水溶液中P123对CaCO3微粒形貌的调控

在三嵌段共聚物P123水溶液体系中,合成了特殊形貌的层面光滑的碳酸钙层状聚集体、具有多级结构的碳酸钙层状聚集体和仙人球状的碳酸钙粒子.探讨了反应时间、聚合物浓度和反应温度对碳酸钙粒子形貌和晶型的影响,采用扫描电子显微镜(SEM)、X射线粉末衍射(XRD)及红外吸收光谱对合成样品的形貌、结构进行了表征.结果表明,聚合物浓度和反应温度对碳酸钙粒子形貌和晶型具有重要的影响.利用周期键链(PBC)理论模型解释了层状结构碳酸钙聚集体的形成过程.     

蔗糖/精氨酸体系中碳酸钙结晶的仿生合成

该文以更加接近生物矿化的方法研究了蔗糖/精氨酸体系对碳酸钙晶体取向、形貌和晶型的控制作用.XRD 分析表明,在蔗糖/L-精氨酸混合体系中合成的晶体主要为碳酸钙的球霰石晶型及少量的方解石型,在单独的蔗糖或L-精氨酸溶液中基本是球霰石晶型.SEM分析表明,蔗糖和L-精氨酸均可诱导形成特殊形貌的碳酸钙.实验结果表明,蔗糖/精...     

柠檬酸钠与碳酸钙晶型和形貌的控制

晶体的晶型和形貌是碳酸钙制备中的关键问题之一。 采用尿素水解均匀沉淀法来控制碳酸钙的晶型和形貌。 利用XRD和SEM等技术手段对CaCO₃晶体的结构和形貌进行了表征。 结果表明,高温条件下(90 ℃)水溶液中得到均匀的针状结构的文石晶体。 添加适量柠檬酸钠后,则得到的是特殊形貌的方解石晶体。 在乙醇/水混合溶剂中,柠檬酸钠对CaCO₃晶体的形貌也有重要影响,通过改变乙醇体积分数,得到了中空绒毛球状的球霰石。     

不同晶型和形貌MnO2纳米材料的可控制备

以KMnO4为锰源, 采用水热技术在180 ℃条件下于不同种类酸溶液中可控制备了α-, β-, δ-MnO2, 系统研究了 K＋, H＋及阴离子对制备产物MnO2晶型和形貌的影响. 研究结果表明, K＋与H＋在反应体系中对于制备产物晶相的生成形成竞争性影响, 其量的大小对制备产物晶型具有控制作用, 高浓度K＋离子有助于生成α-MnO2, 而高浓度的H＋有利于生成β-MnO2; 阴离子的种类和浓度对制备产物MnO2的晶型和形貌无显著影响. 在对制备产物进行XRD, SEM和元素分析的基础上, 提出了不同晶型和形貌MnO2的可能形成机理.     

二次碳化法制备疏水链状纳米碳酸钙

以柠檬酸和十六酸的氨溶液为表面控制剂, 用二次碳化法制备了疏水链状纳米碳酸钙晶体. 用透射电子显微镜、X射线衍射、红外光谱、热重分析和接触角测试对产品进行了分析. 结果表明, 表面控制剂在反应过程中不但可以控制晶体的成核生长, 还能对碳酸钙表面进行修饰. 在不添加表面控制剂的溶液中得到立方体状表面亲水的纳米碳酸钙晶体; 添加柠檬酸和十六酸的氨溶液后所得纳米碳酸钙晶体为链状表面疏水. 将碳酸钙添加到聚乙烯中, 聚乙烯的初始热分解温度提高, 热力学稳定性增加.     

碳酸钙在聚合物胶束控制下的仿生合成

合成了温敏性的聚(N-异丙基丙烯酰胺)-b-聚(L-谷氨酸)(PNIPAM-b-PLGA)嵌段共聚物,在较高温度下制备了以PNIPAM为核、以PLGA为壳的自组装胶束,研究了胶束对碳酸钙晶体生长的控制作用.使用扫描电镜和X射线衍射表征了碳酸钙晶体的形貌和晶型.当聚合物胶束浓度较高时,得到纤维状的文石;当胶束浓度较低时,...     

聚合物控制碳酸钙晶型、形貌的研究

碳酸钙有不同的晶型和形貌,聚合物的加入在改变碳酸钙的晶型和形貌方面起着重要作用。本文综述了不同聚合物对碳酸钙的影响,重点讨论了生物高分子聚合物、双亲水基嵌段共聚物、树枝状聚合物等对碳酸钙晶型、形貌的调控,同时介绍了聚合物与其他添加剂相互协同作用对碳酸钙的影响,并对当前研究中存在的问题和不足进行了评述。通过对碳酸钙的研究,不仅有助于制备不同尺寸、各种形状和不同表面性能的碳酸钙产品,满足不同的工业需求,而且能够更加深入地了解生物矿化的机理,更好地仿生合成和制备各种功能材料。     

二维凝胶体系中碳酸钙分形结构的形成与机理研究

本文研究了二维琼脂凝胶圆盘体系中碳酸钙分形结构的形成过程,发现随着反应时间的增加,碳酸钙的形态经过了细小颗粒-枝晶结构-分形结构的转变过程,该分形结构实际上是由纳微米级碳酸钙晶粒聚集而成的。增加琼脂和反应物的浓度,碳酸钙微晶的形貌和尺寸发生了变化,呈现立方体与球形,由其构成的分形结构的尺寸也随着改变,但碳酸钙的晶型均为方解石型,无明显变化。二维凝胶体系中碳酸钙分形结构的形成主要与琼脂极性基团提供成核位点、多糖的网络结构、沉淀剂离子扩散受限有关。     

水溶性大分子调控碳酸钙结晶的研究进展

结合本课题组的工作综述了水溶性大分子调控碳酸钙合成的研究进展.通过分析生物大分子、合成大分子以及大分子/表面活性剂混合体系对碳酸钙结晶习性的影响,讨论了水溶性大分子对碳酸钙形貌和晶型的调控机理.大分子调控碳酸钙合成的研究不仅为人们制备不同形貌、尺寸和晶型的碳酸钙开拓了思路,也为满足不同的工业需求提供了理论指导.     

pH调节剂对溶液燃烧法制备纳米LaFeO3的影响

以硝酸镧和硝酸铁为氧化剂,柠檬酸为燃料,采用溶液燃烧法制备了钙钛矿型LaFeO3.通过XRD和SEM表征,分别研究了以乙二胺和NaOH溶液为pH调节剂,前驱物溶液在不同pH值条件下,对制备的纳米LaFeO3粉体的晶相组成和微观形貌的影响.结果表明:前驱物溶液pH值对燃烧产物的晶相组成、晶粒大小和微观相貌都有显著的影响....     

Habit modification of calcium carbonate in the presence of malic acid

The ability of malic acid to control calcium carbonate morphology has been investigated by aging calcium chloride solution in the presence of urea in a 90 °C bath. Malic acid favors the formation of calcite. A transition from single block to aggregate with special morphology occurs upon increasing malic acid concentration. The morphological development of CaCO₃ crystal obviously depends on the starting pH. CaCO₃ crystal grows from spindle seed to dumbbell in the pH regime from 7 to 11; while it evolves from spindle seed, through peanut, to sphere at pH=11.5. Both dumbbell and sphere consist of rods that are elongated along c-axis and capped with three smooth, well-defined rhombic {1 0 4} faces. A tentative growth mechanism is proposed based on the fractal model suggested by R. Kniep and S. Busch [Angew. Chem. Int. Ed. Engl. 35 (1996) 2624].     

花球状银催化材料的制备及其对4-硝基苯酚的催化加氢性能

通过室温下将硝酸银水溶液与含有硫酸亚铁和柠檬酸的水溶液直接混合,一步合成由银纳米片自组装而成的银花状球结构。结合X射线粉末衍射(XRD)、扫描电子显微镜(SEM)等结构表征手段,考察硝酸银水溶液的滴加速度、柠檬酸添加量等因素对产物形貌及尺寸的影响,并对银花状球的形成机理进行研究。实验结果表明,通过对硝酸银水溶液滴加速度的简单调控可以实现银颗粒形貌由薄片状到花球状的转变。此外,该形貌的微纳米材料在4-硝基苯酚加氢反应中呈现出优异的催化活性。     

花球状银催化材料的制备及其对4-硝基苯酚的催化加氢性能

通过室温下将硝酸银水溶液与含有硫酸亚铁和柠檬酸的水溶液直接混合,一步合成由银纳米片自组装而成的银花状球结构。结合X射线粉末衍射（XRD）、扫描电子显微镜（SEM）等结构表征手段,考察硝酸银水溶液的滴加速度、柠檬酸添加量等因素对产物形貌及尺寸的影响,并对银花状球的形成机理进行研究。实验结果表明,通过对硝酸银水溶液滴加速度的简单调控可以实现银颗粒形貌由薄片状到花球状的转变。此外,该形貌的微纳米材料在4-硝基苯酚加氢反应中呈现出优异的催化活性。     

Preparation and formation mechanism of three-dimensionally ordered macroporous (3DOM) MgO, MgSO4, CaCO3, and SrCO3, and photonic stop band properties of 3DOM CaCO3

Three-dimensionally ordered macroporous (3DOM) magnesium (Mg) oxide (MgO), MgSO₄, calcium (Ca) carbonate (CaCO₃), and strontium (Sr) carbonate (SrCO₃) were prepared using a colloidal crystal of polymer spheres as a template. Ethanol or ethanol-water solution of metal salts (acetate or nitrate) and citric acid was infiltrated into the void of the colloidal crystal template of a monodispersed poly(methyl methacrylate) (PMMA) sphere. Heating of this PMMA-metal salt-citric acid composite produced the desired well-ordered 3DOM materials with a high pore fraction, which was confirmed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet-visible (UV-vis) diffuse reflectance spectra. The presence of citric acid is crucial for production of the 3DOM structures. Reaction of citric acid with metal salt produces metal citrate solid in the void of PMMA spheres, which is necessary to maintain the 3DOM structure during the calcination process. 3DOM CaCO₃ shows opalescent colors because of it's photonic stop band properties.     

纳米CeO2的形貌控制与表征

以Ce(NO3)3·6H2O和(NH4)2CO3为沉淀源,利用柠檬酸作为络合剂和分散剂,实现了对CeO2前驱体的形貌和尺寸控制,并采用TEM,TGA和XRD等方法对前驱体及其热分解所得纳米CeO2的形貌及结晶性等进行了表征.结果表明,随着柠檬酸加入量的提高,前驱体形貌从纳米线向类球形颗粒变化,焙烧生成的纳米CeO2颗粒的形貌具有明显继承性,所得CeO2属于立方萤石结构,且随焙烧温度的提高,晶化程度增大.     

阴离子氨基酸表面活性剂调控碳酸钙的仿生合成

室温下, 在乙醇或乙醇-水混合体系中, 利用氨基酸表面活性剂N-酰基十二烷基肌氨酸钠(Sar)调控合成碳酸钙, 采用SEM, XRD和FTIR等技术表征了反应产物. 在乙醇体系中, 首先形成多面体形状的文石, 然后逐渐转变为圆球状的无定形碳酸钙. 在乙醇-水混合体系中, 合成了花簇状多级结构碳酸钙晶体. 增加N-酰基十二烷基肌氨酸钠的用量有助于形成球霰石结构, 当n(Ca2+)∶n(Sar)=1∶1 时, 得到的花状碳酸钙为球霰石和方解石的混合物, 当n(Ca2+)∶n(Sar)=1∶2 时, 得到纯净的球霰石, 其形貌为大小较均一的单分散的球, 直径约为7 μm; 另外, 当n(Ca2+)∶n(Sar)=1∶1时, 混合溶剂中水和乙醇的体积比由1.5∶1依次增加为7∶3和3∶1时, 碳酸钙晶体的形貌由花状逐渐向球形过渡, 晶体中球霰石和方解石的含量也随之变化, 其中, 当水和醇的体积比为7∶3时, 产物主要为球霰石型晶体.     

Influence of Crystallization Conditions in Production of Citric Acid on the Properties of Forming Calcium Sulfate

The boundaries of phase equilibria involving calcium sulfate crystal hydrates in a citric acid solution were calculated. The influence exerted by an excess amount of sulfuric acid on the stability of calcium sulfate crystal hydrates in citric acid solutions was considered. The possibility of achieving a hemihydrate mode of citric acid extraction from calcium citrate was studied.     

Precipitation of calcium phosphate and calcium carbonate induced over chitosan membranes: a quick method to evaluate the influence of polymeric matrices in heterogeneous calcification

Precipitation of calcium compounds (phosphate and carbonate) was performed on chitosan porous and dense membranes. In order to observe the influence of acetyl groups on the nature of formed precipitates, some chitosan membranes were acetylated in methanol solution before undergoing calcification. Calcification experiments were performed more quickly than using SBF. In this method, a faster precipitation is induced by soaking the membranes in calcium chloride solutions and, in sequence, immersing the same membranes into sodium phosphate or carbonate solutions. This procedure induced the formation of calcium compound precipitates on membrane surfaces, which were analysed through optical microscopy, X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy with attenuated total reflection apparatus (FTIR-ATR) and small angle X-ray scattering (SAXS). The results indicated the biomimetic influence of the organic matrix on morphology, organization and composition of precipitates. The acetyl group induced the formation of organized calcium carbonate better than phosphate, which may correlate with the fact that these two compounds are commonly found together in nature in structures like shells and nacre.     

Retaining and recovering enzyme activity during degradation of TCE by methanotrophs

To determine if compounds added during trichloroethylene (TCE) degradation could reduce the loss of enzyme activity or increase enzyme recovery, different compounds serving as energy and carbon sources, pH buffers, or free radical scavengers were tested. Formate and formic acid (reducing power and a carbon source), as well as ascorbic acid and citric acid (free radical scavengers) were added during TCE degradation at a concentration of 2 mM. A saturated solution of calcium carbonate was also tested to address pH concerns. In the presence of formate and methane, only calcium carbonate and formic acid had a beneficial effect on enzyme recovery. The calcium carbonate and formic acid both reduced the loss of enzyme activity and resulted in the highest levels of enzyme activity after recovery.