• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.38-41
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• 2009

Debonding behavior of symmetric tilt bicrystal interfaces with <100> misorientation axis is investigated through molecular dynamics simulations. FCC single crystal copper is considered in each grain and the model is idealized as a grain boundary under mechanical loading. Embedded-Atom Method potential is chosen to calculate the interatomic forces between atoms. Constrained tensile deformations are applied to a variety of misorientation angles in order to estimate the effect of grain boundary angle on local peak stress. A new parameter of symmetric grain-boundary structure is introduced and refines the correlation between grain boundary angle and local peak stress.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.255-262
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• 2020

Grain boundaries play a major role in determining device performance, particularly of polysilicon-based photodetectors. Through the post-annealing of as-deposited polysilicon and then, the analysis of electric behavior for a metal-polysilicon-metal (MSM) photodetector, we were able to identify the influence of grain boundaries. A modified model of polysilicon grain boundaries in the MSM structure is presented, which uses a crystalline-interfacial layer-SiO_x layer- interfacial layer-crystalline system that is similar to the Si-SiO₂ system in MOS device. Hydrogen passivation was achieved through a hydrogen ion implantation process and was used to passivate the defects at both interfacial layers. The thin SiO_x layer at the grain boundary can enhance the photosensitivity of an MSM photodetector by decreasing the dark current and increasing the light absorption.

• Korean Journal of Materials Research
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• v.14 no.12
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• pp.829-834
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• 2004

Annealing of $Cu(B)/Ti/SiO_2$ in vacuum has been carried out to investigate the effects of Ti underlayer on microstructure in $Cu(B)/Ti/SiO_2$ structures. For comparison, $Cu(B)/Ti/SiO_2$ structures was also annealed in vacuum. Three different temperature dependence of Cu growth can be seen in $Cu(B)/Ti/SiO_2$; B precipitates- pinned grain growth, abnormal grain growth, normal grain growth. The Ti underlayer having a strong affinity for B atoms reacts with the out-diffused B to the Ti surface and forms titanium boride at the Cu-Ti interface. The formation of titanium boride acts as a sink for the out-diffusion of B atoms. The depletion of boron in grain boundaries of Cu films, as results of the rapid diffusion of B along the grain boundaries and the insufficient segregation of B to the grain boundaries, induces grain boundaries to migrate and causes the abnormal grain growth. The increased bulk diffusion coefficient of B within Cu grains can be responsible for the normal grain growth occurring in the annealed $Cu(B)/Ti/SiO_2\;at\;600^{\circ}C$. In contrast, the $Cu/SiO_2$ structures show only the abnormal growth of grains and their sizes increasing as the temperature increases above $400^{\circ}C$.

• Nuclear Engineering and Technology
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• v.52 no.1
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• pp.148-154
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• 2020

The radiation induced segregation of Cr at grain boundaries (GBs) in Ferritic/Martensitic steels was modeled assuming vacancy and interstitialcy diffusion mechanisms. In particular, the dependence of segregation on temperature and grain boundary misorientation angle was analyzed. It is found that Cr enriches at grain boundaries at low temperatures primarily through the interstitialcy mechanism while depletes at high temperatures predominantly through the vacancy mechanism. There is a crossover from Cr enrichment to depletion at an intermediate temperature where the Cr:Fe vacancy and interstitialcy diffusion coefficient ratios intersect. The bell-shape Cr enrichment response is attributed to the decreasing void sinks inside the grains as temperature rises. It is also shown that low angle grain boundaries (LAGBs) and special Σ coincidence-site lattice (CSL) grain boundaries exhibit suppressed radiation induced segregation (RIS) response while high angle grain boundaries (HAGBs) have high RIS segregation. This different behavior is attributed to the variations in dislocation density at different grain boundaries.

• Journal of the Korean Ceramic Society
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• v.36 no.9
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• pp.937-945
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• 1999

In an effort to protect a RBSC(reaction -bonded SiC) tube SiC films from methyltrichlorosilane(MTS) by low pressure chemical vapor deposition were deposited in hydrogen atmosphere on the RBSC(reaction-bonded SiC) substrates over a range of input gas ratio(${\alpha}=P_{H2}/P_{MTS}=Q_{H2}/Q_{MTS}$=1 to 10) and deposition temperatures(T=1050~1300$^{\circ}C$). At the temper-ature of 1250$^{\circ}C$ the growth rate of SiC films increased and then decreased with decreasing the input gas ratio. The microstructure of SiC films was changed from granular type structure exhibiting (111) preferred orientation in the high input gas ratios to faceted columnar grain structure showing (220) in the low input gas ratios. The similar microstructure change was obtained by increasing the deposition temperature. These results were closely related to a change of deposition mechanism. Double layer structure having granular type and faceted ciolumnar grain structure from the manipulation of mechanism. Double layer structure having granular type and faceted columnar grain structure from the manipulation of the input gas ratio without changing the deposition temperatue was successfully fabricated through in -site process.

• Applied Biological Chemistry
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• v.20 no.1
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• pp.156-170
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• 1977

Some of the recent developments and studies in the area of rice protein are reviewed. Protein content and amino acid composition of rice are briefly described. Emphasis is given to characterization of rice protein fractions, effects of protein content on grain properties and lysine content of rice, occurence of protein in rice grain and biosynthesis of protein during grain development.

• Journal of Welding and Joining
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• v.5 no.2
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• pp.9-16
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• 1987

Post weld heat treatment (PWHT) is carried out to increase the fracture toughness in heat affected zone(HAZ) and remove the residual stress. There occur some problems such as toughness decreement and stress relief cracking(SRC) in the coarse grained HAZ subjected to the effect of tempering treatment. Especially, embitterment of structure directly relates to the mode of fracture and is appeared as the difference of fracture surface, that is, grain boundary failure. Therefore, in this paper, PWHT was carried out under the stress of 0, 10, 20 and $30kg/cm^2$ to simulate residual stress in HAZ welded by heat input of 10, 30 and 40KJ/cm. Applied stress in weld HAZ during PWHT assisted precipitin of over saturated alloying element in the structure, and grain boundary failure according to welding heat input didn't almost appear at the heat input of 10 KJ/cm, but it appeared from being the applied stress of $30kg/cm^2$ at $30KJ/cm and 20kg/mm^2$ at 40KJ/cm.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.2
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• pp.60-69
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• 1998

Polysilicon surface mdoification tecnique is developed to reduce the sticking of microstructures fabricated by micromachining. Modified anti-sticking grain holes are simply formed by two-step dry eth without additional photolithography nor deposition of thin films. Both process-induced sticking and in-use sticking are successfully reduced more than two times by adopting grain holed polysilicon substrate. A sticking model for cantilever beam is derived. This model includes bending moment stems from stress gradient along the thickness directionof structural polysilicon. Because the surface tension of rinse liquid and the surface energy of the solids to be stuk tend to decrease in recently developed anti-sticking techniques, the effect of stress gradient will play an important role to analyze the sticking phenomena. Effect of the temperature during post-release rinse and dry is modelled and verified experimentally. Based on developed anti-sticking polysilicon structure and the sticking model, sticking of microstructure, fabricated by simple wet process including sacrificial layer etch and rinse with deionized water without special equimpment for post-release rinse and dry was alleviated more than 3.5 times.

• Bulletin of the Korean Chemical Society
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• v.6 no.5
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• pp.304-308
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• 1985

Morphological structure of tin oxide thin films was examined by transmission electron microscopy. TEM samples were prepared by chemical etching in hydrogen fluoride solution: firstly floating for 2-3 minutes in acid solution, then suspending on water found to be useful for the preparation of TEM samples. Electron micrographs showed the size of grains of the tin oxide crystal was dependent upon the temperature of the film preparation. Dopant concentration and heating time also influence the grain size. The resistivity of tin oxide material was explained by grain size and grain boundaries in a limited temperature and dopant concentration ranges.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.167-173
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• 2001

The simulated die-casting process in which the traditional plaster casting process is combined with Rapid Prototyping technology is being used to produce AI, Mg, and Zn die-casting prototypes. Unlike in the die-casting process, molten metal in the conventional plaster casting process is fed via a gravity pour into a mold and the mold does not cool as quickly as a die-casting mold. The plaster castings have much larger and grosser grain structure as compared with the normal die-castings and the thin walls of the plaster mold cavity may not be completely filled. Because of lower mechanical properties induced by the large grain structure and incomplete filling, the conventional plaster casting process is not suitable for the trial die-casting process to obtain quality prototypes. In this work, an enhanced trial die-casting process has been developed in which molten metal in the plaster mold cavity is vibrated and pressurized simultaneously. Patterns for the casting are made by Rapid Prototyping technologies and then plaster molds, which have a runner system, are made using these patterns. Pressurized vibration to imparted molten metal has made grain structure of castings much finer and improved fluidity of the molten enough to obtain complete filling at thin walls which may not be filled in the conventional plaster casting process..