP was added into the middle of thetube by a pump. The AP gradually decomposed into NH3 and othergases at 450 ◦C in the furnace under a N2 gas flow. Then these gaseswere trapped in a collection receptacle, and the generated NH3was measured by an ammonia analyzer (GB60, Industrial ScientificCorp., USA).
3. Results and discussion
3.1. Effect of temperature, initial Ni2+ concentration, pH value,and surfactant type on the morphology and chemical constituentof Ni-P alloy microspheres
To shed light on the formation of different Ni-P alloy microstruc-tures, a series of controlled reactions were performed by varyingsome reaction parameters, such as the reaction temperature, ini-
tial Ni2+ concentration, pH value, and the type and concentrationof surfactant.
3.1.1. Reaction temperatureThe conversion ratio of Ni2+ ions under different temperature
was examined by complexometric titration, which was displayedin Fig. S1. It was observed that the conversion ratio of Ni2+ cationsincreased from 83.2 ± 2.9% to 96.3 ± 1.7% as temperature increasedfrom 70 ◦C to 95 ◦C. During the experiment process, we found thatNi2+ cations could not be reduced to Ni-P particles, when the reac-tion temperature was below 65 ◦C. However, when the temperaturerose up to 95 ◦C, large amount of gas (hydrogen, H2) and black pre-cipitate were produced. Once the synthesis was carried out at 90 ◦C,the reaction rate of the system was well controlled with conversionratio of 95.1 ± 2.1%. Hence, 90 ◦C was selected as optimal reactiontemperature due to its higher efficacy of Ni-P product formationwith relatively high conversion ratio of Ni2+ ions.
3.1.2. Initial Ni2+ concentrationThe initial concentration of Ni2+ ions played a significant role in
influencing the morphology and particle size of the as-preparedsamples. When the initial dosages of Ni salts were 0.05 mol/Land 0.10 mol/L, spherical structures were formed with the aver-age dimensions of 2.23 ± 0.27 $m and 2.11 ± 0.15 $m, respectively.Besides, they possessed wider size distribution patterns (Fig. 2a–b),compared with Ni-P(P11-P-3) fabricated at 0.15 mol/L of initialNi2+ ions, which had a smaller size of around 0.55 ± 0.09 $m withnarrower size distribution pattern. When the starting dosage ofNi salt was increased to 0.20 mol/L, plentiful micro- and nano-particles tended to aggregate and co-existed in the final product.If the dosage of NiSO4 was further increased to 0.25 mol/L,these microparticles with rough surface and a mean size of1.15 ± 0.18 $m were dominant for the resultant product (Figs. 1eand 2e). Thus, 0.15 mol/L was fixed as the optimized initial Ni2+ con-tent for the formation of spherical Ni-P alloy with the dimension ofabout 500 nm and good dispersity.
3.1.3. pH valueIn order to preliminarily understand the alteration of these
amorphous Ni-P alloys synthesized under different pH values, EDSanalysis was employed to characterize their chemical composi-tions. As revealed in Fig. S2, the elemental compositions of all theNi-P alloys include Ni, P, and O as the major components. Fig. 3illustrated the Ni and P contents of products determined form EDSanalysis fabricated at different pH values ranging from 8 to 12.Apparently, it could be seen that the Ni content has a decreasedtrend from 92.1 ± 3.6% to 80.3 ± 1.4%, and the P concentration dis-played an enhanced trend from 5.9 ± 0.8% to 8.9 ± 0.7% with theincrease of pH value. To examine the effect of pH value on the for-mation of Ni-P alloys via NaH2PO2 reduction route, powder XRDanalysis was performed (Fig. 4). It was evident that three sharp
264 Y. Deng et al. / Applied Surface Science 425 (2017) 261–271
Fig. 1. SEM images of the obtained Ni-P alloy powders fabricated with different initial Ni2+ concentrations: (a) 0.05 mol/L, (b) 0.10 mol/L, (c) 0.15 mol/L, and (d) 0.20 mol/L,and (e) 0.25 mol/L.
Fig. 2. Size distribution of the obtained Ni-P alloy powders fabricated with different initial Ni2+ concentration: (a) 0.05 mol/L, (b) 0.10 mol/L, (c) 0.15 mol/L, and (d) 0.20 mol/L,and (e) 0.25 mol/L; (f) is the average particle size of these Ni-P alloy powders.
diffraction peaks at 2# = 44.5◦, 51.8◦, and 76.4◦ were well corre-sponded to Miller indices (111), (200), and (220) planes of fcc Ni(JCPDS 04-0850) for products prepared under pH 8 and pH 9. Thisinferred that these two pH values triggered the generation of crys-talline Ni-P product with low P and high Ni concentrations. Asthe pH value increased to 10, the reaction rate greatly acceler-ated and produced a mass of black precipitates. Such phenomena
might result from the acceleration of hypophosphite oxidation inhigher pH value systems [33]. Clearly, the peaks at 2#= 51.8◦ and76.4◦ disappeared, and the sharp peaks at 2#= 44.5◦ changed to abroad background, presenting an armorphous state for Ni-P(P10-P-3). Furthermore, the degree of crystallinity was calculated byJade 6.5 software, and the crystallinity of Ni-P(P8-P-3), Ni-P(P9-P-3), Ni-P(P10-P-3), Ni-P(P11-P-3), and Ni-P(P12-P-3) were 50.21%,
Y. Deng et al. / Applied Surface Science 425 (2017) 261–271 265
Fig. 3. The Ni and P contents of the obtained Ni-P alloy powders determined formEDS analysis at different pH values.
Fig. 4. XRD pattern of the as-prepared Ni-P alloy products fabricated under differentpH values.
26.63%, 3.49%, 3.32% and 1.51%, respectively. We could find that thecrystallinity was reduced, and the coexistence of crystalline andamorphous phases gradually transformed to amorphous feature asthe amount of P content increased.
3.1.4. The type of surfactantThe type of surfactant was also a fundamental factor mainly
affecting the morphologies of products. To find the influence ofsurfactants on the preparation of Ni-P alloy powders, three kindsof surfactants including NNO, Tween-80, and PVP were employed,and each surfactant was dosed at 0.5 wt% and 2 wt%. NNO is ananionic surfactant, while PVP and Tween-80 are nonionic surfac-tants containing both hydrophilic and hydrophobic groups. Allthree surfactants have been widely used in the solution-phasereduction of many kinds of metals and their compounds, and aremainly considered as steric stabilizers or capping agents with themain purpose of protecting crystals from agglomeration [34–36].The products that were synthesized without the protection ofany surfactant contained irregular morphology. Furthermore, thesesamples easily agglomerated because of the van der Waals forceand magnetic attraction. For the NNO group, although sphericalNi-P alloys with the diameter ranging of 1.06 $m-1.84 $m wereattained, they displayed rough surfaces as shown in Fig. 5a–b.Ni2+ ions were inclined to absorb onto the surface of anionicNNO through strong electrostatic interaction between naphtha-lene disulfonic ions (C21H14(SO3)2
2−) and Ni2+, resulting in largesteric hindrance. The large stereo-hindrance effect would restrict
the crystal growth of Ni-P particles, leading to the formation ofrough surfaces. With respect to nonionic dispersants like Tween-80 and PVP, they have unique ability to self-organize in solution,which can modify the interfacial property and enhance the compat-ibility between particles. On the other hand, nonionic dispersantsdissolved in water are inclined to form thermodynamically stablesupramolecular assemblies such as micelles and microemulsions,which can be used as nano-reactors for micro-/nano-particleswith specific morphology and size distribution [37–41]. When theconcentration of Tween-80 increased from 0.5 wt% to 2 wt%, theaverage particle size of the Ni-P products decreased from 3.02 $mto 1.32 $m (Fig. S3). Obviously, rough surface was also observed forNi-P(P11-T-3) using Tween-80 as a template (Fig. 5c–d). The rea-son lies on the following two aspects: 1) compared with NNO andPVP, the addition of Tween-80 substantially increases the viscos-ity of the aqueous system, as well as the difficulty to control themorphology of the Ni-P particles. In such circumstance, the forma-tion of ideal cladding of surfactant micelles to the Ni-P particlesbecomes difficult, and the crystal nuclei can not grow up at thesame rate in all directions; 2) The hydrolysis reaction (saponifica-tion) of Tween-80 occurs in strong basic solution (pH = 11), and itmakes Tween-80 lose its stabilizer role, resulting in formation ofbigger Ni-P alloy products as opposed to the products that wereprepared with NNO and PVP at some concentration. Intriguingly,Fig. 5e–f showed the smooth-faced and homogeneously dispersedNi-P alloy particles that were assisted by PVP. It was understandablethat various diameters of Ni-P products with wide size distributionwere generated under 0.5 wt% PVP, because low concentration ofPVP could not form micelles in the solution. The PVP molecules self-assemble to spherical micelles in the water, and the metallic ionsare prone to anchor or chelate on the side chain of PVP moleculethrough the steric stabilization and appropriate electrostatic inter-action between the quaternary amine (+) or C O(−) groups of thepyrrolidone rings and the Ni2+ ions in order to reduce the surfaceGibbs free energy [42,43]. Subsequently, the H2PO2
− as reducingagent and P source enters into the mini-reactor and converts Ni2+ tosmall Ni-P nanoparticles with the help of OH−. These tiny nanopar-ticles tend to aggregate on account of their high surface energy andmagnetic dipole–dipole attraction. At the same time, the PVP spher-ical micelles limit the range of their growth, which contributes tothe self-assembly of tiny nanoparticles to spheres after reachingequilibrium condition.
3.2. Chemical component and morphology of Ni-P(P11-P-3)particles
3.2.1. Chemical constituent analysisThe XRD analysis of the resulting Ni-P(P11-P-3) powders was
performed to examine the primary phase of product. The only peakthat appeared in the XRD pattern (Fig. 6a) was in fact the super-imposition of a strong sharp peak on a broad background peakat 2#= 44.5◦. The sharp peak was attributed to the (111) planediffraction of nanocrystalline Ni (JCPDS 04-0850), and the broadbackground inferred the existence of amorphous phase in the alloy,indicating that Ni-P alloy was a mixture of fcc nanocrystalline Niand amorphous feature. To identify the presence of elements of theobtained powders, XPS was applied to evaluate their chemical com-position and the Ni to P ratio. As depicted in the overview spectrumof XPS (Fig. 6b), the synthetic powders contained Ni, P, O and C ele-ments, and the Ni/P ratio was about 3.9:1 for Ni-P(P11-P-3) sample(Ni3.9P). The presence of C and O probably could be connected withtheir adsorption on the surface of Ni-P alloys during the XPS analy-sis. Moreover, the high-resolution XPS spectrum of Ni 2p and P 2pwas analyzed to determine the chemical states of Ni and P elementsin Fig. 6c-d. It could be seen that the Ni 2p spectrum exhibited adoublet at 853.6 eV (Ni 2p3/2) and 870.5 eV (Ni 2p1/2), which meant
libo
libo
libo
libo
266 Y. Deng et al. / Applied Surface Science 425 (2017) 261–271
Fig. 5. SEM images of the obtained Ni-P alloy powders fabricated assisted by different surfactants: (a) 0.5 wt% NNO, (b) 2 wt% NNO, (c) 0.5 wt% Tween-80, (d) 2 wt% Tween-80,(e) 0.5 wt% PVP, (f) 2 wt% PVP, and (g) no surfactant.
that the chemical states of Ni element were its elemental state(Ni0) and divalent compounds (Ni2+). As witnessed in Fig. 6c, thepeak around 853.2 eV for Ni 2p3/2 was assigned to Ni%+ in the Ni-Pcompound, which shifted positively by about 1 eV compared withthe metallic Ni peak (852.2 eV) [44,45]. The peaks around 853.8 eVand 857.6 eV were putatively attributed to the divalent compounds(Ni2+) and the satellite of Ni 2p3/2, respectively. The divalent com-pounds (Ni2+) might be associated with Ni(II) oxide or hydroxide,because according to the literary data concerning the solutionswith the pH > 9 used for the electroless nickel film deposition, boththe reduction of Ni(II) with H2PO2
− ions and oxidation of Ni0 can
proceed simultaneously [46,47]. Two peaks corresponding to theNi 2p1/2 level were also observed around 870.5 eV and 874.8 eV,which were attributed to the Ni%+ in the Ni-P compound and thesatellite. As for the P 2p counterpart, two types of P species (reducedP and oxidized P) were detected on the surface of Ni-P powders asshown in Fig. 6d. These XPS spectra were consistent with the pub-lished data for amorphous Ni-P alloy [48,49], indicating that theas-prepared Ni-P(P11-P-3) samples were mainly composed of Ni-Palloy compounds.
Y. Deng et al. / Applied Surface Science 425 (2017) 261–271 267
Fig. 6. XRD pattern (a) and XPS survey scan spectra of Ni-P(P11-P-3) particles: XPS wide spectra (b), high-resolution Ni 2p spectra (c), and high-resolution P 2p spectra (d).
Fig. 7. SEM images (a–b), TEM images (c), and corresponding SAED pattern (d) of the amorphous Ni-P(P11-P-3) alloys.
268 Y. Deng et al. / Applied Surface Science 425 (2017) 261–271
Fig. 8. Size distribution (a) and N2 adsorption-desorption isotherms (b) of Ni-P(P11-P-3) spheres.
3.2.2. Morphology and size of Ni-P(P11-P-3) particlesThe size and morphology of the as-prepared amorphous Ni-
P(P11-P-3) alloy were investigated by SEM, and were displayedin Fig. 7a–b. The panoramic morphology indicated that the Ni-P(P11-P-3) product consisted of a large quantity of well-dispersedsphere-like structures, and manifested that high yield and gooduniformity were achieved via the present aqueous reductionmethod. A zoom-in view of the single particle in Fig. 7b revealeda clear, compact, and well-defined spherical shape with a smoothsurface, having an average diameter of around 500–600 nm. Themicrostructure of Ni-P(P11-P-3) alloy sample was further observedby TEM as shown in Fig. 7c–d. The spherical morphology withsmooth surface was clearly seen, and the size of each Ni-P particlewas about 500 nm which was almost consistent with SEM images.The corresponding SAED pattern in Fig. 7d showed a diffuse elas-tically scattered ring pattern, quintessential for amorphous natureof the Ni-P alloy spheres.
The size distribution of Ni-P(P11-P-3) alloy particles were alsomeasured, and the results were shown in Fig. 8a, from which wecould see that Ni-P(P11-P-3) alloy powders followed normal dis-tribution patterns with the average diameter of about 500 nm,consistent with the SEM and TEM observation. Fig. 8b depictedthe N2 adsorption/desorption isothermal curves of Ni-P(P11-P-3)alloy, and it exhibited the representative type IV isotherms withdistinct hysteresis loop, which was indicative of porous structure.The porous structure could result from the loose packing betweenNi-P alloy spheres as shown in Fig. 8b. The specific surface area ofNi-P(P11-P-3) alloy particles measured using the BET model was65.35 m2 g−1.
3.3. Magnetic behaviors
In order to examine the magnetic behaviors of these Ni-P pow-ders with diverse microspheric structures, magnetic hysteresismeasurement (M-H curve) was carried out at ambient tempera-ture in the applied magnetic field sweeping from −5 kOe to 5 kOe.The results of the amorphous Ni-P alloys were compared with thepure Ni crystals (about 500 nm in size) that were prepared from wetchemical reduction (Fig. 9a). Pure Ni displayed strong ferromag-netic nature with a clear hysteresis loop, and the Ni-P(P9-P-3) andNi-P(P10-P-3) alloy powders presented soft ferromagnetic behav-ior. Compared to pure Ni particles with the values of 10.4 emu/gand 51.3 emu/g respectively, the remanent magnetization (Mr) andsaturation magnetization (Ms) of amorphous Ni-P microspheresshowed a drastic decline. Moreover, the coercivity (Hc) value of theNi-P microspheres were also found to be much lower than that ofpure Ni (127.6 Oe), which originated from the presence of P element
and amorphous phase in the products. The three magnetic param-eters of Ni-P alloys were significantly decreased with the increasein P amount. Interestingly, the remanent magnetization, saturationmagnetization and coercivity of Ni-P(P11-P-3) reached to 0, whichdisplayed a paramagnetic nature. It is well-known that magneticproperties of materials strongly depend on the degree of crys-tallinity, orientation, chemical composition, shape, size and so on[33,50]. From the XRD result, the degree of crystalline dropped withthe augment of P concentration, which decreased the magneticattributes of Ni-P alloys. Furthermore, the unique long-range disor-dered topological structure of noncrystalline Ni-P alloys resulted inpoor magneto-crystalline anisotropy [51]. From Weiss theory, theinteratomic distance of Ni atom increases as the P content increases.In pure Ni, ferromagnetism is from the exchange interaction ofNi–Ni atoms. When P atom takes position between the Ni atoms,the Ni–Ni interaction changes to Ni-P-Ni interaction. This decreasesthe exchange force between the Ni atoms thereby reducing theferromagnetism. At the critical P composition, Ni-P-Ni interactionbecomes more when compared to Ni–Ni interaction, which trans-forms ferromagnetic to paramagnetic state in the Ni-P alloy [52,53].The average crystalline grain sizes were further estimated fromthe XRD patterns according to the Scherrer formula D = "k/(&cos !)[where D is the average crystallite size, k is particle shape factor(about 0.9), " is the X-ray wavelength 0.1542 nm, & denotes theline broadening at half the maximum intensity, after subtractingthe instrumental line broadening (in radians), and # represents theBragg’s angle] with the values of 54 nm, 47 nm, 22 nm, 19 nm, and18 nm for these Ni-P alloys prepared from pH = 8 to pH = 12, respec-tively. It indicated that crystallites sizes declined with the increaseof P content. These were the main reasons that Ni-P(P10-P-3)spheres possessed paramagnetic properties. Overall, the proper-ties of some as-prepared amorphous Ni-P alloy microspheres weretabulated in Table 2. The results revealed that ferromagnetic toparamagnetic phase transition of Ni-P alloys could be achieved asper different P content through the chemical reduction method.
3.4. Catalytic activity in decomposition of ammonium perchlorate
35 Due to good dispersion and small size, the amorphous Ni-P(P11-P-3) spheres were explored as an additive to the thermaldegradation of AP with pure Ni as control group. The TG and DSCcurves of pure AP and AP in the presence of Ni and amorphousNi-P alloy were presented in Fig. 10. According to the previousliterature studies [23,27,54], the thermal process of AP mainly con-sists essentially of three steps: (1) the crystal transformation fromorthorhombic to cubic phase (240–250 ◦C); (2) low-temperaturedecomposition of AP (l-Td, 300–330 ◦C): a solid-gas multiphase
libo
千奥斯特
libo
libo
Y. Deng et al. / Applied Surface Science 425 (2017) 261–271 269
Table 2Properties of some obtained Ni-P powders prepared in aqueous solution.
Sample name Morphology Particle size ($m) Ni amount (wt%) P amount (wt%) Ms (emu/g) Mr (emu/g) Hc (Oe)
Fig. 9. Magnetic hysteresis loop of the amorphous Ni-P powders measured at ambient temperature: (a) pure Ni, (b) Ni-P(P9-P-3), (c) Ni-P(P10-P-3), and (d) Ni-P(P11-P-3).
reaction, including decomposition and sublimation would first takeplace as follows:
NH4ClO4 → NH4+ + ClO4
− → NH3(g) + HClO4(g) (6)
Then, the degradation of HClO4 and the oxidation of NH3by the products of HClO4 degradation would happen; (3) high-temperature decomposition of AP (h-Td, 430–470 ◦C): both theoxidation of NH3 by ClO4
− in gas phase and the decomposition ofAP on solid surface would occur in this step. As shown in Fig. 10a,thermal decomposition of pure AP has three apparent peaks, similarto previous results [55,56]. The first endothermic peak at 244.5 ◦Cwas due to the crystal transformation of AP, and the additives hadlittle effect on the crystallographic transition temperature (Tct).Two obvious exothermic peaks were centered at about 354.5 ◦Cand 441.3 ◦C on the DTA curve of pure AP, which attributed tothe low-temperature decomposition (l-Td) and high-temperaturedecomposition (h-Td), respectively. It was found that the addi-tion of pure Ni powders in AP led to a reduction of l-Td and h-Td(Fig. 10b). In the presence of pure Ni powders, the temperature ofthe two exothermic peak decreased to 318.5 (l-Td) and 402.7 ◦C(h-Td), respectively, indicating that the thermal decomposition ofAP was enhanced. However, it was noted that the first exother-
mic peaks overlapped with the second peak for AP with Ni-P alloysample, and the exothermic peaks of AP shifted to more lower tem-perature at around 340–394 ◦C, demonstrating that the amorphousNi-P(P11-P-3) spheres had a promoted catalytic effect towardsthe thermal decomposition of AP. TG results were also offered inFig. 10b, and the ending temperature of neat AP was 433.7 ◦C. Evi-dently, the addition of pure Ni and amorphous Ni-P alloy led tosignificant reduction of the ending temperature, and the endingtemperature in Ni-P alloy group (396.8 ◦C) was lower than that inpure Ni group (418.2 ◦C). It is well-known that the specific sur-face area of catalysts can significantly affect the decompositionof AP. To analyze the phase transition, the XRD analysis of Ni-P alloy during the catalytic decomposition of AP was conducted,as shown in Fig. S4. The amorphous phase at 2# = 44.5◦ was alsoobserved under 250 ◦C. When temperature rose to 300 ◦C–500 ◦C,metastable phases of Ni12P5, N8P3 and N3P were appeared insamples. At 600 ◦C, the metastable phases of Ni12P5 and N8P3 dis-appeared, and they were replaced by Ni and Ni3P phases. Theresult showed that the metastable amorphous Ni-P structure grad-ually transformed to more stable Ni and Ni3P phase during thethermal decomposition of AP. A 24 h durability test was furtherperformed to examine the stability of Ni-P(P11-P-3) catalyst, and
270 Y. Deng et al. / Applied Surface Science 425 (2017) 261–271
Fig. 10. DSC (a) and TG (b) curves of AP decomposition in the absence/presence ofpure Ni and amorphous Ni-P powders.
the results were shown in Fig. S5. During the test, the NH3 gener-ation ratio initially reaches sharply to about 26.7% within 6 h andthen decreases slowly to about 12% at 10 h, before finally maintain-ing the level for a long time. It suggested that the durability of theNi-P alloy powders for high-efficient decomposition of AP wouldkeep about 10 h. Afterward, the NH3 generation ratio significantlyreduce because amorphous Ni-P alloys mainly transformed to Niphase according to the XRD results. The difference in AP decom-position between them could be caused by smaller specific surfacearea of Ni in comparison with Ni-P alloy powders. From the BETresults (Fig. 8b and Fig. S6), the specific surface area of the amor-phous Ni-P(P11-P-3) spheres was about 65.35 m2 g−1, which wasmuch higher than that of Ni powders with the value of 25.34 m2/g.Moreover, according to the traditional electron-transfer theory[57,58], the presence of partially filled 3d orbit in Ni2+ provideshelp in an electro-transfer process. Besides, the high concentrationof coordinatively unsaturated active sites derived from structuralpeculiarities of amorphous alloys could accept electrons from APion, and its intermediate products accelerate the thermal decom-position of AP. These data were important to the application ofthe developed amorphous Ni-P alloy powders in composite solidpropellants and explosives.
4. Conclusion
In summary, the chemical reduction method has been success-fully used to synthesize amorphous Ni-P alloy ultrafine powderswith the size ranging from 0.55 ± 0.09 $m to 2.23 ± 0.27 $m. Thereaction temperature, initial Ni2+ concentration, pH value, and
surfactant type were the fundamental factors influencing the for-mation of Ni-P micro-crystals. In particular, the amorphous Ni-Pspheres with an average diameter of 500–600 nm were attainedunder specific preparation parameters (temperature = 90 ◦C, ini-tial Ni2+ concentration = 0.15 mol/L, pH = 11, 2 wt% PVP). These Ni-Palloy powders exhibited tunable magnetic attributes from ferro-magnetism to paramagnetism on account of different P contents.Compared to pure Ni powders, the amorphous Ni-P(P11-P-3) pow-ders had enhanced catalytic effect on the decomposition process ofAP due to the high surface area and more unsaturated active sites.Consequently, the chemical reduction method described in thisstudy is propitious to bench-scale production of noncrystalline Ni-Ppowders, and the paramagnetic Ni-P amorphous alloys with favor-able catalytic performance hold a promising use in soft magneticdevices, and composite solid propellants/explosives.
Acknowledgments
This work was jointly supported by Project funded by ChinaPostdoctoral Science foundation (2017M610600), Science andTechnology Program Project of Sichuan Province (2017FZ0046),and Research Program of Star of Chemical Engineering (School ofChemical Engineering, Sichuan University). We would like to thankto Wang Hui (Analytical & Testing Center, Sichuan University) forher help in SEM observations.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.apsusc.2017.07.021.
References
[1] Y. Pei, G. Zhou, N. Luan, B. Zong, M. Qiao, F. Tao, Synthesis and catalysis ofchemically reduced metal-metalloid amorphous alloys, Chem. Soc. Rev. 41(2012) 8140–8162.
[2] Z. Hu, Y. Fan, Y. Chen, Preparation and characterisation of ultrafineamorphous alloy particles, Appl. Phys. A 68 (1999) 225–229.
[3] Z. Ma, L. Zhang, R. Chen, W. Xing, N. Xu, Preparation of Pd-B/TiO2 amorphousalloy catalysts and their performance on liquid-phase hydrogenation ofP-nitrophenol, Chem. Eng. J. 138 (2008) 517–522.
[4] W.H. Wang, Metallic glasses: family traits, Nat. Mater. 11 (2012) 275–276.[5] D.B. Miracle, A structural model for metallic glasses, Nat. Mater. 3 (2004)
697–702.[6] Y. Tan, H. Yu, Z. Wu, B. Yang, Y. Gong, S. Yan, R. Du, Z. Chen, D. Sun,
Noncrystalline structure of Ni-P nanoparticles prepared by liquid pulsedischarge, J. Synchrotron Radiat. 22 (2015) 376–784.
[7] Y.C. Lin, J.G. Duh, Effect of surfactant on electrodeposited Ni-P layer as anunder bump metallization, J. Alloy. Compd. 439 (2007) 74–80.
[8] C. Bernardi, V. Drago, F.L. Bernardo, D. Girardi, Production andcharacterization of sub micrometer hollow Ni-P spheres by chemicalreduction: the influence of Ph and amphiphilic concentration, J. Mater. Sci. 43(2008) 469–474.
[9] G. Xie, Z. Lü, Z. Wang, Z. Cui, Synthesis and catalytic properties of amorphousNi-P alloy hollow microspheres, Catal. Commun. 9 (2008) 1766–1769.
[10] Z. An, J. Zhang, Glass/Ni-P/Co-Fe-P three layer hollow microspheres:controlled fabrication and magnetic properties, Mater. Lett. 85 (2012) 95–97.
[11] H. Li, D. Zhang, G. Li, Y. Xu, Y. Lu, H. Li, Mesoporous Ni-B amorphous alloymicrospheres with tunable chamber structure and enhanced hydrogenationactivity, Chem. Commun. 46 (2010) 791–793.
[12] Q. Meng, H. Li, H. Li, Self-Assembly of mesoporous ruthenium-boronamorphous alloy catalysts with enhanced activity in maltose hydrogenationto maltitol, J. Phys. Chem. C 112 (2008) 11448–11453.
[13] Q. Wang, L. Jiao, H. Du, D. Song, W. Peng, Y. Si, Y. Wang, H. Yuan, Facilepreparation and good electrochemical hydrogen storage properties ofchain-like and rod-like Co-B nanomaterials, Electrochim. Acta 55 (2010)7199–7203.
[14] L. Hui, C. Wang, Q. Zhao, H. Li, Co-B amorphous alloy nanochains withenhanced magnetization and electrochemical activity prepared in a biphasicsystem, Appl. Surf. Sci. 254 (2008) 7516–7521.
[15] X. Cheng, B. Wu, Y. Yang, Y. Li, Synthesis of iron nanoparticles in water-in-oilmicroemulsions for liquid-phase Fischer-Tropsch synthesis in polyethyleneglycol, Catal. Commun. 12 (2011) 431–435.
[18] J.F. Deng, H. Li, W. Wang, Progress in design of new amorphous alloy catalysts,Catal. Today 51 (1999) 113–125.
[19] J. Deng, H. Chen, A novel amorphous Ni-W-P alloy powder and itshydrogenation activity, J. Mater. Sci. Lett. 12 (1993) 1508–1510.
[20] B.J. Liaw, S.J. Chiang, S.W. Chen, Y.Z. Chen, Preparation and catalysis ofamorphous Conib and polymer-stabilized Conib catalysts for hydrogenationof unsaturated aldehydes, Appl. Catal. A-Gen. 346 (2008) 179–188.
[21] G. Bai, L. Niu, M. Qiu, F. He, X. Fan, H. Dou, X. Zhang, Liquid-phase selectivehydrogenation of benzophenone over ultrasonic-assisted Ni-La-B amorphousalloy catalyst, Catal. Commun. 12 (2010) 212–216.
[22] J.V. Wonterghem, S. Mørup, C.J.W. Koch, S.W. Charles, S. Wells, Formation ofultra-fine amorphous alloy particles by reduction in aqueous solution, Nature322 (1986) 622–623.
[23] Y. Zhang, X. Liu, J. Nie, L. Yu, Y. Zhong, C. Huang, Improve the catalytic activityof !-Fe2O3 particles in decomposition of ammonium perchlorate by coatingamorphous carbon on their surface, J. Solid State Chem. 184 (2011) 387–390.
[24] X. Yan, J. Sun, Y. Wang, J. Yang, A Fe-promoted Ni-P amorphous alloy catalyst(Ni-Fe-P) for liquid phase hydrogenation of M- and P-chloronitrobenzene, J.Mol. Catal. A-Chem. 252 (2006) 17–22.
[25] J. Chen, D. Ci, R. Wang, J. Zhang, Hydrodechlorination of chlorobenzene overNiB/SO2 and NiP/SiO2 amorphous catalysts after being partially crystallized: aconsideration of electronic and geometrical factors, Appl. Surf. Sci. 255 (2008)3300–3309.
[26] W.J. Zhang, P. Li, H.B. Xu, R. Sun, P. Qing, Y. Zhang, Thermal decomposition ofammonium perchlorate in the presence of Al(OH)3·Cr(OH)3 nanoparticles, J.Hazard. Mater. 268 (2014) 446–451.
[27] S. Chaturvedi, P.N. Dave, A review on the use of nanometals as catalysts forthe thermal decomposition of ammonium perchlorate, J. Saudi Chem. Soc. 17(2013) 135–149.
[28] Y. Lan, B. Jin, J. Deng, Y. Luo, Graphene/nickel aerogel: an effective catalyst forthe thermal decomposition of ammonium perchlorate, RSC Adv. 6 (2016)82112–82117.
[29] L. Chen, D. Zhu, Effects of different phases of MnO2 nanorods on the catalyticthermal decomposition of ammonium perchlorate, Ceram. Int. 41 (2015)7054–7058.
[30] H. Liu, Q. Jiao, Y. Zhao, H. Li, C. Sun, X. Li, H. Wu, Cu/Fe hydrotalcite derivedmixed oxides as new catalyst for thermal decomposition of ammoniumperchlorate, Mater. Lett. 64 (2010) 1698–1700.
[31] S.N. Piramanayagam, H.B. Zhao, M. Dewi, B.C. Lim, Investigations on annealedNi-P in Al-Mg/Ni-P substrates as soft underlayer for perpendicular recordingmedia, J. Magn. Magn. Mater. 287 (2005) 271–275.
[32] G. Gutzeit, Catalytic nickel deposition from aqueous solution. I–IV, Plat. Surf.Finish. 46 (1959) 1158–1164.
[33] R. Zhou, H. Chen, G. Liu, G. Zhao, Y. Liu, Conductive and magnetic glassmicrosphere/cobalt composites prepared via an electroless plating route,Mater. Lett. 112 (2013) 97–100.
[34] X. Shi, X. Chen, X. Chen, S. Zhou, S. Lou, Y. Wang, Y. Lin, PVP assistedhydrothermal synthesis of biobr hierarchical nanostructures and highphotocatalytic capacity, Chem. Eng. J. 222 (2013) 120–127.
[35] Y. Khan, S.K. Durrani, M. Siddique, M. Mehmood, Hydrothermal synthesis ofalpha Fe2O3 nanoparticles capped by Tween-80, Mater. Lett. 65 (2011)2224–2227.
[36] C. Wang, X. Zhang, F. Lv, L. Peng, Using carbon black nanoparticles to dye thecationic-modified cotton fabrics, J. Appl. Polym. Sci. 124 (2012) 5194–5199.
[37] S.B. Rane, T. Seth, G.J. Phatak, D.P. Amalnerkar, B.K. Das, Influence ofsurfactants treatment on silver powder and its thick films, Mater. Lett. 57(2003) 3096–3100.
[38] L.M. Liz-Marzán, I. Lado-Tourino, Reduction and stabilization of silvernanoparticles in ethanol by nonionic surfactants, Langmuir 12 (1996)3585–3589.
[39] Y. Hou, S. Gao, Monodisperse nickel nanoparticles prepared from amonosurfactant system and their magnetic properties, J. Mater. Chem. 13(2003) 1510–1512.
[40] G.Y. Huang, X.U. Sheng-Ming, L.I. Lin-Yan, X.J. Wang, Effect of surfactants ondispersion property and morphology of nano-sized nickel powders, T.Nonferr. Metal. Soc. 24 (2014) 3739–3746.
[41] W.U. Szu-Han, D.H. Chen, Synthesis and stabilization of Ni nanoparticles in apure aqueous CTAB solution, Chem. Lett. 33 (2004) 406–407.
[42] F.S. Diana, S.H. Lee, P.M.P. And, E.J. Kramer, Fabrication of Hcp-Co nanocrystalsvia rapid pyrolysis in inverse PS-b-PVP micelles and thermal annealing, NanoLett. 3 (2003) 891–895.
[43] W. Yang, D. He, Role of poly(N-vinyl-2-pyrrolidone) in ni dispersion forhighly-dispersed Ni/SBA-15 catalyst and its catalytic performance in carbondioxide reforming of methane, Appl. Catal. A-Gen. 524 (2016) 94–104.
[44] J.F. Deng, J. Yang, S.S. Sheng, H.G. Chen, G.X. Xiong, The study of ultrafine Ni-Band Ni-P amorphous alloy powders as catalysts, J. Catal. 150 (1994) 434–438.
[45] Y. Okamoto, Y. Nitta, T. Imanaka, S. Teranishi, Surface characterisation ofnickel boride and nickel phosphide catalysts by X-ray photoelectronspectroscopy, J. Chem. Soc. Faraday Trans. 75 (1979) 2027–2039.
[46] H. Zhang, Y. Lu, C.D. Gu, X.L. Wang, J.P. Tu, Ionothermal synthesis and lithiumstorage performance of core/shell structured Amorphous@Crystalline Ni-Pnanoparticles, CrystEngComm 14 (2012) 7942–7950.
[47] L. Wang, W. Liu, X. Wang, The preparation and tribological investigation ofNi-P amorphous alloy nanoparticles, Tribol. Lett. 37 (2010) 381–387.
[49] Z. Song, X. Bao, M. Muhler, The effect of tungsten additive on the surfacecharacteristics of amorphous Ni-P alloy, Appl. Surf. Sci. 148 (1999) 241–247.
[50] S. Gao, C. Guo, J. Lv, Q. Wang, Y. Zhang, S. Hou, J. Gao, J. Xu, A novel 3d hollowmagnetic Fe3O4/BiOI heterojunction with enhanced photocatalyticperformance for bisphenol a degradation, Chem. Eng. J. 307 (2017)1055–1065.
[51] R.L. Sommer, C.L. Chien, Role of magnetic anisotropy in themagnetoimpedance effect in amorphous alloys, Appl. Phys. Lett. 67 (1995)857–859.
[52] K. Dhanapal, V. Narayanan, A. Stephen, Effect of phosphorus on magneticproperty of Ni-P alloy synthesized using pulsed electrodeposition, Mater.Chem. Phys. 166 (2015) 153–159.
[53] S.N. Kaul, M. Rosenberg, Magnetic properties of amorphous Ni-B alloys, Phys.Rev. B 25 (1982) 5863–5874.
[54] F. Xiao, X. Sun, X. Wu, J. Zhao, Y. Luo, Synthesis and characterization offerrocenyl-functionalized polyester dendrimers and catalytic performance forthermal decomposition of ammonium perchlorate, J. Organomet. Chem. 713(2012) 96–103.
[55] Y. Zhao, X. Zhang, X. Xu, Y. Zhao, H. Zhou, J. Li, H.B. Jin, Synthesis of NiOnanostructures and their catalytic activity in the thermal decomposition ofammonium perchlorate, CrystEngComm 18 (2016) 4836–4843.
[56] Y. Yang, Y. Bai, F. Zhao, E. Yao, J. Yi, C. Xuan, S. Chen, Effects of metal organicframework Fe-BTC on the thermal decomposition of ammonium perchlorate,RSC Adv. 6 (2016) 67308–67314.
[57] Y. Wang, X. Yang, L. Lu, X. Wang, Experimental study on preparation of LaMO3(M = Fe, Co, Ni) nanocrystals and their catalytic activity, Thermochim. Acta443 (2006) 225–230.
[58] A.A. Said, R. Al-Qasmi, The role of copper cobaltite spinel, CuxCo3-xO4 duringthe thermal decomposition of ammonium perchlorate, Thermochim. Acta 275(1996) 83–91.
