Spark Plasma Sintering System Research Articles

Using the Spark Plasma Sintering System for Fabrication of Advanced Semiconductor Materials.

The interest in the Spark Plasma Sintering (SPS) technique has continuously increased over the last few years. This article shows the possibility of the development of an SPS device used for material processing and synthesis in both scientific and industrial applications and aims to present manufacturing methods and the versatility of an SPS device, presenting examples of processing Arc-Melted- (half-Heusler, cobalt triantimonide) and Self-propagating High-temperature Synthesis (SHS)-synthesized semiconductor (bismuth telluride) materials. The SPS system functionality development is presented, the purpose of which was to broaden the knowledge of the nature of SPS processes. This approach enabled the precise design of material sintering processes and also contributed to increasing the repeatability and accuracy of sintering conditions.

Insight into the design of a Ti3C2 MXene/Ti4O7 composite ceramic membrane boosts the electrocatalytic activity for 1,4-dioxane electro-oxidation

Efficient refractory organic compound (ROC) removal through Ti4O7 ceramic membrane in electrochemical advanced oxidation processes (EAOPs) requires high electrochemical reactivity and stability. Herein, we report on the synthesis and properties of Ti3C2 MXene-doped Ti4O7 ceramic membranes (Ti3C2@Ti4O7) using a spark plasma sintering system, after employing density functional theory calculations to design the electrocatalyst. Doping with Ti3C2 MXene resulted in interfacial Ti–O–Ti chemical bond formation, which greatly improved the electronic structure and the generation of hydroxyl radicals (•OH). Compared with pristine Ti4O7, the charge-transfer resistance of Ti3C2@Ti4O7 decreased from 59.09 to 4.21 Ω, and the •OH generation rate enhanced 2.3 − 2.6-fold. Ti3C2@Ti4O7 could effectively remove 1,4-Dioxane from natural groundwater, and the residual 1,4-Dioxane concentration met the requirements for drinking water. Our study provides a proof-of-concept demonstration using Ti3C2 MXene to manufacture a doped Ti4O7 ceramic membrane for effective ROC removal. The theoretical predictions from this study can inspire novel electrocatalyst designs for EAOPs.

Tailoring microstructure and mechanical properties of CP-Ti through combined treatment of pressure and pulsed electric current

In this work, a new processing technology of pressure plus pulsed electric current treatment (PPEC) was proposed to treat CP-Ti to simultaneously enhance its strength and ductility. Specifically, the CP-Ti was subjected to 50 MPa pressure and pulsed electric current (PEC) with variable intensities (1400A, 1600A, and 1900A) using a spark plasma sintering system. Afterwards, the microstructure evolution, texture change, and mechanical properties were characterized by XRD, EBSD, and tensile tests. The increased grain size and noticeable microstructure change occurred with increasing PEC intensity. Additionally, applying 50 MPa pressure leads to the formation of finer α lamellae colonies and higher content of high-angle grain boundaries, which act as barriers for dislocation motion after yielding, resulting in enhanced strain hardening rate and consequently improved mechanical properties. The processed CP-Ti exhibits a yield strength of 350 MPa, an ultimate strength of 702 MPa, and a significant plastic strain of 39.1%, superior to those of CP-Ti processed by severe plastic deformation and pure PEC treatment. The results provide a new strategy to develop Ti materials for demanding structural applications.

Production of electrodes by spark plasma sintering method of secondary powder materials

The article considers the practical possibility of manufacturing electrodes from secondary powder materials. Obtaining electrodes with desired properties suitable for electrospark alloying processes. Bronze powder obtained from waste metal scrap by electroerosive dispersion was used. The following equipment was also used: spark plasma sintering system SPS 10-3 from Thermal Technology, drying cabinet ShS-80-01 SPU, set of sieves according to GOST 2715—75, analytical balance Acculab ALC-210d4, XRD-6000 Shimadzu diffractometer, X-ray fluorescence spectrometer Niton XL3t 900 GOLDD+. Secondary bronze fine powder was subjected to pressure sintering in an SPS 10-3 spark plasma sintering system from Thermal Technology. The maximum temperature was 910 °C, pressure — 40 MPa. Materials before and after were examined for elemental composition. The resulting briquette was cut into electrodes, and test surfacing was carried out by the method of electrospark alloying. Using spark plasma sintering, it is possible to obtain electrodes from secondary bronze powder materials suitable for electrospark alloying processes.

ANALYSIS OF THE CHARACTERISTICS OF SINTERED PRODUCTS MADE OF CHROMIUM-CONTAINING ELECTROEROSIVE POWDERS

The article presents the results of the analysis of the characteristics of sintered productsmade of chromium-containing electroerosive powders. One of the main directions of the development of mechanical engineering technology at present is the improvement of existing and the development of new waste-free, environmentally friendly, material-saving production processes. Powder metallurgy plays a certain role in solving this problem. In recent years, much attention has been paid to the development of methods for the manufacture of high-density powder materials For the implementation of the planned studies, waste chromium-containing steels SHX15 andH13 have been selected. Powder materials were obtained by electrical erosion at the electro-erosive dispersion unit developed by the authors. Butyl alcohol was chosen as the working medium of dispersion. The powder was consolidated by the spark plasma sintering method using the spark plasma sintering system SPS 25-10 (Thermal Technology, USA). It is established that the microhardness of the sintered steel sample SHH15 is equal to 154 HV. The microhardness of the sintered steel sample H13 is equal to 461 HV. Itwas found that the porosity of the sintered steel sampleH13 is equal to 3.34%, and also that 95 % of the pores have a size of up to 2 microns. The porosity of the sintered steel sample SHH15 is 1.72 %, and also that 90 % of the pores have a size of up to 1 microns. According to the results of the research, it was found that the microhardness of the sintered sample made of steel SHH15 is lower than that of the sample made of steel H13. The porosity of a sample made of steel SHH15 is lower than that of a sample made of steel H13. Therefore, it can be concluded that sintered products made of powder material sta-li H13 have a harder surface and can be used in the production of small loaded parts.

Composition, structure and properties of hard alloy products from electroerosive powders obtained from T5K10 hard alloy waste in kerosene

The paper implements scientific and applied principles of coupling the technology of obtaining new powder materials from waste of hard alloys of the T5K10 brand by electroerosive dispersion and the technology of compacting them by SPS synthesis. The aim of the work was to study the composition, structure and properties of carbide products made from powders obtained by electrodispersing T5K10 alloy waste in kerosene. Electrodispersion of T5K10 alloy waste was carried out in lighting kerosene on a patented installation. The consolidation of the obtained powder was carried out by the spark plasma sintering (SPS) method using the spark plasma sintering system SPS 25-10. The choice of powders obtained by electroerosive dispersion of the T5K10 hard alloy waste was justified by its cost and properties. The resource of tungsten-titanium-cobalt hard alloys from T5K10 electroerosion powders is determined not only by the properties of the feedstock, but also by the technology of their production (SPS synthesis). Based on the conducted experimental studies, it can be concluded that the use of the spark plasma sintering method to produce products from powder obtained by electroerosive dispersion of the T5K10 alloy will ensure high performance of products (cutting tools) due to the uniformity of the surface, favorable structure and low porosity of the product. It is noted that hard alloys made of electroerosion dispersed T5K10 alloy particles obtained by spark plasma sintering under conditions of rapid heating and short working cycle duration have higher physico-mechanical properties compared to industrial alloys from which the initial powder particles were obtained by suppressing grain growth and obtaining an equilibrium state with submicron and nanoscale grain. This study was funded by the Russian Science Foundation, grant No. 22-29-00123, https://rscf.ru/project/22-29-00123/.

High-strength lithography-based additive manufacturing of ceramic components with rapid sintering

Additive manufacturing technology enables the fabrication of technical ceramics and multi-materials with unprecedented geometrical accuracy and complexity, opening the path to new functionalities for engineering applications. A crucial step to consolidate 3D-printed ceramic parts is “sintering”, a time and energy (temperature) intensive densification process. Here we present a strategy for rapid sintering (∼ 300–450 °C/min) of lithography-based additively manufactured alumina ceramics enabling consolidation of ceramic components of complex shapes within minutes. Highly dense, fine-grained microstructures were achieved by controlling densification and limiting grain growth through rapid radiation heat transfer. The high mechanical strength and toughness measured in additively manufactured alumina (∼ 810 MPa and ∼ 4.3 MPa m 1/2 ) sintered at 1600 °C within 2 min was superior to that of conventionally sintered reference parts. This study opens the path for rapid sintering of complex shaped ceramic architectures of high density with tailored microstructure and properties. • 3D-printed ceramics with complex geometry can be sintered within minutes. • Rapid radiation using a customized Spark Plasma Sintering system promotes densification. • Controlling the dwell sintering time allows tailoring of grain size in refined microstructures. • Dense and exceptionally high strength 3D-printed alumina were achieved. • Our sintering protocol may be applied to other 3D printed ceramic materials.

Structure and properties of sintered corrosion-resistant steel manufactured from electroerosive powders

This work solves the problem of saving expensive chrome. This problem is proposed to be solved by grinding their waste of corrosion-resistant steels and reusing them. One of the most promising and industrially non-applicable methods for grinding any electrically conductive material is the electroerosion method. Comprehensive theoretical and experimental research is required to develop technologies for the reuse of electroerosive powders and evaluate the effectiveness of their use. The purpose of this work was to study the structure and properties of sintered samples from electroerosive corrosionresistant powders obtained in butyl alcohol. To perform the planned studies, Kh13 steel waste was selected as the dispersible material. Waste steel Kh13 was processed at a voltage on the electrodes of 100–110 V; the capacity of the discharge capacitors is 45 UF and the pulse repetition rate is 65–75 Hz. Butyl alcohol was used as the working fluid. The resulting powder was consolidated by spark plasma sintering (SPS) using the SPS 25-10 spark plasma sintering system. Based on the conducted experimental studies aimed at studying the structure and properties of sintered samples from electroerosive corrosion-resistant powders obtained in butyl alcohol, the high efficiency of the spark plasma sintering technology is shown, which provides a uniform heat distribution over the sample, controlled porosity and high physical and mechanical properties with a short working cycle time and grain growth suppression. The work was supported by a scholarship of the President of the Russian Federation for young scientists and graduate students (SP-945.2019.1).

Diffusion behavior and bending fracture mechanism of W/Ti multilayer composites

Multilayer composites are effective to improve the toughness of Tungsten (W). To demonstrate the toughing mechanism, a series of W/Ti multilayer composites are prepared by diffusion bonding at different temperatures in a spark plasma sintering system. It shows that the mechanical properties of the composites vary with the change of bonding temperature, which is closely related with the microstructures developed at different bonding temperatures. The bending strength of the composites bonding at 1100 °C is highest, which reaches 1847 MPa. However, the composites bonding at 1200 °C has absorbed the highest fracture energy during three-point bending tests. The different microstructures developed at different bonding temperatures are mainly due to the different diffusion behaviors of W and Ti elements. The activation energy of W diffusion into Ti and Ti diffusion into W is 87.69 KJ/mol and 152.20 KJ/mol, respectively. And the diffusion coefficient of W into Ti is two orders of magnitude higher than that of Ti into W. Thus, β-Ti has formed in the Ti layer due to W diffusion into Ti. Although α-Ti is precipitated in the β-Ti, solid solution strengthening is the main strengthening mechanism in the Ti layer. The toughening mechanism of the W/Ti multilayer composites is mainly crack deflection, and the plastic deformation of the Ti layer. Meanwhile, the fracture modes of these composites are proposed.

Progress of Spark Plasma Sintering (SPS) Method, Systems, Ceramics Applications and Industrialization

The spark plasma sintering (SPS) method is of great interest to the powder and powder metallurgy industry and material researchers of academia for both product manufacturing and advanced material research and development. Today in Japan, a number of SPS products for different industries have already been realized. Today’s fifth-generation SPS systems are capable of producing parts of increasing size, offering improved functionality, reproducibility, productivity, and cost. For instance, pure nano-Tungsten Carbide WC powder (no additives) is fully densified with a nano-grain-sized structure for glass lens application in the optics industry. The SPS is now moving from scientific academia and/or R&D proto-type materials level usage to practical industry use product stage utilizing in the field of electronics, automotive, mold and die, cutting tools, fine ceramics, clean energy, biomaterials industries, and others. This paper reviews and introduces the peculiar phenomenon of SPS and the progress of SPS technology, method, development of SPS systems, and its industrial product applications.

Rapid preparation of [Ca23.04Sr0.96Al28O64]4+(4e−) electrides block by spark plasma sintering

In this paper, the Ca11.52Sr0.48Al14O33 +Ca2.88Sr0.12Al2O6 of a specific stoichiometric ratio is used as a precursor. The [Ca23.04Sr0.96Al28O64]4+(4e-) electrides block with a high electron concentration successfully prepared by in-situ aluminothermic reaction using a spark plasma sintering system(SPS). The sintering temperature is 1050 °C, and the holding time is 5 min. The UV spectrophotometer results showed that (Ca0.96Sr0.04)12A7:e- showed the visible UV absorption peak at around 2.5 eV, and the electron concentration was calculated to reach 2.2 × 1021 cm−3. Simultaneously, the electronic structure is analyzed by a paramagnetic resonance spectrometer, and the result shows that electrons are injected uniformly in the sample. The synchronous thermal analyzer's results showed that (Ca0.96Sr0.04)12A7:e- weight loss occurred above 700 °C was derived from oxygen desorption. These results altogether demonstrate that electrons are efficiently injected into the cage structure of (Ca0.96Sr0.04)12A7:e-. This process provides a new electron-injection method, which significantly shortens the preparation cycle of (Ca0.96Sr0.04)12A7:e- and makes mass production of samples possible. The electronic structure of (Ca0.96Sr0.04)12A7:e- calculated using first-principles. The results show a cage conduction band (CCB) between − 1 eV and 0.7 eV, which is favorable for electrical performance. The results also show that the excellent electrical transport performance of (Ca0.96Sr0.04)12A7:e- mainly comes from Sr, Ca atom s-state electrons, and Al atom p-state electrons.

Development, characterization and comparison of spark plasma-sintered Gr–Cu and Gr–Al composites reinforced with SiC and ZrB2 particles for thermal management

Graphite–copper (Gr–Cu) and graphite–aluminum (Gr–Al) composites are potential candidates for enhanced thermal management for different engineering applications. However, their applications are limited by inadequate thermal conductivity, high coefficient of thermal expansion (CTE) and low microhardness. In this study, SiC and ZrB2 were incorporated into Gr–Cu and Gr–Al powders, and then sintered in a spark plasma sintering (SPS) system to produce Gr–Cu + 8wt%SiC, Gr–Cu + 4wt%SiC + 4wt%ZrB2, Gr–Al + 8wt%SiC and Gr–Al + 4wt%SiC + 4wt%ZrB2 composites. After sintering, the physical, morphological, thermal, electrical and mechanical properties of the composites were evaluated. Results indicated 8.5% increase in relative density for reinforced Gr–Cu composites over the unreinforced Gr–Cu. The porosity of the reinforced Gr–Cu composites is 40.5% lower than that of the unreinforced and ~ 8% for reinforced Gr–Al. For all the sintered samples, Gr–Cu + 4wt%SiC + 4wt%ZrB2 sample has the highest hardness value of 44.5 HV0.1, highest peak intensity ratio of 80.19% and minimum CTE of 2.02 × 10–5/K. The huge increase in the microhardness and peak intensity ratio of Gr–Cu + 4wt%SiC + 4wt%ZrB2 is partially attributed to the formation of hard ZrC phase and three-bond system in ZrB2. This composite is recommended for thermal management of heat sinks and heat spreaders in electronics and pistons in automobiles.

Studying Corrosion Resistance of Weld Joints of Ultrafine-Grained Titanium Alloys

Ultrafine-grained (UFG) samples of PT-3V near-α titanium alloy were subjected to diffusion welding using the Spark Plasma Sintering system. It has been shown that the destruction of welded UFG samples under hot salt corrosion (HSC) is two-staged – first, intercrystalline corrosion is manifested, which then graduates to pitting corrosion. It has been established that the corrosion resistance of weld joints is determined by vanadium concentration at the grain boundaries, the size and volume ratio of β-phase particles and the presence of pores in the weld joints. It has been shown that welded UFG samples possess higher hardness and corrosion resistance than coarse-grained samples.

X-ray spectral microanalysis of W-Ni-Fe pseudoalloy obtained from electroerosive powders

The results of X-ray spectral microanalysis of W-Ni-Fe pseudo-alloy, obtained from electroerosive powders, are presented. Consolidation of the obtained electroerosive powders was carried out by the method of spark plasma sintering using the SPS 25-10 spark plasma sintering system. Using an EDAX energy-dispersive X-ray analyzer built into a Quanta 600 FEG scanning electron microscope, characteristic X-ray spectra were obtained at various points on the sample surface and along a transverse section. As a result of the study, it was found that on the surface of the investigated sintered sample, tungsten, nickel and iron are contained as the main elements, and oxygen, copper and chromium are also present in small amounts.

(Invited) Effect of Cr Concentration on Dissolution of (Mn,Cr)S Inclusions in Stainless Steel

The pit initiation sites for commercial stainless steels have been attributed to sulfide inclusions such as MnS. The chemical composition of the inclusions affects the pitting corrosion resistance of stainless steels. In general, MnS inclusions in stainless steels contain a small amount of Cr, and thus they are accurately written as (Mn,Cr)S inclusions. It has been reported that Cr in (Mn,Cr)S inclusions have an inhibitory effect on the dissolution of the inclusions. However, the extent to which the Cr concentration in the inclusions prevents the dissolution of the inclusions remains unclear. In this study, spark plasma sintering was used in the facile fabrication of stainless steel specimens containing artificial (Mn,Cr)S inclusions with different Cr concentrations.1 A microelectrochemical technique was applied to elucidate the effect of Cr concentration on the dissolution of the inclusions in stainless steel.Type 304 stainless steel powders were mixed with either MnS or Cr2S3 powders to prepare sintered specimens containing 0.06 mass% S. The mixed powders were loaded into a cylindrical graphite die and subsequently compressed into a pellet. The pressed compact was sintered under vacuum conditions and uniaxial pressure in a spark plasma sintering system. The sintered specimens were ground with SiC papers and then polished with diamond pastes. Potentiodynamic polarization was conducted in naturally aerated 0.1 M NaCl (pH 5.5) at 298 K. The specimen surface was masked to make an electrode area of approximately 100 µm × 100 µm containing a single artificial inclusion. All the potentials reported in this study refer to the Ag/AgCl (3.33 M KCl) electrode (0.206 V vs. standard hydrogen electrode at 298 K). During polarization, the electrode area was observed using an in situ real-time optical microscopy system.2 The anodic polarization curves were measured to analyze the dissolution and pit initiation behavior of the artificial (Mn,Cr)S inclusions. The onset potential of inclusion dissolution and the pitting potential increased with increasing Cr concentration in the inclusions. The onset potential of inclusion dissolution reached approximately 0.7 V when the Cr/(Mn+Cr) atomic ratio in the inclusion was more than 0.5. This potential is almost the same as the transpassive region of Type 304 stainless steel. There was not much difference even if the Cr/(Mn+Cr) ratio of the inclusions was higher than 0.5. We concluded that the inhibitory effect of Cr on the dissolution of (Mn,Cr)S inclusions is most effective when the Cr/(Mn+Cr) ratio is 0.5.

Gr–Al composite reinforced with Si3N4 and SiC particles for enhanced microhardness and reduced thermal expansion

Thermal management remains an important consideration for many applications such as automobile pistons, dies in furnaces and heat sinks in electronics, where high thermal conductivity and low coefficient of thermal expansion are desired. In this paper, we report an improved microhardness value and negative coefficient of thermal expansion (CTE) for Gr–Al composites by incorporating silicon nitride (Si3N4) and silicon carbide (SiC) into Gr–Al matrix. Si3N4 and SiC particles (average size of 72 nm) were obtained after 30 and 50 h of ball-milling, respectively. Gr–Al composite were reinforced with Si3N4 and SiC particles (4, 8, 12 and 16 wt% each), and then sintered at a temperature of 560 °C, pressure of 50 MPa, heating rate of 50 °C/min and dwelling time of 10 min using spark plasma sintering system. The sintered samples were characterized for morphology, microhardness, relative density, coefficient of thermal expansion and wear resistance. Addition of 16 wt% Si3N4 reduced relative density from 99.9 to 89.47% indicating lower densification. CTE decreased with increased Si3N4 fraction reaching minimum value of 12.37 × 10–6 °C (which is 42.5% reduction) for Gr–Al + 12 wt% Si3N4. However, Gr–Al + 8 wt% SiC + 8 wt% Si3N4 composite has the minimum negative CTE (− 21 × 10–6 °C), maximum displacement (2.48 mm), maximum displacement rate (1.12 mm/s) and minimum hardness value (26.8 GPa). While the hardness was marginally increased with Si3N4, addition of 12 wt% SiC + 12 wt% Si3N4 raised the hardness by 37%. Also, the wear area increased with applied force. These results indicate that Gr–Al + 8 wt% SiC + 8 wt% Si3N4 composite is suitable for applications requiring combination of low (negative) thermal expansion, high microhardness value and maximum densification. Effectively, the synergic effect of combined SiC and Si3N4 particles has been brought to the fore.

Spark plasma sintering of dielectric BaTaO2N close to the melting point of the BaCN2 additive

The perovskite-type oxynitride BaTaO2N is a promising lead-free relaxor ferroelectric material. However, this material releases a part of its nitrogen during its sintering above 1350 °C. Subsequent annealing of the resulting sintered BaTaO2N0.85 ceramics under an ammonia flow is necessary to recover an insulating, stoichiometric BaTaO2N ceramics. Very recently, molten BaCN2 was reported to be a useful flux for the preparation of BaTaO2N microcrystals without the loss of nitrogen. In the present work, BaTaO2N powder was sintered with a BaCN2 additive under mechanical pressure, using a spark plasma sintering system. Nitrogen loss from the BaTaO2N ceramic was avoided during liquid phase sintering at approximately 900 °C. The stoichiometric BaTaO2N ceramic product with a relative density of 79.8 % was an electrically insulator and it showed its relative dielectric constants, εr, in the range from 320 to 650 and a loss tanδ values from 0.04 to 0.19 at room temperature.

Effect of Nanocrystalline Nickel Powder and Co, Mo, Ta, and Al Additions on Isothermal Oxidation Behavior of Ni–17Cr Alloy

In this paper, the effect of nanocrystalline nickel powder developed via high-energy ball milling process and the addition of Co, Mo, Ta, and Al on the isothermal oxidation behavior of Ni–17Cr binary alloy developed by spark plasma sintering system was investigated. The oxidation behavior of the sintered alloys was studied in air at 1100 °C for exposure period up to 312 h. The oxidation rate and kinetics show that the addition of Al and nanocrystalline nickel enhances the oxidation resistance of the binary alloy followed by Mo, Co, and Ta in their reducing order. The formation of the chromia scale was common to all the sintered alloys investigated as confirmed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy analysis.

Improving mechanical and thermal properties of graphite–aluminium composite using Si, SiC and eggshell particles

Graphite–aluminium (Gr–Al) composites are being used for diverse engineering applications because of their light weight, good electrical conductivity and thermal properties. However, their applications are limited by high coefficient of thermal expansion and low microhardness values which can be enhanced by adding cheap and efficient fillers. This paper reports the effect of addition of eggshell (ES) particles on the properties of sintered Gr–Al-based composites. Five different composites (Gr–Al, Gr–Al + 20 wt.%Si, Gr–Al + 20 wt.%SiC, Gr–Al + 20Si wt.% + 20 wt.%ES and Gr–Al + 20SiC wt.% + 20 wt.%ES) were sintered at a temperature of 540 ℃, holding time of 10 min, heating rate of 52 ℃/min and pressure of 50 MPa using spark plasma sintering system. The sintered samples were characterized based on morphology, microhardness, relative density, coefficient of thermal expansion and electrical conductivity. Based on SEM images, graphite particles of flake-like structure were largely undeformed while Al particles were smaller, round and irregular in shape and fairly uniformly distributed in the composites. The microhardness value of sintered Gr–Al + 20 wt.%SiC + 20 wt.%ES composite was 39.55 HV compared to 30.46 HV for Gr–Al, the least of the samples. The Gr–Al + 20 wt.%SiC + 20 wt.%ES composite also has a very low thermal expansion coefficient (0.98 × 10−5/K) but lowest electrical conductivity at temperature beyond 150 ℃. Highest densification and minimum relative density (94%) were obtained in Gr–Al + 20 wt.%Si + 20 wt.%ES composite. These enhanced performances are largely due to the incorporation of ES particles. This study therefore demonstrated that ESs particles enhanced microhardness and lowered thermal expansion of Gr–Al-based composites which have promising applications in industries especially for thermal management.

Minimization of the sample temperature deviation and the effect of current during high-temperature compressive creep testing by the spark plasma sintering apparatus

Recently, spark plasma sintering (SPS) systems have been used as high-temperature compressive creep testing devices. However, SPS systems can have complex temperature distributions within the experimental configuration that might lead to inaccuracies in the creep test results. For example, sample temperature profiles have been found to deviate from the initial temperature distribution as the sample is deformed during the creep test. Therefore, finite element analysis has been carried out on the SPS creep test mold configuration to evaluate the temperature distribution within an electrically conducting sample in three cases. Then, a multi-step thermal-electrical analysis was conducted to confirm the existence of and quantify a temperature deviation present during sample deformation. Thereafter, a systematic parametric investigation was performed to assess the effect of several geometrical parameters on the deviation in the sample temperature during deformation. Based on its results, recommendations for an optimal mold design that minimizes the sample temperature deviation during creep testing are provided. Finally, it is proposed that the thickness of the graphite felt used on the upper part of the die should be modified to further minimize the sample temperature deviation. The results of this study contribute to the overall understanding of the temperature distribution evolution and the effect of current during creep testing with an SPS apparatus and also provide practical geometrical recommendations for the use of SPS creep testing to achieve minimal sample temperature deviation.