Amorphous Constituents Research Articles

Effect of molecular weight and the molecular weight distribution of a condensed polynuclear aromatic resin on the constituents and properties of their pyrolysis products

Three condensed polynuclear aromatic resins with different molecular weights (MWs) and MW distributions were heated at 900, 1500, 2200, 2600 and 3000 °C for 2 h. The resulting carbons were characterized by XRD, helium pycnometry and a powder electrical resistance test. The graphitic, amorphous and turbostratic constituents in the carbons were obtained from XRD. Results showed that both the MW and the MW distribution in the resins played important roles in the properties and constituents of the carbons produced from them. The larger the MW and the narrower the MW distribution, the higher the graphitic content in the carbons produced at 3000 °C. The larger the MW and the wider the MW distribution, the higher the apparent density of the carbons produced at the same pyrolysis temperature. The effect of MW on the powder resistance of the carbons is negligible.

Evaluation of soil analytical methods for the characterization of alkaline Technosols: II. Amorphous constituents and carbonates

The aims of this study were to identify potential sources of error in common methods for determination of amorphous oxide concentrations and carbonate concentrations, as applied to a Technosolic material (bauxite residue), and where possible, suggest improvements to the methods. An acid ammonium oxalate (AAO) extraction was applied to fresh and weathered bauxite residues, at soil to solution ratios varying from 1:100 to 1:800. Two methods for carbonate concentration were compared: the ‘weight loss’ method, and the ‘difference in total C’ method. These were applied to six weathered bauxite residue samples, with CaCO3 concentrations ranging from 0.1–2 % weight. Chemically extractable amorphous content was underreported in bauxite residue at the standard 1:100 extraction ratio, likely due to Al and Si saturation of the oxalate complex. A 1:400 soil: AAO ratio extracted the highest amount of amorphous material. Some crystalline minerals such as sodalite, inherited from the Technosolic parent material, were soluble in the acid ammonium oxalate extractant. The difference in total C method was more precise than the weight loss method for the determination of carbonate concentration in bauxite residues. The high amorphous content of bauxite residues requires a wider soil to solution ratio (1:400) for acid ammonium oxalate extraction than is used for typical soil materials (1:100). The difference in total C method is recommended for the routine analysis of field samples where small variations in carbonate concentration need to be detected.

Kinetic and thermodynamic studies on the thermal behaviour of fly ash from lignite coals

The kinetic and the thermodynamic characteristics of the physical and the physicochemical processes, taking place under thermal treatment of fly ash (FA) from lignite coals, were investigated. The obtained results are important for the thermal stability of this material, as well as for the determination of appropriate regimes for its zeolitization, vitrification and thermal activation. The thermal treatment is essential for the development of advanced technologies for utilization of ash residues. FA was subjected to differential thermal analysis (DTA) as the heating was performed at different rates: 2.5, 5.5, 11.0, 15.0, 25.0 and 35.0°Сmin−1. The obtained experimental thermograms were divided conditionally in three thermal zones: up to 200°C, 200–675°C and 675–950°C, where the following thermal effects were registered: first zone – an endothermic effect, attributed to the water desorption and the liberation of adsorbed gases; second zone – two exothermic effects, related to the chemical oxidation of the magnetite in the FA composition; third zone – a small endothermic effect in the interval 760–861°C related to the glass transition of the amorphous constituents of the FA. The activation energy Ea of the surface and the bulk oxidation of magnetite to hematite, corresponding to the exothermic peaks in the second zone, was calculated by the derived kinetic equations. The process thermodynamic parameters, such as enthalpy ΔH and entropy ΔS, were computed comparing the areas of the characteristic thermal effects of the investigated FA and an appropriate etalon. The values of Ea, ΔH and ΔS of the low- and the high-temperature oxidation were found to be E¯aL=29.3kJmol−1, ΔHL=1.01kJmol−1, ΔSL=1.67Jmol−1K−1, and E¯aH=51.7kJmol−1, ΔHH=3.97kJmol−1 and, ΔSH=5.05Jmol−1K−1, correspondingly.

Inverse determination of modeling parameters to consider inhomogeneities of semicrystalline thermoplastics in structure simulations

Two semicrystalline thermoplastics, an isotactic polypropylene (iPP, LynedllBasell Moplen HP501L) and a polyethylene-high-density (PE-HD, LynedllBasell Hostalen GC7260), were selected to approve a new approach. The developed approach allows the inverse determination of the amorphous and crystalline mechanical as well as the crystalline geometric constituents’ properties. Commonly, these properties are unknown in structure simulations, and hence, the application of micromechanical models to the inhomogeneous microstructure of semicrystalline thermoplastics is restricted. Rather, a homogenous microstructure is assumed, and only one Young’s modulus and Poisson’s ratio are used in calculations. Thus, the quality and reliability of simulations are limited. In the current study, a new approach was exemplarily conducted for the inverse determination of the required properties by combining a Mori–Tanaka mean field approach with a genetic optimization algorithm. Conclusive results were achieved for both polymers. According to the results, the attained geometric parameters for the crystalline constituents resemble the aspect ratio of the spherulite diameter and the long period of the real crystalline microstructure, and the mechanical properties of the amorphous and crystalline constituents are located within reasonable bounds.

Long-Range Ordered Carbon Clusters: A Crystalline Material with Amorphous Building Blocks

Solid-state materials can be categorized by their structures into crystalline (having periodic translation symmetry), amorphous (no periodic and orientational symmetry), and quasi-crystalline (having orientational but not periodic translation symmetry) phases. Hybridization of crystalline and amorphous structures at the atomic level has not been experimentally observed. We report the discovery of a long-range ordered material constructed from units of amorphous carbon clusters that was synthesized by compressing solvated fullerenes. Using x-ray diffraction, Raman spectroscopy, and quantum molecular dynamics simulation, we observed that, although carbon-60 cages were crushed and became amorphous, the solvent molecules remained intact, playing a crucial role in maintaining the long-range periodicity. Once formed, the high-pressure phase is quenchable back to ambient conditions and is ultra-incompressible, with the ability to indent diamond.

Enhancement of the magnetocaloric effect in composites: Experimental validation

Recent calculations have shown that the refrigerant capacity (RC) of magnetic refrigerants can be enhanced using multiphase materials or composites, which expand the temperature range over which a significant magnetic entropy change can be obtained. This work is a systematic experimental validation of the improvement of RC (RCI) using layered composites comprised of two Fe88−2yCoyNiyZr7B4Cu1 amorphous alloy constituents, with y=8.25 and y=11 compositions. RCI has a nonmonotonic dependence on the applied magnetic field H and the fraction x of the two constituent phases. In contrast to common assumptions, the composite has a smaller RCI than its constituent phases for small values of H and x, and there are critical values of each for which RCI is maximized. This work demonstrates the outstanding agreement between the experimental results and the continuous curves predicted by numerical calculations, indicating that this approach can be used to design magnetic refrigerant materials with enhanced magnetocaloric response for moderate magnetic fields.

A Comparative Overview of Glass-Ceramic Characterization by MAS-NMR and XRD

Glass-ceramics are polycrystalline materials formed by controlled crystallization of parent glasses, which can be studied complementarily by XRD and NMR. XRD probes long-range order, while NMR is more element specific and probes the immediate environment around the atoms. These techniques allow considerable insights into the crystalline and amorphous constituents of glass-ceramics. In this article, we highlight some key issues in the characterization of glass-ceramics: phase identification and quantification, and structural characterization of the residual glass. The application of both NMR and XRD techniques are considered in these areas and their advantages and limitations discussed using our recent work and examples from the literature.

Podzolic soils of Canada: Genesis, distribution, and classification

Sanborn, P., Lamontagne, L. and Hendershot, W. 2011. Podzolic soils of Canada : Genesis, distribution, and classification. Can. J. Soil Sci. 91: 843–880. Podzolic soils occupy 14.3% of the Canadian landmass, and occur in two widely separated areas, eastern Canada (northern Ontario, Quebec, Maritimes) and British Columbia, usually under coniferous forest and on non-calcareous parent materials. Broad climatic control of Podzol distribution and properties is evident at the national scale, with higher organic matter concentrations (Ferro-Humic Podzols) in wetter climates, in contrast to Humo-Ferric Podzols predominating in drier boreal forest regions. Humic Podzols are least abundant and are restricted to the wettest landscape positions. International and Canadian research suggests that a more diverse range of processes is involved in podzolization than was envisioned in the 1960s, and proposed mechanisms must account for observed patterns of organic matter distribution and a diverse array of inorganic amorphous constituents in profiles. Taxonomic concepts of Podzolic soils in the Canadian System of Soil Classification have remained consistent since the late 1970s, and the higher-level criteria defining the order and its great groups have proved to be meaningful in new applications, such as delineating soil carbon stocks across Canadian landscapes. Canadian contributions to pedological research on Podzols declined dramatically after 1990, coincident with shifting research priorities in soil science and diminished activity in soil survey.

Development of ultra high corrosion resistant sprayed amorphous alloy film constituents

Nakayama Steel Works LTD. has succeeded in attaining the cooling rate (105 -106 K/s) necessary for amorphous layering technique by using the innovative idea of immediately cooling the spraying flame. Amorphous alloy (Fe70Cr10P13C7) formed by the new technique displays a corrosion resistance more than 500 times higher than the one of SUS316L in aqua-regia immersion test, while the similarly formed amorphous magnetic alloy film (Fe81B13Si4C2) indicates high magnetism of 15.4 kGauss in magnetic flux density.

Amorphous Ni59Nb40PtxM1−x (M=Ru,Sn) electrocatalysts for oxygen reduction reaction

The oxygen reduction reaction, ORR, on amorphous Ni59Nb40Pt1, Ni59Nb40Pt0.6Ru0.4 and Ni59Nb40Pt0.6Sn0.4 electrocatalysts was analyzed by electrochemical techniques such as cyclic voltammetry, CV; rotating disk, RDE, and ring-disk electrodes, RRDE, in a 0.5 M H2SO4 solution. The reduced amount of platinum and the incorporation of transition metals in the amorphous catalysts were found to have significant effect on the kinetic parameters of the cathodic reaction. The kinetics study (RRDE) performed on the amorphous catalysts showed a high activity towards the ORR, preferentially proceeding via multi-electron (4e−) charge transfer pathway toward water formation, with less than 2.8% H2O2 in the region of PEMFC applications. The performance on Ni59Nb40Pt1 was different, which may be related to changes in the electrode surface enrichment of one or two of the amorphous alloy constituents. The performance towards the cathodic reaction allows to envisage that incorporation of small amounts of Pt in the catalyst, may lead to the fabrication of good amorphous electrocatalytic materials with possible applications as cathode electrodes in polymer electrolyte fuel cells.

The use of net analyte signal orthogonalization in the separation of multi-component diffraction patterns obtained from X-ray powder diffraction of intact compacts

X-ray powder diffraction (XRPD) analysis of intact multi-component consolidated mixtures has significant potential owing to the ability to non-destructively quantify and discriminate between solid phases in composite bodies with minimal sample preparation. There are, however, limitations to the quantitative power using traditional univariate methods on diffraction data containing features from all components in the system. The ability to separate multi-component diffraction data into patterns representing single constituents allows both composition as well as physical phenomena associated with the individual components of complex systems to be probed. Intact, four-component compacts, consisting of two crystalline and two amorphous constituents were analyzed using XRPD configured in both traditional Bragg–Brentano reflectance geometry and parallel-beam transmission geometry. Two empirical, model-based methods consisting of a multiple step net analyte signal (NAS) orthogonalization are presented as ways to separate multi-component XRPD patterns into single constituent patterns. Multivariate figures of merit (FOM) were calculated for each of the isolated constituents to compare method-specific parameters such as sensitivity, selectivity, and signal-to-noise, enabling quantitative comparisons between the two modes of XRPD analysis.

Microwave-Supported Preparation of α-Cellulose for Analysis of δ13C in Tree Rings

The microwave technique is found to be very applicable for the preparation of alpha-cellulose from wood samples and can be recommended for analyzing the stable carbon isotopes in tree rings. At a reaction temperature of 80 degrees C, the extraction time can be decreased from 36 h to 15 min. Microwave-supported prepared cellulose contains more amorphous constituents, resulting in a relatively higher reactivity and amenability for a following nitration with regard to determination of nonexchangeable hydrogen. The delta18O values of microwave-enhanced extracted cellulose remain significantly lighter than reference values, possibly as a result of an increased oxygen isotope exchange between bleaching solution and cellulose under conditions of high energy input. Therefore, this technique cannot be recommended for oxygen isotope analyses in wood cellulose.

Determination of glass content and estimation of glass composition in fly ash using quantitative X-ray diffractometry

The proportion of amorphous or glassy material in a series of fly ashes has been evaluated by X-ray powder diffraction (XRD) using the Rietveld-based SIROQUANT software package. Several different sample preparation and processing methods were investigated, including XRD analysis of samples spiked with known masses of synthetic corundum and zinc oxide as well as techniques based on analysing the raw or unspiked fly ash directly using the SIROQUANT process. In the latter case, two different poorly crystallised silicate mineral patterns, metakaolin and tridymite, were used in the SIROQUANT processing of the raw ash XRD data to represent the amorphous constituents. The results of the different methods based on XRD of spiked samples were found to be mutually consistent, and also consistent with other published data for an international reference fly ash sample. SIROQUANT analysis of the unspiked fly ashes gave similar results, although different poorly crystallised silicate reference patterns seem to be more suited for ashes from Australian and North American sources. The mineralogy of the ashes, including the proportions of quartz, iron oxide and glassy constituents, appears to be related to the nature of the mineral matter in the relevant feed coals. Calculations based on subtracting the inferred chemistry of the crystalline minerals in the fly ashes from the total fly ash chemistry were also used to estimate the overall chemical composition of the glass fraction in each ash. The results indicate that ashes derived from lower-rank coals in the samples studied have different glass compositions to those derived from higher-rank (bituminous) materials. These different glass compositions appear to be related to several other ash properties, including particle density and particle surface area. Evaluation of glass content and composition may be significant in different aspects of ash utilisation, and also in evaluating interactions with water at ash disposal sites.

Swelling of acetylated wood in organic solvents

To investigate the affinity of acetylated wood for organic liquids, Yezo spruce wood specimens were acetylated with acetic anhydride, and their swelling in various liquids were compared to those of untreated specimens. The acetylated wood was rapidly and remarkably swollen in aprotic organic liquids such as benzene and toluene in which the untreated wood was swollen only slightly and/or very slowly. On the other hand, the swelling of wood in water, ethylene glycol and alcohols remained unchanged or decreased by the acetylation. Consequently the maximum volume of wood swollen in organic liquids was always larger than that in water. The effect of acetylation on the maximum swollen volume of wood was greater in liquids having smaller solubility parameters. The easier penetration of aprotic organic liquids into the acetylated wood was considered to be due to the scission of hydrogen bonds among the amorphous wood constituents by the substitution of hydroxyl groups with hydrophobic acetyl groups.

Swelling of acetylated wood I. Swelling in organic liquids

To investigate the affinity of acetylated wood for organic liquids, acetylated yezo spruce wood specimens were soaked in various liquids, and their swellings were compared to those of untreated specimens. The acetylated wood was rapidly and remarkably swollen in liquids having low hydrogen bonding power such as benzene and toluene in which the untreated wood was swollen only slightly or very slowly. On the other hand, the swollen volume of wood in water, ethylene glycol, and alcohols remained unchanged or slightly decreased after the acetylation. The effect of acetylation was greater in liquids having smaller solubility parameters. The easier penetration of aprotic organic liquids into the acetylated wood was considered to be due to the reduction of polarity and the scission of hydrogen bonds in the amorphous wood constituents where the hydrophilic hydroxyl groups were substituted by hydrophobic acetyl groups.

Cycles in Perilacustrine Facies of Late Mesozoic Rift Basins, Southeastern Mongolia

Detailed study of 365 meters of core recovered from southeastern Mongolia reveals fluvial, marginal lacustrine, and profundal lacustrine depositional environments in an Early Cretaceous rift basin. Multiple examples of cyclic sedimentation are superposed on these large-scale facies transitions. In fluvial facies, more than 20 upward-fining successions (2–10 m thick) are present. These contain cross-stratified sandstone units, with erosional bases, that fine upward to mudstone with root marks and burrows. They are interpreted as channel-fill successions in a fluvial depositional environment, whereas finergrained, less erosional intervals with abundant soft-sediment deformation and climbing ripples may represent a transition to fluvial-deltaic environments at the lake margin. Coarse fluvial-deltaic facies form the most likely hydrocarbon reservoirs, as indicated by frequency of oil staining in the core. Physical transport processes dominate well-oxygenated fluvial and marginal lacustrine facies, whereas cycles in more distal lacustrine facies mainly reflect biogeochemical processes. Profundal lacustrine strata include kerogen-rich laminated micrite, distal turbidite beds, and dolomitic breccia reminiscent of lacustrine facies in the Green River Formation of the western United States. Evidence for anoxia at the lake floor includes framboidal (biogenic) pyrite, high TOC content, mainly light amorphous organic constituents, and paucity of trace fossils relative to the rest of the core. Approximately 25 dolomite layers are interbedded with laminated micrite and calcareous siltstone units in poorly defined meter-scale cycles. These beds typically have brecciated or clotted textures, and suggest evaporative concentration of magnesium ions at the lake floor. The profundal lacustrine sequence displays a distinctive high-resistivity, low spontaneous-potential log character that is observed in well logs from several fields in the Zuunbayan subbasin. Correlative units can be traced at least 60 km to the northeast and southwest of the Zuunbayan field, indicating that this is a widespread lacustrine depositional unit. These lacustrine strata include the most likely petroleum source facies found to date, and are likely contemporaneous with other large lake systems in China and Mongolia.

Interaction of copper and zinc with allophane and organic matter in the B horizon of an Andosol

SummaryAndosols developed on basaltic material are naturally rich in metals. Organic matter and allophane, the key colloids of these soils, have a strong affinity for trace metals, but are intimately mixed so that speciation of trace metal is difficult to determine. We used three complementary approaches, namely physical fractionation, chemical extraction and potentiometric measurement, to distinguish them. Physical particle‐size separations and chemical selective dissolution of allophanes and organic matter were combined to demonstrate relations between the occurrence of colloids and contents of Cu and Zn in an andic B horizon. About 22% of total soil Cu and 7% of total soil Zn were present in the < 5‐μm fraction, associated with organic or amorphous mineral constituents. To support this association further, the affinity of soil colloids for Cu and Zn in a mimicked system was demonstrated. An Al‐rich allophane was synthesized, and a portion of the organic matter was extracted from the clay fraction, and their reactivities towards Cu2+ or Zn2+ were studied by potentiometry. The two metallic cations displayed specific affinity towards allophane or soluble organic matter. Furthermore, the behaviour of copper and zinc in the ternary system, allophane + soluble organic matter + trace element, revealed a synergy in the surface complexation. The use of these three speciation approaches highlighted the linkage between metals and constituents, and showed how important the colloidal constituents are in the behaviour of Cu and Zn in Andosols.

Comparison of methods for the quantification of montmorillonite in bentonites

In this paper, we describe and evaluate three methods for measuring the amount of montmorillonite in 10 bentonite samples. Each of these methods is based on certain assumptions that usually result in analyses of low accuracy. In order to assess the attainable accuracy, two procedures for the determination of montmorillonite contents are tested. The first is based on the quantitative separation of the <2-μm fraction in combination with XRD-analysis. The second considers cation exchange capacity (CEC), layer charge (LC) and variable charge. In addition, a third and new method based on the comparison of the CEC of a bentonite with the CEC of the respective pure montmorillonite fraction is proposed. This new method provides accurate values for montmorillonite contents, but is restricted to bentonites, which are free of X-ray amorphous fine-grained constituents. By combining the results of all methods, the layer charge (charges/half unit cell (HUC)) was calculated. Obtained results are comparable with the well-known n-alkylammonium method.

Amorphous matter in kaolins and its geological implications

Selective dissolution with ammonium oxalate was carried out to extract amorphous matter in some kaolins from China. Ammonium oxalate extraction is an effective method to extract amorphous constituents without destroying the kaolinite crystalline structure. The study showed that, absolute amounts of amorphous constituents in kaolins are in the order Al>Si>Fe, but that relative amounts are in the order Fe>Al>Si. The amorphous phases are probably mainly in the form of separate particles, or colloidal particles absorbed on the surface of kaolinite particles. Compared to older kaolins, younger kaolins contain much more amorphous iron content.

Contents, modes of occurrence and origin of chlorine and bromine in coal

Contents, modes of occurrence and origin of Cl and Br in individual coal samples from 34 deposits worldwide (Bulgaria, Australia, the United States, Japan, Canada, South Africa, China, and Ukraine) were studied. Some relationships of Cl and Br contents with chemical and mineral composition, rank, age, ash yield and geographic location of coals are described. Despite of similar chemical and geochemical properties of Cl and Br some distinct differences in the association, behaviour and occurrence of both elements in coal were found and discussed. Chlorine and Br in coal may occur, in decreasing order of significance, as organic compounds, as impurity components in the crystalline and amorphous inorganic constituents, in the fluid constituents and as discrete minerals. Both elements could have an organic occurrence and association with water-soluble (mainly ionic) and water-insoluble (ionic and covalent) organic combinations. Chlorine was identified as an impurity in minerals and inorganic phases such as clay minerals, mica, feldspars, polyhalite, gypsum, siderite, volcanic glass, phosphates and other carbonates and sulphates. A characteristic Br association with illite and to a lesser extent with mica, kaolinite and Fe-bearing minerals was also found. Water molecules, hydroxyl groups and exchangeable cations in various minerals play a leading role for the inorganic occurrence and distribution of both elements. Discrete Cl minerals such as sylvite, halite, chlorapatite and probably carnallite were also identified. Significant amounts of Cl ions may associate with solutions in the inherent moisture of the coal mesoporosity. Limited proportions of both elements may also occur in gas–liquid inclusions of different solid phases. The favourable conditions for Cl and Br enrichments in coal are also discussed.