Mechanical Treatment Conditions Research Articles

Modeling the Chemical Composition of Ferritic Stainless Steels with the Use of Artificial Neural Networks

The aim of this paper is an attempt to answer the question of whether, on the basis of the values of the mechanical properties of ferritic stainless steels, it is possible to predict the chemical concentration of carbon and nine of the other most common alloying elements in these steels. The author believes that the relationships between the properties are more complicated and depend on a greater number of factors, such as heat and mechanical treatment conditions, but in this paper, they were not taken into account due to the uniform treatment of the tested steels. The modeling results proved to be very promising and indicate that for some elements, this is possible with high accuracy. Artificial neural networks with radial basis functions (RBF), multilayer perceptron with one and two hidden layers (MLP) and generalized regression neural networks (GRNN) were used for modeling. In order to minimize the manufacturing cost of products, developed artificial neural networks can be used in industry. They may also simplify the selection of materials if the engineer has to correctly select chemical components and appropriate plastic and/or heat treatments of stainless steel with the necessary mechanical properties.

D0-Ferromagnetism in SHS Titanium Nitride Treated by Ball Milling

In this work, the influence of mechanical treatment (mechanical milling) of the TiN titanium nitride powder produced by self-propagating high-temperature synthesis on the magnetic properties of the milled powders is investigated. The effect of d0-magnetization was observed. The TiN powders were characterized by scanning electron microscopy, X-ray diffraction, vibrating-sample magnetometry, specific surface area measurement, and chemical analysis. The results show that the mechanical treatment of the TiN titanium nitride powder influences the magnetization in a nonmonotonic manner. The conditions of mechanical treatment corresponding to the best value of specific magnetization of milled powders were established. The specific magnetization depended on three measured parameters: specific surface area, coherent scattering region, and average particle size. It was shown that unit cell parameters of milled TiN titanium nitride powders have not been changed with the increasing of duration milling time. The calculated values of CSR of mechanically treated powders decreased with the increasing of duration of milling time. The values of macrostrains were negative. Mechanical treatment of the TiN titanium nitride powders has led to a change in the nitrogen content from 21.4 to 20.0 wt.%. Stoichiometry of the TiN titanium nitride varied from TiN0.903-TiN0.886; therefore, the observed d0-magnetization effect is associated with a defective surface structure of mechanically treated powders.

Effect of alloying elements (Zr, Hf, Co), heat and mechanical treatment conditions on the phase composition and magnetic properties of SmFe11Ti compounds with ThMn12 structure

The results of thermomagnetic, metallographic and X-ray diffraction phase analysis as well as the measurements of specific magnetization (σs), Curie temperature (TC), coercive force (HC) of (Sm,M)(Fe,M)12-xTix alloys samples, where M = Zr, Hf, Co with the ThMn12 main phase structure (1-12) are presented. The effect of the annealing temperature and the cooling rate on the formation of 1-12 phase and its magnetic properties, including the effect of high-energy milling on the magnetic hysteresis properties and alloys structure are described. It was found that the highest magnetic characteristics such as σs = 112.6 emu/g and TC = 600 ºC are attained in the (Sm0.8Zr0.2)(Fe0.75Co0.25)11.4Ti0.6 alloy after its annealing at 1050 °C and rapid cooling. It is noted that a mechanical milling of the alloy leads to 1-12 phase amorphization which accompanied by an α-(Fe) or metal Co phases impurity formation.

Mechanochemical synthesis of vanadium(III) β-diketonates

The effect of the mechanical treatment conditions and of the nature of reactants on the course of the solid-phase reaction of vanadium(III) chloride with sodium β-diketonates and potassium tetramethylheptanedionate, on the yield of the reaction products, and on some properties of the activated mixtures was examined. A method was developed for the synthesis of vanadium(III) β-diketonates by the solid-phase mechanochemical reaction of vanadium(III) chloride with appropriate sodium or potassium β-diketonate, followed by sublimation or extraction.

Use of tungsten single crystals to enhance nuclear reactors structural elements properties

This paper demonstrates advantages of using tungsten single crystal as structural material in science absorbing industry in comparison with polycrystalline material. High-temperature short-term static strength and creep resistance characteristics of polycrystalline tungsten and single crystal alloy were obtained and compared. The results of comparative studies of the mechanical properties of polycrystalline and monocrystalline tungsten – 4% tantalum alloy are presented.It is shown that monocrystalline tungsten based materials have both high-temperature strength and plasticity which makes them most suitable for use under high temperatures and high mechanical stresses. Use of monocrystalline tungsten as a structural material makes it possible to prolong the service life and avoid the failures resulting from embrittlement and strain. Moreover, thermo mechanical treatment of monocrystalline tungsten enhances its high-temperature strength. However, it is necessary to carry out additional experimental research to choose the appropriate thermo mechanical treatment conditions.

Production of nanocellulose fibers from pinecone biomass: Evaluation and optimization of chemical and mechanical treatment conditions on mechanical properties of nanocellulose films

Nanocellulose fibers were produced from pinecone (Jack pine: Pinus banksiana Lamb) using chemical and mechanical treatments. The effects of pretreatment and mechanical grinding on the tensile strength and modulus of the cellulosic fiber sheets were studied to optimize the treatment conditions and grinding process used for the generation of high strength nanocellulose fibers. Pinecone and cellulose fibers were characterized for their chemical composition, morphology, crystallinity, and thermal properties using HPLC, FTIR, SEM, ESEM, XRD, and TGA to provide insight into the mechanism involved in the reactions. Cellulose suspensions that had different pretreatments were processed for different time periods in a Supermasscolloider to produce cellulose nanofibers. The cellulose fibers produced at the optimum chemical concentrations of 4wt% NaOH and 5wt% of acidified sodium chlorite solution contained approximately 89% of cellulose, 4% hemicellulose, and 6% lignin. About 67% of the prepared nanocellulose fibers showed a diameter range between 5 and 25nm. The tensile strength and modulus of the nano fiber films prepared at the optimized grinding condition were 273MPa and 17GPa, respectively. The high crystalline index (70%) and improved thermal stability of the nanofibers indicate their suitability for manufacturing bionanocomposites.

Mechanochemical transformations of natural gas hydrates

Chemical transformations of hydrates of natural gas from the Irelyakh gas and oil field of the Republic of Sakha (Yakutia) upon vigorous mechanical treatment were studied. It was found that a general feature of mechanochemical transformations of natural gas hydrates is an increase in the carbon chain length of hydrocarbons forming the hydrates. It was shown that the constitution of the products of mechanical activation of gas hydrates depends on both their synthesis and mechanical treatment conditions.

Hydrogen absorption processes in Mg2Ni-based systems: Thermal and mechanochemical kinetics

Mg 2 Ni/Ni and LaMg 2 Ni alloy powders were exposed to hydrogen under isothermal and mechanical treatment conditions. In the former case, the amount of hydrogen absorbed tends with time to a final asymptotic value. Once such a value has been reached, further hydrogen absorption can be obtained only by submitting the powders to mechanical processing in the presence of hydrogen. Hydrogen absorption processes under isothermal and mechanical treatment conditions exhibited different kinetics and their rates have been compared on a phenomenological basis starting from kinetic evidences. It appeared that mechanical treatment enhances the rate of hydrogen absorption by four orders of magnitude as a consequence of a mix of surface area enlargement, temperature rise and local structural excitation processes.

Antioxidants in the water-soluble carbohydrate fractions of the moss Sphagnum fuscum and sphagnum peat

The effect of various mechanical treatment conditions on changes in the composition and antioxidant activity of the polysaccharide fractions of the moss Sphagnum fuscum and sphagnum moss peat was studied. It was found that mechanochemical treatment changed the composition of polysaccharide moss and peat fractions, and the antioxidant activity of polysaccharides depended on the hydroxyarene aglycon content of polysaccharides.

A mechanistic study of TiO2 anatase-to-rutile phase transformation under mechanical processing conditions

Abstract A systematic investigation on the mechanistic features of the anatase-to-rutile phase transformation under mechanical treatment conditions has been performed. Mechanical processing was carried out first on pure anatase powders and was demonstrated to induce two consecutive transformations from anatase to TiO 2 II and from this to rutile. Phase transformation kinetics was described by means of kinetic curves and the rate quantified by two rate constants. The mechanical treatment was successively performed on anatase–rutile powder mixtures with different rutile contents. Being the final product of phase transformations, rutile acts here as an inert phase. Its effect on rate constants was carefully ascertained and used to further point out their physical meaning.

Kinetics of allotropic phase transformation in cobalt powders undergoing mechanical processing

The allotropic transition of hexagonal close-packed cobalt powders to the face-centered cubic phase under mechanical treatment conditions has been studied. Processing parameters have been systematically changed to investigate the phase transformation kinetics, which has been related to the number and the average energy of collisions. A phenomenological interpretation of transformation rate constants is also proposed. A minimum threshold energy at impact exists below which no phase transformation is detected.

The size refinement of Cu crystallites under mechanical processing conditions: a phenomenological modeling approach

A phenomenological model is developed for describing the kinetics of the crystallite size refinement process of Cu powder under mechanical treatment conditions. Based on the evidence that collisions represent the elementary events of energy transfer, the rate of crystallite size decrease is related on a statistical basis to the amount of powder trapped at each collision, to the number of collisions and to the collision energy. The mathematical approach allows for identifying the approximate functional form of the kinetic curves obtained at largely different impact energies. The values of the apparent kinetic constants and of the model parameters involved can be thus estimated by fitting the model curves to the experimental data. The results obtained provide a deeper insight into the details of the crystallite size refinement process.

Nanostructure and Phases Formation under Mechanical Alloying of Bynary Powder Mixtures of Fe and sp-Element (M); M = C,B,Al,Si,Ge,Sn

The processes of mechanical alloying of iron and sp-elements (C, B, Al, Si, Ge, Sn) under identical conditions of mechanical treatment have been studied. General regularities and differences in the mechanisms and kinetics of solid state reactions have been ascertained. A microscopic model of mechanical alloying in these systems is suggested.

Mechanically induced self-propagating reactions: Analysis of reactive substrates and degradation of aromatic sulfonic pollutants

Mechanochemical reactions have been identified as a valuable alternative to conventional methodologies for the degradation of toxic pollutants as well as for their abatement in contaminated matrices. This paper discusses the application of the mechanochemical technique to the degradation of sulfonic acids in a contaminated matrix. The degradation of the pollutant compound was carried out by taking advantage of combustive reactions on a suitable reactive system ignited under mechanical treatment conditions. Two systems have been investigated as possible reactive substrates. The first one was a Mg–SiO 2 powder mixture while the second system was a Ca–SiO 2 powder mixture. Milling trials performed under different mechanical processing conditions allowed one to characterise the reactivity of these chemical systems, which basically undergo a reduction/oxidation reaction involving the formation of MgO and Si phases when the Mg–SiO 2 system is considered and CaO and Si phases when the Ca–SiO 2 system is employed, respectively. The systematic change of the stoichiometric ratios Mg:SiO 2 and Ca:SiO 2 permitted to identify the minimum Mg or Ca content necessary for the ignition of the combustive reactions. The experimental runs performed with such systems have shown a greater effectiveness of the Mg–SiO 2 because of less energy inputs required to ignite a combustion. For this reason the Mg–SiO 2 has been considered as a reactive substrate in the following trials. Since the SiO 2 amount in stoichiometric excess may be regarded as inert phase, it was substituted with a different phase consisting of the matrix contaminated by sulfonic acids. This aspect permitted to ignite a combustive reaction with the minimum possible content of Mg–SiO 2 reacting mixture. The chemical analyses performed after the combustive reaction proved the complete removal of the sulfonic acid from the contaminated matrix.

A quantitative approach to mechanochemical processes

A complex methodology has been developed in order to quantify the conditions of mechanical treatment in laboratory and commercial ball mills. The experimental determination of the collision frequency and the impact energy has been paralleled by an accurate numerical modelling of the balls and powder dynamics. The obtained results have been further confirmed by a direct inspection of the motion of balls and powder inside a transparent quartz reactor by means of high-speed video recording. The temperature of mechanochemical reactors has been also continuously monitored during the course of mechanical treatments. The methodology has been systematically applied to characterise on absolute basis the kinetic behaviour of a large variety of mechanically-induced structural and chemical transformations. In particular, systematic investigations have been performed on the amorphisation of intermetallic and binary systems, on the formation of extended solid solutions in immiscible systems, on the ignition of combustion-like reactions in metal-metalloid mixtures and on the hydrogen storage in nanocrystalline and amorphous multicomponent metallic alloys. Mechanochemical transformations appeared to be basically ruled by two different mechanisms characterised by simple asymptotic trends and sigmoidal curves respectively. An attempt to rationalise the observed mechanisms on a phenomenological basis has been made.

Mechanical alloying in binary Fe-M (M = C, B, Al, Si, Ge, Sn) systems

The processes of mechanical alloying of iron and sp-elements (C, B, Al, Si, Ge, Sn) under identical conditions of mechanical treatment have been studied. General regularities and differences in the mechanisms and kinetics of solid state reactions have been ascertained. A microscopic model of mechanical alloying in these systems is suggested.

Solid State Reactions in the Fe-Sn System under Mechanical Alloying and Grinding

Structure-phase transformations in the 68Fe-32Sn system by mechanical alloying from pure elements and mechanical grinding of a multi-phase alloy for different conditions of mechanical treatment in planetary ball mills were studied by X-ray diffraction, 57 Fe Mossbauer spectroscopy and magnetic measurements. The initial stages of structure-phase transformations by mechanical alloying and grinding were found to be different. However, the final product in all cases was nanocrystalline supersaturated solid solution of Sn in α-Fe with the bcc lattice parameter a= 0.2995 nm, the magnetic moment per Fe atom μ Fe =1.9 μ B and the Curie temperature T c =700 K.

Effect of the conditions of mechanical treatment on the reactivity of cellulose

The studies conducted led to the following conclusion: Brief, for no more than 2 min, activation of cellulose by dry grinding produces solutions of cellulose in MMO-DMSO mixture that have elevated homogeneity and require insignificant preparation time; this will probably favor their technological processing into fibres and films.

Raman and far-infrared reflectance investigation of microcrystal orientation in YBa2Cu3O7−δ superconductors

Abstract Raman and far-infrared reflectance measurements were carried out on three samples of YBa 2 Cu 3 O 7−δ prepared under various thermal and mechanical treatment conditions. From the changes in the reflectance phonon spectra and the emission anisotropy of the characteristic line at 502 cm -1 the partial orientation of the microcrystal with the consecutive steps of sample treatment is inferred.

Deformation Substructure in Cemented WC-Co Materials

The cemented refractory carbides represent one of the basic classes of materials used in machine cutting and rock drilling tools. These multiphase materials (a refractory carbide compact with a metallic binder phase) provide a good combination of hardness, toughness, and abrasion resistance which leads to long tool life. The present study investigates the microstructure of several cobalt-based cemented WC materials in response to different types of mechanical loading.The materials were hot isostatically pressed sintered compacts of WC and blends of cobalt and nickel metal powders (∼17 wt %). Three blends of metal powders were used: Co-1, Co-2, and Co-3 (in increasing nickel content). During the high-temperature sintering process, the metallic binder was molten, aiding the sintering reaction and also dissolving some WC into solution. Specimens were examined in the ORNL Hitachi HU-1000 high voltage electron microscope in the undeformed state and following different conditions of mechanical treatment: low (2.1 GPa) and high (3.4 GPa) stress compressive monotonic loading, and low (1.0 GPa) and high (2.1 GPa) stress compressive cyclic loading. The high penetration power of the HVEM allowed the examination of the microstructure of the dense WC grains and thicker binder regions where the dislocation structure would be representative of that in the bulk.