• Journal of the Korean Ceramic Society
• /
• v.30 no.11
• /
• pp.979-985
• /
• 1993

Diamond films were synthesized using CH4-H2-Ar mixture gases by MWCVD, and cutting ability was tested after brazing them onto WC tools. Growth rates were in the range of 0.5~10${\mu}{\textrm}{m}$/hr depending on the deposition conditions, and diamond films with thickness of 100~300${\mu}{\textrm}{m}$ were obtained. Diamond tools brazed by RF induction method showed an enhanced cutting ability in the cutting test of Si single crystal rod.

• Journal of the Korean Ceramic Society
• /
• v.26 no.3
• /
• pp.331-340
• /
• 1989

In this study, it was tried to deposit diamond films from a mixture of CH4 and H2 by the microwave plasma chemical vapor deposition(MWCVD). The MWCVD process was designed and set up from the 2.45GHz microwave generator. And the diamond film was successfully deposited on silicon wafers from the mixture of methane and hydrogen. The microstructures of the deposited diamond films were studied by using the following deposition variables : (a) methane concentration(0.6-10%), (b) reaction pressure(10-100torr), and (c) the substrate temperature(450-76$0^{\circ}C$).

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2007.11a
• /
• pp.134-135
• /
• 2007

Graphite and MoS2 were added respectively as a lubricant to improve the cutting efficiency of micro blades which contains diamond abrasive. Strength, fracture toughness, and life span of micro-blades were observed to decrease with the increase in diamond abrasive and lubricant content. Wearing mode of micro-blades and the cutting efficiency were also found to be affected by the content of diamond abrasive and the addition of lubricants.

• Restorative Dentistry and Endodontics
• /
• v.35 no.1
• /
• pp.13-19
• /
• 2010

The purpose of this study was to compare the microshear bond strength of a self-etching primer adhesive to dentin prepared with different diamond points, carbide burs and SiC papers, and also to determine which SiC paper yield similar strength to that of dentinal surface prepared with points or burs. Fifty-six human molar were sectioned to expose the occlusal dentinal surfaces of crowns and slabs of 1.2 mm thick were made. Dentinal surfaces were removed with three diamond points, two carbide burs, and three SiC papers. They were divided into one of eight equal groups (n = 7); Group 1: standard diamond point(TF-12), Group 2: fine diamond point (TF-12F), Group 3: extrafine diamond point (TF-12EF), Group 4: plain-cut carbide bur (no. 245), Group 5: cross-cut carbide bur (no. 557), Group 6 : P 120-grade SiC paper, Group 7: P 220-grade SiC paper, Group 8: P 800-grade SiC paper. Clearfil SE Bond was applied on dentinal surface and Clearfil AP-X was placed on dentinal surface using Tygon tubes. After the bonded specimens were subjected to uSBS testing, the mean uSBS (n = 20 for each group) was statistically compared using one-way ANOV A and Tukey HSD test. In conclusion, the use of extrafine diamond point is recommended for improved bonding of Clearfil SE Bond to dentin. Also the use of P 220-grade SiC paper in vitro will be yield the results closer to dentinal surface prepared with fine diamond point or carbide burs in vivo.

• Journal of the Korean Vacuum Society
• /
• v.2 no.2
• /
• pp.199-208
• /
• 1993

The effect of nucleation free energy related to Si surface states on diamond film growth behavior has been studied. Ar first, the three kinds of diamond thin films (A, B, C) were deposited on various Si substrates (A-Si, B-Si, C-Si) whose surfaces were polished with 1 ${\mu}m$ diamond paste, 6 ${\mu}m$ Al_2O_3$ powder and 12 ${\mu}m$ Al_2O_3$ powder respectively. And then, relative nucleation free energy calculated is ${\Delta}G_{A-Si}<{\Delta}G_{B-Si}<{\Delta}G_{C-Si}$. Although there are some difference in grain size, shape and nucleated size, the thin films on A-Si and B-Si were diamond including a small amount of DLC which was confirmed by AES, SEM, XRD, and RHEED. Namely, the diamonds of films (B) were not nucleated in scratches but in dents and larger in grain size compare with the film (C) of which diamond sere nucleated not only scratches but also dents. And, the sphere diamond which is not general shape was grown on C-Si. After all, the sphere was turned out to be the diamond including much graphite as a result of the AES in situ depth profiling. Consequently, the diamond shape and quality grown on Si were Changed from the crystal which the (100) and (110) planes were predominent to the crystal in which (111) plane was predominent, and newt to sphere shape diamond including much graphite according as the nucleation free energy increases.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.15 no.1
• /
• pp.10-15
• /
• 2005

Effects of CH₄/H₂ flow rate ratio, chuck bias and microwave power on the structural properties and particle densities of diamond thin films deposited on Ti substrates in microwave plasma CVD were examined. High quality diamond thin films were deposited on Ti substrates in 2∼3 CH₄ Vol.% conditions due to the preferential formation of sp³-bonus ana selective removal of sp²-bonus in the CH₄/H₂ mixtures, and the mechanism for the formation of diamond particles on Ti was analysed. Diamond particle density increased with increasing negative chuck bias to Ti substrate due to bias-enhanced nucleation of diamond and the threshold voltage was found at ∼-50 V. With increasing microwave power the evolution from micro-crystalline graphite layer to diamond layer was observed.

• Journal of the Mineralogical Society of Korea
• /
• v.20 no.3
• /
• pp.175-180
• /
• 2007

FTIR technique was applied to delineate spectroscopic characteristics of natural, synthetic and irradiated diamonds. All of the samples studied in this work show the absorption peaks, which are generally observed in diamond as well as the specific one related to N in diamonds. Synthetic diamond is characterized with both the peaks of 1344 and $1128 cm^{-1}$ related to HPHT synthesis and specific $1050 cm^{-1}$ peak only observed in synthetic diamond, which can be used to discriminate natural from synthetic. Type (natural blue diamond: IIb, electron beam Irradiated blue diamond: Type Ia) can be used to discriminate natural from irradiated diamond. The intensity of specific $1450 cm^{-1}$ peak observed only in irradiated diamond is related with irradiation and annealing process.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.2
• /
• pp.240-248
• /
• 1998

The plasma chemical vapor deposition is one of the most utilized techniques for the diamond growth. As the applications of diamond thin films prepared by plasma chemical vapor deposition(CVD) techniques become more demanding, improved fine-tuning and control of the process are required. The important parameters in diamond film deposition include the substrate temperature, $CH_4/H_2$ gas flow ratio, total, gas pressure, and gas excitation power. With the spectroscopic ellipsometry, the substrate temperature as well as the various parameters of the film can be determined without the physical contact and the destructiveness under the extreme environment associated with the diamond film deposition. It is introduced how the real-time spectroscopic ellipsometry is used and the data are analyzed with the view of getting the growth condition and the accompanied features for a good quality of diamond films. And it is determined the important parameters during the diamond film growth, which include the final sample will be measured with Raman spectroscopy to confirm the diamond component included in the film.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.27 no.4
• /
• pp.149-153
• /
• 2017

Recently, significant amounts of gem-quality colorless HPHT synthetic melee diamond have produced for the jewelry industry. Consequently, there have been reports of cases of fraud in the world diamond business. For example, intentionally selling synthetic diamond as natural diamond or intentionally mixing a natural diamond parcel with a synthetic. As a result, the separation of natural from synthetic melee diamonds has become increasingly critical. At present, 10,000 cubic hinge presses are used for the production of synthetic diamond in China. From among these, reportedly 1,000 presses are used for gem-quality diamond production. One press can produce up to 10ct melee-size diamonds in 24 hours. Randomly occurring pinpoint or flux-metal inclusions are diagnostic identification clues. However, some synthetic diamonds require advanced laboratory method for identification. In order to ensure consumer confidence, it is essential to screen melees so as to distinguish all synthetic goods.

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.66-66
• /
• 2009

Various alloy system, such as Cu-Sn-Ti, Cu-Ag-Ti, and Ni-B-Cr-based alloy are used for the brazing of diamond grits. However, the problem of the adhesion strength between the diamond grits and the brazed alloy is presented. The adhesion strength between the diamond grits and the melting filler alloy is predicted by the contact angle, thereby, instead of diamond grit, the study on the wettability between the graphite and the brazing alloy has been indirectly executed. In this study, Cu-13Sn-12Ti filler alloy was manufactured, and the contact angles, the shear strengths and the interfacial area between the graphites(diamond grits) and braze matrix were investigated. The contact angle was decreased on increasing holding time and temperature. The results of shear strength of the graphite joints brazed filler alloys were observed that the joints applied Cu-13Sn-12Ti alloy at brazing temperature 940 $^{\circ}C$ was very sound condition indicating the shear tensile value of 23.8 MPa because of existing the widest carbide(TiC) reaction layers. The micrograph of wettability of the diamond grit brazed filler alloys were observed that the brazement applied Cu-13Sn-12Ti alloy at brazing temperature $990^{\circ}C$ was very sound condition because of existing a few TiC grains in the vicinity of the TiC layers.