• Bulletin of the Korean Chemical Society
• /
• v.34 no.2
• /
• pp.365-366
• /
• 2013

• Journal of dental hygiene science
• /
• v.9 no.4
• /
• pp.405-412
• /
• 2009

The purpose of this study investigated the effect of Au coating on adhesion between porcelain matrix and metal substructure interface. Titanium, Ni-Cr alloy and Co-Cr alloy are well known as proper metal for the dental restorations. The success of a porcelain fused to metal (PFM) restoration depends upon the quality of the porcelain-metal bond. However, adhesion between dental alloys and porcelain is related to diffusion of oxygen during ceramic firing. The excessive oxidized layers make hard adhesion between dental alloy and ceramic. Ni-Cr and Co-Cr specimens were divided into test and a control group and Titanium specimens were divided into three test groups and a control group. Each group had 20 specimens. The adhesion characteristics of porcelain and metal with Au coating layer and without Au coating layer were observed with scanning electron microscopy(SEM). The adhesion was evaluated by a biaxial flexure test and volume fraction of adherent porcelain was determined by SEM/EDS analysis. Result of this study suggest that Au coating layer is effective barrier to diffuse oxide layer completely protect non-precious alloys from oxidation during the porcelain firing. The SEM photomicrographs of cross-section specimens showed a smooth interface between Au coating layer and metals and porcelain which suggested proper chemical bonding, and no gap, porosity were observed. The mode of failure was mainly adhesive for Ti tested specimens, but mixed failures with adhesive and cohesive were observed in Ni-Cr and Co-Cr specimens. The adhesion between non-precious metals and porcelain would not be improved by Au coating agent. However, It is suggested that the continuous study is required further investigation and development.

• Current Photovoltaic Research
• /
• v.10 no.4
• /
• pp.101-106
• /
• 2022

We prepared a CsPbI₂Br solution using Cesium iodide (CsI), Lead (II) bromide (PbBr₂) and Lead (II) iodide (PbI₂) materials into a polar solvent mixture of N,N-dimethylformamide (DMF) and Dimethyl sulfoxide (DMSO). A simple spin coating technique was used for the fabrication of CsPbI₂Br absorber layer in the solution process. In order to prepare uniform coating of absorber film we adopted a hot-air process in assocation with the spin coating. It was confirmed that the thin film manufactured by the hot-air process had a higher absorption rate than that without it, and the optical band gap was measured 1.93 eV. The thin film of absorber was uniformly prepared and revealed the Black α-Cubic crystal phase as proved through X-ray diffraction analysis. Finally, a perovskite solar cell having an n-i-p structure was manufactured with a CsPbI₂Br perovskite absorption layer. From the solar cell, we obtained a power conversion efficiency (PCE) of 5.97% in a forward measurement.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.204.2-204.2
• /
• 2013

Wide band gap II-VI semiconductors have attracted the interest of many research groups during the past few years due to the possibility of their applications in light-emitting diodes and laser diodes. Among the II-VI semiconductors, ZnO is an important optoelectronic device material for use in the violet and blue regions because of its wide direct band gap (Eg ~3.37 eV) and large exciton binding energy (60 meV). F-doped ZnO (FZO) and undoped ZnO thin films were grown onto quartz substrate by the sol-gel spin-coating method. The doping level in the solution, designated by F/Zn atomic ratio of was varied from 0 to 5 in 1 steps. To investigate the effects of the structure and optical properties of FZO thin films were investigated using X-ray diffraction (XRD), UV-visible spectroscopy, and photoluminescence (PL). In the XRD, the residual stress, FWHM, bond length, and average grain size were changed with increasing the doping concentration. For the PL spectra, the high INBE/IDLE ratio of the FZO thin films doping concentration at 1 at.% than the other samples.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.112.1-112.1
• /
• 2011

The back contact solar cell (BCSC) has several advantages compared to the conventional solar cell since it can reduce grid shadowing loss and contact resistance between the electrode and the silicon substrate. This paper presents the effect of the surface texturing of the silicon BCSC by varying the texturing depth or the texturing gap in the commercially available simulation software, ATHENA and ATLAS of the company SILVACO. The texturing depth was varied from $5{\mu}m$ to $150{\mu}m$ and the texturing gap was varied from $1{\mu}m$ to $100{\mu}m$ in the simulation. The resulting efficiency of the silicon BCSC was evaluated depending on the texturing condition. The quantum efficiency and the I-V curve of the designed silicon BCSC was also obtained for the analysis since they are closely related with the solar cell efficiency. Other parameters of the simulated silicon BCSC are as follows. The substrate was an n-type silicon, which was doped with phosphorous at $6{\times}10^{15}cm^{-3}$, and its thickness was $180{\mu}m$, a typical thickness of commercial solar cell substrate thickness. The back surface field (BSF) was $1{\times}10^{20}\;cm^{-3}$ and the doping concentration of a boron doped emitter was $8.5{\times}10^{19}\;cm^{-3}$. The pitch of the silicon BCSC was $1250{\mu}m$ and the anti-reflection coating (ARC) SiN thickness was $0.079{\mu}m$. It was assumed that the texturing was anisotropic etching of crystalline silicon, resulting in texturing angle of 54.7 degrees. The best efficiency was 25.6264% when texturing depth was $50{\mu}m$ with zero texturing gap in case of low texturing depth (< $100{\mu}m$).

• Journal of Welding and Joining
• /
• v.23 no.3
• /
• pp.76-82
• /
• 2005

Recently the application of laser welding technology has been considered to shipbuilding structure. However, when this technology is applied to primer coated steel, good quality weld beads are not easily obtained. Because the primer-coated layer caused the spatter, humping bead and porosity which are main part of the welding defect attributed to the powerful vaporizing pressure of zinc. So we performed experiment with objectives of understanding spatter and porosity formation mechanism and producing sound weld beads in 6mmt primer coated steels by a $CO_2$ CW laser. The effects of welding parameters; defocused distance, welding speed, coated thickness and coated position; were investigated in the bead shape and penetration depth on bead and lap welding. Alternative idea was suggested to suspend the welding defect by giving a reasonable gap clearance for primer coated thickness. The zinc of primer has a boiling point that is lower than melting point of steel. Zinc vapor builds up at the interface between the two sheets and this tends to deteriorate the quality of the weld by ejecting weld material from lap position or leaving porosity. Significant effects of primer coated position was lap side rather than surface. Therefore introducing a small gap clearance in the lap position, the zinc vapor could escape through it and sound weld beads can be acquired. In conclusion, formation and suspension mechanism of the welding defects was suggested by controling the factors.

• The Journal of Korean Academy of Prosthodontics
• /
• v.39 no.3
• /
• pp.297-305
• /
• 2001

Statement of problem. There have been previous studies about instability according to screw material by means of calculating preload in tightening screw or recording of the torque necessary to loosen screw after tightening screw. Purpose. The purpose of this study was to evaluate screw joint stability through the analysis of fitness at the mating thread surfaces between implant and screw after tightening screws made of different materials. Material and methods. In this study, screws were respectively used to secure a cemented abutment to a hexlock implant fixture; teflon coated titanium alloy screw and titanium alloy screw(Steri-Oss), gold-plated gold-palladium alloy screw and titanium alloy screw(Implant Innovation), gold screw and titanium screw(AVANA Dental Implant System). Each abutment screw was secured to the implant with recommended torque value using a digital torque controller. Each screw was again tightened after 10minutes. All samples were cross sectioned with sandpaper and polished. Then samples were evaluated with an scanning electron microscope analysis. Results. In titanium alloy screw, irregular contact and relatively large gap was present at mating thread surface. Also in teflon-coated titanium screw, incomplete seating and only partially contact was present at the mating thread surface. In gold-plated gold-palladium alloy screw, relatively close and tight contact without the presence of large gap was present by existing of gold coating at the mating thread surfaces. In gold alloy screw, relatively small gap between the mating components was seen. Conclusions. This result suggested that gold plated gold-palladium alloy screw and gold alloy screw achieved a greater degree of contact at the mating thread surfaces compared to titanium alloy screw and teflon-coated titanium alloy screw.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.7
• /
• pp.667-672
• /
• 2006

Ferroelectric $Pb(Zr_{0.52}Ti_{0.48})O_3$ (PZT(52/48)) thick films were fabricated by the screen-Printing method on the alumina substrates, and $PbTiO_3$ (PT) Precursor solution, which prepared by sol-gel method, was spin-coated on the PZT(52/48) thick films to obtain a densification. Its structural and electrical properties of the PZT(52/48) thick films with the treatment of PT precursor solution coating were investigated. The particle size of the thick films was increased with increasing the number of coatings and the thickness of the PZT-6 (6: number of coatings) films was about $60{\mu}m$. The relative dielectric constant increased and the dielectric loss decreased with increasing the number of PT sol coatings. The relative dielectric constant and dielectric loss of the PZT-6 thick film were 475 and 2 %, respectively. The remanent polarization, coercive field and breakdown strength of the PZT-6 film were $32.6{\mu}C/cm^2$, 15 kV/cm and 60 kV/cm, respectively.

• Proceedings of the KIEE Conference
• /
• 2008.05a
• /
• pp.169-170
• /
• 2008

The heterolayered PZT/PT thick films were fabricated by two different methods - thick films of the PZT by screen printing method on alumina substrates electrodes with Pt, thin films of $PbTiO_3$ by the spin coating method on the PZT thick films and once more thick films of the PZT by the screen printing method on the $BaTiO_3$ layer The structural and the dielectric properties were investigated for effect of various stacking sequence of sol-gel prepared $PbTiO_3$ coating solution at interface of the PZT thick films. The insertion of $PbTiO_3$ interlayer yielded the PZT thick films with homogeneous and dense grain structure with the number of $PbTiO_3$ layers. The leakage current density of the PZT/$PbTiO_3-1$ film is less that $4.41{\times}10^{-9}\;A/cm^2$ at 5 V.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.05a
• /
• pp.735-738
• /
• 2000

The characteristics of wire electrical discharge machining (WEDM) are governed by many factors such as the power supply type, operating condition and electrode material. This work deals with the effect of wire electrode materials on the machining characteristics such as, metal removal rate, surface characteristics and surface roughness during WEDM A wire's thermal physical properties are melting point, electrical conductivity and vapor pressure. One of the desired qualities of wire is a low melting point and high vapor pressure to help expel the contaminants from the gap. They are determined by the mix of alloying elements (in the case of plain brass and coated wire) or the base core material(i.e. molybdenum). Experiments have been conducted regarding the choice of suitable wire electrode materials and influence of the properties of these materials on the machinability and surface characteristics in WEDM, the experimental results are presented and discussed from their metallurgical aspect. And the coating effect of various alloying elements(Au, Ag, Cu, Zn, Cr, Mn, etc.) to the Cu or 65-35 brass core on them was reviewed also. The removal rate of some coated wires are higher than that of 65-35 brass electrode wire because the wire is difficult to break due to the wire cooling effect of Zn evaporation latent heat and the Zn oxide on the surface is effective in preventing short circuit. The removal rate increases with increasing Zn content from 35, 40 and Zn coated wire