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931.
J. Bates Q. Zhang L. Spiccia B. O. West 《Journal of Sol-Gel Science and Technology》1994,2(1-3):29-34
Two lead titanium oxyalkoxides with composition Pb2Ti4O2(O2CCH3)2(OC2H5)14 and Pb2Ti2O2(O2CCH3)2(OCH(CH3)2)8 have been isolated and characterised by elemental analysis, IR, 207Pb NMR and molecular weight measurements. X-ray structural analysis of the 1:2 complex confirmed the presence of two Pb2Ti2O units which are linked by a common Pb···Pb edge and are held together by alkoxide and acetate bridges. The acetate groups have migrated from the Pb to the Ti centres during the reaction. Hydrolysis of the 1:1 Pb/Ti complex produced clear gels providing the H2O/complex ratio was less than 4. Heat treatment of the gel results in loss of residual organics below 400°C. The XRD pattern indicates the presence of the pyrochlore and perovskite phases after heating at 500°C but the sample is poorly crystalline. Complete conversion to the perovskite phase of lead titanate occurs on heating to 600°C for 1 hour. Thin films of lead titanate were deposited by dip-coating a solution of this complex in isopropanol. Analyses of the films, carried out using electron microprobe, Scanning Auger Spectroscopy and Rutherford Backscattering, indicated that they were of excellent quality, crystalline after heating at 600°C and with relatively sharp substrate-coating interface. 相似文献
932.
933.
934.
935.
The hydrothermal reaction of VOSO4, As2O5, piperazine and H2O produces [H2N(CH2)4NH2]4[β‐As8V14O42(SO4)]·2HSO4 ( 1 ), which is the first arsenic‐vanadium cluster containing a spherical β‐As8V14O42 shell. The structure of this compound was characterized by single crystal X‐ray diffraction, elemental analysis, TG, and IR spectrum. Crystal data for 1 : Orthorhombic, Cmcm, a = 15.369(1) Å, b = 16.404(1) Å, c = 25.772(1) Å, V = 6497.4(9) Å3, Z = 4. 相似文献
936.
It is well known that porphyrin derivatives play a key role in the primary process of photo-synthesis[1], in which porphyrins directly absorb the sunlight or indirectly acquire excitation en-ergy from light-harvesting antenna system to reach their excited state, and then donate electrons to quinone acceptors to yield a series of charge-separated species. In general, only first singlet ex-cited state of porphyrins is involved in energy transfer process[2]. However, highly excited state (S2 stat… 相似文献
937.
Guo Jin-xin Sun Si-xiu Zhu Rong-xiu Yin Zhi-lei Yu Hai-yun Li Da-zhi Zhang Wei-min Xu Xian-gang Sun Xuan Shao Hua 《Journal of Radioanalytical and Nuclear Chemistry》2004,261(1):221-224
The 222Rn emanation fraction (EF) released from the technically enhanced naturally occurring radioactive material (TE-NORM) wastes
at certain sites of petroleum and gas production was determined. The samples were analyzed by γ-ray spectrometry to determine
the activity concentration of the 226Ra content, of which the 222Rn emanation fraction was calculated. The results showed that the 222Rn emanation fraction differs in the oil and gas production sites and it is independent of the activity concentration of 226Ra.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
938.
2,6-O-diethyl-β-cyclodextrins were prepared and immobilized onto silica gel to develop a fluorosensor for dipyridamole. The
analytical performance characteristics of the proposed sensor for analysis of dipyridamole were as follows: the detection
limit was 0.8 nmol/L with a relative standard deviation of 1.4% for 10 determinations of 50 nmol/L of dipyridamole. The modification
of β-CD improved the sensitivity and selectivity for measuring dipyridamole. The recommended method has been successfully
tested for the determination of dipyridamole in clinical samples (urine and pharmaceutical preparations).
Received: 23 January 1997 / Revised: 14 April 1997 / Accepted: 21 April 1997 相似文献
939.
The styrene-butadiene rubber (SBR) cured by dicumyl peroxide was reinforced by magnesium methacrylate [Mg(MAA)2], which was added into SBR directly or prepared in situ in SBR through the neutralization of magnesium oxide (MgO) and methacrylic acid (MAA). The experimental results show that the SBR vulcanizates reinforced by Mg(MAA)2 prepared in situ have better mechanical properties than those reinforced by Mg(MAA)2 added directly. The SBR vulcanizates with Mg(MAA)2 prepared in situ are semi-transparent, but those with Mg(MAA)2 added directly are opaque. The Fourier transform infrared analysis shows that the polymerization conversion of Mg(MAA)2 in the SBR vulcanizates with Mg(MAA)2 prepared in situ is much higher than that in the SBR vulcanizates with Mg(MAA)2 added directly. The scan probe microscopy photographs show that the particles in the SBR vulcanizates with Mg(MAA)2 prepared in situ are much finer and disperse more evenly than that in the SBR vulcanizates with Mg(MAA)2 added directly. 相似文献
940.
Liancai Wang Xiangjun Bi Aiying Zhang Jianye Zhou 《Polymer Degradation and Stability》2006,91(9):2220-2228
A series of biodegradable aliphatic/aromatic copolyesters, poly(butylene terephthalate)-co-poly(butylene cyclohexanedicarboxylate)-b-poly(ethylene glycol) (PTCG), were prepared by a two-step melt polycondensation method and characterized by means of GPC, FTIR, NMR, DSC, TGA, etc. The effects of aliphatic ester content on the physical, mechanical and thermal properties, as well as in vitro and in vivo degradation behaviors were investigated. The decrease in mechanical strength was observed with an increase in poly(butylene cyclohexanedicarboxylate) (PBC) molar fraction. DSC results showed one melting point and two glass transition temperatures in all samples, and the melting temperature was found to go down gradually as more cyclohexanedicarboxylic acid (CHDA) was added. During the in vitro and in vivo degradation processes, erosion of the surface was dominant as evidenced by scanning electron microscopic observations. The copolyesters containing many CHDA units were featured by the higher water uptake and faster degradation due to much richer amorphous phase within them. 相似文献