Current Smart Materials - Volume 3, Issue 1, 2018

Background: New insights into materials science provide development of smart nano/micro structured materials for advanced applications. Rare earth includes a set of chemical elements (from La to Lu, including Sc and Y) with unique properties, the use of which is evidenced by luminescence applications. Colloidal processing offers great possibilities to obtain smart materials by controlling inter-particle forces, as well as their evolution during ceramic processing. The present article reports a review on colloidal processing with emphasis on rare earth powders. A general view about rare earths properties, including scientific investigations and applications are also presented. Methods: General view on rare earth sources, classification, properties, studies, and applications are reported. Besides, a review on colloidal processing covering particle characteristics, inter- particle forces, dispersion methods, rheology of suspensions, shaping process, drying-sintering stage, and microstructure formation is reported. Results: Yttria is the most used rare earth oxide in phosphors applications (70%). Synthesis routes imply on powder properties. Particle characteristics as size, shape, density, and surface area are important parameters for colloidal processing. The control of inter- particle forces by zeta potential evaluation and using dispersion methods provide conditions to prepare stable suspensions. Consolidation of colloidal particles into a desired shape depends on both viscosity and rheological behavior of suspensions. Drying-sintering conditions are effective on microstructure formation and component characteristics. Bio-prototyping is a low cost method, which provides components with complex shape and cellular architecture. Conclusion: Rare earths exhibit remarkable properties, being applied in diverse technological end-use. Colloidal processing provides opportunities to form smart materials since synthesis of colloids until development of complex ceramic components by shaping methods and thermal treatment. Even though colloidal processing is quite mature, investigations on rare earths involving inter- particle forces, shaping, drying-sintering stage, and microstructure formation are very scarce.

Background: In this review, preparation method with various applications of polyelectrolyte complex is studied with the aim to assess various attributes to different fields. Polyelectrolyte complex is formed when contrarily charged polyelectrolytes are mixed together. Description: The adoption of PEC is benefitting the pharmaceutical and biomedical field with vast applications and reliability. They provide better encapsulation efficiency; control the release rate of drug, immobilization of microbes, bio-sensing, wound healing and used as tissue scaffolds. PECs are used over single electrolyte as they are not been able to show idiosyncratic appositeness in the medicinal field. Conclusion: The scope of this review accentuate on the detailed study of applications of polyelectrolyte complexes and their efficacy so that they may gain more interest progressively. To provide several applications based on polyelectrolyte complex is the eventual objective of this review.

Background: The research of innovative nanostructured materials will be helpful in designing high performance supercapacitor devices in the near future. In this direction, graphenebased structures, such as Vertically Oriented Graphene Nanosheets (VOGNs), have emerged as promising architectures due to their interesting chemical, structural and electrochemical properties. One of the main strategies to enhance the performance of supercapacitive materials consists of the functionalization or modification of their surfaces by means of various approaches focused on doping or the deposition of electroactive material coatings/films among others. Particularly, in this study, the doping effect, by nitrogen plasma, on VOGNs was investigated as innovative electrodes for on-chip supercapacitors. Methods: Nitrogen-doped VOGNs (N-VOGNs) were characterised at morphological (SEM and TEM techniques), structural (XPS and Raman techniques) and electrochemical levels, respectively. Subsequently, the potential of such doped graphene nanostructure was evaluated in a symmetric supercapacitor device using a coin cell configuration. The properties of the supercapacitor were examined in terms of capacitance, energy and power density and lifetime. Results: A maximal N-content of 17% was achieved for VOGNs with a vertical length around 370 nm, through exposure to a N2 microwave-plasma in an electron cyclotron resonance (ECR)-CVD reactor. The deconvolution of N1s spectrum of N-VOGNs reflected the presence of three main peaks corresponding to pyrrolic (400.2 eV), pyridinic (399.0 eV) and graphitic (401.2 eV) nitrogen forms, demonstrating the incorporation of nitrogen into graphene structure. The doping effect reflected an important impact on the morphological (surface defects and reactions, porosity) and structural (conductivity) properties, which allowed to enhance greatly the capacitive properties compared to undoped VOGNs. Conclusion: N-VOGN based supercapacitors have demonstrated excellent capacitive properties such as high volumetric energy (28 mWh cm-3) and power (360 W cm-3) densities as well as an outstanding cycling stability (retention of 80% after 300 000 galvanostatic charge-discharge cycles). These results are very promising compared to the state-of-the art dealing with carbonaceous structurebased supercapacitors. Consequently, this study paves the way to explore the in-depth potential of such nanostructure in the development of innovative high performance supercapacitors.

Background: Enzyme catalysis has always attracted the attention of researchers due to their unique characteristics and advantages. However, they suffer from disadvantages of being poor in yield, inoperative and ineffective in aqueous media and suffer from degradation at elevated temperature. These disadvantages have recently been overcome in new class of catalysts which utilize same enzyme catalyst power with metal ligand attached to double helical scaffold of DNA. The process is unique that it can be carried out in aqueous media at room temperature for a range of organic reactions. In addition to that, process is scalable and has good reproducibility. Methods: 3+2 Cycloaddition reaction is carried out in water at room temperature using a carefully selected amount of DNA as catalyst. Reaction is carried out in three schemes. In first scheme, neutral Platinum Sulfoxide complexes were prepared which are subsequently mixed with 2,2´-bipyrimidine to form Pt(bipym)Cl2 with 68.8% yield. This is mixed with Cu(II)trifloromethanesulfonate and (E) - methyl 2 - (benzylideneamino)acetate in a certain sequence to accomplish the reactions. Whole process takes 6 days with overall yield of 76%. Results: Completion of reaction as manifested by physical change of color and appearance of peaks in NMR spectra mark towards effectivity of catalyst. Appearance of peaks occurring at 8, 9.4 and 9.7 ppm showed the presence of CH node resulting from 2 - pyrimidine and 1benzene in one spectrum while peaks at 7.52, 7.83 and 8.44 ppm show the presence of CH node resulting from benzylidenimin in second spectra. Further, peaks at 3.68 ppm show the presence of CH3 node resulting from methyl group and peaks at 4.51 ppm show the presence of CH2 node resulting from methylene group. Conclusion: This study effectively shows the completion of a difficult to carry 3+2 cycloaddition reaction in water at room temperature owing to the presence of new class of hybrid catalysts which combine the power of enzyme catalysts represented by DNA with transition metal ligand attached to double helix scaffold of DNA to create a synergic effect of enhancement of their effectivity. The study provided a foot print of their effectivity for new series of reactions.

Background: Bismuth titanate (Bi4Ti3O12) is one of the prominent candidates in lead free ferroelectric/piezoelectric materials and also in photocatalytic materials. Moreover, it is mainly utilized in the piezotronic-smart material field. Bi4Ti3O12 demands more efforts to enhance its functional properties by modifying its chemical as well as physical features. Currently, the new class of materials is required to fulfill the necessity of multi-functionality with better performance. In this context, we proposed a novel model material and fabricated it in a facile way. Methods: In this report, we present a one-step route to synthesizing and studying of the smart material xBi-Bi4-xTi3O12-y-Bi4Ti3O12 at real-time mode in High Resolution Transmission Electron Microscope (HRTEM) at micro-scale level. Results: Bi4Ti3O12 shows significant changes under e-beam, which is converted into Bi metal nanocrystals decorated on the non-stoichiometric A-site deficient Bi4-xTi3O12-y microparticle. The surface and electronic characteristics study demonstrates the presence of Bi and also divulges that there is a modification in electronic band structures. The Fermi levels of the non-irradiated and irradiated Bi4Ti3O12 were found to be 1.45 ± 0.1 eV and 1.8 ± 0.1 eV above the valence band maximum, respectively. The chemical composition analysis of the resultant material shows signs of the existence of xBi-Bi4-xTi3O12-y-Bi4Ti3O12. Conclusion: A new class of multifunctional material like metal-n-type semiconductor / ferroelectric (xBi-Bi4-xTi3O12-y-Bi4Ti3O12) is synthesized at a micro-scale level in HRTEM and investigated systematically. The formation of the novel structure may follow the Knotek-Feibelmen mechanism involving the Auger decay of oxygen and local bond-breaking phenomenon in Aurivillius phase double layered perovskite Bi4Ti3O12.

Background: Cellulose is one of the most frequently used natural polymers, and is considered an almost inexhaustible source of raw materials. It has been used as an electrorheological material for many years due to its outstanding properties including possession of polar groups, low density and easy modification, while cellulose has complicated morphologies and crystal structures according to treatment methods. In this work, the influence of these characteristics on electrorheological properties was studied by comparing the electrorheological properties of the hydrolyzed cellulose. Methods: The hydrolyzed cellulose samples were prepared in an acid mixture of HCl and H2SO4 at different times. Their morphologies and structures were studied using scanning electron microscopy, Fourier transforms infrared spectroscopy and X-ray diffraction. The electrorheological behaviors of the raw and hydrolyzed cellulose samples in silicone oil were observed using a rotational rheometer. Results: The morphology and crystal structures of the cellulose were observed to change with hydrolyzation time and closely related to the ER properties of the cellulose. Compared to raw cellulose, hydrolyzed samples showed an initial decrease in the ER effect which was followed by increased ER effect with prolonged hydrolyzation time. Conclusion: The distinct differences in ER effects of the raw and hydrolyzed cellulose samples indicated that with the exception of particle size and shape, the condensed or crystal structures of the particles have significant effects on the ER properties of cellulose. In addition, higher degrees of crystallinity may lead to lower ER effect.

Background: Design against fatigue failure is very significant because a lot of failures in engineering applications occur due to fatigue. Notches and holes are available almost in all engineering applications. Crack initiation has a vital role in fatigue design because once crack initiates it is very difficult to stop. This work is related with design against fatigue failure considering notch at the specimen. Methods: The experimental study shows the initiation of crack caused during fatigue of casting alloys. It explains the crack initiation and fatigue strength of Aluminium alloy mineralized with silicon. By using both mechanical and thermal loading; crack initiation at notch root as well as fatigue life have been computed by means of single and two step loading. Phase life initiation has been reported by applying load sequence effect using four-point rotating and bending fatigue testing machine. A favourable working temperature and environment have been set up for the alloy used and experiments have been performed on rotating and bending fatigue testing machine. Results: The results from the experiments have been plotted in the form of S-N curves and comparison has been conducted between crack initiation to failure at several mechanical loadings with and without thermal loading. Conclusion: It has been concluded that mineralization affects during the case of both mechanical and thermal loading. Logarithmic and power behaviour of material are obtained during two different cases. Mathematical model for experimental data is also reported.