This year, Emerging Materials Research completes eight years since its inception. During these eight years, 366 papers, including 20 review papers, have been published. Authors from 33 countries have contributed to the growth of the journal. Due to the interdisciplinary nature of the journal, the Editor anticipates that Emerging Materials Research will continue to attract a large number of manuscripts from authors based around the world.
As the Editor concludes his Editorials for the journal, fond memories take him back to his attendance at the International School of Materials Science & Solar Energy between 18 March–1 April 1983 in Cairo and Alexandria, Egypt. The meeting was organized by Dr Emmanuel Kaldis (International Union of Crystallography) and Salah Arafa (American University in Cairo), in collaboration with the Egyptian Academy of Scientific Research & Technology and the National Committee on Crystallography. While the meeting was well attended, the Editor had the privilege of meeting Dr John B. Goodenough – the winner of this year’s Nobel Prize in Chemistry for the development of lithium-ion batteries.1 One can argue that creativity is priceless, but it would feel good to be recognized. Dr Goodenough had been nominated for the Nobel Prize in the 1980s (Emmanuel Kaldis, Personal Communication, 12 October 2019).
The global market for rechargeable batteries is projected to exceed $40·9 billion by 2024.2 Supercapacitors/ultracapacitors represent a closely related technology. In 2018, the global market for these energy storage devices was $685 million; it is anticipated to reach $2187 million by 2024.3 Thermal management of rechargeable batteries4–6 and supercapacitors7 continue to be of significant interest to the research community. Infrared imaging facilitates a detailed understanding of the thermal distribution and heat transfer, in real-time, in rechargeable batteries and supercapacitors.8
The first of the papers in this issue of Emerging Materials Research focuses on ‘Optical properties of 2-aminopyridine potassium dihydrogen phosphate cadmium chloride’.9 This paper is by D. Sivavishnu, R. Srineevasan and J. Johnson from the PG & Research Department of Physics, Government Arts College, Tiruvannamalai, India. A good-optical-quality crystal of 2-aminopyridine potassium dihydrogen phosphate cadmium chloride (2APKDPC) was grown using the slow-evaporation technique at room temperature. The transparent and defect-free bulk crystal of 2APKDPC, with dimensions of 23 × 10 × 5 mm3, was grown using the solution growth method over a period of 90–95 d. From the single-crystal X-ray diffraction (XRD) study, the measured lattice parameter values were a = 7·49 Å, b = 7·49 Å, c = 7·03 Å, α = β = γ = 90° and volume V = 394 Å3, which show that the grown 2APKDPC crystal belonged to the tetragonal crystal system. The crystalline nature of the grown crystal was confirmed by powder XRD analysis. Fourier transform infrared (FTIR) analysis was carried out to identify metal coordination and the presence of various functional groups in the 2APKDPC crystal. In the recorded optical transmission spectrum, the ultraviolet cutoff wavelength was found to be 237 nm, and the optical energy bandgap value was also found from the absorption studies.
The second paper by Muhammad Riaz (Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi, Pakistan), Khasan S. Karimov (Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi, Pakistan; Center for Innovative Development of Science and New Technologies of Academy of Sciences of Tajikistan, Dushanbe, Tajikistan) and Jameel-Un Nabi (Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi, Pakistan) is on ‘Investigation of humidity effects on electrical properties of PTB7-Th and PCBM sensor’.10 The authors report the fabrication of semitransparent combined semi-surface-type samples of the indium tin oxide (ITO)/poly{4,8-bis[5-(2-ethylhexyl)thiophen-2-yl]benzo[1,2-b:4,5-b 0] dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophene-4,6-diyl} (PTB7-Th):[6,6]-phenyl C61 butyric acid methyl ester (PCBM)/graphene composite humidity sensor. The transparency of the sensor is 58–60%. The dependence of resistance, impedance and capacitance at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 200 kHz of the ITO/PTB7-Th:PCBM/graphene composite samples on relative humidity in the range of 50–93% is investigated respectively. It was observed that as humidity increased from 50 to 93%, the resistance and impedance (at 1 kHz) of the samples decreased, on average, by a factor of 7·48 and 58·75, respectively. Under the same experimental conditions (1 kHz), the capacitances of the samples increased by a factor of 42. As the frequency was increased from 100 Hz to 200 kHz, the impedance decreased by a factor of 20 and 7 at relative humidity of 50 and 62%, respectively. The corresponding capacitance decreased by a factor of 33 and 178, respectively. The semitransparent PTB7-Th-and-PCBM-based humidity sensors can be used for measurement of humidity as well as a teaching aid in which control of illumination or light intensity is desirable.
The third paper focuses on ‘Review of preparation and application of copper–steel bimetal composites’.11 This paper has been reported by Yiran Wang, Yimin Gao, Yefei Li, Wenyan Zhai, Liang Sun and Chao Zhang from the State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi’an Jiaotong University, Xi’an, People’s Republic of China. With the rapid development of modern science and industrial technology, single metals or alloys are restricted by working conditions and cost. It is challenging to meet the requirements for current applications. Copper–steel bimetal composites have the performance of both metals and a low cost. They have drawn extensive attention worldwide and have been developed by several scholars for many years. The new preparations are studies to promote performances of the copper–steel bimetal composites. Many papers in the literature have also reported various applications of the copper–steel bimetal composites. In recent years, the development of copper–steel bimetal composites has made significant progress. This paper is mainly concerned with the progress of research on the preparation of copper–steel bimetal composites. The preparation methods are classified according to the forming state of copper and steel. Furthermore, the industrial applications of these composites and the prospects of future development are introduced.
The fourth paper ‘Eddy current characterization and electrical properties of nanostructured alloy Cu70Fe30’12 has been reported by Warda Laslouni (Département de Physique, Faculte des Sciences, Université de Blida, Blida, Algeria) and Mohammed Azzaz (Laboratoire de Science et Génie des Matériaux, Université des Sciences et de la Technologie Houari Boumediene, Algiers, Algeria). The nanostructured copper–iron alloy exhibits interesting properties compared with a conventional alloy due to the critical size effect. The nanocrystalline solid solution Cu70Fe30 was elaborated from elemental iron and copper powders using a high-energy ball mill. The complete formation of face-centered cubic copper–iron solid solution was obtained after 24 h of milling. A crystallite size of 9 nm was obtained after 36 h of milling. The characteristics of eddy currents and the electromagnetic properties (resistivity and hysteresis loop) of these alloys were studied. The goal was to follow the evolution of the impedance (found from eddy current control) and to establish a relationship between the electrical and magnetic properties and the structure (crystallite size) of the materials.
‘Effect of cobalt addition on the morphology and mechanical properties of W–Ni–Cu–Co alloy’13 is the fifth paper in this issue of Emerging Materials Research. Natarajan Senthilnathan (School of Mechanical Engineering, Vellore Institute of Technology, Vellore, India), Arunjunai Rajan Raja Annamalai (Centre for Innovative Manufacturing and Research, Vellore Institute of Technology, Vellore, India) and Gopalan Venkatachalam (School of Mechanical and Building Sciences, Vellore Institute of Technology, Chennai, India). This paper investigates the performance of a tungsten (W)–nickel (Ni)–copper (Cu) heavy alloy with 0·5, 1·0, 1·5 and 2·0 wt% cobalt (Co) additions. The alloys are prepared through spark plasma sintering at a sintering temperature of 1400°C following a heating step of 100°C/min. The alloy with 0·5 wt% cobalt is observed to have good mechanical properties in comparison with other alloys. The density and hardness of the alloys follow a decreasing trend with an increase in cobalt addition. Subsequently, microstructural characteristics such as contiguity, average grain size and matrix volume fraction are measured and investigated, as they are found to affect the mechanical properties of the alloys. The average grain growth of the alloys varies around 13 µm. As the cobalt percentage is increased, tungsten–tungsten contiguity is observed to increase. The W–Ni–Cu–0·5Co alloy exhibits higher yield and tensile strength in comparison with other heavy tungsten alloys. The fracture surface analysis shows a predominantly tungsten grain cleavage fracture for 0·5 wt% cobalt alloy. The other alloys show more features of matrix interface failure and tungsten decohesion.
Ziya Ozgur Yazici and Gorkem Sanan from the Department of Materials Science and Engineering, Afyon Kocatepe University, Afyonkarahisar, Turkey, are the coauthors of the next paper – ‘Production and properties of Co-based metallic-glass-reinforced aluminum matrix composites’.14 Cobalt-based metallic-glass-particulate-reinforced aluminum (Al) matrix composites were prepared by microwave sintering in air conditions at a proper temperature that avoids crystallization of reinforcing particles. Composite powders containing 5–20 vol.% metallic glass reinforcement were prepared by high-speed vibrating ball mill, and green compacts were sintered using a microwave heating method at 500°C for 30 min. Microstructural features were investigated by XRD and scanning electron microscopy (SEM). Mechanical properties of the samples were evaluated by compression tests and Vickers hardness measurements. Sintering studies have shown that the metallic glass particles interact with the microwaves during the microwave heating process over a certain temperature (>500°C) and cause excessive heating, and thus leads to overheating of the composite sample in an uncontrollable manner. This has been decisive for the choice of sintering temperature. Nevertheless, microwave heating offered a rapid sintering condition for air atmosphere. Investigations on the microstructure of the samples with the well-distributed reinforcements revealed that a brittle intermetallic phase did not form between the reinforcement and matrix interfaces. The results showed that the composite samples milled for 2 h exhibited significantly higher compressive strength and hardness values as compared to pure aluminum.
Seyed Morteza Hosseyni Khorasgani and Mohammad Reza Dashtbayazi (Department of Mechanical Engineering, Shahid Bahonar University of Kerman, Kerman, Iran) report their studies on ‘Mechanical property modeling of aluminium nanocomposite reinforced with carbon nanotubes’.15 In this work, the mechanical properties of an aluminum matrix nanocomposite reinforced with carbon nanotubes (CNTs) are modeled by using the finite-element method (FEM). The mechanical properties include the Young’s modulus, yield strength and rupture strength of the nanocomposites. The effects of the volume fraction of the CNTs, interfacial type and loading direction on the mechanical properties are studied. The FEM results for the mechanical properties of the nanocomposite are compared with the results of experimental data and the micromechanical models. The FEM predictions for the mechanical properties for different volume fractions of the CNTs provide better results than the micromechanical models. When the volume fraction of the CNTs increases from 0 to 2 vol.%, the Young’s modulus, the yield strength and the rupture strength of the nanocomposite increase by 18, 18 and 29%, respectively. Due to random dispersion of the CNTs in the aluminum matrix, the mechanical properties are approximately the same in different directions. The results show that the friction interface is weaker than the adhesion interface, and that the friction interface causes the mechanical properties of the nanocomposite to weaken.
‘Effect of Y addition on microstructure and mechanical properties of extruded Mg–Mn alloys’16 by Xiaoping Luo, Daqing Fang and Li Kang (Taiyuan University of Science and Technology, Taiyuan, China) is the eighth paper in this issue of Emerging Materials Research. Two homogenized as-cast magnesium (Mg)–1 wt% manganese (Mn) alloys containing 1·0 and 4·0 wt% alloying yttrium (Y) were processed at an extrusion ratio of 17:1 at 400°C using a ram speed of 0·3 mm/s. The effect of yttrium additions on the microstructure and mechanical properties of the extruded alloy was analyzed and compared. The average grain size of the extruded Mg–1Mn–4Y (MW14) alloy was much smaller than that of the extruded Mg–1Mn–1Y (MW11) alloy. In addition, the tensile strength of the MW14 alloy was higher than that of the MW11 alloy at the investigated temperature ranging from room temperature to 200°C, although the former exhibited a lower elongation to failure. The fracture surface of the MW14 alloy exhibited the cleavage fracture mode. Conversely, a dimple was observed in the MW11 alloy; the significant differences in performance between the two alloys are attributed to their yttrium contents.
Shamanth Vasanth (School of Mechanical Engineering, REVA University,Bengaluru, India), Hemanth Krishna (School of Mechanical Engineering, REVA University,Bengaluru, India), Devaraj Sonnappa (School of Mechanical Engineering, REVA University, Bengaluru, India), Hiriyalu Shivegowda Nithin (Department of Mechanical Engineering, Malnad College of Engineering, Hassan, India) and Pramod Kumar Kataraki (School of Mechanical Engineering, REVA University, Bengaluru, India) report their studies on ‘Influence of ageing on kinetics and strain-hardening behaviour of duplex stainless steels’.17 In this work, the effect of long-term isothermal heat treatment on the kinetics of sigma-phase precipitation of super duplex steels was qualitatively and quantitatively examined in detail. Microstructural examination showed that the sigma phase was only an intermetallic phase even after ageing for a longer holding time (4500 min). As the ageing time increased, the amount of sigma-phase precipitation also increased. In order to assess the transformation characteristics, the experimental results were fitted with the Johnson–Mehl–Avrami equation. The results showed that the kinetics of sigma precipitation was very sensitive to the holding time at 900°C. Also, in this investigation, the strain-hardening behaviour was evaluated using Holloman’s model. As the ageing time increased, the tensile strength of the samples also increased because of the sigma-phase precipitation in both the ferritic phase and ferrite–austenite interface. The embrittled ferrite phase was found to be harder than the austenitic phase, and the strain-hardening behaviour of both the austenitic and ferritic phases was found to be monotonic in nature.
‘Laser-melted surfaces fabricated on MAO films in Al and Si electrolytes alloys’18 is the tenth paper in this issue of Emerging Materials Research. Fengbiao Wang (School of Mechanical Engineering, Shenyang Ligong University, Shenyang, China) and Yongqing Wang (School of Mechanical Engineering, Dalian University of Technology, Dalian, China) are the coauthors of this paper. In order to improve the functions of microarc oxidation (MAO) films, the current work investigated the effects of the laser surface melting (LSM) process on MAO films fabricated in different electrolytes. A series of processing experiments was carried out on the composite films. In detail, MAO films using aluminum and silicon (Si) electrolytes were prepared on a Ti–6Al–4V alloy surface and then treated by using the LSM process. At the same time, the properties of the films, such as phases and morphology, were characterized and analyzed by XRD, SEM and energy-dispersive X-ray spectroscopy. The results showed that moderate-intensity plasma was more easily obtained on the silicon MAO (Si-MAO) films than on the aluminum MAO (Al-MAO) ones. Similarly, a higher laser power was necessary to liquefy or gasify alumina (Al2O3). Compared with the defective structure of Al-MAO film after LSM, the structure of the Si-MAO film was almost free of defects. The film morphologies showed that a MAO film with low porosity and a smooth surface can be obtained after LSM treatment using proper parameters. In conclusion, the composite silicate system process using the silicon electrolyte had better modification performance.
Siddhartha Kosti (Department of Mechanical Engineering, Rajkiya Engineering College, Banda, India) reports studies on the ‘Heat flux and convective boundary influence on nanofluid-filled cavity’.19 Electronic devices release heat to the atmosphere from the walls, and system miniaturization results in exponential increase in the heat associated with these high-heat-generating/electronic devices. To analyze this numerically, heat-flux and convective types of boundary condition are considered at the walls, which are the most realistic boundary condition type. In the present work, the physical model consists of nanofluid inside an enclosure with one side subjected to constant heat-flux and the other sides exposed to convective boundaries. The nanofluid is completely confined within the enclosure and flows due to natural convection. Considering the heat-flux varying from 100 W/m2 to 10 kW/m2, three Rayleigh (Ra) numbers are calculated. Results are validated with experimental results also. Results show that increasing Ra and copper nanoparticle concentration results in strengthening the heat transfer and average Nusselt number. Results also show that the thermal boundary layer thickness increases with aspect ratio (AR). Streamline contours show that natural convection strength is higher for low ARs compared to high ARs. For a low Ra number (2 × 104), the viscosity model is more sensitive than the thermal conductivity model, and for a high Ra number (2 × 106), the thermal conductivity model is more sensitive than the viscosity model.
‘Size effects on melting point based on surface energy and coordination number’20 is the twelfth paper in this issue of Emerging Materials Research. Shuai Zhang (College of Materials Science and Engineering, Jilin Jian Zhu University, Changchun, China) and Lei Chen (College of Municipal and Environmental Engineering, Jilin Jian Zhu University, Changchun, China) report their studies on the influence of size on melting point in relation to the surface energy of nanoparticles, due to the increased surface/volume ratio. As the nanoparticle’s size decreases, there are an increased number of different surface shapes, which means the coordination numbers are different from each other. Both the surface energy and coordination number of surface atoms are necessary for understanding the thermal stability of nanoparticles. So, a new model free of any adjustable parameters, based on size-dependent surface energy and calculation of the surface atomic coordination number of nanoparticles, is developed to predict the size-dependent melting point of nanoparticles. The model can be utilized to predict the thermal stability of low-dimensional materials within a large size range. The theoretical predictions in terms of the model are consistent with experimental evidence.
Sakil Mahmud (Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, People’s Republic of China; University of Chinese Academy of Sciences, Beijing, People’s Republic of China), Md. Nahid Pervez (School of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan, People’s Republic of China), K. M. Faridul Hasan (School of Textile Science and Engineering, Wuhan Textile University, Wuhan, People’s Republic of China), Muhammad Abu Taher (Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, People’s Republic of China) and Hui-Hong Liu (School of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan, People’s Republic of China) report their studies on ‘In situ synthesis of green AgNPs on ramie fabric with functional and catalytic properties’.21 The use of natural biopolymers for the green and safe synthesis of silver nanoparticles (AgNPs) on textiles is a novel and interesting approach. This study investigated the use of the natural biopolymer sodium (Na) alginate as a reducing and stabilising agent for the in situ synthesis of AgNPs on ramie fabrics. The morphology, thermal stability and chemical structure of the fabrics were characterized by SEM, thermogravimetric analysis, differential scanning calorimetry and FTIR spectroscopy. The mechanical properties and colorimetric values of the treated fabrics were also measured. The catalytic performance of ramie fabrics incorporating AgNPs was assessed using the reduction of 4-nitrophenol in the presence of sodium borohydride as a model reaction. Treatment with AgNPs substantially improved the ultraviolet-blocking ability of the fabric and resulted in ramie fabric with a remarkable antibacterial activity.
‘Surface charge decay patterns of insulating polymers based on potential-mapping method’22 by Tian-hao, Feng-kai Gao and Hai-kun Shang (School of Electrical Engineering, Northeast Electric Power University, Jilin City, China) is the next paper in this issue of Emerging Materials Research. The accumulation of surface charge on insulators can lead to electric field distortion. Therefore, measurement of the surface potential decay tendency has proven to be a practical technique for evaluation of the charge dissipation characteristics of dielectrics after corona polarization. The traditional method for evaluation of the surface charge dissipation behavior is based on using a stable suspended electrostatic probe. However, this method was found to be inadequate for analysis of the surface charge transport mechanism because the electrostatic probe was focused only on one point on the sample surface. Therefore, a scanning and mapping technique has been applied in the surface potential measurement that uses a movable electrostatic probe. This technique enables measurement of the complete surface charge distribution profile of the cellular electrets and provides a potential-mapping graph that reflects the exact surface charge distribution and decay tendency of the functional dielectric after discharge. This work describes the phenomenon of the surface charge diffusion pattern based on the mapping of the dynamic surface potential profile from a scanning and mapping graph. This method could be developed into an efficient tool for evaluation of surface charge dissipation on insulating polymers used in high-voltage apparatuses and energy-storage devices.
‘Mechanical properties of chemically treated woven banana/polyvinyl alcohol composites composites’23 is by Amaresh Gunge (Department of Mechanical Engineering, Nagarjuna College of Engineering and Technology, Bengaluru, India), Sangshetty Bheemanna Kivade (Department of Mechanical Engineering, Basavakalyan Engineering College, Basavakalyan, India), Mahadevappa Nagamadhu (Department of Mechanical Engineering, Acharya Institute of Technology, Bengaluru, India) and Sangamesh Rajole (Department of Metallurgical and Materials Engineering, National Institute of Technology Karnataka, Mangalore, India). The present work investigated the effect of chemical treatment on the mechanical properties of plain-woven banana fabrics reinforced with a polyvinyl alcohol (PVA) biodegradable matrix. Woven banana fabrics were chemically treated with different concentrations (0·5, 1·0, 2·0, 3·0 and 4·0%) for 4 h at room temperature. The banana fabrics and PVA were used in ratios of 55 and 45% weight fractions, respectively. Composites were prepared using the hand-layup method. The samples were tested according to different American Society for Testing and Materials (ASTM) standards for tensile, flexural and impact strength. The results showed that tensile, flexural and impact properties improved with potassium permanganate treatment. The fabrics treated with 1·0% potassium permanganate showed very good mechanical properties compared with the untreated fabrics and the 0·5, 2·0, 3·0 and 4·0% treated fabrics. The 1% treated fabric composite showed a 68·07% increase in tensile strength compared with the untreated fabric composite. SEM revealed that the 1% treated fabric had better interfacial bonding between the fabric and matrix. This contributes to improvement in the mechanical properties of the composite.
Lutfiye Altay (Department of Mechanical Engineering, Ege University, Izmir, Turkey) reports studies on ‘The effect of hybrid carbon fillers on properties of polyester composites’.24 In this study, synthetic graphite and graphene were used as thermally conductive fillers for polyester-based composites. Orthophthalic polyester resin, methyl ethyl ketone peroxide and cobalt octoate were used as the polymer matrix, catalyst and accelerator, respectively. Hybrid carbon fillers at different weight fractions (up to 45 wt.%) were added into the polymer matrix by using an ultrasonic mixer. Composite test specimens were prepared by using the doctor blade thin-film fabrication method. The in-plane and through-plane thermal conductivity values of the composites were determined by using a Xenon Flash instrument. Furthermore, the change in the morphological structure of the carbon-filled composites was studied in detail by SEM. Mechanical properties were studied by performing tensile tests, and the electrical conductivity of composites was measured using an LCR meter. Significant enhancement of the thermal conductivity by way of hybrid carbon filler incorporation was obtained for polyester-based composites.
The next paper in this issue is on ‘Structure, spectra and bioactivity of pentyl ester of chlorogenic acid: DFT study’.25 This paper is by Ashok Kumar Mishra and Satya Prakash Tewari (Department of Physics, Dr Shakuntala Misra National Rehabilitation University, Lucknow, India). The pentyl ester of chlorogenic acid (C21H28O9) is reportedly a new bioactive biomaterial isolated from the leaves of the Anthocephalus chinensis plant, whose electronic structure and spectral properties are yet to be reported. In this view, the optimized geometry of the titled compound has been modeled using DFT-B3LYP/6-31+G(d,p) methods for the theoretical investigation of the spectroscopic data and electronic structure properties implementing the density functional theory (DFT) approach. The proton (1H) and carbon-13 (13C) nuclear magnetic resonance chemical shifts have also been calculated and compared with experimental values, which reveal a good agreement. A molecular docking study of the titled molecule has also been performed for the prediction of its bioactivity, in which its three-dimensional (3D) shape at the equilibrium geometry has been exploited as a ligand input to interact with 1hsg and 1gcn protein receptors, which result in the final values of the free energy of binding to be −5·70 and −2·06 kcal/mol, respectively. This implies that the titled molecule may be a good natural anti-immunodeficiency and antidiabetic agent. The outcome of the present study may be useful in developing a natural drug agent and identifying the other novel structures for synthesizing the alternative drugs.
The paper ‘Influence of prestress on the natural frequency of a fluid-filled FGM sphere’26 is reported by Surkhay D. Akbarov (Department of Mechanical Engineering, Yildiz Technical University, Istanbul, Turkey; Institute of Mathematics and Mechanics of the National Academy of Sciences of Azerbaijan, Baku, Azerbaijan), Arzu Cilli (Department of Physics, Yildiz Technical University, Istanbul, Turkey) and Nazmiye Yahnioglu (Department of Mathematical Engineering, Yildiz Technical University, Istanbul, Turkey). This paper deals with the study of the influence of the inhomogeneous prestresses (initial stresses) in a hollow sphere made of a functionally graded material (FGM) filled with an inviscid compressible fluid on the natural vibration of this sphere. For this study, the 3D exact-field equations of the linearized theory of elastic waves in bodies with initial stresses are employed. The motion of the fluid is described by the linearized Navier–Stokes equations for inviscid barotropic compressible fluids. The discrete-analytical solution method proposed by the first author is employed for the solution to the corresponding mathematical problems. Numerical results related to the natural vibration of the mentioned sphere and the influence of the problem parameters on these frequencies are presented and discussed. In particular, it is established that the existence of the fluid leads to a decrease in the natural vibration frequencies. However, a change in the FGM properties of the sphere’s material can lead to an increase in these frequencies.
Barış Çalişkan and Zeynep Parlar (Mechanical Engineering Faculty, Istanbul Technical University, Istanbul, Turkey) report a study on the ‘Tool wear assessment of turning operation by 2D finite-element simulation’.27 Tool wear is a critical problem in industrial manufacturing. When tool wear reaches a certain value, it causes a change in tool geometry. This directly affects chip formation, cutting force, temperature distribution, machining quality and so on. Therefore, prediction of tool wear is of great importance for optimizing the cutting process. Numerical analysis is a powerful method for predicting cutting variables that are difficult to obtain by experimental methods. In this paper, the effect of different tool rake angle values on tool wear rate is investigated. A two-dimensional (2D) finite-element simulation is presented for chip formation analysis considering thermal effects. Boundary conditions are defined as stationary for the workpiece and axial velocity to the tool at the cutting direction. Different models are analyzed by changing the tool geometry, and the results of the tool wear are discussed. It is shown that wear rate decreases ten times with the negative rake angle. However, increase in clearance angle causes increase in wear rate.
The paper ‘Machining effects on delamination failure in milling MD-CFRPs with uncoated carbide tools’,28 is reported by Dervis Ozkan (Bartin University, Bartin, Turkey), Mustafa Sabri Gok (Bartin University, Bartin, Turkey), Hasan Gokkaya (Karabük University, Karabük, Turkey) and Abdullah Cahit Karaoglanli (Bartin University, Bartin, Turkey). As one of the main failure mechanisms emerging in the milling of carbon-fiber-reinforced polymer (CFRP) materials, delamination is primarily affected by cutting tool material and geometry, machining parameters and the dynamic loads arising during the machining process. In this study, machinability tests were performed without the use of coolants to examine the effect of machining parameters on multidirectional CFRP composite workpieces, which have a wide application in industries. The tests were applied on a numerical computer controlled vertical processing center at three different cutting speeds (100, 200 and 300 m/min), three different feed rates (0·05, 0·15 and 0·25 mm/tooth) and constant cutting depth (1 mm). Following the tests, the changes in the workpiece were examined in terms of surface roughness, cutting forces, tool wear and delamination failures. The average surface roughness increased with increasing feed rate. Cutting forces also increased with increasing cutting speed, which caused improvements on average surface roughness values. As a machining parameter, feed rate was found to be a determining factor in the machining of CFRP composite materials.
Potta Sivaiah (Department of Mechanical Engineering, Madanapalle Institute of Technology & Science, Madanapalle, India) and Bodicherla Uma (Department of Mechanical Engineering, Jawaharlal Nehru Technological University Ananthapuramu, Anantapur, India), report their studies on ‘Multiobjective optimization of sustainable turning process using TOPSIS method’.29 The minimum-quantity-lubrication (MQL) cooling machining technique is an environmental damage-free manufacturing process. It is very complicated to determine the optimum cutting conditions for multiple-response problems. In the present work, the technique for order preference by similarity to ideal solution (TOPSIS) coupled with the Taguchi method was applied for the selection of optimum cutting conditions in the turning of 17-4 precipitated hardenable stainless steel under MQL. In this experimental investigation, the turning process parameters considered were cutting velocity, feed rate and depth of cut, while the output responses were surface roughness and tool flank wear. From the optimization study, it was found that a velocity of 54 m/min, a feed rate of 0·096 mm/revolution and a cutting depth of 0·2 mm were the optimum cutting conditions. From the conformation test results, it was observed that the optimum cutting conditions determined by the coupled Taguchi and TOPSIS methods reduced surface roughness and tool flank wear by 19·2 and 69%, respectively. The analysis of variance results showed that the turning performance was largely influenced by the feed rate. Linear regression analysis was also carried out to predict the responses as a function of input process variables.
‘Electrochemical characteristic analysis of corrosion of coated steel bars in magnesium oxychloride concrete’30 is reported by Shao-yong Wen (Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province, Lanzhou University of Technology, Lanzhou, China), Hong-xia Qiao (Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province, Lanzhou University of Technology, Lanzhou, China; Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, China), Peng-hui Wang (Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province, Lanzhou University of Technology, Lanzhou, China), Tian-xia Yang (Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province, Lanzhou University of Technology, Lanzhou, China) and Zhen-qing Yang (Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province, Lanzhou University of Technology, Lanzhou, China). In view of the service life of structural buildings of reinforced magnesium oxychloride concrete in western saline soil and the corrosion of chlorine ion content of magnesium oxychloride cement on steel bars, coatings are used to alleviate the degree of corrosion in different environments. The open-circuit potential, polarization resistance and corrosion current density of coated and bare steel bars in different environments were analyzed using a Z350 electrochemical workstation. The products were also analyzed by SEM and XRD microtests. The tests showed that a zincite coating can protect steel bars from corrosion under different environments. The corrosion current densities of coated steel in sulfate, chloride and water were 5·26, 2·33 and 2·86% of that of bare steel, respectively. The average value of the polarization resistance of the coated steel bars was about five times that of the bare steel bars. There were loose porous layers and massive corrosion on the bare steel surface, while the surface of the coated steel had only pitting corrosion. Therefore, the anticorrosion effect of the zincite coating on steel bars in reinforced magnesium oxychloride concrete was obtained, so that concrete with magnesium oxychloride-coated reinforcement has better application prospects in saline soil.
Rosanne C. Villanueva, Faye Dominique A. Lim and Jay-Anne B. Aleño (Department of Chemical Engineering, University of Santo Tomas, Manila, Phillipines) report their studies on ‘Microwaved cement boards with alkali-treated pineapple and water hyacinth fibers’.31 Pineapple fibers (PFs) and water hyacinth fibers (WHFs) were treated with sodium carbonate (Na2CO3) and sodium hydroxide (NaOH) solutions for soaking times of 0·5, 1·0, 1·5 and 2·0 h. Analyses showed that the best treatment parameters for PFs were 2·0 M sodium carbonate for 1·5 h and 2·0 M sodium hydroxide for 0·5 h; those for WHFs were 1·5 M sodium carbonate for 0·5 h and 1·0 M sodium hydroxide for 1 h. The untreated and treated PFs showed similar FTIR spectra ranging from 2924 to 2926 cm−1, which signifies the presence of acidic oxygen–hydrogen stretching vibrations on a carbonyl group. The sodium hydroxide-treated WHFs had the 2926 cm−1 transmittance peak absent compared with the untreated WHFs. The acetylation process on both fibers resulted in increased roughness of fibers, which were analyzed using SEM at 10 μm magnification. The fibers treated under the determined best parameters were then used in the fabrication of cement boards. The specimens underwent microwave curing with regimes under 119 and 280 W. The cement board with aligned sodium carbonate-treated combined PFs and WHFs performed 16–41% better than the cement board with non-woven oriented fibers in terms of flexural strength.
The paper ‘Influence of compression toughness on acoustic emissions of cementitious materials’32 is by R. Vidya Sagar (Department of Civil Engineering, Indian Institute of Science, Bangalore, India), Shahari Shetty (Department of Civil Engineering, National Institute of Technology, Surathkal, India) and Aditi Bhat (Department of Civil Engineering, National Institute of Technology, Surathkal, India). This paper reports on the variation of acoustic emission (AE) characteristics with the compression toughness of cementitious materials. The purpose of the study was to understand the relationship between compression toughness and AE released during the fracture process in cementitious materials. There is limited knowledge about the ‘relation between the compression toughness of cementitious materials and the corresponding AE released’. Specimens of different cementitious mixture compositions were tested as per the ASTM C 39 standard in the laboratory under unconfined uniaxial compression, and simultaneously the released AEs were recorded. Specimens consisted of concrete with 20 mm aggregates, concrete with 12 mm aggregates and mortar. The AE monitoring system with resonant type differential AE sensors were used to record the AE parameters. A detailed analysis revealed that an inverse relation may exist between the AE energy and compression toughness of the cementitious materials. The properties of cementitious materials that influence the relationship between AE energy and compression toughness and the behaviour of AE signals were studied.
‘Characteristics and strength mechanisms of gussasphalt based on the Mohr–Coulomb theory’33 by Min Wang (Chongqing Jiaotong University, Chongqing, China; Chongqing Zhixiang Paving Technology Engineering Co., Ltd, Chongqing, China), Fei Shang (Chongqing Zhixiang Paving Technology Engineering Co. Ltd, Chongqing, China), Deyong Hu (Chongqing Zhixiang Paving Technology Engineering Co. Ltd, Chongqing, China), Zengheng Hao (Chongqing Zhixiang Paving Technology Engineering Co., Ltd, Chongqing, China) and Bo Gao (Chongqing Zhixiang Paving Technology Engineering Co., Ltd, Chongqing, China) is the last paper in this issue of Emerging Materials Research. In order to reveal the properties and strength mechanism of gussasphalt based on the Mohr–Coulomb theory, a uniaxial penetration test and an unconfined compressive strength test were conducted to calculate the characteristic parameters of gussasphalt strength (cohesion, internal friction angle and maximum shear stress). By analyzing the effects of asphalt content and temperature on strength parameters, a study of the strength mechanisms of gussasphalt and the differences between gussasphalt and conventional asphalt mixtures was performed. The results showed that gussasphalt was highly affected by the asphalt content and temperature. The shear resistance strength of gussasphalt was stronger than that of conventional asphalt mixtures at 60°C because of the cohesive force of high-viscosity modified asphalt and high ratio of powder and asphalt. The results of shear strength were consistent with the evaluation results of the penetration and increment indices, and the penetration and increment indices were more suitable for evaluating the stability of gussasphalt at high temperatures and characterizing its strength features.
As the year comes to a close, I join the global scientific community in remembering the distinguished scientists and educators who passed away in 2019; Zhores Alferov (Nobel Prize in Physics 2000 – semiconductor heterostructures); Manfred Eigen (Nobel Prize in Chemistry 1967 – method to time chemical reactions); Roy J. Glauber (Nobel Prize in Physics 2005 – quantum pptics); Charles Kittel (nuclear magnetic moments – Ruderman–Kittel–Kasuya–Yosida interaction, solid state physics); James Livingston (electronic properties of engineering materials); and J. Robert Schrieffer (Nobel Prize in Physics 1972 – Bardeen–Cooper–Schrieffer theory of superconductivity).
The Editor is thankful to the authors, readers, reviewers and the members of the Editorial Board for their contribution, participation and support for the last eight years. In particular, he is very thankful to Mrs Carrie-Ann Baker with whom he had the pleasure of working on the Editorials. He remembers with enormous respect the early days of starting the journal eight years ago with Ms Victoria Rae and Ms Sohini Banerjee at ICE Science, as well as the contributions of his graduate students, post-doctoral fellows and colleagues to several ICE journals.
The Editor joins the Editorial Board and colleagues at ICE in welcoming Dr Iskender Akkurt, Professor of Physics, Süleyman Demirel Üniversity, Isparta-Turkey, as the incoming Editor-in-Chief of Emerging Materials Research. He wishes Professor Akkurt and the journal continued success.
