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71.
AbstractThe structure and the toughening mechanism of nacre have been the subject of intensive research over the last 30 years. This interest originates from nacre’s excellent combination of strength, stiffness and toughness, despite its high, for a biological material, volume fraction of inorganic phase, typically 95%. Owing to the improvement of nanoscale measurement and observation techniques, significant progress has been made during the last decade in understanding the mechanical properties of nacre. The structure, microscopic deformation behavior and toughening mechanism on the order of nanometers have been investigated, and the importance of hierarchical structure in nacre has been recognized. This research has led to the fabrication of multilayer composites and films inspired by nacre with a layer thickness below 1 μm. Some of these materials reproduce the inorganic/organic interaction and hierarchical structure beyond mere morphology mimicking. In the first part of this review, we focus on the hierarchical architecture, macroscopic and microscopic deformation and fracture behavior, as well as toughening mechanisms in nacre. Then we summarize recent progress in the fabrication of materials inspired by nacre taking into consideration its mechanical properties. 相似文献
72.
By a two-step fabrication process of electrolytic deposition and annealing treatment, an MgO/ZrO2 duplex-layer coating has been prepared on AZ91D magnesium alloy as a protective film against corrosion. Owing to the chemical bonding formed after the condensation of precursory hydroxides, the adhesion strength, thickness and compactness of MgO coating on the substrate are significantly enhanced by the intermediate ZrO2 layer which prevents the formation of corrosion product Mg2(OH)3Cl·4H2O. As a result, the MgO/ZrO2 duplex-layer coated specimen reveals relatively high corrosion resistance and superior stability in 3.5 wt% NaCl solution with respect to the MgO single-layer coated specimen. 相似文献
73.
Debabrata Pradhan 《Electrochimica acta》2008,54(2):430-433
Electrodeposition of metallic multilayers on Si is normally preceded by the vapour deposition of a metallic layer. Since vapour deposition produces an additional step in the production process, direct electrodeposition of multilayers on Si is desirable. However, direct electrodeposition on Si has resulted in low magnetoresistance (MR) - of the order of 1% - at room temperature. With the use of (i) electroless plated copper back contact, (ii) composite potentiostatic pulses, (iii) horizontal electrode configuration and (iv) non-continuous mode of deposition, a room temperature MR of 5.8% has been achieved. 相似文献
74.
X.M. Xu 《Thin solid films》2008,516(6):1025-1028
Using reactive radio frequency magnetron sputtering, TiN/ZrN multilayers were deposited on Si (111) substrates at 550 °C. The multilayers were annealed at different temperatures ranging from 500 to 1100 °C in air. The variation of the annealed multilayers has been investigated by X-ray diffraction and transmission electron microscopy. A layer-by-layer oxidation behavior is found in the multilayers annealed at temperatures below 900 °C. The oxidation mechanism of multilayers is discussed in the paper. 相似文献
75.
本文利用化学还原法制备了不同尺寸的金纳米颗粒,并利用离子自组装多层技术在玻璃基底上沉积了基于金纳米颗粒的复合纳米金膜,研究了颗粒尺寸和成膜厚度对复合金膜光学性质的影响。不同比例的柠檬酸钠与氯金酸产生的金纳米颗粒溶液的紫外-可见光谱随着金颗粒直径增大而红移展宽。适量比例的柠檬酸钠与氯金酸能够产生平均直径为14±1.2nm且尺寸分布均匀的金纳米球;其溶液在518nm处有一特征吸收峰。不同大小的金纳米颗粒形成的薄膜的紫外-可见光谱形状不同,局域表面等离子体共振峰的位置随着颗粒直径的减小而向短波方向迁移。薄膜的沉积层数越多,薄膜表面的颗粒分布越均匀,局域表面等离子体峰的峰值变化也将减小。本工作证实了利用离子自组装多层技术能够快速、简易、低成本地在玻璃基底上沉积具有局域表面等离子体共振的复合纳米金膜。 相似文献
76.
Electrodeposition of Zn–Ni coatings performed in acidic baths are not suitable for high strength steels due to their high susceptibility to hydrogen embrittlement.In this work, Zn–Ni coatings were deposited on a high strength steel (4340) upon stirring conditions from an alkaline bath. A complete characterisation of the coatings (corrosion, morphology and composition) has been accomplished, correlating the electrodeposition conditions with these features. The best protective properties of the grown coatings were achieved for the alloys with a single phase structure of γ-Ni5Zn21 and a denser morphology. Additionally, the hydrogen content incorporated is lower than even cadmium-coated 4340 steel which has undergone a postbaking dehydrogenation treatment. 相似文献
77.
Ni–Co–Fe2O3 composite coatings were successfully developed by sediment co-deposition. In order to improve their hot corrosion resistance, a pre-oxidation treatment was conducted at 1000 °C for 6 h. The corrosion behaviour of the oxidised composite coating was investigated at 960 °C in an atmosphere consisting of a mixture of Na3AlF6–AlF3–CaF molten salts and air. They exhibited good hot corrosion resistance due to not only the pre-formed oxide scale with (Ni,Co)O and (Ni,Co)Fe2O4 phases after pre-oxidation, but also the formation of (Ni,Co,Fe)Al2O4 phases in the outer layer and a well-distributed NiFe2O4-enriched phase along the grain boundaries in the subscale area during the corrosion process. 相似文献
78.
79.
80.
Lingling Liu Yeqiang Bu Yue Sun Jianfeng Pan Jiabin Liu Jien Ma Lin Qiu Youtong Fang 《材料科学技术学报》2021,74(15):237-245
Smooth and strong copper foils are highly required for the development of printed circuit boards and Li-ion batteries.Adding additives is an efficient and low-cost method to enhance electrodeposited copper foils.Here we chose Bis-(3-sulfopropyl)-disulfide (SPS) as the additive and investigated its concentration on the surface roughness and tensile strength of the electrodeposited copper foils.A copper foil with the smoothest surface (Rz=2.1 μm) and the highest tensile strength (~338 MPa) was prepared with 1.5 mg/L SPS.The contact angle on the copper foil decreased with the reduction of surface roughness.The enhancing mechanism of the SPS was investigated by scanning electron microscopy and X-ray diffraction.The refined grain and enhanced (220) texture were considered to be the radical reason for the smooth and strong copper foils.The electrochemical results prove the suppressing effect is related to the SPS adsorption. 相似文献