Joint Reduction of NiO/WO3 Pair and NiWO4 by Mg + C Combined Reducer at High Heating Rates

Functional features of Ni-W composite materials combined with successful performance enabled a breakthrough in their broad application. To disclose the formation pathway of Ni-W composite materials at extreme conditions of combustion synthesis in the NiO-WO3-Mg-C and NiWO4-Mg-C systems for the optimization of the synthesis procedure, the process was modeled under programmed linear heating conditions by thermal analysis methods. The reduction kinetics of tungsten and nickel oxides mixture and nickel tungstate by Mg + C combined reducer at non-isothermal conditions was studied at high heating rates (100–1200 °C min−1) by high-speed temperature scanner techniques. It was shown that when moving from low heating to high heating rates, the mechanism of both the magnesiothermic and magnesio-carbothermic reductions of the initial mixtures changes; that is, the transition from a solid-solid scheme to a solid-liquid scheme is observed. The strong influence of the heating rate on the reduction degree and kinetic parameters of the systems under study was affirmed. The simultaneous utilization of magnesium and carbon as reducers allowed the lowering of the starting and maximum temperatures of reduction processes, as evidenced by the synergetic effect at the utilization of a combined reducer. The effective values of activation energy (Ea) for the reactions proceeding in the mixtures NiO + WO3 + 4Mg, NiO + WO3 + 2.5Mg + 1.5C, NiWO4 + 4Mg and NiWO4 + 2Mg + 2C were estimated by Kissinger isoconversional method and were 146 ± 10, 141 ± 10, 216 ± 15 and 148 ± 15 kJ mol−1, respectively.

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The Mechanism of Joint Reduction of MoO3 and CuO by Combined Mg/C Reducer at High Heating Rates

10.20944/preprints202108.0189.v1 ◽

2021 ◽

Author(s):

Hasmik Kirakosyan ◽

Khachik Nazaretyan ◽

Sofiya Aydinyan ◽

Suren Kharatyan

Keyword(s):

Interaction Mechanism ◽

Decisive Role ◽

Isoconversional Method ◽

Reducing Agents ◽

Conversion Degree ◽

Molybdenum Oxides ◽

Heating Rates ◽

Composite Powders ◽

Efficient Delivery ◽

High Heating

Understanding of the decisive role of the interaction mechanism and kinetics in the combustion processes is highly relevant for the elaboration of optimal conditions for obtaining Mo-Cu composite powders. From this perspective, the efficient delivery of the reduction mechanism of copper and molybdenum oxides with combined Mg + C reducing agents at high heating rates is crucial to develop a valuable approach for the combustion synthesis of Mo-Cu composite powders. Herein, we shed light on the mechanism of the reactions in all the studied binary, ternary and quaternary systems contemporaneously demonstrating the effect of the heating rate on the conversion degree. The combination of two highly exothermic and speedy reactions (MoO3+3Mg and CuO+Mg vs MoO3+CuO+4Mg) led to a slow interaction with weak self-heating (dysynergistic effect) due to a change in the reaction mechanism. On the other hand, it has been shown that during the simultaneous utilization of the Mg and C reducing agents, the process begins exclusively with carbothermic reduction, and at relatively high temperatures it continues with magnesiothermic one. The effective activation energy values of the magnesiothermic stages of the studied reactions were determined by Kissinger isoconversional method.

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Safe Conditions for Conducting Tests Using Ballistic Facilities

Proceedings of Higher Educational Institutions Маchine Building ◽

10.18698/0536-1044-2019-9-105-114 ◽

2019 ◽

pp. 105-114

Author(s):

S.I. Gerasimov ◽

I.A. Odzeriho ◽

R.V. Gerasimova ◽

A.V. Salnikov ◽

A.P. Kalmykov ◽

...

Keyword(s):

High Speed ◽

Practical Implication ◽

Structure Change ◽

Heating Rates ◽

Significant Challenge ◽

Modern Engineering ◽

High Heating ◽

Compressed Gas ◽

Strong Compression ◽

Exterior Ballistics

Understanding the physical and thermomechanical response of materials subjected to intense dynamic loading is a significant challenge that has a practical implication for modern engineering. Shock compression followed by expansion precipitates both reversible and irreversible physical and mechanical processes in the material. These processes include strong compression in solids, high heating rates, phase transformations, electronic structure change, work hardening, spalling. Methods and devices for producing intense shock loads can be subdivided into several groups. Presently, in worldwide practice, gun type launchers have gained the widest acceptance in studying dynamic compressibility, strength characteristics, and spallatation phenomena in laboratory conditions. In this type of facility, the launched body moves in a tube under the force of a compressed gas. The facilities differ depending on the gas used and the method of its compression. Specific features of the facilities impose certain limitations on the registration and format of the tests. Examples of determining the boundary between the interior and exterior ballistics, the influence of the launched body supporting elements and the conditions of safe testing at high-speed entry in fuel are considered in this work.

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FEATURES OF MANUFACTURE OF COMPOSITE MATERIAL WITH MACROHETEROGENEOUS STRUCTURE WITH THE APPLICATION OF MAGNETIC FIELDS

Litiyo i Metallurgiya (FOUNDRY PRODUCTION AND METALLURGY) ◽

10.21122/1683-6065-2018-1-124-127 ◽

2018 ◽

pp. 124-127 ◽

Cited By ~ 1

Author(s):

A. S. Kalinichenko ◽

V. A. Sheinert ◽

V. A. Kalinichenko ◽

A. G. Slutsky

Keyword(s):

Composite Materials ◽

High Speed ◽

Experimental Studies ◽

Induction Melting ◽

The Matrix ◽

Optimal Technology ◽

Reinforcing Material ◽

The Stability ◽

High Level ◽

Solid Liquid

Casted composite materials have found application in various branches of industrial production. However, there are still a number of problems related to the choice of optimal technology for their synthesis and the solution of which will help to achieve in practice high level of properties predicted by the theory and provide the control of interfacial interactions to enhance the stability of the structure and properties of composites. There is s need in additional research related to the development of new types of reinforcing elements, which will provide the raise in the level of performance of the composite. It is established that an important role plays not only the type of the matrix but also the chemical composition and microstructure of the reinforcing material. This would require research on optimization of technology for production of composite materials during the solid-liquid synthesis. The paper presents generalized results of experimental studies of peculiarities during the formation of composite materials on the basis of bronze and iron granules with the use of high-speed induction melting. As reinforcing phase iron granules DCHL with a diameter of about 1 mm were used.

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Study of dynamic features of highly energetic reactions by DSC and High-Speed Temperature Scanner (HSTS)

MRS Proceedings ◽

10.1557/opl.2013.144 ◽

2013 ◽

Vol 1521 ◽

Cited By ~ 2

Author(s):

M.A. Hobosyan ◽

Kh.G. Kirakosyan ◽

S.L. Kharatyan ◽

K.S. Martirosyan

Keyword(s):

High Speed ◽

Initial Period ◽

Exothermic Reaction ◽

Dynamic Features ◽

Heating Rates ◽

Scanning Calorimetry ◽

Dsc Measurements ◽

High Heating ◽

Mechanism And Kinetics ◽

Conventional Dsc

ABSTRACTThe dynamic features of Al2O3 - polytetrafluoroethylene (PTFE) and Al - PTFE reactions in non-isothermal conditions are presented. The Differential Scanning Calorimetry (DSC) and High-Speed Temperature Scanner (HSTS) were used to characterize the Al2O3/Al – PTFE reactions at different heating rates. The study shows that the HSTS instrument can give more information about the reaction mechanism and kinetics than the conventional DSC measurements. In this work we show that high heating rates may reveal exothermic reaction between Al2O3 and PTFE that were previously unidentified. The PTFE can potentially remove the oxide layer from aluminum in the initial period of the reaction and increase the direct contact area between oxygen and aluminum, which increases the reaction velocity and improves the energy release abilities of the system.

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The Mechanism of Joint Reduction of MoO3 and CuO by Combined Mg/C Reducer at High Heating Rates

Journal of Composites Science ◽

10.3390/jcs5120318 ◽

2021 ◽

Vol 5 (12) ◽

pp. 318

Author(s):

Hasmik Kirakosyan ◽

Khachik Nazaretyan ◽

Sofiya Aydinyan ◽

Suren Kharatyan

Keyword(s):

Interaction Mechanism ◽

Decisive Role ◽

Isoconversional Method ◽

Reducing Agents ◽

Isothermal Treatment ◽

Molybdenum Oxides ◽

Heating Rates ◽

High Heating ◽

Combustion Processes

Understanding of the decisive role of non-isothermal treatment on the interaction mechanism and kinetics of the MoO3-CuO-Mg-C system is highly relevant for the elaboration of optimal conditions at obtaining Mo-Cu composite powder in the combustion processes. The reduction pathway of copper and molybdenum oxides with combined Mg + C reducing agents at high heating rates from 100 to 5200 K min−1 was delivered. In particular the sequence of the reactions in all the studied binary, ternary and quaternary systems contemporaneously demonstrating the effect of the heating rate on products’ phase composition and microstructure was elucidated. The combination of two highly exothermic and speedy reactions (MoO3 + 3Mg and CuO + Mg vs. MoO3 + CuO + 4Mg) led to a slow interaction with weak self-heating (dysynergistic effect) due to a change in the reaction mechanism. Furthermore, it has been shown that upon the simultaneous utilization of the Mg and C reducing agents, the process initiates exclusively with carbothermic reduction, and at relatively high temperatures it continues with magnesiothermic reaction. The effective activation energy values of the magnesiothermic stages of the studied reactions were determined by Kissinger isoconversional method.

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Comparing fast inductive tempering and conventional tempering: Effects on microstructure and mechanical properties

Metallurgical Research & Technology ◽

10.1051/metal/2018015 ◽

2018 ◽

Vol 115 (4) ◽

pp. 407 ◽

Cited By ~ 4

Author(s):

Annika Eggbauer Vieweg ◽

Gerald Ressel ◽

Peter Raninger ◽

Petri Prevedel ◽

Stefan Marsoner ◽

...

Keyword(s):

Mechanical Properties ◽

Impact Energy ◽

Charpy Impact ◽

Heat Treating ◽

Processing Route ◽

High Heating Rate ◽

Heating Rates ◽

High Heating ◽

Tempering Treatment ◽

Carbide Distribution

Induction heating processes are of rising interest within the heat treating industry. Using inductive tempering, a lot of production time can be saved compared to a conventional tempering treatment. However, it is not completely understood how fast inductive processes influence the quenched and tempered microstructure and the corresponding mechanical properties. The aim of this work is to highlight differences between inductive and conventional tempering processes and to suggest a possible processing route which results in optimized microstructures, as well as desirable mechanical properties. Therefore, the present work evaluates the influencing factors of high heating rates to tempering temperatures on the microstructure as well as hardness and Charpy impact energy. To this end, after quenching a 50CrMo4 steel three different induction tempering processes are carried out and the resulting properties are subsequently compared to a conventional tempering process. The results indicate that notch impact energy raises with increasing heating rates to tempering when realizing the same hardness of the samples. The positive effect of high heating rate on toughness is traced back to smaller carbide sizes, as well as smaller carbide spacing and more uniform carbide distribution over the sample.

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High-Speed Time- and Frequency-Domain Terahertz Tomography of Glass-Fiber-Reinforced Polymer Laminates with Internal Defects

Applied Sciences ◽

10.3390/app11114933 ◽

2021 ◽

Vol 11 (11) ◽

pp. 4933

Author(s):

Ji-Sang Yahng ◽

Dae-Su Yee

Keyword(s):

Composite Materials ◽

Glass Fiber ◽

High Speed ◽

Nondestructive Inspection ◽

Fiber Reinforced Polymer ◽

Glass Fiber Reinforced Polymer ◽

Tomographic Images ◽

Reinforced Polymer ◽

Glass Fiber Reinforced ◽

Thz Tomography

Composite materials are increasingly being utilized in many products, such as aircrafts, wind blades, etc. Accordingly, the need for nondestructive inspection of composite materials is increasing and technologies that allow nondestructive inspection are being studied. Existing ultrasound methods are limited in their ability to detect defects due to high attenuation in composite materials, and radiographic examination methods could pose a danger to human health. Terahertz (THz) wave technology is an emerging approach that is useful for imaging of concealed objects or internal structures due to high transmittance in non-conductive materials, straightness, and safety to human health. Using high-speed THz tomography systems that we developed, we have obtained THz tomographic images of glass-fiber-reinforced polymer (GFRP) laminates with artificial internal defects such as delamination and inclusion. The defects have various thicknesses and sizes, and lie at different depths. We present THz tomographic images of GFRP samples to demonstrate the extent to which the defects can be detected with the THz tomography systems.

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