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41.
Pollen-shape (spiked sphere) hydroxyapatite (HA) particles for drug carrier application are studied. The particle shape and size effect on flow characteristics and deposition are assessed. The pollen-shape HA particles are synthesized to have comparable size as typical carrier particles with mean diameter of 30-50 m and effective density less than 0.3 g/cm 3 . The flow behaviors of HA and commonly used lactose (LA) carrier particles are characterized by the Carr's compressibility index (CI). The HA particle... 相似文献
42.
Eugene Y. Cheung Kenneth D.M. Harris Barbara R. Conway 《Journal of solid state chemistry》2007,180(3):1068-1075
We report the formation and structural properties of co-crystals containing gemfibrozil and hydroxy derivatives of t-butylamine H2NC(CH3)3−n(CH2OH)n, with n=0, 1, 2 and 3. In each case, a 1:1 co-crystal is formed, with transfer of a proton from the carboxylic acid group of gemfibrozil to the amino group of the t-butylamine derivative. All of the co-crystal materials prepared are polycrystalline powders, and do not contain single crystals of suitable size and/or quality for single crystal X-ray diffraction studies. Structure determination of these materials has been carried out directly from powder X-ray diffraction data, using the direct-space Genetic Algorithm technique for structure solution followed by Rietveld refinement. The structural chemistry of this series of co-crystal materials reveals well-defined structural trends within the first three members of the family (n=0, 1, 2), but significantly contrasting structural properties for the member with n=3. 相似文献
44.
A new semiorganic compound, bis(diethylammonium) tetrachloromercurate(II) was grown by slow evaporation solution growth technique at ambient temperature from its aqueous solution. The crystal system and the cell parameters have been identified from the powder X-ray diffraction pattern. The UV–visible absorption of the compound shows absorption at 246 nm and there is absorption observed in the entire visible region indicates that the compound can be used as a nonlinear optical material. The UV–visible transmittance spectrum of grown crystal shows a lower cut-off wavelength at 275 nm and it was found that the crystal is suitable for optoelectronic applications. Thermal studies were carried out to find out the thermal stability and confirm the stoichiometric ratio of the compound. The thermal anomalies in DSC study indicate the occurrence of first order transition in the compound at low temperatures. The FTIR spectrum of the compound characterizes various functional groups. The various kinds of protons and carbons were assigned through NMR (1H and 13C) spectroscopic techniques. The SHG efficiency of the compound was studied by Kurtz-Perry power technique and observed that it has SHG efficiency 1.5 times greater than that of potassium dihydrogen phosphate (KDP). The dielectric constant and dielectric loss of the compound decreases with increase in frequency. 相似文献
45.
S. Pignard H. Vincent E. Flavin F. Boust 《Journal of magnetism and magnetic materials》2003,260(3):437-446
Polycrystalline samples of M-type hexaferrites BaFe12−2xRuxZnxO19 and BaFe12−2xRuxCoxO19 with 0x0.45 have been prepared by a classical sintering method. The evolutions with x of the cell parameters, the saturation magnetization and the magnetic transition temperature have been measured; in this range of small doping ratios, saturation magnetization and Curie temperature of substituted hexaferrites remain close to those of the undoped BaFe12O19. X-ray diffraction measurements on oriented powders show that a change of magnetocrystalline anisotropy from axial to planar occurs in both cases for a small substituting ratio xc=0.375. Microwave electromagnetic characteristics have been studied on the ceramic samples from 0.1 to 10 GHz. The behaviour of the magnetic losses (μ″) corroborates the anisotropy change when doping; a convolution of the dissipation mechanisms (domain wall motions and gyromagnetism) is obtained for xc. The level of the magnetic losses is discussed in relation with others substituted Ba-hexaferrites. 相似文献
46.
本文研制了粉末涂料用柔韧性羧端基不饱和聚酯树脂及其相应的环氧树脂固化的柔韧性不饱和聚酯粉末涂料,讨论了树脂合成,涂料制备及涂层性能,涂层的装饰性能特别是柔韧性能有了较大改善。 相似文献
47.
本文提出脉冲序列45_X~°—t_1—90_(±Y)~°—t_2,从理论和实验上证实了它能够有效地会聚粉末样品中I=3/2四极核中心跃迁的磁化矢量,并对该回波序列的激发谱宽作了数值计算。 相似文献
48.
单道扫描式ICP—AES法测定婴儿乳粉,代乳粉中K,Na,Ca,Mg,P,Fe,Zn,Cu,Mn和Sr 总被引:1,自引:0,他引:1
本文采用HNO_3-HClO_4湿法消解样品,用乳化剂OP解决雾化器堵塞问题,利用单道扫描式ICP-AES仪测定婴儿乳粉、代乳粉中十种元素(K、Na、Ca、Mg、F、Fe、Zn、Cu、Mn和Sr)。方法简便快速,回收率在90-105%,相对标准偏差均小于10%,适用于婴儿乳粉、代乳粉中上述元素的测定。 相似文献
49.
Na3PO2S2 was synthesized from the corresponding undecahydrate by freeze–drying. It dismutates at temperatures above 350 °C into Na3PO3S and Na3POS3. The crystal structure of Na3PO2S2 was determined from X-ray powder diffraction data, and refined using the Rietveld technique (Pbca, a=17.5359(2) Å, b=11.3044(1) Å, c=5.8656(1) Å, RF2=8.45%, Rp=4.80%, Rwp=6.79%). The baricenters of the PO2S2-tetrahedra are arranged in the sense of a hexagonal close packing. One of the P---O bonds of these tetrahedra is oriented parallel to the crystallographic c-axis with the POS2-groups in an eclipsed mutual orientation. The crystal structure of Na3PO2S2 displays a close relationship to the ones of Ca3CrN3 and Na3POS3. Above 330 °C, Na3PO2S2 can be regarded as a fast ionic conductor (with σ>10−5 S cm−1). 相似文献
50.
Finite element simulation for dynamic large elastoplastic deformation in metal powder forming 总被引:4,自引:0,他引:4
In this paper, a transient dynamic analysis of the powder compaction process is simulated by a large displacement finite element method based on a total and updated Lagrangian formulation. A combination of the Mohr–Coulomb and elliptical yield cap model, which reflects the stress state and degree of densification, is applied to describe the constitutive model of powder materials. A Coulomb friction law and a plasticity theory of friction in the context of an interface element formulation are employed in the constitutive modelling of the frictional behaviour between the die and powder. Finally, the powder behaviour during the compaction of a plain bush, a rotational flanged and a shaped tip component are analysed numerically. It is shown that the updated Lagrangian formulation, using a combination of the Mohr–Coulomb and elliptical cap model, can be effective in simulating metal powder compaction. 相似文献