Thermal Explosion Reaction Research Articles

Highly Porous Co-Al Intermetallic Created by Thermal Explosion Using NaCl as a Space Retainer.

Co-Al porous materials were fabricated by thermal explosion (TE) reactions from Co and Al powders in a 1:1 ratio using NaCl as a space retainer. The effects of the NaCl content on the temperature profiles, phase structure, volume change, density, pore distribution and antioxidation behavior were investigated. The results showed that the sintered product of Co and Al powders was solely Co-Al intermetallic, while the final product was Co4Al13 with an abundant Co phase and minor Co2Al5 and Co-Al phases after added NaCl dissolved out, due to the high Tig and low Tc. The open porosity of sintered Co-Al compound was sensibly improved to 79.5% after 80 wt.% of the added NaCl dissolved out. Moreover, porous Co-Al intermetallic exhibited an inherited pore structure, including large pores originating from the dissolution of NaCl and small pores in the matrix caused by volume expansion due to TE reaction. The interconnected large and small pores make the open cellular Co-Al intermetallic suitable for broad application prospects in liquid-gas separation and filtration.

Sputtering Coating on the Surface of Diamond Particles Using High Temperature Generated by Thermal Explosion Reaction

Sputtering Coating on the Surface of Diamond Particles Using High Temperature Generated by Thermal Explosion Reaction

Low-Temperature Synthesis of TiC Coating on Diamond Surface by Thermal Explosion Reaction

Low-Temperature Synthesis of TiC Coating on Diamond Surface by Thermal Explosion Reaction

The effect of Fe in the rapid thermal explosion synthesis and the high-temperature corrosion behavior of porous Co-Al-Fe intermetallic

High porosity Co-Al-Fe intermetallic with 3D-microstructures were one-step synthesized via a novel thermal explosion reaction. A link between pore structure and permeability was established using 3D-XRM technology. The corrosion resistance of the samples with different Fe contents was investigated at 900 °C under an oxygen/sulphur atmosphere for up to 120 h. The results showed that the pore structure of the samples remains stable, and the internal matrices are intact due to the formation of a thin protective layer of Al2O3 and Fe2O3 on the surface of the product skeleton. In addition, inward diffusion of S leads to the formation of FeS nodules.

Research of TE behaviour and compression property of porous Ni–Al–Cr intermetallic compounds in the β phase region

Ni–Al–Cr alloys in the β phase (B2–NiAl) region exhibit remarkable stability and mechanical property. Through thermal explosion (TE) reaction, Ni–Al–Cr intermetallic compounds with high porosity can be obtained. In this study, the focus lies on analyzing the macroscopic morphology, microstructure, phase distribution, TE behaviour, and the mechanical property of porous Ni–Al–Cr in the β phase region. Following the TE reaction, the Al-rich sintered product demonstrates a uniform phase composition and high porosity, reaching 44.39%. The vigorous TE reaction promotes the formation of interconnected pores, while the high porosity structure compromises the mechanical properties of the sample. Conversely, the Al-poor sintered product, due to a moderate TE reaction and low porosity structure, maintains its complete morphology and exhibits excellent compression resistance (yield stress reaching 538 MPa). This study offers valuable insights for the fabrication of porous Ni–Al–Cr materials with exceptional structure and performance.

Thermal explosion synthesis of Cr2AlB2 materials

Abstract Ternary conductive ceramic Cr2AlB2 phase has been widely studied because of its unique physical and chemical properties. However, the preparation of conventional synthetic Cr2AlB2 requires expensive raw materials or higher equipment cost, which is not conducive to its synthesis and promotion. Hence, we synthesized high-content Cr2AlB2 by thermal explosion reaction, a technology with low-energy consumption. Cr2AlB2 was synthesized by thermal explosion reaction from Cr/Al/B mixed powders. The effects of different ignition materials and diamond additive on Cr2AlB2 synthesis were studied systematically. Results showed that the Cr/Al/B system did not undergo a thermal explosion reaction. An aluminothermic reaction between Al and Cr2O3 occurred by introducing a small amount of Cr2O3. The main phase of the thermal explosion products of the Cr/Al/B/Cr2O3 green body was CrB. The addition of an appropriate amount (7.5 % and 10 %) of diamond in the raw material can obviously promote Cr2AlB2 synthesis. The main phases of the product were Cr2AlB2 and CrB. The samples were composed of a large number of fine Cr2AlB2 lath grains. Finally, the mechanism of Cr2AlB2 formation by thermal explosion reaction was proposed.

Effect of the heating rate on the thermal explosion behavior and oxidation resistance of 3D-structure porous NiAl intermetallic

Porous NiAl intermetallic compounds demonstrate great potential in various applications by their high porosity and excellent oxidation resistance. However, to obtain a controllable NiAl intermetallic structure by tuning different process parameters remains unclear. In this work, porous NiAl intermetallic compounds were fabricated by economic and energy-saving thermal explosion (TE) reaction. The relationship between microstructure and process parameters was revealed using three-dimensional X-ray microscopy (3D-XRM) with high resolution and non-destructive characteristics. The geometrical features and quantitative statistics of the porous NiAl obtained at different heating rates (2, 10, 20 °C min−1) were compared. The result of the closed porosity calculation showed that a lower heating rate (2 °C min−1) promoted the Kirkendall reaction between Ni and Al, resulting in a high closed porosity (5.25%). However, at a higher heating rate (20 °C min−1), a homogeneous NiAl phase was observed using the threshold segmentation method, indicating uniform and complete TE reaction can be achieved at a high heating rate. The result of the 3D fluid simulation showed that the sample heated at 10 °C min−1 had the highest permeability (2434.6 md). In this study, we systematically investigated the relationship between the heating rates and properties of the porous NiAl intermetallic, including the phase composition, porosity, exothermic mechanism, oxidation resistance, and compression resistance. Our work provides constructive directions for designing and tailoring the performance of porous NiAl intermetallic compounds.

Coating on the Surface of Diamond Particles by Thermal Explosion Reaction Method

Coating on the Surface of Diamond Particles by Thermal Explosion Reaction Method

Pore formation mechanism and oxidation resistance of porous CoAl3 intermetallic prepared by rapid thermal explosion

Porous CoAl3 is a candidate material in the field of catalytic due to its high porosity, good thermostability and quasicrystal structure. However, its rapid preparation are still a challenge, and the oxidation resistance need to be further investigated. In this work, we have rapidly prepared porous CoAl3 by thermal explosion (TE) reaction and studied its oxidation process. The results show that two exothermic peaks at 616 °C and 646 °C, corresponding to the solid-phase diffusion and TE reaction, respectively. The heat released from the two reactions led to the expansion of the compact, which reached a maximum of 104% at 800 °C, and the corresponding open porosity reached at 53%. The pore sources include the original pores during the green compact pressing process, the Kirkendall pores generated by the solid-phase diffusion process and the in-situ pores generated by the Al consumption after the TE occurs. The cyclic oxidation of porous CoAl3 at 700 °C for 130 h only increased the weight by 1.52%, forming a continuous protective oxide film on the surface of the skeleton. It has been found that porous CoAl3 can combine the oxidation resistance of Co–Al monoliths alloys and the high porosity of porous materials, which have potential applications in the field of catalysis such as methanation at 600–700 °C.

One-step sintering of porous TiAl3 intermetallics using TiH2 as raw material in thermal explosion reaction

Porous TiAl3 intermetallics with high porosity of 56.0% were synthesized by thermal explosion (TE) reaction using TiH2 as raw material, from TiH2-75 at.%Al elemental powders. Results shown that an obvious thermal explosion reaction occurs (1225 ℃) when one-step sintering is carried out without the pre-heat treatment. After TE, TiAl3 was the dominate phase in the sintered products. Porous TiAl3 intermetallics exhibited an open pore structures and uniform pore size distribution, which ensures the application of porous TiAl3 materials in the fields of solid–liquid filtration and separation.

Preparation of high-content MoAlB by thermal explosion from Mo/Al/B2O3 system

MoAlB ceramics containing a small amount of Al2O3 and MoB as impurities were synthesized by thermal explosion technique using Mo, Al, and B2O3 as the raw materials. The effect of Al content on the reaction synthesis of MoAlB materials was investigated. Results showed that adding excess Al could compensate for the Al volatilized during the thermal explosion reaction Moreover, it could remarkably promote the formation of gaseous AlO and inhibit the synthesis of solid-phase Al2O3. Thus, it substantially promoted the synthesis of MoAlB. High-content MoAlB ceramics were prepared at 800 °C for 1 min by using 2Mo/4.6Al/B2O3 as the raw materials. The MoAlB grains were flaky and had a thickness of 500 nm and a length of 1–5 μm.

Oxidation resistance at 900 °C of porous Ni-Al-Cr intermetallics synthesized via rapid thermal explosion reaction

Ni-Al-Cr intermetallic compounds are candidate at extreme environment due to their excellent oxidation resistance at high temperature, and the oxidation resistance of Ni-Al-Cr alloy system has been studied extensively. However, the research on oxidation resistance mechanism of porous Ni-Al-Cr intermetallic compounds is still not deep. In our work, porous Ni-Al-Cr intermetallic compounds were synthesized by thermal explosion, and the oxidation resistance of porous Ni-Al-Cr system was mainly investigated. The results indicate that Cr promotes the formation of highly protective continuous Al2O3 layer, increasing the oxidation resistance at 900 °C of porous Ni-Al-Cr. After oxidation at 900 °C for 120 h, the minimum mass gain of Ni-Al-Cr products is only 6.96%.

Thermal Safety Analysis of On-Site Emulsion Explosives Mixed with Waste Engine Oil

The study of the thermal safety of emulsion explosives mixed with waste engine oil is very important for the safety of these types of explosives used in mine blasting. In order to study the thermal safety of emulsion explosives mixed with waste engine oil, thermal safety tests were carried out using a Differential Scanning Calorimeter (DSC), non-isothermal kinetics, and the Flynn–Wall–Ozawa method. The results show that the minor particle impurities in the filtered waste engine oil are mainly combustibles; after adding different amounts of waste engine oil, the activation energy of the emulsion matrix decreases from 110.33 kJ/mol to 75.39 kJ/mol, 74.50 kJ/mol, and 82.23 kJ/mol, and the critical temperature for thermal explosion changes from 194.16 °C to 169.73 °C, 227.47 °C, and 208.78 °C. The addition of waste engine oil reduces the activation energy of emulsion explosives. The waste engine oil is negatively correlated with the activation energy and the thermal explosion reaction temperature of emulsion explosives, and the correlation coefficient is −0.686 and −0.333. The emulsifier is positively correlated with the critical temperature of thermal explosion of emulsion explosives, and the correlation coefficient is 0.251. The small particles in the waste engine oil create a hot spot in the emulsion explosives, which reduces the thermal safety of the emulsion explosives mixed with waste engine oil. The emulsifier reduces the droplet size of the emulsion explosive, improves the oil-water interface strength, and improves the thermal safety of the emulsion explosives mixed with waste engine oil. The thermal safety of emulsion explosives mixed with waste engine oil can be improved by reducing the proportion of the sensitizer and increasing the proportion of the emulsifier.

Preparation of Fe2AlB2 material via thermal explosion induced by spark plasma sintering

ABSTRACT Fe2AlB2 material was prepared through spark plasma sintering (SPS) by using Fe/Al/B mixed powder as the raw material. The effects of sintering temperature, holding time, and Al content on the phase composition and microstructure of the product were studied to obtain materials with high Fe2AlB2 content. Results showed that when the sintering temperature was increased to approximately 1000°C, SPS induced a thermal explosion reaction, resulting in the formation of a dense sintered sample with high Fe2AlB2 content. The sample contained a small amount of FeB and FeAl3 impurities. The synthesis of Fe2AlB2 could be promoted by optimizing holding time and increasing Al content in the raw materials. The most suitable process parameters for the synthesis of materials with high Fe2AlB2 content were 1000°C, no holding, and 2Fe/1.1Al/2B raw material. The Fe2AlB2 sample had good mechanical properties. Its Vickers hardness and bending strength were 10.5 GPa and 352 MPa, respectively. Given that the synthesized Fe2AlB2 material was unstable, continuously increasing the temperature or extending the holding time would cause it to decompose.

Reaction Behavior of Porous TiAl3 Intermetallics Fabricated by Thermal Explosion with Different Particle Sizes.

Porous TiAl3 intermetallics were prepared by the thermal explosion (TE) and space holder method with different particle sizes of Ti and Al powders, and their reaction behaviors were investigated. The results showed that with the increase in the particle size of the Ti and Al powders, the interfacial contact between the particles decreased, resulting in low interfacial energy and reaction activity, making the process difficult to initiate. Meanwhile, the heat flow rose from 358.37 J/g to 730.17 J/g and 566.74 J/g due to the extension of the solid–liquid diffusion time. The TiAl3 structures obviously expanded, and the formation of connected pore channels promoted the porosity. Only when the Ti and Al particle sizes were both small did the solid–solid diffusion significantly appear. At the same time, the TE reaction weakened, so the product particles had no time to fully grow. This indicates that the particle size of the raw materials controlled the TE reaction process by changing the solid–liquid diffusion reaction time and the degree of solid-phase diffusion.

Coating of diamond by thermal explosion reaction

By using Cr/Al/B/diamond mixed powder as raw material, a CrB-AlN based multi-component composite coating was formed on a diamond surface by thermal explosion synthesis technology. The effects of protective atmosphere (N2 or Ar), Al content of the phase composition, and microstructure of the binder and coating were studied. X-ray diffraction and scanning electron microscopy were used to analyze the phase composition and microstructure of the samples. The results showed that under the protection of Ar, the raw material did not undergo a thermal explosion reaction. A loose and porous bulk structure can be obtained through thermal explosion reaction under the protection of N2. The coating on the diamond surface was mainly composed of CrB and AlN and contained other by-products, such as Cr5Al8 and Cr2AlB2.

Microstructure and properties of Co–Al porous intermetallics fabricated by thermal explosion reaction

Abstract Co–Al porous intermetallics were fabricated by an efficient and energy-saving method of thermal explosion (TE) reactions. The effects of Co/Al molar ratios on the temperature profiles, phase compositions, expansion behaviors, density, pore characteristics, and oxidation resistance were investigated. When the target furnace temperature was set at 700°C, there was an obvious exothermic peak in the temperature profiles. The ignition temperatures were in the range of 600–645°C, and the combustion temperatures were in the range of 984–1,421°C. Co–Al porous intermetallics had the open porosity of 27–43%, and the pores were from nonfully dense green compacts and explosion behaviors of TE. The specimen with Co:Al = 2:9 possessed a higher open porosity of 42.8%, the lowest density of 1.86 g cm−3, and the largest volume expansion of 76.7%. The porous specimens with Co:Al = 1:1 possessed the highest open porosity of 43.2%, the lowest volume expansion of 12.3%, and the highest density of 3.42 g cm−3. All Co–Al porous intermetallics showed excellent oxidation resistance at 650°C in air, especially the specimen with Co:Al = 1:1 had the highest oxidation resistance.

Dissimilar joining mechanism, microstructure and properties of Ni to 316 stainless steel via Ni-Al thermal explosion reaction

Abstract To meet the requirements of energy-efficiency and high quality joining in the emerging industries field, a novel thermal explosion (TE) joining method was developed. The dissimilar Ni/316SS joint was first obtained by the TE reaction technology. The Ni-Al mixed powder was selected as TE reaction system, and the reaction product was used as interlayer. The effect of temperature (800, 850 and 900 °C), hold time (5, 10, 15 and 20 min) and joining pressure (0, 10, 20 and 30 MPa) on interfacial microstructure, diffusion behavior and mechanical properties of Ni/316SS joint were investigated. The maximum combustion temperature of Ni-Al interlayer during heating process was 1655 °C and a significant exothermic phenomenon was lasted for 2 s. 316SS(Al), Fe2Al5(Ni, Cr) and serration-like Ni5Al3 and Ni3Al were detected at the interface containing a reaction layer because of element diffusion. The maximum shear strength of the Ni/316SS joint was 65.2 MPa, and the failure is characterized by typical brittleness fracture. The fracture mode is the combination of partial spalling and fracture of the interlayer. The post heat-treatment assisted TE joining technique significantly shortened the bonding process of the dissimilar Ni/316SS joint at moderate temperatures, realizing the low energy and efficient joining between Ni and 316SS.

Achieving superior performance in thermoelectric Bi0.4Sb1.6Te3.72 by enhancing texture and inducing high-density line defects

Miniaturization of efficient thermoelectric (TE) devices has long been hindered by the weak mechanical strength and insufficient heat-to-electricity conversion efficiency of zone-melted (ZM) ingots. Here, we successfully prepared a robust high-performance p-type Bi0.4Sb1.6Te3.72 bulk alloy by combining an ultrafast thermal explosion reaction with the spark plasma sintering (TER-SPS) process. It is observed that the introduced excess Te not only enhances the (00l)-oriented texture to ensure an outstanding power factor (PF) of 5 mW m−1 K−2, but also induces extremely high-density line defects of up to 1011–1012 cm−2. Benefiting from such heavily dense line defects, the enhancement of the electronic thermal conductance from the increased electron mobility is fully compensated by the stronger phonon scattering, leading to an evident net reduction in total thermal conductivity. As a result, a superior ZT value of ~1.4 at 350 K is achieved, which is 40% higher than that of commercial ZM ingots. Moreover, owing to the strengthening of grain refinement and high-density line defects, the mechanical compressive stress reaches up to 94 MPa, which is 154% more than that of commercial single crystals. This research presents an effective strategy for the collaborative optimization of the texture, TE performance, and mechanical strength of Bi2Te3-based materials. As such, the present study contributes significantly to the future commercial development of miniature TE devices.

The effect of in situ nano-sized particle content on the properties of TiCx/Cu composites

The compression properties, wear resistance and electrical conductivities of TiCx/Cu composites fabricated via thermal explosion reaction combined with hot press in Cu–Ti-CNTs system at various nano-sized TiCx content with similar size were investigated. Results show that nano-sized TiCx can be effectively enhanced the Cu matrix. The σUCS, σ0.2 and wear resistance increased with the increasing content of TiCx particles. The εf and electrical conductivities decreased with increase of TiCx content. The ultimate compressive strength (σUCS), yield strength (σ0.2), Brinell Hardness and wear resistance increase with sacrificing the εf and the electrical conductivities. The 30 vol.% TiCx/Cu composites possess the highest σUCS, σ0.2, Brinell Hardness, wear resistance and the lowest εf, electrical conductivities among the 25–30 vol.% TiCx/Cu.