摘要:

The contribution of mechanical interaction between fuel and cladding to the change in length of a fuel pin has been identified from an analysis of data from the Steam‐Generating Heavy‐Water Reactor. A model which accounts for this effect uses the creep properties of fuel and cladd

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb15516.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Titanium‐doped α‐Al2O3exhibits a high‐temperature conductivity which is ionic at high oxygen pressures and electronic at low oxygen pressures. Both are isotropic. The temperature dependence of conductivity under conditions where equilibrium with the atmosphere is not maintained indicates both the position of the energy level of titanium (TiAlx) in the forbidden gap and the temperature dependence of the mobility of the native ionic defects (Al vacancies,VAlm). Optical absorption responsible for the pink color of the reduced crystals is measured as a function ofpo2and is used to determine concentrations of Ti3+and Ti4+. Parameters for the equilibrium constants of the reactions involving electrons by which the composition of Al2O3:Ti and undoped Al2O3is varied are determined. The chemical diffusion data by Joneset al.are described quantita

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb15517.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The influence of citric acid on paste hydration of 3CaO· Al2O3in the presence of CaSO4·2H2O and Ca(OH)2was studied using X‐ray diffraction, scanning electron microscopy, and conduction calorimetry. The time at which the citric acid is added (either prior to or with the mixing water) determines how it affects the reactivity of the aluminate. Immediately after the paste is gaged citric acid promotes a more rapid reaction, but later reactions are retarded. Hexagonal calcium aluminate hydrates, ettringite, and monosulfate were all detected as early hydration products. The influence of citric acid on the hydration of 3CaO·Al2O3slabs immersed in saturated CaSO4·2H2O solutions was also studied and a reaction scheme pro

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb15518.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Composites consisting of fine stainless steel fibers 6, 12, or 25 μm in diameter in a matrix of wustite were prepared by hot‐pressing. The fracture stress (σF) of unnotched beams and the critical stress‐intensity factor (K1C) for crack initiation in notched beams were measured; both increased linearly with the volume fraction of fiber. These improvements were attributed partially to the action of yielding fibers which bridged the crack surfaces; plastic deformation of fibers at the crack tip was thought to play a role. Large increases (largest for the 25‐μm fibers) in the total work of fracture (γF) were attributed to the work done in fracturing crack‐bridging fibers. For long cracks bridged by fibers, over a substantial fraction of the crack, the critical applied stress intensity factor for further crack propagation increased strongly with increasing bridged crack length. The form of this increase could be accounted for by considering the negative stress intensity factor resulting from the closure forces exerted on the crack by the bridging fibers.Based on a thesis submitted by J. G. Zwissler for the Ph.D. degree at Northwestern University, Evanston, III., June 1976.Supported by the U. S. Office of Scientific Research, Office of Aerospace Research, Grant No. AF–AFOSR–73–2431 and by a fellowship from the Intern

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb15519.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The phase diagram of the system CaF2‐AlF3was established from microscopic, powder X‐ray diffraction, quench, and DTA data obtained from samples encapsulated in sealed Pt tubes and either reacted in the solid state or melted. Two compounds, CaAlF5and Ca2AlF7, melted incongruently at 873°° 3°and 845°°3°C, respectively. Previously unreported Ca2AlF7was successfully indexed as orthorhombic with α0= 18.22 Å,b0=9.06 Å, andc0= 7.11 Å. The only eutectic in the system exists at 836°° 3°C an

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb15520.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The system zirconia‐scandia was investigated using X‐ray diffraction analysis, differential thermal analysis, metallographic analysis, and melting point studies. Results reveal the monoclinic α1phase (0 to 2 mol% Sc2O3), the tetragonal α2’phase (5 to 8% Sc2O3), the rhombohedral β phase (9 to 13% Sc2O3), the rhombohedral γ phase (15 to 23% Sc2O3), the rhombohedral δ phase (24 to 40% Sc2O3), and the cubic % phase (77.5 to 100% Sc2O3). The monoclinic α1phase and the tetragonal α2’phase were found to transform to the tetragonal α2phase over a wide temperature range depending on composition. The β, γ, and α phases transformed to a cubic phase at temperatures of %600%, 1100%, and 1300%C, respectively. A maximum melting point of %2870%C was found at %10% Sc2O3and a eutectic at %2

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb15521.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Potassium‐containing plate‐like precipitates having the βm‐alumina structure were identified within intergranular spinel inclusions in MgO‐doped sintered aluminum oxide ceramics. Transmission electron microscopy revealed the corresponding epitaxial relation: (0001) βm{111} spinel and 1120 βm110 spinel. Chemical analyses and quantitative metallography suggested that in α‐Al2O3the 1800°C solubility limits of magnesium and potassium do not exceed 300 to 400 ppm and 5 to 10 ppm by weight

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb15522.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The irradiation of microspheres of ThO2and Th0.81U0.19O2inthe form of high‐temperature gas‐cooled reactor (HTGR) particles resulted in the buildup of CO as well as Kr + Xe within the particle. The particles were later equilibrated at 1325T2270 K, crushed, and the CO and Kr + Xe contents were measured. Oxygen released as CO can be represented by the expression O/f=74.6Fexp (–7400/T), where O/fis the moles of oxygen released per mole of fissioned actinide,Fis fission per initial heavy‐metal atom, andTis the equilibration temperature. This oxygen release is reasonably consistent with that predicted from thermodynamic data for the oxides of the fuel and fission products. The burnup dependence of the release of Kr and Xe to the void space within the particle was consistent with published data and approached the theoretical value for the233u‐235U system, (Kr+

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb15523.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The hexagonal ferrite W=BaFe2+2Fe3+16O27, which is in equilibrium with oxygen under 0.015 atm at 1350°C, is oxidized in the range 250°to 1100°C in the same atmosphere to BaFe3+16+2xFe22‐3x>xO27with 2–3x<0.03. The metal‐deficient W structure is chemically unstable and decomposes after longer annealing at the same temperature. This difference in oxidation and decomposition rate is attributed to a difference in the diffusion rate of barium and i

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb15524.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Thermodynamic data on activities, activity coefficients, and free energies of mixing in SiO2‐Al2O3solutions were calculated from the phase diagram. Positive deviations from ideal mixing in the thermodynamic data suggest a tendency for liquid immiscibility in both SiO2‐ and Al2O3‐rich compositions. The calculated data were used to estimate regions of liquid‐liquid immiscibility. A calculated metastable liquid miscibility gap with a consolute temperature of ∼1540°C at a critical composition of ∼36 mol% Al2O3was considered to be thermodynamically most probable; the gap extended from ∼11 to °49 mol% Al2O3at 1100°C. SiO2‐rich glass compositions showed evidence of glass‐in‐glass phase separation when examined by direct transmissi

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb15525.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY