Cobalt distribution

Concentration profile of cobalt distribution throughout the sample thickness were constructed by means of micro-X-ray-spectral analysis (MXSA). The regime with the optimal correlation of the parameters mco/m(Ti-c) Pk ti t2 was determined. A complex of parameters was considered as the optimal one when the cobalt layer was melted at the expense of the heat of chemical reaction Ti + C -l- Co -> TiC + Co and... 

Figure 2 presents the concentration profiles of cobalt distribution through the thickness of FGM samples, produced by the SHS-densification technology with the... 

Fig.2. Cobalt distribution on the thickness of diamond containing FGM with (TiC-l-Co) binder, produced at the different relationship of mass layers mco/mri+c+co 28/56 (1) 20/56 (2) 13/56 (3).

All samples were analyzed by means of X-ray diffraction and elemental analysis. Additionally, the cobalt distribution throughout the samples was studied by means of scanning electron microscopy in combination with electron microprobe analysis. Prior to the measurements, the samples were imbedded in resin, cut and subsequently polished with diamond paper. 

We have previously described various important aspects of the alumina support including pore size distribution and alumina phase (Rytter et al., 2002b). A few of these effects will be described in further detail. Generally it is found that for comparable y-aluminas with normal surface areas in the range 170-200 m /g, the Cs+ Selectivity increases with pore volume and pore diameter as depicted in Fig. 3. This effect has also been verified for a larger selection of supports and the nature of it, e.g. in terms of surface diffusion, cobalt distribution or support reactivity, is being looked into. 

Cobalt Distribution Ratio. Extraction Rate and Optimum Extraction pH Value... 

It is showed in Figure 3 that when the mass of the resin is 2g and the pH value is smaller than 4.5, the cobalt extractive content increased with the increase of pH value. When the pH value of the solution is larger than 4.5, the cobalt extractive content is trends to become stable. At this moment, both the cobalt distribution ratio and the extraction rate get the best results. However, when the pH value is too high, the extracted residual liquid is easy to emerge precipitation. Therefore, the pH value of the initial solution should be controlled at 4.6 4.8. 

Cobalt compounds have been in use for centuries, notably as pigments ( cobalt blue ) in glass and porcelain (a double silicate of cobalt and potassium) the metal itself has been produced on an industrial scale only during the twentieth century. Cobalt is relatively uncommon but widely distributed it occurs biologically in vitamin B12 (a complex of cobalt(III) in which the cobalt is bonded octahedrally to nitrogen atoms and the carbon atom of a CN group). In its ores, it is usually in combination with sulphur or arsenic, and other metals, notably copper and silver, are often present. Extraction is carried out by a process essentially similar to that used for iron, but is complicate because of the need to remove arsenic and other metals. 

Fig. 1. Global distribution of seabed mineral deposits, where x represents chromite + barite titanium, zirconium, hafnium, and thorium tin I gold, platinum, and silver 3 sand and gravel shell, calcium carbonate gems marine polymetaUic sulfides phosphorites Cl cobalt cmsts S sulfur and B...

Fig. 5. Micrographs of the microstructure of fully hardened and tempered tool steels produced by the powder metallurgy technique, showing uniform distribution and fine carbide particles in the matrix, (a) M-42 (see Table 6) and (b) cobalt-free AlSl T-15 having a higher concentration of fine carbide...

Arsenic is widely distributed about the earth and has a terrestrial abundance of approximately 5 g/t (4). Over 150 arsenic-bearing minerals are known (1). Table 2 fists the most common minerals. The most important commercial source of arsenic, however, is as a by-product from the treatment of copper, lead, cobalt, and gold ores. The quantity of arsenic usually associated with lead and copper ores may range from a trace to 2 —3%, whereas the gold ores found in Sweden contain 7—11% arsenic. Small quantities of elemental arsenic have been found in a number of localities. 

Mechanical properties depend on the alloying elements. Addition of carbon to the cobalt base metal is the most effective. The carbon forms various carbide phases with the cobalt and the other alloying elements (see Carbides). The presence of carbide particles is controlled in part by such alloying elements such as chromium, nickel, titanium, manganese, tungsten, and molybdenum that are added during melting. The distribution of the carbide particles is controlled by heat treatment of the solidified alloy. 

Some studies of potential commercial significance have been made. For instance, deposition of catalyst some distance away from the pore mouth extends the catalyst s hfe when pore mouth deactivation occui s. Oxidation of CO in automobile exhausts is sensitive to the catalyst profile. For oxidation of propane the activity is eggshell > uniform > egg white. Nonuniform distributions have been found superior for hydrodemetaUation of petroleum and hydrodesulfuriza-tion with molybdenum and cobalt sulfides. Whether any commercial processes with programmed pore distribution of catalysts are actually in use is not mentioned in the recent extensive review of GavriUidis et al. (in Becker and Pereira, eds., Computer-Aided Design of Catalysts, Dekker, 1993, pp. 137-198), with the exception of monohthic automobile exhaust cleanup where the catalyst may be deposited some distance from the mouth of the pore and where perhaps a 25-percent longer life thereby may be attained. 

Good results are obtained with oxide-coated valve metals as anode materials. These electrically conducting ceramic coatings of p-conducting spinel-ferrite (e.g., cobalt, nickel and lithium ferrites) have very low consumption rates. Lithium ferrite has proved particularly effective because it possesses excellent adhesion on titanium and niobium [26]. In addition, doping the perovskite structure with monovalent lithium ions provides good electrical conductivity for anodic reactions. Anodes produced in this way are distributed under the trade name Lida [27]. The consumption rate in seawater is given as 10 g A ar and in fresh water is... 

Cesium fluonde in dimethylformamide catalyzes the isomerization offluori-nated cyclobutenes, perfluorobipyntmdines, and their oligomers to products with expanded rings [30, 31, 32] The product distribution in cobalt tnfluonde fluorina-tion depends strongly on the temperature of the reaction [33] Fluorinated 1-dimethylamino-5,6,7,8-tetrafluoro-l,4-dihydro-l,4-ethenonaphthalene rearranges in protic media to a biphenyl derivative [34] (equation 8)... 

The atomic weight increases regularly across the row except for the inversion at cobalt and nickel. We would expect the atomic weight of Ni to be higher than that of Co because there are more protons (28) in the Ni nucleus than in the Co nucleus (27). The reason for the inversion lies in the distribution of naturally occurring isotopes. Natural cobalt consists entirely of the isotope 2 Co natural nickel consists primarily of the isotopes Ni and Ni, the 58-isotope being about three times as abundant as the 60-isotope. 

Lapidus (LI) described liquid residence-time distribution studies for air-water and air-hydrocarbon in cocurrent, downward flow through a column of 2-in. diameter and 3-ft height. Spherical glass beads of 3.5. mm diameter and cobalt molybdate catalyst cylinders of -in. diameter were used as packing materials. 

Under deposition of cobalt nanocrystals, self-assemblies of particles are observed and the nanocrystals are organized in a hexagonal network (Fig. 2). However, it can be seen that the grid is not totally covered. We do not have a simple explanation for such behavior. In fact, the size distribution, which is one of the major parameters in controlling monolayer formation, is similar to that observed with the other nanocrystals, such as silver and silver sulfide. One of the reasons could be that the nanocrystals have magnetic properties, but there is at present no evidence for such an assumption. 

In this present study, we basically showed dependence of the number of reduced cobalt metal surface atoms on dispersion of cobalt oxides along with the presence of rutile phase in titania. Both XRD and SEM/EDX results (not shown) revealed good distribution of cobalt oxides over the titania support. However, it can not differentiate all samples containing various ratios of rutile/anatase phase. Thus, in order to determine the dispersion of cobalt oxide species on titania, a more powerful technique such as TEM was applied with all samples. The TEM micrographs for all samples are shown in Figure 1. The dark spots represented cobalt oxides species present after calcination of samples dispersing on titania consisting various... 

Highly c/s-selectivity and low molecular weight distribution polymerization of l -butadiene with cobalt(II) pyridyl bis(imine) complexes in the presence of ethylaluminum sesquischloride effect of methyl position in the ligand... 

Figure 8.17. Hydrocarbon distribution of the products formed by Fischer-Tropsch synthesis over cobalt-based catalysts and by additional hydrocracking, illustrating how a two-stage concept enables optimization of diesel fuel yield. [Adapted from S.T. Sie,...

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