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1.
In this paper, biomimetic synthesis of aragonite superstructures using a low molecular weight organic-hexamethylenetetramine (HMT) as an additive in the presence of CO2 supplied by an ammonium carbonate ((NH4)2CO3) diffusion method at room temperature was studied. The products were characterized by scanning or transmission electron microscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray powder diffractometry, and selected area electron diffraction. The results showed the aragonite superstructures especially dumbbell-flower-like ones were obtained. The formation process of calcium carbonate (CaCO3) in HMT aqueous solution was investigated, suggesting that the products transformed from calcite to vaterite primarily, and then changed into a mixture of aragonite and calcite with an increase of reaction time. The formation mechanism of CaCO3 in HMT solution was also discussed, revealing that aragonite might be controlled by HMT molecules and NH4+ ions together.  相似文献   

2.
Barium carbonate (BaCO3) particles have been obtained by the precipitation reaction of CO2 bubbles to barium hydroxide [Ba(OH)2] in the ethanol–water mixed solvents. Various morphologies, from rounded peanut, leaf-like, rod, and needle particles, were controlled by the precipitation step, where CO2 gas was fed to Ba(OH)2 in ethanol–water mixed solvent. The CO2 gas as a carbonate source and Ba(OH)2 slurry as a barium ion source are dissolved in the mixed solvents, within the solubility limit, to precipitate. The reactants dissolve progressively while they precipitate to BaCO3. Ba(OH) 2 slurry becomes translucent and opaque while the reaction proceeds. It becomes more opaque, upon which the dissolution of Ba(OH)2 proceeds and BaCO3 precipitates. The opaqueness of the products depends on the particle size of BaCO3 in the product. The characteristics of BaCO3 were confirmed by the X-ray diffraction (XRD), transmission electron microscope (TEM), and electrophoretic light scattering methods. The amount of water in the mixed solvents and of Ba(OH) 2 in the reaction batch is related to the reaction rate in the nucleation and growing step, so that it was possible to control the shape of particles. Based on the understanding of the size and morphology of BaCO3 in the solid/liquid–gas system, it was possible to obtain a well-dispersed average 40-nm BaCO3 colloid.  相似文献   

3.
竹文坤  罗学刚  张驰  周建 《无机化学学报》2011,27(10):2053-2060
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。  相似文献   

4.
Among Cambridge substances, which always include “organic”carbon, i.e., carbon contained in molecules or molecular ions,ion-molecular crystals (particularly, carbonates or alkaline-earthand alkaline metals) are of special interest. Some of such carbonatescontain pronounced Van der Waals (vdw) contacts between oxygenatoms of carbonate groups. Thus, agglomerates (layers or columns)formed by contacting carbonate groups arise (columns beingconnected in a frame), and in the cavities between these agglomeratescations are situated. The structure looks like an inclusion compound,the carbonate groups being hosts and the cations being guests. Todiscuss this question we used the refined value of vdw radius of oxygenwhich was obtained by statistical treatment of 8200 crystal structuresfrom Cambridge Structural Database (CSD) and is equal to 1.53 Å for the O?O contacts. Hence the length of a normal supporting vdw contact O?O is 3.06 ± 0.15 Å. Such contacts are present in MgCO3 and CaCO3 (calcite) and in α-Na2CO3. There are contacts O?O that are even shorter (2.74–2.81 Å)in CaCO3 (aragonite), SrCO3, BaCO3 and Li2CO3.So it is possible to suppose the existence of specific (partly covalent)contacts O?O in these substances. In β-Na2CO3, all forms of K2CO3, Rb2CO3 and Cs2CO3 the vdw contacts of CO3 groups are absent; therefore they are ionic (not inclusion) compounds.  相似文献   

5.
The crystallization of calcium carbonate (CaCO3) controlled by Pluronic P123 in a room-temperature ionic liquid, ethylamine nitrate (EAN), was investigated. The CaCO3 aggregates were obtained by rapid mixing of ammonium carbonate ((NH4)2CO3) and calcium chloride (CaCl2). Cubic calcite, spherical vaterite, and bagel-like vaterite were obtained easily by changing P123 concentration and reaction temperature. The morphologies of the as-prepared CaCO3 aggregates were investigated by transmission electron microscopy and scanning electronic microscopy. The phase change of the obtained crystals was confirmed by X-ray diffraction and Fourier transform infrared spectroscopy. It was shown that higher P123 concentration and higher reaction temperature favor the formation of vaterite in EAN. Unusual bagel-like vaterite was first obtained at 60 °C in the presence of 5 g/L P123 in EAN. Mineralization of CaCO3 regulated by P123 in EAN is a simple, novel, and environment-friendly strategy for vaterite synthesis.  相似文献   

6.
Nanocrystalline TiO2 powders with different morphologies and grain sizes were successfully synthesized by the hydrothermal method. Different concentrations of hydrochloric acid (HCl), ammonium chloride (NH4Cl), ammonium sulfate [(NH4)2SO4], and ammonium carbonate [(NH4)2CO3] were used as additives in the hydrothermal process to investigate the effect of the concentration of ammonium (NH 4 + ) and chloride ions (Cl?) on the phase compositions, morphologies, and grain sizes of the prepared TiO2. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy, Brunauer–Emmett–Teller analysis, and UV–Vis spectra. XRD results show that the as-synthesized powders are composed of anatase or a mixture of anatase and brookite. The grain size of the synthesized nano-TiO2 powder ranged from 5.0 to 11.3 nm, and the related BET specific surface area varied from 127.5 to 191.0 m2/g. The photocatalytic activities of the prepared TiO2 powders were evaluated by degradation of methylene blue (MB) in aqueous solution under UV light irradiation, and the results show that the photocatalytic performance of TiO2 powders synthesized with additives is improved compared with that of TiO2 prepared without any additives.  相似文献   

7.
The binary system Li2CO3–BaCO3 was studied by means of differential thermal analysis (DTA), thermogravimetry (TG) and X-ray phase analysis. The composition of carbonate and CO2 partial pressure influence on the thermal behavior of carbonate were examined. It was shown that lithium carbonate does not form the substitutional solid solution with barium carbonate, however the possible formation of diluted interstitial solid solutions is discussed. Above the melting temperature the mass loss is observed on TG curves. This loss is the result of both decomposition of lithium carbonate and evaporation of lithium in Li2CO3–BaCO3 system. Increase of CO2 concentration in surrounding gas atmosphere leads to slower decomposition of lithium carbonate and to increase the melting point. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
Zusammenfassung Spuren von Co2+, Ag2+- oder Mn2+-Ionen katalysieren stark den H2O2-Zerfall, wenn sie sich auf Erdalkalicarbonat-Trägern befinden, wofür CaCO3 und BaCO3 sich weit besser eignen als SrCO3. Weniger wirksam waren Cu2+ und Fe3+, während die Ionen Ni2+, Cd2+ und [Fe(CN)6]4– sich fast indifferent in diesem System verhielten.  相似文献   

9.
Macroscopically ordered inorganic thin films have been formed on unidirectionally oriented, liquid‐crystalline chitin matrices. In the presence of poly(acrylic acid) (PAA), unidirectionally oriented chitin films act as templates for the formation of oriented thin‐film crystals of alkaline‐earth carbonates such as SrCO3 and BaCO3. The morphology and orientation of crystals are dependent on the metal ion concentration. For SrCO3 crystallization, unidirectional thin films and hexagonal‐shaped thin films have been deposited from 200 and 25 mm concentration strontium solutions, respectively.  相似文献   

10.
Mixtures of calcium oxide (taken as carbonate) and silica in 2:1 molar ratio containing varying amounts of MgO, SrCO3 and BaCO3 as dopants were subjected to thermal treatment up to 1450°C. The exothermic peaks at 1200°C and above (beyond the decomposition temperature of calcium carbonate) have been examined to elucidate the phases formed. The exothermic peak at 1210°C without dopant was found to conform to the β-dicalcium silicate phase with a significant amount of free lime and cristobalite along with small amounts of the γ-C2S phase. MgO at 0.1–1% leads to the formation of β- and γ-dicalcium silicate phases at 1420–1430°C, while 5% MgO results in the formation of the β-C2 S phase at 1360°C. SrCO3, in the concentration range studied, leads to the stabilization of β-C2S, but does not lower its temperature of formation. BaCO3 at 0.1–1% assists in the formation of the β-dicalcium silicate phase, but 5% BaO forms a mixture of β- and α'H-C2S phases at a lower temperature.  相似文献   

11.
《Solid State Sciences》2012,14(8):1086-1091
Well-dispersed SrCO3:Tb3+ hollow microspheres have been synthesized in the water-ethanol-ethylene glycol solvent system using oleic acid (OA) as an additive without further annealing treatment. X-ray diffraction (XRD), fourier transform-infrared spectroscopy (FT–IR), and field emission scanning electron microscopy (FE-SEM), as well as photoluminescence spectroscopy (PL) were used to characterize the resulting samples. The dosage of OA and the reaction time play key roles in the formation of the final samples. The possible formation mechanism for SrCO3:Tb3+ hollow microsphere is proposed. The SrCO3:Tb3+ phosphors show strong photoluminescence with green emission 5D47F5 (544 nm) as the most prominent group under ultraviolet excitation, which have potential applications in field emission displays. The present synthesis process may be extended to fabricate other inorganic materials with special morphologies and functions.  相似文献   

12.
A series of unique morphologies of ZnO were synthesized by a simple mild solvothermal process using equimolar of Zn(NO3)2/Zn(AC)2–hexamethylenetetramine (HMT) acting as precursors and ethylene glycol (EG) and triethylamine (TEA) as the dispersant and surfactant additive, respectively. When the as-prepared particles were further treated in 0.02 M HMT solution for such a long time as 72 h, screw-like and rose-like crystals with three-dimensional and developed structure could be formed. The deNO x photocatalytic activity was characterized and the analysis results showed that the modified ZnO crystals possessed a three-dimensionally developed structure and had higher deNO x photocatalytic activity compared to that of the as-prepared untreated ZnO.  相似文献   

13.
Time-resolved laser-induced fluorescence has been used to investigate Eu complexes formed with a few main ligands encountered in natural waters: hydroxide, carbonate and humic substances. By varying pH and concentrations of ligands at fixed europium concentration and ionic strength, it was possible, together with free europium Eu3+, to identify spectrally and temporally carbonate complexes, namely Eu(CO3)+, Eu(CO3)2 and Eu(CO3)33− and humate complexes EuHA. For hydroxide complexes, no differences were found in terms of fluorescence spectra and lifetimes. A spectral interpretation is described by using deconvolution for all systems.  相似文献   

14.
In this paper, strontium carbonate particles with different morphologies were prepared by a simple precipitation reaction of sodium carbonate with strontium nitrate in the absence and presence of poly-(styrene-alt-maleic acid) (PSMA). The as-prepared products were characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of the concentration of PSMA on the morphologies and phase structures of strontium carbonate particles were investigated and discussed. The results showed that SrCO3 particles with various shapes, such as bundles, dumbbells, irregular aggregates and spheres could be obtained by varying the concentration of PSMA. A schematic illustration was proposed to account for the shape evolution of the as-prepared SrCO3 particles.  相似文献   

15.
Here, agar hydrogel was selected as diffusion medium and template to control the biomimetic mineralization of calcium carbonate (CaCO3). Due to three dimensional network structures and abundant functional groups (such as, hydroxyl groups), Ca2+ ions were uniformly distributed in the network and electrostatically attracted. The diffusion speed and range of CO32? ions were mediated by the concentration of hydrogel medium. Under the synergistic effect of Mg2+ ions, the crystal CaCO3 was induced by gas phase diffusion method in the hydrogel system. The results showed that the concentrations of Mg2+ ions and agar hydrogel had no obvious effect on the calcite phase of CaCO3, but the morphologies and sizes changed with concentrations of medium and Mg2+ ions. Attribute to template effect, the crystallization behavior and growth rate of CaCO3 crystals were regulated. Since Mg2+ ions were easily adsorbed on the surfaces of unit cell, the unique structure of CaCO3 was precisely controlled. This study provides a useful reference and inspiration for the understandings of the contributions of ion supply rate in bio-mineralization and hydrogel medium in biomimetic mineralization.  相似文献   

16.
The influence of synthetic conditions on the shape and size of SrTiO3 (STO) nanocubes was studied. These were synthesized in aqueous solution using Sr(OH)2 as the Sr2+ source and titanium(IV) bis(ammonium lactate)dihydroxide (TALH) as the TiIV source in the presence of oleic acid and hydrazine. A large excess of OH? at a pH of the precursor solution higher than 12 is necessary for the formation of STO nanocubes without the need for any calcination. Performing the synthesis in a N2 atmosphere additionally prevents the formation of SrCO3 impurity, leading to the creation of uniformly sized STO nanocubes in a reproducible manner. Such size-regulated STO nanocubes are found to align over a large area.  相似文献   

17.
It was found that calcium carbonate (CaCO3) and hydroxyapatite (Ca10(OH)2(PO4)6), which are two crucial constituents of the most abundant minerals in nature and very important bioinorganic components in the tissues of mineralizing organisms, can form solid solutions in a wide range of PO43?/CO32? (P/C) ratios at low temperature when prepared as ultrathin nanowire structures. This is due to the special reactivity of ultrasmall nanocrystals, which can effectively lower the synthetic temperature and promote the formation of solid solutions. The as‐prepared ultrathin nanowires with suitable P/C ratios presented strong blue luminescence due to the existence of abundant defects strengthened by CO32?. If used as the matrix, the as‐prepared ultrathin nanowires demonstrated bright green or red luminescent properties when doped with Tb3+ or Eu3+ ions, and simultaneously retained their original morphologies. These three kinds of fluorescent nanowires could reproduce a full range of luminescence colors based on additive color mixtures of the three primary colors (red, green, and blue). In addition, under the same reaction system, ultrafine rare‐earth‐doped (Ce3+, Tb3+, Eu3+) nanowires (about 1 nm in diameter) were synthesized by using a one‐step hydrothermal process, which further pushed the size of the Ca‐PO4‐CO3 nanobuilding blocks to one unit cell region. These ultrafine nanowires displayed excellent film‐forming properties and the ability to absorb UV radiation.  相似文献   

18.
Crystalline cerium oxide carbonate hydrate (Ce2O(CO3)2·H2O) was grown in aqueous solutions at a low temperature of 80 °C under ambient pressure. When cerium nitrate was used as a starting material, large Ce2O(CO3)2·H2O particles were precipitated through homogeneous nucleation and subsequent fast crystal growth. In contrast, the usage of cerium chloride was found to promote the preferential precipitation of Ce2O(CO3)2·H2O on foreign substrates through heterogeneous nucleation and slow crystal growth. This phenomenon was applied to a chemical bath deposition of Ce2O(CO3)2·H2O films. Immersion of glass substrates in the solution at 80 °C for typically 24 h resulted in formation of solid films with a unique morphology like a micrometer-scale brush. It was also found that samarium could be incorporated into Ce2O(CO3)2·H2O during the crystal growth in the solutions, as evidenced by characteristic photoluminescence of Sm3+ in heating products of CeO2. These results suggest that rare-earth oxide carbonate hydrates with a variety of compositions and morphologies can be synthesized from the aqueous solutions.  相似文献   

19.
Utilisation of CO2 as a chemical reagent is challenging, due to the molecule's inherent chemical stability. However, CO2 reacts promptly at high temperature (∼1000 °C) with alkaline-earth oxides to form carbonates and such reactions are used towards capture and re-utilisation. In this work, this concept is extended and CO2 is utilised as a reagent to modify the crystal structure of mixed-metal inorganic solids. Modification of the crystal structure is a “tool” used by materials scientists to tailor the physical property of solids. CO2 gas was reacted with several isostructural mixed-metal oxides Sr2CuO3, Sr1.8Ba0.2CuO3 and Ba2PdO3. These oxides are carefully selected to show anion vacancies in their crystal structure, to act as host sites for CO2 molecules, leading to the formation of carbonate anions, (CO3)2−. The corresponding oxide carbonates were formed successfully and the favourable formation of SrCO3 as secondary phase was minimised via an innovative, yet simple synthetic procedure involving alternating of CO2 and air. We also derived a simple model to predict the kinetics of the reactions for the cuprates, using first-principles density functional theory and assimilating the reaction to a gas-surface process.  相似文献   

20.
《Solid State Sciences》2007,9(3-4):303-309
(Ba,Ti)-precursor complexes, important for the production of advanced BaTiO3 perovskite-type materials, undergo structural transformations and complex reactions during their thermal decomposition. Based on XRD phase analysis, combined with Rietveld refinement of crystal structure data, and on IR analysis, the intermediate formation of calcite-type BaCO3 is evidenced, which can be explained by the stabilization of this metastable modification in the form of an oxycarbonate phase down to room temperature. Two possible processes, leading to such an oxycarbonate, are discussed: (i) partial substitution of CO32− by O2− in the anionic sublattice, and (ii) topotaxial formation of calcite-type structural domains of BaCO3 by templating with oxygen-deficient titanates, resulting in the oxide–carbonate intergrowth structures.  相似文献   

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