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143. Surface orientations and operating characteristics of some carbon brushes
395
ABSTRACTS
low volatile bituminous coal in ethylenediamine saturated with lithium chloride resulted in addition of 36 hydrogens per 100 carbon atoms. The reduced coal is a tan-grey in color; 73 per cent of this material is soluble in pyridine at room temperature. The solubility of the original coal in pyridine is about 3 per cent. Until this work, the best electrochemical reduction reported was carried out in dimethylformamide and resulted in the addition of 14 hydrogens per 100 carbon atoms. The advantage of ethylenediamine over dimethylformamide is probably connected with the fact that ethylenediamine can solvate lithium. Experiments indicate that lithium acts as an electron transfer agent in the reduction of benzene in the ethylenediamine-lithium chloride system.
141. Oxidation of carbon black with oxygen: formation of surface oxygen groups A. I. Medalia and E. Hagopian (Cabot Corporation, Cambridge, Massachusetts). The oxidation
of pelletized carbon black with oxygen-nitrogen mixtures has been studied in a batch process in a fluid bed reactor. Samples were withdrawn at intervals during each run and analyzed for surface oxygen groups (carboxyl, phenol, quinone, and Iactone) by the method of Rivin (Proceedings of the Fourth Rubber Technology Conference, London, May, 1962, in press). The surface area (by nitrogen adsorption) and the total amount of combined oxygen per gram of carbon increased during an oxidation run, but the rate of combustion and of formation of oxygen groups decreased. The concentration of various oxygen groups per unit surface area reached a limiting value during an oxidation run. The oxygen groups which are analyzed are stable under the reaction conditions and are not intermediates in the combustion. They appear to be formed at a definite concentration on favored sites distributed over the fresh surface area developed by combustion. X-ray diffraction studies indicate that the amorphous carbon or single layer planes are burned away preferentially. 142. Chemical
properties of C,, a dicarbene* P. S. Skell and L. D. Wescott (PennsyZvaniu State University, University Park, Pennsylvania).
The chemical properties of C,, a substance which has been detected in cometary atmospheres (A. E. DOUGLAS, Astrophys. J. 114, 455, 1951), as well as in carbon vapor (W. A. CHUPKA and M. G. INGHRAM, J. Phys. Chem. 59,100,1955), are being investigated. Carbon vapor produced in vacua (10-3-10*-5mm) reacts at a liquid nitrogen cooled surface with olefins to produce homologs of the parent substance bis-ethanoallene. Isobutylene reacts to produce l,l,l’,l’-tetramethyl-bis-ethanoallene. A low voltage mass spectrum shows a parent peak at 148 mass units. A strong adsorption in the infrared at 4.88~ is attributed to the strained allene system (H. D. HARTZLES, J: Amer. Chem. Sot. 83, 4990, 1961). The proton magnetic resonance shows two unsplit absorptions with intensities of 1:3 at 8.67 and 8.722 respectively. In the case of the reaction with propylene, three diasteroismers, in the ratio 1:2:1 are predicted, and found by high resolution gas chromatography. These findings offer chemical proof that C, is the major constituent of carbon vapor and provide a way of more thoroughly studying its chemical properties. *This work was supported Grant AF-AFOSR 62-52.
by the Directorate
of Chemical
Sciences,
Air Force Office of Scientific
Research
under
143. Surface orientations and operating characteristics of some carbon brushes G. Kaye (Morganite Research and Development Limited, Northjields Laboratories, Wandsworth, London, England). Electron diffraction techniques have been used to relate the surface structure of carbon brush materials to their operational behaviour (friction, contact drop, etc.). Two sets of carbons were examined, (a) two-phase carbons prepared from five raw materials (Ceylon graphite, petroleum coke, pitch coke, electrographite and carbon black) which were pitch bonded, kilned at 1250°C and graphitised at 2300 and 2600°C; (b) a set of commercial carbon brush materials. The carbon surfaces were prepared by two techniques, first by multidirectional polishing using diamond pastes and secondly by running on a copper slotted slip ring. The results obtained so far are summarized as follows: (i) On the basis of the
396
CARBON
polishing experiments, the two phase carbons could be classified into four groups according to the spread in the orientation of basal planes; (ii) For a given carbon, the polishing produced a characteristic surface orientation which was independent of any preferred orientation in the hulk; (iii) Under acceptable operating conditions on a slotted slip ring, the two phase materials, in general, possessed comparable surface orientation to that found in the simple polishing experiments. The surface orientation was apparently unaffected by the passage of current or polarity of brush; (iv) In those experiments which had to be discontinued (e.g. unacceptable friction, sparking etc.) it was generally observed that irrespective of brush composition the surface layers showed a random orientation; (v) The friction of non-graphitic carbons under practical running conditions was not less than 0.2 (vi) The mean tilt of the basal planes (y) of about fifty commercial carbons was examined in relation to the coefficient of friction The simple relation p=tan y did not apply under these conditions. under operating conditions. 144. Mechanical and physical properties of the EGCR core graphite James V. Neely (Allis-Chalmers Manufacturing Company, Nuclear Power Department, Washington, D.C.) and Max N. Burkett (National Carbon Company, Division of Union Carbide Corporation, New York, New York). Design and fabrication of the graphite core of the Experimental Gas-Cooled Reactor (EGCR) involved significant departures from past practices for nuclear graphite structures. Critical raw material requirements, based upon results of irradiation damage testing performed at Hanford, were formulated to produce graphite which had a minimum rate of irradiation-induced shrinkage. Also, the EGCR core marks one of the first uses, in a major engineering structure, of graphite primary structural members subject to tensile and flexural stresses. New production and machining techniques, new quality control procedures and rigid cleanliness controls were used to produce the largest nuclear graphite ever made, 16 in.1 square and more than 20 ft long, each piece of which met all chemical, physical, and mechanical property requirements. Specimens from several regions of each graphite column were tested to verify that each furnace lot met specification requirements. Composite test specimens, comprising samples taken from each moderator colu~, were tested in the Hanford 304 reactor to verify that nuclear absorption cross section was within specification limits. Finally, each finished column was subjected to beam flexure tests to verify overall structural integrity. Test results, together with statistical evaluation, are presented herein. 145. Effect of sulphur on the properties of carbon and graphite J. F. Rakszawski (Speer Carbon Company Research Laboratory, Niagara Fails, New York). The effect of sulfur present in filler coke on properties of carbon and graphite was compared to the effect of free sulfur added to the green mix. The filler coke sulfur is not removed by heat treating up to a temperature of lSOO”C, whereas baking to 900°C removes 70-75 per cent of the free sulfur added to the green mix. The filler coke sulfur affects volume contraction during heat treating but has no effect on pitch coking value. Free sulfur added to the green mix increases the volume contraction and the coking value of the pitch binder. Flexural strength and modulus of elasticity are increased and electrical resistivity, CTE, and total pore volume are decreased when the sulfur content of the calcined filler coke increases from 0.5 to 2.3 per cent. When free sulfur is increased from 0 to 9 per cent based on the weight of the filler, electrical resistivity increases and total pore volume decreases. Flexural strength, modulus of elasticity and CTE are maximized at an addition of 6 per cent. 146. The effect of group IIIA to VIA elements and their oxides on graphite oxidation J. F. Rakszawski and W. E. Parker (Speer Carbon Company Research Laboratory, Niagara Falls, New York). The effect of group IIIA to VIA elements and oxides on graphite oxidation was determined. The - 325 mesh additives were dry blended with spectroscopically pure graphite powder before molding in rod-form at 100,000 psi. and room temperature. The concentration was maintained constant at
ABSTRACTS
low volatile bituminous coal in ethylenediamine saturated with lithium chloride resulted in addition of 36 hydrogens per 100 carbon atoms. The reduced coal is a tan-grey in color; 73 per cent of this material is soluble in pyridine at room temperature. The solubility of the original coal in pyridine is about 3 per cent. Until this work, the best electrochemical reduction reported was carried out in dimethylformamide and resulted in the addition of 14 hydrogens per 100 carbon atoms. The advantage of ethylenediamine over dimethylformamide is probably connected with the fact that ethylenediamine can solvate lithium. Experiments indicate that lithium acts as an electron transfer agent in the reduction of benzene in the ethylenediamine-lithium chloride system.
141. Oxidation of carbon black with oxygen: formation of surface oxygen groups A. I. Medalia and E. Hagopian (Cabot Corporation, Cambridge, Massachusetts). The oxidation
of pelletized carbon black with oxygen-nitrogen mixtures has been studied in a batch process in a fluid bed reactor. Samples were withdrawn at intervals during each run and analyzed for surface oxygen groups (carboxyl, phenol, quinone, and Iactone) by the method of Rivin (Proceedings of the Fourth Rubber Technology Conference, London, May, 1962, in press). The surface area (by nitrogen adsorption) and the total amount of combined oxygen per gram of carbon increased during an oxidation run, but the rate of combustion and of formation of oxygen groups decreased. The concentration of various oxygen groups per unit surface area reached a limiting value during an oxidation run. The oxygen groups which are analyzed are stable under the reaction conditions and are not intermediates in the combustion. They appear to be formed at a definite concentration on favored sites distributed over the fresh surface area developed by combustion. X-ray diffraction studies indicate that the amorphous carbon or single layer planes are burned away preferentially. 142. Chemical
properties of C,, a dicarbene* P. S. Skell and L. D. Wescott (PennsyZvaniu State University, University Park, Pennsylvania).
The chemical properties of C,, a substance which has been detected in cometary atmospheres (A. E. DOUGLAS, Astrophys. J. 114, 455, 1951), as well as in carbon vapor (W. A. CHUPKA and M. G. INGHRAM, J. Phys. Chem. 59,100,1955), are being investigated. Carbon vapor produced in vacua (10-3-10*-5mm) reacts at a liquid nitrogen cooled surface with olefins to produce homologs of the parent substance bis-ethanoallene. Isobutylene reacts to produce l,l,l’,l’-tetramethyl-bis-ethanoallene. A low voltage mass spectrum shows a parent peak at 148 mass units. A strong adsorption in the infrared at 4.88~ is attributed to the strained allene system (H. D. HARTZLES, J: Amer. Chem. Sot. 83, 4990, 1961). The proton magnetic resonance shows two unsplit absorptions with intensities of 1:3 at 8.67 and 8.722 respectively. In the case of the reaction with propylene, three diasteroismers, in the ratio 1:2:1 are predicted, and found by high resolution gas chromatography. These findings offer chemical proof that C, is the major constituent of carbon vapor and provide a way of more thoroughly studying its chemical properties. *This work was supported Grant AF-AFOSR 62-52.
by the Directorate
of Chemical
Sciences,
Air Force Office of Scientific
Research
under
143. Surface orientations and operating characteristics of some carbon brushes G. Kaye (Morganite Research and Development Limited, Northjields Laboratories, Wandsworth, London, England). Electron diffraction techniques have been used to relate the surface structure of carbon brush materials to their operational behaviour (friction, contact drop, etc.). Two sets of carbons were examined, (a) two-phase carbons prepared from five raw materials (Ceylon graphite, petroleum coke, pitch coke, electrographite and carbon black) which were pitch bonded, kilned at 1250°C and graphitised at 2300 and 2600°C; (b) a set of commercial carbon brush materials. The carbon surfaces were prepared by two techniques, first by multidirectional polishing using diamond pastes and secondly by running on a copper slotted slip ring. The results obtained so far are summarized as follows: (i) On the basis of the
396
CARBON
polishing experiments, the two phase carbons could be classified into four groups according to the spread in the orientation of basal planes; (ii) For a given carbon, the polishing produced a characteristic surface orientation which was independent of any preferred orientation in the hulk; (iii) Under acceptable operating conditions on a slotted slip ring, the two phase materials, in general, possessed comparable surface orientation to that found in the simple polishing experiments. The surface orientation was apparently unaffected by the passage of current or polarity of brush; (iv) In those experiments which had to be discontinued (e.g. unacceptable friction, sparking etc.) it was generally observed that irrespective of brush composition the surface layers showed a random orientation; (v) The friction of non-graphitic carbons under practical running conditions was not less than 0.2 (vi) The mean tilt of the basal planes (y) of about fifty commercial carbons was examined in relation to the coefficient of friction The simple relation p=tan y did not apply under these conditions. under operating conditions. 144. Mechanical and physical properties of the EGCR core graphite James V. Neely (Allis-Chalmers Manufacturing Company, Nuclear Power Department, Washington, D.C.) and Max N. Burkett (National Carbon Company, Division of Union Carbide Corporation, New York, New York). Design and fabrication of the graphite core of the Experimental Gas-Cooled Reactor (EGCR) involved significant departures from past practices for nuclear graphite structures. Critical raw material requirements, based upon results of irradiation damage testing performed at Hanford, were formulated to produce graphite which had a minimum rate of irradiation-induced shrinkage. Also, the EGCR core marks one of the first uses, in a major engineering structure, of graphite primary structural members subject to tensile and flexural stresses. New production and machining techniques, new quality control procedures and rigid cleanliness controls were used to produce the largest nuclear graphite ever made, 16 in.1 square and more than 20 ft long, each piece of which met all chemical, physical, and mechanical property requirements. Specimens from several regions of each graphite column were tested to verify that each furnace lot met specification requirements. Composite test specimens, comprising samples taken from each moderator colu~, were tested in the Hanford 304 reactor to verify that nuclear absorption cross section was within specification limits. Finally, each finished column was subjected to beam flexure tests to verify overall structural integrity. Test results, together with statistical evaluation, are presented herein. 145. Effect of sulphur on the properties of carbon and graphite J. F. Rakszawski (Speer Carbon Company Research Laboratory, Niagara Fails, New York). The effect of sulfur present in filler coke on properties of carbon and graphite was compared to the effect of free sulfur added to the green mix. The filler coke sulfur is not removed by heat treating up to a temperature of lSOO”C, whereas baking to 900°C removes 70-75 per cent of the free sulfur added to the green mix. The filler coke sulfur affects volume contraction during heat treating but has no effect on pitch coking value. Free sulfur added to the green mix increases the volume contraction and the coking value of the pitch binder. Flexural strength and modulus of elasticity are increased and electrical resistivity, CTE, and total pore volume are decreased when the sulfur content of the calcined filler coke increases from 0.5 to 2.3 per cent. When free sulfur is increased from 0 to 9 per cent based on the weight of the filler, electrical resistivity increases and total pore volume decreases. Flexural strength, modulus of elasticity and CTE are maximized at an addition of 6 per cent. 146. The effect of group IIIA to VIA elements and their oxides on graphite oxidation J. F. Rakszawski and W. E. Parker (Speer Carbon Company Research Laboratory, Niagara Falls, New York). The effect of group IIIA to VIA elements and oxides on graphite oxidation was determined. The - 325 mesh additives were dry blended with spectroscopically pure graphite powder before molding in rod-form at 100,000 psi. and room temperature. The concentration was maintained constant at