Diamond Stone Research Articles

Development of mechanochemical diamond stone containing BaSO4 abrasive

This paper describes a newly developed mechanochemical superabrasive stone containing reactive BaSO4 abrasive. A thermodynamic analysis suggested that BaSO4 reacts with Fe forming oxides. X-ray diffraction patterns revealed that scales that cover steels heated with BaSO4 abrasive consist of Fe3O4, α-Fe and BaS. On the basis of these results, vitrified diamond stones containing BaSO4 abrasive were manufactured and the effect of the BaSO4 abrasive on their performances was evaluated through the superfinishing of bearing steels. It was found that soft BaSO4 abrasive rubs the surface of hardened steel producing smooth surfaces with valleys. The stone reduces both the hardened layer depth and the compressive residual stress in the finished surface because of the formation of a thin white layer. The addition of BaSO4 abrasive improves the wear resistance of diamond stone because the dominant wear mechanism changes from carbon diffusion to oxidization of diamond.

Honing performance of polycrystalline diamond stone

Honing performance of polycrystalline diamond stone

8th International Kimberlite Conference: Selected Papers, Volume I: The C. Roger Clement Volume, Volume II: The J. Barry Hawthorne Volume.: R. H. MITCHELL, H. S. GRUTTER, L. M. HEAMAN, B. H. SCOTT-SMITH, AND T. STACHEL, EDITORS. Volume I: Pp. 593; Volume II: Pp. 949. Hardcover. Elsevier. 2006. reprinted from Lithos, v. 76-77 (1-4). ISBN 0070931097. Price US$235, two-volume set.

The 85 papers contained in this two-volume set and reprinted from the journal Lithos were presented at the 8th International Kimberlite Conference in Victoria, British Columbia, Canada, in June 2003. They represent the most current published compendium of knowledge regarding the wide range of topics that the study of diamonds includes. Those economic geologists wishing to learn about the current state of knowledge in the diamond industry and in exploration for kimberlites will be compelled to read these papers, which cover subjects related to diamond growth, grade assessment, exploration methods, kimberlite petrogenesis, emplacement mechanisms, geochronology, mantle geochemistry, tectonics, and geometallurgy. Examples given are from Australia, Botswana, Brazil, Canada, China, Finland, India, Namibia, Russia, South Africa, Tanzania, USA, Venezuela, West Africa, and Zimbabwe, and from the deep mantle to the crust and the laboratory. These volumes address the interests of the mineral deposit and exploration community by providing the details of diamond formation, emplacement, exploration, and recovery, and then some. In exploration, target selection begins with analysis of craton architecture, regional geological terrain characteristics, prospectivity for kimberlite emplacement, and the potential for geologic diamond-producing or diamond-destructive factors at depth or at the surface. Techniques for indicator mineral analysis and diamond grade assessment, stone color, shape, and resorption characteristics, and resource estimation and geometallurgical factors all influence the viability of a project. Economic geologists will be interested to learn that the diamond business encompasses geology from the earth’s core (ultradeep diamonds) …

Characteristics of diamondiferous Plio-Pleistocene littoral deposits within the palaeo-Orange River mouth, Namibia

The Orange River, the principal conduit transporting diamonds from hinterland sources to the Namibian coast in post-Cretaceous times, is characterised by an extreme wave dominated delta that has given rise to a progression of coarse rudaceous littoral deposits preserved onshore for > 150 km north of the mouth. Under the long-lived, prevailing vigorous wave, wind and northward longshore drift regimes, the Orange River outfall has been reworked into, amongst others, a series of economically viable, diamondiferous Plio-Pleistocene onshore gravel beach deposits. These placers comprise spits and barrier beaches in the proximal reach within the palaeo-Orange River mouth that, after ca. 5 km northwards, merge into extensive but narrow linear beaches that, in turn after ca. 70 km, give way to pocket beaches. Gravel and diamond size decreases northwards away from the ancestral Orange River mouth. The linear and pocket beach types have considerably higher diamond content but lower average diamond stone size than the two proximal units that are characterised by low diamond grade but comparatively large average diamond size. Given the risk of delineating low grade alluvial diamond deposits accurately, we present here sedimentological reconstructions of the subtidal, intertidal and supra-tidal facies that constitute the spit and barrier beach sequences, based largely on face mapping of exploration trenches and open-cast, mine cuts, as well as the results of large tonnage, sampling campaigns. Diamond distribution is also linked convincingly to basic littoral processes that were operational within the palaeo-Orange River mouth during the complex transgression that gave rise to the + 30 m package in Plio-Pleistocene times. In both the spit and barrier beach settings, the intertidal deposits prove to be the most promising targets whereas the subtidal sediments are the least economic. The constant raking associated with coarse, cobble–boulder-sized gravel foreshore deposits in an energetic micro-tidal wave regime increased the average diamond stone size in the intertidal deposits to 1 to 2 carats per stone (cts/stn), but the lack of fixed trapsites (no competent footwall within the palaeo-Orange River mouth at that level) prohibited the accumulation of substantially enriched diamondiferous gravels. Consequently, grades of only 1.5 to 6 carats per 100 tons (cpht) are realised. The highest grades (2 to 6 cpht) are found in the landward-facing, intertidal beach deposits on the spits where gentle reworking in that sheltered environment had somewhat enriched and preserved the diamond content. Significantly, the low average stone size of ca. 0.5 cts/stn in this lower energy setting probably reflects that of the general diamond population available at that time. In contrast, the sand-rich subtidal deposits in the spit sequence return the lowest grades (0.1 to 0.5 cpht), similar to those in the slightly younger, subtidal transgressive boulder lags of the barrier beaches. However, the stone size in the spit subtidal sediments is also low (0.1 to 0.5 cts/stn) due to the highly mobile, fine-grained character of those deposits, whereas that in the subtidal transgressive lag is large (2 to 3 cts/stn) as a result of the local, semi-permanent turbulence associated with the boulder-sized clasts in these gravel sheets. Diamond distribution is therefore also influenced by littoral facies and associated beach types, in addition to the spatial and temporal parameters that have already been documented for the onshore marine placers of the southern Namibian coast.

Processing of Diamond for Integrated Optic Devices Using Q-Switched Nd:YAG Laser at Different Wavelengths

In the present investigation, a Q-switched Nd:YAG laser is used to study the various aspects of diamond processing for fabricating integrated optic and UV optoelectronic devices. Diamond is a better choice of substrate compared to silicon and gallium arsenide for the fabrication of waveguides to perform operations such as modulation, switching, multiplexing, and filtering, particularly in the ultraviolet spectrum. The experimental setup of the present investigation consists of two Q-Switched Nd:YAG lasers capable of operating at wavelengths of 1064 nm and 532 nm. The diamond cutting is performed using these two wavelengths by making the “V”-shaped groove with various opening angle. The variation of material loss of diamond during cutting is noted for the two wavelengths. The cut surface morphology and elemental and structural analysis of graphite formed during processing in both cases are compared using scanning electron microscopy (SEM) and laser Raman spectroscopy. Both the Q-Switched Nd:YAG laser systems (at 1064 nm and 532 nm) show very good performance in terms of peak-to-peak output stability, minimal spot diameter, smaller divergence angle, higher peak power in Q-switched mode, and good fundamental TEM 00 mode quality for processing natural diamond stones. Less material loss and minimal micro cracks are achieved with wavelength 532 nm whereas a better diamond cut surface is achieved with processing at 1064 nm with minimum roughness.

Wear processes of diamond stone in honing of fine ceramics

Wear processes of diamond stone in honing of fine ceramics

Cutting Characteristics of CBN Stone and Diamond Stone with Pulsed Nd:YAG Laser

超砥粒砥石の生産性向上を目標として, パルスNd : YAGレーザを用いた超砥粒砥石の切断に関する研究が行われている. 厚み3mmのCBN砥石およびダイヤモンド砥石を用いて切断実験した結果, ダイヤモンドブレードによる切断と比較して取り代および切断速度が改善され, 切断面の熱変質層には熱亀裂が存在せず, 良好な加工が可能なことを示した.

Analysis of the film thickness of a root canal sealer following three obturation techniques.

The aim of this study was to obtain a quantitative analysis of the film thickness of a root canal sealer formed after filling by three different techniques. Thirty human maxillary incisors were selected and access cavities were prepared using high-speed diamond stones and water spray. A size #15 K-Flexofile was introduced in the canal of each specimen until it was seen just at the apical foramen. The working length was determined to be 1 mm short of that position and the canals were prepared to an apical size of #45 K-Flexofile. Copious irrigation with 5.25% NaOCl (sodium hypochlorite) was used during and after instrumentation. The samples were divided into three groups and obturated as follows: G1 - lateral condensation, G2 - lateral condensation with an accessory cone, and G3 - continuous wave of condensation. The samples were evaluated in the cervical, middle and apical thirds. The film thickness of the root canal sealer was measured through a microscopic evaluation. Statistical analysis was obtained using the Wilcox test. Statistical analysis showed significant differences between G3 and G1, G3 and G2 (p < 0.05). In general, the lowest film thickness was observed in the continuous wave of condensation (G3). Lateral condensation with an accessory cone (G2) and lateral condensation (G1) demonstrated poorer results in this study, showing a higher film thickness. The small film thickness of the sealer obtained by the continuous wave of condensation technique may increase the clinical performance of this technique.

水溶性加工液による耐熱合金の超仕上げ

The water-solution type coolant is used instead of ordinary. oil type coolant and the effect of the coolant on the finishing is investigated experimentally. As work materials, titanium, titanium alloies and Ni-based alloy are used. Electrolytic in-process dressing is employed to promote the ability of metal removal because the water-solution type coolant is inferior to that of oil type one in the permeability. The specific cutting energy k s of these materials are compared with k s of a bearing steel in order to evaluate the machinability of the work materials. The results obtained are as follows. The superfinishing opera-tion using a water-solution type coolant is the effective method to finish the surface of these difficult-to-cut materials when the electrolytic in-process dressing is applied together. The suitable conditions in electrolytic dressing for each work material are obtained, and the titanium which has the highest adhesive property needs the strongest electrolysis among the work materials used in this study. The electrolytic-in-process dressing makes it possible to maintain the cutting ability of the finer grain size stone for a long time, and to obtain the mirror surface of Incoloy 800 with #8000 SD diamond stone.

Pricing the C's of Diamond Stones

Many statistical problems can be satisfactorily resolved within the framework of linear regression. Business students, for example, employ linear regression to uncover interesting insights in the fields of Finance, Marketing, and Human Resources, among others. The purpose of this paper is to demonstrate how several concepts arising in a typical discussion of multiple linear regression can be motivated through the development of a pricing model for diamond stones. Specifically, we use data pertaining to 308 stones listed in an advertisement to construct a model, which educates us on the relative pricing of caratage and the different grades of clarity and colour.

超砥粒ホイールのアブレシブ摩耗に関する研究 （第１報） レジノイドボンド砥石の掘り起こし摩耗の特性

This paper describes the characteristic and the mechanism of the abrasive wear of the super abrasive grinding wheel. The characteristics have been obtained on the lapping equipment by the wear experiment, using the sticks of resinoid diamond stones equal to the composition of abrasive grain layer in the super abrasive grinding wheel. The following results are obtained: the rapid abrasive wear of diamond grinding stone occurs at the pressure above the abrasive grain holding force because of ploughing the bond by the diamond grain, on the other hand, the matrix abrasion occurs slowly at the pressure below it. The influence of the grain size and concentration on the abrasive wear are clarified also. In the selection of the truing, dressing and grinding condition, the experimental results will be useful.

Effect of tooth surface roughness on marginal seating and retention of complete metal crowns

Statement of problem. Retention and marginal adaptation factors have major influence on the failure of cemented complete veneer crowns. Purpose. This study investigated the effect of axial surface roughness on the marginal seating and retention of silver-palladium crowns luted with zinc phosphate, glass ionomer, and resin cements. Material and methods. Coarse and fine diamond stones were used to create various surface roughnesses of premolars. A milling machine was used to control the height and angle of the axial walls of tooth preparations. Ten cast metal crowns in 6 subgroups were luted with 3 cements (Phosphacap, Fuji Cap I, and Panavia 21). Marginal seating was recorded with a Digimatic indicator. Retention was determined by measuring the tensile force required to remove a metal crown with a Lloyd testing machine. Results. Two-way analysis of variance revealed statistically significant differences ( P <.001) in retention for both luting cements and surface roughness. No significant difference was recorded for marginal seating relative to roughness ( P =.860) and interaction effects ( P =.204). Tukey-HSD tests revealed substantial differences in retention among Phosphacap, Fuji Cap I, and Panavia 21 cements. Significant differences were not confirmed in marginal seating between Fuji Cap I and Phosphacap cements with coarse diamonds, and Phosphacap and Panavia 21 cements with fine diamonds. Conclusions. The best retention for complete metal crown was demonstrated for tooth preparations ground with coarse diamonds and cemented with Panavia 21 cement. Differences in axial surface roughness had no effect on the marginal seating of the complete metal crowns. (J Prosthet Dent 1999;81:142-7.)

Analysis of Blade Forces and Wear in Diamond Stone Cutting

The realtime evaluation of normal, tangential and perpendicular cutting forces and spindle vibration provides a simple measure of blade friction, wear performance, diamond-bond wear rate differences, blade stiffness and machine support. These observations can be used to evaluate and diagnose problems in diamond sawing that might inhibit use of high-grade diamond crystals.

超仕上加工における切削性能のファジィ制御

Fuzzy control is applied to the superfinishing in order to optimize the cutting ability of the stone. The finishing performance of vitrified bonded WA stone is regarded as the fuzzy goal. At the beginning of cutting, the stone is in the stage of cutting to get high stock removal rate. But the cutting ability is decreasing as the finishing proceeds and is lost at the end of finishing, resulting in getting the smooth surface. A cutting resistance is used to monitor the cutting condition of stone. The cutting ability of stone is controlled by both the stone pressure and the amount of electricity for electrolytic in-process dressing. A water-solution type coolant and metal bonded diamond stone are used. The main results obtained are as follows. Fuzzy control makes it possible to give the optimized cutting ability to the diamond stone. In the first case, it is possible to get the large stock removal following the smooth surface in a limited time. In second case, it is possible to minimize the finishing time in which the finishing performance intended in stock removal and surface roughness is obtained. In third case, it is possible to keep the cutting ability of stone constant for a long time.

電解水による歯科用器具の消毒とその腐食傾向

The excellent bactericidal activity of the electrolyzed acid water has recently been noticed in dentistry. The authors previously demonstrated the validity of the strong acid water as a disinfectant for impression showing rapid and reliable sterilization effect. In the present study, the applicability of the electrolyzed water to sterilization of dental metallic instruments was examined. The contamination bacteria tested were Streptococcus salivarius (IFO 13956). As the problem with the acid water is that it is potentially corrosive to metals, corrosion tests were also carried out. The instruments having simple configuration such as reamer and explorer could be sterilized by one-minute immersion in the strong acid water, while those of comlicated configuration such as diamond stones and burs required much longer time for equivalent sterilization. When the ultrasonic cleaning action was added in the strong acid water, all the instruments were sufficiently sterilized by one-minute treatment although such a cleaning itself could give little effect of removing bacteria from the instruments even by 20-minute treatment in distilled water. Another type of electrolized water, the week acid water 5.2 in pH showed almost the same effects as the strong acid water. The reamer and diamond stone showed no corrosion in 24-hour immersion in the acid water. The working end of the explorer was also sound while many corrosion pits were observed on its handle. A marked corrosion was found on the overall surface of the steel burs, and a localized loss occurred at the brazed area between the blade and shank of the carbide burs without the blade being harmed. It was confirmed that the week acid water was less corrosive than the strong. Significant damages of the burs by corrosion appeared after 3-hour immersion in the acid water. The term corresponds to 180-time repetitions of one-minute immersion treatment, indicating that such a corrosion behavior may not result in any practically serious problem because it may far exceed the mechanical lives in service of their blades. These findings suggest that both the electrolyzed strong and week acid waters may well be available as the disinfectant for dental instruments.

Diamond Ring Pricing Using Linear Regression

Data presented in a newspaper advertisement suggest the use of simple linear regression to relate the prices of diamond rings to the weights of their diamond stones. The intercept of the resulting ...

ファインセラミックスの超仕上加工 砥石粒度の加工特性への影響

Influence of the grain size of diamond stone on the superfinishing performances is investigated experimentally. The mechanism of chip formation is investigated by observing the shape of chips and the finished surfaces of workpiece with scanning electron microscope. The work materials used are alumina (Al2O3), silicon carbide (SiC), silicon nitride (Si3N4) and zirconia (ZrO2), which are sintered under the atmospheric pressure, and Mn-Zn ferrite, which is sintered under HIP. The grain size of stone is changed from # 500 to # 8 000. The results are as follows. The diamond stone with suitable bonding strength makes it possible to remove the work material as chips even if its grain size is finer than # 1 000. Two types of chips are obserbed; one is the crack-type chips which are made by brittle fracture, and the other is the flow-type chips which are made by plastic deformation. As the grain size of stone becomes smaller, the shape of chips changes from crack-type to flow-type. The critical grain size is dependent on the work materials and it becomes smaller in the order of ZrO2, Mn-Zn ferrite, Al2O3, Si3N4 and SiC. The condition of making the flow-type chips is important to obtain the mirror surface of ceramics.

超仕上における砥石の切れ味制御

A new method of the superfinishing is investigated, in which the cutting ability of diamond stone is controlled by changing the strength of electrolytic in-process dressing. Water-solution type coolant and metal bonded stone are used to employ the electrolytic dressing. As work materials, a carbon steel S 45 C, a bearing steel SUJ 2 and alumina are used. The results obtained are as follows. It is effective for control of electrolytic dressing to change the operating time of electrolysis or the ratio of on-time to off-time in electric pulse. As the dressing becomes stronger, the cutting ability of stone improves and the metal removal rate becomes larger. As the dressing becomes weaker, the cutting ability of stone is lost and then the surface roughness of workpiece becomes smaller. The cutting ability of stone which has been lost in finishing operation can be regenerated again applying the strong electrolysis. This in-process dressing method makes it possible to obtain the intended finishing performances of metal removal rate and surface roughness, and to finish several work materials of different machinability using a same kind of stone.

Effect of Coolant of Water-solution in Superfinishing. Application of Electrolytic In-process Dressing.

In order to simplify the treatment of coolant in production systems, the superfinishing characteristics under the condition of water-solution type coolant are investigated experimentally. This type of coolant is inferior to an oil type coolant in removing chips from the stone because of its poor permeability. Electrolytic in-process dressing is applied to promote the self-dressing of diamond stone. As work materials, alumina which is sintered under atmospheric pressure and soft steel (equivalent to 0.15% carbon steel) are used. The results obtained are as follows. Electrolytic in-process dressing makes it possible to use the coolant of water-solution in superfinishing. The suitable conditions in electrolytic in-process dressing depend on the machinability of work materials. The soft steel whose chips are easy to make a loading on the working surface of stone needs the stronger dressing. A concentration of some percent is sufficient for a coolant to maintain its essential properties. The electrolytic in-process dressing is more effective for harder or finer stone, because it can control the cutting ability of the stone.

Seven-step tooth preparation for a gold onlay

This article describes seven sequential steps for an onlay preparation: penetration and extension, axial reduction, cuspal reduction, supragingival shoulder, supragingival bevel, intracrevicular bevel, and finishing. Details and rationale of each step are reviewed, and the number of burs and diamond stones are minimized. The tooth preparation is designed to provide maximal retention with innocuous occlusal forces, esthetics, and preservation of tooth structure. The slip joint on the facial and lingual walls of the proximal boxes facilitates seating of single- or multiple-unit castings. These seven sequential clinical steps for a gold onlay have been successful.