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931.
932.
采用玄武岩短纤维(BF)增强硅橡胶,制备了BF/硅橡胶复合材料,考察了硅烷偶联剂的种类、BF用量以及硫化条件对复合材料力学性能的影响,并用扫描电子显微镜观察了复合材料的微观形貌。结果表明,用KH 550对BF进行表面处理,所得复合材料的力学性能优于以Si 69处理的材料;当BF用量为20份时,BF/硅橡胶复合材料的力学性能最好;制备复合材料的最佳硫化条件为10 MPa×175℃×25 min;用KH 550处理BF,BF与硅橡胶的相容性比用Si 69处理的好。 相似文献
933.
934.
新疆某石化公司的10-K-302C离心式甲烷制冷压缩机自开机以来,其润滑油管线振动位移一直较大,运用Workbench有限元软件对空管系统进行模态分析,获得管道的固有频率和振型;采用双向流-固耦合的数值模拟方法,分析对比了润滑油在耦合时的压力、速度变化及管道耦合前后的振动频率、位移变化规律;通过将数值模拟振动分析结果与实际管路实测振动结果对比,肯定了数值模拟分析的准确性,得出了共振和管内流体速度在管道弯头处突变而造成瞬间激振力过大是管道振动主要原因的基本结论;依据上述结论,对管路系统进行了减振控制,设计后的数值模拟分析表明,管系振动大幅减少,满足工业化生产要求。 相似文献
935.
936.
Min‐Tsang Hsieh Sheng‐Chu Kuo Hui‐Chang Lin 《Advanced Synthesis \u0026amp; Catalysis》2015,357(4):683-689
The regioselectivity of the [3+2] cyclocondensation of trifluoromethyl‐α,β‐ynones with hydrazines can be readily tuned to preferentially afford either 3‐ or 5‐trifluoromethylpyrazoles through variation of the reaction conditions. Under catalysis with copper(II) acetate (2.0 mol%), cyclocondensation proceeded smoothly to yield 3‐trifluoromethylpyrazoles with high regioselectivity. In contrast, when the reaction was conducted in dimethyl sulfoxide under catalyst‐free conditions, the formation of 5‐trifluoromethylpyrazoles was predominantly observed.
937.
Bao‐Xin Du Zheng‐Jun Quan Yu‐Xia Da Zhang Zhang Xi‐Cun Wang 《Advanced Synthesis \u0026amp; Catalysis》2015,357(6):1270-1276
A general protocol for the chemoselectivity‐controlled C C and C S coupling reactions of di(hetero)aryl disulfides with Grignard reagents catalyzed by ferrocene and palladium acetate has been developed. Ferrocene favored the formation of C S coupled products at low temperature, whereas C C bond couplings were favored when palladium acetate was used. All the reactions proceeded with excellent chemoselectivity and in good yields under mild conditions, and a library of molecules with pyridine and pyrimidine scaffolds was produced.
938.
Keisuke Yotsuji Naoyuki Hoshiya Takaaki Kobayashi Hayato Fukuda Hiroshi Abe Mitsuhiro Arisawa Satoshi Shuto 《Advanced Synthesis \u0026amp; Catalysis》2015,357(5):1022-1028
We describe a nickel‐catalyzed Suzuki–Miyaura arylation of a tertiary iodocyclopropane with arylboronic acids; this is an efficient and convergent strategy for providing various enantioenriched arylcyclopropanes with a quaternary stereogenic center. This is the first metal‐catalyzed coupling between a tertiary alkyl electrophile and a wide range of aromatics, including heteroaromatics. We found that the outcome of the Ni‐catalyzed coupling with halides as electrophiles was dependent on the stability of the radical species formed during the reaction. The use of tert‐butyl alcohol (t‐BuOH) as the reaction solvent was very effective, because of its stability under the radical‐generating reaction conditions.
939.
Farhad Panahi Marzieh Bahmani Nasser Iranpoor 《Advanced Synthesis \u0026amp; Catalysis》2015,357(6):1211-1220
The reductive benzylation of aromatic and aliphatic aldehydes with benzylic halides is reported using a nickel/zinc catalyst system. In addition to benzylic halides, the first report on the addition of benzylic triflates, acetates, tosylates and tritylates to aldehydes is also presented. By this new method a range of alcohols was synthesized efficiently from aldehydes and benzylic substrates at room temperature in moderate to high yields. The mild reaction conditions and good functional group tolerance make this nickel‐catalyzed process synthetically useful for the synthesis of diverse benzylic alcohols.
940.
Electrostatically designing materials opens a new avenue for realizing systems with user‐defined electronic properties. Here, an approach is presented for efficiently patterning the electronic structure of layered systems such as graphene by means of collective electrostatic effects. Using density‐functional theory simulations, it is found that lines of polar elements can strongly modify the energy landscape of this prototypical 2D material. This results in a confinement of electronic states in specific regions of the sample and, consequently, in a local energetic shift of the density of states. The latter is also directly reflected in the details of the band structure of the electrostatically patterned sample. Finally, it is shown that the approach can also be successfully applied to other 2D materials such as hexagonal boron nitride, where the effects are predicted to be even more pronounced than in graphene. 相似文献