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We have studied the kinetic and photoinduced aspects of the transformation of the cluster structure of ultrahard fullerite in the pressure ranges of a new phase diagram of carbon corresponding to the stability regions of diamond (up to 55 GPa) and onion-like structures of the fullerene type (55–115 GPa). A long exposure (for 3 months) at 25 GPa leads to the beginning of the transformation of the sample of ultrahard fullerite into diamond. A further increase to 70 GPa, under the influence of laser irradiation at wavelengths of 405 and 532 nm at doses of 5*1013 J/m2, initiates the formation of onion-like particles in ultrahard fullerite samples, which is accompanied either by a broadening of the high-frequency mode of the Raman spectrum, or its disappearance under high pressure. After pressure release, the high frequency mode of the Raman spectrum is located at 1570–1605 cm−1 at excitation wavelengths of 532 and 405 nm, respectively, which is typical for ultrahard fullerite. Bulk modulus of such an irradiated sample corresponds to a typical value for ultrahard fullerite of about 600 GPa. In addition to the formation of nanodiamonds and onion–like particles, the synthesis of ultrahard fullerite is also accompanied by the appearance in the sample of systems with double bonds of the C=C=C type with a line around 1935 cm−1, the nature of which is not entirely clear. [Display omitted] [ABSTRACT FROM AUTHOR]

Boron doped diamonds (BDD) with boron concentration above 1019 at./cm3, grown under conditions of high isostatic pressure by the temperature gradient method, were studied by Transmission Electron Microscopy methods, EELS analysis and X-ray diffraction analysis. It was shown that boron is distributed unevenly in the grown crystal. It was found that in places of maximum boron content, interplanar distances d 111 increase from 0.206 to approximately 0.2065 nm. Parallel bands were discovered, the boundaries of which are fragments of the intermediate carbon phase (ICP-phase). Numerous twins along the {111} plane, as well as fragments of rhombohedral 9R phase, were discovered. [Display omitted] [ABSTRACT FROM AUTHOR]

Over the years, a wide range of spectral research has been carried out on various carbon forms to explore deeply their structure-property relationship. The structural stability of carbon allotropies remains to be a challenging endeavor yet to be achieved under extreme conditions, especially under acoustical shocked conditions. From the experimental findings, we report the acoustic shock wave response of the amorphous carbon nanoparticles and the resultant degree of crystalline nature, morphological characteristics and magnetic response. Moreover, analytical techniques such as X-ray diffractometry (XRD), Raman spectrometer, High resolution transmission electron microscopy (HR-TEM) and vibrational sample magnetometer (VSM) have been employed to arrive at the relationships of structure – morphology – magnetic properties under shocked conditions. Interestingly, under shocked conditions (0, 250, 500 and 750 shocks), compelling evidence has been found for the short-range amorphous pockets which turn into spatially short-range ordered graphitic domains within the sphere-shaped amorphous nanoparticles whereby the obtained values of the ratio I D /I G of the samples are 0.94, 0.93, 0.95 and 1.01 for 0, 250, 500 and 750 shocked conditions, respectively. Moreover, the saturation magnetization is found to have reduced in the base of the local atomic ordering and the obtained values are found to be 1, 0.64, 0.41, 0.725 emu/g for 0, 250, 500 and 750 shocked conditions, respectively. The structure-property relationship is to be elaborated in the upcoming sections. [Display omitted] • Shock wave induced amorphous carbon to short-range ordered graphitic domains is reported. • The I D /I G intensity ratio of the samples is 0.94, 0.93, 0.95 and 1.01 for 0, 250, 500 and 750 shocked conditions. • The saturation magnetization values are 1, 0.64, 0.41 and 0.725 for 0, 250, 500 and 750 shocked conditions. • The correlation of the magnetic properties and degree of crystalline nature is discussed. [ABSTRACT FROM AUTHOR]

This paper deals with adsorption behavior of ruthenium on Tri-n-butyl phosphate functionalized Multi Walled Carbon Nanotubes (MWCNTs-COO-TBP) from aqueous solution. Adsorption method is significant for trace levels (expected level) removal of ruthenium in bioassay (urine) samples which is mandatory requirement of radiation workers in nuclear environment. Multi Walled Carbon Nanotubes (MWCNTs) were initially converted to carboxylated Multi Walled Carbon nanotubes (MWCNTs-COOH) and subsequently treated with Tri-n-butyl phosphate to MWCNTs-COO-TBP. The synthesized MWCNTs-COOH and MWCNTs-COO-TBP were confirmed by Fourier Transform Infrared Spectroscopy (FTIR). Spectroscopic and microscopic techniques such as X-Ray Diffraction (XRD), Raman Spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) and High Resolution Transmission Electron Microscopy (HR-TEM) were used for its characterization before and after adsorption. Various adsorption parameters such as contact time, pH, metal ion concentration and temperature were studied. Langmuir adsorption isotherm model and Pseudo second order kinetics model were found to be best fitted in terms of standard deviation and regression coefficient. Thermodynamics parameters such as enthalpy (ΔH°), entropy (ΔS°), Gibbs energy (ΔG°), activation energy (E a) and sticking probability (SP*) were calculated. The adsorption capacity was calculated and found to be 141.23 mg.g−1.Moreover, quantification of defects, strains with charge doping states were calculated from Raman mapping and correlation plot. [Display omitted] • Synthesis and characterization of Tri-n-Butyl Phosphate functionalized Multi Walled Carbon Nanotubes (MWCNTs-COO-TBP). • Detailed study on adsorption of ruthenium on MWCNTs-COO-TBP and its kinetics, thermodynamics and isotherm. • Functionalization of MWCNTs by TBP and its adsorption for ruthenium, confirmed by FTIR and EDS analysis. • Quantification of defects and strains with charge doping states were calculated from Raman mapping and correlation plot. • The potential application of MWCNTs-COO-TBP for adsorption of Ru from aqueous solution was explored. [ABSTRACT FROM AUTHOR]

The creep strain of full graphitic cathode blocks has been measured with a laboratory cell. The creep tests were performed three times under extern load 2–6 MPa and at temperature of 950 °C for 15 min, 50 min and 100 min respectively after starting the electrolysis. The deformation mechanisms in the carbon cathodes for aluminum electrolysis have been comprehensively studied at the atomic scale by high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The microstructural observation confirms that the governing deformation mechanism for the carbon cathode is basal plane dislocation pile-ups and dislocation tangles at the stage of transient creep. Microstructure rearrangement of the carbon cathode including deformation bands, rotating, delamination and propagation of microcracks deteriorates its creep resistance at the stage of steady-state creep. The deformation of carbon cathodes is closely correlated with the accumulation and amorphization of the graphite during aluminum electrolysis. Unlabelled Image • The damage and failure mechanism of the carbon cathode were achieved. • Microstructure rearrangement deteriorates the creep resistance of carbon cathodes. • The deformation of carbon cathodes is closely correlated with the amorphization. [ABSTRACT FROM AUTHOR]

Abstract In this study, SnO composites with incorporated nanodiamonds (NDs) were synthesized by a simple ultrasonic reaction method using SnCl 2 and NH 4 HCO 3 as raw materials. Results showed that the SnO/ND composites comprised SnO, SnO 2 , and diamond. High-resolution transmission electron microscopy (HRTEM) results indicated that a tight-contact interface formed between the SnO nanosheets and NDs. All SnO/ND composites exhibited a high efficiency for degrading methyl orange (MO) under visible light. The optimum degradation rate of MO was obtained for SnO/9.2% ND composite (98%) and SnO (16.6%) sample after 45 min of visible-light irradiation. Graphical abstract Unlabelled Image Highlights • SnO/Nanodiamond composites were prepared by simple ultrasonic reaction technology. • A good interface combination between SnO nanosheets and Nanodiamond obviously improved the photoactivity of SnO. • Many diamond nanoparticles were well embedded in the SnO nanosheets • SnO/nanodiamond shows good photocatalytic activity for the degradation of methyl orange. [ABSTRACT FROM AUTHOR]

The multi-walled carbon nanotubes (MWCNTs) were initially functionalized with polyaniline (PANI) through an in-situ polymerization approach. The ternary transition metal phosphate of Ni 0.50 Co 0.25 Zn 0.25 (PO 4) 2 was then chemically grafted onto different masses of PANI/CNTs (20, 40, 60, 100, and 130 mg) aided with probe sonication. The structural morphology and elemental analysis of the nanocomposites were evaluated by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM), whereas chemical grafting and compositional analysis were evaluated by EDX, XRD, Raman spectroscopy and FTIR analysis. The hierarchical structure of ternary metal phosphates nanocomposites with 100 mg PANI/CNTs provided excellent specific capacity of 1438 Cg−1 (2400 Fg−1, at 1.5 Ag−1). An asymmetric supercapacitor device (ASC) of Ni 0.50 Co 0.25 Zn 0.25 (PO 4) 2 -100 mg PANI/CNT//AC demonstrated excellent electrochemical performance with an energy density of 104 Whkg−1 (@540 Wkg−1 and very good cyclic stability and columbic efficiency (100 %)). According to a capacitive-diffusive investigation, the ASC device has 63.5 % diffusive and 33.5 % capacitive behavior at low scan rates. The reason for the excellent electrochemical performance of nanocomposite is the combined contribution of PANI/CNTs and uniform chemical grafting of tri-metallic phosphate structures onto the PANI/CNTs. As a result, the Ni 0.50 Co 0.25 Zn 0.25 (PO 4) 2 -100mg PANI/CNTs composite exhibited good potential to be used in energy storage devices. [Display omitted] • Sonochemical synthesis of Ni-Co-Zn ternary metal phosphate/PANI-CNTs composites • NCZP100 showed excellent C S [1438Cg−1 (2400Fg−1) @1.5 Ag−1] with lowest R s and R CT. • Representative ASC device gave outstanding energy density of 104WhKg−1@0.6 Ag−1 with ~100 % cyclic stability. • The device showed 63.5 % diffusive and 33.5 % capacitive behavior at low scan rates. [ABSTRACT FROM AUTHOR]

Method of in situ synthesis of TiC nanoparticles inside aluminium matrix directly during mechanical alloying from aluminium, titanium and nanodiamonds is developed. For this method, nanodiamonds were used as carbon material and as intensificator of mechanosynthesis during the ball milling. Optimal content of matrix material was determined. If the amount of aluminium falls below the optimal level, the synthesis becomes extremely intensified; it means that during short period a large amount of heat is released, which causes substantial grinding jars heating and frequently results in melting of sealing gaskets and other process failures. In case the amount of aluminium in the mixture grows beyond the optimal level, the synthesis process is slowed down. Optimal composition for obtaining TiC nanoparticles inside aluminium matrix is following: 43%wt Al + 57%wt TiC. Average size of nanoreinforcements of developed composite equals 31 nm. Developed material can be applied in casting technologies as an individual product and as a master alloy. [ABSTRACT FROM AUTHOR]

The present work discusses the effect of nanodiamond (ND) reinforcement in NiAl plasma sprayed coatings. Three different proportions of ND particles (ranging from 0.1 to 1.0 wt%) reinforced NiAl coatings were successfully fabricated over AISI 1020 steel substrate using a plasma spraying technique. The coatings were analyzed for composition, phase and microstructure using X-ray diffraction (XRD), Raman Spectroscopy, Field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The relative density of the coatings was found to increase from 91.34 % to 97 % with a mere addition of 1 wt% of NDs owing to proper melting of powders aided by the NDs. Results showed a remarkable enhancement of 18 % in hardness, and 34.8 % in elastic modulus and a significant reduction in the wear volume loss (41.96 %), wear rate (42.5 %) and coefficient of friction (COF - 80 %). The enhanced properties of the coatings stemmed from exceptionally high mechanical properties offered by NDs along with its spherical morphology, self-lubricating effect and higher coating density. [Display omitted] • NDs reinforced NiAl coatings were developed by plasma spray technique. • The addition of NDs improved the relative density from 91.15 % to 97.06 %. • NiAl-1ND coating showed increase of 18 % in hardness and 34.8 % in elastic modulus. • Significant loss in the wear volume loss (41.96 %) was observed in NiAl-1ND coating. [ABSTRACT FROM AUTHOR]

Using a versatile atmospheric-pressure helium plasma jet, diamond-like carbon (DLC) films were etched in ambient air. We observed that the DLC films are etched at a nominal rate of around 60 nm/min in the treated area (230 μm in diameter) during a 20-min exposure. The etching rate increased after the initial 10-min exposure. During this period, the flat DLC surface was structurally modified to produce carbon nanostructures with a density of ~ 2.4 × 10 11 cm − 2 . With this increase in surface area, the etching rate increased. After 20 min, the DLC film had a circular pattern etched into it down to the substrate where silicon nanostructures were observed with sizes varying from 10 nm to 1 μm. The initial carbon nanostructure formation is believed to involve selective removal of the sp 2 -bonded carbon domains. The carbon etching results from the formation of reactive oxygen species in the plasma. [ABSTRACT FROM AUTHOR]

We observed the effect of high (up to 80 GPa) pressure, catalyst (CS 2) and laser irradiation on the process of three-dimensional (3D) polymerization of fullerene C 60 and the mechanical properties of the 3D C 60 samples. The studies were carried out using resonant Raman spectroscopy and piezospectroscopy, high resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy. We have revealed that the 3D C 60 structure consists of at least two types of clusters formed by covalent bonds with a different set of force constants, while C 60 molecules, as one of the elements of the 3D C 60 structure (clusters), are preserved at least up to a pressure of 80 GPa. The intensity of Raman scattering depends on the wavelength of the exciting radiation (resonance effect) and a set of force constants: the higher their values, the shorter-wavelength exiting radiation is required for Raman scattering observation by such clusters. Clusters with bulk moduli from 454 GPa to 644 GPa are formed depending on methods of C 60 polymerization. According to the set of clusters, 3D C 60 samples with bulk moduli from 506 GPa to 608 GPa were obtained. [Display omitted] • We have revealed that the 3D C 60 structure consists of at least two types of clusters formed by covalent bonds with a different set of force constants. • C 60 molecules, as one of the elements of the 3D C 60 structure (clusters), are preserved at least up to a pressure of 80 GPa. • We observed the effect of high (up to 80 GPa) pressure, catalyst (CS 2) and laser irradiation on the process of three-dimensional (3D) polymerization of fullerene C 60 and the mechanical properties of the 3D C 60 samples. [ABSTRACT FROM AUTHOR]

The magnetic field configuration of magnetron sputtering has an important influence on films' properties. Here, two kinds of magnetic field configurations, Sm2Co17(outer)/Sm2Co17(inner) and Sm2Co17(outer)/Ferrite(inner), were used to deposit amorphous carbon (a-C) films. Tribo-meter, Nano-indentation, Raman spectroscopy, XPS, high resolution transmission electron microscopy as well as OPERA-2D for magnetic field simulation were employed to study the influence of the magnetic field configuration on the mechanical and tribological properties of a-C films. Our results show that higher coefficients of geometrical unbalance induced a higher deposition rate and a higher hardness of a-C films. However, the friction coefficient shows an inverse trend, and the wear life is short, which can be ascribed to saturation effects via adsorption of H, O, and OH and corrosion wear, which would accelerate the wear rate. Our work will booster interesting to study the magnetic field configurations influence on a-C films properties via magnetron sputtering. [Display omitted] • Higher GUC induced higher deposition rate of a-C film in a magnetron sputtering. • Higher GUC induced higher hardness and lower friction of prepared a-C film. • Corrosion wear will accelerate the wear rate leads to short life. • Lower GUC gives the a-C film greater synthetic performance. [ABSTRACT FROM AUTHOR]

Abstract: Amorphous carbon nanotubes (aCNTs), synthesized through a low-temperature simple method have been decorated with chemically synthesized different zinc oxide (ZnO) nanostructures like nanocones and nanoflowers. The as-prepared samples have been characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). It has been found that attachment of ZnO nanostructure can effectively enhance the field electron emission properties of the aCNTs. Modification with ZnO nanoflower-like structure can reduce the turn-on field of aCNTs from 8.91 to 3.64V/μm. The results have been explained in terms of increased roughness which in-turn led to large enhancement of the local electric field and thus facilitated electron emission from this hybrid emitter. [Copyright &y& Elsevier]

Abstract: Two types of chemically pristine polycrystalline cubic boron nitrides (c-BN) are sintered at different conditions using the starting cubic and hexagonal BN powders and their microstructures and grain boundaries are investigated systematically by transmission electron microscopy. The two c-BN samples are found to exhibit a number of twins inside their grains and have a similar grain size, despite their huge differences in the grain size of the starting powders and sintering conditions. Twin width for the c-BN sintered from hexagonal BN is significantly smaller than that for the c-BN sintered from c-BN. Grain boundaries in the two samples can be atomically abrupt without any amorphous or secondary layers and oxygen is detected merely at the grain boundaries of the c-BN sintered from the c-BN powders. Such microstructural differences have a direct impact on mechanical behaviors of the c-BN, as the Vickers hardness of the c-BN sintered from hexagonal BN powders is found to be higher than that of the c-BN sintered from the c-BN powders. [Copyright &y& Elsevier]

Abstract: The early growth stages of chemical vapor deposition (CVD) diamond on a sol–gel TiO2 film with buried ultra dispersed diamond seeds (UDD) have been studied. In order to investigate the diamond growth mechanism and understand the role of the TiO2 layer in the growth process, high resolution transmission electron microscopy (HRTEM), energy-filtered TEM and electron energy loss spectroscopy (EELS) techniques were applied to cross sectional diamond film samples. We find evidence for the formation of TiC crystallites inside the TiO2 layer at different diamond growth stages. However, there is no evidence that diamond nucleation starts from these crystallites. Carbon diffusion into the TiO2 layer and the chemical bonding state of carbon (sp2/sp3) were both extensively investigated. We provide evidence that carbon diffuses through the TiO2 layer and that the diamond seeds partially convert to amorphous carbon during growth. This carbon diffusion and diamond to amorphous carbon conversion make the seed areas below the TiO2 layer grow and bend the TiO2 layer upwards to form the nucleation center of the diamond film. In some of the protuberances a core of diamond seed remains, covered by amorphous carbon. It is however unlikely that the remaining seeds are still active during the growth process. [Copyright &y& Elsevier]

Abstract: Synthetic diamond powder of micron size was annealed in an argon atmosphere at 1900K during 15min. An incomplete phase transition diamond→graphite was studied by the TEM (transmission electron microscopy) methods. Disruption of (111) diamond planes packing and the lonsdaleite layers formation took place in the process of annealing. Particles contained fragments of graphite, diamond and layers with defect structure. Among the fringes with the interplanar spacing d111 =0.206nm, corresponding to {111} diamond planes, some areas with the doubled interplanar distances 2d111 were found, which were formed as a result of some sp3 -bonds rupture during the heating. [Copyright &y& Elsevier]

Abstract: Homoepitaxially grown single crystal diamond (100) surface on polished natural type 2a diamond was carefully prepared and examined for morphology and chemical composition. Atomic force microscopy (AFM) analysis showed smooth polishing scratches consisting of broad and shallow patterns also seen by electron microscope examination in the secondary electron emission detection mode. High resolution electron energy loss spectroscopy (HREELS) was used to determinate different chemical bonding configurations present on the as grown surface and their thermal stability induced by vacuum annealing and exposure to activated hydrogen. In-situ hydrogen terminated surfaces were oxidized by exposure to thermally activated oxygen. Gradual annealing leads to the removal of oxygen containing species and to regeneration of the hydrogenated diamond surface. Annealing results in desorption of peroxide and ether groups and recovers the diamond optical phonon overtones in the HREELS. There was no indication of hydroxyl groups after oxygen exposure. Possible chemical processes involving activated hydrogen and oxygen during the exposures and subsequent annealing are suggested. Activated hydrogen and oxygen possess sufficient energy to attack absorbed species in order to form new chemical bonds absorbed onto the diamond surface. [ABSTRACT FROM AUTHOR]

Abstract: Vertically aligned carbon nanotube (VACNT) arrays were synthesized using a microwave-plasma-enhanced chemical vapor deposition (MPECVD) system for polymer electrolyte fuel cell (PEMFC) electrode applications. Platinum nanoparticles (Pt NPs) were deposited on as grown VACNT arrays by a DC sputtering system. Pt NPs in the size range of 3–5nm were formed on the CNT surfaces. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and electron microscopy were employed to study the structural and chemical bonding changes post deposition of Pt NPs. Variable particle density along the nanotube length was observed with cluster formation on tip ends and individual Pt NPs forming farthest away from tip ends. Change observed in the C1s and N1s core level spectra and its possible implications on the Pt/VACNT properties were also discussed. [Copyright &y& Elsevier]

Abstract: Plasma enhanced chemical vapour deposition (PECVD) and injection chemical vapour deposition (CVD) methods have been used to produce superparamagnetic iron nanoparticles (NPs) encapsulated in carbon nanostructures (core@shell). Morphological and structural properties of the Fe-filled CNTs synthesized by PECVD and CVD were carried out using a scanning and transmission electron microscope (SEM, TEM), high resolution electron microscopy (HRTEM) and selected area electron diffraction (SAED). Magnetometry results and electron microscopy observations reveal magnetic responses with different characteristics associated to the iron particles depending on the deposition method. The magnetic properties of these samples have been described in terms of the carbon nanotube anisotropic structural effects. This magnetic behaviour has potential for biomedical applications. [Copyright &y& Elsevier]

Abstract: Superhard materials like diamond are essential for abrasive or cutting tool applications. In this way, carbon nitrides are of relevant interest because they are expected to exhibit exceptional mechanical properties, high values of bulk modulus being predicted. A smart and simple method was used to synthesize carbon nitrides and allowed elaborating a low-compressibility polymorph. The processing consists in the decomposition of commercial thiosemicarbazide (H2NC(S)N2H3) powder at ambient pressure and 600 °C under nitrogen flow. Besides the presence of a graphitic C3N4 phase, a nanocrystalline material is obtained and is identified as a cubic carbon nitride with a cell parameter of 3.163 Å. Its impressive bulk modulus of 355 GPa propels it as a challenger for cubic boron nitride among low-compressibility materials. Thus, we prove that, in accordance with previous numerous theoretical predictions, crystalline carbon nitrides exhibit exceptional compressibility behaviour. Moreover, our synthesis strategy evidences that, despite usual admitted considerations, severe and expensive pressure and temperature conditions are not mandatory to elaborate low-compressibility covalent materials, which could give new insights for their development. [Copyright &y& Elsevier]

Abstract: Heat treatment on multi-wall carbon nanotubes (CNTs) in ammonia gas was performed in this study. Effects of heating temperature (up to 1000 °C) on material characteristics of the CNTs were systematically investigated. Microstructure of the CNTs was examined using a transmission electron microscope. In addition, their crystallinity and specific surface area were evaluated with a Raman spectrometer and a nitrogen gas sorption analyzer, respectively. It was found that hydrogen storage performance of the CNTs clearly depended on their microstructure and crystallinity, which can be modified by the heat treatment. The hydrogen storage capacity of the as-received CNTs, measured with a high-pressure microbalance under 6.89 MPa, was only 0.39 wt.%. However, this value can be significantly improved to be 2.9 wt.% when the CNTs underwent a heat treatment conducted in the ammonia atmosphere at 1000 °C. [Copyright &y& Elsevier]

Abstract: The diamond nuclei generated by the bias enhanced nucleation (BEN) on iridium are gathered in well defined areas (“domains”). In atomic force microscopy (AFM) measurements they become manifest in a 1 nm downward step. The fine structure of the carbon layer inside and outside these domains has been studied by small spot Auger electron spectroscopy (AES), high resolution transmission electron microscopy (HRTEM), AFM and lateral force microscopy (LFM). The Auger spectra of the carbon KLL peak taken in an ultra high vacuum setup revealed diamond features inside and more graphitic features outside the domains. The comparison with the intensity of the Auger signal originating from the underlying Ir film indicates a carbon coverage inside the domains which is only by about 20% lower than outside. Cross section HRTEM images after BEN and after a short growth step, as well as AFM measurements after softly etching off the carbon layer, give no indication that the Ir had experienced a major modification by the domain formation process. Combining the information deduced from these experiments we conclude a significantly higher density of the carbon matrix within the domains. The lower friction forces measured in these regions by LFM confirm the interpretation of a material with higher elastic modulus. The present results allow to refine our understanding of structure and formation of the BEN layer on Ir. [Copyright &y& Elsevier]

Abstract: Vapor grown carbon fibers (VGCFs) with diameters of several microns were synthesized and investigated by high resolution transmission electron microscopy. It was found that the shell of the VGCFs consisted of densely-packed domains embedded in loosely-packed matrix, and both were highly amorphous. Regular edge planes as observed on the surface of fishbone nanofibers do not exist on VGCFs. Hence, surface treatment is more important for the deposition of catalysts. Ammonium ferric citrate (AFC) was employed for the impregnation of iron, where the high viscosity of the aqueous solution of AFC is beneficial. Calcination was found to be a key step to improve the dispersion of the iron particles, which can be attributed to enhanced interactions between iron and carbon due to the gasification of carbon occurring at the iron–carbon interface. Quantitative analysis by X-ray photoelectron spectroscopy showed that the calcination of the supported AFC led to a higher atomic concentration of iron on the surface, indicating smaller particle size and a higher dispersion. Secondary carbon nanofibers were grown subsequently on the VGCFs from cyclohexane. The specific surface area was enhanced considerably, from less than 1 m2 g−1 to 106 m2 g−1 after the growth of the secondary nanofibers. The obtained composites are promising materials as structured support in heterogeneous catalysis. [Copyright &y& Elsevier]

Abstract: Boron nitride (BN) thin films grown on Si (100) substrates by radio frequency magnetron sputtering, with varying growth parameters, are studied by high-resolution transmission electron microscopy (HRTEM). The HRTEM study reveals the presence of several interesting nanostructures in the BN films. Nanotube-like configurations, nanoarches and nanohorns are observed, as well as well-orientated cubic BN nanocrystals. It is found that several configurations of the turbostratic BN planes (properly orientated or curved) can act, in the same film, as nucleation sites for the growth of the cubic phase. [Copyright &y& Elsevier]

Here we present a simple method to fill multiwalled carbon nanotubes (MWCNT) with silver. This method involves stirring of MWCTs in AgNO 3 solution at room temperature in open air followed by heating in H 2 atmosphere at 250 °C for two hours. Process also leads to small coating of Ag on the surface. We confirmed the presence of crystalline silver in both coating and filling in hybrid MWCNTs by high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy and electron diffraction. After silver coating and filling, bulk thermal diffusivity and thermal conductivity of Ag hybrid MWCNTs were increased by 242% and 255%, respectively. Furthermore, current-voltage measurements using tuna probe in atomic force microscopy showed higher number of charge carriers in the Ag hybrid nanotubes compared to pristine MWCNTs which resulted in up to 173% increase in their electrical conductivity. The Ag hybrid MWCNT based sensor also showed rapid and reversible sensing for I 2 vapors: bulk sensor film demonstrated sensing response of 45% in just ~60 s at room temperature. However, the sensor recovery was slower: after removal of I 2 vapors source, the recovery took 400 s and required heating at 100 °C in air. Response and recovery of sensor film was maintained after repeated cycles of exposure. Finally, the Ag hybrid MWCNTs film displayed high stability and selectivity for I 2 vapors. [Display omitted] • Synthesis of Ag filled MWCNTs using a simple method • Bulk thermal conductivity of Ag hybrid MWCTs is 255% more than of MWCNTs. • Addition of Ag increases the bulk electrical conductivity of MWCNTs by 173%. • More negative charge carriers in the Ag hybrid MWCNTs than pristine MWCNTs • Ag hybrid MWCNTs showed rapid and reversible sensing for I 2 vapors. [ABSTRACT FROM AUTHOR]

Abstract: The control of the crystal size in nanodiamond (ND) powder is crucial, since most of its physical and chemical properties are size-related. In this work we demonstrate a simple method for increasing the crystal size of ND powder by selective oxidation in air. We analyze the oxidized powders by high-resolution transmission electron microscopy, X-ray diffraction and Raman spectroscopy in order to monitor changes in the average crystal size distribution and identify the limitations of these techniques for crystal size measurements. Our studies show that none of these techniques alone is able to provide sufficiently accurate information on size distributions, but can produce complementary results for better understanding of the properties of ND powder. [Copyright &y& Elsevier]

Abstract: Carbon nanotubes (CNTs) have been synthesized using the arc discharge method with a rotating graphite disc as the cathode. Arcing was carried out in open air and without the use of catalysts. The current density was maintained constant through out the experiment, while, the rate of rotation of the cathode and atmosphere under which arcing was carried out were changed during experimentation. Characterization of the samples produced indicates that rotation of the cathode has a significant impact on the quality and yield of the process. It is proposed that rotation of the cathode drags plasma formed between two electrodes away from high temperature region. This results in a sudden quenching of the reactive plasma. The time available for nucleation and growth phenomena is significantly reduced and thus leads to the formation of highly graphitic multi walled CNTs (yield 60%) and traces of double walled CNTs. [Copyright &y& Elsevier]

Abstract: Nanotubes composed of C60 fullerene molecules (C60NTs) were synthesized at ambient pressure and temperature using a modified liquid–liquid interfacial precipitation (LLIP) method in the system of C60–pyridine and isopropyl alcohol (IPA). A marked improvement in the formation of C60NTs was achieved by illuminating the initial C60–pyridine solution with visible light (VIS, 436 nm) and ultraviolet light (UV, 302 nm). It was also found that the growth and diameter of C60NTs are influenced by the combined effect of solvent ratio and incubation temperature. We present a simple approach of fabricating C60NTs designed to optimize rapid growth and to control diameter distributions useful for further discoveries of their chemical and physical properties and in the advancement of their possible applications in nanotechnology. The collected C60NTs were characterized by a variety of analytical techniques including scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. [Copyright &y& Elsevier]

Abstract: Silicon coated with a thin film of cobalt [Si/Co (10 nm)] is exposed to the plasma generated using CH4–H2 gas mixture by making a discharge between Si/Co substrates and Mo bent plate in pulsed discharge plasma chemical vapor deposition. At high plasma temperature and deposition pressure, carbon nanocapsules encapsulating Co nanoparticles are observed to form. They are investigated using high resolution transmission electron microscopy, scanning electron microscopy, visible Raman spectroscopy and X-ray diffraction. Present study indicates that the formation mechanism of carbon nanocapsules lie in the sputtering of Co thin film by the energetic ions from plasma at high deposition pressure which results in the formation of Co nanoparticles, on surface of which graphitic layers gets deposited at high plasma temperature. Present approach provides a novel strategy for the synthesis of high purity carbon nanocapsules encapsulating metal nanoparticles. [Copyright &y& Elsevier]

Abstract: Continuous nanocrystalline diamond (NCD) films were grown in an argon-rich gas atmosphere with relatively high growth rates by sustaining a low power (5 W) DC plasma in a hot filament chemical vapor deposition system (HFCVD). The parameter window for the synthesis of NCD films was studied as a function of argon, methane and hydrogen concentrations, as well as substrate temperature and DC bias. The results are consistent with reports indicating that the DC plasma induces re-nucleation by ion bombardment during the initial growth step and helps to maintain the atomic H and hydrocarbon species near the growing surface. It was found that DC plasma-assisted HFCVD enables high NCD growth rates and expands the parameter window, rendering it unnecessary to heat the filament above 2800 K. [Copyright &y& Elsevier]

Abstract: Carbon nanotubes (CNTs) offer great potential for numerous cold-cathode field emission applications. A less studied need is for high-current cathodes. While work to date has focused on the use of tangled webs of single-wall CNTs, much understanding about field emission has occurred from studies using multi-wall CNTs with controlled geometries. However, the crystalline nature of these multi-wall CNTs typically is far inferior to that of single-wall CNTs. We use high-resolution transmission electron microscopy to demonstrate that growth at temperatures ≤630 °C via thermal chemical vapor deposition can produce highly crystalline multi-wall CNTs, with structures consisting entirely of concentric graphene cylinders. Conversely, growth at temperatures ≥650 °C results in crystalline CNTs embedded in a nanocrystalline graphite, or glassy carbon, sheath. This sheath material is likely a poor electrical conductor, due to phonon scattering, and will have deleterious effects on field emission. Field emission measurements taken from such films are consistent with the best field-emitting multi-wall CNT films in the literature, in terms of total current for a given applied field, but without the benefit of the preferred perpendicular orientation. These results are promising toward the development of reliable high-current field emission cathodes. [Copyright &y& Elsevier]

Abstract: Arrays of freestanding bamboo-type carbon nanofibers were grown on the surface of a porous alumina substrate by laser-assisted catalytic chemical vapor deposition. A continuous wave argon ion laser operated at a wavelength of 488 nm was used to thermally decompose pure ethylene over nickel catalysts. Two different catalyst preparation methods were used and are compared with respect to the synthesis of aligned nanofibers. First, a thin nickel film (50 nm) was evaporated on the substrate and was subsequently laser annealed into nanoparticles. This preparation produced non-aligned nanofiber films. Second, a 50 nm thick catalyst layer was electrochemically deposited within the pores of an alumina substrate. This preparation produced an array of vertically aligned nanofibers. A growth rate dependence on radial position within the irradiated area was observed. Average linear growth rates ranging from 554 nm/s to 25 μm/s are reported. The nanofibers were examined by scanning electron microscopy and Raman spectroscopy. Fiber texture and nanotexture were determined by lattice fringe analysis from high resolution transmission electron microscopy images. The alignment mechanism is also discussed. [Copyright &y& Elsevier]

Abstract: Aligned multiwalled carbon nanotubes (MWCNTs) of high purity, low metal content and narrow size distribution were synthesized by chemical vapour deposition of acetylene along with iron-organometallic compounds in the temperature range 650–850 °C. The obtained MWCNTs were characterized by thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy and N2 adsorption. The effect on the carbon nanotube structure of different parameters such as, reaction temperature, nature of the iron catalyst precursor, the reaction mixture flow rate and the relative proportion of metal precursor to carbon source, has been studied. It was found that the outer and inner diameters of the carbon nanotubes were directly proportional to the iron catalyst concentration. Moreover, the wall numbers and the diameters of the carbon nanotubes were related to their apparent specific surface areas. [Copyright &y& Elsevier]

Abstract: Carbon nanoballs were prepared in the presence of acetylene with coke powder as carbon source by arc discharge technique. The arc plasma was diagnosed in situ by optical emission spectroscopy (OES) in the formation process of carbon nanoballs. Field emission scanning electron microscopy (FE-SEM), field emission scanning and transmission electron microscope (STEM) equipped with energy dispersive X-ray (EDX), X-ray diffraction (XRD), and Raman spectroscopy are used to characterize carbon nanoballs. The electrochemical performance of carbon nanoballs as an electrode was measured on a multi-channel battery test system to analyze the electrochemical response. The FE-SEM and STEM results show that carbon nanoballs are the main products in acetylene medium. Many carbon nanoballs are sintered together with a few carbon nanotubes (CNTs) inserted into the sintered carbon nanoballs except for a few carbon nanoballs that exist as a single ball. The STEM results show that the diameter of carbon nanoball is mainly in the range of 50–100 nm. The XRD analysis shows that the graphitization of carbon nanoballs is relatively high. The charge–discharge curves of carbon nanoballs show that the cell electrode has a high reversible capacity and the capacity retention could reach 73.7%, which might contribute to the conductivity of CNTs inserted into the sintered carbon nanoballs. [Copyright &y& Elsevier]

Abstract: A new self-induced and efficient route to carbon-encapsulated iron nanocrystallites (ca. 30–60 nm in diameter) using the thermolysis of sodium azide–chlorocarbon mixtures in the presence of ferrocene is presented. The product was purified and its composition and morphology were studied by means of HR SEM, HR TEM, XRD, and DTA/TG. The magnetic properties (the coercivities ca. 60–70 Oe and the saturation magnetization ca. 21–22 emu/g) of encapsulates were measured. This autothermal process has inherent advantages, including the use of low cost materials and the simplicity of the production protocol, and can be also used to obtain other nanoencapsulates. [Copyright &y& Elsevier]

Abstract: Open air laser-induced chemical vapor deposition (LCVD) was used to rapidly deposit a carbon nanotube forest on a moving substrate prepared with gold–palladium nanoparticles. Butane and propane were used as the carbon source, which was combined with hydrogen gas. Nanotube growth kinetics and alignment characteristics were strongly dependent on laser power density, substrate velocity, catalyst particle size, and the type of precursor mixture used. An increase in the hydrogen concentration improved the purity of the nanotubes by reducing the formation rate of amorphous carbon on the catalytic surface. A multi-stage growth model was proposed. [Copyright &y& Elsevier]

Abstract: We report on the use of a newly developed “all-laser” process for the growth of single wall carbon nanotubes (SWCNTs) onto various types of substrates, ranging from highly oriented pyrolytic graphite (HOPG) to thermally oxidized silicon or SiN free-standing membranes. The “all-laser” process uses the same UV laser (KrF) to deposit, in a first step, the CoNi catalyst nanoparticles on the substrates and, in a subsequent step, to grow the SWCNTs from the laser ablation of a pure graphite target. It is found that even if the SWCNTs grown onto the various substrates generally share the common feature of exhibiting a lateral growth, their structural packing, morphology and orientation are definitely substrate dependent. Indeed, while highly oriented and straight nanotubes (of ∼1 nm-diam.) were found to self-organize into 2D-planar bundles onto HOPG, they tend to rather form a random network of 3D-bundles of SWCNTs (∼10–20 nm-diam.) on the other substrates. These results demonstrate that by combining the latitude of the “all-laser” process with the appropriate substrate, various SWCNT nanostructures can be achieved. [Copyright &y& Elsevier]

Abstract: Diamond like carbon (DLC) films were prepared by the bipolar-type plasma based ion implantation, and the microstructure was examined as a function of positively and negatively pulsed voltages (V p and V n) by transmission electron microscopy (TEM) and Raman spectroscopy. Densities of the films were obtained from Rutherford backscattering spectrometry, elastic recoil detection analysis and surface profilemeter measurements. It was found that the density of the film was approximately 2.0 g/cm3 and slightly decreased with increasing V p and V n. TEM observation revealed that DLC films were amorphous structure and small size disordered graphite structure appeared as V p increased. With increasing V n, however, turbostratic structure was clearly developed. Raman spectra were fitted by 4 peaks (D 1: 1190 cm−1, D 2: 1380 cm−1, G 1: around 1550 cm−1 and G 2: 1590 cm−1). The G 1 peak shifted to higher wave numbers and the intensity of G 2 peak was increased with increasing V p. In addition, the intensity ratio of D (D 1 + D 2) to G (G 1 + G 2) peaks was also increased. These results suggested that graphite structure was formed as V p increased. With increasing V n, on the other hand, the G 1 peak did not shift so much and the intensity of G 2 peak was decreased. This corresponds to the development of the turbostratic form (t-DLC). The influence of electron and ion bombardment induced by V p and V n on the microstructure was discussed. [Copyright &y& Elsevier]

Abstract: A high surface area and non-microporous submicrometer-sized β-SiC material was successfully obtained according to the Shape Memory Synthesis (SMS) method. The attack by SiO vapors of a nanodiamond preform with sp 3-bound carbon, at 1200–1300 °C under dynamic vacuum, formed β-SiC nanoparticles by carboreduction of the SiO vapors. These β-SiC nanoparticles had a mean size distribution centered at 10 nm and a specific surface area of 140 m2/g. The high carbon to carbide conversion obtained and the location of the remaining unreacted carbon in the core of the β-SiC nanoparticles allowed a direct use of the material as a catalyst support without any stabilizing post-synthesis oxidative treatment. The material showed dispersive properties and a good resistance towards oxidation, due to the presence of a thick and partially oxidized protecting amorphous coating, preventing from the extensive oxidation of SiC into silica. [Copyright &y& Elsevier]

Abstract: Dense, vertically aligned carbon nanotube (CNT) films were rapidly grown using microwave plasma-enhanced chemical vapor deposition (PCVD). Catalytic cobalt (Co) nanoparticles were prepared on the substrate using excimer laser ablation method. No heat pre-treatment was performed for the catalyst prior to the CNT growth. At the initial growth stage, the CNTs grew at an extremely high rate of 300 nm/s. The average outer diameter of the nanotubes was approximately 6 nm. The CNTs were characterized by their relatively large inner diameter (ca. 4 nm) and thinner wall thickness (2–5 concentric layers). [Copyright &y& Elsevier]

Since the first observation of carbon nanotubes in 1991, their synthesis by different techniques has been extensively investigated. Recently, CVD-based methods have attracted much attention because of both their versatility and the quality of the nanotubes obtained. This work is focused on the aerosol pyrolysis process which is a catalytic CVD-based method involving pyrolysis of mixed liquid aerosols composed of both liquid hydrocarbon and catalyst precursor. This process generates clean and aligned multiwalled carbon nanotubes. To analyse and further understand the first nucleation and growth stages of nanotubes in the aerosol pyrolysis process, several samples composed of nanotubes starting to grow were prepared by flowing the aerosol in the reactor for short duration. Samples were analysed by SEM. First results indicate that the first stage involves the formation of a layer of catalyst particles in the [10–100] nm range on top of which nanotubes start to grow. An important issue for nanotube application is the control of their crystalline structure. Therefore, post-annealing treatments under flowing argon were performed on the as-synthesised multiwalled carbon nanotubes. The effects of such treatments on the structure of nanotubes are determined by a comparative HRTEM analysis and a thermogravimetric analysis under air. Results demonstrate that annealing treatment between 1700 and 2000 °C is an efficient way to improve the structure of nanotubes and thus to make them more resistant against oxidative atmosphere. [Copyright &y& Elsevier]

The structure of bulk nanoporous carbon chemically prepared from SiC powders is studied by TEM microdiffraction and HRTEM techniques. The conditions for the formation of diamond and graphite clusters in the carbonization process are analyzed. The experimental data suggest that diamond clusters can be produced near carbonization reaction front in the case of its quick propagation into the precursor. The slower the reaction front, the greater is the chance that graphite or quasi-graphite clusters are formed. [Copyright &y& Elsevier]

Biomass waste is considered as a renewable, low-cost, and environmental friendly carbon source. However, converting a largely disordered carbon materials from biomass wastes into a highly crystalline graphitic carbon nanostructure with low-energy consumption process remains a challenge. Here, we report a simple and low energy process to transform the amorphous carbon structure of coconut coir from Indonesian biomass waste into graphitic nanostructure. A high crystalline graphitic nanostructure has been successfully obtained through two-step process consisting of (1) carbonization process at 500 °C to produce amorphous charcoal, followed by (2) nickel-based catalytic graphitization process at various temperature of 1000 °C to 1300 °C. It is important to note that the temperature process is a main factor in the structural transformation from amorphous to graphitic nanostructures. The structural transformation during catalytic graphitization process was investigated as a function of heat treatment temperature using X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results show that the carbon structure of coconut coir start to transform from amorphous to ordered graphitic nanostructure at 1200 °C, a temperature lower than that of conventional graphite production, with the highest degree of graphitization (82.16%) and IG/ID ratio of 1.16. Observation using high resolution transmission electron microscopy (HRTEM) reveal the well-defined lattice fringes of graphitic nanostructures with an interplanar distance of 0.3369 nm corresponding to the (0 0 2) crystal plane of pure graphite (0.3354 nm) and less than the disorder carbon (0.3440 nm). In conclusion, this simple process and low energy successfully convert the coconut coir waste into a higher value-added product of graphitic materials as well as reduce the environmental impact of coconut waste. [Display omitted] • Temperature has an important driving force for structural transition in catalytic graphitization • The use of coconut waste in graphitic carbon production is a great approach in waste management • Nickel-based catalyst is used to convert the amorphous to graphitic phase of coconut coir carbon [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) were synthesized on zirconium diboride (ZrB 2) through CVD using a Ni catalyst. The influences of the synthesis temperature, time and catalyst amount on the quality and quantity of grown CNTs were studied. The catalyst content determined the temperature at which the CNTs began to grow. When the Ni catalyst content was low, the temperature at which the CNTs began to grow should be higher, and was 1050 °C for 5 wt% Ni content, but was 950 °C for 15 wt% Ni content. Meanwhile, agglomeration of metal atoms was observed if the synthesis temperature was increased until reaching the upper limit temperature for CNT synthesis, which was 1100 °C for 5 wt% and 10 wt% Ni content, but was 1000 °C for 15 wt% Ni content. Increased Ni catalyst content also led to higher catalytic activity as long as the Ni catalyst content did not exceed 15 wt%. Meanwhile, prolonged synthesis time extended the reaction time for the decomposition of C 2 H 2 , but resulted in the agglomeration of carbon atoms when the synthesis time was 150 min. The results showed that the uniform distribution of CNTs can be obtained in ZrB 2 powder and there was no reaction between ZrB 2 and Ni catalyst. The suitable synthesis conditions for obtained uniform size of CNTs grown with a higher degree of graphitization on ZrB 2 that identified in this work were: Ni catalyst content of 10 wt%, synthesis temperature of 1050 °C, and synthesis time of 120 min. [Display omitted] • In-situ synthesis of CNTs on the surfaces of ZrB 2 particles by CVD was investigated. • The effects of the parameters of carbon nanotube growth by using Ni as catalyst were studied. • 10 wt% Ni catalyst, 1050 °C and 120 min were found to be the optimal synthesis conditions. [ABSTRACT FROM AUTHOR]

The observation of intrinsic magnetic correlation phenomena in presence of Moiré-superlattices in twisted-bilayer-graphene, double-bilayer-graphene and graphite has recently attracted important attention. By employing high resolution transmission electron microscopy (HRTEM), in this study we have investigated μm-thin HOPG-lamellae with unusual Moiré-superlattices. Anomalous large periodicities of ~80 nm and ~40 nm, possibly corresponding to θ misfit of 0.18° and 0.35° are reported. X-ray-rocking-curve-analyses, evidenced the presence of non-monotonic signals, a clear indicator of dislocation-rich-properties. Selective area electron diffraction (SAED) of the superlattice further revealed the presence of anomalous doubled diffraction patterns. The angular-dependence of SAED with sample-tilt from 0° to 0.93° evidenced an increase in the pattern-intensity up to a maximum for sample-tilt of 0.33°. Disappearance (of SAED-doubled-pattern and Moiré-superlattice) was found for 0.66° and 0.93° tilt. Re-appearance was further verified, by taking the sample back to 0.33° tilt. Raman-spectroscopy and scanning electron microscopy supported the observed results, revealing 1) presence of D and D' band signals and 2) absence of sample oxidation. Unlabelled Image • Observation of large-period Moiré superlattices is reported in dislocation-rich mm-thin lamellae exfoliated from HOPG. • The superlattice is attributed to existence of dislocations and layer rotation • Electron diffraction of the superlattices reveals unusual doubled diffraction patterns • The intensity of doubled patterns exhibits an angular dependence • Raman-spectroscopy supports existence of dislocation rich-areas in the samples. [ABSTRACT FROM AUTHOR]

Diamond/SiC interlayer with intermediate thermal expansion coefficient is introduced for improving the adhesion of NCD films on Ti substrate. Herein, tetramethylsilane (TMS) gas is added to produce SiC phase, forming a diamond/SiC interlayer. The effect of TMS gas flow on the microstructural evolution of the interfacial layer and the film adhesion is systematically investigated. At TMS gas flow of 5 sccm, the NCD film shows an interlayer of about 15% SiC by phase area statistics in SEM image. This film exhibits the lowest residual compressive stress of 1.64 GPa and the optimum adhesion of about 28.2 ± 2 N against Ti substrate. Increasing TMS gas flow leads to the increase of SiC content and the grain refinement of diamond in the interlayers. It is found that Ti silicide and hydride with increased amount are formed in the Ti substrate at higher TMS gas flow. The presence of these Ti intermetallic compounds with larger thermal expansion coefficient results in the increased residual stress and poorer adhesion in the NCD films. On the basis of reduction of Ti intermetallic compounds, the addition of TMS gas flow at 5 sccm is crucial for the preparation of good-adhesion NCD films on Ti substrate. • NCD films with diamond/SiC composite interlayer were deposited on Ti substrate. • The addition of TMS gas on in-situ formation of Ti intermetallic was studied. • The NCD film deposited at the TMS gas of 5sccm shows the optimized adhesion. [ABSTRACT FROM AUTHOR]

As one kind of traditional and widely used solid lubricant, diamond like carbon films have been approved to have temperature dependent ultra-low friction behaviors. However, the mechanism of this observation is not fully clarified. By using high resolution transmission electron microscopy, Raman spectrum and tribometer, we monitored the nanostructure transformation of wear debris and friction coefficient evolution from 25 °C to 200 °C. High temperature promotes graphitization and enhances the formation of graphene nanoscrolls (GNSs), which results in decrease of friction coefficient. For example, at 150 °C, more spherical shape graphene nanoscrolls appear in debris and a balance between graphitization and nanoscrolls crimping is established, which leads to the lowest friction coefficient at 0.012. However, when the temperature is too high (200 °C), such a balance is destroyed and the nanoscrolls tend to be disordered with sharp edges, which causes the failing of superlow friction state. The results demonstrated that temperature could change the fine structure of graphene nanoscrolls, which ultimately determines the tribological behavior of DLC film. Moreover, the structure evolution of graphene nanoscrolls should be the compulsory result of competition between the thermodynamic formation of graphene layers and the dynamics of nanoscrolls crimping. Unlabelled Image • Friction induced graphene nanoscrolls are the key structural factor of superlow friction of DLC. • Temperature affects the fine structure of graphene nanoscrolls, resulting in interface contact state transformation. • The competition between graphitization and crimping process is the reason for graphene nanoscroll evolution. [ABSTRACT FROM AUTHOR]

We report on the design, fabrication and optical performance of gain mirrors in single crystal diamond substrates for vertical external cavity surface emitting lasers (VECSELs). VECSELs have gained attention recently due to their potential for high emission power in single mode with low beam divergence, yet their maximum output power remains typically limited due to thermal roll-over resulting from insufficient heat dissipation. In order to increase the heat transfer, we exploit the excellent thermal conductivity of single crystal diamond, which is assembled in direct contact with the active structure. The optical cavity is hereby defined by an output coupler and a high reflection grating structure etched into the diamond surface. We here present the design and microfabrication of a diffraction grating that was optimized to reflect light into the 0th order, therefore combining the role of a gain mirror and a heatsink at the same time. Our process involved metal mask deposition onto the diamond surface, e-beam lithography and reactive ion etching. Characterization showed reflection above 95% at a center wavelength of 1550 nm, potentially allowing the integration of the diamond mirror into a vertical external cavity surface emitting laser. Unlabelled Image • Design of high contrast grating in single crystal diamond for integration in VECSEL • Micro-fabrication process for high contrast grating in single crystal diamond • High quality grating demonstrated in single crystal diamond by reactive ion etching • >95% grating reflectivity at a wavelength of 1550 nm experimentally demonstrated [ABSTRACT FROM AUTHOR]

Amorphous carbon films with perfect corrosion resistance have attracted scientific interest for years, but the corrosion behaviors of these films under heat shock conditions have rarely been reported. To reveal these behaviors, the corrosion properties of hydrogenated amorphous carbon (a-C:H) films at temperature of 200–400 °C are evaluated by Electrochemical tests and the variation of its structure detected via Raman spectroscopy, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy and scanning electron microscopy. Under all inspected temperatures, the corrosion properties of the films are better than those of bare silicon due to the chemical inertness of the a-C:H films. In detailed, the corrosion properties improve with increasing temperature up to 250 °C, because of the densification and crystallization of the a-C:H films. Above 250 °C, the corrosion properties weakened a litter as the temperature increased, which can be attributed graphitization induced porosity and promoted the number of ion channels. In a word, the films that annealed at a temperature of 250 °C have optimal corrosion resistance. Interestingly, the surface energy of a-C:H films has little effect on corrosion behaviors. Our result shows that the a-C:H films have superior corrosion resistance even under heat shock conditions. Unlabelled Image • The I D /I G ratios of a-C:H films increase with the increase of annealing temperature. • Anticorrosion properties of a-C:H films were investigated in the annealing temperature range of 25–400 °C. • The a-C:H films with optimal corrosion resistance could be obtained by annealing at 250 °C. • The a-C:H films annealed at 250 °C own the highest contact angle and roughness. [ABSTRACT FROM AUTHOR]

Platinum nanoparticles were deposited on a highly oriented pyrolytic graphite (HOPG) substrate using a coaxial arc plasma gun. The Pt-deposited HOPG substrate was cross-sectioned to prepare a thin foil specimen using focused ion beam milling, and was analyzed by using high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, and electron energy loss spectroscopy. The surface of the HOPG substrate was observed to be disordered by the Pt ion irradiation. The surface was located using the depth profiles of π + σ plasmon peaks and the full width at half maximum of π⁎ peaks. The denaturation of the HOPG substrate by the Pt ion irradiation was observed to a depth of approximately 12 nm. Unlabelled Image • Platinum nanoparticles were deposited on a HOPG substrate using a coaxial arc plasma gun. • The cross-sectional atomic structure of the Pt-deposited HOPG substrate was revealed by HRTEM, STEM and EDX. • The surface position of the Pt-deposited HOPG substrate was located from the depth profile of EELS spectra. [ABSTRACT FROM AUTHOR]