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Densification mechanism of stereolithographical dense Si_(3)N_(4) ceramics with CeO_(2) as sintering additive by field assisted sintering 被引量:1
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作者 RAO Wei-dong LIU Yao +1 位作者 CHENG Li-jing LIU Shao-jun 《Journal of Central South University》 SCIE EI CAS CSCD 2021年第4期1233-1243,共11页
Combining sintering additive with field assisted sintering,stereolithographical dense Si3N4 ceramics was successfully fabricated.Owing to a large amount of polymer during the stereolithography,the green parts have the... Combining sintering additive with field assisted sintering,stereolithographical dense Si3N4 ceramics was successfully fabricated.Owing to a large amount of polymer during the stereolithography,the green parts have the characteristics of low powder loading and high porosity.Adjusting the process parameters such as sintering temperature and soaking time can effectively improve the density of the specimens.The stress exponent n of all specimens is in a range of 1 and 2,which is derived from a modified sintering kinetics model.The apparent activation energy Qd of stereolithographic Si_(3)N_(4) ceramics sintered with applied pressures of 30 MPa,40 MPa,and 50 MPa is 384.75,276.61 and 193.95 kJ/mol,respectively,suggesting that the densification dynamic process is strengthened by raising applied pressure.The grain boundary slipping plays a dominating role in the densification of stereolithographic Si3N4 ceramics.The Vickers hardness and fracture toughness of stereolithographic Si3N4 ceramics are HV10/10(1347.9±2.4)and(6.57±0.07)MPaAbstract:Combining sintering additive with field assisted sintering,stereolithographical dense Si3N4 ceramics was successfully fabricated.Owing to a large amount of polymer during the stereolithography,the green parts have the characteristics of low powder loading and high porosity.Adjusting the process parameters such as sintering temperature and soaking time can effectively improve the density of the specimens.The stress exponent n of all specimens is in a range of 1 and 2,which is derived from a modified sintering kinetics model.The apparent activation energy Qd of stereolithographic Si3N4 ceramics sintered with applied pressures of 30 MPa,40 MPa,and 50 MPa is 384.75,276.61 and 193.95 kJ/mol,respectively,suggesting that the densification dynamic process is strengthened by raising applied pressure.The grain boundary slipping plays a dominating role in the densification of stereolithographic Si3N4 ceramics.The Vickers hardness and fracture toughness of stereolithographic Si3N4 ceramics are HV10/10(1347.9±2.4)and(6.57±0.07)MPa·m^(1/2),respectively. 展开更多
关键词 STEREOLITHOGRAPHY silicon nitride ceramics sintering mechanism DENSIFICATION field assisted sintering
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Thermal Wave Effect and Sintering Activation Energy at the Initial Stage of Field Assisted Sintering Process for Non-conductive Al_2O_3 Powders
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作者 ZHANG Long 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2018年第6期1416-1421,共6页
The effect of thermal wave at the initial stage for non-conductive Al_2 O_3 powders compact in field assisted sintering technique(FAST) was investigated. The Lord and Shulman type generalized thermoselastic theory was... The effect of thermal wave at the initial stage for non-conductive Al_2 O_3 powders compact in field assisted sintering technique(FAST) was investigated. The Lord and Shulman type generalized thermoselastic theory was introduced to describe the influence of thermal-mechanical interaction, as well as the heat transport and thermal focusing caused by thermal wave propagation. The expression of vacancy concentration difference of the particles was deduced by considering transient thermal stress. Subsequently, the relationship between activation energy and vacancy concentration difference was obtained. The mechanism of surface diffusion, volume diffusion, simultaneous surface and volume diffusion was analyzed. The numerical simulations indicate that low sintering temperature can obtain high local temperature by the superposition effect of thermal wave. Vacancy concentration differences were improved during FAST compared with hot-pressure and pressureless sintering, thereby decreasing the sintering time. By contrast, the activation energy declined with the decrease of vacancy concentration difference in the neck growth process. 展开更多
关键词 field assisted sintering technique generalized thermoelastic theory thermal wave vacancy concentration difference sintering activation energy
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Effect of current on the microstructure and performance of (Bi_2Te_3)_(0.2)(Sb_2Te_3)_(0.8) thermoelectric material via field activated and pressure assisted sintering
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作者 陈瑞雪 孟庆森 +1 位作者 樊文浩 王忠 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2011年第7期9-13,共5页
(Bi_2Te_3)_(0.2)(Sb_2Te_3)_(0.8) thermoelectric material was sintered via a field activated and pressure assisted sintering(FAPAS) process.By applying different current intensity(0,60,320 A/cm^2) in the si... (Bi_2Te_3)_(0.2)(Sb_2Te_3)_(0.8) thermoelectric material was sintered via a field activated and pressure assisted sintering(FAPAS) process.By applying different current intensity(0,60,320 A/cm^2) in the sintering process,the effects of electric current on the microstructure and thermoelectric performance were investigated.This demonstrated that the application of electric current in the sintering process could significantly improve the uniformity and density of(Bi_2Te_3)_(0.2)(Sb_2Te_3)_(0.8) samples.When the current intensity was raised to 320 A/cm^2,the preferred orientation of grains was observed.Moreover,positive effects on the thermoelectric performance of applying electric current in the sintering process were also confirmed.An increase of 0.02 and 0.11 in the maximum figure of merit ZT value could be acquired by applying current of 60 and 320 A/cm^2,respectively. 展开更多
关键词 thermoelectric material (Bi_2Te_3)_(0.2)(Sb_2Te_3)_(0.8) microstructure performance CURRENT field activated and pressure assisted sintering
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Microstructural Development and Mechanical Properties of PM Ti-45Al-2Nb-2Mn-0.8 vol.%TiB_2 Processed by Field Assisted Hot Pressing 被引量:2
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作者 R.Munoz-Moreno E.M.Ruiz-Navas +1 位作者 B.Srinivasarao J.M.Torralba 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2014年第11期1145-1154,共10页
A γ-TiAI intermetallic alloy, Ti-45Al-2Nb-2Mn (at.%)-0.8 vol.%TiB2, has been processed from gas atomized praalloyed powder by field assisted hot pressing (FAHP). An initial analysis of the prealloyed powder helpe... A γ-TiAI intermetallic alloy, Ti-45Al-2Nb-2Mn (at.%)-0.8 vol.%TiB2, has been processed from gas atomized praalloyed powder by field assisted hot pressing (FAHP). An initial analysis of the prealloyed powder helped on the understanding of the intermetallic sintering behavior. Atomized powder consisted of α metastable phase that transformed into α2+γ equilibrium phases by thermal treating. Different powder particle microstructures were found, which influence the microstructure development of the FAHP T-TiAI material depending on the sintering temperature. Duplex, nearly lamellar and fully lamellar microstructures were obtained at the sintaring temperatures above 1000 ℃. Lower consolidation temperatures, below 1000 ℃, led to the formation of an AI rich phase at powder particle boundaries, which is deleterious to the mechanical properties. High compressive yield strength of 1050 MPa was observed in samples with FAHP duplex microstructures at room temperature. Whereas nearly lamellar and fully lamellar microstructures showed yield strength values of 655 and 626 MPa at room temperature and 440 and 425 MPa at 750 ℃, respectively, which are superior in comparison to similar alloys processed by other techniques. These excellent properties can be explained due to the different volume fractions of the α2 and γ phases and the refinement of the PM microstructures. 展开更多
关键词 Titanium aluminides Powder metallurgy Microstructure Mechanical properties field assisted sintering
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