ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb13748.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

An experimental unit was developed to allow the application of the glass specimen onto the metal surface at elevated temperatures and under controlled atmospheric conditions. Sodium disilicate glass on Armco iron had a contact angle of 55°± 2° at 900° to 1000° C. in vacuum and poor adherence; on magnetite, 2°± 1°, and excellent adherence. Behavior on oxidized iron was affected by the ability of the glass to dissolve large quantities of oxide rapidly. Glass when dropped onto a lightly oxidized surface spread toward lower angles and retracted essentially to the 55° angle on solution of the oxide; adherence, in this case, correspondingly ranged from good to poor. When the glass dissolved a sufficient amount of iron oxide and etching of the metal occurred, resulting in the appearance of fayalite, the contact angle was in the range 15° to 35° and the best adherence was obtained. Vaporization of iron in vacuum at 1000°C. did not seem to be retarded by thin

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb13749.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

Molten sodium disilicate was found to react with iron powder in vacuum in the temperature range 935° to 1000°C. Under these conditions Fe reacted with Na2O in the glass to form Na gas and essentially FeO in the glas

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb13750.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

Contact angles, and adherence of sodium disilicate glasses with varying iron oxide additions on platinum and iron were studied at 1000°C. in vacuum. In the glass‐platinum systems the iron concentration in the glass did not affect either the contact angle or the adherence. No devitrification occurred in the glass‐platinum systems. The glass‐iron systems showed a lowering of the contact angle with increasing iron content in the glass, ranging exponentially from 55° to approximately 22°. Adherence was poor with no iron in the glass, and it increased as the iron content and reaction at the interface increased. Crystals, identified as fayalite (Fe2SiO4), were observed in some of the glass drops from the glass‐iron systems. Polished cross sections of the glass‐iron assemblies showed a greater attack of the metal surface as the iron content in the glass increased. The configuration suggests greater attack along the grai

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb13751.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

In a hydrogen atmosphere, MgO was vaporized by heating MgO (periclase) in the range 1500° to 1900° C, and the vapor products diffused into Al2O3(sapphire) to form a uniform outer layer of spinel on all surfaces. At 1900°C. a spinel layer 48 mils thick could be obtained in 16 hours. The rates of spinel formation were determined and the activation energy was calculated to be about 100 kcal. per mole. In the spinel layer, the lattice constant, Vickers hardness, and the refractive index varied from the outer surface to the inner boundary in a fairly uniform manner, indicating a continuous change in composition from 1MgO: 1Al2O3to 1MgO: 2–3Al2O3. In conversion to spinel a volume increase of 47% over that of the original sapphire took place. Transparent clear shapes of spinel such as disks and rods were obtained from clear sapphire and from translucent polycrystalline alumina. Clear rods of spinel with polished ends acted as thin lenses, round rods as convex lenses, and flat rods as planocylindrical lenses owing to the increase in refractive index from the outer surface to the inner central portion. Objects made of opaque polycrystalline alumina were also converted to spinel. The MgO periclase blocks were etched in the hydrogen atmosphere, and the vapor products of Al2O3entered the MgO to form tiny spinel droplets in an opalescent border. In an oxidizing atmosphere, spinel was formed only on the surface of the sapphire directly in contact with periclase, in the range 1500° to 1

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb13752.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

Two types of ceramic coatings were formulated for application to Inconel to give (a) the highest possible emittance from room temperature to about 1200°C. and (b) the highest possible reflectance to solar energy (0.4 to 2.0 μ) while having high emissivity in the infrared from 25° to 700° C. or higher. Both types of coatings were formulated from a modified barium silicate frit. This frit was opacified with various black spinels to give the (a)‐type enamels having total normal emittances ranging from 0.74 to 0.87. The (b)‐type enamels were made with equal parts of stannic and eerie oxides as opacifiers. At thicknesses greater than 5 mils, these had hemispherical reflectances varying between 0.67 and 0.62 at wave lengths of 0.6 to 2.6 μ respectively, together with total emittances of 0.75 at 400°C. and 0.60

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb13753.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

The purpose of this study was to develop a method of producing a single small crack on a glass surface which would become the initiating flaw in the fracture process. Techniques for measuring dimensions of this flaw also formed an essential part of the study. The cracks were formed by pressing a wedge‐shaped tungsten carbide point against the glass. Measurements were made from visible patterns found on the fracture surface after the glass was broken. Strict adherence to carefully worked out procedures was found to be essential for obtaining satisfactory cleaved cracks. Based on fracture caused by a semicircular crack 0.002 in. deep, the 1‐second breaking stresses of five different glasses were as follows: lead‐alkali glass 6800, soda‐lime glass 9000, 96% silica glass 11,500, low‐expansion borosilicate glass 12,000, and aluminosilicate glass 13,800 lb. per sq. in. These values are believed to correlate with the intrinsic strengths of the glasses. This method should have definite advantages in the investigation of fracture phenomena in glasses and in other brittle materials, specifically the effects of composition on strength and the causes of stre

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb13754.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

Crystalline thorium borate (ThB2O5) has been synthesized by the reaction of thoria with boric oxide at elevated temperatures; crystals of size suitable for single‐crystal X‐ray studies were grown in molten boric oxide at 1300°C. Crystallographic, chemical, and some physical properties of thorium borate crystals are presented as well as the results of a preliminary phase study of the system ThO2‐B2O3. Amorphous thorium borate gel, formed by reaction of aqueous solutions of borax and thorium nitrate, is transformed into crystalline thorium borate and thoria on firing at elevated temperatures. Boric oxide does not appear to react with either zirconium oxide or uranium dioxide to form any crystalline compounds. The fact that uranium dioxide does not react with boric oxide, but thoria does, affords a basis for effecting a chemical separation of the two oxides from thoria‐urania solid solutions. Preliminary data on the reactions between boric oxide and different thoria‐urania solid solutions

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb13755.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

The electrical conductivity of single‐crystal and polycrystalline aluminum oxide has been measured over the temperature range 1300° to 1750°C. and at oxygen partial pressures of 10° to 10−10atmospheres. Alumina exhibitsp‐type conductivity at high oxygen pressures andn‐type conductivity at low oxygen pressures. The variation of conductivity with temperature depends on the specimen purity, oxygen pressure, and temperature level. Activation energies varying between 2.6 and 5.8 e.v. were found. The conductivity of alumina does not result from any single simple process over wide ranges of temperature and oxygen partial pressure. Apparently intrinsic conduction is found for single crystals at temperatures ab

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb13756.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb13757.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY