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排序方式: 共有408条查询结果,搜索用时 15 毫秒
51.
Franc ZUPANIČ Carlos A. NUNES Gilberto C. COELHO Paula L. CURY Gorazd LOJEN Tonica BONČINA 《中国有色金属学会会刊》2018,28(11):2226-2235
A novel, Nb- and Si-rich and Be-free Ni-based alloy was cast by two methods of investment casting and continuous casting to study the microstructure evolution during solidification and its mechanical properties. The solidification of the alloy started with the primary crystallization of FCC-γ, followed by a binary eutectic reaction, with the formation of a heterogeneous constituent: FCC-γ+G-phase, which replaced the low-melting eutectic (FCC-γ+NiBe) in the Be-bearing alloys. AlNi6Si3 and γ′ formed during the terminal stages of solidification by investment casting, while the formation of AlNi6Si3 was suppressed by continuous casting. The Scheil solidification model agreed very well with the experimental results. 相似文献
52.
Premnath Kumar Arun Prasad Murthy Leticia S. Bezerra Bibiana K. Martini Gilberto Maia Jagannathan Madhavan 《International Journal of Hydrogen Energy》2021,46(1):622-632
Hydrogen production through water splitting is an efficient and green technology for fulfilling future energy demands. Carbon nanotubes (CNT) supported Ni2P has been synthesized through a simpler hydrothermal method. Ni2P/CNT has been employed as efficient electrocatalysts for hydrogen and oxygen evolution reactions in acidic and alkaline media respectively. The electrocatalyst has exhibited low overpotential of 137 and 360 mV for hydrogen and oxygen evolution reactions respectively at 10 mA cm?2. Lower Tafel slopes, improved electrochemical active surface area, enhanced stability have also been observed. Advantages of carbon support in terms of activity and stability have been described by comparing with unsupported electrocatalyst. 相似文献
53.
Carlos Angelo Nunes Belmira Benedita de Lima Gilberto Carvalho Coelho Peter Rogl Paulo Atsushi Suzuki 《Journal of Alloys and Compounds》2004,370(1-2):164-168
The currently assessed V–B phase diagram indicates a peritectoid formation at 1727 °C (V3B4+VBV5B6) for the V5B6 boride. The observation of this phase in several as-cast V–B alloys has lead us to a systematic evaluation of its stability, specially its possible formation from the liquid. In this work, V–B alloys (52–56 at.% B range) were produced through arc melting and heat-treated under high vacuum at 2000 °C for 2 h. The materials in both as-cast and heat-treated conditions were characterized through scanning electron microscopy (SEM) (backscattered electron (BSE) images) and X-ray diffraction (XRD). The features observed in the as-cast samples allowed us to conclude that this phase should be formed from the liquid through the L+V3B4V5B6 peritectic reaction. In spite of not reaching equilibrium condition during heat-treating, the results from the characterization of heat-treated samples have indicated the stability of the V5B6-phase at 2000 °C, in disagreement with the currently accepted V–B phase diagram. 相似文献
54.
Michael K. Hausmann Gilberto Siqueira Rafael Libanori Dimitri Kokkinis Antonia Neels Tanja Zimmermann Andr R. Studart 《Advanced functional materials》2020,30(4)
Cellulose is an attractive material resource for the fabrication of sustainable functional products, but its processing into structures with complex architecture and high cellulose content remains challenging. Such limitation has prevented cellulose‐based synthetic materials from reaching the level of structural control and mechanical properties observed in their biological counterparts, such as wood and plant tissues. To address this issue, a simple approach is reported to manufacture complex‐shaped cellulose‐based composites, in which the shaping capabilities of 3D printing technologies are combined with a wet densification process that increases the concentration of cellulose in the final printed material. Densification is achieved by exchanging the liquid of the wet printed material with a poor solvent mixture that induces attractive interactions between cellulose particles. The effect of the solvent mixture on the final cellulose concentration is rationalized using solubility parameters that quantify the attractive interparticle interactions. Using X‐ray diffraction analysis and mechanical tests, 3D printed composites obtained through this process are shown to exhibit highly aligned microstructures and mechanical properties significantly higher than those obtained by earlier additively manufactured cellulose‐based materials. These features enable the fabrication of cellulose‐rich synthetic structures that more closely resemble the exquisite designs found in biological materials grown by plants in nature. 相似文献
55.
Moacir Godinho Filho Antonio Gilberto Marchesini Jan Riezebos Nico Vandaele Gilberto Miller Devós Ganga 《国际生产研究杂志》2017,55(17):4891-4911
The main goal of this research is to identify whether companies that have implemented the Quick Response Manufacturing (QRM) approach have full knowledge of the QRM principles or have merely applied the elements (principles and tools) that have a close relationship with Lean Manufacturing. Based on a review of the literature regarding the QRM principles, an exploratory survey was conducted for over 20 manufacturing companies from Brazil, Europe and the USA that operate in an Engineer or Make to Order environment system and explicitly have conducted QRM journeys. The results of the present study show that (i) the surveyed companies have difficulty knowing and applying some of the exclusive elements of this approach, even if they started implementing QRM several years ago; (ii) the surveyed companies’ knowledge degree over QRM exclusive elements is apparently higher among US-based companies due to better trained employees and better dissemination and awareness of the QRM exclusive elements; and (iii) a mentality based on productivity, low costs and due date delivery was identified as the main barrier for companies to achieve a higher knowledge degree regarding QRM. 相似文献
56.
Paul C. Rogge Padraic Shafer Gilberto Fabbris Wen Hu Elke Arenholz Evguenia Karapetrova Mark P. M. Dean Robert J. Green Steven J. May 《Advanced materials (Deerfield Beach, Fla.)》2019,31(43)
Interface‐induced modifications of the electronic, magnetic, and lattice degrees of freedom drive an array of novel physical properties in oxide heterostructures. Here, large changes in metal–oxygen band hybridization, as measured in the oxygen ligand hole density, are induced as a result of interfacing two isovalent correlated oxides. Using resonant X‐ray reflectivity, a superlattice of SrFeO3 and CaFeO3 is shown to exhibit an electronic character that spatially evolves from strongly O‐like in SrFeO3 to strongly Fe‐like in CaFeO3. This alternating degree of Fe electronic character is correlated with a modulation of an Fe 3d orbital polarization, giving rise to an orbital superstructure. At the SrFeO3/CaFeO3 interfaces, the ligand hole density and orbital polarization reconstruct in a single unit cell of CaFeO3, demonstrating how the mismatch in these electronic parameters is accommodated at the interface. These results provide new insight into how the orbital character of electrons is altered by correlated oxide interfaces and lays out a broadly applicable approach for depth‐resolving band hybridization. 相似文献
57.
Mario Lemes Proença Jr. Gilberto Fernandes Jr. Luiz F. Carvalho Marcos V. O. de Assis Joel J. P. C. Rodrigues 《International Journal of Network Management》2016,26(2):76-94
Because of constant growth in proportion and complexity of networks, flow analysis has become an indispensable tool for network management mechanisms. Through this resource, a traffic characterization, called digital signature of network segment using flow analysis (DSNSF), is accomplished. The models used for this purpose are the ant colony optimization metaheuristic, the Holt–Winters forecasting method and the statistical procedure, principal component analysis. The obtained DSNSF by each model is compared with the actual traffic of packets and bits and then subjected to specific evaluations in order to measure its accuracy. The experimental results show that the three methods could achieve good correlation indices and low normalized mean square error values between the DSNSF curve and the real traffic movement, indicating a good adaptability and efficiency in characterizing a network traffic segment. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
58.
New 3D geometries of the optical nanowire microcoil resonator are suggested and investigated theoretically. The dependence of the Q factor on coupling parameters is calculated and compared for three different profiles. Results suggest that ultra-high-Q resonators can be fabricated more easily when the nanowire microcoil resonator has a biconical profile. 相似文献
59.
de Paula M Goissis G Martins VC 《Journal of materials science. Materials in medicine》2007,18(9):1683-1690
The present paper describes the rheological properties of anionic collagen gels and anionic collagen:rhamsan composites gels
in the concentration of 0.7, 4 and 6%, estimated to be used as injectable biomaterials for plastic reconstruction. Rheological
studies of these gels showed that independently of pH, composition and concentration the viscoelastic behavior was dependent
on the frequency, with the storage modulus always greater than the loss modulus (G′ > G″ and δ < 45°). Creep experiments showed
that anionic collagen:rhamsan composites equilibrated at pH 7.4 were less elastic and more susceptible to deformation in comparison
to gels equilibrated at pH 3.5. Flow experiments indicated that the force needed for the extrusion of anionic collagen:rhamsan
composites, in comparison to anionic collagen, was significantly smaller and with a smoother flow, suggesting the association
with rhamsan may be a good alternative in the replacement of glutaraldehyde to stabilize the microfibril assembly of commercial
collagen gel preparations. Finally, on the basis of dynamic viscosity profiles found for different preparations, some of these
composites are potential candidates to be utilized in laryngology. 相似文献
60.
We determined the enthalpic and entropic contributions to the thermodynamics of coherently strained nanocrystals grown via deposition of pure Ge on Si(001) surfaces at 600 and 700 degrees C by analyzing their composition profile and local strain. We found that the free energy associated with the entropy of mixing, which drives GexSi1-x alloy formation, was significantly larger than the relaxation enthalpy that produces the islands. Thus, entropy plays a significant role in the evolution of the size and shape of the islands during growth through the strong thermodynamic drive to form an alloy. 相似文献