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A novel low-temperature densification method of nanocrystalline calcium hydroxyapatite (HAp) at a temperature as low as 200 °C with no liquid additives is investigated. To understand the underlying mechanism of the low-temperature sintering of hydroxyapatite, two types of lab-synthesized nanocrystalline HAp, dried (110 °C, 12 h) and calcined (1000 °C, 2 h), were subjected to cold sintering conditions (200 °C, 500 MPa) and compared thoroughly. The dried samples were found to be nanocrystalline, enveloped by an amorphous shell, whereas the calcined samples were fully crystalline, as confirmed by X-ray diffraction, transmission electron microscopy, and solid-state nuclear magnetic resonance techniques. A relative density of 98.8% was achieved for the dried samples; however, the calcined samples could not be sintered. This indicates a clear dependence of densification on the surface chemistry of the nanocrystals involving rearrangement and dehydration of the amorphous layer present on the surface of the nanocrystals under the influence of applied pressure and temperature. Moreover, the calcined sample, which had a fully developed crystalline structure, did not undergo sintering, even with the use of added water. Therefore, it is demonstrated that wet-precipitated and dried nanocrystalline HAp can be cold-sintered to full densification for applications in biomedical materials or radioactive waste immobilization of volatile radionuclides at a considerably low temperature, without the addition of sintering aids.

In past years, the study of magnesium oxychloride cement became fairly widespread, because of its good mechanical properties and environmental sustainability. One of its biggest advantages is its ability to work well with different types of fillers and aggregates. This paper deals with the synthesis and analysis of such material, namely the composite of magnesium oxychloride with diatomite. Three different phases varying in the amount of diatomite were prepared and analyzed using various analytical methods, namely X-ray diffraction, X-ray fluorescence, simultaneous thermal analysis, scanning electron microscopy and energy dispersive spectroscopy. The phase and chemical composition, morphology and thermal behavior were studied as well as the structural, mechanical, hygric, and thermal properties of the hardened materials. This sort of novel and alternative material shows wide-ranging application potential while being eco-friendly and providing great mechanical properties applicable in the extreme conditions.

The potentiality on alkali activation of volcanic tuff with calcium-based materials, fly ash, and their mixtures as additives were comprehensively investigated in this study. Several characterization strategies have been employed for mechanism exploration. CaO and fly ash (FA) brought about more dramatic responses than CaSO4 and alkaline activator on activating the volcanic tuff-based geopolymer, which was relatively stable under the wet-dry alternated conditions. The symmetrical stretching vibration of Si–O–T (T = Al or Si) was right-shifted to the band at approximately 1036 cm−1, implying the incorporation of Ca into Si–O–T. FA accompanying with CaO enhanced the polycondensation, gelation, and hardening of geopolymer. However, too many quartz balls brought into geopolymer paste by an excessive amount of fly ash deteriorated the cementing quality and reduced the mechanical strengths. This work contributes to the module usage of volcanic tuff in the construction industries and supplies an innovative method in activating geopolymerization.

Aluminium alloys are one of the choice materials with ever-increasing demands in manufacturing industries. The aluminium alloy 6 xx series such as AA6061-T6, has emerged as one of the promising materials utilized owing to its combination of favourable properties which include high strength to weight ratio, good ductility, excellent corrosion resistance and relatively low cost. These superior properties are responsible for its emergence and usage in the fabrication of aircraft wings and fuselages, yacht/ship construction, automotive rims and wheel spacers. However, joining of AA6061-T6 including the use of friction stir welding (FSW) has serious concerns because the mechanical and tribological properties of the AA6061-T6 welded joints deteriorate significantly compared with the base metal. This phenomenon has been attributed to the severe softening encountered at the stir zone (SZ) of the aluminium matrix during FSW. Other inherent challenges of FSW such as weld thinning, kissing bond and keyhole formation also contribute to the reduction in the weld joint quality. The softening phenomenon has been linked to the dissolution of the strengthening precipitates (B″-Mg5Si6) as a result of high heat input during the welding process. Hence, this paper attempts to review the various improvement strategies adopted in the existing studies to improve the quality of AA 6061-T6 welded joint. These include parametric optimization, selection of appropriate tool design, pre and post heat treatments, adoption of different groove/hole designs for particle addition as well as the addition of reinforcement particles to the weld joint. The variants of FSW recently developed will also be considered. The findings from the review will generally be useful for future work on FSW of heat treated aluminium alloys. The evolution of FSW and its associated challenges are briefly discussed while the research areas yet to be harnessed are suggested for future works.

Coal and gas outburst is a violent disaster driven by released energy from gas desorption. The initial expansion energy of released gas (IEERG) is a new method to predict coal and gas outburst. In this paper, an instrument for IEERG measurement was developed. Compared with previous setups, the new one which is equipped with three convergent nozzles and quick-release mechanism gets improved in data acquisition and gas sealing and releasing performance. To comprehensively know the effect of gas pressure, particle size, and nozzle area on IEERG, a series of experiments were carried out with this new setup. The variable control test results indicated that the gas pressure-IEERG curves remain the linear trend and the particle size-IEERG curves maintain the negative exponential trend for nozzle areas at 1.13, 2.26, and 3.39 mm2, respectively. The increase in nozzle area leads to deceases in value of IEERG and absolute value of slope of fitting curves in each test. In addition, the orthogonal experiment showed that the influence of gas pressure, nozzle area, and particle size on IEERG decreases in turn. Only gas pressure had a marked impact on IEERG. This work offers great importance in improving the accuracy of prediction of coal and gas outburst.

The disintegration of Cu metal in 1 mol/L HCl and the mitigating effect of the expired Ceftazidime antibiotic were studied. The inhibition efficacy of Ceftazidime depends on its concentration in the medium. The mitigation efficacy increases from 77.7 to 94.2%, as the Ceftazidime concentration increases from 50 to 300 ppm in the corrosive medium. The polarization results confirmed that the antibiotic acts as a mixed-type inhibitor. The adsorption of the antibiotic on the Cu surface belongs to Timken's model. The adsorption constant, Kads, and the standard free energy change ΔGo were estimated. The adsorption of Ceftazidime drug follows a physical-type. Scanning microscopy (SEM) and energy dispersing X-ray (EDX) techniques demonstrated that the expired antibiotic molecules are firmly adsorbed at the copper surface. Electrochemical modulation (EFM), and polarization tests are in good agreement with the weight lack method.

This work concerns Cr3+ and Nd3+ co-activated SrGa12O19 phosphors, which were synthesized by high temperature solid-state method using oxides and carbonates as starting materials. Luminescent samples according to SrGa12O19:Cr3+,Nd3+ comprise Cr3+ for the absorption of UV and visible radiation (250–700 nm) prior to energy transfer to Nd3+. The result of the energy transfer between Cr3+ and Nd3+ is the observation of line emission originating from Nd3+ in the near infrared range. The energy transfer from Cr3+ to Nd3+ is discussed via the variations of the lifetime values of Cr3+, and the thermal quenching behavior is also described. The strong absorption of Cr3+ in the visible range and the efficient energy transfer from Cr3+ to Nd3+ indicate that the herein presented material type can serve as a radiation converter to improve the efficiency of photovoltaic devices based on silicon cells.

The influence of size effect on deformation behaviors at quasi-static strain rate has been widely studied in recent years. However, there is little research about size effect on deformation behaviors of metal foils at high strain rate. To clarify how the size effect influences the deformation behavior of metal foils over a wide range of strain rate, the tensile tests at different strain rates of pure titanium foil with various grain sizes were originally conducted using material testing system (MTS) and a specially designed Split Hopkinson Tension Bar. It is found that microstructure evolution and fracture mechanism show great differences between quasi-static and dynamic tensile tests. Moreover, size effect on flow stress of pure titanium foil also shows obvious distinctions between quasi-static and dynamic tensile tests and this phenomenon was well explained by the proposed twinning refinement physics model. Furthermore, the uniform strain for pure titanium foil is larger at high strain rate than that at quasi-static strain rate, and a larger uniform strain for pure titanium foil with larger grains was observed at high strain rate. A modified Johnson-Cook model coupling effects of grain size and strain rate was proposed to predict the flow stress of pure titanium foil, and the prediction matched well with the experimental results.

The present study monitored the foaming phenomenon originating from the reaction of titanium-bearing blast furnace slag by using the relationship between the current change in a circuit and the foaming height. A series of experiments at room temperature and high temperature were designed to check the feasibility and reproducibility of the experimental apparatus. Experiments at different levels of basicity and TiO2 content at high temperature were designed to determine the effect of these parameters on the relationship between the foaming height and current. It was proved that the electric current method used in this study to monitor the real-time foaming process is feasible and reliable. The relationship between the foaming height and current change was also established.

In this study, a simplified approach to correlate the experimental tensile strength values of the randomly oriented short fiber (SF) reinforced polymer-based composites is presented. For this purpose, a constitutive model to correlate the experimental tensile strength values of SF reinforced composites is derived. The constitutive model was derived based on a rule of mixtures. The experimental results on the Short Carbon Fiber (SCF) reinforced composites reported in our earlier works show a non-linear increase in its tensile strength as the fiber volume fraction is increased. The experimental strength of the composite was found to be significantly dependent on the interfacial stress at the fiber–matrix interface and the percentage of fibers oriented in the loading (tensile) direction. Thus, the orientation dependence of the fibers was incorporated by assuming that the percentage of aligned fibers follow the Weibull Probability Distribution Function (PDF). Additionally, the derived constitutive model was verified against the reported tensile strength data of SCF composites. The correlations of the experimental results from our earlier published work and from other available data in the literature, with the proposed model, were found to be in good agreement. The analytical model was compared to other analytical models and found that the current model showed better agreement with the reported experimental results.

This study investigated phosphorus removal from aqueous solutions using carbonatisation cake, which is a sugar residue containing a significant amount of reactive calcium carbonate. The chemical composition of the carbonatisation cake was determined, and the organic contamination of the carbonatisation cake and calcine in contact with water was determined. In addition, TGA, DTA, XRD, SEM-EDX, BET, FTIR, density, pHzpc and particle size distribution were analyzed for carbonatisation cake, product and post-phosphate removal calcined product. Batch experiments were performed to determine the effect of dose, phosphorus concentration, temperature and contact time on phosphorus removal from aqueous medium. Maximum phosphate adsorption capacity was found to be 65.16 mg g−1 at 25 °C, pH of 6 and adsorbent dosage of 1 g L−1 for a contact time of 180 min. Adsorption experiments were applied to adsorption isotherms. Kinetic, thermodynamic and mass transfer calculations were calculated. The results show that calcines produced by heating the carbonated cake to 600 °C, which is not cost-effective in sugar production, can be used effectively to remove phosphate from wastewaters.

A novel titanium-based alloy with low density, high hardness, and corrosion resistance was manufactured and characterized in this paper. The Ti60Ni9Fe8Co8Si15 alloy was created from its elemental components and subjected to further manufacturing. To reach a homogeneous phase, the samples were broken into small pieces and were repeatedly re-melted with arc-melting. This base alloy was further processed to manufacture an amorphous/nanocrystalline material by ball milling followed by high-pressure torsion (HPT). For subsequent characterization, X-ray diffraction (XRD), pycnometer densitometry, scanning electron microscopy (SEM) with X-ray energy dispersive spectroscopy (EDS), and hardness measurements were performed. X-ray diffractometry confirmed the formation of a amorphous/nanocrystalline structure, as most of the characteristic peaks related to the crystalline phase disappeared or flattened after ball milling. In accordance, the hardness of the manufactured samples increased by nearly 50 HV compared to the base alloy. The density of the final alloy was measured to be 4.125 g/cm3, with a hardness of 762 ± 39 HV, which confirms that an exceptionally light and, at the same time, hard material was manufactured. In order to distinguish the effects of elemental composition and manufacturing on the measured properties of our alloy, a similar Ti-based alloy with a different elemental composition (Ti47Cu40Zr7.5Fe2.5Sn2Si1) was also prepared with the same proposed manufacturing process. This reference composition resulted in significantly lower hardness (489 ± 31 HV) at a significantly higher density (5.767 g/cm3).

The electronic and magnetic properties of armchair-hexagonal (AHEX) and zigzag-triangular (ZTRI) graphene quantum dots doped with alkali metals are investigated using density functional theory. The binding energy confirms the stability of the undoped systems. Although doping decreases stability of single layer structures, in bilayer ones the binding energy between the layers increases. The former is due to the broken bonds and the deformation at the surface, while the later is due to the chemical bonds formation between the layers. We found that the lowest ground state energy for AHEX/AHEX-doped is the singlet/quadruplet spin state. Therefore, AHEX dots experience transformation from diamagnetic to ferromagnetic state after doping. In addition, the optimized spin state for ZTRI/ZTRI-doped is the quintet/sextet spin-polarized state. In few cases, the doped AHEX/ZTRI dots have doublet/quadruplet spin state due to the strong interaction between the flake atoms that passivates some unpaired electrons. Magnetic properties depend also on stacking, for instance pristine bilayer triangular flakes become antiferromagnetic due to pairing between edge states. The energy gap significantly affected by doping, for instance the gap decreases from ~3.7 eV in hexagonal flakes to 1.5 eV when it is doped with Na in the upper position. Electrons from the broken bonds around the doped metal form orbitals loosely bound to the flake consequently decreasing the energy gap. On the other hand, stacking increases the energy gap in bilayer triangular flakes due to the mutual passivation of the reactive edge states from both the layers. The calculated spin up/down density ratio is high in hexagonal flakes leading to high spin polarization (P), for instance P = 0.64 in hexagonal flakes doped with K atom. The found enhanced spin polarization, in addition to the tunable magnetic properties, makes doped graphene flakes promising candidates for spintronic devices.

The relevance of the work is due to the need to extract additional information in the study of the polarization properties of the geological environment from experimental data in the method of ac resistance using multifrequency measurements. The introduction provides a brief review of the literature on the problem of studying the polarization properties of rocks in the frequency domain and the method of frequency dispersion, which is successfully used in prospecting and exploration works in sulfide and copper pyrite deposits. The questions of determining the polarizability of the medium in the frequency domain and the parameter of the polarization process depending on the structural and petrophysical characteristics are discussed. Purpose of this research is to compare the characteristic features of studying the polarization properties of a medium in the frequency domain and to establish the relationship between polarizability and the frequency dispersion coefficient of electrical resistance. To propose an algorithm for determining the polarization characteristics of a medium from the data of multifrequency measurements in the method of resistances on alternating current. Research methodology: substantiation of the choice of the model of induced electric polarization in the frequency domain and the peculiarities of its application to establish the relationship between the frequency dispersion coefficient and the apparent polarizability of the medium. Research methods: theoretical calculations and comparative analysis of the obtained dependences on the model parameters. Results of work. The choice of the model of induced electric polarization Cole-Cole in the frequency domain is substantiated to establish a relationship between the frequency dispersion coefficient and the apparent polarizability of the medium. The possibility of using multifrequency measurements of electrical resistance to study the polarization characteristics of a medium based on this model is shown. An algorithm has been developed and expressions have been obtained that make it possible to determine the polarizability of the medium and the parameter of the relaxation time from the data of measuring the apparent resistance at three frequencies in the method of electric sounding on alternating current. Application area. The obtained results can find application in the processing of data from conductive electrical soundings on alternating current, for the correct interpretation of the frequency effect and the study of the polarization properties of the medium, in particular, when research by the method of frequency dispersion.

This paper reports an experimental investigation on continuous CO2 laser cutting of polymethylmethacrylate (PMMA) sheet. The influence of four process factors (laser power, cutting speed, assisting gas pressure and sheet thickness) on five process responses (kerf deviation, top heat affected zone, bottom heat affected zone, maximum surface roughness and rough area) has been investigated. The experimental plan was established based on Taguchi L18 mixed design. The kerf geometry and heat affected zones have been measured using polarising light microscopy technique, while the surface roughness was evaluated using 3D laser scanning confocal microscope. Regression models have been derived to correlate different process responses with different process factors. The cut surface could be classified into three zones: rough zone, moderate zone and soft zone. The rough area is increased by increasing gas pressure and laser power and by decreasing the sheet thickness and cutting speed. Increased kerf deviation has been observed at high cutting speed, laser power and gas pressure. High laser power and low cutting speed produced worst surface roughness and wide heat affected zone. Therefore, it is recommended to use low laser power and high cutting speed to minimize the heat affected zone and the surface roughness. However, increasing the cutting speed may result in high kerf deviation.

Relevance of the study. Currently, information obtained during monitoring, including monitoring of forest lands, is of particular importance for making informed decisions on the development of natural potential. A feature of these works today is the lack of combination of data collection procedures, their processing with models of structural elements of forest lands, which requires a solution to the problem under consideration. The aim is to form, according to the results of system monitoring, a system of interconnected decision-making algorithms in the field of forest land use in industrial regions. The methodology for the formation of a system of interrelated decision-making algorithms in the field of forest land use in industrial regions is based on the use of mathematical models of natural objects of forest ecosystems, natural phenomena in them and forest-forming processes, on the procedures of a comprehensive assessment and optimization of forest land use in industrial regions in accordance with current provisions of the concept of environmentally sustainable development of territories. Results and their application. The algorithms for decision-making in the use of forest lands based on the results of system monitoring are considered: substantiation of strategic indicators of sustainable development of forest lands in industrial regions in the face of modern challenges and risks; comprehensive ecological and economic assessment of the natural resource potential of forest lands; determination of leeways of permissible use of forest lands in industrial regions in specific climatic and socio-economic conditions; coordination of individual interests of land users on forest lands with public preferences for the development of industrial regions; multi-criteria optimization of the use of forest lands in industrial regions. The main principles of forecasting the parameters of a comprehensive assessment of forest lands, the use of the indicator of consumption of net primary products of forest ecosystems, the sequence of greening the economy of the use of forest lands in industrial regions, justification of concessions to the extreme values of particular criteria in multi-criteria optimization are given. The proposed additional indicators of sustainable development of forest areas in the Middle Urals, the results of calculations on the change in the natural resource potential of forest lands in the subsoil use area are presented; the substantiation of the multicriteria optimization of the use of raw material resources of forest lands is given. Conclusions. The proposed decision-making algorithms in the field of systemic monitoring of forest lands are intellectual support for users in the analysis of information in the field of land relations. They provide a substantive dialogue that allows you to form the necessary information in a user-friendly form, adjust the data processing process and make decisions.

The hard roof difficult to collapse easily causes gas accumulation, which threatens the production safety of coal mine. Therefore, roof pre-cracking is required. Although blasting and hydraulic fracturing can also crack the roof, blasting can easily induce rock bursts, whereas hydraulic fracturing needs complex equipment. In contrast, soundless cracking demolition agents (SCDAs) with noise-free, dust-free, and safe characteristics have obvious advantages. The main component of SCDA is calcium oxide, which reacts with water to produce higher expansion pressure. In this paper, focused on the angles of the borehole, the effect of SCDA is analyzed by numerical simulation based on Pingdingshan coal mine. The research results showed that the azimuthal angle α (between borehole projection and the roadway direction) does not significantly affect the efficacy of SCDAs, whereas the influence of borehole elevation angle β is far more significant than that of the azimuthal angle. Therefore, the angle β is a dominant factor influencing the effect of SCDAs. Based on different effects of SCDAs at different angle of boreholes, the weakening unit was established, so the SCDAs could give full play to roof fracturing. Moreover, field tests validated the importance of borehole angle on weakening the hard roofs.

AlCa75 with equal Ca content was used to replace pure Ca for the preparation of AlSi12 foam in a stable pore structure after foaming for 20 min. The stability mechanism was studied based on the comparison between the macroscopic pore structure evolution and the second phase composition of AlCa75 and pure Ca aluminum foam. It was found that the porosity and average pore size of the AlSi12 foam with AlCa75 were stable without any abnormal large pores, and the foaming stage was prominent. The stability of AlSi12 foam with pure Ca is inferior. After 20 min of foaming, the foam bursts in the center. Combined with the microscopic characteristic analysis, it could see that the second phase produced by AlCa75 is mainly Al2Si2Ca, which can be uniformly dispersed in the matrix. The addition of pure Ca reduces the amount of the second phase and the main phase Al4Ca is easy to agglomerate. The stability mechanism shows that the Al2Si2Ca second phase, formed by AlCa75, demonstrates a better stabilizing effect in different foaming stages. Due to the premature agglomeration caused by Al4Ca and the low content of the second phase, the AlSi12 foam with pure Ca is challenging to long-term stability.

To explore the failure mechanism of roadway in layered soft rocks, a physical model with the physically finite elemental slab assemblage (PFESA) method was established. Infrared thermography and a video camera were employed to capture thermal responses and deformation. The model results showed that layered soft roadway suffered from large deformation. A three-dimensional distinct element code (3DEC) model with tetrahedral blocks was built to capture the characteristics of roadway deformation, stress, and cracks. The results showed two failure patterns, layer bending fracture and layer slipping after excavation. The layer bending fracture occurred at positions where the normal direction of layers pointed to the inside of the roadway and the layer slipping occurred in the ribs. Six schemes were proposed to investigate the effects of layered soft rocks. The results showed that the deformation of ribs was obviously larger than that of the roof and floor when the roadway passed through three types of strata. When the roadway was completely in a coal seam, the change of deformation in ribs was not obvious, while the deformation in the roof and floor increased obviously. These results can provide guidance for excavation and support design of roadways in layered soft rocks.

Composite materials for vehicle parts require lightweight, high strength and good impact properties. In this study, the optimized manufacturing conditions of epoxy foam (EF) were investigated to improving mechanical performance of carbon fiber reinforced plastic (CFRP)/EF/CFRP sandwich composites for vehicle parts such as impact, flexural property. The optimal curing temperature was found to be 60 °C, by measuring the reaction rate, volume increase rate, density, cell size, glass transition temperature, and specific compressive strength of the EF. In addition, foams after 180 °C thermal aging were observed, and the properties of the EF cured at 60 °C were the most stable under the thermal aging. The performance of the sandwich EF composites was investigated using compressive, flexural strength, lap shear strength, and impact tests. The optimized cell condition of the EF was correlated to improving interfacial adhesion of sandwich composite.

In structural applications, catastrophic failure caused by fatigue occurs with more frequency because usually polymers are chosen when reduction in weight is necessary and overload is applied on it. In this study fatigue, crack growth at a humid, and very low temperature in a transparent unsaturated polyester resin has been investigated. The tests were conducted at a constant applied load ratio R = 0.1 using two different crack to width ratios (a/W) of 0.2 and 0.35 at room temperature and −60 °C. Polyester resin specimens are fabricated. The test used for the experiments is ASTM Standard D647 under tension–tension loading. The experimental results have been expressed in terms of Paris Law parameters. The fatigue crack results show that the fatigue resistance increases with decreasing a/w. It also shows that it increases with decreasing temperature up to −60 °C as the material becomes stiffer at the extremely low temperature and the polymer matric particles were much less mobile and ductile and discovered that low temperature has a positive influence on the strength of composites. The dominant failure mode was a polymer matrix -tear failure that was driven by a crack in the x-direction starts with the pre-crack in the case of a/w = 0.35 and it was slow enough in a/w = 0.2 because of the high energy of bonding and networking through the polymer matrix. The results proved that there is no through-the-thickness crack propagation due to fatigue in the polyester matrix.

A nanobainitic matrix composing of nanoscale α phase and carbon-riched γ phase was obtained for the ductile iron by austempering treatment. The microstructure and properties of ductile iron were compared with GCr15. The microstructural characteristic gave rise to a good strength with an ultimate tensile strength higher than 1200 MPa, which was comparable and even superior to conventionally forged steels. The friction coefficient of the ductile iron was approximate 1/3 compared with that of commercial GCr15 under dry sliding wear condition, which was related to the existence of homogeneously distributed spheroidal graphite in ductile iron. The low friction coefficient and moderate strength resulted in a superior wear resistance of ductile iron with nanobainitic matrix by contrast to GCr15.

The ultrasonic shot peening (USP) treatment was adopted to improve the compressive residual stress, microhardness and corrosion resistance of Ti–6Al–4V (TC4) titanium alloy fabricated by selective laser melting (SLM). The optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and hardness test were used to investigate the microstructure evolution. The effect of the USP on electrochemical behaviour of the SLM TC4 alloy in a 3.5 wt. % NaCl solution was studied using potentiodynamic polarization. After USP treatment, compressive residual stress was induced and microhardness significantly increased. Proper USP treatment can effectively improve corrosion resistance of the SLM TC4 alloy, which is manifested by the increase in corrosion potential and decrease in corrosion current density.

The increasing environmental problems as well as demand of energy encourage the research for safe as well as efficient energy sources. As most of the energy sources are not consistent; thus, there is a requirement for highly efficient energy storing systems. Supercapacitors emerge with great researcher interest because of their very high capacity of storing energy. The performance and efficiency of supercapacitor depends directly on the electrode materials. The oxides of transition metals are highly explored as pseudo capacitors material. Nickel based electrode materials, characterized by ultrahigh theoretical capacitance has gained significant attention. These days nickel oxide-based electrodes owing to their high chemical stability, good theoretical specific capacitance, less cost, easy availability as well as non-toxic nature makes it very popular. This review deals with the recent development in the field of nickel-based supercapacitor electrodes by grouping them on the basis different morphologies such as nanoparticles, nanowires, thin films, nanofibers, etc along with challenges as well as future research.

This study presents microstructural, electrochemical, and mechanical characterizations on pure copper fabricated using constrained groove pressing (CGP) in quiescent phosphate buffer solution (pH = 11.73). We tested the effect of surface modifications on electrochemical features using electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis. A three-dimensional simulation via finite element modeling evaluates the CGP effects on the maximum principal stress and the plastic strain distribution. The transmission electron microscopy (TEM) micrographs confirm that the increasing CGP cycles result in a nano/ultrafine grain microstructure. Our electrochemical study showed that the CGP process can positively impact the passive behavior of pure copper. Mott–Schottky analyses illustrated that the point defect densities decline in the p-type semiconducting passive layer upon receiving CGP. Besides, increasing the CGP cycles lowers the corrosion current density and produces less defective passive films.

A plastic temperature-dependent constitutive model is developed for 0.05 mm thickness pure aluminum diaphragms at large strains by using bulge test method. Rupture strain of the material is recorded below two percent according to tensile tests. In order to achieve the material behavior at larger strains, an own bulge test apparatus is used to extract equi-biaxial stress–strain curves at different temperatures, i.e. from room to 150 °C. Effective stress–strain behavior is then computed via a transformation scheme using the plastic work definition as well as the room temperature uniaxial stress–strain curve. It is illustrated that the Johnson–Cook constitutive model is not able to capture this stress–strain behavior. Thus, a modified Johnson–Cook model is developed in which the strain hardening is assumed to be temperature-dependent accompanying by a novel thermal softening relation. Using the Least-square method as well as the Ant colony optimization algorithm, the material parameters of the both models are calculated. It is depicted that the new model follows the material behavior more precisely than the Johnson–Cook model. The new model is then numerically implemented into finite element software via a user subroutine. In order to compare the accuracy of both models in capturing the hot bi-axial deformation of pure aluminum, an experiment is performed and numerically simulated.

Air leakage in underground coal mines presents a serious hazard for coal production and the safety of miners. Coating technology is commonly used as an efficient means for preventing air leakage. To address existing problems with high dust concentrations in large operations involving complex processes and the high cost of traditional coating technology, a novel coating technology that ensures intrinsic safety by utilizing water pressure and wind pressure was developed. This new coating technology was designed to suction and spray, and the technical parameters of its spray performance was also studied. The experimental tests and evaluation indicated the optimum working range is 0.3–0.7 MPa of wind pressure, 1.2–10.2 L/min of water quantity, and 1.0–3.5 m of spraying distance. Moreover, this novel coating technology was tested in the Dashuitou Coal Mine in Gansu Province of China. Compared with conventional counterparts, the proposed new technology is safe, efficient, and convenient to operate. During spraying, dust concentrations were kept at less than 10 mg/m3, and the average rebound ratio resilient rate of solid materials was below 13%. After spraying, the average leakage every 100 m was 4 m3/min, and the oxygen volume fraction in the adjacent goaf was approximately 4%, demonstrating excellent air leakage prevention.

Heteroatom-doped carbon materials with hierarchical porous structures are promising alternatives to replace the use of scarce platinum catalysts in fuel cells for oxygen reduction reaction (ORR). In this work, nitrogen-doped hierarchical porous carbon is developed from abundantly available textile waste activated with calcium chloride as the pore forming agent and inexpensive urea as the nitrogen precursor followed by pyrolysis. The obtained porous carbon, namely TCPB, has a 3D interconnected hierarchical porous structure (sponge-like) with high surface area (495.97 m2 g−1) and good nitrogen doping (2.80 at%). TCPB exhibits excellent ORR activity (E0 = 0.948 V vs RHE) via the 4-electron transfer pathway with low H2O2 production (6.9–8.91%), superior stability (negligible performance loss) and good tolerance to 3 M methanol when compared to commercial Pt in alkaline media. These results indicate the conversion of textile waste with simple synthesis steps able to produce nitrogen doped porous carbon catalyst with excellent performance thus offering great advantage for fuel cell application.

The present work, first detailed study in its nature, introduces wall curl as a source of geometric inaccuracy in the novel Incremental Sheet Forming (ISF) process, and aims at investigating role of the residual stresses, stretching force and process conditions on formation of the curl. A series of metal components are formed by varying the conditions. The curl height, residual stresses (surface, mean and equivalent) and stretching force are determined and their correlations are analyzed. The analysis reveals that curling is strongly influenced by the residual stresses in a way that the curl height increases linearly as their magnitude increases. Similarly, an increase in degree of non-uniformity in the through-thickness stress distribution promotes curling. The increase in stretching force, however, diminishes curling reasoning to reduction in the residual stresses. As regard the conditions, feed rate does not show any effect while mild annealing, greater tool diameter, smaller step size, and lower forming angle and rotation are found conducive to minimize curling. The geometric errors in wall and bottom of the produced parts (i.e., curling and pillowing) are found to show an interesting inverse relationship. The reported results are very useful to deepen the process mechanics and will also prove helpful in simultaneously controlling the two types of errors.

Woven carbon fibers reinforced Al-matrix composites were successfully prepared through a liquid metallurgy process in pulsed magnet field (PMF). Various wetting conditions and PMF application methods were respectively adopted to reveal the infiltration mechanism, based on which a model and hypothesis of the electromagnetic infiltration were developed. There was an exact match between the metallization depth in electroless plating process and the infiltrating depth in spontaneous infiltrating process, and an obvious improvement in the infiltration result was obtained with the introduction of PMF. The finite-element simulation result indicated that the molten matrix in PMF could offer periodic squeeze and impact effects on the fibers. With the application of PMF, the bending strength of the obtained composite improved from 112 to 203 MPa. Furthermore, the electromagnetic infiltration morphology in PMF possessed the gradient and synchronization characteristics, which was different from the spontaneous infiltration morphology with a step-by-step characteristic.

Using first-principles calculations, we predicted different structures of lithium (Li) atoms with solid electrolytes (e.g., ethylene carbonate (EC)) and their coordination number (n = 3) for the first time. Additionally, we explored the unique properties of the EC absorption of the Li atom using both the equilibrium EC solvent and complex cluster of Li+. Vibrational spectral analysis confirmed that only one type of Li coordinates with EC molecules. The coordination number of EC molecules increases with decreasing minimization or optimization energy and the charge of Li ions. Due to electron affinity and ion charges, only the optimized energy investigation supports the coordination of the EC solvent, which can be calculated by Li+Bn n = 1–3, where B is the organic solvent (ethylene).

As a noteworthy salt hydrate, sodium sulfate decahydrate or Glauber salt can be used as a phase change thermal energy storage material. Kinetic parameters of sodium sulfate decahydrate salt solution are evaluated experimentally. Instead of the traditional polythermal and isothermal methods, a novel constant temperature experimental method (based on the turbidity titration) was adopted to experimentally illustrate the induction time and metastable zone width, in unseeded batch crystallization for sodium sulfate decahydrate salt solution at different temperatures (7, 9, 10, 13, 16, 19, 22 °C) and supersaturation ratio (1.01–1.43). We determined crystallization thermodynamics parameters, solubility, and supersolubility, of sodium sulfate decahydrate salt solution under atmospheric pressure and at different temperatures. The solubility data could be well fitted by the solubility carve of sodium sulfate decahydrate in the phase diagram of sodium sulfate. Statistical analysis shows that there was consistency in the result data of solubility. Two models, classical nucleation theory (primary homogeneous) and secondary nucleation, were employed to analyze the experimental data. The secondary nucleation model helped determine the order of nucleation and nucleation kinetic constants.

The tensile-shear strength of laser-welded lap joints developed in abrasion resistance ultra-high strength ARS-600 steel was optimized by evaluating the joints achieved with different welding parameters and various configurations of weld patterns, including multiple continuous longitudinal and transverse weldments. The microstructural evolution of the fusion zone was characterized by electron backscatter diffraction (EBSD) after welding with different values of energy input (60–320 J/mm). Furthermore, in order to better comprehend the shear response of different weld patterns, stress analysis of various longitudinal and transverse lap joints was conducted by the finite element method (FEM).

Uniform and fine in-situ short-fiber/particle hybrid reinforcements were obtained in a SiCf/SiC composite/Ni-based superalloy joint by using a novel AuCuTiB/Mo/AuCuTiB composite filler. The growth of in-situ phases showed a strong dependence on the numbers of nucleation sites and metal atoms on the ceramic side. Inadequate brazing conditions adversely affected the formation of indirect TiB whiskers, and excessive brazing conditions induced an accumulation of metal atoms. As a result, the in-situ phases switched from Ti5Si3 + TiC to Ti5Si3 + Ni + TiB + TiC, and to (Ni, Ti)-(Si, C) + TiB with increasing brazing conditions. The size, type, and composition of the in-situ phases were effectively controlled by adjusting the brazing conditions (B content, brazing temperature, and holding time). In light of this, the shear strength of the joint was optimized at 124.9 MPa. The excellent mechanical performance was ascribed to (i) a suitable interfacial layer and (ii) the effective stress relief of in-situ phases and ductile/rigid/ductile multiple layers. Moreover, the joint exhibited mechanical stability at 973 K because the in-situ phases can serve as a high-temperature resistant second structure.

It is essential to utilize high-phosphorus steel slag (SS) effectively. The retarding effect of phosphate on the setting time is investigated, the retarding mechanism of high-phosphorus SS is concluded. The hydration activation of high-phosphorus SS in cementitious material are studied with additives of calcium oxide and sodium sulfate. The application of high-phosphorus SS with composite admixture of blast furnace slags (BFS) or BFS + fly ash (FA) is investigated. The main properties such as setting time, flexural strength (FS), unconfined compressive strength (UCS), hydration mineral, microstructure, etc., are investigated. The results show that the soluble phosphate would be generated during the depolymerization and dissolution processes of vitreous bodies in high-phosphorus SS, the retardation effect of soluble phosphate is greater than that of insoluble phosphate. The approximate amounts of calcium oxide and sodium sulfate for the hydration activation are 4% and 1%. To ensure sufficient later UCS of concrete, the high-phosphorus SS content is suggested not to be over 35%. To ensure optimal mechanical performance, the range of blended mixture is recommended as 30–40%. The blended proportion of high-phosphorus SS, slag and fly ash is recommended as 1:2:1. This investigation is new at present and important to the recycling of high-phosphorus SS.

With the wide application of titanium alloys in the aerospace industry, the burn resistance properties and surface strengthening processes of titanium alloys have been received increasing attention. In this study, Ti40 burn-resistant titanium alloy was cladded on the surface of TC4 by electron beam cladding, and the surface layer of the nanostructure was prepared by ultrasonic impact treatment (UIT). The nanostructure layer was examined by pulse laser ablation. The results showed that when the moving speed was 16 mm/s, the maximum thickness of the plastic deformation zone of the UIT Ti40 cladding layer reached 150 μm. The highest hardness value was 531 HV, which was approximately 43.5% higher than the original microstructure of the Ti40 cladding layer without UIT. Moreover, the surface microstructure of the Ti40 burn resistant titanium alloy cladding layer was nanocrystalline with uniform distribution and random orientation, and the average grain size was 50 nm. The UIT process can effectively increase the relative content of burn-resistant alloy elements on the surface of the Ti40 cladding layer and increase the content of dense oxidation protective films after laser ablation, which hinders the diffusion and migration of oxygen elements to the matrix alloy in the process of ablation and then improves the burn resistance of the Ti40 cladding layer.

Glass-forming ability (GFA) of the Gd20Dy20Er20Co20Al20 high-entropy bulk metallic glass (HE-BMG) was improved through microalloying Si element. The critical diameter of this rare-earth-based HE-BMG increases from 1.5 to 8.5 mm with 0.5 at.% Si addition without any deterioration of magnetocaloric property. Compared with the Si-free sample, the BMG with 0.5 at.% Si addition exhibits low driving force for crystallization, strong supercooled liquid behavior and sluggish crystallization kinetics, whereas excessive Si addition leads to reverse variations. Furthermore, microalloying Si can enhance nanoscale heterogeneity of elemental distribution, and thus facilitates the formation of local crystal-like structures. The connectivity and competition between icosahedra-like clusters and crystal-like structures promote the formation of stable network structure which frustrates crystallization. As Si content is excessive, icosahedra-like cluster is consumed by the further grown crystal-like structure, leading to the destruction of network and decreasing GFA. This work not only elucidates the underlying mechanism of the GFA enhanced by microalloying, but also sheds light on improving the GFA of HE-BMGs through altering nanoscale elemental distribution and structural heterogeneity.

Pavel Vladimirovich Pokrovskiy was a prominent scientist in the field of mineralogy, geochemistry and ore geology, as well as a specialist in tungsten and gold deposits. He was a talented organizer science and educated 17 candidates of geological and mineralogical sciences.

The effects of Ca addition and equal channel angular pressing (ECAP) on the microstructure evolution and discharge properties of AZ31-1.0Ca alloy were investigated to develop high-performance anodes for seawater-activated battery. Microscopic observations show that the net-like (Mg, Al)2Ca phase replaces the Mg17Al12 phase and distributes along grain boundaries in AZ31-1.0Ca alloy. 12-pass ECAP effectively refines the grains and crushes the (Mg, Al)2Ca phase into fine particles. The discharge measurements reveal that the 12-pass ECAP processed AZ31-1.0Ca anode exhibits desirable discharge properties with the largest power density of 88.1 mW cm−2 and the highest anodic efficiency of 63.3% at 100 mA cm−2, which are 25.0% and 13.6% higher than that of AZ31 anode, respectively. The enhanced discharge performances can be attributed to the modified microstructure with refined grains, fragmented and dynamically precipitated (Mg, Al)2Ca particles.

Non-equilibrium solidification and experienced thermal conditions of deposited 2219 aluminium alloy during wire and arc additive manufacturing (WAAM) result in the grain boundary segregation, which makes it difficult to avoid the appearance of columnar grain. In this work, columnar crystal defects and grain boundary segregation were eliminated by adding TiC nanoparticles (TiCnps) to WAAM-deposited 2219 aluminium alloy. The effects of TiCnps addition on the solidification dynamics, particles distribution, grain boundary structure, solute redistribution, and mechanical properties were investigated. The solidification dynamics of the droplet induced by mesoscopic TiC particles was assessed and the result showed that the addition of c. 80 nm TiCnps could reduce the solid–liquid growth rate (R), besides, the critical movement rate (Rc) of 80 nm TiCnps was much lower than that of R, i.e. TiCnps were inclined to be distributed inside the grains as effective nucleation particles. Micro-pools with multi-site nucleation inhibited grain boundary segregation and increased Cu concentration in Al-matrix. Such a variation in Cu atom concentration promoted the precipitation of the fine spot-like θ′-CuAl2 phase with a diameter of c. 500 nm, besides, the dendritic θ-CuAl2 phase along the grain boundary was all transformed into α-Al+θ-CuAl2 phases with a semi-coherent state. The fine spot-like phase and TiCnps possessed a strong interfacial bonding with the Al-matrix, thereby the mechanical properties of the deposited 2219 aluminium alloy were strengthened. Eventually, the deposited 2219 aluminium alloy with the addition of TiCnps exhibited excellent mechanical properties, i.e. the tensile strength of the samples were around 380 MPa, and the elongation could be up to 21.4%.

Grain boundary segregation engineering (GBSE) is a promising approach for accurately manipulating chemical composition, structure and properties of grain boundaries (GBs). With the aim of attenuating or even removing disadvantages of GBs in nickel-based superalloys, the GB segregation behaviors of 3d (Ti–Co), 4d (Zr–Rh) and 5d (Hf–Ir) transition-metal (TM) solutes X and their effects on the thermodynamic stability and fracture strength of Ni Σ3 [110](111) symmetrical tilt grain boundary were systematically investigated, using first-principles total-energy calculations based on density functional theory. We found that all TM solutes considered herein can segregate towards the Ni Σ3 [110](111) GB. For TM elements from same row of the periodic table, their segregation energies show a concave-up parabolic-like dependency on the atomic number of TM elements. The GB segregations of all considered solutes can lead to a reduction in GB energy and render the Ni GB more stable, and the GB energies of X-segregated GBs vary linearly with the GB segregation energies of solutes X. Except elements Zr, Hf and Rh, the GB segregations of the other 15 TM alloying elements increase the GB fracture strength. The Mn and Re segregations improve the GB fracture strength and thermodynamic stability to a maximum extent, respectively. The underlying mechanisms for segregation-induced GB stabilizing and strengthening effects were further revealed at the electronic level by analyzing the crystal orbital Hamiltonian populations and deformation charge densities. Our work could provide new insights into designing Ni-based superalloys with desired performances based on the concept of GBSE.

Titanium and titanium alloys have been restricted in tribology-related field, because of their disadvantages, such as low surface hardness, high friction coefficient and poor wear resistance. Various surface modification techniques have been applied to improve their deficiencies. As a new technology of severe surface plastic deformation, ultrasonic nanocrystal surface modification (UNSM) technique has been widely used to realize the surface treatment of various materials, and also has attracted wide attention in many engineering fields. This review begins with a brief introductionof the basic concept and the modification mechanism of the UNSM technique. The specific applications of the UNSM technique for improving the tribological and fatigue properties of titanium and its alloys were reviewed and summarized.

To study the seepage and deformation characteristics of coal at high temperatures, coal samples from six different regions were selected and subjected to computed tomography (CT) scanning studies. In conjunction with ANSYS software, 3D reconstruction of CT images was used for the establishment of fluid-solid conjugate heat transfer model and coal thermal deformation model based on the microstructures of coal. In addition, the structure of coal was studied in 2D and 3D perspectives, followed by the analysis of seepage and deformation characteristics of coal at high temperatures. The results of this study indicated that porosity positively correlated with the fractal dimension, and the connectivity and seepage performances were roughly identical from 2D and 3D perspectives. As the porosity increased, the fractal dimension of coal samples became larger and the pore-fracture structures became more complex. As a result, the permeability of coal samples decreased. In the meantime, fluid was fully heated, generating high-temperature water at outlet. However, when the porosity was low, the outlet temperature was very high. The average deformation of coal skeleton with different pore-fracture structures at high temperatures showed a trend of initial increase and subsequent decrease with the increase of porosity and fractal dimension. The maximum deformation of coal skeleton positively correlated with connectivity but negatively correlated with the fractal dimension.

In this paper, laser shock peening (LSP) treatment was performed on Zr35Ti30Cu10Ni5Be20 bulk metallic glass (BMG) and the effects of induced energy on the characteristics of glassy structure were evaluated. The high resolution atomic force microscopy (AFM) and nanoindentation tests were carried out to characterize the nanoscale heterogeneity and micromechanical properties in the depth of material. According to the results, the surface of material showed a high heterogeneous structure, which was the sign of structural rejuvenation. However, with the move into the depth of material, the nanoscale heterogeneity decreased and eventually a relaxed region with the minimum heterogeneity was found in the 1.5–2 mm depth of BMG sample. Passing the relaxed region, again the nanoscale heterogeneity similar to the as-cast sample was observed. The nanoindentation results also confirmed the AFM outcomes. It is suggested that the relaxed region at the neighbor of rejuvenated region is due to the satisfaction of elastic adaptability which is resulted by the nanoscale shear events and the induced stress.

High niobium content TiAl alloys and Al2O3 ceramics were successfully joined using novel Nb particle-reinforced Ag–Cu composite filler. The changes in microstructure brazing at different temperatures were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The corresponding mechanical properties were studied by shear tests. The results showed that the brazed joints prepared at 900 °C can be divided into three zones. The typical microstructure of the brazed joints is high niobium content TiAl/AlCuTi + AlCu2Ti/Ag(s,s)+Cu(s,s)+Nb/Ti3(Cu,Al)3O/Al2O3. The brazing temperature was shown to have a significant influence on the microstructure and reaction layer thickness. After brazing at 810 °C, macrodefects could be observed in the brazing seam. At higher brazing temperatures, brazed joints without any defects were obtained. The addition of Nb particles and the suitable thickness of the Ti3(Cu,Al)3O reaction layer are the main reasons for the high shear strength. When brazing at temperatures higher than 900 °C, the volume fraction of the brittle AlCu(Ti, Nb) phase was increased and a thick Ti3(Cu,Al)3O reaction layer was formed, which deteriorated the shear strength of the joint. The maximal shear strength joint reached 228 MPa at 870 °C for 10 min, which is a substantial increase compared with conventional brazing processes.

This article highlights the natural convection nanofluids flow of in an upright channel undergoing chemical reaction and heat absorption. Five different nanoparticles such as titanium oxide (TiO2), aluminum oxide (Al2O3), copper oxide (CuO), copper (Cu) and silver (Ag) are considered in the analysis in water-based nanofluids. The problem is formulated in the form of partial differential equations. The precise results for the non-dimensional nanofluid concentration, temperature and velocity profiles, and the corresponding Sherwood numbers, Nusselt numbers and skin friction are derived in the form of rapid convergent series via the Laplace and finite sine-Fourier transforms. The comparison of nanofluids with water as base fluid added with five different nanoparticles is drawn and the effects of volume fraction of nanoparticles and diverse physical parameters for specified ranges, such as. 0.01 ≤ φ ≤ 0.05 , 0.5 ≤ S c ≤ 2.0 , 0.5 × 10 − 6 ≤ k c ≤ 1.7 × 10 − 6 , 0.5 ≤ Pr ≤ 2.7 , 5 ≤ Q ≤ 50 , 7 ≤ G r c ≤ 16 , 6 ≤ G r t ≤ 15 , on concentration, temperature and velocity fields are graphically underlined and discussed in details. We conclude that Ag-water has higher temperature due to higher thermal conductivity of Ag particles as compare to other nanoparticles Cu, TiO2, Al2O3 and CuO, while Al2O3-water has greater velocity than other nanofluids due to less density of Al2O3. Further, the expressions of skin friction, Sherwood numbers and Nusselt numbers are resolved on left plate and right plate of vertical channel and numerically expressed in tabular forms. Furthermore, it is originated that the heat transport rate enhances with increasing nanoparticle volume fraction.

Recycling waste materials have attracted considerable attention owing to the increased interest in depressing the negative impact on the environment. The present work investigates the effect of increasing the granite sludge-waste materials from granite manufacture-on the physical, mechanical and electrical properties of magnesia ceramics. The temperature-induced forming (TIF) method is used to shape magnesia-granite sludge ceramics. The sintered ceramics are characterized by XRD and SEM, in addition to measuring the bulk density, apparent porosity, linear shrinkage, microhardness, and electrical resistivity. Sintering of magnesia-granite bodies resulted in the formation of periclase-forsterite ceramics. The XRD results show that the forsterite phase increases reaching 78% at 40 wt% granite. The increase in granite sludge from 10 to 40 wt% increases the bulk density from 1.86 to 2.69 g/cm3 and the apparent porosity decreases from 40 to 15%, respectively. Microhardness is improved by increasing the granite sludge wt% reaching 7.9 GPa. The microstructure of the formed periclase-forsterite is versatile with a rhombohedral structure for periclase and a flower structure for forsterite. The forsterite phase is formed by the diffusion of granite sludge into the formed periclase.

This article presents the results of an experimental investigation on the mechanical behavior of hybrid fiber reinforced Strain Hardening Cementitious Composites (SHCC) subjected to monotonic and cyclic loadings. For the study, PVA, ultra-high molecular weight polyethylene (UHMWPE) and steel fibers were used in a constant volume fraction of 2.0%. To study the synergetic effects between the fibers, hybrid compositions were also produced by replacing PVA and polyethylene by steel fibers in 0.5% and 1.0% volume fractions. The mechanical response was measured under direct tension tests, four-point bending tests on plates and three-point bending tests on notched specimens while the crack pattern was investigated using optical microscopy. To study the mechanical performance of the materials when subjected to loading/unloading cycles, cyclic three-point bending tests were also carried on. The partial replacement of PVA and polyethylene fibers by steel fibers increased the strength and post-cracking stiffness but reduced the ductility of the composites. The hybrid SHCCs presented a good mechanical performance when subjected to cyclic loadings, since the load bearing capacity and the multiple cracking behavior were maintained even for high crack opening values. The stiffness degradation and the dissipated energy over the loading/unloading cycles varied when different fibers combinations were used.

In this study, 6056 aluminum alloy produced through continuous casting direct rolling (CCDR) was investigated. This alloy is used in the automotive industry because of its high corrosion resistance and strength. However, the material may become embrittled as a result of excessive deformation during cold forging. Therefore, preheat treatment was employed to improve the formability of 6056 aluminum alloy. Five different preheating conditions were considered in this study: annealing (O), solution treatment (W), aging for 2 h at 195 °C after solution treatment (SPA195), aging for 2 h at 230 °C after solution treatment (SOA230), and aging for 2 h at 250 °C after solution treatment (SOA250). The results show that the over-aged specimen SOA250 exhibited the best formability and could compress 85% of the original diameter after cold rolling. However, the ductility decreased considerably after cold rolling. To increase ductility and strength, a T6 treatment was applied after cold rolling. The ductility and strength of the specimen were increased significantly, similar to the manner in which the ductility and strength of a raw material that has undergone T6 heat treatment. The CCDR 6056 aluminum alloys subjected to solution treatment and over-aging treatment exhibited good cold rolling formability, and with the subsequent T6 heat treatment, the alloys exhibited high strength and ductility. The materials can thus be used for the manufacture of automotive fasteners.

Relevance is caused by the fact that the achievement of the required performance results is based on the mutual understanding of the workers of a coal mining enterprise and the consistency of their interaction. It is advisable to carry out a socio-economic valuation and mutual assessment of their activities to effectively change these components. For a correct assessment of the activities of employees, it is necessary to determine the criteria and indicators that reflect its socio-economic characteristics and the results achieved by employees. Purpose of the paper is to present a methodological toolkit that allows employees of a coal mining enterprise to carry out a socioeconomic valuation and mutual assessment of their activities, to develop measures for improving its efficiency. Research methodology and methods. The socio-economic valuation of employees work activities is based on the following provisions: 1) the results of the employee’s activities and the process of achieving them are assessed; 2) an employee himself makes the assessment as well as other employees interacting with him (manager, colleagues, subordinates). When substantiating the criteria and indicators, the methods of structural and functional analysis, scientific generalization and expert assessments were used. Results. A set of criteria and indicators have been substantiated reflecting the attitude of employees to activities, the process of their activities and the results they achieve. A method of socio-economic valuation of activities is proposed, the application of which allows identifying discrepancies in assessments, to achieve mutual understanding between interacting employees, their managers and colleagues, to develop relationships that ensure the required results of interaction. Conclusions. Socio-economic valuation of an employee’s work activities of a coal mining enterprise according to the proposed methodology using a reasonable set of criteria and indicators allows you to form an agreed understanding of the requirements for the activity and its results, to develop and implement effective measures to achieve the desired results Keywords: indicators and criteria, methodology, activity, coal mining enterprise, employee, socio-economic valuation, mutual understanding, relationships, interaction, results.