Graphite types

The service life of a rupture disk is difficult to predict, since corrosion, cycling pressures, temperature and other process conditions can all affect the useful life and cause premature failure. A graphite-type disk is shown in Figure 7-9. In some processes it is safer to replace disks on a schedule after the life factor has been established, as a planned shut-down is certainly less costly than an emergency one. 

Figure 9-88. Graphite type HCI absorption tower. Used by permission of Fails Industries, Inc.

TEM-EDS and XPS analyses were conducted on Co/MgO catalysts. The results of surface analyses showed that Co metal is not supported on the MgO as particles, but covers MgO surface in the case of 12 wt.% Co/MgO calcined at 873 K followed by reduction. After the reduction of catalyst at 1173 K, both cobalt oxide and CoO-MgO solid solution are observed on the surface of catalyst. In the steam reforming of naphthalene, two types of coke deposited on the surface of catalyst are observed. These are assigned to film-like and graphite type carbon by TPO analysis. 

Further on, the Co-Ni complexes were used for modification of Hohsen Carbon type (10-10) and Hohsen Graphite type (10-28) anode materials for Li-ion batteries applying similar procedure. These anode materials were tested in 2016 size lithium coin cells with a configuration Li/electrolyte (LP-30)/(modified anode material). The coin cells were assembled by standard technology in dry atmosphere of a glove box and then... 

Figure 9 shows voltage profiles of the initial and modified Graphite-type materials at first charge (A) and subsequent discharge-charge (B) processes. 

Figure 9. Voltage profiles of Hohsen Graphite-Type Material modified with the Co-Ni complex A -first charge, part of it is enlarged in the insert ...

Figure 10. Irreversible capacity losses (A) and reversible capacity at 10-th cycle (B) for two specific current values of modified Graphite-type materials annealed at different temperatures.

Figure 11. Capacity fading of initial and modified Graphite-Type materials in course of continuous cycling.

Modification of Graphite-type materials by the Co-Ni complex pyrolyzed at 500°C improves significantly the performance of these material in the anode of Li battery. The inner mechanism of this effect is still unclear. We suggest the formation of nanosized spinel structures which facilitate the charge transfer across SEI. 

In the first set of measurements the rate of carbon build-up on a Ni(lOO) surface was measured at various temperatures as follows (1) surface cleanliness was established by AES (2) the sample was retracted into the reaction chamber and exposed to several torr of CO for various times at a given temperature (3) after evacuation the sample was transferred to the analysis chamber and (4) the AES spectra of C and Ni were measured. Two features of this study are noteworthy. First, two kinds of carbon forms are evident - a carbidic type which occurs at temperatures < 650 K and a graphite type at temperatures > 650 K. The carbide form saturates at 0.5 monolayers. Second, the carbon formation data from CO disproportionation indicates a rate equivalent to that observed for methane formation in a H2/CO mixture. Therefore, the surface carbon route to product is sufficiently rapid to account for methane production with the assumption that kinetic limitations are not imposed by the hydrogenation of this surface carbon. 

Silicon and germanium as elemental substances are found only in the diamond-type form. The reluctance of Si and Ge to enter into pre-p bonding prohibits a graphite-type structure as a plausible allotrope. These are rather more reactive than diamond the weaker Si-Si and Ge-Ge bonds make disruption of the lattice kinetically easier. Tin occurs in both a metallic form (white tin) and a covalent (diamond-type) form the latter is slightly more stable at low temperatures. Lead forms only a metallic elemental substance. 

The surface is one parallel to the / -surface, so that the two sub-spaces are not equivalent. A tetrahedral joint is built out of 84 atoms in hexagons and heptagons so that each point is a member of two hexagons and one heptagon (62.7). There are thus 2 x 84 atoms per primitive unit cell with space group Fd3 and 8 x 84 = 672 per cubic unit cell with a = 21.8 A (assuming graphite-type bonds). 

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