Scanning Electron Microscopy In Conjunction Research Articles

Convenient determination of polystyrene microplastics in soils by gel permeation chromatography-ultraviolet detection analysis

Microplastics (MPs), especially polystyrene microplastics (PS-MPs), have emerged a new worldwide pollutant, prompting significant public concern regarding their detection in environmental media. Analysis of PS-MPs in soil remains as a challenging task for analysts due to the highly intricate matrices. This work presents a practical approach for detecting PS-MPs in soil, which involves dilute HCl-assisted extraction and gel permeation chromatography- ultraviolet detection (GPC-UV) analysis. The presence of MPs in soil was confirmed through the use of a scanning electron microscope in conjunction with energy dispersive spectroscopy investigation. PS-MPs was isolated from soil, by agitating it with a diluted HCl solution, filtering the resulting liquid, and dissolving the residue on the filter with THF. The extractant was subsequently determined by GPC-UV. The introduction of a small amount of HCl into the extraction system was found to greatly expedite the settling of soil in water and enhance the efficacy of extracting PS-MPs in about 30 min. The linear range of PS-MPs was from 1.0 to 100 μg/mL with R2 > 0.999. Good reproducibility was obtained with the intra-day relative standard deviation (RSD, n = 3) of 1.36 % and the inter-day RSD (n = 3) of 4.78 %. The concentration of PS-MPs in soil samples were N.D. - 2.33 μg/g, and the good recoveries were 76.7–100.3 %. The corresponding AFGEEprer score was calculated to be 0.59, indicating the concept of green analytical chemistry for the pretreatment method. These results indicated that this method has a powerful potential for the accurate and rapid determination of PS-MPs in soil.

Liquidus surface projection and isothermal section at 1500 °C of (Mo-5Nb)-Ti-C pseudo-ternary system

The liquidus surface projection and isothermal section at 1500 °C of the (Mo-5Nb)-Ti-C pseudo-ternary system were experimentally determined. X-ray diffraction analysis and scanning electron microscopy in conjunction with electron-probe microanalysis were carried out to analyze the solidification behavior and phase constituents. The replacement of 5 at.% Mo with Nb was found to negligibly affect the solidification path or the formation of new phases. However, the quasi-peritectic point U2 shifted closer to the (Mo-5Nb)-C border in the liquidus surface projection than in the Mo-Ti-C system. The BCC single-phase region, BCC + TiC two-phase region, and BCC + Mo2C + TiC three-phase region were determined in the isothermal section at 1500 °C. The replacement of 5 at.% Mo with Nb was found to expand the BCC + TiC two-phase region and narrow the BCC + Mo2C + TiC three-phase region by stabilizing the TiC phase. Therefore, the addition of Nb to the Mo-Ti-C system expanded the compositional range of the BCC + TiC two-phase region, leading to variable properties of TiC-dispersed BCC-based alloys and BCC-TiC cermets.

The effect of structural preservation conditions on pore structure of marine shale reservoir: a case study of the Wufeng-Longmaxi Formation shale, Southern Sichuan Basin, China

The marine shale within the Sichuan Basin constitutes China’s significant shale gas production, featuring old formation age, high degree of thermal evolution, multiple tectonic movements, and complex structural conditions. However, there are significant differences in the shale gas preservation conditions and reservoir quality in different areas, limiting future large-scale exploration and development. Pore structure significantly influences shale reservoir quality, gas content, and exploration of shale gas occurrence, migration, and enrichment mechanisms. The influence of structural-dominated preservation conditions on shale pore structures is essential to comprehend for effective shale gas exploitation. This study employs field-emission scanning electron microscopy in conjunction with other techniques (low-temperature N2 adsorption, low-temperature CO2 adsorption, and nuclear magnetic resonance) for detailed analyses of the pore structure across varied structural zones, revealing the influence of structural attributes, fault systems, depth of burial, and formation pressure on pore architecture, and examining the relationship between pore structure and shale gas preservation conditions. The results show that stable structural condition is conducive to the development and preservation of shale pores. Structural compression causes inorganic and organic pores to become narrow and elongated due to shrinkage, with a significant increase in microfractures. The porosity of shale with stable structural conditions exhibits markedly increased porosity compared to samples under structural compressions. Under conditions of similar TOC and mineral composition, the pore size distribution (PSD), pore volume (PV), and specific surface area (SSA) of shale after structural compression are significantly lower than those of samples with stable structural conditions. As the burial depth increases, the shale porosity shows a decreasing trend, but the decrease is limited. Burial depth significantly impacts the SSA and PV of high-TOC samples (3%–6%). As the burial depth increases, both SSA and PV show a significant decreasing trend. When the burial depth reaches 4000 m, SSA and PV tend to concentrate. The formation pressure coefficient is an important factor for the development and preservation of shale pores, and porosity is positively correlated with the formation pressure coefficient. Increased formation pressure coefficient indicates superior preservation conditions and enhanced pore development.

Binder melt: Composite propellants with RDX**

AbstractThe binder melt on the surface of aluminized composite propellants with RDX has been quantified using experimental and computational approaches. A scanning electron microscope in conjunction with energy dispersive spectroscopy was used to analyze the surface of unburnt and extinguished propellant samples. Rapid depressurization technique was used to obtain the extinguished propellants. Five propellants were prepared, keeping the aluminum and binder fraction constant at 4 % and 16 %, respectively. The RDX fraction in the propellants was varied from 3 % to 12 %. It was found that the melt on the surface of the propellant increased from 36.7 % to 43.9 % when the RDX fraction was changed from 3 % to 12 % in the propellant. For propellants containing 3 % to 9 % RDX, a region of plateau burning was observed in the pressure range of 5–7 MPa, while propellants containing 12 % RDX showed plateau burning between 7–10 MPa.

Mallestigite, Pb3Sb(SO4)(AsO4)(OH)6·3H2O, from the type locality – new data, crystal structure, and structural relationships

A report of the supergene mineral mallestigite, Pb3Sb5+(SO4)(AsO4)(OH)6·3H2O, from the type locality Neufinkenstein-Grabanz district, Mallestiger Mittagskogel, Carinthia, Austria, is given in order to close gaps that have been left open since its first description. At the type locality, the dump of an abandoned small copper-lead-zinc mine, the mineral occurs frequently in up to ⁓2 mm long clear colourless idiomorphic hexagonal prisms {100} terminated by the bipyramid {101}. Details of the occurrence, paragenesis, physical properties, a FTIR spectrum and X-ray powder diffraction data are reported. Chemical analysis in a scanning electron microscope in conjunction with a crystal structure analysis gave the empirical formula Pb3.02Sb1.06(SO4)0.96(AsO4)0.97(OH)6·3H2O. An ab-initio crystal structure determination with CCD diffractometer data, MoKα radiation, and a nearly untwinned crystal proved that mallestigite is hexagonal, space group P63, a = 8.9326(4), c = 11.1044(5) Å, V = 767.33(8) Å3, Z = 2, and gave a final R1 = 0.0184 for 1632 independent reflections with I > 2σ(I). Mallestigite belongs to the fleischerite group. The structure is built up from [Sb5+(OH)6]1– octahedra which are linked by triplets of edge-sharing Pb2+ into chains [Pb3Sb(OH)6]5+ extending along a 63 axis. Each three of such chains are bridged by triplets of H2O and by rows of SO42– and AsO43– tetrahedra alternating along a 3-fold axis and showing very different links to the Pb atom. Pb2+ is in a strongly distorted one-sided [9]-coordination by O atoms that makes the structure clearly hemimorphic. Structural relationships to the fleischerite group minerals schaurteite, genplesite, despujolsite and fleischerite as well as to synthetic Ba3Sn4+(SeO4)2(OH)6·3H2O are outlined and changes in the space group symmetry of despujolsite (P6¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline6$$\\end{document}2c → P63/mmc) and fleischerite (P6¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline6$$\\end{document}2c → P63) are proposed.

Geochemical characteristics of Jurassic high-sodium coal in Tatuo Coal Mine, Qinghai Province, China

Sodium in the coals of West China has received persistent attention due to its high contents and severe pollutions’ problems during coal utilization. A total of seven drill samples of the Jurassic coals from Tatuo coalfield, Qinghai Province, were collected and analysed using optical microscopy, scanning electron microscopy in conjunction with energy-dispersive X-ray spectrometry, X-ray powder diffraction, inductively coupled plasma mass spectrometry and X-ray fluorescence spectrometry. The results indicate that the Tatuo coal is of lower-high ash, medium volatile matter and ultra-low sulphur bituminous coal. Tatuo coal contains much more Na2O (> 2%), and belongs to high-sodium coal. The maceral index and element ratios of Sr/Cu, Fe/Mn and Sr/Ba showed that Tatuo coal was formed in a terrestrial peat swamp environment. The minerals in Tatuo coal, including clay minerals and halite, quartz, gypsum and rutile, are mainly concentrated in the bottom and top parts of the coal seam. Combined with scanning electron microscopy in conjunction with energy-dispersive X-ray spectrometry and optical microscope characteristics, the sodium could be carried into the peat/coal after the peat formation by basin fluids. The East Kunlun orogenic belt may be the main source of these minerals.

Effect of a Heterogeneous Network on the Fracture Behavior of Epoxy Resins

Epoxy resins, which possess a three-dimensional network obtained by a curing reaction between epoxy and amine compounds, are in a glassy state at room temperature. They are therefore generally brittle and exhibit rather poor resistance to crack propagation, which is one of the greatest drawbacks for their practical application. To solve this problem, a better understanding of their fracture behavior, which is related to long-term durability, is strongly desired. We herein report on how the extent of network heterogeneity affects the fracture behavior of epoxy resins. Three types of epoxy resins were obtained under different curing conditions, which generated different extents of heterogeneity. The fracture behavior of the three epoxy resins was examined by in situ scanning electron microscopy in conjunction with microbeam X-ray scattering experiments. When the epoxy resin in which a notch was pre-introduced was stretched under a small strain, the internal network structure was deformed, and the extent was more significant with increasing heterogeneity. As further stretching was applied, a crack propagated from the notch. This occurred more easily with increasing heterogeneity. That is, the toughness of the epoxy resins decreased with increasing network heterogeneity. The knowledge obtained here will be useful for understanding and controlling the toughness of epoxy resins.

Pollution and health-risk assessments of Cr-contaminated soils from a tannery waste lagoon, Hebei, north China: With emphasis on Cr speciation

In this paper, heavy metals (i.e., V, Cr, Co, Cu, Zn, Cd, Pb, and Sb) in soils from a tannery waste lagoon, Hebei, north China were investigated. Element concentrates were determined by a portable X-ray fluorescence in situ and an inductively coupled plasma mass spectrometry in the lab. Two sets of indexes, including geological accumulation index, contamination factor, and pollution load index, and hazard quotient and total carcinogenic risk were adopted to evaluate the pollution and health-risk of heavy metals. A scanning electron microscopy in conjunction with an energy dispersive X-ray spectroscopy and an X-ray photoelectron spectroscopy was used to observe chromium occurrence and speciation. With an average of 6493.11 mg/kg, chromium contents in the lagoon soils reached up to 12971.19 mg/kg, 211-times higher than the threshold of Chinese soils (61.00 mg/kg). Elevated Cr contents resulted in significantly high pollution and noncarcinogenic and carcinogenic risks in the studied area. Chromium in most soils occurred predominately as Cr3+ (60–74%), and to a lesser extent, Cr6+. The mechanism responsible for decreasing Cr6+ percentages in soils with increasing depth was summarized: Cr6+ favors aqueous environment; soil moisture decreased with increasing depth; in soils especially in the lower portion, Cr6+ was reduced by Fe0 and Fe2, transforming into Cr3+ and Fe3+. In addition, the alkaline condition promoted Cr3+ to precipitate, resulting more Cr3+ absorbing in soils. The intimate association of Cr and Fe in soils (i.e., Cr mainly occurred in Fe oxides and dolomite) further confirmed our assumptions. A combined application of microorganism (e.g., Aeromonas hydrophila) and biochar (prepared from maize stalk or peanut shells) were recommended to alleviate Cr pollution in the soils.

Microstructure and mechanical response of dissimilar joint of ferritic interstitial-free steel to austenitic low-density steel produced by diffusion bonding

Lightweight Fe–Mn–Al–C steels, also referred as low-density steels (LDS), have gained significant importance in the recent past owing to their reduced density, high strength and ductility, along with good oxidation resistance at elevated temperatures. The present study is aimed at exploring the feasibility of solid-state joining of LDS to the other prominent ferrous alloys, for example, interstitial-free steel (IFS), in order to extend their applications. In the present work, diffusion bonding has been attempted to produce IFS-to-LDS joints with and without the application of nickel (Ni) interlayer. Diffusion bonding is performed at two different temperatures of 850 °C and 950 °C for 30 min at the bonding pressures of 10, 20 and 30 MPa under high vacuum conditions. The interfacial microstructures of the joints are examined using an optical microscope and scanning electron microscope in conjunction with energy dispersive spectroscopy and electron backscattered diffraction. Microhardness and nanoindentation measurements across the interface and shear tests are performed to evaluate the interfacial bond strength of the joints. The joint produced with the application of Ni interlayer at 950 °C under 30 MPa bond pressure exhibited superior shear properties with a maximum shear strength of ∼340 MPa. The formation of stable oxides resulting, especially by diffusion of aluminum from LDS to the faying surfaces is found to be detrimental to establish a good interface at lower bonding parameters. The application of higher bonding pressure and Ni interlayer along with enhanced diffusional activities from LDS to IFS within the austenite phase are found to be effective in achieving a sound joint. The metallurgical aspects involved in the formation of the reaction products and subsequently, the influence of the evolved interface microstructure on the mechanical response of the joints are discussed in-detail.

Morphological of Zinc Ferrite Nanostructure Using the Hydrothermal Synthesis

Over the last two decades, many methods for synthesizing various ZnFe2O4 nanostructures of uniform size and shape, such as nanospheres, nanoflowers, nanorods, and nanotubes, have been developed. It seems challenging to investigate a practical and cost-effective method to synthesize cubic ZnFe2O4 magnetite with cubic morphological properties in an aqueous solution. The morphology of zinc ferrite nanostructures is mostly random and non-uniform. The objective of this study is to create reasonably uniform single-crystal zinc ferrite nanocubes. The hydrothermal method was used to successfully sample zinc ferrite by varying the amount of (En) ethylenediamine (0 - 2.4 mL) in the solution. The outcomes demonstrated that the nanocubes, with a particle size of nearly 48 nm, had a more uniform morphology than other samples. The morphology and dimensions of the samples were examined using scanning electron microscopy in conjunction with energy dispersion X-ray spectroscopy.

Evaluation of the electrical and dielectric behavior of the apatite layer formed on the surface of hydroxyapatite/hardystonite/copper oxide hybrid nanocomposites for bone repair applications

The work aimed to prepare nanocomposites with good electrical and mechanical properties and acceptable bioactivity behavior to be suitable for bone repair applications. In this context, hydroxyapatite (HA) and hardystonite (HT) were prepared by mechanochemical synthesis method. Subsequently, nanocomposites of different contents of HA, HT and copper oxide (CuO) were prepared, sintered and characterized by X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). In addition, bioactivity was evaluated in vitro after treatment in simulated body fluid (SBF) and HA layer formation was confirmed by SEM in conjunction with energy dispersive X-ray analysis (EDX). The electrical and dielectric properties were measured before and after treatment in SBF solution. Elastic and physical properties were also measured. The results clarified that the sintering temperature used along with the successive increase of HT and CuO contents achieved good densification behavior and better mechanical properties, especially compressive strength, to avoid the stress-shielded bone effect. Also, HT and CuO positively enhanced the electrical conductivity and reduced the dielectric properties of nanocomposites prepared. The latter results have a great role in promoting fracture healing. Based on the above results, the prepared nanocomposites are promising for potential use in bone repair applications.

Microstructure and Mechanical Properties of Cast and Hot-Rolled Medium-Carbon Steels under Isothermal Heat-Treatment Conditions

In this study, the changes in the microstructure and mechanical properties during isothermal heat treatment of cast steel before and after hot deformation were investigated using medium-carbon steel with low alloy content. The microstructural characteristics of the cast and hot-rolled medium-carbon steel under isothermal heat-treatment conditions were examined using optical microscopy and scanning electron microscopy in conjunction with electron backscatter diffraction. The variation in the mechanical properties was evaluated using Rockwell hardness and tensile tests. After maintaining an austenitizing condition at 1200 °C for 30 min, an isothermal heat treatment was performed in the range 350–500 °C, followed by rapid cooling with water. Both the cast steel and hot-rolled steel did not completely transform into bainitic ferrite during isothermal heat treatment. The partially untransformed microstructure was a mixture of martensite and acicular ferrite. At 500 °C, the prior austenite phase changed to Widmanstätten ferrite and pearlite. At 450 °C, bainitic ferrite and cementite were coarsened by the coalescence of ferrite and subsequent diffusive growth. The mechanical properties increased as the isothermal heat-treatment temperature decreased, and the hardness of the cast steel was generally higher than that of the hot-rolled steel. Hardness and strength showed similar trends, and overall mechanical properties tend to decrease as the isothermal heat-treatment temperature increases, but there are slight differences depending on complex factors such as various phase fractions and grain size.

Influence of substrate temperature on graphene oxide thin films synthesis by laser ablation technique

In this paper, we studied the influence of the substrate temperature (Ts) on the deposition of carbon thin films by the pulsed laser deposition technique. Thin films were synthesized using a highly oriented pyrolytic graphite target, which was irradiated by the fundamental harmonic (1064 nm) of a Nd:YAG pulsed laser. In the experimental conditions, the Ts varied from room temperature to 500 °C, the gas pressure (oxygen, 50 mTorr) remained the same for all samples, and the ablation time was 5 min for each thin film. The samples were characterized by x-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy in conjunction with energy dispersive x-ray spectroscopy, atomic force microscopy, and contact angle measurement. The characterization results allowed us to determine that the thin films deposited on silicon substrates at 400 and 500 °C (samples S1 and S2) were multilayers graphene oxide. From XRD, Raman spectroscopy, and FTIR results, we concluded that the degree of oxidation and graphitization of the carbon thin films were influenced by the Ts. Additionally, the contact angle measurement showed that for samples S1 and S2, the contact angle was greater than 94°, and for samples S3 and S4 (amorphous carbon), it was less than 62°.

Distribution and enrichment of Al-Li-Ga-REEs in the High-Alumina coal of the Datong Coalfield, Shanxi Province, China

The content, distribution, and origin of aluminum, lithium, gallium, and rare earth elements (REEs) in the Permo-Carboniferous coal of the Datong coalfield, China, were investigated using optical microscopy and field-emission scanning electron microscopy in conjunction with energy-dispersive X-ray spectrometry, X-ray powder diffraction, and inductively coupled plasma mass spectrometry. The Permo-Carboniferous coal of the Datong coalfield had a high volatile bituminous rank (Ro,max = 0.72% on average), and low sulfur and medium ash contents (0.58% and 25.74% on average, respectively). The main minerals in the Datong coal included kaolinite, boehmite, muscovite, calcite, dolomite, siderite, aluminum phosphate, and quartz. Of these, kaolinite, boehmite, calcite, quartz, and phosphates mainly occurred as cell fillings, indicating an authigenic origin. Compared to hard coals worldwide, the Datong coal is enriched in SiO2 (49.12%; up to 89.93%), Al2O3 (38.88%; up to 71.37%), Li (67 μg/g; up to 354.1 μg/g), Ga (18.1 μg/g; up to 70.2 μg/g), Y (20.8 μg/g; up to 46.1 μg/g), La (34 μg/g; up to 158.5 μg/g), Ce (61.3 μg/g; up to 353.8 μg/g), Tb (0.7 μg/g; up to 3.0 μg/g), Er (2.3 μg/g; up to 5.7 μg/g), and Yb (2.2 μg/g; up to 5.4 μg/g). High-alumina coal (Al2O3 content in ash > 40%) occurred in the northern and southern parts of the coalfield. In the No. 3–5 coal seam, the areas of Li enrichment were located in the north and middle of the coalfield. In the Tashan and Chaigou mines, the Ga content exceeded 30 μg/g. An area of REEs enrichment (REEs content > 300 μg/g) was identified in the Tashan and Xiaoyu mines. In the No. 3–5 coal seam, the REEs distribution pattern showed a wide and gentle “V” curve with a high left and a low right limb. These seams were characterized by a marked depletion in Eu (δEu = 0.51) and a weak negative Ce anomaly (δCe = 0.95). In the No. 3–5 coal seam, Al, Li, Ga, and REEs mainly occurred in kaolinite. Boehmite and phosphate minerals were the main carriers of Ga and REEs, respectively. The enrichment in Al-Li-Ga-REEs in the No. 3–5 coal seam was mainly influenced by the sedimentary provenance and the environment of coal accumulation. The sediment sources were oxidized bauxite in the weathering crust of the Benxi Formation and the Middle Proterozoic moyite of the Yinshan Oldland to the north and west of the coalfield. Al, Li, Ga, and REEs were transported from the source region as solutes and colloids, and they became enriched in the swamp facies of the delta plain. The Li, Ga, and REEs contents gradually increased from the bottom to the top of the Permo-Carboniferous coal seam. This increase is mainly attributed to the weak influence of seawater. The marked enrichment in heavy REEs at the bottom of the No. 5 coal seam may be related to marine transgression.

Ancient Pigments in Afrasiab Murals: Characterization by XRD, SEM, and Raman Spectroscopy

The Afrasiab murals discovered in the northeast of Samarkand, Uzbekistan—the center of the ancient Silk Road—are presumed to date to the mid-seventh century during the Sogdian era. Although previous studies have examined the primary materials of the pigments used in these murals using chemical and microscopic analyses, in-depth investigations of the pigment raw material composition have not been conducted to verify the results of these studies. We applied X-ray diffractometry, Raman spectroscopy, and scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy for the first time to identify the raw materials of ancient pigments in fragments obtained from the Afrasiab murals. The results show that lazurite, cinnabar, and amorphous carbon were used as blue, red, and black pigments, respectively. Moreover, we identified that pigments were not directly painted on the wall surface; instead, they were painted on a white undercoat of gypsum plaster, similar to other ancient Silk Road wall paintings. The results of this study can benefit the provision of more accurate information with regard to the composition of raw materials and further support the selection of appropriate substances for the purposes of conservation and restoration of Afrasiab murals.

Reductive acid leaching of valuable metals from spent lithium-ion batteries using hydrazine sulfate as reductant

Abstract Hydrazine sulfate was used as a reducing agent for the leaching of Li, Ni, Co and Mn from spent lithium-ion batteries. The effects of the reaction conditions on the leaching mechanism and kinetics were characterized and examined. 97% of the available Li, 96% of the available Ni, 95% of the available Co, and 86% of the available Mn are extracted under the following optimized conditions: sulfuric acid concentration of 2.0 mol/L, hydrazine sulfate dosage of 30 g/L, solid-to-liquid ratio of 50 g/L, temperature of 80 °C, and leaching time of 60 min. The activation energies of the leaching are determined to be 44.32, 59.37 and 55.62 kJ/mol for Li, Ni and Co, respectively. By performing X-ray diffraction and scanning electron microscopy in conjunction with energy dispersive X-ray spectroscopy, it is confirmed that the main phase in the leaching residue is MnO2. The results show that hydrazine sulfate is an effective reducing agent in the acid leaching process for spent lithium-ion batteries.

Investigation of fatigue behavior of centrifuged series 3000 Al with addition of 26 wt% Cu

More than 70% of mechanical parts in a wide range of engineering fields fail by fatigue. In addition, centrifugal casting is identified as the most effective casting technique for production of high performance cylindrical parts. In this regard, the present work aims to investigate the fatigue behavior of series 3000 Al with addition of 26 wt% Cu produced through horizontal centrifugal casting method. Microstructure characterizations are precisely studied using scanning transmission electron microscopy and field emission scanning electron microscopy in conjunction with image analyzer software. Also, compressive behavior, hardness, coefficient of thermal expansion, and wear rate ( Wr) are measured applying Zwick Z100, Vickers hardness, DIL 805A/D, and pin-on-disc machines, respectively. The results indicate that the main intermetallic compound is Al2Cu-based particle, and a volume fraction of 31 vol.% is obtained. Besides, the compressive strength of 460 MPa, elastic modulus of 10.986 GPa, hardness of 152 HV, coefficient of thermal expansion of 1.7 × 10−5 1/°C, and wear resistance of 3.3 × 10−6 g/mm2 are measured. Finally, the four-point bending fatigue test is performed and the fatigue ratio of 0.109 at about 106 cycles to failure is obtained.

Improvement of the carbon monoxide gas sensing properties of polyaniline in the presence of gold nanoparticles at room temperature

In the present work, the influence of gold (Au) nanoparticles on carbon monoxide gas sensing performance of polyaniline (PAni) at room temperature was comprehensively studied. The Au/PAni nanocomposites were synthesized by the ultrasound mixing of emeraldine salt polyaniline and different amounts of Au nanoparticles colloidal solution. The analyses of field emission scanning electron microscope in conjunction with energy-dispersive X-ray spectroscopy indicated that the surface of PAni fibers was well decorated with Au nanoparticles due to the electrostatic interaction and hydrogen bonding. Then, the gas sensing performance of all sensors was investigated toward various concentrations of carbon monoxide gas ranging from 200 to 6000 ppm at room temperature. The results indicated that the 2.5 %Au/PAni sensor possesses high response(14 %–1000 ppm), low detection limit(33 ppm), the acceptable response time(180 s), wide dynamic range(200−6000 ppm) and good selectivity owing to catalytic properties of Au nanoparticles. Thus, the one-dimensional nanostructure might give a promise for high-performance sensing applications.

A linkage between uranium mineralization and high diagenetic temperature caused by coal self-ignition in the southern Yili Basin, northwestern China

Jurassic sediments in the southern Yili Basin of the Xinjiang Province, northwestern China, host several sandstone-hosted uranium deposits. The Jurassic uranium-enriched white sandstones are in the transitional zone between the oxidized and reduced zones. In addition, burnt rocks are common in nearby outcrops and occur occasionally in drill cores. Mineralogical and geochemical compositions of sediments from the oxidized, the uranium-enriched transitional and the reduced zones were measured using optical microscopy, field-emission scanning-electron microscopy in conjunction with energy-dispersive X-ray spectrometry, X-ray powder diffraction and inductively coupled plasma mass spectrometry (ICP-MS). Chromite, limonite and ilmenite are the typical accessory minerals in the brown sandstones of oxidized zone, whereas calcite and saddle dolomite are typical accessory minerals in the sandstones of transitional zone. The suite of vitrinite reflectance (Ro), illitic crystallinity and homogenization temperature for fluid inclusions in calcites indicates a relatively high diagenetic temperature (>100 °C) in the Jurassic sandstones from both the oxidized and transitional zones in the southern Yili Basin. An interesting relationship was discovered between the diagenetic high-temperature conditions and coal self-ignition. The anomalous uranium concentrations in the burnt claystone from a drill hole and in the altered coals 0–10 cm below the burnt rocks in an outcrop section imply a relationship between the coal self-ignition and uranium mineralization in the southern Yili Basin. One option to interpret the uranium mineralization is a supergene (descending from surface) hydrothermal fluid model in which the downwelling fluids were heated as they penetrated through the warm burnt rocks and then underwent a chemical reaction as they progressively cooled when they traversed down through the underlying permeable sandstone beds. Accordingly we establish the linkage between uranium mineralization and high diagenetic temperature caused by coal self-ignition.

Multi-scale characterization of bamboo bonding interfaces with phenol-formaldehyde resin of different molecular weight to study the bonding mechanism.

Understanding the bonding mechanism of the interfacial region between bamboo and adhesives is essential for accelerating the development of improved adhesives for advanced bamboo-based materials. In this study, Br-labelled phenol-formaldehyde (PF) resins with four different molecular weights (MWs) were used to make bamboo-adhesive interfaces for tracing the adhesives in bamboo. Ultra-depth-of-field microscopy and scanning electron microscopy in conjunction with energy dispersion spectrometry were used to access the distribution and penetration of resin in the bamboo polymer. Fourier transform infrared images and solid-state cross-polarization/magic angle spinning nuclear magnetic resonance spectra were used to access the molecular-scale interactions between PF resins and bamboo cell walls. The results showed that the PF resins with high MW infiltrated into the lumina of damaged bamboo cells near the bondline to form glue nails, while those with low MW penetrated into the bamboo cell wall to form nanomechanical interlocking. Chemical bonds and secondary forces such as polar forces and hydrogen bonds were generated between bamboo and PF resin. Finally, the twice-adhesive dispensing method combining low-MW resins with high-MW resins was used to improve the bonding strength of the interface.