摘要:

AbstractThe variation of hardness of rhombohedral single crystals of calcite with orientation of longer diagonal of Knoop indenter with respect to direction [100] on a cleavage plane (100) is studied. The Knoop hardness numberHwhich has a constant value in the range of high loads (40–80 g) varies with orientationAand quenching temperature. By following phenomenological approach, an empirical relation √HA=mA+Cis developed from these studies. The effects of crystal anisotropy and thermal treatment of specimens after indentation are also discus

ISSN:0232-1300    

DOI:10.1002/crat.2170280118

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170280119

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe microhardness,H, of sillenite‐type monocrystals of undoped Bi12SiO20, Bi12TiO20, Bi12GeO20and Cr‐, Fe‐, Mn‐ doped Bi12SiO20has been investigated. The dependences of H on the surface treatment, dopants and orientation of the materials have been established. It was found that theHand dislocation density,Nd, distribution along the diameter of the sample for undoped (100)‐Bi12SiO20are of M‐ and W‐shape,

ISSN:0232-1300    

DOI:10.1002/crat.2170280120

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170280121

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractFor a novel variant of smectic structures the SA+phase of the homologous 3‐(4‐alkyl‐phenyloxy)‐propane‐1,2‐diols the refractive indicesneandnowere measured in dependence on the temperatue. The polarizability anisotropy, the orientational order parameter, and the packing fraction were calculated using a mean field fitting method. The components of the internal field tensor were included in the fitting procedure. The increasing mobility of the alkyl chain for higher homologues reduces the orientational order in the smectic layers and also the birefringence which is very small. The molecular polarizabilities are increasing nearly linearly with the elongation of the alkyl chain. The small alternation of the polarizabilities corresponds to the alternating change of the length‐to‐breadth ratio. The calculated packing fractions are enhanced for hi

ISSN:0232-1300    

DOI:10.1002/crat.2170280122

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractSwallow‐tailed liquid crystals were mixted with four laterally branched substances in order to investigate the influence of molecular geometry on the correlations of molecules in the short range order. Besides the isobaric phase diagrams the results of dielectric measurements on oriented probes in the frequency range from 10 Hz to 100 kHz are discussed. Microscopic as well as dielectric investigations show that laterally branched molecules destroy the antiparallel arrangement of swallow‐tailed substances and in this way destabilize the smetic A phase. It is possible to put in order laterally branched substances according to its “destroying” in

ISSN:0232-1300    

DOI:10.1002/crat.2170280123

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170280101

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY