摘要:

AbstractLi2CO3single crystals have been grown by zone melting technique in carbondioxide atmosphere. The diameter of the grown crystal depends on the growth rate. The quality of the crystal depends on the growth rate, temperature of the molten zone, choice of the seed and the temperature of the auxiliary furnace. The crystal shows cleavage plane. The etch studies on cleavage planes show that the etch pits are always triangular in character.

ISSN:0232-1300    

DOI:10.1002/crat.2170170802

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractA time‐varying temperature profile method is reported for growing crystals in horizontal closed‐tube arrangements by vapour phase iodine transport. After an initial stage, during which the temperature is linearly raised with time in the source region of the container, in such a way as to control the primary nucleation (a limited number of seed crystals can thus be produced), a second stage follows during which the source temperature is allowed to oscillate in order to favour the secondary nucleation (only the first grown seed crystals are then allowed to grow). A proper choice of the frequency and amplitude of the temperature cycle is shown to control the growth up to the obtainement of solitary crystals per run of CuInS2and CdIn2S4. The role of the slow growing faces in favouring good performances of the method is emphasi

ISSN:0232-1300    

DOI:10.1002/crat.2170170803

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractZeolite crystals (named here VSZ‐3) synthesized at 350°C by hydrothermal method are illustrated and described. These crystals are shown to be analcime type zeolites. It is established that their size is the largest among the zeolite crystals ever reported, and are stable upto 1000°C. The VSZ‐3 crystals are prismatic pyramidal and needle‐like. They are characterized by X‐rays, SEM, TGA, DTA and IR. Their chemical composition is shown to be 5.95 SiO2ṁ Al2O3ṁ 0.91 Na2O ṁ 0.17 H2O. Mechanism of growth of these crysta

ISSN:0232-1300    

DOI:10.1002/crat.2170170804

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractA batch of Bayer gibbsite crystals (particle size range 3 to 70 μm) was prepared by crystal growth onto fine seeds (1 to 3 μm) from sodium hydroxoaluminate/sodium hydroxid‐solution. The internal structures and seed agglomeration of different fractions were examined by optical microscopy, infra‐red spectrophotometry, thermal analysis and chemical dissolution analysis. These physico‐chemical studies confirmed that crystal growth occurs with some seed agglomeration in the early stages, followed by growth onto the ‘agglomerates’. The agglomerated seeds contents (X) were as follows: for fraction DiD (l0= 6.3 μm),X= 0.44; for fraction Gi C (l0= 20 μm),X= 0.41; for fraction Gi B (l0= 38 μm),X= 0.31 and for fraction Gi A (l0=

ISSN:0232-1300    

DOI:10.1002/crat.2170170805

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractEtch pit morphology has been studied on calcite cleavages by different concentration of glacial acetic acid. Lateral reaction rates are very less at high concentration as well as low concentration of glacial acetic Acid. Etch pit morphology changes due to formation of finite or infinite lateral reaction rates at some particular concentration called transition concentration. The underlying chemical equations are given for different etch pit morphology.

ISSN:0232-1300    

DOI:10.1002/crat.2170170806

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractIncrements due to superlattice structure are formulated for the free enthalpy and some other thermodynamic entities as functions of composition, geometry parameters and temperature. Physical contents of the general expressions, derived for simple (quasi‐regular) pseudobinary solutions, are illustrated by numerical data valid for the InxGa1–xAs/GaAs system. It is suggested that the free enthalpy of superlattice, is, at least at higher temperatures, largely dominated by the configuration entropy term. Corrections due to nonideality appear to be quite sizeable for the selected ternary al

ISSN:0232-1300    

DOI:10.1002/crat.2170170807

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractMeasurements of the peak height of the 2γ‐angular correlation curve were carried out during constant rate heating of Fe–Al alloys with an Al‐content between 6.3 and 28.3 at.%. The samples had been quenched form 1000°C into water at room temperature. Two recovery stages are observed. The first stage at 100 to 200°C shows a small decrease of the peak height. The main stage at 300 to 400°C is attributed to the migration and disappearance of monovacancies. From isothermal measurements the migration enthalpy of vacancies is estimated to (1.15 ± 0.1) eV in Fe–Al (19.9 at.%) and to (1.31 ± 0.1) eV in Fe–Al (24.4 at.%). – In samples with an Al‐content between 13.8 and 28.3 at.% a minimum in the peak height at 400°C is found. Obviously a particular stage is formed in these samples during migration of quenched‐in vacancies. Possible causes of th

ISSN:0232-1300    

DOI:10.1002/crat.2170170808

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170170809

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe results of the impurity distribution in W‐doped Molybdenum single crystals grown by electron beam floating zone melting are related to the characteristics of computed steady thermocapillary flow and impurity distribution within the molten zone. Particularly the influence of the number and the strength of eddies in the molten zone on the impurity distribution pattern in the grown crystal for different aspect ratios is considere

ISSN:0232-1300    

DOI:10.1002/crat.2170170810

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170170811

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY