Scanning Electron Microscopy-energy Dispersive Analysis Research Articles

Mining PANI/Ti3AlC2/CeO2 ternary composite CO sensor: Material synthesis, gas sensing performance and mechanism research

To address the issue of poor gas sensitivity in existing mining semiconductor CO sensor materials like PANI at room temperature, this study employed an ice-water bath in conjunction with an in-situ polymerization method to incorporate 2D sheet-like Ti3AlC2 and nano-CeO2 materials with oxygen vacancies into PANI. As a result, nanometer-sized PANI/Ti3AlC2/CeO2 ternary composite nanomaterial was synthesized. The morphology, synthesis mechanism, and thermal stability of the ternary composite material were investigated using scanning electron microscopy-energy dispersive analysis (SEM-EDS), transmission electron microscopy analysis (TEM), spectral analysis, and thermogravimetric methods. Furthermore, the CO gas sensing mechanism of the ternary composite material was also examined. The study discovered that the nano-PANI/Ti3AlC2/CeO2 ternary composite nanomaterial, when deposited on the Au interdigital electrode of the IDE substrate, exhibits superior gas transmission of 400 ppm CO compared to gas sensors based on nano-PANI, nano-PANI/Ti3AlC2, and nano-PANI/CeO2. The sensing response was enhanced by 1.75 times, 1.4 times, and 1.2 times, respectively. This improvement in sensing mechanism can be attributed to the pn heterojunction and interfacial interaction forces between the components. Hence, the nano-PANI/Ti3AlC2/CeO2 ternary composite nanomaterial holds potential as a high-performance CO detection sensing material at room temperature. Additionally, it can serve as a theoretical basis for further research on low-power, integrable sensor materials in coal mines.

Bi Doped TiO2 as a Photocatalyst for Enhanced Photocatalytic Activity

This study is based on the preparation of TiO2 and bismuth doped TiO2 (Bi-TiO2) nanoparticles by surfactant-assisted sol-gel approach. The physiochemical characteristics of prepared samples were examined by X-ray diffraction technique (XRD), Fiel emission scanning electron microscopy-energy dispersive analysis (FESEM-EDS), and UV-visible diffuse reflectance spectroscopy (UV-vis DRS). The XRD patterns revealed that the anatase crystal phase was only formed with high crystallinity. The band gap energies were measured to be of 3.11 eV for TiO2-2 and 3.02 eV for Bi-TiO2 by ultraviolet (UV)-visible diffuse reflectance spectroscopy, revealing that doping Bi improves the efficient interactive relation of the catalyst with visible light. Also, EDS results confirm that Bi particles are immobilized on the surface of TiO2 successfully. The activities of the catalysts were tested by photocatalytic degradation of methylene blue (MB) under the visible light. Bi-TiO2 photocatalyst could achieve the best MB degradation percentage of 70.2% after 180 min. of visible irradiation. Additionally, effect of some experimental parameters such as effect of humic acid (HA) and pH has been evaluated as much as reusability of catalyst. The characterization results confirmed the successful and desired preparation of the catalysts. The Bi-TiO2 presented significant visible light response photocatalytic activity for the degradation of MB.

Morphological and elemental analysis of termite mound and ant nest in agriculturally prominent area

Soil management is important for the farmers to improve the crop yield. In nature some invertebrates serve as bioindicators and biomonitors. Biogenic structure built by insects is important for controlling soil erosion and water reserves. Ants and termites nest architecture along with the elemental analysis was studied to evaluate soil health and possible threats imposed by heavy metals in the area. The soil samples were collected and analyzed for various parameters. Systematic study of porosity, composition, and nutritional values of soil in ant nest and termite mound were done. The Atomic Absorption Spectrophotometer and Inductively Coupled Plasma Mass Spectrophotometer studies showed that ant nest and termite mound samples were found to contain elements viz., zinc, selenium, lead, cadmium, nickel drought and chromium. Based on Scanning Electron Microscope-Energy Dispersive Analysis of X-rays, the size of soil samples collected from ant nest and termite were found to be 27.77 nm and 25.56 nm, respectively. The corrosion resistant zirconium and titanium metals were detected in 0.68 and 0.39% concentration in ant nest and termite mound samples, respectively, representing the insect house as a possible source of rich metals. The ant nest and termite mound materials contain quartz, microcline, kaolinite, and clay minerals. Ant nests and termite mounds can thus be used as hydrological indicators to address the problems of soil erosion.

Extraction of REEs from Blast Furnace Slag by Gluconobacter oxydans

Granulated blast furnace slag (GGBFS) is a potential resource of rare earth elements (REEs), and due to the complex mineralogy, extraction by conventional hydrometallurgical process makes it an acid-consuming method. Bioleaching is thus investigated using a chemo-organotrophic bacterium Gluconobacter oxydans (DSMZ 46616) for REE extraction from GGBFS containing 157 ppm Ce, 90 ppm La, 71 ppm Nd and 40 ppm Er, hosted in a Ca-Al-Si matrix. The gluconic acid generation by G. oxydans was assessed for its role in REE extraction from GGBFS. With 5% (w/v) GGBFS using a mixture of a non-adapted and a GGBFS-adapted culture, a maximum solubilization of 67% and 88% Nd was observed after 12 and 40 days of incubation, respectively. The total amount of gluconic acid excreted by the bacteria increased with leaching duration, which contributed to a rise in metal extraction. Scanning electron microscope-energy dispersive analysis (SEM-EDAX) analysis of the solid residue showed bacterial cells in corrosion pits, and thereby assisting in metal solubilization.

Upcycling of air pollution control residue waste into cementitious product through geopolymerization technology

This study explores the possibility of using geopolymerization technology (GT) to immobilize the potentially toxic elements (PTEs, e.g., Zn, Cu, Cr, As) in the APCr and convert it into useful cementitious product. To maximize its recycling, the amount of APCr in the designed product was increased gradually from 20% to 80% by the total solid mass. Leaching test showed that GT can effectively immobilize the PTEs in the APCr solidified samples without any health and environmental concerns. The compressive strength of samples can exceed 18 MPa at 28 days at a highest amount of 80% APCr through GT. Thermogravimetric analysis (TGA) results showed that solidified samples underwent mass loss due to evaporation of free and physically bound water at low temperatures (<200°C) and melting and evaporation of soluble salts in APCr at high temperatures (>800°C). Characterization of solidified samples conducted through the X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy-Energy dispersive analysis (SEM) revealed the formation of C-A-S-H and N-A-S-H gels in solidified bodies and verified that APCr was successfully solidified and embedded into the geopolymer network structure

Influence of Genetic Processes on Geochemistry of Fe-oxy-hydroxides in Supergene Zn Non-Sulfide Deposits

In supergene Zn non-sulfide deposits, the Fe-oxy-hydroxides (FeO/OH) are mainly concentrated in the residual zones (gossan) on top of the oxidized ore bodies, although they can also be found throughout the whole weathering profile coexisting with the primary and secondary ore assemblages. Fe-oxy-hydroxides are rarely pure as they form in systems where a wide range of metals, most of them of economic importance (e.g., Zn, Pb, Co, REE, Sc, Ga, Ge, V, etc.), freely circulate and can be “captured” under specific conditions. Although their occurrence can be widespread, and they have a potential to scavenge and accumulate critical metals, FeO/OH are considered gangue phases during the existing processing routes of Zn non-sulfide ores. Moreover, very little is known about the role of the deposit type on the geochemistry of FeO/OH formed in a specific association. Therefore, this paper provides a comprehensive assessment of the trace element footprint of FeO/OH from a number of Zn non-sulfide deposits, in order to define parameters controlling the metals’ enrichment process in the mineral phase. To achieve this, we selected FeO/OH-bearing mineralized samples from four supergene Zn non-sulfide ores in diverse settings, namely Hakkari (Turkey), Jabali (Yemen), Cristal (Peru) and Kabwe (Zambia). The petrography of FeO/OH was investigated by means of scanning electron microscope energy dispersive analysis (SEM-EDS), while the trace element composition was assessed using laser ablation-ICP-MS (LA-ICP-MS). Statistical analyses performed on LA-ICP-MS data defined several interelement associations, which can be ascribed to the different nature of the studied deposits, the dominant ore-formation process and subsequent evolution of the deposits and the environmental conditions under which FeO/OH phases were formed. Based on our results, the main new inferences are: (A) Zinc, Si, Pb, Ga and Ge enrichment in FeO/OH is favored in ores where the direct replacement of sulfides is the dominant process and/or where the pyrite is abundant (e.g., Cristal and Hakkari). (B) When the dissolution of the host-rock is a key process during the supergene ore formation (i.e., Jabali), the buffering toward basic pH of the solutions favors the uptake in FeO/OH of elements leached from the host carbonate rock (i.e., Mn), whilst restricting the uptake of elements derived from the dissolution of sulfides (i.e., Zn, Pb, Ga and Ge), as well as silica. (C) The input of exotic phases can produce significant enrichment in “unconventional” metals in FeO/OH (i.e., Cr and Co at Kabwe; Y at Cristal) depending on whether the optimal pH-Eh conditions are attained. (D) In the Kabwe deposit, FeO/OH records heterogeneous geochemical conditions within the system: where locally basic conditions prevailed during the alteration process, the V and U concentration in FeO/OH is favored; yet conversely, more acidic weathering produced Zn- and Si-bearing FeO/OH.

New insights into the genesis of willemite (Zn2SiO4) from zinc nonsulfide deposits, through trace elements and oxygen isotope geochemistry

Willemite is a common mineral mainly occurring in the so-called “hypogene” nonsulfide Zn-Pb mineralizations, deposited from what have been interpreted as high temperature hydrothermal or metamorphic fluids. The literature is currently lacking a comprehensive compilation of geochemical data on willemite so the aim of this study was to elucidate specific geochemical signatures for willemites of contrasting genesis. For this work, we analyzed a range of specimens from the Mineralogy Collection of the Natural History Museum in London. The specimens are from several deposit-types: 1.Stratiform hypogene deposits: Franklin and Sterling Hill (USA);2.Structurally-controlled hypogene deposits: Star Zinc, Excelsior, Surprise (Lusaka area, Zambia), Kabwe (Zambia), Berg Aukas and Tsumeb (Namibia);3.Supposedly supergene deposits: Mumbwa area (Zambia), and Altenberg-Vieille Montagne (Belgium).Textures and structures of the willemite-bearing specimens were initially investigated by scanning electron microscope energy dispersive analysis (SEM-EDS). Trace element concentrations were later measured in situ on selected willemite crystals by laser ablation (LA)-ICP-MS. Statistical analyses (principal component analysis-PCA, multivariate analysis of variance, post hoc Tukey HSD test), conducted on the data obtained by LA-ICP-MS, showed that significant differences exist between willemites derived from the various deposit types studied. High-T, stratiform willemite samples contain significant amounts of Mn and Mg, and are statistically different from all the other analyzed specimens. Structurally-controlled hypogene willemites, characterized by lower Mn and Mg concentrations, and by higher Pb, Cu, As, B, Ge contents, are statistically inhomogeneous, both at the district and at the deposit scale. High-T willemite from the Lusaka area contains more Mn than the low-T hydrothermal deposits, with the latter showing higher concentrations of other elements (e.g. Pb, Cu, Ge). Among the willemite generations associated with the supposedly supergene mineralization, only the Mumbwa willemites form a cluster that is significantly displaced from the other deposits. The δ18O isotopic compositions match the mentioned trace element distribution: willemites with similar origin are characterized by similar oxygen isotopic ratios. On the basis of the present work, willemite-types can be distinguished as follows:•High-T willemites are characterized by high Mn + Mg concentrations (between 100 ppm to unit wt%) and by low, positive δ18O compositions (around 3 to 5‰ V-SMOW);•Low-T hydrothermal willemites show Mn + Mg concentrations below 50 ppm and are associated with high Pb + Cu + As + Ge concentrations (above 100 ppm). They also have high, positive δ18O compositions (between 9 and 15‰ V-SMOW);•Willemites derived from (either cold or warm) meteoric fluids have generally low concentrations of the above elements and negative δ18O compositions (−3 and −9‰ V-SMOW). The supposedly supergene Altenberg-Vieille Montaigne willemite, having low Mn + Mg and high Pb + Ge + As concentrations, and showing δ18O compositions between 11 and 12.5‰, likely formed from low-T hydrothermal fluids.

Regional patterns in medieval European glass composition as a provenancing tool

A legacy dataset of 1329 major element analyses of medieval glass (12th-15th centuries) has been compiled and analysed for geographical distribution of compositional characteristics. Three regional compositional types may be distinguished using simple elemental plots, associated with glass production in northwestern France, in the region around the Rhine, and in central Europe. Distribution maps are presented to aid interpretation and use of the data. The application of the approach is illustrated through three case studies. Late thirteenth-early fourteenth century medieval stained glass from York Minster (n = 91), late fourteenth-century stained glass from New College Oxford (n = 79) and a single medieval mirror found in Egypt were analysed using scanning electron microscopy–energy dispersive analysis. The York coloured and white glasses were identical and consistent with an origin in NW France. In the late fourteenth century, the coloured glass samples from Oxford were from the Rhenish region, while the white glass is consistent with an origin in NW France or England. The mirror glass from Egypt is of central European origin, and similar mirror glass is known from Italy. The apparent dominance of German mirror production may reflect an advantage of the glass, which is low in iron. The meta-analysis of the legacy data shows significant potential for developing an understanding of the production and movement of medieval glass.

Crystal structure, dielectric, magnetic and improved magnetoelectric properties of xNiFe2O4-(1-x)Na0.5Bi0.5TiO3 composites

Magnetoelectric (ME) composites of NiFe2O4 (NFO) and Na0.5Bi0.5TiO3 (NBT) with composition xNiFe2O4-(1-x)Na0.5Bi0.5TiO3 (x = 0.20, 0.40, 0.60) were prepared successfully by solid state reaction method. The crystal structure analysis was carried by using x-ray diffractometer, field emission scanning electron microscope—energy dispersive analysis of x-rays (FESEM-EDX) and Fourier transform infrared spectroscopy (FTIR). The presence of two individual phases corresponding to ferrite and ferroelectric was confirmed by XRD analysis of composites. Rietveld refinement of XRD data further confirms the existence of both cubic (Fd3m) and rhombohedral (R3c) symmetries. FESEM micrographs and EDX spectra revealed the reduction in grain sizes with increase in ferrite content. FTIR spectra depict two prominent absorption bands around 413 cm−1 and 618 cm−1. Dielectric response of these samples was recorded at frequency range 100 Hz–7 MHz for different temperature. Dielectric constant (ε′) and dielectric loss (tanδ) values found higher at low frequencies, decrease with increase in frequencies and become independent at higher frequencies. ε′ and tanδ both enhance with rising temperature and become more stable at higher frequencies. Complex impedance spectroscopy (CIS) investigation was used to understand dielectric relaxation and conduction mechanism in composites. Cole-Cole plots for all samples depict two semicircles and the centre of semicircles is depressed below real axis with temperature. Activation energy rises with increase in ferrite content in composites. Magnetic evaluation of the samples discloses the soft magnetic nature of these composites. The maximum value of saturation magnetization (MS = 22.82 emu g−1) and magnetic moment per formula unit (η = 0.92 μB) is observed for composition having higher NFO content. The highest ME response, α ∼ 1122 μV/cmOe is observed for the composite 0.60NiFe2O4-0.40Na0.5Bi0.5TiO3.

Arsenic biosorption using pretreated biomass of psychrotolerant Yersinia sp. strain SOM-12D3 isolated from Svalbard, Arctic

A Gram-negative, arsenite-resistant psychrotolerant bacterial strain, Yersinia sp. strain SOM-12D3, was isolated from a biofilm sample collected from a lake at Svalbard in the Arctic area. To our knowledge, this is the first study on the ability of acid-treated and untreated, non-living biomass of strain SOM-12D3 to absorb arsenic. We conducted batch experiments at pH 7, with an initial As(III) concentration of 6.5ppm, at 30°C with 80min of contact time. The Langmuir isotherm model fitted the equilibrium data better than Freundlich, and the sorption kinetics of As(III) biosorption followed the pseudo-second-order rate equation well for both types of non-living biomass. The highest biosorption capacity of the acid-treated biomass obtained by the Langmuir model was 159mg/g. Further, a high recovery efficiency of 96% for As(III) was achieved using 0.1M HCl within four cycles, which indicated high adsorption/desorption. Fourier transformed infrared (FTIR) demonstrated the involvement of hydroxyl, amide, and amine groups in As(III) biosorption. Field emission scanning electron microscopy-energy dispersive analysis (FESEM-EDAX) indicated the different morphological changes occurring in the cell after acid treatment and arsenic biosorption. Our results highlight the potential of using acid-treated non-living biomass of the psychrotolerant bacterium, Yersinia sp. Strain SOM-12D3 as a new biosorbent to remove As(III) from contaminated waters.

Facile Co-precipitation synthesis and ethanol sensing performance of Pd loaded Sr doped SnO2 nanoparticles

In the present communication, we have presented a high performance ethanol sensor based on Pd loaded Sr doped SnO2 nanomaterial. The (0.5, 1.5, 2.5 and 3) wt% Pd loaded 4mol% Sr doped SnO2 nanoparticles were prepared using a co-precipitation method. The samples were characterized by X-ray Diffraction (XRD), High Resolution Transmission Electron Microscope (HR-TEM), Selected Area Electron Diffraction (SAED), Field Emission Gun-Scanning Electron Microscope (FEG-SEM), (SEM-EDAX) Scanning Electron Microscope-Energy Dispersive Analysis by X-ray techniques. The gas response studies such as sensitivity, selectivity and stability towards liquid petroleum gas (LPG), ammonia (NH3), acetone (CH3COCH3) and ethanol (C2H5OH) were measured at 100ppm concentrations. The results show that optimum Pd loading (2.5wt%) results in smaller crystallite size (~3.7nm), lower operating temperature (275°C), higher gas response (93%),better selectivity, faster response (~1s) and quicker recovery (~5s) towards ethanol.

Reductive solidification/stabilization of chromate in municipal solid waste incineration fly ash by ascorbic acid and blast furnace slag

Fly ash is a hazardous byproduct of municipal solid waste incineration (MSWI). Cementitious material that is based on ground-granulated blast furnace slag (GGBFS) has been tested and proposed as a binder to stabilize Pb, Cd, and Zn in MSWI fly ash (FA). Cr, however, still easily leaches from MSWI FA.Different reagents, such as ascorbic acid (VC), NaAlO2, and trisodium salt nonahydrate, were investigated as potential Cr stabilizers. The results of the toxicity characteristic leaching procedure (TCLP) showed that VC significantly improved the stabilization of Cr via the reduction of Cr(VI) to Cr(III). VC, however, could interfere with the hydration process. Most available Cr was transformed into stable Cr forms at the optimum VC content of 2 wt%. Cr leaching was strongly pH dependent and could be represented by a quintic polynomial model. The results of X-ray diffraction and scanning electron microscopy-energy dispersive analysis revealed that hollow spheres in raw FA were partially filled with hydration products, resulting in the dense and homogeneous microstructure of the solidified samples. The crystal structures of C–S–H and ettringite retained Zn and Cr ions. In summary, GGBFS-based cementitious material with the low addition of 2 wt% VC effectively immobilizes Cr-bearing MSWI FA.

Carbon fibers modified with molybdenum for sorption of arsenic(V)

Procedure for obtaining new hybrid sorbents based on carbon fibers and chitosan-carbon materials modified with molybdenum, which determines the affinity of the sorbents for arsenate ions, is described. The surface morphology was examined and a qualitative chemical analysis of the surface of the composite sorbents was made by the method of scanning electron microscopy–energy-dispersive analysis. Sorption isotherms were obtained for unmodified materials, carbon fibers and chitosan-carbon materials, and hybrid sorbents in twicedistilled and tap water at low As(V) concentrations.

Optimization and evaluation of reactive dye adsorption on magnetic composite of activated carbon and iron oxide

In this study, the magnetic-activated carbon (MAC) was synthesized and employed as an adsorbent for removing Reactive Blue 5 from aquatic environments. Physical properties and surface morphology of the MAC were analyzed using the transmission electron microscopy, scanning electron microscopy (SEM), SEM–energy dispersive analysis by X-ray, X-ray diffraction, vibrating sample magnetometer and Brunauer–Emmett–Teller techniques. The adsorption efficiency of dye was studied in a batch experiment by investigating the influential parameters such as pH, contact time, adsorbent dosage, initial dye concentration, and temperature. Various models of isotherm and kinetic were used to evaluate the obtained data. The equilibrium time was found to be 15 min. The thermodynamic values indicated that the adsorption process was spontaneous and endothermic. The adsorption isotherms and kinetics follow the Langmuir (R2 > 0.999) and pseudo-second-order models (R2 > 0.995), respectively. On conclusion, MAC due to its quick and easy isolation, not leading to the secondary pollution and high efficiency, is a very suitable adsorbent for dye removal from aquatic media.

Degradation Studies of Wire arc Sprayed FeCrBSiMn Alloy Coating in Molten Salt Environment

The aim of the current investigation is fabricate the FeCrBSiMn alloy coating onto 310S stainless steel substrate by wire arc spraying process and to study degradation behavior of the coating exposed to molten salt environment (Na2SO4-82%Fe2(SO4)3) at 900°C under cyclic conditions after 50 cycles. X-ray diffraction (XRD) and scanning electron microscopy/energy-dispersive analysis (SEM/EDS) were used to characterize morphology of coated and uncoated samples for substantiating the degradation mechanisms. The dense and globular morphology of the coatings is observed from the SEM analysis. The maximum microhardness of coating was found to be (430-1060 HV). The coating showed superior hot corrosion resistance as compared to boiler steel due to the formation of protective scale, Cr2O3. The protective scale formed at high temperature prevents hot corrosion of coated boiler steel as evident from the morphological studies made by using FE-SEM/EDS. The FeCrBSiMn alloy coating showed good adherence to the 310S substrate with negligible microspalling of the scales.

Photocatalysis-assisted water filtration: Using TiO2-coated vertically aligned multi-walled carbon nanotube array for removal of Escherichia coli O157:H7

A porous ceramic was coated with vertically aligned multi-walled carbon nanotubes (MWCNTs) by spray pyrolysis. Titanium dioxide (TiO2) nanoparticles were then coated onto this densely aligned MWCNT. The presence of TiO2/MWCNT interfacial arrays was confirmed by X-ray diffraction (XRD), scanning electron microscope–energy dispersive analysis of X-ray (SEM–EDAX) and transmission electron microscope (TEM). This is a novel report in which water loaded with a most dreadful enterohemorrhagic pathogenic strain of Escherichia coli O157:H7 was filtered through TiO2/MWCNT coated porous ceramic filter and then analysed. Bacterial removal performance was found to be significantly lower in control i.e. plain porous ceramic (P<0.05) as compared to TiO2/MWCNT coated ceramic. The photocatalytic killing rate constant for TiO2-ceramic and MWCNT/TiO2-ceramic under fluorescent light was found be 1.45×10−2min−1 and 2.23×10−2min−1 respectively. Further, when I–V characteristics were performed for TiO2/MWCNT composite, it was corroborated that the current under light irradiation is comparatively higher than that in dark, thus proving it to be photocatalytically efficient system. The enhanced photocatalysis may be a contribution of increased surface area and charge transfer rate as a consequence of aligned MWCNT network.

Metal Accumulation in Cell Wall: A Possible Mechanism of Cadmium Resistance by Pseudomonas stutzeri

A heavy metal resistant strain, Pseudomonas stutzeri (MTCC 101) has been investigated for its cadmium tolerance properties along with its antibiotic resistance. The organism could tolerate cadmium up to 1,200μg/mL with LD50 value 700μg/mL. The gene(s) involved in such high resistance appear(s) to be induced in the presence of the metal. Increasing concentrations of cadmium successively prolonged the lag phase of growth with delayed attainment of the stationary phase. Transmission electron microscope and scanning electron microscope-energy dispersive analysis of X-ray spectroscope analysis showed cadmium adsorption on the bacterial surface with morphological distortion. Atomic absorption spectrometric study corroborated this data, showing highest cadmium accumulation in the cell wall fraction of the bacteria. Additionally, the cell wall fraction showed synthesis of new proteins when grown under metal stress.

Aerosol-assisted chemical vapour deposition of sodium fluoride thin films

Thin films of sodium fluoride were created by the use of aerosol-assisted chemical vapour deposition between 200 and 600 °C on glass substrates. The films were found to be crystalline and single-phase (NaF) using X-ray diffraction. Scanning electron microscopy energy-dispersive analysis of X-rays gave coherent elemental compositions indicating that monophasic NaF was made with negligible impurity levels. The films appeared hazy and showed little optical transmission (5–10%) and reflectance (∼2%).

Densification of LSGM electrolytes using activated microwave sintering

Abstract Lanthanum gallate doped with alkaline rare earths (LSGM) powders were densified using an activated microwave sintering process for developing a dense stable electrolyte layer for applications in intermediate temperature-solid oxide fuel cells (IT-SOFCs). Due to heat generation in situ, the process of sintering gets activated with faster kinetics compared to a conventional sintering process. The effect of various microwave process parameters on the microstructure and phase formation was studied. The sintered pellets were characterized using scanning electron microscopy-energy dispersive analysis (SEM-EDAX), and X-ray diffraction (XRD). The density of LSGM pellets microwave sintered at 1350 °C for 20 min is greater than 95% theoretical density with a fine grained microstructure (∼2–3 μm) and without the presence of other phase(s).

Vermiculitization of Phlogopite in Metagabbro, Central Turkey

AbstractDioctahedral vermiculite occurs in an isolated metagabbro klippe (Kurançalı Metagabbro) that belongs to the Central Anatolian Ophiolites from central Turkey. Both the metagabbro and the structurally underlying high-grade metamorphic rocks are intruded by granitic rocks. The Kurançalı Metagabbro is characterized by its well-developed compositional layering, and the presence of vermiculitized phlogopiterich layers. Petrographic and mineralogie studies show that the primary mineral phases in the host rock are diopside, tschermakitic hornblende, Fe-rich phlogopite, and plagioclase. Secondary minerals are hornblende, actinolitic hornblende, Fe-rich phlogopite, and vermiculite. A two-phase history of alteration involving acidic weathering and alkaline metasomatism is suggested for the dioctahedral vermiculite and secondary Fe-rich phlogopite, respectively. The alteration of phlogopite to dioctahedral vermiculite proceeded both along cleavage planes and at crystal edges. The vermiculite is colorless to pale yellow with weak pleochroism and shows optical continuity with the parent mineral. Vermiculite flakes, analyzed semi-quantitatively by scanning electron microscope-energy dispersive analysis (SEM-EDS) and electron microprobe (EMP), are characterized by partially expanded interlayers, K depletion, and Mg and/or A1 enrichment. X-ray diffraction (XRD) and differential thermal analysis-thermal gravimetric (DTA-TG) analyses indicate that phlogopite is not a pure phase, although it is the dominant one. The XRD patterns show the presence of both dioctahedral vermiculite having dehydrated interlayers and hydroxy-Al interlayers, and interstratified phlogopite-vermiculite. The transformation of phlogopite to vermiculite is thought to represent an initial stage of weathering in an acidic environment.