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硅酸二钙烧成过程动力学参数测定 总被引:1,自引:1,他引:0
对硅酸二钙(C2S)形成过程的各项动力学参数进行了测定计算,得到了不同温度下SiO2转化率G与时间t的关系.采用了金斯特林格(Ginstling)方程作为固相反应模型,对C2S的形成过程进行描述;计算了不同煅烧温度下固相反应的反应速率常数K、钙离子的扩散系数D;得到C2S形成的表观活化能Ea为167.4 kJ·mol-1,指前因子A为20.94. 相似文献
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我国的水泥研究工作者利用红外光谱对水泥矿物性能分析方面了解得不多,很难见到有关这类文章的发表。一般认为,红外光谱主要应用于有机官能团的分析,其实对无机物的应用还要简单。本文就红外光谱应用于硅酸二钙多晶体鉴定进行了论述。 1 红外光谱概述当一束具有连续波长的红外光照射某物质时,该物质的分子就要吸收一部分光能,并将其变成另一种能量,即分子的振动能量和转动能。因此将其透过的光用单色器进行色散,以百分吸 相似文献
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硅酸二钙既是硅酸盐水泥熟料的主要矿物,也是硫铝酸盐水泥熟料的主要矿物,并且有可能成为吸收捕集二氧化碳材料的重要矿物。发展以硅酸二钙为主要矿物组成的低钙、低碳排放胶凝材料正在成为研究热点。本文在简述硅酸二钙结构及其晶型转变的基础上,综述分析了硅酸二钙在高温合成过程中外来离子对其结构与活性的影响;硅酸二钙在水化阶段液相中外来离子对其活性发挥的影响,以及利用硅酸二钙在结构上易发生碳化反应的特点,制备可吸收二氧化碳材料的现状。在此基础上,展望了硅酸二钙结构与活性研究及其应用的发展趋势。 相似文献
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采用分子动力学模拟研究了在真空和水溶液环境下聚乙二醇在β-2CaO·SiO2表面吸附的规律及其机理。在真空环境下聚乙二醇与β-2CaO·SiO2不同晶面的吸附强弱顺序依次为:(110)>(010)>(011)>(001)≈(101)>(100);而在水溶液环境下其吸附强弱顺序为:(010)≈(110)≈(001)>(011)>(101)>(100)。真空和水溶液环境下在343~363 K时温度对聚乙二醇与β-2CaO·SiO2(110)晶面相互作用时的单位面积吸附能影响不大,但当在聚合物链节数较小时单位面积吸附能随链节数的增加而明显增加。在水溶液的环境中,分别构造了β-2CaO·SiO2和聚乙二醇与水分子的径向分布函数,水分子与聚合物、β-2CaO·SiO2表面之间都存在吸附能,由于水分子较小,其对聚合物与晶面的吸附产生排斥作用,导致聚合物在水环境中与硅酸二钙晶体吸附能降低。 相似文献
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掺杂硅酸二钙对硫铝酸钙矿物形成的影响(英文) 总被引:1,自引:0,他引:1
借助化学分析方法、X射线衍射、差示扫描量热仪、扫描电子显微镜研究了硅酸二钙(C2S)对高温物相硫铝酸钙矿物形成过程的影响。结果表明:C2S的掺杂可提高各温度下的固硫率,促进熟料中游离氧化钙(f-CaO)的吸收,增加硫铝酸钙的生成量,降低硫铝酸钙的形成温度,从而改善生料的易烧性;同时可大大降低硫铝酸钙在高温下(≥1350℃)的分解。增大C2S掺量,硫铝酸钙晶粒变小且多,晶体完整且密实。 相似文献
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The kinetics of hydration of five C2SS cements at 0.83C/S were studied at 175 to 300°C. CSH(I) formed as the initial hydration phase in four cements and tobermorite in the other. Amounts of 1.32 and 1.74% CO2 in two cements caused total replacement of xonotlite by scawtite, while 0.34 and 0. 37 CO2 yielded negligible amounts of scawtite (if any). The equilibrium products in the two cements were scawtite and gyrolite at 175 and 200°C and scawtite and truscottite at 250 and 300°C. 相似文献
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F.A. Rodrigues 《Cement and Concrete Research》2003,33(6):823-827
This paper describes the synthesis of cements, chemically and structurally related to Ca2SiO4. Silica was obtained from rice hull after heating at 600 °C. Calcium oxide and small amounts of barium chloride were mixed in order to obtain a final (Ca/Si) or (Ca+Ba)/Si ratio equal to 1.95, 1.90, and 1.80, which is lower than in the conventional cement. The solids were mixed and ultrasonically treated for 1 h with a water/solid ratio of about 20. After drying and grinding, the mixtures were heated up to 1100 °C. It was possible, in some cases, to obtain a cementitious material. These cements are structurally related to β-Ca2SiO4 and the lower (Ca+Ba)/Si ratio obtained was 1.95. The initial chemical compositions of these cements are: (Ca1.83+Ba0.12)SiO4 and (Ca1.79+Ba0.16)SiO4. A further lowering in the (Ca+Ba)/Si ratio changes the nature of the silicates. 相似文献
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In the present work, we examine the simultaneous effect of iron and phosphorus additions on the calcium carbonate decomposition in CaCO3, SiO2, Fe2O3 and P2O5 mixtures at the molar ratio CaCO3/SiO2=2. The formation of the dicalcium silicate Ca2SiO4 is also studied. The temperatures of the decarbonation and the enthalpy evolution during the heating of the mixtures are measured. The additions of Fe2O3 and P2O5 oxides decrease the onset temperature of the CaCO3 decomposition. The energy consumption of decarbonation at about 835 °C is lowered when the dopant concentrations increase. Synthesized solid solutions are analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The free-lime quantity is determined by chemical analysis. The mineralogical analysis at room temperature of the products of the reaction shows the presence of iron-phosphorus-doped β, α′ and α-C2S modifications. 相似文献
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《Journal of the European Ceramic Society》2005,25(9):1507-1514
The beta- and gamma-dicalcium silicate (β- and γ-Ca2SiO4) ceramics were prepared by sintering β-Ca2SiO4 greens at 1100, 1300, and 1450 °C, respectively, after compacting with cold isostatic pressure. The phase transition from β- to γ-phase of polymorphic ceramics occurred at 1100–1300 °C. Bending strength and Vickers hardness of β-Ca2SiO4 ceramic sintered at 1100 °C were only 25.6 ± 3.8 MPa and 0.41 ± 0.05 GPa. In contrast, the mechanical properties of the γ-Ca2SiO4 were improved remarkably when the ceramics were sintered at 1450 °C, corresponding to bending strength, 97.1 ± 6.7 MPa; Vickers hardness, 4.34 ± 0.35 GPa, respectively. The ceramics were soaked in the simulated body fluid (SBF) for various periods were characterized by SEM, XRD, FTIR, and EDS analysis, and the results indicated that the carbonated hydroxyapatite (CHA) was formed on the surface of the ceramics within 3 days. In addition, cell attachment assay showed that the ceramics supported the mesenchymal stem cells adhesion and spreading, and the cells established close contacts with the ceramics after 1 day of culture. These findings indicate that the γ-Ca2SiO4 ceramic possesses good bioactivity, biocompatibility and mechanical properties, and might be a promising bone implant material. 相似文献
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Yan Wu Xiaolin Pan Qiwei Li Haiyan Yu 《International Journal of Applied Ceramic Technology》2020,17(3):1213-1223
In this paper, tobermorite was hydrothermally synthesized from the dicalcium silicate (C2S) in sodium silicate solution, and the crystallization and phase transition process were investigated in detail using XRD, Raman spectra, and SEM. The tobermorite is difficult to synthesize when the temperature is lower than 160°C because it gets converted into xonotlite (without Na2O) or pectolite (with Na2O) when the temperature is higher than 180°C. The crystallization process of tobermorite shows “S” trend with the increase in time, which can be divided into three stages: the nucleation stage, rapid crystal growth stage, and perfect crystal forming stage. During the crystallization, 90% of the crystallization of tobermorite is completed in the stage of rapid crystal growth. Raman spectra and SEM analysis show that with the increase in hydrothermal time, the C2S of monomer (Q0) is first converted into the calcium silicate hydrate of sheet (Q2 and Q3), and then continues to convert into tobermorite of chain (Q2). 相似文献
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A mathematical model has been developed to simulate the pultrusion process, namely the profiles of temperature and the degree of cure in both the axial and radial directions in a pultrusion die of cylindrical shape. For the study, the equations of continuity and energy transport, coupled with a kinetic expression for the curing reaction, were solved numerically, using a finite difference method. For the kinetic expression, we used an empirical expression of the form dα/dt = (k1 + k2αm)(1 ? α)n to describe the curing behavior of both unsaturated polyester and epoxy resins. Differential scanning calorimetry (DSC) was used to investigate the curing behavior of the following systems: unsaturated polyester resin/glass fiber, epoxy resin/glass fiber, and epoxy resin/carbon fiber. The results of DSC runs were used to determine the kinetic parameters, which enabled us to predict the effects on the pultrusion characteristics of the following variables: (1) the type of initiator; (2) the type of fiber reinforcement; (3) the type of resin; and (4) the pulling speed and hence the residence time. 相似文献
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以水玻璃(Na2O·SiO2)为硅源,以磷酸作为催化剂,经超临界二氧化碳干燥后得到了低密度(29.5 kg/m3)、
高比表面积(912 m2/g)、低导热系数[0.018 W/(m·K)]的二氧化硅气凝胶。通过测试水洗后溶液的电导率,系统分析了水的用量、水洗温度、水洗时间等因素对制备二氧化硅的水洗工艺除去钠离子的效率的影响。结果表明:使用5倍体积的水在40 ℃下水洗湿凝胶,经4次水洗之后能够去除91%以上的无机盐离子,缩短了水洗时间的同时避免了大量的水的使用。 相似文献