• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.6
• /
• pp.938-946
• /
• 2008

Fe-base amorphous alloy and two crystalline phases composite were fabricated. The effect of temperature and strain rate on mechanical properties was evaluated utilizing compression test. Mixture of non-crystalline and crystalline phases were found using X-ray diffraction (XRD) and differential thermal analysis (DTA) tests. Based on glass transition temperature and crystallization temperature. compression tests were performed in the temperature ranging from $560^{\circ}C$ to $700^{\circ}C$ with $20^{\circ}C$ interval. Relationship between microstructure, including fracture surface morphology, and mechanical behavior was studied. The peak stress of Fe-base amorphous alloy was over 2GPa and expected to have a good wear resistance, but it is expected hard to deform because of low ductility. The peak stress and elongation of two crystalline phases composite was over 1GPa and about 20%, therefore it is possible to deform high strength wear resistant materials such as engine valve.

• Progress in Superconductivity
• /
• v.10 no.1
• /
• pp.23-28
• /
• 2008

We report refinement of crystalline boron by an attrition ball milling system and the superconducting properties of the $MgB_2$ pellets prepared from the refined boron. In this work, we have conducted the ball milling with only crystalline boron powder, in order to improve homogeneity and control the grain size of the $MgB_2$ that is formed from it. We observed that the crystalline responses in the ball-milled boron became broader and weaker when the ball-milling time was further increased. On the other hand, the $B_{2}O_{3}$ peak became stronger in the powders, resulting in an increase in the amount of MgO within the $MgB_2$ volume. The main reason for this is a greater oxygen uptake. From the perspective of the superconducting properties, however, the sample prepared from boron that was ball milled for 5 hours showed an improvement of critical current density ($J_c$), even with increased MgO phase, under an external magnetic field at 5 and 20 K.

• Bulletin of the Korean Chemical Society
• /
• v.4 no.4
• /
• pp.176-180
• /
• 1983

A series of new liquid crystalline compounds having two identical mesogenic terminal units, the 4-(p-nitrobenzoyloxy)phenoxy group, attached to both ends of a central polymethylene spacer of various lengths was prepared. The mesomorphic properties of the compounds were investigated by differential scanning calorimetry (DSC) and by polarizing microscopy. Almost all of the compounds formed monotropic nematic mesophases. The trimethylene spacer compound was found to be non-liquid crystalline, while the one with the hexamethylene central spacer was enantiotropic. A thermodynamic analysis was performed for the phase transitions of the compounds and the results are discussed in relation to their liquid crystal properties.

• YAKHAK HOEJI
• /
• v.22 no.1
• /
• pp.22-26
• /
• 1978

The purposes of this investigation were to study the characteristic properties of bismuthoxynitrate formed by hydrolysis of bismuthnitrate according to various reaction conditions and to propose the property difference between synthesized pearl pigment and bismuthsubnitrate as pharmaceuticals by means of X-ray diffraction, IR, DTA and TGA. The pearl pigment could be obtained by reaction of bismuth nitrate-diluted nitric acid solution with cold water (5.deg.) agitation at lower pH. The pearl pigment was BiO. NO$_{3}$. 2H$_{2}$O. in composition and crystalline form was thin plate of monoclinic system and its combination with water was assumed to be hydrated hydrous form between Bi-H$_{2}$O bond. On the other hand, bismuthsubnitrate was 5BiO.4NO$_{3}$.6H$_{2}$O in composition and crystalline form was pillar of rhombic system and the bond between Bi and H$_{2}$O molecules was assumed to be hydrous form. The different properties between two compounds in structure are presumed to be caused by the hydrolysing conditions of bismuthnitrate respectively.

• Carbon letters
• /
• v.1 no.3_4
• /
• pp.138-142
• /
• 2001

The effect of electrochemical surface treatments in KOH chemical solution on microstructures of carbon blacks was investigated in terms of surface functional values and XRD measurements. And their mechanical interfacial properties of the carbon blacks/rubber composites were studied by the composite tearing energy ($G_{IIIC}$). It was found that the development of basic-surface functional groups lead to the significant physical changes of carbon blacks, such as, decrease of the interlayer spacing ($d_{002}$), increase of the crystalline size along c-axis ($L_c$), and increase of degree of crystalline (${\chi}_c$). This treatment is possibly suitable for carbon blacks to be incorporated in a hydrocarbon rubber matrix, resulting in improving the hardness and tearing energy of the resulting composites.

• Journal of the Korean Society of Industry Convergence
• /
• v.4 no.4
• /
• pp.413-418
• /
• 2001

The change of crystalline structure and mechanical properties of drawn PP filaments which was treated by tensioned and non-tensioned annealing was investigated. Measurements were carried out with XRD for crystallite size, density gradient tube for crystallinity. and UTM for mechanical properties. Tensioend and non-tensioned annealing were carried out $80^{\circ}C$, $100^{\circ}C$, $120^{\circ}C$: for 10min., 30min., 60min, in oil bath. It was found that the crystallinity and crystallite size of (110) plane of samples were increased with increasing of annealed temperature and time. Also crystallinity and crystallite size of samples which was tensioned annealing were larger than those of non-tensioned annealed samples. Initial modulus and tensile strength of tensioned annealed samples were higher than non-tensioned annealed samples, But elongation of tensioned annealed samples was lower than non-tensioned annealed samples.

• Proceedings of the Korean Fiber Society Conference
• /
• 1998.10a
• /
• pp.236-239
• /
• 1998

The in situ composites based on poly(ethylene 2,6-naphthalate) and thermotropic liquid crystalline polymer (LCP) have been an area of increasing interest and study, since LCP exhibits high chemical stabilities and excellent thermo mechanical properties such as high strength and modulus. In a binary, however, poor compatibility and interfacial adhesions between two phases frequently results in deteriorated mechanical properties. (omitted)

• 한국태양에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.239-244
• /
• 2011

In this paper, we analyzed the electrical characteristics with crack pattern in crystalline solar cell. crystalline solar cells with a thin substrate, even small shocks can be easily damaged. Before the module goes through many processes, because the solar cells are at risk of a crack. That occurred early in the PV module micro-crack is not easily detection by eye test or output test. Because the EL (Electroluminescence) device has been detected using. PV module is made by laminated of a variety of materials. By different properties of each material will affect the crack. For this reason, the crack will grow and affect the output. And We analyzed the three crack patterns in crystalline solar cell. A growth of cracks on crystalline solar cell was interpreted by analysing generated cracks on the PV modules. Based on this interpretation, an electrical output value was calculated by mathematical modeling on electrical output characteristic with each crack patterns.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2009.10a
• /
• pp.1025-1027
• /
• 2009

Novel low temperature deposition process for nano-crystalline Si thin film is developed with the hyper-thermal neutral beam (HNB) technology. By our HNB assisted CVD system, the reactive particles can induce crystalline phase in Si thin films and effectively combine with heating effect on substrate. At low deposition temperature under $80^{\circ}C$, the HNB with proper incident energy controlled by the reflector bias can effectively enhance the nano-crystalline formation in Si thin film without any additional process. The electrical properties of Si thin films can be varied from a-Si to nc-Si according to change of HNB energy and substrate temperature. Characterization of these thin films with conductivity reveal that crystalline of Si thin film can increase by assist of HNB with appropriate energy during low temperature deposition. And low temperature prcoessed nc-Si TFT performance has on-off ratio as order 5.

• Proceedings of the Korean Fiber Society Conference
• /
• 1995.10a
• /
• pp.85-85
• /
• 1995