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91.
Preparation of Mn3O4 nanocrystallites by low-temperature solvothermal treatment of γ-MnOOH nanowires
The preparation of trimanganese tetroxide (Mn3O4) nanocrystallites from γ-MnOOH nanowires under mild conditions has been achieved by two steps: first, γ-MnOOH nanowires with a mean diameter of about 12 nm and lengths of up to several micrometers were directly prepared via hydrothermal reaction between KMnO4 and toluene in water at 180°C for 24 h; then, pure Mn3O4 nanocrystallites could be obtained by solvothermal treatment of the γ-MnOOH nanowires in ethylenediamine (EDA) and ethylene glycol (EG) at 150°C for 24 h. It was found that the Mn3O4 product obtained in EDA comprised well-defined nanocrystallites with the size in the range of 15-35 nm, while the one obtained in EG consisted of aggregated nanoparticles with the size of less than 18 nm.The possible formation mechanism of nanocrystalline Mn3O4 in EDA and EG and reasons for the different effects of various solvents on the products were also proposed. 相似文献
92.
用X-射线荧光光谱法,测定了387例内蒙古牧区蒙古族、汉族成人和儿童的发中铜(Cu)、锌(Zn)、铁(Fe)、锶(St)及钙(Ca)的含量,对同一地区蒙、汉族成人间,成人及儿童间发中五种元素含量进行了比较分析。结果表明:蒙汉族成人发中Cu,Zn、Fe含量不受种族及饮食习惯的影响,其含量无显著性差异;蒙汉族成人发中Sr和Ca含量存在着相平行的显著差异;牧区儿童发Zn含量与牧区成人发Zn含量差异无显著性意义,提示牧区儿童不缺Zn,可能与多动物性食物有关;牧区儿童发中Cu、Fe、Sr、Ca均显著低于牧区成人、可能与儿童发育旺盛和Zn摄入量高对Cu、Fe吸收发生抑制有关。 相似文献
93.
测定了75例厌食小儿、101例呼吸道感染小儿和120例健康儿童发锌、铜,结果表明:厌食儿及易感儿平均发锌值分别为80.90×10-6和75.76×10-6,均极显著低于健康儿(P<0.01);发铜则无显著差异。发锌值在70×10-6以下者有60%以上身高、体重低于正常标准。说明微量元素锌与小儿食欲、免疫功能和生长发育有密切关系。 相似文献
94.
人血清与头发中铜,锌,铁,钙,镁,锰含量的相关分析 总被引:3,自引:0,他引:3
平行测定了54例(男31例,女23例)成人血清和头发中铜,锌,铁,钙,镁和锰的含量,相关分析结果表明,血清与头发中6种元素的不相关两类样品比较,血清测定方法简便,误差小,但在检测人体内元素含量水平时,头发的测量结果比血清更灵敏。 相似文献
95.
T.?L.?Shanker Rao K.?N.?Lad A.?PratapEmail author 《Journal of Thermal Analysis and Calorimetry》2004,78(3):769-774
The crystallization kinetics of amorphous Cu50Ti50 has been studied using differential scanning calorimetry (DSC) under non-isothermal conditions. The curves at different linear heating rates (2, 4, 8 and 16 K min–1) show sharp crystallization peaks. The crystallization peak shifts to higher temperatures with increasing heating rate. The Kissingers method of analysis of the shift in the transformation peak is applied to evaluate the activation energy (E
c). The KJMA formalism, which is basically developed for isothermal experiments, is also used to obtain E
c and the Avrami parameter (n).The DSC data have been analysed in terms of kinetic parameters, viz. activation energy (E
c), Avrami exponent (n) and frequency factor K
0 using three different theoretical models. It is observed that the activation energy values derived from KJMA approach and modified Kissinger equation agree fairly well with each other. The activation energy values obtained from normal Kissinger method, and Gao and Wang expression underestimate the activation energy.The financial support provided by All India Council for Technical Education (AICTE), New Delhi (Govt. of India) is gratefully acknowledged. 相似文献
96.
Ge JP Wang J Zhang HX Wang X Peng Q Li YD 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(6):1889-1894
Three-dimensional, orthogonal lead sulfide (PbS) nanowire arrays and networks have been prepared by using a simple, atmospheric pressure chemical vapor deposition (APCVD) method. These uniform nanowires (average diameter 30 nm) grow epitaxially from the surface of the initial PbS crystal seeds and form orthogonal arrays and networks in space. The growth mechanism has been explored, and the process was classified as homogeneous, epitaxial growth in the 200 directions. Furthermore, Raman spectra of PbS nanowires are reported here, and their characteristic Raman peak (190 cm(-1), no shoulder) could be used as a unique probe for the study of PbS nanomaterials. 相似文献
97.
Crystal Structure of Hexamine Cyclotriphosphazene, P3N3(NH2)6 In the presence of KNH2 hexamine cyclotriphosphazene semi ammoniate (molar ratio 12:1) in NH3 gives crystals of solvent free P3N3(NH2)6 within 5 d at 130°C and p(NH3) = 110 bar. The structure was solved by X-rax methods: P3N3(NH2)6: P21/c, Z = 4, a = 10.889(6) Å, b = 5.9531(6) Å, c = 13.744(8) Å, β = 97.83(3)°, Z(Fo) = 1 721 with (Fo)2 ≥ 3σ(Fo)2, Z(var.) = 157, R/Rw = 0,036/0,041 The structure contains columns of molecules P3N3(NH2)6 all in the same orientation. The six-membered rings within one molecule have boat conformation. The columns are stacked together in a way that one is surrounded by four others shifted by half a lattice constant in direction [010]. Strong hydrogen bridge-bonds N? H…?N connect molecules within the columns and between them. 相似文献
98.
Phase diagram of durene–resorcinol system, determined by the thaw-melt method, shows the formation of a monotectic (0.109
mole fraction of durene) and an eutectic (0.964 mole fraction of durene) with a large liquid miscibility gap in the region
from 0.109 to 0.964 mole fraction of durene. The eutectic, monotectic and consolute temperatures are 78.4, 107.8 and 165.0°C,
respectively. The growth behaviour studied by measuring the linear velocity of crystallization (v) in a capillary at different undercoolings (ΔT) suggests that the data obey the Hillig–Turnbull equation,v=u(ΔT)n, where u and n are constants depending on the nature of materials involved. From the values of enthalpy of fusion of the pure components,
the eutectic and the monotectic determined by the DSC method using Mettler DSC-4000 system, entropy of fusion, enthalpy of
mixing, Jackson’sroughness parameter, size of the critical nucleus interfacial energy and excess thermodynamic functions were
calculated. The microstructures of the eutectic, and the monotectic, determined by the Leitz Laborlux D optical microscope
show their characteristic features.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
99.
Nd-Fe-B磁体烧结过程晶粒长大行为的研究 总被引:4,自引:0,他引:4
定量描述了Nd-Fe-B磁体烧结过程晶粒长大行为,分析了烧结温度、烧结时间、合金粉末粒度及其分布对烧结过程晶粒长大的影响,讨论了烧结过程晶粒长大机制。在Nd-Fe-B磁体烧结过程开始之后的0—1h时间区段,晶粒长大迅速;随着烧结时间的延长,晶粒长大速度减小。合金粉末平均粒度增大,或者合金粉末粒度分布范围增宽,显著促进Nd-Fe-B磁体烧结过程中晶粒的长大。在Nd-Fe-B磁体的烧结过程中,存在两类晶粒长大机制,即Nd2Fe14B颗粒的溶解与析出、Nd2Fe14B颗粒的并合与长大。Nd2Fe14B颗粒的并合与长大不仅使磁体的平均晶粒尺寸增大,也使晶粒尺寸分布范围增宽,是烧结Nd-Fe-B磁体显微组织中出现异常大晶粒的根本原因。 相似文献
100.
In the structure Ba12F19Cl5 [hexagonal space group P6 2m] the two chlorides on the sites Cl(1) and Cl(2) can partially be replaced by bromide ions. Single crystals of the type Ba12F19ClδBr5–δ with a chloride to bromide ratio up to 2 : 3 could be obtained by cooling a flux of 75 mol% BaF2 and 25 mol% BaX2 with X = Cl, Br. The crystal quality decreases with increasing bromide concentration. Structural parameters of five selected single crystals with different chloride/bromide ratio were studied by single crystal X-ray diffraction methods. The refined total Cl?/Br? population ratio in the crystals is close to the one of the flux. The lattice parameters and interatomic distances change in various ways, when the smaller chloride ion is replaced by the bigger bromide ion. The refinements show a statistical disorder on the halide sites with preferential bromide substitution on site Cl(1). 相似文献