ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11125.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Ceramic or inorganic‐type adhesives, which are relatively resistant to thermal and mechanical shock and can sustain strengths at temperatures up to 1500°F, have been developed. Several alterations of the basic glassy phase were studied to attain optimum adhesion properties. Included were the incorporation of metal fillers and recrystallizable materials and the application of special formulation techniques to the basic glassy phase. The basic physical properties, thermal expansion, residual stress, and tensile strength, were correlated with bond strength. Average tensile strength values of 5000 psi at room temperature and 3000 psi at 800°F were found. The addition of selected covalent‐bonding‐type oxides to a barium borosilicate glass resulted in increased strengths at temperatures above 1000°F. The incorporation of metal fillers improved the physical properties of the basic ceramic adhesives. Recrystallized‐type adhesives would not develop strong cohesive bonds unless a glassy phase was al

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11126.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Compositions in the system KNbO3‐NaNbO2have been hot‐pressed to yield ceramics with relative densities greater than 99%. Because these materials lack any degree of pyroplastic behavior, temperatures approaching those required for air sintering are needed. These hot‐pressed specimens exhibit a finer microstructure than that obtainable by conventional processing. Enhanced piezoelectric coefficients are observed, and in certain compositional regions radial coupling coefficients have been increased from 32 to approximately 48%. Dielectric constants increase with densification and ac losses remain relatively high. The fine structure and improved piezoelectric activity, especially near the equimolar composition, make these materials desirable for electromechanical transducers, particularly in the 10 to 20 Mc per second range. The rate equation of Murray, Live, and Williams for hot‐pressing ceramics was found to apply in this

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11127.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Ring fractures generated by a steel ball indenting a flat glass plate occur outside the contact circumference, not at the circumference as theory predicts. It has been proposed by others, and is accepted as a basis for the present work, that the position of ring fracture is not determined by the locus of maximum stress but by the presence of a flaw which is severe enough to initiate fracture under the local condition of stress. The ring fracture radii thus locate flaws of various sizes at various distances from the center of contact. A new statistical method is introduced for calculating the distribution of such flaws with respect to both sizes of flaw and surface density of flaws. Application of this analysis to data taken from indentations of HF‐etched surfaces shows that flaw densities range from 15 to 30 per mm2per 5 A depth interval (150 to 300 flaws per mm2over the range detected by the indenter). Since continued removal of the surface did not change this density distribution, it is concluded that these flaws are due to inhomogeneities in the glass structure rather than to surface flaws which are accidental in origin. The limitation of the strength of flat glass to 300,000 psi is due to these inhomogeneitie

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11128.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The effect of near‐hydrostatic pressure on the synthesis of a lithia‐alumina‐silca glass was studied. It was found that the fusion of the oxides to form a glass melt was seriously impeded. A study also was made of the effect of hydrostatic pressure on the crystallization of a previously synthesized glass of similar composition. The approach to equilibrium in the system was found to be more rapid than at atmospheric pressure. In addition, a minor amount of a phase which could not be synthesized directly from the melt (α‐spodumene) w

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11129.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The binary system Nb2O5— SiO2has been shown to include an extensive two‐liquid region over the range 5 to 80% Nb2O5. The minimum temperature of the two‐liquid area is 1695°C. A eutectic composition occurs at 95% Nb2O5and 1448°C. and another at approximately 5% Nb2O5and 1695°C. The experimental results were obtained by the cone‐fus

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11130.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

An electron microscope study of pyrolytic graphite is presented in which subgrains of 0.1μ are shown. The effect of a cathodic vacuum etch on transverse and normal sections is given. Cracks in the structure are shown to be approximately 4μ long, parallel, and separated by 1

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11131.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

A study was made of the growth of very thin crystals of BaTiO3on platinum substrates by means of evaporation of KF from a KF‐BaTiO3solution. Crystals as thin as 300 A were obtained, but the areal extent was very small (0.2 mm2) for a uniform thickness. The random nucleation on defects located on the substrate appears to be a serious limitation on producing large film area. Growth in adirection resulted in more uniform thickness than growth in thedirection. The technique does provide a useful way of retrieving small single‐domain crystals with one electrode attached and may have useful application in microminiature devi

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11132.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

On the basis of 190 runs made up to 1860°C in sealed noble‐metal containers the following revisions have been made in the equilibrium diagram for the system A12O3–SiO2. Mullite melts congruently at 1850°C. The extent of equilibrium solid solution in mullite at solidus temperature is from approximately 60 mole % Al2O3(3/2 ratio) to 63 mole % A12O3. Metastable solid solutions can be prepared up to about 67 mole % Al2O3. There is no evidence for stable solubility of excess SiO2beyond the 3/2 composition at pressures below 3 kbars. Refractive indices are presented for glasses containing up to 60 mole % Al2O3and from them the composition of the eutectic is confirmed at 5 mole % SiO2. The variation in lattice constants of the mullite solid solution is not an unequivocal guide to composition since mullites at one composition produced at different temperatures show differences in spacing, no doubt reflecting Al‐Si ordering phenomena. The possibility of quartz and corundum being the stable assemblage at some low temperatures and pressures cannot be ruled out. A new anhydrous phase in the system is described, which was previously thought to be synthetic andalusite; it is probably a new polymorph of the Al2SiO5composition with ortho‐rhombic unit‐cell dimensionsa=7.55 A,b=8.27 A, a

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11133.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Phase equilibrium data resulting from quenching experiments are presented for the ternary system CaO‐MnO‐SiO2. An atmosphere of controlled oxygen pressure having Po2, ≅ 10−6atm at 1555°C was used to maintain the manganese in the divalent state. The ternary liquidus surface is largely one of low‐lying liquidus temperatures. Three ternary liquidus minima dominate this surface. These have the following compositions (in weight percent CaO, MnO, and SiO2): (a) 5.0, 48.4, and 46.6%, (b) 17.5, 45.0, and 37.5%, and (c) 15.0, 53.0, and 32.0%. Temperatures measured at these points are (a) 1265° C, (b) 1195°C, and (c) 1204°C. Isofracts of the quenched glasses are presented. Crystallization paths of ternary mixtures are represented by a series of fractionation curves and selected isothermal planes. Partition of manganese between coexisting pairs of crystalline phases (e.g., meta‐silicate, olivine, and (Ca,Mn)O solid solutions) favors concentration of manganese in the more basic phase. Subsolidus equilibria involving these phases and also Ca3Si2O7and Ca3SiO5are discussed. Ca3Si2O7and Ca3SiO6do not admit any appreciable amounts of Mn++into

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11134.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY