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J. D. BUTLER  H. BROWN 《Strain》1970,6(2):67-70
A pneumatically operated lifting mechanism and a fluidic control system have been added to an Izod impact testing machine for automatic repetition and counting of impacts from an adjustable preset striking height of the pendulum hammer and for automatic stopping of the machine on failure of the specimen.  相似文献
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Small-angle neutron scattering data, taken as a function of time from initiation of gelation in colloidal silica suspensions, with silica mass fractions ranging from 15 to 30%, are presented. Over a wide range of initial pH, the measured structure factor S(q) contains a low angle peak that, as time progresses, grows in height and moves to lower wave vectors q. Sometime after the gels have set, this peak stops growing, marking the end of the reaction. The data scale according to the relation, S(q,t)~ (t) (q/q m (t)) , where q m(t) is the wave-vector location of the low angle peak as a function of time t from initiation, d f is a fractal dimension, and is a characteristic structure function. The exponent d f is insensitive to the silica mass fraction but that the form of is mass fraction dependent.  相似文献
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The complexes formed in aqueous mixture suspensions of the synthetic clay mineral Laponite and cetyltrimethylammonium bromide (CTAB) have been investigated by small-angle neutron scattering (SANS). All suspensions were prepared with a constant initial concentration of Laponite, but the amount of CTAB was varied. The SANS intensity patterns verify that suspended Laponite in dilute suspension is in the form of disks of diameter 30nm and thickness 1 nm. SANS indicates that this disk morphology, with the same diameter but with a thickness of about 4 nm, is retained for the suspended complexes, even if the CTAB in the aqueous medium is in considerable excess. SANS and chemical analysis show that a complex must adsorb CTAB to an amount corresponding to at least two multiples of the clay's cation exchange capacity to be dispersed. The amount of CTAB adsorbed as a function of CTAB in the precursor solution is discussed. We also report the effect the presence of clay on CTAB micelle formation as a function of CTAB concentration.  相似文献
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