Change search
Refine search result
1 - 11 of 11
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Anghel, Clara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Dong, Qian
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    A gas phase analysis technique applied to in-situ studies of gas-solid interactions2007In: Journal of materials science. Materials in electronics, ISSN 0957-4522, E-ISSN 1573-482X, Vol. 47, no 10, p. 3440-3453Article in journal (Refereed)
    Abstract [en]

    An ultrahigh vacuum technique using mass spectrometry for in-situ investigations of gas-solid interactions is described in this paper. Examples of chemical reactions (oxidation, hydration) between solids and gas mixtures, dissociation of gases on solid surfaces, outgassing of solid materials and permeation of gases through membranes are discussed where the experimental arrangement is explained in detail. This Gas Phase Analysis (GPA) technique can be used at temperatures from room temperature to 1200 degrees C and at pressures up to 1 atm. Aspects related to sample preparation, isotopic gas mixture selection, data acquisition, calibration and interpretation of the experimental data are also addressed.

  • 2.
    Belonoshko, Anatoly B.
    et al.
    KTH, Superseded Departments, Physics.
    Rosengren, Anders
    KTH, Superseded Departments, Physics.
    Dong, Qian
    KTH, Superseded Departments, Materials Science and Engineering.
    Hultquist, Gunnar
    KTH, Superseded Departments, Materials Science and Engineering.
    Leygraf, Christofer
    KTH, Superseded Departments, Materials Science and Engineering.
    First-principles study of hydrogen diffusion in alpha-Al2O3 and liquid alumina2004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, no 2Article in journal (Refereed)
    Abstract [en]

    We have studied the energetics and mobility of neutral hydrogen in alumina Al2O3 using ab initio density-functional calculations. The mobility of hydrogen was studied in corundum (alpha-Al2O3) as well as in liquid alumina. Using both static as well as molecular-dynamics calculations, and applying classical transition state theory, we derive the temperature-dependent diffusivity of hydrogen in alpha-Al2O3 as D(T)=(21.7x10(-8) m(2)/s)exp(-1.24 eV/kT). The corresponding diffusivity of hydrogen in liquid/amorphous alumina, derived directly from ab initio molecular dynamics calculations, is D(T)=(8.71x10(-7) m(2)/s)exp(-0.91 eV/kT). The computed diffusivity compares very well to experimental data. We conclude that diffusion of neutral hydrogen through the bulk of alumina is a good approximation of the mechanism for hydrogen mobility in corrosion scales. The representation of grain-boundary structures by amorphous alumina is, probably, realistic at higher temperatures.

  • 3.
    Belonoshko, Anatoly B.
    et al.
    KTH, Superseded Departments, Physics.
    Rosengren, Anders
    KTH, Superseded Departments, Physics.
    Dong, Qian
    KTH, Superseded Departments, Materials Science and Engineering.
    Hultquist, Gunnar
    KTH, Superseded Departments, Materials Science and Engineering.
    Leygraf, Christofer
    KTH, Superseded Departments, Materials Science and Engineering.
    First-principles study of hydrogen diffusion in α-Al 2O3 and liquid alumina2004In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 69, no 2, p. 243021-243026Article in journal (Refereed)
    Abstract [en]

    We have studied the energetics and mobility of neutral hydrogen in alumina Al2O3 using ab initio density-functional calculations. The mobility of hydrogen was studied in corundum (α-Al2O 3) as well as in liquid alumina. Using both static as well as molecular-dynamics calculations, and applying classical transition state theory, we derive the temperature-dependent diffusivity of hydrogen in α-Al 2O3 as D(T)=(21.7 × 10-8 m 2/s)exp(-1.24 eV/kT). The corresponding diffusivity of hydrogen in liquid/amorphous alumina, derived directly from ab initio molecular dynamics calculations, is D(T)=(8.71 × 10-7 m2/s)exp(-0.91 eV/kT). The computed diffusivity compares very well to experimental data. We conclude that diffusion of neutral hydrogen through the bulk of alumina is a good approximation of the mechanism for hydrogen mobility in corrosion scales. The representation of grain-boundary structures by amorphous alumina is, probably, realistic at higher temperatures.

  • 4.
    Dong, Qian
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    An experimental method to identify various oxygen species transported in oxides2007In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 306, no 1-2, p. 166-172Article in journal (Refereed)
    Abstract [en]

    Oxygen transport in oxides can take place in molecular, atomic and ionic form. An experimental method is described which separates the contributions of molecules, atoms and ions to the overall oxygen transport in oxides. The method comprises gas phase analysis and the use of oxygen isotopes O-16 and O-18. In the general case, exposure to non-equilibrated O-2 containing 60-70% O-18 is optimal to obtain the highest accuracy in the measurement. The method is exemplified by distinguishing non-ionic (molecular and atomic) oxygen transport from ionic oxygen transport in a commercial yttria-stabilized zirconia (YSZ) sample in the temperature range of 600-900 degrees C. There is approximately 35% molecular, 20% atomic transport and 45% ionic oxygen transport in YSZ at 600 degrees C. It is found that the fraction percent of non-ionic oxygen transport decreases with increasing temperature, and ionic oxygen transport increases sharply with increasing temperature.

  • 5.
    Dong, Qian
    KTH, Superseded Departments, Materials Science and Engineering.
    Studies of transport in some oxides by gas phase analysis2004Licentiate thesis, comprehensive summary (Other scientific)
  • 6.
    Dong, Qian
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Transport in Oxides Studied by Gas Phase Analysis2007Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    The transport in oxides is studied by the use of gas phase analysis (GPA). An experimental method to identify transported species of gases and their contribution to the overall transport of gases in oxides and an experimental method to evaluate the parameters diffusivity, concentration, permeability of gases in oxides and effective pore size in oxides are developed, respectively.

    Pt has two effects on the thermal oxidation of metals. One is to enhance the oxidation of metals which takes place at the oxide-metal interface by promoting a high concentration gradient of dissociated oxygen across the oxide layer. The other effect is to suppress the oxidation of metals by decreasing the contact area between metal and oxygen. The overall effect of Pt on the oxidation of metals depends on the mechanism of oxide growth in the absence of Pt. It is suggested that an appropriate amount of Pt coating induces a balanced oxide growth resulting from stoichimetrical inward oxygen flux to outward metal flux, which leads to a reduced oxidation rate.

    The diffusion of diatomic gases in oxides such as vitreous silica and yttria stabilized zirconia (YSZ) takes place in both molecular and dissociated (atomic or/and ionic) form. The fraction of transport of molecular species decreases with temperatures, and the fraction of transport of dissociated species increases with temperatures. Measured permeabilities of diatomic gases in vitreous silica are higher than the expected permeabilities of their molecules, which are explained by diffusion of molecules combined with a retardation of dissociated species in reversible traps. The diffusion of hydrogen in vitreous silica is concentration dependent and increases with local concentration. Transport paths are shared among transported species and gases at all temperatures in YSZ. Helium shares transport path with molecular oxygen and nitrogen at low temperatures; whereas helium shares transport path with dissociated oxygen and also dissociated nitrogen at high temperatures.

  • 7.
    Dong, Qian
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Transport of gases in yttria-stabilized zirconia2007Article in journal (Other academic)
  • 8.
    Dong, Qian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Hultquist, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Does nitrogen transport in vitreous silica only take place in molecular form?2006In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 100, no 10, p. 104904-Article in journal (Refereed)
    Abstract [en]

    It is generally believed that nitrogen transport in vitreous silica exclusively takes place in molecular form, although no evidence for this is found in the literature. Actually, an analysis of literature data of transport of nitrogen and noble gases in vitreous silica at 900 °C suggests it may not be the case. In order to clarify the operative species of nitrogen transport in this material, experiments of permeation and uptake/release have been performed with the use of gas phase analysis and isotopic labeling of nitrogen. By comparing the relative distributions of N2 14,14, N2 14,15, and N2 15,15 in exposure gas, permeated gas and released gas with distribution of equilibrated nitrogen molecules, the percentage of dissociated nitrogen in the transport has been evaluated at different temperatures. It has then been found that nitrogen undergoes dissociation not only on the surface of vitreous silica but also in its bulk and that the overall dissociation of nitrogen increases with temperature. It is concluded that nitrogen diffuses both in molecular and atomic forms with approximately 15% atomic nitrogen transport at 900 °C. The observed transport rates are explained by diffusion of molecular nitrogen combined with a retardation of dissociated nitrogen in reversible traps.

  • 9.
    Dong, Qian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Tang, Qing
    Li, Wenchao
    Al2O3-TiC-ZrO2 nanocomposites fabricated by combustion synthesis followed by hot pressing2008In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 475, no 1-2, p. 68-75Article in journal (Refereed)
    Abstract [en]

    Al2O3-TiC-ZrO2 nanocomposites were prepared by combustion synthesis followed by hot pressing with TiO2, Al, C and ZrO2 as raw materials. Combustion synthesis is favorable to obtain in situ formed powder with TiC and ZrO2 nanoparticles distributed in Al2O3 matrix. The effects of varying amount of ZrO2 nano-scale additives on the mechanical properties and microstructure of Al2O3-TiC composite were studied. An appropriate amount of ZrO2 nanoparticle additive improves the mechanical properties. The flexural strength and fracture toughness of Al2O3-TiC-10 wt.% ZrO2 composite were approximately 20% higher than that of Al2O3-TiC composite. The addition of ZrO2 nanoparticles reduced the grain size and improved the distribution of different phases. With the ZrO2 addition, the fracture mode changes from intergranular to mixed inter/transgranular fracture. The residual stresses are generated by the thermal expansion coefficient mismatch between different phases, which leads to the generation of dislocations and microcracks around the nanoparticles. The effects of nanoparticles on the deflected propagation, nailing and blocking of the dislocation and microcracks are believed to contribute to the improvement of the strength and toughness of Al2O3-TiC-ZrO2 composite.

  • 10.
    Hultquist, Gunnar
    et al.
    KTH, Superseded Departments, Chemistry.
    Hörnlund, Erik
    KTH, Superseded Departments, Chemistry.
    Dong, Qian
    KTH, Superseded Departments, Chemistry.
    Platinum-induced oxidation of chromium in O-2 at 800 °C2003In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 45, no 12, p. 2697-2703Article in journal (Refereed)
    Abstract [en]

    The effects of porous Pt on the oxidation of Cr at 800degreesC have been studied with the (OSIMS)-O-18 technique, gas phase analysis and XPS. In oxide areas with Pt a pronounced inward oxygen transport takes place and a substantial oxide growth near the Cr substrate is observed. In oxide grown on areas without Pt the counts of CrO ions in SIMS and the binding energy of O (1s) in XPS depend on the distance from the area with Pt. The experimental observations are believed to be a consequence of a high dissociation efficiency of O-2 on areas with Pt in combination with a high diffusivity of O in external and internal oxide surfaces on areas both with and without Pt.

  • 11.
    Rundgren, John
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Dong, Qian
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Hultquist, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Concentration-dependent diffusion of hydrogen in vitreous silica2006In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 100, no 10, p. 104902-1-104902-5Article in journal (Refereed)
    Abstract [en]

    We report diffusion experiments where hydrogen permeates through a 1 mm wall of vitreous silica at 550 °C with applied gas pressures of 70, 460, 840, and 1200 mbars. For each pressure, and at steady state, the flux and the amount of hydrogen in the material are measured. Within the experimental accuracy we find that the flux is proportional to the pressure and that the hydrogen amount increases with a falling gradient with respect to pressure. The result is a relationship between flux and mean concentration. A careful evaluation of the flux versus concentration relationship by means of the steady-state diffusion equation shows that the hydrogen diffusivity in the silica wall is concentration dependent and increases linearly with local concentration.

1 - 11 of 11
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf