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Nagaraja C.M.,Materials Unit | Maji T.K.,Materials Unit | Rao C.N.R.,Materials Unit
Journal of Molecular Structure | Year: 2010

Three new compounds of CoII, NiII and CuII with a flexible dicarboxylate building block 1,3-phenylenediacetate, along with 4,4′-bipyridine, or 4,4′-trimethylenedipyridine co-ligands, with the formula {[Co2(4,4′-bipy)2(1,3-pda)2]·1.5H2O}n (1), {Ni(4,4′-bipy)(1,3-pdaH)2(CH3CH2OH)2}n (2), and {Cu(tmdp)(1,3-pda)}n (3), (where, 1,3-pda = 1,3-phenylenediacetate, 4,4′-bipy = 4,4′-bipyridine, and tmdp = 4,4′-trimethylenedipyridine) have been synthesized and structurally characterized. Compound 1 was synthesized hydrothermally at 180 °C, whereas 2 and 3 were synthesized at room temperature in H2O/ethanol medium. The 2D coordination network of 1 is formed by pillaring the 1D staircase Co2(1,3-pda)2 chain by 4,4′-bipy, whereas the 3D supramolecular framework 2 is constituted by connecting the 2D H-bonded Ni(1,3-pdaH)2(C2H5OH)2 sheets. Compound 3 shows an unusual 2D network which is built by the flexible 1,3-pda and tmdp linkers by connecting Cu2(1,3-pda)2 dimeric building unit. © 2010 Elsevier B.V. All rights reserved.

Madera-Santana T.J.,CINVESTAV | Robledo D.,CINVESTAV | Azamar J.A.,CINVESTAV | Rios-Soberanis C.R.,Materials Unit | Freile-Pelegrin Y.,CINVESTAV
Polymer Engineering and Science | Year: 2010

Low density polyethylene (LDPE) and agar were blended by using the former as an internal mixer and varying the amount of agar. Resulting blends were hot pressed and characterized with regard to their torquerheological, mechanical, dynamic-mechanical, thermal, and morphological properties. The torque rheological properties were determined using classical power law model. Tensile properties of LDPE-agar biocomposites showed that agar improves the tensile modulus (stiffness), but compromise the tensile strength and elongation at break. Viscoelastic behavior of the matrix is clearly influenced by the presence of agar biofiller as shown by the dynamic mechanical analysis (DMA). Thermal behavior of the biocomposites was also investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Morphological observations by scanning electron microscopy (SEM) show the ductile to brittle fracture of LDPE-agar biocomposites subjected to tensile test. This work is an initial reference to identify potential applications of biocomposites based-on agar as a biofiller. POLYM. ENG. SCI., 50:585-591, 2010. © 2009 Society of Plastics Engineers.

Loria-Bastarrachea M.I.,Materials Unit | Aguilar-Vega M.,Materials Unit
Journal of Membrane Science | Year: 2013

Dense membranes were prepared from three different rigid block copolyaramides, one block bearing two bulky hexafluoro (-CF3) groups and a lateral tert-butyl group (-C-(CH3)3), and the second block without the lateral tert-butyl group. The effect of block length, at constant comonomer concentration, on thermal properties as well as gas permeability coefficients and separation factors is analyzed. The results indicate that block copolyaramide membranes present a density that is quite similar but slightly lower, as the length of the blocks that form the copolymer increase, that falls in between the density of the homopolyamides. The fractional free volume, FFV, increases in the block copolymers as the block length increases. This result is attributed to an inefficient packing of the copolymer molecules as the block length gets larger. As a result, the permeability and diffusion coefficients in the block copolymers are larger than those in the parent homopolymers. The gas separation factors remain with a minimum change even though there is a gain in gas permeability; therefore, block copolymerization using highly rigid blocks, due to differences in packing, presents the advantage of a higher gas permeability coefficient with a minimum loss in selectivity. The rigidity of these copolymers presents advantages for high temperature applications. © 2013 Elsevier B.V.

News Article | January 14, 2016

A research team led by Takashi Sekiguchi, a leader of the Nano Device Characterization Group, Nano-Electronic Materials Unit, International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Japan, and Koichi Kakimoto, a professor at the Research Institute for Applied Mechanics, Kyushu University, Japan, has developed a new method to grow high-quality mono silicon at low cost. The research resulted in the invention of a new casting method called a single-seed cast method. It dramatically improved the quality of crystals created compared to conventional casting methods, which potentially leads to the development of more efficient silicon solar cells. As the current conversion efficiency of mainstream silicon-type solar cells has already reached 20%, it is required in future development to increase conversion efficiency even more to add higher value to the cell products. However, this goal is not achievable using conventionally cast polycrystalline silicon. In addition, there is demand for the development of a new silicon material to replace polycrystalline silicon and single-crystal silicon for semiconductors, because dislocation-free single crystal silicon for semiconductors is not adequately competitive pricewise. To address this issue, the research team developed a single-seed cast method, a new silicon casting method using a seed crystal, and succeeded in growing a high-quality single-crystal silicon (mono silicon) ingot with low impurity. In the new casting method, silicon is melted in a crucible, and a single crystal is grown from a small seed crystal. This method is less expensive than the method to create single crystal silicon for semiconductors due to reduced raw material use and manufacturing costs. Moreover, the conversion efficiency of a solar cell prototype created using the crystal grown by this method was as high as 18.7%. This efficiency was very close to the efficiency of dislocation-free single-crystal silicon (Czochralski (Cz) silicon) wafers for semiconductors (18.9%), which were evaluated concurrently. In future studies, the conversion efficiency of mono silicon may exceed that of Cz silicon by further reducing crystal defects and the impact of impurities. It is also feasible to grow an ingot as large as a 50-cm cube using the current facility. As such, the facility is compatible with and can be integrated into the existing production line. In the future, it may be possible to make the solar cell industry market competitive again by transferring this new technology and other technologies derived from it to solar cell manufacturers in Japan. This research was conducted as a part of the NEDO project titled "Development of next-generation high-performance technology for photovoltaic power generation system." This study has been published in the 9-20-2015 issue (Vol. 242) of Solid State Phenomena, and presented at the FY2015 NEDO new energy research report meeting on October 28. Explore further: Team develops new technique for growing high-efficiency perovskite solar cells More information: Takashi Sekiguchi et al. 50 cm Size Seed Cast Si Ingot Growth and its Characterization, Solid State Phenomena (2015). DOI: 10.4028/

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