摘要:

A new method for preparing ultrafine powder of SiC is proposed. A carbon rod is mounted vertically with a block of silicon at the bottom of the system. The apparatus is held in rarefied inert gas and heated by an electric current. The SiC produced by the heating then evaporates forming a smoke, the particles of which are β–SiC<100 nm in di

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09540.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Compositions of La2O3‐Y2O3were sintered to full density by a process which uses a controlled transient solid phase to retard grain growth sufficiently that pores remain on grain boundaries and are eliminated by solid‐state diffusion. The temperature is then decreased into a single‐phase region and the structural transition yields a pore‐free, single‐phase body. Optimum compositions are 8.1 to 12.1 mol% La2O3for a sintering temperature of 2170°C and annealing temperatures of 1920° to 2020°C, resulting in materials with near‐theoretical total transmittances and specular transmittance within 6%

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09551.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Free volume (Vf), defined by Simha and Boyer, was measured for glasses in the system MO‐P2O5(M=Be, Mg, Ca, Ba, Zn) and (1‐x)MO·P2O5‐xAl2O3·3P2O5(M = Mg, Ca, Ba). Experimental Vfof the glasses was ∼0 to 0.3. These results indicate that Vfis not a universal constant (∼0.1) for all glasses as previously reported, but that Vfdepends on the glass backbon

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09542.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

This study shows that the amount ofAl2O3needed to form high density Si3N4‐15Y2‐O3samples can be reduced by using high surface area Si3N4powder and high N2overpressure (high sintering temperatures) during the sintering process. The reduction in AI2O3content results in improved oxidation resistance of the sintered samp

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09543.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The thermal stress resistance of aluminas is strongly influenced by the surface heat transfer coefficient (h). In liquid quenches, h, which is a function of boiling phenomena, varies with bath and sample temperature. Thus, while a 22°C water quench yields ΔTcvalues essentially independent of the alumina properties or correspondingly, sample thickness, t, raising the bath to 100°C leads to a strong size dependence of ΔTc(i.e. ΔTc>>∼250°C for t<

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09544.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Loading rate sensitivity effects at high temperatures are brought about by a viscous metallic Si phase within an SiC mircostructure. The cross‐head speeds were 0.024 and 1260 mm/min. At 0.024 mm/min and 1200°C, KICincreases up to ∼12 MN/m3/2, whereas at 1260 mm/min, KICremains nearly unaffected, comparable with the room temperature value of ∼4 MN/m3/2. The effect contradicts the normal behavior where KICincreases with increasing cross‐head speed. Fracture toughness data should therefore be determined as a Junction of loading rate, to account for viscous reactions at certain temp

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09545.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The metastable β form of bismuth sesquioxide was obtained by doping antimony oxide. The solubility of antimony was 4 to 10 at. %in β specimens, where more than 75% of the antimony atoms were valenced at 5

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09546.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Immiscibility temperature of 13 mol% Na2O‐87 mol% SiO2glass was found to increase with F addition. Electron micrographs indicated that the microstructure size did not change appreciably with F additio

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09547.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The current knowledge of the structure of high‐angle grain boundaries in metals and ceramic oxides is critically reviewed. Particular attention is given to effects due to differences in the bonding and crystal structure in these solid types. The results of recent experimental work and efforts to model grain‐boundary structure using computer simulation methods are described. Important characteristic features of boundaries in these materials are discussed. Difficulties which are presently being encountered in efforts to determine their structure are pointed

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09553.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Photoelastic measurement on rings sliced from soda‐lime glass tubes, ion‐exchanged with electric field assistance, were used to calculate the residual stress in this material. Account was taken of the effect of sample distortion due to slicing. Well below the glass transition the measured surface stresses were independent of time of exchange but increased markedly with decreasing temperature of exchange for both singly and doubly exchanged specim

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09554.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY