Coated Sphere

The nature and the distribution of different types of Fe species in calcined (C) and steamed (S) samples were investigated by means of UV-vis spectroscopy. UV-vis spectra of Fe species were monitored on UV-vis spectrometer GBS CINTRA 303 equipped with a diffuse reflectance attachment with an integrating sphere coated with BaS04 and BaS04 as a reference. The absorption intensity was expressed using the Schuster-Kubelka-Munk equation. 

Fig. 35. The apparatus used by Ray et al. for the investigation of glycerol spheres coated with dioctyl phthalate. Reprinted with permission from Ray, A. K., Devakottai, B., Souyri, A., and Huckaby, J. L., Langmuir 7, 525-531, Copyright 1991, American Chemical Society.

I he field scattered by any spherically symmetrical particle composed of materials described by the constitutive relations (2.7)-(2.9) has the same form as that scattered by the homogeneous sphere considered in Chapter 4. However, the functional form of the coefficients an and bn depends on the radial variation of e and ju. In this section we consider the problem of scattering by a homogeneous sphere coated with a homogeneous layer of uniform thickness, the solution to which was first obtained by Aden and Kerker (1951). This is one of the simplest examples of a particle with a spatially variable refractive index, and it can readily be generalized to a multilayered sphere. 

A special anisotropic particle scattering problem has been treated by Roth and Dignam (1973), who considered an isotropic sphere coated with a uniform film with constitutive relations... 

UV-VIS-NIR diffuse reflectance (DR) spectra were measured using a Perkin-Elmer UV-VIS-NIR spectrometer Lambda 19 equipped with a diffuse reflectance attachment with an integrating sphere coated by BaS04. Spectra of sample in 5 mm thick silica cell were recorded in a differential mode with the parent zeolite treated at the same conditions as a reference. For details see Ref. [5], The absorption intensity was calculated from the Schuster-Kubelka-Munk equation F(R ,) = (l-R< )2/2Roo, where R is the diffuse reflectance from a semi-infinite layer and F(R00) is proportional to the absorption coefficient. 

Figure 4.2.5 Cross section of steatite spheres, coated with a mixed oxide having primary, cylindrical catalyst particles of approximately 200-300 nm in length and 150-180 nm in diameter.

Fig. 5. a SEM image of hollow Ti02 spheres, b TEM image of hollow Ti02 spheres. The spheres were produced after calcining 640 nm diameter PS spheres coated with four layers of Ti02 nanoparticles (5 nm diameter). Each nanoparticle layer was separated by three polyelectrolyte layers. The hollow spheres are composed of anatase crystals. (Adapted from [41] by permission of the American Chemical Society)... 

Fig. 8a-c. Electron microscopy images of hollow titania spheres prepared by calcination of PS spheres coated with seven layer pairs of TALH and PDADMAC at a,b 450°C c 950°C. a and b are hollow anatase (refractive index, n 2.5) titania spheres and c hollow rutile (n 2.6-2.9) macroporous titania spheres. (Adapted from [65], by permission of Wiley-VCH)... 

Snider and Perona3 measured Ksas, the volumetric liquid-solid mass-transfer coefficient, for the case of hydrogenation of a-methyl styrene on 3-mm alumina spheres coated with palladium catalyst. The results were obtained in the bubble-flow regime. The measurements of Ks, the liquid-solid mass-transfer coefficient in a nonreacting system, were first reported by Mochizuki and Matsui.20 They... 

If only a small amount of solid sample is available, it should be placed in the center of a sapphire or suprasil sphere coated with a reflecting layer at those parts of the surface which is not used for illumination of the sample or for observing the Raman radiation (Schrader, 1987) but which have an antiflection coating at these parts. 

Miller RA, Leung EM, Oates RJ. The compression of spheres coated with an aqueous ethylcellulose dispersion. Drug Devel Ind Pharm 1999 25(4) 503-511. 

Mohs hardness 7 (AgCLAD, thick-walled spheres coated with silver), 5-6 (Metalite, glass light spheres coated with silver)... 

AgCLAD TW and Filament 32 - a thick-walled spheres and fiber coated with silver, respectively Metahte SG, CG, SF-20 - light hollow glass spheres coated with silver Toho Rayon Co., Ltd, Tokyo, Japan... 

Figure 2.39. SEM micrographs of silver-coated flakes and spheres. Upper left - Novamet silver coated nickel flakes, upper right - Conduct-O-Fil SC230F8, silver coated copper flakes, bottom - Conduct-O-Fil solid glass spheres coated with silver, left - spheres at lOOx magnification, right - spheres in silicon resin. Courtesy of Novamet Specialty Product Corporation, Wyckoff NJ, USA and Potters Industries, Inc., Valley Forge, PA, USA.

The tip and sample interaction is depicted in Figure 15.14. The data of such studies have been reported on silica surfaces. These measurements showed the deflection of the cantilever between the silica plate and the glass sphere coated with octadecyltrichlorosilane. It is of interest to note that AFM is a very sensitive molecular force microscope. The forces measured by AFM are of the order of 10,000 to 1(X),000 times lower than an insect ( 1 mg) sitting on a surface ... 

Kotler and Nitzan" applied the electrostatic limit to a silver sphere coated with a dye. They found also in this case a double-peak behavior, under certain circumstances. Noteworthy, are the enhancements of the Raman scattering of up to —10", near the particle plasmon resonance. (For their model of a sphere it is at 3.5 eV but for other shapes it can be brought into the visible range). The enhancement is very weakly dependent on the distance from... 

Fig. 9. Normalized UV-visible spectra of dilute dispersions of 640 nm latex spheres coated with five monolayers of Au Si02 nanoparticles. The thickness of the corresponding silica shells is indicated. The trends are consistent with the predictions of Eq. (15) but quantitative agreement is not possible due to the higher volume fraction of the shells in experiments...

The schematic setup of a diffuse reflectance spectrometer which is obtained by supplying a normal UV-VIS spectrometer with a diffuse reflectance accessory is shown in Fig. 18. The core is an integrating sphere coated with a highly reflective material that collects the scattered radiation and leads it to the detector. The light remitted by the sample is compared with that of a white standard as the reference. Zeolite layers of ca. 5 mm depth are generally sufficient to meet the condition of infinite thickness. A typical sample cell furnished with an evacuated Infrasil double window and designed for temperature control and evacuation is depicted in the lower part of Fig. 18 [32]. Other cell constructions have been reported by Klier [31] and Schoonheydt [34]. 

Fig. 24 a Strapped porphyrin cleft 29 as receptor for the synthesis of rotaxanes [67] b gold nanoparticles shaded sphere) coated with methyl-imidazole to bind ZnTPP or triporphyrins [70] c self-assembled mixed multilayers of porphyrins on gold surfaces [72]... 

The fuel pins used in the core are a new type for OCR s. The vast majority of OCR reactors use a TRISO type fuel embedded in a graphite matrix and are thermal neutron spectrum reactors. TRISO fuels are small UC spheres coated with layers of silicon carbide and pyrolitic carbon. While this results in fuels that can be used to extremely high bumup, the uranium density of the fuel is low. A coolant hole is then drilled through the blocks of fuel and these blocks are put in a prismatic array. 

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