Properties Of Silicon Carbide Ceramics Research Articles

Ballistic properties of silicon carbide ceramic under weak support conditions

Ceramic materials play an important role in the composite armor structures used to defend against armor-piercing projectiles. Previous studies have focused on understanding ceramics' energy absorption and ballistic properties under strong constraints. Specifically, this research studied the ballistic properties of silicon carbide (SiC) ceramics under weak support conditions. Ballistic tests were performed to measure the resistance of SiC ceramics with different thicknesses against 7.62×54mmR armor-piercing (AP) projectiles under weak support conditions. The results were then simulated and analyzed using the LS-DYNA software. The study found that even under weak support conditions, the SiC ceramic has a higher ballistic efficiency than the 2024-T351 aluminum alloy. As the thickness of SiC increased from 3 mm to 15mm, the ceramic self-constraint effect on damaged parts was enhanced within ceramics, leading to an increase in energy dissipation during both the dwell and penetration phase, and more projectile kinetic energy transformed into the internal energy of the projectile and the energy of the ceramic. In particular, a 15 mm thick SiC ceramic can effectively defend against 7.62×54mmR AP projectiles. The study highlights the importance of considering the thickness and constraint effect of the ceramic itself when evaluating the ballistic properties of SiC ceramics with poor constraint conditions.

Effect of Particle Grading on Properties of Silicon Carbide Ceramics by Binder Jetting Printing

Effect of Particle Grading on Properties of Silicon Carbide Ceramics by Binder Jetting Printing

Особенности электрических свойств карбидкремниевой керамики с добавками карбида ниобия

Особенности электрических свойств карбидкремниевой керамики с добавками карбида ниобия

Effects of Starting Materials on Preparation and Properties of Pure SiC Ceramics via the HTPVT Method

The method of high temperature physical vapor transport (HTPVT) is an available approach to prepare silicon carbide (SiC) ceramics with high density and high purity. In the present work, α-SiC (6H-SiC) and β-SiC (3C-SiC) powders were used as starting materials respectively to fabricate SiC ceramics with HTPVT process, and the effects of starting materials on nucleation, density, microstructure and mechanical properties of SiC ceramics were investigated. It showed that at high temperature, the decomposition rate of β-SiC was higher than that of α-SiC, and at the initial nucleation stage, the average grain size of SiC crystal obtained with β-SiC starting materials was smaller than that with α-SiC starting materials, because higher vapour pressure of gas phase which decomposed by β-SiC starting materials facilitated nucleation and growth of SiC grains. Density of the resulted SiC ceramics using α-SiC and β-SiC as starting materials was 3.16 g·cm-3 and 3.17 g·cm-3, indicating close values, while, using β-SiC as the starting materials, the grain size was smaller, consequently, the flexure strength was higher. Increasing growth temperature from 2200°C to 2300°C, the densities and the flexure strength of the SiC ceramics using either α-SiC or β-SiC were decreased.

Optimisation of properties of silicon carbide ceramics with the use of different additives

Optimisation of properties of silicon carbide ceramics with the use of different additives

Mechanical and thermal properties of silicon carbide ceramics with yttria–scandia–magnesia

Two different SiC ceramics with a new additive composition (1.87 wt% Y2O3–Sc2O3–MgO) were developed as matrix materials for fully ceramic microencapsulated fuels. The mechanical and thermal properties of the newly developed SiC ceramics with the new additive system were investigated. Powder mixtures prepared from the additives were sintered at 1850 °C under an applied pressure of 30 MPa for 2 h in an argon or nitrogen atmosphere. We observed that both samples could be sintered to ≥99.9% of the theoretical density. The SiC ceramic sintered in argon exhibited higher toughness and thermal conductivity and lower flexural strength than the sample sintered in nitrogen. The flexural strength, fracture toughness, Vickers hardness, and thermal conductivity values of the SiC ceramics sintered in nitrogen were 1077 ± 46 MPa, 4.3 ± 0.3 MPa·m1/2, 25.4 ± 1.2 GPa, and 99 Wm−1 K−1 at room temperature, respectively.

Effect of carbon nanoparticle reinforcement on mechanical and thermal properties of silicon carbide ceramics

This research presents an analysis of the influence of graphene reinforcement on the thermal and mechanical properties of silicon carbide ceramics, at 2.5% (wt%) graphene content. The SiC composites, containing various carbon nanofillers (graphene oxide and graphene nanoparticles), were sintered by the classical two stage spark plasma sintering method. Two current modes were used, the continuous mode and the pulsed current mode. The results from photothermal radiometry and investigations of the mechanical properties showed that graphene additives significantly improve the thermal properties and toughness of material, sintered from a SiC powder. An 45% growth in the toughness was observed, which increased from 1.21 to 1.75 MPa/m1/2. The thermal diffusivity value also increased from 0.60 to 0.71 cm2/s and giving an improvement in thermal properties of 18%. The friction coefficient reached 7% giving an increase in value from 0.62 to 0.66. Microscopic investigations supported the photothermal radiometry (PTR) results. Whilst, thermal imaging revealed homogeneity of the local thermal properties of the products fabricated from the starting SiC powder.

Effect of Moisture on Properties of Silicon Carbide Ceramics

This paper studies the effect of moisture on the extrusion molding of silicon carbide ceramics. We set up the extrusion molding process by discussing the influence of moisture content on the performance of products, and we got the best proportion of ingredients through analyzing the important properties such as the anti-folding strength, porosity and pore size distribution. By studying the properties of the products, the influence of the number of additives is obtained.

Microstructure and mechanical properties of silicon carbide ceramics reinforced with multi-walled carbon nanotubes

A microstructure, a composition and mechanical properties of multi-walled carbon of nanotube-reinforced silicon carbide ceramics were examined. The amount of carbon nanotubes was up to 1% wt. Samples was prepared by spark plasma sintering. It has been found that the optimal sintering temperature is 2000°C with an exposure duration of 5 minutes and a pressure of 50 MPa. The effect of the CNT mass fraction on the Young modulus of silicon carbide ceramics composites was investigated for different temperatures and processing conditions of samples using ultrasonic techniques. It has been established that Young's modulus of ceramics decreases due to addition of CNT. Elastic properties of the composites cross section were characterized using nano-indentation. It has been revealed that the stiffness of the ceramics intergranular phase decreases due to addition of CNT.

Effect of grain growth on electrical properties of silicon carbide ceramics sintered with gadolinia and yttria

The effect of grain growth on electrical properties of SiC ceramics sintered with a new additive system (Gd2O3–Y2O3) was investigated. Hot-pressing of β-SiC with 3vol% Gd2O3–Y2O3 in a nitrogen atmosphere resulted in highly conductive SiC ceramics (∼10−2–10−3Ωcm), whereas hot-pressing of the same specimen in an argon atmosphere resulted in semi-insulating SiC ceramics (∼108Ωcm). This difference was due to the nitrogen (N) doping in SiC ceramics in the former case. The N-doping in SiC ceramics was achieved by grain growth of SiC grains via a solution-reprecipitation mechanism. The electrical resistivity of N-doped SiC ceramics decreased with an increase in grain size of SiC ceramics if there is no β→α phase transformation of SiC. The lowest electrical resistivity obtained was 8.9×10−3Ωcm after 6h sintering at 2000°C under an applied pressure of 40MPa in nitrogen.

Properties of silicon carbide ceramics from gelcasting and pressureless sintering

In this paper, dense silicon carbide ceramics were prepared by aqueous gelcasting and pressureless sintering using dextrin as the carbon source. The influence of carbon content and solid content on the microstructure and mechanical properties of green and as sintered SiC samples was studied. It was shown that the carbon content should be 1wt% or higher for the fully densification of silicon carbide ceramics. The influence of solid content on the green density and the mechanical properties of SiC ceramics was studied. The optimal solid content with 1wt% carbon as sintering additives is around 52vol%. Results showed that dextrin is an effective carbon source for developing SiC ceramics by aqueous gelcasting and pressureless sintering method.

Analysis of size effect and anisotropy of 6H – SiC thermal conductivity

Abstract Silicon carbide has been used in refractories, ceramics, and numerous high-performance applications with very good mechanical properties and high thermal conductivity. Silicon carbide composites have excellent potential as a low-activation structural material for fusion and industrial applications. Thermal properties of silicon carbide ceramics are important for the design and safe operation in these situations. To obtain the thermal properties of silicon carbide ceramics, based on the nonequilibrium molecular dynamics simulation method, the size effect on thermal conductivity in different directions is described. 6H – SiC thermal conductivities in the normal and tangential directions are predicted in a nanoscale cuboid system. It is found that there is an obvious size effect and anisotropy of thermal conductivity in different directions because of the impact of the boundary scattering. The normal and tangential thermal conductivity equations have been obtained as good power function expressions. The results show that boundary scattering is strong in phonon transport in different directions within thin film silicon carbide.

Preparation and properties of silicon carbide ceramics enhanced by TiN nanoparticles and SiC whiskers

SiC-based ceramics reinforced with SiC whiskers or/and TiN nanoparticles were produced by pressureless sintering. The introduction of SiC whiskers and TiN nanoparticles improved the densification and mechanical properties of the SiC-based ceramics. The relative densities of the SiC-based ceramics increased from 95.8% to 98.1%. Vickers’ microhardness was improved from 18.19 to 26.65 GPa for SiC/TiN. The highest of fracture toughness value achieved, 8.69 MPa m1/2, was for a SiC/TiN composite, while the value of flexural strength ranged from 416 to 1122.81 MPa.

Sintering behavior, microstructure and mechanical properties of silicon carbide ceramics containing different nano-TiN additive

Silicon carbide ceramics with nano-TiN additive were liquid phase sintered at 1950 °C for 15 min and subsequently sintered at 1850 °C for 1 h. The influence of the additive content on the sintering behaviors of silicon carbide ceramics was investigated by analyzing sintering behaviors, phase compositions, microstructure observation and mechanical properties testing. The results show that the addition of nano-TiN particles restrains the densification of silicon carbide ceramic, inhibits the grain growth of ceramic. And the reactions of TiN with SiC and Al 2O 3 to form new phases of TiC and AlN may benefit the silicon carbide ceramics in a certain range of nano-TiN addition. The silicon carbide ceramic with 5 wt.% of nano-TiN possesses high densification, uniform microstructure and superior mechanical properties. The toughening mechanism of nano-TiN on silicon carbide ceramic mainly comes from thermal residual stresses, crack deflection and crack bridging.

Improvement of piezoresistance properties of silicon carbide ceramics through co-doping of aluminum nitride and nitrogen

The piezoresistance coefficient was measured on co-doped silicon carbide ceramics. Evaluation samples of α-silicon carbide ceramics were first fabricated by glass capsule HIP method using powder mixture of silicon carbide and aluminum nitride with various ratios. The resultant aluminum nitride added silicon carbide ceramics were doped with nitrogen by changing the post-HIP nitrogen gas pressure. The lattice parameter increased with the amount of adding aluminum nitride indicating that the incorporated aluminum substituted smaller silicon atoms. After post-HIP treatment, lattice parameter then decreased with nitrogen gas pressure. The piezoresistive coefficient increased with the addition of aluminum nitride, it further increased with the nitrogen doping pressure.

On the Role of Grain-Boundary Films in Optimizing the Mechanical Properties of Silicon Carbide Ceramics

AbstractThrough control of the grain-boundary structure, principally in the nature of the nanoscale intergranular films, a silicon carbide with a fracture toughness as high as 9.1 MPa.m1/2 has been developed by hot pressing β-SiC powder with aluminum, boron, and carbon additions (ABC-SiC). Central in this material development has been systematic transmission electron microscopy (TEM) and mechanical characterizations. In particular, atomic-resolution electron microscopy and nanoprobe composition quantification were combined in analyzing grain boundary structure and nanoscale structural features. Elongated SiC grains with 1 nm-wide amorphous intergranular films were believed to be responsible for the in situ toughening of this material, specifically by mechanisms of crack deflection and grain bridging. Two methods were found to be effective in modifying microstructure and optimizing mechanical performance. First, prescribed post-annealing treatments at temperatures between 1100 and 1500°C were seen to cause full crystallization of the amorphous intergranular films and to introduce uniformly dispersed nanoprecipitates within SiC matrix grains; in addition, lattice diffusion of aluminum at elevated temperatures was seen to alter grain-boundary composition. Second, adjusting the nominal content of sintering additives was also observed to change the grain morphology, the grain-boundary structure, and the phase composition of the ABC-SiC. In this regard, the roles of individual additives in developing boundary microstructures were identified; this was demonstrated to be critical in optimizing the mechanical properties, including fracture toughness and fatigue resistance at ambient and elevated temperatures, flexural strength, wear resistance, and creep resistance.

Effects of SiO<sub>2</sub> and Rare-Earth Oxide Additions on Densification and Mechanical Properties of Silicon Carbide Ceramics

Effects of SiO<sub>2</sub> and Rare-Earth Oxide Additions on Densification and Mechanical Properties of Silicon Carbide Ceramics

Tailoring the mechanical properties of silicon carbide ceramics by modification of the intergranular phase chemistry and microstructure

Abstract Liquid-phase-sintered SiC has attracted increasing interest for its ability to form an in-situ toughened material and its potentially superior mechanical properties relative to the solid-state-sintered SiC. In the present work, a submicron-size β-SiC powder was densified with additives of various combinations of rare-earth oxides (RE 2 O 3 ; RE=La, Nd, Y and Yb) and alumina by hot-pressing, and the hot-pressed materials were further annealed at higher temperatures. The phase compositions, microstructures and mechanical properties of the hot-pressed and the annealed materials were characterized. It was found that the mechanical properties were strongly influenced by the type of the sintering additives. The additives also affected the microstructural development during annealing. While the fracture toughness of all the annealed materials continuously increased with increasing annealing temperatures, however, the flexural strength either increased or decreased with annealing temperatures, depending on the kinds of the RE 2 O 3 additives. By using appropriate rare-earth oxides, e.g. La 2 O 3 or Nd 2 O 3 , fracture toughness and flexural strength synergetically improved after an annealing treatment.

Mechanical properties and microstructure of biomorphic silicon carbide ceramics fabricated from wood precursors

Silicon carbide based, environment friendly, biomorphic ceramics have been fabricated by the pyrolysis and infiltration of natural wood (maple and mahogany) precursors. This technology provides an eco-friendly route to advanced ceramic materials. These biomorphic silicon carbide ceramics have tailorable properties and behave like silicon carbide based materials manufactured by conventional approaches. The elastic moduli and fracture toughness of biomorphic ceramics strongly depend on the properties of starting wood preforms and the degree of molten silicon infiltration. Mechanical properties of silicon carbide ceramics fabricated from maple wood precursors indicate the flexural strengths of 3441+/-58 MPa at room temperature and 230136 MPa at 1350C. Room temperature fracture toughness of the maple based material is 2.6 +/- 0.2 MPa(square root of)m while the mahogany precursor derived ceramics show a fracture toughness of 2.0 +/- 0.2 Mpa(square root of)m. The fracture toughness and the strength increase as the density of final material increases. Fractographic characterization indicates the failure origins to be pores and chipped pockets of silicon.