X-ray Diffraction Spectrometer Research Articles

Effect of Y addition on the aging hardening behavior and precipitation evolution of extruded Mg-Al-Zn alloys

Abstract: The 443 K aging hardening behavior and microstructure evolution of extruded Mg-Al-Zn-Y alloys was investigated in aspects of yttrium (Y) content (0.2–0.8 wt%), holding time (0.5–156 h) and the initial states (as-extruded, solution treated). The grain size, precipitation evolution, phases and chemical composition were characterized by the optical microscope, scanning electron microscope, X-ray diffraction, and energy dispersive spectrometer, respectively. The corresponding mechanical response, including the hardness, uniaxial tensile strength were measured with the Vickers hardness tester and universal testing machine, respectively. The results show that, firstly, there is reversal hardness anisotropy between extrusion direction and normal direction in as-extruded Mg-Al-Zn-Y sheets compared with T5 treated ones. Secondly, the short-term aging softening exist at the beginning of T5 treatment which results in a lower hardness even be close to that of solution treated ones, but not for T6 conditions. Thirdly, the suppression of discontinuous precipitation during the aging treatment become more remarkable with increasing Y addition which because of the reduction of diffusional coherency strain near grain boundary, increasing activation energy for the discontinuous precipitates (β-Mg17Al12 phase, DPs) formation and the dilution region of Al near the Al2Y. Serrated GBs can also provide more nucleation sites for DPs and lead to relatively more precipitates during T5 treatment. Moreover, the proportional precipitation strengthening in yield strength and hardness was verified in Mg-Al-Zn-Y alloy during the aging process.

Substitution effects on magnetic properties of Mg1.3-xMnxAlyFe1.8-yO4 ferrite

Mg1.3-xMnxAlyFe1.8-yO4 (x = 0.1–0.2, y = 0.15–0.3) spinel ferrites were prepared using conventional ceramic technique. Highly densified Mg–Mn–Al ferrites (with 99% theoretical density) were obtained, and the influence of Mn and Al substitution on the characteristics of these ferrites has been systematically studied. The microstructure, magnetic properties, and ferromagnetic resonance linewidth (ΔH) of the Mg–Mn–Al ferrites have been analyzed by X-ray diffraction, B-H analyzer, and ferromagnetic resonance (FMR) spectrometer. The results showed that all of the samples were single spinel phase. As Mn content increases and Al content decreases, both saturation magnetization (4πMs) and squareness ratio increase, while the coercivity (Hc) first increases and then decreases. In addition, good ferromagnetic resonance linewidth properties were also obtained as 143.8 Oe at 9.3 GHz for the sample with x = 0.17 and y = 0.20. The results imply that Mg1.3-xMnxAlyFe1.8-yO4 ferrites may be applicable for X-band (8–12 GHz) microwave devices.

Combined X-ray diffraction and alpha particle X-ray spectrometer analysis of geologic materials

The shallow interrogation depth of the lightest elements (Na, Mg, Al, and Si) detected by the particle-induced X-ray emission branch of the Curiosity Rover's alpha particle X-ray spectrometer suggests that the X-rays of these elements very likely emerge from a single mineral grain. This reality violates the assumption of atomic homogeneity at the micron scale made in both existing spectrum-reduction approaches for the alpha particle X-ray spectrometer. Consequently, analytical results for these elements in igneous geochemical reference materials exhibit deviations from certified concentrations in a manner that can be related to the total alkali-silica diagram. A computer code is introduced here to provide quantitative prediction of these deviations using the mineral abundances determined from X-ray diffraction. The latter are converted to area coverage fractions to represent the sample surface, and a fundamental parameters computation predicts the elemental X-ray yields from each mineral and sums these. In this process, the chemistry of each individual mineral has to be varied by an iterative simplex approach; X-ray yields are computed and compared with the peak areas from the fit of the bulk sample. When the difference between mineral yields and peak areas for each element are minimized, the mineral formulae are set and elemental X-ray yields provided. The ratio between the summed mineral X-ray yields and the corresponding yields based on the homogeneity assumption may then be compared directly with the concentration deviations measured in our earlier work. For several rock types, good agreement is found, thereby consolidating our understanding of the effects of sample mineralogy on alpha particle X-ray spectrometer results. Copyright © 2017 John Wiley & Sons, Ltd.

Synthesis of hydrophilic acid-resistant Ge-ZSM-5 membranes via secondary growth method using silicalite-1 zeolite as seeds

Hydrophilic acid-resistant Ge-ZSM-5 membranes were synthesized via secondary growth method on porous α-Al2O3 substrates with Silicalite-1 zeolite as seeds. The membranes were characterized by means of scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectrometer to look into the microstructures and element contents of the membranes. The separation performance of the membranes was investigated for separating water from acetic acid solution by pervaporation. The results show that membranes fabricated by the conventional secondary growth method have a high flux, but the selectivity of them is rather limited. Preheating the secondary synthesis sol and using the supernatant as the secondary synthesis sol for membrane fabrication were found to be ef-fective to lower the concentration of the nutrient to constrain re-nucleation, at the same time, lower the Al content in the membranes. The membrane obtained exhibited improved separation performance with a separation factor of 83 at a flux of 0.67 kg·m–2·h–1 at 353 K for a feed concentration of 98% acetic acid solution.

Enhanced Photocatalytic Properties of Pure and Cr-Modified ZnS Powders Synthesized by Precipitation Method

Zinc sulfide photocatalysts doped with chromium (1:1)% were synthesized via precipitation technique. Their characteristics were studied by X-ray diffraction (XRD), AFM and Florescence spectrometer. The photocatalytic reaction was applied under light intensity equal to 1.45 × 10-7 Einstein mol-1 to investigate the kinetics and thermodynamic parameters for photo-decolorization of reactive black 5 dye in collide solution of bare and Cr-doped ZnS. The mean crystal size and particle size for bare ZnS are more than those values for prepared Cr loaded ZnS.

Preparation and Photocatalytic Performance of Ti3C2/TiO2/CuO Ternary Nanocomposites

Ti3C2/TiO2/CuO nanocomposites were synthesized via the decomposition of a mixture of Ti3C2 (a novel two-dimensional carbide) and cupric nitrate under an argon atmosphere. The morphology and structures of the obtained samples were characterized. X-ray diffraction and energy dispersive spectrometer analysis indicate that the sample is composed of Ti3C2, anatase-TiO2, and CuO. Scanning electron microscopy images show that CuO and TiO2 nanoparticles were evenly distributed on the surface of Ti3C2. The particles size increased with an increase in the cupric nitrate content. Photocatalytic degradation of methyl orange shows that the Ti3C2/TiO2/CuO nanocomposite has good photocatalytic degradation efficiency. A possible photocatalytic mechanism of the Ti3C2/TiO2/CuO nanocomposites was proposed. The data indicated that CuO and Ti3C2 effectively promote the separation of photoelectrons from vacancies.

Synthesis and crystal structure of a highly selective colorimetric and fluorometric sensor for hydrogen sulfide.

A novel Cu(II) complex chemosensor for hydrogen sulfide with azo as the colorimetric group has been synthesized. The complex and ligand crystals were obtained and the molecular structures were characterized by X-ray diffraction and Electrospray ionization High resolution mass spectrometer (ESI-HRMS). The photophysical and recognition properties were examined. The complex can recognize S2- , with an obvious color change from yellow to red based on a copper ion complex displacement mechanism. By contrast, no obvious changes were observed in the presence of other anions (AcO- , H2 PO4- , F- , Cl- , Br- and I- ). We present a simple, easily prepared, yet efficient, inorganic reaction-based sensor for the detection of S2- . The complex should have many chemical and analytical applications in the sensing of hydrogen sulfide.

Effects of La2O3 on Mechanical Properties and Corrosion Resistance of H62 Brass

In this article, the effects of lanthanum oxide (La2O3) on the microstructure and mechanical properties of H62 brass were investigated by using the universal testing machine, Brinell hardness tester, optical microscope, and scanning electron microscope (SEM). Immersion corrosion and electrochemical measurements were carried out to identify the influence of La2O3 on the corrosion behavior of the H62 brass. The phase constitution, microstructure, and phase composition of the H62 brass were analyzed by x-ray diffraction, SEM, and energy-dispersive spectrometer, respectively. The results show that the microstructure of α phase changes from dendrite grains to equiaxed grains, and the content and distribution of β phase are improved significantly. When the La2O3 content reaches 0.8 wt.%, the H62 brass obtains favorable comprehensive mechanical properties and the strength and hardness decrease but elongation increases, which is conducive to plastic processing. In addition, under the optimum amount of 0.8 wt.% La2O3 content, the corrosion rate of immersion corrosion attains the minimum values: As 12.6 g m−2 h−1, it decreases by 24%; as the corrosion potential changes from −1.1327 V to −0.328 V, it increases by 70.9%; and as the corrosion current density decreases from −2.833 mA mm−2 to −3.28 mA mm−2 corrosion, it decreases by 15.78%, when compared with H62 brass.

Enhanced performance of thermal-assisted electron field emission based on barium oxide nanowire

In this paper, thermal-assisted field emission properties of barium oxide (BaO) nanowire synthesized by a chemical bath deposition method were investigated. The morphology and composition of BaO nanowire were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SED), X-ray diffraction (XRD), and energy dispersive X-ray spectrometer (EDX) respectively. The turn-on field, threshold field and the emission current density could be affected relatively due to the thermal-assisted effect when the electric field was applied, in the meanwhile, the turn-on field for BaO nanowire was measured to be decreased from 1.12V/μm to 0.66V/μm when the temperature was raised from 293K to 593K, whereas for the threshold field was found to decrease from 3.64V/μm to 2.12V/μm. The improved performance was demonstrated due to the reduced work function of the BaO nanowire as the agitation temperature increasing, leading to the higher probability of electrons tunneling through the energy barrier and enhancement of the field emission properties of BaO emitters.

Two-step approach of fabrication of interconnected nanoporous 3D reduced graphene oxide-carbon nanotube-polyaniline hybrid as a binder-free supercapacitor electrode

This paper describes the characterization of a three-dimensional (3D) reduced graphene oxide (RGO)-carbon nanotube (CNT)-polyaniline (PANI) hybrid fabricated by combining electrophoretic deposition (EPD) and floating catalyst chemical vapor deposition (FCCVD), followed by in-situ anodic electrochemical polymerization (AEP). Firstly, the RGO-CNT is prepared by combining EPD of GO onto nickel foams (NF) and then growth of uniformly aligned CNT on the surface of RGO via FCCVD. Secondly, the 3D RGO-CNT-PANI hybrid is successfully fabricated by in situ AEP of aniline monomers onto the surface of the RGO-CNT. The structures and morphologies of the hybrid have been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectrometer (XPS). Electrochemical properties are studied by cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy. The results reveal that the as-prepared hybrid based on the two-electrode system displays very high specific capacitance of 741 F g−1 with a high energy density of 92.4 Wh kg−1 and high power density of 6.3 kW kg−1 at the scan rate of 10 mV s−1. Additionally, the hybrid shows good cycling stability with a retention ratio of 95% after 5000 cycles. These attractive results suggest that this 3D RGO-CNT-PANI hybrid has a great potential as an electrode material for high performance supercapacitors.

Creep Behavior of P92 Steel in the Steam Environment at 600 °C Using Miniature Three-Point Bend Test

A miniature three-point bend test system with steam-circulating device was introduced in order to study the interaction behavior between steam oxidation and tensile, compressive creep of P92 steel at 600 °C. It was observed that the formation of oxidation scale accelerated creep deformation which induced by reducing the effective stress on underlying metal. The oxidation mechanisms as well as oxidation kinetics on tensile and compressive surface were examined by scanning electron microscope, x-ray diffraction and energy-dispersive spectrometer. It can be revealed that applied tensile and compressive loading had strong influence on oxidation rate rather than on oxidation mechanism. Furthermore, a mechanical model coupled with oxidation scale growth was proposed to predict the deformation rate of the miniature three-point specimen which could agree well with the experimental results.

Mechanical properties and formation mechanism of Ti/SiC system gradient materials fabricated by in-situ reaction laser cladding

Ti/SiC system gradient materials were designed and fabricated by in-situ reaction laser cladding technique using Ti and SiC powder. The microstructures of the gradient material were analyzed by a scanning electron microscope (SEM) and an oxford energy dispersive spectrometer (EDS). An X-ray diffraction (XRD) spectrometer was used for determination of the reaction products in the composite layers. It was found that chemical reactions took place between Ti and SiC in the clad layers, and the reaction products included TiC, Ti5Si3, Ti5Si4, TiSi2, and Ti3SiC2. Some residual SiC particles were observable in the gradient layers with SiC volume of no less than 50%. A delamination phenomenon occurred at the 70%Ti+30%SiC layer within the 6.6mm thickness FGM sample. Finally, a FGM sample with the total thickness of 1.5mm was successfully fabricated without evident defects and it was believed that the “ductile” Ti3SiC2 phase played an important role in the good forming of the FGM. The average three-point bending strength of the overall TC4/90%SiC FGM was 286MPa at room temperature, and the microhardness of the outermost layer reached 1607.9HV.

The Characterization of Intracellular and Extracellular Biomineralization Induced by Synechocystis sp. PCC6803 Cultured under Low Mg/Ca Ratios Conditions

ABSTRACTIn order to simulate the precipitation process of microbial limestone at the offshore of the ancient ocean, different calcites induced by Synechocystis sp. PCC6803 in culture media with low Mg/Ca ratios (0.01 M Ca2+, Mg/Ca = 0, 0.2, 0.4, 0.6) were investigated, and the characteristics of intracellular and extracellular biomineralization were described. Carbonic anhydrase activity of Synechocystis sp. PCC6803 in different culture medium was further detected. The ultrathin slices of Synechocystis sp. PCC6803 cells were analyzed by transmission electron microscope (TEM) and selected area electron diffraction (SAED). Then the precipitates were analyzed by polarizing microscope, scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The results showed that the biomineralization precipitates of Synechocystis sp. PCC6803 under low Mg/Ca ratios were mainly calcites with different morphologies. The CA accelerated the pivotal rate limiting step of the calcite precipitation. It was also found that the morphology, microstructure, particle size, preferred orientation, crystallinity and cell volume of calcites changed gradually with the increasing Mg2+ concentrations. What is more important, it was found that Synechocystis sp. PCC6803 had the ability of intracellular biomineralization without crystal structure. The intracellular biomineralization product could be divided into two types. This study can provide some useful information for further understanding the characteristics and mechanisms of biomineralization and even the diagenetic environment research of microbial limestone.

Green synthesis of silver nanoparticles by pepper extracts reduction and its electocatalytic and antibacterial activity

Stable silver nanoparticles were synthesized with the aid of a novel, non-toxic, eco-friendly biological material namely, green pepper extract. The aqueous pepper extract was used for reducing silver nitrate. The synthesized silver nanoparticles were analyzed with transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). TEM image shows the formation of silver nanoparticles with average particle size of 20 nm which agrees well with the XRD data. The main advantage of using pepper extract as a stabilizing agent is that it provides long-term stability for nanoparticles by preventing particles agglomeration. To investigate the electrocatalytic efficiency of silver nanoparticles, silver nanoparticles modified carbon-paste electrode (AgNPs–CPE) displayed excellent electrochemical catalytic activities towards hydrogen peroxide (H2O2) and hydrogen evolution reaction (HER). The reduction overpotential of H2O2 was decreased significantly compared with those obtained at the bare CPE. An abrupt increase of the cathodic current for HER was observed at modified electrode. Also, the antibacterial activity of silver nanoparticle was performed using Escherichia coli and Salmonellae. The approach of plant-mediated synthesis appears to be cost efficient, eco-friendly and easy methods.

3D Graphene hydrogel – gold nanoparticles nanocomposite modified glassy carbon electrode for the simultaneous determination of ascorbic acid, dopamine and uric acid

A sensitive and selective electrochemical sensor based on three-dimensional graphene hydrogel and gold nanoparticles nanocomposite (3DGH-AuNPs) for simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA) has been successfully developed in present work. The morphologic appearance and crystal structure of the 3DGH-AuNPs nanocomposite were studied by field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray Diffraction (XRD) and Energy Dispersive X-ray Spectrometer (EDX). The electrochemical characteristics and catalytic behavior of prepared electrodes for the simultaneous determination of AA, DA and UA were systematically investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) and demonstrated three well-resolved oxidation peaks for the aforementioned analytes. Under optimum conditions, the 3DGH-AuNPs/GCE exhibits linear responses to AA, DA and UA in the ranges 1.0–700, 0.2–30, 1–60μM, respectively, with detection limits (S/N=3) calculated to be 28nM (AA), 2.6nM (DA) and 5nM (UA). Moreover, interference from some normally coexisting substances (like lysine, glycine, glucose, citric acid, etc) in real samples were nearly negligible. Finally, the developed sensor was successfully applied to the detection of AA, DA and UA in human serum samples with satisfactory results. The 3DGH-AuNPs nanocomposite show promising applications in the development of electrochemical sensors for chemical or biomolecules determinations.

Preparation of Ti-coated diamond particles by microwave heating

Depositing strong carbide-forming elements on diamond surface can dramatically improve the interfacial bonding strength between diamond grits and metal matrix. In the present work, investigation on the preparation of Ti-coated diamond particles by microwave heating has been conducted. The morphology, microstructure, and the chemical composition of Ti-coated diamond particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive x-ray spectrometer (EDX). The thickness of Ti coating was measured and the interfacial binding strength between Ti coating and diamond was analyzed. The results show that the surface of the diamond particles could be successfully coated with Ti, forming a uniform and continuous Ti-coated layer. The TiC was found to form between the surface of diamond particles and Ti-coated layer. The amount of TiC as well as the thickness of coating increased with increasing coating temperature, furthermore, the grain size of the coating also grew gradually. The interfacial bonding strength between coating and diamond was found to be best at the temperature of 760°C.

PREPARATION OF TiO2/PERLITE COMPOSITES BY USING 23-1 FRACTIONAL FACTORIAL DESIGN

Successive impregnation and calcination process was performed in order to produce TiO 2 /perlite composites. 2 3-1 fractional factorial design was first applied to optimize the production conditions of TiO 2 /perlite photocatalysts. Seven TiO 2 /perlite composites (including three central point experiments) were produced by manipulating three process parameters (amount of TiO 2 used in impregnation process, particle size of perlite and calcination temperature). Prepared TiO 2 /perlite photocatalysts were characterized by X-Ray Diffraction Spectrometer and SEM. XRD patterns indicated that anatase was the main crystalline phase for all produced samples. Degradation capacities of produced TiO 2 /perlite composites were investigated in methylene blue degradation process. The linear models of TiO 2 loading (%) and methylene blue degradation (%) of TiO 2 /perlite composites were developed by regression analysis of the experimental data. As a result of analysis of variance, it was found that developed models were statistically significant with the p-value of 0.0040 and 0.0003, for TiO 2 loading (%) and methylene blue degradation (%), respectively. According to the coefficient of determination (0.9821 and 0.9970 for the models of TiO 2 loading and methylene blue degradation, respectively) and error analysis, developed models fit well to the experimental data. Effect of process parameters was investigated by using response surface plots. Amount of TiO 2 and particle size were found as the most effective parameters on both TiO 2 loading (%) and degradation efficiency (%). Calcination temperature did not affect TiO 2 loading but methylene blue degradation capacity.

Effects of carbon doping on the microstructural, micro/nano-mechanical, and mesenchymal stromal cells biocompatibility and osteogenic differentiation properties of alumina

It has been demonstrated that carbon (C) doped aluminium oxide (Al2O3) nanocomposite (C −0.012wt%) had greater wear resistance and lower surface grains pull out percentage when compared with monolithic Al2O3. In the present study, we investigated the physicochemical, micro- and nanomechanical, cell attachment, in vitro biocompatibility and osteogenic differentiation properties of Al2O3 doped carbon (0.012wt%) nanocomposite (Al2O3/C). Data were compared to values obtained for monolithic alumina (Al2O3). The calcined Al2O3/C nanocomposite was densified using cold isostatic pressing and followed by pressureless sintering. For physicochemical and microstructural characterisation, Energy dispersive X-ray (EDX), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoemission spectrometer (XPS) were used. EDX, XRD peaks and Raman spectroscopy demonstrated correlating to Al2O3/C. Surface profiling and contact angle investigations demonstrated highly contoured micro-surface topography. The micro and nano-hardness indicate an improved wear resistance of the Al2O3/C when compared with monolithic Al2O3. SEM, confocal images and alamar blue reduction assay suggested good cell attachment and proliferation of human bone marrow derived mesenchymal stromal cells (hBMSCs). Osteogenic protein and gene expression indicated Al2O3/C had a significant osteogenic potential (p<0.05) when compared with Al2O3. In conclusion, our novel Al2O3/C nanocomposite had improved mechanical properties. It also supports cell attachment and proliferation which are comparable to Al2O3. However, Al2O3/C has a significant osteogenic potential than that of Al2O3. These findings suggest that Al2O3/C nanocomposite is superior to Al2O3 and thus has a greater potential for use in orthopaedic applications.

Study on the microstructure of the multilayer glaze of the 16th-17th century export blue-and-white porcelain excavated from Nan’ao-I Shipwreck

The study aims to analyse the devitrification and multilayer structure of the glaze of the Zhangzhou export blue-and-white porcelain excavated from Nan’ao-I shipwreck in Shantou district, Guangdong province. Digital microscope, polarizing microscope and scanning electron microscope are applied to observe the glaze layer. X-ray Diffraction and X-ray Energy Dispersive Spectrometer are applied to analyse the chemical compositions of the glaze. Anorthite crystals are found in the outer glaze layer, which cause the decrease in transparency of the glaze. The appearance and chemical compositions of the multilayers of the glaze are different and cobalt pigments are located between the glaze layers. It is inferred that part of the 16th–17th century export blue-and-white porcelain produced by Zhangzhou kiln in Ming dynasty was glazed twice.

A facile method to fabricate superhydrophobic ZnO nanostructure with petal effect

ZnO nanostructures were fabricated on glass substrate through a convenient deposition process. Firstly, ZnO seed layers were deposited on glass substrates through sol–gel method. Secondly, the ZnO nanostructures were then grown in a Teflon-lined stainless steel autoclave by immersing the seed layers into aqueous solution containing zinc nitrate hexahydrate and ammonia. The microstructures, morphologies, photoluminescence spectra and hydrophobicity of the nanostructures were analyzed by X-ray diffraction spectrometer, field emission scanning electron microscopy, laser micro-Raman spectrometer and contact angle apparatus, respectively. It can be seen that ZnO nanostructures display different surface morphologies such as ZnO nanorods parallel to the substrate surface, like-pencil ZnO nanorods and bending ZnO nanorods by altering the PH value. The largest intensity ratio of the UV/visible emission and the superhydrophobic surfaces (CA = 156°) with high adhesion can be achieved in the sample grown in the solutions with the PH value of 11.2. The high adhesion may be attributed to the strong capillary force and the ZnO nanostructures with petal effect can be explained by Wenzel model.