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1.
Ruiqun Pan Guiqing Chen Xinmin Yu Yusen Yang Wenbo Han 《Journal of the European Ceramic Society》2021,41(4):2247-2254
Solvothermal treatment was used to synthesize nanoscale 4TaC-HfC (Ta4HfC5) powder at a relatively low calcination temperature and in a short period (1400 °C, 2 h). The obtained powder had uniform size distribution and dispersion. Ta4HfC5 ceramics were then consolidated via spark plasma sintering at 2100 °C. Ceramics had a better densification and smaller mean grain size at a shorter sintering time compared with that of materials sintered using mechanical ball milling method. The densification behavior of ceramics deriving from synthesized or ball milled powders was analyzed and the mechanical properties of different samples were investigated. To further increase the mechanical properties, a nearly fully dense Ta4HfC5-MoSi2 ceramic was sintered using the synthesized powder. The mechanical properties of the ceramic composite doubled the strength values. This processing route demonstrated to be a viable approach to synthesize nanoscale Ta4HfC5 powder with high purity and uniformity, and obtain higher performances ceramics once sintered. 相似文献
2.
Jin-Hao Yuan Qiu-Yu Liu Yang You Ling-Yong Zeng Ming-Wen Bai Lewis R. Blackburn Wei-Ming Guo Hua-Tay Lin 《Ceramics International》2021,47(11):15843-15848
With the view to improve the densification behaviour and mechanical properties of ZrB2-SiC ceramics, three synthesis routes were investigated for the production of ZrB2, prior to the fabrication of ZrB2-20 vol. % SiC via spark plasma sintering (SPS). Two borothermal reduction routes, modified with a water-washing stage (BRW) and partial solid solution of Ti (BRS), were utilised, alongside a boro/carbothermal mechanism (BRCR) were utilised to synthesise ZrB2, as a precursor material for the production of ZrB2-SiC. It was determined that reduction in the primary ZrB2 particle size, alongside a diminished oxygen content, was capable of improving densification. ZrB2-SiC ceramics, with ZrB2 derived from BRW synthesis, exhibited a favorable combination of high relative density (98.6%), promoting a marked increase in Vickers hardness (21.4 ± 1.7 GPa) and improved thermal conductivity (68.7 W·m-1K-1). 相似文献
3.
《Journal of the European Ceramic Society》2022,42(15):7209-7218
How to improve the strength of fibrous porous ceramics dramatically under the premise of no sacrificing its low density and thermal conductivity has remained a challenge in the high-temperature thermal insulation field. In this paper, a new kind of high-strength mullite fiber-based ceramics composed of interlocked porous mullite fibers was prepared by nanoemulsion electrospinning and dry pressing method. Results show that as to the porous ceramics with the same density (~ 0.8 g/cm3), the three-dimensional skeleton structure composed of porous mullite fibers was much denser than that composed of solid mullite fibers. Therefore, porous mullite fiber-based ceramics exhibited a higher compressive strength (5.53 MPa) than that of solid mullite fiber-based ceramics (3.21 MPa). In addition, porous mullite fiber-based ceramics exhibited a superior high-temperature heat insulation property because the porous structure in fibers could reduce the radiant heat conduction. This work provides new insight into the development of high-temperature thermal insulators. 相似文献
4.
《Journal of the European Ceramic Society》2020,40(5):2090-2096
Mullite fibrous porous ceramics is one of the most commonly used high temperature insulation materials. However, how to improve the strength of the mullite fibrous porous ceramics dramatically under the premise of no sacrificing the low sample density has always been a difficult scientific problem. In this study, the strategy of using mullite nanofibers to replace the mullite micron-fibers was proposed to fabricate the mullite nanofibrous porous ceramics by the gel-casting method. Results show that mullite nanofibrous porous ceramics present a much higher compressive strength (0.837 MPa) than that of mullite micron-fibrous porous ceramics (0.515 MPa) even when the density of the mullite nanofibrous porous ceramics (0.202 g/cm3) is only around three quarters of that of the mullite micron-fibrous porous ceramics (0.266 g/cm3). The obtained materials that present the best combination of mechanical and thermal properties can be regarded as potential high-temperature thermal insulators in various thermal protection systems. 相似文献
5.
《Journal of the European Ceramic Society》2022,42(5):2188-2194
Ta substitution in K0.5Na0.5NbO3 lead free piezoelectrics helps to prevent grain growth and has been shown to improve the piezoelectric properties but always leads to hetereogeneous microstructures. Two synthesis routes have been studied to prepare K0.5Na0.5Nb0.8Ta0.2O3 (KNNTa) substituted powders. Then highly densified KNNTa ceramics have been obtained by spark plasma sintering (SPS). The use of a synthesized oxide precursor Nb1.6Ta0.4O5 during the ceramic elaboration process clearly shows through accurate Rietveld study a successful Ta substitution with 92% of Amm2 K0.485(8)Na0.515(8)Nb0.819(6)Ta0.181(6)O3 phase, confirmed by SEM-EDS analysis and a more homogeneous chemical composition. This leads to enhanced electromechanical coupling coefficients with an improvement of 50% of kt, 15% for kp and low electrical losses, compared to the conventional synthesis method with a simple mixing of commercial precursors. 相似文献
6.
《Ceramics International》2022,48(8):10472-10479
Porous mullite ceramics are widely used in heat insulation owing to their high temperature and corrosion resistant properties. Reducing the thermal conductivity by increasing porosity, while ensuring a high compressive strength, is vital for the synthesis of high-strength and lightweight porous mullite ceramics. In this study, ceramic microspheres are initially prepared from pre-treated high-alumina fly ash by spray drying, and then used to successfully prepare porous mullite ceramics with enhanced compressive strength via a simple direct stacking and sintering approach. The influence of sintering temperature and time on the microstructure and properties of porous mullite ceramics was evaluated, and the corresponding formation mechanism was elucidated. Results show that the porous mullite ceramics, calcined at 1550 °C for 3 h, possess a porosity of 47%, compressive strength of 31.4 MPa, and thermal conductivity of 0.775 W/(m?K) (at 25 °C), similar to mullite ceramics prepared from pure raw materials. The uniform pore size distribution and sintered neck between the microspheres contribute to the high compressive strength of mullite ceramics, while maintaining high porosity. 相似文献
7.
Guillaume BonnefontGilbert Fantozzi Sandrine TrombertLionel Bonneau 《Ceramics International》2012,38(1):131-140
A high transmittance/small grain size combination for pure spinel ceramics from commercially available nanopowders without sintering aids can be obtained by SPS sintering. By using a low heating rate ≤10 °C/min and a sintering temperature ≤1300 °C, a transparent polycrystalline MgAl2O4 spinel was fabricated by SPS with an in-line transmission of 74% and 84% for 550 nm (visible) and 2000 nm (NIR) wavelengths respectively. A small average grain size of about 250 nm was obtained and the pores located at the multiple grain junctions have a mean size of about 20 nm. The high in-line transmission is linked not only to the low residual porosity but particularly to the very small size of pores. 相似文献
8.
《Journal of the European Ceramic Society》2020,40(1):12-18
Fully dense β-SiAlON ceramics with excellent mechanical properties and good thermal conductivity were fabricated by two-stage spark plasma sintering (SPS) processes without and with applying pressure respectively, using α-Si3N4 powder and 6 Al2O3-3 AlN-6 Y2O3 (in wt.%, label with 636), 424 and 422 additives. In the first stage SPS process without pressure, the relative dense β-SiAlON ceramics with interlock microstructures of elongated grains and density of 3.14˜3.18 g cm−3, hardness of 14.00˜14.82 GPa and fracture toughness of 6.00˜6.63 MPa m1/2 were obtained by sintering at about 1600 °C for 20 min. In the second stage SPS process at about 1425 °C for 5 min under pressure of 24 MPa, the fully dese β-SiAlON ceramics with density of 3.22˜3.24 g cm−3, high hardness of 15.68˜15.95 GPa, high fracture toughness of 6.38˜7.03 MPa m1/2 and thermal conductivity of 13.5˜19.6 Wm-1K-1 were obtained. The reaction between the samples and the graphite mold can be avoided in this fabrication method. 相似文献
9.
Ebrahim Karimi Saeidabadi Touradj Ebadzadeh Esmaeil Salahi 《Ceramics International》2018,44(17):21053-21066
In the present study, the in-situ synthesized mullite has been prepared successfully by mixing kaolinite with alumina and aluminum nitrate nonahydrate (ANN) powders through high energy milling followed by spark plasma sintering (SPS). Using a high-energy ball-mill, the stoichiometric compositions of the starting powders, considering their final transformation to Al2O3 and SiO2, have been mixed. The SPS process has been performed at 1400 and 1375?°C for the specimens containing Al2O3 and ANN, respectively. XRD patterns of the milled powders after 30?h showed the formation of quartz from kaolinite for both starting batches. The displacement-temperature-time (DTT) curves and the corresponded vacuum changes indicated the dehydration and phase transformation of ANN and kaolinite at different stages of the sintering process. The XRD patterns of the sintered samples revealed the formation of mullite alongside un-reacted Al2O3 and crystobalite for the batches containing Al2O3 and ANN, respectively. The results of the physical and mechanical properties tests showed higher amounts of bending strength (397?±?18?MPa), Vickers hardness (16.32?±?0.21?GPa) and fracture toughness (3.81?±?0.24?MPa?m?1/2) alongside a lower porosity (0.070?±?0.02%) for the prepared sample containing Al2O3, than those of the sample containing ANN. 相似文献
10.
《Ceramics International》2022,48(9):12006-12013
B4C-based composites were synthesized by spark plasma sintering using B4C、Ti3SiC2、Si as starting materials. The effects of sintering temperature and second phase content on mechanical performance and microstructure of composites were studied. Full dense B4C-based composites were obtained at a low sintering temperature of 1800 °C. The B4C-based composite with 10 wt% (TiB2+SiC) shows excellent mechanical properties: the Vickers hardness, fracture toughness, and flexural strength are 33 GPa, 8 MPa m1/2, 569 MPa, respectively. High hardness and flexural strength were attributed to the high relative density and grain refinement, the high fracture toughness was owing to the crack deflection and uniform distribution of the second phase. 相似文献
11.
《Journal of the European Ceramic Society》2022,42(9):3720-3729
Ta4HfC5 powder was synthesized using TaCl5, HfCl4 and phenolic resin as raw materials. Then, Ta4HfC5–10 vol% MoSi2 ceramics and Ta4HfC5–10 vol% MoSi2 with different proportions of ZrB2 (10 – 30 vol%) ceramics were sintered by spark plasma sintering. Zr atoms substituted Ta and Hf atoms in Ta4HfC5 during the sintering process at 2000 °C. The sintering behavior and microstructure evolution upon the ceramics are discussed. The mechanical properties of the composites were improved compared to the pure Ta4HfC5 ceramics. The hardness of Ta4HfC5–MoSi2 with 30 vol% ZrB2 increased from around 10 GPa to almost 13 GPa, the flexural strength increased from around 245–435 MPa, and the fracture toughness increased from 2.56 ± 0.12 MPa?m1/2 to 4.46 ± 0.20 MPa?m1/2. 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.
《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
14.
《应用陶瓷进展》2013,112(5):308-312
ZrB2 based composites containing 10 vol.-% carbon nanotubes (CNTs) are synthesised by spark plasma sintering at temperatures ranging from 1600 to 18008C and at an applied pressure of 25?MPa. The effects of sintering temperature on densification behaviour, microstructural evolutions and mechanical properties are presented. Results indicate that ZrB2-CNT composites fabricated at 16508C have the optimal combination of dense microstructure and properties. The fracture toughness is sensitive to the temperature change and reaches 7.2?MPa m1/2 for the CNT toughened ZrB2 ceramics, which is higher than the measured result for monolithic ZrB2 (3.3?MPa m1/2). The crack deflection and CNT pullout are the dominant toughening mechanisms. 相似文献
15.
《Journal of the European Ceramic Society》2022,42(13):6015-6024
A novel approach to fabricate porous mullite ceramics with homogeneous pore size and high-strength using green non-toxic and cost-effective poly-γ-glutamic acid (γ-PGA) gelling system was reported for the first time. Effect of γ-PGA addition, additive amount and solid loading on rheological behavior of the slurries, and microstructure and properties of samples were investigated systematically. By optimizing the solid loading of mullite samples, we are able to get the sample with small pores (< 200 µm) dominating (93.3% of the total pores), and compressive strength of the sample reaches up to 26.62 MPa. In addition, the mullite ceramics exhibited high porosity of 75.7% with low thermal conductivity of 0.279 W/(m·K) at room temperature. This study not only provides a green and non-toxic gelling system but also offers porous mullite ceramics with low thermal conductivity and excellent mechanical strength as an energy-saving thermal insulation material. 相似文献
16.
《Journal of the European Ceramic Society》2022,42(2):354-363
So far many attempts have been made to synthesize phase-pure Ti3AlC2 MAX-phase. But still the challenge posed by the presence of TiC and Ti-Al based intermetallic transient impurity phases in the final product is a persisting problem. Spark plasma sintering (SPS) technique has been the most successful method to decrease the impurity content of the final product. Even so, synthesis of phase-pure Ti3AlC2 MAX-phase, without any TiC and Ti-Al based intermetallic impurities, has not been achieved and reported in literature with substantial evidences. Further, high purity Ti3AlC2 MAX-phase synthesized using SPS technique has shown lack of phase and microstructural stability above 1350°C temperature. In this work, we have reported an optimized method for producing phase-pure Ti3AlC2 MAX-phase (having more than 99 % purity) using commercial grade Ti, Al and C elemental powders through SPS technique. The final product also showed very good high temperature stability up to 1500°C under flowing Argon inert atmosphere. 相似文献
17.
《Journal of the European Ceramic Society》2017,37(3):1131-1134
Porous SiC/SiCN composite ceramics with heterogeneous pore structure and rod-like SiCN grains were fabricated by foaming and reaction sintering. The mixture slurry containing SiC and silicon as raw materials, cornstarch as binder, Y2O3 as sintering additive and an electrosteric dispersant was stirred with foams derived from pre-foaming using foaming agent. The casted green body was sintered at 1650 °C under nitrogen atmosphere. The results demonstrated that the porous SiC/SiCN ceramics exhibited hierarchical vias ranging from 1 μm to 1 mm and the rod-like crystalline SiCN grains generated in the SiC matrix. 相似文献
18.
《Ceramics International》2015,41(7):9009-9017
Porous mullite ceramics were prepared via foam-gelcasting using industrial grade mullite powder as the main raw materials, Isobam-104 as the dispersing and gelling agent, sodium carboxymethyl cellulose as the foam stabilizing agent, and triethanolamine lauryl sulfate as the foaming agent. The effects of processing parameters such as type and amount of additive, solid loading level and gelling temperature on rheological properties and gelling behaviors of the slurries were investigated. The green samples after drying at 100 °C for 24 h were fired at 1600 °C for 2 h, and the microstructures and properties of the resultant porous ceramic samples were characterized. Based on the results, the effects of foaming agent on the porosity level, pore structure and size and mechanical properties of the as-prepared porous mullite ceramics were examined. Porosity levels and pore sizes of the as-prepared samples increased with increasing the foaming agent content up to 1.0%, above which both porosity levels and pore sizes did not change. The compressive strength and flexural strength of the as-prepared sample with porosity of 76% and average pore size of 313 μm remained as high as 15.3±0.3 MPa and 3.7±0.2 MPa, respectively, and permeability increased exponentially with increasing the porosity. 相似文献
19.
Yang Wang Qiang Liu Biao Zhang Haoqian Zhang Yicheng Jin Zhaoxin Zhong Jian Ye Yuhan Ren Feng Ye Wen Wang 《Ceramics International》2021,47(8):10665-10671
Almost fully-dense B4C–SiC–TiB2 composites with a high combination of strength and toughness were prepared through in situ reactive spark plasma sintering using B4C and TiSi2 as raw materials. The densification, microstructure, mechanical properties, reaction, and toughening mechanisms were explored. TiSi2 was confirmed as a reactive sintering additive to promote densification via transient liquid-phase sintering. Specifically, Si formed via the reaction between B4C and TiSi2 that served as a transient component contributed to densification when it melted and then reacted with C to yield more SiC. Toughening mechanisms, including crack deflection, branching and bridging, could be observed due to the residual stresses induced by the thermoelastic mismatches. Particularly, the introduced SiC–TiB2 agglomerates composed of interlocked SiC and TiB2 played a critical role in improving toughness. Accordingly, the B4C–SiC–TiB2 composite created with B4C-16 wt% TiSi2 achieved excellent mechanical performance, containing a Vickers hardness of 33.5 GPa, a flexural strength of 608.7 MPa and a fracture toughness of 6.43 MPa m1/2. 相似文献
20.
《Ceramics International》2019,45(15):18988-18993
Aiming to prepare high-performance electromagnetic interference (EMI) shielding materials, chopped carbon fibers were incorporated into mullite ceramic matrix via rapid prototyping process of spark plasma sintering (SPS). Results indicate that Cf/mullite composites with only 1 wt% of carbon fibers exhibit highest shielding effectiveness (SET) over 40 dB at a small thickness of 2.0 mm, showing great advantages both in terms of performance and thickness compared with many mature carbon/ceramic composites. The high EMI shielding properties mainly depend on two mechanisms of absorption and reflection in this present work. The enhanced absorption and reflection of electromagnetic wave are ascribed to the promotional electrical conductivity arising from the formation of conductive network by introduction of carbon fibers. Regarding enhanced electrical conductivity, notable intensified interfacial polarization on a large number of interfaces between mullite matrix and carbon fibers is also the key factor to the improved absorption, which makes absorption play a dominant role in the significant improvement of EMI SET. The Cf/mullite composites with excellent EMI shielding properties and thin thickness show great potential application as EMI materials. 相似文献