Research on the Ignition Height and Reaction Flame Temperature of PTFE/Al/Si/CuO with Different Mass Ratios of PTFE/Si

Recent studies have shown that the energy release capacity of Polytetrafluoroethylene (PTFE)/Al with Si, and CuO, respectively, is higher than that of PTFE/Al. PTFE/Al/Si/CuO reactive materials with four proportions of PTFE/Si were designed by the molding–sintering process to study the influence of different PTFE/Si mass ratios on energy release. A drop hammer was selected for igniting the specimens, and the high-speed camera and spectrometer systems were used to record the energy release process and the flame spectrum, respectively. The ignition height of the reactive material was obtained by fitting the relationship between the flame duration and the drop height. It was found that the ignition height of PTFE/Al/Si/CuO containing 20% PTFE/Si is 48.27 cm, which is the lowest compared to the ignition height of other Si/PTFE ratios of PTFE/Al/Si/CuO; the flame temperature was calculated from the flame spectrum. It was found that flame temperature changes little for the same reactive material at different drop heights. Compared with the flame temperature of PTFE/Al/Si/CuO with four mass ratios, it was found that the flame temperature of PTFE/Al/Si/CuO with 20% PTFE/Si is the highest, which is 2589 K. The results show that PTFE/Al/Si/CuO containing 20% PTFE/Si is easier to be ignited and has a stronger temperature destruction effect.     

Effects of Al Particle Size on the Impact Energy Release of Al-Rich PTFE/Al Composites under Different Strain Rates

Polytetrafluoroethylene (PTFE)/Al reactive material with different aluminum particle sizes were prepared by molding and sintering, and the effect of aluminum particle size on the impact behavior of PTFE/Al reactive material with a mass ratio of 50:50 was investigated. The results show that aluminum particle size has significant effects on the shock-reduced reaction diffusion, reaction speed, and degree of reaction of the PTFE/Al reactive material. At a moderate strain rate, the reaction delay of PTFE/Al increased, and the reaction duration and degree decreased, with the increase of aluminum particle size. Under the strong impact of explosive loading, aluminum particle size has little effect on the reaction delay, which maintains at about 1.5 μs–2.5 μs, but the reaction durability and degree of reaction of PTFE/Al decrease with increasing aluminum particle size. There is also a strain rate threshold for the shock-induced reaction of PTFE/Al reactive material, which is closely related to aluminum particle size. The shock-induced reaction occurs when the strain rate threshold is exceeded.     

Influence of Molding Parameters on Quasi-Static Mechanical Properties of Al-Rich Al/PTFE/TiH2 Active Materials

Preforming pressure and the pressure holding time are important parameters of the molding process, which directly affect the mechanical properties of materials. In order to obtain the best molding parameters of Al-rich Al/PTFE/TiH₂ composites, based on the quasi-static compression test, the influence of molding parameters on the mechanical properties of Al-rich Al/PTFE/TiH₂ composites was analyzed, and the microstructure characteristics of Al-rich Al/PTFE/TiH₂ specimens were analyzed by SEM. An X-ray diffractometer was used to analyze the phase of the residue after quasi-static compression experiment. The results show that: (1) With the increase in molding parameters (preforming pressure and the pressure holding time), the compressive strength, failure strain and toughness of Al-rich Al/PTFE/TiH₂ specimens first increase and then decrease. The best molding process parameters of Al-rich Al/PTFE/TiH₂ materials are preforming pressure 240 MPa and the pressure holding time 100 s. (2) For unsintering specimens, when the preforming pressure is less than 150 MPa, the porosity of the specimen increases slowly at first and then decreases. When the preforming pressure is greater than 150 MPa, the porosity of the specimen increases first and then decreases. When the pressure holding time is no more than 100 s, the porosity of the specimen decreases gradually. When the pressure holding time is more than 100 s, the porosity of the specimen increases first and then decreases. For sintered specimens, when the preforming pressure is less than 100 MPa, the porosity of the specimen decreases gradually. When the preforming pressure is greater than 100 MPa, the porosity of the specimen first increases and then decreases. With the increase in the pressure holding time, the porosity first increases and then decreases. For each preforming pressure specimen, compared with that before sintering, the porosity after sintering either decreases or increases. For each the pressure holding time specimen, the porosity increases after sintering compared with that before sintering. The microstructure of PTFE crystal inside the specimen is mainly planar PTFE crystal. The size and number of planar PTFE crystals are significantly affected by the molding parameters, which further affects the mechanical properties of Al-rich Al/PTFE/TiH₂ specimens. When the preforming pressure is less than 100 MPa, the planar PTFE crystals are small and few, which results in the worst mechanical properties of the specimens. When the preforming pressure is more than 100 MPa and does not contain 240 Mpa, the planar PTFE crystals are small and there are more of them, which results in better mechanical properties of the specimens. When the preforming pressure is 240 MPa, the planar PTFE crystals are large and numerous, which results in the best mechanical properties of the specimen. When the pressure holding time is 100 s, the planar PTFE crystals are large and there are more of them, which results in the best mechanical properties of the specimen. (3) The reactivity of Al-rich Al/PTFE/TiH₂ specimens with TiH₂ the content of 10% under quasi-static compression is not significantly affected by the molding parameters.     

Molecular-Dynamics Study on the Impact Energy Release Characteristics of Fe–Al Energetic Jets

Fe–Al energetic material releases a large amount of energy under impact loading; therefore, it can replace traditional materials and be used in new weapons. This paper introduces the macroscopic experiment and microscopic molecular-dynamics simulation research on the energy release characteristics of Fe–Al energetic jets under impact loading. A macroscopic dynamic energy acquisition test system was established to quantitatively obtain the composition of Fe–Al energetic jet reaction products. A momentum mirror impacting the Fe–Al particle molecular model was established and the microstructure evolution and impact thermodynamic response of Fe–Al particles under impact loading were analyzed. The mechanism of multi-scale shock-induced chemical reaction of Fe–Al energetic jets is discussed. The results show that the difference in velocity between Fe and Al atoms at the shock wave fronts is the cause of the shock-induced reaction; when the impact strength is low, the Al particles are disordered and amorphous, while the Fe particles remain in their original state and only the oxidation reaction of Al and a small amount intermetallic compound reaction occur. With the increase of impact strength, Al particles and Fe particles are completely disordered and amorphized in a high-temperature and high-pressure environment, fully mixed and penetrated. The temperature of the system rises rapidly, due to a violent thermite reaction, and the energy released by the jet shows an increasing trend; there is an impact intensity threshold, so that the jet release energy reaches the upper limit.     

Development of a Kinetic Model for the Redox Reactions of Co2.4Ni0.6O4 and SiO2/Co2.4Ni0.6O4 Oxides for Thermochemical Energy Storage

One of the possible solutions for the transition of the actual energetic model is the use of thermal energy storage technologies. Among them, thermochemical energy storage based on redox reactions involving metal oxides is very promising due to its high energy density. This paper deals with the development of the kinetic study based on data extracted from the thermogravimetric analysis of a cobalt-nickel mixed oxide (Co_2.4Ni_0.6O₄) without and with the addition of SiO₂ particles to improve the cyclability. The results show that in the reduction reaction the activation energy is not affected by the addition of SiO₂ particles while in the oxidation reaction an increase in the activation energy is observed. The theoretical models fitting with the experimental data are different for each material in the reduction reaction. The mixed oxide is controlled by a nucleation and growth mechanism for conversion ratios higher than 0.5, while the added material is controlled by diffusion mechanisms. In the oxidation reaction, the two materials are controlled by a nucleation and growth mechanism for conversion ratios higher than 0.5.     

Study on the Impact-Induced Energy Release Characteristics of Zr68.5Cu12Ni12Al7.5 Amorphous Alloy

As a new kind of multifunctional energetic structural material (MESM), amorphous alloy will undergo a chemical reaction and release energy under impact load. In this paper, an analysis method for the impact-induced reaction parameters of solid materials was derived based on a three-term equation of state and Avrami–Erofeev equation. The relation between the degree of reaction, pressure, and temperature of Zr_68.5Cu₁₂Ni₁₂Al_7.5 amorphous alloy was obtained. The influence of participation of an oxidizing reaction on the material energy release efficiency was analyzed. The relation between the energy release efficiency and impact velocity was achieved by an experiment in which Zr_68.5Cu₁₂Ni₁₂Al_7.5 amorphous alloy fragments impact a steel plate. The variations of pressure and temperature during the impact process were obtained. In the end, a reaction kinetic model was modified, and the kinetic parameters for the impact-induced reaction of materials in an air environment were obtained.     

Impact of Zr-Doped Bi2O3 Radiopacifier by Spray Pyrolysis on Mineral Trioxide Aggregate

Mineral trioxide aggregates (MTA) have been developed as a dental root repair material for a range of endodontics procedures. They contain a small amount of bismuth oxide (Bi₂O₃) as a radiopacifier to differentiate adjacent bone tissue on radiographs for endodontic surgery. However, the addition of Bi₂O₃ to MTA will increase porosity and lead to the deterioration of MTA’s mechanical properties. Besides, Bi₂O₃ can also increase the setting time of MTA. To improve upon the undesirable effects caused by Bi₂O₃ additives, we used zirconium ions (Zr) to substitute the bismuth ions (Bi) in the Bi₂O₃ compound. Here we demonstrate a new composition of Zr-doped Bi₂O₃ using spray pyrolysis, a technique for producing fine solid particles. The results showed that Zr ions were doped into the Bi₂O₃ compound, resulting in the phase of Bi_7.38Zr_0.62O_12.31. The results of materials analysis showed Bi₂O₃ with 15 mol % of Zr doping increased its radiopacity (5.16 ± 0.2 mm Al) and mechanical strength, compared to Bi₂O₃ and other ratios of Zr-doped Bi₂O₃. To our knowledge, this is the first study of fabrication and analysis of Zr-doped Bi₂O₃ radiopacifiers through the spray pyrolysis procedure. The study reveals that spray pyrolysis can be a new technique for preparing Zr-doped Bi₂O₃ radiopacifiers for future dental applications.     

Structural,Optical and Electrical Properties of Al+MoO3 and Au+MoO3 Thin Films Prepared by Magnetron Codeposition

Structural, optical and electrical properties of Al+MoO₃ and Au+MoO₃ thin films prepared by simultaneous magnetron sputtering deposition were investigated. The influence of MoO₃ sputtering power on the Al and Au nanoparticle formation and spatial distribution was explored. We demonstrated the formation of spatially arranged Au nanoparticles in the MoO₃ matrix, while Al incorporates in the MoO₃ matrix without nanoparticle formation. The dependence of the Au nanoparticle size and arrangement on the MoO₃ sputtering power was established. The Al-based films show a decrease of overall absorption with an Al content increase, while the Au-based films have the opposite trend. The transport properties of the investigated films also are completely different. The resistivity of the Al-based films increases with the Al content, while it decreases with the Au content increase. The reason is a different transport mechanism that occurs in the films due to their different structural properties. The choice of the incorporated material (Al or Au) and its volume percentage in the MoO₃ matrix enables the design of materials with desirable optical and electrical characteristics for a variety of applications.     

Effects of Different Types of Interlayers on the Interfacial Reaction Mechanism at the Cu Side of Al/Cu Lap Joints Obtained by Laser Welding/Brazing

The influence of tin foil and Ni coatings on microstructures, mechanical properties, and the interfacial reaction mechanism was investigated during laser welding/brazing of Al/Cu lap joints. In the presence of a Zn-based filler, tin foil as well as Ni coating strengthened the Al/Cu joints. The tin foil only slightly influenced the joint strength. It considerably improved the spreading/wetting ability of the weld filler; however, it weakened the bonding between the seam and the Al base metal. The Ni coating considerably strengthened the Al/Cu lap joints; the highest tensile strength was 171 MPa, which was higher by 15.5% than that of a joint without any interlayer. Microstructure analysis revealed that composite layers of Ni₃Zn₁₄–(τ₂ Zn–Ni–Al ternary phase)–(α-Zn solid solution)–Al₃Ni formed at the fusion zone (FZ)/Cu interface. Based on the inferences about the microstructures at the interfaces, thermodynamic results were calculated to analyze the interfacial reaction mechanism. The diffusion of Cu was limited by the Ni coating and the mutual attraction between the Al and Ni atoms. The microstructure comprised Zn, Ni, and Al, and they replaced the brittle Cu–Zn intermetallic compounds, successfully strengthening the bonding of the FZ/Cu interface.     

Effect of Tantalum Pentoxide Addition on the Radiopacity Performance of Bi2O3/Ta2O5 Composite Powders Prepared by Mechanical Milling

Among the various phases of bismuth oxide, the high temperature metastable face-centered cubic δ phase attracts great attention due to its unique properties. It can be used as an ionic conductor or an endodontic radiopacifying material. However, no reports concerning tantalum and bismuth binary oxide prepared by high energy ball milling and serving as a dental radiopacifier can be found. In the present study, Ta₂O₅-added Bi₂O₃ composite powders were mechanically milled to investigate the formation of these metastable phases. The as-milled powders were examined by X-ray diffraction and scanning electron microscopy to reveal the structural evolution. The as-milled composite powders then served as the radiopacifier within mineral trioxide aggregates (i.e., MTA). Radiopacity performance, diametral tensile strength, setting times, and biocompatibility of MTA-like cements solidified by deionized water, saline, or 10% calcium chloride solution were investigated. The experimental results showed that subsequent formation of high temperature metastable β-Bi_7.8Ta_0.2O_12.2, δ-Bi₂O₃, and δ-Bi₃TaO₇ phases can be observed after mechanical milling of (Bi₂O₃)₉₅(Ta₂O₅)₅ or (Bi₂O₃)₈₀(Ta₂O₅)₂₀ powder mixtures. Compared to its pristine Bi₂O₃ counterpart with a radiopacity of 4.42 mmAl, long setting times (60 and 120 min for initial and final setting times) and 84% MG-63 cell viability, MTA-like cement prepared from (Bi₂O₃)₉₅(Ta₂O₅)₅ powder exhibited superior performance with a radiopacity of 5.92 mmAl (the highest in the present work), accelerated setting times (the initial and final setting time can be shortened to 25 and 40 min, respectively), and biocompatibility (94% cell viability).     

Investigation of Deoxidation Process of MoO3 Using Environmental TEM

In situ environmental transmission electron microscope (ETEM) could provide intuitive and solid proof for the local structure and chemical evolution of materials under practical working conditions. In particular, coupled with atmosphere and thermal field, the behavior of nano catalysts could be directly observed during the catalytic reaction. Through the change of lattice structure, it can directly correlate the relationship between the structure, size and properties of materials in the nanoscale, and further directly and accurately, which is of great guiding value for the study of catalysis mechanism and the optimization of catalysts. As an outstanding catalytic material in the application of methane reforming, molybdenum oxide (MoO₃)-based materials and its deoxidation process were studied by in situ ETEM method. The corresponding microstructures and components evolution were analyzed by diffraction, high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectrum (EELS) techniques. MoO₃ had a good directional deoxidation process accompanied with the process of nanoparticles crushing and regrowth in hydrogen (H₂) and thermal field. However, in the absence of H₂, the samples would exhibit different structural evolution.     

Self-Assembly of Bi2Te3-Nanoplate/Graphene-Nanosheet Hybrid by One-Pot Route and Its Improved Li-Storage Properties

A sandwich structured Bi₂Te₃-nanoplates/graphene-nanosheet (Bi₂Te₃/G) hybrid has been synthesized by a facile in situ solvothermal route and has been investigated as a potential anode material for Li-ion batteries. Bi₂Te₃ grows during the solvothermal process with the simultaneous reduction of graphite oxide into graphene. The in situ formation process of the hybrid has been investigated by X-ray diffraction and X-ray photoelectron spectra. The Li-storage mechanism and performance of Bi₂Te₃/G and bare Bi₂Te₃ have been studied by galvanostatic cycling and cyclic voltammetry. The Bi₂Te₃/G sandwich exhibits an obviously improved cycling stability compared to bare Bi₂Te₃. The enhancement in electrochemical performance can be attributed to the combined conducting, confining and dispersing effects of graphene for Bi₂Te₃ nanoplates and to the self-assembled sandwich structure.     

A Cleanable Self-Assembled Nano-SiO2/(PTFE/PEI)n/PPS Composite Filter Medium for High-Efficiency Fine Particulate Filtration

A silicon dioxide/polytetrafluoroethylene/polyethyleneimine/polyphenylene sulfide (SiO₂/PTFE/PEI/PPS) composite filter medium with three-dimensional network structures was fabricated by using PPS nonwoven as the substrate which was widely employed as a cleanable filter medium. The PTFE/PEI bilayers were firstly coated on the surfaces of the PPS fibers through the layer-by-layer self-assembly technique ten times, followed by the deposition of SiO₂ nanoparticles, yielding the SiO₂/(PTFE/PEI)₁₀/PPS composite material. The contents of the PTFE component were easily controlled by adjusting the number of self-assembled PTFE/PEI bilayers. As compared with the pure PPS nonwoven, the obtained SiO₂/(PTFE/PEI)₁₀/PPS composite material exhibits better mechanical properties and enhanced wear, oxidation and heat resistance. When employed as a filter material, the SiO₂/(PTFE/PEI)₁₀/PPS composite filter medium exhibited excellent filtration performance for fine particulate. The PM2.5 (particulate matter less than 2.5 μm) filtration efficiency reached up to 99.55%. The superior filtration efficiency possessed by the SiO₂/(PTFE/PEI)₁₀/PPS composite filter medium was due to the uniformly modified PTFE layers, which played a dual role in fine particulate filtration. On the one hand, the PTFE layers not only increase the specific surface area and pore volume of the composite filter material but also narrow the spaces between the fibers, which were conducive to forming the dust cake quickly, resulting in intercepting the fine particles more efficiently than the pure PPS filter medium. On the other hand, the PTFE layers have low surface energy, which is in favor of the detachment of dust cake during pulse-jet cleaning, showing superior reusability. Thanks to the three-dimensional network structures of the SiO₂/(PTFE/PEI)₁₀/PPS composite filter medium, the pressure drop during filtration was low.     

Fabrication of Manganese Oxide/PTFE Hollow Fiber Membrane and Its Catalytic Degradation of Phenol

P-aminophenol is a hazardous environmental pollutant that can remain in water in the natural environment for long periods due to its resistance to microbiological degradation. In order to decompose p-aminophenol in water, manganese oxide/polytetrafluoroethylene (PTFE) hollow fiber membranes were prepared. MnO₂ and Mn₃O₄ were synthesized and stored in PTFE hollow fiber membranes by injecting MnSO₄·H2O, KMnO₄, NaOH, and H₂O₂ solutions into the pores of the PTFE hollow fiber membrane. The resultant MnO₂/PTFE and Mn₃O₄/PTFE hollow fiber membranes were characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and thermal analysis (TG). The phenol catalytic degradation performance of the hollow fiber membranes was evaluated under various conditions, including flux, oxidant content, and pH. The results showed that a weak acid environment and a decrease in flux were beneficial to the catalytic degradation performance of manganese oxide/PTFE hollow fiber membranes. The catalytic degradation efficiencies of the MnO₂/PTFE and Mn₃O₄/PTFE hollow fiber membranes were 70% and 37% when a certain concentration of potassium monopersulfate (PMS) was added, and the catalytic degradation efficiencies of MnO₂/PTFE and Mn₃O₄/PTFE hollow fiber membranes were 50% and 35% when a certain concentration of H₂O₂ was added. Therefore, the manganese oxide/PTFE hollow fiber membranes represent a good solution for the decomposition of p-aminophenol.     

The Effect of Temperature and Sputtered Particles on the Wettability of Al/Al2O3

Two kinds of Al₂O₃ ceramic samples with and without Al film deposited were designed respectively. The influences of temperature and high kinetic energy sputtering particles on the wettability and interface strength of Al/Al₂O₃ were studied by comparing the wetting behavior of molten aluminum on two samples. The results show that molten aluminum does not wet the Al₂O₃ sample without Al film deposited at 700 °C, the contact angle is 165°, and the interfacial shear strength is 28 MPa. With the increase of temperature, the contact angle decreases continuously, and the interface shear strength gradually increases. The fracture of the brazed joint is transferred from the interface to the brazing seam. In comparison, the sample deposited with Al film is wetted by molten aluminum at 700 °C, and the contact angle is only 12°. The interface shear strength is about 120 MPa and is less affected by temperature. The shear fracture of the joint occurs in the brazed seam of Al metal. Therefore, the high energy generated by either the temperature increase or the particle sputtering enable the Al atoms to overcome the energy barrier to form Al–O bonds with the O atoms on the Al₂O₃ ceramic surface, thereby improving the wettability of Al/Al₂O₃.     

Boosting Piezo/Photo-Induced Charge Transfer of CNT/Bi4O5I2 Catalyst for Efficient Ultrasound-Assisted Degradation of Rhodamine B

Strain-induced internal electric fields present a significant path to boosting the separation of photoinduced electrons and holes. In addition, piezo-induced positive/negative pairs could be released smoothly, taking advantage of the excellent electroconductibility of some conductors. Herein, the hybrid piezo-photocatalysis is constructed by combining debut piezoelectric nanosheets (Bi₄O₅I₂) and typical conductor multiwalled carbon nanotubes (CNT). The photocatalytic degradation efficiency that the hybrid CNT/Bi₄O₅I₂ exhibits was remarkably increased by more than 2.3 times under ultrasonic vibration, due to the piezo-generated internal electric field. In addition, the transient photocurrent spectroscopy and electrochemical impedance measurement reveal that the CNT coating on Bi₄O₅I₂ enhances the piezo-induced positive/negative migration. Therefore, the piezocatalytic activity of CNT/Bi₄O₅I₂ could be improved by three times, compared with pure Bi₄O₅I₂ nanosheets. Our results may offer promising approaches to sketching efficient piezo-photocatalysis for the full utilization of solar energy or mechanical vibration.     

Fabrication of Multi-Layer Metal Oxides Structure for Colored Glass

This study proposes front colored glass for building integrated photovoltaic (BIPV) systems based on multi-layered derivatives of glass/MoO₃/Al₂O₃ with a process technology developed to realize it. Molybdenum oxide (MoO₃) and aluminum oxide (Al₂O₃) layers are selected as suitable candidates to achieve thin multi-layer color films, owing to the large difference in their refractive indices. We first investigated from a simulation based on wave optics that the glass/MoO₃/Al₂O₃ multi-layer type offers more color design freedom and a cheaper fabrication process when compared to the glass/Al₂O₃/MoO₃ multi-layer type. Based on the simulation, bright blue and green were primarily fabricated on glass. It is further demonstrated that brighter colors, such as yellow and pink, can be achieved secondarily with glass/MoO₃/Al₂O₃/MoO₃ due to enhanced multi-interfacial reflections. The fabricated color glasses showed the desired optical properties with a maximum transmittance exceeding 80%. This technology exhibits promising potential in commercial BIPV system applications.     

Cysteine-Induced Hybridization of 2D Molybdenum Disulfide Films for Efficient and Stable Hydrogen Evolution Reaction

The noble, metal-free materials capable of efficiently catalyzing water splitting reactions currently hold a great deal of promise. In this study, we reported the structure and electrochemical performance of new MoS₂-based material synthesized with L-cysteine. For this, a facile one-pot hydrothermal process was developed and an array of densely packed nanoplatelet-shaped hybrid species directly on a conductive substrate were obtained. The crucial role of L-cysteine was determined by numerous methods on the structure and composition of the synthesized material and its activity and stability for hydrogen evolution reaction (HER) from the acidic water. A low Tafel slope of 32.6 mV dec⁻¹, close to a Pt cathode, was registered for the first time. The unique HER performance at the surface of this hybrid material in comparison with recently reported MoS₂-based electrocatalysts was attributed to the formation of more defective 1T, 2H-MoS₂/MoO_x, C nanostructures with the dominant 1T-MoS₂ phase and thermally degraded cysteine residues entrapped. Numerous stacks of metallic (1T-MoS₂ and MoO₂) and semiconducting (2H-MoS₂ and MoO₃) fragments relayed the formation of highly active layered nanosheets possessing a low hydrogen adsorption free energy and much greater durability, whereas intercalated cysteine fragments had a low Tafel slope of the HER reaction. X-ray photoelectron spectroscopy, scanning electron microscopy, thermography with mass spectrometry, high-resolution transmission electron microscopy, Raman spectroscopy techniques, and linear sweep voltammetry were applied to verify our findings.     

Metallothermic Reduction of MoO3 on Combustion Synthesis of Molybdenum Silicides/MgAl2O4 Composites

Combustion synthesis involving metallothermic reduction of MoO₃ by dual reductants, Mg and Al, to enhance the reaction exothermicity was applied for the in situ production of Mo₃Si–, Mo₅Si₃− and MoSi₂–MgAl₂O₄ composites with a broad compositional range. Reduction of MoO₃ by Mg and Al is highly exothermic and produces MgO and Al₂O₃ as precursors of MgAl₂O₄. Molybdenum silicides are synthesized from the reactions of Si with both reduced and elemental Mo. Experimental evidence indicated that the reaction proceeded as self-propagating high-temperature synthesis (SHS) and the increase in silicide content weakened the exothermicity of the overall reaction, and therefore, lowered combustion front temperature and velocity. The XRD analysis indicated that Mo₃Si–, Mo₅Si₃– and MoSi₂–MgAl₂O₄ composites were well produced with only trivial amounts of secondary silicides. Based on SEM and EDS examinations, the morphology of synthesized composites exhibited dense and connecting MgAl₂O₄ crystals and micro-sized silicide particles, which were distributed over or embedded in the large MgAl₂O₄ crystals.