Variation in maceral chemistry within and between coals of varying rank: An electron microprobe and micro-Fourier transform infra-red investigation

Electron microprobe and reflectance micro-Fourier infra-red techniques have been used to document the evolution of maceral chemistry from lignite to anthracite as well as to determine chemical variations between macerals and within macerals in iso-rank coals. This study shows that the evolution of elemental composition and functional groups in vitrinite differs from those of liptinite. In vitrinite, there is a decrease in the absorbance of both aliphatic stretching bands (2800–3000 cm^—1) and the aromatic band (1600 cm^—1) with an increase in rank from high-volatile bituminous to anthracitic coals. The change in functional groups is associated with an increase in C content from about 86 up to 94% and a decrease in O content from 7 to 1%. In sporinite, carboxyl/carbonyl bands (1710 cm^—1), distinct in sub-bituminous and high-volatile bituminous ranks, disappear at higher rank. The 1600 cm^—1 band is relatively weak in liptinite and increases dramatically when liptinite and vitrinite coalification paths merge. These changes in sporinite functional groups are accompanied by an increase in C content from 73 to 88–89%, decrease in O from 14 to 4% and decrease in H from more than 9 to less than 4%. Variations in chemistry between macerals and within macerals depend on coal rank. Up to high-volatile bituminous rank, liptinite macerals have higher absorbances of aliphatic stretching bands and lower absorbances of the aromatic 1600 cm^—1 band than any other macerals. At medium-volatile bituminous rank, aliphatic stretching bands are distinct in vitrinite and semifusinite and very weak to absent in other inertinite macerals. At anthracitic rank, variations both in elemental composition and in functional groups between maceral groups are of the same magnitude as within maceral groups.     

Current uses of fluorescence microscopy in coal petrology

Fluorescence analysis of the liptinite maceral content of various U.S. coal seams has shown that these macerals are consistently under-counted in conventional white-light analysis. Fluorescence analysis revealed a greater variety of liptinite macerals as well as a large amount of fluorescing vitrinite in all of the coals studied. However, pseudovitrinite was not observed to fluoresce. Textures and structures not visible in normal viewing are also seen in fluorescence analysis. Quantitative spectral analysis of single coals has shown that most liptinite macerals can be both petrographically and statistically separated on the basis of fluorescence parameters, with the wavelength at maximum intensity and the red/green quotient being the most significant. In coals of the Illinois Basin, one or more forms of fluorinite, resinite, sporinite and cutinite can be distinguished. As the rank of the coal increases, the fluorescence intensity decreases and the spectral maxima shift toward longer wavelengths. In some Rocky Mountain coals these effects occur at a much lower rank (<0.85% reflectance) than in the coals of the Appalachian Basin. Similar changes in fluorescence properties have also been found in naturally weathered coals. Fluorescence analysis of resinite-rich Rocky Mountain coals has shown that two major forms of resinite are present; one is the ‘normal’ resinite, and the other is a much more abundant fissure-filling resinite that carries coal xenoliths, shows flow structure, and has a spectral maximum well below that of the ‘normal’ resinite.     

Heterogeneity of shale documented by micro‐FTIR and image analysis

In this study, four New Albany Shale Devonian and Mississippian samples, with vitrinite reflectance [R_o] values ranging from 0.55% to 1.41%, were analyzed by micro‐FTIR mapping of chemical and mineralogical properties. One additional postmature shale sample from the Haynesville Shale (Kimmeridgian, R_o = 3.0%) was included to test the limitation of the method for more mature substrates. Relative abundances of organic matter and mineral groups (carbonates, quartz and clays) were mapped across selected microscale regions based on characteristic infrared peaks and demonstrated to be consistent with corresponding bulk compositional percentages. Mapped distributions of organic matter provide information on the organic matter abundance and the connectivity of organic matter within the overall shale matrix. The pervasive distribution of organic matter mapped in the New Albany Shale sample MM4 is in agreement with this shale's high total organic carbon abundance relative to other samples. Mapped interconnectivity of organic matter domains in New Albany Shale samples is excellent in two early mature shale samples having R_o values from 0.55% to 0.65%, then dramatically decreases in a late mature sample having an intermediate R_o of 1.15% and finally increases again in the postmature sample, which has a R_o of 1.41%. Swanson permeabilities, derived from independent mercury intrusion capillary pressure porosimetry measurements, follow the same trend among the four New Albany Shale samples, suggesting that micro‐FTIR, in combination with complementary porosimetric techniques, strengthens our understanding of porosity networks. In addition, image processing and analysis software (e.g. ImageJ) have the capability to quantify organic matter and total organic carbon – valuable parameters for highly mature rocks, because they cannot be analyzed by micro‐FTIR owing to the weakness of the aliphatic carbon–hydrogen signal.     

Application of micro‐FTIR mapping and SEM to study compositional heterogeneity of siltstones: Example from the Late Devonian–Early Mississippian Middle Bakken Member

This paper explores the applicability of micro‐FTIR mapping to study heterogeneity of organic matter‐lean siltstones. Closely spaced samples of Late Devonian dolomitic siltstones of the Middle Bakken Member were analysed with micro‐FTIR, powder X‐ray diffraction, and scanning electron microscopy (SEM) to explore the distribution and chemical properties of organic matter (OM), muscovite/feldspar/clay group, carbonates, and quartz, and their influence on porosity and permeability of these rocks. Our results show that quartz is the dominant component of the samples, and the main mineralogical differences between the samples are reflected in the abundance of carbonate minerals. Organic matter content is usually far below 1 wt. % and dominantly represented by terrestrially derived vitrinite and inertinite. Micro‐FTIR mapping demonstrates that the more spatially connected quartz and muscovite/feldspar/clays become, the larger permeability in the rock develops, and these correlations are especially strong for planes parallel to bedding. In contrast, carbonate connectivity shows a strong negative correlation with permeability. No correlations between connectivity of components and porosity have been detected. These observations suggest that micro‐FTIR not only can document compositional heterogeneity of siltstones, but also has potential to help understanding their permeability systems.     

New synthetic esters with a complex structure considered as tribological fluids

The paper presents results concerning synthesis and characterisation as lubricant fluids of some esters of different monocarboxylic acids with variable chain length, along with aliphatic‐aromatic complex alcohols and/or with superior alcohols (exclusive of aliphatic). The monocarboxylic acids taken into account were n‐butyric, n‐octanoic and oleic, respectively, while the alcohols considered were isodecyl and isotridecyl as purely aliphatic, and 2‐phenoxy‐ethanol, 2‐[(o‐sec‐butyl)phenoxy]ethanol and 2‐[(p‐nonyl)phenoxy]ethanol, as part of the complex aliphatic‐aromatic alcohols group. Under these circumstances, it became possible to study the influence of the structure on the main physico‐chemical properties of these synthetic oils as well as on their tribological representative features. The results recorded certified the validity of the proposed research programme. Copyright © 2009 John Wiley & Sons, Ltd.     

Electron stimulated decomposition of fluorocarbons on amorphous hydrogenated carbon (<Emphasis Type="Italic">a</Emphasis>-CH<Subscript>x</Subscript>) overcoats used in data storage media

The electron-induced surface chemistry of perfluoropolyalkylether (PFPE) lubricants on a-CH_x films has been probed by studying the impact of free electrons on perfluorodiethylether, (CF₃CF₂)₂O, and 2,2,2-trifluoroethanol, CF₃CH₂OH, as models of the chemical functionality of PFPE lubricants such as Fomblin Zdol. Electron-stimulated decomposition of (CF₃CF₂)₂O and CF₃CH₂OH on fresh and oxidized a-CH_x is observed when the sample is unbiased and in the presence of 70 eV free electrons. Electron-induced decomposition is indicated by the deposition of fluorine onto the surface of the a-CH_x film following desorption of molecular (CF₃CF₂)₂O and CF₃CH₂OH by heating in front of a mass spectrometer. Biasing the sample to −80 V successfully eliminates the decomposition by preventing the impingement of electrons onto the surface. The electron-stimulated decomposition of PFPE lubricants may contribute to lubricant decomposition during normal drive operation.     

Tribological Properties of Nanocomposite CrC<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/a-C:H Thin Films

Recently we showed that coatings, prepared by unbalanced magnetron sputtering from a metallic Cr target in an Ar/CH₄ discharge are composed of nanocrystalline CrC _x embedded in an a-C:H matrix. This work investigates the structural correlation of such nanocomposite CrC _x /a-C:H coatings to their tribological properties. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize the phase composition and the chemical bonding in the films deposited at different experimental conditions. The coating microstructure was investigated on selected samples by high-resolution transmission electron microscopy. For CrC _x -dominated coatings deposited at CH₄ partial to total pressure ratios (p_CH4/p_t) < 0.42, only minor changes regarding the friction coefficients and the abrasive wear rates were observed although microstructural changes towards a higher degree of crystallinity were proven by transmission electron microscopy and substantiated with XPS results. For a-C:H dominated coatings deposited at p_CH4/p_t > 0.42, the friction coefficients and abrasive wear rates were shown to decrease with increasing a-C:H phase content and its more sp²-like bonding configuration. It can be concluded that the microstructural changes in terms of CrC _x crystallite coarsening and bonding configuration of the a-C:H matrix phase are responsible for the observed changes of the friction coefficients and wear rates.     

Adsorption of Water on Lubricated and Non Lubricated TiC Surfaces for Data Storage Applications

In this work we have studied the adsorption of water on TiC-coated quartz crystals to evaluate the use of TiC as a potential candidate for overcoats on magnetic media. It was observed that at room temperature the amount of adsorbed water onto thick sputtered TiC films, up to 20 nm in thickness, was similar to the amount of water adsorbed on standard amorphous 1.0–5.0 nm thick CHx films, which are currently used as protective overcoats on magnetic media. The sputtered TiC lubricated with Fomblin ZO3 in Vertrel XF solution also shows similar amounts of water adsorption as compared to unlubricated CH _x films. The amount of water adsorbed on TiC and CH _x films was measured in-situ by a quartz-crystal microbalance apparatus in an ultra-high vacuum chamber.     

Influence of UV irradiation in low frictional performance of CNx coatings

The influence of ultraviolet (UV) irradiation on low frictional performance of CN_x coatings with 100 nm thickness having nitrogen contents of 9%, 14% and 19% deposited on Si(100) substrate by ion beam mixing was investigated in N₂ atmosphere environment. Three UV lights of 254, 312 and 365 nm were used to irradiate the surface of CN_x / Si(100) for 60 min. The changes of N / C ratio and atomic binding energy in the coating were analysed using Auger electron spectroscopy and X‐ray photoelectron spectroscopy, respectively. The friction coefficient of Si₃N₄ ball sliding against CN_x was measured by a pin‐on‐disc tribometer, and wear tracks were analysed by the transmission electron microscope image. The results showed that UV irradiation on CN_x coating can decrease the critical frictional cycles for low friction coefficient and that the mechanism is due to the formation of graphite‐like structure in the topmost CN_x coating. Copyright © 2012 John Wiley & Sons, Ltd.     

Applicability of micro‐FTIR in detecting shale heterogeneity

Samples of Late Devonian/Early Mississippian New Albany Shale from the Illinois Basin, having maturities ranging from early mature to postmature, were analysed using micro‐Fourier transform infrared (FTIR) spectroscopy, ImageJ processing software and scanning electron microscopic X‐ray spectroscopy to explore the distribution, connectivity and chemical composition of organic matter, clay minerals, carbonate minerals and quartz, and to further test the applicability of micro‐FTIR mapping to study shale heterogeneity. Each sample was analysed in planes parallel and perpendicular to the bedding to investigate anisotropy in component distribution, with a possible implication for better understanding anisotropy in porosity and permeability in organic‐matter‐rich shales. Our results show that for low‐maturity samples, organic matter is better connected in the plane parallel to the bedding than in the plane perpendicular to the bedding. Organic matter connectivity decreases with increasing maturity as a result of kerogen transformation. Clay minerals are very well connected in both planes, whereas carbonate minerals are not abundant whilst dominantly isolated in most samples, independent of maturity. This study demonstrates that micro‐FTIR mapping is a valuable tool for studying shale heterogeneity on a micrometre to millimetre scale that becomes even more powerful in combination with scanning electron microscopy techniques, which extend observations to a nanometre scale. However, to obtain meaningful and comparable results, micro‐FTIR mapping requires very careful standardization, precise selection of peak heights/areas and mapping conditions (such as aperture size, scan numbers, resolution, etc.) well suited for the analysed samples.     

Potential of 'flat' fibre evanescent wave spectroscopy to discriminate between normal and malignant cells in vitro

The present study focuses on evaluating the potential of flattened AgClBr fibre‐optic evanescent wave spectroscopy (FTIR‐FEWS) technique for detection and identification of cancer cells in vitro using cell culture as a model system. The FTIR‐FEWS results are compared to those from FTIR‐microspectroscopy (FTIR‐MSP) method extensively used to identify spectral properties of intact cells. Ten different samples of control and malignant cells were measured in parallel by the above two methods. Our results show a significant similarity between the results obtained by the two methodologies. The absorbance level of Amide I/Amide II, phosphates and carbohydrates were significantly altered in malignant compared to the normal cells using both systems. Thus, common biomarkers such as Amide I/Amide II, phosphate and carbohydrate levels can be derived to discern between normal and cancer cells. However, marked differences are also noted between the two methodologies in the protein bands due to CH₃ bending vibration (1480–1350 cm⁻¹). The spectral differences may be attributed to the variation in the penetration depth of the two methodologies. The use of flattened fibre rather than the standard cylindrical fibre has several practical advantages and is considered as an important step towards in vivo measurements in real time, such as that of skin nevi and melanoma using special designs of fibre‐optic–based sensors.     

The structure and continuous stoichiometry change of 1DTbBrx@SWCNTs

HRTEM and HAADF STEM of 1DTbBr_x@SWCNT meta‐nanotubes reveal three structural modifications of 1D nanocrystals within single wall carbon nanotube channels attributed to a different stoichiometry of the guest crystal. For SWCNTs with diameters D_m > 1.4 nm a most complete tetragonal unit cell is observed. When crystallization occurs inside SWCNT with D_m < 1.4 nm 1D TbBr_x crystal deforms a nanotube to elliptical shape in cross section. In this case the 1D crystal unit cell becomes monoclinic, with possible loss of a part of bromine atoms. Two modifications of a monoclinic unit cell appear. One of them is characterized by single or pair vacancies in the structure of the 1D crystal. Another structure is explained by peripheral and central bromine atoms loss. An appearance of such modifications can be stimulated by electron irradiation. The loss of bromine atoms is in agreement with chemical analysis data. Electronic properties of obtained meta‐nanotubes are investigated using optical absorption and Raman spectroscopy. It is shown that intercalation of terbium bromide into SWCNTs leads to acceptor doping of SWCNTs. According to local EDX analysis and elemental mapping this doping can arise from significant stoichiometry change in 1D nanocrystal indicating an average Tb:Br atomic ratio of 1:2.8 ± 0.1.     

New citric esters with aromatic content and a complex structure considered for use as tribological fluids

This paper presents the results of research carried out to produce synthetic ester oils with a mixed structure, based on citric acid, with beneficial tribological properties and potential biodegradability. Two series of unsymmetrical triesters have been synthesised by varying the molar relationship between aliphatic alcohols from C₁, to C₁₃ along with an alcohol of a complex alkyl‐aryl structure, namely 2‐[(p‐nonyl)phenoxy]ethanol. The variation of the principal properties as a function of the length of the aliphatic chain introduced by the aliphatic alcohol and the aromatic content introduced by the alkyl‐aryl alcohol has been assessed. The wide range of viscosities of these triesters demonstrates their versatility, and the natural citric acid origin holds potential for their having good ecological characteristics.     

Structural analyses of Nd-doped CeO2 thin films deposited by pulsed laser deposition

CeO₂ thin films doped with neodymium oxides for application to gas sensors have been elaborated by the pulsed laser deposition technique. The films were deposited on orientated Si (100) substrates with variable deposition times (t = 90, 180 and 360 s) and molar fractions of Nd₂O₃ (0, 6.5, 15, 21.5 and 27 at.%). The resulting Nd–CeO₂ thin films were characterized by means of X‐ray diffraction analysis, scanning electron microscopy and transmission electron microscopy equipped with EDS (Energy Dispersive Spectrometer) microanalysis. From X‐ray diffraction analyses, it is clearly established that the texture is modified by Nd additions. The preferred (111) orientations of the CeO₂ crystals change into the (200) orientation. The morphology of the CeO₂ grains changes from triangles, for pure CeO₂ thin films, to spherical grains for Nd‐doped films. In addition, cell parameter analyses from X‐ray diffraction data show that a partial chemical substitution of Ce by Nd should occur in the face‐centred cubic lattice of ceria: this should give rise to Ce_1‐xNd_xO_2?z phases with oxygen non‐stoichiometry.     

The response of SiC fibres to vacuum plasma spraying and vacuum hot pressing during the fabrication of titanium matrix composites

Vacuum plasma spraying (VPS) and vacuum hot pressing (VHP) have been used to fabricate Ti-6Al-4V matrix composite material reinforced longitudinally with DERA Sigma C coated SiC 1140+ fibres. VPS of Ti-6Al-4V onto Sigma 1140+ SiC fibres caused no fibre/matrix interfacial reaction. During VHP a fibre/matrix reaction occurred, producing a mixture of fine (< 50 nm) TiC_x (x ≤ 1) adjacent to the fibre coating and coarse-grained (0.3–0.5 μm) equiaxed TiC_x adjacent to the Ti matrix. A decrease in C concentration with increasing distance from the C coating is proposed, and is consistent with the evidence presented. A similar thickness and morphology of reaction product arose from conventional foil–fibre foil processing, but the matrix coated fibre/hot isostatic pressing process led to a slightly thicker reaction layer. The TiC_x reaction product acted as a diffusion barrier, inhibiting further reaction more effectively than in experiments on earlier SiC fibres having a C coating. Surface damage was shown to be a factor in lowering 1140+ SiC fibre failure stress. Surface damage to 1140+ fibres resulted from both VPS and VHP, the former causing a slight reduction in mean ultimate tensile strength (UTS), and a large reduction in the bend strain to failure Weibull modulus. This damage was caused by both fibre winding and by deposition of metal during VPS, giving rise to coating flaws, and is not in itself considered to be a major problem. Surface damage increased after VHP, reducing the mean UTS and tensile Weibull modulus, and the mean bend strain to failure. This damage arose from bending and flattening of the rough monotapes, and from the fibre/matrix reaction caused by thermal exposure. The level of damage to 1140+ SiC fibre from VHP was reduced by modification of the process path. Increasing the VHP temperature and lowering the pressure ramp rate reduced fibre damage sufficiently to enable a macroscopic composite UTS of 95% of the theoretical maximum to be achieved.     

Study of two tungstates Ca0.5Cd0.5WO4 and Ca0.2Cd0.8WO4 by transmission electron microscopy

To better understand the role of crystal structures and local disorder in the photonic properties of the system (1 ? x)CaWO₄ ? xCdWO₄ with 0 < x < 1, two specific phases with compositions x = 0.5 (scheelite phase) and 0.8 (wolframite phase) have been studied by scanning and transmission electron microscopies. High‐resolution electron microscopy images and image simulations, associated with X‐ray diffraction data, allowed confirming the lattices and space groups I4₁/a and P2/c of the two scheelite and wolframite phases, at the local scale. The electron microscopy data show the existence of a high degree of crystallization associated with statistical distribution of Ca or Cd atoms on a Ca_1?xCd_x site in each lattice.     

Electron energy-loss near edge structure (ELNES) of InGaN quantum wells

Lasers and light‐emitting diodes (LEDs) that emit in the blue to green region are often based on In_xGa_1–xN quantum well structures. Ionization edges in the electron energy‐loss spectrum contain fine structures (called the energy‐loss near edge structure (ELNES)) and provide information about the electronic structure. In this paper we compare the experimental and calculated ELNES for the N‐K ionization edge of In_xGa_1–xN quantum wells. When the effects of the core‐hole are included in the calculations, agreement between experimental and calculated spectra is very good. Strain has been shown to accentuate the effects of In on the ELNES and moves the ionization edge onset down in energy, relative to the other features. These results suggest that ELNES may provide an alternative method to lattice imaging to determine the presence of strain in this system.     

Tribological behavior of a multialkylated cyclopentane oil under ultrahigh vacuum conditions

An ultrahigh vacuum, ball-on-flat test apparatus has been built to study the performance of candidate oils intended for spacecraft applications. Tests have been conducted on a multialkylated cyclopentane base oil using steel balls and disks. Different results are obtained when this oil is tested under vacuum conditions than when it is tested under a nitrogen environment. These differences are dramatic when the tests are conducted under starved conditions. Analyses of gases evolved during rubbing reveal that large quantities of methane are evolving from the process. A mechanism is proposed whereby oxide-free steel surfaces combine with tribological activity to crack the hydrocarbon oil to produce CH _x radicals. These CH _x radicals abstract hydrogen from the surrounding oil to produce methane. The increased volatility of the oil fragments remaining after methane formation leads to material loss by evaporation, thereby explaining the differences in vacuum and nitrogen performance of the oil.     

Microstructure and interfacial chemistry of pure and La‐doped BiFeO3 thin films

We report on the microstructure and interfacial chemistry of thin films of pure and La‐doped multiferroic bismuth ferrite (Bi_1‐xLa_xFeO₃ or BLFO), synthesized on Indium Tin Oxide‐coated glass substrates by solution‐deposition technique and studied using scanning transmission electron microscopy. Our results show that undoped and La‐doped thin films are polycrystalline with distorted rhombohedral structure without any presence of any line or planar defect in the films. In addition, the films with La doping did not show any structural change and maintain the equilibrium structure. Cross section compositional analysis using X‐ray energy dispersive spectrometry did not reveal either any interdiffusion of chemical species or formation of reaction product at the film‐substrate interface. However, a closer examination of the microstructure of the films shows tiny pores along with the presence of ～2–3 nm thin amorphous layers, which may have significant influence on the functional properties of such films. Microsc. Res. Tech. 76:1304–1309, 2013. © 2013 Wiley Periodicals, Inc.     

Pecularities of nanocrystal formation in rapidly quenched (FeCo)MoCuB amorphous alloys

The effect of the substitution of Fe by Co on the enhancement of glass‐forming ability limits and subsequent nanocrystallization was studied in a rapidly quenched amorphous system (Fe_xCo_y)₇₉Mo₈Cu₁B₁₂ for y/x ranging from 0 to 1. The effect of Cu on nanocrystallization was investigated by comparison with Cu‐free amorphous Fe₈₀Mo₈B₁₂. Systems partially crystallized at the surface layer were prepared for y/x = 0 using different quenching conditions. The effect of heat treatment of master alloys used for ribbon casting was also assessed. The microstructure and surface/bulk crystallization effects were analysed using transmission electron microscopy and electron and X‐ray diffraction in relation to the expected enhancement of high‐temperature soft magnetic properties, drastically reduced grain sizes (～5 nm) and Co content. Unusual surface phenomena were observed, indicating the origin of possible nucleation sites for preferential crystallization in samples with low Co content.