Search

The finite element method is the most common method used to solve engineering and mathematical model problems. Related solution areas include structural analysis, heat transfer, mass transport and electromagnetic potential. FEM is a specific numerical method used to solve partial differential equations in two or three space variables. To solve a problem, FEM breaks up a large system into smaller, simpler parts called finite elements. First, a three-dimensional model of the system to be analyzed is produced. While defining the model, the materials and connection types found in the model are also deter-mined. Afterwards, the model is divided into small parts and analyzed under specified conditions. A crash test will be conducted in this study. For this, the conditions of the vehicle parts will be examined by hitting a wall under the conditions of which the model design of the vehicle is determined. Crash tests were carried out for two different bumper thicknesses on the same vehicle and the test results were examined. The vehicle speed is modeled as 20 m/s in the simulation carried out from the moment of impact until 0.14 seconds later. The effect of buffer thickness on axial displacements at impact and energy changes are presented.

This paper reviews the properties of methanesulfonic acid (MSA) and its potential for use in hydrometallurgy. Although MSA is much less known than sulfuric, hydrochloric or nitric acid, it has several appealing properties that makes it very attractive for the development of new circular flowsheets in hydrometallurgy. Unlike other organic acids such as acetic acid, MSA is a very strong acid (pKa = − 1.9). In addition, it is very stable against chemical oxidation and reduction, and has no tendency to hydrolyze in water. In terms of its environmental impact, MSA has low toxicity and is biodegradable. In nature, it is part of the geochemical sulfur cycle. A useful property is the high solubility of its salts in water: methanesulfonate salts have a much higher solubility in water than sulfate salts. Additionally, MSA and its salts are compatible with the electrowinning of metals because the anode reaction involves the formation of oxygen gas (unlike chlorine gas formation in chloride electrolytes) and no cathodic reduction of the anion occurs (unlike nitrate reduction in nitrate electrolytes). MSA is particularly interesting for lead hydrometallurgy, where it offers more environment-friendly alternatives to HBF4 and H2SiF6. However, MSA can also be adopted in all hydrometallurgical processes that require strong Brønsted acids. It can be used in the metallurgy of copper, zinc, cobalt, nickel, and rare earths, as well as in the recycling of metals from end-of-life products. Although MSA itself is a non-oxidizing acid, in combination with hydrogen peroxide it yields strongly oxidizing lixiviants that can leach copper from chalcopyrite or dissolve metallic silver. The global production of MSA is expected to increase rapidly in the near future thanks to both the industrialization of a new sustainable synthesis process and its many applications (cleaning fluids, electrolytes for electroplating, redox-flow batteries, catalysts in organic synthesis, and as a solvent for high-molecular-weight polymers). As a result, MSA will become more widely available and a lower price will make it an increasingly attractive option. Graphical Abstract

In this academic position paper, we propose the 12 Principles of a novel and more sustainable approach to hydrometallurgy that we call “circular hydrometallurgy.” The paper intends to set a basis for identifying future areas of research in the field of hydrometallurgy, while providing a “sustainability” benchmark for assessing existing processes and technological developments. Circular hydrometallurgy refers to the designing of energy-efficient and resource-efficient flowsheets or unit processes that consume the minimum quantities of reagents and result in minimum waste. The application of a circular approach involves new ways of thinking about how hydrometallurgy is applied for both primary and secondary resources. In either case, the emphasis must be on the regeneration and reuse of every reagent in the process. This refers not only to the acids and bases employed for leaching or pH control, but also any reducing agents, oxidizing agents, and other auxiliary reagents. Likewise, the consumption of water and energy must be reduced to an absolute minimum. To consolidate the concept of circular hydrometallurgical flowsheets, we present the 12 Principles that will boost sustainability: (1) regenerate reagents, (2) close water loops, (3) prevent waste, (4) maximize mass, energy, space, and time efficiency, (5) integrate materials and energy flows, (6) safely dispose of potentially harmful elements, (7) decrease activation energy, (8) electrify processes wherever possible, (9) use benign chemicals, (10) reduce chemical diversity, (11) implement real-time analysis and digital process control, and (12) combine circular hydrometallurgy with zero-waste mining. Although we realize that the choice of these principles is somewhat arbitrary and that other principles could be imagined or some principles could be merged, we are nevertheless convinced that the present framework of these 12 Principles, as put forward in this position paper, provides a powerful tool to show the direction of future research and innovation in hydrometallurgy, both in industry and in academia. Graphical Abstract

UNLABELLED: A hydrometallurgical process is described for conversion of an aqueous solution of lithium chloride into an aqueous solution of lithium hydroxide via a chloride/hydroxide anion exchange reaction by solvent extraction. The organic phase comprises a quaternary ammonium chloride and a hydrophobic phenol in a diluent. The best results were observed for a mixture of the quaternary ammonium chloride Aliquat 336 and 2,6-di-tert-butylphenol (1:1 molar ratio) in the aliphatic diluent Shellsol D70. The solvent extraction process involves two steps. In the first step, the organic phase is contacted with an aqueous sodium hydroxide solution. The phenol is deprotonated, and a chloride ion is simultaneously transferred to the aqueous phase, leading to in situ formation of a quaternary ammonium phenolate in the organic phase. The organic phase, comprising the quaternary ammonium phenolate, is contacted in the second step with an aqueous lithium chloride solution. This contact converts the phenolate into the corresponding phenol by protonation with water extracted to the organic phase, followed by a transfer of hydroxide ions to the aqueous phase and chloride ions to the organic phase. As a result, the aqueous lithium chloride solution is transformed into a lithium hydroxide solution. The process has been demonstrated in continuous counter-current mode in mixer-settlers. Solid battery-grade lithium hydroxide monohydrate was obtained from the aqueous solution by crystallization or by antisolvent precipitation with isopropanol. The process consumes no chemicals other than sodium hydroxide. No waste is generated, with the exception of an aqueous sodium chloride solution. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40831-022-00629-2. ispartof: JOURNAL OF SUSTAINABLE METALLURGY vol:9 issue:1 pages:107-122 ispartof: location:Netherlands status: published

ispartof: ISIJ INTERNATIONAL vol:62 issue:8 pages:1573-1585 status: published

Bu çalışmada, farklı oranlarda %3yttria stabilize zirkonyum oksit (ZrO2) ilavesinin atık koyun femur kemiklerinden elde edilmiş olan hidroksiapatite (KHA) etkisi incelenmiştir. Bu amaçla 4 farklı kompozit hazırlandı ve preslendikten sonra 1100-1300oC arasında 4 saat süre ile sinterlendi. Saf koyun hidroksiapatit için artan sinterleme sıcaklıkları ile yoğunluk, kısmi yoğunluk, sertlik ve kırılganlık indeksi artarken, en yüksek yatay (8.23±0.28 MPa) ve dikey basma (82.48±5.50 MPa) mukavemeti ve kırılma tokluğu (0.70±0.11 MPam1/2) 1200oC’ de elde edildi. Saf KHA’ in 1300oC’ de sinterlenmesi beta trikalsiyum fosfat (β-TCP), alfa trikalsiyum fosfat (α-TCP) ve kalsiyum oksit (CaO) fazlarına dekompoze olmasına neden olmuştur. Bu sıcaklık için saf KHA’ daki dekompoze olma oranı %4.1 olarak hesaplandı. KHA-ZrO2 kompozitlerinde dekompoze olma oranı, artan sinterleme sıcaklığı ve ZrO2 oranı ile %48.1’ e kadar artmıştır. KHA-ZrO2 kompozitlerinde iki farklı kalsiyum zirkonat (CaZr4O9 ve CaZrO3) fazı dedekte edilmiş olup, bu kompozitlerde dekompozisazyonun artışının CaZrO3 fazından kaynaklandığı kanaatine varılmıştır. 1200oC’ de sinterlenen KHA-2.5ZrO2 kompozitinin KHA-ZrO2 kompozitleri içerisinde en iyi özelliklere sahip olduğu belirlendi. Bu kompozitin kırılma tokluğu 1.25±0.08 MPam1/2, dikey ve yatay basma mukavemeti değerleri ise 122.0±2.12 MPa ve 11.21±0.42 MPa’ dır. Ancak; KHA-ZrO2 kompozitinin yetersiz kırılma tokluğu özelliği nedeniyle insan vücudunda yüke dayanım gerektirmeyen uygulamalarda kullanılması önerilmektedir.

In this study, with the help of the known effect of Fe2O3, which is a sintering aid additive for sintering, it is possible to synthesize products at temperatures much lower than 1500°C, which is the known sintering temperature in the phase diagram of the mullite-zircon system. In addition to the phase and microstructure analysis of the produced products as a result of the addition of sintering aid additive (Fe2O3) and reaction sintering process, mechanical characterizations were performed. The sintering aid additive (Fe2O3) was mixed into the Mullite-Zircon structure by adding 1 wt.%, 2 wt.% and 3 wt.%. 1% by weight of PAN was used as the binder. This mixture was formed into pellets before sintering under the selected pressing force of 2500 psi. These pellets were sintered at 1500°C, 1450°C, and 1400°C sintering temperatures, respectively, with a sintering time of 5 hours for each temperature. As a result of these processes, the effect of sintering temperature and the effect of the amount of sintering aid additives were examined by using characterization methods. It was aimed to determine the optimum parameters for this material, considering the important properties of ceramics such as porosity, hardness, density, and microstructure of the product to be produced with these additives and parameters. X-Ray Diffraction analyses were performed, and the phases formed as a result of the reaction were determined. Microstructure analyses were made for sintering temperatures of 1500°C, 1450°C, and 1400°C using an optical microscope. The optimum sintering temperature for the parameters used in this study and the amount by weight of the sintering aid additive to be used were selected considering variable factors in this study, and it was aimed to find the product with the best properties and the lowest cost.

Brass alloys assign a considerable portion of the industrial components\" material due to their outstanding characteristics. These materials are manufactured using hot forging or extrusion techniques, according to the application for different purposes. In this work, the metallographic and mechanical characteristics of three environmentally friendly brass alloys - CuZn40Pb2 (CW617N), CuZn38As (CW511L) and CuZn21Si3P (CW724R) - extruded and multi-directionally hot forged have been examined. By focusing on the flat bottom drilling operation, the effects of the process and type of alloying have been investigated. The examination has been accomplished on experimental data about tensile strength, impact fracture energy, cutting forces, entrance and exit burr diameters, as well as hole quality. The findings demonstrate that the most crucial criteria impacting the machining outcomes are the presence of limited Pb element and material microstructural phases, their content and mechanical characteristics, as well as the type manufacturing process.

Lower limb rehabilitation robots (lower back exoskeleton) are one of the robotics fields where research is still ongoing to find solutions to the problems of paralysis and movement restriction caused after an accident as a result of various reasons. Hemiplegia, commonly known as stroke, causes loss of movement or restriction of movement in patients with the right and left parts of the body being affected as a result of blockage in the cerebral vessels. Physical therapy and rehabilitation are very important in such disease situations. For hemiplegic patients, the rehabilitation applications applied include exercises for strengthening of muscles, occupational therapy, treatment determined according to the patient, such as hip and knee joints, physical therapy such as exercise methods and speech therapy, rehabilitation methods and devices used in applications. When evaluated from this point of view, it is important to use walking robots in the treatment methods we mentioned above. In this thesis project, Walking robot (Rehabilitation Robot or Exoskeleton Robot) is used for individuals with congenital joint disorders, for individuals with disabilities, for individuals who have difficulty in movement and walking as a result of subsequent hemiplegia, fall, slip, injury, for occupational diseases related to lower extremities in workers working in the business sector, for individuals with lower skeletal system in the construction industry, paint industry and heavy-work industry. It is a robot model that can also be used for occupational diseases related to lower extremities in workers working in the business sector, for individuals with lower skeletal system disorders due to natural disasters such as work accidents and earthquakes, and for individuals with walking and movement restrictions. For this reason, walking robot (Rehabilitation Robot or Exoskeleton Robot) will be studied in the research. By creating walking robot design, simulation and prototype, it is aimed to create products and be useful to the sector.

The past 10–20 years have seen numerous academic papers describing the benefits of ionic liquids (ILs) and deep-eutectic solvents (DESs) for leaching, solvent extraction and electrowinning. The scientific community—including the authors of this opinion article—have frequently proclaimed these neoteric solvents as game-changers in extractive metallurgy. Despite this, there have been no commercial breakthroughs. In this paper we reflect on the reasons why ILs and DESs seem to have failed to impact on the metallurgical industry. These include: (1) issues with high viscosity; (2) limited chemical stability under the conditions of metallurgical processes; (3) difficulties with recycling and reuse; (4) a lack of demonstrated unit processes and flowsheets on the pilot scale; (5) insufficient material-property data available for engineering purposes; (6) the administrative burden of obtaining licenses and safety permits; (7) very high costs for large-scale operations; and (8) minimal added value compared to state-of-the-art hydrometallurgical processes. Our belief is that innovations in hydrometallurgy based on ILs or DESs are unlikely. Instead, we should be aiming for a deeper understanding of hydrometallurgical processes at the molecular level. This is because advances are more likely to derive from the refocused efforts of experienced IL/DES researchers investigating the speciation and chemical thermodynamics of hydrometallurgical solutions, which will then hasten the transition from linear to low-energy-input, circular hydrometallurgy. Graphical Abstract

This study focused on chromium addition (0 wt%, 3 wt%, 6 wt%, 9 wt% and 12 wt%) on the boride layer formation, microhardness, fracture toughness and elevated temperature friction and wear behaviour of alloys formed by powder metallurgy (P/M). The boride layers obtained on P/M alloys were characterized by examining density, porosity, surface roughness, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray difraction, surface proflometry, microhardness, and fracture toughness. The addition of Cr has a signifcant efect on both boride layer formation and friction-wear behaviour of P/M alloys. Increasing the Cr addition up to 6 wt% has an improving efect on the microhardness, fracture toughness and wear resistance of the P/M alloys, whereas in the case of 9–12 wt% Cr addition causes exfoliation in the boride layer and low fracture toughness, thus reducing wear resistance. Coefcients of friction and wear volume losses at elevated temperatures are higher than room temperature. The best wear resistance at room temperature was obtained in the sample containing 3 wt% Cr with the highest fracture toughness, while the best wear resistance at 250 °C and 500 °C was obtained in the sample containing 6 wt% Cr, where the highest hardness value was obtained.

In this experimental research; It has been studied to improve the properties of polypropylene grape stalk and paddy mixtures by adding waste glass fiber. The potential of waste grape stalk and paddy to be a reusable material has created another curious subject. Polypropylene grape stalk and paddy were mixed in a twin screw extruder to provide a homogeneous mixture. Paddy; It is known as rice husk. Grape stalk-paddy was added to the PP at the rate of 20%. Glass fiber was added at 10-15% and 20% rates. Then the test samples were molded on the injection machine. Molded samples; Tensile, hardness, impact, density and scanning electron microscopy tests were performed. By examining the results of the tests, the effects of grape stalk-paddy and glass fiber amount on polypropylene were determined. Bu deneysel araştırmada; polipropilen (PP) üzüm sapı ve çeltik karışımlarının özelliklerinin atık cam elyaf ilavesi ile geliştirilmesi üzerine çalışılmıştır. Atık olan üzüm sapı ve çeltiğin yeniden kullanılabilir bir malzeme olma potansiyeli diğer merak edilen bir konuyu oluşturmuştur. Polipropilen üzüm sapı ve çeltik çift vidalı ekstrüderde homojen bir karışım sağlamak için karıştırılmıştır. Çeltik; pirinç kabuğu olarak bilinmektedir. PP içerisine %20 oranında üzüm sapı-çeltik katılmıştır. Cam elyaf ise %10-15 ve 20 oranlarında katılmıştır. Daha sonra enjeksiyon makinesinde test numuneleri basılmıştır. Kalıplanan numunelere; çekme, sertlik, darbe, yoğunluk ve taramalı elektron mikroskobisi testleri yapılmıştır. Testlerin sonuçları incelenerek üzüm sapı-çeltik ve cam elyaf miktarının polipropilen üzerindeki etkileri belirlenmiştir.

In this study, it is aimed to improving core material by using eloxal sludge for production B2 composite panel. The calcination study of eloxal sludge which arises from anodic oxidation process has a highest Al2O3 percentage by weight was performed with different temperature and time. It was focused how will be used the eloxal sludge such as relative humidity, dried or calcine because of tend to agglomerate structure. Optimal calcine eloxal sludge form was obtained at heat treatment regime with 700 C-0 and 270 minutes. The milling process with a different time was performed for obtaining fine grain size distribution. Also it was aimed to investigate possible agglomerate form in the polyurethane. The X-Ray Diffraction (XRD) and particle size analysis were performed to understand detailed structural analysis. Grain size distribution was obtained 306 mu m, 247 mu m and 203 mu m for different milling time. The eloxal sludge was respectively doped with different percentage with 15 % and 6 % in the polyurethane for obtaining core material. . B2 composite panels were produced as 1250-1500 mm as a standard. The mechanical properties were measurement for different doped of eloxal sludge. The highest mechanical properties was obtained by using 15 % eloxal sludge has a 247 mu m when it was observed that surface defects such as air bubbles. Also the thickness of the composite panel was measurement for all samples with 3.8 mm-4.2 mm.

A new method that utilizes theories of thermally activated deformation and repeated transient stress-relaxation tests has been proposed and validated in this study for the characterization and modeling of the stress-relaxation aging (SRA) behavior of aluminum alloys and its dependence on stress and temperature. Using the new method, key deformation-related variables, i.e., stress components, activation volume, and activation energy, of the aerospace grade heat-treatable aluminum alloy AA7B04 have been obtained as a function of aging temperature (388 K, 413 K and 438 K), stress (both elastic and plastic), and SRA time (up to 4 hours). It has been found that the apparent activation energy Qa of the material remains constant in the elastic region but decreases with the increase in strain in the plastic region, and also decreases with the increase in temperature for all initial loading stresses. These characteristics contribute to a much higher degree of stress relaxation in the plastic region and at higher temperatures than in the elastic region and/or at lower temperatures. The obtained changing activation volume V and Qa indicate that the deformation rate is controlled by forest dislocation interactions in the elastic region (V decreases from over 200b3 to less than 100b3), and by a cross-slip mechanism at high stress levels in the plastic region (V decreases to a few tens of b3). Based on these theories and results, a novel and simple constitutive model has been proposed, with which the stress-relaxation behavior of AA7B04 at different aging temperatures (388 K to 448 K), preloaded from elastic to plastic regions for up to 16 hours has been successfully predicted. The proposed model eliminates the limitations of conventional SRA models which mainly deals with elastic loading and isothermal conditions, and provides a foundation to effectively predict the springback after advanced non-isothermal SRA forming of aluminum alloy structures in the aerospace industry.

This study compares the cementation performance of metallic iron, metallic aluminum, and metallic tin in terms of the reaction conditions and parameters in synthetic antimony chloride solutions. The effects on the antimony recovery (%) caused by the cementators\" types, stirring speed, reaction time, and temperatures were explored thoroughly. The cementation kinetics of antimony were also explored for each cementator. The activation energies were determined to be 10.99, 9.09, and 13.58 kJ mol(-1) for Al, Fe, and Sn, respectively. The results reveal that the reaction is diffusion controlled, and comparable results were obtained for each cementator. At 25 degrees C, 40 mg of iron powder was found to reduce all antimony ions (i.e., approx. 99% recovery), but even when 100 mg of Al and Sn cementators were used, the antimony recovery did not reach 100%. This result shows that iron is the best candidate to cement antimony out of the solution.

ispartof: JOURNAL OF SUSTAINABLE METALLURGY vol:8 issue:1 pages:297-309 status: published

The depletion of high-grade ore deposits, as well as the generation of large quantities of tailings by mining and metallurgical activities, necessitates an urgent search for not only more cost-effective, but also more eco-friendly methods of recovering minerals from low-grade deposits and secondary resources. Research in the bioflotation process appears to be an answer to this search, thanks to the contribution of the microbial world. This study constitutes the first systematic and the most comprehensive review on bioflotation. The bioflotation studies in the literature were examined in a certain chronological order and by classifying the reagents in terms of both their origin and their use in flotation. Aside from the benefits of bioreagents to the mining industry, the review attempted to reveal the issues that prevent the transition to industrial application. This review aims to raise awareness of future research opportunities for mining and biology researchers while also presenting current bioflotation studies.

The resistance of wear protective coatings against oxidation is crucial for their use at high temperatures. Here, three nanocomposite AlCr(Si)N coatings with a fixed Al/Cr atomic ratio of 70/30 and a varying Si-content of 0 at.%, 2.5 at.% and 5 at.% were analyzed by differential scanning calorimetry, thermogravimetric analysis and X-ray in order to understand the oxidation behavior depending on their Si-content. Additionally, a partially oxidized AlCrSiN coating with 5 at.% Si on a sapphire substrate was studied across the coating thickness by depth-resolved cross-sectional X-ray nanodiffraction and scanning trans-mission electron microscopy to investigate the elemental composition, morphology, phases and residual stress evolution of the oxide scale and the non-oxidized coating underneath. The results reveal enhanced oxidation properties of the AlCr(Si)N coatings with increasing Si-content, as demonstrated by a retarded onset of oxidation to higher temperatures from 1100°C for AlCrN to 1260°C for the Si-containing coatings and a simultaneous deceleration of the oxidation process. After annealing of the AlCrSiN sample with 5 at.% Si at an extraordinary high temperature of 1400°C for 60 min in ambient air, three zones developed throughout the coating strongly differing in their composition and structure: (i) a dense oxide layer comprising an Al-rich and a Cr-rich zone formed at the very top, followed by (ii) a fine-grained transition zone with incomplete oxidation and (iii) a non-oxidized zone with a porous structure. The varying elemental composition of these zones is furthermore accompanied by micro-structural variations and a complex residual stress development revealed by cross-sectional X-ray nanodiffraction. The results provide a deeper understanding of the oxidation behavior of AlCr(Si)N coatings depending on their Si-content and the associated elemental, microstructural and residual stress evolution during high-temperature oxidation. peerReviewed

In this study, the 3 dimensional description of the quaternary subsolidus slag system alumina-silica-calcia-magnesia is evaluated using Mathematica programming based on previous experimental research data. The lever rule in the tetrahedra is then applied for a given arbitrary liquid composition A% + %B + %C + %D = 100 in order to calculate the solid phases present (neglecting solid solutions) with their relative proportions after the solidification is completed. A novel transformation and algorithm are then developed using simple geometry and MathLab programming which can also be used for other subsolidus systems in case appropriate data are provided.

Wire and arc additive manufacturing (WAAM) technology has recently become attractive due to the fact of its high production capacity and flexible deposition strategy. One of the most prominent drawbacks of WAAM is surface irregularity. Therefore, WAAMed parts cannot be used as built; they require secondary machining operations. However, performing such operations is challenging due to the fact of high waviness. Selecting an appropriate cutting strategy is also challenging, because surface irregularity makes cutting forces unstable. The present research determines the most suitable machining strategy by assessing the specific cutting energy and local machined volume. Up- and down-milling are evaluated by calculating the removed volume and specific cutting energy for creep-resistant steel, stainless steel, and their combination. It is shown that the main factors that affect the machinability of WAAMed parts are the machined volume and specific cutting energy rather than the axial and radial depths of the cut due to the fact of high surface irregularity. Even though the results were unstable, a surface roughness of 0.1 µm was obtained with up-milling. Despite a two-fold difference in the hardness between the two materials in the multi-material deposition, it is found that hardness should not be used as a criterion for as-built surface processing. In addition, the results show no machinability difference between multi- and single-material components for a low machined volume and low surface irregularity. ispartof: MATERIALS vol:16 issue:5 ispartof: location:Switzerland status: published

We study, using non-equilibrium Green's function simulations combined with first-principles density functional theory, the edge-state transport in two-dimensional topological insulators. We explore the impact of electron-phonon coupling on carrier transport through the protected states of two widely known topological insulators with different bulk gaps, namely stanene and bismuthene. We observe that the transport in a topological insulator with a small bulk gap (such as stanene) can be heavily affected by electron-phonon scattering, as the bulk states broaden into the bulk gap. In bismuthene with a larger bulk gap, however, a significantly higher immunity to electron-phonon scattering is observed. To mitigate the negative effects of a small bulk gap, finite-size effects are studied in stanene ribbons. The bulk gap increases in ultra-narrow stanene ribbons, but the transport results revealed no improvement in the dissipative case, as the states in the enlarged bulk gaps aren't sufficiently localized. To investigate an application, we also used topological insulator ribbons as a material for field-effect transistors with side gates imposing a lateral electric field. Our results demonstrate that the lateral electric field could offer another avenue to manipulate the edge states and even open a gap in stanene ribbons, leading to an ION/IOFF of 28 in the ballistic case. These results shed light on the opportunities and challenges in the design of topological insulator field-effect transistors. ispartof: MATERIALS vol:16 issue:4 ispartof: location:Switzerland status: published

Freeze lining is a solidified layer of slag formed on the inner side of a water-cooled pyrometallurgical reactor, which protects the reactor walls from thermal, physical, and chemical attacks. Because of the freeze lining's high thermal resistance, the reactor heat losses strongly depend on the freeze lining thickness. In a batch process such as slag fuming, the conditions change with time, affecting the freeze lining thickness. Determining the freeze lining thickness is challenging as it cannot be measured directly. In this study, a conceptual framework based on the morphology and microstructure of freeze lining and the rheology of the slag is discussed and experimentally evaluated to determine the freeze lining thickness. It was found that the bath/freeze lining interface lies just below critical viscosity temperature. The growth of the freeze lining is primarily controlled by the mechanical and thermal degradation of the crystals forming at the interface. The bath/freeze lining interface temperature for the measured slag lies in the range of 1035–1070°C.

Two ingots weighing 400 g and 5 kg with nominal compositions of Fe–8Mn–4Al–2Si–0.5C–0.07V–0.05Sn were produced to investigate the effect of processing variables on microstructure development. The larger casting has a cooling rate more representative of commercial production and provides an understanding of the potential challenges arising from casting-related segregation during efforts to scale up medium Mn steels, while the smaller casting has a high cooling rate and different segregation pattern. Sections from both ingots were homogenized at 1250 $$^{\circ} $$ ∘ C for various times to study the degree of chemical homogeneity and $$\delta $$ δ -ferrite dissolution. Within 2 hours, the Mn segregation range (max–min) decreased from 8.0 to 1.7 wt pct in the 400 g ingot and from 6.2 to 1.5 wt pct in the 5 kg ingot. Some $$\delta $$ δ -ferrite also remained untransformed after 2 hours in both ingots but with the 5 kg ingot showing nearly three times more than the 400 g ingot. Micress modeling was carried out, and good agreement was seen between predicted and measured segregation levels and distribution. After thermomechanical processing, it was found that the coarse untransformed $$\delta $$ δ -ferrite in the 5 kg ingot turned into coarse $$\delta $$ δ -ferrite stringers in the finished product, resulting in a slight decrease in yield strength. Nevertheless, rolled strips from both ingots showed $$>900$$ > 900 MPa yield strength, $$>1100$$ > 1100 MPa tensile strength, and $$>40$$ > 40 pct elongation with $$ < 10 pct difference in strength and no change in ductility when compared to a fully homogenized sample.

Multi-principal element alloys (MPEAs) occur at or nearby the centre of the multicomponent phase space, and they have the unique potential to be tailored with a blend of several desirable properties for the development of materials of future. The lack of universal phase diagrams for MPEAs has been a major challenge in the accelerated design of products with these materials. This study aims to solve this issue by employing data-driven approaches in phase prediction. A MPEA is first represented by numerical fingerprints (composition, atomic size difference , electronegativity , enthalpy of mixing , entropy of mixing , dimensionless $$\Omega$$ Ω parameter, valence electron concentration and phase types ), and an artificial neural network (ANN) is developed upon the datasets of these numerical descriptors. A pyMPEALab GUI interface is developed on the top of this ANN model with a computational capability to associate composition features with remaining other input features. With the GUI interface, an user can predict the phase(s) of a MPEA by entering solely the information of composition. It is further explored on how the knowledge of phase(s) prediction in composition-varied $$\hbox {Al}_x$$ Al x CrCoFeMnNi and $$\hbox {CoCrNiNb}_x$$ CoCrNiNb x can help in understanding the mechanical behavior of these MPEAs. Graphic Abstract

In this study; a polymer composite was produced by adding different proportions of polystyrene (PS), styrene ethylene butadiene styrenethermoplastic block copolymer (SBS) and montmorillonite nanoclay into low density polyethylene (LDPE). Six different polymercomposites were produced by mixing all materials in a twin screw extruder. Later, standard test samples were molded from the obtainedpolymer composites by injection molding method. To learn about the various mechanical properties of polymer composite materialsobtained; tensile, three point bending, hardness, impact tests were conducted to obtain information about the various mechanical propertiesof the composite. In addition, in order to see the distribution of nanoclay powders in the matrix, photographs of the broken surfaces obtainedfrom the impact tests were taken with scanning electron microscopy (SEM). According to the results of the tests, with the increase ofnanoclay powder ratio in the matrix; elasticity modulus, tensile strength, flexural modulus, maximum bending strength and hardness valueswere increased but % elongation, impact strength and bending elongation values were found to decrease. Bu çalışmada; düşük yoğunluklu polietilen (LDPE) içerisine farklı oranlarda polistiren (PS), stiren etilen bütadien stiren termoplastik blok kopolimeri (SBS) ve montmorillonite nanokil katarak bir polimer kompoziti üretilmiştir. Tüm malzemeler çift vidalı ekstrüzyon makinesinde karıştırılarak altı farklı polimer kompoziti elde edilmiştir. Daha sonra elde edilen bu polimer kompozitlerinden enjeksiyon kalıplama yöntemi ile kalıplama yaparak standart test numuneleri basılmıştır. Kompozitin çeşitli mekanik özellikleri hakkında bilgi edinmek için çekme testi, üç nokta eğme testi, sertlik testi ve darbe testleri yapılmıştır. Ayrıca nanokil tozlarının matris içerisinde dağılımlarını görmek için darbe testleri sonucundan elde edilen kırık yüzeylerden taramalı elektron mikroskobisi (SEM) ile fotoğrafları çekilmiştir. Yapılan testlerin sonuçlarına göre, matris içerisinde nanokil toz oranının artmasıyla; elastiklik modülü, çekme mukavemeti, kopma mukavemeti, eğilme modülü, maksimum eğilme mukavemeti ve sertlik değerlerinin arttığı buna karşılık kopma uzaması, darbe mukavemeti ve eğilme uzaması değerlerinin düştüğü tespit edilmiştir.

In this study, rose oil was encapsulated with stearic acid substituted polyvinyl alcohol macromolecule. In the first part of the study, stearic acid substituted polyvinyl alcohol macromolecule was synthesized and its chemical structure was elucidated by ATR-FTIR and ¹HNMR. Then, rose oil was encapsulated using this obtained polymer. The chemical structure of the obtained capsules was made by ATR-FTIR, and dimensional analysis was done by scanning electron microscope (SEM). After the obtained capsules, a paper coating formula was prepared and coated on 80 g/m² paper. The resulting scented papers were printed using the screen printing technique. The color, gloss, and deformation of the capsules on the surface of the printed and unprinted papers were determined by spectrophotometer, glossmeter and SEM. As a result, it was determined that the synthesized polymer could encapsulate the rose oil and the papers using these capsules could be printed without deformation.

ispartof: Journal Of Materials Research And Technology-Jmr&T vol:21 pages:4512-4525 status: published

To study the influence of mineral admixtures on concrete's mechanical properties after a low-temperature exposure, green concrete was prepared by mixing fly ash and slag at different replacement rates. By analysing the changes to concrete's mechanical properties and the damage layer thickness under different ambient temperatures (20, -10, -20, -30, and -40 °C), the change rule of concrete at low temperatures was explored. The results revealed that the compressive strength of concrete, containing either fly ash or slag, peaked at 30 °C; moreover, the slag concrete's flexural and splitting tensile strength peaked at -40 °C. The best mechanical properties were observed for a fly ash-to-slag ratio of 1:2 (F10S20; i.e., 10% fly ash and 20% slag) and its compressive strength at different temperatures was higher than that of concrete, containing 30% fly ash (F30) or 30% slag (S30), but the flexural and splitting tensile strength was lower than S30. Further, as the temperature decreased, the fly ash concrete's damaged layer thickness gradually increased. When the content of fly ash and slag were both 15% (F15S15), the damaged layer thickness was minimal at different low temperatures, especially at -30 °C, where the thickness was only 8.31 mm. ispartof: MATERIALS vol:15 issue:21 ispartof: location:Switzerland status: published

The automotive industry is among the priority technology areas of our country, and the reduction of vehicle weight and fuel consumption and thus CO2 emissions without compromising safety criteria are among the priority research areas. For this reason, R&D studies on increasing the use of polymer-based materials in the automotive industry are of great importance. In order to produce “high strength and weight reduction parts” in plastic moulding technologies, advanced technologies that focus on cost reduction and efficiency are being implemented rapidly. The chemical foaming process, which provides many advantages such as reducing the consumption of plastic material used, reducing the total moulding cycle time, using less tonnage injection moulding machines, and thus reducing the energy costs, is one of the innovative technologies that have been implemented since a very recent time. In this study, chemical foaming agent were being reinforced at the rate of 1-2-3% in natural fiber-reinforced recycled composite polypropylene raw material. The samples obtained in the injection machine was be moulded in the sizes and shapes in accordance with the standards. Tensile, hardness, impact and three points bending tests would be done. By examining the test results, the mechanical, and morphological properties of natural fiber reinforced polypropylene materials at different chemical agent percentages were examined. With increasing the amount of foaming agent, mechanical properties decreased.

Twin-roll casting (TRC) is a process in which liquid metal is introduced directly between counter-rotating water-cooled rolls, where it solidifies and is rolled to a strip having final thickness of 3 to 8 mm. TRC for aluminum is best suited to those alloys having a narrow freezing range with little susceptibility to hot tearing, such as 1XXX, 3XXX, 5XXX, and 8XXX. TRC offers advantages over conventional DC casting followed by hot and cold rolling for these alloys due to its lower capital cost, and decreased downstream processing operational cost and energy consumption, since hot rolling is not required. The microstructure formed in the strip must be carefully controlled, because as a near-net shape product used mostly for non-age-hardenable alloys, there is limited opportunity to modify it by subsequent processing. In particular, the near-surface microstructure has a strong effect on performance in forming applications. In this article, we present a computational model of TRC, and validate it for AA1050 aluminum alloy in a production environment. The novel aspect of this work is that the model is used to predict the final microstructure and crystallographic texture of the cast strip. The model is validated in plant trials for strip cast at a range of thicknesses, casting speeds, and caster setup by comparing the predicted microstructure, texture, and process outcomes such as roll separating force and forward slip to their corresponding measured values. We then apply the validated model to explore process parameters outside the standard practices, including feed inlet setback, casting speed, metal inlet temperature, and changing roll material to demonstrate how the microstructure and texture can be controlled via these parameters. (C) The Minerals, Metals & Materials Society and ASM International 2022

The goal of this study was to design and fabricate a 3D-printed wound dressing using chitosan as a bioink, with the ability to release the antibiotic drug amoxicillin (AMX) in response to mild electrical stimulation. This was achieved through the incorporation of bismuth ferrite (BFO) nanoparticles, which have both magnetic and ferroelectric properties. The chitosan-based scaffolds containing various concentrations of BFO were analyzed using Fourier transform infrared spectroscopy, and the release of AMX from the scaffolds was evaluated in vitro under electrical stimulation. The results demonstrated that the scaffolds had a suitable structure for drug loading and release, and the release of AMX was successfully controlled by the applied electrical stimulus. The maximum tensile strength (4.97 ± 0.34 MPa) was observed at the ratio of 6% CHT/0.025% BFO scaffolds and the scaffold with 6% CHT/0.075% BFO had the maximum cell viability of (~130%) at 168 h incubation time. This study highlights the potential of BFO to deliver therapeutic drugs from a 3D-printed chitosan scaffold in a controlled manner.

Different weight ratios of cerium (0.5, 1 and 2 wt.%) were produced in a controlled atmosphere by High Pressure Die Cast method to Mg-6Al-0.3Mn-1Sn alloy. The influence of cerium on microstructure and high-temperature mechanical properties was investigated. The microstructure study revealed that the main alloy contains intermetallic phases such as alpha-Mg, beta- Mg17Al12, Mg2Sn and Al11Ce3. The hardness values of the alloys were increased with the addition of 0.5%, 1 and 2 cerium. With the addition of 0.5 wt.% Ce, the yield strength increased to 145 MPa. With the addition of 2 wt.% of Ce, it was found to be 160 MPa with an increase of 14%. Tensile strength was obtained as 190 MPa. Elevated temperature tensile test was carried out at 120 degrees C, 180 degrees C and 240 degrees C, to all the alloys. It was found that increased Ce ratio increased the high-temperature mechanical strength. At 120 degrees C, the highest tensile and yield strength values were obtained with 159 MPa and 147 MPa, respectively, in the alloy with 2% wt. cerium added. In the tensile test performed at 180 degrees C, the highest tensile and yield strength were measured as 91 MPa and 77 MPa, respectively. The operating temperature of Mg alloys produced industrially by HPDC has a significant effect on mechanical properties. High operating temperatures reduce mechanical properties. However, the mechanical properties at high test temperatures were increased by the addition of Ce metal to the AM60-1Sn-XCe alloy produced with HPDC.

ispartof: ISIJ INTERNATIONAL vol:61 issue:9 pages:2400-2409 status: published