Corrosion behavior of Mg-Gd-Zn based alloys in aqueous NaCl solution

The corrosion behavior of Mg-10Gd-xZn(x=2,6 wt.%)alloys in 0.5 wt.%NaCl solution was investigated.Microstructures of both the alloys consisted of(Mg,Zn)_(3) Gd phase and lamellar long period stacking ordered(LPSO)phase.The morphology of the second phase at the grain boundary differed in both alloys:it was a continuous network structure in Mg-10Gd-6Zn,whereas it was relatively discrete in Mg-10Gd-2Zn.The dendrites were finer in size and highly branched in Mg-10Gd-6Zn.The corrosion results indicated that the increase in Zn content increased the corrosion rate in Mg-10Gd-xZn alloys.Micro-galvanic corrosion occurred near the grain boundary in both alloys initially as the grain boundary phase was stable and acted as a cathode,however,filiform corrosion dominated in the later stage,which was facilitated by the LPSO phase in the matrix.Severe micro-galvanic corrosion occurred in Mg-10Gd-6Zn due to the higher volume of second phase.The stability of the second phase at the grain boundary was altered and dissolved after the long immersion times.Probably the NaCl solution chemically reacted with the grain boundary phase and de-stabilized it during the long immersion times,and was removed by the chromic acid used for the corrosion product removal.

Investigation on mechanical properties and creep behavior of stir cast AZ91-SiC_(p) composites

The room temperature mechanical properties and high temperature creep behavior of AZ91 alloy reinforced with SiC_(p) synthesized via stir casting have been evaluated.The mechanical properties showed improvement with respect to the amount of reinforcement content.The creep testing of the composites carried out at a temperature of 175 ℃ under constant stress of 80,100 and 120 MPa reveals different creep characteristics depending upon the reinforcement content and the applied load.The true stress exponents of different composites calculated from minimum creep rate indicate the possible mechanisms of creep deformation.

Phytochemical composition of Caesalpinia crista extract as potential source for inhibiting cholinesterase and β-amyloid aggregation: Significance to Alzheimer's disease

Objective: To screen plant extract fractions and elucidate the components present in Caesalpinia crista(C. crista) leaves for cholinergic and anti-amyloidogenic activities for the treatment of Alzheimer's diseases. Methods: This work has been carried out to study the action of C. crista extracts from nonpolar to polar solvents toward inhibition of oxidative stress, cholinergic and amyloidosis. The antioxidant activity was studied using DPPH total antioxidant assay; cholinergic assay by Ellman's method and anti-amyloidogenic assay by thioflavin-T fluorescence and transmission electron microscopy. Results: The quantification of polyphenols was carried out following C. crista methanolic extract(CCMeOH) HPLC fingerprinting, along with LC-MS and elucidated by MS LAMPS database. GC-MS of CCMeOH was screened for potential moieties. In vitro experimental results showed that the CCMe OH was potential extract that exhibited active inhibition of antioxidant property, cholinergic enzymes acetylcholinesterase and butyrylcholinesterase. For anti-amyloidogenic evaluations, among all the extracts, the CCMe OH was found to have the potential toward inhibiting the oligomers, fibrillation of Aβ42 with good defibrillation of amyloid cascading properties. Conclusions: These results are also supported by the presence of polyphenols as the active ingredients. Multi-potent target drug therapy is a promising option in treating the Alzheimer's diseases. Methanolic extract of C. crista shows potential activity against cholinergic enzymes, Aβ42 aggregation with antioxidant activity.

Blue emitting exciplex for yellow and white organic light‑emitting diodes

White organic light-emitting diodes(WOLEDs)have several desirable features,but their commercialization is hindered by the poor stability of blue light emitters and high production costs due to complicated device structures.Herein,we investigate a standard blue emitting hole transporting material(HTM)N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine(NPB)and its exciplex emission upon combining with a suitable electron transporting material(ETM),3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole(TAZ).Blue and yellow OLEDs with simple device structures are developed by using a blend layer,NPB:TAZ,as a blue emitter as well as a host for yellow phosphorescent dopant iridium(III)bis(4-phenylthieno[3,2-c]pyridinato-N,C2')acetylacetonate(PO-01).Strategic device design then exploits the ambipolar charge transport properties of tetracene as a spacer layer to connect these blue and yellow emitting units.The tetracene-linked device demonstrates more promising results compared to those using a conventional charge generation layer(CGL).Judicious choice of the spacer prevents exciton difusion from the blue emitter unit,yet facilitates charge carrier transport to the yellow emitter unit to enable additional exciplex formation.This complementary behavior of the spacer improves the blue emission properties concomitantly yielding reasonable yellow emission.The overall white light emission properties are enhanced,achieving CIE coordinates(0.36,0.39)and color temperature(4643 K)similar to daylight.Employing intermolecular exciplex emission in OLEDs simplifes the device architecture via its dual functionality as a host and as an emitter.

Physical,Mechanical,and Tribological Attributes of Stir-Cast AZ91/SiC_p Composite

In the present investigation, composites with silicon carbide particle （SiCp） as reinforcement and AZ91 magnesium alloy as matrix have been synthesized using liquid metal stir-casting technique with optimized processing conditions. The composites with good particle distribution in the matrix, and better grain refinement and good interfacial bonding between the matrix and reinforcement have been obtained. The effect of SiCp content on the physical, mechanical, and tribological properties of Mg-based metal matrix composite （MMC） is studied with respect to particle distribution, grain refinement, and particle/matrix interfacial reactions. The electrical conductivity, coefficient of thermal expansion, microas well as macro-hardness, tensile and compressive properties, and the fracture behavior of the composites along with dry sliding wear of the composites have been evaluated and compared with the base alloy.

Developments in Processing of Functionally Gradient Metals and Metal–Ceramic Composites:A Review

Functionally gradient/graded materials （FGMs）, an emerging new class of materials, are the outcome of the recent innovative concepts in materials technology. FGMs are in their early stages of evolution and expected to have a strong impact on the design and development of new components and structures with better performance. FGMs exhibit gradual transitions in the microstructure and/or the composition in a specific direction, the presence of which leads to variation in the functional performance within a part. The presence of gradual transitions in material composition in FGMs can reduce or eliminate the deleterious stress concentrations and result in a wide gradation of physical and/or chemical properties within the material. Functionally graded metal-ceramic composites are also getting the attention of the researchers. Among the fabrication routes for FGMs such as chemical vapour deposition, physical vapour deposition, the sol-gel technique, plasma spraying, molten metal infiltration, self propagating high temperature synthesis, spray forming, centrifugal casting, etc., the ones based on solidification route are preferred for FGMs because of their economics and capability to make large size products. The present paper discusses and compares various solidification processing tech- niques available for the fabrication of functionally gradient metals and metal-ceramic composites and lists their properties and possible applications. The other processing methods are briefly described.

Self-lubricating bidirectional carbon fiber reinforced smart aluminum composites by squeeze infiltration process

Self-lubrication is one of the smart material properties required for producing components with enhanced wear resistance and low coefficient of friction.Bidirectional(BD)satin weave polyacrylonitrile(PAN)based carbon fiber(Cf)fabric preform was successfully infiltrated with Al 6061 alloy by squeeze infiltration process.The infiltrated composite shows uniform distribution of carbon fibers in the matrix with the elimination of porosities,fiber damage and close control on the formation of deleterious aluminum carbide(Al4C3)phase.Cf/Al composite exhibits remarkable wear resistance compared to unreinforced alloy due to the formation of self-lubricating tribolayer on the pin surface,which intercepts the contact of matrix metal to counter surface.The BD carbon fiber enhanced the hardness and compressive strength of the composite by restraining the plastic flow behavior of matrix.High resolution transmission electron microscopy shows the presence of Al2O3 and MgAl2O4 spinel,confirmed by EDS and SAD pattern,at the composite interface.The composite shows a lower density of 2.16 g/cm^3 which is a major ad vantage for weight reduction compared to the monolithic alloy(2.7 g/cm^3).

Value-addition of water hyacinth and para grass through pyrolysis and hydrothermal liquefaction

Hydrothermal liquefaction(HTL)and pyrolysis(Py)of Loktak lake biomass mixture of water hyacinth(WH)and para grass(PG)were carried out at 260-300℃ and 300-500℃ to compare the products yield and chemical characteristics of the products.In case of HTL,the maximum bio-oil yield was obtained 13.34 wt.%at 280℃ while for Py,the maximum bio-oil yield was observed 38.8 wt.%at 350℃.The obtained bio-oils and bio-chars were analyzed using GC-MS,FT-IR,NMR,TGA,TOC,and SEM.GC-MS analysis of the bio-oils were showed that the HTL bio-oil majorly contains of nitrogen containing compounds whereas the Py bio-oil contains majority of phenolic compounds.Other compounds like ketones,alcohols,acids were also observed in bio-oil.Higher intensity broad band at 3300-3500 cm^(−1) was observed in the Py bio-oil compared to HTL bio-oil.TGA and proximate analysis of bio-char revealed the higher devolatilization occured during the HTL compared to Py process.The surface morphology of the HTL bio-char was found to be rough and fragmented as compared to the pyrolysis bio-char,clearly showing the biomass macromolecules breakdown differently in HTL and Py process.

Ethanol production by a filamentous fungal strain Byssochlamys fulva AM130 under alternating aerobic and oxygen-limited conditions

Byssochlamys fulva AM130,a novel strain of filamentous fungus,could produce ethanol from glucose,xylose,and alkali pretreated rice straw(PRS),while the efficiencies were very low with PRS.Ethanol production of 11.84 g/L was attained by the fungus when grown in glucose,indicating that the limitations while growing on PRS were related to low hydrolytic efficiency.Enzyme profiling of the fungus showed 365 IU/ml of beta-glucosidase and 89 IU/ml of xylanase activity,while endoglucanase and filter paper activity were negligible,which accounts for the low hydrolytic efficiency.The fungus could survive for extended periods under oxygen-limited conditions and produce ethanol.The fungal mycelia could also be used for repeated cycles of anaerobic fermentation,wherein the ethanol yield improved with each consecutive cycle.