Thermite Research Articles

Advanced One-Dimensional Modeling of Thermite Reaction for Thermal Plug and Abandonment of Oil Wells

Advanced One-Dimensional Modeling of Thermite Reaction for Thermal Plug and Abandonment of Oil Wells

In-situ formation of particle reinforced Aluminium matrix composites by laser powder bed fusion of Fe2O3/AlSi12 powder mixture using laser melting/remelting strategy

In-situ preparation of particle reinforced Al matrix composites (PRAMCs) by laser powder bed fusion (LPBF) is a promising strategy to strengthen Al-based alloys. The laser-driven thermite reaction can be a practical mechanism to in-situ synthesise PRAMCs. However, the introduction of elements oxygen by adding Fe2O3 makes the powder mixture highly sensitive to form porosity and Al2O3 film during LPBF, bringing challenges to prepare dense materials. This work develops an LPBF processing strategy combined with consecutive high-energy laser melting scanning and low-energy laser remelting scanning to prepare dense PRAMCs from Fe2O3/AlSi12 powder mixture. A high relative density (98.2 ± 0.55 %) was successfully obtained by optimising laser melting (Emelting) and remelting energy density (Eremelting) to Emelting = 35 J/mm2 and Eremelting = 5 J/mm2. Results reveal the necessity to increase Emelting to improve metal liquid’s spreading/wetting by breaking up Al2O3 films surrounding molten pools; however, the high-energy laser melting produced much porosity. Low-energy laser remelting could close the resulting internal pores, backfill open gaps and smoothen solidified surfaces. Although with two-times laser scanning, the microstructure still shows fine cellular Si networks with Al grains inside (grain size 370 nm) and in-situ nano-precipitates (Al2O3, Si and Al-Fe(-Si) intermetallics). Finally, the fine microstructure, nano-structured dispersion strengthening and high-level densification strengthen the prepared in-situ PRAMCs, reaching yield strength of 426 ± 4 MPa and tensile strength of 473 ± 6 MPa. Furthermore, the results can provide valuable information to process other powder mixtures with severe porosity/oxide-film formation potential considering the evidenced contribution of laser melting/remelting strategy to densify material and obtain good mechanical properties during LPBF.

Research on temperature propagation law based on thermite plugging and abandonment technology

The continuous exploration and development of oil wells increases the risk of leakage from abandoned wells and brings challenges to the traditional plugging and abandonment technology. In order to overcome the above problems, a thermite plugging and abandonment technology is proposed in this field. The technology uses the aluminothermic reaction to melt the original or set material for sealing. The natural convection under different confinement conditions directly affects the heat flux transfer in the heat transfer process. In order to study the melting effect of the thermite reaction on sandstone, based on the heat conduction theory, a heat conduction model based on the temperature release law of the thermite reaction was established. The numerical simulation results show that the surrounding heat transfer conditions are the key factors affecting the heat transfer effect in the axial and radial directions without considering the particle size and dosage of the thermite itself. This work is of great significance for studying the temperature law of thermite reaction release and the future research of thermite plugging and abandonment technology.

THERMODYNAMIC ASPECTS OF OXIDES REDUCING BY ALUMINUM AND TITANIUM AT THE THERMIT WELDING OF RAILS

During aluminothermic welding of rails, formation of aluminum oxides can take place, which become centers of residual stresses forming resulting in cracks formation followed by fracture and destruction of the welding joint. It was proposed to add titanium scrap in the form of preliminary made powders to the welding thermites composition. At the replacement of aluminum by titanium, titanium oxides formation takes place providing higher resistance against cracks formation. Comparative estimation of thermodynamic properties [∆rH°(T), ∆rG°(T)] of thermite reactions with aluminum and titanium in the systems metal oxide – aluminum and metal oxide – titanium under standard conditions presented. As reaction components for calculation of thermodynamic properties, oxides of iron, manganese, silicon and chrome were used. Thermodynamic analysis of 6 reactions with aluminum and 30 reactions with titanium were carried out. It was established that all the reactions under consideration are thermodynamically probable. However, reactions of both aluminum and titanium with iron oxides had the highest probability and correspondently the highest heat generation. Reducing of silicon oxide had the lowest probability and correspondently the lowest heat generation. The reaction with oxides of manganese and chrome had an intermediate position. By the reducing ability titanium is not worse than aluminum and in reactions with iron oxide even exceeds it, particularly in the temperature range over 2000 K. Enthalpies of reducing reactions of iron oxide by titanium is in the same area of values as the enthalpies of reaction of reducing by aluminum. A thermodynamic analysis showed that application of titanium as a reducing agent at the thermit welding is quite acceptable along with aluminum.

Formation of dispersed Al/MoO3 interfaces and their effect on the energy release performance of Al–Ni composites

To find an efficient approach to tailoring the energy release performance of Al–Ni composites, flake-like α–MoO3 was added. Flake-like, micron-sized MoO3 particles assemble at the grain boundaries of Al matrix due to the weak interlayer bonding of α–MoO3 and the high affinity of Al and MoO3. At the Al/MoO3 interfaces, charge transfer takes place and increases the onset temperature of the Al–Ni intermetallic-forming reaction. The onset temperatures for the intermetallic-forming and Al–MoO3 thermite reactions are close together, leading to the interaction of these two reactions and higher reaction intensities. In addition, MoO3 distributes at Al grain boundaries, causing intergranular fracture and providing more, fresh, activated Al surfaces that can be oxidized during impact loading. The energy release performance of the Al–Ni composites was significantly improved by co-contribution from intermetallic formation and thermite and oxidation reactions due to the formation of dispersed Al/MoO3 interfaces.

Detonation of a nitromethane-based energetic mixture driven by electrical wire explosion

The combination of energetic material (EM) and an electrical wire explosion (EWE) is an important way to achieve effective release and conversion of electrical and chemical energy, e.g. by generating strong underwater shock waves (SWs) that can be used for dynamic reservoir fracturing in unconventional gas exploitation. This letter proposes a mud-like EM composed of nitromethane, aluminium and copper oxide powder, which can be detonated directly by a tungsten wire explosion. The detonation and successive deflagration result in notably enhanced SWs: with 2.8 g EM, the SW amplitude, impulse and energy are respectively increased by 1.7, 2.1, and 7.9 times compared to an optimal underwater EWE. A direct thermal initiation mechanism for the detonation process is proposed, with the exploding wire, the Joule heating along the current path in the EM and the Al/CuO thermite reaction all serving as heat sources. It is found that the Joule heating and chemical reactions reinforce each other, which is likely the key to the ‘easy’ detonation of nitromethane.

Thermodynamics of thermite reactions for a new thermal plug and abandonment process

Thermodynamics of thermite reactions for a new thermal plug and abandonment process

Development of a 3-D Dynamic Fracture Process Analysis code to Simulate Intermediate Loading Rate

For the stimulation solutions for oil and gas wells, the creation of multiple fractures that extend deep into surrounding rock formation is important to improve productivity or injectivity. For this purpose, the application of “not too slow but not too fast dynamic loading rate (hereafter intermediate dynamic loading rate)” has been proposed in the literature, which utilizes solid propellants. While previous researchers have experimentally demonstrated their applicability, our understanding of the detailed mechanism of rock fracturing for such an intermediate dynamic loading rate has not been mature enough. We have self-developed a state-of-the-art 3D combined finite-discrete element simulator that can model the complex dynamic fracture process of rocks. This paper applied the developed code to investigate its applicability to this class of problem characterized by the intermediate dynamic loading rate. NRC (new rock cracker) based on the water vaporized pressure due to the thermit reaction of the non-explosive ingredients was used. Based on the measured pressure as an input to the developed code, the 3D dynamic fracture process analysis (DFPA) was conducted. The involving dynamic fracture process and resultant fracture pattern were discussed. In addition, the required future tasks for more reasonable numerical simulation were also pointed out.

Thermite reaction driven pyrotechnic formulation with promising functional performance and reduced emissions

Green pyrotechnics/firecrackers reported herein are driven by thermite reactions for self-contained and self-sustained exothermic chemical reactions to make heat and sound by the usage of minimal fuel (aluminum), oxidizer (potassium nitrate), and Sulfur. These firecrackers have the potential for generating less emissions (70%) compared to commercial firecracker-based counterparts due to the presence of additives and are therefore designated as “Green firecrackers” or reduced emissions firecrackers. The functional performance and long-term stability of the composition was investigated through sound measurement and different tests, including ageing, thermal stability, and moisture test. The thermodynamics of the facilitated thermite reaction was cross-checked with experimental and theoretical methods. Prevalent mechanism for a substantial reduction in emissions to the tune of about 70% has been discussed. Cost of the green firecrackers is at par with the commercial firecrackers as cost of raw materials being used to prepare the formulation is comparable to the relatively toxic oxidizer substituted. “Green firecrackers” developed and reported here are environmentally benign in nature with higher business potential as far as a green chemistry-based sustainable solution for the society is required.

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.

Microstructure characterization of in-situ ZrC composite coating with graceful toughness and improved tribological properties prepared by plasma spraying

Substantial brittleness is still a problem to be solved for ceramic coatings. ZrC composite coating was prepared by plasma spraying ZrO2-SiC-Al composite powder utilizing in-situ reactions. As a comparison, ZrC-ZrSi2-Al2O3 composite powder was also used to prepare ZrC composite coating by plasma spraying via ex-situ approach. The reactions occurred in ZrO2-SiC-Al system during the plasma spraying process could be described as the thermite reaction between ZrO2 and Al and the self-propagating reaction between Zr and SiC. The corresponding formation mechanism of the composite coatings were also revealed. The resultant materials could melt fully under the effect of the plasma jet and the exothermic reactions. In-situ fabricated ZrC composite coating was featured with higher densification and better interlayer compactness compared to the coating prepared by ex-situ method. In-situ generated fine-grained microstructure, which was further confirmed by TEM, was homogenously distributed in the coating prepared by ZrO2-SiC-Al composite powder. Elevated toughness and excellent wear resistance observed in the coating prepared by plasma spraying ZrO2-SiC-Al composite powder could be attributed to the denser microstructure tailored by in-situ reactions.

Enhanced reactivity of copper complex-based reactive materials via mechanical milling

A prior investigation by the authors demonstrated that incorporating 25% of copper complex (Cu(NH3)4(NO3)2) into Al/CuO nanothermite enables to produce highly-reactive gas-generating energetic composites for emerging micro-airbag applications. To further improve the decomposition of the copper complex into gaseous species (N2, O2, N2O), during the thermite reaction, we employed ball milling technique to diminish its grain size down to the nanoscale. Results show that premilling the copper complex i.e. refining its grains without much modifying their structures, increases the pressure generation and burn rate by a factor 1.5 and 2, respectively. It also maintains a high degree of performances along with a wider range of thermite to copper complex mass ratio.

Generation of simulated corium using thermite process

Nuclear reactors are built with many inherent and engineered safety features with defence in depth philosophy, to maintain integrity of core during normal as well as accidental conditions. However, a severe accident scenario such as hypothetical core meltdown has to be considered in safety analysis of the plant, towards demonstrating a safe and coolable geometry of degraded core. Progression of corium, its subsequent interaction with coolant and settlement in the reactor vessel determines the extent of core damage and needs thorough investigation for ensuring safe mitigation of the accident. A comprehensive experimental program has been taken up at IGCAR to investigate severe accident phenomena in Sodium cooled Fast Reactors (SFR). Highly exothermic thermite reaction is used to generate a high temperature melt consisting of ceramic and iron simulating the corium. A dedicated test facility ‘THEME’ has been setup and few small scale simulation experiments were conducted to study various phenomena like subassembly melting, corium interaction with coolant and settlement of debris on corecatcher.

Aluminized Energetic Coordination Polymers Constructed from Transition Metal Centers (Co, Ni, and Cu)

AbstractThe afterburning effect of aluminized explosives makes them have strong damage ability to soft targets, but the aluminum particles in the composition often cannot achieve proper combustion. The high ignition temperature of micron aluminum powder is one of the main reasons. In this work, we introduce nanothermite reaction with low onset temperature (<660 °C) into aluminized explosives by replacing the base explosives with energetic coordination polymers (ECPs). The decomposition products of many ECPs contain corresponding metal oxides that will react with aluminum via thermite reaction. Three kinds of ECPs ([CoC2H4N8O4]n, [NiC2H4N8O4]n and [CuC2H4N8O4]n) are constructed and compounded with nano‐aluminum (nano‐Al) particles to form aluminized ECPs. The influence of metal ion species and Al/Metal (Al/Me) molar ratio on their energetic properties are systematically studied. The results show that the exothermic thermite reaction with low onset temperature plays an important role in the combustion propagation of aluminized ECPs, and the possible mechanism is proposed. When the Al/Me molar ratio is 3–4, the aluminized ECPs have the best peak pressure and pressurization rate. At the optimum molar ratio, the pressure and pressurization rate of aluminized ECP(Co) are much higher than those of aluminized ECP(Ni) and ECP(Cu). Among the three kinds of aluminized ECPs, the aluminized ECP(Co) has the best energetic characteristics and can be used as a preferred choice. However, for the applications that require a long‐time heat supply, aluminized ECP(Cu) will be suitable.

Study on Indium (III) Oxide/Aluminum Thermite Energetic Composites

Thermites or composite energetic materials are mixtures made of fuel and oxidizer particles at micron-scale. Thermite reactions are characterized by high adiabatic flame temperatures (>1000 °C) and high heats of reaction (>kJ/cm3), sometimes combined with gas generation. These properties strongly depend on the chemical nature of the couple of components implemented. The present work focuses on the use of indium (III) oxide nanoparticles as oxidizer in the elaboration of nanothermites. Mixed with an aluminum nanopowder, heat of reaction of the resulting Al/In2O3 energetic nanocomposite was calculated and its reactive performance (sensitivity thresholds regarding different stimuli (impact, friction, and electrostatic discharge) and combustion velocity examined. The Al/In2O3 nanothermite, whose heat of reaction was determined of about 11.75 kJ/cm3, was defined as insensitive and moderately sensitive to impact and friction stimuli and extreme sensitive to spark with values >100 N, 324 N, and 0.31 mJ, respectively. The spark sensitivity was decreased by increasing In2O3 oxidizer (27.71 mJ). The combustion speed in confined geometries experiments was established near 500 m/s. The nature of the oxidizer implemented herein within a thermite formulation is reported for the first time.

Comparison of pyrometry and thermography for thermal analysis of thermite reactions.

This study examines the thermal behavior of a laser ignited thermite composed of aluminum and bismuth trioxide. Temperature data were collected during the reaction using a four-color pyrometer and a high-speed color camera modified for thermography. The two diagnostics were arranged to collect data simultaneously, with similar fields of view and with similar data acquisition rates, so that the two techniques could be directly compared. Results show that at initial and final stages of the reaction, a lower signal-to-noise ratio affects the accuracy of the measured temperatures. Both diagnostics captured the same trends in transient thermal behavior, but the average temperatures measured with thermography were about 750 K higher than those from the pyrometer. This difference was attributed to the lower dynamic range of the thermography camera's image sensor, which was unable to resolve cooler temperatures in the field of view as well as the photomultiplier tube sensors in the pyrometer. Overall, while the camera could not accurately capture the average temperature of a scene, its ability to capture peak temperatures and spatial data make it the preferred method for tracking thermal behavior in thermite reactions.

Chemical Analysis of the Cause of Thermal Runaway of Lithium-Ion Iron Phosphate Batteries

Due to the lack of effective methods to determine the cause of thermal runaway of lithium-ion batteries (LIBs), many fires are wrongly classified as LIBs fires. In this paper, we conducted different types of LIBs experiments to study the stage of thermal runaway and the distribution of combustion products. Through experiments analysis, we discovered for the first time the characteristic elements associated with the cause of thermal runaway of LIBs in the solid combustion products. Under overcharge conditions, the aluminum element was detected for the combustion products. The main reason is that a large amount of metal oxides precipitated from electrode materials react with aluminum foil at high temperatures to form alumina (Al2O3). However, under heating conditions, the aluminum element was not detected because of the lack of sufficient conditions for thermite reactions. The conclusion was verified by multiple sets of repeated experiments.

Exothermic behaviour of aluminium and graphene as a fuel in Fe2O3 based nanothermite

Abstract The main frontier of this research is to study the influence of multi-layer graphene (MLG) and aluminium as a fuel in Al/Fe2O3 and MLG/Fe2O3 nanothermites, fabricated by physical mixing and ultrasonication techniques. To study the structural and energy release properties, prepared samples were characterized by XRD, FESEM, EDS, FTIR, Raman spectroscopy and DSC. The X-ray diffraction (XRD) technique showed that all the phases remain intact during the synthesis. Field emission electron microscopy (FESEM) micrographs displayed the surface morphology of the samples, and besides this, energy dispersive spectroscopy (EDS) was used to check the elemental composition of samples. Raman spectroscopy revealed that the ultrasonication waves did not deteriorate the aromatic structure of graphene sheets. Fourier transform infrared spectroscopy (FTIR) spectra were used to observe the information about various functional groups present in the thermite samples. The exothermic energy released by the thermite reaction in both the samples was investigated by differential scanning calorimetry (DSC) and the observed values of energy release for Al/Fe2O3 and MLG/Fe2O3 are 215 J/g and 1640 J/g.

Connecting agglomeration and burn rate in a thermite reaction: Role of oxidizer morphology

Agglomeration (sintering) of aluminum particles has been commonly observed in solid propellants and pyrotechnics and it is believed to play a key role on the combustion performance of these materials. One of the most commonly studied nanothermites – Al/CuO – has also been well documented to exhibit this agglomeration phenomenon. In this work, high-speed in-operando microscopy and pyrometry were used to observe agglomeration in an Al/CuO reaction with different oxidizer particle size and shape (microparticles, microwires and nanoparticles). We found that the use of a microwire oxidizer resulted in propagation velocities and agglomerate sizes more similar to nanoparticles rather than microparticles. Replacing CuO microparticles (5 µm) with similarly-sized CuO microwires (equivalent diameter: 3 µm) was shown to dramatically elevate the burn rate by ~27 × (2 m/s vs 55 m/s) and increased the flame temperature from 2550 K to 3200 K, resulting in ~30 × higher heat flux (energy release rate). Adding 10 wt.% polymer into the above three thermite systems slowed down the burn rates from ~m/s to ~cm/s, which allowed our microscopic system to probe the details of the agglomeration process. The agglomeration size was found to be reduced from ~40 µm to ~13 µm when replacing CuO microparticles with microwires in the 3D printed Al/CuO composites, similar to that of CuO nanoparticles case. Our results point to a “pocket” model to explain these trends. In a reactive composite, CuO microwires should create an Al “pocket” closer in size to that when using CuO NPs and considerably smaller that with CuO microparticles. The reduced pocket size should also enhance burn velocity. These results also suggest the “pocket” offers a pathway to think about architectures to minimize the sintering size which is known to lead to two-phase losses in propellants.

The Impact of Metastable Intermolrecular Nanocomposite Particles on Kinetic Decomposition of Heterocyclic Nitramines Using Advanced Solid‐Phase Decomposition Models

Surface oxygen of oxide catalyst has low coordination number; they are negatively charged. Surface oxygen can act active site for decomposition of energetic nitramines (i.e. HMX). Additionally hydrous catalyst surface can release active OH radicals. Colloidal oxide particles can fulfil these requirements. Furthermore oxide particles can induce thermite reaction with aluminium particles. This study reports on the facile fabrication of colloidal ferric oxide particles of 5 nm average particle size. Aluminium nanoplates of 100 nm particle size were dispersed in ferric oxide colloid. Colloidal Fe2O3/Al binary mixture was integrated into HMX matrix via co-precipitation technique. SEM micrographs demonstrated uniform dispersion of nanothermite particles into energetic matrix. Naonothermite particles experienced dramatic change in HMX thermal behaviour with increase in total heat release by 63% using DSC. The impact of thermite particles on HMX kinetic decomposition was evaluated via an integral isoconversional method using KAS, and Kissinger models. The mean value of apparent activation was reduced by 23.5 and 24.3% using Kissinger and KAS models respectively. This dramatic change in HMX decomposition could be ascribed to ferric oxide reactivity. Facile integration of colloidal thermite particles into HMX can secure high interfacial surface area.