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1

Digitale Medien

Structure of Glassy Carbon (1971)

JENKINS, G. M. ; KAWAMURA, K.

[s.l.] : Nature Publishing Group

Nature 231 (1971), S. 175-176

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ISSN: 1476-4687

Quelle: Nature Archives 1869 - 2009

Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik

Notizen: [Auszug] The lack of information about the starting materials and the carbonization process given by manufacturers precludes the elucidation of the structure of the material; it is necessary to study carbonization mechanisms in well-defined starting materials. We have previously shown that glassy carbon ...

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1038/231175a0

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2

Digitale Medien

Dislocations and twins in Czochralski-grown gallium phosphide single crystals (1970)

Laister, D. ; Jenkins, G. M.

Springer

Journal of materials science 5 (1970), S. 862-868

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ISSN: 1573-4803

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau

Notizen: Abstract An etching and electron microscopy study has been carried out on {111} oriented slices of gallium phosphide (GaP) taken from Czochralski-grown ingots. The correlation of the etched structure with substructural defects as revealed by transmission electron microscopy has been determined, It has been found that GaP grown by this technique has a high dislocation density and exhibits polygonisation and mechanical twinning. It is found that there is a one-to-one correspondence between surface etch pits and grown-in and mechanically induced dislocations. Stacking faults are also revealed in the etching studies and are shown to be twins in the matrix of the {111} 〈112〉 type. It is proposed that the twinning occurs due to the severe growth conditions and may arise by dissociation of dislocations in the sub-boundaries.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00574857

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3

Digitale Medien

A new glassy carbon fibre (1970)

Kawamura, K. ; Jenkins, G. M.

Springer

Journal of materials science 5 (1970), S. 262-267

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ISSN: 1573-4803

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau

Notizen: Abstract It is shown that phenol-hexamine polymers may be extruded from the melt to produce fibres which may be carbonised to form fine high-strength glassy carbon fibres with a tensile strength of up to 2 GNm−2 (300 000 Ib in−2) after 900° C heat-treatment. The fibres have a specific modulus of ∼5 Mm compared with ∼14 Mm for carbonised polyacrylonitrile fibres and ∼3 Mm for silica glass fibres. Both strength and modulus increase rapidly with decrease in diameter. The fibres are subjected to no special surface treatment after extrusion but electron microscopy indicates the presence of a thin textured sheath surrounding a true glassy carbon core in the final fibre. The fibres have the advantages of glassy carbon (inertness to chemical attack, resistance to abrasion) and give promise of a new range of cheap high-strength carbon fibres derived from coal tar fractions.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00551003

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4

Digitale Medien

Mechanical properties of glassy carbon fibres derived from phenolic resin (1972)

Kawamura, K. ; Jenkins, G. M.

Springer

Journal of materials science 7 (1972), S. 1099-1112

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ISSN: 1573-4803

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau

Notizen: Abstract Mechanical properties of glassy carbon fibres produced from a phenolic resin were determined by static tensile testing. These specimens are of special interest because they consist of an isotropic core surrounded by a sheath of oriented material of varying relative thickness. The chemistry of pyrolysis of the resin is summarized and the changes in mechanical properties of the fibres are discussed in terms of the pyrolysis mechanisms. The results are compared with hardness measurements made on discs produced from the same starting material. Scanning electron microscope studies revealed that the fibres have various types of flaws both in the surface and in the core. The effect of these flaws on the fibre strength is discussed by applying Griffith crack theory.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00550191

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5

Digitale Medien

Deformation of single crystals of gallium arsenide (1973)

Laister, D. ; Jenkins, G. M.

Springer

Journal of materials science 8 (1973), S. 1218-1232

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ISSN: 1573-4803

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau

Notizen: Abstract Deformation of single crystals of gallium arsenide is reported in bend and tension up to 1000° C whilst maintaining stoichiometry in an arsenic atmosphere. Surface defects and impurity segregation are shown to be dislocation sources. The dislocation density is low enough, however, to show large yield drops which are analysed in detail. Strains of 39% are possible. The activation energy for dislocation movement is increased by heat-treatment owing to an increase in point defect population. Electron microscopy shows that the predominant slip systems are {111} 〈110〉 and the majority of dislocations have b=a/2 〈110〉, the axes lying along 〈110〉 and 〈112〉 directions. Sub-cell formation occurs with sub-boundaries lying along 〈110〉 directions.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00549336

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