草酸钙型尿结石的研究进展

尿结石是危害人体健康的泌尿系统疾病,其中以草酸钙型结石最为常见。从化学与医学相结合的角度,综述了近年来不同的模拟体系对这种尿结石的形成因素的研究进展,以期为探讨其形成机理和临床治疗提供一些启示。     

YBCO Oxalate Coprecipitation in Alcoholic Solutions

A process for synthesis of ultrafine YBa₂Cu₃O_7–x powder by oxalate coprecipitation from nearly saturated solutions of the metal acetates and a 2-propanol solution of oxalic acid was developed. The coprecipitation was complete within 5 min in an ice bath at 0–2°C. The final stoichiometry was Y:Ba:Cu = 1:1.994:2.991, while the particle size and surface area in the homogeneous coprecipitated powder were 0.1–0.2 pm and 24.9 m².g⁻¹, respectively. Because of the uniformity and particle size of the coprecipitated material, reactive YBCO powder with a surface area of 1.7 m².g⁻¹ can be obtained at 780°C in about 12 h.     

Characterization of Calcium Lanthanum Oxalate Powders Coprecipitated from Different Binary Solvent Mixtures

White amorphous powders of well-mixed calcium and lanthanum oxalates were prepared by coprecipitation of calcium and lanthanum nitrates with 1 M oxalic acid. SEM observation showed particle shapes of cubes, flakes, and agglomerates when water-organic solvent mixtures were employed as the precipitation media. The measured specific surface area and the median particle diameter ( D ₅₀) ranged between 1.5–76 m²/g and 0.9–14 μm, respectively, as a result of the divergent particle morphology. The morphology changes were attributed to a change of precipitation rate in different solvent mixtures. An attempt was made to explain the rate changes by the solvation energy change of ions which resulted in interfacial energy change within the depositing surface region.     

Pseudo‐polymorphic Behavior of Precipitated Calcium Oxalate

The precipitation of calcium oxalate pseudo‐polymorphs was studied in a Y‐mixer in series with a reaction tube. Experiments were performed with the aim to identify the decisive variables influencing the phase composition of the precipitate. Initial supersaturation, stoichiometric ratio of the lattice ions, ionic strength and pH were varied. The resulting phase distribution was determined with the help of DSC measurements. Mixing conditions were chosen such that mixing of the reactants had no influence on the experiments. Increasing supersaturation, ionic strength and pH each favor formation of the metastable calcium oxalate dihydrate over the thermodynamic stable monohydrate, although the influence of the two latter parameters is comparatively weak. If the ratio from calcium to oxalate activities was increased in the experiments a steep change in the phase composition from approximately 50 mass percent of the monohydrate to pure monohydrate was observed. Modeling of the experimental results is successful using a combination of classical nucleation theory with an equation that relates the adsorption of potential determining ions to the interfacial tension. The interfacial tension for the uncharged particles was obtained by regression from the experimental determined dependence of the phase distribution on the supersaturation.     

钙铝酸盐红外玻璃的微晶化

采用真空熔制方法制备出钙铝酸盐红外玻璃,通过热处理方法对玻璃进行微晶化获得钙铝酸盐微晶玻璃。研究了晶核剂ZrO_2对钙铝酸盐玻璃析晶机制的影响,以及不同微晶化条件下钙铝酸盐玻璃的析晶情况和红外透过性能。结果表明:晶核剂的引入改变了钙铝酸盐玻璃的析晶机制,未添加ZrO_2的铝酸钙玻璃的析晶主要为表面析晶,析出晶相主要是BaAl_2O_4、Ba_3Al_2O_6;添加ZrO_2后,玻璃向整体析晶转化,析出晶相以Ca_3Al_2O_6为主;在930~970℃范围内,通过控制处理温度和时间可以获得透明的含ZrO_2铝酸钙微晶玻璃,在3~5μm波段具有良好的红外透过性能,玻璃硬度达到8.04 GPa以上。     

酸性废水体系中硫酸钙反应结晶过程研究(英文)

The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater dis charged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirring speed and the metal ions on the reactive crystallization process of calcium sulfate between sulfuric acid and lime were systematically investigated. The morphology of the precipitated crystals evolved from plateletlike and nee dlelike shape to rodlike shape when the temperature was increased from 25 to 70 ℃. An increase in the agglom.     

Production of Neptunium Oxide from Impure Solutions by Anion Exchange Followed by Oxalate Precipitation

Abstract

The stabilization of the neptunium solutions stored at the Savannah River Site (SRS) has generated additional recycle solutions that contain a different mix of impurities. A list of expected purities and the known laboratory and production data for purification from those impurities has been accumulated. An evaluation has been performed of the options for modifying the current process to ensure oxide product purity does not significantly change when recycle solutions are processed. This paper discusses the details of the reduction of the major impurities utilizing both known production quality analyses and laboratory flowsheet development data and proposes modifications to the anion wash volumes to remove higher levels of each impurity.     

氯化钙在甲醇水溶液中的结晶

通过显微镜,观察了氯化钙在甲醇水溶液中的结晶情况,发现在不同的结晶方法和条件下会形成许多不同形状的结晶体,有立方形、片形、三角形、六角形、十字形、六边形等;研究了结晶体的形状和大小与结晶温度、结晶时间和溶液浓度等的关系,发现在蒸发结晶过程中,开始形成的结晶体棱角分明,随着静置时间的延长,小颗粒溶解,大颗粒长大,结晶体的棱角趋于平缓,形状趋于一致,形成不规则多面体;浓度较高时,形成的结晶体粒度较小,浓度较低时形成的结晶体粒度较大;与蒸发结晶相比,自然结晶出的颗粒较大,而通过蒸发结晶出的颗粒较小,并初步探讨了结晶现象的本质规律。     

Kinetics of Nucleation and Growth of Calcium Carbonate and Calcium Sulphate Crystals from Aqueous Solutions

Theoretical Foundations of Chemical Engineering - The dependence of the induction period on supersaturation during the nucleation of CaCO3 and CaSO4 ? 2H2O is experimentally determined and...     

超细碳酸钙的合成及结晶过程

首先在不加添加剂的条件下,对超细碳到钙ＣａＣＯ３的结晶过程进行了研究,结果表明,ＣａＣＯ３的结晶过程是先形成线呸状物,随着碳化反应的继续,线束状物断裂,最后得到粒径为４０～７０ｎｍ的立方颗粒,通过加入添加剂,分别合成了短链状和棒状ＣａＣＯ３,并对它们的形成机理进行了分析。     

草酸亚铁法水热合成磷酸铁锂的晶化条件研究

以草酸亚铁为原料,通过水热晶化法制备了锂电池正极材料磷酸铁锂(LiFePO_4)S1~S6、S8和S10,进一步以葡萄糖为碳源,w(C)=6%时,制得Li Fe PO4/C复合正极材料S7和S9。采用XRD和FE-SEM对产物的结构进行了表征,对水热晶化条件进行了优化,利用扣式电池充放电方法考察了S7的电化学性能。结果表明:水热晶化的最佳反应时间为10 h,最低晶化温度为190℃。当水热晶化温度达到280℃时,无碳产物(S10)中的部分Fe(Ⅱ)会被氧化为Fe(Ⅲ),生成FePO_4·2H_2O杂质相,而葡萄糖的添加则可以抑制Fe(Ⅱ)向Fe(Ⅲ)的转化。以草酸亚铁为铁源,当晶化温度为240~260℃、晶化时间为10 h时,可以通过水热法制备出颗粒团聚程度轻微的磷酸铁锂正极材料。S7的0.1 C放电比容量达到154 m Ah/g,经过42个循环测试,其0.1 C放电比容量仍可达到149 m Ah/g。与硫酸亚铁为铁源的传统水热法相比,每制备1 t纯相LiFePO_4,锂源(氢氧化锂)的使用量从190 16 mol降低到6 339 mol。     

草酸亚铁法水热合成磷酸铁锂的晶化条件研究

以草酸亚铁为原料,通过水热晶化法制备了锂电池正极材料磷酸铁锂（LiFePO4）S1~S6、S8和S10,进一步以葡萄糖为碳源,w(C)=6%时,制得LiFePO4/C复合正极材料S7和S9。采用XRD和FESEM对产物的结构（structure）与织构（texture）进行了表征,对水热晶化条件进行了优化,利用扣式电池充放电方法考察了S7的电化学性能。结果表明：水热晶化的最佳反应时间为10h。最低晶化温度为190℃。当水热晶化温度达到280℃时,无碳产物（S10）中的部分Fe(II)会被氧化为Fe(III),生成FePO4•2H2O杂质相,而添加葡萄糖的产物S9则可以抑制Fe(II)向Fe(III)的转化。以草酸亚铁为铁源、晶化温度为240～260℃、晶化时间10h时,可以通过水热合成工艺制备出颗粒团聚程度轻微的磷酸铁锂正极材料,S7的0.1C放电比容量达到154 mAh/g,经过42个循环测试,其0.1C放电比容量仍可达到149 mAh/g。每制备1t纯相LiFePO4,与硫酸亚铁传统水热法相比,锂源（氢氧化锂）的摩尔量从19016 mol降低到6339 mol。     

尿素对硫酸钙结晶过程影响的研究

以试剂磷酸二氢钙、硫酸和尿素为原料，模拟磷矿-硫酸脲(尿素硫酸加合物)反应中的硫酸钙结晶过程，在MSMPR结晶器中研究了尿素对硫酸钙结晶的影响。结果表明，与无尿素的结晶过程相比，尿素使出现结晶的时间延长了150％，但悬浮液密度增加50％，结晶在长度和宽度上均有所增加，特别是宽度上的增长超过50％。粒度分布的定量分析显示，尿素硫酸摩尔比为3．6：1，过程温度80℃时，硫酸钙的成核速率减少了25％，但结晶成长速率增加了1.2倍，结晶粒度分布中心由72．8μm增大到142．8μm，平均粒径由70．98μm增加为105．45μm。两者叠加的结果体现为硫酸钙结晶过程总速率的增加。     

Preparation of High-Strength Calcium Phosphate Glass-Ceramics by Unidirectional Crystallization

Unidirectionally crystallized CaO-P₂O₅ glass-ceramics were produced by reheating glass rods between 450° and 580°C (glass transition temperature ∼500°C) under a temperature gradient of 30°C/cm. These glass-ceramics exhibit high bending strength (∼650MN/m²) and toughness. Sample preparation is described and compared with conventional unidirectional solidification of melts. The characteristic mechanical properties are discussed in terms of the texture of the glass-ceramics.     

Hydrothermal Crystallization of Zirconia and Zirconia Solid Solutions

Zirconia as well as yttria-zirconia and calcia-zirconia solid-solution powders were crystallized under hydrothermal conditions from (co)precipitated hydroxides. The morphology of the powder particles is strongly dependent on the crystallization conditions. The powders crystallized in a water solution of Na, K, and Li hydroxides show elongated particles of much larger sizes than those which result from the process carried out in pure water or a water solution of Na, K, or Li chlorides. The shapes of the latter particles are isometric. The growth mechanism of the elongated particles is suggested.     

二水硫酸钙结晶过程研究进展

目前世界上的磷酸工业都以湿法为主,而湿法磷酸生产的关键技术是硫酸钙的结晶.结晶的质量会影响到整个的生产工艺.本文综述了二水硫酸钙结晶过程的最新研究进展,从各个角度介绍了外部条件对硫酸钙结晶的影响,以达到对二水硫酸钙结晶的各种技术有一种比较客观综合的理解和认识,最后对未来二水硫酸钙结晶过程的研究方向作了探讨.     

AA/HPA/AMPS对草酸钙晶相组成及晶粒形貌影响的研究

采用环境扫描电镜(SEM)和X射线衍射(XRD)技术,研究AA/HPA/AMPS在水体系中对草酸钙晶化习性的影响。结果表明:随着添加剂浓度的增加,一水草酸钙(COM)的生长受到抑制,晶粒的聚集度和尺寸降低,棱角变得圆钝,相反,二水草酸钙(COD)和三水草酸钙(COT)的成核得到促进。当添加剂浓度较高时,COD为唯一的晶相。控制单一变量,发现高的过饱和度降低了AA/HPA/AMPS对草酸钙亚稳态晶相的稳定能力,而高p H则增强了AA/HPA/AMPS的调控作用。由分子动力学(MD)模拟可知,AA/HPA/AMPS在草酸钙晶粒的富Ca2+晶面吸附力较强。     

硫酸软骨素A对草酸钙晶体生长和聚集的影响

用体外模拟方法研究了硫酸软骨素 A(简称 C4S)对草酸钙晶体矿化热力学的影响 ,并对纯水体系和 C4S- H2 O体系中形成的草酸钙晶体进行了物相分析与形貌观察。发现 C4S不但在热力学过程中有利于提高溶液中 Ca2 + 存在的浓度 ,而且能诱导一水草酸钙 ( COM)晶体的 ( 1 0 1 )晶面优先生长 ,并抑制 COM的二维生长和聚集。     

影响硝酸磷肥硝钙结晶过程的因素

结合硝酸磷肥装置生产实践,从硝钙结晶动力学和体系平衡相图两个方面,分析影响硝钙过程的因素,并指出合理的工艺条件。