排序方式: 共有29条查询结果,搜索用时 15 毫秒
21.
Polyelectrolyte solutions of nylon-4,6 in 99 vol.% formic acid were electrospun, and then the concentration effect on the solution spinnability was studied. The microstructure of the as-spun nanofibers was characterized by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). Based on the solution rheology, the concentration of the entangled regime and the concentrated regime (? D ) were 1 and 10 wt.%, respectively. To prepare bead-free fibers, the minimum polymer concentration used was 10 wt.%, yielding a fiber diameter of 49?±?13 nm. The fiber diameter (d f) was dependent on the solution viscosity ( $ {\eta_{\mathrm{o}}} $ ) or the polymer concentration (?w) through the following simple scaling law relation: d f?~? $ \eta_{\mathrm{o}}^{0.62 } $ and d f?~? $ {{({\phi_{\mathrm{w}}}/{\phi_{\mathrm{D}}})}^{2.25 }} $ . DSC heating trace on the as-spun nanofibers exhibited double-melting behavior. However, after cooling, the second heating trace showed a single melting peak. WAXD intensity profiles showed that the as-spun nanofibers possessed lamellae with small lateral dimensions, and the lattice parameter difference between a-axis and b-axis was significantly reduced due to the rapid electrospinning process. Both structural features induce the occurrence of the Brill transition of nylon-4,6 in the nanofibers at a much lower temperature of 80 °C than that in the melt-processed film, as-revealed by the temperature-variable WAXD. 相似文献
22.
Sheng-Hung Wu Jen-Hao Chi Chun-Chin Huang Nung-Kai Lin Jiou-Jhu Peng Chi-Min Shu 《Journal of Thermal Analysis and Calorimetry》2010,102(2):563-568
Hydrogen peroxide (H2O2), historically, due to its broad applications in the chemical industries, has caused many serious fires and explosions worldwide.
Its thermal hazards may also be incurred by an incompatible reaction with other chemical materials, and a runaway reaction
may be induced in the last stage. This study applied thermal analytical methods to explore the H2O2 leading to thermal accidents by incompatibility and to discuss what might be formed by the upset situations. In this study,
the thermal hazard analyses were conducted with various solvents, propanone (CH3COCH3), Fe2O3, FeSO4, H2SO4, HCl, HNO3, H3PO4, NaOH, LiOH, and KOH which were deliberately selected to individually mix with H2O2 for investigating the degree of hazard. Differential scanning calorimetry (DSC) was employed to evaluate the thermal hazard
of H2O2-mixed ten chemicals. The results indicated that H2O2 is highly hazardous while separately mixed with ten materials, as a potential contaminant. Fire and explosion hazards could
be successfully reduced if the safety-related data are suitably imbedded into manufacturing processes. 相似文献
23.
Jen-Hao Chi 《Journal of Thermal Analysis and Calorimetry》2013,113(2):641-648
PU foam samples which had caused fire to spread in an actual arson case were collected for thermal analysis experiments. The experiments were conducted at three different heating rates to obtain thermal reaction parameters including ~3,518.23–5,127.81 J g?1 of heat release at temperatures between 395 and 433 °C. The thermal analysis data were treated as the input data for the Fire Dynamics Simulator program. Results of smoke layers falling in the simulation space were compared and verified with the heights of smoke traces at the actual fire scene to obtain heating rates which are close to the actual conditions for the reconstruction of the entire fire scene. In addition to serving as a reference for the investigation and reconstruction of other fire cases, these research findings can also increase the awareness of the harmful aspects of PU foam for fire prevention in the future. 相似文献
24.
Liu YM Lin YC Chen WC Cheng JH Chen YL Yap GP Sun SS Ong TG 《Dalton transactions (Cambridge, England : 2003)》2012,41(24):7382-7389
This paper describes the synthesis of 1-(pyridine-4-ylmethyl) NHC and their Pd(II) and Ag(I) complexes, which are fully characterized. Interestingly, we have also synthesized a Pd complex 3a-CO(3) using a more direct treatment of K(2)CO(3) with PdCl(2). 3a-CO(3) represents the first reported solid structure of a Pd η(2)-carbonato complex stabilized by an NHC framework. 3a-CO(3) can be easily converted to a PdCl(2) derivative by treating it with chloroform. We have found these palladium complexes mediate the Heck-Mizoroki coupling with a low catalyst loading. Furthermore, we also expand such catalytic manifold toward constructing fused polyaromatic substrates, a highly useful class of compounds in optoelectronic chemistry. 相似文献
25.
A c-axis orientated aluminium nitride (AlN) film on a 128° Y-X lithium niobate (LiNbO3) surface acoustic wave (SAW) device which exhibit a large electromechanical coupling coefficient (k2) and a high SAW velocity property, is needed for future communication applications. In this study, a c-axis orientated (B, Al)N film (with 2.6 at.% boron) was deposited on a 128° Y-X LiNbO3 substrate by a co-sputtering system to further boost SAW device properties. The XRD and TEM results show that the (B, Al)N films show highly aligned columns with the c-axis perpendicular to the substrate. The hardness and Young's modulus of (B, Al)N film on 128° Y-X LiNbO3 substrates are at least 17% and 7% larger than AlN films, respectively. From the SAW device measurement, the operation frequency characteristic of (B, Al)N film on 128° Y-X LiNbO3 is higher than pure AlN on it. The SAW velocity also increases as (B, Al)N film thickness increases (at fixed IDT wavelength). Furthermore, the k2 of (B, Al)N on the IDT/128° Y-X LiNbO3 SAW device shows a higher value than AlN on it. 相似文献
26.
This work presents a novel method to form polycrystalline Cu(In(1-x)Ga(x))Se(2) (CIGS) thin film by co-sputtering of In─Se and Cu─Ga alloy targets without an additional selenization process. An attempt was also made to thoroughly elucidate the surface morphology, crystalline phases, physical properties, and chemical properties of the CIGS films by using material analysis methods. Experimental results indicate that CIGS thin films featured densely packed grains and chalcopyrite phase peaks of (112), (220), (204), (312), and (116). Raman spectroscopy analysis revealed chalcopyrite CIGS phase with Raman shift at 175 cm(-1), while no signal at 258 cm(-1) indicated the exclusion of Cu(2-x)Se phase. Hall effect measurements confirmed the polycrystalline Cu(In,Ga)Se2 thin film to be of p type semiconductor with a film resistivity and mobility of 2.19×10(2) Ω cm and 88 cm(2)/V s, respectively. 相似文献
27.
28.
Lai CC Ke CP Liu SK Jheng DY Wang DJ Chen MY Li YS Yeh PS Huang SL 《Optics letters》2011,36(6):784-786
A significant advancement of cw lasing in Cr4+:Y3Al5O12 (Cr4+:YAG) double-clad crystal fiber grown by the codrawing laser-heated pedestal growth technique was demonstrated at RT. The optical-to-optical slope efficiency of 33.9% is the highest, to the best of our knowledge, among all Cr4+:YAG lasers, whether they are in bulk or fiber forms. The low-threshold lasing of 78.2?mW and high efficiency are in good agreement with the simulation. The keys to the high laser efficiency are twofold: one is the improved Cr4+ emission cross section and fluorescence lifetime due to release of the strain on the distorted Cr4+ tetrahedron, which also mitigates photobleaching in Cr4+:YAG; the other is the improved core uniformity at long fiber lengths. In addition, because of the low threshold, the impact of excited state absorption of the pump light is significantly reduced. The effects of crystal-orientation, self-selected, and pump-dependent linear polarization states were also addressed. 相似文献
29.
Kuan Chou Hou Po Chien Chou Stone Cheng Yue Jheng Lin Yi Chiu Jin Chern Chiou 《Optical Review》2011,18(1):60-65
In this investigation, a small-form-factor (SFF) pickup head with a holographic optical element (HOE) is fabricated. The system
employs a finite-conjugate object lens to focus a light beam. A holographic optical element is used to simplify the optical
configuration. It provides a better means of alignment of fabrication and reduces the size of system relative to reflective
light route. Micro prisms are fastened with HOE and a silicon substrate, laser diode and photodiode are integrated into the
optical system. The pickup head system based on discrete components and a flip chip bonder with highly accurate alignment
was to integrate it. The micro holographic optical pickup head is fabricated and tested. Experimental results including the
spot diameter and the focusing error signal (FES), demonstrate that the optical system is a feasible. 相似文献