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81.
The concept of the residence time τksp of an atom in a kink site has recently been suggested to understand the processes in electrochemical deposition of alloys
and intermetallic compounds. Different kink sites with different residence times must be defined for alloys and intermetallic
compounds. Based on this model, the finite Markov chain theory is applied to describe the selectivity of the growth process.
An analytical relationship between the alloy composition and the metal ion concentrations in the electrolyte is derived. General
model parameters are ratios g
i = K
ii/K
ij of equilibrium constants of the reaction of electrolyte ions with different kink sites on the surface (i, j representing different alloy components). These ratios are called selectivity constants. For simple conditions, the equation
g
i ≈ τii/τij connects the g
i values with the residence times. The theory is tested in the deposition of alloys Co-Ni (anomalous co-deposition) and Ni-Mo
(induced co-deposition). Additionally, Bi2Te3, an example of stoichiometric semiconductor deposition, is treated.
Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 10, pp. 1216–1223.
The text was submitted by the authors in English. 相似文献
82.
83.
84.
Two new alkaline-earth Nd selenite chlorides MNd10(SeO3)12Cl8 (M=Ca, Sr) were obtained using crystal growth from alkaline-earth chloride melts in quartz tubes. These new compounds crystallize in the orthorhombic system in space group C cca (#68). The compounds were studied by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction. It was shown that both compounds adopt the same structure type, constructed by complex [M11(SeO3)12]8+ slabs separated by chloride anion layers perpendicular to the longest cell parameter. The SeO3 groups show a pyramidal shape and may be described as SeO3E tetrahedra. Such SeO3 groups decorate the Nd-O skeletons forming the [M11(SeO3)12]8+ slabs. 相似文献
85.
Pt(PPh_3)_2Cl_2在碱性介质中,与一氧化碳直接进行还原及羰基化反应,得到五种膦取代的羰基铂配合物:Pt_5(μ_2-CO)_5(CO)(PPh_3)_4 1,Pt_3(μ_2-CO)_3(PPh_3)_3 2,Pt_3(μ_2-CO)_3(PPh_3)_4 3,Pt_4(μ_2-CO)_5(PPh_3)_4 4,以及Pt(Cl)(PPh_3)_2(COOCH_3) 5。经X-射线单晶衍射分析,确定了新的三核铂羰基簇2以及配合物5的分子结构。还讨论了1和5的生成机理。 相似文献
86.
用硒与尿素化合,新生的由杂环有机硒所组成的Zs-93硒剂治疗移植性S180肉瘤,有显著的抑瘤作用(P<0.01),其作用表现出一定的剂量效应,以5μg/只小鼠为最适,抑瘤率达60.76%,治疗组小鼠的T细胞、SOD活性均有增强。 相似文献
87.
Summary The purity of the investigational antibacterial Abbott-086719.1 (I) which is 8[(3S)-3-amino-1-pyrrolidinyl]-1-cyclopropyl-7-fluoro-9-methyl-4-oxo-4H-quinolizine-3-carboxylic acid hydrochloride is determined using gradient elution HPLC. The chromatographic separation was optimized and the chromatographic parameters critical to separation are discussed in detail. Most acceptable separations were achieved using an Alltima C18 column (5 m) measuring 4.6 mm I.D.×15 cm with 0.01M–0.03M citrate eluents which were modified with acetonitrile or with mixtures of acetonitrile and methanol. Related substances in I were determinable to 0.05%. Repeatability (RSD values) for determining related substances at levels of 0.50 to 0.06% ranged from ±1.9 to ±10%. Determinations of I in 5% dextrose in water and in hydroxypropyl methylcellulose were made using the same column and a simple isocratic system. The determination of I was stability indicating with precision (RSD values) of ±0.5% to ±2.0% and good agreement with theory for formulations containing I at 1.0 to 95 mg/mL concentrations. Recoveries of I from the vehicles were quantitative and linearity of the detector response of I was demonstrated to at least 0.10 mg/mL. 相似文献
88.
Hamada Fumio Kondo Yoshihiko Ito Riko Suzuki Iwao Osa Tetsuo Ueno Akihiko 《Journal of inclusion phenomena and macrocyclic chemistry》1993,16(3):273-281
The crystal structure of thiamine iodide sesquihydrate has been determined by X-ray diffraction methods as a host-guest model for coenzyme-substrate interactions. The asymmetric unit contains two chemical units. Both the thiamine molecules A and B, which are crystallographically independent, assume the usualF conformation and have a disordered hydroxyethyl side chain. An iodide anion (or a water molecule) bridges the pyrimidine and thiazolium rings of molecule A (or B) by forming a hydrogen bond with the amino group and an electrostatic contact with the thiazolium ring to stabilize the molecular conformation. In the crystal the thiamine molecules self-associate to form a pipe-like polymeric structure, in which four thiamine hosts surround an iodide guest and hold it through C(2)-H...I hydrogen bonds and thiazolium...I electrostatic interactions. Crystal data: C12H17N4OS+·I– · 1.5 H2O, monoclinic,P21/c, a=12.585(2), b=25.303(5), c=12.030(2) Å, =115.15(1)°,V=3468(1) Å3,Z=8,D
c=1.606 g cm–3,R=0.045 for 3328 observed reflections.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP. 82156 (13 pages). 相似文献
89.
Preparation of cellulose and cellulose derivative azo compounds 总被引:1,自引:0,他引:1
Maha Ibrahim 《Cellulose (London, England)》2002,9(3-4):337-349
Wood pulp and cotton linter are the most common sources of cellulose forindustrial use. Methyl cellulose (MC) and cellulose sulfate (CS) were preparedusing bleached wood pulp and cotton linter. Coloured azo compounds were alsoprepared from coupling cellulose, wood pulp, MC and CS with aromatic diazoniumsalt. The presence of electron-releasing or withdrawing substituents affectedthe electrophilic substitution reaction. The produced azo compounds werecharacterized by FT-IR methodology, as well as mass spectrometry, in which thefunctional groups and the ion fragments of the products were analyzed. 相似文献
90.
以钛氧有机物为前驱物制备具有高光催化活性的纳米二氧化钛晶体 总被引:9,自引:0,他引:9
纳米二氧化钛的制备方法及前驱物的差别影响其光催化活性.将20ml钛酸丁酯及30ml乙酐在密闭容器中与50ml环己烷混合,在70~85℃反应30min,生成微细的非晶钛氧有机物;经FT-IR和TGA分析,该物质被确认为计量式是TiOOOCCH3)2和TiO(OC4H9)(OOCCH3)的混合体.该钛氧有机物前驱物经焙烧后得到具有高光催化活性的纳米二氧化钛晶体.表征结果表明,钛氧有机物在焙烧过程中,其表面的吸附物及键合有机基团在400℃以前发生脱附和氧化分解;在389~405℃间形成锐钛矿型晶体,在600℃出现金红石晶型;600℃焙烧3h所得样品的比表面积为86m2/g,其二次粒子呈200~300nm条形体,孔隙大于20nm;单分散粒子为球形单晶,粒径为22nm;表面物理吸附水量为1.21%,加热至800℃时失重1.48%,粉体稳定纯净.光催化实验结果表明,以钛氧有机物为前驱物制备的纳米二氧化钛晶体具有高的光催化活性,光降解丁基罗丹明溶液的反应速率常数约为溶胶-凝胶法制备的催化剂样品的4倍.表面氧空缺和一定量的表面羟基可能是粉体具有高光催化活性的重要因素. 相似文献