SHS Technology Research Articles

Investigation of physical, chemical, and technological properties of titanium powder obtained by thermal dehydrogenation in vacuum

In recent times, there has been significant interest in powder metallurgy, driven primarily by the active development of additive manufacturing. Consequently, a pressing task is the development of methods for producing initial metal powders that are cost-effective while meeting high consumer standards. This research is a continuation of studies on titanium powders obtained through SHS hydrogenation and thermal dehydrogenation. The titanium hydride powders, previously obtained using SHS technology, were sieved, resulting in fractions that matched the granulometric composition of titanium powders of PTK, PTS, PTM, and PTOM grades. Subsequently, the titanium hydride powder samples underwent dehydrogenation through vacuum annealing in an electric resistance furnace. Throughout the dehydrogenation process, the kinetics of hydrogen release from the titanium powder were examined as a function of particle size. The macro- and microstructure, chemical composition, and technological properties of the dehydrogenated powders were thoroughly analyzed. It was determined that the titanium powder maintained its original polygonal fragmented shape after dehydrogenation. The average particle size decreased by 5–20 %, and “satellites” were observed on larger particles. Chemical analysis revealed that larger samples contained a higher level of residual hydrogen and gas impurities (Σ 0.77 wt. %) compared to finer powders (Σ 0.26 wt. %). Regarding the study of technological properties, the resulting powders exhibited the necessary characteristics for use in titanium powder metallurgy, with the exception of low flowability due to the particle shape and microstructural heterogeneity). In conclusion, this research has demonstrated the potential of the SHS hydrogenation and thermal dehydrogenation method in producing high-quality titanium powders.

Dependence of pore space structure and characteristics of SiC-based ceramic materials on the morphology of the initial components

Ultrafine silicon carbide powders of two types were used as fillers for synthesis of porous ceramics. The first powder was obtained by the furnace method (SiCF), the second sample was synthesized using the SHS technology (SiCSHS). The fillers had identical average particle size, but different morphology of their surface. It is established that with the same size, the morphology of initial powder components determined structural parameters and characteristics of the synthesized porous ceramics. It determines effective applicability of various materials for ultrafiltration or catalysis processes.

Obtaining Ti–Cu–C system composite materials by SHS process

The aim of the research is to obtain wear-resistant products from composite materials of a new type using the SHS technology. The Ti–Cu–C system was selected taking into account the data available in the scientific and technical literature. Various SHS charge compositions consisting of titanium powder, copper powder, and carbon black were experimentally burned to determine compositions that can burn during the SHS process and provide a melt containing titanium carbide and titanium cuprides as a binder featuring higher mechanical properties and lower melting points than pure copper. Model samples of products in the form of bushings with an outer diameter of 70 and 110 mm were produced by burning the SHS charge with selected compositions in a reactor followed by the compaction of the resulting melt with a force of 50–60 t. After the rough workpiece electrical discharge machining, samples were cut out for phase analysis, X-ray spectral analysis, and wear tests. With an optimal ratio of SHS charge components, titanium carbide and a binder in the form of titanium cuprides of different compositions were revealed in the model sample material. Using the method of testing for wear when sliding on a fixed abrasive under a specific pressure of 1 MPa, it was determined that the relative abrasive resistance of the new material at a hardness of 50–52 HRC is 1.8–2.0 units in comparison with the hardened tool and die steel Kh12MFL. In order to implement the technology in practice, an algorithm was developed for calculating the compositions of the newly formulated SHS charge, while its principle is such a ratio of components where the introduced carbon forms titanium carbide with titanium, and the added excess titanium forms titanium cuprides with copper. The developed material can be considered as promising for use as elements of equipment operating under abrasive wear conditions. This development is patented, Patent No. 2691656 (Russian Federation).

Effect of superheated steam and conventional steam roasting on nutraceutical quality of several vegetables

The superheated steam technology (SHST) is a heat treatment that involves a heated saturated steam. To date, the use as cooking technology has not been evaluated in depth in terms of retention of phytochemicals. In this study, the use of SHST was compared with a conventional saturated steam (CS) oven in order to evaluate their impact on different vegetables (tomato fruits, spinach leaves and artichoke inflorescences). At biochemical level, phenolic compounds, total ascorbic acid content, some specific antioxidant compounds and, consequently, the antioxidant activity have been evaluated. Results reported a decrease of bioactivity in the tomato cooked samples (in both the heat treatments) when compared with the fresh sample. Instead, spinach leaves and artichoke inflorescences reported an increase of phytochemicals and antioxidant activity in CS or SHS samples when compared with fresh ones. Few differences in the content of bioactive compounds were observed after the use of the CS or SHS technology. Further analyses are required to verify the differences between the use of superheated or conventional steam on vegetables.

Contribution on Fundamentals of SHS and the Implementation of SHS Technology in Industry

Contribution on Fundamentals of SHS and the Implementation of SHS Technology in Industry

Solar House System Adoption among Rural Community

West Bandung Regency experiences inequality in access to electricity due to difficulties in the distribution process. One possible solution to overcome this problem is to utilize solar energy. Therefore, the purpose of this research is to determine importance of Solar House to be done with the intention of identifying the factors that influence the adoption of SHS technology among the public. This study used a modified TAM model consisting of perceived usefulness, perceived ease of use, social factors, and resource factors. The method of data collection is through the distribution of questionnaires to 185 respondents in rural areas of West Bandung Regency. Furthermore, Partial Least Square Modeling is used as an analytical method to test hypotheses. The results reveal that social factors are the most important determinant for the adoption of SHS. From a theoretical perspective, this study broadens our understanding of the adoption of SHS technology customers in rural areas. Furthermore, from managerial applications, this research suggests a social marketing strategy that can be carried out by solar panel entrepreneurs and the government to encourage rural communities to adopt SHS technology by expanding their existing knowledge.

SHS TECHNOLOGY OF COMPOSITION FERROALLOYS PART I. METALLURGICAL SHS PROCESS. SYNTHESIS OF FERROVANADIUM AND FERROCHROMIUM NITRIDES

The article presents research findings in the development of a specialized SHS technology for composite ferrous alloys for steel melting and blast furnace iron-making. To resolve the principle goal of creating metallurgical production lines it was developed a new approach to practical implementation of the SHS method – a metallurgical SHS process. The metallurgical version of SHS is based on using different metallurgical alloys as the main raw stock; those include dust-type wastes of ferrite alloys production. In this case, the process of synthesis by combustion is implemented via exothermic exchange reactions. Here, composite materials form; they are based on inorganic compositions bound with iron and/or an alloy based on iron. It has been shown that depending on the aggregate state of source reagents, metallurgical SHS processes can be gasless, gasabsorbing or gas-yielding. Combustion modes for these processes largely differ. To arrange for metallurgical SHS process in weakly exothermic systems, one can use different versions of the thermal bonding principle. The authors have investigated self-propagating high-temperature synthesis of nitrided ferrovanadium and ferrochrome. It has been shown that the phase composition of the source alloy has strong impact on the consistent behaviors of the combustion flow and the combustion mechanism of ferrovanadium (if combustion is taking place in nitrogen atmosphere). In the course of nitriding σ-(Fe – V), process activation takes place; the activation is related to the transformation of the intermetallide into α-solid solution when the phase transition temperature is reached (~1200 °C). The composition structure of ferrovanadium nitride products is formed by the confluence of solid-liquid droplet-particles that consist of molten Fe and solid vanadium nitride. A 3-phase mechanism of ferrochrome interaction with nitrogen facilitates the achievement of a high degree of nitriding. It was shown that the combustion rates of ferrochrome (and chrome) during nitriding in coflow filtration mode increase as the nitrogen flow rate is increased. Here, the degree of ferrochrome nitriding during forced filtration (4.7 – 7.5 % N) is much less than that during non-forced filtration (8.8 – 14.2 % N).

Perovskite Matrix Form by Using SHS Technology for Immobilization HLW

Perovskite Matrix Form by Using SHS Technology for Immobilization HLW

Combustion synthesis of mica-crystalline materials based on fluorphlogopite using mineral raw materials and aluminum production waste

The paper considers possible use of aluminum production waste (recycled cryolite Na3AlF6) and quartz sand (SiO2) as the main reagents in the synthesis of mica-crystalline materials based on fluorphlogopite under ambient conditions. The combustion process is shown to depend on the energy additive in the initial mixture and occurs at a rate of 2–5 mm/s in the temperature range of ~700 to 1600°C. The identity of the SHS-fluorphlogopite and pyrogenic fluorphlogopite structures is established. The conditions that allow synthesizing fluorphlogopites with the final product melting in the combustion wave or without it are determined. It appears to be possible to synthesize items by a direct method from dense (2.57 g/cm3) and porous materials based on SHS fluorphlogopites. The possibility of synthesizing materials with the open porosity of up to 35% is demonstrated. A material based on monoclinic sodium fluorphlogopites of NaMg3AlSi3O10F2 and Na4Mg6Al4Si4O20F4 compositions is obtained. The results of investigations can be used to develop the SHS technology of item production from mica-crystalline materials.

Nitride nanopowders by azide SHS technology

Azide SHS technology with NaN3 powder as a nitriding agent was used to fabricate TiN–BN, AlN–BN, and Si3N4–TiN nanopowders using Nа2TiF6, (NH4)2TiF6, KBF4, NH4BF4, Nа3AlF6, AlF3, Na2SiF6, and (NH4)2SiF6 as precursors. Mixtures of the above salts with sodium azide NaN3 readily burned in an SHS reactor to yield agglomerated nanosized or fine target powders. Phase composition of combustion products not always corresponded to expectations and often contained insoluble byproducts. Reported are optimal green compositions and procedures that afford the preparation of target TiN–BN, AlN–BN, and Si3N4–TiN nanopowders free of byproducts.

Study of Possibility of Obtaining Nanopowder Composition of "Aluminum Nitride – Boron Nitride" by Azide SHS Technology

Processes and products of combustion of systems of "sodium azide – aluminum and boron halides " are studied. Halide salts AlF3, Na3AlF6, KBF4 and NH4BF4 are used as precursors of Al and B elements. The measured combustion temperature is in the range from 900 to 1800°C. It is established that the end product of combustion synthesis consists of several phases, not only the target phases (AlN and BN), but also the by-products (Na3AlF6, К2NaAlF6, NaF, KF), part of which is removed by water washing. The composite powder of AlN-BN is formed only in the case of AlF3 as precursor of Al; in doing so, it is formed with side, impurity product К2NaAlF6 or Na3AlF6. In the case of precursor Na3AlF6, the washed product of SHS may only be a by-product К2NaAlF6 or Na3AlF6 or along with the by-product, it may contain AlN or BN, but not their composition. That is explained by different combustion temperature.The structure formation of the composite powder is investigated. The obtained agglomerated nitride nano- and micropowders have an irregular and predominantly acicular shape with an average particle size of 50-170 nm in the agglomerates.

Application of the nanopowder production of azide SHS technology for the reinforcement and modification of aluminum alloys

The survey for types and fabrication methods of aluminum matrix composite materials discretely reinforced with ceramic particles and nanoparticles of refractory compounds is given. It is shown that the azide technology of self-propagating high-temperature synthesis (SHS-Az), which uses sodium azide NaN3 as a solid nitriding agent, makes it possible to fabricate numerous comparatively inexpensive micropowders and nanopowders of nitrides, carbonitrides, carbides, and their compositions, which are of interest for the reinforcement and modification of aluminum alloy. Along with the mentioned target ceramic particles, the SHS-Az product contains side haloid salts (sodium and potassium chlorides and fluorides), which can play the role of fluxes with the addition of ceramic particles into the aluminum melt. The results of experiments on the introduction of the nanopowder composition into the melt of AK6M2 alloy, %, β-SiC 48.6, α-Si3N4 27.0, β-Si3N4 5.8, and Na3AlF6 18.6 in the composition of the compacted pseudo-master alloy with the copper powder, which evidence the modifying effect, are presented.

Obtaining the Nanostructured Nitride Composition TiN-BN Powder by the Self-Propagating High-Temperature Synthesis from the Azide KBF<sub>4</sub>-NaN<sub>3</sub>-Na<sub>2</sub>TiF<sub>6</sub> and "NH<sub>4</sub>BF<sub>4</sub>-NaN<sub>3</sub>-Na<sub>2</sub>TiF<sub>6</sub> Systems

This paper presents the results of a study on the preparation of nanostructured nitride composition TiN-BN in the boron halide - sodium azide - titanium halide system by the azide SHS technology. SHS-Az technology makes it possible to produce powders having the desired properties, only in one step, without blending separately prepared powders of titanium nitride and boron nitride, and to obtain the final product in the form of micro-and nanosized powder nitride compositions TiN-BN by using complex halides of titanium and boron. Thus, the composite powder TiN and BN obtained from the KBF4-NaN3-Na2TiF6» and «NH4BF4-NaN3-Na2TiF6 systems can be classified as a nanostructured powder (nanopowder).

Resistometry and impedance spectroscopy for characterization of powders used in SHS reactions

Presented are some examples of successful application of dc resistometry and impedance spectroscopy to characterization of micro and nano powders commonly used in SHS technology.

Some advanced applications of SHS: An overview

INTRODUCTION The SHS technology has been used to produce anew class materials based on metals, alloys, metaloxides, and spinels for various applications. A widerange of materials have been SHSproduced and characterized by various physicochemical methods andmechanical tests. This is a concise overview of SHSproduced materials for wide range of applicationsstudied in the Laboratory of SHS Catalysts and Pigments at the Institute of Combustion Problems (Kazakhstan) and then in the Laboratory of AdvancedMaterials at the Institute of Materials Science, NCSRDemokritos (Greece), for over the last 30 years.

Development of refractory materials prepared by SHS technology

Scientific bases of self-propagating high-temperature synthesis of refractory materials, recipes, and methods for their creation from local raw material are developed. Thermochemical and kinetic parameters for solid-phase synthesis of systems based on chamotte, chromite, magnesium, and aluminum sulphate, and also phase composition, thermodynamic and physicomechanical properties of the products obtained are determined.

Dehydrogenation of cyclohexane over SHS-produced Nickel-Zirconium alloy

Ni-Zr alloys were SHS-produced from Ni-Zi powder mixtures containing 4% Teflon powder as a chemical activator. In the presence of Teflon, the burning velocity increased by a factor of 15, at a combustion temperature of 1550°C. The synthesized powder was found to contain NiZr and Ni10Zr7 with a particle size of 1–5 μm and pores 100–300 μm in their size. In dehydrogenation of cyclohexane, the alloy exhibited a catalytic activity commencing from 160°C; at 500°C, the cyclohexane conversion attained a value of 78%. Our results illustrate the potential of SHS technology in production of heterogeneous catalysts active at relatively low temperatures.

Theoretical aspects of the creation of highly efficient refractories on the basis of SHS technology

The theoretical principles behind the self-propagating high-temperature synthesis of refractory materials are established. The physico-chemical characteristics of these materials are studied and the technology for their production is optimized. The thermochemical and kinetic parameters of the solid-phase combustion of systems based on fireclay, chromite, magnesium sulfate, and aluminum are examined; the phase composition and thermodynamic and physico-mechanical characteristics of the combustion products are determined and formulations are developed for refractory concretes and gunites.

Effect of batch pelletizing on a course of SHS reactions: An overview

Such a simple technological trick as pelletizing (granulating) green powder mixtures (popular in conventional powder technology) has seldom been used in SHS technology. We have demonstrated that pelletizing green powder mixtures can markedly affect the parameters of various SHS reactions (SHS in a mode of infiltration-mediated combustion, SHS with a reduction stage, combustion of thermit mixtures, SHS in aluminum melt) and properties of their products.

Wear and corrosion of metal-matrix (stainless steel or NiTi)-TiC coatings

Different spraying technologies (plasma and High Velocity Oxi-Fuel) have been use to obtain TiC - stainless steel or NiTi matrix coatings. The starting feedstock powders have been obtained by SHS technology. After crushing and sieving, the fraction of particles between 20 and 63μm, have been selected for thermal spray. The obtained coatings have been characterized by XRD and SEM-EDS to observe the surface and cross section. The coatings adhesion, wear (ball-on-disk and rubber wheel tests) and electrochemical corrosion test have been carried out.Results show that the plasma sprayed coatings with NiTi have better adhesion than the stainless steel matrix coatings. However, the opposite happens for HVOF coatings. NiTi matrix coatings exhibit higher wear resistance both for plasma and HVOF spraying processes.