Effect of silica particle size

The results of the studies on the effect of silica particle size on sorption indicate that, in the range of silica diameter of 1.4 X 10 2 to 3.9 X 10 2 cm, there is very little difference in the final amount of plutonium sorbed, as shown in Table III, the total weight of silica being the same for each size fraction. The only differences lie in the surface density of the sorbed species and the rate at which the equilibrium was approached. As the surface area decreased (i.e., as the silica size increased), there was more plutonium deposited per unit area of surface. Also, the smaller size particles with the higher surface areas sorbed the plutonium at a faster rate. These results are difficult to interpret, except with the model of a limited number of sorbable species, all of which are taken up eventually by the silica. They would not, however, be consistent with the model of a limited number of sorbing sites. 

Moshtaghioun BM, Monshi A, Abbasi MH, Karimzadeh F (2011) A study on the effects of silica particle size and milling time on synthesis of silicon carbide nanoparticles by carbothermic reduction. Int J Refract Metal Hard Mater 29 645-650... 

M.-R. Pourhossaini, M. Razzaghi-Kashani, Effect of silica particle size on chain dynamics and frictional properties of styrene butadiene rubber nano and micro composites. Polymer, ISSN 0032-3861 55 (9) (April 25, 2014) 2279-2284. http //dx.doi.0rg/lO.lOl6/j. polymer.2014.03.026. 

R. A1 Akoum, B. Haidar, A. Vidal. Effect of silica particle size on polymer adsorption. Morphological, energetic and conformational relationships. Macromol. Symp., 221,271-280,2005. 

It was shown that the effect of the particle size is not significant in HOPC (1). The experiments were conduced using silica gels of the same pore size but with a different average particle size between 15 and 100 /urn. A kinetic effect— enrichment of the mobile phase with high MW components is better at short times before equilibrium is reached—was cited as a possible reason for almost equal quality of separation by large particles. The back-pressure problem was not serious in that range of the particle size. 

Stone et al. (S29) developed by a mathematical analysis the functional relationship between the rate of extraction of silica from pure quartz in sodium hydroxide solution and time, temperature, sodium hydroxide concentration, and particle size. With the use of response surface methodology, a comprehensive picture of this dissolution process was obtained from a few well-chosen experiments. The fractional extraction of silica can be expressed by a second-order equation. The effect of quartz particle size and temperature are predicted to be about equal and greater than the influence of sodium hydroxide concentration and reaction time. The reaction rate is controlled by the surface area of the quartz. An increase in sodium hydroxide concentration increases the activation energy for the reactions and is found to be independent of quartz size. 

Major results Figure 14.16 shows the effect of mean particle size of spherical silica (flame-fused synthetic silica) on acoustic emission. The emission increases with the particle size of filler increasing. The source of this increase in acoustic emission is thought to be related to the fracture of particles, debonding of particles from... 

Figure 14.16. The effect of mean particle size of silica on total acoustic emission of epoxy filled with 70% silica. [Data from Ohta M, Nakamura Y, Hamada H, Maekawa Z, Polym. Polym. Composites, 2, No.4, 1994, 215-21.]...

The selection of the carrier is relatively simple. It may be imposed by the type of reaction to be promoted. For instance, if the latter requires a bifunctional catalyst (metal + acid functions), acidic supports such as silica-aluminas, zeolites, or chlorinated aluminas, will be used. On the other hand, if the reaction occurs only on the metal, a more inert support such as silica will be used. In certain cases, other requirements (shock resistance, thermal conductivity, crush resistance, and flow characteristics) may dominate and structural supports (monoliths) have to be used. For the purpose of obtaining small metal particles, the use of zeolites has turned out to be an effective means to control their size. However, the problem of accessibility and acidity appearing on reduction may mask the evidence of the effect of metal particle size on the catalytic properties. 

Vedenyapin A.A., Klabunovskii E.I., Talanov Yu.M., Areshidze G.Kh. (1978) Effect of the particle size of Rulheniiun in Ru-silica catalyst for its catalytic and as3mimetrizing properties, Izv. Acad. Sci. SSSR. Ser. Khim. 2628-2630, Chem. Abstr. 86, 89128u (1977). 

The effect of the particle size on the DRIFTS intensity for a monolayer of dodecyl amine adsorbed on quartz particles is shown in Figs. 2Ala, b. The spectral contrast is higher for the <5-p,m fraction than for the 38-150-p.m one. This is akin to the data for adsorption of a photosensitizer on silica gel [115]. The results of Kim and co-workers [168] indicate that contrast of the DRIFTS of 4-dimethylaminobenzoic acid adsorbed on 2-3.5-p,m Ag particles, for which the SEIRA phenomenon is expected, and 30-nm Ti02 powder is practically identical. For both DRIFTS and DTlF l S, the particle size should be smaller than the shortest wavelength in the spectral range, as particles of a size comparable to the... 

Fig. 8 Effect of limestone particle size on free CaO content at various burning temperatures (from Lehman/Locher/Thormann, 1964) dp — average particle size of a fraction lime standard KStI = 96 silica modulus = 3.0 alumina modulus = 2.2 At/At = 5to K/min. t = 30min. clay component illite...

S. H. Overbury, L. Ortiz-Soto, H. G. Zhu, B. Lee, M. D. Amiridis, and S. Dai, Comparison of Au catalysts supported on mesoporous titania and silica Investigation of Au particle size effects and metal-support interactions, Catal. Lett. 95(3-4), 99-106 (2004). 

The service performance of rubber products can be improved by the addition of fine particle size carbon blacks or silicas. The most important effects are improvements in wear resistance of tire treads and in sidewall resistance to tearing and fatigue cracking. This reinforcement varies with the particle size, surface nature, state of agglomeration and amount of the reinforcing agent and the nature of the elastomer. Carbon blacks normally are effective only with hydrocarbon rubbers. It seems likely that the reinforcement phenomenon relies on the physical adsorption of polymer chains on the solid surface and the ability of the elastomer molecules to slip over the filler surface without actual desorption or creation of voids. 

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