E. Zalnezhad

Fabrication and deformation behaviour of multilayer Al2O3/ Ti/TiO2 nanotube arrays

In this study, titanium thin films were deposited on alumina substrates by radio frequency (RF) magnetron sputtering. The mechanical properties of the Ti coatings were evaluated in terms of adhesion strength at various RF powers, temperatures, and substrate bias voltages. The coating conditions of 400W of RF power, 250°C, and a 75V substrate bias voltage produced the strongest coating adhesion, as obtained by the Taguchi optimisation method. TiO2 nanotube arrays were grown as a second layer on the Ti substrates using electrochemical anodisation at a constant potential of 20V and anodisation times of 15min, 45min, and 75min in a NH4F electrolyte solution (75 ethylene glycol: 25 water). The anodised titanium was annealed at 450°C and 650°C in a N2 gas furnace to obtain different phases of titania, anatase and rutile, respectively. The mechanical properties of the anodised layer were investigated by nanoindentation. The results indicate that Youngs modulus and hardness increased with annealing temperature to 650°C.

Rapid Immunoglobulin M-Based Dengue Diagnostic Test Using Surface Plasmon Resonance Biosensor

Surface plasmon resonance (SPR) is a medical diagnosis technique with high sensitivity and specificity. In this research, a new method based on SPR is proposed for rapid, 10-minute detection of the anti-dengue virus in human serum samples. This novel technique, known as rapid immunoglobulin M (IgM)-based dengue diagnostic test, can be utilized quickly and easily at the point of care. Four dengue virus serotypes were used as ligands on a biochip. According to the results, a serum volume of only 1 μl from a dengue patient (as a minimized volume) is required to indicate SPR angle variation to determine the ratio of each dengue serotype in samples with 83–93% sensitivity and 100% specificity.

Optimized fabrication and characterization of TiO2–Nb2O5–Al2O3 mixed oxide nanotube arrays on Ti–6Al–7Nb

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.

A Study on Surface Modification of Al7075-T6 Alloy against Fretting Fatigue Phenomenon

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.

Estimation of Tsunami Bore Forces on a Coastal Bridge Using an Extreme Learning Machine

This paper proposes a procedure to estimate tsunami wave forces on coastal bridges through a novel method based on Extreme Learning Machine (ELM) and laboratory experiments. This research included three water depths, ten wave heights, and four bridge models with a variety of girders providing a total of 120 cases. The research was designed and adapted to estimate tsunami bore forces including horizontal force, vertical uplift and overturning moment on a coastal bridge. The experiments were carried out on 1:40 scaled concrete bridge models in a wave flume with dimensions of 24 m × 1.5 m × 2 m. Two six-axis load cells and four pressure sensors were installed to the base plate to measure forces. In the numerical procedure, estimation and prediction results of the ELM model were compared with Genetic Programming (GP) and Artificial Neural Networks (ANNs) models. The experimental results showed an improvement in predictive accuracy, and capability of generalization could be achieved by the ELM approach in comparison with GP and ANN. Moreover, results indicated that the ELM models developed could be used with confidence for further work on formulating novel model predictive strategy for tsunami bore forces on a coastal bridge. The experimental results indicated that the new algorithm could produce good generalization performance in most cases and could learn thousands of times faster than conventional popular learning algorithms. Therefore, it can be conclusively obtained that utilization of ELM is certainly developing as an alternative approach to estimate the tsunami bore forces on a coastal bridge.

On the Dependence of Mechanical and Tribological Properties of Sputtered Chromium Nitride Thin Films on Deposition Power

In the past decade, Al 5083 has attracted considerable attention due to its promising potential applications in military vehicles. This paper reports the improvement of mechanical and tribological properties of Al 5083 coated with chromium nitride. Chromium nitride thin films were deposited by DC magnetron sputtering technique on Al 5083 substrate at different deposition powers (150 to 300 W in steps of 50 W). A FESEM was used for surface morphology and chemical composition studies. The thickness of the films was determined by quartz crystal monitor and checked with FESEM cross-section images. Films thickness was 2±0.01 μm for all samples. The mechanical and tribological properties were investigated by nanoindentation and scratch tests, respectively. The results showed that grains size decreases with the deposition power, while the samples produced at higher powers had a denser structure. The results also showed that by increasing the deposition power film hardness increased and the friction coefficient and scratch volume decreased.

Designing a Non-invasive Surface Acoustic Resonator for Ultra-high Sensitive Ethanol Detection for an On-the-spot Health Monitoring System

Surface acoustic wave (SAW) sensors–based on piezoelectric crystal resonators–are extremely sensitive to even very small perturbations in the external atmosphere, because the energy associated with the acoustic waves is confined to the crystal surface. In this study, we present a critical review of the recent researches and developments predominantly used for SAW-based organic vapor sensors, especially ethanol. Besides highlighting their potential to realize real-time ethanol sensing, their drawbacks such as indirect sensing, invasive, time initializing, and low reliability, are properly discussed. The study investigates a proposed YZ-lithium niobate piezoelectric substrate with interdigital transducers patterned on the surface. Design of the resonator plays an important role in improving mass sensitivity, particularly the sensing area. Accordingly, a tin dioxide (SnO2) layer with a specific thickness is generated on the surface of the sensor because of its high affinity to ethanol molecules. To determine the values of sensor configuration without facing the practical problems and the long theoretical calculation time, it is shown that the mass sensitivity of SAW sensors can be calculated by a simple three-dimensional (3-D) finite element analysis (FEA) using a commercial finite-element platform. In design validation step, different concentrations of ethanol are applied to investigate the acoustic wave properties of the sensor. The FEA data are used to obtain the surface and bulk total displacements of the sensor and fast Fourier transform (FFT) on output spectrum. The sensor could develop into highly sensitive and fast responsive structure so that a positive intensity shift of 0.18e-2 RIU is observed when the sensor is exposed to 15 ppm ethanol. It is capable of continuously monitoring the ethanol gas whether as an ultra-high sensitive sensor or switching applications for medical and industrial purposes.

Three-dimensional analysis of surface acoustic resonator for ultra-high sensitive ethanol disclosure as non-invasive biosensor

Surface acoustic wave (SAW) sensors provide desirable characteristics for ethanol detection because of their small size, low fabrication cost, ease of integration and high sensitivity.1‒4 Unlike surface plasmon resonance (SPR) technique.5‒7 Which is one of the known optical techniques with high sensitivity in gas detection, SAW can be integrated into a chip-based high throughput arrays due to high working frequency, with affordable expenses. In this study, there is numerically analysed the proposed ethanol sensor based on SAW technology using COMSOL Multiphysics. As presented in Figure 1, the sensor comprises of a YZ-Lithium Niobate (LiNbO3) substrate with interdigital electrodes (IDT) patterned on the surface. This sandwichlike structure contains the insulator and sensing medium as well. In this work, aluminium is preferred to be used for IDT material because of its electrical resistance and cost. IDT has two ends including receiver and transmitter end, in which they are geometrically symmetry. The thickness is 200nm approximately which makes the IDT to have light mechanical load to the surface and enough lower electrical resistance. The design of the resonator plays an important role in improving mass sensitivity, particularly the sensitive area that supplies a lower detection limit when an optimal configuration is performed in the SAW gas chromatogram (SAW-GC) sensors with the cost reductions as well as higher sensitivity for SAW biological and chemical sensors. Accordingly, a tin dioxide (SnO2) layer with a specific thickness is generated on the surface of the sensor because of its high affinity to ethanol molecules. With increasing ethanol absorption on the sensor surface, there is a changing in the density of SnO2 layer as a sensing medium (due to the bound ethanol molecules to SnO2 film) and subsequently produced voltage vibrations in output terminal. Through time-dependent analysis, the frequency response for describing a small variation at output voltage is adequately obtained as shown in Figure 2. There is presented a baseline as a reference along with the spectrum of 20ppm concentration. With a simple comparison, it can be realized that the intensity change is along the vertical direction at the frequency resonance (65MHz). It means the amount of material (density of sensing medium) has been changed because of sensing a new concentration of ethanol (with 20ppm). It is obvious the intensity variation of other ethanol concentration can be easily calculated according to the baseline.

Erratum to: Evaluation of the Mechanical Properties of AA 6063 Processed by Severe Plastic Deformation

DAVOUD MASHHADI JAFARLOU, Researcher, and NOOR AZIZI BIN MARDI, Senior Lecturer, are with the Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia, and also with the Centre of Advanced Manufacturing & Material Processing (AMMP), 50603 Kuala Lumpur, Malaysia. ERFAN ZALNEZHAD, Assistant Professor, is with the Department of Mechanical Convergence Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, 133-791 Seoul, Korea. Contact e-mail: erfan@hanyang.ac.kr ABDELMAGID SALEM HAMOUDA, Professor, is with the Mechanical and Industrial Engineering Department, College of Engineering, Qatar University, P.O. Box 2713, Doha, Qatar. GHADER FARAJI, Assistant Professor, is with the School of Mechanical Engineering, College of Engineering, University of Tehran, 11155-4563 Tehran, Iran. MOHSEN ABDELNAEIM HASSAN MOHAMED, Associate Professor, is with the Department of Mechanical Engineering, Faculty of Engineering, University of Malaya and Centre of Advanced Manufacturing & Material Processing (AMMP), and also with the Department of Mechanical Engineering, Faculty of Engineering, Assiut University, Assiut 71516, Egypt. The online version of the original article can be found under doi:10.1007/s11661-015-2806-7. Article published online April 7, 2015

Fuzzy modeling to predict the adhesion strength of TiN ceramic thin film coating on aerospace AL7075-T6 alloy

In this research work, predicting of titanium nitride (TiN) coating adhesion on AL7075-T6 is presented. First TiN was coated on Al7075-T6 in different conditions and the surfaces adhesion of TiN coated specimens were measured using micro scratch force machine. Second a fuzzy logic model was established to predict the TiN coating adhesion with respect to changes in input process parameters, DC power, DC bias voltage, and nitrogen flow rate. Finally, new five experimental tests were carried out to verify the predicted results achieved via fuzzy model. The result indicated settlement between the fuzzy model and experimental results with 95.534% accuracy.