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排序方式: 共有207条查询结果,搜索用时 15 毫秒
81.
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Aitala EM Amato S Anjos JC Appel JA Ashery D Banerjee S Bediaga I Blaylock G Bracker SB Burchat PR Burnstein RA Carter T Carvalho HS Copty NK Costa I Cremaldi LM Darling C Denisenko K Fernandez A Gagnon P Gerzon S Gobel C Gounder K Halling AM Herrera G Hurvits G James C Kasper PA Kwan S Langs DC Leslie J Lundberg B MayTal-Beck S Meadows B de Mello Neto JR Milburn RH de Miranda JM Napier A Nguyen A d'Oliveira AB O'Shaughnessy K Peng KC Perera LP Purohit MV Quinn B Radeztsky S Rafatian A 《Physical review letters》1996,77(12):2384-2387
84.
J. Martinez-Salazar M. Sánchez Cuesta F. J. Baltá Calleja 《Colloid and polymer science》1987,265(3):239-245
New equilibrium melting point data, for polyethylene containing chain defects, are tested in the light of random copolymer predictions. A simplified expression for the melting point depression of random copolymers containing small amounts of non-crystallizable units is derived. Non-equilibrium melting data for rapidly quenched polyethylene samples are also reported. The fusion enthalpyH(X), and the surface free energy
e
for crystals containing defects are evaluated using crystallinity, equilibrium meltingtemperatures and X-ray long period data. It is shown that increasing defect penetration within crystals induces a decrease ofH(X) withX in accordance with theoretical predictions. Finally
e
is, similarly, shown to decrease with increasing number of chain defects attached to the crystal surface. 相似文献
85.
Serrano DP Calleja G Sanz R Pizarro P 《Chemical communications (Cambridge, England)》2004,(8):1000-1001
A new mild crystallization procedure has been applied after a synthesis route in the presence of a non-ionic surfactant, leading to the preparation of bimodal micro-mesoporous TiO2, with remarkable textural properties and pore walls formed by anatase nanocrystals, which exhibit photocatalytic activity. 相似文献
86.
Electrochemistry: A Tool for Characterization of Hybrid Materials Obtained by Non-Hydrolytic Sol-Gel Route and Containing Ferrocene Derivatives 总被引:3,自引:0,他引:3
G. Calleja G. Cerveau P. Labbé L. Coche-Guérente 《Journal of Sol-Gel Science and Technology》2003,26(1-3):307-310
The 1,1-ferrocenediyldichlorosilane 1 was introduced into oxide matrices (SiO2, TiO2, Al2O3) by non-hydrolytic sol-gel route. In all cases some degradation of the ferrocenyl moiety occurred. The materials were immobilized onto an electrode surface as a composite film with PTFE and their cyclic voltammograms were studied. For each sample a reduction wave around –375 mV was evidenced which was attributed to the reduction of [FeIII Cl
x
]3 – x
species arising from the decomposition of ferrocenyl species during the condensation process. 相似文献
87.
A. Flores J. Aurrekoetxea R. Gensler H. H. Kausch F. J. Baltá Calleja 《Colloid and polymer science》1998,276(9):786-793
The influence of molecular weight on the mechanical properties of isotactic poly(propylene) (iPP) and iPP blended with ethylene-propylene
copolymers has been investigated by means of the microhardness technique. The hardness (H) of iPP is shown to slightly decrease with increasing molecular mass, within the range of molecular weights investigated.
The H-decrease is correlated to a loss of crystallinity as the average molecular weight increases. On annealing, the mechanical
properties are enhanced as a consequence of an increase in both, the degree of crystallinity and the crystalline lamellar
thickness. A value of H
∞
c for iPP crystals of infinite thickness in the α-form is proposed for the first time. The inclusion of EPR particles in the
iPP matrix softens the material. This result could be explained in terms of an increase in the basal surface free energy of
the iPP crystals with increasing amount of rubber content.
Received: 2 February 1998 Accepted: 11 May 1998 相似文献
88.
H. G. Kilian W. Schrodi F. Ania R. K. Bayer F. J. Baltá Calleja 《Colloid and polymer science》1991,269(9):859-866
The compressive stress-strain behavior of biaxially oriented polyethylene (PE), obtained by pressing uniaxially oriented samples, is described with the aid of the van der Waals equation of state. Results are discussed in terms of two parameters: the biaxiality (B) and the biaxial draw ratio (), which offer a measure of the strain along the two principal directions and of the average draw ratio on the film plane, respectively. Comparison of experimental and calculated data indicates that after compression up to very large deformations the maximum average strain (
m
), which is proportional to the square root of the chain length of the network, remains constant. This result supports the view that the network of entanglements is not destroyed after compression. Experiments carried out on isotropic melt crystallized PE show the presence of a network having a not very different chain length. Finally, it is shown that the segment length of this network is close to the X-ray long period of the initial structure. This result implies the existence of a high density of entanglements (two entanglements every three adjacent lamellae), which are rejected into the defective layer of the crystals. 相似文献
89.
Dopico G MS González R MV Castro R JM González S E Pérez I J Rodrı́guez T M Calleja A Vilariño JM 《Talanta》2003,59(3):561-569
Triazine herbicides form a wide group of substances that belong among the most common agrochemicals applied for pre- and post-emergence weed control. So, they can be found in the environment at trace level. In order to determine their concentrations in water samples by the usual analytical techniques, a preconcentration step is commonly necessary. In this paper, a simple analytical method for the quantification of eight triazines (three chlorotriazines, four methylthiotriazines and one methoxytriazine) in water samples by solid phase extraction-reversed phase liquid chromatography (LC) has been developed. LC shows good analytical performance for simultaneous multiple triazine analysis (repeatability <2%, reproducibility <3%), except for prometon (repeatability 5.52%, reproducibility 16%). The results, obtained by using carbograph and polymeric sorbents for solid phase extraction (SPE), have been compared. The limits of quantification achieved permit the application of the proposed SPE-LC method for the determination of eight triazines in water samples (0.0065-0.028 μg l−1). 相似文献
90.