ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1954.tb14047.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

In some of the older vacuum tubes operating at 1‐mc. frequency or lower glass envelopes and porous ceramic refractories were used for internal supports. Some of the more modern electronic tubes operating at 10,000 mc. (3‐cm. wave length) require vacuum‐tight envelopes with (1) physical stability at operating temperatures (preferably a highly crystalline composition), (2) good mechanical strength, (3) surfaces which will take metallizing, (4) metal or alloy components of comparable thermal expansions, and (5) low dielectric losses, even after being heated in a reducing atmosphere such as hydrogen, or in a vacuum. After providing a brief historical background, the author discusses changes in properties of a few crystals and glasses and gives many detailed composition studies of four types of bodies, including such properties as linear thermal expansion and dielectric properties at 3‐cm. wave length, viz.: alumina,K8.4,PF0.0006; forsterite,K6.3,PF0.0006; zircon‐talc, k7.5,PF0.0026; and steatite,K6.6,PF0.0005. A brief account is presented of the development of sealing techniques and some details are given for three modern methods of making ceramic‐metal seals by using (1) Mn‐Mo, (2) MoO3, and (3) TiH2as the active metal

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1954.tb14048.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

Using techniques developed by Goldschmidt and lately utilized by Foster, solid‐state equilibria were studied in the system MgO‐Al2O3‐SiO2ZrO2. The ternary systems MgO‐Al2OrSiO2and MgO‐SiO2‐ZrO2are the only faces of this four‐phase system that have beep studied extensively. Compositions in each of the four faces were heated to temperatures below their fusion point and, after they had been cooled, they were examined by X rays to identify the phases present. After solid‐state equilibria had been established or verified in the four faces of the system, quaternary compositions were studied to determine the Alke

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1954.tb14049.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

Brightness temperatures were determined by measuring the densities of the photographic images produced by hot objects. Temperatures corresponding to these densities were obtained from film calibration curves. Each film was calibrated with exposures of a standard tungsten ribbon‐filament lamp. Within limits the calibration curves (film density vs. reciprocal temperature) were straight lines. The method is shown to be useful where an optical measurement of temperature is desirable but where conditions are changing too rapidly for measurement with the optical pyrometer. Continuous variations of temperature were recorded by moving the film behind a slit through which the image was focuse

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1954.tb14050.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

A high‐temperature X‐ray camera capable of operating as high as 2200°C. is described. The specimen is heated by a simple tantalum resistance heater. Temperature control is maintained by a constant power input. A sliding film holder permits a number of successive pictures to be taken without disturbing the specimen or appar

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1954.tb14051.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

An investigation was made of the effects of (a) the firing time and (b) the weight of nickel deposited from the nickel‐dip solution on the adherence developed by a cobalt‐free and a cobalt‐bearing ground‐coat enamel on both enameling iron and a titanium‐bearing low‐carbon steel. At 1550°F. the nickel improved the measured adherence index the most during the 2‐minute firing. The effect of the nickel, however, decreased markedly with longer firing times. There was an optimum nickel deposit for maximum adherence, an optimum that varied from 50 to about 120 mg. per sq. ft., depending on the type of cleaning used and on the type of enamel applied. The nickel dip reduced the tendency to fish‐scale. Furthermore, there was an apparent relation between fish‐scaling resistance and good adherence; no specimen with an adherence index of 70 or above showed fish‐scaling tendencies. Metallographic studies of the interface of coated specimens showed that nickel dipping of the steel before enameling brought about a surface roughening during the firing operation. A relationship was noted between the degree of roughening and the measured adherence index. The roughening of the steel surface was ascribed t

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1954.tb14052.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

The effect of heat‐treatment in the transformation range on the density of a borosilicate crown glass was studied by the method of quenched samples. An empirical equation is presented which satisfactorily represents the approach of the density to its equilibrium value at three temperatures. The density‐temperature relation in the special case of cooling at a constant rate is discussed theoretically and experimentally. It is shown that if the initial temperature is sufficiently high, the density‐temperature relations for different cooling rates are identical except for a displacement along the equilibrium density‐temperature line by an amount proportional to the logarithm of the cooling rate. The final density reached after cooling through the entire transformation range is also shown to depend linearly on the logarithm of the rate. The implications of these results are di

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1954.tb14053.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

The results of some studies on the effect of (1) ball‐milling time, (2) granulating by “slugging,” and (3) dry pressing of pure oxide ceramic bodies are presented. When the compressive strength of specimens of single‐component bodies was plotted against ball‐milling time (in revolutions), minima in the curves were found between 30,000 and 50,000 revolutions. For a multicomponent body of the porcelain type and one of the oxide porcelain type, when the same data were plotted, maxima in the curves were found between 30,000 and 40,000 revolutions. Granulating by slugging provided 30% greater compressive strength, 1.5% less shrinkage, and 1% less absorption in the specimens as compared with specimens formed from ungranulated material. High‐pressure forming, preferably by hydrostatic pressure, was desirable; however, there appeared to be an optimum pressure for the physical properties of ea

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1954.tb14054.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

The turbidimetric method of determining particle‐size distribution, developed by Musgrave and Harner, has been modified and adapted for use with tales, clays, and similar nonmetallic minerals and ceramic raw materials. Results obtained by this method have been found to be reproducible to within ±2%, and check with those obtained by the Andreasen pipette method within the same limits of accuracy. The turbidimetric method is useful for the direct determination of sizes from 60 to 0.25μ, equivalent spherical diameter. The entire procedure for a complete particle‐size‐distribution analysis usually requires less than 1 hour as compared with several days for the analysis of similar materials by the pipette

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1954.tb14055.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY