硅酸二钙烧成过程动力学参数测定

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.     

硅酸二钙多晶体的红外光谱鉴定

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     

硅酸二钙的结构与活性

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。     

聚乙二醇在硅酸二钙表面吸附的分子动力学模拟

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。     

y型硅酸二钙碳酸化反应动力学

硅酸钙矿物碳酸化胶凝材料是极具发展潜力的新型低碳建筑材料。在硅酸钙矿物中,γ型硅酸二钙具有较高的常温碳酸化反应活性。以γ型硅酸二钙润湿粉末为研究对象,探明了其碳酸化程度随反应时间、颗粒粒径、温湿度、分压和水固比等的发展规律,结合优化的缩核模型和经验方程,建立了碳酸化反应动力学方程。结果表明:动力学模型和实际结果的拟合程度良好,由于碳酸化产物的包裹阻碍溶出离子的扩散是碳酸化反应的主要控制因素。     

机械力化学作用对硅酸二钙晶体结构的影响

采用X射线衍射技术和红外光谱分析手段对β—C2S单矿物在高能球磨作用下的微观结构与化学键的变化进行了研究。结果表明，在机械力的持续作用下，不仅β-C2S的晶粒尺寸大小、显微应变和有效Beff参数增大．并显示出明确的阶段性，而且导致了Si-O键的断裂与重组、振动能提高和晶体的无序化，最终使β-C2S发生机械力化学变化，活性增强。     

掺杂硅酸二钙对硫铝酸钙矿物形成的影响

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。     

含氟硅酸三钙的水化

用化学分析、XRD、传导量热仪和测定抗压强度等手段研究了含氟C_3S的水化。结果表明,随着(?)含量的增加,1d龄期的水化程度、化学结合水、水化放热速率和抗压强度均降低,而3d后均提高。随(?)含量增加,液相中Ca~(2+)和OH~-离子浓度达最大值的时间推迟,(?)固溶量越大,时间推迟越明显。在1d特别是3d后,所有试样的Ca~(2+)和OH~-离子浓度均趋于相同。在C_3S水化时,外掺的CaF_2对液相中的Ca~(2+)和OH~-离子浓度和浆体抗压强度的影响均很小。     

β-硅酸二钙对腐殖酸钠的吸附特性

通过考察β-硅酸二钙(β-C2S)对腐殖酸钠的吸附动力学及热力学,研究了其对腐殖酸钠的吸附行为,并探讨了吸附前后β-C2S表面zeta电位的变化规律。结果表明:根据吸附等温曲线的相关数学模型拟合,得出β-C2S对腐殖酸钠的吸附过程符合Langmuir吸附等温式模型,同时符合二级吸附动力学。吸附自由能变为–20～0kJ/mol,表明此过程属于物理吸附和化学吸附共存,以物理吸附为主的自发吸热过程。表面zeta电位的测定表明在铝酸钠溶液中β-C2S表面带负电荷。     

磷硫复合掺杂对硅酸二钙晶型结构的影响

通过XRD、FT-IR测试方法,并结合Rietveld理论,深入分析了磷单掺及磷硫复掺对硅酸二钙(C2 S)晶型结构的影响规律.结果表明,磷单掺条件下,有效稳定硅酸二钙的最佳掺量为1.64％左右.当样品中含有1.88％左右SO3时,P2 O5最佳掺量为0.83％,说明SO3可以促进P2 O5的稳定活化效果.且与未掺杂样品相比,元素掺杂有效提高了[SiO4]的对称性.     

Hydrothermal reactions of dicalcium silicate and silica

The kinetics of hydration of five C₂SS 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.     

Synthesis of chemically and structurally modified dicalcium silicate

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: (Ca_1.83+Ba_0.12)SiO₄ and (Ca_1.79+Ba_0.16)SiO₄. A further lowering in the (Ca+Ba)/Si ratio changes the nature of the silicates.     

Elaboration and thermal study of iron-phosphorus-substituted dicalcium silicate phase

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.     

Development of a mathematical model for the pultrusion process

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 + k₂α^m)(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.     

气流干燥器的数学模型研究

在聚氯乙烯干燥过程中,目前通常采用的是气流-旋风两段式干燥,通过对固体干燥原理、干燥过程的分析,将干燥过程分为表面汽化干燥与升温干燥2个阶段,根据气流干燥器的特点,结合各个阶段传质、传热的特点,分段建立了传质速率、传热速率方程,物料衡算、热量衡算方程。通过对气流干燥器的分析研究,确定了计算机模拟过程中的各个参数,从而确立了气流干燥器的数学模型。