The Mg_(2)Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction.This paper studies the effects of holding time and reaction temperature on the particle size and the properties of th...The Mg_(2)Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction.This paper studies the effects of holding time and reaction temperature on the particle size and the properties of the material,and also studies effects of doping elemental Sb,Te and their doping seqence on the properties of the material.The result shows that excessively high temperature and elongated holding time of solid-state reaction are harmful,there is a range of particle size to ensure optimum properties and the doping sequence of Sb or Te without influencing the properties.展开更多
An investigation was made on the influences of mechanical stirring on microstructure of hyper-eutectic Al-30%Si alloy (inmass fraction) during solidification. The primary Si crystals formed in the alloy melt were grad...An investigation was made on the influences of mechanical stirring on microstructure of hyper-eutectic Al-30%Si alloy (inmass fraction) during solidification. The primary Si crystals formed in the alloy melt were gradually changed from elongated platelets tonear-spherical shapes by mechanical stirring. The spheroidization of primary St crystals occurs by the mechanism of bending and fractureof Si platelets, wear and collision between Si crystals, and coalescence of small Si particles. The influence of under-cooling and coolingrate of the alloy melt on primary Si crystals of semi-solid processed alloys is investigated as well. The increase of under-cooling andcooling rate decreases the size of primary Si crystals.展开更多
Solid-state crystallization process and mechanism of B-Al-ZSM-5 zeolite from a dry gel of B2O3. A12O3 ? SiO2 in the mixture of ethylamine and water vapour were studied by11B,27Al,29Si,13C MAS NMR, XRD and IR. The extr...Solid-state crystallization process and mechanism of B-Al-ZSM-5 zeolite from a dry gel of B2O3. A12O3 ? SiO2 in the mixture of ethylamine and water vapour were studied by11B,27Al,29Si,13C MAS NMR, XRD and IR. The extranetwork trigonal BO3 units in the gel play an important role in the process of crystallization. The change of chemical environment around Al atoms is complicated in the process of crystallization. Octahedral Al-O groups existing in the intermediate products do not appear in both the initial gel and final product. Silicon is mainly present as hydroxyl compounds, and the extrastructural Si-O groups detected in the process of crystallization disappear after complete crystallization. Ethylamine plays the role of both template and reactant. It acts with the boron-, aluminum-, and silicon-hydroxyls through hydrogen bonding and promotes the crystallization process. The relative crystallinity of the final & A1-ZSM-5 product is about 93% as measured with11B MAS NMR and IR.展开更多
文摘The Mg_(2)Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction.This paper studies the effects of holding time and reaction temperature on the particle size and the properties of the material,and also studies effects of doping elemental Sb,Te and their doping seqence on the properties of the material.The result shows that excessively high temperature and elongated holding time of solid-state reaction are harmful,there is a range of particle size to ensure optimum properties and the doping sequence of Sb or Te without influencing the properties.
文摘An investigation was made on the influences of mechanical stirring on microstructure of hyper-eutectic Al-30%Si alloy (inmass fraction) during solidification. The primary Si crystals formed in the alloy melt were gradually changed from elongated platelets tonear-spherical shapes by mechanical stirring. The spheroidization of primary St crystals occurs by the mechanism of bending and fractureof Si platelets, wear and collision between Si crystals, and coalescence of small Si particles. The influence of under-cooling and coolingrate of the alloy melt on primary Si crystals of semi-solid processed alloys is investigated as well. The increase of under-cooling andcooling rate decreases the size of primary Si crystals.
文摘Solid-state crystallization process and mechanism of B-Al-ZSM-5 zeolite from a dry gel of B2O3. A12O3 ? SiO2 in the mixture of ethylamine and water vapour were studied by11B,27Al,29Si,13C MAS NMR, XRD and IR. The extranetwork trigonal BO3 units in the gel play an important role in the process of crystallization. The change of chemical environment around Al atoms is complicated in the process of crystallization. Octahedral Al-O groups existing in the intermediate products do not appear in both the initial gel and final product. Silicon is mainly present as hydroxyl compounds, and the extrastructural Si-O groups detected in the process of crystallization disappear after complete crystallization. Ethylamine plays the role of both template and reactant. It acts with the boron-, aluminum-, and silicon-hydroxyls through hydrogen bonding and promotes the crystallization process. The relative crystallinity of the final & A1-ZSM-5 product is about 93% as measured with11B MAS NMR and IR.
