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Using Camellia oleifera shell as raw materials to preparative SiC ceramics by warm‐press forming and sintering is proposed in this paper. Warm‐press forming before preparing for the C. oleifera shell‐based SiC ceramics is beneficial to obtain the internal uniform and suitable pore structure of the cylindrical sample. Thermogravimetric analysis with differential scanning calorimetry was applied to analyze the pyrolysis behavior of C. oleiefra shell and phenolic resin. The scanning electron microscope and X‐ray diffraction were used to investigate the properties of C. oleifera shell‐based SiC ceramics. Then, the response surface method was applied to establish a multivariate prediction model based on the process parameters of warm‐press forming. And the regression equations of porosity and bending strength of COS‐SiC are obtained. The result demonstrated that the predicted and experimental values can be in good agreement for the model. By comparing the F‐value, it is found that the forming temperature and pressure during the process of warm‐press forming have a more significant influence on the porosity and bending strength of SiC ceramics. The optimization process parameters were obtained as follows: forming temperature 153°C, pressure 35 MPa, and holding time 30 min. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) is a new sintering method having shorter sintering time and higher densification speed than the traditional sintering methods. In this paper, the Si3N4/TiC ceramic tool material is sintered by SPS. The microstructure and mechanical properties of the material under different sintering parameters are compared. The sintering process of the material is then analyzed, and the best sintering parameters are obtained. Heat the material to 1600°C and keep the temperature for 15 min, then continue to heat to 1700°C and keep the temperature for 10 min, Si3N4/TiC ceramic tool material has high mechanical properties, its bending strength, fracture toughness, and Vickers hardness are 959 MPa, 8.61 MPa·m1/2, and 15.21 GPa, respectively. The scanning electron microscope (SEM) analysis shows that under this condition, the sintering additives and Si3N4/TiC material form the liquid phase, which makes the Si3N4 particles rearrange, dissolve, precipitate, and transform into rod shape β‐Si3N4. In addition, under the action of pulse current and external pressure, electric sparks are generated between TiC particles, which allows the material transfer and particle refinement. Therefore, the β‐Si3N4 has uniform grain size, and it is vertically and horizontally arranged in the structure, which makes the material have excellent mechanical properties. [ABSTRACT FROM AUTHOR]

In this paper, SiC coating was prepared using the polymer‐derived ceramic method; then the effect of nano‐alumina as a filler material was studied. First of all, polycarbosilane(PCS) was dissolved in xylene; after that, different amounts of nano‐alumina particles were added to the solution. The coating was deposited on the alumina substrate using the dip‐coating method; this was followed by sintering at 1200℃. The phase content and microstructure of the samples were studied by X‐ray diffraction and scanning electron microscope methods, respectively. Nanohardness, Young's modulus, and coating adhesion were investigated by a nanoindentation method. The sheet resistance was evaluated using the four‐point probe technique; also, the wear resistance of the coating was studied by applying the pin‐on‐disk method. It was found that the addition of the nano‐alumina filler up to 20 wt% drastically improved the adhesion and wear resistance of the SiC coating. [ABSTRACT FROM AUTHOR]

A 3D architecture carbon fiber preform, specifically fine‐woven cloth and punctured felt preform, is used to manufacture a novel advanced Cf/C‐SiC‐ZrC composite. The composite matrix is produced by chemical vapor infiltration (CVI) plus precursor infiltration and pyrolysis (PIP) process and finalized by using a chemical vapor deposition (CVD) of SiC coating to make the final density of the material reach 1.95 g/cm3. The organic precursors of SiC and ZrC have a weight ratio of 4:1 in a xylene solute. The composite mechanical properties, such as tensile, compression, bending, shear, and Z‐direction load bearing, are introduced under analysis to find possible applications for the composite. What is more, scanning electron microscope (SEM) images are employed to illustrate the failure behavior of the ceramic composite. The results showed that the punctured filament tows will be beneficial, not only for the composite to withstand compression force up to 308.6 MPa and shear strength to 18.14 MPa but also for the alternatively stacked weave piles and short fiber layers to support the punctured bundles, as well as to hold the composite structure under mechanical forces from different orientations, which is believed to reinforce the ceramic matrix for some high pressure and severe ablation applications. [ABSTRACT FROM AUTHOR]

The hardness and toughness of regenerated cemented carbides, in general, are contradictory. Therefore, it is critical to explore regenerated cemented carbides with both high hardness and high toughness. In this study, regenerated WC‐8‐wt% Co cemented carbide with SiC nanowhisker were prepared by low‐pressure sintering. The influence of SiCw contents on the microstructure and mechanical properties of regenerated WC‐8‐wt% Co cemented carbide was investigated. The results indicated that the hardness, density, flexural strength, and fracture toughness of regenerated cemented carbide first increased and then decreased with the addition of SiCw. The Vickers hardness, density, flexural strength, and fracture toughness could reach 1575 HV, 14.6 g/cm3, 2204 MPa, 16.85 MPa·m1/2, respectively, with SiCw content 0.5 wt%, which were increased by 14.4%, 0.7%, 12.2%, and 17.3%, respectively, when compared with the regenerated cemented carbide without SiCw. The lowest friction coefficient and the best wear resistance could be also reached when 0.5‐wt% SiCw was added. The fracture mechanism of the regenerated cemented carbide contained both transgranular and intergranular fracture through the microscopic observation of fracture surface via scanning electron microscope. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the influence of surface treatments and artificial aging on surface roughness (Ra), phase transformation, and flexural strength of yttria‐stabilized tetragonal zirconia polycrystalline (Y‐TZP) ceramics. Two‐hundred and eighty specimens from four types of Y‐TZP were divided into seven groups, according to the surface treatments and aging used: control, air‐abrasion, air‐abrasion + aging, grinding, grinding + aging, erbium: yttrium‐aluminum‐garnet (Er:YAG) laser, Er:YAG laser + aging. The Ra values were measured using a profilometer. X‐ray diffraction (XRD) analysis was performed to determine phase transformation. Specimens were subjected to a three‐point bending test and loaded until fracture. Scanning electron microscope (SEM) and atomic force microscope (AFM) analyses were performed on one specimen per group. Grinding and air‐abrasion groups exhibited higher Ra values than the others (P < 0.05). The differences in the roughness and flexural strength values between the laser and control groups were not significant. For all materials, the highest amount of monoclinic phase was found after air‐abrasion. Grinding groups showed lower flexural strength values compared with the control groups (P < 0.05), while there was no significant difference between the control and air‐abrasion groups. Aging did not affect the roughness and flexural strength (P > 0.05). The grinding process is not recommended in clinical usage for Y‐TZP because of the remarkable decrease in flexural strength and reliability. [ABSTRACT FROM AUTHOR]

Abstract: In this work, TiN‐based cermets with excellent performance and uniform microstructure were successfully manufactured by conventional vacuum sintering with 0‐5 wt% carbon addition at 1500°C. Influence of carbon addition on the microstructure and mechanical properties of cermets was investigated by scanning electron microscope, transmission electron microscope, X‐Ray diffraction, electron probe microanalysis, and mechanical tests. The results showed that small amount of carbon helped to improve significantly the wettability between TiN and Ni/Co, leading to well‐distributed structure and perfect core‐rim phases. As the carbon content increased from 0 to 5 wt%, mechanical properties of cermets increased initially, displayed a maximum and then decreased. For the experimental conditions considered, the cermets with 3 wt% carbon addition revealed best mechanical properties. The relative density, the transverse rupture strength, fracture toughness, and Rockwell hardness of the cermets were 99.78%, 1836 MPa, 14.7 MPa m1/2, and 88, respectively. [ABSTRACT FROM AUTHOR]