• Title/Summary/Keyword: Double oxidation

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The effect of preheat treatment on ceramic to metal bond strength (도재-금속의 결합 강도에 미치는 비금속 합금의 열처리 효과)

  • Kim, Chi-Young;Kim, Young-Gon; Cho, Hyun-Seol
    • Journal of Technologic Dentistry
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    • v.24 no.1
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    • pp.33-41
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    • 2002
  • In dental prosthetics, the application of metal-ceramic restorations has steadily increased since their introduction. This is due to excellent esthetics in combination with high mechanical stability. In order to optimum bond strength between metal and ceramics, controlled oxidation of metal substructure is essential factor. Beryllium containing and beryllium free Ni-Cr alloys for metal-ceramic restorations were evaluated for the metal-ceramic bond strength by changing heat treatment for oxide formation. A mechanical three-point bending test was employed to evaluate the interfacial bond strength of metal-ceramic. In each metal, plate type specimens were used for mechanical three-point bending test. With Ni-Cr alloys for metal ceramics, mechanical three-point bending test showed that double degassing was more available preheat treatment method than another. It was found that beryllium containing Ni-Cr alloys are more effective than beryllium-free for metal-ceramic bond strength.

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A Plastic BGA Singulation using High Thermal Energy of $2^{nd}$ Harmonic Nd:YAG Laser

  • Lee, Kyoung-Cheol;Baek, Kwang-Yeol;Lee, Cheon
    • KIEE International Transactions on Electrophysics and Applications
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    • v.2C no.6
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    • pp.309-313
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    • 2002
  • In this paper, we have studied minimization of the kerf-width and surface burning, which occurred after the conventional singulation process of the multi-layer BGA board with copper, polyethylene and epoxy glass fiber. The high thermal energy of a pulsed Nd:YAG laser is used to cut the multi-layer board. The most considerable matter in the laser cutting of the multi-layer BGA boards is their different absorption coefficient to the laser beam and their different heat conductivity. The cut mechanism of a multi-layer BGA board using a 2$^{nd}$ harmonic Nd:YAG laser is the thermal vaporization by high temperature rise based on the Gaussian profile and copper melting point. In this experiment, we found that the sacrifice layer and Na blowing are effective in minimizing the surface burning by the reaction between oxygen in the air and the laser beam. In addition, N2 blowing reduces laser energy loss by debris and suppresses surface oxidation. Also, the beam incidence on the epoxy layer compared to polyimide was much more suitable to reduce damage to polyimide with copper wire for the multi layer BGA singulation. When the polyester double-sided tape is used as a sacrifice layer, surface carbonization becomes less. The SEM, non-contact 3D inspector and high-resolution microscope are used to measure cut line-width and surface morphology.

Fracture Toughness of Leadframe/EMC Interface (리드프레임/EMC 계면의 파괴 인성치)

  • 이호영;유진
    • Journal of the Korean institute of surface engineering
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    • v.32 no.6
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    • pp.647-657
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    • 1999
  • Due to the inherently poor adhesion strength of Cu-based leadframe/EMC (Epoxy Molding Compound) interface, popcorn cracking of thin plastic packages frequently occurs during the solder reflow process. In the present work, in order to enhance the adhesion strength of Cu-based leadframe/EMC interface, black-oxide layer was formed on the leadframe surface by chemical oxidation of leadframe, and then oxidized leadframe sheets were molded with EMC and machined to form SDCB (Sandwiched Double-Cantilever Beam) and SBN (Sandwiched Brazil-Nut) specimens. SDCB and SBN specimens were designed to measure the adhesion strength between leadframe and EMC in terms of critical energy-release rate under quasi-Mode I ($G_{IC}$ ) and mixed Mode loading ($G_{C}$ /) conditions, respectively. Results showed that black-oxide treatment of Cu-based leadframe initially introduced pebble-like X$C_2$O crystals with smooth facets on its surface, and after the full growth of $Cu_2$O layer, acicular CuO crystals were formed atop of the $Cu_2$O layer. According to the result of SDCB test, $Cu_2$O crystals on the leadframe surface did not increase ($G_{IC}$), however, acicular CuO crystals on the $Cu_2$O layer enhanced $G_{IC}$ considerably. The main reason for the adhesion improvement seems to be associated with the adhesion of CuO to EMC by mechanical interlocking mechanism. On the other hand, as the Mode II component increased, $G_{C}$ was increased, and when the phase angle was -34$^{\circ}$, crack Kinking into EMC was occured.d.

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Chemical Composition of the Rice Germ from Rice Milling and its Oil Stability during Storage (쌀 도정시 분리되는 쌀눈의 일반성분과 저장 중 유지 안정성)

  • Shin, Dong-Hwa;Chung, Chong-Ku
    • Korean Journal of Food Science and Technology
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    • v.30 no.1
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    • pp.241-243
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    • 1998
  • The chemical composition of rice germ, a by product of rice milling, was analyzed and its oil stability was evaluated by acid value and Rancimat method during storage. The predominent components of the germ were carbohydrate (36.5%). crude lipid (21.6%) and crude protein (18.7%). The time taken to double the acid value was 2 days for common rice germ, while it took 31 days to increase 1.15 times for rice germ dried at $80^{\circ}C$ for 6 hours. Induction periods of the lipid oxidation from common or dry germ stored at different temperature were not significantly different.

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Oxidation Behavior around the Stress Corrosion Crack Tips of Alloy 600 under PWR Primary Water Environment (PWR 1차측 환경에서 Alloy 600 응력부식균열 선단 부근에서의 산화 거동)

  • Lim, Yun Soo;Kim, Hong Pyo;Hwang, Seong Sik
    • Corrosion Science and Technology
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    • v.11 no.4
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    • pp.141-150
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    • 2012
  • Stress corrosion cracks in Alloy 600 compact tension specimens tested at $325^{\circ}C$ in a simulated primary water environment of pressurized water reactor were analyzed by analytical transmission electron microscopy and secondary ion mass spectroscopy (SIMS). From a fine-probe chemical analysis, oxygen was found on the grain boundary just ahead of the crack tip, and chromium oxides were precipitated on the crack tip and the grain boundary attacked by the oxygen diffusion, leaving a Cr/Fe depletion (or Ni enrichment) zone. The oxide layer inside the crack was revealed to consist of a double (inner and outer) layer. Chromium oxides existed in the inner layer, with NiO and (Ni,Cr) spinels in the outer layer. From the nano-SIMS analysis, oxygen was detected at the locations of intergranular chromium carbides ahead of the crack tip, which means that oxygen diffused into the grain boundary and oxidized the surfaces of the chromium carbides. The intergranular chromium carbide blunted the crack tip, thereby suppressing the crack propagation.

Synthesis and Cobalt-Complexes of 1,2,3,4,5,6-Hexaalkyl-1,4-dibora-2-cyclohexene (1,2,3,4,5,6-Hexaalkyl-1,4-dibora-2-cyclohexene의 생성과 착물 생성)

  • Uhm, Jae-Koouk;An, Hee-Won
    • Journal of the Korean Chemical Society
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    • v.41 no.11
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    • pp.586-589
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    • 1997
  • 1,2,3,4,5,6-Hexaalkyl-1,4-dibora-2-cyclohexene was not produced by the general preparation method in our laboratory because of difficulties in the preparation of $B_2Cl_4.$ 2,3-Dietyl-1,4,5,6-tetramethyl-1,4-dibora-2-cyclohexene, 2 was synthesized by the reduction-oxidation reaction of potassium and methyliodide from 1,4-dimethyl-2,3-diethyl-1,4-dibora-2-cyclohexene, 1 as a substrate. Cobalt sandwich-complexes, 6, 7 and 8 were synthesized by the reaction of 2,3-diethyl-1,4,5,6-tetramethyl-1,4-dibora-2-cyclohexene with $({\eta}5-C_5H_5Co(C_2H_4)_2.$.

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Influence of Wax Molecular Weights on Wax Migration and Evaporation of Rubber Vulcanizates at Room Temperature (상온 노화 후 고무가황물에서 왁스의 이동과 증발에 미치는 왁스의 분자량 분포)

  • Im, Song-Hee;Choi, Sung-Seen
    • Elastomers and Composites
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    • v.44 no.4
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    • pp.397-400
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    • 2009
  • Ozone caused the crack on the surface of a rubber article by oxidation of double bond at room temperature. Wax migrates to the surface of a rubber article and makes a physical barrier to prevent process of ozonation. We investigated change of molecular weight distribution of waxes in unfilled NR, SBR, and BR vulcanizates before and after aging at room temperature for 6 months. Migration and evaporation behaviors of wax in a rubber article at ambient conditions help understand a role of wax as an antidegradant and appearance contamination of a rubber article. The relative intensity distribution of n-alkanes of the NR specimen after the aging was shifted to higher molecular weight compared with the relative intensity distribution before the aging, while those of the SBR specimen before and after the aging did not show a big difference.

Biological Functions and Production Technology of Carotenoids (Carotenoids의 생리 기능성과 생산기술)

  • 홍상필;김명희;황재관
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.27 no.6
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    • pp.1297-1306
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    • 1998
  • Carotenoids are yellow to orange red pigments that are ubiquitous in the nature and its annual pro duction amounts to one hundred million ton. This review discussed physicochemical properties, antiox idative activity, anticancer activity of carotenoids and its production technology. Carotenoids, mainly used as food colourants, are characterized by its strong reactive conjugated double bonds, related to oxidation by heat, light, acid, and metal ions. The provitamin A activity of carotenoids is higher in trans form than in cis form. Antioxidative properties of carotenoids are related to ionone structure and long, conjugated polyene chain number. In particular, carotene, astaxanthin, canthaxanthin, and lycopene possess strong antioxidant activity, compared with tocopherol. Especially, carotene, astaxanthin, carotene, fucoxanthin, halocynthiaxanthin and peridinin impart strong anticancer activity against lung cancer, breast cancer, buccal pouch cancer and nerve cell cancer. Carotene and astaxanthin are produced by biotechnology using algae such as Dunaliella salina and Haematococcus pluvalis. But the change of cultivation conditions and screening of algae, efficiently producing carotenoids, are needed for its commercial production. Carotenoids are expected to be used in the various fields through explanation of its biological activity and establishment of commercial production technology.

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MODELLING OF PYROLYSIS PROCESSES OF POLYACRYLONITRILE

  • Lipanov, A.M.;Kodolov, V.I.;Ovchinnikova, L.N.;Savinsky, S.S.;Khokhriakov, N.V.;Sarakula, V.L.
    • Proceedings of the Korea Institute of Fire Science and Engineering Conference
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    • 1997.11a
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    • pp.112-119
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    • 1997
  • The modelling of carbon substances obtaining, for instance, carbon fibers which have high fire resistance, has been realized on the example of the polyacrylonitrile pyrolysis modelling. The pyrolysis is considered as a double step process when the formation of a liquid phase and the oxidation of substance are excluded. Three main reactions are considered: a) with the evolution of ammonia; b) with the evolution of hydrogen cyanide; c) with the evolution of hydrogen. Reactions b) and c) are sequential, and a) and b) are parallel. The problem is formulated as one-dimensional. The equations of energy, masses or concentrations, porosity and thermal conductivity are proposed. The mathematical model of the carbonization process is designed using tile kinetic characteristics of the above reactions and the thermodynamic parameters of reagents and products in these reactions. The equations received are calculated by Runge-Cutta method and by Adams method of the fourth order accuracy.

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Failure Path of the Brown-oxide-coated Copper-based Leadframe/EMC Interface under Mixed-Mode Loading (혼합하중 조건하에서 갈색산화물이 입혀진 구리계 리드프레임/EMC 계면의 파손경로)

  • 이호영
    • Journal of the Korean institute of surface engineering
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    • v.36 no.6
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    • pp.491-499
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    • 2003
  • Copper-based leadframe sheets were oxidized in a hot alkaline solution to form brown-oxide layer on the surface and molded with epoxy molding compound (EMC). The brown-oxide-coated leadframe/EMC joints were machined to form sandwiched double-cantilever beam (SDCB) specimens and sandwiched Brazil-nut (SBN) specimens for the purpose of measuring the fracture toughness of leadframe/EMC interfaces. The SDCB and the SBN specimens were designed to measure the fracture toughness of the leadframe/EMC interfaces under nearly mode-I loading and mixed-mode (mode I + mode II) loading conditions, respectively. Fracture surfaces were analyzed by various equipment such as glancing-angle XRD, SEM, AES, EDS and AFM to elucidate failure path. Results showed that failure occurred irregularly in the SDCB specimens, and oxidation time of 2 minutes divided the types of irregular failures into two classes. The failure in the SBN specimens was quite different from that in the SDCB specimens. The failure path in the SBN specimens was not dependent on the phase angle as well as the distance from tips of pre-cracks.