Spark Plasma Sintering of Ultra High Temperature ceramics Lili Nadaraia, Nikoloz Jalabadze, Levan Khundadze, Levan Lortkipanidze and Givi Sharashenidze Georgian Technical University, Republic Center for Structure Researches (RCSR) nadaraia@gtu.ge

Ultra-High Temperature Ceramics UHTC Carbides Compositions TiC SiC B4C TiB2 ZrB2 HfB2 TiB2-TiC, B4C-SiC, Ti3SiC2 Borides

Refractory applications Armor low density high hardness  wear resistance  high melting poin  thermal stability as neutron radiation absorbent  Abrasion resistance Nozzles Abrasives UHTC Nuclear applications Refractory applications

Manufacturing methods of UHTC Methods producing the Powder reaction of elemental boron and carbon powder between reagents carbothermal synthesis, carbothermal vapor–liquid–solid growth mechanism self-propagating high-temperature synthesis (SHS) = Combustion Synthesis (CS), arc melt process, etc… Methods producing the Dense bodies hot press, hot isostatic pressing (HIP), Cold compaction and high temp. sintering pressureless sintering, self-propagating high-temperature synthesis (SHS) under the pressure, Spark Plasma Sintering, etc…..

Advantages and disadvantages of spark plasma sintering Fast sintering process; Uniform sintering; Low grain growth (nano-grain materials may be prepared); Compaction and sintering stages are combined in one operation; Binders are not necessary; Better purification and activation of the powder particles surfaces; Different materials (Metals, Ceramics, composites) may be processed; High energy efficiency; Easy operation. Disadvantages of spark plasma sintering: Only simple symmetrical shapes may be prepared; Expensive pulsed DC generator is required. Expensive SPS device

Spark plasma between powder particle Fig.1. Scheme of the SPS the process of sintering – PDC - pulsed DC, GD - graphite die, S – powder sample, P – pressure loading, EC- electric current, s – spark, sp – spark plasma and p- powder particles. SPS mechanism by SPS SYNTEX INC Company; (a) I- Flow direction of electrons during DC current, (b) I- Flow directions of electrons during AC current.

DC current shapes Pulse DC current Shape in the developed device: a- at the frequency of 400 Hz, b- during different frequencies (T), different duration pulses (t) and different duration pauses (T-t); Current Shapes to be used after retrofitting the SPS device: during different frequencies (T), different duration pulses (t) and different duration pauses (T-t);

SPS Device Press molds for synthesize nanopowder (a) and sintering dense bodies (b) of composite materials 1-upper plug, 2-lower plug, 3-Matrix.

Self-propagating high-temperature synthesis (SHS), (combustion synthesis CS) Poly SHS Sintering process a: Self-Propagating High-Temperature Synthesis (SHS), b: SPS accompanied with poly SHS. A. G. Merzhanov. 2006, Advances in Science and Technology, 45, 36- 44.

Borides 2HfB2+4CO 2TiB2+4CO 2ZrB2+4CO HfB2 TiB2 ZrB2 2TiO2 B4C 2ZrO2 2HfO2 2TiB2+4CO 3C B4C 2TiO2 2ZrB2+4CO 3C B4C 2ZrO2 HfB2 TiB2 ZrB2

Titanium Diboride TiB2 X-Ray and SEM images of Titanium Diborides a- TiB2 powder synthesis at 10000C 1h, b- sintered via SPS at 16000C ; C- SEM image of sintered via SPS at 16000C

Zirconium Diborides ZrB2 X-Ray and SEM images of Zirconium Diborides a- ZrB2 powder synthesis at 10000C 1h, b- sintered via SPS at 16000C ; C- sintered via SPS at 17000C SEM images of Zirconium Diborides sintered via SPS at 17000C

Hafnium Diborides HfB2 X-Ray and SEM images of Hafnium Diborides sintered via SPS at 18000C ;

Carbides C Si C 4B C Ti SiC B4C TiC

Carbides SiC TiC X-Ray images of Titanium Carbide sintered via SPS at 14000C -3 min; X-Ray images of Silicium Carbide sintered via SPS at 18000C -1 min;

Boron Carbide B4C a- XRD pattern of B4C powder (SPS 14000C-3 min) b- SEM image of B4C bulk material (SPS 17000C-10min) A-XRD patterns of B4C powder materials obtained by standard (a), SPS methods (b) ; B- SEM image of nanopowder B4C obtained by SPS method (14000C-3min).

Composition 4B Si 2C SiC B4C 50% SPS sintered B4C – SiC (17000C-5min): a-X-ray diffraction pattern; c- SEM image B4C – SiC Sintered via SPS b- SEM image of B4C – SiC powder produce via SPS.

Composition 3Ti Si 2C Ti3SiC2 Ti Si C 0,77 0.14 0.12 X –Ray of Ti3SiC2 composition of sintered via SPS at 14500C

Composition Vickers hardness 29.5 Gpa TiB2 - TiC TiB2 TiC B4C 2TiO2 TiB2 TiC Vickers hardness 29.5 Gpa X –Ray and SEM images of TiB2 - TiC composition of sintered via SPS at 14500C

SPS OPERATING MODES WITH RELATIVELY DENSITY Sample# Regime SPS-B4C powder SPS- B4C SPS HfB2 TiB2 B4C-SiC TiB2- TiC SPS Ti3SiC2 SPSCurrent (V/A) 9/1370 9.2/2060 10/2700 9/2700 9.5/2300 Temp. (0C) 1600 1700 1800 1450 Holding Time (min) 5 10 6 Pressure MPa 20 25 30 Density (% of theoretical) - 94 85 92 95 98 97 Shapes of materials sintered via SPS

Plastic (Ti-6Al-4V)/textile Ballistic Testing Test is conducting according Standards of National Institute of Justice (NIJ) (type-IV) Additional energy is absorbed by each successive layer of material in the ballistic panel. http://www.bodyarmornews.com/  Size of the plate -120x120mm; Size of the plate fragments 60x60mm; Weight - 50-100g. The plate presented a package armored with ballistic textile (Kevlar, tvarin, denima); Weight of the package was 0,6 – 0,8 kg; Fire tests were provided by shooting from the Mosin’s Rifle; Bullets - armor-piercing Bullet Mass – 10.8±0,1; Bullet speed - 869±10 m/sec. Standard shooting method, distance - 10m towards a plasticine target. Bullet direction Backing material Plastic (Ti-6Al-4V)/textile Hard Blend (B4C, SiC, B4C-TiB2, B4C-SiC )

Ballistic testing 120mm BFS  40mm NIJ requirements - Max Back face signature (BFS) depth is 44mm

Conclusion There was developed new technology for manufacturing of nanocrystalline composite materials. Poly SHS process were detect during SPS and were use for UHTC materials fabrication Diborides of transaction metals Ti, Zr, Hf, were produced Nanocrystalline Powders of carbides of metals Ti, Si, and B were obtain after Poly SHS process Effective composition materials TiB2 - TiC, Ti3SiC2, B4C - SiC were developed. Ballistic testing gives promising results and further effort will be directed to improve the characteristics. Modernization of SPS device is undergoing process (replacing of pulse DC current unit with pulse AC current unit). Further work will be directed to detect impacte of DC current at the sintering process and at the materials properties.

Acknowledgement The part of research described in this presentation was made possible in scope of projects funded by Shota Rustaveli National Science Foundation. Project # 12/34 Presidential Grants for Young Scientists.

Thank you for attention nadaraia@gtu.ge