Tensile Properties and Creep Behavior of SiC-Based Fibers under Various Oxygen Partial Pressures

2005 ◽  
Vol 475-479 ◽  
pp. 1333-1336 ◽  
Author(s):  
Jan Ji Sha ◽  
J.S. Park ◽  
Tatsuya Hinoki ◽  
Akira Kohyama ◽  
J. Yu
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Tensile Properties ◽  
Creep Behavior ◽  
Elevated Temperatures ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
Sic Fibers ◽  
Partial Pressures ◽  
Ar Gas

Three kinds of atmospheres (air, highly-pure Ar and ultra highly-pure Ar gas) with different oxygen partial pressures were applied to investigate the tensile properties and creep behavior of SiC fibers such as Hi-NicalonTM and TyrannoTM-SA. These fibers were annealed and crept at elevated temperatures ranging from1273-1773 K in such environments. After annealing at 1773 K, the room temperature tensile strengths of SiC-based fibers decreased with decreasing the oxygen partial pressure and the near stoichiometric fiber TyrannoTM-SA shows excellent strength retention. At temperatures above the 1573 K, the creep resistance of SiC fibers evaluated by bending stress relaxation (BSR) method under high oxygen partial pressure was lower than that of in low oxygen partial pressure. The microstructural features on these fibers were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD).

Characterization of Ruo2 Films Prepared by Rf Reactive Magnetron Sputtering

1998 ◽  
Vol 541 ◽  
Author(s):  
Li-jian Meng ◽  
M.P. dos Santos
Keyword(s):  
Magnetron Sputtering ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Total Pressure ◽  
High Stress ◽  
Reactive Magnetron Sputtering ◽  
Reactive Magnetron ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
Partial Pressures

AbstractRuthenium dioxide films have been prepared by rf reactive magnetron sputtering at different oxygen partial pressures and total sputtering pressures. The films have been characterized by scanning electron microscopy, X-ray diffraction and electrical conductivity. The films prepared at low oxygen partial pressure and total pressure show a strong preferred orientation along the [110] direction. As both pressures increased, the peak intensity decreases. All the films are subject to a compressive stress. As the total pressure is decreased and the oxygen partial pressure is increased, the stress increases. When the total pressure is lower than 6 × 10−3 mbar and the oxygen partial pressure is higher than 1 × 103 mbar, the films peeled off automatically from the substrate because of the high stress. The films prepared at high oxygen partial pressure and high total pressure have a rough surface and those prepared at low pressure show smooth surface. In this paper, these phenomena have been discussed. In addition, the electrical properties of the films are also discussed.

scholarly journals Process-Parameter-Dependent Structural, Electrical, and Optical Properties of Reactive Magnetron Sputtered Ag-Cu-O Films

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
P. Narayana Reddy ◽  
A. Sreedhar ◽  
M. Hari Prasad Reddy ◽  
S. Uthanna ◽  
J. F. Pierson
Keyword(s):  
Optical Properties ◽  
Substrate Temperature ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Rf Magnetron Sputtering ◽  
Low Oxygen ◽  
Electrical And Optical Properties ◽  
Partial Pressures ◽  
Effect Of Oxygen ◽  
Parameter Dependent

Silver-copper-oxide thin films were formed by RF magnetron sputtering technique using Ag80Cu20target at various oxygen partial pressures in the range 5 × 10−3–8 ×10−2 Pa and substrate temperatures in the range 303–523 K. The effect of oxygen partial pressure and substrate temperature on the structure and surface morphology and electrical and optical properties of the films were studied. The Ag-Cu-O films formed at room temperature (303 K) and at low oxygen partial pressure of 5 × 10−3 Pa were mixed phase of Ag2Cu2O3and Ag, while those deposited at 2 × 10−2 Pa were composed of Ag2Cu2O4and Ag2Cu2O3phases. The crystallinity of the films formed at oxygen partial pressure of 2 × 10−2Pa increased with the increase of substrate temperature from 303 to 423 K. Further increase of substrate temperature to 523 K, the films were decomposed in to Ag2O and Ag phases. The electrical resistivity of the films decreased from 0.8 Ωcm with the increase of substrate temperature from 303 to 473 K due to improvement in the crystallinity of the phase. The optical band gap of the Ag-Cu-O films increased from 1.47 to 1.83 eV with the increase of substrate temperature from 303 to 473 K.

Role of Oxygen Vacancies on the Ferroelectric Properties of Pzt Thin Films

1991 ◽  
Vol 243 ◽  
Author(s):  
Chi Kong Kwok ◽  
Seshu B. Desu
Keyword(s):  
Thin Films ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Vacancy Concentration ◽  
Ferroelectric Properties ◽  
Sol Gel ◽  
Low Oxygen ◽  
Partial Pressures ◽  
Pzt Films

AbstractThe properties of ferroelectric thin films can be significantly influenced by the presence of point defects. The concentration of vacancies presented in these thin films is known to be one of the key parameters causing the degradation of these films when these films are subjected to polarization reversals.To study the effects of the vacancy concentration on the ferroelectric properties, sol gel PZT films and powders were annealed in different oxygen partial pressures. For the PZT films, the reduction of oxides to pure metals was not observed even with films annealed at 2×10−5 atmosphere of oxygen partial pressure. Samples annealed at low oxygen partial pressure (for instance, 10−3 and 2×10−5 atmosphere), which has more Pb and O2 depletions and consequently has more Pb and O2 vacancies, cannot be switched easily. The ratios of coercive field after and before fatigue increase as the defect concentrations of the annealed samples increase.

Effect of Oxygen Partial Pressure on Stability of High-Tc Phase in Sintered Bi-Pb-Sr-Ca-Cu-O Superconductos

1989 ◽  
Vol 169 ◽  
Author(s):  
H.K. Lee ◽  
K.W. Lee ◽  
D.H. Ha ◽  
J.C. Park
Keyword(s):  
Phase Transformation ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Superconducting Phase ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
High Tc ◽  
X Ray ◽  
High Tc Phase ◽  
Effect Of Oxygen

AbstractThe effect of oxygen partial pressure on stability of high-Tc phase in Bi-Pb-Sr-Ca-Cu-O system has been investigated using x-ray diffraction, resistivity and a.c. susceptibility measurements. It was found that part of the high-Tc phase in Bi-Pb-Sr-Ca-Cu-O system was transformed into the low-Tc phase (80 K) and insulating phases by heating in the temperature range 600 C to 880°C in O2 of one atmosphere. The original high-Tc phase was restored upon retreatment in a low oxygen partial pressure of 0.1 atmosphere. The reversible superconducting phase transformation is discussed in conjunction with the formation mechanism of the high-Tc phase in Bi-Pb-Sr-Ca-Cu-O system.

Si-N nanowire formation from Silicon nano and microparticles.

2003 ◽  
Vol 789 ◽  
Author(s):  
Chandana Rath ◽  
A. Pinyol ◽  
J. Farjas ◽  
P. Roura ◽  
E. Bertran
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Crystalline Silicon ◽  
Silica Layer ◽  
Whisker Formation ◽  
Low Oxygen ◽  
Partial Pressures ◽  
Precursor Material ◽  
Different Temperatures ◽  
First Time

ABSTRACTWe report silicon nitride whisker formation from hydrogenated amorphous silicon (a-Si:H) nanoparticles grown by PECVD for the first time. We compared the results with the kinetics of whisker formation from ball milled crystalline silicon (c-Si) microparticles. Whisker formation is analyzed at different temperatures (900–1440 °C) and oxygen partial pressures. At temperatures equal or above 1350 C and at low oxygen partial pressure we observe monocrystalline α-Si3N4 whiskers having 30–100 nm diameter and several microns length. By increasing the oxygen partial pressure, the structure of whiskers is completely changed, as shown by electron microscopy. In this case we observe α-Si3N4 whiskers covered by an amorphous silica layer at 1350 C. Finally, when the precursor material is silicon microparticles, thicker (170–330 nm) and longer whiskers are formed.

Ovine ill-thrift in Nova Scotia. 4. The survival at low oxygen partial pressure of fungi isolated from the contents of the ovine rumen

1972 ◽  
Vol 18 (7) ◽  
pp. 1119-1128 ◽  
Author(s):  
D. Brewer ◽  
J. M. Duncan ◽  
S. Safe ◽  
A. Taylor
Keyword(s):  
Carbon Dioxide ◽  
Nova Scotia ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Low Oxygen ◽  
Mucor Rouxii ◽  
Permanent Pasture ◽  
Method Of Determination ◽  
Partial Pressures

Aspergillus fumigatus, Mucor rouxii, and Sporormia minima have been isolated from the rumen contents of sheep grazing permanent pasture at Nappan, Nova Scotia. To determine the ability of these fungi to survive and grow at the low oxygen partial pressure present in the rumen, a method of determination of oxygen, nitrogen, and carbon dioxide has been developed. The lowest partial pressures of oxygen [Formula: see text] and nitrogen that could be detected were 0.0005 cm Hg and the precision of the determination was ±0.001 cm Hg. Carbon dioxide was determined with slightly less precision than achieved for oxygen and nitrogen. Using this method, respiration was detected in cultures of all the fungi named at [Formula: see text] Hg and growth was observed at [Formula: see text] Hg in the case of M. rouxii. It is concluded that all these fungi are capable of survival in the ovine rumen.

Effect of Low Oxygen Partial Pressure on the Chromium Partition in CaO-MgO-SiO2-Cr2O3-Al2O3Synthetic Slag at Elevated Temperatures

2013 ◽  
Vol 84 (7) ◽  
pp. 670-679 ◽  
Author(s):  
Galina Albertsson ◽  
Lidong Teng ◽  
Bo Björkman ◽  
Seshadri Seetharaman ◽  
Fredrik Engström
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Elevated Temperatures ◽  
Low Oxygen

Stability of monoclinic and tetragonal zirconia at low oxygen partial pressure

2000 ◽  
Vol 15 (2) ◽  
pp. 377-381 ◽  
Author(s):  
Niels Mommer ◽  
Theresa Lee ◽  
John A. Gardner
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Angular Correlation ◽  
Perturbed Angular Correlation ◽  
Tetragonal Zirconia ◽  
Cubic Phase ◽  
Monoclinic Zirconia ◽  
Low Oxygen ◽  
Partial Pressures

We have found that both tetragonal and monoclinic zirconia annealed at temperaturess in the range of 1100 to 1300 °C in atmospheres of low oxygen partial pressures (down to 10−26 Pa) transform slowly to an apparently cubic phase. The transformation can be reversed by increasing the oxygen partial pressure sufficiently, i.e., exposing the sample to air again. These observations were made by 111In/Cd perturbed angular correlation (PAC) measurements of undoped zirconia samples. Upon annealing under various reducing atmospheres PAC spectra show a steadily increasing fraction of Cd probe atoms in a locally cubic environment with the fraction of probe atoms in tetragonal or monoclinic sites decreasing accordingly.

Electrical Conductivity Prediction in Langasite for Optimized Microbalance Performance at Elevated Temperatures

2002 ◽  
Vol 756 ◽  
Author(s):  
Huankiat Seh ◽  
Harry Tuller ◽  
Holger Fritze
Keyword(s):  
Electrical Conductivity ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
High Temperatures ◽  
Gas Sensors ◽  
Elevated Temperatures ◽  
Operating Conditions ◽  
Total Conductivity ◽  
Defect Model ◽  
Partial Pressures

ABSTRACTThe performance of the langasite-based crystal microbalance is limited due to reductions in its resistivity at high temperatures and reduced oxygen partial pressures. In this work, we utilize a recently developed defect model to predict the dependence of the ionic and electronic contributions to the total conductivity of langasite on temperature, oxygen partial pressure and acceptor and donor dopants. These results are used to select the type and concentrations of dopants expected to provide extended operating conditions for langasite-based gas sensors and crystal microbalances.

scholarly journals Magnesium protoporphyrin chelatase activity in Rhodopseudomonas spheroides. Studies with whole cells

1972 ◽  
Vol 127 (1) ◽  
pp. 97-106 ◽  
Author(s):  
A. Gorchein
Keyword(s):  
Protein Synthesis ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Pure Oxygen ◽  
Low Oxygen ◽  
Anaerobic Conditions ◽  
Whole Cells ◽  
Partial Pressures ◽  
Deficient Medium ◽  
Rhodopseudomonas Spheroides

1. Whole cells of Rhodopseudomonas spheroides grown under semi-anaerobic conditions in the light incorporated magnesium into exogenous protoporphyrin when incubated with EDTA or the related chelators EGTA, N-(2-hydroxyethyl)-ethylenediamine-NN′N′- triacetate and trans-1,2-diaminocyclohexanetetra-acetate. 2. The reaction was demonstrated under anaerobic conditions in the light or at low oxygen partial pressure in the dark. Partial pressures of oxygen greater than 15% inhibited the reaction. 3. Cells grown under pure oxygen were completely inactive, but on adaptation to growth under low oxygen partial pressure (O2+N2, 5:95) the development of activity paralleled the synthesis of bacteriochlorophyll. 4. The reaction with normal cells did not require protein synthesis, but cells that had lost their activity by being illuminated in Mg2+-deficient medium did not recover it in the absence of protein synthesis. 5. The product of the reaction was magnesium protoporphyrin monomethyl ester. 6. Evidence is presented that insertion of magnesium is obligatorily coupled with methylation and it is concluded that the reaction is dependent on a multienzyme complex.

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