文石型碳酸钙晶须的制备研究

采用碳酸化法在MgCl2-Ca(OH)2-CO2体系中合成了文石型碳酸钙晶须,研究了碳酸钙晶须的成型原因,分析了pH值、氢氧化钙的纯度对晶须生长的影响,运用SEM和XRD对晶须的形貌和组成进行了表征.结果表明:Mg(OH)2沉淀促使文石相碳酸钙异相成核,取向生长成针状;控制pH值不超过8.5,可以连续添加精制石灰水合成碳酸钙晶须.     

碳酸化工艺参数对碳酸钙结晶习性的影响

研究了搅拌速度、反应温度和镁钙离子浓度比三种工艺参数对碳酸钙结晶习性的影响．指出反应温度的升高有利于碳酸钙以文石相结晶,但在无镁离子存在的高纯原料情况下,并不能使文石相碳酸钙形成;镁钙离子浓度比是影响碳酸钙结晶习性的决定性因素．     

碳酸钙晶须在鼓式刹车片中的性能研究

选用碳酸钙晶须用于汽车制动器衬片,研究了其增摩减磨性能.通过XD-MSM定速式摩擦试验机研究了石棉、重质碳酸钙和碳酸钙晶须摩擦性能并作了比较;利用扫描电镜对其形貌作了分析,根据其分散状况推测其增强耐磨机理.结果表明:当配方含15%碳酸钙晶须时,具有高温摩擦系数稳定、磨损率小、力学性能好等优点,综合性能及性价比高,是石棉的理想取代品.     

文石碳酸钙晶须的制备与应用进展

文石碳酸钙晶须是一种价格低廉、制备工艺简单、性能优异、应用十分广泛的环保型材料,引起了材料与工程技术学家的广泛关注.分析了文石碳酸钙晶须在增强高分子材料、作为造纸助剂及增强摩擦材料方面的应用,综述了国内外文石碳酸钙晶须的制备方法研究进展,并归纳了助剂对合成晶须的影响,对我国碳酸钙晶须的产业化生产现状作了评述.     

针状碳酸钙制备中氯化镁晶型导向剂的套用研究

以MgCl₂为晶型导向剂制备了形貌规整的文石相针状碳酸钙, 其粒径为2.5~5.0μm, 长径比为10~20. 采用EDTA络合滴定碳化后回收滤液中Ca²⁺、Mg²⁺含量以确定需补加MgCl₂量, 并在相同的碳化工艺条件下逐步改进套用回收液的方法制备针状碳酸钙. 产品用SEM、XRD进行形貌观察和晶型组成分析. 结果表明, 随着套用次数的增加, 碳酸钙产品中文石相的含量逐渐降低, 当文石相的含量低于80%时, 针状碳酸钙的长径比也大幅下降, 同时生成大量微细立方状方解石相碳酸钙, 将不适合继续套用. 直接套用回收液时只能循环使用1次, 而将套用的回收液经补加Mg²⁺、加酸调节pH等优化处理后可使套用次数延长至12次, 这将大幅降低针状碳酸钙的生产成本.     

天然胶乳/碳酸钙晶须医用复合材料的制备与性能

本文将超声分散后的改性碳酸钙晶须分散液加入天然胶乳,对其进行补强,制得绿色环保高性能的改性碳酸钙晶须/天然胶乳医用复合材料。系统研究了该医用复合材料的力学性能、抗菌性能及热稳定性能。结果表明,使用硬脂酸改性后的碳酸钙晶须与天然胶乳基体材料有极佳的相容性。医用复合材料的力学性能、抗菌性能及热稳定性能均比纯胶有所提高。当改性碳酸钙晶须用量为4%时,医用复合材料的各项性能达到最佳。     

碳酸钙晶须增强水泥基复合材料压缩性能随温度的变化规律

碳酸钙晶须可以有效改善水泥基复合材料在常温下的压缩性能,但是高温作用后碳酸钙晶须对材料压缩性能的影响尚不清楚。研究了不同体积掺量(0%、0.5%、1%、2%)的碳酸钙晶须增强水泥基复合材料分别在常温以及200,400,600和800℃高温作用后的压缩性能。试验结果表明,常温下随着晶须掺量的提高,试件的抗压强度和压缩韧性呈先上升后下降的趋势,其中掺入1%碳酸钙晶须的材料压缩性能最好。200℃条件下材料的抗压强度和压缩韧性较常温均有明显提高,而当目标温度超过200℃后,高温对材料的压缩性能劣化作用明显,其抗压强度和压缩韧性持续衰减,800℃作用后各组的压缩性能已没有明显差距,但在每个目标温度作用下,碳酸钙晶须均可以提高高温作用后的抗压强度值和压缩韧性值,说明碳酸钙晶须的掺入对提高材料在高温作用后的压缩性能有积极作用。     

碳酸钙晶须对混杂纤维增强高延性水泥基复合材料力学性能的影响

为了探究碳酸钙晶须对钢纤维/PVA混杂纤维增强高延性水泥基复合材料(HyFRHDCC)力学性能的影响,利用2%体积掺量的廉价碳酸钙晶须替代部分纤维,研究了不同纤维掺量HyFRHDCC的压缩性能和拉伸性能,利用扫描电子显微镜观察了HyFRHDCC的微观结构。研究结果表明,引入碳酸钙晶须能够提高HyFRHDCC的初裂拉伸应变和峰前压缩韧性;在1.5%PVA+0.25%钢纤维HyFRHDCC中掺入2%碳酸钙晶须可以改善材料的拉伸性能;当PVA纤维减少至1%时,HyFRHDCC出现了明显的应变软化行为。微观形貌分析发现,碳酸钙晶须能够通过裂纹偏转、晶须拔出以及裂缝桥联等微观机制改善HyFRHDCC的应变硬化行为。     

旋转填充床中合成微细晶须碳酸钙的试验研究

通过试验研究筛选出MgCl2与H3PO4两种在旋转填充床(RPB)中促使微细晶须碳酸钙合成的晶形控制剂,单因素试验探明了各晶形控制剂条件下合成微细晶须碳酸钙的较佳工艺条件,正交试验研究了各因素对粒子长径比影响的显著性.研究表明:与常重力场中合成晶须碳酸钙的方法相比,RPB产生的超重力场中合成晶须碳酸钙反应温度降低约20℃、合成等物质的量晶须碳酸钙所需时间约为其他方法的1/36～1/18、粒子短轴直径达到80～250 nm微细程度;使用MgCl2时只有反应温度对粒子长径比有显著影响,而使用H3PO4时反应温度、RPB转速和气体体积流量对产品粒子长径比均有显著影响.     

烧水壶水垢矿物组成及成因分析

用XRD、IR、SEM研究了家用烧水壶水垢矿物物相组成、相含量以及矿物形貌,并探讨了各物相成因。研究发现,家用热水壶水垢化学成分主要为碳酸钙,矿物物相主要由文石和方解石组成,以文石相为主,质量占92．8％,方解石占7．2％。文石相主要形成于70～90℃,而方解石则主要形成于较低温度。     

重质碳酸钙生产现状及其发展

综述了以方解石、石灰石、大理石、白垩等为原料 ,经干法或湿法研磨制造重质碳酸钙的国内外生产现状、应用领域 ,探讨了采用湿法研磨及改性新工艺和先进研磨设备 ,开发超细重质碳酸钙系列产品 ,生产粘接剂和密封剂、造纸、医药、日化、塑料、涂料等专用重质碳酸钙系列产品的市场需求和企业效益     

沉淀碳酸钙(PCC)的发展及应用

简述碳酸钙的分类、用途、工业现状、国内外在碳酸钙多相合成体系流变学及转递行为、碳酸钙形成机理和形态控制技术以及结晶生长成核理论的研究成果 ,并讨论了碳酸钙粉末表面处理的方法、机理。对高档卷烟纸专用碳酸钙的性能要求进行了探讨     

Mineralization of calcium carbonate by controlled release of carbonate in aqueous solution

The generation of carbon dioxide from organic precursors in aqueous media in presence of calcium chloride and under conditions where calcium carbonate is formed was investigated. Photochemical decomposition of pyruvic acid, 2-nitro-phenylacetic acid and 4-benzoylphenyl acetic acid gave ill-defined morphologies of calcium carbonate contaminated by organic by-products. Alkaline hydrolysis of dimethyl- and diethyl-carbonate yielded amorphous calcium carbonate in form nanospheres of narrow distribution of radii if the precipitation occurred under quiescent conditions. Addition of a polymer surfactant gave spherical particles as well, however consisting of vaterite.The formation of spherical particles of amorphous calcium carbonate is rationalized in terms of a liquid–liquid phase separation followed by rapid gelation of the droplet phase of high concentration of calcium carbonate. A lower critical solution temperature is postulated and its value was estimated as 10 °C.     

Taking Advantage of Disorder: Amorphous Calcium Carbonate and Its Roles in Biomineralization

Amorphous calcium carbonate (ACC) in its pure form is highly unstable, yet some organisms produce stable ACC, and cases are known in which ACC functions as a transient precursor of more stable crystalline aragonite or calcite. Studies of biogenic ACC show that there are significant structural differences, including the observation that the stable forms are hydrated whereas the transient forms are not. The many different ways in which ACC can be formed in vitro shed light on the possible mechanisms involved in stabilization, destabilization, and transformation of ACC into crystalline forms of calcium carbonate. We show here that ACC is a fascinating form of calcium carbonate that may well be of much interest to materials science and biomineralization.     

薄膜用碳酸钙种类选择研究

测试了不同细度的重质碳酸钙和轻质碳酸钙的吸油率，以及重质碳酸钙填充母料和轻质碳酸钙填充母料的熔体流动性和成膜性。结果表明，不论重质碳酸钙还是轻质碳酸钙，细度越高，吸油率越高，加工流动性越差；重质碳酸钙的吸油度低于同等目数的轻质碳酸钙，而加工流动性和成膜性则优于后者，重质碳酸钙是制造填充薄膜的适宜材料。     

How much calcium to shell out? Eggshell calcium carbonate content is greater in birds with thinner shells,larger clutches and longer lifespans

The avian eggshell is a bio-ceramic structure that protects the embryo. It is composed almost entirely of calcium carbonate and a small amount of organic material. An optimal amount of calcium carbonate in the eggshell is essential for the embryo''s development, yet how the ratio of calcium carbonate to organic matter varies between species has not been investigated. Calcium is a limiting resource for most birds, so its investment in their eggs should be optimized for a bird''s life history. We measured the relative calcium carbonate content of eggshells in 222 bird species and tested hypotheses for how this trait has evolved with the life-history strategies of these species and other traits of their respective egg physiologies. We found that (i) eggshell calcium carbonate content was positively correlated with species having thinner eggshells and smaller than expected eggs relative to incubating parental mass, (ii) species with small mean clutch sizes had lower calcium carbonate content in their eggshells, and (iii) for species with larger clutch sizes, eggshell calcium carbonate content was negatively correlated with their mean lifespan. The pattern of lower eggshell calcium carbonate in longer lived, larger clutched birds suggests that calcium provision to the eggshell has long-term costs for the individual.     

A two-fluid model for calcium carbonate precipitation in highly supersaturated solutions

Precipitation of calcium carbonate is a common phenomenon in nature, which has attracted attention from researchers due to its importance in biomineralization processes, climatic changes, and especially incrustations in pipelines. In this work, a two-fluid model is proposed for homogeneous crystallization of calcium carbonate in highly supersaturated solutions. By making an analogy between the dynamics of a granular gas and the dynamics of a solid dispersion, the proposed model not only accounts for the interaction forces between the solid particles and dispersion medium, but also for the mass transfer and changes in the particles size during the precipitation reaction. Moreover, by using a numerical scheme based on an iterative algorithm, 3D numerical simulations are performed for the homogeneous crystallization of calcium carbonate, and the results are compared with experimental particles size distributions and curves of pH versus time. The good agreement between theoretical and experimental results indicates that the two-fluid model can be successfully used to evaluate the growth kinetics of calcium carbonate nuclei.     

电石渣的综合利用及制备轻质碳酸钙的研究进展

简述了电石渣在生产水泥等化工产品、环保等方面综合利用的现状，并重点评述了以电石渣为原料制备轻质碳酸钙和纳米碳酸钙的研究进展。以电石渣为原料生产有较高附加值的轻质碳酸钙和纳米碳酸钙，具有重要的开发价值。     

超微碳酸钙的表面改性研究及应用

在分析超微碳酸钙研究现状及表面改性重要性的基础上,对其表面改性的过程机理、方法、改性剂、设备及效果评价进行了综述;介绍了其工业化应用现状,并对其发展前蒂进行了展望。     

化学法制备超细碳酸钙

在传统轻质碳酸钙生产的基础上 ,利用添加剂控制碳酸钙粒径和形态 ,用化学法合成超细碳酸钙。主要讨论了添加剂用量、加入时间、Ca(OH) 2 初始浓度、CO2 质量分数、搅拌速度等因素对碳酸钙的形成及颗粒粒径的影响 ,并探讨了形成机理。