Dispersion external surface

Internal surfaces were covered with a tan deposit layer up to 0.033 in. (0.084 cm) thick. The deposits were analyzed by energy-dispersive spectroscopy and were found to contain 24% calcium, 17% silicon, 16% zinc, 11% phosphorus, 7% magnesium, 2% each sodium, iron, and sulfur, 1% manganese, and 18% carbonate by weight. The porous corrosion product shown in Fig. 13.11B contained 93% copper, 3% zinc, 3% tin, and 1% iron. Traces of sulfur and aluminum were also found. Near external surfaces, up to 27% of the corrosion product was sulfur. 

Table 2.7 lists techniques used to characterise carbon-blacks. Analysis of CB in rubber vulcanisates requires recovery of CB by digestion of the matrix followed by filtration, or by nonoxidative pyrolysis. Dispersion of CB within rubber products is usually assessed by the Cabot dispersion test, or by means of TEM. Kruse [46] has reviewed rubber microscopy, including the determination of the microstructure of CB in rubber compounds and vulcanisates and their qualitative and quantitative determination. Analysis of free CB features measurements of (i) particulate and aggregate size (SEM, TEM, XRD, AFM, STM) (ii) total surface area according to the BET method (ISO 4652), iodine adsorption (ISO 1304) or cetyltrimethylammonium bromide (CTAB) adsorption (ASTM D 3765) and (iii) external surface area, according to the dibutylphthalate (DBP) test (ASTM D 2414). TGA is an excellent technique for the quantification of CB in rubbers. However, it is very limited in being able to distinguish the different types of... 

Layered materials are of special interest for bio-immobilization due to the accessibility of large internal and external surface areas, potential to confine biomolecules within regularly organized interlayer spaces, and processing of colloidal dispersions for the fabrication of protein-clay films for electrochemical catalysis [83-90], These studies indicate that layered materials can serve as efficient support matrices to maintain the native structure and function of the immobilized biomolecules. Current trends in the synthesis of functional biopolymer nano composites based on layered materials (specifically layered double hydroxides) have been discussed in excellent reviews by Ruiz-Hitzky [5] and Duan [6] herein we focus specifically on the fabrication of bio-inorganic lamellar nanocomposites based on the exfoliation and ordered restacking of aminopropyl-functionalized magnesium phyllosilicate (AMP) in the presence of various biomolecules [91]. 

In order to combine the catalytic activity of highly dispersed metal species and that of zeolites, metals can be deposited in the pores and on the external surface of zeolite particles. In this way, a catalyst is formed with both a metal functionality, e.g., redox or hydrogenation activity, and an acidic function. The metals can be deposited by different methods. Impregnation of a zeolite with a metal... 

High Diffusivity Low Viscosity Figure 15.21 Proposed mechanism of PtRh nanoparticles highly dispersed in HMM-1, which is prepared by H2 reduction of the PtRh salt-impregnated in FSM-16 or HMM-1 after the SCCO2 treatment, while the larger Rh and Pt particles are formed on the external surface of mesoporous supports by the conventional method. 

UV-Visible diffuse reflectance spectra also show that vanadium is mainly present as V in V-containing silicalite samples. TPR and XPS results are in agreement with this conclusion. In addition, XPS data indicate that V is homogeneously dispersed in VSU545, whereas in VSill 17 part of the vanadium is segregated on the external surface of the silicalite samples. 

Methane dehydroaromatization on zeolites Mo/HZSM-5 was also investigated by solid-state MAS NMR spectroscopy 162. Both variation of the state of the transition metal component and products (such as ethane, benzene, and ethylene) adsorbed in zeolite were observed after reaction at high temperature (900-1000 K). Molybdenum carbide species, dispersed on the external surface or in the internal channels of the zeolite catalysts, had formed during the reaction 162. ... 

Kubo et al. (3) and Boudart et al. (4) showed the effectiveness of the zeolites for preparing well dispersed platinum catalysts. Ni(I)-zeolites were also subjected to hydrogen reduction the data gave strong evidence that nickel was not atomically dispersed and that metal atoms diffuse out of the pores to form crystals at the external surface of the zeolite (5,6). 

Allows a better dispersion of molybdenum trioxide from the external surface of the mesoporous support into its internal nanochannels. The active sites (possibly pairs of neighboring molybdenum cations) thus increases. As the result of better dispersion, the reduced molybdenum oxide species formed during the course of reaction through its entire surfaces and thus lowers the possibility of sintering in a reduced environment. Here, we see that the deactivation rate is the highest in Mo/Si02 catalyst due to the lowest surface area. 

Spontaneous wetting of the external surface of a solid is associated with zero contact angle, otherwise some work is necessary for complete wetting to be achieved. In the case of a powder we must also consider the penetration of liquid into the small channels inside and between the aggregates of the dry powder, and this is theoretically spontaneous only when 0 < 90° (assuming a hypothetical cylindrical pore). It may therefore be assumed that for the powder to be dispersed in the liquid as fine particles it is necessary for 0 < 90°, and that only when 0 = 0 would we expect the whole wetting process to be spontaneous—i.e.,... 

In dispersive mixing the clusters of particles held together by cohesive forces (agglomerates) are successively broken apart by hydrodynamic stresses imposed on the external surfaces of the deforming liquid matrix, which in turn generate internal stresses within the cluster (40). A detailed review of dispersive mixing was given by Manas-Zloczower (41), and in this section we will follow her discussion. 

Figure 7.67 shows an extremely irregular attack of the external surface of a longitudinal section of rock bolt. The presence of the oxide layer in Figure 7.67 and the dispersion of a metallic piece in Figure 7.68 support the analysis that, for this particular rock bolt, corrosion attack was rigorous and probably contributed in the failure of the rock bolt. 

Sylvester and Pitayagulsarn53,54 considered combined effects of axial dispersion, external diffusion (gas-liquid, liquid-solid), intraparticle diffusion, and the intrinsic kinetics (surface reaction) on the conversion for a first-order irreversible reaction in an isothermal, trickle-bed reactor. They used the procedure developed by Suzuki and Smith,51,52 where the zero, first, and second moments of the reactant concentration in the effluent from a reactor, in response to a pulse introduced, are taken. The equation for the zero moment can be related to the conversion X, in the form... 

Sprays Medicated liquids prepared for dispersal by atomizers or nebulizers, usually on external surface or mucous membranes of the respiratory tract. In the United States Pharmacopoeia, sprays were called inhalatio the National Formulary referred to them as nebulae. Sprays of the early twentieth century were formulated with aromatics dissolved in light mineral oil. As injuries from inhaled oils became apparent, especially among children, these sprays were displaced by buffered aqueous solutions. ... 

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