• The korean journal of orthodontics
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• v.22 no.1
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• pp.43-65
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• 1992

Bonding orthodontic adhesive resins to glazed porcelain surface is not attainable. The aim of this investigation was to examine, in vitro, the effect of three methods of porcelain surface pretreatment on the shear bond strength of orthodontic adhesives, and to compare the shear strength of orthodontic bracket bonding to porcelain surface by the best results that to human enamel. Porcelain disks ($Ceramco^{(TM)}$ and $Vita^{(TM)}$) baked in the laboratory were roughened by sandpapers, #320, #600, #800, #1000 and #1200, and were pretreated with silane and dried at the various temperatures, room temperature, $50^{\circ}C$, $70^{\circ}C$ and $90^{\circ}C$, and were etched by 3% hydrofluoric acid solution for 1, 3, 5, 7, and 9 minutes, orthodontic adhesives (System $1+^{(TM)}$ and $Unite^{(TM)}$) were applied on them, and shear bond strengths were measured by Instron. The best results of pretreatment of each method were determined by the shear bond strengths. Again, porcelain disks were pretreated by the determined best results and human enamel were etched by 37% hydrofluoric acid solution, orthodontic brackets were bonded on them by the orthodontic adhesives, and the shear bond strengths were measured and compared between them. 1. Roughening porcelain surfaces with coarse sandpaper (#300) showed higher shear bond strength than that with finer sandpapers, but it $(22.44Kgf/cm^2)$ was distinguishably low compared to that from etched human enamel $(144.11Kgf/cm^2)$. 2. There were disparities in shear bond strengths upon the orthodontic resins, which was presumably related to the contents of fillers in orthodontic adhesive resins. Also there were disparities in shear bond strength upon the porcelains which had different composition. 3. Silane enhanced the shear bond strength of orthodontic resins to porcelain surfaces ($25.20Kgf/cm^2$ at $50^{\circ}C$), which was markedly low compared to that from etched human enamel. 4. Etched porcelain surface with 3% hydrofluoric acid solution for 1 to 9 minutes showed no difference in shear bonding strength of orthodontic adhesive resins. Shear bond strength from etched porcelain $(97.43-120.72Kgf/cm^2)$ were as high as clinically available, but low compared to that from etched human enamel. 5. Roughening with #300 sandpaper and etching by 3% hydrofluoric acid followed silane application on porcelain surface showed lower shear bond strength than etched human enamel, but were as high as clinically useful. 6. The results suggest that etching porcelain surface by 3% hydrofluoric acid solution might provide comparatively high shear bond strength as much as clinically favorable.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.5
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• pp.91-97
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• 2015

Papermakers wish to increase the filler content of printing and writing grades because it allows saving in production cost through fiber replacement and improving the formation, and optical and printing properties of the paper. However, high filler loading in the base paper has negative side effects. It reduces the mechanical properties of paper and induces cracking at the fold after coating process. Fold cracking is one of the most frequent quality complaints for magazines, high quality books, etc. Two approaches were examined as methods to reduce fold cracking. One approach was to use preflocculated fillers, which was expected to reduce the fold cracking because it would decrease the interfiber bonding. The other approach was to use a new coating binder that gives greater binding power and thereby provides an opportunity of reducing the fold cracking of coated paper. When filler preflocculation was employed in producing the base paper, fold cracking becomes more severe than conventional filler loading condition. On the other hand, use of nano sized binder in coating improved the tensile properties of the coating layer and thereby decreased the crack area. It was shown that tensile properties of coating layer played an important role in fold cracking of coating.

• International Journal of Highway Engineering
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• v.11 no.3
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• pp.1-11
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• 2009

This study focuses on evaluating the applicability of an acryl based polymer concrete to the thin bridge deck pavements. The acryl concrete developed in this study is composed of Methyl Methacrylate(MMA) resin, benzol peroxide and fillers. To study the effects of the types and amounts of the components on the physical characteristics of the acryl concrete, viscosity, compressive strength and bending tests were conducted. The optimum mixture design was then determined based on the testing results. Several different types of laboratory tests, such as water and chlorine ion penetration tests, shrinkage and thermal coefficients tests, and tensile bonding strength tests were performed for the optimum acryl concrete and conventional cement concrete. The testing results show that water and chroline ion resistance, bonding strength between acryl and cement concrete and crack resistance of the acryl concrete is better than those of the conventional cement concrete. There are shortcomings that the conventional acryl concrete has a higher shrinkage and thermal coefficients. However, it was confirmed that to use newly developed rubberized MMA resin in this study reduces the crack resistance with substantially increased ductility.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.29 no.1
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• pp.36-42
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• 1997

The fiber wall filling(FWF) technology, which is based on Precipitatin of fillers in the micropores of the cell wall structure of never-dried chemical pulp fiber, has been developed to improve filling and loading process in papermaking. In presenting FWF technique here, micropores of pulp fiber are first impregnated with an ionic solution of water soluble salt and consecutively impregnated with the second salt solution. This procedure generates an insoluble precipitate within the micropores of cell wall by chemical interaction of these two ionic salt solutions This is the first attempts to use FWF technology for the quality of waste paper grade which is recycled in papermaking, even though this FWF technology has been impressively improved for never-dried chemical pulp in filling and loading process of papermaking. The precipitated amount of CaCO$_3$ and SrCO$_3$ reached 5-6% and 4-5% of the waste paper weight respectively, which was measured by ash content of the burned waste paper fiber. On the other way the precipitated amounts of those materials impregnated into never-dried chemical pulp fiber have reached 17-18% and 16-18% respectively. The micropore loading technique gives optical and physical properties to the handsheets formed with celt-wall-filled fibers which are better than those handsheet properties resulting from conventional loading. The papers made from the cell-wall-filled pulps are stronger than those with the customary location of filler between the fibers.

• Applied Chemistry for Engineering
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• v.23 no.4
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• pp.372-376
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• 2012

Carbon nanotubes (CNT) are considered as one of ideal nano-fillers in the field of composites with their excellent electrical, mechanical, and thermal properties. Therefore CNT composites are increasingly used in fabricating conductive materials, structural materials with high strength and low weight, and multifunctional materials. The main problem of the CNT composites is difficulty in the dispersion of CNT in the polymer matrix. In this study multi-walled carbon nanotubes (MWNT) were pretreated by the physical process utilizing a wrapping method. After the pretreatment polymer/MWNT nanocomposites were prepared by melt processing. The effect of functionalization MWNT by wrapping with styrene acrylonitrile (SAN) on the mechanical and electrical properties of acrylonitrile butadiene styrene resin (ABS)/MWNT composites was studied by comparing the properties of ABS mixed with the neat MWNT. Electrical and mechanical properties of ABS/MWNT nanocomposites were studied as a function of the functionalization and content of MWNT. The tensile strength of the ABS/MWNT nanocomposites increased, but the impact strength decreased. The polymer wrapping in ABS system has little effect on the improvement of electrical properties.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.140-140
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• 2018

The 3D interconnect technologies have been appeared, as the density of Integrated Circuit (IC) devices increases. Through Silicon Via (TSV) process is an important technology in the 3D interconnect technologies. And the process is used to form a vertically electrical connection through silicon dies. This TSV process has some advantages that short length of interconnection, high interconnection density, low electrical resistance, and low power consumption. Because of these advantages, TSVs could improve the device performance higher. The fabrication process of TSV has several steps such as TSV etching, insulator deposition, seed layer deposition, metallization, planarization, and assembly. Among them, TSV metallization (i.e. TSV filling) was core process in the fabrication process of TSV because TSV metallization determines the performance and reliability of the TSV interconnect. TSVs were commonly filled with metals by using the simple electrochemical deposition method. However, since the aspect ratio of TSVs was become a higher, it was easy to occur voids and copper filling of TSVs became more difficult. Using some additives like an accelerator, suppressor and leveler for the void-free filling of TSVs, deposition rate of bottom could be fast whereas deposition of side walls could be inhibited. The suppressor was adsorbed surface of via easily because of its higher molecular weight than the accelerator. However, for high aspect ratio TSV fillers, the growth of the top of via can be accelerated because the suppressor is replaced by an accelerator. The substitution of the accelerator and the suppressor caused the side wall growth and defect generation. The suppressor was used as Single additive electrodeposition of TSV to overcome the constraints. At the electrochemical deposition of high aspect ratio of TSVs, the suppressor as single additive could effectively suppress the growth of the top surface and the void-free bottom-up filling became possible. Generally, copper was used to fill TSVs since its low resistivity could reduce the RC delay of the interconnection. However, because of the large Coefficients of Thermal Expansion (CTE) mismatch between silicon and copper, stress was induced to the silicon around the TSVs at the annealing process. The Keep Out Zone (KOZ), the stressed area in the silicon, could affect carrier mobility and could cause degradation of the device performance. Cobalt can be used as an alternative material because the CTE of cobalt was lower than that of copper. Therefore, using cobalt could reduce KOZ and improve device performance. In this study, high-aspect ratio TSVs were filled with cobalt using the electrochemical deposition. And the filling performance was enhanced by using the suppressor as single additive. Electrochemical analysis explains the effect of suppressor in the cobalt filling bath and the effect of filling behavior at condition such as current type was investigated.

• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1143-1148
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• 2002

Precipitated calcium carbonate is one of the most versatile mineral fillers and is consumed in an wide range of products including paper, paint, plastics, rubber, textiles, sealants, adhesives and printing ink and can be produced by several methods. Calcium carbonate has three isomorphism; vaterite, aragonite and calcite, with numerous variations of morphology in the natural mineral or organism. Formation process of vaterite in the reaction of system $Ca(OH)_2-CH_3OH-H_2O-CO_2$ were investigated by measuring the electrical conductivity, $Ca^{2+}$ ion concentration, pH in the slurries and by means of X-ray diffraction and electron microscopic observation. It was clearly established that the reaction temperature is important variable in the carbonation process; in general over 50${\circ}C$, the vaterite was precipitated with the calcite and aragonite. SEM and XRD observations revealed that the vaterite formation could be prepared the temperature range of 40 to 50${\circ}C$ and mean size of particles in this range is controlled from 0.5 to 0.8 ${\mu}m$.

• Journal of the Korean Magnetics Society
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• v.19 no.6
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• pp.203-208
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• 2009

Magnetic and Ka-band absorbing properties have been investigated in Ti-Co substituted M-type barium hexaferrites with $BaTi_{0.5}Co_{0.5}Fe_{11}O_{19}$ composition. The ferrite powders were prepared by conventional ceramic processing technique and used as absorbent fillers in ferrite-rubber composites. The magnetic properties were measured by vibrating sample magnetometer. The complex permeability and dielectric constant were measured by using the WR-28 rectangular waveguide and network analyzer in the frequency range 26.5~40 GHz. For the Ti-Co substituted M-hexaferrites, the ferromagnetic resonance is observed at Ka-band (29.4 GHz). The matching frequency and matching thickness are determined by using the solution map of impedance matching. A wide band microwave absorbance is predicted with controlled ferrite volume fraction and absorber thickness.

• Polymer(Korea)
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• v.30 no.5
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• pp.385-390
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• 2006

In this work, the effect of carbon nanofiber (CNF) on thermal properties, and friction and wear behavior of CNF/PMMA composites were examined. While thermal properties of the composites were investigated with differential scanning calorimetry, thermograyimetric analyzer, and dynamic mechanical analyzer friction and wear behaviors were examined using a friction and wear tester. The glass transition temperature (Tg), integral procedural decomposition temperature (IPDT), storage modulus (E'), and tan ${\delta}$ appeared at higher temperatures with increasing CNF content, which were probably attributed to the presence of strong interactions between the carbonaceous fillers and the PMMA resins matrix. The wear loss in the composites decreased at 0.1 wt% CNF and then increased with 5-10 wt% CNF content. This was due to the existence of large aspect ratio CNF in PMMA which led to an alignment of PMMA chains and an increase of mechanical interlocking, resulting in the formation of crosslinked structures between CNF and PMMA in the composite.

• Polymer(Korea)
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• v.36 no.5
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• pp.612-616
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• 2012

In this work, the effect of chemical treatments of multi-walled carbon nanotubes (MWNTs) on the mechanical interfacial properties of carbon fiber fabric-reinforced composites was investigated. The surface properties of the MWNTs were determined by acid and base values, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. The mechanical interfacial properties of the composites were assessed by interlaminar shear stress (ILSS) and critical stress intensity factor ($K_{IC}$). The chemical treatments based on acid and base reactions led to a significant change of surface characteristics of the MWNTs, especially A-MWNTs/carbon fibers/epoxy composites had higher mechanical properties than those of B-MWNTs and non-treated MWNTs/carbon fibers/epoxy composites. These results were probably due to the improvement of interfacial bonding strength, resulting from the acid-base interaction and hydrogen bonding between the epoxy resins and the MWNT fillers.