Microscopic metals metal blacks

The TEM is one of the most generally useful microscopes many thousands of them ate in daily use throughout the world. They ate appHcable to the study of ultrafine particles (eg, pigments abrasives and carbon blacks) as well as microtomed thin sections of plant and animal tissue, paper, polymers, composites of all kinds, foods, industrial materials, etc. Even metals can be thinned to sections thin enough for detailed examination. 

Metal hydrogenation catalysts may be employed in any one of a variety of forms (a) macroscopic forms as wires, foils or granules (b) microscopic forms as powders obtained by chemical reduction, colloidal suspensions, blacks or evaporated metal films (c) supported catalysts where varying concentrations of metal are dispersed to a varying degree on a carrier such as alumina, silica or carbon. 

The tri-iodide forms black, very hard, metallic, glistening needles, M.pt. 65° C., possessing a vile smell and somewhat volatile above 100° C. It is insoluble in water, somewhat soluble in hot alcohol or ether. The platinichloride forms yellow, microscopic, quadratic plates, blackening at 100° C., insoluble in water or alcohol. 

Sections for microscopic examination were mounted in poly (methyl methacrylate) and polished to a 0.1/ finish. Examination of reflected light revealed the metallic particles as white features against a black continuous background of PVC. Evidence that the samples were homogeneous from one plane to another was provided by estimating the volume fraction of metal by quantitative metallography (6) in every case estimates were within 2% of the made-up values. 

In the case of powders, if the particles are of fairly simple form, the surface area (excluding submicroscopic cracks) can be estimated from microscopic measurement of the size of the particles.5 Powders, or porous solids composed of aggregations of small particles, can have the particle size approximately estimated by the width, and imperfection of definition, of the lines in an X-ray diffraction photograph.6 This method has been used by Levi and others7 for finely divided metal such as platinum black the particles were usually extremely small, of the same order of size as the particles in a colloidal sol of the metal. For the platinum group, the size of crystalline particles was estimated as from 20 to 120 A. across only. 

When platinum wire is heated in ammonia gas at 800° C., its surface becomes dull, and shows a more or less blistered appearance under the microscope. A fine deposit of platinum black also gradually collects on the surface of the metal due to disintegration of the compact platinum.5... 

Ghromous Thiophosphite, Cr3(PS3)2, is prepared by heating metallic ehromium with a mixture of sulphur and red phosphorus to a cherry-red heat in a closed vessel for twenty hours. It yields black, hexagonal, microscopic crystals, possessing metallic lustre. 

Adams et al. [78,79] have reported a series of synthesis of mixed-metal cluster compounds. One example, Pt2Ru4(CO)is, is depicted in Figure 1(b). This mixed cluster compound was investigated to study the effect of Pt-Ru nanoparticles developed after the precursor annealing on carbon [80]. In line with the spectroscopic and microscopic measurements, the authors demonstrated that mixed Pt-Ru nanoparticles, with an extremely narrow size distribution (particle size 1.4nm), reflect an interaction that depends on the nature of the carbon support. Furthermore, as revealed by EXAFS, the Pt-Pt, Pt-Ru, and Ru-Ru coordination distances in the precursor (2.66, 2.64, and 2.84 A) [79] changed to 2.73, 2.70, and 2.66 A, respectively, on the mixed-metal nanoparticles supported on carbon black, with an enhanced disorder [80]. Furthermore, some metal segregation could be... 

After cutting a specimen of AlN/W FGM in the direction of the gradient, we polished the surface to a mirror finish and observed the microstructure by Scanning Electron Microscope. Photo 1 shows the results of backscattered electron image of the microstructure. The black distributed areas are metallic tungsten particles. The dispersed particles are also distributed inside the aluminum nitride crystal grain and grain boundary. 

The inactivity of Graphon in the contacts with the white solids despite the near equivalence of its work function with that of BPL demonstrates an absence of coupling of the delocalized tr electron system of Graphon with the localized Bronsted and Lewis sites of the white solids. It is to be noted that electron transfer between the tt electron systems of different carbon blacks occurs quite readily. The oxide structures of carbon blacks are seen to play a fundamental role in this viewpoint at the microscopic level akin, for example, to the critical importance of the molecular structures of the adsorbates in chemisorption from the gas phase onto metals (41, 42) and metal oxides(43). 

Many attempts have been made to produce the diamond artificially. In 1880 Hannay obtained diamonds of microscopic size by heating to dull redness for many hours a mixture of paraffin and bone oils with metallic lithium in a closed wrought-iron tube. On opening the tube minute isotropic crystals were extracted from the black residue they were sufficiently hard to scratch all other crystals. For many years doubt was expressed as to the identity of these crystals with diamond, but X-ray examination has justified Hannay s claimf. 

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