Abrasive power and grain strength of rhombohedral?-boron

1973 ◽  
Vol 12 (8) ◽  
pp. 650-653
Author(s):  
G. V. Samsonov ◽  
A. A. Adamovskii ◽  
A. I. Bezykornov ◽  
V. V. Uvarov ◽  
N. Ya. Nemtsova ◽  
...  
Keyword(s):  
Abrasive Power ◽  
Rhombohedral Boron

Abrasive power of some nonmetallic refractory compounds

1968 ◽  
Vol 7 (3) ◽  
pp. 189-192
Author(s):  
G. V. Samsonov ◽  
V. V. Stasovskaya ◽  
V. K. Kazakov
Keyword(s):  
Refractory Compounds ◽  
Abrasive Power

Activation energies of monocrystalline beta-rhombohedral boron

1964 ◽  
Vol 25 (7) ◽  
pp. 701-706 ◽  
Author(s):  
Robert A Brungs ◽  
Vincent P Jacobsmeyer
Keyword(s):  
Activation Energies ◽  
Rhombohedral Boron

Determination of Resistance to Abrasive Wear. VIII. Influence of Softeners in Tests with the Akron-Croydon and Du Pont Machines

1949 ◽  
Vol 22 (1) ◽  
pp. 259-262
Author(s):  
J. F. Morley
Keyword(s):  
Unit Area ◽  
Published Data ◽  
The Road ◽  
Abrasive Surface ◽  
Abrasive Power ◽  
The Difference ◽  
On The Road ◽  
The Right ◽  
Abrasion Testing

Abstract These experiments indicate that softeners can influence abrasion resistance, as measured by laboratory machines, in some manner other than by altering the stress-strain properties of the rubber. One possible explanation is that the softener acts as a lubricant to the abrasive surface. Since this surface, in laboratory abrasion-testing machines, is relatively small, and comes repeatedly into contact with the rubber under test, it seems possible that it may become coated with a thin layer of softener that reduces its abrasive power. It would be interesting in this connection to try an abrasive machine in which a long continuous strip of abrasive material was used, no part of it being used more than once, so as to eliminate or minimize this lubricating effect. The fact that the effect of the softener is more pronounced on the du Pont than on the Akron-Croydon machine lends support to the lubrication hypothesis, because on the former machine the rate of wear per unit area of abrasive is much greater. Thus in the present tests the volume of rubber abraded per hr. per sq. cm. of abrasive surface ranges from 0.03 to 0.11 cc. on the du Pont machine and from 0.0035 to 0.0045 cc. on the Akron-Croydon machine. On the other hand, if the softener acts as a lubricant, it would be expected to reduce considerably the friction between the abrasive and the rubber and hence the energy used in dragging the rubber over the abrasive surface. The energy figures given in the right-hand columns of Tables 1 and 3, however, show that there is relatively little variation between the different rubbers. As a test of the lubrication hypothesis, it would be of interest to vary the conditions of test so that approximately the same amount of rubber per unit area of abrasive is abraded in a given time on both machines; this should show whether the phenomena observed under the present test conditions are due solely to the difference in rate of wear or to an inherent difference in the type of wear on the two machines. This could most conveniently be done by considerably reducing the load on the du Pont machine. In the original work on this machine the load was standardized at 8 pounds, but no figures are quoted to show how abrasion loss varies with the load. As an addition to the present investigation, it is proposed to examine the effect of this variation with special reference to rubbers containing various amounts and types of softener. Published data on the influence of softeners on the road wear of tire rubbers do not indicate anything like such large effects as are shown by the du Pont machine. This throws some doubt on the value of this machine for testing tire tread rubbers, a conclusion which is confirmed by information obtained from other workers.

scholarly journals In vitro and in vivo evaluation of diamond-coated strips

2016 ◽  
Vol 87 (3) ◽  
pp. 455-459 ◽  
Author(s):  
Roberta Lione ◽  
Francesca Gazzani ◽  
Chiara Pavoni ◽  
Stefano Guarino ◽  
Vincenzo Tagliaferri ◽  
...  
Keyword(s):  
Contact Point ◽  
Sem Analysis ◽  
Tribological Test ◽  
In Vivo Evaluation ◽  
Wear Performance ◽  
Abrasive Grains ◽  
Abrasive Power ◽  
In Vivo Analysis

ABSTRACT Objective: To test in vitro and in vivo the wear performance of diamond-coated strips by means of tribological testing and scanning electronic microscope (SEM). Materials and Methods: To evaluate the in vitro wear performance, a tribological test was performed by a standard tribometer. The abrasive strips slid against stationary, freshly extracted premolars fixed in resin blocks, at a 2-newton load. At the end of the tribological test, the residual surface of the strip was observed by means of SEM analysis, which was performed every 50 meters until reaching 300 meters. For the in vivo analysis, the strip was used for 300 seconds, corresponding to 250 meters. Results: The strips presented a fenestrated structure characterized by diamond granules alternating with voids. After the first 50 meters, it was possible to observe tooth material deposited on the surface of the strips and a certain number of abrasive grains detached. The surface of the strip after 250 meters appeared smoother and therefore less effective in its abrasive power. After 300 seconds of in vivo utilization of the strip, it was possible to observe the detachment of diamond abrasive grains, the near absence of the grains and, therefore, loss of abrasive power. Conclusions: Under ideal conditions, after 5 minutes (300 meters) of use, the strip loses its abrasive capacity by about 60%. In vivo, a more rapid loss of abrasive power was observed due to the greater load applied by the clinician in forcing the strip into the contact point.

scholarly journals Rhombohedral Boron Nitride Epitaxy on ZrB2

2020 ◽  
Author(s):  
Laurent Souqui ◽  
Justinas Palisaitis ◽  
Naureen Ghafoor ◽  
Henrik Pedersen ◽  
Hans Högberg
Keyword(s):  
Electron Microscopy ◽  
Boron Nitride ◽  
Photoelectron Spectroscopy ◽  
Amorphous Material ◽  
Limited Area ◽  
Sem Images ◽  
Plan View ◽  
Minute Amount ◽  
X Ray ◽  
Rhombohedral Boron

<div>Epitaxial rhombohedral boron nitride films were deposited on ZrB<sub>2</sub>(0001)/4H-SiC(0001) by chemical vapor deposition at 1485 °C from the reaction of triethylboron and ammonia and with a minute amount of silane (SiH<sub>4</sub>). X-ray diffraction (XRD) φ-scans yield the epitaxial relationships of 𝑟−𝐵𝑁(0001)∥𝑍𝑟𝐵2(0001) out-of-plane and 𝑟−𝐵𝑁(1120)∥𝑍𝑟𝐵2(1120) in-plane. Cross-section transmission electron microscopy (TEM) micrographs showed that epitaxial break down of r-BN film occurs approximatively after 10 nm, above which epitaxial growth proceeds only in limited area up to 80 nm of film thickness. Both XRD and TEM demonstrate the formation of carbon- and nitrogen-containing cubic inclusions at the ZrB<sub>2</sub> surface. Quantitative analysis from X-ray photoelectron spectroscopy of the r-BN films shows B/N ratios between 1.30 to 1.20 and an O content of 3 to 4 at.%. Plan-view scanning electron microscopy (SEM) images reveal a surface morphology where an amorphous material comprising B, C, and N is surrounding the epitaxial twinned r-BN crystals. SiH<sub>4</sub> exposure prior to growth was found to reduce the amount of the amorphous phase on the surface. Defects such as pitting were also observed on the ZrB<sub>2</sub> template surface.</div><div><br></div>

scholarly journals Thermal Chemical Vapor Deposition of Epitaxial Rhombohedral Boron Nitride from Trimethylboron and Ammonia

2018 ◽  
Author(s):  
Laurent Souqui ◽  
Henrik Pedersen ◽  
Hans Högberg
Keyword(s):  
Chemical Vapor Deposition ◽  
Boron Nitride ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Epitaxial Relationship ◽  
Out Of Plane ◽  
Α Al2o3 ◽  
Favorable Conditions ◽  
Relationship Of ◽  
Rhombohedral Boron

Epitaxial rhombohedral boron nitride films were deposited on α-Al2O3(001) substrates by chemical vapor deposition, using trimethylboron, ammonia, and with a low concentration of silane in the growth flux. The depositions were performed at temperatures from 1200 to 1485 °C, pressures from 30 to 90 mbar and N/B ratios from 321 to 1286. The most favorable conditions for epitaxy were: a temperature of 1400 °C, N/B around 964, and pressures below 40 mbar. Analysis by thin film X-ray diffraction showed that most deposited films were polytype-pure epitaxial r-BN with an out-of-plane epitaxial relationship of r-BN[001]∥ w-AlN[001]∥ α-Al2O3[001] and with two in-plane relationships of r-BN[110]∥ w-AlN[110]∥ α-Al2O3[100] and r-BN[110]∥ w-AlN[110]∥ α-Al2O3[1̅00] due to twinning.

High-Yield Synthesis of Rhombohedral Boron Nitride Triangular Nanoplates.

ChemInform ◽  
2007 ◽  
Vol 38 (43) ◽  
Author(s):  
Liqiang Xu ◽  
Jinhua Zhan ◽  
Junqing Hu ◽  
Yoshio Bando ◽  
Xiaoli Yuan ◽  
...  
Keyword(s):  
Boron Nitride ◽  
High Yield ◽  
Rhombohedral Boron

Metal impurities in crystallographic voids of beta-rhombohedral boron lattice: Binding energies and electron levels

2012 ◽  
Vol 14 (11-12) ◽  
pp. 1673-1682 ◽  
Author(s):  
Levan Chkhartishvili ◽  
Ivane Murusidze ◽  
Maguli Darchiashvili ◽  
Otar Tsagareishvili ◽  
Domenti Gabunia
Keyword(s):  
Binding Energies ◽  
Metal Impurities ◽  
Rhombohedral Boron
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