一种假单胞菌诱导CaCO3结晶

选用实验室自培育斯氏假单胞菌,通过测定pH值、电导率变化研究了细菌液、菌体液对碳酸钙结晶过程的影响,并通过SEM、XRD、红外等测试技术对生成的碳酸钙进行表征。 研究表明,斯氏假单胞菌细菌液与菌体液对碳酸钙结晶过程具有抑制作用,浓度增加,抑制作用越显著。 SEM、XRD和红外光谱的分析结果显示,细菌液可诱导亚稳态球霰石生成,菌体液能诱导出中孔方解石型碳酸钙。     

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.     

预处理对丝素蛋白膜调控羟基磷灰石晶体生长的影响

以丝素蛋白膜为基质, 在模拟体液中诱导羟基磷灰石晶体在其表面沉积和生长. 利用XRD, SEM, HRTEM, AFM和FTIR等表征手段研究了不同预处理方法对羟基磷灰石晶体的形成及其微观形貌的影响. 结果表明, 丝素膜可有效地诱导羟基磷灰石晶体在其表面沉积和生长; 较长的矿化时间有利于形成较多结晶度良好的HAP晶体; 而不同预处理方法对丝素膜的表面结构产生了不同影响, 进而调制在其表面沉积的羟基磷灰石的形貌和生长方向. 同时对丝素蛋白膜调控羟基磷灰石晶体生长的机制进行了必要的探讨.     

多肽Langmuir膜控制下方解石晶体的生长

本文研究了聚β-苯甲基天门冬氨酸(PBA)Langmuir膜对碳酸钙成核和生长的诱导控制作用。在PBA Langmuir单分子膜作用下,我们得到形状规则、边缘清晰的花瓣状碳酸钙晶体。XRD分析表明所得碳酸钙晶体为沿(104)和(208)晶面取向生长的方解石晶型;AFM、TEM和SEM观察显示了方解石形貌的变化过程。结果表明多肽PBA Langmuir单分子膜对碳酸钙的结晶、生长取向和形貌具有良好的诱导和调控作用。     

牛血清白蛋白LB膜诱导方解石的生长

采用模拟生物矿化的方法,研究了牛血清白蛋白(BSA) LB膜对碳酸钙晶体成核和生长的诱导控制作用。XRD、SEM结果表明：在BSA单层LB膜诱导下,形成形状规则、边缘清晰的多层盘状方解石晶体,且沿(104)晶面取向生长。说明牛血清白蛋白(BSA) LB膜对碳酸钙的形貌、生长取向性有很好的调控作用。     

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...     

聚苯乙烯磺酸钠/L-谷氨酸协同作用下碳酸钙微球的设计与合成

通过CO₂缓慢扩散,在聚苯乙烯磺酸钠(PSSS)/L-谷氨酸(L-Glu)二元体系中,与富集在有机/无机界面钙离子相结合,合成碳酸钙微球。本文系统地研究了室温下各种因素对碳酸钙晶体形貌和晶型的影响。实验表明,pH值、表面活性剂和PSSS/L-Glu的浓度比起着重要作用。通过改变实验条件,除了得到主要的球形晶体外,我们还得到了矩形、立方体形和饼形等。取向聚积机理解释了微球的形成,PSSS和L-Glu间的协同作用在晶体化过程中起着重     

3-巯基丙酸自组装单层控制碳酸钙晶型及形貌的研究

采用碳酸铵分解产生的NH3和CO2扩散并溶入氯化钙溶液中,得到了碳酸钙晶体。研究结果表明,3-巯基丙酸自组装单层和溶液温度对碳酸钙晶体的晶型和形貌具有重要影响。25℃条件下,纯溶液中得到了方解石,文石和球霰石三种晶型的混合沉淀物,而在自组装单层存在条件下只得到了表面光滑的菱面体方解石。改变温度,自组装单层调控得到的方解石晶体具有不同的形貌。在60℃得到了多孔方解石,与25℃时典型菱面体方解石有重要区别。XRD分析表明自组装膜上所得碳酸钙晶体为沿着(104)和(006)晶面取向生长的方解石。     

微生物诱导碳酸钡沉淀

利用巴斯德芽孢杆菌繁殖过程产生的酶化作用,适时引入Ba2+,形成碳酸钡沉淀,通过用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FTIR)、综合热分析仪(DSC-TG)对碳酸钙样品形貌、结构、热性质等进行表征。结果表明,巴斯德芽孢杆菌诱导沉淀的碳酸钡与纯水中的不同,含有少量有机物质,晶形转变温度降低。主要为花簇状和放射状,属于正交晶系。菌体和代谢物在碳酸钡晶体成核、生长及堆积过程中扮演重要的角色。     

非洲绿猴肾上皮细胞的损伤模型及其对草酸钙生长的调控作用

采用H₂O₂对非洲绿猴肾上皮细胞(Vero)进行了损伤, 通过检测细胞存活率、培养基中超氧化物歧化酶(SOD)浓度、丙二醛(MDA)释放量和细胞表面晶体粘附分子骨桥蛋白(OPN)的表达量变化, 检测了细胞的损伤程度. H₂O₂对Vero细胞的损伤作用呈现时间依赖性和浓度依赖性|细胞损伤后, MDA释放量增加, SOD浓度降低, OPN表达量显著增加, 导致粘附的晶体量增加. 利用扫描电子显微镜(SEM)和X射线衍射(XRD)研究了细胞损伤前后对草酸钙(CaOxa)晶体生长的调控作用. 对照组细胞诱导生成的CaOxa晶体棱角圆钝, 同时含有一水草酸钙(COM)和二水草酸钙(COD)晶体|而损伤细胞诱导生成的晶体形状不规则, 棱角尖锐, 主要为COM晶体, 因此, 细胞损伤后增加了草酸钙结石形成的危险性. 所建立的Vero细胞氧化损伤模型有助于从细胞水平上阐明草酸钙结石的形成机制.     

Tuning the Stability of CaCO3 Crystals with Magnesium Ions for the Formation of Aragonite Thin Films on Organic Polymer Templates

Thin‐film growth of aragonite CaCO₃ on annealed poly(vinyl alcohol) (PVA) matrices is induced by adding Mg²⁺ into a supersaturated solution of CaCO₃. Both the growth rate and surface morphology of the aragonite thin films depend upon the concentration of Mg²⁺ in the mineralization solution. In the absence of PVA matrices, no thin films are formed, despite the presence of Mg²⁺. Molecular dynamics simulation of the CaCO₃ precursor suggests that the transition of amorphous calcium carbonate to crystals is suppressed in the presence of Mg²⁺. The role for ionic additives in the crystallization of CaCO₃ on organic templates obtained in this study may provide useful information for the development of functional hybrid materials.     

Assembled structures of nanocrystals in polymer/calcium carbonate thin-film composites formed by the cooperation of chitosan and poly(aspartate)

Assembled structures of calcium carbonate (CaCO₃) nanocrystals have been examined for polymer/CaCO₃ thin-film composites synthesized through a self-organization process inspired by biomineralization. For the crystallization of CaCO₃, a thin-film matrix of chitosan has been used as a polymeric substrate. When the matrix is immersed into a supersaturated aqueous solution of CaCO₃ containing 1.4 × 10⁻³ wt % poly(aspartate) (PAsp), thin-film crystals of CaCO₃ are formed spontaneously. Three kinds of disklike films have been observed under a polarizing optical microscope. Electron diffraction analyses of each film have revealed that one is aragonite, displaying radial orientation of the c axes, and the others are vaterite, exhibiting different orientations. Detailed observation by scanning electron microscopy has clarified that these films are assemblies of crystalline particles 10–20 nm in size. The thin-film composites have been obtained over a PAsp concentration range of 4.4 × 10⁻⁴ to 1.0 × 10⁻² wt %. Vaterite formation becomes dominant when the concentration of PAsp is increased. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5153–5160, 2006     

Influence of N,O-carboxymethyl chitosan on the properties of octadecanoic acid/octadecylamine monolayers and the fractal structure of calcium carbonate

The properties of octadecanoic acid-otctadecylamine monolayers and growth of calcium carbonate (CaCO₃) induced by the monolayers on the surface of supersaturated CaCO₃ solution with N,O-carboxymethyl chitosan (CMC) are studied. The results suggest that CMC is either adsorbed on or inserted into the monolayers, as is confirmed by π-A, dπ/dA-A, and π-t isotherms. The adsorption of CMC changes the properties of the monolayers, a process that results in the transformation of the shape of CaCO₃ particles from crystal-like into the fractal pattern beneath the monolayers. Different fractal morphologies, such as butterfly and wicker branches consisting of hollow ellipsoidal, solid ellipsoidal, and spherical particles, correspondingly, are observed; these morphologies depend on the CMC concentration in the subphase. The dimensions of fractal patterns are determined. The mechanisms of the formation of CaCO₃ crystals and fractal structures are discussed. The text was submitted by the authors in English.     

Effects of Hydroxypropylmethylcellulose macromolecules used as organic template on the crystallization of CaCO<Subscript>3</Subscript>

Hydroxypropylmethylcellulose (HPMC) was used as an organic template to synthesize calcium carbonate. Crystals were synthesized in HPMC solution and HPMC hydrogel, respectively. For the mineralization system of HPMC solution, the effects of adding HPMC and rotating the reaction system on the crystal polymorph and morphology of CaCO₃ were investigated by X-ray diffractometer (XRD) and scanning electron microscope (SEM). The results showed that the presence of HPMC induced the formation of aragonite. And its content became higher when the concentration of solution increased or when rotating the system with the presence of HPMC. Moreover, it can be seen from SEM that bundle-like CaCO₃ appeared and became more with the increase of concentration. The structure and shape of the crystal had close relationship with the condition of mineralization. On the other hand, for the first time, CaCO₃ was synthesized in HPMC gel, SEM results indicated that a special structure, a long bar with some slight slots at intervals on the surface, of the crystals which may be caused by the network structure of the gel was found. Thermogravimetry (TG) results showed that CaCO₃ crystal products contained some HPMC. Further research on how the gel network modulates the growth of crystals is left to be done in the future.     

Crystal growth of calcium carbonate on the cellulose acetate/pyrrolidon blend films in the presence of L-aspartic acid

The morphogenesis and growth process of calcium carbonate on the cellulose acetate/polyvinyl pyrrolidone (CA/PVP) blend films in the presence of L-aspartic acid was carefully investigated. The results showed that the concentration of L-aspartic acid, the initial pH value of reaction solution and temperature turned out to be important factors for the control of morphologies and polymorphs of calcium carbonate. Complex morphologies of CaCO₃ particles, such as cubes, rose-like spheres, twinborn-spheres, cone-like, bouquet-like, etc. could be obtained under the different experimental conditions. The dynamic process of formation of rose-like sphere crystals was analyzed by monitoring the continuous morphological and structural evolution and components of crystals in different crystal stages. This research may provide a promising method to prepare other inorganic materials with complex morphologies.     

Peanut-shaped aggregation of CaCO<Subscript>3</Subscript> crystallites in the presence of an amphiphilic derivative of carboxymethylchitosan

An amphiphilic derivative of carboxymethylchitosan (CMCS), (2-hydroxyl-3-butoxyl)propyl-CMCS (HBP-CMCS), was used as an organic additive in the precipitation process of calcium carbonate (CaCO₃). HBP-CMCS molecules can interact with calcium ions, the functional groups of which act as active sites for the nucleation and crystallization of CaCO₃. Simultaneously, HBP-CMCS molecule also functionalizes as a colloidal stabilizer to prohibit the sedimentation of the grown CaCO₃ crystals, depending upon the molar ratio of the initial Ca²⁺ ions to the repeat units of HBP-CMCS molecules. The combination investigations of scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy on the precipitated CaCO₃ crystals proved that concentrations of HBP-CMCS and Ca²⁺ exert great influence on the crystallization habit of CaCO₃, such as the nucleation, growth, morphology, crystal form, etc. The formation of the peanut-shaped CaCO₃ particles suggests the template effect of HBP-CMCS molecules on the aggregation behavior of CaCO₃ nanocrystals.     

Studies of the reaction of crystalline calcium carbonate with aqueous solutions of NH4F,KF and NaF

The reaction between solid calcium carbonate and the aqueous fluorides NH₄F, KF, and NaF has been completely investigated. The reaction of CaCO₃ (solid) is completely independent of the dimensions of its polycrystalline particles and gives calcium fluoride. The calcium fluoride is formed in the same form and size as the grains of the original calcium carbonate. A course crystalline fluorite is formed at a satisfactory rate and with a sufficiently high mechanical strength to be of industrial interest.The course of the reaction appears to involve penetration of the fluoride solution into the body of a grain through voids which develop in the solid material owing to the formation of polycrystalline CaF₂ with a different molar volume as compared with CaCO₃. Data were obtained on the rate of formation and nature of the fluoride formed.The fluorite which is formed around the dissolving calcite was shown by X-ray diffraction and electron microscopy to have a polycrystalline aggregated structure and an estimate is made of crystallite size.The fluorite grains are pseudomorphs of the calcite crystals and there is crystallographic orientation of the product with respect to the parent phase.     

Calcium Carbonate Scale Formation in Pipes: Effect of Flow Rates,Temperature, and Malic Acid as Additives on the Mass and Morphology of the Scale

It is well recognized that calcium carbonates (CaCO₃) is one of the main components of scale that is commonly encountered in chemical and related industries. The calcium carbonate scale often grows extensively on equipment and parts, causing major operational difficulties. This paper presents experiments on calcium carbonate scale formation and control in a piping system where the scale-forming solution flowed in a laminar manner: 30, 40, and 50 mL/min, respectively. Other parameters evaluated were: solution temperature (25, 30 and 40 °C), and concentrations of malic acid (C₄H₆O₅) added as impurities (3.00 and 5.00 ppm). The scale-forming solution was made by mixing equimolar solutions of CaCl2 and Na2CO3, respectively. The scale formation process was monitored by measuring the conductivity of the solution coming out of the piping system. It was found that in all experiments, conductivity decreased abruptly after a certain induction period, during which time the conductivity remained steady. The induction period varied from 17 min to 34 min, which means that the scale starts forming 17 min to 34 min after the mixing of the solution. Higher flow rates resulted in more calcium carbonate scale mass, which indicate that the fluid flow enhances the scale formation. Similarly, increasing the temperature of the solution (25, 30, and 40 °C) resulted in the increase of the scale mass. Overall, higher malic acid concentrations resulted in longer induction time and less scale mass. Depending on the temperature and the malic acid concentration tested, the reduction in scale mass could be ≥ 200%. This drastic reduction in scale mass suggests that malic acid could be an effective anti-scalant for calcium carbonate scale. SEM imaging and its associated EDS analysis confirmed that the scale formed corresponds to that of calcite (CaCO3). The X-ray diffraction analysis of the scale showed that the scale consisted of crystalline matter which corresponds to the powder diffraction data for calcium carbonate. The addition of malic acid in trace amounts (0.00 to 5.00 ppm) was able to alter the morphology of the scale crystals, indicating the preference adsorption of malic acid on specific crystal surface.