• Journal of Adhesion and Interface
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• v.3 no.2
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• pp.9-16
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• 2002

In the synthesis of water-based polyurethane using self-emulsification process, after being neutralized, polyurethane pre-polymers containing ionic pendant groups are dispersed by simple convective mixing. Preparation of dispersion is followed by chain extension reaction, which is considered as important step for growth of the molecular weight of polyurethane. In this work, pH variations in the aqueous phase were monitored during the chain extension process in the presence of water-soluble diamines. The optimum degree of chain extension and the average particle size in the polyurethane dispersions were examined with varying ionic pendent group contents, type of chain extenders, and feed rate of chain extenders, The initial pH value in the aqueous phase linearly increased and the optimum chain extension point could be obtained from the intersection of two linear lines having different slopes, All average particle sizes before chain extension reaction were almost same, however, the final average particle size increased as feed rates of chain extenders increased, In addition, as the ionic pendant group contents increased, the particle size decreased since the hydrophilicity and hydrodynamic volume increased. As carbon numbers of the chain extenders increased, the final particle size increased significantly. From the results, it was concluded that the chain extension reaction took place among the particles not only in a particle.

• Resources Recycling
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• v.14 no.5 s.67
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• pp.13-17
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• 2005

As a basic study for recycling molten converter slag as an ordinary portland cement (OPC) by a conversion process, the reaction mechanism and the rate of the formation of $C_4AF$ which is one of the main components of OPC were investigated. The converter slag whose basicity was controlled by adding reagent grade $SiO_2$ was melted and hold for 30 minutes in MgO crucible at $1300^{\circ}C{\sim}1350^{\circ}C$. Then, the sintered CaO pellet heated at the same temperature was dipped into the molten slag and hold for $10{\sim}30$minutes. After the reaction, the crucible was cooled in air and the specimen was cut off to the horizontal direction of the crucible. The dissolution rate of $C_3A$ pellet was measured by the change of radius of the sintered $C_3A$ pellet, and the formed phase of $C_4AF$ was observed by SEM/EDX. As a result, the dissolution rate of $C_3A$ pellet into molten slag was increased from $0.75{\times}10^{-4}(cm/sec)$ at $1300^{\circ}C$ to $1.67{\times}10^{-4}(cm/sec)$ at $1350^{\circ}C$, and the mixed layer of $C_4AF$ and $C_{12}A_7$ was found between slag and $C_3A$ pellet.

• Korean Journal of Materials Research
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• v.3 no.3
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• pp.282-291
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• 1993

Joining ${Al}_{2}{O}_{3}$ and STS 304 stainless steel by active metal brazing method with using CuI Owt % Ti and Cu -7 .5wt % Zr insert metal, their interfaces were analyzed and strength of the joint brazed with Cu-7.5wt % Zr insert metal also investigated with shear strength testing method. In brazing with Cu-lOwt% Ti insert metal, the single reaction layer was formed by the reaction with Ti and ${Al}_{2}{O}_{3}$ at the interface between ${Al}_{2}{O}_{3}$ and insert metal, but the double reaction layer was found in brazing with Cu-7.5wt % Zr insert metal because of the difference of their wettability on the surface of ${Al}_{2}{O}_{3}$. Fracture shear strength about 86MPa was obtained from ${Al}_{2}{O}_{3}$/Cu-7.5wt% Zr/STS 304 stainless steel joint and reasonable strength of the joints is attributed to the formation of double reaction layer at the interface.

• Journal of Powder Materials
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• v.20 no.2
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• pp.114-119
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• 2013

In the DBC (direct bonding of copper) process the oxygen partial pressure surrounding the AlN/Cu bonding pairs has been controlled by Ar gas mixed with oxygen. However, the direct bonding of Cu with sound interface and good adhesion strength is complicated process due to the difficulty in the exact control of oxygen partial pressure by using Ar gas. In this study, we have utilized the in-situ equilibrium established during the reaction of $2CuO{\rightarrow}Cu_2O$ + 1/2 $O_2$ by placing powder bed of CuO or $Cu_2O$ around the Cu/AlN bonding pair at $1065{\sim}1085^{\circ}C$. The adhesion strength was relatively better in case of using CuO powder than when $Cu_2O$ powder was used. Microstructural analysis by optical microscopy and XRD revealed that the interface of bonding pair was composed of $Cu_2O$, Cu and small amount of CuO phase. Thus, it is explained that the good adhesion between Cu and AlN is attributed to the wetting of eutectic liquid formed by reaction of Cu and $Cu_2O$.

• Journal of Adhesion and Interface
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• v.10 no.2
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• pp.98-105
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• 2009

Poly(amic acid) was synthesized from the reaction of p-PDA/ODA and PMDA/BPDA and silane oligomer containing epoxy group was also synthesized from the reaction of tetramethylorthosilicate (TMOS) and glycidol. After hybridizing poly (amic acid) and silane oligomer, they were effectively converted into polyimide/silica hybrid films by thermal imidization process. As the silica contents in hybrid films increased, CTE values decreased from 17 ppm/K to 10 ppm/K and the tensile modulus increased, in spite of decreasing tensile strength. In addition, the peel test showed that the adhesion strength of hybrid film was enhanced from $0.43kg_f/cm$ to $1.02kg_f/cm$. Therefore, it could be concluded that the polyimide/silica hybrid film is effective to enhance adhesion strength for FCCL films.

• Journal of the Korean Ceramic Society
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• v.41 no.6
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• pp.430-434
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• 2004

The values of fracture energy and mechanical flexural strength of Fiber Reinforced Cement (FRC) with polypropylene (PP) fiber modified by Ion Assisted Reaction (JAR), by which functional groups were grafted on the surface of PP fiber, was improved about 2 times as those of fracture energy and flexural strength of cement reinforced by untreated PP fiber. PP fiber was irradiated in O$_2$ environment by Ar$\^$+/ ion. The contact angle of PP treated by IAR decreased largely when compared with untreated PP. From this result, we expected that surface energy and interfacial adhesion force of treated PP fiber increased. The strain hardening occurred in the strain-stress curve of FRC including PP treated by IAR when compared with that of FRC with untreated PP. These enhanced mechanical properties might be due to strong interaction between hydrophilic group on modified PP fiber and hydroxyl group in cement matrix. This hydrophilic group on surface modified PP fiber was confirmed by XPS analysis. We clearly observed hydration products that were fixed at modified PP fiber due to the strong adhesion force of interface in cement reinforced modified PP by SEM (Scanning Electron Microscopy) study.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.27-36
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• 2007

In this study, we investigated the interfacial reactions between various Sn-Ag-Cu(SAC) solder alloys and ENIG(Electroless Ni Immersion Gold) and Cu-OSP(Organic Solderability Preservative) pad finish. In the case of the interfacial reaction between Sb added SAC solder and ENlf thinner P-rich Ni layer was formed at the interface. In the case of the interfacial reaction between Ni added SAC solder and Cu-OSP, the uniform $Cu_6Sn_5$, intermetallic compounds(IMCs) were formed and $Cu_6Sn_5$ grain did not grow after multiple reflows. Thinner $Cu_3Sn$ IMCs were farmed at the interface between $Cu_6Sn_5$ and Cu-OSP after $150^{\circ}C$ thermal aging.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.2
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• pp.142-149
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• 2005

[ $LiNiO_2$ ] was mixed with $TiO_2$ or ZnO for the preparation of a cathode. The electrochemical properties of the cathode were investigated and the effects of the addition of $TiO_2$ or ZnO were discussed. The first discharge capacity decreased as the quantity of the added $TiO_2$ or ZnO increased. It is probably due to the decrease in the area of reaction interface according to the increase in the amount of the added oxide. When 2wt.% and 5wt.% of oxides are added, the discharge capacity increased as the number of cycles increased. It is considered that this results from the increase in the area of reaction interface because the oxide is detached from the $LiNiO_2$ with the increase in the number of cycles. The 1wt.% $TiO_2$ or ZnO-added $LiNiO_2$ had a larger first charge capacity than $LiNiO_2$. This is considered to result from the deintercalation of Li ions in the Ni sites along with the Li ions in the Li sites.

• Composites Research
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• v.29 no.2
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• pp.85-89
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• 2016

This paper aims at estimating the fracture behavior at the bonded part of composite material. CFRP is manufactured as the type of TDCB. The static analysis of Mode 1 due to the configuartion factor of m is carried out. Four kinds of specimens have the configuartion factor(m) of 2, 2.5, 3 and 3.5. As the study result, the displacements at specimens are shown to be similar each other in these four cases. At m of 3.5, the reaction force becomes highest as 412 N and is shown to be improved as much as 14% by comparing m of 2. The data on defection of the bonded interface and reaction force are thought to be contributed to the structural design of CFRP and the safe design.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.140-140
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• 1999

Ti/Ni multilayered films (MLF) are ideal for neutron optics particularly in neutron guides and focusing devices. This system also possesses the tendency of amorphization through a solid-state reaction (SSR). This behaviors are closely related to the electronic structures and both magneto-optical (MO) and optical properties of metals depend strongly on their electron energy structures. Mutual inter-diffusion of the Tin and Ni atoms in the MLF caused by a low temperature annealing should decrease the thickness of pure Ni, as well as change the chemical and atomic order in the reactive zone. The application of the MO spectroscopy to the study of SSR in the MLF allows us to obtain an additional information on the changes in the atomic and chemical orders in the interface region. The optical one has no restriction on the magnetic state of the constituent sublayers. Therefore, the changes in magnetic, MO and optical properties of the Ti/Ni MLF due to SSR can be expected. To the best of our knowledge, the MO and optical spectroscopies were not used for this purpose. SSR has been studied in the series of the Ti/Ni MLFs with bilayer periods of 0.65-22.2nm and constant ratio of the Ti to Ni sublayers thickness by using MO and optical spectroscopies as well as an x-ray diffraction. The experimental MO and optical spectra are compared with the computer-simulated spectra, assuming various interface models. The relative changes in the x-ray diffraction spectra and MO properties of the Ti/Ni MLF caused by annealing are bigger for the multilayers with "thick" sublayers, or the SSR with the formation of amorphous alloy takes place mainly in the Ti/Ni multilayers with "thick" sublayers, while in the nominal threshold thickness of the Ni-sublayer for the observation of the equatorial Kerr effect in the as-deposited and annealed Ti/Ni MLFs of about 3.0 and 4.5nm thick is explained by the formation of amorphous alloy during the deposition or the formation of the nonmagnetic alloyed regions between pure components as a result of the SSR. For the case of Ti/Ni MLF the MO approach is more sensitive for the determination of the thickness of the reacted zone, while x-ray diffraction is more useful for structural analyses.structural analyses.