MgO Wt Research Articles

Unraveling the role of MgO in the Ru-Ba/MgO catalyst for boosting ammonia synthesis: Comparative study of MgO and MgAlOx supports

The growing emphasis on decarbonization and the use of renewable energy has sparked considerable interest in ammonia (NH3) synthesis under mild conditions, accompanied by the concurrent development of catalysts. Among these catalysts, BaO-promoted Ru has often been reported as a highly efficient catalyst for this reaction. Despite MgO being traditionally regarded as an optimal support for this catalytic system, its precise role has remained ambiguous. This study aims to elucidate the specific role of MgO as a support for Ru-BaO catalysts. Using pure MgO and MgO-Al2O3 mixed oxide (MgAlOx) with different MgO contents (MgO wt% = 5, 30, and 70) as supports, catalysts impregnated with equal amounts of Ba and Ru were prepared and analyzed to explore their NH3 synthesis activity and structural properties. Our observations reveal that while MgO does not directly promote Ru, it maintains robust basicity of BaO, enabling BaO to effectively function as an electronic promoter. In contrast, BaO supported on AlOx domain shows suppressed basicity, resulting in inertness as a promoter. Consequently, the Ru-Ba/MgO catalyst forms highly active Ru-BaO-MgO interfacial sites, leading to significantly higher activity, lower activation energy, and a distinct reaction mechanism compared to Ru-Ba/MgAlOx catalysts. This work sheds light on the importance of sequential interactions, i.e. support–promoter and promoter–active center interactions, in facilitating catalytic activity, thereby providing valuable insights essential for the design of advanced catalysts.

Magnesium isotope behavior during titanomagnetite fractionation in basaltic lavas

Knowledge of the behavior of magnesium (Mg) isotopes during magmatic differentiation is a prerequisite for applying Mg isotopes as a tracer of crustal recycling and mantle heterogeneity. Crystal fractionation of mafic silicate minerals leads to limited Mg isotope fractionation; hence, Mg isotopic variations in basalts largely result from contributions of subducted crustal materials into their mantle sources. However, recent studies have revealed that the segregation of iron oxides, such as chromite during early-stage basaltic differentiation and titanomagnetite and ilmenite during late-stage differentiation, can potentially modify Mg isotopic compositions of mantle-derived lavas. Titanomagnetite is much more commonly observed in terrestrial basaltic lavas than chromite and ilmenite, and can also form during early-stage basaltic differentiation. To constrain the effects of titanomagnetite crystallization on Mg isotopic systematics of basaltic magma, we report Mg isotopic data for a suite of well-characterized alkaline basaltic lavas (MgO wt% = 4.99 to 6.52) from Gerba Guracha, western Ethiopian Plateau, which have undergone extensive titanomagnetite fractionation. Their δ26Mg values range from −0.29‰ to −0.17‰ and do not correlate with indicators of titanomagnetite fractionation such as TiO2 and V. These observations suggest that the segregation of titanomagnetite produced limited Mg isotope fractionation, possibly because of its composition-dependent, highly variable Δ26MgTi-Mgt−melt (Δ26MgTi-Mgt−melt = δ26MgTi-Mgt − δ26Mgmelt) values. Considering that most iron oxides occur as complex solid solutions that are controlled by the oxygen fugacity of magmas, the effects of oxide segregation on Mg isotopic systematics of basalts require further evaluation.

Linear/nonlinear optical properties of functional inorganic MgO nano-filler in PVA transparent polymer for flexible optoelectronic devices

Structural features of different PVA/MgO nanocomposite films, where 0≤MgOwt%≤5, using XRD and Raman spectra were correlated with their linear/nonlinear optical properties. The XRD spectra revealed a decrease in the crystallinity of the PVA semi-crystalline polymer with the addition of 1 wt% of MgO nano-filler in the host polymer along with an increase with further increase of the MgO nano-filler concentration. The Raman spectra along with the calculated increase in the width of localized states Ee within the optical energy gap with increasing MgO wt% suggested formation of new structural disorders, defects and impurities at the internal grain boundaries between the dispersed MgO nano-filler and the PVA matrix. The linear/nonlinear optical properties of different PVA/MgO nanocomposites films such as energy gap, linear/nonlinear refractive index, optical conductivity, the third order susceptibility, dispersion energy, and other optoelectronic parameters were evaluated using UV/Vis/NIR spectrophotometer. All the calculated optical parameters were found to be MgO wt% dependent and revealed a guide for tuning the optical properties of PVA films using MgO nano-filler for usage in flexible optoelectronic applications.

Effects of MgO and Fe2O3 Addition for Upgrading the Refractory Characteristics of Magnesite Ore Mining Waste/By-Products

In the context of a circular economy/zero-waste, the conversion of extractive wastes into new products is of particular importance. At the Grecian Magnesite SA mine (Chalkidiki, N. Greece), millions of tons of waste accumulate in the operation field. To achieve these goals, the effect of caustic calcined magnesia (MgO) at 10, 15, and 20 wt.% was investigated in combination with 0.5, 1, 2.5, and 5 wt.% Fe2O3 at 1300 °C and 1600 °C for 120 min. The main refractory properties were determined along with the mineralogical content. The morphological examination has been performed by SEM-EDS analysis. The addition of MgO increases the desired olivine and eliminates the unwanted pyroxenes, causing the formation of magnesium-ferrite and periclase. MgO wt.% addition resulted in the decrease of firing shrinkage at 1300 °C but increased with Fe2O3. At 1600 °C, firing shrinkage had a minimum value at the optimum MgO dose. Mechanical strength at 1600 °C achieved a maximum value at the optimum MgO dose plus 5 wt.% MgO and 2.5 wt.% Fe2O3 due to sintering process/magnesioferrite formation. These results indicate that MgO and Fe2O3 upgrade the refractoriness of magnesite mining wastes due to the diffusion of Fe2O3 in MgO excess.

Removal of Al3+ and Mg2+ ions in wet-process phosphoric acid via the formation of aluminofluoride complexes

ABSTRACT With the decrease in the phosphate rock grade, the minor element ratios (MER) [(Fe2O3 wt% + Al2O3 wt% + MgO wt%)/P2O5 wt%] of wet-process phosphoric acid (WPA) exhibits a linear upward trend. This can lead to a huge challenge for the high-quality production of feed calcium phosphate salt (FCPS). In the present study, we proposed a novel and economical strategy to precipitate Al3+ and Mg2+ via the formation of aluminofluoride complexes (NaMgAlF6·H2O) with the anhydrous sodium sulfate (Na2SO4) and hydrofluoric acid (HF) as precipitation agents. Because of the low solubility of the complexes in WPA, the removal efficiencies of Al3+ and Mg2+ ions could reach 99.5% and 64.8%, respectively. The maximum mass loss of P2O5 was less than 0.5%. The precipitates could be separated and converted into the HF and Na2SO4 for reuse, thus further decreasing the cost of WPA purification.

Study and synthesis of polymer-blend PVA-PEG doped with 5wt% MgO and different wt% of Co3O4 Thin Film

In this study, Poly (vinyl alcohol) - Poly (ethylene glycol) (PVA-PEG) poly-blend and its composite with 5wt.% and different wt.% (2, 4, and 6) of Co3O4 films were synthesized using blend casting method. The characterization was considered such as; Fourier transforms infrared (FT-IR), electrical properties, and its application for gamma ray shielding. The electrical properties showed that the dielectric constant and dielectric loss for all different rates of Co3O4 particles decreases with the increase of the electric field frequency, and that its values increase with the increasing of the wt.% of Co3O4 particles. The (PVA-PEG) poly-blend and its composite with and different wt.% of Co3O4 films have good linear attenuation coefficients for gamma ray radiation.

Geochemistry and petrogenesis of I-type granitoid rocks around Nasb-Zurar intrusion, West Wadi Allaqi, South Eastern Desert, Egypt

Granitic rocks surrounding Nasb-Zurar intrusion at North West Wadi Allaqi comprise two varieties: tonalite and granodiorite of older granite (OG), and monzogranite of younger affinity (YG). Plagioclase crystals in OG are generally zoned and range in composition from andesite to oligioclase with An (21.0–46.4), Ab (52.9–78.1), and Or (0.7–1.1); meanwhile, they have albite composition in YG with Ab (87.4–93.3). Alkali feldspars are perthitic microcline and orthoclase. Muscovite has phengite composition with Si:Aliv being greater than 3:1. Biotite varies between Al-poor biotite end-members annite and phlogopite. Chlorite in OG has ripidolite composition, while that from YG is brunsvigite. The OG granite has SiO2 wt.% of 67.7 to 71.9, with high Al2O3 wt.% of 12.9 to 16.2 and low TiO2 wt.% of 0.26 to 0.52, MgO wt.% of 0.47 to 2.07, Fe2O3 wt.% of 1.91 to 4.5, P2O5 wt.% of 0.05 to 0.13, CaO wt.% of 2.01 to 3.92, K2O wt.% of 0.36 to 3.63, and Na2O wt.% of 3.63 to 5.64. YG is rich in SiO2 wt.% (73 to 75), and Al2O3 wt.% ranges 13.3–14.4, K2O wt.% elevated between 3.7 and 4.6, CaO wt.% ranges 0.18–1.59, and Na2O wt.% is high (3.52–4.18), while TiO2, Fe2O3, and MgO wt.% contents show relatively lower values. All studied granites have peraluminous characters and evolve as I-type granites within volcanic arc environment. The OG are believed to form by melting of metagreywackes surrounding the area at about 680 °C; meanwhile, the YG is supposed to crystallize under relatively lower temperature (average ~ 630 C°) by re-melting and differentiation of OG.

Textural and Geochemical Evidence for Multiple, Sheet-like Magma Pulses in the Limeira Intrusion, Paraná Magmatic Province, Brazil

Abstract Quantitative petrographic, structural, and textural parameters are integrated with geological, geochemical, and Sr-isotope data to examine the emplacement, growth processes, and magmatic evolution of the high-Ti tholeiitic Limeira Intrusion, in the Paraná Magmatic Province of SE Brazil. Our data strongly support a multiple-stage evolution, owing to the nested emplacement of distinct crystal-bearing magma pulses that probably evolved independently, except at their boundaries. A stage of cooling and crystallization between magma injections results in a stepwise T–t path, leading to variations in the plagioclase residence times and effective growth rates inwards, also occasioning sudden changes in crystal shape and size at the boundaries of each magma pulse. The time delay between pulses allows preservation of internal ‘chilled margins’ and the development of near-rigid surfaces at their contacts, increasing the alignment and clustering of crystals during magma replenishment. Isotopic and textural data demonstrate a complex assembly history, in which the appearance of mixed plagioclase populations between magma pulses coincides with the onset of initial Sr isotope ratio increase, which can be attributed to a locally enhanced cooling rate, and the extraction of residual melts from the previous crystallizing batches and mixing with the younger pulses. Typical C- and S-shaped MgO (wt%) compositional profiles within individual pulses indicate that the first one probably evolved by in situ fractional crystallization followed by melt migration inward, whereas the younger ones have contributions from both compaction of the lowermost crystallization front and compositional convection. Mafic globular structures are found at the boundaries of magma pulses and constituting the mafic-rich layers in layered rocks. They are interpreted as evidence for chemical disequilibrium, arguably associated with the trigger of silicate liquid immiscibility. The upwards compositional convection of the silica-rich residual liquid and the accumulation of the Fe–Ti–P-rich crystalbearing end-member in the bottom of the latest magma pulses might represent the most significant mechanism of differentiation in the Limeira Intrusion.

Evidence of Rapid Phenocryst Growth of Olivine During Ascent in Basalts From the Big Pine Volcanic Field: Application of Olivine‐Melt Thermometry and Hygrometry at the Liquidus

AbstractThe Quaternary Big Pine (BP) volcanic field in eastern California is notable for the occurrence of mantle xenoliths in several flows. This points to rapid ascent of basalt through the crust and precludes prolonged storage in a crustal reservoir. In this study, the hypothesis of phenocryst growth during ascent is tested for several basalts (13–7 wt% MgO) and shown to be viable. Phenocrysts of olivine and clinopyroxene frequently display diffusion‐limited growth textures, and clinopyroxene compositions are consistent with polybaric crystallization. When the most Mg‐rich olivine in each sample is paired with the whole‐rock composition, resulting (olivine‐melt) values (0.31–0.36) match those calculated from literature models (0.32–0.36). Application of a Mg‐ and a Ni‐based olivine‐melt thermometer from the literature, both calibrated on the same experimental data set, leads to two sets of temperatures that vary linearly with whole‐rock MgO wt%. Because the Ni thermometer is independent of water content, it provides the actual temperature at the onset of olivine crystallization (1247–1097°C), whereas the Mg thermometer gives the temperature under anhydrous conditions and thus allows ΔT (=TMg − TNi = depression of liquidus due to water) to be obtained. The average ΔT for all samples is ~59°C, which is consistent with analyzed water contents of 1.5–3.0 wt% in olivine‐hosted melt inclusions from the literature. Because the application of olivine‐melt thermometry/hygrometry at the liquidus only requires microprobe analyses of olivine combined with whole‐rock compositions, it can be used to obtain large global data sets of the temperature and water contents of basalts from different tectonic settings.

A precise geochemical volcano-stratigraphy of the Deccan traps

This geochemical study is based on 69 volcanic rocks representing the entire volcano-stratigraphy of the 12 lava formations of the Deccan Traps (DT) of the Indian peninsula. The DT constitutes one of the largest continental flood basalt province (CFB) in the world. More than 90% of the lavas of this province are considered to have erupted in less than one million years by plume volcanism, coinciding with the Cretaceous-Paleogene (K-Pg) boundary, leading to the speculation that this volcanism had a major role in the end-Cretaceous mass extinction. The current study was undertaken to fully geochemically characterize the DT plume with respect to major-trace element composition as well as their correlated Sr-Nd-Pb and Hf isotope geochemistry of each lava formation in step-by-step sampling the entire Deccan vertical stratigraphy of over 60 samples mostly on the Western Ghat Escarpment as collected by Beane (1988).The upper lava formations from Poladpur to Panhala-Desur, the Wai subgroup, are sharply distinguishable geochemically by all the geochemical parameters from the lower lava formations of the Lonavala and Kalsubai subgroups. This distinction is remarkable as they are on samples in a continuous supposedly vertical sequence in space and time. The Wai subgroup shows restricted range in FeO/MgO ratios at a given MgO wt% but indicating a more Fe-rich mantle source than many other CFB (average Mg# 46.7 as opposed to the 53.3 Mg# for the lower subgroups) province; the lower subgroups show a widely variable FeO/MgO ratios, interpreted as results of partial melting of subducted eclogitic slab. This interpretation is supported by the trace elements including the rare earths, and the isotopic ratios of Nd, Sr, Pb and Hf that were all measured in the same lava samples. Our high precision Pb isotopic measurements reveal the gist of the Deccan plume characteristics as Pb content in the mantle is low in contrast with their higher abundance in the continental crust. The Wai subgroup demonstrates a relatively consistent initial 206Pb/204Pb ratios as opposed to their heterogeneous compositions in the lower formations of Lonavala and Kalsubai. In addition, the Pb isotopes in a 206Pb/204Pb vs 207Pb/204Pb plot define an age of 2604 ± 140 Ma that we interpret as the “provenance” age of the subducted slab that sourced the lower formation lavas. Interestingly, this “errorchron” is also consistent with the “Dupal anomaly” concept developed on the sub Indian Oceanic mantle derived basalts.The combined multiple isotopic volcano-stratigraphy shows the geochemical contrast more dramatically than any other previous study on the Deccan. This high precision multiple isotopic study of the Deccan is consistent with recent U-Pb and Ar-Ar geochronologic studies on the rapid eruption of the Deccan, mostly the plume head, interpreted here constituting the upper lava formations of the Wai subgroup as without much interaction with the continental crust.

Transient mantle cooling linked to regional volcanic shut-down and early rifting in the North Atlantic Igneous Province

The Paleocene to Early Eocene Faroe Islands Basalt Group (FIBG) comprises a c. 6.5-km-thick lava flow–dominated sequence located within the centre of the North Atlantic Igneous Province (NAIP). The currently defined pre-breakup and syn-breakup sequences of the FIBG are separated by a significant volcanic hiatus, during which time the coal-bearing Prestfjall Formation was deposited. This major volcanic hiatus is identified across large parts of the NAIP and was preceded on the Faroe Islands by a reduction in eruption rate evidenced by an increased number and thickness of inter-lava sedimentary beds between the simple lava flows of the pre-breakup Beinisvørd Formation. High tempo eruptions resumed after this hiatus with the development of the compound lava flow fields of the Malinstindur Formation which reveal limited evidence for inter-lava breaks. In order to investigate this key transition, flow by flow geochemical sampling of a composite c.1.1-km-thick lava flow sequence spanning this transition were collected and analysed. Three chemically distinct groups are defined based on rare earth elements (REEs) and incompatible trace element signatures. Two high-Ti groups (TiO2 > 2 wt%), B2 and B3, dominate the sampled Beinisvørd Formation and display light REE-enriched signatures (La/YbN c. 2.9–5.9) and evidence for garnet in the source melting region (Dy/YbN c. 1.5–1.6). At the very top of the Beinisvørd Formation, a distinct group of lava flows, B1, displaying lower TiO2 for a given MgO wt% (TiO2 c. 1–2 wt%), weakly light REE-enriched profiles (La/YbN c. 1.7–2.4) and a spinel-dominated mantle melting signature (Dy/YbN c. 1.1–1.2) is identified. Sr, Nd and Pb isotopic signatures for the three groups overlap, revealing limited evidence of crustal contamination, and therefore supporting a mantle melting origin for inter-group variations, rather than source composition or contamination. The group B1 lava flows form a unique stratigraphic occurrence on the islands and provide clear evidence for both a reduction in the initial pressure of melting, alongside an increase in the overall degree of partial melting relative to groups B2 and B3. Increased partial melting is interpreted as evidence for the early onset of rifting and lithospheric thinning to the north of the Faroe Islands. The accompanying reduction in initial pressure of melting provides the first petrological evidence that a transient reduction in mantle temperature leads to the province-wide volcanic hiatus. Our study demonstrates an intimate linkage between rifting history and fluctuations in mantle temperature highlighting that any over-arching model for the evolution of the NAIP must take both into equal account.

Thermochemical analysis of smelting of ferruginous manganese ore for silicomanganese production

Ferruginous manganese ores contain high concentrations of iron and having low Mn/Fe ratio and are not suitable to produce standard grade of silicomanganese. Thermochemical calculations based on available thermodynamics databases were used to understand the smelting behavior of the ore mix consisting of ferruginous manganese ore and slag from high carbon ferromanganese. A basicity map was constructed in terms of input burden material basicity B (= (CaO wt%+MgO wt%)/SiO2 wt%) and input R (= (CaO wt%+ MgO wt%)/Al2O3 wt%) value for estimating the optimum operating basicity window for low manganese and silicon partition ratio or high alloy recovery. Various experiments were conducted to check the maximum grade and recovery of the alloy based on the thermochemical equilibrium simulation study. The present study reveals usefulness of preliminary thermochemical calculations to facilitate process design and development of silicomanganese smelting using ore mix consisting of ferruginous manganese ore and slag from high carbon ferromanganese.

Modulatory effect of simultaneously released magnesium, strontium, and silicon ions on injectable silk hydrogels for bone regeneration

Injectable silk hydrogels are ideal carriers of therapeutic agents due to their biocompatibility and low immunogenicity. Injectable silk hydrogels for bone regeneration have been previously developed but often utilize expensive biologics. In this study, we have developed an injectable silk composite incorporated with a triphasic ceramic called MSM-10 (54 Mg2SiO4, 36 Si3Sr5 and 10 MgO (wt%)) capable of simultaneously releasing magnesium, silicon, and strontium ions into its environment. These ions have been previously reported to possess therapeutic effects for bone regeneration. MSM-10 particles were incorporated into the silk hydrogels at various weight percentages [0.1 (SMH-0.1), 0.6 (SMH-0.6), 1 (SMH-1) and 2 (SMH-2)]. The effects of the released ions on the physicochemical and biological properties of the silk hydrogel were comprehensively evaluated. Increased MSM-10 loading was found to hinder the gelation kinetics of the silk hydrogel through the reduction of beta-sheet phase formation, which in turn affected the required sonication time for gelation, compressive strength, force of injection, microstructure and in vitro degradation rate. Primary human osteoblasts seeded on SMH-0.6 demonstrated increased proliferation and early alkaline phosphatase activity, as well as enhanced osteogenic gene expression compared to pure silk hydrogel and SMH-0.1. In vivo results in subcutaneous mouse models showed both decreased fibrous capsule formation and increased number of new blood vessels around the injected SMH-0.1 and SMH-0.6 implants compared to pure silk hydrogels. The results in this study indicate that the ions released from MSM-10 is able to influence the physicochemical and biological properties of silk hydrogels, and SMH-0.6 in particular shows promising properties for bone regeneration.

Geochemistry of garnet in pegmatites from the Boroujerd Intrusive Complex, Sanandaj-Sirjan Zone, western Iran: implications for the origin of pegmatite melts

Pegmatite-hosted garnets from four localities in the Boroujerd region, Lorestan (Western Iran), have been analysed for major and selected trace element compositions. The mineral assemblage of the granitic pegmatites is primarily quartz, plagioclase (albite), and alkali feldspar (orthoclase-microcline), as well as garnet, muscovite, fluorapatite, tourmaline (schorl-foitite), andalusite and zircon. The mineralogical and geochemical characteristics of the pegmatites indicate that they are peraluminous to slightly metaluminous I-type granites. Based on mineral assemblages and whole-rock geochemistry, the pegmatites are classified as muscovite-type pegmatites. Electron-probe micro-analysis reveals that garnets have concentric compositional zoning and are almandine-spessartine solid solutions with lesser pyrope, grossular and andradite components. Concentric zoning of major elements in the garnet is attributed to magmatic growth from a melt. On a MnO + CaO versus FeO + MgO (wt%) plot, the composition of garnet is consistent with crystallisation from weakly to moderately evolved melts. The garnets from the Boroujerd pegmatites are characterised by decreasing Y, HREE, Ti, Zr, Nb, Ta, Hf, and U abundances from core to rim. The garnets also have high chondrite normalized HREE abundances with nearly flat patterns (YbN/SmN = 0–508), lower LREE contents, and negative Eu anomalies (Eu/Eu* < 0.3). Variation in these elements from core to rim is attributed to increasing magma fractionation. The composition and major and trace element zoning patterns in the garnet of the Boroujerd pegmatites are compatible with a magmatic origin and crystallisation from variably fractionated I-type magmas demonstrating that garnet crystal-chemistry is an important tool for deciphering the origins of pegmatite magmas.

Immiscible melt droplets in garnet, as represented by ilmenite–magnetite–spinel spheroids in an eclogite-garnet peridotite association, Blanský les Granulite Massif, Czech Republic

![Figure][1] Interlayered eclogite and symplectitic garnet rock that is interpreted as former garnetite are found in the Gfohl Unit of the Bohemian Massif. They show unusual Fe–Ti-rich compositions, characterized by TiO2 contents up to 2.34 wt%, and Mg# of 59.8 and 51.6, respectively. Equilibration conditions of 1250 °C and 4.0 GPa are calculated for eclogite. The petrogenesis of this rock association can be best explained as high-temperature and ultrahigh-pressure magmatic cumulates. Highly decoupled Sr-Nd isotopic composition with nearly constant radiogenic 87Sr/86Sr values and a slightly negative e Nd value suggests interaction of aqueous fluid most likely derived from a subducting slab and/or from parental magmas. The garnetite contains large (up to 0.5 mm) Fe–Ti-rich spheroids of ilmenite–magnetite–spinel, interpreted as frozen droplets of a melt incorporated in the growing garnet. The interstices between these garnet crystals are filled by ilmenite–magnetite–spinel aggregates, with concave outer surfaces with trapped Fe–Ti-rich melt. These ilmenite–magnetite–spinel spheroids represent possibly the first record of such an oxidized assemblage in mantle rocks, and probably the first description of Fe–Ti-rich melt in eclogite-garnetite mantle rocks. A calculation based on mineral proportions in the spheroids and mineral composition indicates that the immiscible Fe–Ti-rich melt consisted of 28.7 TiO2, 3.7 Al2O3, 0.2 Cr2O3, 27.9 Fe2O3, 37.0 FeO, 0.8 MnO, and 1.7 MgO wt%. Petrology and geochemistry of the garnetite indicates an unusual composition for an upper mantle melt with a high oxygen fugacity and relatively high Fe content. [1]: pending:yes

Improved CO2 adsorption capacity and cyclic stability of CaO sorbents incorporated with MgO

The CO2 adsorption capacity of CaO sorbents with different MgO wt% (calcination temperature 800 °C, carbonation at 650 °C with 100% CO2, and de-carbonation at 800 °C in 100% N2).

Synthesis, Structural and Optical Characterization of MgO Nanocrystalline Embedded in PVA Matrix

Nano-magnesium oxide (MgO) was prepared by wet chemical method using magnesium chloride and sodium hydroxide as precursors and soluble gelatin as stabilizing agent in this paper. The synthesized nano MgO was characterized by XRD, SEM, and FTIR. The results showed that the size of nano-MgO was about 20.62 nm. Polyvinyl alcohol (PVA) polymer based nanocomposites, with different concentrations of MgO (1, 2, 3, 4 wt%), have been prepared using solvent casting technique. The results of SEM revealed that the MgO nanoparticles are uniformly distributed in PVA polymer matrix. FTIR analysis evidently saw the interaction between MgO with hydroxyl group of PVA through hydrogen bonding. The influences of MgO nanoparticle on the optical characterisation of PVA have been considered using UV–Vis–NIR spectroscopy. Energy band gap and tail of localized state of PVA/MgO nanocomposites have been calculated by using Tauc and Urbach relations, respectively. The band gap of the nanocomposites samples decreases as MgO wt% increases. Wemple-DiDomenico single-oscillator model has been applied to analyze the dispersion of the refractive index of the films, and the dispersion parameters are calculated to obtain the information about disorder degree.

Evaluation of aluminosilicate glass sintering during differential scanning calorimetry

The aim of this work is to investigate a difference in heat flow observed in the differential scanning calorimetry curves when aluminosilicate glasses are analyzed. Glasses with nominal composition 56.21 SiO2 18.65 Al2O3 25.14 MgO (wt%) were produced by the conventional melting process. Glass frits were milled and sieved in the range of 45–63µm. The material was analyzed by X-ray fluorescence spectrometry, X-ray diffraction, differential scanning calorimetry (DSC), and differential thermal analyses (DTA). The particle size distribution was determined by laser diffraction technique. The microstructures of the samples were observed by scanning electron microscopy after removing them from the DSC sample holder. The density was determined by He picnometry. The difference in heat flow in the DSC curves is assigned to the sintering process occurring during the heating cycle, which was confirmed by the neck formation in the particle interface, DSC signal variation in isothermal measurements, no change in the heat flow when monolith specimen are analyzed, and in subsequent DSC analysis after cooling. The concurrent crystallization was also determined.

Oxide (Co3O4, NiO, Mn3O4, MgO) promoted Au/C catalyst for glycerol electrooxidation in alkaline medium

Glycerol has a very high value of onset potential on the Au/C electrode, so it is difficult to be electrochemically oxidized on the pure Au electrocatalyst. When Co3O4, NiO, Mn3O4 and MgO are added to the Au/C, the values of onset potential of glycerol oxidation shift negatively 171, 191, 156 and 215mV than that on the Au/C. Au–Co3O4(wt 4:1)/C, Au–NiO(wt 5:1)/C, Au–Mn3O4(wt 5:1)/C and Au–MgO(wt 2:1)/C show the highest activity for glycerol electrooxidation for respective oxide promoted Au/C. The addition of oxides to the Au/C obviously promotes the catalytic activity and stability for glycerol electrooxidation.

Discovery of a Kimberlite Pipe near Budikonda, Dharwar Craton, South India: Field Approaches, Preliminary Petrography and Mineral Chemistry

Abstract: Multi-parametric and systematic exploration for kimberlite search was made in the vicinity of the Kalyandurg area within the Closepet granite, Dharwar craton, south India involving Remote Sensing and Airborne Geophysical Surveys (100 and 200 m spacing; 60 m AGL), Stream Sediment Sampling as well as Electron Probe analysis of heavy indicator minerals. The bipolar aeromagnetic anomaly (pronounced by high-low pair) falls in the positive drainage catchment delineated by stream sediment sampling. Subsequent drilling by a private party over the suspected anomalous zone resulted in the discovery of kimberlite. This is being reported here as the KL-7 kimberlite of the Kalyandurg cluster. Petrographically, the kimberlite shows typical porphyritic texture with macrocrystal olivine grains (∼ 500-4500 µm) set in a groundmass composed of abundant phlogopite, perovskite and microcrystal olivine and clinopyroxene. Xenocrystic chromite grains were also observed. Preliminary studies on the mineral chemistry indicates that the olivine grains are foresterite-rich (Fo = 88-92) with an average MgO wt. % of 49.61. Groundmass phlogopites are of kimberlitic affinity with high Mg# (Mg/Mg+Fe2+) ranging between 0.88 and 0.91. The Cr-spinel macrocrysts with high Cr2O3(&amp;gt; 62 wt. %) are considered to have formed from a primary garnet-peridotite-derived melt. The ilmenites have 8 to 12 wt % MgO and indicate kimberlitic affinity. Based on the current discovery, a suitable investigation strategy is also being suggested here for future kimberlite exploration in the area within the Closepet granite of the Dharwar craton, South India.