Low Silica Content Research Articles

A comprehensive electrochemical evaluation of the corrosion inhibition by sodium silicate on carbon steel

Sodium silicate (SS) is investigated as a sustainable green corrosion inhibitor for carbon steel in saline environment under both static and dynamic flow conditions. Potentiodynamic scans and Electrochemical Impedance Spectroscopy revealed that silica is both highly efficient in static and flowing water conditions (up to 98 and 99% resp.). An increased inhibition efficiency (IE) is seen as a function of silica concentration as a result of decreased defects in the resulting silica film (Mott–Schottky). The film forming behaviour changes at increasing flow speed, producing a more defect-rich structure at both low and high silica concentration, although showing improved IE at intermediate flow speed for low SS concentrations.

Zircon U-Pb-Hf isotopes constraints on the petrogenesis of Neoarchean granitic rocks from the Northeastern part of the Eastern Dharwar Craton, Southern India

In the present study, we integrate bulk rock chemistry and in-situ zircon U-Pb-Hf isotopes of high-K Neoarchean granitoids from the northeastern part of the Eastern Dharwar Craton (EDC) to investigate their source, petrogenesis, and plausible tectonic setting. Based on the mineral assemblage, in coherence with their geochemical characteristics, these granitoids are classified as Hornblende-biotite granite (HBG) with Microgranular enclaves (ME), Biotite granite (BTG) and Monzogranite (MG). Field observations and zircon U-Pb ages reveal coeval emplacement of these granitoids between 2.53 and 2.50 Ga. The HBG, including ME, has low silica, metaluminous affinity, and high ferromagnesian element content, consistent with their derivation from a mafic source. Some of the HBG and ME samples are strongly enriched in incompatible elements, similar to the sanukitoids. The geochemical attributes and strongly evolved zircon Hf isotopic compositions (ɛHf(t) = −4.3 to +1.8 and −7.3 to +0.2) of the HBG and ME suggest their derivation from a mantle source metasomatized by subducted sediments. The BTG and MG are compositionally similar, with high silica, low ferromagnesian element content, and moderate peraluminous affinity, suggesting the involvement of felsic crustal sources. The sub-chondritic to chondritic zircon Hf isotopic compositions (ɛHf(t) = −2.7 to +1.4 and −6.9 to +1.9) of these granitoids support the involvement of heterogeneous ancient crustal sources. While all granitoids exhibit similar zircon Hf isotopic compositions, their geochemical attributes suggest distinct sources. The HBG reflects juvenile crustal additions, whereas BTG and MG are products of the crustal reworking. We propose that these granitoids formed during the continent-continent collision between Western and Eastern Dharwar cratons, that took place after the break-off of the eastward subducting slab. The asthenospheric upwelling induced by slab break-off and/or lithospheric delamination of thickened crust led to the genesis of metasomatized mantle derived magma, which drove the crustal reworking. The observed zircon Hf isotopic composition of the EDC granitoids are similar to the present day Phanerozoic Alpine-Himalayan type orogenies supporting subduction followed by continental collision model for the stabilisation of Archean cratons. Evidence for the existence of Paleo- Mesoarchean felsic crust from this part of the EDC warrants further studies to test the three-terrane model for the Dharwar Craton.

Rice Straw‐Derived Biochar as Anode Material for Lithium‐Ion Battery: A Step toward Sustainable Development

In the present study, sustainable upscaling of rice straw, an agri‐residue, is explored as the way to obtain active material to prepare anode for use in lithium‐ion batteries (LIBs). The biochar having high carbon and low silica content is prepared by initial chemical treatment of rice straw followed by its pyrolysis. The pristine and modified biochar are characterized using Brunauer‐Emmett‐Teller surface area, energy dispersive X‐ray spectroscopy, carbon hydrogen nitrogen sulphur elemental analysis, scanning electron microscopy, X‐Ray power diffraction, Fourier transform infrared spectroscopy and Raman analysis and the modified biochar show an enhancement in graphitic carbon content. A coin cell is assembled using anode prepared from modified biochar. The coin cell is subjected to electrochemical testing and had a discharge capacity of 352 mA.h g−1. Further, the coin cell is tested for 100 cycles and a columbic efficiency of 99.7% was obtained. Therefore, biochar derived from pyrolysis of rice straw has the potential to be used as anode material for LIBs.

A Study on the Valorization of Rice Straw into Different Value-Added Products and Biofuels

This work depicts that rice straw (RS), which is one of the major lignocellulosic wastes all over the world and causing many environmental problems, has considerable amounts of protein, ash, macronutrients, and micronutrients of approximately 11.38%, 16.77%, 2.27 mg/kg, and 771.9 mg/kg, respectively; besides, a C/N ratio of 15.18, a total N, P2O5, and K2O content of 1.85%, and a considerably low concentration of undesirable heavy metals and silica of approximately 77.69 mg/kg and 109 mg/kg are also present, which recommends its applicability as a precursor feedstock for the production of organic fertilizer and animal fodder. The batch solid-state fermentation (SSF) of RS by Trichoderma longibrachiatum DSMZ 16517 produced considerable amount of total reducing sugars (TRS) of approximately 339.2 mg TRS/g RS under the optimum operatic conditions of 20% (w:v) substrate concentration, pH 7, 1% inoculum size, a 9-day incubation period, and 30°C incubation temperature. The readily available and cost-effective agroindustrial waste, sugarcane molasses, proved to enhance the fungal biomass growth and (hemi) cellulolytic enzymes activities. The inoculated RS-SSF batch process with T. longibrachiatum precultured on 10% molasses enhanced the (hemi) cellulolytic enzymatic activities and TRS production rate by approximately 5.82 and 3.8 folds, respectively, relative to that inoculated by T. longibrachiatum precultured in the conventional potato dextrose broth medium. The separate hydrolysis and fermentation processes by different yeast strains Candida tropicalis DSM 70156, C. shehatae ATCC 58779, and Saccharomyces cerevisiae ATCC 64712 revealed an efficient bioethanol yield and productivity that ranged between 0.36 and 0.38 g/g sugars and 0.22 and 0.23 g/L/h, respectively, with concomitant competent fermentation efficiencies that ranged between 48.35% and 51.25%. The proximate analysis of rice straw before and after fungal hydrolysis proved calorific values of approximately 15.8 MJ/kg and 16.05 MJ/kg, respectively, recommending their applicability as primary and secondary solid biofuels. Thus, this study proved the waste prosperity of RS for environmental opulence and sustainability.

Synergic regulation of crystalline phase, composition and morphology of SAPO-34 via metal assistance and in situ etching strategy

SAPO-34 with low silica content and good mass transfer property is highly desired catalytic material for syngas-to-olefins and methanol-to-olefins (MTO) reactions. However, the synthesis of low-silica SAPO-34 by common low-cost template remains a challenge as the product is always bothered by impurity contamination or CHA/AEI intergrowth. Here, a metal assistance (Me = Zn, Mg, Co, Mn) and in situ etching strategy was developed to allow the construction of hollow low-silica SAPO-34, which exhibited long catalytic lifespan and ultra-high ethylene plus propylene selectivity (86.9 wt%) in MTO reaction. The crystallization process was studied by monitoring the evolution of a Zn-containing low-silica gel with triethylamine (TEA) as the template. It was revealed that Zn atoms were more active than Si atoms to participate in the nucleation of ZnAPSO-34, which effectively inhibited the CHA/AEI intergrowth. ZnAPSO-34@SAPO-34 was obtained with further crystallization. The selective etching of Zn-containing components occurred in subsequent cooling stage owing to inhomogeneous distribution of framework T atoms, leading to the hollow low-silica SAPO (Si/(Si + Al + P) ≈ 0.07 in mole) with pure CHA phase. This work provides a facile approach for the synergic regulation of crystal phase, composition and morphology of SAPO materials.

Evaluating silicosis risk: Assessing dust constitution and influence of water as a primary prevention measure in cutting and polishing of silica agglomerates, granite and marble

An increasing number of silicosis cases have been reported related to the use of silica agglomerates. Many studies agree on the severity of this disease, which often presents with severe clinical forms in young workers and after a short latency period.Are there differences in the composition of dust generated by cutting and polishing with silica agglomerates versus granite and marble? Does the use of water injection reduce the risk associated with the use of these materials?We carried out a comparative observational-analytical study, measuring the concentration of dust generated during different machining operations on three different materials: granite, marble, and silica agglomerates. The effect of water injection on dust generation was evaluated.Personal sampling pumps were used, connected to a cyclone with polyvinyl chloride filters. The flow rate of the pumps was adjusted using a piston flowmeter. Measurements with a cascade impactor were made to assess the size distribution of respirable crystalline silica particles within the respirable fraction. In addition, environmental measurements with a spectrometer were made.10 tests were carried out on granite and silica agglomerates for each procedure. In the case of marble, with very low silica content, only 2 tests of each type were carried out. Duration of each measurement was between 6 and 25 min. Cleaning times were set for each of the operations.The amount of dust collected in the respirable fraction was 70.85, 32.50 and 35.78 mg/m3 for dry cutting; 6.50, 3.75 and 3.95 mg/m3 for wet cutting; and 21.35, 13.68 and 17.50 mg/m3 for dry polishing, for granite, marble, and silica agglomerates respectively.Dry procedures in marble, silica agglomerates and granite showed higher dust concentration of particles smaller than 0.5 μm. Silica agglomerates showed higher concentrations of respirable crystalline silica particles than granite and marble, mainly with dry procedures. The greater production of small particles in dry and wet procedures with silica agglomerates shows that water injection is an insufficient preventive measure.

Design Synthesis of Low-Silica SAPO-34 Nanocrystals by Constructing Isomorphous Core-Shell Structure: An Effective Catalyst for Improving Catalytic Performances in Methanol-to-Olefins Reaction.

It is well known that low-silica SAPO-34, with an extra porosity (meso- and/or macropores) system, affords excellent catalytic performance in the methanol-to-olefins (MTO) reaction, while the direct synthesis of low-silica SAPO-34 with a hierarchical structure is difficult to achieve, principally because the crystal impurities are usually formed under a low silica content in a gel precursor. Herein, low-silica SAPO-34 nanocrystals were successfully fabricated for the first time by constructing an isomorphous core-shell structure in an epitaxial growth manner. In which, low-silica, ultrasmall nanosquare-shaped SAPO-34 crystals with the same growth orientation along the (100) crystal plane compactly grow on the monocrystal SAPO-34 cores. Crucially, the external surface acid properties of the core SAPO-34 with the Si-rich outer layer are effectively modified by the low-silica SAPO-34 shell. Furthermore, the growth process and Si-substitution mechanism of the shell zeolite were comprehensively investigated. It was found that with the prolonged crystallization time, more and more coordinated Si(4Al) and Si(3Al) structures via two substitution mechanisms (SM2 and SM3) are generated in the nanocrystalline SAPO-34 shell, which endow moderate acidity of the core-shell SAPO-34. Compared to the uncoated SAPO-34, the core-shell SAPO-34 performs a longer lifespan and a higher average selectivity of light olefins (ethylene plus propylene) when applied to the MTO reaction, which is attributed to the positive effects of the luxuriant interstitial pores offering a fast diffusion channel and the moderate acid density depressing the hydrogen transfer reaction of light olefins. This work provides new insights into the fabrication of low-silica SAPO-34 nanocrystals, which are based on the rational design of the isomorphous core-shell zeolite.

A rapid and eco-friendly approach for the synthesis of low-silica SAPO-34 with excellent MTO catalytic performance.

A rapid and eco-friendly route has been developed for the synthesis of SAPO-34 with short crystallization time (1-3 h), low silica content (as low as 6.2 wt%) and excellent methanol-to-olefin (MTO) catalytic performance by utilization of a recycled mother liquid at elevated crystallization temperature.

Silica Geothermometry Studies of Shallow Aquifer in Kelantan

The study aimed to analyze the spatial and temporal distribution of silica concentrations in shallow quaternary aquifers across Kelantan, Malaysia. This assessment was crucial for understanding groundwater dynamics, including residence times and potential contamination sources. A total of 32 (29 groundwater and 03 surface water) samples were collected during both pre-monsoon and post-monsoon periods in 2016. Silica concentrations ranged from 6.3 mg/l to 23.4 mg/l pre-monsoon and 6.2 mg/l to 23.5 mg/l post-monsoon. Silica geo-thermometry, based on the chalcedony equation, estimated temperatures ranging from 3.09°C to 37.61°C pre-monsoon and 0.90°C to 37.79°C post-monsoon. Under typical geothermal conditions with an average heat flow of 30°C/km, these temperatures corresponded to depths ranging from 0.02 km to 0.32 km pre- monsoon and 0.01 km to 0.32 km post-monsoon. The shallow depths (less than 0.32 km) indicate relatively rapid groundwater circulation, which aligns with the observed low silica concentrations. These findings suggest minimal anthropogenic influence and short residence times, emphasizing recent meteoric input and surface water inflow as dominant factors shaping water quality in the area.

Evaluation of Mechanical and Thermal Properties of Polypropylene-Based Nanocomposites Reinforced with Silica Nanofillers via Melt Processing Followed by Injection Molding

Polymer nanocomposites have been of great interest to packaging, energy, molding, and transportation industries due to several favorable properties including a higher resistance to stress and cracking even under flexed conditions, and also a chemical resistance to water, acids, and alkalis. The current work disseminates the studies on the mechanical and thermal properties of the polypropylene HHR102 polymer reinforced with nano dispersoids of silicon dioxide at varied weight fractions. The nanocomposites, fabricated via melt processing followed by injection molding, were tested for tensile strength, % elongation, tensile modulus, and impact toughness. Further, the samples were also subjected to dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) to determine the dynamic storage modulus and thermal stability. The addition of nano-silica in polypropylene HHR102 resulted in enhanced ductility and well-balanced tensile modulus; however, the tensile strength and impact toughness were found to be decreased. On the other hand, the storage modulus was significantly increased for all nano-silica (NS)-containing polypropylene HHR102 matrices. With the increased nano-silica content, the storage modulus was optimal. Further, with the lower weight loss of 30% and 50%, the thermal stability of the increased silica content PP nanocomposites was much affected. However, it improved at a weight loss of 30% for the lower silica content PP nanocomposite (PP-1%NS). The imbibition was found to increase with the increase in NS. The increase in imbibition is attributed to the micro-voids generated during ageing. These micro-voids act as channels for water absorption. Further, the degree of crystallinity of the nanocomposites was decreased as a result of inhibition by the nano-particles on the regular packing of polymer molecules. The structure–property correlations were explicated based on the achieved mechanical properties.

Petrography and Geochemistry of the Baska Piwaza Ore Mineralization, Halgurd Mountain, Iraqi Kurdistan Region: Insights on the Genesis

This paper is the first attempt to study the mineralogical and geochemical features of mineralization hosted within the volcanic rocks of the Baska Piwaza section, at Halgurd Mountain, which is the highest mountain in Kurdistan and the whole of Iraq. The host lithologies in the studied section represent mostly volcanic rocks (basalts to andesites), and secondary sedimentary lithologies, such as radiolarian chert. There are two main stages of oxide and sulfide mineralization that can be recognized under three-time epochs which are early, middle and late stages that caused the formation of oxide and sulfides ore minerals. The most dominant oxide mineral is hematite, with minor contribution of magnetite, goethite, and rutile. In terms of sulfides, pyrite is the predominant mineral phase with secondary contribution of chalcopyrite. The petrographic study and XRD data of the host volcanic rocks reveal that the most abundant minerals are plagioclase, K-feldspar, pyroxene, and amphibole, while the secondary minerals are quartz, calcite, clinochlore, sericite, prehnite, pumpellyite, and muscovite. Additionally, the radiolarian chert is comprised by quartz, hematite, calcite, ankerite, clay minerals, and apatite which is characterized by low silica content and high iron oxide. Low concentration of TiO2 ,and Fe2O3 are suggesting the quartz vein occurred with the volcanic rocks are formed due to low hydrothermal fluid. Field observation, petrographical and geochemical data indicate that the rocks of the Baska Piwaza section are influenced by hydrothermal alteration, due to the high value of Loss On Ignition (LOI) and the high ratio of alkalis (Na2O+K2O). Moreover, evidences of chloritization and sericitization of the mafic minerals, and feldspar minerals respectively support the hydrothermal impact.

The use of rice husk in the substrate composition increases Pleurotus ostreatus mushroom production and quality

Rice husk is a waste generated in large quantities in various countries, although its reuse is limited due to low nutritional quality and high silica content. Therefore, this study sought to evaluate using raw or carbonized rice husks to partially substitute eucalyptus sawdust in substrates to produce the edible mushroom Pleurotus ostreatus. The substrates were formulated with proportions of 0 to 100% of eucalyptus sawdust and raw or carbonized rice husks. P. ostreatus was grown for 90 days on the substrates to evaluate mycelial growth, fresh mass production, biological efficiency, and protein and fat content. The organoleptic quality of the mushrooms produced was evaluated by sensory analysis. The substrates’ moisture, pH, and C and N contents were evaluated before and after cultivation. The substrates with 25 and 50% of raw or carbonized rice husk in a mixture with sawdust provided nitrogen and water more adequately to the fungus, improving the fresh mass production, the protein content of mushrooms, and biological efficiency (75–83%) compared to the reference substrate (100% eucalyptus sawdust), without altering the sensory quality. Given the environmental issues caused by carbonization, using raw rice husk in a mixture of up to 50% eucalyptus sawdust is recommended for P. ostreatus production.

Tearing on the southward subducting Kelameili oceanic lithosphere in the early Devonian: Evidence from the magmatism in the Harlik arc, southern Altaids

The coexistence of adakites, high-Mg andesites (HMAs) and Nb-enriched basalts (NEBs) records special subduction geodynamics, for instance, subduction initiation, subduction of oceanic ridges or slab tearing, which are widespread in the circum-Pacific subduction zone. The Altaids in Central Asia shared similar tectonic evolution to the western Pacific. However, slab tearing has not been widely reported, which hinders a better comparison between the Altaids and the western Pacific. In this study, we report the contemporaneous early Devonian granodiorites and mafic microgranular enclaves (MMEs) in the Sidingheishan area of the Harlik arc, southern Altaids. The granodiorites have high Sr (534–683 ppm) but low Y (7.79–10.2 ppm) and Yb (0.71–1.68 ppm) contents, with corresponding high Sr/Y values (29.78–76.93). In combination with their juvenile isotopes (initial 87Sr/86Sr = 0.70333–0.70356, εNd(t) = +7.4 − +8.01) and high Mg# numbers (50.9–53), they indicate that their primitive magmas were derived from slab melting. The MMEs show similarly high Sr contents (507–696 ppm), and identically juvenile isotopic signatures (initial 87Sr/86Sr = 0.70346–0.70356, εNd(t) = +7.14 − +7.5) to their host granodiorites. However, their relatively low silica contents (55–60 wt%), evolved Mg# numbers (44.8–55.2) and high Nb contents (12.7–24.7 ppm) demonstrate that they are the fractionation products of NEBs, which were produced by the partial melting of the mantle that was previously metasomatized by these adakitic magmas. Considering all the available evidence, we propose a slab tearing model in which the southward subducting Kelameili oceanic lithosphere underneath the Harlik arc underwent rollback in the early Devonian and its differential rollback rates caused slab tearing. Subsequent asthenosphere upwelling stimulated the Kelameili oceanic lithosphere to melt, producing the adakitic magmas, some of which intruded the crust after limited interaction with the mantle peridotites and underwent crystallization of dominant amphibole in the crust. The rest reacted completely with the mantle peridotites, which underwent further melting to produce the Nb-enriched basaltic magmas. They intruded into the adakitic magma chamber after fractional crystallization of olivine, clinopyroxene and garnet in the deep, forming the MMEs and promoting the remobilization of those hornblendites. This study reveals the development of slab tearing that are closely associated with slab rollback in the Altaids, providing further evidence that argues for the similarity between the Altaids and the western Pacific.

Cellulose acetate/silica composites: Physicochemical and biological characterization

Cellulose acetate is of remarkable scientific interest, becoming more useful when is used in obtaining of the composite materials containing nanoparticles, as result of its improved properties. Thus, cellulose acetate/silica composite films obtained by casting the solutions of cellulose acetate (CA)/tetraethyl orthosilicate (TEOS) in different mixing ratios were analyzed in this paper. The impact of TEOS addition, and implicitly of the silica nanoparticles on the mechanical strength, water vapor sorption properties and antimicrobial activity of the cellulose acetate/silica films were mainly monitored. The results of the tensile strength tests were discussed in correlation with data obtained from Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. It was found that samples with low TEOS content show improved mechanical strength compared to samples with high amounts of TEOS. The microstructural characteristics of the studied films affect their moisture sorption capacity so that the weight of the adsorbed water increases with the addition of TEOS. These features are complemented with the antimicrobial activity against Staphylococcus aureus and Escherichia coli bacterial species. The obtained data show that the cellulose acetate/silica films, and especially those with low silica content have improved properties that can recommend them for applications in the biomedical field.

Effect of nano silica on solidification/stabilization of heavy metal in alkali-activated MSWI fly ash solidified body

Municipal solid waste incineration fly ash (MSWIFA) containing considerable heavy metals is classified as a hazardous waste. Alkali-activated technology can effectively improve the environmental safety of MSWIFA. Due to the low silica content of MSWIFA, the addition of nano silica (NS) solves the problem to enhance the ability of solidification/stabilization (S/S) and maximize the utilization of MSWIFA. NS/MSWIFA solidified body was prepared by alkali-activated technology in this work. The mechanical and environmental properties of NS/MSWIFA solidified body with various dosages (0–3 wt%). NS were characterized by compressive strength, leaching concentration, and chemical speciation distribution of heavy metals. A comparative study of MSWIFA and solidified bodies for exploring S/S mechanisms was investigated using XRD, FTIR, TG/DTG, NMR, and SEM/EDS tests. The results showed that the leaching concentration of Pb in MSWIFA based on different leaching methods was 23.54 mg/L and 31.7 mg/L, 19.6 times higher than the standard of hazardous waste landfill and 126.8 times higher than the standard of landfill site of municipal solid waste, respectively. The total amount of Zn and Pb was 4739 mg/kg and 2451 mg/kg, respectively, exceeding other heavy metals by 1–2 orders of magnitude. When the addition of NS was 2 wt% and 3 wt%, the compressive strength and the leaching concentration of heavy metals in solidified bodies reached the highest and the lowest, respectively. Comparative analysis indicated that adding NS promoted heavy metals in MSWIFA to be converted into a stable state, and increased hydration product C-(A)-S-H gels formation, making the structure denser. On a broader perspective, NS/MSWIFA solidified body was developed as a low-carbon and environment-friendly binder.

Genome wide association studies and candidate gene mining for understanding the genetic basis of straw silica content in a set of Oryza nivara (Sharma et Shastry) accessions.

Rice is a high-silica (SiO2·nH2O) accumulator. Silicon (Si) is designated as a beneficial element associated with multiple positive effects on crops. However, the presence of high silica content is detrimental to rice straw management, hampering its use as animal feed and as raw material in multiple industries. Rice straw management is a serious concern in north-western India, and it is eventually burned in situ by farmers, contributing to air pollution. A practical solution could lie in reducing the silica content in rice while also attaining sound plant growth. A set of 258 Oryza nivara accessions along with 25 cultivated varieties of Oryza sativa was used to assess the variation in straw silica content using the molybdenum blue colorimetry method. A large continuous variation was observed for straw silica content in O. nivara accessions, ranging from 5.08% to 16%, while it varied from 6.18% to 15.81% in the cultivated varieties. The O. nivara accessions containing 43%-54% lower straw silica content than the currently prominent cultivated varieties in the region were identified. A set of 22,528 high-quality single nucleotide polymorphisms (SNPs) among 258 O. nivara accessions was used for estimating population structure and genome-wide association studies (GWAS). A weak population structure with 59% admixtures was identified among O. nivara accessions. Further, multi-locus GWAS revealed the presence of 14 marker-trait associations (MTAs) for straw silica content, with six of them co-localizing with previously reported quantitative trait loci (QTL). Twelve out of 14 MTAs showed statistically significant allelic differences. Thorough candidate gene analyses revealed the presence of promising candidate genes, including those encoding the ATP-binding cassette (ABC) transporter, Casparian thickening, multi-drug and toxin extrusion (MATE) protein, F-box, and MYB-transcription factors. Besides, ortho-QTLs among rice and maize genomes were identified, which could open ways for further genetic analysis of this trait. The findings of the study could aid in further understanding and characterizing genes for Si transport and regulation in the plant body. The donors carrying the alleles for lower straw silica content can be used in further marker-assisted breeding programs to develop rice varieties with lower silica content and higher yield potential.

The structures and properties of yttrium aluminosilicate glasses with low, medium, and high silica contents

Yttrium aluminosilicate glasses with 25–78 mol% silica were studied using molecular dynamics simulations to understand their structural and property changes. The results show that Al3+ ions primarily exist as four-fold coordinated, with <5% in higher-coordinated states that increase with decreasing silica content. The formation of significant concentrations (4–9%) of oxygen tri-clusters and small amounts of free oxygen were also observed, suggesting a perturbed glass network structure. An average Y-O bond distance of 2.26 Å and Y coordination number of 6.3 were found. The glass transition temperatures are relatively insensitive to composition, agreeing with experiments. A 16% and 30% increase in Young's and bulk moduli, respectively, was observed with decreasing silica contents which was explained by the strong Y-O bond and formation of oxygen tri-clusters that aggregate higher coordinated Al species. These results were discussed in the context of optical and acoustic properties of YAS optical fibers that exhibit reduced nonlinearities.

Chemical analysis Dendrocalamus asper bamboo and suitability for pulp and paper

The chemical analysis of bamboo species, namely Dendrocalamusasper or popular named as BuluhBetong has been evaluated. From the age of 3 years, this species shows different chemical properties related to holocellulose,  cellulose, solvent extraction, alkali solubility, lignin, hot water solubility, cold water solubility, ash, silica and pentosan. Holocellulose content of about 60.48% to 64.75%,  cellulose content of about 35.73% to 43.14%, for all bamboo segments indicated as a suitable material for pulp and papermaking. Low level of solvent extractive of about 5.09% to 6.23%, hot water soluble of about 6.29% 9.49% and cold water soluble of about 9.35% to 10.49% also produced the content that cannot interfere with the paper-making process. In addition, the low ash and silica content for all sections of bamboo will indicate a normal alkali consumption and give little challenge to the operational process. High pentosan content in the middle and top sections between 16.32% and 20.88% and lignin content of around 39.27% to 32.51% also promise little challenge for pulping as compared to the bottom section. Therefore, based on the overall findings, the middle section, and the top section had an advantage over the bottom section. As a result, the middle and top sections are best used as a new material in pulp and paper making process.

Influence of curing methods on properties of mine overburden-based geopolymer aggregate

Many earlier studies have focused on using calcined clay rather than raw clay for conventional geopolymerization methods to manufacture coarse aggregate. This paper deals with utilizing overburden soil, having low silica and alumina content, which is available in large quantities from the mining industry, as coarse aggregate, through pelletization. This study adopted geopolymerization for the effect of sodium-silicate-hydroxide activators and geopolymer precursors such as fly ash and ground granulated blast furnace slag by varying the alkaline concentration. Unlike the conventional sintering-based hardening method, the present study used oven-curing and short-duration microwave sintering as hardening methods. We assessed the effect of mix and hardening methods on the relative performance of aggregates through density, strength, water absorption, and strength-to-density relationship of geopolymer aggregates. Increased alkaline concentration improved the pelletization efficiency and fineness modulus of aggregates. The aggregate's density and water absorption primarily depend on the alkaline activator concentration and the curing parameters for both oven and microwave curing methods. Short-duration microwave curing led to aggregates of similar density and strength compared to longer oven curing. Volumetric heating during microwave curing caused densification, development of additional fused surface coating, strength gain, and reduced water absorption of the aggregate.

Forest buffer-strips mitigate the negative impact of oil palm plantations on stream communities

The global area cultivated with oil palm has doubled in the past two decades, causing deforestation, land-use change, freshwater pollution, and species loss in tropical ecosystems worldwide. Despite the palm-oil industry been linked to severe deterioration of freshwater ecosystems, most studies have focused on terrestrial environments, while freshwaters have been significantly less studied. We evaluated these impacts by contrasting freshwater macroinvertebrate communities and habitat conditions in 19 streams from primary forests (7), grazing lands (6), and oil palm plantations (6). In each stream, we measured environmental characteristics, e.g., habitat composition, canopy cover, substrate, water temperature, and water quality; and we identified and quantified the assemblage of macroinvertebrates. Streams in oil palm plantations lacking riparian forest strips showed warmer and more variable temperatures, higher turbidity, lower silica content, and poorer macroinvertebrate taxon richness than primary forests. Grazing lands showed higher conductivity and temperature, and lower dissolved oxygen and macroinvertebrate taxon richness than primary forests. In contrast, streams in oil palm plantations that conserved a riparian forest, showed a substrate composition, temperature, and canopy cover more similar to the ones in primary forests. These habitat improvements by riparian forests in the plantations increased macroinvertebrate taxon richness and maintained a community resembling more the one in primary forests. Therefore, the conversion of grazing lands (instead of primary forests) to oil palm plantations can increase freshwater taxon richness only if riparian native forests are safeguarded.