Ceylon Graphite Research Articles

Fabrication of r-GO/GO/α-Fe2O3/Fe2TiO5 Nanocomposite Using Natural Ilmenite and Graphite for Efficient Photocatalysis in Visible Light

Hematite (α-Fe2O3) and pseudobrookite (Fe2TiO5) suffer from poor charge transport and a high recombination effect under visible light irradiation. This study investigates the design and production of a 2D graphene-like r-GO/GO coupled α-Fe2O3/Fe2TiO5 heterojunction composite with better charge separation. It uses a simple sonochemical and hydrothermal approach followed by L-ascorbic acid chemical reduction pathway. The advantageous band offset of the α-Fe2O3/Fe2TiO5 (TF) nanocomposite between α-Fe2O3 and Fe2TiO5 forms a Type-II heterojunction at the Fe2O3/Fe2TiO5 interface, which efficiently promotes electron-hole separation. Importantly, very corrosive acid leachate resulting from the hydrochloric acid leaching of ilmenite sand, was successfully exploited to fabricate α-Fe2O3/Fe2TiO5 heterojunction. In this paper, a straightforward synthesis strategy was employed to create 2D graphene-like reduced graphene oxide (r-GO) from Ceylon graphite. The two-step process comprises oxidation of graphite to graphene oxide (GO) using the improved Hummer's method, followed by controlled reduction of GO to r-GO using L-ascorbic acid. Before the reduction of GO to the r-GO, the surface of TF heterojunction was coupled with GO and was allowed for the controlled L-ascorbic acid reduction to yield r-GO/GO/α-Fe2O3/Fe2TiO5 nanocomposite. Under visible light illumination, the photocatalytic performance of the 30% GO/TF loaded composite material greatly improved (1240 Wcm-2). Field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) examined the morphological characteristics of fabricated composites. X-ray photoelectron spectroscopy (XPS), Raman, X-ray diffraction (XRD), X-ray fluorescence (XRF), and diffuse reflectance spectroscopy (DRS) served to analyze the structural features of the produced composites.

An Improved Technique for the Exfoliation of Graphene Nanosheets and Utilization of their Nanocomposites as Fuel Cell Electrodes

Graphene is a flat monolayer of carbon atoms tightly packed into a two-dimensional 2D honeycomb lattice. The graphene sheets in graphite interact with each other through van der Waals forces to form layered structure. The first graphene sheets were obtained by extracting monolayer sheets from the three-dimensional graphite using a technique called micromechanical cleavage in 2004 [. There are numerous attempts in the literature to produce monolayer graphene sheets by the treatment of graphite. The first work was conducted by Brodie in 1859 and GO was prepared by repeated treatment of Ceylon graphite with an oxidation mixture consisting of potassium chlorate and fuming nitric acid [. Then, in 1898, Staudenmaier produced graphite oxide (GO) by the oxidation of graphite in concentrated sulfuric acid and nitric acid with potassium chlorate [. However, this method was time consuming and hazardous. Hummers and Offeman found a rapid and safer method for the preparation of GO and in this method graphite was oxidized in water free mixture of sulfuric acid, sodium nitrate and potassium permanganate [.

Development of low-background vacuum extraction and graphitization systems for 14C dating of old (40–60 ka) samples

At the University of Arizona's Desert Laboratory, we recently constructed new low-background vacuum extraction and graphitization systems that are dedicated to preparing old (40–60 ka) samples for 14C dating. These systems are designed to minimize the amount of contaminant carbon, specifically atmospheric carbon, that is introduced to a sample during laboratory processing. Excluding contaminants is particularly important for 14C dating of old samples because the impact of contamination increases with sample age. In this study, we processed 20 pretreated and 4 untreated aliquots of Ceylon graphite (a naturally-occurring geological graphite) to determine the total procedural background level, and hence the practical limit, of our systems. Samples were heated under vacuum at 240 °C for 1 h to drive off water vapor and other atmospheric gases, and then combusted in ultra-high-purity (UHP) O 2 at 500 and 850 °C to monitor the removal of contaminants and to ensure complete combustion. After SO X , NO X , and halide species were removed, sample CO 2 was converted to graphite via catalytic reduction of CO. Fe and Zn powders used in the graphitization process were oxidized, “scrubbed”, and reduced with UHP O 2, He, and H 2, respectively, to remove sorbed atmospheric C species. Graphite targets were stored in UHP Ar until measurement by accelerator mass spectrometry (AMS) to avoid potential interaction with atmospheric gases. Based on the AMS results, the background level of our system is characterized by a nonlinear inverse relationship with sample mass (adjusted R 2=0.75; n=24). For a 1 mg graphite target, the total procedural blank, including chemical pretreatment, combustion, cleanup, graphitization, storage, and AMS measurement, is 0.05±0.01 pMC (2 σ), equivalent to a 14C “age” of 61.1±1.8 ka. This should not be taken as the upper limit of our system, however, because if the 14C activity of a sample is statistically indistinguishable from the appropriate mass-dependent blank value at the 95% confidence level (2 σ), then its age is considered to be “infinite”. Thus, for a 1 mg target, the practical limit of our system is actually ∼55 ka; for a 0.5 mg target, the practical limit is ∼50 ka. Although our extraction system can accommodate inorganic samples (e.g., calcite, aragonite), the above limits are only applicable to geological graphite, charcoal, and organic samples that are processed via combustion. Future work will be directed toward determining the appropriate background levels for inorganic materials.

Intercalation compounds as precursors for oriented catalysts

The oxyhydrolysis of MoCl 5 Ceylon graphite intercalation compounds, in the 400 – 500 °C temperature range, gives MoO 3-graphite oriented catalysts. (010) MoO 3 crystalline faces are parallel to the (001) graphite sheets. Catalytic properties in propylene oxidation are governed by the distribution of the MoO 3 faces and controlled by the temperature of preparation. From the example of the MoO 3-graphite system, it appears that intercalation compounds can be precursors for oriented catalysts with a strong interaction of the graphite support with the active phase, which improves the catalytic properties.

Relation entre les proprietes acides de graphites naturels et leur activite catalytique dans l'isomerisation de l'oxyde de styrene

The surface properties of two natural graphites have been investigated by catalytic activity in the isomerisation of styrene oxide to phenylacetaldehyde and by programmed thermodecomposition (TDP) combined with mass spectrometry gas analysis. The oxygen and water vapour influence has been studied in both cases. The two catalysts are respectively a natural Ceylon graphite (GC solid) with a 3.0 m 2/g BET area and a natural Madagascar graphite (GM solid) which has been ground and has a 10.6 m 2/g BET area (Table 1). The catalytic isomerisation runs were carried out at 305°C and the results are summarised in Table 2 for different gas mixture compositions. Oxygen directly favours the conversion (TTG) while water vapour mainly influences the selectivity (S). The thermodecomposition products of these solids are mainly CO and CO 2 as shown on Fig. 1. However the relative percentage of CO 2 which is related to the acidic properties of graphites (24) is very different, 16% of the BET area for the GC solid, but only 2% for the GM solid (Table 3). When the catalyst CC is pretreated at 300°C in oxygen instead of nitrogen, the TDP spectrum remains the same but the number of sites remarkably increases as shown in Table 4. Moreover the comparison of Tables 2 and 4 shows a parallelism between isomerisation activity and acidic properties. For this reason, we further investigated the influence of gaseous atmosphere by studying the TDP of the two graphites, first degassed at 850°C and then pretreated at 300°C with air or nitrogen in presence (or not) of water vapour. Important modifications are observed in the spectra (Figs. 2 and 3). Oxygen increases the total number of acid sites. The effect of water vapour is weaker. However, for the GM solid it increases the relative percentage of strong acid sites, i.e. desorbing at the lowest temperatures. For the GC solid, the effect is opposite. These results suggest that only a fraction of the acid functional groups is active for isomerisation, specifically those desorbing CO 2 near the reaction temperature. This assumption is also supported by the fact that a used catalyst presents such groups, while a fresh one does not, as shown on Fig. 4, which means that catalytic sites have been developed during reaction. Their number is increased when oxygen is present in the gaseous phase, and their stability is modified by the presence of water vapour.

Carbonaceous Material in Some Metamorphic Rocks of New England and Other Areas

Carbonaceous material in regionally metamorphosed coal, black slate, graphite schist, and mica schist shows the following continuous changes with increasing metamorphic grade: increase in particle size; loss of hydrogen, nitrogen, and oxygen ; increase in the carbon content; a decrease in the peak width of the (002) reflection; and a shift of the (002) reflection to a higher $$2\theta$$ position. These changes are greatest in the chlorite zone, where distinct (111) lines replace an unmodulated (111) band. In this study, only carbonaceous material from the staurolite and sillimanite zones is pure carbon. A large extent of layer ordering is acquired in the chlorite and biotite zones, but well-ordered graphite, comparable with Ceylon graphite, is limited to the sillimanite zone. There is little growth in the carbonaceous particles until the staurolite zone; in lower-grade zones, they rarely exceed 0.02 mm. The temperature at which layer ordering first appears in regionally metamorphosed rock is roughly 300°-...

Geology of bogala mine, ceylon and the origin of vein-type graphite

The unique vein-type graphite deposits of Ceylon occur in high-grade metamorphic terrain of Early Precambrian metasedimentary series. At the Bogala graphite mine, the rocks are of the granulite and almandine amphibolite metamorphic facies. The direction of veins is strongly controlled by the two major regional lineation directions; veins with a third direction are also present. The veins are very irregular in length, width, and local attitude and contain only minor amounts of other minerals than pure graphite. Each vein is made up of a number of parallel graphite sheets oriented parallel to the vein. It is suggested that the Ceylon graphite veins, and possibly all similar deposits, form by lateral secretion. The graphite is obtained from the surrounding carbon-rich sediments and transported in the solid phase as the slippery graphite grains move along grain boundaries down a pressure gradient. The graphite accumulates along the relatively low-pressure zones of fractures. Each graphite sheet within the vein represents a period of pressure release along the fracture.

Structure of Kish and Other Graphites

FRANKLIN1 assumed that there were only two types of layer in graphitic carbons: parallel and oriented and parallel but disoriented layers. The disoriented layers occur randomly with a probability p, between the oriented layers. From this assumption she obtained a simple formula for the intensity curve in reciprocal space: where l is the crystallographic index and U = 1 − p. This is a special case of the more general intensity formula for X-rays scattered from disordered layer lattices2,3. All Franklin's intensity curves of the 11&2bar;2 line, obtained with graphitized carbons heated to between 1,720° and 3,000° C., are very close to the theoretical curves, estimated p values ranging from 0.9 to 0.1. Bacon4 showed that the formula was also applicable to well-crystallized graphites, such as Ceylon graphite, and to three artificial samples.

On the Thermal Expansion of Graphite

c-dimensions of Ceylon graphite have been measured by X-ray diffraction method in the range 25-800°C with a camera specially designed for this purpose. The diameter of the camera is 24 cm, NiKα1 rays being used for 0008 line. The shifts of the line by temperature rise are fairly large and about 4 mm per 100°C, which permit four or more diffracted lines at different temperatures to be photographed on a fixed film through a movable aperture. The changes of the c-dimensions are determined from the records obtained in this way.An empirical formula of the c-dimensions as a function of temperature and a graphic chart plotting the measured points together with the points obtained by other authors are presented.

Rate of Transformation of Rhombohedral Graphite at High Temperatures

THE hexagonal modification of graphite (common graphite) is composed of identical layers of stacking sequence ABAB …, while in the rhombohedral modification the sequence is ABCABC …, the latter modification being confirmed by Lipson and Stokes1. The occurrence of this modification and the enhancement and weakening of the X-ray diffraction lines belonging to it by chemical, mechanical and thermal treatments have been described by Hofmann2, who states that it is transformed to the hexagonal modification in a graphitizing oven in an atmosphere of carbon monoxide at 3,000° C. In the course of experiments on the thermal expansion of graphite by X-ray diffraction3, I observed that the corresponding lines were markedly weaker at much lower temperatures in vacuo. The rates of transformation were measured using the following improvements in technique. (1) Plate specimens were used in place of rods; to achieve a definite degree of orientation of crystals, 21 mgm. of powder of Ceylon graphite of average diameter 0.05 mm., purified with hydrochloric and hydrofluoric acids, was compressed to a plate 0.5 mm. thick and 6 mm. in diameter with a pressure of 40 kgm. without adding any adhesive substances. (2) The plate was mounted on a Debye–Scherrer camera 20 cm. in diameter so as to bisect the angle between the incident and diffracted rays and oscillated about this angle with a half-amplitude of 30°. (3) Since, with cobalt K-radiation, the curvatures of the diffraction lines were not large, a stepped absorber made by piling aluminium foils was placed in front of the photographic film so that the blackening of each line was graded by known ratios, permitting more accurate determination of the intensities than by the use of intensity marks photographed on one side of a film.

Low Temperature Heat Capacity of Ceylon Graphite

Low Temperature Heat Capacity of Ceylon Graphite

A high-temperature, X-ray diffraction, powder camera

A high-temperature Debye-Scherrer camera fitted with a small carbon-tube furnace, which is capable of attaining temperatures as high as 1800° C, is described. The furnace is housed in an evacuated cylinder having a slot covered with an aluminium foil. The scattered X-rays pass through the foil and impinge on a photographic film 20 cm in diameter. The camera records a comparison pattern on a film. The coefficients of thermal expansion of the Ceylon graphite determined with the camera are 0.95 × 10-6 and 28.09 × 10-6 respectively for a- and c- dimensions in the temperature range 1000-1800° C.

The Thermal Expansion of Various Carbons, its Thermal Dependence, and Carbons having Negative Expansion Coefficient

Thermal expansion of various carbons brerared at 1200°C or graphitized, have been measured over the temperature range frome room temperature (20°C) to about 600°C by using a dilatometer, shown in Fig 1.The mean thermal expansion coefficient “α” of various carbons are found to differ largely with each other in its kind. Some of these as anthracite and Ceylon graphite was anisotropic in α. Particulary, pitch coke which is anisotropic in its bubble pore and is heated at 1200°C or graphitized, and anthracite which is graphitized, have showed a “negative α”, up to certain temperature along its layer direction. A specimen, molded with mixed powder of Ceylon graphite and pitch, showed also a negative α in a direction perpendicular to the molding pressure. Expansion of most carbons and contraction of anisotropic pitch cokes with increasing temperature is seen in Fig 2. The α values of these specimens showed a linear increase with increasing temperature in these temperature range as is seen in Fig 3. The coefficient of the temperature dependence of α was 1.8×10-9 for petroleum or pitch cokes and this is not affected whether it is block of raw material or formed article and it is graphitized or not. Other carbons such as metallurgical coke have different cofficient of thermal dependence of α respectively.

The thermal expansion of graphite from 15 c. to 800 c.: part I. Experimental

The variation with temperature of the a and c unti-cell dimensions of hexagonal Ceylon graphite has been measured over the temperature range 15°-800°c. by the X-ray powder method. At 14°6c., a=2.4562±0.0001 kx. c=6.6943±0.0007 kx. The carbon-carbon bond length, C-C=1.4210±0.0001a. The a dimension shows a slight contraction up to about 400°c., a small expansion occurring above this temperature. The thermal expansion in the c direction is large; the average value for a over the temperature range is 28.3 × 10-6. The complex nature of the expansion in both directions is discussed qualitatively.

Shape of the Modified Compton Line for Hydrogen and Ceylon Graphite Scatterers

Shape of the Modified Compton Line for Hydrogen and Ceylon Graphite Scatterers

Effect of Temperature on Diffraction of Slow Electrons and its Application

WE have investigated the influence of temperature on the intensity (IT) maxima due to the diffraction of slow electrons from a cleavage plane of Ceylon graphite, using the method of constant Bragg angle (θ = 65°). The apparatus used in these experiments is described in detail elsewhere1.

Attack of Oxygen Molecules upon Highly Crystalline Graphite

THE accompanying photographs (Fig. 1) illustrate an observation made while studying the oxidation of graphite. A thin flake of Ceylon graphite (99.9 per cent carbon) was oxidised during many hours at 900° C. in a stream of oxygen at 1 mm. pressure. (The product is about 50 per cent carbon dioxide and 50 per cent carbon monoxide.) Photomicrographs were taken at intervals ; the two reproduced show the state of the flake when probably more than four-fifths of the original graphite had been oxidised away. In both, the flake is viewed, roughly, perpendicularly to the cleavage plane, A by light reflected from this plane, B by transmitted light.

A Search for Preferentially Directed Electron Velocities in Crystalline Graphite with the Multicrystal Spectrograph

The author's theory of the broadening of the Compton line as a Doppler effect of electron velocities is briefly reviewed and it is pointed out that only the component velocity along a direction which nearly bisects the angle between primary and scattered x-ray beams should be effective in broadening the line. Crystalline Ceylon graphite possesses properties which lend hope to the belief that a class of weakly bound or structure electrons in this crystal might have momenta restricted uniquely to parallelism with one plane in the crystal: the (0001) plane. A composite scatterer was built up out of blocks consisting of the crystal flakes all orientated with their (0001) planes in mutual parallelism and the blocks in turn were so orientated that the normals to these planes bisected the angle formed by the primary and scattered x-ray beams. If the electron momenta are orientated parallel to the plane of the graphite flakes one should expect the contribution of such electrons to the shifted scattering to give a sharp line or peak superposed on the broader structure caused by the remaining isotropically distributed momenta. Details of the experimental set-up are described and the spectrum obtained from scattering by the Ceylon graphite scatterer is compared with the spectrum from an isotropic Acheson graphite scatterer. The breadth and structure of the shifted line proves to be quite identical in the two cases and the conclusion is drawn that if a class of electrons having selectively orientated momenta exists in the crystal-line graphite it constitutes less than 5 percent of the total number. The bearing of this result on related questions is discussed.

Possible Narrowing of Compton Line Breadth by Preferentially Directed Electron Momenta in Ceylon Graphite

According to a theory of the author first published in Phys. Rev. 33, 643 (1929), the considerable natural spectral breadth of the Compton modified line was ascribed to the initial momenta of electrons in the scattering body and as one consequence a mathematical expression was derived for the behavior of this breadth as a function of the primary wavelength and scattering angle (formula 23, page 657, above article).