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The effect of copper oxide doping (0.05–1 wt%) on the densification, microstructure evolution and mechanical characteristics of alumina toughened zirconia (ATZ: 80 wt% Y-TZP + 20 wt% Al2O3) ceramic composites was investigated. Green samples were pressureless sintered using a short hold time of 12 min at temperatures varying from 1250 °C to 1500 °C. The incorporation of up to 0.2 wt% copper oxide was beneficial in promoting densification at low sintering temperature and improving the mechanical properties of ATZ without affecting the tetragonal phase stability. It was found that 0.2 wt% copper oxide addition was most efficacious, and the samples could attain a relative density of approximately 92% at 1250 °C, approximately 97% dense at 1350 °C and above 99% dense at 1450–1500 °C. This approach was also accompanied by an improvement in the Vickers hardness (12.7 GPa) and fracture toughness (6.94 MPam1/2) when consolidated at 1450 °C/12 min. In comparison, the undoped composite exhibited relative densities of approximately 80% at 1250 °C, 87% at 1350 °C and approximately 97%–98% at 1450 °C-1500 °C. However, the study also found that higher dopant levels (0.5 wt% and 1 wt%) was not beneficial because the tetragonal zirconia phase was disrupted upon cooling from sintering, resulting in the monoclinic phase formation. In addition, low densification and poor mechanical properties were obtained.

About 20% of people older than forty years old face more bone degenerative diseases. The older population is increasing quite rapidly than before which increases the need for knee or hip implants tremendously. One of the major problems of the current implants is their short lifetime and their impact on the surrounding human tissue. The short life can be attributed to implant wear, loosening, and misalignment, which often cause pain and discomfort to the patient. Functional failure of the implant may be followed by a revision surgery, which is often painful and has a relatively low success rate. Moreover, to avoid unexpected failure and unnoticed deterioration of the implant, it is important to make provision for monitoring implants’ performance. Instrumented implants can provide accurate monitoring of the loosening state of the implant, which can delay the revision surgeries and its consequences. This study provides a comprehensive review of the technological development of instrumented hip implants to monitor the status of the implants. The main requirements for the implants are highlighted by reviewing different aspects of the instrumented hip implant systems. In-vivo studies reported in the literature were summarized. Vibration and Acoustic Emission (AE) measurement based loosening detection were found to be the most common methods for in-vitro studies. A comprehensive review of power supply and communication modules was presented. Despite the advancement in this field, current systems are not yet able to provide effective monitoring of the implant’s status during the daily activities of patients.

In this work, nickel cobaltite (NiCo2O4) nanosheets with a porous structure were fabricated on nickel foam as a working electrode for supercapacitor applications. The nanosheets were fabricated by electrochemical deposition of nickel–cobalt hydroxide on the nickel foam substrate at ambient temperature in a three-electrode cell followed by annealing at 300 °C to transform the coating into a porous NiCo2O4 nanosheet. Field emission scanning electron microscopy and transmission electron microscopy revealed a three-dimensional mesoporous structure, which facilitates ion transport and electronic conduction for fast redox reactions. For one cycle, the NiCo2O4 electrodeposited nickel foam has a high specific capacitance (1734.9 F g−1) at a current density (CD) of 2 A g−1. The electrode capacitance decreased by only approximately 12.7% after 3500 cycles at a CD of 30 A g−1. Moreover, a solid-state asymmetric supercapacitor (ASC) was built utilising the NiCo2O4 nanosheets, carbon nanotubes, and a polyvinyl alcohol-potassium hydroxide gel as the anode, cathode, and solid-state electrolyte, respectively. The ASC displayed great electrochemical properties with a 42.25 W h kg−1 energy density at a power density of 298.79 W kg−1.

In the current research work undertaken, an oxide film was grown by performing hard anodizing process on a pure aluminum layer deposited by PVD magnetron sputtering process on AA7075-T6 alloy. The corresponding tribo-mechanical properties were evaluated and compared with those of the base alloy. The dry sliding wear experiments were carried out to investigate wear resistance of anodized AA7075-T6 against the AISI SS316 counter-body by means of a reciprocating tribo-testing setup. The hardness of AA7075-T6 after the anodizing process exhibited an enhancement of about 1.94 times. Results revealed that the wear of anodized coating was exceptionally less when compared with the substrate. Based on morphology and chemistry changes of worn-out surfaces and debris, it was determined that severe abrasive and oxidative wear was the primary wear mechanism for AA7075-T6. The anodizing process increased the friction coefficient from 0.33 to 0.46 but reduced the wear severity by altering the wear mechanism into mild polishing and abrasion. Anodizing enhanced the wear resistance of AA7075-T6 to about three times, and the wear rate decreased to around 4.3 times.

Hydroxyapatite/graphene oxide/platinum (HA/GO/Pt) nanocomposite was synthesized and electrodeposited on a pure zirconium substrate. The coated zirconium was annealed at 200, 300, 400, and 600°C in vacuum furnace in presence of argon gas. The structure and morphology of the coated samples were characterized. Biocompatibility and wear and corrosion resistances of specimens were examined. The result of corrosion tests shows that the graphene into HA/Pt composites significantly improves their corrosion resistance. The wear tests results of uncoated and coated samples before and after annealing show that coated samples annealed at 300°C had better wear resistance compared with uncoated and coated samples at other temperatures. Furthermore, the biocompatibility test shows that the coatings improved the cell attachment and proliferation compared to the pure zirconium substrate.

In the current study, hydrostatic tube cyclic expansion extrusion (HTCEE) was proposed as a new severe plastic deformation (SPD) method for producing relatively long and large ultrafine-grained (UFG) tubes. In this process, a moving mandrel placed inside the hollow tube sample and also using high fluid pressure are the cores of this technology. To investigate the applicability of the process, commercially pure copper tube was processed and mechanical properties and microstructure were examined. It was shown that the grain size was reduced to below 150 nm after the only a single pass of HTCEE from the initial value of 65 μm. The results demonstrated that both yield and ultimate strengths were increased to 270 MPa and 345 MPa after one pass of HTCEE from the initial value of 75 MPa and 207 MPa respectively while the elongation was reduced to 41% from 55%. It is realized that the remarkable increase in the strength is obtained with a very low ductility loss. Microhardness was also enhanced to about 133 Hv from the initial value of 59 HV after HTCEE process while exhibiting excellent hardness homogeneity. Reducing the total load, increasing the processable tube length and interestingly achieving simultaneous strength and ductility are important advantages of HTCEE. This method seems to be very interesting and very promising for the future industrial application.

We report the synthesis of α-Fe2O3/polyaniline nanotube (PAn NTs) composite as an electrochemical sensor for uric acid (UA) detection. Field emission scanning electron microscopy (FESEM) indicates a hexagonal shape of the α-Fe2O3 while a nanotube morphology of the PAn. Impedance spectroscopy results confirm a significant decrease in the charge transfer resistance of the glassy carbon electrode (GCE) modified with α-Fe2O3/PAn NTs due to the presence of PAn NTs. The results show that the increase in the conductivity of α-Fe2O3 in the presence of PAnNTs could improve the catalytic performance of α-Fe2O3/PAn NTs composite, compared to the pure α-Fe2O3 nanoparticles. From differential pulse voltammetry, a linear working range for the concentration of UA between 0.01 µM and 5 µM, with a LOD of 0.038 µM (S/N = 3) was obtained. The sensitivity of the linear segment is 0.433 μA µM−1. The reliability of the modified electrode towards the detection of UA was investigated in the presence of interfering acids such as ascorbic acid, citric acid and succinic acid.

In this study, a combination of reverse microemulsion and hydrothermal techniques were used to synthesize HA. A hydrothermal method was used to synthesize HA/TiO2/CNT nanocomposite powders. Cold and hot isostatic pressing techniques were used to fabricate tablet-shaped samples. To investigate the biocompatibility and tribo-mechanical properties of HA/TiO2 and HA/TiO2/CNTs, four samples were prepared with different percentages of CNTs, namely, HA/TiO2 (S0), HA/TiO2/CNT (S1.0), HA/TiO2/CNT (S2.0), and HA/TiO2/CNT (S3.0). The microstructure and morphology of the HA/TiO2/CNTs were characterized by transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Hardness test results show that S3.0 displayed the highest surface hardness (285 HV) compared to other samples. The wear rate of HA/TiO2/CNT with the highest CNT content showed a decrease compared with those of the other samples. The results from nanoindentation tests showed that Young’s modulus of the S3.0 sample was 58.1% greater than that of the S0 sample. Furthermore, the human MDA-MB-231 cell line demonstrated good binding to the surface of the samples in the in-vitro biocompatibility evaluation of the HA/TiO2/CNT composites.

In this study, a combination of reverse microemulsion and hydrothermal techniques were used to synthesize HA. A hydrothermal method was used to synthesize HA/TiO2/CNT nanocomposite powders. Cold and hot isostatic pressing techniques were used to fabricate tablet-shaped samples. To investigate the biocompatibility and tribo-mechanical properties of HA/TiO2 and HA/TiO2/CNTs, four samples were prepared with different percentages of CNTs, namely, HA/TiO2 (S0), HA/TiO2/CNT (S1.0), HA/TiO2/CNT (S2.0), and HA/TiO2/CNT (S3.0). The microstructure and morphology of the HA/TiO2/CNTs were characterized by transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Hardness test results show that S3.0 displayed the highest surface hardness (285 HV) compared to other samples. The wear rate of HA/TiO2/CNT with the highest CNT content showed a decrease compared with those of the other samples. The results from nanoindentation tests showed that Young’s modulus of the S3.0 sample was 58.1% greater than that of the S0 sample. Furthermore, the human MDA-MB-231 cell line demonstrated good binding to the surface of the samples in the in-vitro biocompatibility evaluation of the HA/TiO2/CNT composites.

The goal of this study was to examine the tribomechanical properties of hydroxyapatite (HA)/ZnO and HA/ZnO/CNT composite ceramics (carbon nanotubes; with different ratios 0.5 wt%, 1.0 wt%, and 1.5 wt%). The composites were synthesized using the hydrothermal method in an autoclave. The structure and morphology of the composites were analyzed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX) and transmission electron microscope (TEM). The consolidation process was performed by sintering the compounds at 1150 C under an argon gas atmosphere. The effects of ZnO and CNT on the mechanical properties and wear resistance of the HA-nanoparticle-based ceramic composites were investigated using a Vickers hardness tester, nanoindentation, and reciprocating wear tester equipment. The nanohardness and elastic modulus of the sintered samples increased and the friction coefficient of the sintered samples decreased as the fraction of CNTs increased compared to the pure HA and HA/ZnO compounds. Furthermore, the wear loss of HA/ZnO/CNT composites decreased with the increase in the CNT content compared to the HA and HA/ZnO samples. We acknowledge Hanyang University's financial support through the Young Faculty Forum Fund (number 201600000001555 ). Also, some parts of the research were supported by the Fusion Research Program for Green Technologies through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (No. NRF-2015R1A2A2A11027580 ). Scopus

The present study describes the synthesis of HA/rGO/Pd nanocomposite thin film coating on stainless steel 304 using electrodeposition method. In this regard, an attempt is made to investigate the corrosion and biocompatibility behavior of HA/rGO/Pd nanocomposite thin film. Biocompatibility tests were carried out on uncoated, HA-coated, HA/rGO-coated, and HA/rGO/Pd coated SST 304 substrates using the human cell line MDA-MB-231 possessing a green fluorescent protein as a reporter for living cells. The tests revealed that the biocompatibility of the SST 304 surface permitted the most improved cell spreading and proliferation with HA/rGO/Pd nanocomposite coating. Corrosion testing carried out in the synthetic medium confirmed that the corrosion resistance of HA/rGO/Pd coated SST 304 was significantly higher than the uncoated, HA-coated, and HA/rGO-coated SST 304. Furthermore, the HA/rGO/Pd coated SST 304 substrates were annealed at different temperatures including 200, 300, 400, and 600 °C and the corrosion and wear behaviors of annealed samples were investigated. We acknowledge Hanyang University's financial support through the Young Faculty Forum Fund (number 201600000001555 ). Scopus

Layered double hydroxides (LDH) as active electrode materials have become the focus of research in energy storage applications. The manufacturing of excellent electrochemical performance of the LDH electrode is still a challenge. In this paper, the production of CoAl-LDH@Ni(OH)2 is carried out in two steps, including hydrothermal and electrodeposition techniques. The prominent features of this electrode material are shown in the structural and morphological aspects, and the electrochemical properties are investigated by improving the conductivity and cycle stability. The core of this experimental study is to investigate the properties of the materials by depositing different amounts of nickel hydroxide and changing the loading of the active materials. The experimental results show that the specific capacity is 1810.5F·g−1 at 2 A/g current density and the cycle stability remained at 76% at 30 A g−1 for 3000 cycles. Moreover, a solid-state asymmetric supercapacitor with CoAl-LDH@Ni(OH)2 as the positive electrode and multi-walled carbon nanotube coated on the nickel foam as the negative electrode delivers high energy density (16.72 Wh kg−1 at the power density of 350.01 W kg−1). This study indicates the advantages of the design and synthesis of layered double hydroxides, a composite with excellent electrochemical properties that has potential applications in energy storage.

The electrochemical nitrogen reduction reaction (NRR) over single-atom catalysts (SACs) anchored on Mo vacancies of Mo 2CO 2 MXene nanosheets under ambient conditions suffers from poor selectivity, low yield, and low Faradaic efficiency because of their sluggish kinetics and the competing hydrogen evolution reaction. Herein, density functional theory calculations are performed to improve the understanding of the selectivity and yielding of ammonia through NRR over various isolated SACs, that is, from Sc to Au, anchored on the Mo vacancy of the Mo 2CO 2 MXene nanosheet (denoted as MO 2CO 2-M SA). The potential-determining step of the NRR shows that eight candidates (i.e., Y, Zr, Nb, Hf, Ta, W, Re, and Os) confined on the defective Mo 2CO 2 layer could promote the electroreduction from N 2 to NH 3. Among these, Mo 2CO 2-Y SA presented the lowest reported reaction Presents the lowest reported reaction energy barrier (0.08 eV) through the distal pathway and high selectivity to NRR compared with the previously synthesized Mo 2CO 2-Ru SA with a relatively high energy barrier (0.65 eV) and poor selectivity. In addition, the formation energy of Mo 2CO 2-Y SA is more negative than that of the Mo 2CO 2-Ru SA catalyst, suggesting that the experimental preparation of the Mo 2CO 2-Y SA catalyst is highly feasible. This work lays a solid foundation for improving the rational design of MXene-based systems as efficient electrocatalysts for the synthesis of ammonia.

This study examines the influence of thin layer coatings of CrAlTiN and CrN/NbN, deposited via physical vapor, on the biocompatibility, mechanical, tribological, and corrosion properties of stainless steel 304. The microstructure and morphology of the thin CrAlTiN and CrN/NbN layers were characterized by scanning electron microscopy (SEM), EDX, and X-ray diffraction. The pin on disc wear test was performed on bare and metal-nitride coated SST 304 under a 15 N load at 60 rpm and showed that the wear rates of the thin CrAlTiN and CrN/NbN film coatings were lower than the bare substrate wear ratio. The coefficients of friction (COFs) attained were 0.64, 0.5, and 0.55 for the bare substrate, CrN/NbN coating, and CrAlTiN coating, respectively. Nano indentation tests were also performed on CrAlTiN-coated and CrN/NbN-coated SST 304. The nanohardnesses and Young's moduli of the coated substrates were 28 GPa and 390 GPa (CrN/NbN-coated) and 33 GPa and 450 GPa (CrA1TiN-coated), respectively. For comparison, the nanohardness and Young's modulus of the uncoated substrate were 4.8 GPa and 185 GPa, respectively. Corrosion tests were conducted, and the behaviors of the bare and metal nitride-deposited substrates were studied in CaCl2 for seven days. The corrosion Tafel test results showed that the metal-nitride coatings offer proper corrosion resistance and can protect the substrate against penetration of CaCl2 electrolyte. The CrN/NbN-coated substrates showed better corrosion resistance compared to the CrAlTiN-coated ones. In evaluating the biocompatibility of the CrAlTiN and CrN/NbN coatings, the human cell line MDA-MB-231 was found to attach and proliferate well on the surfaces of the two coatings.

Efficient and excellent non-enzymatic electrochemical sensors for H 2 O 2 detection, consisting of reduced graphene oxide (rGO) and palladium (Pd) nanowalls with different rGO loadings, were electrochemically deposited in a layer-by-layer fashion onto indium tin oxide (ITO) glass. The structure and morphology of the as-fabricated non-enzymatic sensor electrodes were confirmed by X-ray diffraction, field-emission electron microscopy, and Raman spectroscopy. The effective combination of Pd nanowalls and rGO nanosheets provides many benefits in electrochemical detection, such as charge carriers with rapid transport and a greater number of sensing sites; thus, the Pd-rGO-modified ITO electrode with 0.5 mg ml −1 rGO displays the best electrochemical sensitivity with regard to H 2 O 2 detection. The responses to H 2 O 2 differ linearly with the concentration (from 100 μM to 12 mM). These devices showed a lowest detection limit of 0.24 μM, excellent stability, and high reproducibility. The enhanced sensitivity of the sensor electrode is due to the synergistic effect between the electrocatalytic activity of the Pd nanowalls and the high conductivity and large surface area of rGO.

Water-soluble Prussian blue nanoparticles (PB NPs) supported on nitrogen-doped graphene (N-graphene) with high dispersion was fabricated for high performance energy storage hybrid electrodes. An efficient loading of the PB NPs and nitrogen doping of graphene were achieved. The structure and morphology of the composite was determined by X-ray diffraction, transmission electron microscopy, Raman spectrometry and X-ray photoelectron spectrometry. The energy storage performance was assessed by cyclic voltammetry and galvanostatic charge/discharge techniques. The nanocomposite was fabricated as a hybrid battery-supercapacitor electrode and exhibited excellent performance with the highest capacity of 660 C g −1 at 1 A g −1 , which was higher than pure PB NPs and N-graphene electrodes. Moreover, the synergistic effect of N-graphene and the PB NPs prevented the N-graphene from shrinking and swelling and increased the cycle stability to 84.7% retention after 1500 cycles at 6 A g −1 , compared to the pure N-graphene.

Flower-like NiO (F-NiO) and ball-flower-like NiO/Ag (BF-NiO–Ag) were synthesized in the presence of L-glutamine as an electrochemical sensor for lead(II) detection. The structure and morphology of the F-NiO and BF-NiO–Ag were studied by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Energy dispersive X-ray confirmed the presence of Ag on the surface of the BF-NiO–Ag. The results confirmed that Ag+ was reduced to Ag metal in the presence of L-glutamine. The FESEM images confirmed the effect of L-glutamine and Ag on the morphology and the available surface area. Electrochemical impedance spectroscopy results confirmed the effect of the loaded Ag on the conductivity of the BF-NiO–Ag. Differential pulse voltammetry results gave a linear working range for the concentration of lead(II) between 1.5 and 10 nM with a LOD of 0.06 nM (S/N = 3). The sensitivity of this linear segment is 0.3 μA nM−1. The average recoveries, recovery percentage and relative standard deviation obtained from four determinations (n = 4) confirmed the feasibility of the proposed method for the quantitative detection of certain concentration ranges of Pb2+.

Developments in the aquaculture industry have increased the production of shellfish. However, the lack of a proper recycling method for discarded shells is resulting in marine environmental pollution. For the sustainable management of shellfish byproducts, pulverized oyster and scallop shell powder were used as major raw materials in cement-clinker production, replacing 100 wt% of limestone. The characteristics of the synthesized cement clinkers and hydrated cement pastes were analyzed via scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), strength tests, thermogravimetric analysis, isothermal calorimetry, and X-ray diffraction (XRD) with Rietveld refinement. The analysis results for the synthesized oyster-shell cement (OSC) and scallop-shell cement (SSC) were compared with those of limestone-based cement and commercial ordinary Portland cement (OPC). Anhydrous cement-clinker phases such as C3S, C2S, C3A, and C4AF were successfully formed in all the synthesized clinkers, similar to the OPC. Additionally, the OSC and SSC yielded the same main hydration products (C–S–H and portlandite) as the OPC, and the morphology of the hydration products in the OSC and SSC was very similar to that in the OPC. The results indicate that oyster and scallop shells are suitable substitutes for limestone as a raw material for cement.

In this study, the effect of microstructural evolution of TiO2 nanotubular arrays on wettability and optical properties was investigated. Pure titanium was deposited on silica glass by PVD magnetron sputtering technique. The Ti coated substrates were anodized in an electrolyte containing NH4F/glycerol. The structures of the ordered anodic TiO2 nanotubes (ATNs) as long as 175 nm were studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The result shows a sharp peak in the optical absorbance spectra around the band gap energy, 3.49–3.42 eV for annealed and non-annealed respectively. The thermal process induced growth of the grain size, which influence on the density of particles and the index of refraction. Furthermore, the wettability tests' result displays that the contact angle of intact substrate (θ = 74.7°) was decreased to 31.4° and 17.4° after anodization for amorphous and heat treated (450 °C) ANTs coated substrate, respectively.

Zirconia (ZrO2) nanotube arrays were fabricated by anodizing pure zirconium (Zr) coated Ti–6Al–7Nb in fluoride/glycerol electrolyte at a constant potential of 60 V for different times. Zr was deposited atop Ti–6Al–7Nb via a physical vapor deposition magnetron sputtering (PVDMS) technique. Structural investigations of coating were performed utilizing X-ray diffraction (XRD) analysis. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to characterize the morphology and microstructure of coatings. Unannealed ZrO2 nanotube arrays were amorphous. Monoclinic and tetragonal ZrO2 appeared when the coated substrates were heat treated at 450 °C and 650 °C, while monoclinic ZrO2 was found at 850 °C and 900 °C. Mechanical properties, including nanohardness and modulus of elasticity, were evaluated at different annealing temperatures using a nanoindentation test. The nanoindentation results show that the nanohardness and modulus of elasticity for Ti–6AL–7Nb increased by annealing ZrO2 coated substrate at 450 °C. The nanohardness and modulus of elasticity for coated substrate decreased with annealing temperatures of 650, 850, and 900 °C. At an annealing temperature of 900 °C, cracks in the ZrO2 thin film coating occurred. The highest nanohardness and elastic modulus values of 6.34 and 218 GPa were achieved at an annealing temperature of 450 °C.

Diffuse solar radiation is a fundamental parameter highly required in several solar energy applications. Despite its significance, diffuse solar radiation is not measured in many locations around the world due to technical and fiscal limitations. On this account, determining the amount of diffuse radiation alternatively based upon precise and reliable estimating methods is indeed essential. In this paper, a coupled model is developed for estimating daily horizontal diffuse solar radiation by integrating the support vector machine (SVM) with wavelet transform (WT) algorithm. To test the validity of the coupled SVM–WT method, daily measured global and diffuse solar radiation data sets for city of Kerman situated in a sunny part of Iran are utilized. For the developed SVM–WT model, diffuse fraction (cloudiness index) is correlated with clearness index as the only input parameter. The suitability of SVM–WT is evaluated against radial basis function SVM (SVM–RBF), artificial neural network (ANN) and a 3rd degree empirical model established for this study. It is found that the estimated diffuse solar radiation values by the SVM–WT model are in favourable agreements with measured data. According to the conducted statistical analysis, the obtained mean absolute bias error, root mean square error and correlation coefficient are 0.5757 MJ/m 2 , 0.6940 MJ/m 2 and 0.9631, respectively. While for the SVM–RBF ranked next the attained values are 1.0877 MJ/m 2 , 1.2583 MJ/m 2 and 0.8599, respectively. In fact, the study results indicate that SVM–WT is an efficient method which enjoys much higher precision than other models, especially the 3rd degree empirical model.

Highly oriented arrays of TiO2–Nb2O5–Al2O3 mixed oxide nanotubes were fabricated via physical vapor deposition (PVD) to sputter a niobium film on Ti–6Al–7Nb (Ti67) and subsequent electrochemical anodization in ethylene glycol/ammonium fluoride/ionized water (5 wt%) electrolyte. Parametric optimization for higher adhesion strength and microhardness was conducted using Taguchi experimental design methodology. The highest adhesion strength and microhardness of the as-deposited Nb film was achieved at 350 W DC power, 20 sccm argon flow rate and a 90 V bias voltage. The microstructural features were found to depend on the anodization time and subsequent thermal treatment. The anodization of Nb/Ti67 for 4 h resulted in a homogeneous ordering of the mixed oxide nanotubes. Upon annealing at a low heating and cooling rate of 1 °C at 440 °C for 30 min in an atmospheric furnace, a highly ordered nanotube array contained a mixture of TiO2, Al2O3 and Nb2O5 phases, wherein the composition of the oxide nanotubes was strongly influenced by the chemistry of the phases present in Ti67. The results of in vitro bioactivity indicated that the crystallized mixed oxide nanotubes could induce a quick apatite formation after immersion in simulated body fluid (SBF). The above findings may contribute to the development of novel nanostructured materials for metallic orthopedic implants.

Wind energy poses challenges such as the reduction of the wind speed due to wake effect by other turbines. To increase wind farm efficiency, analyzing the parameters which have influence on the wake effect is very important. In this study clustering methods were applied on the wake effects in wind warm to separate district levels of the wake effects. To capture the patterns of the wake effects the PCA (principal component analysis) was applied. Afterwards, cluster analysis was used to analyze the clusters. FCM (Fuzzy c-means), K-mean, and K-medoids were used as the clustering algorithms. The main goal was to segment the wake effect levels in the wind farms. Ten different wake effect clusters were observed according to results. In other words the wake effect has 10 levels of influence on the wind farm energy production. Results show that the K-medoids method was more accurate than FCM and K-mean approach. K-medoid RMSE (root means square error) was 0.240 while the FCM and K-mean RMSEs were 0.320 and 1.509 respectively. The results can be used for wake effect levels segmentation in wind farms.

Ti-6Al-4V is widely used for arthroprostheses, particularly in metal-on-metal (MoM) hip joints. In spite of the suitable wear and corrosion resistance, metallic wear particles and metal ion release occur on a large timescale. In addition, metal ion levels in patients' blood and urine often reportedly increase according to clinical data. Neurological disease, inflammatory response and cell necrosis can potentially develop consequently. The aim of this research is to fabricate a thin, hard film coating on Ti-6Al-4V in order to improve mechanical properties, such as the adhesion strength, surface hardness and surface roughness of Ti-6Al-4V, which should lead to substrate biocompatibility mitigation through reduced debris production, ion release and cytotoxicity. Physical vapor deposition (PVD) magnetron sputtering treatment is applied to obtain an enriched tantalum oxide (Ta-O) thin film coating. In this regard, pure tantalum (Ta) as a biocompatible metal is deposited atop Ti-6Al-4V substrate in the presence of oxygen gas and different parameter conditions, including substrate temperature, argon flow rate, oxygen flow rate and DC power. The results indicate that the surface hardness and surface roughness of the Ta-O coated substrate significantly improve compared to uncoated substrate. The adhesion strength between Ta-O thin film and substrate is examined using a micro scratch tester, and maximum adhesion of 2500 mN is achieved.

Various severe plastic deformation (SPD) processes have been developed to produce metal tubes with ultrafine grain (UFG) structures. However, most techniques are complex and limited to working with components that are short in length to avoid tube failure during SPD processes. To overcome such limitations, this study suggests the use of an equal channel angular pressing (ECAP) process for the production of tubular aluminum alloy 6061. To mitigate plastic instability effects such as tube buckling and fracture during processing, hydraulic oil was used to fill the tube cavity. Finite element analysis (FEA) using Abaqus/Explicit 6.13 was carried out to examine the feasibility of the proposed method and deformation mechanism during ECAP. A series of investigations were performed, including: microstructure analysis, torsion, and micro hardness tests to evaluate the effects of tube-ECAP treatment. Test results indicated that the resultant 60% reduction in grain size led to significant mechanical property improvements including yield shear strength, ultimate shear strength, and microhardness. However, the ductility of the material decreased slightly for the ECAP-treated samples. To resolve this issue, a heat treatment process using the T6 method was performed, leading to a notable ductility enhancement in addition to further improvements in shear strength and microhardness. the Ministry of Higher Education, Malaysia, with high impact research (HIR) grant numbers HIR-MOHE-16001-D000001. Human Resources Program in Energy Technology of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20154030200900).

An unbalanced physical vapor deposition (PVD) magnetron sputtering technique was used to deposit a titanium/titanium nitride/hydroxyapatite (Ti/TiN/HA) multilayer coating on Ti–6Al–4V. The Taguchi optimization method with an orthogonal array of L9 was utilized to determine the optimal conditions of coating for better surface integrity. The effects of the temperature, DC bias voltage, nitrogen flow rate, and DC power on the adhesion strength, coefficient of friction, surface hardness, and surface roughness were investigated. In achieving the optimized coating parameters, the signal to noise (S/N) response analysis method was implemented. Confirmation tests were carried out to demonstrate the improvement using the best combination of parameters obtained from the optimization process. The surface hardness of the Ti/TiN coated and uncoated specimens was enhanced by 14% and 48%, respectively. The adhesion strength of the coating to the substrate, coefficient of friction, and surface roughness were improved by 5.1%, 43%, and 10.52%, respectively. Finally, hydroxyapatite was successfully deposited atop Ti/TiN coated Ti–6Al–4V using a PVD sputtering technique to improve the biocompatibility of the substrate. The presence of Ti/TiN interfacial thin layers between the HA layer and substrate enhanced the adhesion strength of the HA coating on the substrate by 44.57% compared to the HA-coated substrate without the interfacial layers.

In this study, Titanium alloy (Ti–6Al–4V) substrate was coated with 4 μm tantalum oxide (Ta–O) ceramic layers using physical vapor deposition magnetron sputtering (PVDMS). The coated sample surfaces were heat treated at 300, 400 and 500 °C in a box furnace to enhance the adhesion strength. Field Emission Scanning Electron Microscopy (FESEM) together with energy dispersive X-ray spectroscopy (EDX), X-ray diffraction analysis (XRD) and Vickers microhardness testing was used to distinguish the Ta–O coatings in terms of morphology, surface elements, structure and surface hardness, and to compare untreated and hardened sample conditions. The effect of heat treatment on adhesion was tested with scratch test equipment. The coating thin film adhesion strength improved from 713 to 1907 mN throughout the thermal surface treatment duration. The effect of thermal treatment on surface hardness was examined, and evidently, the surface hardness increased from 446.24 to 535.5 HV on account of the surface treatment at 500 °C.

Joining cylindrical and bar-shaped components manufactured from dissimilar materials is frequently required in various industrial applications. The current study focuses on developing equal channel angular pressing (ECAP) as a severe plastic deformation process for solid state joining of tubular aluminium alloy 6061 components and SAE 1018 steel rods. The influence of using a 0.1 mm thick 60Ag–30Cu–10Sn interlayer in addition to annealing at 220, 320, 420 and 520 °C for 60 min is investigated as well. Finite element analysis (FEA) is performed in order to evaluate the deformation behaviour of the workpieces during the ECAP joining process. XRD and EDX analyses as well as nanoindentation and shear tests are carried out to evaluate the joints' characteristics. The FEA outcomes show remarkable accumulation of equivalent plastic strain with relatively low strain inhomogeneity. Moreover, the experimental results indicate that with increasing annealing temperature, joint strength exhibits improvement as well. It is also revealed that the application of an interlayer at any specific annealing temperature leads to achieving higher shear strength values. According to the results, shear strength of up to 32 MPa is feasible by having an interlayer and with subsequent annealing at 520 °C. Keywords: Dissimilar metal joining, Equal channel angular pressing, Aluminium alloy 6061, Steel SAE 1018, Ag–Cu–Sn Interlayer, Annealing

A novel severe plastic deformation method entitled cyclic flaring and sinking (CFS) is presented for producing ultrafine-grained thin-walled cylindrical tubes. CFS process includes two different flaring and sinking half-cycles. At flaring half cycle, the flaring punch with two stepped regions is pressed into the tube. Shear and normal tensile strains are applied as a result of the existence of shear zones and increase in the tube diameter. In the second half cycle, the tube is pressed to the sinking die that applies same shear strains and normal compression strain. The results indicate that the yield and ultimate strengths of the CFS processed Al tube significantly increases to 155, and 168 MPa, respectively from the initial values of 35, and 80 MPa. The elongation to failure decreases to about 15 % after three cycles from the initial value of 56 %. In addition, the hardness increases to ~38 Hv after ten cycles of CFS from ~23 Hv.

In this study, the microstructural features and corrosion behavior of self-organized TiO 2 nanotubular arrays on Ti–6Al–7Nb (Ti67) produced from different electrolytes, namely glycerol (G) and ethylene glycol (EG) were investigated. From the XRD data, the TiO 2 characteristic peaks were absent after the anodization, but TiO 2 crystallization occurred during annealing at 600 °C for 2 h, and consequently, led to the formation of highly crystalline TiO 2 (anatase). The corrosion resistance of the anodized samples was higher than the substrate after 30 min of immersion in phosphate buffer saline (PBS) solution. In fact, the surface modification of Ti67 with a nanotubular TiO 2 layer was effective in enhancing the passive layer resistance and reducing the corrosion current density ( I corr ) compared to the substrate. Due to the decrease in I corr , the corrosion rate decreased and reached a minimum of 6.38×10 −2 mm y −1 for the nanotubes (anodized sample in G) annealed at 600 °C for 2 h. These results show that the corrosion behavior of the nanotubular structure was affected by the type of electrolyte and subsequent thermal treatment.

Nanosize Zr-doped carbonated chlorapatite (n-ZCCA) was developed as a novel bioceramic by a ball milling process. Results showed that the microstructural characteristics of the product were affected significantly by the degree of substitution and subsequent annealing at 800 °C for 1 h. In the absence of zirconium, mechanical activation for 3 h resulted in the formation of carbonated hydroxyapatite (CHA). With the addition of various amounts of zirconium, nanosize Zr-doped carbonated chlorhydroxyapatite (n-ZCCHA) and n-ZCCA were formed as a result of progressive mechanochemical reactions. From the HR-TEM images, the preferential substitution of Zr onto the ac or bc chlorapatite crystal facets (rich in calcium ions) led to a c-axis oriented crystal growth of crystalline nanoneedles with an average size of around 40–60 nm in length and 10–20 nm in width. UM High Impact Research Grant UM-MOHE UM.C/625/1/HIR/MOHE/ENG/44 (Regenerative Biomechanics of Human Body) from the Ministry of Higher Education Malaysia and University of Malaya Grant number RP021C-13AET

The present study describes the anodic growth of TiO2 nanotube thin layer on stainless steel 304 in ethylene glycol/water/ammonium fluoride electrolyte. In this regard, pure titanium was coated on stainless steel 304 substrates by a physical vapor deposition magnetron sputtering (PVDMS) technique. The adhesion strength of the coating to the substrate was investigated. TiO2 nanotubes were generated on the top of the Ti coated substrates by means of anodization technique at a 25 V potential and times of 20, 40, and 60 min in an ammonium fluoride electrolyte solution. The anodized Ti-coated samples were heat-treated at 280 °C, 430 °C and 620 °C in a N2 gas furnace to attain diverse phases. The mechanical properties of TiO2 nanotube arrays coated substrate were explored by a nanoindentation apparatus. The results illustrate that the Young׳s modulus and surface hardness of TiO2 nanotube-coated substrates are increased with increasing annealing temperatures (280 °C, 430 °C and 620 °C). The scratch test results show that heat treatment at 430 °C and 620 °C can improve the adhesion strength of Ti/TiO2 coated samples by up to 2860 and 3140 mN, respectively. UMRG Grant, NC2/RC/261/1/1/RP021C-13AET from the University of Malaya, Malaysia

In the present study, a self-organized nanotube TiO2 layer on Ti–6Al–7Nb was fabricated. The influence of acidic electrolytes including glycerol (G) and ethylene glycol (EG) on the anodization, microstructural features and surface wettability was explored. The phase compositions and morphological characteristics were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. According to the results, due to the intrinsic amorphous feature of ceramic oxide, the characteristic TiO2 peaks were not detected in the XRD profiles. After annealing in normal atmosphere at 600 °C for 2 h, TiO2 crystallized and consequently, nanotubular TiO2 arrays containing anatase and rutile phases formed. From a microstructural point of view, the average length and diameter of the nanotube array ranged from 2.23 to 4.22 μm and 160 to 170 nm, respectively. Besides, the type of acidic electrolyte and subsequent annealing noticeably affected the surface wettability of the products. University of Malaya, grant Nos.: UM TNC2/RC/261/1/1/RP021C-13AET and HIR UM.C/HIR/MOHE/ENG/27

In this study, the mechanical properties, including surface hardness, tensile strength, fatigue, and fretting fatigue behavior of AA 6063 processed by equal channel angular pressing as the most efficient severe shear plastic deformation (SPD) technique, were investigated. Following the SPD process, samples were subjected to heat treatment (HT), hard anodizing (HA), and a combination of HT and HA. Rotating–bending fretting fatigue tests were performed to explore the samples’ response to the fretting condition. From the experimental fatigue and fretting fatigue tests, it was apparent that the SPD treatment had a positive effect on enhancing the fatigue and fretting fatigue lives of the samples at low and high-cyclic loads compared with the HT technique by 78 and 67 pct, and 131 and 154 pct respectively. The results also indicate that the SPD + HT technique significantly increased the fatigue and fretting fatigue lives of the samples at high and low cycles by 15.56 and 8.33 pct, and 14.4 and 5.1 pct respectively, compared with the SPD method. HA of AA6063 increased the fatigue and fretting fatigue lives of SPD + HT-processed samples at low cycle by 15.5 and 18.4 pct respectively; however, at high cycle, HA had reverse effects, whereby the fatigue and fretting fatigue lives of SPD + HT-processed samples decreased by 16.7 and 30 pct, respectively. Ministry of Higher Education, Malaysia, with high impact research (HIR) Grant Numbers HIRMOHE- 16001-D000001; and UM.TNC2/RC/261/1/1/RP021-13AET (UMRG), RP021C-13AET

Binary (Ti/TiN and Cr/CrN) and ternary (TiCr/TiCrN) thin films were deposited on AL7075-T6 by magnetron sputtering. Microhardness, adhesion strength and pin-on-plate wear tests were performed to investigate coating performance. Field emission scanning electron microscope integrated with focused ion beam milling and energy dispersive X-ray spectroscopy was employed for microstructural and chemical characterizations. The tribo-mechanical test results revealed that Cr/CrN promoted up to 5 times greater hardness, Ti/TiN showed the highest scratch resistance and up to 8 times reduced wear, while TiCr/TiCrN favored the least friction and surface roughness. Furthermore, the excellent tribological properties of coatings correlated with their superior adhesion to AL7075-T6.

Carbonated fluorapatite–titania composite nanopowders were successfully synthesized by a facile room-temperature mechanochemical process. Mixtures of calcium carbonate, phosphorous pentoxide and calcium fluoride with different amounts of titania (0, 3, 6, and 9 wt%) were milled using a high-energy planetary ball mill for 10 h. Results showed that a gradual transformation occurred during the mechanical activation. In the absence of titania, nanosized B-type carbonated fluorapatite with crystallite size of 6973 nm was formed. In the presence of 3–9 wt% titania, mechanochemical reaction caused the formation of carbonated fluorapatite–titania composite nanopowders. The crystallite size declined drastically and reached 1271 nm when the titania content was increased to 9 wt%. In contrast, the lattice strain and volume fraction of grain boundary increased notably from 0.004570.0002 to 0.008470.0004 and from 470.21% to 2171.07%, respectively, while the titania content rose from 0 to 9 wt%. From the data obtained, the unit cell volume of carbonated fluorapatite was influenced strongly by the titania content, whereby the sharp increase in unit cell volume from 524.42 to 530.40 A 3 was due to the increase of the titania content from 0 to 9 wt%, respectively. Microscopic observations indicated that the product had a cluster-like structure with an average particle size of about 75 nm. & 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

In this study, the fabrication and characterization of Al/Al2O3 nanotubular arrays on Ti–6Al–4V substrate were carried out. To this end, aluminum thin films were deposited as a first coating layer by direct current (DC) magnetron sputtering with the coating conditions of 300 W, 150 °C and 75 V substrate bias voltage. Al2O3 nanotube array as a second layer was grown on the Al layer by electrochemical anodisation at the constant potential of 20 V within different time periods in an electrolyte solution. For annealing the coated substrates, plasma treatment (PT) technique was utilized under various conditions to get the best adhesion strength of coating to the substrate. To characterize the coating layers, micro scratch test, Vickers hardness and field emission of scanning electron microscopy (FESEM) were used. Results show that after the deposition of pure aluminum on the substrate the scratch length, load and failure point were 794.37 μm, 1100 mN and 411.43 μm, respectively. After PT, the best adhesion strength (2038 mN) was obtained at RF power of 60 W. With the increase of the RF power up to 80 W, a reduction in adhesion strength was observed (1525.22 mN). From the microstructural point of view, a homogenous porous structure with an average pore size of 40–60 nm was formed after the anodisation for 10–45 min. During PT, the porous structure was converted to dense alumina layer when the RF power rose from 40 to 80 W. This led to an increase in hardness value from 2.7 to 3.4 GPa. Based on the obtained data, the RF power of 60 W was the optimum condition for plasma treatment of Al/Al2O3 nanotubular arrays on Ti–6Al–4V substrate.

Due to the increasing demand on ethanol gas sensors for several applications such as automation transportation or environmental monitoring the need for more sensitive and reliable sensors with an on spot response time is required Indirect sensing invasive bulky time initializing and low reliability in strip tests are some drawbacks of ethanol sensing measurements at the present To overcome these leakages there is focused on modelling and simulation of a proposed ethanol sensor based on surface acoustic wave technique using finite element method

Battery-type electrodes of three-dimensional (3D) hierarchical cobalt hydroxide carbonate arrays on Ni foam were fabricated using a hydrothermal method for use in supercapacitors. X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy were used to characterize their structures and morphologies. The cobalt hydroxide carbonate synthesized with 10 h reaction time showed the highest specific capacitance (1381 F g1 at a current density of 2 A g1) and excellent cycling stability (92% capacitance retention after 5000 cycles). Moreover, its capacitance increased by 33% at 2 A g1 and by 10% at 20 A g1 after 5000 charge-discharge cycles. This cobalt hydroxide carbonate composite is a promising candidate for electrochemical energy-related applications. This work was performed at the Thin Film Coating Laboratory, Engineering Center, Hanyang University. The work was supported fnancially by Hanyang University, Young Faculty Forum and by a grant (16TBIP-C111710-01) from the Technology Innovation Program funded by the Ministry of Land, Infrastructure and Transport of the Korean Government. Scopus

article i nfo Article history: Received 11 February 2014 Accepted in revised form 16 July 2014 Available online xxxx Herein, the fretting fatigue behavior of zirconium nanotube arrays on the surface of Ti-6Al-4V is studied. Initially, a thin film of pure zirconium (Zr) was deposited onto a Ti-6Al-4V substrate using physical vapor deposition (PVD) magnetron sputtering for the primary layer at varying DC power, temperature and substrate bias voltage values. To obtain higher adhesion strength, the Taguchi optimization method was used to estimate the optimum coating pa- rameters, while a Pareto ANOVA was employed to determine the significant parameters. The strongest coating ad- hesion, as determined by a scratch force test, was achieved at 300 W DC power, 200 °C and a 75 V bias voltage. Consequently, nanotubes were produced via Zr anodization in an NH4F electrolyte solution (95 glycerol:5 water) at different times and at a constant potential of 60 V (second layer). The fretting fatigue behavior of anod- ized samples annealed at 400 °C and 800 °C was investigated. The results indicate that the fretting fatigue life of the ZrO2 nanotube-coated samples was significantly improved at low and high cyclic fatigue at an annealing temperature of 400 °C compared to the uncoated samples.

The probabilistic distribution of wind speed is among the more significant wind characteristics in examining wind energy potential and the performance of wind energy conversion systems. When the wind speed probability distribution is known, the wind energy distribution can be easily obtained. Therefore, the probability distribution of wind speed is a very important piece of information required in assessing wind energy potential. For this reason, a large number of studies have been established concerning the use of a variety of probability density functions to describe wind speed frequency distributions. Although the two-parameter Weibull distribution comprises a widely used and accepted method, solving the function is very challenging. In this study, the polynomial and radial basis functions (RBF) are applied as the kernel function of support vector regression (SVR) to estimate two parameters of the Weibull distribution function according to previously established analytical methods. Rather than minimizing the observed training error, SVR_poly and SVR_rbf attempt to minimize the generalization error bound, so as to achieve generalized performance. According to the experimental results, enhanced predictive accuracy and capability of generalization can be achieved using the SVR approach compared to other soft computing methodologies.

Chromium nitride (CrN) coating has emerged as a new alternative in machining applications. CrN has good thermal stability, low deposition temperature, and excellent wear and corrosion resistance. However, no precise informa- tion exists yet regarding the ideal coating parameter condi- tions that lead to higher surface integrity. For this reason, an optimization study is desired—a study on the parameters of CrN coating on aerospace Al7075-T6 alloy using physical vapor deposition magnetron sputtering. The present research work investigates the effects of temperature as well as nitro- gen flow rate and DC power on coated samples' surface hardness, adhesion, surface roughness, and microstructure. To carry out the investigation, the Taguchi optimization meth- od with L16 (3 4 ) orthogonal array was applied. However, to obtain optimum parameters for superior surface integrity, signal/noise (S/N) response analysis method was employed. Finally, confirmation tests with the best parameter combina- tions attained in the optimization process were carried out to demonstrate the progress made. Ultimately, surface hardness of coated Al7075-T6 was enhanced by 15.33 %, adhesion by 24.3 %, and surface roughness by 7.22 %.

In this study, the fretting fatigue resistance of AL7075-T6 alloy is investigated using surface treatment Ti–TiN multilayer coating by physical vapor deposition (PVD) magnetron sputtering technique. A fuzzy logic model was established to forecast the surface roughness of Ti–TiN coating on AL7075-T6 with respect to changes in the input process parameters of DC power, temperature, DC bias voltage, and nitrogen flow rate. The results indicate an agreement between the fuzzy model and experimental results with 95.349% accuracy. The fretting fatigue lives of Ti–TiN-coated specimens with the lowest surface roughness resulting from fuzzy logic were enhanced by 18% at low cyclic fatigue, while at high cyclic fatigue the result was reversed.

Aircraft engines, fuselage, automobile parts, and energy saving strategies in general have promoted the interest and research in the field of lightweight materials, typically on alloys based on aluminum. Aluminum alloy itself does not have suitable wear resistance; therefore, it is necessary to enhance surface properties for practical applications, particularly when aluminum is in contact with other parts. Fretting fatigue phenomenon occurs when two surfaces are in contact with each other and one or both parts are subjected to cyclic load. Fretting drastically decreases the fatigue life of materials. Therefore, investigating the fretting fatigue life of materials is an important subject. Applying surface modification methods is anticipated to be a supreme solution to gradually decreasing fretting damage. In this paper, the authors would like to review methods employed so far to diminish the effect of fretting on the fatigue life of Al7075-T6 alloy. The methods include deep rolling, shot peening, laser shock peening, and thin film hard coatings. The surface coatings techniques are comprising physical vapor deposition (PVD), hard anodizing, ion-beam-enhanced deposition (IBED), and nitriding.