Alkali Metal Oxides Research Articles

Synthesis and Characterization of Cement Clinker Using Waste Glass and Oyster Shells as Natural Ore Substitutes

This study investigates the process of synthesizing eco-cement clinker using recycled powdered glass (RPG) and oyster shell residue (OSHL) as primary raw materials. Analysis of the mineral composition of RPG revealed that it primarily consists of silica and contains a high level of alkali metal oxides, while OSHL comprises a high-purity trigonal calcite structure, similar in chemical composition to limestone. Comparative analysis of the synthesized ecological cement and its hydration products showed that, after heat treatment at 1200 °C, the alkali metal content in the H12 sample significantly decreased, thereby meeting the standards for cement raw materials. The hydration process of RPG and OSHL ecological cement (ROEC) exhibited greater reactivity, with the presence of alkali ions (such as Na⁺ and K⁺) accelerating the cement hydration reaction and significantly enhancing early strength. Furthermore, as the curing time increased, the hydration products of ROEC became more uniform, ultimately consisting primarily of calcite. These findings indicate that the combination of RPG and OSHL offers a novel approach to cement synthesis, while reducing the content of alkali metal oxides, thereby aligning the cement clinker more closely with modern production standards.

Design of alkali metal oxide adsorbent for direct air capture: Identification of physicochemical adsorption and analysis of regeneration mechanism

Direct air capture (DAC) represents an advanced negative carbon emission technology, with the key being high-performance CO2 adsorbents. First, this work carefully identifies CO2 physisorption and chemisorption by CaO/HcATP (CaO loaded on acid-modified attapulgite) as DAC adsorbent. The chemisorption of amorphous "CaO" plays a crucial role in both the adsorption capacity and rate, with contributions of 66.8 % and 50.85 %, respectively. The adsorption capacity of CaO/HcATP is only 212.4 ± 25.7 µmol/g via the simple CO2 physisorption and improved by 426.7 µmol/g owning to the chemisorption of amorphous CaO. Second, the concentration of silanol groups on CaO/HcATP plays a pivotal role in the adsorption process. The concentration of silanol groups decreases to 3.85 OH/nm2 after undergoing 30 cycles of adsorption-desorption. Then it increases to 9.54 OH/nm2 by adsorbing the moisture in the air, resulting in a recovered adsorption capacity of 90.7 %. Furthermore, the pseudo-first-order adsorption kinetics model effectively predicted the experimental results. Finally, the dual loop of CO2 capture and regeneration is summarized using the CaO/HcATP as DAC adsorbent. The amorphous "CaO" interacts with the surface silanol of HcATP, synergistically capturing CO2 in the form of "CaO···CO2", which reduces desorption energy consumption. The wetting property of HcATP contributes to the regeneration of CaO/HcATP. This work contributes to establishing fundamental principles for designing cost-effective DAC adsorbents.

Unveiling Biodiesel Production: Exploring Reaction Protocols, Catalysts, and Influential Factors

AbstractAn environmentally responsible and sustainable replacement for finite fossil fuels is biodiesel. Because of its amazing qualities, biodiesel is becoming more and more popular as a renewable fuel around the globe. The many approaches, feedstocks, catalysts, comparison standards, reaction kinetics, final product analysis, and final product characterization of biodiesel are covered in this review article. Researchers have used a variety of techniques to produce biodiesel throughout history, with transesterification emerging as the most effective approach in more recent times. Numerous studies on biodiesel feedstock and catalysts to produce high biodiesel yields have been published; nevertheless, it should be highlighted that the type of feedstock must be considered while choosing a catalyst. The review paper highlights the significance of several parameters that are crucial to the manufacture of biodiesel, without which achieving a high yield would be challenging. The literature has also discussed the limitations and advantages of different catalysts, and scientists are currently working to identify the ideal catalyst within certain optimal parameters for the manufacture of biodiesel. Homogeneous reaction‐based biodiesel synthesis has a number of drawbacks, though, such as water content, a laborious purification procedure, and a low tolerance for free fatty acids. To address these issues, scientists have started investigating heterogeneous reactions involving solid catalysts. A large pore network, a moderate‐to‐high density of strong acid sites, a hydrophobic surface, and the ability to control surface hydrophobicity to avoid deactivation are all desirable characteristics of an ideal solid catalyst. Ion exchange resins, sulfated oxides, heterogeneous base catalysts, boron group‐based heterogeneous catalysts, alkaline earth metal oxides, mixed metal oxides, alkali metal oxides, heterogeneous catalysts derived from waste materials, and different approaches to biodiesel synthesis that employ enzymes, carbon‐based heterogeneous catalysts, and ionic liquids as catalysts are among the categories of catalysts that can be used in the production of biodiesel. The finest benchmarks to compare the quality of biodiesel with European and American Society for Testing Material standards. For detailed characterization of the finished product, gas chromatography and nuclear magnetic resonance are the most effective methods.

Role of Sintering Aids in Electrical and Material Properties of Yttrium- and Cerium-Doped Barium Zirconate Electrolytes

Ceramic proton conductors have the potential to lower the operating temperature of solid oxide cells (SOCs) to the intermediate temperature range of 400–600 °C. This is attributed to their superior ionic conductivity compared to oxide ion conductors under these conditions. However, prominent proton-conducting materials, such as yttrium-doped barium cerates and zirconates with specified compositions like BaCe1−xYxO3−δ (BCY), BaZr1−xYxO3−δ (BZY), and Ba(Ce,Zr)1−yYyO3−δ (BCZY), face significant challenges in achieving dense electrolyte membranes. It is suggested that the incorporation of transition and alkali metal oxides as sintering additives can induce liquid phase sintering (LPS), offering an efficient method to facilitate the densification of these proton-conducting ceramics. However, current research underscores that incorporating these sintering additives may lead to adverse secondary effects on the ionic transport properties of these materials since the concentration and mobility of protonic defects in a perovskite are highly sensitive to symmetry change. Such a drop in ionic conductivity, specifically proton transference, can adversely affect the overall performance of cells. The extent of variation in the proton conductivity of the perovskite BCZY depends on the type and concentration of the sintering aid, the nature of the sintering aid precursors used, the incorporation technique, and the sintering profile. This review provides a synopsis of various potential sintering techniques, explores the influence of diverse sintering additives, and evaluates their effects on the densification, ionic transport, and electrochemical properties of BCZY. We also report the performance of most of these combinations in an actual test environment (fuel cell or electrolysis mode) and comparison with BCZY.

Experimental Evaluation of Blockage Resistance and Position Caused by Microparticle Migration in Water Injection Wells

Offshore oil field loose sandstone reservoirs have high permeability. However, during the water injection process, water injection blockage occurs, causing an increase in injection pressure, making it impossible to continue injecting water on site. Current research mainly focuses on the factors causing water injection blockage, with less attention given to the blockage locations and the pressure increase caused by water injection. There is a lack of research on the change in the law of injection capacity. This paper establishes a simulation experiment for water injection blockage that can accommodate both homogeneous and heterogeneous cores. The experimental core is 1 m long and capable of simulating the blockage conditions in the near-well zone during water injection, thereby analyzing the core blockage position and blockage pressure. The study clarifies the influence of water quality indicators, heterogeneity, and core length on the blockage patterns in reservoirs during water injection. The research findings are as follows: I. The reservoir blockage samples were characterized using scanning electron microscopy (SEM), casting thin sections, and X-ray diffraction (XRD) analysis. The results indicate that the main factors causing blockage are clay, silt, and fine particulate suspensions, with the fine particles mainly consisting of hydrated silicates and alkali metal oxides. The primary cause of blockage in loose sandstone is identified as the mechanism of migration and accumulation of clay, fine rock particles, and suspended matter in the injected water. II. By monitoring pressure and permeability changes in the core flooding experiments, the impact of reservoir heterogeneity on water injection capacity was evaluated. The evaluation results show that the blockage locations and lengths in heterogeneous cores are twice those in homogeneous cores. III. For heterogeneous reservoirs, if the initial permeability at the inlet is lower than in other segments of the core, significant blockage resistance occurs, with the final resistance being 1.27 times that of homogeneous cores. If the initial permeability at the inlet is higher than in other parts, the final blockage resistance is close to that of homogeneous cores. This study provides theoretical support for the analysis of blockage locations and pressures in loose sandstone water injection and offers technical support for the design of unplugging ranges and pressures after blockage in heterogeneous formations. At the same time, it provides a theoretical basis for selecting the direction of acidizing after blockage occurs in loose sandstone.

Particle Conditioning for Improving Blockage Resistance of Denitration Catalysts in Sintering Flue Gas

The stability and safety of selective catalytic reduction (SCR) systems are threatened by potential catalyst blockages caused by fly ash deposition. This paper proposes to improve the blockage resistance of denitration catalysts for sintered fly ash through particle conditioning. X-ray fluorescence spectroscopy, scanning electron microscopy, and laser particle analyzer were combined with laboratory heating experiments and field tests for systematic research. The results indicate that the composition and morphology of sintered fly ash are intrinsic factors contributing to catalyst blockage, while heating conditions act as external triggers. The sintered fly ash primarily exhibits a fluffy, branched cotton-like structure. Its main components are K2O, Fe2O3, Na2O, and CaO, with the alkali metal oxides of potassium and sodium comprising 20% to 50%. At ambient temperature, sintered fly ash presents no agglomeration, but significant agglomeration occurs as temperature increases. Particle conditioning effectively inhibits the agglomeration tendency of sintered fly ash. Field tests show that catalyst activity remains unaffected even under severe blockage conditions. The pressure drop across the catalyst layers increases progressively, with the first layer displaying the least pressure drop and the third displaying the most. After particle conditioning, the pressure drop across the catalyst is stabilized at values below 600 Pa, effectively mitigating the blockage issue in the denitrification catalyst for sintering flue gas. This research provides critical technical support for the stable ultra-low emission of NOx from sintering flue gas.

FEATURES AND EXPERIENCE OF CONVERTING GAS-OIL BOILERS OF INDUSTRIAL CHP PLANTS TO BURNING BIOMASS AND SUB-BITUMINOUS COAL

The paper examines the features of biomass as a fuel and substantiates that for agrobiomass waste with a high content of alkali metal oxides and slag properties of ash, it is more appropriate to burn it in a dense bed in the form of pellets, which ensures a temperature at the exit from the furnace of no more than 900 °C, a low part of fly ash and low content of unburned carbon in it, and so eliminates the risk of smoldering deposits with their melting and slagging. Technical solutions are given and the experience is presented of gas and oil boilers of CHP plants of sugar factories reconstruction with their transfer to the burning of biomass and/or coal in a dense bed on a direct-flow grate with the replacement of the air heater with air-water heater, with the addition of stages of the boiling economizer to compensate for the decrease in the heat perception of the furnace screens, maintaining the overall height of the boiler and the plane of the boiler cell. The reconstruction of boilers according to the developed technical solutions is possible to perform in the interval between production seasons, its implementation on boilers BKZ-75 GMA of Radekhiv and Chortkiv sugar factories allowed to achieve acceptable technical, economic and environmental indicators and ensured payback due to the difference in commercial prices of gas and of agrobiomass pellets. It is proposed to replicate the positive experience in the creation of decentralized regulating thermal generation capacities of the country. Bibl. 30, Fig. 3, Tab. 4.

Feedstock recycling of single-use garment simultaneously using CO2 and MSW incinerator bottom ash

This study is aimed at proposing a feedstock recycling approach to make value-added monomer from single-use garment like stocking waste (SW) using incinerator bottom ash catalyst (IBAC). SW is made mainly of nylon 6 (>80 wt%) with minor components such as polyurethane. Thermochemical SW decomposition pathways are identified by evolved gas analysis and single-shot pyrolysis analysis, confirming that caprolactam (a value-added chemical re-used for manufacturing nylon 6) is the major product. IBAC is composed mainly of alkaline metal oxides (e.g., CaO). The use of IBAC in thermochemical SW conversion at 500 °C under CO2 atmosphere increases the yield of caprolactam reaching 70.8 wt% (20 % higher than non-catalytic SW conversion (59.2 wt%)). Moreover, the caprolactam yield corrected to the nylon 6 content of SW is 86.8 wt%. The enhancement of caprolactam production by IBAC in CO2 is most likely due to the synergistical effect of IBAC and CO2 on promoting the molecular interaction of amide groups present on SW. It is hoped that this study brings the idea of new applications of concurrently reusing textile waste (e.g., SW) and municipal solid waste-treatment byproduct (e.g., IBAC).

Research on the microscale effects of fuel pellets carrying chemical pesticide distillation residues

To effectively deal with organic hazardous wastes generated in the production processes of chemical pesticide industries. In this study, the strong shear force generated by high-speed rotating blades was utilized to fully mix and stir pasty or viscous liquid organic hazardous wastes with porous solid fuels. The wastes were broken down into small molecular clusters and evenly distributed on the surfaces of the pores of porous solid fuel particles. This study then investigated the thermal characteristics of fuel particles carrying the distillation residues of chemical pesticides under microscale effects, the volatilization and destruction removal characteristics, the formation of pollutants, and the migration and transformation of F and Cl elements. The results showed that when the average diameter of the fuel particles was 6 mm and the mass ratio of the chemical pesticide distillation residue to the fuel particles was 2:3, small molecular clusters of the residue were evenly distributed on the surfaces of the fuel particles, with a dispersity of 67 %. The volatilization rate of the irritating odors in the coated particles was less than 2 %. With an increase in the proportion of the chemical pesticide distillation residue, the ignition temperature of the particles decreased, the thermal stability increased, the burnout temperature rose, and the maximum weight loss rate first increased and then decreased. The Ca and alkali metal oxides in the fuel particles had a significant effect on fixing chlorine and fluorine.

Facile co-precipitation synthesis of nano-molybdenum-doped BaO nanoparticles and their physical characterization

Alkaline metal oxides have received significant attention recently due to their abundance, inherent conductivity, optical absorption, and thermal stability. Here, a straightforward co-precipitation method was employed to obtain both undoped BaO and Mo-doped BaO nanoparticles. Various techniques were used to characterize the synthesized nanoparticles’ structural, Raman spectral, optical, thermal, and electrical properties. X-ray diffraction (XRD) results revealed that Mo was successfully doped into tetragonal nanocrystalline BaO. The W-H plot showed that as Mo doping increases from 2 % to 6 %, the crystallite size grows while the lattice structure remains well-ordered with even strain distribution. Scanning electron microscopy (SEM) was used to examine its surface features. The purity and crystalline character of the samples were further confirmed via Raman spectroscopy, which shows that the peak intensity of the spectra increases with the increase of particle size owing to the rise in the force constant. UV spectroscopy was used to observe the energy band gap, which is found to decrease from 4.2 eV to 3.8 eV, and then it drops to 3.4 eV as the Mo content increases. This is reasonable because of the size-dependent attraction between metallic ions and conduction electrons. PL spectra concluded that Mo doping leads to the enhancement of the optical characteristics of BaO. Adding Mo to BaO also modifies the material’s thermal properties, potentially affecting its suitability for applications that require thermal durability. This finding exhibits that even slight doping of Mo4+ into BaO can significantly impact their structural, thermal, optical, and electrical characteristics. It enriches the existing body of knowledge of BaO nanoparticles and lays the foundation for its future research.

Sodium-Poor, Hydroxyl-Rich, Defective Na2Ti3O7 Prepared by γ-Irradiation and Its Enhanced Proton Conductivity.

The use of γ-irradiation to tailor the physicochemical properties of materials is not widely applied to layered alkali metal oxides. Herein, we show that γ-irradiation (up to 400 kGy) of Na2Ti3O7 leads to a sodium-poor, hydroxyl-rich analogue where the layered structure, plate-like morphology, and textural properties are preserved. The deintercalation of sodium ions modifies the Ti-O bond lengths and expands the unit cell; the latter is supported by density functional theory (DFT) calculations. 23Na solid-state NMR suggests the transport of the symmetric, 7-fold Na2 sites to an intermediate environment, which is closer to the asymmetric, 9-fold Na1 sites. An 8 wt % mass loss (1.4 mol water/mol titanate) is observed, indicating an increased concentration of protons/hydroxyls. These hydroxyl groups (i.e., lattice protons) possess higher thermal stability than solely surface-adsorbed ones in the nonirradiated sample. At 200-400 kGy, the proton conduction (50 °C and ∼70% RH) of ∼10-6 S·cm-1 is 1 order of magnitude larger than that in the nonirradiated sample; the relaxation time decreases from 30 to 2-6 μs with γ-irradiation. The γ-dose dependence of dielectric loss is also present and analyzed using the Jonscher universal power law, indicating the low-frequency dispersion behavior characteristics of high charge densities.

(Invited) Nanowire Catalysts and Adsorbents

The unique properties of nanowire materials like fast charge transport, short diffusion length, controlled surface sites and single crystal nature make them ideal for designing high performance catalysts, adsorbents and electrocatalysts by design. To realize any of these applications, one would need either large quantities of nanowire powders or nanowire arrays on large areas. In this presentation, we will highlight our group’s efforts with scalable methods for continuous manufacturing of nanowire powders and arrays for oxides1 and III-nitride materials.2 The process for producing metal oxide nanowires has been scaled up to ton-scale. The resulting nanowire powders can be used to formulate unique catalyst and adsorbent products.Zinc oxide nanowires alloyed with catalytically active metals and have been formulated into ultra-deep desulfurization catalytic adsorbents.3,4 These materials exhibited ultra-deep desulfurization with sulfur removal down to 1 ppm or below for liquid hydrocarbons (diesel, gasoline and naphthalene) and to less than 1 ppb for natural gas. The desulfurization mechanism does not involve formation of H2S species unlike that typically observed with hydro-desulfurization process involving sulfided catalysts.Titania nanowires supported with nickel and molybdenum clusters have also shown to exhibit high activity and durability as hydro-desulfurization catalysts for removal of sulfur from hydrocarbons by forming H2S.5 The synergistic activity with MoS2 and titania are expected to contribute to enhanced activity with desulfurization.Alloying of nanowires with other elements is also studied to produce compound and alloyed nanowires. Fundamental studies have shown that alloying process occurs at much lower temperatures than decomposition temperatures for precursors used. Alloying studies have clearly shown that the solubility in nanowires to be much more than that expected for bulk materials systems. This presentation will provide several examples in which nanowires were alloyed with elements at compositions more than that expected for thermodynamic solubility.In the case of CO2 sorbents, alkali metal oxide nanowires have shown high capacity for CO2 sorption as high as 75% by wt. The alkali metal oxide nanowires have been alloyed with alkali hydroxides to produce alkali metal oxide compound nanowires. These solid sorbents showed selective CO2 sorption from a variety of streams including air, exhausts containing CO2 at various concentrations. Nanowire geometry for these nanowires allow for non-sinterability, and smaller length scales for rapid diffusion of alkali ions allow for fast kinetics and regenerability. 6,7 Acknowledgements: Authors also acknowledge contributions from Drs. Juan He, Sivakumar Vasireddy, Vivekanand Kumar, Veerendra Atla and Tu Nguyen. Partial support from National Science Foundation (NSF) and US Department of Energy (DOE) EPSCOR programs and full support from NSF and DOE SBIR programs and Kentucky Cabinet for Economic Development for Advanced Energy Materials, LLC are highly appreciated.

INVESTIGATION OF THE EFFECT OF ZEOLITES ON THE TECHNOLOGICAL PROPERTIES OF ADHESIVES

The article is devoted to the analysis of the effect of the addition of zeolites on the properties of adhesives used in the woodworking industry. Zeolites with adsorption and catalytic properties were used as modifiers of adhesive systems. This work contributes to the creation of environmentally friendly adhesives for the woodworking industry, reducing the impact on the environment. The aim of the study is to modify adhesive compositions with different concentrations of zeolite and to study their effect on technological parameters. The methods of synthesis of modified adhesives and methods of their testing are described. The results show that the introduction of zeolites into the composition of adhesives accelerates the gelatinization process due to the catalytic action of alkali metal oxides contained in aluminosilicates. This reduces the polycondensation time and allows you to maintain the performance of the CF-LT-15 glue for 89 hours, which corresponds to technological standards. However, an increase in the size and concentration of aluminosilicate particles increases the conditional viscosity of the adhesive from 52 to 95 seconds, which complicates its application to substrates. In this regard, it is recommended to limit the filler content to 8 mass parts. This article summarizes the results of the study and offers recommendations for the industrial use of modified adhesives. The results may be of interest to both the scientific community and the woodworking industry, which is striving to create more efficient and environmentally friendly adhesives.

Understanding the Competition Mechanism between Na2O and CaO for the Formation of the Initial Layer of Zhundong Coal Ash

The contents of alkali and alkaline earth metals are higher in Zhundong coal, and there are serious problems of slagging and fouling during the combustion process. Therefore, it is of great significance to reveal the mechanism of slagging and fouling in the boiler of Zhundong coal. In this paper, first-principle calculations based on density functional theory are used to study the competition mechanism of alkaline metal oxides during the combustion process in Zhundong coal by establishing the Na2O(110)/CaO(100)-SiO2(100) double-layer interface model. The results show that the bond lengths of the surface of Na2O(110) and CaO(100) with SiO2(100) after adsorption were generally lengthened and the value of bond population became smaller, which formed a stable binding energy during the reaction. The electron loss of Na is 0.05 e, the electron loss of Ca is 0.03 e, and the electron loss of Na2O is greater than that of CaO. The charge transfer on the surface of Na2O with SiO2 is obviously higher than that of CaO and the orbital hybridization on the surface of CaO with SiO2 is weaker than that on the surfaces of Na2O with SiO2. Na2O is easier to react with SiO2 than CaO. The adsorption energies on the surface of Na2O and CaO with SiO2 are −5.56 eV and −0.72 eV, respectively. The adsorption energy of Na2O is higher than that of CaO, indicating that Na2O is more prone to adsorption reactions and formation of Na-containing minerals and other minerals, resulting in more serious slagging. In addition, the XRD analyses at different temperatures showed that Na-containing compounds appeared before Ca-containing ones, and the reaction activity of Na2O is stronger than that of CaO in the reaction process. The experimental results have good agreement with the calculation results. This provides strong evidence to reveal the slagging and fouling of Zhundong coal.

Volcanic eruption-inspired co-melting treatment of municipal solid waste incineration fly ash

The resourceful disposal of municipal solid waste incineration fly ash (MSWI FA) is a major global challenge. Inspired by volcanic eruptions, a method to lower the melting point of MSWI FA and to promote heavy metal chlorination volatilization was proposed. The introduction of river mud transformed melting products from crystalline to amorphous, obtaining glass products with low heavy metal residues. The volatilization efficiencies of Cu, Zn, Pb, and Cd reached 82.67 %, 100 %, 100 %, and 100 %, respectively, the heavy metal and salts were enriched in secondary ash. Alkali metal oxide induced the transformation of bridging oxygen to non-bridging oxygen, providing binding site for Cl in the form of Ca-Cl coordination and increasing the chlorine content. Then chlorine reacted with CuO converted from Cu2S and promoted the Cu volatilization. The outcomes fundamentally solved the problem of heavy metal residues in MSWI FA melting treatment, supporting resourceful and harmless treatment of MSWI FA.

DEVELOPMENT OF Na0.7Ni0.6Mn0.2Co0.2O2 EMPLOYING SOL-GEL APPROACH AS CATHODE MATERIAL FOR SODIUM ION BATTERIES

Layered structural materials based on alkali metal oxide - transition metal oxide compositions are under scrutiny as promising candidates for positive electrodes in sodium ion batteries. In this study, we have successfully synthesized Na0.7Ni0.6Mn0.2Co0.2O2 utilizing the sol-gel method in conjunction with calcination processes. The findings reveal that the synthesized material exhibits a P3 structure ideally suited for deployment as a positive electrode in sodium ion batteries. The material Na0.7Ni0.6Mn0.2Co0.2O2 demonstrates a peak specific capacity of 109.0 mAh g-1 at a current density of 5 mA g-1, retaining 66.8% of this capacity following 50 consecutive charge-discharge cycles at a current density of

Judd-ofelt analysis and luminescent properties of the Dy3+-doped borosilicate glass

B2O3-SiO2-WO3-Ga2O3 glasses doped with Dy3+ were synthesized using the high-temperature melting method. The effects of different B2O3/SiO2 ratios, different Dy3+ ions doping concentrations, and alkali metal oxides on the glass structure and optical properties were investigated through the test methods of X-ray diffraction, differential scanning calorimetry, Fourier infrared spectra, and photoluminescence spectra. The oscillator strength and intensity parameters were determined using Judd-Ofelt theory, and the optical band gap for both indirect and direct allowed transitions were calculated. The glasses exhibited optimal luminous performance when the B2O3/SiO2 ratio was 50:33, Dy2O3 doping concentration was 0.5 mol%, and K2O concentration was 4 mol%, excited by a wavelength of 388 nm. The CIE coordinates falling within the white light region suggest the potential application of these glasses in white solid-state lighting.

Study of Conduction Mechanisms in Alkali and Transition Metal Oxides Doped Borosilicate Glasses

Objectives: To synthesise a unique set of borosilicate glasses of composition, xLi2O + 0.15SiO2 + 0.45B2O3 + 0.05ZnO + (0.35 – x) WO3; (0.25 ≤ x ≤ 0.34) and to investigate conduction mechanisms. Methods: Glasses were synthesized by melt quenching technique. From the XRD spectra samples were conformed to be non-crystalline in nature. Density has been measured by following Archimedes principle and is found to decrease with Li2O mole fractions in the range 2.900 gm/cm3 – 2.495 gm/cm3. DC-conductivity was measured for the temperature range 303K – 525 K using two probe technique. Findings: It was found that these glasses behave like semiconductors in terms conductivity variation with temperature. Conductivity decreased with Li2O content up to 0.33 mole fractions and increases for higher mole fractions. High temperature conductivity variation i.e., above ϴD/2 (ϴD = Debye’s temperature) is found to follow the Mott’s small polaron hopping (SPH) model. Activation energy for conduction above ϴD/2 is found to be in the range 0.282 eV-0.702 eV. Decrease of conductivity and activation energy with increase of Li2O content has been explained in terms of dynamic nature of network and formation of cation-polaron neutral entities. The conductivity below ϴD/2 has been found to follow Mott’s variable range hopping (VRH) models. The density of states at Fermi level derived from Mott’s VRH are found to be of the order of 1023 eV-1cm-3 which are in close agreement with reported ranges for transition metal oxides doped glasses. Novelty: A unique set of mixed conducting borosilicate glasses have been prepared and investigated thoroughly for conduction mechanisms. Keywords: Borosilicate glasses, Density, Conductivity, Activation energy, Density of states

Effect of Deashing Treatment on Ash Fusion Characteristics of Biochar from Bamboo Shoot Shells.

To investigate the influence of deashing on fusion characteristics, a combined method of water and acid washing with different sequences (water washing followed by acid washing, and acid washing followed by water washing) was used to treat the biochar of bamboo shoot shells (BBSSs). The results show that deashing decreased the K content of the biochar from 50.3% to 1.08% but increased the Si content from 33.48% to 89.15%. The formation of silicates and aluminosilicates from alkali metal oxides with silicon was an inevitable result of ash phase transformation at the high temperatures used to improve the fusion temperature (>1450 °C). The thermochemical behavior of ash mainly occurs at 1000 °C. The deashing treatment significantly reduced the reaction intensity during the high-temperature process. This significantly increased the thermal stability of the ash. The adjustment of the washing sequence had a slight impact on the chemical compositions, but the differences in ash micromorphology were obvious. Deashing treatments with different washing sequences can significantly improve ash fusion properties effectively and reduce the risk of scaling, slagging, and corrosion. This study provides a new and reasonable strategy for the deashing of biochar to commercially utilize bamboo shoot shell resources.

Relational model of compositions of enamel coatings and sintering temperature based on back propagation neural network algorithm

Declining the sintering temperature of enamel coatings is traditionally by reducing the content of network-forming agents (such as SiO2) and increasing the content of flux (for example, alkali metal oxides), which will lower the density of the [-Si-O-] network structure, and adversely affect the corrosion resistance of enamel coatings. To ensure a low sintering temperature of enamel coatings as much as possible under a high SiO2 content, it is essential to develop novel enamel coating formulas. However, abundant compositions of enamel coatings cause enormous verification workloads. To address this issue, this paper establishes a relational model of the compositions of enamel coatings and the sintering temperature using the back propagation (BP) neural network algorithm and proposes a formula that meets the requirement of lower the sintering temperature under a high SiO2 content. When the SiO2 content is 55 %, the sintering temperature can be diminished to around 400 °C. Furthermore, the influences of common enamel components on the sintering temperature are identified in this paper using the sensitivity algorithm. The obtained general law of formulas is that the total weight value of the formula at low sintering temperatures should be around −0.3. This paper can provide valuable theoretical guidance for subsequent research and expand the application range of enamel coatings.