共查询到20条相似文献,搜索用时 15 毫秒
1.
Annika Pille Mohamed Amamra Andrei Kanaev Frédéric Schoenstein 《Ceramics International》2019,45(7):9625-9630
Self-synthesized and commercial alumina (boehmite, γ-Al2O3, α-Al2O3) powders were consolidated using an identical spark plasma sintering cycle, and optically translucent samples were obtained. The benefit of higher pressure is remarkable grain growth suppression. Additionally, the shorter dwell time at higher pressure advantageously leads to a reduction in grain size while conserving the optical transparency and without affecting the density. 相似文献
2.
Xiao-Tong Jia Zhao-Hui Zhang Tian-Hao Xu Luo-Jin Liu Yuan-Hao Sun Xian-Yu Li Qiang Wang Zhao-Hu Jia Yang-Yu He Xing-Wang Cheng 《Journal of the American Ceramic Society》2023,106(10):6301-6316
Aluminum oxynitride (AlON) ceramics doped with different sintering aids were synthesized by spark plasma sintering process. The microstructures, mechanical, and optical properties of the ceramics were investigated. The results indicate that the optimal amount of sintering aids is 0.06 wt% La2O3 + 0.16 wt% Y2O3 + 0.30 wt% MgO. The addition of La3+ and Mg2+ decreases the rate of grain boundary migration in ceramics, promotes pore elimination, and inhibits grain growth. The addition of Y3+ facilitates liquid-phase sintering of AlON ceramics. Moreover, the addition of Mg2+ effectively promotes twin formation in the ceramics, which hinders crack propagation and dislocation motion when the ceramics are loaded. Hence, the AlON ceramic doped with 0.06 wt% La2O3 + 0.16 wt% Y2O3 + 0.30 wt% MgO exhibits a relative density of 99.95%, an average grain size of 9.42 μm, and a twin boundary content of 10.3%, which contributes to its excellent mechanical and optical properties. 相似文献
3.
Haiyue Xu Ji Zou Weimin Wang Hao Wang Wei Ji Zhengyi Fu 《Journal of the European Ceramic Society》2021,41(1):635-645
Fully dense ceramics with retarded grain growth can be attained effectively at relatively low temperatures using a high-pressure sintering method. However, there is a paucity of in-depth research on the densification mechanism, grain growth process, grain boundary characterization, and residual stress. Using a strong, reliable die made from a carbon-fiber-reinforced carbon (Cf/C) composite for spark plasma sintering, two kinds of commercially pure α-Al2O3 powders, with average particle sizes of 220 nm and 3 μm, were sintered at relatively low temperatures and under high pressures of up to 200 MPa. The sintering densification temperature and the starting threshold temperature of grain growth (Tsg) were determined by the applied pressure and the surface energy relative to grain size, as they were both observed to increase with grain size and to decrease with applied pressure. Densification with limited grain coarsening occurred under an applied pressure of 200 MPa at 1050 °C for the 220 nm Al2O3 powder and 1400 °C for the 3 μm Al2O3 powder. The grain boundary energy, residual stress, and dislocation density of the ceramics sintered under high pressure and low temperature were higher than those of the samples sintered without additional pressure. Plastic deformation occurring at the contact area of the adjacent particles was proved to be the dominant mechanism for sintering under high pressure, and a mathematical model based on the plasticity mechanics and close packing of equal spheres was established. Based on the mathematical model, the predicted relative density of an Al2O3 compact can reach ~80 % via the plastic deformation mechanism, which fits well with experimental observations. The densification kinetics were investigated from the sintering parameters, i.e., the holding temperature, dwell time, and applied pressure. Diffusion, grain boundary sliding, and dislocation motion were assistant mechanisms in the final stage of sintering, as indicated by the stress exponent and the microstructural evolution. During the sintering of the 220 nm alumina at 1125 °C and 100 MPa, the deformation tends to increase defects and vacancies generation, both of which accelerate lattice diffusion and thus enhance grain growth. 相似文献
4.
Yann Aman Vincent Garnier Elisabeth Djurado 《Journal of the European Ceramic Society》2009,29(16):3363-3370
The present investigation gives a quantitative correlation between different green microstructures, and their sintering behaviour during spark plasma sintering. The green microstructures were elaborated via various green shaping processes such as direct casting and direct coagulation casting compared to uniaxial compaction of the as-received sub-micron grained corundum powder. Narrowing pore size distribution and reducing pore size (≈40 nm) in the green compact could favour cold densification during initial uniaxial pressing by grain sliding and rearrangement. This is attributed to the soft homogeneous touching network in direct-cast green samples. Consequently, grain growth was impeded and the onset of shrinkage was delayed. Moreover, the small pores and the narrow pore size distribution in the homogeneous green bodies led to higher final densities, with better optical properties compared to the less homogeneous green samples. 相似文献
5.
《Ceramics International》2020,46(6):7510-7516
In this study, zirconia-toughened alumina (ZTA) samples with different amounts of CeO2 were prepared by the spark plasma sintering method. The phase composition and microstructure of the samples were examined by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The addition of CeO2 results in grain refinement and density increase; moreover, CeO2 stabilises the high-temperature metastable phase. As the amount of CeO2 reaches 7 wt%, a new CeAl11O18 phase appears. The Vickers hardness, modulus, and fracture toughness of the samples depend to a large extent on the grain size, relative density, and existence of the second phase. Among the composites, that with 5 wt% CeO2 shows the best performance with the highest values of relative density, Vickers hardness, and fracture toughness: 96.51%, 1688 HV, and 9.91 MPa.√m, respectively. 相似文献
6.
《Journal of the European Ceramic Society》2020,40(10):3656-3662
The dependence of grain size on the heating rate has been investigated for alumina ceramics prepared via spark plasma sintering (SPS). For this purpose, the local grain size has been determined via position-dependent microscopic image analysis, using two independent grain size measures (mean chord length and Jeffries grain size). For alumina ceramics prepared with heating rates between 5 and 100 °C/min (pressure 80 MPa, maximum temperature 1300 °C) it is found that for higher heating rates the grain size is smaller. However, the microstructural non-uniformity is so large that any grain size determination that does not take this non-uniformity into account becomes meaningless, because grain size gradients from the specimen periphery to the center are larger than the differences in grain size due to different heating rates. Temperature and pressure gradients are discussed as the most plausible reasons for the microstructural non-uniformity. 相似文献
7.
8.
Ahrong Jeong Koichiro Suekuni Michitaka Ohtaki Byung-Koog Jang 《Ceramics International》2021,47(17):23927-23934
In this study, indium (In)- and gallium (Ga)-doped zinc oxide (ZnO) ceramics, [Zn(1?x?y)GaxIny]O (x = 0, 0.02; y = 0, 0.005, 0.01, 0.02), were fabricated via spark plasma sintering (SPS) at 1423 K. Crystal structure and microstructural analyses were conducted to confirm the solubility of the dopants and understand the correlations between the crystallographic phases and the various compositions. It was confirmed that the solubility of Ga (x = 0.02; y = 0.005) was promoted by doping with In and Ga, and the highest power factor of 0.99 mW K?2 m?1 was acquired at 1046 K. Furthermore, the thermal conductivity at 340–530 K was reduced by doping with In and Ga. 相似文献
9.
《Ceramics International》2022,48(11):15613-15621
To explore the impact of the sintering rate on the microstructure and mechanical properties of cermets, the preparation of (Ti,W)C cermets by ultrafast sintering via spark plasma sintering (SPS) is reported. Compared with a slow heating rate, the electric field produced by an ultrafast heating rate enhances the liquid phase mass transfer of the metal binder phase, thus achieving rapid densification of (Ti,W)C cermets and effectively inhibiting abnormal grain growth. However, an excessive heating rate will lead to an “overflow” phenomenon, which reduces the grain growth difficulty and the bonding strength between grains. The results show that when the heating rate is 500 °C/min, the liquid phase mass transfer is moderate, the densification degree is the highest and the mechanical properties are excellent. The flexural strength, Vickers hardness and fracture toughness are 1340.90 ± 23.55 MPa, 18.42 ± 0.46 GPa and 11.96 ± 0.23 MPa?m1/2, respectively. 相似文献
10.
Rafael A. Raimundo Kaio V.A. Santos Cleber S. Lourenço Franciné A. Costa Marco A. Morales Daniel A. Macedo Angelus G.P. Silva Uílame U. Gomes 《Ceramics International》2021,47(1):677-685
Al2O3-10 wt% Co composites were prepared by high energy milling in the presence of ethyl alcohol and with subsequent spark plasma sintering (SPS). The powders milled for 5 and 30 h were sintered by SPS at 1350 °C for 5 min. The effect of milling time on the sinterability and mechanical properties was studied. The morphology and structure of milled powders were investigated by scanning electron microscopy, dynamic light scattering and X-ray diffraction. The Co phase forms plate-like particles of different sizes, while finely fragmented Al2O3 particles are incorporated in the Co phase, forming composite particles. The average size of the composite particles decreases with increasing milling time, achieving 1.33 μm after 30 h. Crystallite size and micro-strain are inversely proportional. Overall, all the samples display homogeneous microstructures, high density (85.29–91.60%) and microhardness in the range 11.41–14.37 GPa. 相似文献
11.
《Journal of the European Ceramic Society》2014,34(10):2169-2175
B4C based ceramics were fabricated with different Fe3Al contents as sintering aids by spark plasma sintering at relatively low temperature (1700 °C) in vacuum by applying 50 MPa pressure and held at 1700 °C for 5 min. The effect of Fe3Al additions (from 0 to 9 wt%) on the microstructure and mechanical properties of B4C has been studied. The composition and microstructure of as-prepared samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA) equipped with WDS (wavelength dispersive spectrometry) and EDS. The mixtures of B4C and Fe3Al underwent a major reaction in which the metal borides and B4C were encountered as major crystallographic phases. The sample with 7 wt% of Fe3Al as a sintering aid was found to have 32.46 GPa Vickers hardness, 483.40 MPa flexural strength, and 4.1 MPa m1/2 fracture toughness which is higher than that of pure B4C. 相似文献
12.
《Journal of the European Ceramic Society》2022,42(5):2004-2014
Homogenous distribution of whiskers in the ceramic matrix is difficult to be achieved. To solve this problem, B4C-SiCw powder mixtures were freeze dried from a slurry dispersed by cellulose nanofibrils (CellNF) in this work. Dense B4C ceramics reinforced with various amounts of SiCw up to 12 wt% were consolidated by spark plasma sintering (SPS) at 1800 °C for 10 min under 50 MPa. During this process, CellNF was converted into carbon nanostructures. As iron impurities exist in the starting B4C and SiCw powders, both thermodynamic calculations and microstructure observations suggest the dissolution and precipitation of SiCw in the liquids composed of Fe-Si-B-C occurred during sintering. Although not all the SiCw grains were kept in the final ceramics, B4C-9 wt% SiCw ceramics sintered at 1800 °C still exhibit excellent Vickers hardness (35.5 ± 0.8 GPa), flexural strength (560 ± 9 MPa) and fracture toughness (5.1 ± 0.2 MPa·m1/2), possibly contributed by the high-density stacking faults and twins in their SiC grains, no matter in whisker or particulate forms. 相似文献
13.
《Ceramics International》2019,45(15):18943-18950
In the present research, polycrystalline magnesium oxide (MgO) bodies were fabricated using spark plasma sintering (SPS) at different temperatures and times from MgO nanopowder. Microstructural development, densification, and optical properties were investigated during SPS. The critical pressure of plastic deformation of the MgO compacts during sintering was also analyzed. The results showed that the plastic deformation phenomenon had a profound effect on the grain size and optical properties. In addition, the optical properties and microstructure of MgO bodies were strongly dependent on sintering temperature and time. Full-dense infrared-transparent magnesium oxide with a relative density of 99.99% was prepared at 1200 °C for 5 min under the pressure of 80 MPa. The spark plasma sintered MgO demonstrated the highest infrared transmittance of 72% in the 3–7 μm wavelength range, which was comparable with the values reported for MgO single crystal. 相似文献
14.
《Journal of the European Ceramic Society》2020,40(14):4818-4824
Conductive Al2O3/graphene composites were manufactured by SPS from Al2O3 powders coated with a few graphene layers. Composite powders with a total carbon content of 0.1, 0.6 and 1.0 wt. % were manufactured by chemical vapour deposition. The effect of the graphene content on the microstructure, mechanical and electrical properties of the compacts were studied. Graphene, homogenously located along the grain boundaries, dramatically hindered the Al2O3 grain growth. The continuous interconnected graphene network enhanced electrical properties, achieving percolation threshold as low as 0.6 wt. % of graphene. The content of 1 wt. % of graphene increased electroconductivity by 13 orders of magnitude as compared to the monolithic alumina. The indentation fracture toughness increased by 20 % in specimens with 0.6 wt. % graphene content as compared to pure alumina. The presence of 1.0 wt. % of graphene resulted in a slight decrease of elastic modulus and hardness, but strength decreased by 40 %. 相似文献
15.
《Journal of the European Ceramic Society》2022,42(8):3550-3558
Alumina is an engineering ceramic material with excellent comprehensive properties as well as the inherent shortcoming of the low fracture toughness. Y2O3-stabilized t-ZrO2 (TZP) is an effective additive to improve its fracture toughness. In this work, rotary chemical vapor deposition (RCVD) was applied to uniformly coat TZP nanoparticles on α-Al2O3 powder, and then the powder was compacted via spark plasma sintering. The content of TZP increased from 0.56 to 4.7 wt% with increasing the deposition temperature from 500 to 800 °C but decreased at 900 °C. The RCVD-TZP nanoparticles homogeneously surrounded the α-Al2O3 grains and inhibited its growth after sintering. The relative density, fracture toughness and hardness of the ZTA composites had the maximum values of 99.2%, 7.28 ± 0.33 MPa m1/2, and 19.5 ± 0.5 GPa at 1500 °C and 4.7 wt% RCVD-TZP, respectively, much higher than the ZTA composites directly mixed with TZP commercial powder. 相似文献
16.
《Ceramics International》2023,49(5):8032-8038
The low mechanical properties limit the application of chalcogenide glasses in the infrared lens. This paper proposes a general method for enhancing the mechanical strength of chalcogenide glasses. A series of GaAs crystal-doped Ge10As20Se17Te53 and ZnS crystal-doped As2S5 glass-ceramics were prepared by spark plasma sintering (SPS). The effects of crystal doping on the optical and mechanical properties of glass-ceramics were studied utilizing FTIR, XRD, SEM, ultramicroscopy, and Vickers hardness. The results show that adding GaAs crystal and ZnS crystal significantly improves the hardness and fracture toughness of the chalcogenide glasses. The infrared transmittance and mechanical properties can be further improved by reducing the crystal size. 相似文献
17.
Zengbin Yin Juntang Yuan Weiwei Xu Jiadong Ye Kui Liu Shiyu Yan 《Ceramics International》2019,45(1):752-758
A fine grained Ti(C, N) cermet tool material was prepared by two-step spark plasma sintering. Microstructure evolution and densification mechanisms of Ti(C, N) during spark plasma sintering were studied. Effect of two-step sintering process and Ni content on microstructure and mechanical properties were also investigated. The critical activated densification temperature of Ti(C, N) is about 1300?℃, and the rapidest densification rate takes place at 1300?℃~1400?℃. Grains are in the size of 1?µm when the Ti(C, N) cermet was prepared by two-step spark plasma sintering. The optimal flexural strength, fracture toughness and Vickers hardness are 1094?±?42?MPa, 7.2?±?0.5?MPa?m1/2 and 18.3?±?0.4?GPa, respectively. The Ti(C, N) cermets containing more content of Ni have higher toughness, which is due to the remarkable toughening effect of crack bridging by large grains. 相似文献
18.
《Ceramics International》2023,49(7):10748-10755
Ultra-high temperature HfB2 ceramic with nearly full densification is achieved by using gradient sintering process of SPS without any additives. The effect of the sintering temperature on the densification behavior, relative density, microstructure, mechanical and thermionic properties is systematically investigated. The results show that the fast densification of HfB2 ceramic occurs at the heating stage, and the highest relative density of 96.75% is obtained at T =1950 °C, P = 60 MPa and t =10min. As the temperature is increased from 1800 to 1950 °C, the grain size of HfB2 increases from 6.12 ±1.33 to 10.99 ± 2.25 μm, and refined microstructure gives the excellently mechanical properties. The highest hardness of 26.34 ±2.1GPa, fracture toughness of 7.12 ± 1.33 MPa m1/2 and bending strength of 501 ±10MPa belong to the HfB2 ceramic obtained at T =1950°C. Moreover, both the Vickers hardness and fracture toughness obey the normal indentation size effect. HfB2 ceramic also exhibits the thermionic emission characterization with the highest current density of 6.12 A/cm2 and the lowest work function of 2.92 eV. 相似文献
19.
A comparative study has been carried out on densification, microstructure, and creep with oxide-scale formation in ZrB2-20 vol.% SiC-(7, 10 or 14 vol.%) LaB6 composite containing B4C and C as additives, and prepared by spark plasma sintering at 1800 °C under 70 MPa ram pressure. Addition of LaB6 has promoted densification of composites by scavenging oxygen impurity, thereby increasing their hardness. Constant load compressive creep tests at 1300 °C under 47 and 78 MPa stresses have shown the lowest creep rate in the 10 vol.% LaB6 composite. The stress exponents obtained for composites having 10 vol.% LaB6 (~1.3 ± 0.1) and 14 vol.% LaB6 (~2.6 ± 0.2) suggest respectively, grain boundary diffusion with intergranular glassy phase formation and dislocation glide as operating mechanisms. Intergranular cracking caused by grain boundary sliding appears as the damage mechanism. Oxide scales formed during creep exhibit greater thickness and defect concentration than those by isothermal exposure at 1300 °C within similar duration. 相似文献
20.
《Journal of the European Ceramic Society》2023,43(8):3053-3061
The traditional way of densifying high-melting-point ceramics at high temperatures with long soaking time leads to severe grain coarsening, which degrades the mechanical properties of ceramics. Here, highly dense (∼98%) zirconium carbide (ZrC) ceramics with limited grain growth were obtained by spark plasma sintering (SPS) at relatively low temperatures, 1900 ℃, with a high pressure up to 200 MPa in a reliable carbon-fiber-reinforced carbon composite (Cf/C) mold. Subgrains and high-density dislocations formed in the high-pressure sintered ceramics. The hardness and fracture toughness of the prepared highly dense ZrC ceramics reached 20.53 GPa and 2.70 MPa·m1/2, respectively. The densification mechanism was mainly plastic deformation under high pressure. In addition, ZrC ceramics sintered at high pressure possessed a high dislocation density of 7.30 × 1012 m−2, which was suggested to contribute to the high hardness. 相似文献