• 폴리머
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• 제28권2호
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• pp.149-153
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• 2004

황산수소 세슘(CsHSO$_4$) 결정은 14$0^{\circ}C$ 이상의 온도에서 상온보다 $10^3$-$10^4$배 높은 양성자 전도성을 나타내는 초양성자 전도성 물질로서, 최근 연료 전지 분리막으로의 응용성이 크게 부각되고 있다. 그러나 연성과 흡습성 때문에 그 응용성에 한계가 있다. 본 연구에서는 기계적 물성이 우수한 얇은 전해질 막을 얻기 위하여 황산수소 세슘과 폴리아크릴로나이트릴 고분자와의 복합체를 제조하고 복합체의 이온 전도성과 상전이 현상을 조사하였다. 황산수소 세슘의 함량이 80 vol% 정도 되면 분리막으로 응용가능 한 전도도인 1${\times}$$10^{-3}$S$cm^{-1}$ /에 이르고 기계적 물성이 우수한 얇은 막으로 합성할 수 있었다.

• 소성∙가공
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• 제16권8호
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• pp.596-602
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• 2007

LGP (Light Guiding Plate) of LCD-BLU (Liquid Crystal Display - Back Light Unit) is one of the major components that affect the product quality of LCD. The optical patterns of LGP(2.2") molds are fabricated by three different methods, namely, (1) laser ablation, (2) chemical etching and (3) LiGA-reflow, respectively. The characteristics of surface patterns and roughnesses of molds and injection molded parts were compared to evaluate the optical characteristics. The optical patterns of injection molded LGP with mold fabricated by LiGA - reflow method showed the best geometric structure. The surface roughness (Ra) of LGP#s with molds fabricated by (1) laser ablation: $Ra={\sim}31nm$, (2) chemical etching: $Ra={\sim}22nm$, and (3) LiGA-reflow: $Ra={\sim}4nm$.

• 소성∙가공
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• 제21권5호
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• pp.285-290
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• 2012

In spite of progress in predicting ductile failure, the development of a macroscopic yield criterion to describe damage evolution in HCP (hexagonal close-packed) materials remains a challenge. HCP materials display strength differential effects (i.e., different behavior in tension versus compression) in their plastic response due to twinning. Cazacu and Stewart(2009) developed an analytical yield criterion for porous material containing randomly distributed spherical voids in an isotropic, incompressible matrix that shows tension-compression asymmetry. The goal of the calculations in this paper is to investigate the effect of the tension-compression asymmetry on necking induced by void nucleation, evolution and consolidation. In order to investigate the effect of the tension-compression asymmetry of the matrix on necking and fracture initiation, three isotropic materials A, B, and C were examined with different ratios of tension-compression asymmetry. The various types of material had BCC, FCC, and HCP crystal structures, respectively. The ratio between tension and compression in plastic flow significantly influences the fracture shape produced by damage propagation as well as affecting the localized neck.

• 소성∙가공
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• 제17권8호
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• pp.657-661
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• 2008

Recently, products of electronic industry and related parts are required to have the thickness thinner and thinner to reduce the part weight. To go with this trend, LGP(light guide plate) of LCD-BLU(Liquid Crystal Display-Back Light Unit: It is one of kernel parts of LCD) for cell phone has the thickness of ${\sim}0.3mm$ and the battery case of cell phone has ${\sim}0.25mm$. Accordingly, high speed injection molding is required to mold products which have thinner parts. To achieve high speed injection and proper control of hydraulic unit, various design was applied to conventional injection unit. In the present paper, we concentrated on the molding stability of hydro-mechanical high speed injection machine to make an LGP of 0.3mm thickness.

• 소성∙가공
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• 제21권4호
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• pp.240-245
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• 2012

With the increasing demand for light-weight materials to reduce fuel consumption, the automobile industry has extensively studied magnesium alloys which are light weight metals. The intrinsic poor formability and poor ductility at ambient temperature due to the hexagonal close-packed (HCP) crystal structure and the associated insufficient number of independent slip systems restricts the practical usage of these alloys. Hot working of magnesium alloys using a forging or extrusion enables net-shape manufacturing with enhanced formability and ductility since there are several operative non-basal slip systems in addition to basal slip plane, which increases the workability. In this research, the thermomechanical properties of AZ80 Mg alloy were obtained by compression testing at the various temperatures and strain rates. Optical microscopy and EBSD were used to study the microstructural behavior such as misorientation distribution and dynamic recrystallization. The results were correlated to the hardening and the softening of the alloy. The experimental data in conjunction with a physical explanation provide the optimal conditions for net-shape forging under hot or warm temperatures through control of the grain refinement and the working conditions.

• 한국재료학회지
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• 제15권11호
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• pp.697-704
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• 2005

The deformation behavior of a bulk amorphous and crystallized amorphous $Zr_{22.5}Ti_{14}Cu_{12.5}Ni_{10}Be_{22.5}$ alloy extracted from a commercial golf club head was characterized at room temperature ana $300^{\circ}C$. At room temperature, amorphous specimens revealed higher yield stress and ductility than partially crystallized alloy specimens. Amorphous alloy displayed some plasticity before fracture, which resulted from strain hardening and repeated crack initiation and propagation. The fracture is mainly localized on one major shear band, and the compressive fracture angle of the amorphous specimen between the stress axis and the fracture plane was about $40^{\circ}$ Scanning electron microscope observations revealed mainly a vein-like structure in the amorphous alloy But the fracture surface of partially crystallized amorphous alloy consisted of vein-like and featureless fracture structure. The partially crystallized alloy extracted from the thick part of the club fractured in the elastic region, at a much lower stress level than the amorphous, suggesting that relatively coarse crystal particles formed during cooling cause the brittle fracture.

• 한국식품과학회지
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• 제24권3호
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• pp.251-255
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• 1992

라아드의 가소성 영역을 확대시켜 작업성을 향상시키기 위한 수단의 하나로서 무작위 에스테르교환을 이용하여, 에스테르화 라아드의 물리화학적 성질 및 파이제조용 유지에 대한 그 적용성을 검토하였다. 에스테르화 전후의 라아드의 지방산 조성 및 트리글리세라이드 조성은 변화가 없었다. 라아드는 에스테르화에 의하여 SFI $5{\sim}25$의 온도범위가 $18{\sim}29.5^{\circ}C$에서 $13{\sim}30^{\circ}C$로 변화하여 저온의 범위가$5^{\circ}C$ 정도 증가하였다. 특히, SFI $15{\sim}25$의 온도범위가 $18{\sim}23.5^{\circ}C$에서 $13{\sim}19.5^{\circ}C$로 저하하여 저온에서의 작업성이 향상됨으로써 겨울철에 이용시 유리할 것으로 판단된다. 에스테르화 라아드는 결정형의 변화로 인하여 신전성이 감소되어 파이 반죽의 층형성이 불가능하였다. 따라서, 에스테르화 라아드는 파이의 팽화율, 외관, 쇼트니스를 불량하게 하여, 단독 사용시 파이용 유지로서는 부적합하였다. 그러나, 에스테르화 라아드에 신전성이 우수한 유지를 혼합하여 사용할 경우, 파이 껍질의 제조는 가능했으며 50%까지 에스테르화 라아드를 혼합하여도 파이 껍질의 품질은 우수하였다.

• 소성∙가공
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• 제29권3호
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• pp.163-171
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• 2020

We present a multi-step cold drawing for a non-equiatomic Co₁₀Cr₁₅Fe₂₅Mn₁₀Ni₃₀V₁₀ high entropy alloy (HEA) with a simple face-centered cubic (FCC) crystal structure. The distribution of strain in the cold-drawn Co₁₀Cr₁₅Fe₂₅Mn₁₀Ni₃₀V₁₀ HEA wires was analyzed by the finite element method (FEM). The effective strain was expected to be higher as it was closer to the surface of the wire. However, the reverse shear strain acted to cause a transition in the shear strain behavior. The critical effective strain at which the shear strain transition behavior is completely shifted was predicted to be 4.75. Severely cold-drawn Co₁₀Cr₁₅Fe₂₅Mn₁₀Ni₃₀V₁₀ HEA wires up to 96% of the maximum cross-sectional reduction ratio were successfully manufactured without breakage. With the assistance of electron back-scattering diffraction and transmission electron microscope analyses, the abundant deformation twins were found in the region of high effective strain, which is a major strengthening mechanism for the cold-drawn Co₁₀Cr₁₅Fe₂₅Mn₁₀Ni₃₀V₁₀ HEA wire.

• 소성∙가공
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• 제14권3호
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• pp.282-290
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• 2005

Nowadays, TFT-LCD is widely used as display unit of many digital devices. And, the backlight unit(BLU) is used as a light source of TFT-LCD module. In the backlight unit, the most important component is a light guide, which guides the input light to the TFT-LCD module uniformly. Recently, many researchers have focused on improving the efficiency of BLU by changing the design and structure of a light guide. In the present paper, a series of simulation was performed to find the optimal luminance distribution of emanated light from the given geometry as the first step. From the results of simulations for the light guide with given V-groove pattern, the emanated light from it is mostly affected by the groove angle. In the case of acute angle, about 74 degrees was found as optimal angle to satisfy the restrictions of angular luminance distribution, FWHM, the maximum luminance, etc. However, as far as the average luminance value was concerned, the case of 120 degrees(abtuse angle) was found to be the best while prism films were added to the BLU. As a next step the light guide samples of 74 and 120 degrees were manufactured by DSF method, which was recently proposed by the authors. Of course, most of design parameters were chosen by the aid of simulation results. Finally, the results of average luminance values were compared between the simulation and DSF molded samples.

• 소성∙가공
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• 제27권1호
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• pp.48-53
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• 2018

Aluminum nitride (AlN) is used by the semiconductor industry that has requirements for high thermal conductivity. The theoretical thermal conductivity of single crystal AlN is 320W/mK. Whereas, the values measured for polycrystalline AlN ceramics range from 20 W/mK to 280 W/mK. The variability is strongly dependent upon the purity of the starting materials and non-uniform dispersibility of the sintering additive. The conventional AlN sintering additive used yttria ($Y_2O_3$), but the dispersibility of the powder in the mixing process was important. In this study, we investigated the mechanical and thermal conductivity of yttrium nitrate ($Y(NO_3)_3{\cdot}6H_2O$), as a sintering additive in order to improve the dispersibility of $Y_2O_3$. The sintering additives content was in the range of 2 to 4.5wt.%. The density of AlN gradually increased with increasing contents of sintering additive and the flexural strength gradually increased as well. The flexural strength of the sintered body containing 4 wt% of $Y_2O_3$ and $Y(NO_3)_3{\cdot}6H_2O$ was 334.1 MPa and 378.2 MPa, respectively. The thermal conductivities were 189.7W/mK and 209.4W/mK, respectively. In the case of hardness, there was only a slight difference and the average value was about 10 GPa. Therefore, densification, density and strength values were found to be proportional to its content. It was confirmed that AlN using $Y(NO_3)_3{\cdot}6H_2O$ displayed relatively higher thermal conductivity and mechanical properties than the $Y_2O_3$.