Epoxies for Nb3Sn superconducting accelerator magnets - an update
Shijian Yin, Tengming Shen
Lawrence Berkeley National Laboratory
June 20, 2018
Presented at the U.S. Magnet Development Program meeting
With technical helps and discussions from Diego Arbelaez, James Swanson, and Dan Dietderich
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Outline
• Results of thermal shock tests of several epoxies including CTD101k and NHMFL mix61
• CTD-101k versus NHMFL mix 61 – key properties
• Other ongoing/incoming works relevant for quench training of Nb3Sn accelerator magnets
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Thermal shock test
Room T to LN2 to Room T
Size of the samples: Diameter 70 mmThickness 10 mm
Epoxy resin blocks• contain an insert• without insert
The insert chosen is a brass screw.1/4-20 1.3/4”
Al mold
Brass screw 3
Test samples
NHMFL 61
CTD101K
CTD101K 0.3 wt% Boron nitride nano particles
Stycast 2850 FT
4
CTD101K
5
CTD101K 0.3 wt% Boron nitride nano particles
6
Stycast 2850 FT
7
NHMFL 61
8
During the test
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After one-time thermal cycle After 5-times thermal cycle
After 10-times thermal cycle After 20-times thermal cycle
CTD101K
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After one-time thermal cycle After 5-times thermal cycle
After 10-times thermal cycle After 20-times thermal cycle
CTD101K
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After one-time thermal cycle After 5-times thermal cycle
After 10-times thermal cycle After 20-times thermal cycle
CTD101KWith Powders
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After one-time thermal cycle After 5-times thermal cycle
After 10-times thermal cycle After 20-times thermal cycle
CTD101KWith Powders
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After one-time thermal cycle After 5-times thermal cycle
After 10-times thermal cycle After 20-times thermal cycle
STYCAST 2850FT
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After one-time thermal cycle After 5-times thermal cycle
After 10-times thermal cycle After 20-times thermal cycle
STYCAST 2850FT
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After one-time thermal cycle After 5-times thermal cycle
After 10-times thermal cycle After 20-times thermal cycle
NHMFL 61
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After one-time thermal cycle After 5-times thermal cycle
After 10-times thermal cycle After 20-times thermal cycle
NHMFL 61
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After one-time thermal cycle
No screw With Screw
CTD101K Y Y
CTD101KBoron nitride nanoparticles
Y Y
Stycast 2850 FT N N
NHMFL 61 N N
Crack at first cycle
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Thermal Cycles prior to failure
Epoxy Sample Cycles prior to failure
CTD101K No Screw 0
CTD101K With Screw 0
CTD101K Boron nitride nano particles
No Screw
0
CTD101K Boron nitride nano particles
With Screw
0
Stycast 2850 FT No Screw >20
Stycast 2850 FT With Screw >20
NHMFL 61 No Screw >20
NHMFL 61 With Screw 1119
Summary
• CTD101K had the worst thermal shock property in all the test samples.With the increase of the test times, the change of the crack pattern was not evident,but the phenomena of fracture was getting steadily worse.
• There was no significant improvement for the performance of the samples with 0.3 wt% Boron nitride nano particles.
• Even though the sample with screw cracked at the 12th test, NHMFL 61 had a superior shock property to CTD101K.
• The Stycast 2850 FT samples with or without screw could survive more than 20-times cycles.But we need to note that very small thin line appeared on the surface of the samples after 10-times cycles.
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RC coils potted by CTD101k and NHMFL mix61
LBNL_RC5, CTD 101K LBNL_RC3, NHMFL 61
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Properties of CTD101K and NHMFL- mix 61Properties CTD-101k NHMFL-mix61
Chemistry liquid epoxy resin +
anhydridehardener
bisphenol-A based liquid epoxy resin +
amine hardener+ high molecular weight additive
Elongation at break (%) [RT]
0.97 10.2
Glass transition temperature Tg
(°C)
113 65
Radiationhardness
Ok at 30 MGy for high-lumi IR
magnets
Unknown
Pros: Low viscosity,Long pot life
High toughnessHigh thermal
shock resistance
Cons: Brittle Low toughness
Higher viscosityShorter pot life
RT, test standard - ASTM-D638
NHMFL 61 mix
F
F
Warning: Vapor pressures of mix61 components are unknown and suspected to be high for at least one of them.
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Viscosity and pot life at 60 oC: CTD-101k vs NHMFL-mix 61 Results of shear and compression tests (77 K) F
F
Properties of CTD101K and NHMFL- mix 61
[1] CTD-101K Epoxy Resin System, data sheet[2] PROPERTIES OF EPOXY NHMFL 61 FOR SUPERCONDUCTING MAGNET IMPREGNATION W. D. Markiewicz,l 1. R. Dixon,l J. L. Dougherty,l K. W. Pickard,l and A. B. Brennan2
[1] Compressive-Shear Measurements of NHMFL 61 Epoxy – S-glass to Stainless Steel with and without Surface Abrasion, Iain Dixon Yuhu Zhai Vince Toplosky[2] CTD101K Epoxy Resin System, data sheet
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954 Aluminum Bronze
Double lap shear test
SandblastedGlass beads
layer of epoxy around conductor
Superconductor
F
CCT
ANSYS model created by Lucas Brouwer
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Double lap shear test (Room T)
Mold
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Double lap shear test
Sample No. Sand blast Thickness of the two epoxy layers (mm) Stress at break (Mpa)
10 N 0.46 13.2
3 N 0.5 10.9
4 N 0.5 12.8
9 N 0.86 13.2
6 N 0.87 13.4
8 N 0.9 12
1 Y 0.9 13.0
2 Y 0.9 13.5
5 N 0.96 12
7 N 1 12.7
Test results NHMFL 61
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Ongoing work 1 – Improving epoxy properties with new formulations
• Promising low-viscosity epoxy systems not yet carefully explored for dipoles:
– DGEBF has a lower viscosity than DGEBA.
– Jeffamine polyetheramines + Araldite (elongation at break > 10%, and excellent thermal shock resistance.)
– Modifying epoxy chain to reduce viscosity of amine cured epoxies with PPGDGE while increasing toughness. Notable example – RP Reed and D Evans ATLAS end cap toroid epoxy.
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Ongoing work 2: Engineering the interface between epoxy and Ti-alloys/Bronze and quick-turn-around verification tests
F
F
Ti-alloy/bronze
S2-glass/epoxy
Mica + S2-glass/epoxy + Mica
QXF coil 2D cross-section
At this pole/winding interface, compression decreases with I2 while shear stress increases, to 40 Mpa or more.
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Summary
NHMFL 61 has a better thermal shock resistance than CTD101K.
NHMFL 61• Plastic under tension• Higher viscosity• Shorter pot life• High toughness
Ongoing works• Improving epoxy properties with new formulations• Engineering the interface between epoxy and Ti-alloys/Bronze and quick-turn-around
verification tests
CTD101 K• Brittle under tension• Low toughness• Lower viscosity and longer pot life
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