Graphite Unit Research Articles

Evolution of fluids associated with metasedimentary sequences from Chaves (North Portugal)

In order to identify and characterise fluids associated with metamorphic rocks from the Chaves region (North Portugal), fluid inclusions were studied in quartz veinlets, concordant with the main foliation, in graphitic-rich and nongraphitic-rich lithologies from areas with distinct metamorphic grade. The study indicates multiple fluid circulation events with a variety of compositions, broadly within the C–H–O–N–salt system. Primary fluid inclusions in quartz contain low salinity aqueous–carbonic, H 2O–CH 4–N 2–NaCl fluids that were trapped near the peak of regional metamorphism, which occurred during or immediately after D2. The calculated P– T conditions for the western area of Chaves (CW) is P=300–350 MPa and T∼500 °C, and for the eastern area (CE), P=200–250 MPa and T=400–450 °C. A first generation of secondary fluid inclusions is restricted to discrete cracks at the grain boundaries of quartz and consists of low salinity aqueous–carbonic, H 2O–CO 2–CH 4–N 2–NaCl fluids. P– T conditions from the fluid inclusions indicate that they were trapped during a thermal event, probably related with the emplacement of the two-mica granites. A second generation of secondary inclusions occurs in intergranular fractures and is characterised by two types of aqueous inclusions. One type is a low salinity, H 2O–NaCl fluid and the second consists of a high salinity, H 2O–NaCl–CaCl 2 fluid. These fluid inclusions are not related to the metamorphic process and have been trapped after D3 at relatively low P (hydrostatic)– T conditions ( P<100 MPa and T<300 °C). Both the early H 2O–CH 4–N 2–NaCl fluids in quartz from the graphitic-rich lithologies and the later H 2O–CO 2–CH 4–N 2–NaCl carbonic fluid in quartz from graphitic-rich and nongraphitic-rich lithologies seem to have a common origin and evolution. They have low salinity, probably resulting from connate waters that were diluted by the water released from mineral dehydration during metamorphism. Their main component is water, but the early H 2O–CH 4–N 2–NaCl fluids are enriched in CH 4 due to interaction with the C-rich host rocks. From the early H 2O–CH 4–N 2–NaCl to the later aqueous–carbonic H 2O–CO 2–CH 4–N 2–NaCl fluids, there is an enrichment in CO 2 that is more significant for the fluids associated with nongraphitic-rich lithologies. The aqueous–carbonic fluids, enriched in H 2O and CH 4, are primarily associated with graphitic-rich lithologies. However, the aqueous–carbonic CO 2-rich fluids were found in both graphitic and nongraphitic-rich units from both the CW and CE studied areas, which are of medium and low metamorphic grade, respectively.

Exploring through cover – the integrated interpretation of high resolution aeromagnetic, airborne electromagnetic and ground gravity data from the Grant’s Patch area, Eastern Goldfields Province, Archaean Yilgarn Craton. Part C: Combining geophysical meth

Archaean lode gold deposits usually follow narrow structures, such as lithological contacts, ductile shears and brittle cross-faults. These features cannot be identified directly in covered areas and are often impossible to correlate between exploration drillholes. High-resolution geophysical methods provide dense, regularly spaced coverage for mapping continuity of structure and the geometry of the regolith at depth. Such geophysical ?pattern mapping? contrasts to direct anomaly targeting in that it requires image processing and integration of geological and geochemical data to produce ?holistic? regolith and bedrock geology maps used for targeting gold bearing structures. Grant?s Patch is a semi-mature lode gold corridor located 45 km NW of Kalgoorlie in Western Australia. The southern part of this corridor is covered by high-resolution aeromagnetic, airborne electromagnetic and gravity data, has uniform exploration drillhole coverage to non-weathered bedrock, and has very little surface disturbance from mining infrastructure. These geophysical methods are shown to produce effective results, yet no method is superior as they each provide complementary information. At Grant?s Patch, aeromagnetics identifies magnetic greenstone units, such as mafic to ultramafic sills and dolerite horizons, faults as disruptions crossing magnetic units, and paleochannels containing ferruginous gravel. Gravity maps density differences between greenstone rock units, identifies buried granitic intrusions, and identifies large paleochannels. High-pass filtered grids of gravity data reveal differential weathering between rock units and along faults zones, even where no pattern is revealed in the aeromagnetic data. The airborne electromagnetic (AEM) response is dominated by conductive clays, predominately in situ as saprolite, and saline groundwaters in the regolith that usually follow litho-dependant weathering of bedrock units. AEM data can also identify graphitic shale units as bedrock conductors where conductive regolith overburden is thin and allows for penetration. Cross-faults are mapped as disruptions of the conductive units and may themselves be either conductive or resistive.

Atomic hydrogen beam etching of carbon superstructures on 6H-SiC (0001) studied by reflection high-energy electron diffraction

Abstract A route for the regeneration of smooth √3×√3 R30 face on 6H-SiC(0001) by atomic hydrogen beam etching following the carbonization of the SiC surface at high temperatures had been investigated. The various stages during the segregation of carbonaceous super-structures at high temperatures as well as the layer-by-layer restructuring of the 6H-SiC(0001) surface by atomic H beam were studied by reflection high energy electron diffraction (RHEED). A smooth silicate-terminated √3×√3 R30 surface could be obtained after hydrogen-plasma beam treatment at 800°C. Annealing the √3×√3 R30 face to 900°C readily resulted in the segregation of 1×1 graphite islands on the surface, with the basis vectors of the graphite unit cell rotated 30° with respect to the bulk SiC. Further annealing to temperatures between 1000 and 1200°C resulted in the coalescence of the graphite islands to form an epitaxial layer, which adopted an incommensurate 6√3×6√3 R30-C structure with respect to the bulk. The epitaxial 6√3×6√3 R30-C layer acted as a template for the further growth of smooth single-crystalline graphite multilayers upon prolonged annealing. Atomic force microscopic (AFM) analysis revealed that the epitaxial graphite formed by this method was atomically smooth. Re-exposing the graphite-covered surface to a second hydrogen-plasma treatment readily converted the carbonized surface to a silicate-terminated √3×√3 R30 face. The layer-by-layer etching mechanism of the carbonized SiC by the atomic-H beam source constituted an effective route for the regeneration of the smooth silicon face.

Anodic performance and insertion mechanism of hard carbons prepared from synthetic isotropic pitches

Anodic performances and structures of hard carbons prepared from synthetic isotropic pitches through solid phase oxidation were investigated to discuss their insertion sites for lithium ion and correlation between the capacity and structure. The derived hard carbons showed complicated voltage profiles of charge and discharge, indicating five kinds of insertion sites; partially charge transferring surface site (Type I), intercalation site like graphite (Type II), cluster gap between edges of carbon hexagon clusters (Type III), microvoid surrounded by hexagonal planes (Type IV) and atomic defect created by evolution of heteroatom (Type V). Types I–III are common to those found in the soft carbon. Very unique capacities of the present hard carbons calcined at 1000°C were found at the potentials of 0–0.13 V (Type IV) and 0.5–2.0 V (Type V) and varied markedly with oxidization extent and heteroatom contents of precursor pitch, respectively. The microvoid among the hexagonal planes and atomic defects created by evolution of heteroatom are suggested to serve such insertion sites of Types IV and V, respectively. The microvoid holds reduced lithium ions with different extents of charge transfer to the carbon, which exist independently at 140 K but exchange rapidly at room temperature to their averaged chemical shift in 7Li-NMR. Type V showed very similar charge–discharge behaviors to that of Type III, which was found more in the soft carbon carbonized at around 700°C and decreased sharply by the heat-treatment at 1000°C due to the coupling of hexagon clusters. The amount of microvoid or capacity at 0–0.13 V is correlated to XRD parameters and oxygen content of the precursors. Smaller crystal, lower stacking or more oxygen content in the precursor allows apparently larger capacity. Random assemble of smaller graphitic units may induce the microvoid among the cluster units, although the microvoid has not been specifically defined yet.

Adsorption of potassium and oxygen on graphite: A theoretical study

We have performed electronic structure calculations of the interaction of potassium and oxygen with graphite (GR), individually and as coadsorbates. We use up to three graphite planes to represent the graphite surface, but we show that the main physics is correctly described by a single graphite layer. At low coverage the potassium–graphite bond is largely ionic, and the variation of the K–GR bond energy with the lateral position of the K atom in the graphite unit cell is very small. We study the interaction between atomic oxygen and graphite. We find that O binds strongest at the bridge site, but the barrier for diffusion is rather small. The frequency for the perpendicular O–graphite vibrational mode is remarkably low (53 meV), reflecting the relative slow variation of the O–graphite interaction energy with the separation z between the O atom and the graphite surface. We consider the adsorption of O2 on a clean graphite surface and on a graphite surface with a low concentration of potassium. On the clean surface the O2–graphite interaction is found to be repulsive (the weak attractive van der Waals interaction is not included in our theoretical method), in accordance with the extremely low sticking coefficient observed for O2 on clean graphite. When potassium is adsorbed on the graphite surface, O2 chemisorbs at the potassium sites which is consistent with the large sticking coefficient observed for O2 on a potassium covered surface. The energy barrier towards dissociation of O2 on the clean graphite surface is estimated to be similar to that of gas phase O2. For O2 on K/graphite we find that O2 chemisorbs “side-on” K, and that the barrier for dissociation is much smaller than in the gas phase or on the clean graphite surface.

A model for surface diffusion of ethane and propane in activated carbon

In this paper we present a model for surface diffusion in heterogeneous activated carbon. A structural model for activated carbon was first assumed, upon which a model for the surface diffusion mechanism was proposed. This model allows for the penetration of molecules into graphitic layer units, diffusion through it and evaporation out of it. Upon leaving the graphitic units, molecules then rejoin with other molecules diffusing through the porous medium via the larger void space parallel to the graphitic layers. They in turn then diffuse through the amorphous region of the activated carbon. The sequence of these steps repeats itself in a periodic pattern. The model gives rise to an ‘apparent’ surface diffusivity which is an explicit function of temperature and concentration of the adsorbed species. The activation energy of this ‘apparent’ surface diffusivity was found to take values between the activation energy for diffusion through the graphitic units and the heat of adsorption. Under proper conditions, it can be equal to the heat of adsorption. In terms of the concentration dependence, this model shows a very strong dependence of the surface diffusivity on the adsorbed concentration; for example, when the Langmuir isotherm prevails, the dependence of D s on fractional loading takes the following form: D s = D s(0) (1− θ) 2 which exhibits a much stronger dependence on the concentration than the traditional Darken relation, D s = D s(0) (1 − θ) . Experimental data of surface diffusion of ethane and propane on activated carbon obtained in our laboratory exhibit this strong dependence on the adsorbed concentration.

Identification and Treatment of Potential Acid-Producing Rocks and Water Quality Monitoring Along a Transmission Line in the Blue Ridge Province, Southwestern North Carolina

Geologic mapping, petrographic analysis, and Acid-Base Accounting testing of rocks along the corridor of a transmission line in the Blue Ridge Province of southwestern North Carolina indicated a potential for acid production in certain areas related to road and tower construction. The potential acid-producing rocks are graphite schist units in the Great Smoky Group (Anakeesta Formation), graphitic metasiltstones of the Murphy Belt (Nantahala Formation), and thin layers of sulfidic rock within the Great Smoky Group (Ammons Formation—Horse Branch Member). Net Neutralization Potential (NNP) for the graphite schist units ranges from −19.27 to 1.81 tons CaCO 3 per 1,000 tons of excavated material (an NNP value of −5 tons CaCO 3 or less is interpreted as predicting acid drainage). NNP for the graphitic metasiltstones of the Nantahala Formation range from −43.56 to −11.39 tons CaCO 3 per 1,000 tons of material. The NNP for a sulfide-rich layer in the Ammons Formation is −26.03 tons CaCO 3 per 1,000 tons of material. Treatment for the potential acid-producing material involves stockpiling topsoil, mixing agricultural lime with the excavated material in a ratio based on the lowest NNP value for the particular rock unit, and covering the excavated material with a least 2 (two) ft of stockpiled topsoil to isolate the sulfidic material from the atmosphere, retarding the oxidation of the sulfides. When the treated material is spoiled in a roadbed, a base of limestone aggregate is placed on the existing roadbed, followed by the treated, compacted material with additional lime added after every lift. This is followed by topsoil (compacted) to encapsulate the limestone base and treated material, with limestone aggregate applied as the final road surface. Drainage is provided to divert water from the fills and tower foundation excavations. A monitoring program, in-place before, during, and after construction, was used to identify water-quality variations that might indicate ail effect on stream chemistry from disturbance of potential acid-producing materials. Results of the monitoring program suggest that the methods used to identify and treat the materials have been effective in minimizing the impact of their disturbance on the environment.

Axial nano-scale microstructures in graphitized fibers inherited from liquid crystal mesophase pitch

Nano-scale structures of a mesophase pitch based carbon fiber were characterized using a high-resolution scanning electron microscope (HR-SEM) and a scanning tunneling microscope (STM). Fibril was found to be sectioned by a number of pleat units, being aligned parallel along the fiber axis. The periodical size, thickness and height of pleat unit was estimated as 30–60 nm, 20–30 nm and around 7 nm, respectively. In a pleat, graphitic units of 30–60 nm long and 2–4 nm wide run principally perpendicular to the axis. The basal plane of graphite was observed at the largest magnification. Such a series of nano-structures should be related intimately to the performance of the fibers. The formation mechanism of such series of nano-structural units is discussed in relation to the nano-structure of the liquid crystal mesophase pitch and its deformation during the spinning.

Calibration, drift elimination, and molecular structure analysis

A new automated technique for the estimation of the lateral calibration factors and for the drift in the fast scanning direction of SXM instruments is introduced. It is based on the detection of the reciprocal unit cell in Fourier space. The estimated calibration and drift factors are used for the restoration of distorted images containing self-assembled didodecylbenzene (DDB) molecules physisorbed on graphite. From the corrected images, the DDB unit cells are calculated in the Fourier domain. The long unit cell vector of the DDB molecules is calculated more accurately from images showing the graphite unit cells and the DDB lamellas simultaneously. By use of a correlation averaging technique, the structures of the DDB molecules within the unit cells are furthermore analyzed. The benzene ring and the C2H4 groups are thereby identified in the alkyl chains.

Spectroscopic and chemical characterisation of “fullerene black”

The electric arc method of fullerene preparation leaves about 90% of the carbon as insoluble soot. Unprotected storage of C 60 also leads to insoluble carbonaceous material. This “fullerene black” has been characterised with respect to its structural, electron spectroscopic and chemical properties. Comparison of the results with data obtained from industrial carbon black shows that the insoluble residue has nothing in common with conventional soot which is composed of small graphitic structural units. Fullerene black as well as pure C 60 and C 70 were all found to exhibit high reactivities in combustion reactions under realistic conditions.

Electrothermal vaporisation interface for sample introduction in inductively coupled plasma mass spectrometry

An electrothermal vaporisation (ETV) device was developed for inductively coupled plasma mass spectrometry by modifying a commercial graphite furnace unit. A detailed description of the modifications are presented. The new ETV interface is designed to increase sample transport efficiency by converting analyte vapour into micro-particles in the furnace. The characterisation and optimisation of the device are also discussed. Ten consecutive firings of a 30-pg sample of Pb resulted in relative standard deviations (RSD) of 4% for peak-height and 1.6% for peak-area measurements. The absolute detection limit, determined by comparing the response obtained for a 3-µl sample of a 10 ng ml–1 Pb solution in 1% HNO3 with that obtained for blanks containing 1% HNO3 only, was 10 and 14 fg, for a dwell time of 10 µs, for peak area and peak height, respectively. The linear dynamic range for Pb extends over three orders of magnitude, from 300 fg to 300 pg.

A (2-amino-2-methylpropanedioato)(optically active cyclen)cobalt(III) complex

cis-(SSSR)-fll-[ (R)-2-Amino-2-methylmalonato] (2R,5R,8R, 11R-2,5,8,11-tetraethyl1,4,7,10tetraazacyclododecane)cobalt(III) perchlorate 2.5hydrate, [Co(C4HsNO4)(CI6H36N4)]C104.2.5H20, M r = 619.00, triclinic, PI , a = 10.455 (5), b = 31.715(15), c 1 0 . 4 9 2 ( 7 ) A , a = 1 1 0 . 5 0 ( 5 ) , f l= 116.74(5), y = 8 0 . 3 6 ( 5 ) °, U = 2 9 1 0 ( 3 ) A 3, Z = 4 , D m = 1.410, D x = 1.415 Mg m -3, 2(Mo Ka) = 0.71073 A, l z = 0 . 7 4 m m -1, F (000)= 1316, T = 296 K, final R = 0.068 for 7646 unique reflections with IFol >3cr(IFol ). The geometries of the four independent molecules in the unit cell are essentially the same. In each octahedral molecule, the Co Ill ion is surrounded by four N of the macrocycle, and by N and O atoms of pro-R carboxylate in the amino acid. The * Part 9 of the series Metal Complexes ofChiral Cyclen. Part 8: Tsuboyama, Takishima, Sakurai & Tsuboyama (1987). To whom correspondence should be addressed. 0108-2701/89/040669-04503.00 uncoordinated carboxyl group forms an intramolecular hydrogen bond to one of the N atoms in the macrocyclic ligand, in molecule 1 [N(1)-H .... O(17)2:2.98 (1) A , / N ( 1 ) H . . . O ( 1 7 ) 2 : 1 5 9 (12)°]. Experimental. The crystal was obtained from the same reaction product as the monoclinic one whose structure had already been reported (Tsuboyama, Takishima, Sakurai & Tsuboyama, 1987). The density was measured by flotation in CC14-benzene. Details of data collection and structure refinement are given in Table 1. Structure solved by direct methods with MULTAN78 (Main, Fiske, Hull, Lessinger, Germain, Declercq & Woolfson, 1978). Calculations performed using the program system UNICS-III (Sakurai & Kobayashi, 1979) on a FACOM M-780. The four independent molecules are labelled 1, 2, 3 and 4. The molecular geometries of these are almost identical to that of the monoclinic crystal. The H atom attached to © 1989 International Union of Crystallography 670 [Co(C4HsNO4)(C 16H36N4)] CIO4. 2. 5H20 Table 1. Experimental details Crystal Orange-red, pillar, 0.24 x 0.36 x 0.40 mm Diffraetometer used Rigaku A F C automated four-circle Monoehromator Graphite Unit cell 16 reflections, 25.0 > 20 > 20.0 ° Data correction applied Lorentz and polarization, not absorption Mode to, o7-20 (20 > 30 °) Scan rate (deg min -~) 4.0 Scan ranges of h, k, l -13--,13, ---4 l-L4_ 1, 0--13 Standards 300, 0 16 0, 293, 007 e . t . . . No. of reflections between 150, no mtenmy variation standards 20range (o) 55 Reflections observed 11 812 No. of unobs, reflections 6489 [criterion: IFol > 3o( IFol )] Parameters refined 1498 R 0.068 wR 0.073 Maximum shift/e.s.d. 0.35 * Max. height in final map (e A -3 ) 0.7 * Except for disordered ethyl groups and anions.

Direct measurement of forces during scanning tunneling microscope imaging of graphite

The normal force acting on a scanning tunneling microscope tip while imaging a graphite surface in air has been measured directly. Forces in the range of 10 −7 to 10 −6 N are required to achieve tunneling. Further, the force needed to maintain a constant current varies considerably as the tip scans from one part of the graphite unit cell to another. Our results are consistent with a model, originally suggested by Mamin et al., in which the force between the tip and the surface is mediated by a contamination layer, and tunneling occurs at the end of an asperity which pierces this layer. However, we cannot rule out a model where a graphite flake is dragged across the graphite surface to generate an STM image.

LaBarge Project: Availability of CO2 for Tertiary Projects

Abstract Exxon Co., USA is constructing a large gas processing facility northeast of Kemmerer on the Lincoln-Sweetwater County line in southwest Wyoming. The plant will process raw gas from three Exxon operated units northwest of LaBarge, in Sublette County. The LaBarge Field is being developed primarily to recover and sell methane; however, the field is also a significant source of carbon dioxide, sulfur and helium. As a source of CO, the LaBarge Field will provide oil producers in the Rocky Mountain area an opportunity to increase production in their mature fields through EOR projects. A 649-mile pipeline is planned to transport up to 650 Mcfd of CO, to users throughout Wyoming and Willisiton Basin. Exxon's CO, marketing survey indicates potential CO, demand of 4.4 trillion cubic feet in the planned marketing area for enhanced oil recovery. About 25% of the CO2 demand identified is already contracted. LaBarge CO2 will allow Northern Rocky Mountain 'operators to potentially recover an additional one billion barrels of oil reserves. Introduction Exxon's gas plant, scheduled for startup this year, is designed to process 480 million cubic feet per day of raw gas yielding 114 Mcfd ( m = million, G = billion, T = trillion) of methane, and 250 mcfd of CO2. The initial phase of the plant is currently being built and a future expansion is under evaluation. Expansion timing will depend on the economic climate and commitments for plant products. while methane is the primary product being developed in the LaBarge Project, the field will also produce marketable quantities of CO2, sulfer, and helium. The CO2 is being offered for sale to operators in Colorado, Wyoming, North Dakota, Montana, and Canada as an injectant for their EOR projects. Background The well field consists of three Exxon operated units covering over 63 square miles (see Fig. 1). These units are located about 10 miles northwest of the town of LaBarge in Sublette County. Exxon owns an average of 95% (Jan.'86, leased committed acreage) of the Lake Ridge, Fogarty Creek, and Graphite Units. Production is from the Madison, a 900 foot thick carbonate reservoir ranging in depth from 14,000 to 18,000 feet. Structurally the Madison Reservoir is located on a large NW-SE trending anticline. The boundaries have not yet been accurately defined but do extend beyond the three Exxon operated units. The National Petroleum Council estimated that the LaBarge-Big Piney area contains 20–25 Tcf of CO2 reserves alone (EOR, p.33, 1984). P. 249^

Structure determination for the intermediate-density S2 monolayer phase of ethane physisorbed on graphite.

Low-energy electron diffraction has been used to determine the unit mesh of the intermediate-density ${S}_{2}$ monolayer phase of ethane physisorbed on graphite at 40 K. The proposed unit mesh is rectangular with sides 7.39\ifmmode\pm\else\textpm\fi{}0.07 and 5.24\ifmmode\pm\else\textpm\fi{}0.05 \AA{}. The short side is rotated 5.7\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}0.2\ifmmode^\circ\else\textdegree\fi{} with respect to the graphite unit mesh. Analysis of published neutron-diffraction data indicates that ${S}_{2}$ is a herringbone structure with two molecules per unit mesh.

Characteristics of high energy interactions II. Production spectra of Gamma-rays in graphite

Twenty high energy nuclear interactions produced in the graphite units of an emulsion chamber were recorded. The emulsion chamber was exposed to cosmic rays at an atmospheric depth of 10 g cm−2 for about 7 hr over Hyderabad, India. Fourteen interactions which radiated energyΣ Er⩾1000 GeV in the form ofγ-rays were analysed in detail. The median energy 〈Σ Er〉 of the interactions was 1600 GeV. Results concerning the multiplicity, the transverse and longitudinal momentum distributions, and the fractional energy distribution ofγ-rays in these interactions are presented. The average transverse momentum ofπ0—mesons is found to increase very slowly with the primary energyE0 and it can be approximated by the function =0·238E00.06.

Vulcanizate Performance as a Function of Carbon Black Morphology

Abstract A new nomenclature is proposed for carbon black morphology to be based on actual quantitative electron microscopical measurements. Carbon black is now defined in terms of “paracrystalline graphitic units” which are composed of interlocking “domains of rotational graphitic layer orientation”. The measurement of “unit” or “domain” dimensions replaces the earlier imprecise concepts of structure and particle size. Automated measuring procedures have been developed for determining carbon black unit and domain size functions using a Quantimet Image Analyzing Computer. Unit dimensions are expressed in terms of total projected length (L), average width (W), two-dimensional projected area (A), and form factor (L/W). Domain size (d) measurements have been programmed to give comparable results to earlier carbon black “particle” size determinations using a Zeiss Particle Size Analyzer. The new program enables measurement of similar classes of blacks (e.g., tread grades) under identical instrumental conditions, thus greatly reducing the problem of operator subjectivity. Meaningful correlations have been determined for several vulcanizate properties in terms of the above carbon black parameters. Domain size was found to be the most significant variable in the correlations with resilience, showing a positive relationship. Increasing unit form factor, indicated a depressing effect on resilience and was also the most significant single variable in regard to heat build-up and hardness, showing a positive relationship with both of these properties. A significant inverse correlation with heat build-up and hardness was observed for unit or domain size, when the full range of rubber grade carbon blacks were evaluated. Tensile strength showed an inverse relationship with unit or domain size in the SBR and SBR/BR systems that were studied. In natural rubber, however, there was also a significant depressing effect on tensile strength, attributable to increasing unit form factor. Modulus showed a strong positive correlation with unit length or form factor and an inverse relationship with domain or unit size. High unit form factor was also the most significant variable in reducing extrusion swell. High abrasion resistance (treadwear) was favored by high form factor, low unit size, and low domain size in that order of significance.

Electron Phase Contrast Images of Molecular Detail

Electron phase contrast images with a resolution of at least 2 A have been obtained using a modified commercial electron microscope. A “phase column” approximation for interpreting such images is briefly discussed and applied to images of graphite, evaporated carbon, and a synthetic polypeptide. Hexagonal features about 5 A in diameter are attributed to the graphite unit cell imaged by the six first-order prism plane reflections. The image so produced is a next-nearest neighbor representation.

Observations of Crystal Structure And Particle Shape in Electron Micrographs of Several Carbon Blacks

As a sequel to an earlier paper, electron micrographs are shown which demonstrate crystal structure directly in so‐called amorphous carbon blacks. The crystalline particles of such a substance have a smaller mean size than the amorphous particles in the total distribution. The effect of variable particle shape upon such things as mean particle diameter and specific surface calculations is pointed out. It is suggested from all the experimental evidence, including electron and x‐ray diffraction data, that the crystal particles are small graphitic units, and that the graphitic nature of the carbon black is a surface rather than a volume phenomenon. The presence of the crystalline component in a carbon black distribution seems to be an intrinsic property of acetylene black made at high temperature.