• Title/Summary/Keyword: Metal-Al2O3-Si

Search Result 309, Processing Time 0.033 seconds

The Oxide Coating Effects on the Magnetic Properties of Amorphous Alloys

  • 배영제;Jang, Ho G.;Chae, Hee K.
    • Bulletin of the Korean Chemical Society
    • /
    • v.17 no.7
    • /
    • pp.621-625
    • /
    • 1996
  • A variety of metal oxides were coated by sol-gel process from their metal alkoxides on the ribbons of Co-based and Fe-based amorphous alloys, and the effects of surface oxide coating on the magnetic properties of the alloy are investigated. The core loss is found to be reduced significantly by the oxide coating, the loss reduction becoming more prominent at higher frequencies. The shape of the hystersis loop is also dependent upon the kind of the coated metal oxide. The coatings of MgO, SiO2, MgO·SiO2 and MgO·Al2O3 induce tensile stress into the Fe-based ribbon whereas those of BaO, Al2O3, CaO·Al2O3, SrO·Al2O3 and BaO·Al2O3 induce compressive stress. These results may be explained by the modification of domain structures via magnetoelastic interactions with the shrinkage stress induced by the sol-gel coating.

Toxicity evaluation based on particle size, contact angle and zeta potential of SiO2 and Al2O3 on the growth of green algae

  • Karunakaran, Gopalu;Suriyaprabha, Rangaraj;Rajendran, Venkatachalam;Kannan, Narayanasamy
    • Advances in nano research
    • /
    • v.3 no.4
    • /
    • pp.243-255
    • /
    • 2015
  • In this investigation, ecotoxicity of nano and micro metal oxides, namely silica ($SiO_2$) and alumina ($Al_2O_3$), on the growth of green algae (Porphyridium aerugineum Geitler) is discussed. Effects of nano and micro particles on the growth, chlorophyll content and protein content of algae are analysed using standard protocols. Results indicate that $SiO_2$ nano and micro $SiO_2$ particles are non-toxic to P. aerugineum Geitler up to a concentration of 1000 mg/L. In addition, $Al_2O_3$ microparticles are less toxic to P. aerugineum Geitler, whereas $Al_2O_3$ nanoparticles are found to be highly toxic at 1000 mg/L. Moreover, $Al_2O_3$ nanoparticles decrease the growth, chlorophyll content, and protein content of tested algae. In addition, zeta potential and contact angle are also important in enhancing the toxicity of metal oxide nanoparticles in aquatic environment. This study highlights a new insight into toxicity evaluation of nanoparticles on beneficial aquatic organisms such as algae.

Protective Metal Oxide Coatings on Zinc-sulfide-based Phosphors and their Cathodoluminescence Properties

  • Oh, Sung-Il;Lee, Hyo-Sung;Kim, Kwang-Bok;Kang, Jun-Gill
    • Bulletin of the Korean Chemical Society
    • /
    • v.31 no.12
    • /
    • pp.3723-3729
    • /
    • 2010
  • We investigated the high-excitation voltage cathodoluminescence (CL) performance of blue light-emitting (ZnS:Ag,Al,Cl) and green light-emitting (ZnS:Cu,Al) phosphors coated with metal oxides ($SiO_2$, $Al_2O_3$, and MgO). Hydrolysis of the metal oxide precursors tetraethoxysilane, aluminum isopropoxide, and magnesium nitrate, with subsequent heat annealing at $400^{\circ}C$, produced $SiO_2$ nanoparticles, an $Al_2O_3$ thin film, and MgO scale-type film, respectively, on the surface of the phosphors. Effects of the phosphor surface coatings on CL intensities and aging behavior of the phosphors were assessed using an accelerating voltage of 12 kV. The MgO thick film coverage exhibited less reduction in initial CL intensity and was most effective in improving aging degradation. Phosphors treated with a low concentration of magnesium nitrate maintained their initial CL intensities without aging degradation for 2000 s. In contrast, the $SiO_2$ and the $Al_2O_3$ coverages were ineffective in improving aging degradation.

A Study on the Fabrication of Shrinkage-Free Mullite--$ZrO_2$ Ceramics with Al-Additives (Al첨가에 의한 무수축 Mullite-$ZrO_2$ 요업체의 제조에 관한 연구)

  • Kim, Jeong-Uk;Kim, Il-Su
    • Korean Journal of Materials Research
    • /
    • v.5 no.7
    • /
    • pp.888-896
    • /
    • 1995
  • In this paper the manufacture of shrinkage-free in situ Mullite-ZrO$_2$ceramics through the addition of Al base metal powder to the mixture of ZrSiO$_4$and A1$_2$O$_3$was attempt. The ZrO$_2$-strengthened mullite ceramics was prepared after the following reaction form, 3(Al+Al$_2$O$_3$)+2ZrSiO$_4$longrightarrow3A1$_2$O$_3$.2SiO$_2$+2ZrO$_2$Al metal powder was added from none to 30 weight percent to the A1$_2$O$_3$. The powders were mechanically mixed, isostatically pressed and reaction sintered at 1450-1$600^{\circ}C$ for 3hours. The specimens were sintered with and without intrim soaking time for 5 hours at 125$0^{\circ}C$ for the oxidation of Al-powder The addition of aluminium accelerates the reaction and compensate the shrinkage during the sintering through an increase in volume of oxidized Al. Because coarse flake type Al metal powders were not effectively milled, oxidized Al resulted in the relative large pore in the specimen.

  • PDF

Effect of metal oxides on the types of SiO$_2$ Phase of vitreous porcelain body (금속 산화물이 도자기 소지중 SiO$_2$상 생성에 미치는 영향)

  • 김윤주
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.7 no.4
    • /
    • pp.658-664
    • /
    • 1997
  • The effect of metal oxides($K_2O, MgO, CaO,Al_2O_3$, and $TiO_2$) on the kinds of pure $SiO_2$ phase, and $SiO_2$ phases in the composition of vitreous porcelain body was investigated. Also, the effect of the ratio $SiO_2$ to $Al_2O_3$ in the composition of porcelain body with stabilized of cristobalite phase was investigated. In the case of the addition of $K_2O, MgO, CaO, Al_2O_3$, and $TiO_2$ to pure $SiO_2$, the major phase was $\alpha$-cristobalite, $\alpha$-cristobalite, $\alpha$-quartz, $\alpha$-quartz and amorphous, respectively. As the ratio of $SiO_2$ to $Al_2O_3$ in the composition of porcelain body was decreased, the stabilization of cristobalite phase was promoted and only the critical value of $SiO_2/Al_2O_3$ ratio that stabilizing the cristobalite phase in it was 68.10/22.75. The addition of $K_2$O, MgO, CaO,Al_2O_3$, and $TiO_2$ to the composition of porcelain body stabilized already did not affect on the formation of $\alpha$-cristobalite phase which degraded the thermal properties of porcelain body, and suppressed the formation of a, $\beta$-cristobalite.

  • PDF

Formation of $Al_2O_3$-Ceramics by Reactive Infiltration of Al-alloy into Insulation Fiber Board (Al-합금의 단열섬유판 반응침투에 의한 $Al_2O_3$-세라믹스의 형성)

  • 김일수
    • Journal of the Korean Ceramic Society
    • /
    • v.34 no.5
    • /
    • pp.483-490
    • /
    • 1997
  • Al2O3/metal composites were fabricated by oxidation and reaction of molten Al-alloy into two types of commercial Al2O3-SiO2 fibrous insulation board. The growth rate, composition and microstructure of these materials were described. An AlZnMg(7075) alloy was selected as a parent alloy. Mixed polycrystalline fiber and glass phase fiber were used as a filler. The growth surface of an alloy was covered with and without SiO2. SiO2 powder was employed as a surface dopant to aid initial oxidation of Al-alloy. Al-alloy, SiO2, fiber block and growth inhibitor CaSiO3 were packed sequentially in a alumina crucible and oxidized in air at temperature range 90$0^{\circ}C$ to 120$0^{\circ}C$. The growth rate of composite layer was calculated by measuring the mass increasement(g) per unit surface($\textrm{cm}^2$). XRD and optical microscope were used to investigate the composition and phase of composites. The composite grown at 120$0^{\circ}C$ and with SiO2 dopant showed rapid growth rate. The growth behavior differed a little depending on the types of fiber used. The composites consist of $\alpha$-Al2O3, Al, Si and pore. The composite grown at 100$0^{\circ}C$ exhibited better microstructure compared to that grown at 120$0^{\circ}C$.

  • PDF

Synthesis of $\alpha$-Sialon Ceramics from an Alkoxide and Their Mechanical Properties(I) (알콕사이드로부터 $\alpha$-Sialon 세라믹스의 제조 및 기계적 성질(I))

  • 이홍림;윤창현;조덕호
    • Journal of the Korean Ceramic Society
    • /
    • v.28 no.2
    • /
    • pp.130-140
    • /
    • 1991
  • The powders of the system Si3N4-Y2O3-AlN were prepared using Si(OC2H5)4 and YCl3.6H2O together with commercial AlN powder. $\alpha$-Si3N4 was prepared by the carbothermal reduction and nitridation of the hydrolyzed gel at 135$0^{\circ}C$ for 10h in N2 atmosphere. YCl3.6H2O was observed to be changed to Y2O3 during the reaction. $\alpha$-Sialon(X=0.2, 0.4, 0.6) ceramics were obtained by hot-pressing the Si3N4-Y2O3-AlN mixture at 178$0^{\circ}C$ for 1h under 30 MPa. The content of $\alpha$-Sialon increased with increasing metal solubility(x value) and $\alpha$-Sialon single phase was obtained at the metal solubility of 0.6. With increasing metal solubility, flexural strength, fracture toughness and thermal shock resistence were decreased, while the microhardness was increased. Large elongated $\beta$-Si3N4 grains were mainly observed at lower metal solubility. Mechanical prorerties of the sintered ceramics with X=0.2 were measured as follows : flexural strength ; 650 MPa, fracture toughness ; 3.63 MN/m3/2, hardness ; 14.7 GPa, thermal shock resistence temperature ; 58$0^{\circ}C$.

  • PDF

Fabrication and Properties of Reaction Squeeze Cast ($Al_2O_3{\cdot}SiO_2+Ni$)/Al Hybrid Metal Matrix Composites (반응 용탕단조한($Al_2O_3{\cdot}SiO_2+Ni$)/Al 하이브리드 금속복합재료의 제조 및 특성)

  • Kim, Sang-Suk;Park, Ik-Min;Kim, Sung-Joon;Choi, Il-Dong
    • Journal of Korea Foundry Society
    • /
    • v.17 no.4
    • /
    • pp.338-346
    • /
    • 1997
  • Mechanical properties of ($10%Al_2O_3{\cdot}SiO_2+5%Ni$)/Al hybrid composites fabricated by the reaction squeeze casting were compared with those of ($15%Al_2O_3{\cdot}SiO_2$)/Ai composites. Al-Ni intermetallic compounds ($10{\sim}20 {\mu}m$) formed by the reaction between nickel powder and molten aluminum were uniformly distributed in the Al matrix. These intermetallic compounds were identified as $Al_3Ni$ using X-ray diffraction analysis and they resulted in beneficial effects on room and high temperature strength and wear resistance. Microhardness values of ($10%Al_2O_3{\cdot}SiO_2+5%Ni$)/Al hybrid composite were greater by about 100Hv than those of ($15%Al_2O_3{\cdot}SiO_2$)/Al composite. Wear resistance of ($10%Al_2O_3{\cdot}SiO_2+5%Ni$)/Al hybrid composites was superior to that of ($15%Al_2O_3{\cdot}SiO_2$)/Al composites regardless of the applied load. While tensile and yield strength of ($10%Al_2O_3{\cdot}SiO_2+5%Ni$)/Al hybrid composites were greater at room temperature and $300^{\circ}C$, strength drop at high temperature was much smaller in hybrid composites.

  • PDF

Fraccture Behavior of Recation Squeeze Cast ($AI_20_3{\cdot}SiO_2+Ni$)/Al Hybrid Metal Matrix Composites (반응 용탕단조한(AI203 . SIO2+Ni)/Al하이브리드 금속복합재료의 파괴거동 특성)

  • 김익우;김상석;박익민
    • Proceedings of the Korean Society For Composite Materials Conference
    • /
    • 2000.04a
    • /
    • pp.67-70
    • /
    • 2000
  • Mechanical properties of (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al hybrid composites fabricated by the reaction squeeze casting were compared with those of (15%$AI_20_3{\cdot}SiO_2$)/Al composites. Intermetallic compound formed by reaction between molten aluminum and reinforcing powder was uniformly distributed in the Al matrix. These intermetallic compounds were identified as $Al_3$NI using EDS and X-ray diffraction analysis. Microhardness and flexural strength of hybrid composites were higher than that of (15%$AI_20_3{\cdot}SiO_2$)/Al Composite. In-Situ fracture tests were Conducted on (15%$AI_20_3{\cdot}SiO_2$)/Al Composites and (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al hybrid composites to identify the microfracture process. It was identified from the in-situ fracture test of (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al composites, microcracks were initiated mainly at the short fiber / matrix interfaces. As the loading was continued, the crack propagated mainly along the separated interfacial regions and the well developed shear bands. It was identified from the in-situ fracture test of (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al hybrid composites, microcracks were initiated mainly by the short fiber/matrix interfacial debonding. The crack proceeded mainly through the intermetallic compound clusters

  • PDF