钙镁复合助熔剂对长平煤灰熔融特性影响研究

以高灰熔融温度长平煤为对象,分别向其中添加单助熔剂CaO、MgO和钙镁复合助熔剂,在高温还原性气氛下,分别利用X-射线衍射仪(XRD)、扫描电子显微镜-能谱仪(SEM-EDX)研究钙镁复合助熔剂对煤灰熔渣晶体矿物转化过程、微观形貌和微区化学组成的影响,揭示钙镁复合助熔剂的助熔机理.结果表明:添加6％钙镁复合助熔剂(WCao/WMgo=1),可将煤灰熔融温度降至1297℃,且助熔效果优于单助熔剂CaO、MgO;煤灰熔融过程中,离子半径较小的Ca2+、Mg2+容易进入空隙中,引起硅酸盐结构重组,分别形成架状硅酸盐钙长石、岛状硅酸盐镁橄榄石、镁堇青石等;钙长石与镁橄榄石等镁质矿物之间低温共熔体的生成,是钙镁复合助熔剂能够显著降低煤灰熔融温度的主要原因.     

镁钙耐火材料与钢水作用的热力学研究

通过扫描电镜能谱分析,研究了镁钙耐火材料与ARO16钢的作用,通过热力学数据,结合试验结果,进行了热力学研究,结果表明:含游离CaO的镁钙耐火材料在1600℃下与ARO16钢发生作用,在耐火材料表面形成反应层,推测有CaS、3CaO·Al2O3、CaO·Al2O3、CaO·2Al2O3、CaO·6Al2O3、3CaO·SiO2、2CaO·SiO2、3CaO·2SiO2、MnO、FeO等物质生成.     

CO2处理镁钙砖表面研究

本文研究了利用CO2处理镁钙砖表面的防水化效果,利用XRD检测了新生成相的矿物组成,采用SEM观察和分析了新生成相的微观形貌分布,应用煮沸实验法测试试样的防水化效果,得出以下结论:用CO2处理镁钙砖表面,当CO2流量为5 L/min,反应时间为60 min,处理温度为600℃时镁钙砖的抗水化效果最好;当CO2流量为5L/min,反应温度为600℃时,反应时间越长镁钙砖的抗水化效果越好;通过XRD衍射分析结果可知,不同温度处理后镁钙砖表面都生成了CaCO3,反应温度越高衍射峰越强,CaCO3含量越大;通过扫描电镜分析可知CO2处理后的镁钙砖表面反应层为CaCO3,并且随着反应温度的升高,试样表面的反应层厚度逐渐增加.     

氩氧脱碳炉用后镁钙砖的资源再生利用

以氩氧脱碳(AOD)炉用后镁钙砖为原料,配以电熔镁砂在1873K保温2h,分别合成出MgO含量(质量分数)分别为80%、70%、60%的再生镁钙砖样品。研究了样品物相、显微结构、常温力学性能、高温抗折强度与抗水化性能。结果表明:样品组成主要为MgO、CaO、少量Ca3SiO5和4CaO Al2O3 Fe2O3。MgO以较大颗粒连续弥散分布,CaO被MgO包裹呈孤岛状均匀分布。随用后镁钙砖加入量的增加,常温力学性能增强,高温(1373K)抗折强度仅在MgO含量为60%的样品中出现明显下降。样品具有良好的安定性和抗水化性能,最大水化质量增加率仅为0.82%,随用后镁钙砖加入量的增加,抗水化性能变差。     

井陉钙镁企业成气候

在河北并陉县采访钙镁企业时，记者看到一辆辆装满钙镁产品的货车正陆续驶出井陉，运往全国30多个省市，有的还远销美国、日本、欧盟等十多个国家和地区。并陉县工业局副局长张云林告诉记者，素有“中国钙镁之乡”的井陉县依靠技术创新，不断加快钙镁企业提档升级，有效地促进了钙镁产业集群发展。截至目前，井陉钙镁企业已达115家，钙镁产量已达145万吨，占全国市场份额的1／3，初步形成了全国最大的钙镁化工基地。     

H2C2O4和CO2复合表面处理镁钙砂及其浇注料的性能

首先采用H2C2O4溶液对镁钙砂进行表面浸溃,然后在CO2气氛下于450℃1 h热处理而制得抗水化的镁钙砂,再以此镁钙砂和电熔镁砂为原料制成不同CaO质量分数(0、10%、20%、30%)的浇注料,并研究表面处理后镁钙砂的抗水化性,镁钙浇注料的抗水化性、物理性能、抗渣渗透性及其对钢水的脱磷和脱硫效果.结果表明,经H2C2O4和CO2处理后的镁钙砂,其表面形成了一层均匀的、在低温(低于600℃)下主要由CaC2O4和CaCO3构成的保护膜,使其抗水化效果优于用H3PO4或单独用CO2处理的.采用这种镁钙砂制成的镁钙浇注料具有良好的抗水化性能,其常规物理性能优于镁质浇注料和用未处理镁钙砂制的浇注料,抗渣渗透性能强于镁质浇注料的,脱磷、脱硫效果也较未处理镁钙浇注料的更显著.     

镁钙系耐火材料在炉外精炼炉上的应用

综述了镁钙砂、烧成镁钙砖和不烧镁钙碳砖等镁钙系耐火材料的发展现状、生产工艺及性能,介绍了镁钙系材料在AOD炉、VOD炉、LF-VD炉、GOR炉等炉外精炼炉上的应用情况。     

EDTA络合滴定钙,镁方法的改进

研究了用改进的ＥＤＴＡ络合滴定直接测定钙，镁的方法，即用乙酰丙酮掩蔽镁测定钙和用草酸钙沉淀除钙后直接测定镁的方法，结果表明，该新方法简单，快速，准确度和精密度高。     

植酸钙镁的生产和应用

一、植酸钙镁的存在植酸钙镁,又叫菲丁。它广泛存在油料植物种子中,不同的种子植酸钙镁含量各不相同,几种油料植物种子植酸钙镁含量列于表1,从表1中可看出,脱脂米糠植酸钙镁含量最高。     

新型钙镁矿物抑制剂在磷矿正浮选中的应用

以木质素磺酸盐为原料,制备了一种高效的钙镁矿物抑制剂YG,将其应用于放马山三层矿正反浮选工艺流程中,通过单因素实验和正交实验得到了正浮选工艺的最佳药剂制度。与不添加抑制剂YG以及添加放马山工业浮选抑制剂Y-FMS相比,添加YG后正浮选精矿的各项指标均为最优,经过简单正浮选流程得到了精矿P2O5品位17.81%,回收率91.22%,精矿MgO品位仅为6.40%,脱除率达14.28%的良好指标,为后续反浮选优化了条件,说明YG是一种性能优良的钙镁矿物抑制剂。     

高模数硅酸钾溶液及其富锌涂料的制备

以低模数硅酸钾溶液、碱性硅溶胶为主要原料,采用有机硅氧烷作为改性剂制备了稳定的高模数硅酸钾溶液,与锌粉按30:70的质量比例配制富锌涂料.探讨了模数、固含量、有机硅氧烷的种类以及添加量对高模数硅酸钾溶液贮存稳定性和富锌涂料性能的影响.结果表明:硅酸钾溶液的模数在5.5、固含量在25%、γ-缩水甘油醚丙基三甲氧基硅烷(Z-6040)占总质量的3%时,贮存稳定期超过30 d(50℃),由改性后的高模数硅酸钾溶液所配制的富锌涂料涂膜致密且防腐性能优异,可作为长效重防腐涂料使用.     

从含碱硅酸钠溶液中水热合成硅灰石

以含碱硅酸钠溶液为原料,在常压下加入石灰乳,先水热合成CaO·SiO2·H2O,再将CaO·SiO2·H2O在850℃下焙烧2 h可制备硅灰石.研究了溶液中SiO2浓度、钙硅摩尔比(C/S)及反应时间对硅灰石合成的影响.热力学计算结果表明,常压下Na2O-CaO-SiO2-H2O体系中,最有可能形成CaO·SiO2·H2O及2CaO·SiO2·1.17H2O.实验结果表明:当C/S为1.0时,随着溶液中硅浓度的增加,硅酸根离子的聚合程度增加,有利于硅灰石的制备;随着时间的延长,硅灰石结晶程度越高;当C/S为0.6、0.8、1.0时,最终产物为CaSiO3;当C/S为1.5、2.0时,最终产物中含有大量的Ca2SiO4.适宜的水热合成条件为:SiO2浓度>30 g/L、C/S 0.6～1.0、温度98℃、反应时间>3 h.     

Thermodynamics of Calcium Silicate Hydrates and Their Solutions

The solution that surrounds hydrating cement particles contains dissolved species which are important in the overall process. A method, based on the Gibbs-Duhem equation for a three-component system, has been developed for computing the composition of one phase from values for its equilibrium solubility in a second phase. The method has been used to compute the CaO:SiO₂ ratio for two types of calcium silicate hydrate (C-S-H) gel, one of which is thought to form from hydrating tricalcium silicate (Ca₃SiO₅), and the other by precipitation from appropriate solutions. The results agree well with measured values reported in the literature. They have also been used to help define the probable composition of the C-S-H layer which forms on tricalcium silicate surfaces during the early stages of hydration when the reaction is slow. A chemical potential phase diagram is constructed from which thermodynamic quantities can be computed directly. The free energies of formation have been estimated for two types of C-S-H formed from CaO, SiO₂, and H₂O, These results provide insight into the structure and composition of C-S-H, which is the most abundant product in portland cement systems.     

粉煤灰预脱硅液动态水热合成硅酸钙晶须的影响因素

以分析纯试剂模拟粉煤灰预脱硅液,采用动态水热法合成硅酸钙晶须,研究了反应体系碱浓度、反应温度、反应时间、溶液中铝硅(Al2O3与SiO2)和钙硅(CaO与SiO2)质量比对产物物相组成及其形貌的影响. 结果表明,控制碱浓度80 g/L以下,反应温度220℃,反应时间6 h,铝硅质量比0.06以下,钙硅质量比0.9,可制备出纯度83%以上的硅酸钙晶须,晶须长度可达20 mm.     

硅酸乙酯为原料反相微乳液法制备纳米二氧化硅

采用NP-5/环己烷/去离子水体系制备反相微乳液,绘制了该体系的三元相图,并以正硅酸乙酯(TEOS)为原料,在碱性条件下受控水解反应制备了纳米SiO2粒子,探讨了[n(水)∶n(表面活性剂)](用R表示)和[n(水)∶n(TEOS)](用H表示)对SiO2纳米粒子粒径的影响。通过扫描电镜(SEM)和激光粒度仪对样品形貌和粒子大小和粒径分布进行了表征。结果显示:扫描电镜下观察到的SiO2粒子为无定型球形颗粒,粒径在200～500 nm的范围,激光粒度仪分析得到的平均粒径随着R和H的增大而增大。     

聚合物/层状硅酸盐纳米复合材料

目前,聚合物／层状硅酸盐纳米复合材料是重要的工程材料之一。由于层状硅酸盐的特殊结构,聚合物层状硅酸盐纳米复合材料的各项性能得到较大改善。聚合物／层状硅酸盐纳米材料的制备、表征、结构与性能的研究取得了重要进展。本文简要概述了聚合物／层状硅酸盐的结构及其有机改性机理,研究表明,插层剂和离子交换容量是插层的重要因素。最后,讨论了聚合物／层状硅酸盐纳米复合材料的制备方法和性能。     

硅丙乳液改性高模数硅酸钾水性无机富锌涂料的研究

以硅溶胶、氢氧化钾为主要原料,硅丙乳液为改性剂,制备了一种稳定的高模数硅酸钾有机-无机复合基料,与锌粉以1∶2比例配制高模数硅酸钾水性无机富锌涂料.探讨了模数、固含量、反应时间、硅丙乳液用量对高模数硅酸钾溶液贮存稳定性和涂料性能的影响.采用正交实验的方法,确定了涂料的最优工艺条件.制备的水性无机富锌涂料是一种经济实用的绿色涂料.     

Pore Structure of Calcium Silicate Hydrate in Hydrated Tricalcium Silicate

Adsorption of N₂ and water vapor was studied in completely hydrated tricalcium silicate and in fully hydrated tricalcium silicate from which Ca(OH)₂ had been extracted. Compared with results obtained using N₂, water vapor adsorption led to increased values for small-pore volume, peak shifts to smaller sizes, and decreased values for large-pore volume. Marked hysteresis was observed in the case of water vapor adsorption; the resorption branch apparently represents the true pore structure. Extraction of Ca(OH)₂ from the paste increased the calculated volume of small pores strikingly, suggesting that adsorption is hindered by Ca(OH)₂; this tendency is more obvious in water vapor adsorption. The adsorption measurements indicate the existence of two kinds of pores, i.e. a wider intergel-particle pore and a smaller pore existing within the gel particle. The latter pore was further classified into intercrystallite and intracrystallite pores.     

Synthesis of Calcium Silicate Hydrate in Highly Alkaline System

Synthesis of calcium silicate hydrate (C‐S‐H) was conducted over the range of 50°C–90°C and C/S ratio of 0.86–2.14 in the highly alkaline Na₂O–CaO–SiO₂–H₂O system for silicon utilization in high alumina fly ash. Structural change in C‐S‐H formed in the highly alkaline system was investigated using XRD and ²⁹Si MAS NMR spectra. X‐ray photoelectron spectroscopy was used to confirm the amount of sodium ions in C‐S‐H. Conversion of Si may reach 99% under optimum conditions. A higher degree of polymerization of silicate was obtained at lower temperature and C/S ratio. Na⁺ was confirmed to exist as Na–OSi and Na–OH. The amount of Na⁺ is the least at C/S ratio of 1.43, which conform to the prediction of topological constraint theory. High Ca/Si ratio leads to the increasing in Na⁺ combined in the interlayer. Increasing in the Na⁺ concentration in the system also increases the amount of Na⁺ combined in the interlayer and reduces the polymerization. Ion exchange was proven to be an effective way to remove Na⁺ combined in the interlayer of C‐S‐H.     

Extended X-ray Absorption Fine Structure Investigation of Calcium Silicate Hydrates

²⁹Si MAS-NMR, and Ca-EXAFS experiments have been conducted on calcium silicate hydrates (C-S-Hs) with structure derived from wollastonite. Crystalline compounds (wollastonite, xonotlite, hillebrandite, foshagite, 1.1 nm and 1.4 nm tobermorites, and jennite) and C-S-H were synthesized and characterized. ²⁹Si NMR provides information on silicate chains and EXAFS on calcium environment. The refined EXAFS values are in agreement with XRD data, except for tobermorite. The calcium order in C-S-H (C/S molar ratio from 0.7 to 1.4) is similar to that of tobermorite but different from that of jennite. Structural models of C-S-H are discussed.