摘要:

AbstractA study has been made of the energy absorbed in rupturing a road binder film in a pendulum impact machine. At high temperatures the energy is absorbed by viscous traction, at low temperatures by elastic strain energy, and in the intermediate visco‐elastic region the energy rises to a marked maximum providing optimum conditions for stone retention by the binder.A standard test at − 10° gives an energy value, under conditions of brittle fracture, which is demonstrated to be suitable for comparing tars of known equiviscous temperatures and which reflects the width of the visco‐elastic peak, giving a measure of resistance to brittle failure of the

ISSN:0021-8871    

DOI:10.1002/jctb.5010190601

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe kinetics of alkaline hydrolysis of a variety of esters (liquid and solid), which are sparingly soluble in water, was studied by using the theory of mass transfer accompanied by fast pseudo first‐order reaction. This method, under certain conditions, can cover a wide range of second‐order rate constants (∼ 1 to 1041/g mole sec). Whenever possible the values of the rate constants obtained by the above method were compared with those obtained by a study of the kinetics in the homogeneous

ISSN:0021-8871    

DOI:10.1002/jctb.5010190602

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe formation of crystalline aluminium trihydroxides from aqueous suspensions of pseudoboehmite, obtained by the hydrolysis of aluminium s‐butoxide, has been examined byX‐ray diffractometry, nitrogen adsorption and dilatometry.The results obtained have been interpreted in terms of a mechanism involving dissolution of the pseudoboehmite. For those suspensions with which the recrystallisation was followed dilatometrically, first‐order kinetics were found, suggesting that random nucleation of trihydroxide crystals is involved. The rate of recrystallisation was decreased by the addition of organic solvents to the aqueous suspension and also, initially, by an increase in temperature. At the same time the proportion of gibbsite produced in admixture with bayerite was reduced and that of nordstrandite increased. It is concluded that the retardation is due, at least in part, to an increase in the crystallinity of pseudoboehmite which has been found to accompany the introduction of the organic solvents. The increased crystallinity must result in a decrease in the solubility and rate of solution of pseudoboehmite; under these conditions nordstrandite formation appears to be promoted.Neutron activation and spectroscopic analysis of hydroxide samples showed that storage of aqueous suspensions in glassware resulted in pick‐up of sodium and silica at the ppm level. The changes in these levels as recrystallisation occurred suggested that retention of the products of glass dissolution was occurring in a way which depended on the surface area of the hydroxide. No variation related to the phase composition of the trihydroxide mixtures was o

ISSN:0021-8871    

DOI:10.1002/jctb.5010190603

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractFlotation kinetics of calcite in a semi‐batch froth flotation system corresponds approximately to a second‐order rate equation, the order varying between 1·60 to 2·40 for different particle sizes and aeration conditions. Rate constant increases slightly with decrease in particle size and sharply with increase in air flow rate. It is postulated that flotation rate should depend on the magnitudes of solid/liquid and liquid/gas interfacial areas, besides other physico‐chemical par

ISSN:0021-8871    

DOI:10.1002/jctb.5010190604

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe reactivities of boron, aluminium and silicon nitrides have been compared. Samples of these nitrides have been converted to oxides by being calcined in air. Changes in phase composition, surface area, crystallite and aggregate sizes have been correlated with oxidation time and temperature.Crystallites of alumina, α‐Al2O3, split off from the remaining aluminium nitride before they sinter and inhibit further oxidation. The diboron trioxide, B2O3, and silica, SiO2(α‐cristobalite), immediately act as mineralisers for the remaining boron and silicon nitrides, and progressively retard the oxida

ISSN:0021-8871    

DOI:10.1002/jctb.5010190605

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe reactivities of the interstitial titanium and zirconium nitrides have been compared. Samples of these nitrides have been converted to oxides by being calcined in air. Changes in phase composition, surface area, crystallite and aggregate sizes have been correlated with oxidation time and temperature.Crystallites of rutile, TiO2, split off from the remaining titanium nitride before they sinter, and inhibit further oxidation. Zirconium nitride oxidation is complicated by formation of tetragonal ZrO2at higher temperatures, particularly over 1200°, and monoclinic ZrO2at lower temperatures. The nitride initially forms the so‐called ‘amorphous’ cubic ZrO2, notably between 400–600°, which may be stabilised somewhat by the remaining cubic ZrN. Subsequently, there is a further fractional volume increase while formation of monoclinic ZrO2is being

ISSN:0021-8871    

DOI:10.1002/jctb.5010190606

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

ISSN:0021-8871    

DOI:10.1002/jctb.5010190607

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

ISSN:0021-8871    

DOI:10.1002/jctb.5010190608

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY