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Additive manufacturing (AM) is an advanced manufacturing process that provides the opportunity to build geometrically complex and highly individualized lightweight structures. Despite its many advantages, additively manufactured components suffer from poor surface quality. To locally improve the surface quality and homogenize the microstructure, friction stir processing (FSP) technique was applied on Al-Si12 components produced by selective laser melting (SLM) using two different working media. The effect of FSP on the microstructural evolution, mechanical properties, and corrosion resistance of SLM samples was investigated. Microstructural investigation showed a considerable grain refinement in the friction stirred area, which is due to the severe plastic deformation and dynamic recrystallization of the material in the stir zone. Micro-hardness measurements revealed that the micro-hardness values of samples treated using FSP are much lower compared to SLM components in the as-built condition. This reduction of hardness values in samples treated with FSP can be explained by the dissolution of the very fine Si-phase network, being characteristic for SLM samples, during FSP. Surface topography also demonstrated that the FSP results in the reduction of surface roughness and increases the homogeneity of the SLM microstructure. Decreased surface roughness and grain size refinement in combination with the dissolved Si-phase network of the FSP treated material result in considerable changes in corrosion behavior. This work addresses the corrosion properties of surface treated additive manufactured Al-Si12 by establishing adequate microstructure-property relationships. The corrosion behavior of SLM-manufactured Al-Si12 alloys is shown to be improved by FSP-modification of the surfaces.

The conditions for increasing the hot workability and extending the temperature range for the safe hot working of M2 high-speed steel (HSS) were studied and revealed. This was enabled by combination of two approaches, i.e. results obtained by an analysis of so individual as well as spatial influences of chemical elements on the hot workability using a conditional average estimator neural networks in combination with the results obtained from hot-compression tests that revealed the appropriate soaking conditions. The Latin Hypercube Sampling technique was used to model the uncertainty of the collected data used in the analysis. The obtained results reveal new, surprisingly complex, typically spatial and (highly) non-linear relationships between the chemical elements and the hot workability of M2 HSS, i.e. common mutual influence of carbon, carbide-forming elements as well as elements, i.e. Si, Mn and Co, which indirectly influence the formation of carbides. Further also new allowed upper limits for contents of some harmful elements like S, P, Al, Sb, Cu, Sn, As, Ni, etc. at which transition from higher to lower workability takes place were revealed. Finally, by applying a specially developed procedure for hot-compression tests the appropriate soaking time and temperature were assessed. New findings explain and considerably improve the intrinsic hot workability and extend the temperature range for safe hot working at its upper and lower limits.

The objective of the present work is to investigate the feasibility of the synthesis of copper matrix composite reinforced with in-situ nanosized Al2O3 particle powder via combustion synthesis method from metal nitrates followed by reducing process at high temperature. The starting nitrates Cu(NO3)2.3H2O and Al(NO3)3·9H2O composition corresponds to Cu-30%Al2O3. X-ray Diffraction (XRD) patterns of the obtained powders indicated the presence of the oxides CuO and CuAl2O4. The powder had the size of 75 ± 10 nm after deagglomerating by soft ball milling for 24h. After reducing in CO at 1000oC for 3h, the peaks of the oxides were no longer observed and were replaced by the peaks of Cu and -Al2O3. The morphology of the reduced powders observed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis showed well distribution of the -Al2O3 particles within the Cu matrix with an average particle size of 40 nm.

A magnesium alloy AZ31 as plate of dimensions (60 x 60 x 3) mm has been constrained groove pressed (CGP) four deformation passes (16 pressings) at 250 oC by simulation and experiments. On the basis of the analysis of calculation results about the deformation distribution in the alloy AZ31 workpieces, the mechanism for its microstructure evolution during the severe plastic deformation (SPD) process was partly clarified. On the other hand, deformation heterogeneity distribution developed in the workpieces by applying CGP caused the evolution of a non-uniform microstructure. The TEM microstructure analysis results provided clear evidence that across the plate both the banded deformed microstructure where dislocation cell structure and/or partially or fully recovered polygonized subgrain microstructure are present. The recovering dynamic and local polygonization process contributes significantly to the formation of ultra-fine materials (UFG) microstructure.

The present paper is devoted to the possibilities to classify the spatial arrangement of the elements (features) of a stochastic process with geometrical objects. The fundamental quantities describing point processes were introduced. Experimental possibilities of structural objects determination, possibilities of evaluation of the size distribution of the secondary phases, testing of planar point structures (estimation of the process intensity, square method and characteristics of the second order) were estimated. Interparticle distances, namely mean interparticle distance, mean minimum distance, mean visibility and mean path of spherical contact were defined. Selected processes were described and demonstrated from simulated realizations on Al-Al4C3 dispersion strengthened material, prepared by a powder metallurgy method of reaction milling. Interparticle distances of Al4C3 particles were evaluated. Polygonal methods and quadrant counts method were used for characterization of the particle arrangement.

Dominating globally and within Ukraine, the blast-furnace practice for iron production requires iron ore sintering preparation wherein the significant amount of fossil fuel is consumed, accompanied by harmful emissions into the environment. Pursuing the purpose to mitigate this negative impact, we address the promising direction of biomass utilisation for a partial replacement of fossil fuels in iron ore sintering. This paper considers the benefits of fossil fuels substitution with biomass, the world practice of biomass utilisation in iron ore sintering and the scope of the biomass energy potential in Ukraine. The study for obtaining sinters with the use of raw biomass fuels (sunflower husk, walnut shell) and charcoal has been carried out via lab-scale sintering pot. The influence of various biomaterials types on the process of iron ore sintering have been investigated and the obtained sinter quality in comparison with the conventional types of the fuels allows establishing the feasibility of replacing 25 % of coke breeze by charcoal or by walnut shell. The sunflower husk application is possible if preliminary preparation of the material for increasing bulk density is assumed to be carried out, for instance, by pressing.

Advancing the application of safety and health (S&H) technologies is likely to remain a value in the mining industry. However, any information that technologies generate must be translated from the organization to the workforce in a targeted way to result in sustainable change. Using a case study approach with continuous personal dust monitors (CPDMs), this paper argues for an organizational focus on technology integration. Although CPDMs provide mineworkers with near real-time feedback about their respirable coal dust exposure, they do not ensure that workers or the organization will continuously use the information to learn about and reduce exposure sources. This study used self-determination theory (SDT) to help three mines manage and communicate about information learned from the CPDM technology. Specifically, 35 mineworkers participated in two mixed-method data collection efforts to discuss why they do or do not use CPDMs to engage in dust-reducing practices. Subsequently, the data was analyzed to better understand how organizations can improve the integration of technology through their management systems. Results indicate that using the CPDM to reduce sources of dust exposure is consistent with mineworkers’ self-values to protect their health and not necessarily because of compliance to a manager or mine. Keywords: Autonomous organization, Continuous personal dust monitor, Respirable coal mine dust, Safety and health management system, Self-determination theory

In recent years, numerous scientific and technological innovations have been introduced in the fields of medicine and dentistry. The application of computer-based engineering techniques has enabled significant improvement in the design and performance of biomedical components, including implants and prostheses. Innovative and flexible manufacturing methods, such as single point incremental forming (SPIF), allow the cost-effective production of these “custom-made” components. The SPIF technology has been employed to manufacture a metal denture base plate (framework) of a complete maxillary (upper) denture to replace a traditional prosthodontic procedure based on a lost-wax technique, which is time-consuming and requires much manual work. Stainless steel sheet of quality X6Cr17 and thickness of 0.5 mm was adopted due to its biocompatibility, good mechanical properties, and reasonable price. The SPIF process was completely designed in a digital environment with a focus on achieving high quality and accuracy of the part followed by experimental verification. For validation, the formed part was compared in terms of the geometry and mechanical strength with the reference one fabricated using the lost-wax technique. The results obtained confirmed the high dimensional accuracy and good strength of the SPIF-made part. The experimental investigations also included analysis of sheet thinning, surface roughness, and microstructure.

Estimating the overall floor stability in a coal mine using deterministic methods which require complex engineering properties of floor strata is desirable, but generally it is impractical due to the difficulty of gathering essential input data. However, applying a quantitative methodology to describe floor quality with a single number provides a practical estimate for preliminary assessment of floor stability. The coal mine floor rating (CMFR) system, developed by the University of New South Wales (UNSW), is a rock- mass classification system that provides an indicator for the competence of floor strata. The most significant components of the CMFR are uniaxial compressive strength and discontinuity intensity of floor strata. In addition to the competence of the floor, depth of cover and stress notch angle are input parameters used to assess the preliminary floor stability. In this study, CMFR methodology was applied to a Central Appalachian Coal Mine that intermittently experienced floor heave. Exploratory drill core data, overburden maps, and mine plans were utilized for the study. Additionally, qualitative data (failure/non-failure) on floor conditions of the mine entries near the core holes was collected and analyzed so that the floor quality and its relation to entry stability could be estimated by statistical methods. It was found that the current CMFR classification system is not directly applicable in assessing the floor stability of the Central Appalachian Coal Mine. In order to extend the applicability of the CMFR classification system, the methodology was modified. A calculation procedure of one of the CMFR classification system’s components, the horizontal stress rating (HSR), was changed and new parameters were added to the HSR.

Since 2009, the Mine Safety and Health Administration (MSHA) has required mines to install refuge alternatives (RAs) in underground coal mines. One of the biggest concerns with occupied RAs is the possible severity of the resulting thermal environment. In 30 CFR 7.504, the maximum allowable apparent temperature (AT) for an occupied RA is specified as 35 °C (95 °F). Manufacturers must conduct heat/humidity tests to demonstrate that their RAs meet the 35 °C (95 °F) AT limit. For these tests, heat input devices are used to input the metabolic heat of actual miners. A wide variety of test methods, sensors, and heat input devices could be used when conducting such tests. Since 2012, the National Institute for Occupational Safety and Health (NIOSH) has conducted over thirty 96-hour heat/humidity tests on four different RAs. This paper discusses the test equipment and procedures used during these investigations. This information is useful for RA manufacturers conducting RA heat/humidity tests, for other researchers investigating RA heat/humidity buildup, and for those who need to assess the thermal environment of any confined space where people may be trapped or are seeking refuge. Keywords: Refuge chamber, Refuge alternative, Confined space, Thermal environment, Test method, Temperature

Coal mines are continuously seeking to determine the performance of entries with different ground control products and installation methods. There are many factors that impact how an entry will perform which include but are not limited to geology, overburden, bolting type and pattern, and mine design. At the National Institute for Occupational Safety and Health (NIOSH), research has been instituted to examine the relationship of the parts of a coal mine entry as a system and not as individual components. To study this relationship, the first step in this study was to create a numeric rating system that accurately reflects visual observations of the mine entry and is easy to implement. NIOSH researchers devised this rating system to improve upon previous ideas, offering increased flexibility which can be incorporated into an overall entry condition that offers different levels of confidence based on the user’s time devoted to the inspection. This new entry rating system was implemented at three different mines over varying periods of time to evaluate the ground response to the geology, bolt installation pattern, stress changes by mining, overburden, and time dependency.

This research belongs to the field of rock physics. In recent years, in solid state physics and materials science, new knowledge has emerged about microplastic strain of various materials, including rocks. These data were obtained using high-precision micro- and nanoscale strain measurements. The very fact of the existence of the poorly studied rock property in the earth sciences requires the study of the possible influence of the rock microplasticity on the propagation of seismic and acoustic waves. The studies were carried out using three alternative methods and under different observation conditions. The field measurements were carried out in the zone of low velocities in crosshole space with transmitted waves of frequency of 240–850 Hz. The laboratory measurements were carried out on sandstone samples with transmitted (6.8 kHz) and reflected (1 MHz) waves at the strain of 10−8–10−6. The manifestations of microplasticity were recorded using high-resolution recording of signals with discretization time tdiscret = 1 μs – 40 μs and 32.5 ns. The wave amplitude variation was provided in a closed cycle: discrete increasing the amplitude from minimum to maximum and return to the initial value (A1+ → A2+ → … Amax … → А2– → A1–). In this amplitude range, an amplitude hysteresis was observed, a sign of which was the inequality of wave velocities on the upward and downward amplitude courses. This effect was recorded for all three measurement methods at different frequencies. However, the amplitude hysteresis of the wave velocity was not observed only in the measurements at full water saturation of loam. The largest amplitude-dependent change in the wave velocity reached 2% (at the accuracy of 0.02%), and the change in the attenuation value amounted to 5%. The reason for this effect could be microplastic inelasticity, which manifested itself by amplitude plateaus located within the waveform. The amplitude microhysteresis forms overall picture of the amplitude dependence of the wave velocity in wide amplitude range. Proposals for the potential use of the obtained data for solving some applied problems have been presented.

Environmental protection is a complex ecological and economic problem, including the need to develop and implement a number of environmental protection measures to mitigate the negative impact of mining waste on all natural environment components and human health. In this regard, the study purpose was to assess the impact of Pb, Cd, Cr, and As compounds on the environment and health of the population of the Solnechny miner’s village. Based on the purpose, the following tasks were set: 1) review and systematization of literature data on the problem of technogenic dust pollution; 2) assessment of the mining industrial system as a source of ecosystem pollution with toxic elements within the closed mining enterprises impact areas; 3) development of proposals for mitigating the impact of mining activities on ecosystems and human health. The paper presents the findings of the study of the elemental status of children and adolescents living within the closed town-forming enterprise JSC Solnechny GOK impact area. The relationship between the level of technogenic pollution of the natural environment and the changes in the elemental status of the children was shown. A feature of the elemental status of the children in the study group was high content of heavy metals, including Pb, Cr, and As. Our research confirmed the data that a growing child’s body actively adsorbs compounds of toxic chemical elements. Deficiency and imbalance of microelements in the body can cause ecologically-related diseases in the child population. Individual and population carcinogenic risks (CR) caused by the As, Pb, and Cr pollution were calculated. In accordance with the acceptance criteria for the risk caused by exposure to the pollutants, the individual carcinogenic risk CR (Cr) = 1,05 · 10–3 belongs to the fourth range and is unacceptable neither for the population, nor for occupational groups. This is De manifestis risk, and when it is reached, it is necessary to carry out emergency curative measures to mitigate it. The individual risks CR (As) = 7,05 · 10–4 also exceed the acceptable level for the population. This level of pollution is subject to permanent monitoring, requires development and implementation of planned curative measures to improve the indicators of the human environment, one of which is the organization of the environmental monitoring system in the study area.

This paper describes the influence of deformation by equal-channel angular pressing (ECAP) on the solid particle erosion resistance of the AlSi7Mg0.3 alloy and AlSi7Mg0.3 based composite material reinforced with the addition of 4 % of fly ash (FA) particles. Both, alloy and composite samples were produced using the compo-casting method. The samples have been subjected to ECAP in multiple passes with the rotation of samples around the vertical axis for the angle of 90° after each pass. Particles of silicon carbide (SiC) have been used as erodent while their impact angle was varied (30° and 90°). Observed samples of AlSi7Mg0.3 alloy generally showed higher wear resistance at 90° angle where material fatigue predominates, than at a 30° angle where abrasion-related phenomena predominate. On the other hand, AlSi7Mg0.3 based composite material exhibited erosion wear at 30° angle less than at 90° angle after one ECAP pass. Evaluation of the erosion resistance has been made based on mass and volume loss. After two passes of ECAP, the matrix structure of the AlSi7Mg0.3 based composite material, as well as that of the AlSi7Mg0.3 alloy was improved from the aspect of erosion resistance.

Three stationary hydrodynamic theoretical problems are solved, in which filtrations obey only the General nonlinear law. Simple flows occur in tasks: plane-parallel, plane-radial, and hemispherical-radial. All derived formulas – oil flow rate, filtration rate, pressure gradient, etc. – should be used to solve various practical problems of the development of these deposits and even when drawing up a project for the development of such deposits. It should be noted that a plane-parallel simple filtration flow of oil originates from a strip-like reservoir to a straight gallery. In addition, such a simple filtration fluid flow also occurs when the oil field under development has several parallel rectilinear rows of production production wells and, in some cases, there may be rows of injection water wells in the reservoir. In oil-bearing areas between parallel adjacent rows, oil filtration is also plane-parallel. Hence, the practical significance of solving the first problem of a plane-parallel oil flow in this scientific article becomes clear. Planar-radial simple filtration flow of oil originates from a circular horizontal formation to a central production well. In addition, such a simple filtration fluid flow also occurs when a strip-like oil field being developed has several (usually three or four) parallel straight rows of production production wells. In the drainage zones of these wells, a simple flat-radial filtration flow also occurs. From the foregoing, the practical significance of a radial plane oil flow becomes clear. Hemispherical – a radial simple filtration flow of oil originates from a hemispherical reservoir to a central well, barely penetrated by the reservoir by its hemispherical concave bottom. By analyzing these calculation formulas, you can identify the specific features of the development of deposits, develop and implement measures to eliminate undesirable phenomena.

Relevance of the research. Stable parameters of dumps are critical in mining operations ensuring their safety and economic efficiency. This problem is particularly acute for mining enterprises engaged in surface mining and for coal open pit mines, in particular. One of the main problems of this issue is related to the substantiation of rigorous methods for assessing stability and determining the limiting parameters of external and internal dumps filling an embankment on weak gently dipping interface. In the technical and regulatory literature, this issue has been considered for a long time. However, there are no specific recommendations for finding the most dangerous sliding surfaces on slopes, as well as methods for calculating shearing and restraining forces along these surfaces. All the signs are that the reason for the stability loss of operated dumps is the absence of theoretically substantiated design schemes, respectively, there are errors in the design of dumping. Purpose of the work is to develop reliable methods for calculating the limiting parameters of dumps on weak gently dipping interface. The main idea of the work is to apply a new, not previously used scheme for calculating the stability of dumps on weak gently dipping interface. Research methods. The work deals with the apparatus of flow mechanics and more specifically, the rigid-plastic model (the method of limit equilibrium), and the variational, integral and differential branches of calculus act as a mathematical apparatus. Results and conclusions. Based on the results of previous studies, a new scheme for calculating the stability of the dump during its destruction along weak interface was proposed, which implies the absence of a curved section of the sliding surface under the slope and the convex shape of the sliding surface under the berm. In contrast to the existing calculation schemes, such a calculation scheme predicts significantly lower values of the critical parameters of dumps. It means that the use of the proposed scheme will prevent the destruction of dumps by landslides along the dumpbasement interface and increase the economic efficiency of enterprises. Because a sufficiently large overestimation of the critical parameters of dumps at weak interface limited by current regulatory documents has been determined, it is recommended to revise these parameters for the designed and operated dumps using the proposed schemes for calculating their stability.

Relevance. The assessment of uncertainties for the calculation of hydrocarbon reserves is a timely topic. The quality of hydrocarbon reserves is declining as old oil fields are depleted. Rates of discovery are in decline since most of the territories prospectively rich in hydrocarbon resources have already been explored. Newly discovered fields are classified as small and medium in terms of the amount of hydrocarbon reserves and difficult in terms of the quality of reserves. Purpose of the research is to determine important reservoir properties that have the greatest impact on the variability of the initial hydrocarbon reserves using sensitivity analysis and conducting a probabilistic hydrocarbon reserves assessment by the Monte Carlo method. Methods of research. The probabilistic hydrocarbon reserves assessment was carried out by the Monte Carlo method with the corresponding frequency curves of the probability distribution of volumetric parameters, which were performed using the Oracle Crystal Ball application. The sensitivity analysis of volumetric parameters that have the greatest impact on the amount of the initial hydrocarbons reserves was performed using the Oracle Crystal Ball application as well. Results and their application. An assessment of uncertainties and risks is necessary both for newly discovered fields in order to negate the risk of drilling unproductive wells and mature fields for a targeted program of geological and technological measures (GTM). Conclusions. The formation of bedded sand bodies of the Vasyugan (SE11, SE12, SE13) and Tyumen (SE2) suites took place in various sedimentation conditions, which could not but affect the quality of the reservoir of the studied formations. The analysis of the sensitivity of parameters has shown that different parameters affect the amount of hydrocarbon reserves in places SE11, SE12, SE13 and place SE2 .

Relevance of the work. The Iset river basin contains the most extensive outcrops of volcanogenic formations of the Beklenishchevsky complex of the East Ural megazone, the age of which is determined as Early Carboniferous by the ratio of volcanic rocks with faunistically characterized sedimentary deposits. Volcanics here compose flows of andesite-basaltic and andesitic lavas and lava breccias. There are no geochronological dates specifying the age of the rocks, which makes it difficult to assess their role in the formation of the megazone. Therefore, isotopic dating of these formations is very important. Methods. The U – Pb age and data on the geochemistry of zircons were obtained by laser ablation (LA – ICP – MS). Purpose of the research is to study the features of the geological structure, the material composition of volcanic rocks in the Iset river basin, the geochemistry of zircons from andesites and the determination of their isotopic age. Results of the work and the scope of their application. Lava flows of andesites and basaltic andesites with minor amounts of basalts and dacites have tectonic contact with sedimentary rocks of the Early Carboniferous age. The distribution of rare elements in volcanics is typical of supra-subduction formations. Zircons in andesites are represented by prismatic and isometric crystals. Prismatic differences in the nature of the distribution of REE and the content of Li, Ti, Sr, Th, U refer to zircons of magmatic genesis, isometric – to “hydrothermal”. According to the U / Yb – Y ratios, the former correspond to the zircons of the ocean floor, while the latter are related to the continental ones. Isotopic dating of zircons from andesites was carried out for the first time. Their age was 311 million years. The data can be used in geological mapping, as well as in the compilation of large-scale geodynamic maps and diagrams. Conclusions. Volcanic rocks in the Iset river basin were formed in supra-subduction continental-marginal geodynamic conditions that took place in the Urals in the Carboniferous. The obtained value of the age of zircons from andesites, possibly, fixes the stage of their transformation. Keywords: East-Ural megazone, volcanic rocks, zircon, isotopic age.

Relevance and purpose of the work. Currently, the area of development of Tomsk is increasing. New neighborhoods are growing on previously undeveloped land (for example, on the left bank of the river Tom). The central part of the city is being redeveloped and reconstructed. It is impossible to develop a high-quality territory without taking into account the dynamics, mechanisms, factors and patterns of development of dangerous natural and technological processes, the forecast of their development. The purpose of the work is to establish the patterns of gully erosion, assess the intensity of its development, and predict the probability of its occurrence within the new city boundaries. Methods of research. We performed an assessment and forecast of the development of gully erosion in Tomsk using GIS technologies, which are an important tool in the city management process due to their ability to process and analyze multidimensional data about the geological environment. We compared the traditional model of data-driven frequency ratio (FR) and expert-based multi-criteria assessment, i.e. analytical hierarchical process by weighting of gulley conditioning factors. Results of the work. We constructed a map of the distribution of gullies on the territory of the city, including 23 polygons. These polygons were then randomly divided into training (16 polygons or 70%) and validation data (7 polygons or 30%). We used seven gulley-conditioning factors for the two models to produce gulley susceptibility maps: slope angle, slope aspect, curvature, elevation, geological structure of the territory; types of filtration sections; distance to the river, to analyze the spatial patterns that determine the development of gully erosion. The spatial correlation between gulley locations and the conditioning factors were identified using GIS-based statistical models. We constructed gulley susceptibility maps based on the ranking of each factor by two methods using a training data set. Receiver operating characteristics (ROC) were used to validate the resulting susceptibility maps. The area under the curve (AUC) was 0.905 for the AHP model and 0,800 for the FR model, respectively, which indicates excellent and high quality of forecast maps. We proved that both methods are beneficial for assessment the susceptibility of the territory to gully erosion. We recommend using the constructed maps for regional planning and hazard mitigation, as well as in education by teaching the discipline “Engineering geodynamics”.

In this study, the development of surface features of Inconel 718 samples fabricated by selective laser melting under different laser powers and scanning speeds has been studied and correlated with the powder melting behaviors through both experimental and modeling approaches. The interaction between laser beam and powder particles was studied by a three-dimensional model using the height function-lattice Boltzmann method. Different process parameters were introduced to perform the simulations, revealing the underlying physics of the surface morphology. Through the calculation of the surface forces, some new insights were given about the powder melting behaviors and the resultant surface features. It was found that the surface tension rather than recoil pressure pulled the melted powder into the molten pool during the SLM process. As for low energy input, the powder tended to fuse together with the neighboring particles before entering the molten pool, which was found to be the main cause of the formation of surface fluctuations and the subsequent surface pores. To some extent, the existence of recoil pressure was favorable for a relatively stable flow and a flat surface morphology. The simulation results of the top surface morphology were compared with experimental results, and they were in good agreement.

In multi-seam mining, the interlayer rock strata between the upper coal seam (UCS) and the lower coal seam (LCS) appear damage and strength weakening after mining the UCS. Ground stability control of the gob-side entry retaining (GER) under the gob with close distance coal seams (CDCS) is faced with difficulties due to little attention to GER under this condition. This paper focuses on surrounding rock stability control and technical parameters design for GER under the gob with CDCS. The floor rock strata damage characteristics after mining the UCS is first evaluated and the damage factor of the interlayer rock strata below the UCS is also determined. Then, a structural mechanics model of GER surrounding rock is set up to obtain the main design parameters of the side-roadway backfill body (SBB) including the maximum and minimum SBB width calculation formula. The optimal SBB width and the water-to-cement ratio of high water quick-setting material (HWQM) to construct the SBB are determined as 1.2 m and 1.5:1.0, respectively. Finally, engineering trial tests of GER are successfully carried out at #5210 track transportation roadway of Xingwu Colliery. Research results can guide GER design under similar mining and geological conditions.

Inorganic perovskite nanostructures based on neodymium (Nd) were processed in form of nanostructures for bi-functional electrocatalytic reactions. The active role of Co ions in influencing the material characteristics of Nd-ferrite (NdFeO3) were investigated in detail. The nanostructural characteristics were adjudged through the aid of diffraction and high-resolution microscopic studies. Evidences relating to the co-occurrence of neodymium oxides (Nd2O3) were also noticed. The valency of Nd, Co and Fe ions and their nature of interaction in the ferrite architecture was studied through X-ray photoelectron spectroscopy. Here, convincing affirmations relating to the partial substitution of Co ions in place of Nd and Fe sites were also made. NdFeO3 and NdxCo1-xFeO3 nanostructures were studied for their electrocatalytic functions under varied alkaline pH (10 and 14) conditions. The improved conductivity studied via electrochemical impedance analysis in Co incorporated ferrites were noted to accelerate oxygen/hydrogen production in the corresponding electrodes. The overpotential values corresponding to oxygen evolution reactions reduced to 198 mV from 227 mV, while hydrogen evolution reactions lowered to 206 mV from 239 mV upon Co substitution. Similarly, the related Tafel slope values got improved in Co substituted ferrite matrix. The overall stability related electrochemical data suggested the processed ferrites as viable bi-functional electrocatalysts possessing essential features required for effective oxygen and hydrogen evolution reactions.

A multi-functional composite coating was fabricated on magnesium (Mg) AZ31 alloy through micro-arc oxidation (MAO) combined with self-assembly technology. Polyethyleneimine (PEI) as a medium was assembled on MAO coating based on the chemical bonding and electrostatic interactions. Adhered PEI successfully mediates the self-assembly of functional silver nanoparticles (Ag NPs) with a formation of Ag NPs/PEI/MAO (APM) composite coating. The morphology and microstructure of as-prepared APM coating were characterized by using of different technologies (e.g. scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy). Its corrosion behavior in simulated body fluid and the corresponding antibacterial performance against Staphylococcus aureus (S. aureus) were also investigated. The potentiodynamic polarization results showed that the corrosion current density of APM coated AZ31 decreased more than three orders of magnitude in comparison with that of uncoated AZ31, indicating an enhanced anticorrosive ability. Electrochemical impedance spectroscopy results further revealed that the improvement of corrosion resistance was attributed to a synergistic effect of Ag NPs/PEI and MAO. The hydrogen evolution tests confirmed that APM coating provided AZ31 an excellent corrosion protection during a relatively long term. And the antibacterial research showed that APM coated AZ31 had a great antibacterial activity. This study presents a promising approach to fabricate a multi-functional composite coating on Mg alloy, which improves the anticorrosive performance of the substrate and endows it an antibacterial activity to meet a better demand in the applications.

The target of this research study was to evaluate the shear-tensile and fatigue behavior of aluminum 6061 alloy welds, in two different heat treatment conditions, joined by the recently developed intermediate layer friction stir spot welding (FSSW) technique. The keyhole, which is the disadvantage of the conventional FSSW process, was avoided using an additional intermediate layer (IL) accompanied by a simple tooling. Shear-tensile experiments demonstrated acceptable mechanical performance of IL-FSSW joints in comparison with that obtained using alternative methods. Fatigue behavior of the joints revealed a dependency to pre-processing temper especially at high cyclic load levels with improved life for the aged condition. Observations on the failure regions under shear-tensile experiments exhibited plug type and shear-plug type fracture modes for the aged and annealed conditions, respectively. In contrast, the fracture mode showed variation with respect to the load level but not to the type of temper during cyclic loading.

Relevance. When mapping the vast areas of the Precambrian polymetamorphic complexes in the North Yenisei Ridge, there is a problem of metamorphism interpretation and phasing of geological development of a particular area along with thrust tectonics. The solution of these issues is also of great importance for the purposes of areas delineation of metamorphic rocks that are favorable for the detection of high-alumina (andalusite, kyanite, sillimanite) schists. Purpose of the work: to substantiate and itemize some geological prospecting, mineralogical and petrological indicator criteria for the development of high-alumina garnet-kyanite-staurolite blastomylonites of dislocation metamorphism formed by andalusite-bearing rocks of regional metamorphism. Research methodology: detailed mapping of structural-metamorphic zoning of dislocation (collisional) metamorphism in the Mayakon key area with sampling of polymetamorphic rocks for petrographic studies of mineral parageneses. Investigation of polished thin sections of polymetamorphic rocks by microprobe analysis with elucidation of minerals zoning, their chemical composition, calculation of the Р–Т paths of metamorphism and determination of the absolute age of blastomylonite formation based on the 40Ar/39Ar dating of biotite. Analysis and generalization of the results obtained for the Mayakon area and their comparison with other key areas of the North Yenisei Ridge. Results. At the Mayakon potential area, a progressive metamorphic zoning of kyanite-bearing blastomylonites has been identified, and the transitional I, outer II, middle III, and inner zones are determined as the dislocation metamorphism intensifies towards the Panimba thrust fault. Based on the compositions of garnets, biotite, and plagioclase, the P–T paths of the early regional metamorphism of andalusite-sillimanite type and late local kyanitesillimanite type were calculated. A list of geological prospecting, petrological and isotope-geochronological criteria for recognizing blastomylonites among rocks of regional metamorphism in thrust zones has been substantiated and itemized. Conclusions. Method of polymetamorphism reconstruction in the North Yenisei Ridge shows that tectonic inversion conditions took place in the Neoproterozoic, in the late Tonian era (~850 Ma ago In terms of occurrences, they are related to the final stage of the Grenville orogeny (1.1–0.85 Ga). The formation of blastomylonites of dislocation (collisional) metamorphism by metapelites of regional metamorphism in thrust zones is accompanied by an increase in the number of mineral phases and leads to a reduction in usable space of high-alumina andalusite schists.

In the loose and fractured coal seam with particularly low uniaxial compressive strength (UCS), driving a roadway is extremely difficult as roof falling and wall spalling occur frequently. To address this issue, the jet grouting (JG) technique (high-pressure grout mixed with coal particles) was first introduced in this study to improve the self-supporting ability of coal mass. To evaluate the strength of the jet-grouted coal-grout composite (JG composite), the UCS evolution patterns were analyzed by preparing 405 specimens combining the influential variables of grout types, curing time, and coal to grout (C/G) ratio. Furthermore, the relationships between UCS and these influencing variables were modeled using ensemble learning methods i.e. gradient boosted regression tree (GBRT) and random forest (RF) with their hyperparameters tuned by the particle swarm optimization (PSO). The results showed that the chemical grout composite has higher short-term strength, while the cement grout composite can achieve more stable strength in the long term. The PSO-GBRT and PSO-RF models can both achieve high prediction accuracy. Also, the variable importance analysis demonstrated that the grout type and curing time should be considered carefully. This study provides a robust intelligent model for predicting UCS of JG composites, which boosts JG design in the field.

In order to study the factors of columnar to equiaxed transition (CET) of high-Nb TiAl alloys, Ti46Al7Nb0.4W0.6Cr0.1B alloy has been fabricated by cold crucible directional solidification (CCDS) technique under different pulling rate from 3.3 μm/s to 16.7 μm/s. The marco/micro-structure and phase composition near solid–liquid interface have been characterized. Results show that the CET of the high-Nb TiAl alloy occurs with the increase of the pulling rate at the constant temperature gradient. The microstructure of the columnar grain is composed of α2/γ lamellar matrix and a coupling structure of striped-like B2+γ phases. The lamellar colonies in a columnar grain possess the same orientation, while the arrangement direction between the striped-like B2 phase and growth direction is 0° or 45°. A solidification map for CCDS is established which predicts columnar or equiaxed morphology according to the growth rate (R) and temperature gradient (G). The dendrite morphology at the solid–liquid interface after quenching and the CET is controlled by the actual temperature gradient at the tip of the dendrite. Meanwhile, the increase of growth rate and the satisfaction of heterogeneous nucleation conditions are the main factors for CET. The decrease of actual temperature gradient caused by quenching or the increase of liquidus gradient caused by increasing growth rate can increase the maximum supercooling degree ΔTC. When it reached the supercooling degree ΔTN required to form a new nucleus, equiaxed grains will be produced. In addition, the boride in this alloy can act as a heterogeneous nucleation core to promote CET.

The films of alizarin yellow GG (AYGG)–CuCl2 blended with polyvinyl alcohol (PVA) have been successfully synthesized by casting method. The results show that the dielectric properties of AYGG–Cu(II) blended with PVA are enhanced by lowering selected frequency while σac(ω) increases monotonically with frequency, acting in accordance with the correlated barrier hopping model. At low temperature, the DC electrical resistivity of AYGG–Cu(II) blended with PVA film is temperature independent, while it is decreasing with high temperature. Al/(AYGG – Cu(II) blended with PVA)/ITO is fabricated as organic photovoltaic cell, concluding that there are many mechanisms can control the current flow. Al/(AYGG – Cu(II) blended with PVA)/ITO solar cell under illumination of green light be most effective compared to illuminations of others. It is concluded that Al/(AYGG – Cu(II) blended with PVA)/ITO solar cell is very important, with potential advantages such as low cost and low-temperature fabrication processes. It is recommended that this material can be used in different applications such as temperature sensors, inrush current limiters, thermistors, and NO2 sensor.

In the present investigation, nanochitosan-polyurethane dispersions (NCS-PUs) were prepared via polymerization process and applied on polyester cotton fabric (PCF) as a finishing agent. A prepolymer of PU with NCO functionality was synthesized using isophorone diisocyanate (IPDI), polyethylene glycol (PEG) and DMPA (2, 2-dimethylol propionic acid) was extended with NCS. The structural characterization of NCS-PUs was monitored by FTIR analysis. Pad dry cure technique was adopted for the application of NCS-PUs on pre-dyed and printed PCF samples. The PCF samples (dyed and printed) were tested for antibacterial activity, Ultraviolet protection factor (UPF) and tear & tensile strength properties. The UPF values in case of 10% PUB1 to PUB6 application was recorded to be 40.5, 42.30, 44.10, 47.50, 54.30 and 37.80, respectively, whereas the tensile strength improved up to 8.1% in case of 10% NCS-PUs application and these value was increased when 20% NCS-PUs was applied. Antimicrobial activity was evaluated against Gram positive and negative strains (S. aureus and E. coli). The PCF samples finished with NCS-PUs showed higher antimicrobial activity, protection against UV and tensile strength versus unfinished sample with NCS-PUs. Results revealed that the NCS-PUs significantly improved the properties of PCF (both of dyed and printed samples), hence, the NCS-PUs can be applied as finishing agent to enhance the antimicrobial activity along with protection from UV radiation.

Relevance of the research. Construction sands are the largest functional group of sands widely used in construction industry. This natural material is one of the most demanded for the production of manufactured products in the construction industry of the region. Purpose of the researchis to study the engineering-geological conditions of construction sands deposit for the production of the manufactured products of OAO Sebryakovsky plant of asbestos-cement products, as well as for construction organizations of the region. Research methods. Based on the analysis of extensive collection materials using laboratory and statistical methods, as well as the results of additional research, the physical-geographical, engineering-geological and technogenic conditions of the study area were examined. Results and their application. The useful stratum of the deposit is composed of Upper Quaternary alluvial sands, the average thickness of which is 8.6 m, penetrated thickness is up to 12.3 m. Overburden within the study area is represented by the soil-vegetation horizon – up to 0.2 m. The extracted raw materials are used in the production of mortars, which is confirmed by tests of a cement-sand grout, and as a filler in fine-grained concrete. The reserves of the deposit are calculated in categories A + B + C1 in the amount of 2313.2 thousand m3. The development of the deposit is recommended by the open method. Explored and recoverable reserves will ensure the operation of the enterprise with an annual demand of 100 thousand m3 per year for a period up to 2030. Conclusions. Based on the results of the studies, it should be noted that the Sidorsky deposit of construction sands is assessed as profitable and competitive in relation to the exploited deposits of sand in the Volgograd region.

This paper presents a novel approach to investigate the relations between drilling signals and bit wear condition in real world full-scale mining operations. This research addresses the increasing demand for automation in mining to increase the efficiency, safety, and ability to work in harsh environments. A crucial issue in fully autonomous unmanned drilling is to have a system to detect the bit wear condition through the drilling signals analysis in real time. In this work, based on extensive field studies, a novel qualitative method for tricone bit wear state classification is developed and introduced. The relations between drilling vibration as well as electric motor current signals and bit wear are investigated and bit failure vibration frequencies, regardless of the geological conditions, are introduced. Bit failure frequencies are experimentally investigated and analytically calculated. Finally, the effect of bit design parameters on the failure frequencies is presented for the application of bit wear condition monitoring and bit failure prediction.

Soft zone formation in dissimilar Cr–Mo welding occurs during post weld heat treatment that could compromise the integrity of the weldment. The decomposition of martensite could cause this formation at the weld heat affected zone adjacent to the fusion boundary. There could not yet determine the actual width of this zone. The extent of martensite decomposition in soft zone Cr–Mo steel dissimilar weld was observed in semi in-situ stages using the x-ray absorption spectroscopy (XAS) at Synchrotron facility. 2.25Cr–1Mo was welded using ER90S–B9 using GTAW process. PWHT was performed at 730 °C for 0.5 h and 2.0 h in a chamber with opening for Synchrotron light analysis at various locations away from the fusion boundary. This was complemented by microstructure and grain size analysis. The results showed the decomposition of martensite started at the fusion boundary and could extend beyond 1000 microns covering both CGHAZ and FGHAZ. Since the experiment was performed in normal atmosphere, the oxide film could form during PWHT on the surface of the specimen. More oxide formed was observed more in the location with high carbide contents. There was more oxide formation at the locations further distance from fusion boundary due to less martensite decomposition. Therefore, the extent of the phenomena could be stated by using information from oxide formation and martensite decomposition which could help to determine the risk on both creep life and oxidation.

High-speed impact tests were conducted in transverse direction with strain rates (SRs) ranging from 1000 s−1–6000 s−1 to investigate the deformation mechanism and adiabatic shearing behavior of extruded Mg-8.0Al-0.1Mn alloy in as-extruded (AE), low temperature solution-treated (ST1) and high temperature solution-treated (ST2) states. At SR of 6000 s−1, the flow stress exhibits a slight drop after reaching its peak, except that of the ST2 sample. The highest strain rate hardening results in the highest peak stress of the ST1 sample. Deformation is first dominated by basal slip, and then gradually converts to be dominated by a coordinated mechanism between basal slip and twinning. In late stage, it shifts to be dominated by non-basal slip supplemented with twinning and basal slip, and then by a coordinated mechanism between non-basal slip and dynamic recrystallization (DRX). Heat treatment only affects the scope of the dominated mechanism. The adiabatic shear band occurs only at SR of 6000 s−1 with strain of 0.30, which strongly affects the crack propagation and DRX. Interestingly, the DRX only occurs in the AE sample due to the combined effect of adiabatic temperature rise and pre-existing twins.

Magneto-optical Kerr effect (MOKE) microscopy is a versatile technique to image magnetic domains and evaluate the behavior of magnetic materials. However, MOKE has been rarely applied to the research of low magnetic steels with complex microstructure including micron-sized features. This study reveals the potential of implementing MOKE microscopy for analyzing the microstructure and stress state of martensitic steels with high carbide density (example conducted on AISI M2 steel grade). For the first time, the resulting MOKE domain images are used to analyze the size and morphology of martensite lath structures without chemical etching of the material's surface. Furthermore, MOKE microscopy allowed the confirmation and volumetric fraction estimation of retained austenite, despite the small size and volumetric fraction of under 1%. The validity of the MOKE microscopy analysis is cross-checked with scanning electron microscopy of etched samples and X-ray diffraction. Finally, MOKE microscopy in combination with Vickers indentation is applied to determine the residual stress state of the selected steel, which was varied by processing the steel material with conventional heat treatment scheme and heat treatment including deep cryogenic treatment (DCT). The method is proven effective in indicating the residual stress qualitatively. The measurements proved, that the residual stresses are significantly reduced in DCT steel samples, as theoretically anticipated. The conducted pioneering work provides important research towards the application of MOKE microscopy for the research of steel microstructure, properties and residual stresses as well as delivers a new perspective for determining the effectiveness of DCT on the steel properties.

With increasing depth of exploration and process boreholes (at small drilling diameters), the probability of deviation of the borehole path from design trajectory increases many times; i. e. zenith curvature and azimuth deviation of the borehole path occur. Therefore, developing methods for keeping vertical path of the borehole when drilling deeper horizons of ore bodies is a very topical issue. The paper presents the results of developing a new bottom-hole assembly for drilling boreholes in soft rocks using screw casing centralizers, which provide good stabilizing and centering effects to mitigate horizontal departure of the hole axis from the design direction and minimize vertical curvature of the hole path (zenith angle) while maintaining sufficient drill string flexibility. The developed technical solutions provide simplicity of design and ability to adapt to wide range of mining, geological and technological drilling conditions. The feasibility of manufacturing the centralizers by own efforts and the technological feasibility of quick and easy connecting the centralizer with other elements of the bottom-hole assembly have been substantiated. The manufacture efficiency is proved by the use of inexpensive and wear-resistant materials in the centralizer armouring, for which tungsten-cobalt or titanium-cobalt hard-alloy inserts were used. In addition, prevailing volume of borehole drilling in soft rocks allowed using replaceable centering elements, as well as their repair and restoration to increase their service life. The manufactured centralizer has a low production cost due to the design simplicity and the use of inexpensive wearresistant material and will compete in the market of drilling tools and technical devices for drill string stabilization. The economic effect from the introduction of the self-produced centralizers amounted to more than 170,000 tenge per a borehole.

The microstructural evolution and mechanism of grain refinement during rapid solidification of Ni–Cu alloys were studied by molten glass purification and cyclic superheating. The maximum undercooling has achieved 320 K for Ni65Cu35, 295 K for Ni55Cu45 and 280 K for Ni50Cu50 alloys. Two mechanisms were found to be responsible for the grain refinements under small undercooling and large undercooling, respectively. The grain refinement at small undercooling is mainly caused by dendrite superheating and remelting, whereas that for large undercooling is mainly due to recrystallization occurred at high angle grain boundary and high proportion of twin boundaries. Meanwhile, almost no dislocations and other defects were observed in the substructure of the alloy with large undercooling.The average microhardness was found a sharp decrease in the alloy with large undercooling, which indicates that the plastic strain accumulated in the microstructure formed under large undercooling is completely dissipated in post-recalescence, and the deformation energy can offer the driving force for recrystallization in the microstructure.

Halogenated Bromide (Br −) was subsequently dosed to aqueous electrolyte solution to enforce the capacitance features of activated carbon (AC) electrodes in electric double-layer supercapacitor devices for electrical energy storage. Physicochemical properties for AC with sodium sulfate (Na2SO4) and KBr redox additive were assessed by different characterization tools such as XRD, SEM, EDS, surface roughness, and BET techniques. Cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), electrochemical impedance spectroscopy (EIS), and the stability after 1000 cycles have been used to monitor the electrochemical behaviors of the prepared electrodes. The presence of halogen atom exhibited large faradaic resembling battery like-type in charge–discharge curves. In the aqueous solution, the investigated electrode showed a high specific capacitance of 957.8 F g−1 at a specific current of 0.46 A g−1 using a certain concentration of KBr added to Na2SO4. The single AC electrode showed specific energy of 133 Wh kg−1 and specific power of 859.6 W kg−1. Besides, the AC electrode displayed excellent long-term stability in Na2SO4@KBr electrolyte, preserving retention capacitance of 174%. AC/AC symmetric supercapacitor cell demonstrated excellent electrochemical performance, including specific energy of 57.15 Wh kg−1, specific capacitance of 127 F g−1, specific power of 5262 W kg−1 at a specific current of 3.8 A g−1, and 82.8% capacitance retention after 10,000 cycles.

Quenching and partitioning (Q&P) treated steels are traditionally alloyed with silicon (Si), but its precise role on microstructural mechanisms occurring during partitioning is not thoroughly understood. In this study, dilatometric analysis has been combined with detailed microstructural characterization to unravel the competing mechanisms occurring during partitioning either in parallel or in succession. Three 0.4 wt.% carbon steels with varying Si contents were quenched to 150 °C for ~20% untransformed austenite, and partitioned for 10–1000 s in the temperature range 200–300 °C. The steel with low Si content (0.25 wt.%) exhibited substantial bainitic transformation during partitioning at 300 °C and only 4% retained austenite (RA) at room temperature (RT) even after 1000 s hold. In contrast, a high Si fraction (1.5 wt.%) enabled retention of ~18% austenite under similar conditions. While η-carbides precipitated within the martensite laths in the high-Si steel, cementite precipitated in the low-Si variant. Furthermore, carbide precipitation and growth were strongly suppressed by high Si content. Secondary martensite formation occurred from carbon-enriched austenite during final cooling, irrespective of Si-content. Results illustrate that Si retards austenite decomposition at higher partitioning temperatures but does not improve carbon partitioning at lower temperatures.

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 oxidation kinetics, oxide layers composition and thicknesses of X70 steel, Y55 steel and 304 stainless steel are investigated. The results show that the oxidation rate of X70 steel increases rapidly at 1000 °C, while that of Y55 steel and 304 stainless steel increases rapidly at 1100 °C. The oxidation kinetic coefficients of X70 steel, Y55 steel and 304 stainless steel are exp (10.7), exp (11.58) and exp (30.15), respectively, and the apparent activation energy of oxide layer are 196879.7 J/mol, 207608.1 J/mol and 469284.3 J/mol, respectively. The cross-sectional morphology and element distribution of oxide layer are obtained. With the oxidation time increases from 30min to 80 min at 1100 °C, the oxide layer thickness of X70 steel and Y55 steel increases by 1242.33 μm and 965.59 μm respectively when the weight of steels increases by 1 mg/mm2, and the oxide layer of Y55 steel is denser than that of X70 steel. A variable temperature oxidation mathematical model of the slab surface is established to predict the oxide layer thickness of slab surface.

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.

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.