Fine Diamond Powder Research Articles

Comparison of Enamel Surface Roughness between Light-cured and Self-cured Composites used in Orthodontic Bonding by using Atomic Force Microscopy

Introduction: Debonding is a procedure of removing orthodontic attachments along with the entire residual adhesives from the surface of enamel following orthodontic treatment completion. The objective of the orthodontists should be to restore the surface of enamel as closely as possible to natural enamel without inducing iatrogenic injury and with minimal loss of enamel structure. Bonding of brackets on enamel involves surface etching, application of primer, and adhesive. All these steps involve the risk of damaging the enamel surface and changing its original morphology. Upon completion of orthodontic treatment, the debonding procedure followed by residual resin removal further damages the enamel, producing scratches, cracks, grooves, removal of fluoride-rich external enamel layer, and increasing the enamel roughness. The rough enamel surface inhibits proper cleaning and thus invites plaque deposition, bacterial retention, stain formation, and thus dampening the aesthetic appearance of the teeth. Restoring the enamel to its original morphology is a challenge. A variety of mechanical methods have been proposed to achieve satisfactory resin removal with least possible enamel damage following bracket debonding. The Enhance finishing and Pogo polishing system (Dentsply, Milford, USA) is also widely used and is made up of polymerized urethane dimethacrylate resin, aluminium oxide, silicon dioxide, and fine diamond powder. Methods: The sample of 50 tooth extracted for orthodontic purpose was procured as per the inclusion criteria. Buccal surfaces of teeth on the area where bracket is bonded and then debonding is done. After residual resin removal with Enhance system finishing and polishing bur. Measurements for each specimen were measured and mean was calculated and evaluated with the help of Atomic Force Microscopy (Baseline roughness data). Result: Self cure composite gives relatively lesser surface roughness when compared to light cure composites. Conclusion: The study shows that the self cure adhesive gives the smoother enamel surface when compared to the tooth treated with light cure adhesive after debonding and finishing and polishing.

The increasing in operating characteristic of medical rotating cutting tool by introduction abrasive smaller grain size powder into the galvanic bond

The results of studies on strengthening the galvanic bond by introduction an abrasive smaller grain size powder into it are discussed. A comparative analysis of a standard abrasive tool and a tool, the working part of which consists of modified abrasive particles, the size of which is 1/3 of the size of the working abrasive tool, is presented. As indicators wear, cutting ability, and wear resistance are studied. The positive effect of the proposed method is confirmed by the results of comparative tests of a medical rotating cutting tool made with the introduction of fine diamond powder into a metal bond of a dental bur and electrocorundum of a similar fraction into the working part of a podology bur.

In-situ synthesis and superhigh modulus of network structured TiC/Ti composites based on diamond-Ti system

Abstract In order to enhance the elastic modulus and strength of titanium, novel continuous network structured TiC particle reinforced Ti (TiC/Ti) composites were successfully fabricated by hot pressing sintering based on diamond-Ti system. The results showed that 5 vol% fine diamond powders can be homogeneously adhered onto the surface of large Ti powders by lower energy ball milling process of 250 rpm/5 h/3:1. The mixed powders resulted in equiaxed network microstructure of TiC/Ti composites formed by continuous TiC particle reinforcement around large Ti powders after in-situ reaction between diamond and Ti. However, high energy ball milling process of 300 rpm/10 h/10:1 must be employed due to excessive diamond powders, which can result in TiC/Ti composites with a novel flattened network microstructure. Among the composites, the one introduced by 10 vol% diamond exhibited the highest elastic modulus of 184 GPa, which was increased by 64% compared with pure Ti (112 GPa). The composites with 5 vol% and 7.5 vol% diamond presented 830 MPa and 1480 MPa compressive yield strengths respectively, which were 1.9- and 3.4-fold that of pure Ti (429 MPa). The superior elastic modulus and strength of the composites was mainly attributed to the continuous TiC network microstructure and remained reinforcement-lean region based on the Hashin-Shtrikman theory.

Enhanced strength of nano-polycrystalline diamond by introducing boron carbide interlayers at the grain boundaries.

Polycrystalline diamond with high mechanical properties and excellent thermal stability plays an important role in industry and materials science. However, the increased inherent brittle strength with the increase of hardness has severely limited its further widespread application. In this work, we produced well-sintered nano-polycrystalline (np) diamond by directly sintering fine diamond powders with the boron carbide (B4C) additive at high pressure and high temperatures. The highest hardness value of up to ∼90 GPa was observed in the np-diamond (consisting of fine grains with a size of 16 nm) by adding 5 wt% B4C at 18 GPa and 2237 K. Moreover, our results reveal that the produced samples have shown noticeably enhanced strength and toughness (18.37 MPa m0.5) with the assistance of the soft phase at the grain boundaries, higher than that of the hardest known nano-twined diamond by ∼24% and a little greater than that of the toughest CVD diamond (18 MPa m0.5). This study offers a novel functional approach in improving and controlling the hardness and stiffness of polycrystalline diamond.

적층형 셀과 아연도금층을 이용한 고온고압 합성다이아몬드의 압력변화에 따른 물성 연구

Fine diamond powders are synthesized with a 420 φ cubic press and stack-cell composed of Kovar (Fe54Ni29Co17) (or Kovar+7 μmthick Zn electroplated) alloy and graphite disks. The high pressure high temperature (HPHT) process condition was executed at 1500 oC for 280 seconds by varying the nominal pressure of 5.7∼10.6 GPa. The density of formation, size, shape, and phase of diamonds are determined by optical microscopy, field emission scanning electron microscopy, thermal gravimetric analysis-differential thermal ammnlysis (TGA-DTA), X-ray diffraction (XRD), and micro-Raman spectroscopy. Through the microscopy analyses, we found that 1.5 μm super-fine tetrahedral diamonds were synthesized for Zn coated Kovar cell with whole range of pressure while ∼3 μm superfine diamond for conventional Kovar cell with < 10.6 GPa. Based on 750oC exothermic reaction of diamonds in TGA-DTA, and characteristic peaks of the diamonds in XRD and micro-Raman analysis, we could confirm that the diamonds were successfully formed with the whole pressure range in this research. Finally, we propose a new process for super-fine diamonds by lowering the pressure condition and employing Zn electroplated Kovar disks.

Low energy ion beam smoothening of artificially synthesized single crystal diamond chips with initial surface roughness of 0.08–0.4 nm rms

High quality ultra- smooth single crystal diamond chips are used as molds for nano-imprints, mirrors for X-ray free-electron lasers, and so on. Conventional mechanical process using lap plate of fine diamond powder cannot be applied in thinning down of diamond materials to the order of 10μm. Therefore we applied ion beam machining for the smoothening of the surface of artificially synthesized single crystal diamond chips (100) with the initial surface roughness of 0.08–0.4nm rms. We found that by 1.0keV Ar+ ion beam at a normal angle of ion incidence, the processed surface became ultra-smooth with the surface roughness of 0.10nm rms and waviness of 0.12nm rms. However, the speed of processing by Ar+ ion beam was low. In order to increase the speed, 0.5keV O2+/O+ beam was applied for the smoothening of the diamond surface at normal incidence angle. In this method, we successfully obtained ultra-smooth surface with a surface roughness of 0.10nm rms at a much higher processing rate. We also observed that in ion beam machining, a rough surface becomes smooth and smooth surface becomes rough and both trends tend to saturate towards a roughness level at a particular dose. To understand this contrasting phenomenon, we conducted power spectral density (PSD) profile analysis of the un-processed and processed surfaces, and studied the roughening and smoothening mechanisms taking place on the diamond chip surface during its ion beam machining.

Development of a high-precision, wear-resistant micro-holes structure

Nickel ions and fine diamond powder are utilized as metal–matrix composites to improve wear-resistance in the development of micro-hole structures. The reinforced microstructure is produced on a specular substrate through a precision extrusion wax and electrochemical co-deposition technique. Oily wax is employed as sacrificial material to draw and grow a feature shape. Co-deposition, in which nickel sulphamate solution and diamond powder are regularly mixed, is conducted for electroforming a layer of metal–matrix composites onto the substrate. The formed micro-holes structure displays excellent geometric and dimensional accuracy of the holes. Satisfactory diamond content provides the wear-resistant metal–matrix composites.

A Method for an Improvement in the Quality of Diamond Composite Thermostable Material

It is still in focus the problem of obtaining high quality polycrystalline materials by means of sintering fine diamond powders. The most important task of this problem is the consolidation or improvement of the processed polycrystalline diamond. It is worldwide recognized that the plastic deformation of the diamond particles performs the most important role on the diamond powder consolidation. In some cases, the contact and shear tensions reconstruct the compact structure. In this work the sintering process used a mixture of micro and nanodiamonds. The sintering process was carried out in a toroidal high-pressure device. The effects of nanodiamond addition and sintering conditions on the microstructure and mechanical properties sintered diamond bodies were studied. The sintering parameters were pressure of 6.8 GPa and a temperature of 1850 K, and these conditions were maintained for 1 minute. Homogeneous sintered bodies were obtained, which have a Vickers' hardness over 40 GPa, and fracture toughness around 7.1 – 7.9 MPa.m1/2.

Synthesis of Diamond Particles under Alkaline Hydrothermal Conditions

Very fine diamond powder (1-3 ~m) was readily sintered under hydrothermal conditions, with new bond formation occurring between the diamond particles in a l0M-NaOH solution at 573 K maintained at 1 GPa pressure, for 24 hours. This new bonding material can be formed by carbonization, from a chlorinated hydrocarbon such as dichloromethane and 1, 1,1–trichloroethane. The carbonized material forms a new bond between the hydrogenated diamond particles by the release of hydrogen chloride. Using Raman spectroscopy and hydrogenated cubic boron nitride substrates it was indisputably demonstrated that diamond was synthesized under these alkaline hydrothermal conditions. The surface morphology of the hydrothermal product on the cubic boron was similar to the new growth on the diamond substrates.

Influence of synthesis conditions and of neutron irradiation on physical properties of spontaneous crystalline diamonds

The influence of fine crystalline diamond powder synthesis conditions and their further irradiation by the neutrons of fission spectrum on the processes of natural and impurity defect (AlN) formation has been investigated. Non-monotonous change of paramagnetic nickel-containing defect concentration has been determined as being dependent both on the synthesis duration and on the influence of neutron irradiation. It is shown that the behavior of impurities in crystals depends on the processes occurring during their synthesis. Some similar changes of the paramagnetic nickel concentration under the influence of various factors (time, size and radiation) have been established. It has also been determined that the change in defects with g = 2.003 concentration is due to the change of the lattice point nitrogen defect concentration. The obtained results may be used to determine the conditions of spontaneous diamond crystallization in a closed system under high pressures and temperatures.

Preparation of Diamond Film Coatings on Multi-Spectrum ZnS

In the present investigation a specially designed ceramic interlayer, which is able to supply suitable protection of the ZnS substrate against chemical attack by atomic hydrogen, and is helpful to reduce the thermal stress, has been developed. Nano-crystalline diamond films were successfully deposited on to the pre-coated multi-spectrum ZnS. It was found that diamond nucleation on the ceramic interlayer could be greatly enhanced by a metal or semiconductor mask placed on top of the pre-coated ZnS substrate, whereas diamond nucleation will not happen even by long time seeding in ultrasonic bath with fine diamond powder suspension. It was found that diamond nucleation is induced by the presence of the metal or semiconductor mask. To our knowledge this kind of phenomena of induced nucleation has not been reported. Detailed results and discussions were presented.

Friction and wear of diamond-containing polyimide composites in water and air

Polyimide-based composites containing fine diamond powder were fabricated using spark plasma sintering. The based material was polyimide (PI) containing a small amount of polytetrafluoroethylene (PTFE). Two types of diamond powder were used: one synthesized by statically high pressure, i.e., high-pressure diamond (HD), and the other synthesized by shock compression, i.e., shock-compression diamond (SD). We evaluated their tribological properties using a reciprocating friction tester in water and air using an Al 2O 3 mating ball. Adding HD to the polyimide–PTFE-based material decreased the composite's friction in water, but the effect of this addition in air was negligible. The specific wear rate of composites with different HD content was similar to that of the based material alone in water, while the wear of composites decreased with the addition of diamond in air. The effect of diamond powder size on friction and wear of composites was generally low in both water and air. The addition of SD decreased the friction coefficient of composites, but SD content only negligibly affected the friction in water and air. The specific wear rate was minimal at SD content of 5 vol.%, when diamond content was varied. Wear was almost independent of diamond powder size. SD reduced composite friction and wear better than HD; regardless of environment, its friction coefficient was less than 0.1 and the specific wear rate was in the level of 10 −7 mm 3/N m in both water and air.

Diamond growth on Ir/CaF 2/Si substrates

A new multi-layered structure of heteroepitaxial (1 0 0) and (1 1 1) Ir grown on CaF 2-buffered (0 0 1) and (1 1 1) Si wafers by UHV electron-beam evaporation was prepared for the deposition of diamond films. A two-step process of bias-enhanced nucleation and a subsequent growth by controlling the α growth parameter was performed to deposit (0 0 1) and (1 1 1) diamond films by chemical vapor deposition, respectively. Scratching or seeding by fine diamond powders was also attempted on the (1 1 1) substrates to enhance the diamond nucleation density. Raman spectroscopy, X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy were used to characterize the Ir/CaF 2/Si substrates as well as the diamond films grown on top of iridium layer. Heteroepitaxial relationship between the deposited diamond grains and (0 0 1) substrates has been observed.

Nano-crystalline diamond films prepared by microwave argon plasma vapor deposition on optical glass

Nano-crystalline diamond films have been prepared on glass substrate in argon and methane environments by microwave plasma chemical vapor deposition. The suitable processing parameters are methane concentration 3% in argon; total deposition pressure 13.3 kPa; substrate temperature 500°C heated by plasma. In this film, the grain size is <30 nm; the roughness is about 13 nm; the boundary between grains is undefined; and there are non-crystalline structures evidently. Before deposition, the substrate must be pretreated by fine diamond powder grinding; this is to ensure that no large quadrangular grains appear and the film is continuous. The mechanical and optical performance have also been investigated.

Covalent immobilization of DNA on diamond and its verification by diffuse reflectance infrared spectroscopy

Immobilization of DNA on diamond surfaces and detection of its covalently bonded nature were explored by direct spectroscopic analysis. Fine diamond powder was successfully modified by oxidation, followed by esterification. DNA covalently immobilized onto diamond through ester linkage was detected by diffuse reflectance infrared spectroscopic analysis.

The preparation of (001) textured diamond films with large areas

The (001)-textured diamond films were deposited on a 4-inch Si wafer by a three-step method. First, fine diamond powder was seeded on the substrate by a dipping method to obtain high diamond nuclei density and low interface state density. Then a H ion etching and annealing was performed for 1 h by setting an electric potential of −120 V to improve the adhesion between diamond and substrate and obtain high (001)-textured films. At last, diamond films were deposited under the condition for (001)-textured growth. A SEM was used to analyze the morphology of diamond crystallites and the film formed with the above three steps and Raman spectra was applied to obtain the phase purity of the films. The results show that large area, low interface state density, uniform and (001)-textured diamond films can be synthesized by this three-step process.

Hydrothermal behavior of diamond

Abstract The interaction of two diamond powders and synthetic diamond single crystals with H2O has been studied in the temperature range of 650–850 °C under pressures up to 500 MPa. The reaction products were characterized using electron paramagnetic resonance (EPR), Raman and Fourier transform infra-red spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM) and selected area diffraction. A noticeable interaction of fine grain diamond powders with H2O starts at approx. 700 °C while single crystals are stable up to 800 °C. At 800–850 °C, etching pits appear on the single crystal diamond surface. Thermodynamic calculations predict the formation of hydrogen, carbon oxides and hydrocarbons. Formation of graphitic carbon via the fluid is observed. Redeposition of nanocrystalline diamond and healing of crystal defects are suggested by TEM and EPR investigations.

CVD diamond formation in the carbon/water pseudobinary system

Results of investigations on chemical vapor deposition of diamond films in the carbon/water pseudobinary system are presented. Mixtures of methyl formate, HCOOCH 3 , and water, H 2 O, vapors have been used as starting materials. The use of the above starting reactants ensured the constant value of 2 of the H/O atomic ratio that is required for the carbon-water system. The gas phase was activated to the state of plasma with the aid of microwave energy. Diamond films were deposited on silicon (100) wafers at the substrate temperature from 950 to 1000 °C and total pressure from 10 to 20 Torr. Prior to the deposition, surfaces of the substrates were scratched with a fine diamond powder or paste and subsequently ultrasonically cleaned in methanol and water. The films were identified and characterized by means of scanning electron microscopy and Raman spectroscopy. It follows from results of thermodynamic analysis of the system that at conditions at which diamond films of best phase purity and crystallinity deposited (i) the concentration of water vapor in the gas phase was relatively high and (ii) the gas phase was carbon under-saturated with respect to both diamond and graphite.

Sintering behaviour of the diamond-super invar alloy system at high temperature and pressure

In the diamond-super invar alloy system, effect of the grain size of the starting diamond powder on the sintering behaviour was investigated at 5.8 G Pa and 1300 to 1500 ° C for 30 to 60 min. Abnormal grain growth was often observed in the sintered diamond using fine diamond powder, but a homogeneous sintered diamond was easily synthesized using 5 to 10μm diamond. By the rigorous control of sintering conditions, a 3μm grain size homogeneous sintered diamond was synthesized under conditions of 5.8 G Pa and 1350 ° C for 30 min. The Vickers hardness and thermal resistance of the fine grained sintered diamond was examined.

Shock consolidation of diamond powders

Fine and coarse diamond powders were shock-compacted at peak pressures of 77, 90, and 108 GPa. The densification and consolidation mechanisms of diamond powders under shock compression were investigated. The densification behaviour of the diamond powders depended strongly on the particle size of the starting materials. Fine diamond powders were densified primarily by plastic deformation, while coarse diamond powders were densified mainly by particle fracture. The relative densities of the compacted diamond samples increased with an increase in the initial particle size of the diamond and with shock pressure. The consolidation mechanism of the diamond powders under shock compression was closely related to the densification mechanism, and depended on the initial particle size of the diamond. At a shock pressure of 90 GPa, particle sizes of 2 to 4 μm grade and 10 to 20 μm grade were desirable as the starting material in order to produce well-bonded diamond compacts. Diamond compacts having microhardness values over 80 GPa were obtained from 2 to 4 μm grade and 10 to 20 μm grade diamond powders at a shock pressure of 90 G Pa, and their relative densities were 88.5% and 91.0%, respectively.