The paste was prepared by mixing MgO, microsilica and H2O in the presence of water reducer at different reaction ratios and temperatures, and characterized by XRD, DTA, TGA, IR, and solid-state 29Si NMR. The experimen...The paste was prepared by mixing MgO, microsilica and H2O in the presence of water reducer at different reaction ratios and temperatures, and characterized by XRD, DTA, TGA, IR, and solid-state 29Si NMR. The experimental results showed that, besides Mg（OH）2, magnesium silicate hydrate （M-S-H） was formed at a low temperature such as 25 and 50 ℃. At a high temperature of 100 ℃, Mg（OH）2 can be further transformed into M-S-H completely, for instance, within ca. 1 month in an excess of microsilica. The average composition and structure of M-S-H was mainly related to the reaction mixture and curing temperature and was discussed in detail.展开更多
It was proved that MgO and MicroSilica can react at room temperature, giving a hardened product primarily comprised of Mg （ OH ）2 and Magnesium Silicate Hydrate （ M- S- H ）. The reaction ratio and process and the ...It was proved that MgO and MicroSilica can react at room temperature, giving a hardened product primarily comprised of Mg （ OH ）2 and Magnesium Silicate Hydrate （ M- S- H ）. The reaction ratio and process and the chemical composion of M- S- H were studied and analyzed by QXRD and DTA- TG. The experimental results indicate that much Mg（ OH）2 and less M-S-H were formed at early period. After 7 days there is no change in the quantity of Mg（ OH）2, while M-S-H was increased slowly. The chemical composion of M-S-H would vary with the mix proportion in the hydrution process , but M1.32 SH2.37 is finally the approximute form.展开更多
Calcium aluminate cement bonded corundum castable specimens were prepared using brown fused corundum （8 - 5, 5 - 3, 3 - 1 mm ） , white fused corundum （ ≤ 1, ≤0. 045 mm）, micro-sized α-Al2O3 and microsilica as s...Calcium aluminate cement bonded corundum castable specimens were prepared using brown fused corundum （8 - 5, 5 - 3, 3 - 1 mm ） , white fused corundum （ ≤ 1, ≤0. 045 mm）, micro-sized α-Al2O3 and microsilica as starting materials. This work focused on investigating the relationship between the bond change in the castable matrix and the strength of the castable with 5 mass% microsilica or without microsilica after heat treatment at 110, 800 and 1 000 ℃, respectively. Chemical bond changes between the microsilica and hy- drates of calcium aluminate cement after drying at 110 ℃ or firing at 800 ℃ were investigated by XPS and FTIR. The results show that Si-O-Al bonds form be- tween the microsilica and hydrates of calcium aluminate cement after drying at 110 ℃ or firing at 800 ℃. Therefore, the increased strength of castable specimens is attributed to the formation of Si-O-Al bonds from 110 ℃ to 800 ℃.展开更多
The main objective of this work is to research complex physical-chemical processes of Al(l)-SiO2 interface and develop a new technology for producing foundry silumins based on amorphous microsilica obtained from silic...The main objective of this work is to research complex physical-chemical processes of Al(l)-SiO2 interface and develop a new technology for producing foundry silumins based on amorphous microsilica obtained from silicon production waste. Effective methods for producing hypoeutectic, eutectic, and hypereutectic silumins using amorphous microsilica were developed. Alloys with a silicon content of 7 wt.% were obtained by blowing preheated amorphous microsilica into the aluminum melt(t=900 ℃) along with the stream of argon followed by intense mixing. Alloys with a silicon content of 21 wt.% were manufactured by induction melting of a silicon-containing mixture(60% Si O2, 40%Al + 20%3 Na F·2 Al F3) subjected to the presintering when the amorphous microsilica was reduced to crystalline silicon. It is found that crystalline silicon, which is formed during the roasting of the tableted burden, is smoothly absorbed by the aluminum melt. Aluminum oxide, obtained during the redox reaction, dissolves in cryolite, after which aluminum and silicon are fused together and transferred to the melt. The calculation of the economic efficiency of producing silumins using amorphous microsilica demonstrates a quick project payback period, as well as a high level of its profitability.展开更多
基金Funded by the National "973 Project"(2009CB623104)the Fundamental Research Funds for the Central Universities(2009ZZ0044)the Funds of Key Laboratory of Advance Civil Engineering Materials of the Ministry of Education
文摘The paste was prepared by mixing MgO, microsilica and H2O in the presence of water reducer at different reaction ratios and temperatures, and characterized by XRD, DTA, TGA, IR, and solid-state 29Si NMR. The experimental results showed that, besides Mg（OH）2, magnesium silicate hydrate （M-S-H） was formed at a low temperature such as 25 and 50 ℃. At a high temperature of 100 ℃, Mg（OH）2 can be further transformed into M-S-H completely, for instance, within ca. 1 month in an excess of microsilica. The average composition and structure of M-S-H was mainly related to the reaction mixture and curing temperature and was discussed in detail.
文摘It was proved that MgO and MicroSilica can react at room temperature, giving a hardened product primarily comprised of Mg （ OH ）2 and Magnesium Silicate Hydrate （ M- S- H ）. The reaction ratio and process and the chemical composion of M- S- H were studied and analyzed by QXRD and DTA- TG. The experimental results indicate that much Mg（ OH）2 and less M-S-H were formed at early period. After 7 days there is no change in the quantity of Mg（ OH）2, while M-S-H was increased slowly. The chemical composion of M-S-H would vary with the mix proportion in the hydrution process , but M1.32 SH2.37 is finally the approximute form.
文摘Calcium aluminate cement bonded corundum castable specimens were prepared using brown fused corundum （8 - 5, 5 - 3, 3 - 1 mm ） , white fused corundum （ ≤ 1, ≤0. 045 mm）, micro-sized α-Al2O3 and microsilica as starting materials. This work focused on investigating the relationship between the bond change in the castable matrix and the strength of the castable with 5 mass% microsilica or without microsilica after heat treatment at 110, 800 and 1 000 ℃, respectively. Chemical bond changes between the microsilica and hy- drates of calcium aluminate cement after drying at 110 ℃ or firing at 800 ℃ were investigated by XPS and FTIR. The results show that Si-O-Al bonds form be- tween the microsilica and hydrates of calcium aluminate cement after drying at 110 ℃ or firing at 800 ℃. Therefore, the increased strength of castable specimens is attributed to the formation of Si-O-Al bonds from 110 ℃ to 800 ℃.
文摘The main objective of this work is to research complex physical-chemical processes of Al(l)-SiO2 interface and develop a new technology for producing foundry silumins based on amorphous microsilica obtained from silicon production waste. Effective methods for producing hypoeutectic, eutectic, and hypereutectic silumins using amorphous microsilica were developed. Alloys with a silicon content of 7 wt.% were obtained by blowing preheated amorphous microsilica into the aluminum melt(t=900 ℃) along with the stream of argon followed by intense mixing. Alloys with a silicon content of 21 wt.% were manufactured by induction melting of a silicon-containing mixture(60% Si O2, 40%Al + 20%3 Na F·2 Al F3) subjected to the presintering when the amorphous microsilica was reduced to crystalline silicon. It is found that crystalline silicon, which is formed during the roasting of the tableted burden, is smoothly absorbed by the aluminum melt. Aluminum oxide, obtained during the redox reaction, dissolves in cryolite, after which aluminum and silicon are fused together and transferred to the melt. The calculation of the economic efficiency of producing silumins using amorphous microsilica demonstrates a quick project payback period, as well as a high level of its profitability.
