Mesoporous plasmonic Au–TiO2 nanocomposites for efficient visible-light-driven photocatalytic water reduction

The mesoporous Au–TiO₂ nanocomposites with different Au concentrations were prepared via a co-polymer assisted sol–gel method. The structures have been characterized by powder X-Ray diffraction, N₂ adsorption–desorption isotherms, diffuse reflectance UV–Vis spectroscopy, X-ray photoemission spectroscopy, transmission electron microscopy. Most generated Au nanoparticles were embedded in the mesoporous TiO₂ matrix. The prepared Au–TiO₂ nanocomposites exhibit remarkable visible-light activity for H₂ evolution from photocatalytic water reduction in the presence of ascorbic acid as the electron donor. By comparing with Pt–TiO₂ samples, we found that the visible-light activity of the Au–TiO₂ nanocomposites could be partially contributed by the defects/impurity states in the TiO₂ matrix, while the gold surface plasmons could significantly enhance the weak visible-light excitation of TiO₂ matrix. In addition, further studies by controlling irradiation wavelengths suggest that some plasmon-excited electrons could transfer from Au nanoparticles to the contacting TiO₂ to reduce water for H₂ generation. We believe that these Au–TiO₂ nanocomposites as well as the mechanistic studies would have considerable impact on future development of metal-semiconductor hybrid photocatalysts for efficient solar hydrogen production.     

Slurry Erosive Wear Evaluation of HVOF-Spray Cr2O3 Coating on Some Turbine Steels

In this study, Cr₂O₃ coatings were deposited on CF8M and CA6NM turbine steels by high-velocity oxy-fuel (HVOF)-spray process and analyzed with regard to their performance under slurry erosion conditions. High Speed Erosion Test Rig was used for slurry erosion tests, and the effects of three parameters, namely, average particle size, speed (rpm), and slurry concentration on slurry erosion of these materials were investigated. SEM micrographs on the surface of samples, before and after slurry erosion tests, were taken to study the erosion mechanism. For the uncoated steels, CA6NM steel showed better erosion resistance in comparison with CF8M steel. The HVOF-sprayed Cr₂O₃-coated CF8M and CA6NM steels showed better slurry erosion resistance in comparison with their uncoated counterparts. It may be due to the higher hardness as a result of HVOF-sprayed Cr₂O₃ coating in comparison with the uncoated CF8M and CA6NM steels.     

Investigations on the Behavior of HVOF and Cold Sprayed Ni-20Cr Coating on T22 Boiler Steel in Actual Boiler Environment

High temperature corrosion accompanied by erosion is a severe problem, which may result in premature failure of the boiler tubes. One countermeasure to overcome this problem is the use of thermal spray protective coatings. In the current investigation high velocity oxy-fuel (HVOF) and cold spray processes have been used to deposit commercial Ni-20Cr powder on T22 boiler steel. To evaluate the performance of the coatings in actual conditions the bare as well as the coated steels were subjected to cyclic exposures, in the superheater zone of a coal fired boiler for 15 cycles. The weight change and thickness loss data were used to establish kinetics of the erosion-corrosion. X-ray diffraction, surface and cross-sectional field emission scanning electron microscope/energy dispersive spectroscopy (FE-SEM/EDS) and x-ray mapping techniques were used to analyse the as-sprayed and corroded specimens. The HVOF sprayed coating performed better than its cold sprayed counterpart in actual boiler environment.     

Studies on the Sliding Wear Performance of Plasma Spray Ni-20Cr and Ni3Al Coatings

Two metallic powders namely Ni-20Cr and Ni₃Al were coated on AISI 309 SS steel by shrouded plasma spray process. The wear behavior of the bare, Ni-20Cr and Ni₃Al-coated AISI 309 SS steel was investigated according to ASTM Standard G99-03 on a Pin-on-Disc Wear Test Rig. The wear tests were carried out at normal loads of 30 and 50 N with a sliding velocity of 1 m/s. Cumulative wear rate and coefficient of friction (μ) were calculated for all the cases. The worn-out surfaces were then examined by scanning electron microscopy analysis. Both the as-sprayed coatings exhibited typical splat morphology. The XRD analysis indicated the formation of Ni phase for the Ni-20Cr coating and Ni₃Al phase for the Ni₃Al coating. It has been concluded that the plasma-sprayed Ni-20Cr and Ni₃Al coatings can be useful to reduce the wear rate of AISI 309 SS steel. The coatings were found to be adherent to the substrate steel during the wear tests. The plasma-sprayed Ni₃Al coating has been recommended as a better choice to reduce the wear of AISI 309 SS steel, in comparison with the Ni-20Cr coating.     

Some Observations on Microstructural Changes in a Mg-Based AE42 Alloy Subjected to Friction Stir Processing

The main aim of the current study is the analysis of friction stir processing (FSP) of Mg-based alloys as a possible tool for nanocomposites production. The study reports microstructural changes taking place in a Mg-based alloy (AE42) subjected to FSP under different cooling conditions. The FSP process was carried out with single as well as multipass options. The friction stir processed samples were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), focused ion beam (FIB)-scanning ion microscopy (SIM), and X-ray diffraction (XRD). It was observed that FSP tends to fragment the elongated precipitates and produces near homogeneous distribution of fine particles. The smallest particle size was observed to be produced by double-pass FSP supplemented by rapid cooling, thereby generating in situ nanocomposites. Vickers microhardness testing was done along the thickness (transverse direction) of the specimen to study and understand the variation of hardness with thickness. Nearly a two-times increase in the microhardness of AE42 was observed in the case of double-pass, FSP AE42 with cooling at temperature of approximately 253 K (–20 °C). To confirm these observations, another magnesium alloy AM50 was also friction stir processed under similar conditions. The fine submicron grain structure produced in AE42 alloy contributed immensely toward grain boundary strengthening and Orowan strengthening had only marginal influence. Subgrain boundary pinning by in situ nanoparticles contributed significantly in the strengthening process.     

Ligand exchange based paraoxon imprınted QCM sensor

In the present work, a paraoxon imprinted QCM sensor has been developed for the determination of paraoxon based on the modification of paraoxon imprinted film onto a quartz crystal combining the advantages of high selectivity of the piezoelectric microgravimetry using MIP film technique and high sensitivity of QCM detection. The paraoxon selective memories have formed on QCM electrode surface by using a new metal–chelate interaction based on pre-organized monomer and the paraoxon recognition activity of these molecular memories was investigated. Molecular imprinted polymer (MIP) film for the detection of paraoxon was developed and the analytical performance of paraoxon imprinted sensor was studied. The molecular imprinted polymer were characterized by FTIR measurements. Paraoxon imprinted sensor was characterized with AFM and ellipsometer. The study also includes the measurement of binding interaction of paraoxon imprinted quartz crystal microbalance (QCM) sensor, selectivity experiments and analytical performance of QCM electrode. The detection limit and the affinity constant (K_affinity) were found to be 0.06 μM and 2.25 × 10⁴ M^? 1 for paraoxon [MAAP–Cu(II)–paraoxon] based thin film, respectively. Also, it has been observed that the selectivity of the prepared paraoxon imprinted sensor is high compared to a similar chemical structure which is parathion.     

Development of Resource-Saving Technology of Linseed Harvesting

ABSTRACT

The traditional technology of linseed harvesting involves the cutting of the stems with subsequent threshing. During cutting part of the stem remains on the field, which causes significant losses of fibrous raw materials. Threshing of stems by traditional technology also causes significant damage to the linseed straw. Developed resource-saving technology of linseed harvesting provides first linseed thrashing on the plants with subsequent pulling of stems. With this sequence of technological operations, all linseed stems and seeds are preserved without damage. For the implementation of resource-saving technology proposed design of flax thresher and flax puller. The results of experimental studies of the properties of linseed fibre obtained from the linseed showed that such fibre is suitable for the production of non-woven materials, technical textiles and paper. The introduction of resource-saving technology of linseed harvesting will save the harvest of seeds and straw with minimal losses and damage. Resource-saving technology will increase the profitability of linseed cultivation.     

Effect of Superficially Applied Y<Subscript>2</Subscript>O<Subscript>3</Subscript> Coating on High-Temperature Corrosion Behavior of Ni-Base Superalloys

Inhibitors and oxide additives have been investigated with varying success to control high-temperature corrosion. Effect of Y₂O₃ on high-temperature corrosion of Superni 718 and Superni 601 superalloys was investigated in the Na₂SO₄-60 pct V₂O₅ environment at 1173 K (900 °C) for 50 cycles. Y₂O₃ was applied as a coating on the surfaces of the specimens. Superni 601 was found to have better corrosion resistance in comparison with Superni 718 in the Na₂SO₄-60 pct V₂O₅ environment. The Y₂O₃ superficial coating was successful in decreasing the reaction rate for both the superalloys. In the oxide scale of the alloy Superni 601, Y and V were observed to coexist, thereby indicating the formation of a protective YVO₄ phase. There was a distinct presence of a protective Cr₂O₃-rich layer just above the substrate/scale interface in the alloy. Whereas Cr₂O₃ was present with Fe and Ni in the scale of Superni 718. Y₂O₃ seemed to be contributing to better adhesion of the scale, as comparatively lesser spalling was noticed in the presence of Y₂O₃.     

A design approach for myoelectric arm with hand and wrist motions using single actuator

This paper relates to the development of prosthetic myoelectric hand that performs many functions of real human hand like opening and closing of fingers and wrist rotation. This dual movement of prosthetic hand is controlled by a single DC motor. Below-elbow amputee persons with missing limbs can append this prosthetic hand with the available stump and can do some of the hand operations with multiple degrees of freedom by voluntary activation of muscles using electromyogram (EMG) electrodes. To rehabilitate such a person, facilities like opening, closing, grasping, and lifting objects of different weight with variable grip force are available like natural hand. The main design consideration includes degrees of freedom, number of actuators, power of actuators, reliability, electronic control, light weight, economic viability, wrist rotation, variable grip force pattern, and ease of attachment with limb. Use of electromagnetic clutches along with the coupling logic of DC motor and microcontroller based on grip force generation and wrist rotation based on EMG signals imparts a new function to the device. It will be useful for both robotic and prosthetic industry.