High-Performance Ceramics III

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Authors: Yong Zheng, Wen Jun Liu, Quan Yuan, Lei Wen, Wei Hao Xiong
Abstract: Several Ti(C,N)-based cermets with different grain growth inhibitor were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX). The microstructure and mechanical properties of a cermet as a function of the content of the typical grain growth inhibitors, such as vanadium carbide (VC) and chromium carbide (Cr3C2), was revealed. VC addition could remarkably refine the grains, but it reduced the wetting of the ceramic grains by liquid metal during sintering. Thus it still reduced the performances of the cermet. Cr3C2 addition was found to inhibit grains from growing to lower extent during sintering. However it reduced the wetting of the ceramic grains by liquid metal slightly. Most of chromium element congregated in the rim phase and improved the plasticity of the rim. With Cr3C2 added properly, the performances of the cermets were improved remarkably.
Authors: Xian Juan Ni, Long Hao Qi, Wei Wang, Wei Pan
Abstract: In this paper, the Ti(C,N)-based cermets were fabricated with ultrafine Ti(C,N) powders and metal binders Mo and Ni, in which the ratio of Mo to Ni was 1:1 and total metal content ranged from 10wt% to 20wt%. The specimens were first CIP and pressureless sintered at various temperatures ranged from 1450°C to 1600°C and then treated at 1350°C for 20mins by HIP at the pressure of 140MPa. Results revealed that Post-HIP treatment could dramatically improve the density of specimens if their densities after pressureless sintering could reach the required standard. At the same sintering temperature, the grains became finer with increasing metal contents. The grain sizes increased dramatically with increasing sintering temperature from 1550°C to 1600°C. Compared to those obtained by hot pressing, the cermets obtained by pressureless-HIP sintering had better mechanical properties.
Authors: Yan An Wang, Ke Xin Chen, He Ping Zhou
Abstract: Titanium carbonitride powders were synthesized directly by a combustion synthesis process between titanium and carbon in a nitrogen atmosphere. The relationships between properties of the final product and the combustion reaction parameters were systematically investigated. Especially, the effects of nitrogen pressure on the phase formation and microstructure of the as-synthesized products were experimentally investigated. The reaction mechanism of Ti(C,N) was proposed through quench experiment, the variation of combustion temperature on time and thermodynamics analysis.
Authors: Wei Ping Shen, Wen Ma, Shu-Yuan Gu, Ye Zhang
Abstract: TiC-Ti porous materials have been successfully prepared using combustion synthesis in this paper. Adiabatic temperature of Ti-C and Ti-C-TiC systems was calculated. As to the Ti-C system, the studies show that when the ratio of C/Ti is the range of 0.5-0.6, the pressure of protecting atmosphere is 2-4 MPa, and the density of green compact is about 60%, the synthesized sample exhibits excellent properties such as porosity of 40%, volume density of 2.6 g/cm3, compressive strength over 4 MPa. Pore size is as large as 5-25 µm and the majority pores belong to interconnected pore.
Authors: Ke Gang Ren, Ke Xin Chen, G.H. Liu, Hai Bo Jin, Xiao Shan Ning, He Ping Zhou
Abstract: In present works, the low cost TiO2 powders were partially introduced to raw mixture as playing roles of both reactant and dilution. The experimental results showed that increasing the ratio of TiO2 to titanium powders up to 70wt%, the combustion synthesis reaction could still proceed by self-sustained mode. Single phase of TiNxC1-x with ultra fine particle size could be prepared by using TiO2 as dilution. Influences of TiO2 addition on phase formation and microstructure of product were also investigated. It was found that the combustion temperature and as-synthesized TiNxC1-x particle size decreased as increasing the amount of TiO2 addition.
Authors: Chang Qing Hong, Xing Hong Zhang, Jie Cai Han, Qiang Xu, Xiao Dong He
Abstract: TiB2 -Cu cermet with the relative density of 92% was produced from titanium, boron and copper powders by combustion synthesis and subsequently pseudo hot isostatic pressing. To improve its mechanical and thermal physical properties, the two-time hot pressing sintering test was carried out at 1050°, 1090° and 1150°C respectively. The deformation behavior and variation of micro- structure and mechanical properties were investigated in detail. The results showed that the relative density and the flexural strength increase remarkably after two-time hot pressing. The relative density reaches 605.5MPa and the flexural strength reaches 96% when the two-time pressing temperature is at 1090°C, and the values increase 12% and 6% compared to that before two-time pressing.
Authors: Yue Feng Sun, Qiang Xu, Xing Hong Zhang, Jie Cai Han, Jin Huai Liu
Abstract: TiB2-Cu matrix composites from titanium, boron and copper powders were in-situ fabricated by exothermic reaction. The effect of the applied pressure on the mechanical properties of the composite was investigated. The results showed that when the applied pressure increasing, the relative density, bending strength, fracture toughness and hardness of the composites were on the increase due to the formation of fine microstructure and the improvement of densification with the pressure increasing. The high pressure is beneficial to the better mechanical properties.
Authors: Qiang Xu, Xing Hong Zhang, Jie Cai Han, Xiao Dong He
Abstract: Large-scale (Ti,Cr)B2-Cu composite from Ti, Cr, B and Cu powders was produced by combining combustion synthesis with Pseudo Hot Isostatic Pressing. The diameter of the synthesized product is 240 millimeter. The product was identified using X-ray diffraction and the result showed that only (Ti,Cr)B2 and Cu phases, without other phases, existed in the product. The analysis of the microstructure indicated that the skeletal structure had been formed in the (Ti,Cr)B2 solid solution phase. Fine (Ti,Cr)B2 reinforcement grew in near equivalent axis-like shape and some sintering neckings were found between the solid solution phases. The relative density of the synthesized product was 93.6% because the skeletal structure baffled the densification of the composite. The bending strength and fracture toughness of the product were 476 MPa and 6.8 MPa·m1/2 respectively.
Authors: Guo Gang Zhao, Fu Ming Deng
Abstract: Ni-P-CNTs composite coating were deposited by electroless plating. The factors which influenced the content of carbon nanotubes in deposits, such as the types of agitation, surfactants and carbon nanotubes concentration in the plating bath, were examined. The surface morphology, structure and properties, such as microhardness, wear resistance and friction coefficient of the -CNTs coating, were investigated. The results showed that the Ni-P-CNTs composite coating greatly increased the hardness and wear resistance and decreased the coefficient of friction with the increase of the content of carbon nanotubes in deposits, and the introduced carbon nanotubes did not change the structure of the Ni-P marix of the composite coating.
Authors: Hyun Ah Park, Hyun Seok Hong, Sun Keun Hwang, Chong Mu Lee
Abstract: Ternary Ti-Zr-N thin films were synthesized by rf-reactive sputtering in Ar–N2 plasma. Effects of the substrate temperature in the sputtering process on the microstructures of Ti-Zr-N thin films were investigated using SEM, TEM, XRD and AES techniques. The hardness of the Ti-Zr-N film increases as the substrate temperature in reactive sputtering increases. The reactive sputtered Ti-Zr-N film is characterized as polycrystalline in nature with two dominant orientations of (111) and (200). A substrate temperature of 300°C is suggested for getting a densely packed film structure with the highest hardness.

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