scholarly journals Surface Porosity of Natural Diamond Crystals after the Catalytic Hydrogenation

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1341
Author(s):  
Aleksei Chepurov ◽  
Valeri Sonin ◽  
Dmitry Shcheglov ◽  
Egor Zhimulev ◽  
Sergey Sitnikov ◽  
...  
Keyword(s):  
Catalytic Hydrogenation ◽  
Materials Science ◽  
Crystal Surface ◽  
Natural Diamond ◽  
Substrate Material ◽  
Diamond Surfaces ◽  
Diamond Crystals ◽  
Type Ia ◽  
Strong Resemblance ◽  
Natural Type

The study of diamond surfaces is traditionally undertaken in geology and materials science. As a sample material, two natural diamond crystals of type Ia were selected, and their luminescence and nitrogen state was characterized. In order to etch the surface catalytic hydrogenation was performed using Fe particles as an etchant. Micromorphology of the surface was investigated by scanning electron and laser confocal microscopy. It was demonstrated that etching occurred perpendicular to the crystal surface, with no signs of tangential etching. The average depth of caverns did not exceed 20–25 μm with a maximal depth of 40 μm. It is concluded that catalytic hydrogenation of natural type Ia diamonds is effective to produce a porous surface that can be used in composites or as a substrate material. Additionally, the comparison of results with porous microsculptures observed on natural impact diamond crystals from the Popigai astrobleme revealed a strong resemblance.

The value of Electron Microscope studies of imperfect natural diamonds

1990 ◽  
Vol 48 (4) ◽  
pp. 194-195
Author(s):  
J C Walmsley ◽  
A R Lang
Keyword(s):  
Electron Microscope ◽  
Classification Scheme ◽  
Natural Diamond ◽  
Sudden Change ◽  
Growth Conditions ◽  
Diamond Growth ◽  
Major Constituent ◽  
Natural Diamonds ◽  
Type Ia ◽  
Platelet Defects

Interest in the defects and impurities in natural diamond, which are found in even the most perfect stone, is driven by the fact that diamond growth occurs at a depth of over 120Km. They display characteristics associated with their origin and their journey through the mantle to the surface of the Earth. An optical classification scheme for diamond exists based largely on the presence and segregation of nitrogen. For example type Ia, which includes 98% of all natural diamonds, contain nitrogen aggregated into small non-paramagnetic clusters and usually contain sub-micrometre platelet defects on {100} planes. Numerous transmission electron microscope (TEM) studies of these platelets and associated features have been made e.g. . Some diamonds, however, contain imperfections and impurities that place them outside this main classification scheme. Two such types are described.First, coated-diamonds which possess gem quality cores enclosed by a rind that is rich in submicrometre sized mineral inclusions. The transition from core to coat is quite sharp indicating a sudden change in growth conditions, Figure 1. As part of a TEM study of the inclusions apatite has been identified as a major constituent of the impurity present in many inclusion cavities, Figure 2.

Effect of pressure on synthetic diamond crystals at high temperatures and pressures in Fe/Ni catalyst system

CrystEngComm ◽  
2021 ◽  
Author(s):  
Shuai Fang ◽  
Yongkui Wang ◽  
Liangchao Chen ◽  
Zhiyun Lu ◽  
Zhenghao Cai ◽  
...  
Keyword(s):  
Nitrogen Content ◽  
Growth Mechanism ◽  
Synthetic Diamond ◽  
Natural Diamond ◽  
Catalyst System ◽  
Necessary Condition ◽  
Ni Catalyst ◽  
Effect Of Pressure ◽  
Diamond Crystals ◽  
System P

Pressure is a necessary condition for the growth of natural diamond. Studying the effect of pressure on the nitrogen content of diamond is important for exploring the growth mechanism of...

Dechannelling and the nature of defect structures in natural type Ia diamonds

1980 ◽  
Vol 168 (1-3) ◽  
pp. 195-202 ◽  
Author(s):  
R.W. Fearick ◽  
J.P.F. Sellschop
Keyword(s):  
Defect Structures ◽  
Type Ia ◽  
Natural Type

The Influence of Diamond Surface Perfection on the Preferential Nucleation of SP2 Carbon During Methane Pyrolysis

1992 ◽  
Vol 280 ◽  
Author(s):  
B. Y. Lin ◽  
C. P. Beetz ◽  
D. W. Brown ◽  
B. A. Lincoln
Keyword(s):  
Natural Diamond ◽  
High Energy ◽  
Diamond Surface ◽  
Structural Defects ◽  
High Energy Electron ◽  
Diamond Surfaces ◽  
Preferential Nucleation ◽  
Cvd Diamond Film ◽  
Surface Morphologies ◽  
Methane Pyrolysis

ABSTRACTWe report a set of CH4 pyrolysis experiments in a UHV system on diamond surfaces having varying degrees of surface roughness or perfection. Scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and reflection high energy electron diffraction (RHEED) were used to examine the formation of graphite and the resulting surface morphologies. A (100) type Ha natural diamond having 3 sputtered craters on the surface was used as the substrate, sp2 carbon was formed preferentially on the structurally defective crater surfaces after ∼3×1010 L of CH4 exposure at 900°C, whereas essentially no sp2 carbon was found on the flat portions of the diamond surface. Similar experiments were also carried out on a polycrystalline CVD diamond film and sp2 carbon was formed on that surface afte ∼4×109 L of CH4 exposure at 900°C. These results indicate that structural defects on diamond surfaces are a crucial factor in the preferential nucleation of sp2 carbon during CH4 pyrolysis.

Electrical Properties of Thin Film and Bulk Diamond Treated in Hydrogen Plasma

1989 ◽  
Vol 162 ◽  
Author(s):  
Sacharia Albin ◽  
Linwood Watkins
Keyword(s):  
Natural Diamond ◽  
Hydrogen Plasma ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Silicon Substrates ◽  
Free Standing ◽  
Before And After ◽  
Type Ia ◽  
Bulk Diamond

ABSTRACTCurrent-voltage characteristics of type Ia synthetic diamond, type IIb natural diamond and free-standing diamond films were measured before and after hydrogenation. The diamond films were polycrystalline, deposited on sacrificial silicon substrates using a microwave chemical vapor deposition process. On hydrogenation, all the samples showed several orders of magnitude increase in conductivity. Hydrogenation was carried out under controlled conditions to study the changes in the I-V characteristics of the samples. The concentration of electrically active hydrogen was determined from the I-V data. Hydrogen passivation of deep traps in diamond is clearly demonstrated.

Selection of Reinforcing Agent in Metal Composite Matrix and Study of its Particle Composition

2019 ◽  
Vol 945 ◽  
pp. 476-481
Author(s):  
M.N. Safonova ◽  
A.A. Fedotov ◽  
A.S. Syromiatnikova
Keyword(s):  
Materials Science ◽  
Natural Diamond ◽  
Metal Composite ◽  
Metal Base ◽  
Particle Composition ◽  
Reinforcing Agent ◽  
Materials Science And Engineering ◽  
And Performance ◽  
Actual Target ◽  
Selection Of

The problem of creation of new materials and performance characteristics increasing of known matrix composite alloys is an actual target of research in materials science and engineering. It is known that the application of dispersed fillers, including ultra-and nanoscale dimensionality materials in the composites is an effective way to solve this problem. The article describes the feasibility of application ultradisperse powders of natural diamond as a reinforcing agent instead of synthetic in composite materials on a metal base and study of its particle composition.

Frictional anisotropy in nonmetallic crystals

1966 ◽  
Vol 295 (1442) ◽  
pp. 244-258 ◽  
Keyword(s):  
Magnesium Oxide ◽  
Plastic Flow ◽  
Lithium Fluoride ◽  
Crystal Surface ◽  
Shear Stresses ◽  
Depth Of Penetration ◽  
Diamond Crystals ◽  
Deformation And Fracture ◽  
Fluoride Crystals ◽  
The Difference

A study is made of the effect of the crystallographic direction of sliding on the friction of the (001) surfaces of diamond, magnesium oxide and lithium fluoride crystals. The friction shows marked anisotropy and with all the crystals it is greatest in the <100> directions and least in the <110> directions. The degree and magnitude of the anisotropy is dependent upon the shape of the slider and the ease with which it penetrates the crystal surface. Sharp sliders increase the degree of brittle failure and this leads to deeper penetration and to the removal of more material during sliding. With these crystals the depth of penetration is greater in the <100> directions then in the <110> and it is this which is primarily responsible for the frictional anisotropy. An explanation of frictional anisotropy is proposed which is based on the difference in the magnitude and distribution of resolved shear stresses during sliding in various crystallographic directions. This analysis is used to predict the effect of crystallographic orientation on the frictional behaviour when a (110) surface of magnesium oxide replaces the cube (001) surface used in the other experiments. Mechanisms of deformation and fracture associated with the friction are described. Brittle behaviour predominates in diamond crystals and only cleavage cracks are observed. Appreciable plastic flow occurs in both magnesium oxide and lithium fluoride crystals. With these crystals the initial plastic deformation leads to dislocation interactions which result in cracking and fracture along the {110} planes. These interact with cleavage cracks on {100} planes which are produced by tensile stress and cause surface fragmentation and wear of the crystal. Plastic flow is the only mode of deformation observed on (001) lithium fluoride surfaces when a very smooth blunt slider is used. This causes ‘pile-up’ of material along <110> directions (as previously observed in copper crystals) but it does not produce any appreciable anisotropy in the friction.

Contact electrization of natural diamond crystals

2010 ◽  
Vol 36 (2) ◽  
pp. 162-165 ◽  
Author(s):  
E. V. Ryabov ◽  
Yu. S. Mukhachev
Keyword(s):  
Natural Diamond ◽  
Diamond Crystals
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