Metathesis synthesis and characterization of complex metal fluoride, KMF3 (M = Mg, Zn, Mn, Ni, Cu and Co) using mechanochemical activation

Metathesis synthesis of complex metal fluorides using mechanochemical activation has been reported. The high lattice energy of the byproduct KCl helps the reaction towards product formation in under 20 min. The proposed process, in contrast to the available methods of synthesis, is very rapid, economical and results in products with controlled morphology. The structural, optical and chemical properties of synthesized powders are determined by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, magnetization measurements and diffused reflectance spectra in the UV-VIS range.     

Multi-response optimization of Micro-EDM process parameters on AISI304 steel using TOPSIS

The Technique for order preference by similarity to ideal solution (TOPSIS) method of optimization is used to analyze the process parameters of the micro-Electrical discharge machining (micro-EDM) of an AISI 304 steel with multi-performance characteristics. The Taguchi method of experimental design L27 is performed to obtain the optimal parameters for inputs, including feed rate, current, pulse on time, and gap voltage. Several output responses, such as the material removal rate, electrode wear rate, overcut, taper angle, and circularity at entry and exit points, are analyzed for the optimal conditions. Among all the investigated parameters, feed rate exerts a greater influence on the hole quality. ANOVA is employed to identify the contribution of each experiment. The optimal level of parameter setting is maintained at a feed rate of 4 μm/s, a current of 10 A, a pulse on time of 10 μs, and a gap voltage of 10 V. Scanning electron microscope analysis is conducted to examine the hole quality. The experimental results indicate that the optimal level of the process parameter setting over the overall performance of the micro-EDM is improved through TOPSIS.     

Quasi-synchronous checkpointing: Models, characterization, andclassification

Checkpointing algorithms are classified as synchronous and asynchronous in the literature. In synchronous checkpointing, processes synchronize their checkpointing activities so that a globally consistent set of checkpoints is always maintained in the system. Synchronizing checkpointing activity involves message overhead and process execution may have to be suspended during the checkpointing coordination, resulting in performance degradation. In asynchronous checkpointing, processes take checkpoints without any coordination with others. Asynchronous checkpointing provides maximum autonomy for processes to take checkpoints; however, some of the checkpoints taken may not lie on any consistent global checkpoint, thus making the checkpointing efforts useless. Asynchronous checkpointing algorithms in the literature can reduce the number of useless checkpoints by making processes take communication induced checkpoints besides asynchronous checkpoints. We call such algorithms quasi-synchronous. In this paper, we present a theoretical framework for characterizing and classifying such algorithms. The theory not only helps to classify and characterize the quasi-synchronous checkpointing algorithms, but also helps to analyze the properties and limitations of the algorithms belonging to each class. It also provides guidelines for designing and evaluating such algorithms     

Pt and W ohmic contacts to p-6H-SiC by focused ion beam direct-write deposition

Low resistance Pt and W ohmic metallizations to p-type 6H-SiC, using focused ion beam (FIB) surface-modification and in-situ direct-write metal deposition without annealing, are reported. FIB (Ga) surface-modification and in-situ deposition of Pt, and W showed minimum contact resistance values of 2.8 × 10⁻⁴ ohm-cm² to 2.5 × 10⁻⁴ ohm-cm², respectively. A comparison with ex-situ pulse laser deposited Pt on surface-modified areas showed comparable contact resistance values and similar behavior. Auger and secondary ion mass spectroscopy analysis showed a significant (∼4% a.c.) incorporation of Ga within a 15 nm distance from the SiC surface with surface-modification. Atomic force micros-copy studies showed that surface-modification process smooths out the SiC surface significantly.     

3D printed polylactide-based zirconia-toughened alumina composites: fabrication,mechanical, and in vitro evaluation

Fused deposition modeling (FDM) has been a commonly used technique in the fabrication of geometrically complex biodegradable scaffolds for bone tissue engineering. Generally, either individual polylactide (PLA) or its combination with calcium phosphates or bioglass has been employed to design scaffolds through the principles of FDM. In this study, FDM protocol has been employed to design 3D printed PLA/zirconia-toughened alumina (ZTA). A series of PLA/ZTA combinations have been attempted to determine the feasibility of the resultant in filament extrusion and their subsequent capacity to obtain a stable 3D printed component. A maximum of 80 wt.% PLA and 20 wt.% ZTA has been determined as an optimum combination to yield a stable 3D structure beyond which an enhanced ZTA content in the PLA matrix yielded a fragile filament that lacked effectiveness in 3D printing. 5 and 10 wt.% of ZTA addition in the PLA matrix produced a better 3D design that reasonably displayed good mechanical properties. Depending on the ceramic content, a homogeneous dispersion of the constituent elements representative of ZTA has been determined throughout the PLA matrix. Simulation studies through finite element analysis (FEA) exhibited good corroboration with the test results obtained from the mechanical studies.     

A review on front end conversion in ocean wave energy converters

Harvesting the energy from ocean waves is one of the greatest attractions for energy engineers and scientists. Till date, plenty of methods have been adopted to harvest the energy from the ocean waves. However, due to technological and economical complexity, it is intricate to involve the majority of these energy harvesters in the real ocean environment. Effective utilization and sustainability of any wave energy harvester depend upon its adaptability in the irregular seasonal waves, situation capability in maximum energy extraction and finally fulfilling the economic barriers. In this paper, the front end energy conversions are reviewed in detail which is positioned in the first stage of the wave energy converter among other stages such as power take off (PTO) and electrical energy conversion. If the recent development of these front end energy conversion is well known then developing wave energy converter with economic and commercial viability is possible. The aim of this review is to provide information on front end energy conversion of a point absorber and emphasize the strategies and calamity to be considered in designing such kinds of devices to improve the energy harvesting competence. This will be useful to the engineers for speeding up the development of a matured point absorbing type wave energy converter.     

2D and 3D mapping of microindentations in hydrated and dehydrated cortical bones using confocal laser scanning microscopy

We report on responses of hydrated and dehydrated cortical bone tissues to mechanical loading applied by a Vickers indenter. The Vickers indentations were imaged in two- and three-dimensions (2D and 3D) using confocal laser scanning microscopy (CLSM) to understand mechanical behavior of bone tissues. Serial optical sections of indentation patterns of dry and wet bones were collected using CLSM. The indention surface structures were mapped using topographical CLSM imaging. The observation of CLSM shows the fundamental indentation responses for both the hydrated and dehydrated bone tissues were plastic deformation. No visible fracture was observed in the Vickers indentation patterns in the wet bone tissue, while non-propagating lamellar microcracks occurred in the dry bone tissue. This indicates that drying resulted in increased brittleness of the bone tissue. The Vickers hardness values of dry bone tissue were significantly higher than those of wet bone tissue at any applied loads (analysis of variation, ANOVA, p < 0.05). The resolution limits of confocal microscopy were also discussed for bone tissue scanning.     

Electrodeposition of amorphous silicon anode for lithium ion batteries

Amorphous silicon has been successfully electrodeposited on copper using a SiCl₄ based organic electrolyte under galvanostatic conditions. The electrodeposited silicon films were characterized for their composition, morphology and structural characteristics using glancing angle X-ray diffraction (GAXRD), scanning electron microscopy (SEM), and Raman spectroscopy. GAXRD and Raman analyses clearly confirm the amorphous state of the deposited silicon film. The deposited films were tested for possible application as anodes for Li-ion battery. The results indicate that this binder free amorphous silicon anode exhibits a reversible capacity of ∼1300 mAh g⁻¹ with a columbic efficiency of >99.5% up to 100 cycles. Impedance measurements at the end of each charge cycle show a non-variable charge transfer resistance which contributes to the excellent cyclability over 100 cycles observed for the films. This approach of developing thin amorphous silicon films directly on copper eliminates the use of binders and conducting additives, rendering the process simple, facile and easily amenable for large scale manufacturing.     

Synthesis,characterization, and electrochemical performance of the ternary layered composite (1-x-y) LiNi1/3Co1/3Mn1/3O2·xLi2MnO3·yLiCoO2

Composite ceramic cathodes represented by the formula (1-x-y) LiNi_1/3Co_1/3Mn_1/3O₂·xLi₂MnO₃·yLiCoO₂ were studied. A ternary compositional diagram was built with these ceramic materials as end-members, and selected points were chosen to represent the compositional space. Synthesized ceramic composite materials were investigated as to whether integration of structurally compatible units leads to improved electrochemical performance. Detailed structural (X-ray diffraction – XRD), elemental (X-ray photoelectron spectroscopy-XPS), microstructure (Scanning electron microscopy – SEM), and electrochemical (galvanostatic testing of half-cells) studies were performed and are presented. Within eight samples studied three compositions are found to exhibit first discharge capacity of around 230 mAh/g.     

Hydrogen-iodide decomposition over PdCeO2 nanocatalyst for hydrogen production in sulfur-iodine thermochemical cycle

A highly active and stable catalyst for hydrogen-iodide decomposition reaction in sulfur-iodine (SI) cycle has been prepared in the form of PdCeO₂ nanocatalyst by sol-gel method with different calcination temperatures (300 °C, 500 °C, and 700 °C). XRD and TEM confirmed a size around 6–8 nm for PdCeO₂ particles calcined at 300 °C. Raman study revealed large number oxygen vacancies in PdCeO₂-300 when compared to PdCeO₂-500 and PdCeO₂-700. With increase in calcination temperature, the average particle size increased whereas the specific surface area and number of oxygen vacancies decreased. Hydrogen-iodide catalytic-decomposition was carried out in the temperature range of 400°C–550 °C in a quartz-tube, vertical, fixed-bed reactor with 55 wt % aqueous hydrogen-iodide feed over PdCeO₂ catalyst using nitrogen as a carrier gas. PdCeO₂-300 showed hydrogen-iodide conversion of 23.3%, which is close to the theoretical equilibrium conversion of 24%, at 550 °C. It also showed a reasonable stability with a time-on-stream of 5 h.