Papers by Keyword: Diphosphate

Abstract: The diphosphate and triphosphate of an antiviral 2’,3’-dideoxynucleoside, d4T, were synthesized via a P(V)–N activation method. The key d4T phosphoropiperidate intermediate was obtained by a redox condensation method based on 2,2’-dithiodipyridine/triphenylphosphine system. The reaction of the phosphoropiperidate with phosphate and pyrophosphate in the presence of acidic 4,5-dicyanoimidazole activator afforded the desired d4T diphosphate and triphosphate in high isolated yields.

Abstract: The ternary oxide compositions xZrO2-(0.5–x/2)Al2O3-yP2O5(x=0.8, 0.9, 0.95, 1.0; y=1.0, 1.2, 1.4) and 0.9ZrO2-0.05In2O3-1.4P2O5, xSiO2-(0.5–x/2)Al2O3-1.4P2O5(x=0.9, 1.0) were synthesized by sol-gel methods, and their conductivities were investigated by ac-impedance spectroscopy. The conductivity increased with increasing P2O5 content and with decreasing heat-treatment temperature. The maximum conductivities reached over 10-2 Scm-1 at 150°C for 0.9ZrO2-0.05Al2O3-1.4P2O5 and at 225°C for 0.9SiO2-0.05Al2O3-1.4P2O5.

Abstract: Shell-core type TiP2O7-based electrolytes were synthesized by a low-temperature sol-gel method, and their conductivities were investigated by ac-impedance spectroscopy. The samples heat-treated at 500°C showed higher proton conductivities of 3.8 × 10-2 - 1 × 10-2 Scm-1 at intermediate temperatures (100 - 300°C). The conductivity decreased by reheat-treatments at 600°C and 700°C due to a decrease in the amount of the conductive amorphous shells. However, the mechanical strength of the sample pellet significantly increased by the reheat-treatment. The sample reheat-treated at 600°C kept high conductivities of 8.8 × 10-3 - 1 × 10-3 Scm-1 in a range of 100°C - 300°C.

Abstract: Phase studies and ac-conductivity measurements were carried out in the compositions M0.8In0.2Li0.2P2O7 [MILP] (M=Sn, Zr, Ti). The bulk conductivities were of the order of ~10-5 Scm-1 at 623 K and higher in the order of TiILP≥ZrILP>SnILP. The activation energies, as expected, became lower in the order of ZrILPSnILP in bulk conductivities were not correlated with that of the activation energies probably because of the impureness of the ZrILP sample.

Abstract: In this study the setting times, compressive strengths and microstructures of cements formed using pyrophosphoric acid solution and b-tricalcium phosphate (β-TCP; Ca3(PO4)2) were compared with those of cement formed using orthophosphoric acid solution and b-TCP. It was found that cement formed using pyrophosphoric acid solution set more slowly than that formed using orthophosphoric acid and could be mixed to a higher powder to liquid ratio, facilitating the production of cement exhibiting compressive strengths, without pre-compaction, as high as 25 MPa. The use of pyrophosphoric acid as opposed to orthophosphoric acid resulted in a marked change in the microstructure of the cement.