ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1957.tb12599.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

The formation and removal of black cores in structural clay products was studied to provide the industry with a broader understanding of this defect. Analytical procedures indicated that carbonaceous matter was responsible for the formation of black cores, but the properties of the core were actually dependent on the state of oxidation of the iron. For the removal of black cores, time, temperature, and kiln atmosphere were varied to find the optimum conditions for core oxidation. Such conditions were found at higher temperatures than were usually recommended and with more excess air than was heretofore thought necessary. Ammonium compounds were incorporated into clay bodies to assist in core oxidation. The action of these reagents was found to be more mechanical than chemical. Ammonium chloride and ammonium hydroxide increased the porosity of the ware in such a way as to allow a better penetration of oxygen into the center. These additions greatly accelerated the oxidation of clay products, but they did not substitute for atmospheric oxygen. The experiments conducted indicated the importance of cooling as an oxidation period.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1957.tb12600.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

An examination was conducted to determine the mechanism of peeling of fire‐clay brick in the low‐temperature region of a blast furnace where 3 to 10% K2O is the principal contaminant. In laboratory tests, as‐received high‐duty and superduty fire‐clay brick and 70% alumina brick treated with KCl‐K2CO3mixtures showed no peeling at a temperature of 1600°F. Cracks were found in high‐duty brick that were treated with KCN at 1500°F. under partially reducing conditions. X‐ray diffraction studies of mixtures of crushed brick and K2CO3indicated the formation of leucite (K2O.Al2O3.4SiO2) and kaliophilite (K2O.‐Al2O3.2SiO2) at temperatures below 1700°F. These latter data, confirmed by specimens from used blast‐furnace linings, showed that silica is the first constituent attacked by alkali. Since the formation of leucite and kaliophilite in fire‐clay brick is the probable cause of peeling, the increased reaction of silica, in a dense Al2O3.SiO2refractory of higher silica content than fire‐clay brick, should confine the alkali attack to the surface of the brick in lo

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1957.tb12601.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

The addition of 0.25% or more of certain lithium compounds, particularly the halides, facilitates the pressing and sintering of reactive forms of high‐purity magnesium oxide. Densities up to 3.46 gm. per cm.3have been obtained at 1400°C. with reagent‐grade magnesium oxide containing 0.5% lithium chloride as an additive. The effectiveness of lithium salts as sintering catalysts for magnesium oxide depends on the original surface area and particle size of the MgO. After autoclaving at 150 lb. per sq. in. gauge for 2 hours, samples of MgO sintered at 1400°C. with 0.5%of LiCl showed a water absorption comparable to that of fused magnesium oxide. Similar samples of lithium‐treated periclase had about the same resistance to attack by a NaOH‐FeO melt as pure MgO fired at 1800°

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1957.tb12602.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

The microstructure of polycrystalline barium titanate as seen in polished and etched specimens is more complicated than that in the single crystal. The greater complexity is revealed in the form of a banded structure which is considered to be due to the stress configuration arising from mutual impingement of randomly oriented grains during the cubic‐tetragonal phase transformatio

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1957.tb12603.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

From the ternary phase diagrams of Al2O3–SiO2with CaO, MgO, or FeO, it can be concluded that the free energies of formation of kyanite, andalusite, and sillimanite, according to the reaction Al2O3+ SiO2= Al2O3.SiO2, are of the order of magnitude of 0 to –10 kcal. rather than the previously accepted value of –40 to –45 kcal. However, this result may be expected from the general variation of free energies of formation with the ionic potential of the silicate‐forming cation; this conclusion is supported by a plot for some silicates, carbonates, and

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1957.tb12604.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

A series of ferrites was prepared in the form Ni1‐αCoαFe2O4, where α varied from 0.00 to 0.05. It has been shown experimentally that the width of the curve of magnetic loss versus magnetic field can be minimized by the proper value of α. The large crystal anisotropy of cobalt enables one to choose the composition where the resultant crystal anisotropy constant should equal zero. Techniques are discussed which could increase the resistivity of these fer

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1957.tb12605.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Survey experiments have been made to find the effect of pressure on relaxation rates and volume in the transformation range of glass. An empirical equation used to describe relaxation effects for volume changes at atmospheric pressure has been extended to describe the influence of pressure. Data for glass cooled at a constant rate through the transformation range under pressure are adequately described by this empirical equation. The effect of pressure on the volume of liquid glass has been measured indirectly using a sample rapidly cooled under pressure, providing an approximate value for the compressibility of liquid glass.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1957.tb12606.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY