Mechanosynthesis of nanostructured composites copper-fullerite,copper-graphite

Comparative studies of the influence of carbon allotropic form on the formation of the structural-phase composition of copper-based composites have been performed by means of Scanning Electron Microscopy, X-ray and Thermal analysis and Raman spectroscopy. It has been stated that the kinetics of solid state reactions in the systems Cu-C_60/70 and Cu-C_g obtained in process of mechanosynthesis depend on deformational stability and oxidation-reduction properties of fullerite and graphite. It has been shown that partial destruction of fullerene molecules in the Cu-C_60/70 sample results in the formation of an amorphous fullerite-like phase, copper oxide Cu₂O, and supersaturated solid solution Cu(C, O). Total destruction of fullerene molecules in the system Cu-C_60/70 results in the formation of supersaturated solid solution Cu(C), just like in the case of the composite Cu-C_g.     

Synthesis and characterisation of nanostructured silica-powellite-HAP composites

Well-defined calcium molybdate (CaMoO₄) and hydroxyapatite (HAP) nanocrystals were developed by thermal treatment on the surface of a SiO₂–CaO–P₂O₅–MoO₃ amorphous precursor synthesised at room-temperature by sol–gel route. The structural and morphological characterisaions were performed by several techniques: energy dispersive X-ray spectroscopy, thermal analyses (DTA/TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy, electron paramagnetic resonance. Complementary, Fourier transform infrared and Raman spectroscopies provided a clear picture regarding the short range order structure, emphasising beside the CaMoO₄ phase development, the presence of HAP nanocrystals. The vibrational spectroscopic techniques proved to be valuable tools for evidencing very small HAP nanocrystallites that cannot be clearly observed by XRD and TEM analyses.     

Stability aspects of bulk nanostructured metals and composites

The requirement of thermal stability of nanocrystalline materials can be fulfilled with a composite approach. However, utilizing a two-phase approach includes additional constraints concerning the synthesis and processing, especially of massive nanostructured materials. Here, the potential of deformation processing for synthesizing nanoscale composite structures with uniform microstructures in bulk shape is analyzed for a series of Cu-rich alloys. The results are discussed with respect of governing materials properties that determine the feasibility of a composite approach in combination with severe plastic deformation to obtain massive nano-composite materials with high thermal stability.     

Processing and characterization of nanostructured Cu-carbon nanotube composites

Carbon nanotube (CNT) reinforced nanostructured Cu matrix composite with a grain size less than 25 nm has been successfully fabricated via a combination of ball milling and high-pressure torsion. CNTs were found to be homogeneously dispersed into the metal matrix, leading to grain refinement with a narrow grain size distribution and significant increase in hardness.     

Microstructure of AA2024-SiC nanostructured metal matrix composites

Nanostructured metal matrix composites (NMMCs) in large-dimension billets were fabricated by hot isostatic pressing (HIPing) of cryomilled powders consisting of AA2024 alloy reinforced by 25 wt.% SiC particles. Microstructure of the bulk nanostructured composites and cryomilled powders was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). In addition, mechanical properties of the bulk nanocomposites were also addressed.     

纳米结构的炭钌复合物-一种提高超级电容器性能的电极材料

报道了一种利用氧化硅模板,裂解简单易得的含钌有机物制备纳米结构炭/钌复合物的方法.在该复合物中,钌纳米颗粒均匀地分布在多孔的炭基体中.该复合物被电氧化所得炭/RuO2·xH2O的超级电容性质明显提高(10 mV/s 时229 F/g ).     

Defining the nanostructured morphology of triblock copolymers using resonant soft X-ray scattering

The morphologies of a poly(1,4-isoprene)-block-polystyrene-block-poly(2-vinyl pyridine) (IS2VP) copolymer were investigated using resonant soft X-ray scattering (RSoXS) together with scanning force microscopy, small-angle X-ray scattering, and electron microscopy. Differences in the nanoscopic morphologies in the bulk and thin film samples were observed arising from the competition between segmental interactions between the blocks and the substrate and the surface energies of each block. Using soft X-rays at selected photon energies to isolate the scattering contribution from different polymer blocks, RSoXS unambiguously defined the complex morphology of the triblock copolymer. In the bulk sample, two nested, hexagonal arrays of P2VP and PI cylindrical microdomains residing in the PS matrix were observed. The cylindrical microdomains of one component were found to be located at the interstitial sites of the hexagonal array of the other component that has the larger d spacing. In solvent-annealed thin films with 40 nm in thickness, a hexagonal array of core-shell microdomains of P2VP cores with PS shells that reside in a PI matrix were observed.     

Preparation and characterization of GA/RDX nanostructured energetic composites

Graphene aerogel (GA) with nano-porous structure was assembled through the formation of physical cross-links between graphene sheets by a facile sol–gel method and supercritical CO ₂ drying process. Then hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) was added and trapped in the nano-porous three-dimensional networks of GA to obtain a novel GA/RDX nanostructured energetic composite. The composition, morphology and structure of the obtained GA/RDX nanostructured energetic composite were characterized by elemental analysis, scanning electron microscopy, nitrogen sorption tests and X-ray diffraction. Moreover, the thermal decomposition characteristic was investigated by thermogravimetry and differential scanning calorimetry. The results showed that GA could be a perfect aerogel matrix for the fabrication of GA/RDX nanostructured energetic composite due to its unique nano-porous structure and attributes. It was also demonstrated that RDX homogeneously disperses in the as-prepared GA/RDX nanostructured energetic composite at nanometric scale. GA showed promising catalytic effects for the thermal decomposition of RDX. After incorporating with GA, the decomposition of RDX was obviously accelerated.     

High capacitive performance of nanostructured Mn-Ni-Co oxide composites for supercapacitor

Nanostructured Mn-Ni-Co oxide composites (MNCO) were prepared by thermal decomposition of the precursor obtained by chemical co-precipitation of Mn, Ni and Co salts. The chemical composition and morphology were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The electrochemical capacitance of MNCO electrode was examined by cyclic voltammetry, impedance and galvanostatic charge-discharge measurements. The results showed that MNCO electrode exhibited the good electrochemical characteristics. A maximum capacitance value of 1260 F g⁻¹ could be obtained within the potential range of −0.1 to 0.4 V versus saturated calomel electrode (SCE) in 6 mol L⁻¹ KOH electrolyte.     

Photovoltaic properties of nanostructured copper sulfide incorporated silicon rich composites

In the present experimentation, the photovoltaic properties of CuS incorporated SiO₂ nanocomposites were investigated. The nanocomposite between CuS and SiO₂ were prepared by solid state diffusion method. During the process of solid state diffusion, silicic acid was used as source of silicon. The prepared composites characterized by X-ray diffractions, scanning electron microscopy, ultraviolet–visible spectrophotometers, Raman spectroscopy, photoluminescence spectroscopy and thermal analysis and photovoltaic measurements. IV characteristics of PV cell shows that performance of cell is sensitive to concentration of CuS in composite. The optimized power conversion efficiency was 1.11% found to be for 15 wt% CuS loaded SiO₂ composite having fill factor 0.189 under the power incidence of 0.0104 W/m².     

Processing and behavior of nanostructured metallic alloys and composites by cryomilling

Recent interest in nanostructured materials stems, not only from their potential use in a variety of applications, but also from the reported discovery of novel fundamental phenomena. The consolidation of cryomilled powder provides a potential pathway towards large scale manufacturing of nanostructured metallic materials. This approach typically engenders the mechanical attrition of powders in liquid nitrogen, followed by consolidation, using established commercial techniques, such as isostatic pressing and extrusion. In this overview paper, published data are reviewed and discussed with particular emphasis on the following topics: nanostructure evolution mechanisms; primary consolidation and secondary processing methods; thermal stability of cryomilled materials; and mechanical behavior of consolidated materials. Recent mechanical behavior data and the associated mechanisms of cryomilled Al alloys are discussed in an effort to shed light into the fundamental behavior of ultrafine grained and nanostructured materials.     

Hybrid silicon-carbon nanostructured composites as superior anodes for lithium ion batteries

We have successfully fabricated a hybrid silicon-carbon nanostructured composite with large area (about 25.5 in²) in a simple fashion using a conventional sputtering system. When used as the anode in lithium ion batteries, the uniformly deposited amorphous silicon (a-Si) works as the active material to store electrical energy, and the pre-coated carbon nanofibers (CNFs) serve as both the electron conducting pathway and a strain/stress relaxation layer for the sputtered a-Si layers during the intercalation process of lithium ions. As a result, the as-fabricated lithium ion batteries, with deposited a-Si thicknesses of 200 nm or 300 nm, not only exhibit a high specific capacity of >2000 mA·h/g, but also show a good capacity retention of over 80% and Coulombic efficiency of >98% after a large number of charge/discharge experiments. Our approach offers an efficient and scalable method to obtain silicon-carbon nanostructured composites for application in lithium ion batteries.      

Synthesis and electrochemical behavior of nanostructured cauliflower-shape Co-Ni/Co-Ni oxides composites

Nanostructured Co-Ni/Co-Ni oxides were electrochemically deposited onto stainless steel electrode by electrochemical method and characterized for their structural and supercapacitive properties. The SEM images indicated that the obtained Co-Ni/Co-Ni oxides had cauliflower-type nanostructure. The X-ray diffraction pattern showed the formation of Co₃O₄, NiO, Co and Ni. The EDX elemental mapping images indicated that Ni, Co and O are distributed uniformly. The deposited Co-Ni/Co-Ni oxides showed good supercapacitive characteristics with a specific capacitance of 331 F/g at 1 mA/cm² current density in 1 M KOH electrolyte. A mechanism of the formation of cauliflower-shape Co-Ni/Co-Ni oxides was proposed. A variety of promising applications in the fields such as energy storage devices and sensors can be envisioned from Co-Ni/Co-Ni oxides.     

Predicting fracture of layered composites caused by internal instability

The present paper estimates the critical strain at which ply instability occurs in compressible layered composites under uniaxial or biaxial compression. This is achieved by using two methods: the continuum approach and the model of piecewise-homogeneous medium in conjunction with the three-dimensional stability theory. The accuracy of the continuum theory is examined by taking into account the influence of layer thickness, stiffness properties and biaxiality of loads. Also, upper and lower bounds for the critical buckling strain of laminates with interfacial defects (cracks with connected edges) are determined using the results for perfectly bonded and sliding layers.     

UHMWPE纤维增强LDPE复合材料的界面形态研究

为实现聚乙烯单聚合物复合材料(PE SPC)的嵌件注射成型,研究基体与增强体间的界面非常关键.本文采用超高分子量聚乙烯(UHMWPE)纤维增强低密度聚乙烯(LDPE)基体,对纤维和基体进行了差示扫描量热仪测试,在偏光显微镜下模拟了基体与纤维的复合过程,研究不同因素对复合材料界面结晶形态的影响.根据DSC确定了UHMWPE和LDPE复合的温度范围在110.98~147.14℃;合适的温度和剪切作用都有利于界面横晶的产生,从而使基体和纤维产生更好的粘结,提高复合材料的力学性能;温度比剪切的影响更大,注射温度设置在125~135℃可在保证纤维与基体复合的情况下不破坏纤维的增强作用;纤维丝之间会相互影响界面结晶形态,部分界面有横晶产生,说明在实际注射成型过程中纤维束或纤维布的结构对基体渗透和界面形成有较大影响.     

Interface morphology of carbon fibre/PEEK composites

The morphology of high-performance thermoplastic composites (APC-2) based on continuous carbon fibres embedded in a poly-ether-ether-ketone matrix is studied by means of scanning electron microscopy. Samples with different degrees of crystallinity obtained using different thermal treatments are investigated. The effect of the crystallinity content seems to be crucial for fibre/matrix adhesion, as can be detected by SEM analysis.     

Predicting failure in textile composites using the Binary Model with gauge-averaging

First introduced over a decade ago, the Binary Model has evolved into a computationally efficient tool for predicting the properties of textile composites. Key to the formulation is the question of what details of the textile composite and the distributions of stress, strain, temperature, etc., are necessary and sufficient to represent the physics of the problem adequately and to ensure useful engineering predictions. This paper is concerned specifically with the prediction of the ultimate strength in cases where failure follows a single substantial local damage event, such as the rupture or kinking of a tow or the creation of a shear band mediated by matrix damage, without further increase in the external load. The accuracy of predictions is assessed for some triaxially braided carbon/epoxy composites. A gauge length is introduced that is suggested by the micromechanics of the failure mechanisms. Predictions are made by reference to strains that are averaged over a volume whose sides are commensurate with this gauge, but nevertheless retain spatial variations associated with the textile architecture. Failure criteria for tow rupture and matrix shear failure are taken from a single un-notched tensile test; the calibrated model then successfully predicts the failure mechanism (matrix shear or fiber rupture) and ultimate strength in un-notched and open-hole tension tests for any orientation of the textile fabric relative to the load axis, as well as bending and simple shear tests. The successful predictions are made using strains calculated for an entirely elastic representation of the material, which is possible because of the brittle character of the stress-strain curves. Predictions are also attempted using strains computed under the assumption that the textile material is homogeneous. These predictions are significantly inferior.