Papers by Keyword: Process Temperature

Abstract: The agro-industrial sector of many countries generates considerable quantity of waste biomass and potential exploitation of this reside is necessary for economic and environmental reasons. Pakistan is an agricultural based country with widespread amount of crop residue generated annually. This study utilized rice husk, sawdust and bagasse residues to investigate the effects of microwave absorber loading on process temperature, pyrolysis products, and bio-oil composition using multimode microwave pyrolysis system operated at 300W and 2.54GHz. The results indicated that pyrolysis process temperature depends on the type of waste residue and microwave absorber loading. The maximum bio-oil yield of 22.41wt%, 33.61wt% and 19.1wt% were produced at 75wt% microwave absorber loading from rice husk, sawdust and bagasse, respectively. The D-Allose of 21.95 %area, dodecanoic acid of 71.22 %area and octasiloxane of 74.50 %area under GC-MS in rice husk, sawdust and bagasse bio-oils, respectively suggests potential use as chemical feedstock. Keywords: Waste biomass; microwave absorber; microwave assisted pyrolysis; process temperature; product distribution; bio-oil composition

Abstract: Chemical mechanical polishing (CMP) has become the preferred technology to achieve global planarization of wafer surfaces. Especially in oxide CMP, mechanical factors have a greater effect on the removal rate than chemical factors. So, the effects of mechanical parameters in CMP can be expressed as friction force and heat caused by friction. The friction force can be evaluated by a CMP friction force monitoring system and process temperature can be obtained by an infrared rays (IR) sensor. Furthermore, friction energy can be calculated from the friction force monitoring system. In this paper, research on the correlation between frictional and thermal characteristics of SiO2 slurry and CMP results was conducted. This data, which was obtained by using integrated monitoring system for CMP, will lead to the efficient prediction of CMP results.

Abstract: SiC has been extensively studied for high temperature components in advanced energy system and gas turbine because of its excellent high temperature mechanical properties and good thermal-chemical stability etc. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, SiCf/SiC composites can be considered as a promising for various structural materials, because of their good fracture toughness compared with monolithic SiC. But, high temperature and pressure lead to the degradation of the reinforcing fiber during the hot pressing. Therefore, reduction of sintering temperature and pressure is key requirements for the fabrication of SiCf/SiC composites by hot pressing method. In the present work, monolithic Liquid Phase Sintered SiC (LPS-SiC) was fabricated by hot pressing method in Ar atmosphere at 1800oC under 20MPa using Al2O3, Y2O3 and SiO2 as sintering additives. The starting powder was high purity β-SiC nano-powder with an average particle size of 30nm. The characterization of LPS-SiC was investigated by means of SEM and three point bending test. Base on the composition of sintering additives-, microstructure- and mechanical property correlation, the compositions of sintering additives are discussed.

Abstract: SiC materials have excellent high temperature strength, low coefficient of thermal expansion, good resistance to oxidation and good thermal and chemical stability etc. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. Therefore, in the interests of safety, we are required to measure fracture toughness of materials. In the present work, monolithic Liquid Phase Sintered SiC (LPS-SiC) was fabricated by hot pressing method under 20MPa using sintering additives at different temperature such as 1760oC, 1780oC, 1800oC and 1820oC. The starting powder was high purity β-SiC nano-powder with an average particle size of 30nm. Compositions of sintering additives were Al2O3 / Y2O3 = 0.7 and 1.5 (wt. %). Monolithic LPS-SiC was evaluated in terms of sintering density, hardness and fracture toughness through indentation fracture method by the Vickers hardness tester. Sintered density, hardness and fracture toughness of fabricated LPS-SiC increased with the increase of sintering temperature. They are higher than those of fabricated SiC by the chemical vapor deposition method.

Abstract: SiC materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine. SiCf/SiC composites are promising for various structural materials. But, high temperature and pressure lead to the degradation of the reinforcing fiber during the hot pressing. Therefore, reduction of the process temperature and pressure is key requirements for the fabrication of SiCf/SiC composites by hot pressing method. In the present work, monolithic LPS-SiC was fabricated by hot pressing method at various temperatures. The starting powder was high purity β-SiC nano-powder with an average particle size of 30nm. Compositions of sintering additives were Al2O3 / Y2O3 = 0.7 and 1.5 (wt.%). Monolithic LPS-SiC was evaluated in terms of sintering density, micro-structure, flexural strength, elastic modulus and so on. Sintered density, flexural strength and elastic modulus of fabricated LPS-SiC increased with increasing the process temperature. Particularly, relative density of LPS-SiC fabricated at 1820oC with additive composition of Al2O3/Y2O3=1.5(wt.%) was 95%. Also, flexural strength and elastic modulus were 900MPa and 220GPa, respectively. In the fracture surface of this specimen, the size and shape of SiC grains grew up and changed. Also, tortuous crack paths and occurrence of interfacial debonding were observed.