• Title/Summary/Keyword: Oxygen ion diffusion

검색결과 45건 처리시간 0.029초

MgO.$nAl_2O_3$ 스피넬에 대한 증발속도의 측정으로부터 산소의 확산계수의 결정 (Determination of Oxygen Diffusion Coefficient from Vaporization Rate of MgO.$nAl_2O_3$ Spinel)

  • 이홍림;배철훈
    • 한국세라믹학회지
    • /
    • 제20권2호
    • /
    • pp.129-134
    • /
    • 1983
  • MgO.$Al_2O_3$ polycrstalline spinel powder was subjected to vaporization over the temperature range of 1150-130$0^{\circ}C$ under H2 atmosphere. Diffusion coefficient of oxygen ion through the spinel were calculated using the measure vaporization rates as follows : D=28.4 exp(-901500/RT) Reference data of the vaporization rates of MgO.$8Al_2O_3$ single crystal spinel were applied to the vaporiza-tion model proposed in this study and were calculated to give the oxygen ion diffusion coefficients over the tempera-ture 1700-195$0^{\circ}C$. The obtained diffusion coefficients are as follows: $D=3.20{\times}106$ exp(-155600/RT)

  • PDF

Development of a Mass Transfer Model and Its Application to the Behavior of the Cs, Sr, Ba, and Oxygen ions in an Electrolytic Reduction Process for SF

  • 박병흥;강대승;서중석;박성원
    • 방사성폐기물학회지
    • /
    • 제3권2호
    • /
    • pp.85-93
    • /
    • 2005
  • Isotopes of alkali and alkaline earth metals (AM and AEM) are the main contributors to the heat load and the radiotoxicity of spent fuel (SF) . These components are separated from the SF and dissolved in a molten LiCl in an electrolytic reduction process. A mass transfer model is developed to describe the diffusion behavior of Cs, Sr, and Ba in the SF into the molten salt. The model is an analytical solution of Fick's second law of diffusion for a cylinder which is the shape of a cathode in the electrolytic reduction process. And the model is also applied to depict the concentration profile of the oxygen ion which is produced by the electrolysis of Li$_{2}$O. The regressed diffusion coefficients of the model correlating the experimentally measured data are evaluated to be greater in the order of Ba, Cs, and Sr for the metal ions and the diffusion of the oxygen ion is slower than the metal ions which implies that different mechanisms govern the diffusion of the metal ions and the oxygen ions in a molten LiCl.

  • PDF

SiC의 산화반응 기구 (Oxidation Mechanism of SiC)

  • 최태운;이홍림
    • 한국세라믹학회지
    • /
    • 제18권2호
    • /
    • pp.79-82
    • /
    • 1981
  • SiC powder was heated in air over the temperature range of 1100-135$0^{\circ}C$. $\beta$-cristobalite was formed to cover the surfaces of SiC particles by the reaction: $SiC(s)+20_2(g)=SiO_2(s)+CO_2(g)$. It is assumed that the diffusion of oxygen ion through the formed surface layer of $\beta$-cristobalite controls the oxidation of the SiC particles. The diffusion coefficient of oxygen ion through the $\beta$-cristobalite layer was obtained as the following equation: $D=3.84{\times}10^{-17}$exp(-14.7/RT)

  • PDF

Rutile 단결정에서 산소의 확산과 점결합 (Oxygen Diffusion and Point Defects in Single Crystal Rutile)

  • 김명호;박주석;변재동
    • 한국세라믹학회지
    • /
    • 제28권12호
    • /
    • pp.989-995
    • /
    • 1991
  • By means of the secondary ion mass spectrometer, the tracer diffusion of oxygen in rutile single crystal was measured as function of temperature and oxygen partial pressure. The tracer diffusivity was determined from the depth profile of 18O. The Po2 dependence of D suggests that the dominant defects in TiO2-y are oxygen vacancies (V{{{{ { ‥} atop { o} }}) and interstitial titanium ions (Ti{{{{ {‥‥} atop {i} }}). The doubly ionized oxygen vacancies are prominent at low temperature and Po2. However, the tetravalent interstitial titanium ions predominate at teperature above 120$0^{\circ}C$.

  • PDF

$Si_3N_4$의 산화반응 기구 (Oxidation Mechanism of $Si_3N_4$)

  • 이홍림;최태운;김종우
    • 한국세라믹학회지
    • /
    • 제17권4호
    • /
    • pp.197-202
    • /
    • 1980
  • The oxidation mechanism of the not sintered pellets and sintered bodies of $Si_3N_4$ was investigated. in air over the temperature range of 800~130$0^{\circ}C$. The $\beta$-cristobalite was instantaneously formed and covered the particles of powder packed in the not sintered and weakly sintered porous $Si_3N_4$ bodies by molecular diffusion of oxygen through the porous Si3N4 bodies and an immediate oxidation. The diffusion of oxygen ion through the formed $\beta$-cristobalite surface layer is assumed to control the further oxidation of the $Si_3N_4$ particles of the porous $Si_3N_4$ bodies. The diffusion coefficients and activation energies of oxygen ion through the $\beta$-cristobalite layer were obtained by the use of a derived equation.

  • PDF

Effect of B-Cation Doping on Oxygen Vacancy Formation and Migration in LaBO3: A Density Functional Theory Study

  • Kwon, Hyunguk;Park, Jinwoo;Kim, Byung-Kook;Han, Jeong Woo
    • 한국세라믹학회지
    • /
    • 제52권5호
    • /
    • pp.331-337
    • /
    • 2015
  • $LaBO_3$ (B = Cr, Mn, Fe, Co, and Ni) perovskites, the most common perovskite-type mixed ionic-electronic conductors (MIECs), are promising candidates for intermediate-temperature solid oxide fuel cell (IT-SOFC) cathodes. The catalytic activity on MIEC-based cathodes is closely related to the bulk ionic conductivity. Doping B-site cations with other metals may be one way to enhance the ionic conductivity, which would also be sensitively influenced by the chemical composition of the dopants. Here, using density functional theory (DFT) calculations, we quantitatively assess the activation energies of bulk oxide ion diffusion in $LaBO_3$ perovskites with a wide range of combinations of B-site cations by calculating the oxygen vacancy formation and migration energies. Our results show that bulk oxide ion diffusion dominantly depends on oxygen vacancy formation energy rather than on the migration energy. As a result, we suggest that the late transition metal-based perovskites have relatively low oxygen vacancy formation energies, and thereby exhibit low activation energy barriers. Our results will provide useful insight into the design of new cathode materials with better performance.

초기 산소 농도가 고에너지 이온 주입시 발생하는 산소 축적 및 불순물 확산에 미치는 영향 (Effcets of Initial Oxygen Concentration on Oxygen Pileup and the Diffusion of Impurities after High-energy Ion Impaltation)

  • 고봉균;곽계달
    • 전자공학회논문지D
    • /
    • 제36D권4호
    • /
    • pp.48-56
    • /
    • 1999
  • 본 논문에서는 초기 산소 농도가 고에너지 이온 주입시 결정 격자 손상에 의해 발생하는 산소 축적(pileup) 현상 및 주입된 불순물의 확산에 미치는 영향을 실험적으로 고찰하였다. 초기 산소 농도가 11.5, 15.5 ppma인 p-type (100)실리콘 웨이퍼에 \sup 11\B\sup +\ \sup 31\P\sup +\ 이온을 각각 1.2 MeV, 2.2 MeV 의 에너지로 1×10\sup 15\cm\sup 2\ 주입하고, 700℃(20시간)+1000℃(10시간)의 2단계 열처리를 거치 후 주입된 불순물 및 산소 농도의 분포를 이차이온질량분석기 (Secondary Ion Mass Spectrometry, SIMS)로 관찰하였으며 잔류 2차 결함의 분포는 투과전자현미경(Transmission Electron Microscopy, TEM)으로 관찰하였다. SIMS 측정 결과 산소의 축적이 {{{{ { R}_{ } }}}}\sub p\(projected range) 부근에서 관찰되었으며 열처리 후에도 상당한 양의 2차 결합 띠가 {{{{ { R}_{ } }}}}\sub p\부근에서 관찰되는 것으로 보아 2차 결함에 의해 산소가 포획되었음을 알 수 있다. 또한 붕소와 인의 확산은 웨이퍼의 초기 산소 농도가 클수록 벌크 방향으로의 확산이 증대되는 현상을 볼 수 있었다.

  • PDF

강 기판위에 이온 플레이팅된 TiCrN 박막의 산화기구 (Oxidation Mechanism of TiCrN Coatings Ion-plated on Steel Substrate)

  • 이동복;김기영
    • 한국재료학회지
    • /
    • 제13권7호
    • /
    • pp.420-423
    • /
    • 2003
  • Coatings of TiCrN ion-plated on a steel substrate was oxidized at $800^{\circ}C$ in air, and their oxidation mechanism was presented. During oxidation, substrate elements and Ti and Cr in the coating always diffused outwardly to form the oxide scale. Simultaneously, oxygen from the atmosphere diffused inward1y to react with Ti and Cr to form $TiO_2$and $Cr_2$$O_3$, respectively. Also, the counter-diffusion of cations and oxygen resulted in some oxygen dissolution in the unoxidized TiCrN coating, and Fe dissolution in the oxide scale. When the Ti content in the coating was high, the $TiO_2$-forming tendency was strong, while when the Cr content was high, the $Cr_2$$O_3$-forming tendency was strong.

RECENT DEVELOppMENTS IN STUDIES ON DIAMOND FILMS BY ppLASMA CVD FOR FUTURE ELECTRONIC DEVICES

  • Hiraki, Akio
    • 한국진공학회:학술대회논문집
    • /
    • 한국진공학회 1993년도 제4회 학술발표회 논문개요집
    • /
    • pp.6-6
    • /
    • 1993
  • With brief instroduction of fabrication methods of dia.ond fillls by plasma CVD, recent progress in diamond research mainly done in the author's laboratory at Osaka University is reviewed.especially on the following topics: "low temperature diallond fabrication", "ion implantation", "hydrogen plasma treatment of ion-implanted diaaond to remove ion-induced damage", "Oxygen diffusion into the bulk assisted by the hydrogen treatllent", and "hole-burning effect".ffect".

  • PDF

분위기와 첨가제가 TiO2 세라믹스의 입자성장에 미치는 영향 (Effects of Additives and Atmospheres on the Grain Growth of TiO2 Ceramics)

  • 박정현;최헌진;박한수
    • 한국세라믹학회지
    • /
    • 제25권4호
    • /
    • pp.390-398
    • /
    • 1988
  • Effects of atmospheres and adidtives on the grain growth of TiO2 ceramics were investigated. In the range of 1300~140$0^{\circ}C$, grain growth was increased in CO2 as compared with O2 atmosphere and the grain boundary migration activation energy was lower than the diffusion activation energy of oxygen ion in TiO2. Also, in the case of addition of oxides, the grain growth was increased by oxides acting as a acceptor andinhibited by oxides acting as a donor. From the above results, when the oxygen vacancy concentration was increased, the intrinsic grain boundary mobility was increased and the pore drag force was decreased due to the rapid densification. Also it seems that the pore was migrated by the surface diffusion rather than lattice diffusion.

  • PDF