Papers by Keyword: Conductive Ceramic

Abstract: Fcc-TiBCN powder synthesized by boronizing of Ti was pressured into monolithic block by hot pressing (HP) method. Then the block material was machined by wire-cut EDM. The machinability and the material removal mechanisms were discussed of Fcc-TiBCN block in wire-cut EDM. Results show that the machinability of Fcc-TiBCN is satisfying. The discharge current has little relationship on surface roughness in the range of factory-adjusted optimum settings. The discharge duration and pulse interval time play an important role on the quality of machined surface and EDM machining efficiency. In order to obtain excellent quality of the machined surface, the number of power tube turned on can not exceed 6, and the pulse interval time must be as long as possible. The mini roughness of machined surface is 0.4μm～0.6μm as the number of power tube turned on is 5, the pulse interval time and discharge duration is set in the range of 20～22μs and 65～75μm, respectively. There are three material removal mechanisms of TiBCN conductive ceramic in the EDM machining process: spalling, melting and evaporation. Spalling is the main mechanism resulted by thermal stress superposing.

Abstract: Multiple target magnetron sputtering technique was employed for the deposition of (Cr,V)2AlC thin films, on the substrate of Si wafer at temperatures ranging from ambient to 840 K. The chemical composition and crystal structure of the deposited thin films were analyzed, surfaces as well the cross sections observed. The experimental results demonstrated that the temperature of the substrate does not affect the chemical composition of the deposited thin films. Deposition at room temperature or moderate elevated temperatures was found to result in amorphous films, whereas crystalline MAX phase thin films were obtained at high temperature. The transition of the substrate temperature was found to be around 743 K. The thin films deposited at temperatures below the transition showed the featureless flat surfaces. At high substrate temperatures, crystalline MAX thin films were formed. When deposited at temperatures near the transition, amorphous/nanocrystalline double layer thin films were deposited.

Abstract: Some materials have been applied in many surrounding conditions as sensors, electronic devices and other applications. Inexpensive and reliable temperature and flow measurement are important in many applications including, for example, environmental monitoring and control, indoor air conditioning, weather forecasting, automotive and aerospace systems. Special ceramics are an example of such materials. Neodymium-Barium-Copper is a special ceramic that has high electrical conductivity and airflow sensor characteristics. This property is influenced by high energy milling of the powder, when it is not sintered. To evaluate the influence of this type of milling it was carried out an analysis of particle size as a function of milling time. SEM images and granulometric analysis showed significant reduction of particle size with the increase of milling time. For longer times of milling the mixture of precursor powders is favored, resulting in better homogeneity of the ceramic. This is reflected in the properties of airflow sensor.

Abstract: Copper-plated TiB2-Cu-graphite composite, Cf-TiB2-Cu-graphite composite and Cf-copper-plated TiB2-Cu-graphite composite with the same TiB2 content were prepared by the powder metallurgy method. Physical and mechanical properties of these composites were tested. The dry friction tests of the composites under sliding velocity of 10m/s and load of 4.9N were conducted for 36h. The results show that the properties of the Cf-copper-plated TiB2-Cu-graphite composite such as electric conductivity, hardness, bending strength and wear resistance are increased remarkably than those of either Cf-TiB2-Cu-graphite or copper-plated TiB2-Cu-graphite composites.

Abstract: Material removal mechanisms of Al2O3-based conductive ceramics machined by electric discharge milling in deionized water are investigated. The main components of conductive ceramic samples are Al2O3 (80%), TiC (11%) and WC (9%). The material removal mechanisms by low electric discharge energy are mainly spalling and melting. The material removal mechanisms by high electric discharge energy are mainly melting, evaporation and spalling. With high discharge energy and insufficient cooling conditions, chemical reactions will happen, where TiC and WC are oxidized to dielectric TiO2 and WO3, which will slow down the electric discharge milling processand finally make it stopped.