Synthesis,structure and optical studies of inorganic–organic hybrid semiconductor,NH3(CH2)12NH3PbI4

Synthesis, crystal structure and optical properties of two-dimensional layered inorganic–organic hybrid NH₃(CH₂)₁₂NH₃PbI₄ are presented. Intercalation strategy has also been used to fabricate single crystal and thin films of the same. As thin film, they are well oriented and stacked along the [l 0 0] direction with strong room-temperature excitonic absorption and emission characteristics. Exciton features were correlated with the relative inorganic network crumpling and conformation of alkylammonium chains. The structural features are compared with those of similar hybrid, (H(CH₂)₁₂NH₃)₂PbI₄.     

Structural,Electrical, and Ferroelectric Properties of Nb‐Doped Na0.5Bi4.5Ti4O15 Thin Films

Ferroelectric Na_0.5Bi_4.5Ti₄O₁₅ (NaBTi) and donor Nb‐doped Na_0.5Bi_4.5Ti_3.94Nb_0.06O₁₅ (NaBTiNb) thin films were prepared on Pt(111)/Ti/SiO₂/Si(100) substrates using a chemical solution deposition method. The doping with Nb⁵⁺‐ions leads to tremendous improvements in the ferroelectric properties of the NaBTiNb thin film. Room‐temperature ferroelectricity with a large remnant polarization (2P_r) of 64.1 μC/cm² and a low coercive field (2E_c) of 165 kV/cm at an applied electric field of 475 kV/cm was observed for the NaBTiNb thin film. The polarization fatigue study revealed that the NaBTiNb thin film exhibited good fatigue endurance compared with the NaBTi thin film. Furthermore, the NaBTiNb thin film showed a low leakage current density, which was 1.48 × 10^?6 A/cm² at an applied electric field of 100 kV/cm.     

Influence of sugar ring conformation on the transportability of nucleosides by human nucleoside transporters

The conformational preference of human nucleoside transporters (hNTs) with respect to sugar ring was examined using conformationally fixed purine and pyrimidine nucleosides built on a bicyclo[3.1.0]hexane template. These fixed-conformation nucleosides, methanocarba-deoxyadenosine or methanocarba-deoxycytidine in North (C3'-endo, N-MCdA and N-MCdC) or South (C2'-endo, S-MCdA and S-MCdC) conformations, were used to study inhibition of equilibrative (hENT1-4) and concentrative (hCNT1-3) nucleoside transport by individual recombinant hNTs produced in Saccharomyces cerevisiae cells or Xenopus laevis oocytes. Our results indicated that nucleosides in the North conformation were potent inhibitors of transport mediated by hCNTs whereas South nucleosides were inhibitors of hENTs, thus showing differences in the interaction with the hNTs. In summary, hCNTs exhibited strong preferences for North nucleosides whereas hENTs exhibited slight preferences for South nucleosides, demonstrating for the first time different conformational preferences among members of the two families of hNTs.     

Optimization of microwave-assisted fluidized-bed drying of carrot slices

The drying of carrot slices in a microwave-assisted fluidized-bed drying (MWFBD) system was investigated. The drying conditions such as the initial microwave power density and the inlet air temperature were optimized. The effects of different pretreatment processes such as water blanching, osmotic drying with 20% sugar solution, and 1% citric acid solution on the drying of carrot slices were investigated under the optimized drying conditions. The drying kinetics and the physical properties of the dried carrot slices were analyzed. Different mathematical models of the drying process were explored and fitted to the drying of carrot slices in MWFBD. The pretreatment of the carrot slices reduced the drying time required and improved the qualities such as color and textural strength of the dried carrot slices.     

Reinforcement of Si3N4 nanoparticles in polypropylene single fibers through melt extrusion process and their properties

We have successfully aligned/dispersed the rod and spherical‐shaped Si₃N₄ nanoparticles in the polypropylene (PP) fibers through melt extrusion process to fabricate polymer nanocomposite (PNC) single fibers. The alignment/dispersion of Si₃N₄ nanoparticles in PP/Si₃N₄ PNC fibers has been carried out in a systematic manner to produce uniform single fibers. The PNC fibers were first uniformly stretched and stabilized using a two‐set Godet machine. The as‐extruded single PNC fibers were tested for their thermal and tensile properties. The test results of PNC fibers were compared to neat PP polymer single fibers fabricated using the same procedure as PNC fibers. These results show that the PNC fibers are much (307%) higher in tensile strength and modulus (>1000%) when compared with the neat PP polymer single fibers. The field emission scanning electron microscope results clearly show the alignment of rod‐Si₃N₄ nanoparticles in polymer matrix. The differential scanning calorimetry results show ～ 12% increase in crystallinity for rod‐Si₃N₄ PNCs when compared with the neat PP single fibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Development of hard/soft ferrite nanocomposite for enhanced microwave absorption

Nickel and zinc substituted strontium hexaferrite, SrFe₁₁Zn_0.5Ni_0.5O₁₉ (SrFe₁₂O₁₉/NiFe₂O₄/ZnFe₂O₄) nanoparticles having super paramagnetic nature are synthesized by co-precipitation of chloride salts using 7.5 M sodium hydroxide solution. The resulting precursors are heat treated (HT) at 900 and 1200 °C for 4 h in nitrogen atmosphere. During heat treatment, transformation proceeds as a constant rate of nucleation and three dimensional growth with an activation energy of 176.79 kJ/mol. The hysteresis loops show an increase in saturation magnetization from 1.042 to 59.789 emu/g with increasing HT temperatures. The ‘as-synthesized’ particles with spherical and needle shapes have size in the range of 20–25 nm. Further, these spherical and needle shaped nanoparticles tend to change their morphology to hexagonal plate and pyramidal shapes with increase in HT temperatures. The effect of such a systematic morphological transformation of nanoparticles on dielectric (complex permittivity and permeability) and microwave absorption properties are estimated in X band (8.2–12.2 GHz). The maximum reflection loss of the composite reaches −29.62 dB (99% power attenuation) at 10.21 GHz which suits its application in RADAR absorbing materials.     

Effect of surface roughness and mass transfer enhancement on the performance characteristics of nickel-hypophosphite electroless plating baths for metal–ceramic composite membrane fabrication

Mass transfer enhanced electroless plating is a relatively new concept in the field of metal–ceramic composite membrane fabrication. In this article, we present the effect of substrate surface roughness along with various mass transfer enhancement techniques such as solution stirring, membrane stirring and sonication on metal conversion, plating efficiency, thickness, and percent pore densification using electroless plating of nickel on a porous disk shaped ceramic support with a nominal pore size of 700 nm. The plating characteristics were investigated for three different roughness values, stirrer speeds (0–300 rpm) and a loading ratio (defined as membrane area per unit volume of plating solution) value of 196 cm²/L. It was evaluated that stirring as well as sonication had a profound effect on sodium hypophosphite based electroless nickel baths. This led to a reduction in average membrane pore size by 100 nm for stirring and 130 nm for sonication when compared to the base case. Surface roughness was observed to influence the metal deposition characteristics for base case without mass transfer enhancement. Sonication, irrespective of surface roughness, provided the maximum values of selective conversion, densification and membrane thickness along with acceptable values of plating efficiency.     

Review of: “ TRANSPORT IH FLUIDIZED PARTICLE SYSTEMS”edited by L.K. Doraiswamy and A.S. Mujumdar published by ELSEVIER,Amsterdam - Oxford - Hew York - Tokyo, 1989

This paper is the second part of (1)and it shows an attempt to define a suitable model, which would make it possible to predict the drying rate for pastelike and bulk materials in a conventional Nautamixer applied as a direct dryer. As it was shown in (1), (2), (3) all influential variables were studied, and from the results it can be seen that the system is highly complex. By means of system simplification an empirical model is defined, suitable for drying rate calculation for this type of dryer, in the accuracy range of ±25%. For the practical purpose, it seems that this simple model offers a reliable starting point for drying process design for similar systems.     

Effects of Microwave-Assisted Hot Air Drying and Conventional Hot Air Drying on the Drying Kinetics,Color, Rehydration,and Volatiles of Moringa oleifera

In this study, the fresh Moringa oleifera pods (Drumsticks) were dehydrated by microwave-assisted hot air drying (MAHD) and conventional hot air drying methods. The samples were dried at three different temperatures, viz. 50, 60, and 70°C, with and without the application of microwaves. Microwave power density of 1 W/g was used for the MAHD. The final moisture content was targeted as 13% wb. The drying curves and drying rate curves were plotted and compared. The kinetics of drying obtained experimentally were correlated with the Page equation. The constants K and N of the Page equation were determined to predict the drying kinetics for varying conditions. The quality attributes, namely, color, rehydration ratio, and volatile compounds, were analyzed and compared with that of the fresh Moringa pods. The volatile compounds were analyzed using z-Nose (an electronic nose; Electronic Sensor Technology, Newbury Park, CA) and bioactive molecules were analyzed using gas chromatography–mass spectrometry. The results showed that the MAHD method had significantly (P < 0.05) reduced the loss of volatiles during drying. Also, MAHD preserved most of the bioactive molecules when compared to the conventional hot air drying method. The samples dried at 50°C using MAHD were the best in terms of all of the quality attributes tested in this study. Also, the results established that the z-Nose can be used as a quick and inexpensive means to assess the effect of different process parameters on the aromatic quality of the product and quantitatively classify quality based on aroma.