摘要:

Crack tips in thin SiO2glass films were observed directly by high‐resolution/high‐voltage electron microscopy. An elliptical crack with radius of curvature ∼ 1.5 nm was observed. When the glass film with the crack was soaked in water at 90°C for 7 d, the crack tip became blunt by a process of dissolution and precipi

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1984.tb19748.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The design and testing of structural parts from materials which exhibit subcritical crack growth can be improved by introducing auxiliary quantities into the classical concepts of fracture mechanics. The equivalent static stress, equivalent loading time, standardized loading time, and standardized lifetime, as well as the decrease in lifetime and residual lifetime, are defined, with examples of their application.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1984.tb19749.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Experimental work on melt synthesis, solidification behavior, and characterization of alloys in mixed II‐IV‐V2chalcopyrite semiconducting systems is reported. Melting relations diagrams and transformations in solidified alloys in the pseudo‐binary systems ZnGeAs2‐ZnSnAs2and ZnGeAs2‐CdGeAs2were studied by thermal analysis. Decomposition of a 10 wt% ZnGeAs2‐90 wt% CdGeAs2glass, characterized by transmission electron microscopy, revealed the onset of phase instabilit

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1984.tb19750.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Alumina‐glass composites with a small amount of a continuous glassy phase and closed pores were prepared and isostatically hot‐pressed under varied conditions. Induced macropore structure showed partiallcomplete pore filling with glass and some evidence of pore collapsing. Pore filling was achieved by viscous from of the glass from the grain boundary to the macropores, which causes a simultaneous localized rearrangement of the alumina grain struct

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1984.tb19751.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Y‐Si‐A1‐O‐N glasses containing up to 15 at.% nitrogen were prepared. Comparisons of properties of glasses with the same cation composition but with varying N:O ratios show that glass transition temperature, viscosity, and microhardness all increase with increasing nitrogen

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1984.tb19752.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Raman spectra were measured for a series of Na2O·xZnO·ySiO2glasses where x=O to 2 and y = 1,2, or 3. The spectra exhibit bands characteristic of sheet‐like and chain‐like strucrural units. Frequency and intensity shifts with ZnO content suggest that Zn2+is a simple network modifier over this composition

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1984.tb19753.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Thermogravimetry and differential thermal analyses were conducted on the mixture 2CsNO3+A12O3+2TiO2up to 1530 K. The resultant phase was identified as orthorhombic Cs2Al2Ti2O8with lattice parameters aO=0.996, b0=0.898, and co=0.573 nm. Simultaneous TG/DTA was performed to quantify weight loss and volatilization of cesium and to monitor the development and/or stability of the phase as a function of temperature.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1984.tb19754.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

To enhance the sinter ability of Si3N4, powders mixed with 0, 2, and 5 wt% Y2O3were explosively shock‐treated. Compacts of these powders were encapsulated in 96% silica glass containers and isostatically hot‐pressed. The shocked Si3N4with 5 wt% Y2O3was pressed to a density of 3.09 g/cm3(95.4% of theoretical) at 1400°C under 430 MPa for 3 h, whereas the unshocked material attained only 82.4% of theoretical density under the same hot isostatic pressing condit

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1984.tb19755.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Fracture toughness, strength, and elastic modulus of poly‐(methyl methacrylate) (PMMA) ‐ and poly(butyl methacrylate) (PBMA)‐impregnated alumina ceramics were measured as a function of polymer volume fraction, mean polymer particle size, and interfacial bonding between the polymer and ceramic. Fracture toughness was found to increase with increasing polymer volume fraction and decreasing polymer particle size. Interfacial bonding played a very important role in determining the fracture mode, which was interparticle and intra‐particle when the interface was coupled and uncoupled, respectively. Poly(methyl methacrylate) increased the fracture toughness of the ceramic 1.5 to 2 times more effectively than poly (butyl methacrylate). The elastic modulus was found to be unaffected by impregnation. The previously reported Bowie model was modified and proved to be useful. Single‐ and double‐crack versions of this model predicted strengths somewhat higher than those measured. This discrepancy and the scatter in the data were explained by the crack‐path tortuousity and the possibility of different mechanisms operating in different samples. Fractographs of the selected bend specimens were taken to support

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1984.tb19733.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Alumina and Al2O3/ZrO2(1 to 10 vol%) composite powders were mixed and consolidated by a colloidal method, sintered to>98% theoretical density at 1550°C, and subsequently heat‐treated at temperatures up to 1700°C for grain‐size measurements. Within the temperature range studied, the ZrO2inclusions exhibited sufficient self‐diffusion to move with the Al2O34‐grain junctions during grain growth. Growth of the ZrO2, inclusions occurred by coalescence. The inclusions exerted a dragging force at the 4‐grain junctions to limit grain growth. Abnormal grain growth occurred when the inclusion distribution was not sufficiently uniform to hinder the growth of all Al2O3grains. This condition was observed for compositions containing ≤2.5 vol% ZrO2, where the inclusions did not fill all 4‐grain junctions. Exaggerated grains consumed both neighboring grains and ZrO2, inclusions. Grain‐growth control (no abnormal grain growth) was achieved when a majority (or all) 4‐grain junctions contained a ZrO2inclusion, viz., for compositions containing ≥5 vol% ZrO2. For this condition, the grain size was inversely proportional to the volume fraction of the inclusions. Since the ZrO2inclusions mimic voids in all ways except that they do not disappear, it is hypothesized that abnormal grain growth in single‐phase materials is a result of a nonuniform distribution of voids during the

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1984.tb19734.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY