Solution Combustion Synthesis of Nanoscale Materials

A new approach in the one-step synthesis of α-MnO2 via a modified solution combustion procedure

Manganese oxides were synthesized systematically via the solution combustion procedure using two kinds of fuels, namely glycine and urea. The influences of the type of fuel and the fuel ratio were deeply investigated to explain the phase evolution and morphology of the product. The synthesized nanostructured powder was characterized by X-ray diffraction, particle size analysis, and FESEM. Furthermore, the thermodynamic aspects of all the synthesis reactions were studied by the calculation of the adiabatic temperature. Various manganese oxides, such as MnO, Mn₃O₄, Mn₂O₃, and MnO₂, were obtained by varying the fuel ratio from 0.15 to 2. It was found that decreasing the fuel ratio promoted the formation of MnO₂ by declining the combustion temperature and reductive conditions of the system. However, α-MnO₂ could be simply achieved by adding KNO₃ in a modified solution combustion process under fuel-lean conditions. Further heat treatment of the product was found to increase the crystallinity of the α-MnO₂ nanoparticles.

Luminous LaAlO3 :Dy3+ perovskite nanomaterials: Synthesis, structural and luminescent characteristics for WLEDs

Single-phase perovskite LaAlO₃ :Dy³⁺ phosphor was synthesized via gel-combustion method at 600 °C utilization Hexamethylenetetramine (HMT) as a fuel. Further calcination of the samples was carried out (800 and 1000 °C) to investigate the resultant effect on the crystalline and luminescence behaviour. The crystal structure having cubic unit cell (space group Pm3̅m) was examined via Rietveld refinement using X-ray diffraction (XRD) data. Additionally, Debye-Scherrer's and Williamson-Hall equations were applied to determine other structural features. The particle size and morphology of phosphors were evaluated using Transmission electron microscope (TEM). Diffraction measurements were supported by the various metal-oxygen vibration modes studied with the help of Fourier transform infrared (FTIR) spectroscopy. Energy dispersive X-ray analysis (EDX) verified the chemical composition of synthesized sample. Luminescence spectra of LaAlO₃ :Dy³⁺ phosphors exhibited intense bands for ⁴ F_9/2 → ⁶ H_15/2 (482 nm, bluish region) and ⁴ F_9/2 → ⁶ H_13/2 (574 nm, yellowish region) transitions. Commission Internationale de L'Eclairage (CIE) and Correlated Color Temperature (CCT) data confirmed cool-white emission of samples under UV-excitation. The interesting and advantageous luminescence characteristics of LaAlO₃ :Dy³⁺ phosphors make them potential materials for WLEDs.

Converting Chrysotile Nanotubes into Magnesium Oxide and Hydroxide Using Lanthanum Oxycarbonate Hybridization and Alkaline Treatment for Efficient Phosphate Adsorption

Magnesium oxide and hydroxide nanomaterials comprise a class of promising advanced functional metal nanomaterials whose use in environmental and material applications is increasing. Several strategies to synthesize these nanomaterials have been described but are unsustainable and uneconomic. This work reports on a processing strategy that turns natural magnesium-rich chrysotile into magnesium oxide and hydroxide nanoparticles via nanoparticle hybridization and an alkaline process while enabling La-based nanoparticles to coat the chrysotile nanotube surfaces. The adsorbent's resulting hybrid nanostructure had an outstanding capacity for phosphate uptake (135.2 mg P g^-1) and enhanced regeneration performance. Furthermore, the adsorbent featured wide applicability with respect to the coexistence of competitive anions and a broad range of pH conditions, and its high-performance phosphate removal from sewage effluent was also demonstrated. Spectroscopic and microscopic analyses revealed the scavenging ability of phosphate by the La-based and Mg-based nanoparticles and the multiple capture mechanisms involved, including surface complexation and ion exchange. This proposed approach expands chrysotile's potential use as a magnesium-rich nanomaterial and harbors great promise for the removal of pollutants in a variety of real-world settings.

Solution combustion synthesis: the relevant metrics for producing advanced and nanostructured photocatalysts

The current developments and progress in energy and environment-related areas pay special attention to the fabrication of advanced nanomaterials via green and sustainable paths to accomplish chemical circularity. The design and preparation methods of photocatalysts play a prime role in determining the structural, surface characteristics and optoelectronic properties of the final products. The solution combustion synthesis (SCS) technique is a relatively novel, cost-effective, and efficient method for the bulk production of nanostructured materials. SCS-fabricated metal oxides are of great technological importance in photocatalytic, environmental and energy applications. To date, the SCS route has been employed to produce a large variety of solid materials such as metals, sulfides, carbides, nitrides and single or complex metal oxides. This review intends to provide a holistic perspective of the different steps involved in the chemistry of SCS of advanced photocatalysts, and pursues several SCS metrics that influence their photocatalytic performances to establish a feasible approach to design advanced photocatalysts. The study highlights the fundamentals of SCS and the importance of various combustion parameters in the characteristics of the fabricated photocatalysts. Consequently, this work deals with the design of a concise framework to link the fine adjustment of SCS parameters for the development of efficient metal oxide photocatalysts for energy and environmental applications.

Light-induced Li extraction from LiMn2O4/TiO2 in a water-in-salt electrolyte for photo-rechargeable batteries

Photocharging of high-potential spinel LiMn₂O₄ is demonstrated by using a water-in-salt electrolyte and TiO₂ nanoparticles. In a developed half-cell system with an electron acceptor, Li extraction from LiMn₂O₄ proceeds under the illumination of UV-visible light at an estimated rate of ∼23 mA g^-1. This work paves the way for high-potential cathode materials in photo-rechargeable batteries.

Catalyst supports based on ZnO-ZnAl2O4 nanocomposites with enhanced selectivity and coking resistance in isobutane dehydrogenation

Development of coking resistant supports and catalysts for hydrocarbons conversion is challenging, especially when using such acidic materials as alumina. Apparently, this problem can be mitigated by using spinels that are less acidic, being, however, thermally stable. In this study, a series of ZnO-ZnAl₂O₄ nanocomposites with different ZnO loading were prepared by urotropine-nitrate combustion synthesis to be used as supports for isobutane dehydrogenation catalysts. The nanocomposites were characterized by XRD, SEM, N₂-physisorption analysis, EDS, H₂-TPR, TPD of NH₃ and tested in isobutane dehydrogenation. Spinels with small amounts of ZnO displayed higher acidity and specific surface areas than samples with a higher ZnO content (30-40 mol%). At the same time, the maximum activity and the lowest selectivity to by-products (CH₄ and C₃H₆) after 10 min of the reaction were observed for the nanocomposite containing 20 mol% of ZnO. The obtained nanocomposites have demonstrated better resistance to coking compared to commercial alumina.

Flame Retardant Coatings: Additives, Binders, and Fillers

This review provides an intensive overview of flame retardant coating systems. The occurrence of flame due to thermal degradation of the polymer substrate as a result of overheating is one of the major concerns. Hence, coating is the best solution to this problem as it prevents the substrate from igniting the flame. In this review, the descriptions of several classifications of coating and their relation to thermal degradation and flammability were discussed. The details of flame retardants and flame retardant coatings in terms of principles, types, mechanisms, and properties were explained as well. This overview imparted the importance of intumescent flame retardant coatings in preventing the spread of flame via the formation of a multicellular charred layer. Thus, the intended intumescence can reduce the risk of flame from inherently flammable materials used to maintain a high standard of living.

Short-Range Diffusion Enables General Synthesis of Medium-Entropy Alloy Aerogels

Medium-entropy alloy aerogels (MEAAs) with the advantages of both multimetallic alloys and aerogels are promising new materials in catalytic applications. However, limited by the immiscible behavior of different metals, achieving single-phase MEAAs is still a grand challenge. Herein, a general strategy for preparing ultralight 3D porous MEAAs with the lowest density of 39.3 mg cm^-3 among the metal materials is reported, through combining auto-combustion and subsequent low-temperature reduction procedures. The homogenous mixing of precursors at the ionic level makes the short-range diffusion of metal atoms possible to drive the formation of single-phase MEAAs. As a proof of concept in catalysis, as-synthesized Ni₅₀ Co₁₅ Fe₃₀ Cu₅ MEAAs exhibit a high mass activity of 1.62 A mg^-1 and specific activity of 132.24 mA cm^-2 toward methanol oxidation reactions, much higher than those of the low-entropy counterparts. In situ Fourier transform infrared and NMR spectroscopies reveal that MEAAs can enable highly selective conversion of methanol to formate. Most importantly, a methanol-oxidation-assisted MEAAs-based water electrolyzer can achieve a low cell voltage of 1.476 V at 10 mA cm^-2 for making value-added formate at the anode and H₂ at the cathode, 173 mV lower than that of traditional alkaline water electrolyzers.

Highly Durable and Efficient Ni-FeOx/FeNi3 Electrocatalysts Synthesized by a Facile In Situ Combustion-Based Method for Overall Water Splitting with Large Current Densities

Ni-/Fe-based materials are promising electrocatalysts for the oxygen evolution reaction (OER) but usually are not suitable for the hydrogen evolution reaction (HER). Herein, a durable and bifunctional catalyst consisting of Ni-FeO_x and FeNi₃ is prepared on nickel foam (Ni-FeO_x/FeNi₃/NF) by in situ solution combustion and subsequent calcination to accomplish efficient alkaline water splitting. Density functional theory (DFT) calculation shows that the high HER activity is attributed to the strong electronic coupling effects between FeO_x and FeNi₃ in the Janus nanoparticles by modulating ΔG_H* and electronic states. Consequently, small overpotentials (η) of 71 and 272 mV in HER and 269 and 405 mV in OER yield current densities (j) of 50 and 1000 mA cm^-2, respectively. The catalyst shows outstanding stability for 280 and 200 h in HER and OER at a j of ∼50 mA cm^-2. Also, the robustness and mechanical stability of the electrode at an elevated j of ∼500 mA cm^-2 are excellent. Moreover, Ni-FeO_x/FeNi₃/NF shows excellent water splitting activities as a bifunctional catalyst as exemplified by j of 50 and 500 mA cm^-2 at cell voltages of 1.58 and 1.80 V, respectively. The Ni-FeO_x/FeNi₃/NF structure synthesized by the novel, simple, and scalable strategy has large potential in commercial water electrolysis, and the in situ combustion method holds great promise in the fabrication of thin-film electrodes for different applications.

Pt-Anchored CuCrO2 for Low-Temperature-Operating High-Performance H2S Chemiresistors

Recent advances in heterogeneous catalysts indicate that single atoms (SAs), anchored/stabilized on metal oxide nanostructures, exhibit not only high catalyst atom efficiency but also intriguing reactivity and selectivity. Herein, isolated Pt SA-anchored CuCrO₂ (CCO) has been designed by a glycine-nitrate solution combustion synthesis (SCS) route. The density of isolated Pt SAs achieves the highest value of ∼100 μm^-2 for the 1.39 wt % Pt-anchored CCO sample, which results in the drastically boosted H₂S response characteristics, including a high response of 1250 (35 times higher than that of pure CCO) at 10 ppm H₂S and a low operating temperature of 100 °C. Except for CH₄S, the responses of a 1.39 wt % Pt-anchored CCO chemiresistor to diverse vapors with concentrations of 50-100 ppm are less than 2, exhibiting excellent selectivity. Various ex situ characterizations indicate that the spillover catalytic effect of Pt SA sites, other than the conventional sulfuration-desulfuration mechanism, plays a dominant role in the outstanding H₂S response characteristics.

Ni-CeO2 Catalyst with High Ni Loading Prepared by Salt-Assisted Solution Combustion for CO2 Methanation

An Ni-CeO2 catalyst with high Ni loading (50 wt.%) prepared by a salt-assisted solution combustion method was characterized by different methods and used for CO2 methanation. The specific surface area of the Ni-CeO2 catalyst prepared by salt-assisted solution combustion is 7 times that of the catalyst prepared by conventional solution combustion. The Ni-CeO2 catalyst prepared by salt-assisted solution combustion has smaller particle sizes of Ni and exhibits excellent activity at low temperatures. The high Ni loading and small Ni particle size can provide more metal Ni site and Ni-CeO2 interface, which help to improve the CO2 methanation performance.

Room-Temperature Postannealing Reduction via Aqueous Sodium Borohydride and Composition Optimization of Fully Solution-Processed Indium Tin Oxide Films

Solution-processed transparent conductive oxides offer the advantages of low-cost, high-throughput fabrication of electronic devices compared to the specific requirements of vacuum deposition techniques. However, adapting the current state of the art to ink deposition calls for optimization of the precursor ink composition and the postdeposition process. Solution processing of indium tin oxide films can be accomplished at reduced temperatures (250-400 °C) by annealing soluble precursor metal salts together with a fuel/oxidizer, causing an exothermic reaction with elevated local temperatures. Following layer-by-layer cycles of deposition and annealing, a postprocessing step is required via heating (300 °C) under a 5% H₂ reducing atmosphere. To address the discrepancy between the versatility of ink deposition and the limitations of controlled atmosphere postprocessing, here we investigate the effects of postprocess dipping in aqueous sodium borohydride at room temperature as an alternative, which allows for a completely solution-based process from ink to film. In addition to postprocessing, the solution composition was also optimized by removing the fuel additive and by adjusting the In/Sn content. Indium tin oxide (ITO) films were spin-coated and annealed in air at 250, 300, and 400 °C and characterized by UV/vis spectroscopy to obtain optical transmittance, atomic force microscopy to obtain film thickness and surface morphology, and a Hall effect system for electrical parameters. Additional data from X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) indicate that crystallinity is affected by the reducing environment. Results revealed an order-of-magnitude improvement of the Haacke figure of merit (FOM) from 4.3 × 10^-4 Ω^-1, 382 Ω/□ sheet resistance (R_s), and 84% transmittance (%T) for the traditional 9:1 In/Sn precursor ink with fuel additive followed by 300 °C of 5% H₂-furnace post-treatment compared to that of the optimized fully solution-processed 8.5:1.5 In/Sn ink without fuel followed by an ambient air at 25 °C dipping in aqueous sodium borohydride, leading to 3.0 × 10^-3 Ω^-1 FOM, 84.5 Ω/□ R_s, and 87%T including the glass substrate.

An effective natural mineral-catalyzed heterogeneous electro-Fenton method for degradation of an antineoplastic drug: Modeling by a neural network

In this study, the heterogeneous electro-Fenton method was used to remove Paclitaxel as an antineoplastic medicine. The cathode based on three-dimensional graphene (3DG) was applied as a gas diffusion electrode. The potential of five eco-friendly and recyclable iron minerals derived from nature (Magnetite, Siderite, Hematite, Limonite, and Pyrite) was investigated. Among the applied iron minerals, Pyrite showed the best, and Magnetite and Siderite showed good catalytic activity at pH 3.0. The current intensity of 300 mA, pH_i 7.0, Paclitaxel concentration of 3 mg L^-1, amount of Pyrite 4.5 g L^-1, and time of 120 min was the optimum condition of the process with the removal efficiency of 99.13% in the presence of Pyrite. Repeating the experiments eight times revealed the reusability of the prepared 3DG as a cathode. Also, using radical scavengers indicated the principal role of the hydroxyl radicals (OH) in the treatment process. Analysis of total organic carbon reached 77.64% mineralization of 3 mg L^-1 Paclitaxel at 360 min. Finally, ten by-products of small molecules were identified by gas chromatography-mass spectrometry device.

Electrochemical evaluation of porous CaFe2O4 anode material prepared via solution combustion synthesis at increasing fuel-to-oxidizer ratios and calcination temperatures

The drawbacks of common anodes in lithium-ion batteries (LIBs) and hybrid supercapacitors (HSCs), such as the high voltage plateau of Li₄Ti₅O₁₂ (1.55 V vs. Li/Li⁺) and the moderate capacity of graphite (372 mAh-g^-1), have established a need for better materials. Conversion materials, and in particular iron oxide and CaFe₂O₄ (CFO), have amassed recent attention as potential anode replacements. In this study, we evaluate the material and electrochemical effects of the solution combustion synthesis (SCS) of porous CFO across novel fuel-to-oxidizer ratios and calcination temperatures. We demonstrate that nearly doubling the amount of fuel used during synthesis increases capacities between 120 and 150% at high current densities (~ 1000 mA-g^-1) and across 500 additional charging-discharging cycles, an effect brought on in part by enhanced compositional purity in these samples. However, in order to ensure long-term cyclic stability, it is necessary to also calcine porous CFO to 900 °C to enhance crystallite size, particle size and spacing, and compositional purity.

Synthesis, Structure, and Antimicrobial Performance of NixZn1−xFe2O4 (x = 0, 0.3, 0.7, 1.0) Magnetic Powders toward E. coli, B. cereus, S. citreus, and C. tropicalis

The active development of water purification functional materials based on multicomponent spinel ferrites makes it necessary to search for new efficient methods of obtaining initial nanostructured powders. In this study, a two-stage method for the synthesis of perspective pollutant absorption agents based on NixZn1−xFe2O4 (x = 0, 0.3, 0.7, 1.0) spinel ferrites are proposed and implemented. The approach is based on the synthesis of the initial powder using the solution combustion method and its subsequent thermal treatment in the air. It was found that synthesized samples are single-phase Ni-Zn ferrites with an average crystallite size of 41.4 to 35.7 nm and a degree of crystallinity of ~95–96%. The analysis of antimicrobial activity against four diverse test-cultures: Escherichia coli ATCC 11229 (non-spore-forming gram-negative), Bacillus cereus ATCC 10702 (spore-forming gram-positive), Staphylococcus citreus NCTC 9379 (non-spore-forming gram-positive), and Candida tropicalis ATCC 750 (yeast) showed that almost all of the synthesized powders exhibit an advanced ability to inhibit the growth of the microorganisms mentioned above. The compositions obtained can be a perspective basis for both natural and wastewater purificators with magnetic separation ability and can find biotechnological and biomedical applications as promising antimicrobial materials.

Magnetic Adsorbents for Wastewater Treatment: Advancements in Their Synthesis Methods

The remediation of water streams, polluted by various substances, is important for realizing a sustainable future. Magnetic adsorbents are promising materials for wastewater treatment. Although numerous techniques have been developed for the preparation of magnetic adsorbents, with effective adsorption performance, reviews that focus on the synthesis methods of magnetic adsorbents for wastewater treatment and their material structures have not been reported. In this review, advancements in the synthesis methods of magnetic adsorbents for the removal of substances from water streams has been comprehensively summarized and discussed. Generally, the synthesis methods are categorized into five groups, as follows: direct use of magnetic particles as adsorbents, attachment of pre-prepared adsorbents and pre-prepared magnetic particles, synthesis of magnetic particles on pre-prepared adsorbents, synthesis of adsorbents on preprepared magnetic particles, and co-synthesis of adsorbents and magnetic particles. The main improvements in the advanced methods involved making the conventional synthesis a less energy intensive, more efficient, and simpler process, while maintaining or increasing the adsorption performance. The key challenges, such as the enhancement of the adsorption performance of materials and the design of sophisticated material structures, are discussed as well.

Part I: NiMoO4 Nanostructures Synthesized by the Solution Combustion Method: A Parametric Study on the Influence of Synthesis Parameters on the Materials’ Physicochemical, Structural, and Morphological Properties

The impact of process conditions on the synthesis of NiMoO₄ nanostructures using a solution combustion synthesis (SCS) method, in which agar powder and Ni(NO₃)₂ were utilized as fuel and as the oxidant, respectively, was thoroughly studied. The results show that the calcination temperature had a significant implication on the specific surface area, phase composition, particle size, band gap, and crystallite size. The influence of calcination time on the resulting physicochemical/structural/morphological properties of NiMoO₄ nanostructures was found to be a major effect during the first 20 min, beyond which these properties varied to a lesser extent. The increase in the Ni/Mo atomic ratio in the oxide impacted the combustion dynamics of the system, which led to the formation of higher surface area materials, with the prevalence of the β-phase in Ni-rich samples. Likewise, the change in the pH of the precursor solution showed that the combustion reaction is more intense in the high-pH region, entailing major implications on the physicochemical properties and phase composition of the samples. The change in the fuel content showed that the presence of agar is important, as it endows the sample with a fluffy, porous texture and is also vital for the preponderance of the β-phase.

Characterization of Surface Species during Benzene Hydroxylation over a NiO-Ceria-Zirconia Catalyst

NiO/ceria-zirconia (CZ) is a promising catalyst for the selective oxidation of benzene, as the Lewis-acidic NiO clusters can activate C-H bonds and the redox-active CZ support can activate O₂ and supply active oxygen species for the reaction. In this study, we used transmission in situ infrared (IR) spectroscopy to examine surface species formed from benzene, water, oxygen, phenol, and catechol on a NiO/CZ catalyst. The formation of surface species from benzene and phenol was compared at different temperatures in the range of 50-200 °C in the presence and absence of water vapor. We also examined the role of the NiO clusters and the CZ support during benzene activation by comparing the surface species formed on NiO-CZ with those formed on a Ni-free CZ support and on a NiO/SiO₂ catalyst. The spectrum of surface species from dosing benzene at 180 °C provides evidence for C-H bond activation. Specifically, the observation of C-O stretching vibrations indicates the formation of phenolate species. Introduction of water enhances these IR signals and introduces several additional peaks, indicating that a variety of different surface species are formed. These results show that NiO/CZ could catalyze direct conversion of benzene to phenol.

Solution combustion synthesis of Ni-based hybrid metal oxides for oxygen evolution reaction in alkaline medium

Oxygen evolution reaction (OER) has arisen as an outstanding technology for energy generation, conversion, and storage. Herein, we investigated the synthesis of nickel-based hybrid metal oxides (Ni _x M_1-x O _y ) and their catalytic performance towards OER. Ni _x M_1-x O _y catalysts were synthesized by solution combustion synthesis (SCS) using the metal nitrates as oxidizer and glycine as fuel. Scanning electron microscope (SEM) micrographs display a porous morphology for the hybrid binary Ni _x M_1-x O _y , the common feature of combusted materials. X-ray diffraction (XRD) of Ni _x M_1-x O _y depicted well-defined diffraction peaks, which confirms the crystalline nature of synthesized catalysts. The particle size of as-synthesized materials ranges between 20 and 30 nm with a mesoporous nature as revealed by N₂-physisorption. The electrocatalytic performance of the as-prepared materials was evaluated towards OER in alkaline medium. Among them, Ni _x Co_1-x O _y showed the best catalytic performance. For instance, it exhibited the lowest overpotential at a current density of 10 mA cm^-2 (404 mV), onset potential (1.605 V), and Tafel slope (52.7 mV dec^-1). The enhanced electrocatalytic performance of Ni _x Co_1-x O _y was attributed to the synergism between cobalt and nickel and the alteration of the electronic structure of nickel. Also, Ni _x Co_1-x O _y afforded the highest Ni³⁺/Ni²⁺ when compared to other electrocatalysts. This leads to higher oxidation states of Ni species, which promote and improve the electrocatalytic activity.

Large-scale synthesis of ultrafine Fe3C nanoparticles embedded in mesoporous carbon nanosheets for high-rate lithium storage

Fe₃C modified by the incorporation of carbon materials offers excellent electrical conductivity and interfacial lithium storage, making it attractive as an anode material in lithium-ion batteries. In this work, we describe a time- and energy-saving approach for the large-scale preparation of Fe₃C nanoparticles embedded in mesoporous carbon nanosheets (Fe₃C-NPs@MCNSs) by solution combustion synthesis and subsequent carbothermal reduction. Fe₃C nanoparticles with a diameter of ∼5 nm were highly crystallized and compactly dispersed in mesoporous carbon nanosheets with a pore-size distribution of 3–5 nm. Fe₃C-NPs@MCNSs exhibited remarkable high-rate lithium storage performance with discharge specific capacities of 731, 647, 481, 402 and 363 mA h g⁻¹ at current densities of 0.1, 1, 2, 5 and 10 A g⁻¹, respectively, and when the current density reduced back to 0.1 A g⁻¹ after 45 cycles, the discharge specific capacity could perfectly recover to 737 mA h g⁻¹ without any loss. The unique structure could promote electron and Li-ion transfer, create highly accessible multi-channel reaction sites and buffer volume variation for enhanced cycling and good high-rate lithium storage performance.

Fe₃C modified by the incorporation of carbon materials offers excellent electrical conductivity and interfacial lithium storage, making it attractive as an anode material in lithium-ion batteries.

Catalytic performance of mixed MxCo3−xO4 (M = Cr, Fe, Mn, Ni, Cu, Zn) spinels obtained by combustion synthesis for preferential carbon monoxide oxidation (CO-PROX): insights into the factors controlling catalyst selectivity and activity

A series of mixed cobalt spinel catalysts (MxCo3−xO4 (M = Cr, Fe, Mn, Ni, Cu, Zn)) was synthesized and tested in the CO-PROX reaction and in sole CO oxidation and H2 oxidation as references.

Porous materials formed by four self-construction processes

Multiple self-construction behavior of cyclic oligoesters is described.

Rapid reduction of real-time industry effluent using novel CuO/MIL composite

In this study, a series of novel metal organic framework based composite materials was synthesized using a facile combustion synthesis method. The synthesized materials were characterized using standard analytical techniques for crystallite size, surface functional groups, surface area, porosity, optical properties, and particle size. The increase in the amount of CuO in the composite material resulted decrease in surface area and pore volume. The band-gap energy of the synthesized composites reduced with increase in the amount of CuO. Among the composite, 0.9 CuO:0.1 MIL displayed least emission intensity indicating lower electron-hole recombination and thereby superior charge separation of the material. The increase in the amount of CuO NPs in the composite resulted in increase in the average particle size and decrease in the zeta potential. As an application, the NaBH₄-mediated reduction of Methyl orange dye was studied using the synthesized materials. The increased amount of CuO in the composite resulted in the higher activity of the material. Highest activity was observed with the composite containing 9:1 ratio of CuO and MIL, and this material was further used to investigate the reduction of methylene blue, Rhodamine B, 4-nitrophenol, 2-nitrophenol, and 2, 4-dichlorophenol. The material exhibited excellent activity for all the selected organic pollutants. Finally, the composite containing 9:1 ratio of CuO and MIL was employed for the reduction of a real-time industry effluent and the observed results were encouraging. The reusability aspect of the synthesized material was investigated. Based on the LC-MS analysis, a possible reduction mechanism is proposed.

Hyperstoichiometric Uranium Dioxides: Rapid Synthesis and Irradiation-Induced Structural Changes

Uranium dioxide (UO₂), the primary fuel for commercial nuclear reactors, incorporates excess oxygen forming a series of hyperstoichiometric oxides. Thin layers of these oxides, such as UO_2.12, form readily on the fuel surface and influence its properties, performance, and potentially geologic disposal. This work reports a rapid and straightforward combustion process in uranyl nitrate-glycine-water solutions to prepare UO_2.12 nanomaterials and thin films. We also report on the investigation of the structural changes induced in the material by irradiation. Despite the simple processing aspects, the combustion synthesis of UO_2.12 has a sophisticated chemical mechanism involving several exothermic steps. Raman spectroscopy and single-crystal X-ray diffraction (XRD) measurements reveal the formation of a complex compound containing the uranyl moiety, glycine, H₂O, and NO₃^- groups in reactive solutions and dried combustion precursors. Combustion diagnostic methods, gas-phase mass spectroscopy, differential scanning calorimetry (DSC), and extracted activation energies from DSC measurements show that the rate-limiting step of the process is the reaction of ammonia with nitrogen oxides formed from the decomposition of glycine and uranyl nitrate, respectively. However, the exothermic decomposition of the complex compound determines the maximum temperature of the process. In situ transmission electron microscopy (TEM) imaging and electron diffraction measurements show that the decomposition of the complex compound directly produces UO₂. The incorporation of oxygen at the cooling stage of the combustion process is responsible for the formation of UO_2.12. Spin coating of the solutions and brief annealing at 670 K allow the deposition of uniform films of UO_2.12 with thicknesses up to 300 nm on an aluminum substrate. Irradiation of films with Ar²⁺ ions (1.7 MeV energy, a fluence of up to 1 × 10¹⁷ ions/cm²) shows unusual defect-simulated grain growth and enhanced chemical mixing of UO_2.12 with the substrate due to the high uranium ion diffusion in films. The method described in this work allows the preparation of actinide oxide targets for fundamental nuclear science research and studies associated with stockpile stewardship.

Synthesis of non-phosphorylated epoxidised corn oil as a novel green flame retardant thermoset resin

This study aimed to produce a new potential flame retardant thermoset resin from epoxidised corn oil through a one-pot method using liquid inorganic catalysed with hydrogen peroxide. Using a gas chromatography-mass selective detector, attenuated total reflectance-fourier transform infrared spectroscopy, proton nuclear magnetic resonance imaging, optical microscopy, and scanning emission microscopy, we synthesised a bio-based resin based on newly designed parameters. The flame retardant capacity was fully established using thermogravimetric analysis and a micro calorimeter. The produced epoxidised corn oil had a relative percentage conversion of oxirane of approximately 91.70%, wherein the amount of double bonds converted into epoxides was calculated. A significant reduction from 17 to 40% in peak heat rate release (pHRR) and 26-30% in total heat release was observed, confirming its flame retardant property. Thus, the potential of epoxidised corn oil was demonstrated.

New Solvent-Free Melting-Assisted Preparation of Energetic Compound of Nickel with Imidazole for Combustion Synthesis of Ni-Based Materials

In this work two approaches to the synthesis of energetic complex compound Ni(Im)₆(NO₃)₂ from imidazole and nicklel (II) nitrate were applied: a traditional synthesis from solution and a solvent-free melting-assisted method. According to infrared spectroscopy, X-ray diffraction, elemental and thermal analysis data, it was shown that the solvent-free melt synthesis is a faster, simpler and environmentally friendly method of Ni(Im)₆(NO₃)₂ preparation. The results show that this compound is a promising precursor for the production of nanocrystalline Ni-NiO materials by air-assisted combustion method. The combustion of this complex together with inorganic supports makes it possible to synthesize supported nickel catalysts for different catalytic processes.