Metal Silicate Research Articles

Use of Fatty Acid Metal Salts for Preventing Maillard Reaction-Driven Browning of Lecithins.

We previously reported that fluid soybean lecithin (SL) undergoes heat deterioration by the newly reported pseudo-Maillard rearrangement reaction. To inhibit heat deterioration, SLs were treated with metal silicates, such as magnesium silicate and calcium silicate. When soybean fatty acid was added to SL before treatment with calcium silicate, the color index after heating improved significantly as the acid value increased from 10 to 35 mg KOH/g. To elucidate the role of soybean fatty acid, calcium silicate treatment was carried out by adding several fatty acids to SL. Although saturated fatty acids had no effect on the heat deterioration of SL, unsaturated fatty acids were significantly more effective at inhibiting heat deterioration. Furthermore, for unsaturated fatty acids, it was confirmed that the calcium concentration increased in SL. Based on these results, several fatty acid metal salts were added to confirm whether heat deterioration while heating SL could be inhibited. It was observed that the heat deterioration of SL could be inhibited with fatty acid metal salts, regardless of whether the fatty acids were saturated or unsaturated and whether the metal was monovalent, divalent, or trivalent. Therefore, in this study, we clarified that the heat deterioration of SL could be inhibited by adding fatty acid metal salts to SL. Among sodium stearate, calcium stearate, magnesium stearate, barium stearate, and aluminum tristearate, the divalent fatty acid metal salts had a stronger inhibitory effect on heat deterioration than the monovalent and trivalent salts.

In situ creation of multi-metallic species inside porous silicate materials with tunable catalytic properties.

Porous metal silicate (PMS) material PMS-11, consisting of uniformly distributed multi-metallic species inside the pores, is synthesized by using a discrete multi-metal coordination complex as the template, demonstrating high catalytic activity and selectivity in hydrogenation of halogenated nitrobenzenes by synergistically activating different reactant molecules via Ni and Co transition metal centers, while GdIII Lewis acid sites play a role in tuning the catalytic properties.

Calcination Behaviour of Nsuta Rhodochrosite Ore in the Presence and Absence of End-of-Life High Density Polyethylene

This research investigated the calcination behaviour of the Nsuta Rhodochrosite (MnCO3) in the presence and absence of end-of-life high density polyethylene (HDPE) using a custom-made palm kernel shell fired furnace. Samples of pulverised Nsuta rhodochrosite were heated rapidly for 30, 40, 50 and 60 minutes, coupled with temperature measurements to determine the maximum temperature attained in the fireclay crucible. The procedure at 60 min was repeated using three blends of rhodochrosite samples containing different masses of HDPE (30 g, 40 g and 50 g) and heated for an hour. For gas analyses studies during calcination, cylindrical compacts of rhodochrosite ore in a LECOTM crucible were heated rapidly with and without high density polyethylene (HDPE at C/O ratio = 1.0, 1.5, and 2.0) in a horizontal tube furnace for 600 s at 1150 °C under high purity argon gas and the off gas was continuously analysed for CH4, CO and CO2 using an online infrared gas analyser. The content of H2 in the off gas was detected using a GC3 gas chromatographic analyser equipped with a thermal conductivity detector. The Nsuta rhodochrosite ore was found to consist of a mixture of manganese II carbonate (MnCO3), silica (SiO2), mixed transition metal carbonate of the form Ca(Mn, Mg)(CO3)2 and mixed metal silicate of the form Ca0.6Mg1.94Si2O6. Calcination results indicated visible colour changes (from grey to dark brown), along with significant changes in the mass before and after calcination. In the absence and presence of the polymer, measured temperatures in the crucible ranged from 1001 °C to 1366 °C and 1361 °C to 1369 °C, respectively. Analyses by XRF showed marginal increase in the content of Mn in the calcined ore with HDPE addition. Gas analyses indicate that blending the carbonate with HDPE before heating results in significant decrease in the amount of CO2 emitted.
 
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Alkali etching metal silicates derived from bamboo leaves with enhanced electrochemical properties for solid-state hybrid supercapacitors

Metal silicates are demonstrated to be potential electrode materials for rechargeable batteries and supercapacitors (SCs). However, their electrochemical properties applied to SCs in the literatures are far less than the expectation. Herein, we propose a strategy of alkali etching process to improve the electrochemical properties of metal silicates. First, nickel silicate (NiSi), cobalt silicate (CoSi) and manganese silicate (MnSi) with the interconnected nanosheets are derived from bamboo leaves (BLs) by a calcination in combination with a facile hydrothermal method. Then 3 M NaOH aqueous solution was used to soak the metal silicates for alkali etching to obtain the etching metal silicates (denoted as e-NiSi, e-CoSi, e-MnSi). The alkali etching can enlarge the accessibility for electrolyte ions and improve the electrochemical performance of metal silicates. In the three-electrode system, the e-NiSi-3, e-CoSi-3 and e-MnSi-3 exhibit higher specific capacitances and cycling performances than that of NiSi-3, CoSi-3 and MnSi-3. The solid-state hybrid supercapacitor (HSC) devices are fabricated by using the metal silicates as the positive material and activated carbon (AC) as the negative material. In the two-electrode system, the e-MSi-3//AC HSC devices (M = Ni, Co and Mn) deliver higher areal specific capacitances and energy densities and better cycle performance than those of MSi-3//AC HSC devices, for instance, e-NiSi-3//AC HSC device (412 mF cm−2 at 4 mA cm−2, 3.2 Wh m−2 at 3.8 W m−2) is superior to NiSi-3//AC HSC device (207 mF cm−2 at 4 mA cm−2, 1.6 Wh m−2 at 3.8 W m−2). This work proves that the alkali etching process can enhance the electrochemical performance of metal silicates and e-MSi-3 can be hopeful and prominent electrode materials applied to high-performance SCs.

Mantle–melt partitioning of the highly siderophile elements: New results and application to Mars

AbstractTrace elements and extant and extinct isotopic attributes in Martian meteorites have been used to argue that Mars accreted quickly, differentiated into core and mantle, and established several mantle reservoirs, possibly within 10 Ma of T0. The partitioning of trace elements in the deep mantle has been relatively unstudied, despite the need for such knowledge in understanding magma ocean crystallization and the origin of depleted and enriched mantle reservoirs. The siderophile element composition of the Martian mantle and lithophile isotopic systems such as Sr, Hf, and Nd are thought to record evidence for early metal–silicate equilibrium and deep magma ocean at an intermediate depth and pressure of 800 km or 14 GPa. We have carried out experiments across this pressure range to better understand the mineral/melt partitioning of a wide range of elements. These new data are used to evaluate differentiation models for Mars and to help interpret the available isotopic data. The relatively incompatible nature of Re compared to mildly compatible Os means that the crystallization of a deep magma ocean will lead to residual liquids with superchondritic Re/Os, and solids with subchondritic Re/Os. Such material available in the mantle could be the source of enriched isotopic reservoir that produced shergottites with +γOs values. Slightly subchondritic Re/Os ratios in the crystallizing solids would provide a reservoir that could produce −γOs values. Melting of mixtures of these two enriched and depleted endmembers could explain the Nd‐Os isotopic correlations and systematics of shergottites.

Metal–silicate partitioning of W and Mo and the role of carbon in controlling their abundances in the bulk silicate earth

The liquid metal–liquid silicate partitioning of molybdenum and tungsten during core formation must be well-constrained in order to understand the evolution of Earth and other planetary bodies, in particular because the Hf–W isotopic system is used to date early planetary evolution. The partition coefficients DMo and DW have been suggested to depend on pressure, temperature, silicate and metal compositions, although previous studies have produced varying and inconsistent models. Additionally, the high cationic charges of W and Mo in silicate melts make their partition coefficients particularly sensitive to oxygen fugacity. We combine 48 new high pressure and temperature experimental results with a comprehensive database of previous experiments to re-examine the systematics of Mo and W partitioning, and produce revised partitioning models from the large combined dataset. W partitioning is particularly sensitive to silicate and metallic melt compositions and becomes more siderophile with increasing temperature. We show that W has a 6+ oxidation state in silicate melts over the full experimental fO2 range of ΔIW −1.5 to −3.5. Mo has a 4+ oxidation state, and its partitioning is less sensitive to silicate melt composition but also depends on metallic melt composition. DMo stays approximately constant with increasing depth in Earth. Both W and Mo become more siderophile with increasing C content of the metal: we therefore performed experiments with varying C concentrations and fit epsilon interaction parameters: εCMo = −7.03 ± 0.30 and εCW = −7.38 ± 0.57.W and Mo along with C are incorporated into a combined N-body accretion and core–mantle differentiation model, which already includes the major rock-forming elements as well as S, and moderately and highly siderophile elements. In this model, oxidation and volatility gradients extend through the protoplanetary disk so that Earth accretes heterogeneously. These gradients, as well as the metal–silicate equilibration pressure, are fitted using a least squares optimisation so that the model Earth-like planet reproduces the composition of the bulk silicate Earth (BSE) in terms of 17 simulated element concentrations (Mg, Fe, Si, Ni, Co, Nb, Ta, V, Cr, S, Pt, Pd, Ru, Ir, W, Mo, and C). The effects of the interaction of W and Mo with Si, S, O, and C in metal are included. Using this model with six separate terrestrial planet accretion simulations, we show that W and Mo require the early accreting Earth to be sulfur-depleted and carbon-enriched so that W and Mo are efficiently partitioned into Earth’s core and do not accumulate in the mantle. When this is the case, the produced Earth-like planets possess mantle compositions matching the BSE for all simulated elements. However, there are two distinct groups of estimates of the bulk mantle’s C abundance in the literature: low (∼100 ppm) and high (∼800 ppm), and all six models are consistent with the higher estimated carbon abundance. The low BSE C abundance would be achievable when the effects of the segregation of dispersed metal droplets produced in deep magma oceans by the disproportionation of Fe2+ to Fe3+ plus metallic Fe is included.

Ag isotopic and chalcophile element evolution of the terrestrial and martian mantles during accretion: New constraints from Bi and Ag metal-silicate partitioning

The Earth's timing of accretion and acquisition of moderately volatile compounds is uncertain. Hafnium-W and Mn-Cr isotopic data can bracket the timing of early planetary differentiation and core formation. The Ag-Pd system has also been utilized but its application has been limited by a lack of high pressure and temperature metal-silicate partitioning for Pd and Ag. Because Ag (and Bi) are volatile chalcophile siderophile elements, understanding their early distribution can constrain the origin of volatile elements in differentiated bodies and planets. Unfortunately, neither Ag or Bi have been studied across the wide range of pressure and temperature conditions that are relevant to accretion and core-mantle differentiation. Here, new high-pressure and temperature multi-anvil metal-silicate equilibrium experiments for Bi and Ag have been carried out at conditions relevant to planetary accretion and metal silicate differentiation that allow a more refined and complete understanding of element partitioning during core formation. The new metal-silicate partitioning data are combined with previously reported data, and utilized to predict the distributions of Bi, Pd, and Ag at conditions of accretion relevant for Earth and Mars. Application of the new partitioning results to Earth shows that D(Bi) and D(Ag) (D = metal/silicate concentration ratio) are lowered due to the effect of pressure and Si alloyed in the metallic liquid, resulting in higher predicted mantle Bi and Ag abundances than in the bulk silicate Earth (BSE), as well as high and variable Pd/Ag. The unradiogenic Ag isotopic composition of the BSE could have been generated by early accretion of volatile-poor (high Pd/Ag) pre-cursors, followed by later accretion of volatile–rich (low Pd/Ag) material, in agreement with earlier studies of Pd-Ag and Mn-Cr (Schönbächler et al., 2010). However, these main accretion phases would have to be followed by segregation of a sulfide liquid (at least 1.5% of magma ocean) at high pressures (>30 GPa), to explain the primitive upper mantle (PUM) Bi, Pd, and Ag, as well as Au, Pt, Cu and Ni concentrations as proposed previously. If the early accreted bulk Earth was volatile depleted with high Pd/Ag ratios, portions of the mantle may contain ancient domains that developed positive 107Ag isotopic anomalies (as also argued by noble gases, Nd, W, and Os isotopes). In comparison, Bi, Pd, and Ag concentrations in the martian mantle could have been set by simple metal-silicate equilibrium. Mars accreted and differentiated relatively rapidly, while also developing a deep magma ocean with a high Pd/Ag ratio that could have evolved positive 107Ag anomalies, in contrast to Earth. Measurements on shergottites may reveal these predicted Ag isotopic anomalies.

Hf‐W chronology of a macrochondrule from the L5/6 chondrite Northwest Africa 8192

AbstractA large, igneous‐textured, and 2 cm‐sized spherical object from the L5/6 chondrite NWA 8192 was investigated for its chemical composition, petrography, O isotopic composition, and Hf‐W chronology. The petrography and chemical data indicate that this object closely resembles commonly found chondrules in ordinary chondrites and is therefore classified as a “macrochondrule.* As a result of metal loss during its formation, the macrochondrule exhibits elevated Hf/W, which makes it possible to date this object using the short‐lived 182Hf‐182W system. The Hf‐W data provide a two‐stage model age for metal–silicate fractionation of 1.4 ± 0.6 Ma after Ca‐Al‐rich inclusion (CAI) formation, indicating that the macrochondrule formed coevally to normal‐sized chondrules from ordinary chondrites. By contrast, Hf‐W data for metal from the host chondrite yield a younger model age of ~11 Ma after CAIs. This younger age agrees with Hf‐W ages of other type 5–6 ordinary chondrites, and corresponds to the time of cooling below the Hf‐W closure temperature during thermal metamorphism on the parent body. The Hf‐W model age difference between the macrochondrule and the host metal demonstrates that the Hf‐W systematics of the bulk macrochondrule were not disturbed during thermal metamorphism, and therefore, that the formation age of such objects can still be determined even in strongly metamorphosed samples. Collectively, this study illustrates that chondrule formation was not limited to mm‐size objects, implying that the rarity of macrochondrules reflects either that this process was very inefficient, that subsequent nebular size‐sorting decimated large chondrules, or that large precursors were rare.

Fire risk assessment of cypress wood coated with metal oxide and metal silicate flame retardant using cone calorimeter

This study investigated the fire risk properties of cypress wood for the construction of interiors, especially focusing on heat and smoke hazard properties in fire scenarios. Fire risk characteristics were measured using a cone calorimeter (ISO 5660-1). The external heat flux was maintained at 50 kW/m2. The flame retardants used were metal oxide and metal silicate; they were mixed with a water glass solution. Flame retardants and the silicon compound were dispersed in a concentration of 20 wt% versus 80 wt%, respectively, during 24 h using a magnetic stirrer. The fire performance indexes of the specimens increased by 3–16 times, compared with uncoated specimen and the fire growth index of the specimens increased by 70%–92%. The smoke performance index of the specimens increased by 9–66 times, compared with uncoated specimens. The smoke risk as shown by the smoke performance index increased in the following order: SnO < mica < Co3O4 < ZrSiO4 < cypress. The smoke growth index decreased from 93% to 98%, compared with uncoated wood. The smoke risk due to smoke growth index increased in the following order: SnO < mica < ZrSiO4≈ Co3O4 < cypress. The smoke intensity decreased from a minimum of 85% to a maximum of 99%, compared with uncoated wood. The concentration of CO gas generated after combustion was decreased by 24%–67%. They increased in the following order: mica ≈ ZrSiO4 < SnO < Co3O4 < cypress. A comprehensive assessment of fire performance shows that flame retardants decreased heat hazards, smoke hazards, and CO toxicity.

The Effect of the Starting Mineralogical Mixture on the Nature of Fe-Serpentines Obtained during Hydrothermal Synthesis AT 90°C

AbstractThe formation conditions and stability fields of Fe-serpentines are still poorly understood in both terrestrial (natural or anthropic) and extraterrestrial environments. Knowledge of the effects of physical-chemical parameters on compositional and structural features of Fe-serpentines is lacking, and only a few thermodynamic parameters of these minerals are available in the literature. To fill these gaps, the synthesis of these minerals, while controlling all the physicochemical experimental parameters, was undertaken. Two hydrothermal syntheses were carried out at 90°C to investigate the effect of two different starting mineralogical mixtures on the nature of Fe-serpentines. The run products were identified by several analytical techniques (powder X-ray diffraction, transmission, and scanning electron microscopy). Berthierine crystals were synthesized from a starting mixture of kaolinite and metal iron. The berthierines synthesized show different morphologies and iron contents (~3–38 at.%). From a starting mineralogical mixture composed of quartz and metal iron, cronstedtite crystallizes. Most of the crystals are 1M polytypes. Magnetite is always associated with both berthierine and cronstedtite. Lepidocrocite was observed only in the experiment with kaolinite. These experimental results demonstrated that Fe enrichment in serpentines depends on the silicate precursor (kaolinite or quartz) of the starting mixture. The results are also in agreement with the geochemical equilibrium predicted by thermodynamic modeling, i.e. the formation of berthierine and cronstedtite in association with magnetite at the expense of metal iron and silicates.

Dynamics of core-mantle separation: Influence of viscosity contrast and metal/silicate partition coefficients on the chemical equilibrium

The composition of the Earth's core and mantle is set by the chemical equilibrium between metals and silicates during core/mantle segregation. The metallic core separated from the mantle by gravitational descent in the form of diapirs in a magma ocean, and therefore the dynamics of the diapir's downward movement has an influence on the chemical equilibrium. In this study, we characterize the descent of metallic droplets into a molten silicate using numerical models. By varying the silicate and metal viscosities (between 0.1 and 1000 Pa·s for each phase) as well as the partition coefficient between metal and silicate (Dmet/sil, varying between 1 and 1000), we obtained quantifying parametrizing equations for the degree of equilibrium between molten metal and molten silicate, in a regime characterized by low We (We < 10) and low Re (10−3 < Re<102). We showed that the main parameters controlling the equilibrium for a siderophile element are the viscosity of the silicate and the partition coefficient. We applied our parameterization for Ni and Co in the context of late accretion on Earth so as to quantify the variation of the Ni/Co ratio after a large impact as a function of the magma ocean viscosity, for an iron-rain scenario of metal/silicate segregation. Using previous models (Canup, 2004) of the Moon–forming impact, we showed that the Moon formation had an effect on the current Ni/Co ratio. Depending on the radius of Theia's core and the viscosity of the magma ocean produced after the impact between the proto-Earth and Theia, the Moon formation could account for 0.45% to 3% of the current Ni/Co ratio for magma ocean viscosities of 0.1 to 100 Pa·s, respectively.

Ureilite meteorites provide a new model of early planetesimal formation and destruction

Ureilite meteorites are ultramafic rocks derived from parts of the depleted silicate mantle of their parent planetesimal. We used Monte Carlo modelling to explain the observed array of oxygen isotopes and major element chemistry shown by bulk ureilites, after restoration of their missing core and silicate melt components. Despite using a wide range of primitive nebular material, our modelling shows that only a combination of proxy material resembling Allende-type FeO-rich and MgO-rich chondrules, can account for the ureilite oxygen isotope trend and the reconstructed ureilite major element chemistry. Our model predicts formation of a radial gradient in major elements and oxygen isotopes within the planetesimal, with a more Mg-rich silicate interior and a more Fe-rich silicate exterior. Temperatures recorded by ureilites were not high enough to form a magma ocean but were sufficiently high to form a metallic core and silicate melts. The ureilite parent planetesimal was then disrupted by impact. Re-accretion of the outer layers of more Fe-rich silicate material, at the expense of the more MgO-rich material and the core, explains the observed distribution of bulk rock and mineral compositions.

In Situ TEM Study on Conversion-Type Electrodes for Rechargeable Ion Batteries.

Conversion-type materials have been considered as potentially high-energy-density alternatives to commercially dominant intercalation-based electrodes for rechargeable ion batteries and have attracted tremendous research effort to meet the performance for viable energy-storage technologies. In situ transmission electron microscopy (TEM) has been extensively employed to provide mechanistic insights into understanding the behavior of battery materials. Noticeably, a great portion of previous in situ TEM studies has been focused on conversion-type materials, but a dedicated review for this group of materials is missing in the literature. Herein, recent developments of in situ TEM techniques for investigation of dynamic phase transformation and associated structural, morphological, and chemical evolutions during conversion reactions with alkali ions in secondary batteries are comprehensively summarized. The materials of interest broadly cover metal oxides, chalcogenides, fluorides, phosphides, nitrides, and silicates with specific emphasis on spinel metal oxides and recently emerged 2D metal chalcogenides. Special focus is placed on the scientific findings that are uniquely obtained by in situ TEM to address fundamental questions and practical issues regarding phase transformation, structural evolution, electrochemical redox, reaction mechanism, kinetics, and degradation. Critical challenges and perspectives are discussed for advancing new knowledge that can bridge the gap between prototype materials and real-world applications.

Microwave Assisted Co/SiO2 preparation for Fischer-Tropsch synthesis

Cobalt catalyst has been widely used for Fischer-Tropsch (FT) Synthesis in Industry. The most common method to prepare cobalt catalyst is impregnations. Metal is deposited on porous support by contacting dry support with solution containing dissolved cobalt precursor. This step will follow by drying, calcination and reduction. The heating step used in this conventional method, however, may lead to the formation of metal silicate which is inactive site for catalysis. In this study, author explore the use of microwave to prepare catalyst compared to conventional drying method. Cobalt catalyst with SiO2 support was prepared and characterized. Particle size, surface area, and cobalt content were investigated. Crystallite size of 3-8 nm was formed which was reported to be the optimum size for cobalt catalyst in FT Synthesis. Scanning Electron Microscope (SEM) and Transmission Electron Microscopy (TEM) image revealed that microwave catalyst showed better uniformity and cobalt dispersion on silica support. Thermo-Gravimetric Analysis (TGA) study also indicated that this catalyst has good stability at Low Temperature Fischer-Tropsch Synthesis. The catalysts were then applied plasma assisted FT process over a range of power plasma (20-60W) to investigate the effect on the conversion and selectivity. The results showed that microwave catalyst exhibit lower CO conversion at 42.06% compared to conventional method at 68.32%. However, microwave catalyst is more favourable for long chain hydrocarbon selectivity.

Rational design of integrated nanocatalysts with hollow mesoporous transition metal silicates for chemoselective hydrogenation of cinnamaldehyde

The chemoselective hydrogenation of α, β-unsaturated aldehydes are highly dependent on both the electronic and structural effects of the catalysts. In this study, hydrogenation of cinnamaldehyde was carried out over a series of integrated nanocatalysts consisting of Pt nanoparticles and hollow transition metal silicates which were prepared by either one-pot method or sol-immobilization method. The hollow transition metal silicates not only served as mesoporous support materials for high-efficient loading of Pt but also provide tunable Fe/Ni as promoters to improve the catalysis process. It was revealed that using hollow Fe silicate as support generally exhibited low activity but high selectivity due to the strong interaction of CO bond, whereas, using hollow Ni silicate as support showed enhanced activity but low selectivity, which was attributed to the different electronic effects as evidenced by H2-TPR and XPS. In addition, electronic effects among the ternary catalysts with Pt loading on Fe-Ni bimetallic silicates were critical to the observed high turnover frequencies, that is, Pt sites contributed to H2 activation, Fe sites favored the preferential adsorption of CO bond in cinnamaldehyde, while Ni sites promoted the formation of Pt0 rather than Ptδ+.

Influence of C–O–H Volatiles on Ni, Co, and P Partition between Silicate Melt and Liquid Metal Fe Alloy at 4 GPa, 1550°C

A set of experiments was carried out in the system NaAlSi3O8–FeO–NiO–CoO–SiC–NaH2PO4 at 1550°C, 4 GPa, and oxygen fugacity (fO2) 0.5–2.9 log. units below the iron–wustite (IW) buffer to estimate how C–O–H components can affect Ni, Co, and P partition between silicate melt and a liquid metallic phase at redox conditions under which the metallic phase is segregated into melting products of the early reduced mantles of the Earth and other planetary bodies. It has been established that the Ni, Co, and P partition coefficients D(М)met/sil between silicate melts saturated with carbon and containing dissolved C–O–H volatiles (mainly in the form of OH groups, H2 and CH4) at relatively oxidized conditions (fO2 > IW – 1.5) correspond to D(М)met/sil values expected of metal–silicate melt equilibrium in volatile-free systems at analogous P, T, fO2, and nbo/t parameters. Under more reduced conditions (fO2 ≤ IW – 2), the presence of C–O–H volatiles leads to a decrease in D(М)met/sil for Ni and P compared to that in “dry” melts. This difference increases with decreasing fO2 and reaches ~0.5 and more than one order of magnitude for Ni and P, respectively, at fO2 = IW – 2.9. The effect of volatiles on D(Co)met/sil is much weaker, and hence, a decrease in fO2 leads to that D(Ni)met/sil and D(Co)met/sil converge. The Raman spectra of the experimental glasses and their SIMS analyses for hydrogen show that water content (OH + H2O) in the melts decreases with decreasing fO2, whereas the contents of CH4 and complexes with C–H bonds significantly increases. The likely reasons for the decrease in D(М)met/sil under strongly reduced conditions may be changes in the structure of the silicate melts and the origin of complex compounds of siderophile elements with volatiles in these melts.

Spatial Ensembles of Copper-Silica with Carbon Nanotubes as Ultrastable Nanostructured Catalysts for Selective Hydrogenation.

Catalyst deactivation is one of the most important issues in heterogeneous catalysis. Constructing a stable nanoscale structure that maintains efficient activity and prolonged stability under redox conditions for catalysis, particularly hydrogenation reactions, remains attractive albeit the flourishing nanoscience. This work presents a facile route to synthesize a semi-encapsulated transition metal by assembling three-dimensional transition metal silicate nanotubes onto carbon nanotubes (CNTs) as precursors. The obtained materials expose an active surface of the transition metal for efficient catalysis and form a specific structure to inhibit the migration of metal nanoparticles (NPs) by establishing strong metal-support interactions. Cu@SiO2 prepared by common precipitation shows an inferior activity, and its performance is easily attenuated because of the aggregation of Cu NPs. The addition of CNTs as a carrier doubles the intrinsic activity of Cu catalysts. This hybrid catalyst, which consists of Cu species, SiO2, and CNTs, is among the best catalysts for dimethyl oxalate hydrogenation with boosting activity of 25 h-1 and enhanced stability of more than 200 h.

Syntheses, characterization and calculations of LimAnM6O15 (A=Rb, Cs; M=Si, Ge; m+n=6)

Alike phosphates, silicates and germanates exclusively containing tetrahedral basic building units (BBUs) can also exhibit ultraviolet (UV) even deep-UV transitions. They are important for the design of new UV or deep-UV nonlinear optical (NLO) materials. In this paper, four new alkali metal silicates and germanates, Li2Rb4Si6O15, Li2Cs4Si6O15, Li3Rb3Ge6O15 and Li3Cs3Ge6O15 were successfully synthesized by a high temperature solid state reaction. They obey the general formula of LimAnM6O15 (A=Rb, Cs; M=Si, Ge; m+n=6) and all exhibit the Sr2Be2B2O7 (SBBO)-like structures. More importantly, Li3Rb3Ge6O15 and Li3Cs3Ge6O15 crystallize in the noncentrosymmetric (NCS) structures and exhibit remarkable phase-matched second harmonic generation (SHG) effect, 0.8×KH2PO4 (KDP) and 1×KDP, respectively. These indicate that they are potential as UV or deep-UV NLO materials. Furthermore, their optical and NLO properties as well as thermal properties were measured. The structure-property relationships were studied by the dipole moment calculations and the first-principles calculations.

Decoupling the effects of solid and liquid phases in a Pb-water glass mixture on the selective flotation separation of scheelite from calcite

In this study, lead ion was combined with water glass to separate scheelite from calcite using flotation. The effects and underlying mechanisms of the liquid and solid phases generated in this combined depressant (Pb-water glass, a mixture of lead ion and water glass) on the flotation performance of scheelite and calcite were investigated through micro-flotation experiments, X-ray diffraction (XRD) measurements, ultraviolet–visible (UV–Vis) spectrophotometer measurements, fourier transform infrared spectrometer (FTIR) analysis, zeta potential measurements, and X-ray photoelectron spectroscopy (XPS) tests. The flotation results indicate that the selective flotation separation of scheelite from calcite results from the liquid phase, not the solid phase. The XRD and FTIR results indicate that under different mass ratios of lead ion to water glass, the solid phases are the lead-silicate with amorphous structures, while the UV–Vis results reveal significant absorption differences in the liquid phases under different mass ratios of lead ion to water glass. The zeta potential and XPS results indicate that less metal silicate polymers are adsorbed on the scheelite surface than on the calcite surface, allowing NaOL to be adsorbed on the scheelite surface, but not on the calcite surface, and selective flotation separation of scheelite from calcite is therefore achieved. XPS results further reveal that the metal silicate polymers in the liquid phase are adsorbed on both mineral surfaces by firstly breaking the Ca-O group and then reacting with the Ca active sites.

Fabrication and electrochemical properties of manganese dioxide coated on cobalt silicate nanobelts core-shell composites for hybrid supercapacitors

It has attracted increasing interest that creating a series of novel supercapacitor electrode materials with promising property. Among many kinds of electrode materials, transition metal silicates and metal oxides have been widely developed as electrode materials for supercapacitors because of their structural stabilization and extremely high theoretical capacity. In our work, manganese dioxide (MnO2) coated on cobalt silicate (Co2SiO4) nanobelts core-shell composites (Co2SiO4 nanobelts@MnO2, abbreviated as CoSi NBs@MnO2) as the improved electrodes for hybrid supercapacitors (HSCs) have been designed and fabricated by a template method. These two electrode materials complement each other and display an excellent synergistic effect. Thanks to the special nanostructures and the capacitance contribution of the two materials, the capacitance value of CoSi NBs@MnO2 can achieve 490.5 F·g−1 at 1 A·g−1 and the capacitance retention with ca. 80% after 5000 cycles. Furthermore, the HSC device fabricated by activated carbon (AC) and CoSi NBs@MnO2 shows the areal capacitance of 328.1 m F·cm−2 at 1 mA·cm−2. Meanwhile, the energy density and power density of the CoSi NBs@MnO2//AC HSC device measure to be 0.89 Wh·m−2 and 42 W·m−2, respectively. The novel and reasonable structural design allows Co2SiO4 and MnO2 to make the contributions in the direction of electrode materials for supercapacitors.