摘要:

At steelmaking temperatures, carbon and oxide constituents of BOF refractories react via the vapor phase. The mechanism of these reactions involves the production of metal or suboxide vapor in a region of low O2pressure and may include reoxidation and condensation in a region of highpO2. The faster wear rate of pitch‐bonded brick in high‐wear areas of the BOF, as compared to burned impregnated brick, is attributed to the pronounced porous region created near the hot face when internal oxidation‐reduction reactions consume the carbon

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12392.x-i1

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Recovery of creep‐resistant substructure in rutile was studied at 1000°, 1020°, and 1040°C. Specimens were crept under a stress of 10,000 psi to a strain early in the secondary stage of creep and then allowed to recover for varying periods under a residual stress of 400 psi. Recovery was detected by the increased creep strain which occurred when the 10,000 psi stress was reapplied. An apparent activation energy of 135,000 cal/mol was obtained for the recovery process. Experimental evidence suggests that the primary recovery mechanism involves the sweeping out of dislocation barriers within the material by the migration of dislocation walls or subgrain bounda

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb13407.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The fatigue response of single‐crystal MgO in compressive‐compressive loading was characterized at 800° and 1300°C. Fracture initiation mechanisms were observed for specimens loaded inanddirections; these loading directions independently activated the primary and secondary slip systems, respectively. For both loading directions, failure at 800°C resulted from cleavage cracks formed between parallel slipbands and that at 1300°C occurred at slipband intersections. At both temperatures, (111)slip was observed for cyclic loading in thedi

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb13386.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Alpha uranium dicarbide disks coated with pyrolytic carbon migrate, relative to the carbon, up a temperature gradient, leaving behind a layer of rejected graphite. A model for the migration process based on solution of carbon at the hot UC2‐C interface, transport across the UC2phase by thermal diffusion, and rejection as graphite at the cool UC2‐C interface was developed. The rate of migration may be described by:The apparent activation energy for migration is 76.5±9 kcal/mol, compared to a literature value for carbon self‐diffusion inα‐UC2of 90.2 kcal/mol. This difference in temperature dependence may be considered preliminary evidence that the heat of transport decreases with increasing temperature. The average value of the heat of transport, calculated using literature values for carbon self‐diffusion inα‐UC2, is

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb13387.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The Cahn‐Fullman method was used to determine three‐dimensional grain size distributions from experimentally measured two‐dimensional chord distributions in high‐purity MgO and magnesiowustite (0.10 and 0.48 wt% Fe2O3). Using the standard deviation of the three‐dimensional distributions, the constant which relates average three‐ and two‐dimensional grain sizes was evaluated by the procedure of Mendelson. The characteristics of the grain size distributions were correlated with steady state, abnormal, and terminal grain growth in MgO and magnesiowustite from 1300° to 1500°C. The distribution parameters were particularly useful in characterizing anomalous (i.e. abnormal and terminal) grain

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb13388.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The lattice constants of Ag2O are temperature‐dependent, with an apparent maximum at ∼200°C; this effect is similar for annealing in vacuum and in O2. The maximum appears to result from lack of thermal equilibrium in the oxide at temperatures<∼200°C. The lattice expansion was interpreted in terms of a change in the concentration of lattice vacancies in the Ag2O st

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb13390.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Conditions for preparing stoichiometric 50NiO/50ZnO ferrite were determined, and the effect on its magnetic properties of replacing up to 1.0 mol% of the NiO and ZnO with CoO was studied. The anisotropy of the ferrite containing 0.5 mol% CoO was zero; this phenomenon is the probable cause of the fact that the magnetic loss of this ferrite at 2.5 MHz can be calculated from 60‐Hz hysteresis dat

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb13391.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The effects of magnesioferrite precipitates on the mechanical properties of MgO single crystals were determined in samples with Fe/(Fe+Mg) ratios of 0.14 to 3.65%. Microhardness, slip‐band length, and 4‐point bending and compression strengths were measured. Maximum strength occurs for very short aging times, e.g. after 7° min at 700°C for samples with 3.65 cation % Fe, the hardness and critical resolved shear strength were 2300 and 35 kg/mm2, respectively. On further aging, the strength decreases rapidly at first from the peak value and then decreases slowly. Particles with diameters of ∼40 Å give maximum strength; fracture stresses>100,000 psi were observed. The strengthening is attributed to stacking faults in the particles and particle‐matrix surface area created when dislocations cut particles. The sharp peak in the strength vs aging curve is attributed to the particle‐matrix surface area and the main hardening to stacking faults. The critical resolved shear strength values are related quantitatively to the volume fraction and size of the precipitates in the theoretical treatme

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb13392.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The dimensional changes and the thermograms of cement specimens were determined during temperature cycles (+5° to ‐ 60°C, 0.33°C/min). In each case, freezing processes at ‐8° and ‐40°C and melting processes at ‐11° and 0°C were observed. The results could be explained by a theory previously developed for the porous‐glass‐water system. At the higher temperature, freezing occurs on the outer surface of the specimen; at the lower temperature, it occurs in the pores after redistribution of the water. Because water does not freeze in pores filled on adsorption, it migrates out of these pores when the relative humidity (expressed in terms of the vapor pressure of undercooled water), unavoidably decreases on cooling. Expansion is deleterious when the water content of the paste is significantly greater than the equilibrium value at the prevailing relative humidity. The effects of the water/ cement ratio, degree of saturation, air entrainment, sample dimensions, and cooling rate were consiste

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb13393.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

A glass‐forming region in the As‐Te system extends from 42 to 52 at.% Te when conventional cooling rates are used. The glasses exhibited nonmemory and memory switching during ac pulsing, depending on the electrical treatment. X‐ray diffraction, DTA, and photomicroscopy were used to characterize structural changes occurring in glassy 48As‐52Te during conductance transition and switching. These data are interpreted to indicate that nonmemory switching in this bulk glass is caused by intermittent heating and cooling of a microvolume of glass during ac pulsing; memory switching is caused by the formation and melting of a crystalline As2Te3f

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb13394.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY