Papers by Keyword: Ceramic Composite

Abstract: This study investigates the piezoelectric properties of a composite comprising polar hydroxyapatite (HA) and BaTiO₃ using an analytical model. The analysis covers the piezoelectric coefficients d₃₃ ​and d₃₁, and the specific acoustic impedance. The findings reveal that HA exhibits an unconventional d₃₃​ behavior, while the composite demonstrates a decrease in d₃₁​ and an increase in d₃₃​, with minimal BaTiO₃ content achieving d₃₃​ values similar to those of human bone (< 1 pC/N). Additionally, the d₃₁ coefficient of HA showed an unconventional behavior, highlighting its potential usage in the transverse direction. The impedance also increases from 23.5 MRayls to 31.5 MRayls, which improves acoustic wave transmission for medical imaging and therapeutic devices. These results highlight the composite's promise for bone regeneration, implantable ultrasound transducers, and energy harvesting applications.

Abstract: In this study, B₄C-TiB₂ ceramic composites were manufactured by hot pressing method. The raw materials for the in-situ synthesis of TiB₂ were TiO₂ and TiC. After being sintered at 1900°C for 60min under a pressure of 30MPa, compact composites samples with a TiB₂ volume fraction range from 0 to 11.05% were prepared. The relative density, fracture toughness and flexural strength of different sample were tested. Microstructures on the fracture surface were studied by SEM. The result shows that B₄C-TiB₂ ceramic composites sintered from B₄C-TiC had a better mechanical property than the one sintered from B₄C-TiO₂. When the content of TiB₂ (reacted from TiC) was 11.05vol.%, the strength and toughness of B₄C-TiB₂ ceramics can reach 598MPa and 6.45MPa·m^1/2. The toughening mechanisms of B₄C-TiB₂ composites include micro-crack toughening and energy consumption by the pulling out process of second phase.

Abstract: The article is devoted to tribological studies of a ceramic composite with a zirconia-based die in order to replace carbide wire drawing dies with ceramic. Sliding friction was done according to the scheme finger-disk without lubrication and with lubrication. The wear rate and friction coefficients were determined, on the basis of which it is proposed to produce portage dies-blanks from zirconium ceramics. The influence of sintering temperature on the mechanical properties of ceramics, especially cracking resistance, was studied. The optimum sintering temperature was determined by the criterion of fracture toughness. The formation of defects after the final firing was investigated. It was found that sintering at a temperature of 1600 ° C is more promising. An trial batch of zirconium ceramic dies showed positive results in the process of drawing copper wire in industrial situations.

Abstract: The possibility of obtaining effective wall materials and technological lightweight products for high-temperature insulation by introducing the expanded vermiculite into the ceramic mass is investigated. Mineralogy of used clays and vermiculites was studied. They are represented by minerals of the same class, and therefore weak adhesion of smooth surfaces of vermiculite grains is compensated by common genetic origin with the matrix of the basic material of the composite. Thermotechnical studies of the process of swelling of vermiculite in a quartz furnace showed that to obtain a relatively high mechanical strength of vermiculite grains, it is necessary to select the maximum temperature and the mode of swelling, so that the planar shape of vermiculite plates remains and there is no pronounced warping. The degree of thermal delamination is influenced by the particle size, the increase of which entails a deterioration in physical and mechanical properties. The introduction of a high percentage of vermiculite additives in the charge allows to obtain lightweight thermal insulation products.

Abstract: This paper introduced a novel carbon fiber reinforced inorganic polymer non-sintering ceramic composite. It is composed of a low temperature curing material system, and can be manufactured by a traditional process for resin matrix composites. According to relevant test standards, the performances including the mechanical properties, the coefficient of linear expansion and the ablation ration were studied. The results show that the tensile strength is more than 150MPa, the bending strength is more than120MPa, the average coefficient of linear expansion is less than 0.213×10^-6/°C(between room temperature and 800°C), the ablation ratio is less than 0.0715mm/s, the mass retention ratio after ablation at 1000°C for 600s is less than98%. The composite could be used for the micro ablative in large area thermal protection such as national defense, aircraft and so on.

Abstract: Development of creep-resistant 8mol% Yttria-stabilized Zirconia (YSZ) ceramic has received much interest due to its potential use in fuel cells and thermal barrier coatings. In this research, Spark Plasma Sintering was used to develop a high-density 10 mol% La₂0₃ + YSZ composite. Compressive creep testing was performed at 1300 oC at 45 – 78 MPa load. The mechanism of plastic deformation of the composite was studied using Scanning Electron Microscopy and X-Ray Diffraction. The results suggest that lattice diffusion and grain boundary sliding were the active creep mechanisms.

Abstract: The processing methods, strengthening methods, water-proof coating procedures, and some ways to improve the transmission of microwaves have been reviewed in relation to fused silica ceramics and their composites for radome applications. Fused silica ceramics are characterized by a residual porosity (up to 18%), low dielectric constant (3.06-3.32), low loss tangent (0.00053-0.0065), excellent thermal properties, but low mechanical strength (37-65 MPa). To achieve higher mechanical strength and better transmission efficiency, new randome materials would be those engineered composites consisting, for instance, of a dense layer-porous core structure, a continuous fiber reinforcement, a multilayered structure, and/or frequency selective surface (FSS) layer (s)/metamaterials.

Abstract: ZrB₂-SiC ceramic composites with the addition of carbon black were fabricated by hot pressed sintering at 1900 °C for 60 min at a uniaxial pressure of 30 MPa in an argon atmosphere. The mechanical properties of ZrB₂-SiC ceramic composites were improved, adapting to the use requirements of ceramic parts. The precision electromachining technology of complicated structure components was investigated. The processing surface roughness was evaluated.

Abstract: This work reports on a novel route to produce porous matrixes for fibre reinforced ceramic matrix composites. This route relies on a reaction bonding process involving an intermediary carbide phase with subsequent oxidation. A slurry was prepared by mixing mullite powder, phenolic resin and aluminium powder in ethanol, which was used to impregnate Nextel fibres 610 (3M) by dip coating under ultrasonic vibration. The composites were vacuum-dried and submitted to a thermal treatment that consisted of a reaction step at 1250°C in Ar-atmosphere to convert the phenolic resin into carbon, which reacted with aluminium, leading to a carbide phase. The samples were then oxidized at 1250°C for 1h in air and subsequently sintered at 1300°C for 2h. Mechanical properties of composites and of matrix were determined at room temperature by 3-and 4-point bending tests, respectively. The microstructure of the composites was evaluated by optical-and scanning electronic microscopy, which revealed an apparent flawless microstructure.

Abstract: The resistance pressure was the key to solve these problems that long rod projectiles penetrated ceramic targets at high velocity. Based on the twin shear united strength theory and the A-T model, the penetration depth were calculated. But the calculation result didn’t agree with experiment data. So the tension-compression ratio was redefined to apply to the dynamics problems according to the experiment data. And satisfied results were obtained.