ISSN:0232-1300    

DOI:10.1002/crat.2170270124

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractGrowth experiments with sucrose dependent on temperature and supersaturation of solutions were carried out to find the conditions for appearance of the three different growth types. Measurements of growth rates of {110} and {110} faces at 50°C and supersaturationcs= 10% resulted in the known feature that in pure solutions a crystal grows faster in positiveb‐direction than in the negative one. Addition of raffinose stopped growth of {110}. In an electric field generated by 20 kV direct voltage (crystal orientation: negative pole ofb‐axis pointed towards the negative electric pole) the crystal grew in negativeb‐direction three times faster than in the positive one. In the presence of raffinose the growth rates in both directions become equal. If the crystal is turned by 180° in the solution (pure solution and in the presence of raffinose) the growth behaviour is the same as without an electric field. These results can be interpreted in such way that in pure solutions sucrose molecules adsorb to {110} (bonds exist between the fructose rings of molecules in liquid and solid phases) and that in presence of raffinose these molecules adsorb to {110} (bonds exist between glucose (solid) and galactose rings (liquid phases)). By the electric field the adsorption is hindered. The theory is in accordance with the fact that crystals situated in a suspension of the solution can intergrow with a host crystal in twin positions (in pure solutions on {110} and in the presence of raffinose on

ISSN:0232-1300    

DOI:10.1002/crat.2170270102

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170270125

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170270126

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe crystals of deuterated triglycine sulphate substituted with L‐alanine (LADTGS) were grown from nonpolar {001} growth sectors by four different methods.35 mol% of L‐alanine (LA) in the growth solution give a stable unipolarity of the crystals. A distribution of LA was measured by the electrical switching method using “hysteresis current” loops. A defect structure was observed in a microscope on the etched surface of crystals. Most uniform crystals have been obtained using an isothermal method without stirring of the growth so

ISSN:0232-1300    

DOI:10.1002/crat.2170270103

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170270127

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe electrical properties of GaAs epilayers doped with donor impurities Te and Sn during LPE from mixed Ga  Bi melts in temperature intervals from 850 to 820 °C and from 700 to 630 °C were investigated. The analysis of incorporation of Te and Sn into crystallizing GaAs considering preliminary association of impurity and compound component atoms in the liquid agree satisfactory with experimental data providing the presence of additional concentration of nonequilibrium arsenic vacancies on the (111)B surface of growing layer, which is not conditioned by activity of compound components in the liquid. It is shown that the main factor, determining the incorporation of donor impurities Te and Sn into GaAs during epitaxy from mixed Ga  Bi solvents, is the change of Ga and As concentrations ratio in the l

ISSN:0232-1300    

DOI:10.1002/crat.2170270104

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractCalcium oxalate monohydrate (COM) formation on the semi‐batch precipitation of CaCl2and Na2C2O4solutions in the stoichiometric ratio carried out at pH = 6 and 37 or 70°C, respectively, was studied. When a certain level of supersaturation in the system is reached, individual COM crystals of a rather uniform size are formed. These crystals then grown and form ‘loose’ agglomerates that later develop into compact and spherical particles. The particle size distribution (PSD) rapidly shifts during early stages of precipitation towards larger sizes as a result of crystal growth and agglomeration. Later the PSD reaches a shape and position on the size axis that remain virtually constant with progressing precipitation. COM agglomerates consisting of mainly intergrown crystals are formed by mechanism of primary and secondary agglomeration. The primary agglomeration can constitute an important factor in urolit

ISSN:0232-1300    

DOI:10.1002/crat.2170270105

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170270106

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractCalcium phosphates are precipitated at 25 °C from solutions of medium (Ca = P = 50 mM) and low (Ca = P = 10 mM) concentrations in the presence of magnesium. Experiments are also performed with solutions in which Ca + Mg = P = 50 mM and Ca + Mg = P = 10 mM. An amorphous calcium phosphate, Ca3(PO4)2· nH2O, and brushite, CaHPO4· 2 H2O, are the phases first nucleated. The phases occurring one year later are brushite in the more concentrated solutions, hydroxyapatite (Ca5OH(PO4)3) and whitlockite (Ca9MgH(PO4)7) in the others. Octacalciumphosphate, Ca8H2(PO4)6· 5H2O, occurs as transitory phase. The effects of concentration, pH, supersaturation and magnesium on the precipitation and evolution of calcium phosphates, and the conditions for phase stability are discus

ISSN:0232-1300    

DOI:10.1002/crat.2170270107

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY