Comparative investigations of ternary thermite Al/Fe_(2)O_(3)/CuO and Al/Fe_(2)O_(3)/Bi_(2)O_(3) from pyrolytic,kinetics and combustion behaviors

To develop new energy enhancement energetic materials with great combustion performance and thermal stability,two kinds of ternary thermite,Al/Fe_(2)O_(3)/CuO and Al/Fe_(2)O_(3)/Bi_(2)O_(3),were prepared and analyzed via mechanical ball milling.The samples were characterized by SEM,XRD,TG-DSC,constant volume and constant pressure combustion experiments.The first exothermic peaks of Al/Fe_(2)O_(3)/CuO and Al/Fe_(2)O_(3)/Bi_(2)O_(3) appear at 579°C and 564.5°C,respectively.The corresponding activation energies are similar.The corresponding mechanism functions are set as G(a) = [-ln(1-a)]^(3/4) and G(a) =[-ln(1-a)]2/3,respectively,which belong to the Avrami-Erofeev equation.Al/Fe_(2)O_(3)/CuO has better thermal safety.For small dose samples,its critical temperature of thermal explosion is 121.05°C higher than that of Al/Fe_(2)O_(3)/Bi_(2)O_(3).During combustion,the flame of Al/Fe_(2)O_(3)/CuO is spherical,and the main products are FeAl_(2)O_(4) and Cu.The flame of Al/Fe_(2)O_(3)/Bi_(2)O_(3)is jet-like,and the main products are Al_(2)O_(3),Bi and Fe.Al/Fe_(2)O_(3)/Bi_(2)O_(3)has better ignition and gas production performance.Its average ignition energy is 4.2 J lower than that of Al/Fe_(2)O_(3)/CuO.Its average step-up rate is 28.29 MPa/s,which is much higher than 6.84 MPa/s of Al/Fe_(2)O_(3)/CuO.This paper provides a reference for studying the thermal safety and combustion performance of ternary thermite.

Novel Insight into the Preparation of Ti-6Al-4V Alloy Through Thermite Reduction Based on the Mass Action Concentration

Based on the mass action concentration theory,a novel thermodynamic analysis for the raw material ratio in the procedure of preparing Ti-6Al-4V alloy by aluminothermic reduction process is proposed in this paper,which is originated from TiO_(2),Al particles,and V_(2)O_(5) as feedstocks,and the relevant equilibrium thermodynamics was calculated through this new method.The results show that the range of aluminum addition coefficient in raw material to experiment should be controlled within 61.5%-100%,which can significantly reduce the number of experimental groups.This method is ready to regulate the matter of excessive aluminum content in reactants for materials preparation,especially for those reactions including elements that are effortless to combine with aluminum to form the corresponding intermetallics or alloys.In addition,it can also be used in general metallurgy or material preparation process to effectively predict the composition and proportion of equilibrium components under certain conditions.

Microstructure and Wear Behaviour of Laser-Induced Thermite Reaction Al_2O_3 Ceramic Coatings on Pure Aluminum and AA7075 Aluminum Alloy

Wear-resistant laser-induced thermite reaction Al2O3 ceramic coatings can be fabricated on pure Al and AA7075 aluminum alloy by laser cladding （one-step method） and laser cladding followed by laser re-melting （two-step method） using mixed powders CuO-Al-SiO2 in order to improve the wear properties of aluminum and aluminum alloy, respectively. The microstructure of the coatings was characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The wear resistance of the coatings was evaluated under dry sliding wear test condition at room temperature. Owing to the presence of hard α-Al2O3 and γ-Al2O3 phases, the coatings exhibited excellent wear resistance. In addition, the wear resistance of the coatings fabricated by two-step method is superior to that of the coatings fabricated by one-step method.

Fabrication of an r-Al_2Ti intermetallic matrix composite reinforced with α-Al_2O_3 ceramic by discontinuous mechanical milling for thermite reaction

In this study, a powder mixture with an Al/TiO2 molar ratio of 10/3 was used to form an r-Al2Ti intermetallic matrix composite （IMC） reinforced with α-Al2O3 ceramic by a novel milling technique, called discontinuous mechanical milling （DMM） instead of milling and ignition of the produced thermite. The results of energy dispersive X-ray spectroscopy （EDX） and X-ray diffraction （XRD） of samples with varying milling time indicate that this fabrication process requires considerable mechanical energy. It is shown that Al2Ti-α-Al2O3 IMC with small grain size was produced by DMM after 15 h of ball milling. Peaks for γ-TLA1 as well as Al2Ti and Al2O3 are observed in XRD patterns after DMM followed by heat treatment. The microhardness of the DMM-treated composite produced after heat treatment was higher than Hv 700.

钢铁业副产物衍生Thermite熔剂熔融处理及回收都市垃圾焚化飞灰之研究

创新熔融技术之研究——利用具有高温自传播特性的工业副产物衍生Thermite反应熔融处理及回收都市垃圾焚化飞灰。选定两种钢铁业副产物-转炉矿泥及热轧矿泥与铝业下脚料——铝屑混合成Thermite熔剂(文中称Thermite A、Thermite B),应用于熔融处理都市垃圾焚化飞灰及回收金属资源与熔渣之研究。两种副产物与铝屑衍生Thermite熔剂之最佳配比与理论值相符,分别为28．1%铝屑混合71．9%转炉矿泥、25．2%铝屑混合74．8%热轧矿泥。反应具自传播特性之最大飞灰添加量分别为21．1%、15．7%范围,自传播特性不受辅助热源影响。以两种钢铁业副产物衍生Thermite熔剂熔融处理都市垃圾焚化飞灰结果:反应温度分别可达2048℃～1236℃及1766℃～1200℃高温．产物包括熔渣与金属锭,经辅助热源修正后,两者分离效果良好,总固体物回收率分别介于81．8%-96．3%及81．4%-94．6%;熔渣呈现黑色坚硬玻璃质状, XRD分析其主要物种为Al2O3、Fe、CaAl4O7、SiO2:TCLP溶出结果符合环保署法规限值,显示熔渣安定性及可再利用价值。金属锭中铁含量介于91．8%-97．9%,以理论配比所得之金属锭含铁量最高,辅助热源提升反应温度可提高金属锭之含铁量。综合评估,利用工业废弃资材自身化学反应热能提供作为熔融热源,处理有害事业废弃物,同时回收金属资源及熔渣。技术精进创新、节省能源、环境友善最终处理、废弃物资源化等优点．对于建立永续发展之循环型环境而言,为极具价值之技术。

Microstructure and Wear Behaviour of Laser-induced Thermite Reaction Al_2O_3 Ceramic Coating on AA7075 Aluminum Alloy

The microstructure and wear behaviour of the thermite reaction coating produced by the hybrid laser claddingremelting on AA7075 aluminum alloy for the systems of Al-CuO-SiO2, Al-Cr2O3-SiO2, Al-Fe2O3-SiO2, and Al-TiO2-SiO2 were studied. The results of the X-ray diffraction （XRD） analysis show that in all the four reaction coatings, α-Al2O3 and γ-Al2O3 phases were present at the top surface, together with various intermetallic phases, the corresponding reduced metal and Al phase in the fusion zone. Under the dry sliding condition, the wear resistance, in terms of weight loss, of the laser-clad specimens was considerably higher than that of the untreated specimen. The predominant wear mechanism of the former specimens was abrasive wear, while for the latter, it was the adhesive wear that prevailed.

Chemical Reaction of In-situ Processing of NiAl/Al_2O_3 Composite by Using Thermite Reaction

NiAl/Al2O3 composite were synthesized by thermite reaction of nickel oxide and aluminum powder mixtures.The phase,the microstructure of the composite,as well as the thermite reaction mechanism,were investigated by X-ray diffractomety（XRD0,scanning electron microscopy（SEM） combined with differential scanning calorimetry（DSC）.The experimental results show that the thermite reaction leads to the interpenetrating network structure of NiAl/Al2O3 at 1223K for 60min and the chemical reaction apparent activation energy is Eap=166.960±13.496kJ·mol^-1 in the NiO/Al system.

Design,preparation,and characterization of a novel ZnO/CuO/Al energetic diode with dual functionality:Logic and destruction

Self-destructing chips have promising applications for securing data.This paper proposes a new concept of energetic diodes for the first time,which can be used for self-destructive chips.A simple two-step electrochemical deposition method is used to prepare ZnO/CuO/Al energetic diode,in which N-type ZnO and P-type CuO are constricted to a PN junction.This paper comprehensively discusses the material properties,morphology,semiconductor characteristics,and exploding performances of the energetic diode.Experimental results show that the energetic diode has typical rectification with a turn-on voltage of about 1.78 V and a reverse leakage current of about 3×10^(-4)A.When a constant voltage of 70 V loads to the energetic diode in the forward direction for about 0.14 s or 55 V loads in the reverse direction for about 0.17 s,the loaded power can excite the energetic diode exploding and the current rises to about100 A.Due to the unique performance of the energetic diode,it has a double function of rectification and explosion.The energetic diode can be used as a logic element in the normal chip to complete the regular operation,and it can release energy to destroy the chip accurately.

Sulfur distribution in preparation of high titanium ferroalloy by thermite method with different CaO additions

Ferrotitanium is used as a deoxidizer and alloying agent during steelmaking process,which has a high demand for sulfur control.Sulfur was introduced from raw materials in the process of producing ferrotitanium by thermite method,where CaO was used as fluxing agent.At the same time,CaO has a great desulfurization capability.Effects of CaO addition on the distribution of sulfur in high titanium ferroalloy prepared by thermite method were studied in this work.The equilibrium diagram of Ti-AlFe-S system was calculated by FactSage 6.4 software package with FactPS and FTmisc database.The alloy and slag samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),inductively coupled plasma atomic emission spectrometer(ICP-AES),X-ray fluorescence(XRF)and high-frequency infrared ray carbon sulfur analyzer.The result indicates that the sulfur in the alloy firstly exists in the form of liquid FeS,thereafter TiS(s)and eventually Ti2 S(s)during cooling.The sulfur is mainly distributed in the alloy,and only a small amount of sulfur remains in the slag.Moreover,it is noted that the sulfur in the alloy does not distribute homogeneously,and it exists in the form of solid solution phase,(Ti,Al,Fe)S.S content in the slag,the sulfur capacity of the slag and the sulfur distribution ratio(LS)all increase with the increment of CaO addition,while S content in alloys decreases.

Oxygen content of high ferrotitanium prepared by thermite method with different melt separation temperatures

High ferrotitanium prepared directly by the thermite method has a disadvantageously high O content(≥10 wt%)because of the short slag-metal separation time.In this study,CaO and CaF2 are added to the melt to improve the basicity of the slag and melt separation under heat preservation is performed to strengthen slag-metal separation.The thermodynamics of the step-by-step reduction process of TiO2 in the Ti-Al-Fe-Si-O system whose composition is close to the alloy after melt separation were calculated.Samples of alloys and slags before and after melt separation were systematically analyzed.The result indicates that the reaction that TiO is reduced by Al to Ti is the limited step in the reduction process of TiO2.The O content of the alloys slightly decreases with temperature from 1873 to 2023 K,which agrees with the changes in the law of deoxidation limit.It is mainly attributed to the movement of chemical reactions in the alloy melt at different temperatures and slag-metal interfacial reaction.The addition of Al2 O3-CaO-CaF2 slag and high temperature promote the removal of Al2 O3 and titanium suboxides.The minimum contents of O and Al in the alloy reach 1.84 wt% and 3.26 wt%,respectively.

Multistage desulfurization mechanism to reduce sulfur content of high ferrotitanium prepared using thermite method

High ferrotitanium is used as a deoxidizer and alloying agent in steelmaking processes and is mainly produced using high-cost remelting processes.The thermite method is a simple and low-cost method for preparing low ferrotitanium.However,the high levels of S,Al,and O residues in the product severely restrict its applicability in the low-cost preparation of good-quality high ferrotitanium.In this study,a novel multistage deep reduction method for preparing high-quality high ferrotitanium is proposed,and the multistage desulfurization mechanism is systematically investigated.The results indicate that multistage desulfurization is an effective method for reducing the S content of high ferrotitanium prepared via the thermite method.During the strong desulfurization stage,Ti_(2)S reacts with CaO at the slag-metal interface and produces CaS.The S content decreases,while the O content increases,with the increase of CaO in the CaO-Al_(2)O_(3)-based slag.During the deep desulfurization,Ti_(2)S is deeply reduced by the Ca and produces CaS,thus further reducing the S content.The S content decreases with the incremental addition of Ca and can be reduced to 0.035 wt%after multistage desulfurization.

Electrophoretic deposition of hybrid organic-inorganic PTFE/Al/CuO energetic film

Thermite films are typical energetic materials(EMs)and have great value in initiating explosive devices.However,research in thermite film preparation is far behind that of research in thermite powders.Electrophoretic deposition(EPD)is an emerging,rapid coating method for film fabrication,including of energetic composite films.In this work,a polytetrafluoroethylene(PTFE)/Al/CuO organic-inorganic hybrid energetic film was successfully obtained using the above method for the first time.The addition of lithocholic acid as a surfactant into the electroplating suspension enabled PTFE to be charged.The combustion and energy release were analyzed by means of a high-speed camera and differential scanning calorimetery(DSC).It was found that the combustion process and energy release of PTFE/Al/CuO were much better than that of Al/CuO.The main reason for the excellent combustion performance of the hybrid PTFE/Al/CuO system was that the oxidability of PTFE accelerated the redox reaction between Al and CuO.The prepared PTFE/Al/CuO film was also employed as ignition material to fire a B-KNO_3 explosive successfully,indicating considerable potential for use as an ignition material in micro-ignitors.This study sheds light on the preparation of fluoropolymer-containing organic-inorganic hybrid energetic films by one-step electrophoretic deposition.

Enhancing energetic performance of metal-organic complex-based metastable energetic nanocomposites by spray crystallization

Energetic metal-organic complexes have been involved in nanothermites as novel oxidants.However,the existing preparation methods often lead to mixing inhomogeneity and small contact area of ingredients,the reactivity and functionality of the novel energetic nanocomposites are still limited.In this work,spray crystallization(SC)method was used to prepare novel energetic nanocomposites,the high-energy metal-organic complex[Ni(CHZ)_(3)](ClO_(4))_(2)(CHZ=1,3-diaminourea)was composited with nanoaluminum(n-Al).Results showed that n-Al/[Ni(CH_(2))_(3)](ClO_(4))_(2)energetic nanocomposites prepared by SC method increased heat release to 2977.6 J/g and peak pressure to 3.91 MPa with higher pressurization rate(1324.06 MPa/s),decreased sensitivity thresholds(>100 mJ)to electrostatic discharge(ESD)and enhanced detonation ability compared with[Ni(CHZ)_(3)](ClO_(4))_(2)alone and physically mixed(PM)n-Al/[Ni(CHZ)_(3)](ClO_(4))_(2).These results proved that it is significant to introduce energetic metal-organic complexes with inherent high energy in new-concept n-Al/energetic metal-organic complexes nanocomposites through SC method for a better performance of its application.

Use of Intermetallic Alloys as Reactive Materials for Warhead Applications

With this communication we want to suggest the system ZrW2,a high-density and very hard intermetallic compound that reacts/burns highly exothermic with air at high temperature.This intermetallic phase should provide a very suitable reactive material for warhead applications.

Combustion characteristics of aluminium-iron oxide in SHS-gravitational process

In order to get high quality of products, the combustion of aluminium-ironoxide thermite in SHS-gravitational process must be under control. The effects of thermite fillingdensity, hole in thermite and inclined angle of pipe on combustion rate were studied. It shows thatthe combustion rate decreases with the decrease of filling density. The thermite combusts downwardsthe pipe much more quickly if there are holes in the thermite. And the combustion rate increaseswith the increase of the inclined angle of pipe. The experiment results show that the combustion ofthermite is predominantly controlled by gas phase reaction, which is attributed to the hightemperature of the thermite combustion.

反应堆热工水力子通道分析程序ATHAS的研发

介绍了具有自主知识产权的反应堆热工水力子通道分析程序ATHAS的物理模型和数值解法。利用ATHAS对西屋四环路压水堆进行全堆芯热工水力子通道分析,并与COBRA-EN和THERMIT-2的预测值进行对比,结果表明:ATHAS能够准确预测大型压水堆堆芯内的热工水力参数分布。本文对ATHAS研发的思路和方法,对我国核电站热工水力软件自主化的设计开发具有借鉴意义。

Preparation of CuCr alloys by thermit-reduction electromagnetic stirring

The influences of the additive CaF2, different molds, mold pre-heating temperature, electromagnetic stirring, and alloying elements on CuCr have been investigated respectively during the preparation of CuCr alloys by thermit-reduction electromagnetic stirring. The results indicate that the reasonable reactant mass ratio of CuO： Cr2O3：Al is 100：140：160; CaF2 can reduce the solidification point of slags to improve the metal separating efficiency from slags; the crystal particles become thinner because of the high cooling velocity in the metal mold; while casting in the graphite mold, the casting properties of CuCr improve with the increase of pre-heating temperature; the compact alloys are prepared at 500℃; electromagnetic stirring can prevent the growth of dendrite crystal into refine crystal particles, as well as homogenize Cu and Cr to improve the CuCr properties; the optimal stirring time is 7 min; when the alloying elements Ni and Co are added to the reactants, elements Cu and Cr can distribute evenly but the crystal particles become thick.

STUDY OF PREPARATION PROCESS OF TUNGSTEN POWDER BY SHS WITH A MAGNESIUM THERMIT STAGE

Tungsten powder was fabricated from the system CaWO4-Mg by self-propagating high-temperature synthesis (SHS) with a magnesium thermit stage. The physic-chemical change during heating and the effects of pressure of sample and diluents (W powder) on product have been studied. The experimental results show that the porosity of combustion product and the particle size of final tungsten powder decrease with increasing pressure of sample. Addition of diluents could increase the particle size of final tungsten powder. The purity of tungsten is improved by leaching in NaOH solution. The results of spectral analysis and particle size distribution of final tungsten powder show that the final Tungsten powder has a median diameter of 0.87μm,specific surface area of 1.09m2/g and purity of above 99.0%.

Application of heat treatment technology for thermit welds at Da-qin railway

A kind of heat treatment technology of thermit welds was introduced in this paper. Through the heal treatment not only the mechanical properties are improved, but the hardness of head was redistributed. Heat treatreatment alleviated the soften of the quenched rail clue to welding. The technology has been successfully applied to lay the lines and crosses at Da-qin continuous line.