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For improving the mechanical strength of cast irons, a fully pearlitic matrix is sought by alloying with tin, copper and manganese. This applies in particular to the compacted graphite irons considered here. While average macro- and micro-hardness values were similar for the four fully pearlitic alloys under study, it was found that high copper and low tin content showed some very high maximum micro-hardness values, significantly higher than the corresponding mean. Such values may be seen as hard points in the material that would certainly impair machinability. Discussion of the reasons for these extreme values opens directions for further studies. [ABSTRACT FROM AUTHOR]

Isotropic polycrystalline graphite samples were irradiated with ~1 GeV 197Au and 238U ions of fluences up to 5 × 1013 ions/cm2. Beam-induced changes of thermophysical properties were characterized using frequency domain photothermal radiometry (PTR) and the underlying structural transformations were monitored by Raman spectroscopy. The ion range (~60 µm) was less than the sample thickness, therefore thermal diffusivity contributions of the irradiated as well as non-irradiated layer were considered when analyzing the PTR data. At the highest applied fluences, the thermal effusivity of the damaged layer degrades down to 20% of the pristine value and the corresponding calculated values of thermal conductivity decrease from 95 Wm−1K−1 for pristine material to 4 Wm−1K−1, a value characteristic for the glassy carbon allotrope. This technique provides quantitative data on thermal properties of ion-irradiated polycrystalline graphite and is very valuable for the prediction of lifetime expectancy in long-term applications in extreme radiation environments. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract Nanocomposite microstructures dominating the anisotropic elastic properties in carbon fibers were studied, to construct a micromechanics model that can explain the anisotropic elastic properties of carbon fibers. Aluminum-based composites containing five types of carbon fibers were prepared, and their anisotropic elastic properties were measured using resonant ultrasound spectroscopy combined with electromagnetic acoustic resonance. Then, all the independent elastic stiffness components of the carbon fibers were extracted from those of the composites using a composite model based on Eshelby's inclusion theory, Mori–Tanaka mean-field theory, and effective-medium approximation. Moreover, we newly developed a nanocomposite microstructure model that can fully reproduce all the anisotropic constants of carbon fibers exhibiting a wide variety of Young's moduli. In the developed model, the microstructures of carbon fibers were approximated as nanocomposites comprised of an amorphous carbon matrix and graphite-crystal inclusions that are aggregations of graphite nanocrystallites. Based on this nanocomposite microstructure model, the shape of the graphite-crystal inclusions and the elastic properties of the amorphous carbon matrix were analyzed, considering the volume fraction and orientation of the graphite nanocrystallites, as determined using X-ray diffraction. The analysis revealed that the shapes of the graphite-crystal inclusions are flat ellipsoids elongated along the fiber axis, and the aspect ratio of the graphite-crystal inclusions dominantly affects the anisotropy in the Young's modulus. This indicates that the graphite nanocrystallites are connected along the in-plane directions of the graphitic layers, and not the shape of nanocrystallites but their two-dimensional connectivity dominates the anisotropic elastic modulus in carbon fibers. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Two vastly different types of load-displacement responses observed in graphitic nanostructures under nano-compression are compared in terms of serration behaviors. Different from commonly encountered linear/nonlinear elastic deformation, a periodic serration behavior related to plastic flow is observed in amorphous carbon nanospheres. The true stress-strain relation exhibits a sole feature of type C serration, and comprehensive statistical, dynamical and fractal analyses further demonstrate a chaotic characteristic of dynamics for those serration events. When entering a quasi-steady flow stage, the elastic stress in each serration event could maintain a relatively stable level near ∼135 MPa, very close to the interlayer shear stress (ISS) of single crystalline graphite (∼140 MPa). This finding indicates the dependence of shear deformation on weak van der Waals interaction (elastic constant C 44), instead of other structural factors associated with high elastic constants of graphite cells. Based on the experimental results, a microscale ISS-driven shearing mechanism is proposed. The local flexibility induced by small graphene lamellas may facilitate interfacial slip between neighboring domains with commensurate contact. Such slip mode may be responsible for the mechanical serration phenomenon in graphitic materials. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Nanocomposite films containing silver nanowires (Ag NWs) and graphene-oxide nanoplatelets (GONPs) were formed on glass, and the nanocomposite films were then transferred to poly(methylmethacrylate) (PMMA) films. Scanning electron microscopy images showed that Ag NWs with a length of 20 μm and a width of 80 nm, together with GONPs with a size of 15 μm, had been formed on the PMMA film and that the Ag NWs on the PMMA film were partially covered with the GONPs. While the transmittance of the PMMA film with the Ag NWs and the GONPs was almost the same as that of the PMMA film with the Ag NWs alone, the corresponding sheet resistance was decreased due to the generation of quaternary nitrogen in the GONPs, which the results of X-ray photoelectron spectroscopy and Raman spectroscopy confirmed. The transmittance and the sheet resistance of the PMMA film containing Ag NWs and GONPs were approximately 90% at 550 nm and 24 Ohm/sq, respectively. [ABSTRACT FROM AUTHOR]

Carbothermic reduction of manganese oxide under various gases in the temperature range of 1273-1573 K in order to understand the formation reaction of manganese carbide is investigated. The experimental results indicate that the formation reaction of manganese carbide depends on the temperature, the CO partial pressure, and the activity of carbon. The reaction rate for MnC formation is shown to be correlated with the CO gas diffusivity of the atmosphere in that the CO partial pressure acts as the driving force for the formation reaction in question. Furthermore, the results indicate that the reaction rate of MnC formation under H gas is significantly faster than that under He gas; that is because methane gas that is formed by the reaction between H with carbon accelerates the overall reduction process. On the other hand, a high CO partial pressure is shown to retard the formation reaction of MnC. [ABSTRACT FROM AUTHOR]

Several formulas for determining the concentration dependence of diffusion coefficients are introduced for a one-dimensional semi-infinite diffusion problem, applying the Boltzmann-Matano method to 'S-shaped' concentration profiles approximated by model functions. The functions are expressed in terms of the Gauss error function, hyperbolic tangent, exponential, and inverse tangent. For all model profiles the corresponding formulas for the diffusion coefficient are calculated. Rapid estimates of the diffusion coefficient are also provided as simple expressions obtained by evaluating the formulas at the center of the concentration profile. The results for the individual profiles are compared, and it is demonstrated that even very similar profiles can lead to rather different diffusion coefficients, especially at low concentrations. Using two examples of different diffusion processes, it is demonstrated that the results can be employed to rapidly calculate diffusion coefficients. In addition, it is shown that a finite diffusion coefficient at low concentrations only occurs if the corresponding concentration profile decays at a Gaussian rate or faster. [ABSTRACT FROM AUTHOR]

This work reports on a tribological study of magnetron-sputtered silicon-containing amorphous carbon thin films vs. their alumina counterparts. Temperature cycling during ball-on-disk tests in humid air revealed a decrease in the coefficient of friction from 0.3 to <0.02 beyond 240 ± 15 °C. Systematic variation of the environment confirmed oxygen to be responsible for the low friction. X-ray photoelectron spectroscopy of the wear tracks indicates oxidation of Si C bonds and formation of Si O C bonds, followed by further oxidation to SiO 2 above 450 °C. Ab initio molecular dynamics simulations of gas interactions with the a-C surface revealed dissociation of O 2 and the formation of oxides. Additional density functional theory calculations of Si incorporation into a graphene layer, resembling the surface of the film, showed preferential attraction of gaseous species (H, O, OH, H 2 O), to Si-sites as compared to C-sites. Hence, the temperature- and atmosphere-induced changes in friction coefficient can be understood based on correlative X-ray photoelectron spectroscopy and ab initio data: the formation of Si O C bonds stemming from a reaction of the as-deposited coating with atmosphere in the tribological contact is observed by theory and experiment. [ABSTRACT FROM AUTHOR]

The in-plane shear property of carbon fiber laminates is one of the most important structural features of aerospace and marine structures. Fiber-matrix debonding caused by in-plane shear loading is the major failure mode of carbon fiber composites because of the stress concentration at the interfaces. In this study, carbon nanotube mats (CNT mat) were incorporated in two different types of carbon fiber composites. For the case of woven fabric composites, mechanical interlocking between the CNTs and the carbon fibers increased resistance to shear failure. However, not much improvement was observed for the prepreg composites as a result of incorporation of the CNT mats. The reinforcement mechanism of the CNT mat layer was investigated by a fractographic study using scanning electron microscopy. In addition, the CNT mat was functionalized by three different methods and the effectiveness of the functionalization methods was determined and the most appropriate functionalization method for the CNT mat was air oxidation. [ABSTRACT FROM AUTHOR]

Abstract: We have, for the first time, fabricated chromium (Cr) carbide nanostructures on multiwalled carbon nanotubes (MWCNTs) in a MWCNT–copper (Cu) composite by adding small amounts of Cr. A single nanocrystal of carbide was epitaxially grown on the sidewall of chemically treated MWCNTs through the diffusion of solute Cr atoms to defects in the MWCNTs. Carbide has an island-shaped morphology with a maximum size of several hundred nanometers. The phase of the generated Cr carbide nanostructures was mostly Cr7C3, as determined by electron beam diffraction using the nanobeam diffraction mode of a transmission electron microscope. In particular, the Cr carbide nanostructures formed at radially unzipped sites were connected to the outermost wall and some inner walls of the MWCNTs. This is expected to increase the load-bearing capacity of the MWNCTs because the inner walls contribute to the load transfer, which is very effective for improving the mechanical and thermomechanical properties of the composites. [Copyright &y& Elsevier]

Ni-P-CNT composite coatings were deposited on micro-sized aluminum particles using electroless plating technique and the effect of different process parameters on the microstructural characteristics of the produced composite coatings were investigated. The results showed that a uniform Ni-P-CNT composite coating could be successfully deposited on the aluminum particles provided the electroless processing parameters were adjusted carefully. The most favorable coating quality was achieved at bath temperature of 80 °C, bath pH of 5.5 and CNT concentration of 1.25 g/lit. While a higher CNT concentration resulted in increased CNT agglomeration and poor CNT distribution in the Ni-P matrix, a lower CNT concentration resulted in fewer incorporated CNTs. Higher bath temperatures intensified the hydrogen gas evolution during the process and resulted in poor uniformity and presence of porosity in the coating. Low bath pH resulted in poor CNT incorporation and distribution in the Ni-P matrix and clustering of a large part of CNTs out of the coating. [ABSTRACT FROM AUTHOR]

In the present study, liquation behavior including the constitutional liquation phenomena in the weld heataffected zone (HAZ) of nodular cast iron with 4% Si was investigated. The thermal cycle of the weld HAZ was simulated using a Gleeble simulator at various peak temperatures and a fast heating rate of 1000 °C/sec was selected to observe the constitutional liquation phenomenon. Differential thermal analysis has shown that the eutectic constituents of γ + Laves and γ + FeC begin to melt at 1120 °C and 1140 °C, respectively. Meanwhile, constitutional liquation by γ/graphite reaction occurred above 1140 °C, due to carbon enrichment around the graphite nodules. [ABSTRACT FROM AUTHOR]

Diamond like carbon (DLC) thin films with metallic interfacial layers of aluminum and nickel-chromium (Al and Ni-Cr) were grown using a low cost hybrid technique involving a resistive heating thermal evaporator and radio frequency plasma enhanced chemical vapor deposition techniques. Stress, hardness, elastic modulus, bonding, phase, and electrical conductivity of these films were investigated. Introduction of interfacial Al and Ni-Cr layers in DLC led to drastic improvement of its conductivity along with a significant reduction in residual stress but with some reduction of hardness and the elastic modulus. The structural and surface properties of thin films were studied using X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques. [ABSTRACT FROM AUTHOR]

Nano-sized SnO particles supported on ball-milled graphite were manufactured by the in situ NaBH reduction method and were used as an anode active material in lithium-ion batteries. Their physical and electrochemical characteristics were investigated using various characterization techniques: Raman spectroscopy, x-ray diffraction (XRD), transmission electron microscopy (TEM), and cyclic voltammetry (CV). From coin half-cell tests, the SnO particles supported on graphite that was ball-milled for 24 hr showed a reversible capacity better than that of commercial graphite and other SnO/graphite materials for which the graphite was ball-milled for longer lengths of time. [ABSTRACT FROM AUTHOR]

In this study, we have attempted to describe the phenomenon of vacancy formation in various types of diamonds (natural type IaAB, synthetic type Ib, synthetic type IIa, and type IaABC suspected of having been pretreated with an unknown method) using electron beam irradiation. After the electron beam irradiation, vacancies were formed in the natural type IaAB and synthetic type IIa diamonds, whereas vacancies were not formed in the synthetic type Ib and pre-treated type IaABC diamonds. From these results, we suggest a model of vacancy creation by electron beam irradiation in various types of diamonds. The irradiation was performed with electron dose densities of 1-6×10/cm at 10 MeV, and with a heat treatment of two hours at a temperature of 900 °C. Electron beam-irradiated and heat-treated samples were analyzed using UV-Vis-NIR, FT-IR, and PL spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: The recyclability of carbon nanotube (CNT) sponges in terms of oil absorption was studied. The sorption capacities of these sponges are greater than 100gg–1 for many organics and oils with viscosities of 3–200cP, and they maintain sorption capacities of 20–40gg–1 after 10 cycles of absorption. About 98% of absorbed oil can be recovered by squeezing or converted to heat by directly burning the oil within the sponges. The sorption process has been described by a second-order kinetic model. The results demonstrate that CNT sponges are promising oil sorbents with good recyclability. [Copyright &y& Elsevier]

Composites were prepared by the electrostatic interaction between carboxylated multi-walled carbon nanotubes (c-MWNTs) and either cadmium telluride (CdTe) or cadmium selenide (CdSe) nanoparticles. Multi-walled carbon nanotubes (MWNTs) were oxidized by an aqueous acid mixture, and both the CdTe and CdSe nanoparticles were stabilized by 2-(dimethylamino) ethanethiol hydrochloride in water to develop negatively and positively charged outer surfaces, respectively. Optical properties were investigated by UV/Vis and photoluminescence (PL) analyses. CdX (X = Te, or Se) nanoparticles showed emissions at the same position regardless of the existence of c-MWNTs. This result suggests that the interaction between CdX and c-MWNTs does not affect the photoluminescence of CdX nanoparticles in their composites. The binding energies and redox potential positions of the CdX nanoparticles in their c-MWNT-CdX composites shifted from those of the pure nanoparticles. These changes indicate that the electron densities on the interfaces of CdX nanoparticles and c-MWNTs were redistributed after the formation of composites due to the strong electrostatic interaction between the components. [ABSTRACT FROM AUTHOR]

In the case of employing brake discs as a key component of mechanical brake equipment, the initiation of thermal cracking owing to repetitive thermal shock generated during braking may potentially lead to higher maintenance costs, worsened braking performance, and greater risk of railway accidents. The purpose of this study is to gain basic data to facilitate application of compacted vermicular (C. V.) graphite cast iron to brake discs in order to obtain high thermal crack resistance and improved lifetime. To this end, this study developed three types of C. V. graphite cast iron with differing content of key elements, including Ni, Cr, and Mo. Each test specimen underwent numerous tests for evaluation of materials characteristics, and the results were compared with those obtained for existing materials. The test results show that the thermal fatigue lifetime of material C is nearly double that of the conventional material. This demonstrates the suitability of material C as a material for brake discs in mid- to high-speed railway vehicles. [ABSTRACT FROM AUTHOR]

The microstructure of carbon nanotube reinforced copper matrix (CNT/Cu) nanocomposites, processed by molecular-level mixing, exhibits CNTs homogeneously dispersed in the Cu matrix. Measured thermal conductivity of the fabricated CNT/Cu nanocomposites decreased as the CNT volume fraction increased from 5% to 10%. A low coefficient of thermal expansion (CTE) was obtained from the 10vol.% CNT/Cu nanocomposite. These results indicate that embedded CNTs provide CNT/metal interfaces as thermal barriers but also stiffen the metal matrix composites. [Copyright &y& Elsevier]

Damage that occurs on graphite electrode surfaces during electrochemical cycling, simulating lithium-ion battery conditions, was observed in-situ using a digital microscope. Microscopical evidence revealed particle removal during the de-lithiation stage that continued until the potential difference, exerted on graphite, reduced beyond a critical value. The rate of graphite particle loss increased at a lower voltage scan rate. Experiments, initiating from the peak voltage, promoted formation of a surface film on graphite which reduced graphite degradation during the course of lithiation. [Copyright &y& Elsevier]

In this study, the effect of the microstructure and mechanical properties of austempered high-carbon (0.9 %C) high-silicon (2.3 %Si) cast steel were investigated. The specimens were austenitised for 60 min. at 900 °C, and austempered at 260 °C, 320 °C, and 380 °C for periods of time ranging from 30 min to 240 min. After receiving this heat treatment, the mechanical properties were measured using both a tensile test and hardness test. To analyze the microstructure, an optical microscope was used and an X-ray diffraction (XRD) analysis was carried out. In this study, high carbon high silicon cast steel without graphite and with higher tensile strength (1300 MPa to 2200 MPa) and elongation (∼25 %), when compared to austempered ductile cast iron (ADI), was developed. When the austempering temperature was at 260 °C, the microstructures were low ausferrite, but at 380 °C, an upper ausferrite structure was formed. As the austempering temperature increased from 260 to 380 °C, the ultimate tensile strength and hardness decreased, but the elongation and retained austenite volume fraction increased. In addition, the microstructures were coarser. [ABSTRACT FROM AUTHOR]

We proposed to evaluate the contact resistance between carbon nanotubes from bulk measurement on their tangle. Compression tests with simultaneous measurement of the ohmic resistance were performed on carbon nanotube tangles. The experimental data were analyzed using a contact network model to get an estimate of the contact resistance between carbon nanotubes. It was found that in some cases the contact resistance decreased by up to one order of magnitude and reached values in the order of 100kΩ. [Copyright &y& Elsevier]

Abstract: Multi-walled carbon nanotube/cadmium sulfide hybrid heterostructures were easily synthesized by employing a thermal decomposition of thioacetamide as a sulfide-ion source in an aqueous regime. The resulting cadmium-sulfide phase is comprised of a zinc-blende structure of spherical polycrystalline nanoparticles (cadmium-sulfide nanoclusters) with the subunits of ca. 15nm, deposited on the nanotube surface. The formation of the cadmium-sulfide nanoparticles with zinc-blende structure (cubic crystal) suggests that the local concentrations of reacting ion species in the vicinity of the nanotube surface are different from those in the reaction solution. The cadmium-sulfide nanoparticles are comprised of a stoichiometrically ideal chemical-composition ratio (cadmium: sulfur=1:1.02) of cadmium and sulfur with the valence states of +2 and −2, respectively. The optical responses of the cadmium-sulfide phase for ultraviolet-visible light and photoluminescence spectroscopes show the proper size-effect and inherent optical properties of the cadmium-sulfide nanoparticles. [Copyright &y& Elsevier]

The compression properties of coke were investigated at slow strain rates, using a traditional Instron materials tester. To further characterize the failure mechanism, X-ray microtomography was used to visually examine the internal deformation of the coke during compression. It was found that the coke samples failed in a progressive layering manner, and were still able to maintain load for the duration of the compression test. [Copyright &y& Elsevier]

Abstract: Ultra-nanocrystalline diamond is a polycrystalline material with crystalline diamond grains in the nanometer size regime. We study the structure and mechanical properties of this material as a function of the average grain size, employing atomistic simulations. From the calculated elastic constants and the estimated hardness, we observe softening of the material as the size of its grains decreases. We attribute the observed softening to the enhanced fraction of interfacial atoms as the average grain size becomes smaller. We provide a fitting formula for the scaling of the cohesive energy and bulk modulus with respect to the average grain size. We find that both these properties scale as quadratic polynomials of the inverse grain size. Our formulas yield correct values for bulk diamond in the limit of large grain sizes. [Copyright &y& Elsevier]

Abstract: The paper presents a novel concept for the automated recognition and identification of different classes of porosity. This is applied to the porosity network in thermally oxidized nuclear graphite samples, which has been observed using computed X-ray tomography. The analysis is used to predict the dependence of thermal conductivity on thermal oxidation-induced weight loss. The model predictions, based on the Euler approach, are successfully compared with experimental measurements of thermal conductivity, obtained using the laser flash method. [Copyright &y& Elsevier]

Conventional analysis of nanoindentation data considers only the unloading curve, but this may be misleading for materials that are very elastic. An alternative method that considers the loading and unloading curve may be more appropriate. Results for a carbonaceous material with a high hardness (or yield stress) relative to its elastic modulus are presented. An analysis considering the whole nanoindentation cycle gives a ratio of H/E that is significantly higher than that obtained from just the loading or unloading curve. [Copyright &y& Elsevier]

Polypropylene (PP)/multiwalled carbon nanotube (MWNT) nanocomposites were prepared via melt-compounding. The dielectric and conductive properties of the nanocomposites were examined. It was found that better dispersion of MWNTs in PP matrix can be achieved in a Haake mixer by intensive shearing. Accordingly, PP/MWNT nanocomposites prepared at high shear rates exhibited much lower percolation thresholds than composites fabricated at low shear rates. The resistivity results revealed that the PP/MWNT nanocomposites with a high MWNT content exhibited a positive temperature coefficient effect. [Copyright &y& Elsevier]

Abstract: Cobalt nanoparticles encapsulated in graphitic shells were successfully synthesized using an advanced and cost-effective synthesis method. The graphite-encapsulated nanoparticles were synthesized using an electric plasma discharge generated in an ultrasonic cavitation field of liquid ethanol, followed by the separation, drying and annealing of particles. Prior to annealing, the core-shell structured nanoparticles were characterized by high-resolution transmission electron microscopy and X-ray diffraction, which revealed the presence of a Co3C and carbon supersaturation in the face-centered cubic β-Co phase in the core of carbon nanocapsules; some cores were discovered in an amorphous state. The majority of carbon nanocapsules were found to be spherical particles, less than 10nm in diameter. The annealed powder samples, in which cobalt carbides and amorphous inner cores transformed to crystallized α-Co and β-Co cores, showed coercivity values of 15.5kAm−1and saturation magnetization values of about 50Am2 kg−1, which is approximately 32% of the value of bulk cobalt particles. [Copyright &y& Elsevier]

Abstract: The detailed evolution of the graphitized microstructure of carbon steel during annealing has been studied by thin-foil transmission electron microscopy, enabled by the refined dispersion of small graphite nodules produced. The graphitization annealing of 0.38wt.% carbon steel in the quenched martensitic state resulted in the formation of graphite nodules, of the order of 2–5μm in diameter, after 2–4h. Two types of graphite nodules were observed to form: one possesses an irregular morphology and exhibits a coring particle (either a nitride or an oxide), whilst the other is more regularly spheroidal and apparently without a nucleating particle at its core. Analytical electron microscopy has been employed to characterize the microstructure of the graphite nodules formed, in order to provide a better understanding of their nucleation and growth, in particular, the mechanism of formation of the spheroidal graphite nodules without an apparent nucleating particle. For these more spherical nodules, the results showed that the outer mantles had a strong graphitic character, whilst the core regions exhibited a more amorphous carbon structure. It is deduced from the available experimental evidence that the nucleation sites most likely to result in this structure are dissolving cementite particles in the martensite. [Copyright &y& Elsevier]

Abstract: Nanoporous materials such as high surface area activated carbons (AC), single-walled carbon nanotubes (SWNTs) and metal–organic frameworks (MOFs) have been proposed as storage media for hydrogen. In this paper we discuss the use and limitations of physisorption as a storage technology for hydrogen. Currently physisorption of hydrogen on undoped carbon nanostructures and MOFs falls short of the DOE targets for vehicular applications. Meeting these targets will require qualitative changes to the sorption process beyond structural optimization. [Copyright &y& Elsevier]

Graphite nano-sheets, having a thickness of the order of 10nm, high shape asymmetry, and a well preserved crystalline order, have been prepared by a mechanical method based on the grinding of graphite powder under low energy pure shear milling using water as a lubricant. The small applied stress activates the plastic deformation process mainly on the easy gliding (001) hexagonal planes so that planar flakes bounded by the basal planes are obtained by a purely mechanical process. [Copyright &y& Elsevier]

Abstract: This paper reports an investigation of the influence of initial stress on the flexural vibration of an individual multi-wall carbon nanotube with simply supported ends, based on a laminated elastic beam model considering the van der Waals force interaction between two adjacent nanotubes. The results obtained show that the influence of initial stress in carbon nanotubes on their natural frequency is obvious, but the influence of initial stress in carbon nanotubes on the intertube resonant frequency of multi-wall carbon nanotubes is not obvious, especially for large aspect ratios. The influence of initial stress in carbon nanotubes on their flexural vibration modes is dependent on the tension or compression forms of the initial stress. This investigation on the influences of initial stress in multi-wall carbon nanotubes on natural frequency and intertube resonant frequency may be used as a useful reference for the application and design of nano-oscillators, nano-drive devices, nano-sensors and actuators in which multi-wall carbon nanotubes act as basic elements. [Copyright &y& Elsevier]

Abstract: The three-dimensional (3D) structure of carbon foams is difficult to infer from two-dimensional characterizations. In particular, regular models cannot capture the interaction between the pores in real materials with morphological dispersity. In this paper, the actual 3D structure of a pitch-based carbon foam is captured and used to build solid models for finite element analyses of thermal and mechanical properties. [Copyright &y& Elsevier]

Polycrystalline thin films show transverse isotropy (or hexagonal symmetry) and show five independent elastic constants because of columnar structure, texture, residual stress, and local incohesive bonds (or microcracks). In this paper, we developed an advanced method for measuring the anisotropic elastic constants of thin films using resonance ultrasound spectroscopy and determined the elastic constants of chemical-vapor-deposition diamond thin films. Mechanical resonance frequencies of a film/substrate layer specimen were measured, from which elastic constants of the thin film were determined by an inverse calculation. Mode identification for observed resonance frequencies is the key for their successful determination. We achieved this by measuring the displacement distribution on the vibrating-specimen surface. Determined elastic constants are smaller than those of bulk diamond, and they are elastically anisotropic between in-plane and out-of-plane directions. We attribute these compliant and anisotropic thin films to the incohesive bond at grain boundaries. A micromechanics model consistently explains the observation. [Copyright &y& Elsevier]

Zirconia powder with an average particle size of 10 nm was prepared by adding carbon nanotubes (CNTs) in the hydrolytic process of ZrO(NO3)2. The formation of zirconia nanoparticles was attributed to the addition of CNTs, which affected the zirconia precursor structure. The relation between the stability of cubic (c) and tetragonal (t) phase zirconia at room temperature, and the zirconia particle size and addition of carbon was studied. It was revealed that zirconia particles with nanometer size had took the form of t-phase and that the addition of carbon tended to favor m-phase ZrO2 to c-phase ZrO2 transformation and c-phase ZrO2 stabilization at low temperature. [Copyright &y& Elsevier]

Nanocomposites obtained by mechanical milling of graphite and magnesium with organic additives (benzene, cyclohexene or cyclohexane) have been studied with the aim of preparing novel hydrogen storage materials. The organic additives were very important in the milling processes to determine the characteristics of the resulting carbon nanocomposites. The mechanical milling with high energy resulted in the generation of large amounts of dangling carbon bonds in graphite with simultaneous decomposition of graphite structure. Such dangling bonds of carbon acted as sites to take up hydrogen. It has been proved by temperature programmed desorption (TPD) and neutron diffraction measurements that the hydrogen taken up in the nanocomposites exists in at least two states; in the form of C–H bond formation in the graphite component and in the form of hydride in the magnesium component. The relative amounts of two types of hydrogen strongly depended upon differences in additives used (benzene, cyclohexene or cyclohexane). When C6D6 besides C6H6 was used as additive, the hydrogen taken up was discussed from the standpoint of isotope effects. Upon addition of titanium tetraisopropoxide, the features of hydrogen uptake by the nanocomposites changed completely. [Copyright &y& Elsevier]

The deformation micromechanics of flake and spheroidal graphitic cast irons have been studied for the first time using Raman spectroscopy. It has been found that the Raman band peak positions of the graphite shift to a lower wavenumber during tensile deformation, and to a higher wavenumber in compression. The elastic properties of the cast irons have been investigated using various theoretical models. It has been shown for flake iron that the Young’s modulus is in close agreement with the models for disk-shaped inclusions, and with models for spherical inclusions for the spheroidal iron. In the case of the graphite stress at 1% strain, the same models underestimate the stress reached in the graphite possibly due to breakdown of the interface between the graphite particles and the iron matrix. It has been shown further that Raman spectroscopy can follow the elastic recovery of the cast iron and can pinpoint the onset of permanent plastic deformation by comparing the peak positions of the Raman before and after unloading. [ABSTRACT FROM AUTHOR]

Nanocrystalline soft magnetic Fe73Si16B7Nb3Cu1 (at.%) powders were mixed with fine multi-walled carbon nanotube (MWNT) powders and polyurethane based binders. The mixtures were tape-cast, dried and then cold-rolled to form EM wave absorption sheets. The MWNT powders were added to the Fe-based powders up to 1 wt.% to improve the EM wave absorption properties. The processed sheets with 0.5 mm in thickness were cut into toroidal shape to measure the S-parameter, permeability, permittivity, and power loss at the high frequency of 10 MHz to 10 GHz. As a result, improved absorption properties were obtained from the sheets incorporating MWNT. The results were caused by the increase of dielectric loss of the absorption sheets, which was due to the addition of MWNT powder inducing a notable increase in complex permittivity. [ABSTRACT FROM AUTHOR]

This paper establishes an analogy between the adhesion of liquid drops and single-walled nanotubes. Carbon nanotubes are found to be “super-hydrophobic” for radii smaller than ∼6Å, whereas the “hydrophobic/hydrophilic” transition takes place at a radius of ∼16Å. The liquid drop analogy provides simple laws for treating the complex problem of the adhesion of highly deformed single-walled nanotubes. We compare our findings with atomistic or continuum simulations and elastica solutions, finding a relevant agreement. [Copyright &y& Elsevier]

We investigated a facile method for producing conductive polymer composites for the construction of microelectrodes already integrated into microsystems, as promising for microfluidic application. The porous morphology, high conductivity and large surface area of the composites which in turn influences its electrochemical performance can be simultaneously achieved by optimizing the composition and nanostructure of the conductive material and polymer. Three different carbon materials (i.e. graphite, graphene, carbon nanofibers) were combined with poly(methyl methacrylate) (PMMA) polymer and all the subsequent carbon-PMMA composites were assessed electrochemically using cyclic voltammetry in the presence of ferrocyanide as a model redox analyte. The results indicated that graphite was well dispersed and incorporated throughout the composite to form a highly electrically conductive network that proved to be even better than the graphene sheets and carbon nanofibers. In order to demonstrate the ease of composite fabrication with tailored properties for intended analytical applications, the optimal graphite-PMMA composite was further investigated to incorporate Prussian blue, as a model mediator for H 2 O 2 detection. • Carbon materials (graphite, graphene, CNF) were comparatively composited with PMMA. • The PMMA-based composites are evaluated as integrated electrodes into PMMA microchip. • The composite electrodes were assessed electrochemically in the presence of ferrocyanide. • Optimal graphite/PMMA/Prussian blue composite exhibited high electroactivity toward H 2 O 2. [ABSTRACT FROM AUTHOR]