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制备纳米硫酸钙(CaSO4)颗粒的关键在于采用适宜的制备工艺条件配制反相微乳液,使CaSO4晶体在理想的环境中生长。采用AOT、OP-10复合表面活性剂/环己烷/正戊醇/水溶液反相微乳液反应体系,在水与表面活性剂的摩尔比(水表比)ω=20、反应物浓度n([Ca2+])/n([SO24-])=0.125mol/L、陈化时间t=10min的条件下,制备出了形貌均一,平均粒径为70nm的球形CaSO4颗粒。用扫描电子显微镜(SEM)对产物形貌和大小进行了表征。实验分析了水表比ω、反应物浓度n([Ca2+])/n([SO24-])值、陈化时间t等因素对纳米CaSO4颗粒粒径的影响。 相似文献
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采用水溶液(W)/环己烷(O)/Triton X-100(S)/正戊醇(A)反相微乳液体系制备出粒径为20~60nm的球状羟基磷灰石(Hap)颗粒,并用TEM、XRD、IR和动态激光散射等手段对合成的样品进行形貌和结构表征.研究结果表明,合成的Hap具有弱结晶性,与人骨结构较相似.改变水油比可实现对纳米Hap颗粒尺寸的控制.微乳液经超声处理后,可制得尺寸为80nm×(5~15)nm的Hap纳米针状晶体.增加Hap微乳液的搅拌时间对纳米Hap的颗粒度、粒度分布影响不大. 相似文献
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应用电导率法研究了TritonX-100/正戊醇/环己烷体系中各组分及条件对微乳液最大增溶水量的影响。结果表明:当表面活性剂TritonX-100用量为3ml,助表面活性剂选正戊醇用量为1ml,环己烷为油相,温度为48℃,Ca(NO3)2溶液与(NH4)2HPO4溶液分别为0.24和0.14mol/L时,体系增溶水量最大,可得到较高产率的纳米羟基磷灰石。并且用XRD和TEM手段对产物进行了表征。 相似文献
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用Triton X-100/正己醇/环己烷/水四元反相微乳液体系制备了纳米羟基磷灰石(HA)粉体,确定了影响制备过程的最佳pH值和煅烧温度等工艺条件.x-射线衍射仪、TEM、SEM对羟基磷灰石的颗粒进行表征和分析表明:颗粒分散均匀,呈杆状,a轴尺寸为20~40nm左右,c轴尺寸为60~80nm,此方法可以有效地控制和改变HAP的分散性和粒度大小. 相似文献
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在一定pH值条件下,采用水溶液(W)/环己烷(O)/OP-10(S)/正辛醇(A)四元反相微乳液体系并结合撞击流技术制备出粒径为20-50nm的针状纳米羟基磷灰石(HA)晶体。红外光谱(IR)、X射线衍射(XRD)和透射电镜(TEM)对羟基磷灰石颗粒进行表征和分析表明:颗粒分散均匀,成针状,沿C轴方向的微晶尺寸约30nm,沿a轴方向为20nm左右。并主要考察了表面活性剂、杂质、反应和静置时间等对HA的微观形貌的影响。 相似文献
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含镉羟基磷灰石的形成及其稳定性 总被引:2,自引:0,他引:2
采用液相共沉淀方法合成了不同镉摩尔含量Xcd(即:Cd/(Ca Cd))的镉羟基磷灰石.通过XRD,FT-IR,FE-SEM,TG-DTG-DSC-MS和TCLP对产物的组成、形貌、热稳定性及化学稳定性进行了探讨.结果表明,随着Xcd的增加, Cd2 进入到羟基磷灰石的晶格中依次形成Ca3.9(Ca4.7Cd0 7)(PO4)6(OH)1.8,Ca3.s(Ca4 1Cd0.73)(PO4)6(OH)1,8,Ca3.6(Ca4 5Cd0.76)(PO4)6(OH)1.6和Cd5(PO4)3OH;这些产物在500℃以下均可稳定存在,且热稳定性随着Xcd的增加明显提高;毒性浸出结果显示,Cd2 能够进入到羟基磷灰石的晶格中,但产物的化学稳定性不高. 相似文献
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采用液相包裹法由NiC2O4·2H2O/BaTiO3前躯体热分解制得Ni/PTC陶瓷复合材料,并对其结构和性能进行了表征.Ni/PTC陶瓷复合材料具有多孔性结构和较好的分散性,Ni主要以微细金属颗粒的形式分布于晶界和孔隙中;在Ni/PTC陶瓷复合材料中氧化Ni导致室温电阻率增大,对PTC效应产生消极影响;采用石墨扣烧的方法能避免金属Ni氧化,制得的Ni/PTC陶瓷复合材料具有非常低的室温电阻率,但几乎失去了PTC效应,在烧成后热处理过程中晶界氧的吸附可使其恢复PTC效应;Ni/PTC陶瓷复合材料结构的多孔性和金属Ni的充分分散有利于PTC效应的恢复. 相似文献
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喷射电沉积Co-Ni纳米合金沉积层的组织和性能 总被引:4,自引:0,他引:4
用高速喷射电沉积法快速制备了块体纳米晶Co-Ni合金,研究了喷镀工艺参数(主盐浓度、电解液喷射速度和电流密度等)对沉积层成分、微观组织结构及性能的影响.结果表明:提高喷射电沉积电解液的搅拌强度能有效减小扩散层的厚度,使电沉积在较高的极限电流密度下进行,提高沉积速度.极限电流密度的增大使阴极过电位增大,从而提高合金的形核速率,使沉积层晶粒的尺寸减小、显微硬度升高.随着电解液中Co2 含量的增加,沉积层中Co含量增加,导致沉积层相结构由单相α-Co(Ni)转变为α-Co(Ni)和ε-Co(Ni)双相组织,并使表面的形貌发生明显的变化. 相似文献
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Varaporn Buraphacheep Junyaprasert Panee Boonsaner Sujitra Leatwimonlak Prapaporn Boonme 《Drug development and industrial pharmacy》2013,39(8):874-880
Microemulsions of water/isopropyl palmitate (IPP)/Aerosol OT (AOT)/1-butanol were developed as alternative formulations for topical delivery of clindamycin phosphate. Effect of AOT:1-butanol ratios on microemulsion region existence in the pseudoternary phase diagrams was investigated. The 2:1 AOT:1-butanol provided the largest microemulsion region. Five microemulsions of 1% w/w clindamycin phosphate were prepared and characterized. The permeation through human epidermis of the microemulsions was evaluated and compared with the 70% isopropanol solution using modified Franz diffusion cells. The drug permeation from all microemulsions was found to be significantly greater than that from the solution, indicating the enhancement of the skin permeation by the microemulsions. Within the same microemulsion type, the drug permeation increased with increasing the amount of AOT:1-butanol. The drug permeation from oil-in-water (o/w) microemulsions was relatively higher than that from water-in-oil (w/o) microemulsions. In addition, all microemulsions were stable for at least three months at 30 ± 1°C. 相似文献
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Junyaprasert VB Boonsaner P Leatwimonlak S Boonme P 《Drug development and industrial pharmacy》2007,33(8):874-880
Microemulsions of water/isopropyl palmitate (IPP)/Aerosol OT (AOT)/1-butanol were developed as alternative formulations for topical delivery of clindamycin phosphate. Effect of AOT:1-butanol ratios on microemulsion region existence in the pseudoternary phase diagrams was investigated. The 2:1 AOT:1-butanol provided the largest microemulsion region. Five microemulsions of 1% w/w clindamycin phosphate were prepared and characterized. The permeation through human epidermis of the microemulsions was evaluated and compared with the 70% isopropanol solution using modified Franz diffusion cells. The drug permeation from all microemulsions was found to be significantly greater than that from the solution, indicating the enhancement of the skin permeation by the microemulsions. Within the same microemulsion type, the drug permeation increased with increasing the amount of AOT:1-butanol. The drug permeation from oil-in-water (o/w) microemulsions was relatively higher than that from water-in-oil (w/o) microemulsions. In addition, all microemulsions were stable for at least three months at 30 ± 1°C. 相似文献
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三元青铜/环境界面上物质转移的化学行为 总被引:1,自引:0,他引:1
用模拟闭塞电池法(O.C.)研究了青铜在模拟环境介质0.028 mol·L-1NaCl 0.01 mol·L-1Na2SO4 0.016 mol.L-1NaHCO3中的局部腐蚀孔内或裂纹内的化学变化.通电32 h后闭塞区内溶液的Ph值由7.00降至5.02,与此同时Cl-和SO24-向闭塞区内迁移,其浓集倍数分别是6.31和2.93;测定了闭塞区内外Cu、Sn、Pb金属离子的浓度,据此计算出溶解因子fsn/Cu小于1,fpb/Cu大于 1,表明青铜中各元素选择性腐蚀的顺序为Pb>Cu>Sn,腐蚀速度Pb>Cu>Sn;用XRD分析了腐蚀产物的组成,解释了青铜文物表面腐蚀产物的分层现象,即从里到外为CuCl,CuCl和Cu2O,Cu的二价化合物. 相似文献
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LALCHAND A PATIL DINESH N SURYAWANSHI IDRIS G PATHAN DHANASHRI G PATIL 《Bulletin of Materials Science》2013,36(7):1153-1160
The objective of the present paper is to investigate the effect of variation of precursor concentration (0·01, 0·02 and 0·03 M) on the structural, microstructural, optical and gas sensing properties of TiO $_{2}$ thin films. Titanium dioxide (TiO $_{2}$ ) films were prepared from aqueous solution of titanium chloride (TiCl $_{3}\cdot $ 6H $_{2}$ O, 99·9% pure, Merck made, Germany) onto the glass substrates heated at a temperature of 350 °C by the spray pyrolysis technique. Bandgap energy of the films vary from 3.28 to 3.29 eV. X-ray diffraction shows that films to be nanocrystalline with anatase phase having tetragonal crystal structure. The d values calculated from electron diffraction patterns (TEM) were observed to be matching with d values calculated from XRD. Transmission electron microscopy (TEM) reveled that grain sizes were observed to increase (10–29 nm) with an increase in the concentration of precursor solution. The gas sensing performance of the films was tested. 相似文献
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W. Zhou X. Li X. Zhou F. F. Yuan Y. Ding J. C. Zhuang Y. Sun H. L. Zhou Z. X. Shi 《Journal of Low Temperature Physics》2014,175(3-4):543-553
High-quality superconducting K $_{x}$ Fe $_{y}$ Se $_{2}$ single crystals were synthesized using an easy one-step method. Detailed annealing studies were performed to make clear the phase formation process in K $_{x}$ Fe $_{y}$ Se $_{2}$ . Compatible observations were found in temperature-dependent X-ray diffraction patterns, back-scattered electron images and corresponding electromagnetic properties, which proved that good superconductivity performance was closely related to the microstructure of superconducting component. Analysis based on the scaling behavior of flux pinning force indicated that the dominant pinning mechanism was $\Delta T_\mathrm{c}$ pinning and independent of connectivity. The annealing dynamics studies were also performed, which manifested that the humps in temperature-dependent resistance curves were induced by competition between the metallic/superconducting and the semiconducting/insulating phases. 相似文献
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JIANXU DING BING LIU SHENGLAI WANG XIAOMING MU SHENGJUN ZHU GUANGXIA LIU WENJIE LIU YUN SUN LIN LIU DUANLIANG WANG 《Bulletin of Materials Science》2013,36(5):939-943
Potassium dihydrogen phosphate (KDP) crystals were grown in the presence of a series of chromate (CrO $_{4}^{2-}$ ) additive concentrations via rapid growth method. CrO $_{4}^{2-}$ made KDP crystals were coloured by yellow-green, suggesting CrO $_{4}^{2-}$ had entered into the crystal lattice. The elemental analysis indicated that Cr element in KDP crystal was at ppm level. High resolution X-ray diffraction data revealed that the crystalline perfection of these as-grown KDP crystals was destroyed after CrO $_{4}^{2-}$ entered into crystal lattice, embedded in the full width at half maximum was broadened and satellite peaks appeared. Additionally, the extinction ratio was decreased with rise of CrO $_{4}^{2-}$ concentration. CrO $_{4}^{2-}$ introduced two absorption peaks centred at 360 and 280 nm and enhanced the intrinsic absorption near 220 nm, which were at the same band positions compared with the CrO $_{4}^{2-}$ or HCrO $_{4}^{-}$ transmittance spectra. Additionally, CrO $_{4}^{2-}$ could increase the size of light scattering, which was attributed to the point defects and microscopic defects by the replacement by CrO $_{4}^{2-}$ at PO $_{4}^{3-}$ position. 相似文献
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Ruslan V. Vovk Nikolaj R. Vovk Oleksandr V. Dobrovolskiy 《Journal of Low Temperature Physics》2014,175(3-4):614-630
The effect of jumpwise temperature variation and room-temperature storing on the basal-plane electrical resistivity $\rho _{ab}$ of underdoped ReBa $_2$ Cu $_3$ O $_{7-\delta }$ (Re = Y, Ho) single crystals is investigated. Reducing the oxygen content has been revealed to lead to the phase segregation accompanied by both, labile component diffusion and structural relaxation in the sample volume. Room-temperature storing of ${\text {YBa}}_2{\text {Cu}}_3{\text {O}}_{7-\delta }$ single crystals with different oxygen hypostoichiometries leads to a substantial widening of the rectilinear segment in $\rho _{ab}(T)$ in conjunction with a narrowing of the temperature range of existence of the pseudogap state. It is established that the excess conductivity obeys an exponential law in a broad temperature range, while the pseudogap’s temperature dependence is described satisfactory in the framework of the BCS-BEC crossover theory. Substituting yttrium with holmium essentially effects the charge distribution and the effective interaction in CuO planes, thereby stimulating disordering processes in the oxygen subsystem. This is accompanied by a notable shift of the temperature zones corresponding to transitions of the metal-insulator type and to the regime of manifestation of the pseudogap anomaly. 相似文献
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Mahmoud Aly Hamad 《International Journal of Thermophysics》2013,34(6):1158-1165
Based on a phenomenological model, the electrocaloric effect (ECE) accompanied with the ferroelectric-to-paraelectric phase transition in a PbZr $_{0.95}$ 0.95 Ti $_{0.05}$ 0.05 O $_{3}$ 3 thin film was investigated. The extracted data reveal many features of the ECE such as electrocaloric entropy changes, heat capacity changes, and temperature changes as functions of temperature due to different electric fields shifts. From the behavior of the PbZr $_{0.95}$ 0.95 Ti $_{0.05}$ 0.05 O $_{3}$ 3 thin film in phase transitions, it leads to a large change of heat capacity of 105.94 J ${\cdot }\,$ · kg ${^{-1}}\,{\cdot }\,{^{\circ }}$ ? 1 · ° C, a temperature change of 22.44 K, and a relative cooling power of 1469 J ${\cdot }$ · kg $^{-1}$ ? 1 . 相似文献