The mineral component of human cardiovascular deposits: morphological,structural and crystal‐chemical characterization

Complementary experimental techniques were applied to characterize bioapatite nanocrystals from pathological cardiovascular deposits. The investigated collection included the leaflets from aortic valve, leaflets from mitral valve, leaflets from tricuspid valve and calcified aorta's wall. XRD, EDX and FTIR data have shown that all studied samples consist of imperfect apatite with different crystallinity and variable chemical composition. In accordance with TEM data, the crystals of pathological calcified deposits frequently have oblong or rod‐like shape (length of 60‐90 nanometers, width of 20‐30 nanometers). At the same time, in the SEM and TEM experiments, the complex spheroid assemblies and planar sheet‐like shaped formations with crystal structure close to apatite were observed. Probably, the different shape and morphology of the particles are caused by different ways of crystal nucleation and growth, although the exact mechanisms remain an open question.     

Composition and kinetic characteristics of vapour phase during mercuric iodide growing

The results of thermodynamical analysis of the vapour phase are presented for mostly often used growth conditions. It is shown that the vapour phase may contain: HgI₂(g), Hg(g), I₂(g), I(g). However, the degree of decomposition does not exceed one percent. Moverover, the following dependences are calculated and presented in a graphic form for HgI₂ + I₂ vapour mixture: the coefficient of dynamic viscosity from composition and temperature; the coefficient of diffusion with temperature and pressure; the coefficient of heat conductivity from composition and temperature.     

The effects of surface morphological mechanics on liquid crystal alignment characteristics using photo-activators

Abstract

Photo-activators, which produce carbon dioxide, are highly reactive radical generators upon UV light illumination. In this study, the generated radicals selectively reacted with the polyimide (PI) main chains and created a liquid crystal alignment layer with a high level of azimuthal anchoring energy. The thickness of the photo-irradiated PI alignment layer was reduced dramatically by photo-induced radical crosslinking, which induced surface wrinkling and roughness. Moreover, the carbon dioxide and methane gases that were generated during photo-irradiation produced many micro-pores, which also attributed to holding the LC molecules tightly on the PI surfaces. The level of azimuthal anchoring energy that was obtained by photo-alignment was better than what was obtained by the rubbing method with the same PI, specifically, the maximum value of the photo-alignment with the photo-activator was 6.92 x 10^?5 J/m² than 1.11 x 10^?5 J/m² of the rubbing. We proposed a mechanism based on a high anchoring energy, a rough surface, a hydrophilic surface, and rapid photo-reactions.     

Controlled deposition and transformation of amorphous calcium carbonate thin films

Controlled synthesis of amorphous calcium carbonate (ACC) films was realized by using the multiple templates, which are composed of a self‐assembled film (SAF, insoluble Poly (ε‐caprolactone) film) and a soluble modifier (poly allylamine), as modifiers. The formation of self‐assembled film was analyzed by monitoring the morphologies using atomic force microscopy. Even more noteworthy, using anhydrous ethanol as media, the ACC‐to‐vaterite‐to‐calcite transformation was also investigated, and the obtained products were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction. The results demonstrated that organic solvent has profound influence on transformation of amorphous calcium carbonate thin films. In the air of anhydrous ethanol, the controlled synthesis of calcium carbonate films with different morphologies, such as planar films with a few sporadic particles, symmetric rhombohedral crystals, novel crystals with symmetrical terraced convexity formation of calcite, was obtained by the fine‐tuning of induction time. It provides a new and simple method to prepare polymorphic CaCO₃ crystal films from the ACC films by controlling the crystallization process (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermal transformations of the mineral component of composite biomaterials based on chitosan and apatite

Composite biomaterials based on chitosan and calcium apatite with different chitosan/apatite ratio were prepared by chemical synthesis of apatite in chitosan solution using one‐step co‐precipitation method. Initial and annealed samples were characterized by X‐ray diffraction, FTIR spectroscopy and scanning electron microscopy coupled to energy‐dispersive electron X‐ray spectroscopy. The data obtained suggest that the formation of the calcium‐phosphate mineral in chitosan solution is substantially modulated by the chemical interaction of the components; apparently, a part of calcium is captured by chitosan and does not participate in the formation of the main mineral phase. The apatite in the composite is calcium‐deficient, carbonate‐substituted and is composed of dispersed nano‐sized crystallites, i.e. has properties that closely resemble those of bone mineral. Varying synthesis, drying and lyophilization conditions, the composite materials can be produced with the desirable chitosan/apatite ratio, both in the dense and porous form. The structural analysis of composite samples after annealing at certain temperatures is examined as an approach to elucidate the mechanism of co‐precipitation by one‐step method. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Microstructural characterization of CPPD and hydroxyapatite crystal depositions on human menisci

Meniscus is a fibrocartilaginous tissue composed mainly of water and a dense elaborate collagen network with a predominantly circumferential alignment. Crystal formation and accumulation on meniscal tissue is frequently observed especially in elderly. In this study, we used X‐ray diffraction (XRD), FTIR and FT‐Raman for the structural identification of the depositions and Optical microscopy, Scanning Electron microscopy (SEM/EDX) and Atomic Force microscopy (AFM), in order to investigate the structural relationship between the crystal deposits and the collagen fibers of human meniscal tissues. We are reporting on the formation of intercalary “colonies” of Calcium Pyrophosphate Dihydrate (CPPD) crystals with two distinct morphologies corresponding to the monoclinic and the triclinic phase, as well as the formation of micro‐aggregations composed of nano‐crystalline HAP aggregations which are developed along the longitudinal axis of collagen fibers without extensively disturbing the collagens arrangement.     

Synthesis of rhombohedral strontium carbonate aggregates at the water/hexamethylene interface with cetyltrimethylammonium bromide

Unusual rhombohedral strontium carbonate (SrCO₃) aggregates have been synthesized in situ from strontium nitrate by the slow release of carbon dioxide by alkaline hydrolysis of diethyl carbonate at the water/hexamethylene interface in the presence of cetyltrimethylammonium bromide (CTAB). Transmission electron microscopy, Fourier transform infrared spectroscopy and X‐ray powder diffractometry were used to characterize the products. The results indicate that rhombohedral SrCO₃ aggregates are obtained with weaker crystallinity and sizes of several micrometers. The possible formation mechanism of the SrCO₃ aggregates at the interface is discussed, which can be interpreted by particle‐aggregation based non‐classical crystallization laws. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Impact of magnetic field on the nucleation and morphology of calcium carbonate crystals

The influence of static magnetic field of strength 0.75 T on the nucleation of calcium carbonate crystals has been investigated. Particle size analysis shows that magnetic field can cause marked difference in distribution. One of the major impacts of magnetic exposure is the increase in number of the critical nuclei formed. Also, magnetic field promotes the formation of parallelepipedic calcite crystals and the dissolution of the smaller crystals by Ostwald ripening mechanism. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure and Composition of Polished PbS Surfaces

{100} surfaces, produced from sublimation grown PbS single crystals by cutting, mechanical and chemical polishing, were characterized with regard to topography, structure and chemical composition. For this purpose, some methods independent from another were used, for instance profile measuring, dislocation etching, X-ray rocking-curves, RHEED, Rutherford backscattering (RBS), and AES. The results allow to describe the change of structural perfection with the depth (damage depth), the concentration profile of the main components (half-quantitatively), and the significant decreasing of contamination. Following from this study, the model of the damage layer near the surface discussed earlier for PbTe is modified slightly.     

Growth and morphological study of copper oxide single crystals

Experiments on the growth of CuO single crystals by crystallization from flux in the CuO-Bi₂O₃-PbO-PbF₂, CuO-Bi₂O₃-Li₂O, CuO-Bi₂O₃-B₂O₃, CuO-BaO-Y₂O₃, and CuO-MO_x systems (M = P, V, or Mo) have been performed. The best results were obtained in crystallization in the CuO-Bi₂O₃-PbF₂ system: prismatic single crystals of platelet-and needlelike or isometric habit with dimensions up to 1 × 10 × 10, 1 × 1 × 20, or 6 × 6 × 8 mm, respectively, have been grown. The CuO crystals show polysynthetic twinning in the form of numerous alternating light and dark bands bound by systems of parallel straight lines on the {110} and {111} faces. A possible model of twinning associated with the Cu₂O → CuO transformation is considered.     

On growth and morphological studies of TGS single crystals

The effect of various growth parameters; seed morphology, growth-temperature and pH of the mother solution on the growth of TGS single crystals is studied. The effect of these variables on the crystal morphology and perfection is reported. It is shown that; (i) The crystal quality is much dependent on the seed and the growth temperature and (ii) the pH-control is a simple and an effective method for obtaining TGS crystals of required morphology.     

Precipitation and characterization of hollow calcite nanoparticles

A method for preparation of significant amount of hollow rhombohedral calcite nanoparticles, based on carbonation of calcium hydroxide suspension, is described. The mineralogical and morphological analyses of the precipitate confirmed the existence of exclusively stable polymorphic modification, calcite, with the mean particle size of about 100 nm and the diameter of the holes observed at the surfaces that are about 50 nm. The analysis of carbonation kinetics pointed out to a complex mechanism of hollow particles formation at high initial supersaturation, that assumed nucleation of amorphous precursor calcium carbonate phase and its solution mediated transformation into nanosized crystalline calcite. The holes obtained at the calcite surfaces are most probably the imprints remained after the dissolution of amorphous calcium carbonate particles.     

Molecular structure of (tBu)3Al[O=C(OPh)2]

The molecular structure of (^tBu)₃Al[O=C(OPh)₂] has been determined. The increase in the C=O bond distance [1.258(4) Å] when compared to free O=C(OPh)₂ [1.191(3) Å], is presented in respect to the activating ability of aluminum Lewis acids. Crystal data: monoclinic, P2₁/n, a = 10.653(2), b = 18.486(4), c = 14.551(3) Å, = 108.07(3)°, and V = 2724.3(9) ų for Z = 4.     

硫酸软骨素/L-谷氨酸对碳酸钙形貌及晶体生长影响的研究

根据生物矿化原理,通过CO2的缓慢扩散,在硫酸软骨素(CSB)/L-谷氨酸二元体系中,与富集在有机/无机界面钙离子的结合,合成了不同形貌的碳酸钙.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.产物用XRD、SEM和FT-IR进行表征,FT-IR和XRD分析表明:所得的晶体为方解石的晶型,SEM表明体系中CSB的浓度,pH值,CSB/L-谷氨酸的浓度比对碳酸钙形貌起着重要作用.通过改变实验条件得到了椭球型,哑铃型等形貌碳酸钙晶体,并对其可能的形成机理进行了分析.     

MgO晶须的物相组成和微观形貌多样性

采用适当MgO-Al比例物料,压制成型后放入气氛炉中于1500℃烧制6h,最终在样块表面得到 MgO晶须.晶须的物相组成为方镁石,显微结构研究表明多数呈细长的柱状,顶端尖锐,长约600～800μm ,长径比100～200;晶须发育的纹理特征有多种,晶须的横截面有扁六边形、正六边形、菱形和正四边形以及不规则形状等多种,能谱分析表明晶须的形貌与化学组成有关.     

花生状碳酸钡粒子的制备与表征

本文以BaCl2·2H2O和Na2CO3为原料,采用共沉淀法合成了碳酸钡粒子.通过添加合适的晶形控制剂,选择合适的用量,合成了花生状的碳酸钡粒子,利用扫描电子显微镜(SEM)和X射线衍射仪(XRD)进行了表征,结果表明:当控制剂WHB-1用量在85;以上时,生成的花生状碳酸钡粒子为正交晶系,粒度分布均匀,在500nm左右,且粒子分散性良好,几乎没有团聚现象.并对花生状碳酸钡粒子的形成机理进行了初步的探讨.     

Composition and polyamorphism in supercooled yttria-alumina melts

By extending recent work on liquid-liquid transitions in supercooled yttria-alumina AYx liquids we draw attention to the compositional dependence of the structure factor of the high density liquid, arguing that this is sufficiently sensitive to discriminate between liquids at the level of a few %. Comparing structure factor differences between liquids of different compositions and in the same liquid AY20 between high and low temperatures straddling the transition at 1788 K between a high density liquid (HDL) and a low density liquid (LDL) enables compositional phase separation to be ruled out. It points instead to kinetic changes in polyhedral configurational order being the drivers for this polyamorphic transformation. Rotor behaviour observed in levitated liquid drops used in the high temperature experiments enables the reversibility of the LLT transition (LLT) and the associated changes in entropy and density to be identified. Evidence for critical-like behaviour in the structural relaxation time and in the fluctuation correlation length is presented. By re-examining recent work which failed to find the structural and thermal signatures for the LLT in liquid AY20 at 1788 K we present evidence for the LLT occurring instead in liquid AY15 at 1940 K, suggesting that the liquid-liquid transition temperature in AYx liquids decreases with increasing yttria content.     

Preparation and structure of calcium peroxide‐templated porous calcium carbonate crystals

Crystalline calcium carbonate with randomly dispersed porous structure was prepared through co‐ crystallization with calcium peroxide and the following template elimination by a post heating treatment and washing with water. The artificial CaCO₃ possess abundant macro‐mesopores structures and high surface area. This approach may open a new general route for the preparation of crystals with high porosity and structure specialty. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Morphologies of calcium carbonate crystallites grown from aqueous solutions containing polyethylene glycol

Calcium Carbonate has been precipitated from aqueous solutions containing different concentrations and different molecular weight of Polyethylene Glycol (PEG). The precipitations were analyzed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT‐IR) and X‐ray diffraction (XRD). The results demonstrated that PEG has profound influence on the nucleation and crystal growth of CaCO₃, under condition of low PEG6000 (refer to PEG M_W=6000) concentration, it favored the formation of calcite, while high PEG6000 concentration promoted vaterite formation. Additionally, low molecular weight PEG can stabilize vaterite phase. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation of Li2CO3 by gas‐liquid reactive crystallization of LiOH and CO2

A spinning disk reactor (SDR) was used in this research to prepare Li₂CO₃ by gas‐liquid reactive crystallization of LiOH and CO₂. It was found that the end pH value of the above reaction should be controlled within the range of 9.0‐9.5 to obtain a high yield of Li₂CO₃. The effects of operational parameters (including the temperature, the concentration of LiOH solution, the rotation rate of the spinning disk, the circulation rate of LiOH slurry, the flow rate of CO₂ and the ultrasound field) on the particle size and the yielding rate were investigated by an orthogonal experiment. The results show the significant factors influencing the particle size are the ultrasound field, the temperature and the flow rate of CO₂. As for the yielding rate, the temperature, the concentration of LiOH solution and the flow rate of CO₂ exert obvious impacts, while the effects of ultrasound field and the rotation rate of the spinning disk are limited. The SEM images show the Li₂CO₃products are flower‐like particles, which are composed of plate‐like primary crystals. The size analysis shows the volume mean particle size of the Li₂CO₃products ranges 37‐90 μm depending on the various experimental conditions. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)