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排序方式: 共有1311条查询结果,搜索用时 15 毫秒
81.
Jonas
rtegren Philippe Busson Mikael Lindgren David S. Hermann Per-Otto Arntzen Fredrik Sahlen Mikael Trollss Ulf W. Gedde Anders Hult Lechezar Komitov Sven T. Lagerwall Per Rudquist Bengt Stebler 《Optical Materials》1998,9(1-4):220-225
Second harmonic generation in novel pyroelectric liquid crystal polymers (PLCP) made from a series binary mixtures, was studied using 1100 nm as the fundamental wavelength. The PLCPs were prepared by photo-polymerization of binary mixtures of two monomers which exhibit a smectic C* phase, A2c (4″-(R)-(−)-2-[(10-acrylo-yloxy)decyl]oxy-3-nitrophenyl 4-{4′-[(11-acryloyloxy)-undecyloxy]phenyl}benzoate) and Alb (4″-((R)-(+)-2-octyloxy)-3″-nitrophenyl 4-(4′-(11-acryloyloxy)undecyloxy)-phenyl)-benzoate). The highest d16 and d23 coefficients were found to be in the range 0.65–0.8 pm/V, and differed depending on the detailed preparation of the sample. All cases of polymers formed from the chiral smectic C* phase showed an SHG-signal with no external field present, indicating that polar order became fixed. The SHG-signal was found to increase with the tilt angle of the FLC molecules. 相似文献
82.
T. M. Maccagno S. Yue J. J. Jonas K. Dyck 《Metallurgical and Materials Transactions A》1993,24(7):1589-1596
An investigation was carried out on the effects of changing the hot-working, cold-working, and annealing parameters on the
interaction between A1N precipitation and recrystallization in low- carbon steels containing significant amounts of Al and
N. The primary aim was to determine whether laboratory torsion testing can be helpful in analyzing precipitation behavior
in these steels. The approach taken was first to establish the baseline annealing behavior of material that was hot- and cold-worked
in a mill and then to compare this with the behavior of material in which the hot and cold working were simulated by torsion
testing. It was found, first of all, that torsion testing can indeed provide a good simulation of the industrial process of
hot and cold working followed by annealing, even to the extent that a process as subtle as the inhibition of recrystallization
by A1N precipitation can be accurately reproduced. The results also show that the interaction between precipitation and recrystallization
during annealing is significantly influenced by the reheat temperature before hot working, as well as by the cooling rate
after hot working. 相似文献
83.
Chiradeep Ghosh Vladimir V. Basabe John J. Jonas Young-Min Kim In-Ho Jung Stephen Yue 《Acta Materialia》2013,61(7):2348-2362
Recent observations regarding the dynamic transformation of deformed austenite at temperatures above the Ae3 are reviewed. Experimental results obtained on four different steels over the temperature range from 743 to 917 °C and at strains up to ε = 5 are described. It is shown that there is a critical strain for the formation of superequilibrium ferrite and that the volume fraction of transformed ferrite increases with the strain. The structures observed are Widmanstätten in form and appear to have nucleated displacively. The effect of deformation on the Gibbs energy of austenite is estimated by assuming that the austenite continues to work-harden after initiation of the transformation and that its flow stress and dislocation density can be derived from the experimental flow curve by making suitable assumptions about two-phase flow. By further taking into account the inhomogeneity of the dislocation density, Gibbs energy contributions (driving forces) are derived that are sufficient to promote transformation as much as 100 °C above the Ae3. The C diffusion times required for the dynamic formation of the cementite particles observed are estimated. These range from ~25 to 100 μs and are therefore consistent with the times available during rolling. The Gibbs energy calculations suggest that growth of the Widmanstätten ferrite is followed by C diffusion at the lower carbon contents, while it is accompanied by C diffusion at the higher carbon levels. 相似文献
84.
Jonas Mindemark 《Polymer》2011,52(25):5716-5722
To increase the diversity in functional aliphatic polycarbonates, a series of novel chloro- and bromo-functional six-membered cyclic carbonate monomers were synthesized. Despite asymmetry in the monomer functionalities, homopolymerization of the monomers afforded semicrystalline polycarbonates with a high tendency to crystallize from the melt and/or on precipitation from a THF solution. Melting points were found in the 90-105 °C or 120-155 °C range for polymers comprising methyl or ethyl moieties, respectively, in the backbone. The monomers were further copolymerized with trimethylene carbonate to form random copolymers. Even among some of these random copolymers elements of semicrystallinity were found as confirmed by melting endotherms in DSC. The results clearly show that the incorporation of alkyl halide functionalities in aliphatic polycarbonates may lead to materials with a high ability to form crystallites, even in random copolymers, likely driven by polar interactions due to the presence of the halide functionalities. 相似文献
85.
This study shows the effects of three different nanofillers on the viscosity properties and fire behavior of a halogen‐free flame retardant system. The original system, based on ethylene‐acrylate copolymer, calcium carbonate, and a silicone elastomer, shows good flame retardant properties. One of the nanofillers, montmorillonite (MMT), significantly increases the viscosity above 250°C, resulting in reduced dripping and decreased heat release rate. The ash residue, however, is very brittle, indicating poor interactions between the MMT and other components of the system. The second nanofiller, sepiolite, shows no improvement on the flame retardant properties of the system. Reduced dripping is observed when a small amount of the third nanofiller, polyhedral oligomeric silsesquioxane, POSS, is incorporated into the system. In this case, high silica content on the surface indicates char formation originating from the POSS. However, an increased heat release is observed when POSS is used in the system. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
86.
In distillation and absorption processes, entrainment above trays or packings reduces stage and column efficiency. A modified version of the optical multimode online probe enables a seminal insight and, thus, quantification of entrained droplets on various axial and radial positions. A purging mechanism inhibits precipitation of droplets on the front lenses, while telecentric optics and illumination provide distance‐independent and precise imaging of entrained droplets between two valve trays. Experiments were performed in a DN 450 cold flow (air‐water) test rig. The results were compared with noninvasive phase Doppler anemometry data. 相似文献
87.
Kim Bini Desta Gedefaw Caroline Pan Jonas M. Bjuggren Anirudh Sharma Ergang Wang Mats R. Andersson 《应用聚合物科学杂志》2019,136(27):47729
An easily accessible anthraquinone-benzodithiophene-based high bandgap polymer (PTAq) was synthesized by Stille coupling reactions in remarkably high yield (96.5%). The highest occupied molecular orbital energy level of the polymer was estimated from the onset of oxidation in a cyclic voltammetry study to be −5.7 eV. PTAq showed an orange-to-green color switching with the application of a 1.0-V external potential to the polymer film, which was visible to the naked eye. The optical behavior change was also monitored using ultraviolet–visible absorption spectroscopy and revealed a respectable 75% transmittance change when the polymer film was subjected to a 1.0-V external potential. The high color contrast observed makes PTAq one of the most promising materials for electrochromic device applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47729. 相似文献
88.
Jonas Hedlund 《Journal of Porous Materials》2000,7(4):455-464
Single crystal silicon and quartz wafers were seeded with colloidal TPA-silicalite-1 crystals. Hydrothermal treatment of the seeded substrates was used to grow dense MFI films. The preferred orientation of the crystals constituting the films as a function of the amount and size of seeds, film thickness and hydrothermal treatment conditions was investigated. In thin films, most of the crystalline material was found to be oriented with the b-axes close to perpendicular to the substrate surface. In thick films, the a- or c-axes were close to perpendicular to the substrate surface depending on the conditions used for hydrothermal treatment. The seed size and amount was found to affect the rate of change in preferred orientation as a function of film thickness. A film growth mechanism which is able to explain the experimental results is proposed. 相似文献
89.
Mono- and multilayer graphene sheets have been successfully produced from commercial graphite powder in a wet grinding process under mild milling conditions. The shear forces in the milling chamber lead to a continuous delamination of ultrathin graphene flakes which are dispersed in a liquid medium. To avoid agglomeration of the exfoliated flakes the anionic surfactant sodium dodecyl sulfate was used. By adjusting the process parameters in a way to overcome the weak interlayer forces between the sheets without breaking them leads to the fabrication of thin flakes with high aspect ratios. The presented scalable process allows a high-yield and low-cost production of free-standing graphene sheets for various applications. 相似文献
90.