The celebration of the 500th anniversary of Leonardo da Vinci’s passing away, taking place across the world this year,1–5 is a reminder of the genius’ unique ability to integrate the arts, engineering, science and technology.6,7 This year is also the 150th anniversary of Dmitri Mendeleev’s discovery of the periodic table.8 The periodic table has laid the foundation for the continued evolution in inventions and innovations in materials science, engineering and technology.
Of late, there has been renewed interest in the use of magnetic fields for a variety of applications. These include magnetic nanoparticles in drug delivery systems,9 robotic assembly10 and the magnetic heart.11
The first of the papers in this issue of Emerging Materials Research focuses on ‘Emerging magnesium-based biomaterials for orthopedic implantation’.12 This paper is by Aidin Bordbar-Khiabani (Bioengineering Research Group, Nanotechnology and Advanced Materials Department, Materials and Energy Research Center, Tehran, Iran), Benyamin Yarmand (Bioengineering Research Group, Nanotechnology and Advanced Materials Department, Materials and Energy Research Center, Tehran, Iran) and Masoud Mozafari (Bioengineering Research Group, Nanotechnology and Advanced Materials Department, Materials and Energy Research Center, Tehran, Iran; Department of Tissue Engineering and Regenerative Medicine, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences, Tehran, Iran). Orthopedic implants, such as those made of stainless steel, cobalt (Co)-based alloys and titanium (Ti) alloys, are commonly used to stabilize, protect, improve, replace or regenerate damaged musculoskeletal tissues, both anatomically and functionally, in millions of bone injury patients. The biggest drawback of these metallic biomaterials is their non-degradability in the body environment. Magnesium (Mg) and magnesium-based alloys are a new generation of degradable implant materials that have attracted great attention in the past 10 years. There are several advantages of magnesium-based alloys for orthopedic application over other metallic biomaterials. First, magnesium is an essential element for many biological activities, including enzymatic reactions, the formation of apatite and bone cell adsorption. Second, their mechanical properties, including density, elastic modulus and compressive yield strength, are much closer to those of natural bone and, therefore, they can avoid the stress-shielding effect. Third, magnesium alloys can eliminate the necessity of a second surgery to remove permanent bone implants. Recent results show that alloying of magnesium with aluminum (Al), zinc (Zn), calcium (Ca), zirconium (Zr), yttrium (Y) and rare-earth elements can significantly improve its corrosion resistance and mechanical strength. This paper reviews and compares the mechanical properties, corrosion resistance and biocompatibility of currently researched magnesium-based alloys for use in medical implant applications.
The second paper by Asim Mantarcı (Department of Physics, Faculty of Art and Science, Muş Alparslan University, Muş, Turkey) is on the ‘Role of RF power in growth and characterization of RF magnetron sputtering GaN/glass thin film’.13 Gallium nitride (GaN) thin films were grown on a soda lime glass substrate using radio frequency (RF) magnetron sputtering under various RF powers. The X-ray diffraction (XRD) results confirmed that the thin film had a hexagonal gallium nitride structure with a (100) plane. The structural properties (grain size, strain and stress) of the gallium nitride thin film varied with change in RF power. The reasons for this variation are discussed. The Raman results showed the characteristic E2 (high) optical phonon mode of hexagonal gallium nitride. From scanning electron microscopy (SEM) analysis, agglomerations were observed in some regions of the surface of the thin film. From the atomic force microscopy images, the almost homogeneous, nanostructured and low-roughness surface of the thin film can be observed. The optical bandgap energy of the thin film showed non-linear variation with change in RF power. The reason for this is discussed and the agreement between the experimental measurements is examined. In summary, the morphological, optical and structural properties of the gallium nitride thin film can be controlled by altering the RF power.
The third paper, ‘On improvement of films growth from gas with natural convection and chemical interaction’,14 has been reported by Evgeny L. Pankratov (Nizhny Novgorod State University, Nizhny Novgorod, Russia; Nizhny Novgorod State Technical University, Nizhny Novgorod, Russia) and Elena A. Bulaeva (Nizhny Novgorod State University, Nizhny Novgorod, Russia). In this paper, the authors introduce an analytical approach for the analysis of mass and heat transfer during the growth of film in reactors for gas-phase epitaxy. The epitaxial processes were analyzed with natural convection and possibility of changing the rate of chemical interaction between reagents. As a result of the analysis, the authors obtained conditions on physical and technological parameters for increasing the homogeneity of the grown epitaxial layers. The authors compare growth regimes at normal and low pressure of reagents and gas-carrier. The authors analyzed the dependence of properties of epitaxial layers on the frequency of rotation of substrate holder, the diffusion coefficients of reagents, the kinematic viscosity and the input velocity. The authors compared their calculation results with recently obtained experimental data and obtained a good agreement. All analytical results, without experimental verification, have been verified by numerical simulation using independent approaches.
The fourth paper, ‘Luminescence and energy-transfer mechanism of a praseodymium material’,15 has been reported by Qian Liu (Jiangxi Province Key Laboratory of Coordination Chemistry, Institute of Applied Chemistry, School of Chemistry and Chemical Engineering, Jinggangshan University, Ji’an, China), Wen-Tong Chen (Jiangxi Province Key Laboratory of Coordination Chemistry, Institute of Applied Chemistry, School of Chemistry and Chemical Engineering, Jinggangshan University, Ji’an, China; Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle, Nanchang Hangkong University, Nanchang, China; State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, China), Hui Luo (Health Science Center, Jinggangshan University, Ji’an, China) and Han-Mao Kuang (Jiangxi Province Key Laboratory of Coordination Chemistry, Institute of Applied Chemistry, School of Chemistry and Chemical Engineering, Jinggangshan University, Ji’an, China). In this research, a praseodymium (Pr) material, [Pr(isonicotinic acid)2(H2O)4]nnNO3, was synthesized through a solvothermal reaction and was characterized by single-crystal XRD. It is characterized by a one-dimensional chain-like structure. The [Pr(isonicotinic acid)2(H2O)4]nn+ cationic chains and isolated nitrate (NO3 −) anions are interlinked by hydrogen (H)-bonding interactions, yielding a three-dimensional (3D) supramolecular network. Solid-state photoluminescence measurements revealed that it exhibits a yellow-light emission. The photoluminescence emission bands originate from the characteristic emission of the 4f electron intrashell transitions of 3P1 →3H5 and 3P0 →3H6 of the praseodymium ion (Pr3+). The energy-transfer mechanism is explained by the energy-level diagram of the praseodymium ion and the isonicotinic acid (C6H5NO2) ligand. The praseodymium material has remarkable (Commission Internationale de l’Éclairage) chromaticity coordinates of (0·4251, 0·4646). Therefore, it is a promising color converter for lighting and displays. It is found that isonicotinic acid is not an ideal ligand to excite praseodymium ions – that is, not a good ‘antenna’. The purity of the bulky sample was confirmed by powder XRD. The Fourier transform infrared (FTIR) bands of the title complex were assigned. The title complex is thermally stable at about 90°C.
‘Crystallization of starting powders of LLZO induced by attrition milling’16 is the fifth paper in this issue of Emerging Materials Research. Xiaojuan Lu (Hebei Key Lab of Power Plant Flue Gas Multi-pollutants Control, Department of Environmental Science and Engineering, North China Electric Power University, Baoding, People’s Republic of China; MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing, People’s Republic of China), Rui Wang (Hebei Key Lab of Power Plant Flue Gas Multi-pollutants Control, Department of Environmental Science and Engineering, North China Electric Power University, Baoding, People’s Republic of China; MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing, People’s Republic of China), and Fanli Meng (Hebei Key Lab of Power Plant Flue Gas Multi-pollutants Control, Department of Environmental Science and Engineering, North China Electric Power University, Baoding, People’s Republic of China; MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing, People’s Republic of China) are the coauthors of this paper. Attrition-milling was used to treat the starting powders of lithium-ion conductor, Li6·4Ga0·2La3Zr2O12, which was prepared via solid-state reaction in this study. The milling durations varied from 0 to 96 h and all the milled powders were then thermally treated at 850°C for 4 h. For the powders that had been milled for less than 96 h, only lanthanum zirconate (La2ZrO7) and lithium oxide (Li2O) formed. After milling for 96 h, a cubic Li6·4Ga0·2La3Zr2O12 phase developed in the milled powders, which indicates that appropriate attrition-milling is capable of inducing the formation of a cubic garnet phase at a low temperature of 850°C, which was much lower than the reported values in the literatures (i.e. 1230°C). The total conductivity of the sample made of 96 h milled powders was the highest and its activation energy was the lowest, which indicates that crystallization prior to pelletizing could boost ionic transport in the sintered lithium-ion conductor of Li6·4Ga0·2La3Zr2O12.
Ali Atta (Physics Department, College of Science, Jouf University, Sakaka, Saudi Arabia; Radiation Physics Department, National Center for Radiation Research and Technology, Atomic Energy Authority, Cairo, Egypt), Hassan Mohamed Abdel-Hamid (Diagnostic Radiology Department, Applied Medical Sciences Faculty, Jazan University, Jazan, Saudi Arabia; Radiation Physics Department, National Center for Radiation Research and Technology, Atomic Energy Authority, Cairo, Egypt), Yasser Hassan Ali Fawzy (Radiation Physics Department, National Center for Radiation Research and Technology, Atomic Energy Authority, Cairo, Egypt) and Mohamed Mahmoud El-Okr (Physics Department, Faculty of Science, Al-Azhar University, Cairo, Egypt) report their studies on ‘Characterization and optimization of low-energy broad-beam ion source’.17 In this work, a cold-cathode ion source was modified to produce a broad beam that could be successfully used in a variety of applications. The ion source features gave reliable, long-term, maintenance-free operation. The ion source was surrounded by a magnetic field to produce uniform plasma in limited volume at low gas pressures (10−3 torr). The output ion beam current was up to 700 mA, and the diameter of the cold cathode was broad (∼25 mm). The stainless steel cathode disk and the cylindrical anode were separated by a Teflon flange. The fabrication of the source was simple and a stable discharge medium was obtained by adjusting the operating conditions, such as discharge voltage, magnetic field intensity and argon (Ar) gas pressure. The output ion beam was measured at different acceleration voltages. The ion beam profile is characterized at different magnetic field intensities.
‘Ag nanoparticles with a gradient structure prepared by diffusion method on a biomembrane’18 by Fanggong Cai (Key Laboratory of Fluid and Power Machinery of Ministry of Education, School of Materials Science and Engineering, Xihua University, Chengdu, China), Xi Chen (Key Laboratory of Fluid and Power Machinery of Ministry of Education, School of Materials Science and Engineering, Xihua University, Chengdu, China), Jun Chen (Key Laboratory of Fluid and Power Machinery of Ministry of Education, School of Materials Science and Engineering, Xihua University, Chengdu, China), Qinyong Zhang (Key Laboratory of Fluid and Power Machinery of Ministry of Education, School of Materials Science and Engineering, Xihua University, Chengdu, China) and Yong Zhao (College of Physics and Energy, Fujian Normal University, Fuzhou, China; Key Laboratory of Magnetic Levitation Technologies and Maglev Trains of Ministry of Education, Superconductivity and New Energy R&D Center, Southwest Jiaotong University, Chengdu, China) is the seventh paper in this issue of Emerging Materials Research. Silver (Ag) nanoparticles (NPs) with a gradient structure were successfully immobilized on a natural eggshell membrane (ESM) using a diffusion-controlled method. The ESM had a cross-linked network fibrous structure. The exposed functional group on the surface of the fiber can act as reactive sites for the preparation of metal NPs. Silver ions anchored on fibers of ESM were reduced by borohydride (BH4 −) ions to form silver NPs. The ESM acted as a stabilizer of silver NPs. The synthesized silver NPs@ESM composites were characterized by field-emission SEM, XRD and ultraviolet–visible diffuse reflectance spectroscopy in detail. It was found that silver NPs immobilized on the ESM exhibited a gradient distribution of size and density along the direction perpendicular to the ESM surface. This phenomenon may be attributed to the difference in diffusion velocity between silver and borohydride ions flowing through the ESM. This diffusion-controlled method may be expanded to prepare other metals or compounds with a gradient structure. Additionally, silver NPs@ESM composites can be recycled and exhibited good catalytic activity.
Zhiqiang Liu (School of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang, China), Qi Sun (School of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang, China), Mingqiang Wang (School of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang, China), Tianyu Zhu (School of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang, China) and Feifei Ji (School of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, China) report their ‘Study on the constitutive model of porous titanium alloy’.19 Porous titanium alloys usually need high-speed precision machining before they are put into practical applications. Therefore, it is necessary to study the materials’ mechanical properties under conditions of larger strain rate and higher temperature in order to understand the processing mechanism and determine the appropriate processing parameters. In this study, the mechanical properties of porous titanium alloys of two porosities were firstly investigated by quasi-static compression tests and split Hopkinson pressure bar tests under different conditions. Then, the constitutive models of the flow stress were fitted. From the results of quasi-static compression tests, it was found that the static mechanical properties of porous titanium alloys decreased rapidly with increase in porosity. From the split Hopkinson pressure bar tests, the strain rate sensitivity and temperature sensitivity of porous titanium alloys were determined. The mechanical properties of porous titanium alloys increased with strain rate increase in the range 1000–3000 s−1. The alloys exhibited a temperature-softening effect at 100°C, while they had a temperature-hardening effect at 300°C. The constitutive model could describe the strain-hardening rate of the material appropriately, but the accuracy of the simulated results needed to be improved compared with experimental values.
‘Influence of dielectric flushing conditions during WEDM of TiNiCu shape memory alloys’20 is the ninth paper in this issue of Emerging Materials Research. Abhinaba Roy (Department of Mechanical Engineering, National Institute of Technology Karnataka, Mangalore, India) and Narendranath Sanna Yellappa (Department of Mechanical Engineering, National Institute of Technology Karnataka, Mangalore, India) are the coauthors of this paper. In this study, the effect of dielectric flushing pressure and direction on the machining responses of wire electrodischarge machining (WEDM) was investigated. Vacuum-melted titanium–nickel–copper (TiNiCu) shape memory alloy Ti50Ni25Cu25, homogenized at 500°C, was used as the workpiece material. The flushing pressure was varied from 0·5 to 1·5 kg/cm2 along with pulse-on time, pulse-off time, servo voltage and wire feed rate for Taguchi’s L27 experiments. Cutting rate and kerf width were selected as major WEDM responses, and at the optimal cutting rate, the effect of the flushing direction on surface characteristics was studied. It was found that the surface morphology depended mainly on process parameter values and was greatly affected by the flushing pressure. Also, the amount of molten and resolidified debris on samples, machined with the upward-direction flow, was much higher compared with that for the downward-direction flow.
Sivaraman Arunkumar (Department of Mechanical Engineering, Anjali Ammal Mahalingam Engineering College, Kovilvenni, India), Thangaraju Deepan Bharathi Kannan (Department of Mechanical Engineering, SRM Institute of Science and Technology, Kattankulathur, India) and Paulraj Sathiya (Department of Production Engineering, National Institute of Technology, Tiruchirappalli, India) report their studies on the ‘Optimization, characterization and heat treatment of TIG-welded AA2219-T87 alloy’.21 Among 2000 series aluminum alloys, AA2219 exhibits excellent weldability and good combination of strength and toughness at very low temperatures. This study focused on the optimization of process parameters in tungsten (W) inert gas (TIG) welding of AA2219 using gray relational analysis. The input parameters selected in this work were welding current, voltage and welding speed. Transverse shrinkage, tensile strength and microhardness were measured as performance characteristics. The experiments were conducted in accordance with the L9 orthogonal array. Analysis of variance was used to assess the significance of the input parameters on the weld quality. The properties were correlated with the help of metallurgical characterization. Post-weld heat treatment was performed on the optimized weld, and it was observed that heat treatment of the welded samples resulted in a reduction of transverse shrinkage, improvement in tensile strength and increase in microhardness by 30–40%.
‘Effect of thick slurry and stepped deformation on mechanical properties of AA6061 alloy’22 is the eleventh paper in this issue of Emerging Materials Research. Mayank Agarwal (Department of Mechanical Engineering, Pranveer Singh Institute of Technology, Kanpur, India) and Rajeev Srivastava (Department of Mechanical Engineering, Motilal Nehru National Institute of Technology, Allahabad, India) report their studies on the modification on aluminum-based components with low porosity for applications in aluminum industries. Furthermore, porosity and surface crack problems are the most common problems with the components produced by the casting process alone. However, several modifications have been proposed to minimize these problems. A mounting component of motor brackets was produced with the influence of thick mushy-stage slurry as the primary process and stepped angular deformation (SAD) as the secondary process. SAD provides an advantage of plastic deformation for the thick slurry cast (between 220 and 360°C) and, as a result, a fine microstructure with excellent level density is achieved. The fabricated component was analyzed according to the microstructure pattern along the cross-section, microindentation hardness and wear behavior. The experimental results revealed a dense microstructure, whereas phase analysis confirmed the presence of aluminum oxide (Al2O3), magnesium oxide (MgO), Mg2Si3 and Al3FeO2 intermetallics.
Khushbu Dash (Indian Institute of Technology Madras, Chennai, India) reports on ‘Analysis of high-temperature flexural behaviour of copper–alumina micro- and nanocomposites’.23 Copper (Cu)-based composites were studied for their high-temperature mechanical response. Copper is a high-temperature, high-strength material. When combined with harder reinforcements, it finds application in engine components. High-temperature flexural testing of copper–alumina (Al2O3) micro- and nanocomposites, fabricated by powder metallurgy, was carried out at temperatures of 100 and 250°C. The composition of micro- and nanocomposites varied as 5, 10 and 20 vol.% and 1, 3 and 5 vol.%, respectively. The variation in the flexural strength of the composites at high-temperature testing is reported and compared with the ambient test values here and, subsequently, deformation mechanisms of the composites are discussed. Fractography was performed to predict the mode of failure. The ductile mode of failure in microcomposites is contradictory to quasicleavage in nanocomposites. Nanocomposites show higher flexural strength at 100°C compared to their microcomposite counterparts. Interfacial de-cohesion and particle pull-out are the results of the thermal gradient across the matrix to the reinforcement.
‘Detailed study of dynamic mechanical analysis for nanocomposites’24 by Sunirmal Saha (C.V. Raman College of Engineering, Bhubaneswar, India) and Smrutisikha Bal (Central Instruments Facility, National Institute of Technology, Rourkela, India) is the next paper in this issue. The present study focuses primarily on dynamic mechanical analysis of neat epoxy and multiwalled carbon nanotube (MWNT)/epoxy composites. The results demonstrated a profound increment in storage modulus, loss modulus and damping parameter in the case of nanocomposite samples compared to that of neat epoxy. Furthermore, the coefficient of the C factor, reinforcement efficiency factor, MWNT/epoxy interfacial adhesion factor and degree of entanglement density were evaluated for the MWNT/epoxy nanocomposites. Maximum reinforcement efficiency and the interfacial adhesion factor in nanocomposites with 0·75 wt.% MWNT loading (C0·75) indicated a strong interaction between MWNTs and epoxy. The degree of entanglement factor was found to increase with increasing MWNT contents, while the C factor declined with an increase in MWNT loading. The Cole–Cole plot of all the samples have been analysed, and it was found that the semicircular nature provided by the nanocomposite samples revealed the efficient adhesion between epoxy and MWNTs.
‘Regression modelling on wear behaviour of nano fly ash–aluminium alloy matrix composites’25 is by Srinivasa Prasad Katrenipadu (University College of Engineering, Jawaharlal Nehru Technological University Kakinada, Vizianagaram, India) and Swami Naidu Gurugubelli (University College of Engineering, Jawaharlal Nehru Technological University Kakinada, Vizianagaram, India). The demand for particle-reinforced composites has been increasing progressively. Hence, there is an exigency to use low-cost particles or solid waste particles as a reinforcement phase in order to reduce the cost of the composite. Fly ash is a solid waste consisting of various oxides such as silicon dioxide (SiO2), aluminium oxide and iron (III) oxide (Fe2O3), which contribute to improving wear resistance. Hence, an attempt is made to use nanostructured fly ash as particle reinforcement to produce high-wear-resistant composite materials. Microsized fly ash was converted to nanostructured material by high-energy ball milling, and the crystallite size was reduced to 27 nm after 30 h of milling. The influence of applied load, sliding speed, sliding time and fly ash reinforcement on dry sliding wear of the metal matrix composites is determined. Wear resistance was increased with increase in fly ash fraction, and beyond 10 wt% it was decreased. The increased frictional thrust at higher load resulted in increased debonding and wear rate. The regression model was developed by using the statistical software Minitab R17.1.0 to predict the wear behaviour of the composites under conditions of different normal loads and time periods. The model has been validated and a good agreement was observed.
Venkatachalam Gopalan (School of Mechanical and Building Sciences, Vellore Institute of Technology, Chennai, India), Akshay Ingle (School of Mechanical Engineering, Vellore Institute of Technology, Vellore, India), Giriraj Mannayee (School of Mechanical Engineering, Vellore Institute of Technology, Vellore, India), Vignesh Pragasam (School of Mechanical Engineering, Vellore Institute of Technology, Vellore, India), Aamer Arshad Kazi (School of Mechanical Engineering, Vellore Institute of Technology, Vellore, India) and Rishi Dam (School of Mechanical Engineering, Vellore Institute of Technology, Vellore, India) report their studies on ‘The effect of fiber size on tensile characteristics of natural-fiber-reinforced composites.26 Composite materials are extensively used in a wide range of applications. Natural-fiber-reinforced polymer matrix composites play a dominant role in the field of composites. The primary objective of this research was to investigate the effect of fiber size on the tensile properties of natural-fiber-reinforced polymer composites. The composite was fabricated by solution-casting technology using jute, coir and banana fibers, varying the fiber ratio as 3, 2 and 1% (weight/weight) and varying the fiber length as 10, 5 and 1 mm. Taguchi’s design of experiments was followed to study the mechanical characteristics of samples by recording Young’s modulus, modulus of resilience and yield stress through tensile tests. Analysis of variance was used to determine the effect of distinctive parameters on the tensile properties through main-effects plots, contour plots and regression equations. It was concluded from the results that the epoxy/jute sample showed good tensile characteristics followed by the epoxy/coir sample. The epoxy/jute sample, with 10 mm size and 3% fiber ratio, exhibited the highest Young’s modulus of 3568 MPa.
The next paper in this issue of Emerging Materials Research is on ‘Optimization of drilling parameters of untreated JFRP PU foam sandwich by Taguchi method’.27 This paper is by Sathishkumar Srinivas Rao (Department of Mechanical Engineering, Rajiv Gandhi Institute of Technology, Bangalore, India), Suresh Arakalagudu Venkataramaiah (Department of Mechanical Engineering, B.M.S. Institute of Technology, Bangalore, India) and Nagamadhu Mahadevappa (Department of Mechanical Engineering, Acharya Institute of Technology, Bangalore, India). Many researchers have studied the fabrication of composite materials and their mechanical and thermomechanical properties and applications. In contrast, limited work in the field of machining of composite materials has been reported in the literature. The aim of this work is to optimize the drilling parameters such as speed, feed rate and drill diameter using a high-speed steel (HSS) twist drill and a titanium aluminum nitrate (TAN)-coated carbide twist with a drill angle of 118°. The present experimental work has been carried out using Taguchi design analysis of L27 orthogonal array on jute-fiber-reinforced plastic polyurethane (JFRP PU) foam sandwich composites. A coordinate measuring machine was used to measure the drilled hole diameter to optimize the quality of the drilled hole with the combination of drilling parameters. Minitab 16 was used to investigate the variance (analysis of variance) of the test, which led to determining the significance of each parameter on drilling. The results show that the HSS-twist-drilled hole exhibited a minimum thrust force of 90 N at a 3 mm dia. hole with a feed of 80 mm/min, a speed of 1500 revolutions per minute (rpm) and a torque of 0·14 Nm. In contrast, the TAN-coated-carbide-drilled hole exhibited a thrust force of 88 N at a 3 mm dia. hole with a feed rate of 80 mm/min, a speed of 1500 rpm and a torque of 0·13 Nm. Regression analysis showed that drill diameter has the most significant effect, feed rate has a marginally significant effect and speed does not have any significant effect on minimizing the thrust force for both HSS- and TAN-drilled holes. However, the influence of torque has a marginally smaller variation for TAN compared to that for HSS. Speed and drill diameter have the most significant effect on delamination of both entrance and exit holes using the HSS tool, whereas, for delamination of both the TAN-twist-drilled entrance and exit holes, drill diameter is a more significant factor compared to speed and feed.
The paper ‘Dynamic symmetrical mode III interface crack issues between unalike materials’28 is reported by Nianchun Lu (School of Material Science and Engineering, Shenyang Ligong University, Shenyang, China), Qian Xiang (School of Material Science and Engineering, Shenyang Ligong University, Shenyang, China), Guodong Hao (Department of Chemistry, Mudanjiang Normal College, Mudanjiang, China) and Yuntao Wang (College of Mechanical Engineering, Liaoning Technical University, Fuxin, China). Using the theory of complex variable functions, analytical solutions for dynamic symmetrical mode III interface cracks of two unalike materials were investigated. The issues considered could be very easily translated into Riemann–Hilbert problems according to the methods of self-similar functions. Analytical solutions of the stresses, displacements and dynamic stress intensity factors for the edges of symmetrical mode III interface cracks subjected to moving enhancive loadings, Pt6/x6 and Px7/t6, are obtained. The solutions were obtained by application of the superposition principle. The solutions of discretionally intricate queries could be readily acquired.
Neslihan Gokce (Civil Engineering Department, Center for Sustainability, Middle East Technical University Northern Cyprus Campus, Guzelyurt, North Cyprus), Ulku Yilmazer (Middle East Technical University, Ankara, Turkey) and Serkan Subasi (Department of Civil Engineering, Düzce University, Düzce, Turkey) report a study on the ‘Effect of fiber and resin types on mechanical properties of fiber-reinforced composite pipe’.29 The aim of this study was to evaluate the effects of the types of fiber and resin on the mechanical properties of polyester composite pipes. Orthophthalic, isophthalic and vinyl ester resins were used as the matrix; E-glass, electrical/chemical resistance (ECR)-glass and basalt fibers were used as reinforcement; and 98% silica sand was used as a filler in mixtures. Samples were produced by the centrifugal casting method. Samples cut from the produced pipes were tested to determine stiffness and longitudinal and circumferential tensile strength. It was found that mixtures with orthophthalic resin had the highest stiffness and mixtures with vinyl ester resin had the highest circumferential tensile strength. Samples containing basalt fibers showed 10·8% higher stiffness, the highest longitudinal tensile strength, and 18·8% higher circumferential tensile strength compared with the mixture with E-glass fibers. Samples with ECR-glass fibers showed 20·2% higher longitudinal tensile strength and 5·9% higher circumferential tensile strength. The basalt-reinforced composite pipe had 2·6% less resin than the E-glass-fiber-reinforced pipe. As a result, the mechanical properties of the polyester composite pipes changed with different types of resin and fiber. Vinyl ester resin and basalt fiber-reinforced pipes showed better mechanical performance than orthophthalic resin and E-glass-fiber-reinforced pipes. The fiber–matrix bonding surfaces were investigated by SEM.
The paper ‘Characterization of 3D-printed acrylonitrile-butadiene-styrene with nanoparticles’30 is reported by Fei-Shuo Hung (Department of Leisure, Recreation and Tourism Management, Southern Taiwan University of Science and Technology, Tainan, Taiwan). In addition to being used to produce prototypes rapidly, 3D printing is now being used in the fabrication of functional materials, such as capsule hotels and energy-saving youth apartments, which can be manufactured through 3D printing at a cost advantage. Due to the small internal space and high-density arrangements of capsule hotels, the antistatic, fireproofing and electromagnetic shielding properties of the construction materials are important. Furthermore, an outdoor-type capsule hotel requires significant toughness (impact strength) to cope with unexpected events. In this study, a natural serpentinite was ground into nanopowder and added into fireproof acrylonitrile-butadiene-styrene (ABS) plastic material to 3D-print test specimens. Then, the hardness, tensile strength and impact strength and antistatic and electromagnetic properties of the mineral-particle-reinforced ABS plastic were investigated. The experimental results showed that adding 3 wt.% sintered magnesium silicate–iron nanopowder into the ABS material to form ABS materials (ABSM) resulted in a higher degree of hardness and improved wear resistance, tensile strength and impact strength. After 3D printing, the ABSM molecular bonding characteristics had no significant change (fireproofing was maintained), as examined through FTIR spectroscopy. However, the antistatic force and electromagnetic shielding both increased significantly. Accordingly, ABSM can be used to enhance public safety and health.
Jun Li (School of Civil Engineering and Architecture, Kaifeng University, Henan, China; State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, China), Yong-sheng Ji (State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, China) and Zhishan Xu (State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, China) report their studies on ‘Improvement in the water resistance of MAPC coatings as a function of NaCl concentration’.31 This study focuses on the waterproofing effectiveness of magnesium ammonium phosphate cement (MAPC) coatings at different sodium chloride (NaCl) concentrations (0, 3, 5 and 7%). It includes qualitative analyses and quantitative tests of the effect of sodium chloride on three characteristics: tensile strength, water absorption rate and thickness of coatings. The influence of the changes in the structure and composition of MAPC coatings on their water resistance performance is also analyzed. It is found that 3% sodium chloride concentration could improve the waterproofing effect of MAPC coatings. Another finding shows that tensile strength, water absorption rate and coating thickness increases at the very beginning but these decrease as the sodium chloride content is increased. Moreover, compared with other concentrations, the structure and composition of MAPC coatings, containing 3% sodium chloride, are found to be stable in water. The coatings are bonded to the concrete more tightly, which results in a more compact structure and thus a higher water resistance effect.
‘Effects of fly ash and slag on the properties of magnesium oxysulfate cement’32 is reported by Na Zhang, (Department of Civil Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China), Hongfa Yu, (Department of Civil Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China), Yongshan Tan, (Department of Civil Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China), Nan Wang (Department of Civil Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China), Wanli Bi (School of High Temperature Materials and Magnesium Resource Engineering, University of Science and Technology Liaoning, Anshan, China), Wei Gong (Department of Civil Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China) and Chengyou Wu (School of Civil Engineering, Qinghai University, Xining, China). In this paper, the effects of fly ash and ground granular blast-furnace slag (GGBS) on the setting time, mechanical properties, composition and microstructure of hydration products of magnesium oxysulfate cement (MOSC) are investigated. Various specimens were prepared with different proportions of fly ash or GGBS ranging from 10 to 50% of light-burned magnesia (MgO) weight. The hydration products and microstructure were performed by quantative XRD, SEM and mercury intrusion porosimetry. The results indicated that the incorporation of fly ash or GGBS at low levels (10–30%) can significantly enhance hydration reaction of MOSC by dilution effect to shorten the setting time, and increase the production of 5·1·7 phase and magnesium hydroxide (Mg(OH)2), thus reducing the amount of amorphous phase. Meanwhile, fly ash and GGBS can effectively fill the large pores by packing effect and nucleation effect of the fine particles, reducing the pore diameter of MOSC matrix. Therefore, the incorporation of fly ash or GGBS into MOSC at low levels can significantly optimize the composition of hydration products and compact microstructure, and thus improve the mechanical properties. The contribution of GGBS to early compressive strength of MOSC is more than fly ash, and that of late compressive strength is less than fly ash.
Yaopeng Wu (School of Civil Engineering, Xi’an University of Architecture and Technology, Xi’an, People’s Republic of China; Key Lab of Engineering Structural Safety and Durability, Xi’an University of Architecture and Technology, Xi’an, People’s Republic of China), Kaixuan Gao (School of Civil Engineering, Xi’an University of Architecture and Technology, Xi’an, People’s Republic of China) and Bo Wu (State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou, People’s Republic of China) report their studies on ‘Influence of fly ash on the compressive strength of concrete containing recycled aggregate’.33 It is well known that the mechanical properties of concrete containing recycled aggregate are generally inferior to those of concrete made with natural aggregate. The residual compressive strength of concrete after exposure to high temperature and freeze–thaw cycling was investigated experimentally, and the influence of adding fly ash was examined. Two hundred and twenty-eight 100 mm cubes were compression-tested to failure. The water–binder ratios tested were 0·34, 0·40 and 0·50. The recycled aggregate replacement ratios were 0, 30, 50, 70 and 100%, and the fly ash replacement levels were 0, 30 and 50%. The high-temperature exposure was 3 h at 400°C. Fifteen cycles of freezing to −18°C and thawing to +5°C were applied. Increasing the water/binder ratio or the fly ash or recycled aggregate content generally weakened the concrete. Fly ash in the mix minimized, to some extent, the adverse effect of exposure to high temperature, but the concrete’s freeze–thaw performance was poorer with fly ash in the mix.
The next paper, ‘Investigation of SCC characterizations incorporating supplementary cementitious materials’,34 is by Pedram Alipour (Department of Civil Engineering, Islamic Azad University–UAE Branch, Dubai, UAE), Babak Behforouz (Department of Civil Engineering, Dehaghan Branch, Islamic Azad University, Dehaghan, Iran), Ehsan Mohseni (School of Architecture and Built Environment, University of Newcastle,Newcastle, Australia) and Behnam Zehtab (Young Researchers and Elite Club, Dehaghan Branch, Islamic Azad University, Dehaghan, Iran). An experimental study was performed to assess the effect of metakaolin (MK) as supplementary cementitious material (SCM) and limestone powder (LP) and nano-titanium dioxide (NT) as mineral admixtures on the pore structure, mechanical and durability of self-compacting concrete (SCC). The fresh-state performance was evaluated by slump flow, T50, V-funnel and L-box tests, and hardened-state parameters were analyzed through compressive strength, water absorption, density and electrical resistivity. Furthermore, permeability was analyzed by means of the rapid chloride permeability test and mercury intrusion porosimetry. Using additives resulted in improvement of rheological properties and compressive strength. Additionally, the density and electrical resistivity of SCC mixes containing SCMs and NT were higher than those of the control SCC mixes. Low absorption and permeability values were obtained for the mixes containing 5% NT. The results herein reported suggest that replacement ratios of 15% MK, 10% LP and 5% NT can be considered as optimal from a cost–benefit point of view in terms of fresh- and hardened-state performance. Predictive models for the hardened properties analyzed have been obtained using artificial neural networks, which have been proven to be an appropriate alternative method for predicting the hardened properties of SCC mixes.
‘Reliability analysis of freeze–thaw damage of fiber concrete based on Miner theory’35 by Jiangchuan Li (Engineering Research Center of the Western Ministry of Education for Civil Engineering of Disaster Prevention and Disaster Reduction, Lanzhou University of Technology, Lanzhou, China), Hongxia Qiao (Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province, Lanzhou University of Technology, Lanzhou, China) and Feifei Zhu (Engineering Research Center of the Western Ministry of Education for Civil Engineering of Disaster Prevention and Disaster Reduction, Lanzhou University of Technology, Lanzhou, China) is the last paper in this issue of Emerging Materials Research. In the cold regions of north China, due to special climatic and environmental factors, the degradation of concrete durability caused by freeze–thaw cycles has been a widespread concern among researchers. Freeze–thaw damage is considered the main form of damage that causes concrete durability to deteriorate. Aiming at investigating the influence of freeze–thaw damage on the service life of concrete structures in building structures, a freeze–thaw test was carried out in this work to study the frost resistance of the formed concrete under different fiber blending modes. The durability degradation of fiber concrete under different freeze–thaw cycles was analyzed, and the concrete microstructure was evaluated by SEM. This study found that the frost resistance of single-fiber concrete is not obvious, the frost resistance of integral fiber concrete is greatly improved, and layered hybrid fiber concrete has excellent frost-resistance performance. In addition, based on the fatigue cumulative damage, Miner theory, the reliability calculation model of freeze–thaw damage is established. This can directly reflect the relationship between the reliability of the test sample and the freeze–thaw cycle. The reliability of concrete with different fiber-blending methods gradually decreases to varying degrees. This theory has good applicability in the reliability analysis of concrete freeze–thaw.
The editor is thankful to the authors, readers, reviewers and the members of the Editorial Board for their contribution, participation and support.
