• Title/Summary/Keyword: $Y_2O_3$ particle

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Synthesis and Characterization of Al2O3/ZrO2, Al2O3/TiO2 and Al2O3/ZrO2/TiO2 Ceramic Composite Particles Prepared by Ultrasonic Spray Pyrolysis

  • Shim, In-Soo;Lee, Chang-Seop
    • Bulletin of the Korean Chemical Society
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    • v.23 no.8
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    • pp.1127-1134
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    • 2002
  • Fine ceramic particles of zirconia toughened alumina (ZTA), titania toughened alumina (TTA), and zirconia-titania toughened alumina (ZTTA) have been synthesized by ultrasonic spray pyrolysis (USP) at various temperatures from starting salt solutio ns of various compositions aiming for the development of catalytic material. These particles were characterized for properties such as shape, size and size distribution, diffraction pattern, and chemical and phase composition of elements by scanning electron microscopy (SEM), particle size analyzer (PSA), x-ray diffraction (XRD), and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Chemical compositions and sizes of ceramic composites have been controled by the stoichiometry of salt solutions and the flow rate of spraying solutions. The optimum experimental conditions for the various composite particle syntheses have been proposed.

Characteristics of the Bottom Ash in Municipal Solid Waste Incineration Ash (생활 폐기물 소각재 중 바닥재의 特性)

  • 안지환;한기천;김형석
    • Resources Recycling
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    • v.10 no.4
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    • pp.48-57
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    • 2001
  • The main consistent materials and main elements of the bottom ash in municipal solid waste incineration ash according to particle size were investigated and the environmental hazards were considered by investigating the content of dioxin and heavy metals in bottom ash and the concentration of heavy metals in its leachate. The main materials of bottom ash are glasses, ceramics, scraps of iron. As the particle size increases, their percentage weight also increases and their percentage weight was over 70% in 4 mesh~25 mm particle size fraction. The main elements of bottom ash are CaO, $SiO_2$, $Fe_2$$O_3$,$ A1_2$$O_3$and the content of CaO decreases and the content of $SiO_2$increases as particle size increases. The heavy metals accumulate in small particle size fraction. The concentration of heavy metals in each leachate by domestic leaching test is almost similar. As the aging period is prolonged, pH of bottom ash lowers gradually and the leached concentration of Cu and Pb diminishes.

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Characterization of Aerosols Collected at a Subway Station Platform Using Low-Z Particle Electron Probe X-ray Microanalysis (Low-Z particle EPMA 단일입자 분석법을 이용한 지하철 승강장에서 미세입자 특성 분석)

  • Hwang HeeJin;Oh MiJung;Kang Sun-ei;Kim HyeKyeong;Ro Chul-Un
    • Journal of Korean Society for Atmospheric Environment
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    • v.21 no.6
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    • pp.639-647
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    • 2005
  • A single particle analytical technique, named low-Z particle electron probe X-ray microanalysis (EPMA), was applied to characterize samples collected at a subway station and ambient samples in Seoul. According to their chemical composition, many distinctive particle types were identified. For samples collected at the subway station platform, the major chemical species are carbon-rich, organic, aluminosilicates (AlSi), AlSi/C, AlSi/$CaCO_{3},\;CaCO_{3},\;SiO_{2},\;and\;Fe_{2}O_{3}$. For outdoor samples, carbon-rich, organic, AlSi, $CaCO_{3},\;SiO_{2},\;NaNO_{3},\;(Na,Mg)NO_{3},\;Na(CO_{3},NO_{3},SO_{4}),\;and\;(NH_{4})_2SO_4$, are abundantly encountered. Samples collected at the subway station show very high contents of $Fe_{2}O_{3}$, both in coarse and fine fractions, which come from brake block, subway train wheel, electric contact materials, etc. It is demonstrated that the single-particle characterization using this low-Z particle EPMA technique provided detailed information on various types of chemical species in indoor and outdoor samples.

Effect of Precipitants and Precipitation Conditions on Synthesis of β-Ga2O3 Powder (침전제의 종류 및 침전 공정의 변화가 β-Ga2O3 분말 합성에 미치는 영향)

  • Hwang, Su Hyun;Choi, Young Jong;Ko, Jeong Hyun;Kim, Tae Jin;Jeon, Deok Il;Cho, Woo Suk;Han, Kyu Sung
    • Korean Journal of Materials Research
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    • v.24 no.4
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    • pp.214-220
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    • 2014
  • In this research, a precipitation method was used to synthesize ${\beta}-Ga_2O_3$ powders with various particle morphologies and sizes under varying precipitation conditions, such as gallium nitrate concentration, pH, and aging temperature, using ammonium hydroxide and ammonium carbonate as precipitants. The obtained powders were characterized in detail by XRD, SEM, FT-IR, and TG-DSC. From the TG-DSC result, GaOOH phase was transformed to ${\beta}-Ga_2O_3$ at around $742^{\circ}C$, and weight loss percent was about 14 % when $NH_4OH$ was used as a precipitant. Also, ${\beta}-Ga_2O_3$ formed at $749^{\circ}C$ and weight loss percent was about 15 % when $(NH)_2CO_3$ was used as a precipitant. XRD results showed that the obtained $Ga_2O_3$ had pure monoclinic phase in both cases. When $(NH)_2CO_3$ was used as a precipitant, the particle shape changed and became irregular. The range of particle size was about $500nm-4{\mu}m$ based on various concentrations of gallium nitrate solution with $NH_4OH$. The particle size was increased from $1-2{\mu}m$ to $3-4{\mu}m$ and particle shape was changed from spherical to bar type by increasing aging temperature over $80^{\circ}C$.

Geochemical Dispersion and Enrichment of Fluvial Sediments Depending on the Particla Size Distribution (입도분포에 따른 하상퇴적물의 지구화학적 분산 및 부화)

  • 이현구
    • Economic and Environmental Geology
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    • v.32 no.3
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    • pp.247-260
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    • 1999
  • Geochermical characteristics of the fluvial sediments deprnding on particle size distribution size were investigated in the respect of majir, minor and rare eath element chemisitry. Ratios of $Al_{2}O_{3}/Na_{2}O$ and $K_{2}O/Na_{2}O$ of the sediments show the homogeneous valus, and partly positive correlation with $SiO_{2}/Al_{2}O_{3}$, respecively. Characteristics of minor element ratios (V/Ni, Cr/V, Ni/Co and Zr/Hf)are within the lower and narrow range. Thesesuggested that sediment sources may be acidic to intermediate granitic rock, and may be explained by simple weathering and sedimentation. With increasing SiO2 contents, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO and MgO decreased, but those of $K_{2}O$ and $Na_{2}O$ increased, Concentrations of Ba, Be, Cs, Cu, Li, Ni, Sr, V and Zr show comparatively normal negative and some positive trends. Compared with the mean composition of granite, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, MnO, CaO and MgO in the sediments of the study area were highly enriced. Among some minor and rare earth elements, concentrations of As, Cd, Cu, and V were enriched, but those of Be, Ce, Rb, Sc, Sr and Zn were depleted when compared with average composition of granite. By decreasing of particle size fractions, SiO2, Rb and Sr conterts decreased, but concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO, MgO, $TiO_{2}$, MgO, $P_{2}O_{5}$, Be, Cu, Hf, Pb, V and Zr increased. From the correlations between particle size fractions and element concenreations, some elements of $Fe_{2}O_{3}$, CaO, MgO, $P_{2}O_{5}$, Cu, Ni, Zn and Zr showed typical trends in the secondary contramination sediments. These trends are typically shown under 100 mesh fractions. It indicates that the fraction of minus 100 mesh is the optimum size fraction for geochemical and environmental survey.

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A Study of (Ba, Sr)$TiO_3$ Synthesis by Direct Wet Process ((Ba, Sr)$TiO_3$ 습식 직접 합성법)

  • 이경희;이병하;김준수
    • Journal of the Korean Ceramic Society
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    • v.23 no.1
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    • pp.27-32
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    • 1986
  • This study is aimed at synthsizing high dielectric material (Ba, Sr)$TiO_3$ through direct wet process. Pure and ultra fine particle of (Ba, Sr)$TiO_3$ Powder was synthesized from $BaCl_2$ $SrCl_2$ and TiCl4 aqeous solution at KOH Solution in the $N_2$ gas atmosphere. $BaCl_2$ $SrCl_2$ and TiCl4 were Mixed with the mole ratio of 1:9, 3:7:10, 5:5:10, 7:3:10, 9:1:10 and sythesized at 4$0^{\circ}C$~9$0^{\circ}C$ for 10min~15hrs. The particle size particle shape crystallinity and synthesis condition of (Ba, Sr)$TiO_3$ powder with the variation of temperature and reaction time in the aqueous solution studied by the exprimental instruments of DTA. TGA, X-ray diffratometer SEM.

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Effect of the Particle Size of SnO2:Ni on Gas Sensing Properties (입자크기에 따른 SnO2:Ni 가스센서의 감응 특성)

  • Lee, Ji-Young;Yu, Il
    • Korean Journal of Materials Research
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    • v.21 no.4
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    • pp.207-211
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    • 2011
  • Ni 8 wt.%-doped tin oxide ($SnO_2$) thick films were fabricated into gas sensors by the method of screen printing onto alumina substrates. The particle size of $SnO_2$ was controlled by changing the ball-mill time between 0~120 h. The structural and morphological properties of these thick films were investigated using X-ray diffraction and scanning electron microscopy. The structural properties of $SnO_2$ powders showed a tetragonal phase with (110) dominant orientation. The particle size of the $SnO_2$:Ni powders after ball-mill of 120 h was about 0.05 ${\mu}m$. The gas sensitivity (S = Rg/Ra) to 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas was measured at room temperature by comparing the resistance in air (Ra) with that of the target gases (Rg). The sensitivity of the $SnO_2$ gas sensors was enhanced by increasing the ball-mill time. There was an association between the sensitivity of both the $CH_4$ gas and the $CH_3CH_2CH_3$ gas and the particle size of the $SnO_2$. $SnO_2$ gas sensors prepared by 72 h ball-mill showed a sensitivity of about 13 to 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas. The response time of the $SnO_2$:Ni gas sensors to the $CH_4$ gas was about 20 seconds.

The effect of repeated surface treatment of zirconia on its bond strength to resin cement

  • Maciel, Lucas Campagnaro;Amaral, Marina;Queiroz, Daher Antonio;Baroudi, Kusai;Silva-Concilio, Lais Regiane
    • The Journal of Advanced Prosthodontics
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    • v.12 no.5
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    • pp.291-298
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    • 2020
  • PURPOSE. The aim of this study is to evaluate the influence of repeated surface treatments on wettability and surface roughness for zirconia surface and bond strength of zirconia-based ceramics to resin cement. MATERIALS AND METHODS. Seventy blocks (10 × 10 × 3 mm) of zirconia-based ceramics were fabricated and divided into two groups according to the surface treatments: (A) 110 ㎛ Al2O3 airborne-particle abrasion and (R) 110 ㎛ silica modified Al2O3 airborne-particle abrasion. At stage 2, each group was subdivided into 5 groups according to the surface retreatments: (a) 110 ㎛ Al2O3 airborne-particle abrasion, (r) 110 ㎛ silica modified Al2O3 airborne-particle abrasion, (D) diamond bur, (Da) diamond bur + 110 ㎛ Al2O3 airborne-particle abrasion, and (Dr) diamond bur + 110 ㎛ silica modified Al2O3 airborne-particle abrasion. Cylinders of self-adhesive resin cement were cemented onto each treated ceramic surface and subjected to micro-shear bond strength test. Additional specimens were prepared for roughness and wettability analyses. The data were subjected to t-test and One-way ANOVA followed by Tukey's post hoc test (α=.05). RESULTS. At stage 1, group R presented higher bond strength values than group A (P=.000). There was a statistically significant increase of bond strength at stage 2 for group A (P=.003). The diamond bur influenced the surface roughness, increasing the values (P=.023). Group R provided better wettability. Regardless of the applied surface treatment, most of failures were adhesive. CONCLUSION. The combination of application and reapplication of Rocatec Plus showed the best results of bond strength. Surface retreatment and recementation might be an indicated clinical strategy.

The Synthesis of $Fe_3O_4$ Powder through Glycothermal Process (Glycothermal Process에 의한 $Fe_3O_4$ 분말 합성)

  • 노준석;조승범;최상흘
    • Journal of the Korean Ceramic Society
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    • v.34 no.11
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    • pp.1159-1164
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    • 1997
  • Magnetite(Fe3O4) powders were synthesized through glycothermal reaction by using crystalline $\alpha$-FeOOH as precursor and ethyleanne glycol as solvent. The phase, morphology and particle size of synthesized powders were characterized by XRD and an SEM. When only ethylene glycol was used as solvent, the phase was transformed from $\alpha$-FeOOH to $\alpha$-Fe2O3 and finally Fe3O4 at 27$0^{\circ}C$ for 6hr without morphological change. But by addition of water, Fe3O4 powders were synthesized at 23$0^{\circ}C$ for 3hr through solution-recrystalization process. As the content of water addition increased, the particle shape changed from sphere to octahedron and the partcle size increased. When the excess amount of water added, residual $\alpha$-FeOOH or $\alpha$-Fe2O3 was recrystalized.

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