Addition Of Metal Oxides Research Articles

Exploring the influence of metal oxides on the pyrolytic behavior and decomposition mechanism of the green gas generating agent 5-Aminotetrazole

5-Aminotetrazole (5AT) is widely used as a green gas-generating agent in fire extinguishers, but it exhibits low combustion stability. To enhance its combustion rate and modify gas production performance, this study investigated the catalytic effects of adding different metal oxides (Bi2O3, PbO, TiO2, and CoO) on its pyrolysis process and decomposition mechanism. The pyrolysis behavior and pyrolysis products of 5AT were studied by simultaneous thermal analyzer (thermogravimetry - differential thermal analysis, TG-DTA) and TG-FTIR/MS (mass spectrometry and fourier transform infrared spectroscopy) hyphenated instrument. Isoconversional methods were used to calculated kinetic parameters, and reaction mechanism was also speculated by combining the experimental and calculational results. The experimental results indicated that Bi2O3, PbO, TiO2 and CoO have minimal impact on the ring opening reaction process of 5AT, but they catalyzed the polymer decomposition process of 5AT, especially CoO. Consequently, the addition of metal oxides as catalysts to 5AT holds significant potential for improving its thermal safety and enhancing its suitability as a solid propellant gas generator.

Investigating the electronic properties and reactivity of polyaniline emeraldine base functionalized with metal oxides

Due to its appealing qualities, such as its miniature size and the ability to modify physical properties through chemical synthesis and molecular design, polymer material offers considerable advantages over traditional inorganic material-based electronics. Conjugate polymers are particularly interesting because of their molecular design capabilities, which enable the synthesis of conducting polymers with a variety of ionization potentials and electron affinities (EA), and their ability to control the energy gap and electronegativity (χ). Accordingly, density functional theory (DFT) at the B3LYP/SDD model was used to present possible interactions between polyaniline (PANi) and both alkali and heavy metal oxides. Total dipole moment (TDM), HOMO–LUMO band gap energy (ΔE), ionization energy (IE), EA, chemical hardness (η), chemical potential (μ), electrophilicity index (ω), chemical softness (S), and χ are calculated. TDM of PANi increased while ΔE decreased due to functionalization. The distribution of electronic charge density in molecular electrostatic potential (MESP) maps together with the results of ω reflected the electrophilic nature. The obtained results confirmed that the addition of metal oxides significantly improves the TDM, ΔE, and reactivity descriptors. A strong correlation between the experimental and calculated IR spectra was observed. Additionally, PANi–2MgO and PANi–2MnO model molecules exhibited the highest reactivity. Accordingly, PANi functionalized with MgO and MnO are promising candidates for energy storage devices.

Easy fabrication of PVA-CaO-CuO composite films for efficient photocatalyst: Towards distinct luminescence property, morphology and thermal stability

PVA-CuO-CaO composites in the film form were synthesized by loading the different compositions of metal oxides (CuO and CaO) ranging from 5 to 25 wt% via solvent casting approach. The applications of the prepared composites as photocatalysts were assessed together with the findings of photoluminescence (PL) characteristics, optical clarity, morphological features, and thermal properties. Fourier-transformed infrared (FTIR), ultraviolet–visible (UV–vis), and photoluminescence (PL) spectra exposed the systematic and viableintegration of metal oxides (CuO-CaO) into the PVA matrix in PVA-CuO-CaO composites. The modifications of PL property of PVA-CuO-CaO composites were recognized rather than bare PVA. The prepared composite films exhibited excellent optical transparency irrespective of the addition of metal oxides. Both TGA and DSC data showed that the thermal properties of the composites could be significantly enhanced by incorporating CuO and CaO. DSC measurements demonstrated that the Tm of PVA-CuO-CaO composites is improved substantially (∼7 to 38 °C) than PVA. The distinct morphological structures of the obtained composites were identified with variations in CuO and CaO addition remaining diameter in the 30–200 nm range. The photocatalytic assessments revealed the better photocatalytic performance of PVA-CuO-CaO composites for removing methylene blue (MB) than bare PVA. By eliminating organic pollutants, the current study may provide a new perspective on the preparation of water-processable PVA-CuO-CaO photocatalysts for wastewater management.

Reduction of Emission and Fuel Consumptions based on Mingled Nano Additives in Biodiesel

Using the lipids identified as well as extra residual cooking oil, vegetable, and animal fats, bio-diesel a substitute for fuels derived from petroleum can be produced. Since the 1970s oil crisis, there has been a resurgence of interest in using biodiesel as a fossil fuel substitute due to the fuel's rapidly rising prices, availability uncertainties, and growing environmental and greenhouse gas (GHG) concerns.To produce biodiesel, glycerin and fat or vegetable oil are separated chemically through a process termed transesterification. Glycerin, a valuable byproduct that is typically sold to be used in soaps and other products, and methyl esters, the chemical term for biodiesel, are the two products left over from the process. The industrial term for diesel derived from petroleum, petro diesel, and biodiesel have similar viscosities. Due to the nearly zero sulfur content,it is recommended to be used as an additive in diesel oil formulations to improve the lubricity of pure ultra-low sulfur diesel (ULSD).The current work focuses heavily on reducing emissions and fuel consumption in automobiles. In addition to lowering pollutants and fuel consumption, the transition metal oxide (Copper oxide) additions in nanocrystalline particle form aid in molecular combustion. To create a stable Nano fluid, soap nut biodiesel is combined with metal oxide additive and ultrasonicated. For our experimental investigation, single cylinder, air cooled, constant speed Kirloskar engine is used. The reduction of hydrocarbon (HC), carbon monoxide (CO) and nitrogen oxide (NOx) emissions is investigated. The highest break power of the biodiesel employed in the study is 3.82 KW, greater than the typical diesel's 3.23 KW. The result shows improved engine efficiency, reduced emissions, and better brake thermal efficiency.

Enhancing PA-PBI Composite Membrane with Metal Oxides Incorporation for HT-PEMFC Operating Above 200 oc

High-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) are renowned for their excellent CO tolerance and rapid reaction kinetics [1]. Among the various membrane types, phosphoric acid doped polybenzimidazole (PA-PBI) membranes, phosphoric acd (PA) acts as a proton conductor, facilitating proton transfer through hydrogen bond rearrangement between PA molecules and the PBI backbone [2]. However, the operating temperature of PA-PBI membrane-based HT-PEMFC is constrained by the condensation of PA, limiting their use to below 180 oC and posing a significant challenge for achieving efficient operation above 200 oC.Recent research endeavors have focused on enhancing PA-PBI membranes by incorporating metal oxides to extend their operational temperature range beyond 180 oC. The addition of metal oxides into PA solution leads to the formation of metal hydrogen phosphate, effectively preventing PA evaporation at elevated temperatures ( > 180 oC) and maintaining membrane performance without degradation. Furthermore, the presence of metal oxides facilitates proton transfer to the metal hydrogen phosphate surface, thereby improving ionic conductivity even at temperatures exceeding 200 oC.In this study, we present the synthesis of poly(2,2’-(1,4-phenylene)-5,5’ bibenzimidaozle) (pPBI) composite membranes through an in-situ method, where various metal oxides (SnO2, TiO2, ZrO2) are introduced into the synthesis solution. Through systematic investigation, we evaluate the impact of these metal compounds on fuel cell performance and durability at high temperatures exceeding 200 oC. Our findings shed light on the potential of metal oxide-modified PA-PBI composite membranes for advancing the performance and reliability of HT-PEMFCs in demanding operating conditions.

Single-Layer Graphene Incorporation in PEMFCs for Enhancing Membrane Durability and Its Impact on Catalyst Layer Properties

In the realm of heavy-duty vehicle (HDV) applications, the primary technological hurdle facing Proton Exchange Membrane Fuel Cells (PEMFCs) is durability. HDVs necessitate an exceptional lifespan of 1 million miles, 6.5 times longer than their light-duty vehicle (LDV) counterparts1. Two pivotal components, the polymer electrolyte membrane and the catalyst layer, have been identified as crucial for achieving durability.Chemical degradation of perfluorinated polymer electrolyte membranes, e.g., Nafion, is attributed to the small but finite H2 and O2 gas crossover through the polymer electrolyte from the anode and cathode, respectively. These crossover gases generate active oxygen radical species, such as -OH and -OOH, which attack the polymer backbone or side chains. Additionally, Pt particles have been observed migrating into the membrane, creating another site for radical formation2. This process results in pinhole formation, membrane thinning, carbon support, and platinum catalyst degradation3. Analyzing effluent water for fluoride ion release rate is the primary method for evaluating the membrane degradation rate.Recent approaches involve the utilization of cerium and manganese additives to mitigate radical formation and chemical degradation induced by radicals. However, a limitation associated with metal and metal oxide additives is their propensity for migration and agglomeration, causing alterations in membrane morphology and subsequently affecting proton conductivity. As an alternative to metal oxide additives, defect-free monolayer graphene, which is chemically stable, has been explored. It has been discovered that defect-free monolayer graphene is impermeable to all atoms and molecules but permeable to protons4. The incorporation of monolayer graphene with small defects may significantly reduce gas crossover while allowing the transport of water and protons. We also hypothesize that the graphene layer will serve as a barrier to catalyst ion transport (Pt2+ or Co2+) into the membrane, which can have an interesting impact on catalyst electrochemically active surface area (ECSA) and catalyst layer ionic resistance.In this study, we showcase the enhanced chemical durability of the Nafion membrane by introducing an atomically thin chemical vapour deposition (CVD) single graphene layer onto the PEM. Accelerated stress tests (AST), such as open circuit voltage (OCV) in H2 /Air at 30 %RH and 80oC, are used to evaluate the chemical durability of membranes within a relatively short time. Water collected from both the anode and cathode side were analyzed for fluoride emission rate and sulphate content. Catalyst layer ECSA, H2 crossover, membrane and catalyst layer ionic resistance were monitored every 24-28 hours. The insights gained from these results will be invaluable in assessing the promise and the challenges of employing 2D-material-modified PEM for HDV applications. Reference: (1) Cullen, D. A.; Neyerlin, K. C.; Ahluwalia, R. K.; Mukundan, R.; More, K. L.; Borup, R. L.; Weber, A. Z.; Myers, D. J.; Kusoglu, A. New Roads and Challenges for Fuel Cells in Heavy-Duty Transportation. Nat. Energy 2021, 6 (5), 462–474. https://doi.org/10.1038/s41560-021-00775-z.(2) Kim, T.; Lee, H.; Sim, W.; Lee, J.; Kim, S.; Lim, T.; Park, K. Degradation of Proton Exchange Membrane by Pt Dissolved/Deposited in Fuel Cells. Korean J. Chem. Eng. 2009, 26 (5), 1265–1271. https://doi.org/10.1007/s11814-009-0212-9.(3) Inaba, M.; Kinumoto, T.; Kiriake, M.; Umebayashi, R.; Tasaka, A.; Ogumi, Z. Gas Crossover and Membrane Degradation in Polymer Electrolyte Fuel Cells. Electrochim. Acta 2006, 51 (26), 5746–5753. https://doi.org/10.1016/j.electacta.2006.03.008.(4) Hu, S.; Lozada-Hidalgo, M.; Wang, F. C.; Mishchenko, A.; Schedin, F.; Nair, R. R.; Hill, E. W.; Boukhvalov, D. W.; Katsnelson, M. I.; Dryfe, R. A. W.; Grigorieva, I. V.; Wu, H. A.; Geim, A. K. Proton Transport through One-Atom-Thick Crystals. Nature 2014, 516 (7530), 227–230. https://doi.org/10.1038/nature14015.

The influence of Nano-composite metal oxides on the thermal decomposition performance of RDX

Abstract In order to investigate the effect of nano-composite metal oxides on the thermal decomposition performance of hexogen (RDX), this study prepared nano nickel-iron (NFO), nickel-cobalt (NCO), and nickel-iron-cobalt (NFCO) composite oxides by liquid-phase co-precipitation method. The precursor of Prussian blue analogs was synthesized and then calcined in air at 600°C. The addition of nano nickel-iron (NFO), nickel-cobalt (NCO), and nickel-iron-cobalt (NFCO) composite oxides to RDX has a significant impact on its thermal decomposition process. The peak exothermic temperatures were delayed by 8.4°C, 8.5°C, and 8.3°C, respectively, after adding the nano-composite metal oxides, and the heat release also increased to a certain extent. Among them, the addition of NCO nano-composite metal oxides had the greatest impact on the exothermic peak temperature of RDX, while the addition of NFCO nano-composite metal oxides resulted in the largest increase in heat release. This indicates that the addition of NFO, NCO, and NFCO to RDX altered the thermal decomposition reaction process to some extent.

Impacts of metal oxide crystalline structure on the decomposition of solid propellants under combustion heating rates

Ammonium perchlorate (AP) has been the oxidizer of choice for composite solid propellants for decades and has been the object of decomposition studies for safety monitoring. Typically, studies perform differential scanning calorimetry (DSC) or thermogravimetric analysis (TGA) to show how metal oxides (MO) commonly incorporated into propellants alter AP decomposition rates and completeness of reaction. Most past decomposition work studies temperatures below the crystal phase transition (240°C) from orthorhombic phase to cubic, which impose internal stresses within the lattice of AP particles. Phase change induces a partial decomposition, which does not follow a shrinking core behavior; instead, it develops a network of pores up to a few microns in size throughout. During low-temperature decomposition, particles lose approximately 30-40 % of their mass. Simultaneous DSC/TGA (STA) use low heating rates for combustion environments but offer information on MO's catalytic and electron transport modifications. This work demonstrates how the crystalline morphology MO additives mechanistically alter the combustion properties of composite propellants by identifying modes for promoting decomposition in AP and HTPB. MO morphology determines the electron structure of the molecule, which sets the band gap properties of the particles. This study evaluated different morphologies and a range of MOs to identify the most active MO for decomposing A.P. Kissinger analysis was applied using STA data at heating rates of 10-, 20-, and 30-°C/min revealing significant shift in the high-temperature decomposition with a range of metal oxides. Higher heating rates were evaluated using CO2 laser ignition to identify the time to first gas using the MO that offers the best heat absorption, such as the aluminum oxides. This higher heating rate was found do more accurately represent the changes in the combustion rates in the final propellant mixture. Additionally, it was shown that electron transport additives like CuO show the most significant impact on combustion, and thermal absorbers offer the lowest impact on AP/HTPB combustion. This understanding offers a new approach to propellant design not previously presented and suggests future testing for tailoring the use of metal oxides in propellants.

Elucidating the influence of metal oxides on pyrolytic behaviors and combustion performance of green gas generating agent 5-Aminotetrazole/Sr(NO3)2

5-Aminotetrazole/strontium nitrate (5AT/Sr(NO3)2) propellant is widely utilized as green gas generating agent in fire extinguishers. To enhance the combustion rate and modify the gas production performance of 5AT/Sr(NO3)2 propellant, this study investigated the catalytic effects of adding different metal oxides (Bi2O3, PbO, TiO2, and CoO) on its pyrolysis and combustion process. The pyrolysis behavior, pyrolysis mechanism and combustion performance of 5AT/Sr(NO3)2 propellants were studied by using thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning caborimetry (DSC), mass spectrometry (MS), fourier transform infrared spectroscopy (FTIR) analysis and closed bomb vessel tests. Experimental results indicated that Bi2O3 and PbO predominantly facilitated the thermal decomposition process of 5AT, while TiO2 and CoO primarily catalyzed the thermal decomposition of Sr(NO3)2. Certainly, the addition of metal oxides as catalysts to 5AT/Sr(NO3)2 propellant holds significant potential for improving the application as a gas generating agents in fire extinguishers.

Improving the Performance of a Co-CeO2 Catalyst for Hydrogen Production via Water Gas Shift Reaction by Addition of Transition Metal Oxides

Improving the Performance of a Co-CeO₂ Catalyst for Hydrogen Production via Water Gas Shift Reaction by Addition of Transition Metal Oxides

The long-term effect of Fe3O4 in activating persulfate to degrade refractory organic contaminants for groundwater remediation

Highly reactive metal-based materials for persulfate activation have been intensively studied for treatment of groundwater contaminants. However, the long-term efficacy of the readily available metal-oxide additives, which can be more important for groundwater remediation practice, has received minimal attention. In this study, the results of preliminary experiments demonstrated that Fe3O4 was superior to seven metal oxides (MnO, Fe2O3, MnO2, CuO, Cu2O, CoO, NiO) and zero-valent iron for activating persulfate to degrade 1,2-dichloropropane. Experiments were then conducted to examine the long-term effects of Fe3O4-activated persulfate degradation of four contaminants, i.e., 1,2-dichloropropane, 1,1,2-trichloroethane, 1,4-dioxane, and methyl tert-butyl ether (MTBE). The system achieved complete removal of the contaminants in approximately 72 h, which was contrasted to a removal efficiency less than 35 % in the absence of Fe3O4. Highly efficient use of persulfate for contaminant degradation was observed with insignificant production of soluble Fe before depletion of the contaminants. Production of sulfate radical (SO4•−) and hydroxyl radical (HO•) via surface reactions was likely the process responsible for the degradation. Ten and five cycles of 1,2-dichloropropane degradation experiments were conducted in deionized water and actual groundwater. These results suggested that the Fe3O4 could retain 80 % of its original activation capacity after 5 cycles, but partial oxidation of Fe3O4 eventually occurred. Production of some Cl-containing degradation-resistant intermediates from degradation of 1,2-DCP was observed and could be mitigated under specific conditions. The results show that Fe3O4 has a long-term effect in activating persulfate for contaminant degradation, which is promising for applications such as permeable reactive barriers and nanoparticle injection for groundwater remediation.

The effect of ZnO and MnO2 as sintering aids in the preparation of potassium sodium niobate ceramics and electrical characterizations

Potassium sodium niobate (KNN) is an environmentally compatible piezoelectric material for substituting harmful lead-based ceramics. KNN-based ceramics have excellent piezoelectric properties with high Curie temperature. But, KNN faces difficulties during the processing like volatilization of alkali elements, chemical inhomogeneity, low densification, etc. The objective of this research is to investigate the impact of certain metal oxides additions like ZnO and MnO2 as sintering aids to solve the problems of the preparation and hence study the structural and electric properties of K0.5N0.5NbO3 (KNN) ceramics. ZnO and MnO2 added potassium sodium niobate, K0.5N0.5NbO3 was prepared by using the ceramic method. The prepared samples were sintered at 1000 °C for 2h conventionally. The structural properties of the ceramics have been analyzed by using X-Ray Diffractometer. The study demonstrates the formation of the orthorhombic-symmetric perovskite phase in all the prepared samples. The microstructural behavior of the ceramics has been characterized by techniques such as scanning electron microscopy (SEM) and compositional properties were studied by energy dispersive x-ray (EDAX). The effects of metal oxide additions on the electronic properties such as dielectric constant, dielectric loss, impedance properties, Nyquist plot, etc., were studied. The results have been analyzed and discussed in the paper.

Alkaline Earth Metal Oxide Supported on Zeolite as a Heterogenous Basic Catalyst for Clean Fuel (Biodiesel) Production: A Mini Review

The depletion of fossil fuel reserves, worsening greenhouse gas effects, and global warming issues have driven the development of renewable energy sources, such as biodiesel. Biodiesel is as an alternative fuel to petrodiesel, typically produced through a transesterification reaction of triglycerides and alcohol in the presence of a catalyst. Alkaline earth metal oxide supported on zeolite are heterogeneous basic catalysts that are widely used in biodiesel synthesis. The addition of alkaline earth metal oxide to zeolite enhances the distribution of active sites, leading to an increase in catalytic activity. Zeolite is widely used as catalyst support due to its high surface area, good thermal stability, shape selectivity, and porous structure. This article presents recent developments in the synthesis and application of alkaline earth metal oxide supported on zeolite for transesterification reaction. The challenges and prospects of catalyst development are also discussed. This article aims to provide information and inspire the development of alkaline earth metal oxide supported on zeolite as a basic catalyst for biodiesel synthesis.

Propylene Production via Oxidative Dehydrogenation of Propane with Carbon Dioxide over Composite MxOy-TiO2 Catalysts.

The CO2-assisted oxidative dehydrogenation of propane (ODP) was investigated over titania based composite metal oxides, 10% MxOy-TiO2 (M: Zr, Ce, Ca, Cr, Ga). It was found that the surface basicity of composite metal oxides was significantly higher than that of bare TiO2 and varied in a manner which depended strongly on the nature of the MxOy modifier. The addition of metal oxides on the TiO2 surface resulted in a significant improvement of catalytic performance induced by a synergetic interaction between MxOy and TiO2 support. Propane conversion and propylene yield were strongly influenced by the nature of the metal oxide additive and were found to be superior for the Cr2O3-TiO2 and Ga2O3-TiO2 catalysts characterized by moderate basicity. The reducibility of the latter catalysts was significantly increased, contributing to the improved catalytic performance. This was also the case for the surface acidity of Ga2O3-TiO2 which was found to be higher compared with Cr2O3-TiO2 and TiO2. A general trend was observed whereby catalytic performance increased significantly with decreasing the primary crystallite size of TiO2. DRIFTS studies conducted under reaction conditions showed that the adsorption/activation of CO2 was favored on the surface of composite metal oxides. This may be induced by the improved surface basicity observed with the MxOy addition on the TiO2 surface. The Ga2O3 containing sample exhibited sufficient stability for about 30 h on stream, indicating that it is suitable for the production of propylene through ODP with CO2 reaction.

Cold-Sintered ZnO Ceramic Composites Co-Doped with Polytetrafluoroethylene and Oxides.

Grain boundaries play a significant role in determining the performance of ceramic-based materials. The modulation of interfacial structures provides a promising approach to improve the physicochemical and electrical properties of ceramic materials. In this work, the grain boundary structures of ZnO-based ceramics were manipulated by incorporating polytetrafluoroethylene (PTFE) and metal oxides through the cold sintering process (CSP). It was found that the grain size of ZnO-based ceramics can be effectively reduced from 525.93 nm to 338.08 nm with an addition of PTFE and metal oxides of CoO and Mn2O3. Microstructural results show that most of the PTFE phase and metal oxides were distributed along the grain boundaries, which may lead to the increased grain boundary resistance from 1.59 × 106 ohm of pure ZnO to 6.21 × 1010 ohm of ZnO-based ceramics doped with PTFE and metal oxides, and enhanced Schottky barrier height from 0.32 eV to 0.59 eV. As a result, the breakdown field and nonlinear coefficient of the ZnO-based ceramics were improved to 3555.56 V/mm and 13.55, respectively. Therefore, this work indicates that CSP presents a feasible approach to design functional ceramic composites through the integration of polymer and metal oxides.

Flow and heat transfer characteristics of microencapsulated phase change material slurry in bonded triangular tubes for thermal energy storage systems

Three nanoscale metal oxides composed of nano TiO2, nano Al2O3, and nano MgO were added to the phase change microcapsule slurry for optimising the heat transfer behaviour. The thermal and rheological properties of the resulting microencapsulated phase change materials (MPCMs) and microencapsulated phase change material slurries (MPCSs) were characterized to determine the effects of added metal oxides in optimising the performance of MPCSs. The impacts of factors like metal oxides, concentrations, and flow rates on the heat transfer behaviour of MPCSs were investigated by forced convective heat transfer experiment with various working conditions. Compared to 6 wt% MPCSs, the heat transfer coefficients (hx) of 6 wt% slurries containing 1 wt% TiO2, 1 wt% Al2O3, and 1 wt% MgO increased by 4.0 %, 2.5 %, and 7.13 %, respectively. Nano-MgO showed the most significant heat transfer enhancement effect on MPCSs. Moreover, the heat transfer performance gradually enhanced as a function of the concentration for nano MgO. Overall, the addition of metal oxides enhanced heat transfer by increasing the thermal conductivity of the slurry, as well as improved the micro-convection effect. The proposed MPCSs are promising for applications in solar photovoltaic/thermal (PV/T) systems, chip cooling, thermal management, buildings, and automotive cooling.

Electronic properties and molecular electrostatic potential mapping of edge functionalized GQDs with ZnO, CuO, and TiO2

Graphene quantum dots (GQDs) are a cutting-edge material that has excellent electrical, thermal, and mechanical characteristics, as well as minimal toxicity and powerful photoluminescence. These unique properties give GQDs the ability to be used in different electrical, optical, and optoelectronic applications. GQDs with hexagonal and triangular cuts with armchair and zigzag ends (ATRI, AHEX, ZTRI, and ZHEX) were decorated with different metal oxides such as ZnO, CuO, and TiO2. Metal oxides (MOs) were employed to tune the band gap and electrical properties of GQDs for usage in certain applications. The influence of functionalization on the GQDs electronic properties was examined utilizing HOMO–LUMO orbital distribution and molecular electrostatic potential (MESP) mapping calculations. The model structures were calculated using density functional theory (DFT: B3LYP/ LanL2DZ). The band gap energies of AHEX C42, ZHEX C54, ATRI C60, and ZTRI C46 were found to be 3.508, 2.886, 3.177, and 0.305 eV, respectively. The findings show that addition of MOs increases the total dipole moment (TDM) while decreasing the band gap energy ∆E. The most effective metal MO on GQDs band gap and electronic properties was TiO2, which enhanced the band gap energy ∆E for AHEX C42-TiO2, ZHEX C54-TiO2, ATRI C60-TiO2, and ZTRI C46-TiO2 to 0.391, 0.530, 0.287, and 0.250 eV, respectively. Accordingly, GQDs seem to be excellent for certain applications. Accordingly, GQDs functionalized with ZnO could be used for sensors, due to their increased responsiveness and energy gap variation while GQDs functionalized with TiO2 is excellent to be applied as optoelectronic materials.

Insights on the additive formulation for the energy-efficient production of fused calcium magnesium phosphate fertilizer from waste sludge

The production of the fused calcium magnesium phosphate fertilizer (FCMP) from sludge is a sustainable alternative to phosphate ore route. However, the distinct compositions of sludge and extensive energy input make the process under great uncertainty for the commercialization. In this study, a new method was proposed to determine the optimal addition amount of CaO and MgO to sludge, realizing the high phosphorus (P) availability and simultaneously reducing the melting point of the system for energy saving. The effect of P content on the product structure and P availability was first investigated at different metal oxide addition levels. The modified non-bridging oxygen to tetrahedral cation equation (NBO/T) was used to establish the linear relationship between the NBO/T and the P availability. The threshold value of the modified NBO/T ≥ 2.3 guaranteed a P-availability beyond 90%. Further, FTIR and Raman spectra showed that there was a strong correlation between the modified NBO/T and the actual glass structure. Finally, on the reference value of NBO/T = 2.30, the system exhibited the minimum melting point at 1292 °C when MgO/CaO = 0.83. This method offers a powerful tool to guide the optimal amount of CaO and MgO addition to sludge ash by simple calculations.

Enhancing the thermoelectric characteristics of thermoelectric cement matrix composites by (Ca0.87Ag0.1La0.03)3Co4O9 binary metal oxide

In recent years, the expansion of urban buildings has caused buildings and road surfaces to absorb large amounts of heat energy during the summer, exacerbating the heat island effect. The application of thermoelectric cement matrix composites can convert the surface heat energy of roads and buildings into electrical energy. The performance enhancement for thermoelectric cementitious composites is shown by the addition of carbon materials and metal oxides, and great research progress has been made. The current research on metal oxides as functional fillers is mostly for monomeric metal oxides and less for binary metal oxides. In this study, (Ca0.87Ag0.1La0.03)3Co4O9 was produced by co-precipitation, and a strategy to enhance the thermoelectric characteristics of thermoelectric cement matrix composites was suggested. To reduce surface defects, this approach involved pretreating the (Ca0.87Ag0.1La0.03)3Co4O9 with hydrochloric acid. Using acid etching to transform the metal oxides' morphology from granular to layered, the interface was expanded, improving carrier scattering and, in turn, the Seebeck coefficient. The thermoelectric characteristics of cement substrates with low content, acid-treated (Ca0.87Ag0.1La0.03)3Co4O9, and a fixed mass fraction of expanded graphite were compared to a control group without acid treatment. The results showed that the method resulted in an increase of the Seebeck coefficient to −100.5 μV/°C and the introduction of nano-silver inclusions caused an increase of the conductivity to 13.5S/cm. The improvement of the Seebeck coefficient and electrical conductivity has increased the power factor to 13.8μWm−1K−2. This study proposes a method to improve the thermoelectric properties of cement matrix composites.

Influence of the addition of different metal oxides on physicochemical and biological properties of calcium fluorosilicate/PCL bone cement

Calcium silicate cements have been greatly developed in the last decades through different approaches. Among these approaches, the inclusion of antibacterial agents or addition of metal oxides. Herein, calcium silicate cement containing fluorine (CFS) was developed from sodium fluorosilicate precursor for the first time using chemical perception method. Afterwards, metal oxide Bi2O3 or MgO or ZrO2 was individually mixed with CFS powder and blended together using Polycaprolactone polymer (PCL). The cement mixtures were characterized using DSC, XRD, FTIR and SEM/EDX to determine the effect of metal oxide on the pure CFS. Furthermore, mechanical, antibacterial and cell viability properties were evaluated for the developed CFS mixture cements. Moreover, these CFS mixture cements were implanted in male Wistar rats to determine the effect of metal oxides on the rate of bone reformation. The findings of physicochemical and morphological characterization showed no remarkable effects on the pure CFS after mixing with each metal oxide. However, enhanced compressive strengths (up to 104.07N/cm2), antibacterial activity and cell viability (up to 96%) were achieved for the CFS cement mixtures. Finally, the in vivo studies confirmed the biocompatibility of the CFS cement mixtures and especially those mixed with Bi2O3 or ZrO2. Therefore, this study supports that CFS blends with Bi2O3 or ZrO2 can be novel promising cementing materials for bone restoration.