摘要:

AbstractThe kinetics of nucleation at constant supersaturation are analyzed when the process occurs at changing density of those monomers (atoms or molecules) that start the nucleation chain of consecutive bimolecular reactions. The Zeldovich kinetic equation is solved for arbitrary time variation of the monomer density and exact general expressions are obtained for the time dependence of the nonstationary nucleation rateJand the densityNof nuclei formed in the system up to timet. Exponential decrease and increase of the monomer density are considered as examples, and the correspondingJ(t) andN(t) dependences are analytically found.

ISSN:0232-1300    

DOI:10.1002/crat.2170200602

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170200603

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractElectrolytical coloration of quartz crystals with induced smoky quartz striations has been investigated, and compared with the arrangement of smoky quartz stripes after X‐irradiation. Investigations have been made on z‐, s‐, −x‐ and +x‐regions of the crystal after application of an electrolytical current in

ISSN:0232-1300    

DOI:10.1002/crat.2170200604

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractTheoretical expressions are developed suggesting how the non‐steady state dopant incorporation is influenced by the parameters of the layer deposition process. Expressions for the transient doping profile are dealt with taking into account two different mechanisms of the overall rate controlling step. The one is based on the assumption made by Reif and Dutton that the adsorption step, which is followed by a solution equilibrium, is the rate controlling step, the other is based on the idea that the dopant incorporation reaction and its backreaction, following after the adsorption of dopant particles, are controlling the overall incorporatio

ISSN:0232-1300    

DOI:10.1002/crat.2170200605

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170200607

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractMagnesium aluminium hydroxides were coprecipitated from different mixed metal cation solutions — at total CM= 0.1 M and Mg/Al2ratios from 1 to 6 — with sodium hydroxide solution at ambient temperature, with different pre‐ageing conditions for the aluminium hydroxide pre‐precipitate. The coprecipitations were monitored by potentiometric (pH) titration and the final precipitate compositions were examined by chemical analysis, infrared spectrophotometry and thermal analysis.Magnesium hydroxide was coprecipitated onto completely recrystallised aluminium hydroxide as a simple mixture.Generally, with no to three days pre‐ageing, microcrystalline aluminium hydroxide was first precipitated at pH about 4; this then partially redissolved on further addition of sodium hydroxide (to form hydroxoaluminate anion) and magnesium aluminium hydroxide coprecipitates were formed continuously at pHs from 8.0–8.7 to 12.0–12.5. Their compositions were similar to the magnesium hydroxoaluminate hydrates formed by direct precipitation from high pH sodium hydroxoalumin

ISSN:0232-1300    

DOI:10.1002/crat.2170200608

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe crystal and molecular structure of 3‐methoxy‐estra‐1,3,5(10)‐triene‐14β,17β‐diol has been determined by single crystal X‐ray analysis. It crystallizes in the orthorhombic space group P212121with cell parametersa= 8.965(2),b= 30.520(7), andc= 6.031(2) A. The structure was solved by the POSIT system and refined by least‐squares calculations to the conventionalRfactor of 0.075. The steroid rings A, B, and C have planar, 7α, 8β‐half chair, and chair conformations, respectively. The ring D is intermediate between 13α, 14β‐half chair and 13α‐envelope. Rings B and C are trans‐fused, and rings C and D are cis‐fused. There are intra‐ as well as intermolecular hydrogen bonds between both hydro

ISSN:0232-1300    

DOI:10.1002/crat.2170200609

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe heterotypism of Mn may be interpreted energetically when a temperature dependent valence electron concentration is supposed which takes on values between 2.2 and 0.6 electrons per atom. The room temperature phase Mn.r (= αMn) belongs to a series of structural types: Cr3Si, U.h1(= βU), Mn.r, which occur in alloy systems such as MoReM(M= undetermined mole number) at certain values of the averaged group number (AGN) of the perodic system of chemical elements (rule of Raub). An interpretation of the series by means of the plural‐correlations model becomes possible when instead of the (Ekmanian) AGN count another (non‐Ekmanian) electron count is used. The phase Mo3Re (Cr3Si‐type) yields a simple bonding type (binding) which undergoes moderate transformations to form the phases Mo2Re3(U.h1) and MoRe3(Mn.r) and the binding of MoRe3may be taken to be valid also for Mn.r; it corresponds to the valence electron concentrationN′Ab= 2.16. For the high temperature phases Mn.h1(= βMn) and Mn.h2(= γMn) the valuesN′Ab= 1.6 and 1.0 are probable and allow the brass‐like structures Mn.h1(C20) and Cu(Fl). The binding of Mn.h2, incidentally, explains the occurrence of the tetragonal metastable phase Mn.m. finally Mn.h3(= δMn) crystallizing in the W‐type is isodesmic to Fe.h2(= δFe), i.e.

ISSN:0232-1300    

DOI:10.1002/crat.2170200610

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170200611

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe Keating model with one bond‐stretching and one bond‐bending force constant and a localized effective charge to account for long‐range Coulomb forces and dipole‐dipole interactions is used to analyse the lattice vibrational properties of sphalerite‐structure binary compounds. It is shown that the trends in the model parameters can be readily explained in terms of the bond length and the bond

ISSN:0232-1300    

DOI:10.1002/crat.2170200612

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY