ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1955.tb14575.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

The primary fields of cristobalite, tridymite, Li2O·2SiO2, Li2O·SiO2, MgSiO3, Mg2SiO4, and a new compound, Li2O·MgO·SiO2, have been located for the system lithium metasilicate‐forsterite–silica. Most of the primary field for the compound Li2O·MgO·SiO2lies below the join Li2O·SiO2‐Mg2SiO4, but a small portion of it lies in the composition triangle Li2SiO3‐Mg2SiO4‐MgSiO3. The positions of four invariant points and three composition triangles have

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1955.tb14576.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

A furnace with a tungsten coil as the heating element has been designed and built for use with the X‐ray diffraction spectrometer in the study of phase changes and equilibria at high temperatures. Tests indicate that temperatures up to 2000°C. can be reached and maintained for long periods of time in a neutral atmosphere. Materials which are not readily affected by the tungsten vapors that are present can be heated successfully in this type of furnace.SummaryWith this furnace, samples may be heated to and held at temperatures up to 2000° C. while X‐ray spectrometer data are obtained. Phase changes and equilibrium conditions existing at temperatures considerably above those obtainable with Pt alloy elements and at different time intervals at constant temperatures can thus be readily and positively determined. It should be noted, however, that materials which are readily reduced by tungsten vapors cannot be satisfactorily heat‐treated in this particular type of

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1955.tb14577.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

The sintering mechanism of aluminum oxide was studied with attention to the influence of time, temperature, and particle size. Mechanisms proposed by other investigators are reviewed as they pertain to the information obtained from the study. Shrinkage, density, and grain growth are considered; they indicate that rate and degree of sintering increase with decreasing particle size. Loose powders are shown to exhibit sintering phenomena when the particle size is small.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1955.tb14578.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Ceramic coatings were prepared from materials having low absorption coefficients for thermal neutrons. They were specifically designed for application to typical high‐temperature alloy parts for use in nuclear reactors. Best results were obtained with boron‐free coatings of the frit‐refractory type, in which a high‐barium frit containing small amounts of phosphate, beryllia, lime, zinc oxide, and titania was milled with additions of ceria or mixtures of chromic oxide and ceria. Coating compositions and test data are given.Summary and ConclusionsA total of 85 new frits and more than 200 new coatings were prepared and tested in the development of ceramic coatings for the protection of high‐temperature alloys against oxidation in air at elevated temperatures. The coatings which were designed especially for use in nuclear reactors, where only materials of low absorption coefficients for thermal neutrons can be used, may be suitable for more conventional purposes. The development work is still in progress, but the results to date may be summarized as follows:(1) Boron‐free frits have been developed and tested that have average neutron absorption coefficients in the range 0.15 to 0.50 barn, fritting temperatures of 2600°F. or below, and fiber‐deformation softening temperatures of 1450°F. or above.(2) The best frits developed to date are of the barium silicate type and contain small amounts of BeO, CaO, ZnO, and P2O5. Some of them also contain TiO2.(3) Coatings containing these frits, with admixtures of clay and various refractory oxides, have been developed and tested. The firing temperatures of the most promising of these coatings are in the range 1850° to 2250°F.(4) Of the refractory oxides used as mill additions in the coatings, best results were obtained with Cr2O3and CeO2and mixtures of the two.(5) The best ratio of frit to refractory oxide for all frits is 65 to 35 parts by weight.(6) Coatings were applied and adhered well to all the following alloys: types 309, 310, and 321 stainless steel, Inconel, Nichrome V, Stellite 25, and S‐816.(7) The protection given to the various coated alloy specimens varied with the composition of the alloys as well as with the composition of the coatings. Type 321 stainless steel was the most difficult to protect, and Nichrome V and Inconel were the easiest to protect. Type 310 stainless steel was relatively easy to protect.(8) The best evaluation of the degree of oxidation of a coated specimen during long‐time heating in air was obtained by microscopic comparison of metallographic sections of tested and untested coated specimens and determinations of the depth of external oxidation, maximum depth of stringer penetration, and number of stringers per inch of specimen.(9) The better coatings reduced greatly both the depth of stringer penetration and number of stringers per inch on type 310 stainless steel tested at 1900°F. for a

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1955.tb14579.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

A replica technique was developed for reproducing the corroded surface of glass containers. Before this development a wide variety of techniques had been studied which involved the use of various sheet plastics, such as ethyl cellulose, and various solvents. Most of the methods tried were of little value for curved surfaces because of the difficulties in pressing the plastic sheet uniformly upon the irregular contour of the bottle glass sample. A liquid plastic composed of Vinylite dissolved in methyl isobutyl ketone or acetone gave encouraging results when it was properly applied and dried. The previously weathered samples of bottle glasses were dipped in the plastic solution; after careful drying under controlled conditions, the plastic film was stripped from the surface to give an accurate reproduction of the corroded glass surface. The degree of surface deterioration, as shown by the replica, was then determined with a photoelectric haze meter. Some typical results taken from a study of various container glasses indicated that, as a rule, the inside of the container deteriorated; more rapidly than the outside. The pattern of corrosion on the outside of the container was quite irregular and was distinguished by long flowing lines, such as feeder marks, cutter marks, and mold marks. The inside of the container showed considerably fewer irregularities. Differences were found in the per cent haze vs. time curves for container glasses of varying composition. It was shown that these differences were generally associated with changes in the alumina and magnesia content of the glass.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1955.tb14580.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Data are presented on the changes in the room‐temperature refractive index and density of a borosilicate crown glass produced by different heat‐treatments. Measurements on a large number of samples with widely varying thermal history show that the refractive index is a single‐valued function of the density. The increase in refractive index for a given density change is smaller than that calculated by the Lorentz‐Lorenz theory; the apparent contribution of the induced polarization to the local electric field is very small. This may be due to a reduction in the ionic polarizabilities that accompany the density increase; alternatively, the Lorentz‐Lorenz form of the theory may not be valid in solid materials such as glass. Data of other investigators are shown to agree with the data repo

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1955.tb14581.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY