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排序方式: 共有1314条查询结果,搜索用时 765 毫秒
131.
Zhang Xihua Liu Changxia Li Musen Bai Yunqiang Sun Junlong 《Ceramics International》2009,35(5):1969-1973
Hydroxyapatite/alumina/diopside ceramic composites were fabricated by hot-pressing. The hardness, fracture toughness and bending strength of the new fabricated composites were measured. The compositions of hydroxyapatite matrix ceramic composites were discussed by XRD and FT-IR analysis. Microstructures of the composites were studied on fracture surfaces. The bending strength and fracture toughness of 58 vol.% hydroxyapatite, 40 vol.% alumina and 2 vol.% diopside sample, were 200 MPa and 2.80 MPa m1/2, respectively. 相似文献
132.
分别用HCl和H2SO4处理从棉纤维中提取的纤维素,100℃下回流水解30~60 min得到微晶纤维素(MCC),并对其进行醋酸酯化表面改性.采用X-射线衍射(XRD)、热重分析(TG)、红外光谱(IR)技术研究酸处理对MCC的聚合度、结晶度和热稳定性的影响,探讨了改性方法对产物性能的影响.结果表明,纤维素微晶化后仍保持原来的晶型以及晶区和非晶区共存的微细结构,结晶度不能达到100%.扫描电子显微镜(SEM)测试结果表明,不同酸处理后所得产物的形态和热性能有所不同,MCC的最高适用温度不宜超过270℃.适宜的醋酸酯化改性条件为:硫酸和水体积比1∶8、温度60~70℃、改性处理3~5 h.改性后微晶纤维素的内部结晶区结构没有变化,在有机溶剂中的分散性得到良好的改善. 相似文献
133.
《Synthetic Metals》2004,146(2):207-212
Pitch fibers were prepared from identical petroleum-derived isotropic pitch precursors (IPPs) by both meltspinning and electrospinning. The fibers obtained were stabilized, carbonized, and then finally activated by steam at various conditions. The specific surface area of the noble electrospun (E-spun) fibers was calculated to be 6.4 times larger than that of meltspun (M-spun) fibers due to their finer diameter. The activation was considered as first-order reaction with frequency factor 6.55 × 10−4 s−1 and the activation energy of 162.3 kJ/mol for E-spun fibers, and for the M-spun fibers with respective values of 4.45 × 10−4 s−1 and 183.5 kJ/mol. The activation rates of the E-spun fibers were calculated to be 13–20 times faster than those of M-spun fibers in the activation temperatures. The higher activation rates for the E-spun fibers were rationalized on the basis of the higher frequency factors and the lower activation energy due to their finer diameters and less ordered structure than those of M-spun fibers. 相似文献
134.
以高浓度葡萄糖为碳源的L-苏氨酸发酵工艺研究 总被引:1,自引:0,他引:1
以L-苏氨酸生产菌TRFC为供试菌株,研究了高葡萄糖浓度下各种生长因子和培养条件对L-苏氨酸发酵的影响。结果表明,脯氨酸可以解除高浓度葡萄糖对L-苏氨酸发酵的抑制作用,生物素可以提高L-苏氨酸生产菌的细胞得率及L-苏氨酸的产量,利用摇瓶发酵确定最佳用量分别为60mg/L和120μg/L;控制pH7.0和采用控制溶氧的脉冲补料方式L-苏氨酸产量得到进一步的提高。在最优条件下,利用10L发酵罐发酵38h,L-苏氨酸产量可达110.2g/L,糖酸转化率为45.7%。 相似文献
135.
136.
137.
《Inorganic chemistry communications》2002,5(5):369-371
α-MnSe crystallites were prepared by solvothermal reaction in ethylenediamine at 190 °C. X-ray diffraction gave the α-MnSe phase of product, X-ray photoelectron spectroscopy indicated the valence state of Mn2+ and Se2−. The flaky morphology was found by the transmission electron microscope images. The optimal synthetic conditions were explored by using other nitrogen-containing solvents, and lowering the reaction temperature. 相似文献
138.
Both silane and multiwall carbon nanotubes (CNTs) were grafted successfully onto carbon fibers (CFs) to enhance the interfacial strength of CFs reinforced methylphenylsilicone resin (MPSR) composites. The microstructure, interfacial properties, impact toughness and heat resistance of CFs before and after modification were investigated. Experimental results revealed that CNTs were grafted uniformly onto CFs using 3-aminopropyltriethoxysilane (APS) as the bridging agent. The wettability and surface energy of the obtained hybrid fiber (CF-APS-CNT) were increased obviously in comparison with those of the untreated-CF. The CF-APS-CNT composites showed simultaneously remarkable enhancement in interlaminar shear strength (ILSS) and impact toughness. Moreover, the interfacial reinforcing and toughening mechanisms were also discussed. In addition, Thermogravimetric analysis and thermal oxygen aging experiments indicated a remarkable improvement in the thermal stability and heat oxidation resistance of composites by the introduction of APS and CNTs. We believe the facile and effective method may provide a novel interface design strategy for developing multifunctional fibers. 相似文献
139.
Yuguang Chao Peng Zhou Jianping Lai Weiyu Zhang Huawei Yang Shiyu Lu Hui Chen Kun Yin Menggang Li Lu Tao Changshuai Shang Meiping Tong Shaojun Guo 《Advanced functional materials》2021,31(24):2100923
Designing a semiconductor-based heterostructure photocatalyst for achieving the efficient separation of photogenerated electron-hole pairs is highly important for enhancing H2 releasing photocatalysis. Here, a new class of Ni1−xCoxSe2–C/ZnIn2S4 hierarchical nanocages with abundant and compact ZnIn2S4 nanosheets/Ni1−xCoxSe2 C nanosheets 2D/2D hetero–interfaces, is designed and synthesized. The constructed heterostructure photocatalyst exposes rich hetero-junctions, supplying the broad and short transfer paths for charge carriers. The close contacts of these two kinds of nanosheets induce a strong interaction between ZnIn2S4 and Ni1−xCoxSe2 C, improving the separation and transfer of photo-generated electron-hole pairs. As a consequence, the distinctive Ni1−xCoxSe2 C/ZnIn2S4 hierarchical nanocages without using additional noble-metal cocatalysts, display remarkable H2-relaesing photocatalytic activity with a rate of 5.10 mmol g−1 h−1 under visible light irradiation, which is 6.2 and 30 times higher than those of fresh ZnIn2S4 nanosheets and bare Ni1−xCoxSe2 C nanocages, respectively. Spectroscopic characterizations and theory calculations reveal that the strong interaction between ZnIn2S4 and Ni1−xCoxSe2 C 2D/2D hetero-interfaces can powerfully promote the separation of photo-generated charge carriers and the electrons transfer from ZnIn2S4 to Ni1−xCoxSe2 C. 相似文献
140.
Chuanpeng Li Lunwu Zhang Zhonghai Lu Rui Ding Xiaodong Zhao Bin Wang Hongtao Cui Jie Liu 《工业材料与腐蚀》2021,72(4):732-742
The waterline corrosion behaviors of carbon steel partially immersed in a 3.5 wt% NaCl solution were investigated using the wire beam electrode technique, and the effects of corrosion products on the processes of waterline corrosion were analyzed. The results demonstrated that the initial stage and development stage of waterline corrosion were mainly controlled by the concentration and diffusion of dissolved oxygen, respectively, and the deceleration stage of waterline corrosion was mainly affected by corrosion products. The main component of the yellow corrosion products was γ-FeOOH, and γ-FeOOH that exhibited a high reduction reactivity could be involved in the cathodic reaction. The black corrosion products were mainly composed of Fe3O4 with strong thermodynamic stability and the processes of dissolved oxygen diffusion and ion transports were obviously affected due to the continuous accumulation of Fe3O4 on the surface of the electrodes. Polarity reversals were observed on the single electrodes below the waterline, but the reasons for the phenomena were different from each other. 相似文献