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应用熔盐路线通过控制温度和时间成功合成了微立方和纳米片层形貌的SrFeO3-δ化合物。X射线衍射、场发射扫描电子显微镜、透射电子显微镜和能量色散X射线光谱(EDS)以及热重分析(TGA)结果表明,微立方形貌化合物SrFeO2.86为四方相,空间群I4/mmm,纳米片层形貌化合物SrFeO2.62是钙铁矿(空间群Ibma)和正交相(空间群Cmmm)的复合物。磁学性能研究表明,SrFeO3-δ形貌对其性能有明显地影响;自旋失挫的减少与铁磁相互作用的增加密切关联;尽管成分几乎相同,但是形貌上的各向异性导致了明显不同的磁学性能。 相似文献
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以某原油及其对应的减压渣油、加氢原料和加氢产品为研究对象,通过柱色谱分离法和溶剂抽提法,对油样中铁和钙化合物在组分中的含量、分布以及存在形态进行了研究。研究结果表明,柱色谱分离过程中,油样中的含铁或钙的化合物在色谱柱上产生吸附,损失了58%的铁化合物和76%的钙化合物;溶剂抽提法能够有效减少组分中金属元素的损失。原油中97%以上的铁和钙分布在减压渣油馏分中,减压渣油中60%-90%的铁和钙分布在胶质、沥青质组分中。渣油加氢反应过程中,铁、钙化合物主要是从胶质中得到脱除,整体脱除率接近30%,铁化合物更易结合在沥青质中而难以脱除。原油经过常减压蒸馏后,油溶性铁相对分布由95.6%降低为64.7%,水溶性铁相对分布由4.4%升高为35.3%。经过加氢反应后,38%左右的油溶性铁在反应中转化为水溶性铁,30%左右的油溶性钙在反应中转化为水溶性钙。 相似文献
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铝钙包芯线是一种炼钢用的冶炼脱氧剂,由铝粉、铁粉和Ф1mm的钙粒按配比进行物理混匀,然后用薄铁皮包成包芯线。由于钙的化学性质非常活泼,很容易被空气氧化及吸收空气中的水分,使钙的化合物发生变化,按常规操作测定铝和钙,则测定结果与配比(铝20%~30%、钙20%~30%)相差很大,测定结果偏低。本文对铝钙包芯线的取样、制样及分析方法进行探讨,采用分段直接剪取试样、 相似文献
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颜世铭 《广东微量元素科学》2009,16(7):16-16
钙:当饮水及食物中含钙量高时,可与植酸盐形成植酸钙,在pH为碱性的小肠内形成不溶性复合物而妨碍锌吸收。还有报导指出,高锌尿与高钙尿有关。推测,饮食中钙含量高导致的低锌,不仅系钙能妨碍锌吸收,也由于它能增加锌从尿中的排泄。钙不利于氟的吸收,主要与氟结合成牢固的化合物而减少氟化物的吸收利用。相反食物缺钙可增进氟吸收。应用大剂量的钙治疗氟中毒也是基于钙的这一特点。过量钙存在会阻碍锰和铁的吸收。此外,实验证明高钙饲料可抑制大鼠对铅的吸收。 相似文献
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综述了过渡金属均相催化的炔烃复分解反应进展,主要分为两部分:一是炔烃复分解反应在炔烃合成中的应用,即从六、七十年代Mortreux催化剂的发现能均相催化炔烃的歧化反应,经过一系列的条件改造,合成了炔醚和二芳基乙炔等化合物,并提出了可能的两种机理:金属卡宾和金属卡拜机理;金属钼和钨的卡拜络合物相继合成,发现此类络合物能够催化官能化的二炔的复分解反应,合成一系列的大环化合物。二是炔烃复分解反应在合成高聚物中的应用,即钙和钨的卡拜络合物被用来催化ROMP和ADIMET反应合成高聚物,改良了的Mortreux催化剂也能催化高聚物的生成,这些高聚物在发光器件、有机"塑料"激光、液晶显示器上都有应用。 相似文献
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颜世铭 《广东微量元素科学》2009,16(6):67-67
钙:当饮水及食物中含钙量高时,可与植酸盐形成植酸钙,在pH为碱性的小肠内形成不溶性复合物而妨碍锌吸收。还有报导指出,高锌尿与高钙尿有关。推测,饮食中钙含量高导致的低锌,不仅钙能妨碍锌吸收,也由于它能增加锌从尿中的排泄。钙不利于氟的吸收,主要与氟结合成牢固的化合物而减少氟化物的吸收利用。相反食物缺钙可增进氟吸收。应用大剂量的钙治疗氟中毒也是基于钙的这一特点。过量钙存在会阻碍锰和铁的吸收。此外,实验证明高钙饲料可抑制大鼠对铅的吸收。有人发现澳大利亚南部牧羊需铅量较大,与同时摄入大量的碳酸钙有关。 相似文献
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本世纪初即开始了有机钙化合物的研究,但这方面的发展是缓慢的。本文简要地介绍有机钙化合物近年来的进展及其发展缓慢的原因。 相似文献
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Anhydrous Amorphous Calcium Oxalate Nanoparticles from Ionic Liquids: Stable Crystallization Intermediates in the Formation of Whewellite
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Aaron Gehl Dr. Michael Dietzsch Dr. Mihail Mondeshki Sven Bach Dr. Tobias Häger Dr. Martin Panthöfer Dr. Bastian Barton Dr. Ute Kolb Prof. Dr. Wolfgang Tremel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18192-18201
The mechanisms by which amorphous intermediates transform into crystalline materials are not well understood. To test the viability and the limits of the classical crystallization, new model systems for crystallization are needed. With a view to elucidating the formation of an amorphous precursor and its subsequent crystallization, the crystallization of calcium oxalate, a biomineral widely occurring in plants, is investigated. Amorphous calcium oxalate (ACO) precipitated from an aqueous solution is described as a hydrated metastable phase, as often observed during low‐temperature inorganic synthesis and biomineralization. In the presence of water, ACO rapidly transforms into hydrated whewellite (monohydrate, CaC2O4 ? H2O, COM). The problem of fast crystallization kinetics is circumvented by synthesizing anhydrous ACO from a pure ionic liquid (IL‐ACO) for the first time. IL‐ACO is stable in the absence of water at ambient temperature. It is obtained as well‐defined, non‐agglomerated particles with diameters of 15–20 nm. When exposed to water, it crystallizes to give (hydrated) COM through a dissolution/recrystallization mechanism. 相似文献
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Direct Observation of the Distribution of Gelatin in Calcium Carbonate Crystals by Super‐Resolution Fluorescence Microscopy
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Meifang Fu Dr. Anhe Wang Dr. Xiaoming Zhang Prof. Dr. Luru Dai Prof. Dr. Junbai Li 《Angewandte Chemie (International ed. in English)》2016,55(3):908-911
Biological organic–inorganic hybrid materials often achieve excellent properties and provide inspiration for the design of advanced materials. The organic phase plays a key role in determining the properties of biogenic materials, and the spatial arrangement of organic and inorganic phases provides direct evidence for interaction between the two phases. Super‐resolution fluorescence microscopy was used to visualize the gelatin distribution in two different crystalline polymorphs of calcium carbonate (vaterite and calcite) and to investigate the process by which gelatin is excluded from the crystals. The results demonstrated that gelatin is distributed through vaterite microspheres in the form of nanoparticles, whereas it tends to accumulate on the edges of the calcite rhombohedra. 相似文献
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Biomineralization is believed to be achieved by the intimate cooperation of soluble macromolecules and an insoluble matrix at the specific inorganic–organic interface. It has been reported that positively charged matrices play an important role in controlling the structure of CaCO3 at surfaces, although detailed mechanisms remain unclear. In this work, we studied the transformation from amorphous CaCO3 to calcite crystals on surfaces by using thin films of poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) and its quaternized form. The positively charged PDMAEMA film was found to possess unique properties for CaCO3 crystallization: individually separated, single calcite crystals were formed on the PDMAEMA film in the absence of poly(acrylic acid) (PAA), while circularly fused calcite crystals were formed in the presence of PAA. The circularly fused (rosette‐shaped) calcite crystals could be changed from a completely packed rosette to a ring‐shaped, hollow structure by tuning the crystallization conditions. A number of factors, such as reaction time, amount of (NH4)2CO3, concentration of PAA, and charge of matrix‐films, were varied systematically, and we now propose a mechanism based on these observations. 相似文献
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Seunghoon Choi Sungjin Park Minjoo Park Yerin Kim Kwang Min Lee O-Mi Lee Hong-Joo Son 《Molecules (Basel, Switzerland)》2021,26(10)
Biomineralization, a well-known natural phenomenon associated with various microbial species, is being studied to protect and strengthen building materials such as concrete. We characterized Rhodococcus erythreus S26, a novel urease-producing bacterium exhibiting CaCO3-forming activity, and investigated its ability in repairing concrete cracks for the development of environment-friendly sealants. Strain S26 grown in solid medium formed spherical and polygonal CaCO3 crystals. The S26 cells grown in a urea-containing liquid medium caused culture fluid alkalinization and increased CaCO3 levels, indicating that ureolysis was responsible for CaCO3 formation. Urease activity and CaCO3 formation increased with incubation time, reaching a maximum of 2054 U/min/mL and 3.83 g/L, respectively, at day four. The maximum CaCO3 formation was achieved when calcium lactate was used as the calcium source, followed by calcium gluconate. Although cell growth was observed after the induction period at pH 10.5, strain S26 could grow at a wide range of pH 4–10.5, showing its high alkali tolerance. FESEM showed rhombohedral crystals of 20–60 µm in size. EDX analysis indicated the presence of calcium, carbon, and oxygen in the crystals. XRD confirmed these crystals as CaCO3 containing calcite and vaterite. Furthermore, R. erythreus S26 successfully repaired the artificially induced large cracks of 0.4–0.6 mm width. 相似文献
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Due to unique properties, KCa2Nb3O10 compound has received great attention worldwide. High-temperature solid-state reaction is the common route for the synthesis of this compound. In order to propose a new low-temperature method (i.e. hydrothermal synthesis), which could improve the final properties of KCa2Nb3O10, this study has been planned and performed. The preliminary experiments in KOH-Nb2O5 and Ca(OH)2-Nb2O5 systems revealed that KCa2Nb3O10 could be hydrothermally synthesized from a KOH-Ca(OH)2-Nb2O5 system using an alkaline condition (i.e. 5 M < KOH <10 M). However, the experimental results showed that the product only consisted of KNbO3 and Ca2Nb2O7 phases. To initiate the reaction between KNbO3 and Ca2Nb2O7, the obtained KNbO3-Ca2Nb2O7 mixture was heat-treated in an air atmosphere. The results showed that KCa2Nb3O10, with a high crystallinity and good purity, has been successfully obtained at 800 °C. This temperature is the lowest temperature, reported for the synthesis of KCa2Nb3O10 compound so far. The SEM investigations revealed that the obtained KCa2Nb3O10 powder has plate-like morphology due to its layered structure. 相似文献