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Title: Optical studies on diamond surfaces
Author: Pandeya, Daya Chand
Awarding Body: University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1959
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A brief review of the existing information on diamonds, including their physical properties and characteristic growth and solution features, is given in Part I. Part II deals with a short account of all the experimental techniques used in the present optical and interferometric studies of the microstructures of diamonds. Although Octahedron diamonds occur more frequently than the dodecahedron, yet in some mines the dodecahedron diamonds dominate not only in quantity but also in size. This fact is not consistent with the commonly accepted view that the dodecahedron form has developed due to the solution of Octahedron faces. It is expected that the present investigations on the microstructures of diamonds will throw some light on the conditions of their growth. The microstructures of dodecahedron diamonds are classified under two headings, namely (i) rare type of microstructures and (ii) common type of microstructures. Part III deals with the rare type of microstructures and in Chapter 3 are described unusual circular patterns which have been observed on three dodecahedral diamonds. Certain circular features which were illustrated by Sutton in 1928 with pencilled drawings resemble those described here. These features consist of slightly raised circular discs usually placed eccentrically one over the other and at times are overlapping and intersecting each other. The origin of these features has been discussed and their formation is attributed to a mechanism in which it is shown that liquid or gaseous bubbles were sticking on the faces of the crystal whilst the dissolution of the dodecahedral faces was taking place everywhere excepting the regions which were protected by the bubbles. Chapter IV deals with a brief review of the etch methods and the information on artificial etching of diamonds. Natural etch patterns not observed previously on the dodecahedron diamonds are also described in this Chapter. According to the experimental evidence these etch pits are expected to be canoe-shaped and perpendicular to the longer diagonal of the rhombic face. However, the natural etch pits are (a) canoe-shaped (b) oblong-shaped and (c) oval-shaped. The deviation in shape of these etch pits and their occurrence is explained. These natural etch pits uniquely arrange themselves in circular arrays and this has been attributed to the formation of liquid bubbles on the surface before natural etching started. Common microstructures of dodecahedral faces of diamonds as observed are (i) striations (ii) irregular network and (iii) rectilinear parallelogram network. It is suggested that the striations and irregular network owe their existence to growth and that subsequent solution of the faces reveals these features. The rectilinear parallelogram network is considered to be due to the solution of the faces of diamond which shows up those (111) planes along which diamond grows. These (111) planes are those which intersect (110) faces normally. The study of common microstructures of dodecahedron diamonds affords a further confirmation of the view that the dodecahedral faces of diamond are much more susceptible to solution than the octahedron faces. In Appendix A, observations made on trigons occurring on the octahedron faces of diamonds are described. The presence of a flat-bottomed trigon whose base is at the same level as a neighbouring area, the occurrence of slip and the presence of growth hills only on octahedron diamonds appears to be conclusive proof that they are growth features. In Appendix B, some graphitization experiments are given and it is concluded that graphitization sets in at a slow a temperature as 1060°C. when diamond is heated in a graphite crucible in an atmosphere of Nitrogen.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Physical Chemistry