No abstract

No abstract

Successful synthesis of stable MFe2O4 nanoparticles@C has been realized by applying the novel concept of using levulinic acid possessing carboxyl and carbonyl groups to facilitate the interaction with metal ions (M(2+) and Fe(3+)) and the carbon source (phloroglucinol) in the sol-gel polymerization method. All the samples have been characterized by XRD, SEM, FT-IR, TEM, HRTEM, ICP-AES, CHNS, and N2 adsorption-desorption, and were studied for their performance towards hydrogenation reaction of styrene. Out of three samples NiFe2O4 gave excellent selective hydrogenation activity of styrene to ethyl benzene (100% conversion and 100% selectivity). Optimal production of ethyl benzene over NiFe2O4 nanoparticles@C has been established at 80 °C reaction temperature after 24 h reaction time under 40 bar hydrogen pressure.

In order to determine how bolted joints behave under conditions of tensile external loading, tests were conducted on bolts which had been tightened into joints by means of (a) elastic range, (b) yield, and (c) over-yielding tightening. The loading tests showed that the maximum clamp load which the bolt would exert on the joint without permanent extension was the uniaxial tensile yield load of the bolt. This was observed even when torsional stress was present in the as-tightened bolt, and for all three tightening methods.

Viscosity changes in concentrated natural rubber latex under different experimental conditions were investigated with the object of determining the mechanism of zinc oxide thickening and to find reasons for inconsistencies in correlating results of the zinc oxide thickening or ZOT test with other latex tests. It has been found that small variations of the amount of naturally occurring soap are of great importance in the thickening of latex containing zinc oxide, especially at the low ammonia content used for the ZOT test. The effect of added soap on the ZOT test was found to vary from latex to latex and to be different for different soaps. Less than about 0.3 per cent of various soaps added to latex prior to the zinc oxide reduced the degree and rate of thickening. With more than this amount of soap, the thickening depended on the soap used. A similar investigation in which the mechanical stability of latexes containing varying amounts of added soap and a standard amount of zinc oxide was measured, showed that the latexes varied anomalously with the amount and the type of soap added. The results of the work presented in this paper show that new tests for the zinc sensitivity of latexes must take into account a number of hitherto unsuspected factors, particularly when such tests are required to have a bearing on processing behavior.