摘要:

A study was made of the bloating mechanism in two clays which contained large amounts of organic carbon, alkalis, and sulfates. Controlled preheating of spherical pellets at about 550oto 600° C. for relatively short times caused the loss of organic carbon and other gas‐forming constituents from the outer rim of the specimens. A second flash firing at about 1250oC. produced a partly liquefied rim, which trapped gas formed in the central portion. The pellets thus formed were characterized by a large central cavity and a strong porous wall. Variation of firing times, temperature, pellet sizes, and composition allowed considerable control of the nature of the final bloated pellets. It was concluded that bloating was caused by the formation of SO2and CO. The specific gravity of such pellets was between 0.45 and 0.60. They could be produced in all sizes and fell within the A.S.T.M. specifications C 130‐42 (Lightweight Aggregates for Concr

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb11662.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

The microstructure of massive, sugary, and mylonitic varieties of raw chrome ores has been examined with the aid of polished sections and the difference in the surface area and homogeneity of the natural chromite spinels has been noted. The behavior of the chromite spinels on oxidation, reduction, and with and without the additions of magnesia is illustrated in a series of photomicrographs; the complex reactions occurring are discussed briefly and their significance in the behavior of chrome ore‐containing refractories in slag‐free environments is indicated. The usefulness of reflected‐light techniques in studying diffusion phenomena is shown for several solid‐state reactions, including the formation of synthetic spinels, artificial modifications of a natural spinel, and iron oxide b

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb11663.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

Pyrolytic graphite is a vapor‐deposited form of carbon which is characterized by strong anisotropic properties. The anisotropy is caused by the tendency of the individual crystallites to align themselves in such a way that their c axes are perpendicular to the surface of deposition. The Individual crystallites are composed of parallel graphitic layers which are randomly oriented with respect to the c axis. The ultimate strength of pyrolytic graphite in tension, bending, and compression has been found to increase considerably with increasing test temperatures. Other properties such as thermal conductivity and electrical resistivity give extremely high and low conduction parallel and perpendicular to the basal planes, respectively, in addition to varying considerably with increasing test temperatures. Properties are also influenced by the as‐deposited microstructure and by the amount of graphitization to which the material has been subjected. The properties and possible uses of this unique material are presented, discussed, and compared with the properties of other high‐temperature mate

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb11664.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

The viscosity‐temperature relation for the network liquids is considered in the light of the results for associated liquids and polymers. A critical examination of all the data available indicates that for liquid B2O3, SiO2, and BeF2the energy of activation for flow is temperature dependent. Liquid GeO2is possibly an anomaly. Empirical equations which satisfactorily describe the viscosity of associated liquids are not applicable to liquid B2O3and SiO

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb11665.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

The glass formation of the aluminoborates of Group II metal oxides depends on the atomic weight of the oxide and on the electronic configuration of the metal ion. The participation of zinc, cadmium, and magnesium ions as network formers in the glass is shown from measurements of thermal expansion. The linear thermal expansion of the alkaline‐earth aluminoborates varies from 4.7 × 10−6to 16 × 10−

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb11666.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

Electron micrographs were made of replicas of a weathered soda‐lime glass surface before and after various chemical and fire polishing treatments. These micrographs were compared with an electron micrograph of a replica of a fractured soda‐lime glass surface which was used as a typically smooth surface. Using this comparison, the smoothest surfaces were formed by dilute hydrofluoric acid, dilute phosphoric acid, sodium citrate solution, a solution of the disodium salt of ethylenediaminetetraacetic acid, and a fire polish‐water wash combination. On the other hand, alkaline solutions tended to roughen the glass surface and leave residues on it. Selected electron micrographs are shown to illustrate the effect of these treatments on soda‐lime‐t

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb11667.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

The rate of nickel ferrite formation is influenced by the milling technique and in the case of wet milling by the type of liquid media used. The reactivity of different types of α‐Fe2O3of spherical shape decreases with an increase of the surface area ratio of α‐Fe2O3to NiO. The particle shape of the iron oxides also affects their reactivity; cubical α‐Fe2O3has the least reactivity in the formation of nickel ferrite. The validity of Jander's equation in ferrite formation is reviewed. Based on present findings the rate of ferrite formation is best represented by the equationdx/dt= (a‐x)/t, in whichxis the percentage of ferrite formed,tthe time, andathe kinetic isothermal reaction rate coefficient which is related to the surface area ratio of the reacting oxides. The application of the foregoing equation to the formation of magnesium ferrites from data found in the literature is also sa

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb11668.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

The conversion of boehmite to transition aluminas and to alpha (corundum) was studied with (a)fibrillar colloidal boehmite, about 50 a.u. in diameter,(b)finely divided boehmite in the form of thin elongated platelets, and(c)macroscopic boehmite crystals. In the range 500oto 700oC.,(a)was converted to fibrillar gamma, essentially unchanged in size or shape,(b)was dehydrated to gamma, but the platelets appeared to be partly cracked longitudinally about every 70 a.u., and(c)was similarly cracked into much smaller crystallites of gamma. At about 1000oC.,(a)yielded only rodlike theta alumina, whereas(b)and(c)appeared to give a mixture of theta and delta aluminas, characterized by round holes or pores developed from the cracks. In the range 1000oto 1100oC., all the aluminas were converted to alpha, at a rate which was strongly dependent on temperature. The conversion of(a)and(b) to alpha could be followed by subsequent examination with the electron microscope. The alpha crystals, once nucleated, apparently grew rapidly to 0.5 or 1.0μin size, since there was no evidence of smaller alpha crystals. The smaller alpha crystals appeared to grow while embedded in a glassy matrix which must have been amorphous alumina. This phase acted as a bridge between the diminishing theta particles and the growing alpha crystals and may have consisted of the alumina which was in the process of being transported

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb11669.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY

摘要:

The relations between the structure, crystal chemistry, chemical bonds involved, and the infrared spectra of layer‐structure silicates established on the basis of recent experiments are discussed and summarize

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1961.tb11670.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.tb11671.x

出版商:Blackwell Publishing Ltd    

年代:1961

数据来源: WILEY