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排序方式: 共有144条查询结果,搜索用时 46 毫秒
1.
Thermogravimetric analysis of hydroxyl terminated polybutadiene (HTPB) and its fractions of different molecular weights separated by preparative GPC shows two major stages of weight loss of different nature in a nitrogen atmosphere. The first stage is primarily depolymerisation, cyclisation and crosslinking of molecules and the second stage is mainly the decomposition of the residue from the first stage. The kinetic parameters, viz. activation energy E and pre-exponential factor A using four different non-isothermal integral equations show a systematic increase with increase in molecular weight for the first stage, whereas for the second stage, the effect of molecular weight on E and A values is not prominent. The increase in E and A values for the first stage is attributed to the formation of greater number of cyclised and crosslinked products from molecules of higher dimensions. Quantitative correlations between the kinetic constants and the molecular weight parameters were derived for the first stage as a quadratic curve following the equation: E or ln A = K1 − K2/M (where K1 and K2 are empirical constants whose values are different for the different molecular weight averages, viz. Mn, Mw and Mz and for the different equations). 相似文献
2.
H. Karimian 《Journal of Dispersion Science and Technology》2013,34(4):457-464
Dispersion behavior of colloidal Al2O3 aqueous suspensions was investigated in the presence of highly charged CeO2 nanoparticles and polymeric additives. It was found that among the investigated parameters, ceria nanoparticles concentration had the highest significant effect on the stability of Al2O3-CeO2 suspensions. However, the low influence of dispersant concentration may be due to significant role of ceria nanoparticles stabilizing alumina microspheres by “nanoparticle halo” formation. The stabilization of the bidispersed suspensions was also evidenced by scanning electron microscopy and elemental analysis of the sediment layers after three weeks. 相似文献
3.
4.
Yuanyuan Yu Huihui Gao Jiadeng Zhu Dazhe Li Fengxia Wang Chunhui Jiang Tianhaoyue Zhong Shuheng Liang Mengjin Jiang 《中国化学快报》2021,32(1):203-209
Low-cost silicon microparticles(SiMP),as a substitute for nanostructured silicon,easily suffer from cracks and fractured during the electrochemical cycle.A novel n-type conductive polymer binder with excellent electronic and ionic conductivities as well as good adhesion,has been successfully designed and applied for high-performance SiMP anodes in lithium-ion batteries to address this problem.Its unique features are attributed to the stro ng electron-withdrawing oxadiazole ring structure with sulfonate polar groups.The combination of rigid and flexible components in the polymer ensures its good mechanical strength and ductility,which is beneficial to suppress the expansion and contraction of SiMP s during the charge/discharge process.By fine-tuning the monomer ratio,the conjugation and sulfonation degrees of the polymer can be precisely controlled to regulate its ionic and electronic conductivities,which has been systematically analyzed with the help of an electrochemical test method,filling in the gap on the conductivity measurement of the polymer in the doping state.The experimental results indicate that the cell with the developed n-type polymer binder and SiMP(~0.5 μm) anodes achieves much better cycling performance than traditional non-conductive binders.It has been considered that the initial capacity of the SiMP anode is controlled by the synergetic effect of ionic and electronic conductivity of the binder,and the capacity retention mainly depends on its electronic conductivity when the ionic conductivity is sufficient.It is worth noting that the fundamental research of this wo rk is also applicable to other battery systems using conductive polymers in order to achieve high energy density,broadening their practical applications. 相似文献
5.
Volume expansion and polysulfide shuttle effect are the main barriers for the commercialization of lithium-sulfur(Li-S) battery.In this work,we in-situ polymerized a cross-linked binder in sulfur cathode to solve the aforementioned problems using a facile method under mild conditions.Polycarbonate diol(PCDL),triethanolamine(TEA) and hexamethylene diisocyanate(HDI) were chosen as precursors to prepare the cross-linked binder.The in-situ polymerized binder(PTH) builds a strong network in sulfur cathode,which could restrain the volume expansion of sulfu r.Moreover,by adopting functional groups of oxygen atoms and nitrogen atoms,the binder could effectively facilitate transportation of Li-ion and adsorb polysulfide chemically.The Li-S battery with bare sulfur and carbon/sulfur composite cathodes and cross-linked PTH binder displays much better electrochemical performance than that of the battery with PVDF.The PTH-bare S cathode with a mass loading of 5.97 mg/cm^2 could deliver a capacity of 733.3 mAh/g at 0.2 C,and remained 585.5 mAh/g after 100 cycles.This in-situ polymerized binder is proved to be quite effective on restraining the volume expansion and suppressing polysulfide shuttle effect,then improving the electrochemical performance of Li-S battery. 相似文献
6.
7.
The humidity and water tolerance of a sol-gel derived binder prepared using a cheap, multicomponent precursor has been studied.
The sol was prepared by dissolving the precursor in water under acidic conditions using either formic acid or a mixture of
formic acid and citric acid for pH adjustments. It is shown that a post-treatment temperature of 400 °C or higher is needed
in order to achieve full binder stability under excess water conditions, as thermal decomposition of metal carboxylates leads
to a pronounced decrease in water solubility of the gels. The mesoporous gel can be made hydrophobic by post-treatments with
either a silane or an organophosphonate, showing that both silica and metal oxides are exposed on the surface of the binder.
Surface functionalization is especially effective for gels heat-treated at higher temperatures where the metal carboxylates
have decomposed to the corresponding oxides or carbonates. The results are expected to be of great importance for the use
of this cheap binder in large scale industrial applications.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
8.
Vasant R Choudhary Chinta Sivadinarayana Kshudiram Mantri 《Journal of Chemical Sciences》1999,111(5):669-676
The acidity and initial and time-on-stream activity in propane aromatization (at 550°C, space velocity of 3100 cm3g−1
(zeolite)h−1) of Ga-impregnated H-ZSM-5 zeolite without or with binders (50 wt%), such as silica, alumina and kaolin, have been investigated.
Both the acidity and catalytic activity of the zeolite are influenced by the presence of binder in the catalyst, depending
upon the binder. The influence is found to be lowest for alumina and highest for kaolin. Among the binders, alumina is the
most preferred binder for the zeolite catalyst. 相似文献
9.
Adhesive ability of a heat-resistant double-chain polymer and the strength of CFRP based on it 总被引:1,自引:0,他引:1
Yu. A. Gorbatkina V. G. Ivanova-Mumjieva A. M. Kuperman I. I. Ponomarev V. I. Sidorenko 《Mechanics of Composite Materials》2008,44(4):371-378
The adhesive ability of a heat-resistant polyiminoquinazolindione (PIQD) binder, based on a double-chain polymer, and the
physicomechanical characteristics of unidirectional CFRPs made with it are investigated. It is shown that, at room temperature,
the strength of model adhesive joints (PIQD-steel wire) and of the CFRPs in shear and bending is rather low — about half of
that of similar specimens based on an epoxy binder. At the same time, all their mechanical characteristics, to a large measure
(50%), are retained at temperatures up to 450°C, which considerably exceeds the heat resistance of all polymer matrices used
at the present time. The elastic modulus of the CFRPs in bending practically remains the same up to 450°C.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 535–546, July–August, 2008. 相似文献
10.
《中国化学》2017,35(12):1844-1852
The binder‐free composite films of reduced graphene oxide (rGO ) and activated carbon derived from cotton (aCFC ) have been fabricated and used as electrodes for electrochemical capacitors (ECs ) to avoid the decrease of capacitive performance in traditional process caused by the additional binder. The optimal aCFC is prepared at 850 °C when the mass ratio of carbon and potassium hydroxide is 1 to 4. The optimal composite film prepared from the mass ratio of aCFC /GO =2/1 exhibits porous structure, and has a specific surface area of 849.6 m2•g−1 and a total pore volume of 0.61 mL •g−1. Based on the two‐electrode system testing in 6.0 mol/L KOH electrolyte, the optimal composite has specific capacitance of about 202 F•g−1, 374 mF •cm−2 and 116 F•cm−3 in terms of mass, area and volume, and shows excellent rate capability and good cyclic stability (91.7% retention of the initial capacitance after 5000 cycles). Furthermore, the assembled solid‐state ECs by using KOH /polyvinyl alcohol as electrolyte show good mechanical stability and capacitive performances after repeated bending cycles. It is proved that this method is effective to fabricate binder‐free electrodes for ECs and will open up a novel route for the reuse of waste cotton. 相似文献