Processing of Piezocomposites by Fused Deposition Technique

Piezoelectric ceramic/polymer composites were made by a fused deposition (FD) technique, which is a solid-freeform fabrication (or layered manufacturing) technique where three-dimensional (3-D) objects are built layer by layer from a computer-aided design (CAD) file on a computer-controlled fixtureless platform. Indirect and direct FD methods were used to fabricate lead zirconate titanate (PZT)/polymer composites. For the indirect method, a CAD file for the negative image of the final part was created. A polymer mold was made via FD using a thermoplastic filament, and composite formation was completed via a lost mold technique. In the direct FD method, a thermoplastic polymeric filament that was filled with 50–55 vol% of PZT powder was used to form a positive image of the desired structure. Three-dimensional honeycomb ("3-D honeycomb") composites and "ladder" composites with 3-3 connectivity, which were formed via the FD technique, showed excellent electromechanical properties for transducer applications. In addition, the FD technique showed the ability to form composites with controlled phase periodicity, various volume fractions, and a variety of microstructures and macrostructures that are not possible with traditional composite-forming techniques.     

Hydrogen peroxide sensing properties of PVA/TiO2/I2 nanocomposite‐based free standing membranes

The nanocomposite of titanium‐di‐oxide (TiO₂)/iodine (I₂) in polyvinyl alcohol (PVA) matrix has been explored to be used in hydrogen peroxide (H₂O₂) sensing applications for the first time. The proposed nanocomposite can be easily casted in the form of thin film on glass substrates as well as free standing membranes. These nanocomposite films and membranes exhibit reduced resistance values and easily observable colour changes in the presence of H₂O₂. The films also exhibit significant quenching in photoluminescence emission properties upon H₂O₂ exposure. These sensor responses have been attributed to redox reactions at nanocomposite films and H₂O₂ interface. This study indicates an easy to fabricate, flexible and environmental friendly sensing platform for H₂O₂. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42257.     

Flash sintering of a three‐phase alumina,spinel, and yttria‐stabilized zirconia composite

Three‐phase ceramic composites constituted from equal volume fractions of α‐Al₂O₃, MgAl₂O₄ spinel, and cubic 8 mol% Y₂O₃‐stabilized ZrO₂ (8YSZ) were flash‐sintered under the influence of DC electric fields. The temperature for the onset of rapid densification (flash sintering) was measured using a constant heating rate at fields of 50‐500 V/cm. The experiments were carried out by heating the furnace at a constant rate. Flash sintering occurred at a furnace temperature of 1350°C at a field of 100 V/cm, which dropped to 1150°C at a field of 500 V/cm. The sintered densities ranged from 90% to 96%. Higher electric fields inhibited grain growth due to the lowering of the flash temperature and an accelerated sintering rate. During flash sintering, alumina reacted with the spinel phase to form a high‐alumina spinel solid solution, identified by electron dispersive spectroscopy and from a decrease in the spinel lattice parameter as measured by X‐ray diffraction. It is proposed that the solid solution reaction was promoted by a combination of electrical field and Joule heating.     

Silica Solubilization Potential of Certain Bacterial Species in the Presence of Different Silicate Minerals

Silicate solubilisng bacteria (SSB) are distributed in soil, water, aquatic sediments and in silicate minerals but their population is smaller than the total bacteria indicating their uniqueness. Pond sediment showed a higher SSB with 40×10⁴ g^?1 while sugarcane field soil recorded 31×10⁴ g^?1 dry weight. SSB population in silicate minerals varied with the highest in phyto-sil followed by muscovite but very low in quartz and illite. The silicate solubilisation potential of the six isolates tested on eight minerals varied with the isolates and mineral. Magnesium trisilicate was more easily solubilised than, quartz, or muscovite. Four of the elite isolates were characterized by 16S r RNA sequencing and were found to be Bacillus flexus, B. mucilaginosus, B. megaterium and Pseudomonas fluorescens. The GC/MS analysis of organic acids produced in the medium containing feldspar and quartz by Bacillus flexus and B. muicilaginosus showed variation with the minerals. The release of silica in solution serves as a nutrient for life forms.     

Simplified MATLAB Solution Schemes of Heat Transfer Equations

A simplified generalized finite difference solution using MATLAB has been developed for steady‐state heat transfer in a bar, slab, cylinder, and sphere. Solutions are given for all types of boundary conditions: temperature and flux boundary conditions. A generalized solution for 2D heat transfer in a slab is also developed. Solutions have been compared with analytical solutions and there is very good agreement between computed and analytical solutions. The solution can easily be extended to similar types of situations in fluid flow and mass transport operations.     

Various strategies for reducing Nox emissions of biodiesel fuel used in conventional diesel engines: A review

Energy demand, decreasing fossil fuel reserves, and health-related issues about pollutants have led researchers to search for renewable alternative fuels to either partially or fully replace fossil fuels. Among many alternative fuels, biodiesel became one of the most popular choices due to similar properties to that of conventional diesel. Biodiesel produces slightly lower brake thermal efficiency compared to that of conventional biodiesel, but has an advantage of reduced emissions of CO₂, CO, HC, and smoke. However, biodiesel shows higher NOx emission which, when used in increased biodiesel market, may become a serious problem. Various strategies were attempted by different researcher to reduce NOx emissions. In this paper, various strategies, adapted for reducing NOx emissions of biodiesel fuel used in diesel engines for automobile applications, are reviewed and discussed. The strategies are grouped into three major groups, namely combustion treatments, exhaust after-treatments, and fuel treatments. Among various strategies discussed, fuel treatments, such as low temperature combustion, mixing fuel additives and reformulating fuel composition, reduce NOx emission without compromising other emission and performance characteristics and they seem to be promising for future biodiesel fuel.     

Isothermal crystallization kinetics of polypropylene in melt‐mixed composites of polypropylene and multi‐walled carbon nanotubes

The isothermal crystallization behaviour of the polypropylene (PP) phase in PP/multi‐walled carbon nanotubes (MWCNTs) composites has been investigated via differential scanning calorimetric analysis, which showed the influence of the varying dispersion level of MWCNTs in the respective PP matrix. PP/MWCNTs composites were prepared via melt‐blending technique, wherein two different grades of MWCNTs of varying average “agglomerate” size and varying entanglements (N‐MWCNTs and D‐MWCNTs) were utilized. Furthermore, the influence of melt‐viscosity of the PP phase was investigated on the crystallization kinetics of the PP/MWCNTs composites. Heterogeneous nucleation ability of MWCNTs has resulted in a decrease in half time of crystallization (t _1/2) from ～14 min for pure PP to ～6 min for PP/N‐MWCNTs and ～11 min for PP/D‐MWCNTs composites at 1 wt% of MWCNTs at 132 °C. Overall rate of crystallization (k) has significantly increased to 4.9 × 10^?2 min^?1 for PP/N‐MWCNTs composite as compared with 6.2 × 10^?3 min^?1 for PP/D‐MWCNTs composite at 0.5 wt% of MWCNTs at 132 °C. Moreover, the effect of a novel organic modifier, Li‐salt of 6‐amino hexanoic acid along with a compatibilizer (PP‐g‐MA) has also been investigated on the crystallization kinetics of the PP phase in PP/MWCNTs composites. POLYM. ENG. SCI., 57:1136–1146, 2017. © 2017 Society of Plastics Engineers     

Evaluation of polycaprolactone − poly‐D,L‐lactide copolymer as biomaterial for breast tissue engineering

The potential of the copolymer polycaprolactone‐co‐ poly‐d ,l ‐lactic acid (PCLLA ) as a biomaterial for scaffold‐based therapy for breast tissue engineering applications was assessed. First, the synthesized PCLLA was evaluated for its processability by means of additive manufacturing (AM ). We found that the synthesized PCLLA could be fabricated into scaffolds with an overall gross morphology and porosity similar to that of polycaprolactone. The PCLLA scaffolds possessed a compressive Young's modulus (ca 46 kPa ) similar to that of native breast (0.5 ? 25 kPa ), but lacked thermal stability and underwent thermal degradation during the fabrication process. The PCLLA scaffolds underwent rapid degradation in vitro which was characterized by loss of the scaffolds' mechanical integrity and a drastic decrease in mass‐average molar mass (M _w) and number‐average molar mass (M _n) after 4 weeks of immersion in phosphate buffer solution maintained at 37 °C. The tin‐catalysed PCLLA scaffold was also found to have cytotoxic effects on cells. Although the initial mechanical properties of the PCLLA scaffolds generally showed potential for applications in breast tissue regeneration, the thermal stability of the copolymer for AM processes, biocompatibility towards cells and degradation rate is not satisfactory at this stage. Therefore, we conclude that research efforts should be geared towards fine‐tuning the copolymer synthesizing methods. © 2016 Society of Chemical Industry     

Mesoporous Pt–Ni catalyst and their electro catalytic activity towards methanol oxidation

Mesoporous Pt/Ni architecture has been prepared by template assisted electrochemical deposition of Pt–Ni over anodized aluminum oxide template followed by controlled de-alloying with nitric acid. Surface characteristics of the ordered bimetallic mesoporous Pt/Ni structure were systematically characterized through XRD, SEM, AFM and XPS analyses. It is designated by XPS analysis that presence of Ni significantly modifies surface characteristics and electronic states of Pt accompanied with a downshift in the d-band character of Pt. Mesoporous morphology is highly beneficial to offer readily accessible Pt catalytic sites for methanol oxidation reaction. The prepared bimetallic Pt/Ni was used as electro catalyst for DMFC. Comparison of electrocatalytic activity of bimetallic mesoporous Pt/Ni with bimetallic smooth Pt/Ni was interrogated using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy analyses. Distinctly enhanced electrocatalytic activity with improved CO tolerance associated with bimetallic mesoporous Pt/Ni electrode towards methanol oxidation stems from a synergy existing between mesoporous structure with bi-metallic composition.