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Abstract A one-dimensional (1D) graphene fiber with a novel structure has been prepared by a heat treatment of rice husk, a natural by-product that contains high amounts of silica. A step-by-step heat treatment of rice husk revealed that (i) carbonization yields porous carbon and silica, (ii) 1D β -SiC nanowires are formed by the carbothermic reduction of silica, (iii) finally 1D graphene fibers are created by silicon sublimation from 1D β -SiC nanowires. Raman spectroscopy and electron microscopy studies revealed that the graphene fiber is composed of a turbostratic multilayer structure. The SiC-derived material exhibits a large crystalline size and turbostratic stacking making each layer as quasi-free-standing graphene, which is confirmed by the 3.9 times higher Raman G′-band intensity over the G-band intensity. Molecular dynamics simulations revealed a high diffusion rate of Si atoms and a volume reduction of the SiC structure at the sublimation temperature. Since the silicon sublimation occurred from multiple points of the SiC nanowire, this led to radially-collapsed fibers and faceted structures with thick-graphitic-layer that are inter-connected (deflated-balloons and inter-connected balloon-like fibers). This facile synthesis route opens up a new avenue to the cost-effective and etching-free production of self-standing graphene for its bulk usage. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Linear carbon chains (LCCs) consisting of sp -hybridized carbon atoms are considered a fascinating 1D system and could be used in the fabrication of the next-generation molecular devices because of its ideal linear atomic nature. A large portion of long LCCs inside multi-walled carbon nanotubes (MWCNTs) were synthesized by atmospheric arc discharge in the presence of boron. Closed-end growth of MWCNTs in the arc process is suggested as a critical condition for the simultaneous growth of LCCs within the inner cores of carbon nanotubes. The strong Raman line around 1850 cm −1 was used to characterize the degree of filling as well as their structural stability under high temperature thermal treatments. We observed a distinctive change in the electrical conductivity of the MWCNT assembly before and after the disappearance of LCCs due to the expected strong coupling interaction between the LCCs and the innermost tube. This work demonstrates for the first time the enhanced effect of confined linear carbon chains on the overall electrical conductivity of MWCNT assemblies. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs)/lead sulfide (PbS) quantum dots (QDs) nanohybrids have been synthesized through the controlled decoration of CNTs by PbS-QDs by means of the pulsed laser deposition technique. The size of the PbS-QDs and their surface coverage of the CNTs' surface are monitored through the number of laser ablation pulses. Here, while comparing both single-walled (SW) and double-walled (DW) CNTs based nanohybrids, focus is put on the investigation of their interfacial structure and the effect of inner tube. Anchoring PbS through direct sulfur-carbon chemical bonding between CNTs' outer wall and PbS-QDs, which are thought to be profitable for efficient charge transfer but not for charge transport along CNT's tube axis, are confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy. In the case of double-walled CNTs (DWCNTs), inner tube remains unaffected by ablated PbS species, then it serves efficient conduction way for transferred photo-generated charges. This unique feature of the DWCNTs based nanohybrid, where the photocharges are generated by the chemically bonded PbS-QDs to the outer tube and then efficiently conveyed by the inner tube of the nanotubes, is highly likely at the origin of their significantly higher photo-activity (several hundred times than in SWCNTs-based nanohybrids). [ABSTRACT FROM AUTHOR]

Abstract: Late in January 2004 slope instability evidence such as cracks and subsidence appeared on a retaining wall along National Highway 168, near Otomura (Nara Prefecture, Japan). This road plays a strategic role as a long distance route for passenger vehicles and trucks, therefore detailed investigations and constant surveillance have to be carried out in order to manage the induced risk situations. Six months later, on August 10th, a large landslide occurred due to heavy rainfalls related to typhoons #10 and #11 that hit Japan on the first week of August. Field and aerial surveys of the site were carried out soon after the appearance of the first geomorphologic evidence of landslide movements, and a monitoring system was immediately set up. Landslide displacements have been measured since the early stage of movement and road traffic was strictly controlled in order to minimize possible damage. This paper illustrates the effects of landslide activation and the investigations carried out in order to assess landslide hazard and predict the time of failure. Suitable methods for risk management oriented to increase the public safety and including risk control and crisis mitigation acts are also discussed. [Copyright &y& Elsevier]

Abstract: A simple but effective way of producing short cup-stacked carbon nanotubes with high quality is demonstrated using sonication in an ethanol/distilled water mixture. The substantial removal of amorphous carbon deposited on the truncated conical layer-stacked nanotubes by controlled air oxidation was a critical precondition to cut the nanotubes without substantial structural degradation. The short nanotubes (below 1μm) prepared by a sonication-generated shear force exhibited a narrow length distribution (median length=0.2μm) and chemically active edges in the outer surface, thereby resulting in high dispersibility in an aqueous solution. [Copyright &y& Elsevier]

A method is developed for the explicit identification of solid-void interfaces in a Bayesian framework using a statistically efficient gradient based Markov Chain Monte Carlo (MCMC) algorithm called Hamiltonian Monte Carlo (HMC). The elastodynamic inversion is carried out in a Finite Element discretized domain considering parameterized representations of the actual interface between the elastic solid and void embedded in the solid itself. Using a reference configuration, a parameter update procedure is designed, to ensure reversibility of the HMC algorithm, thereby satisfying the detailed balance condition. The quality of mesh at every parameter update is maintained through a simple mesh moving strategy that introduces volume scaled Elastic modulus in the mesh moving stage. HMC gradient computation procedure is detailed for a general parameterization of the interface. Integration of these techniques with the HMC algorithm enables the continuous variation of parameters and maintains continuity of the Hamiltonian. The performance of the proposed method is investigated with respect to two solid-void interface identification problems, one of well-defined and the other of arbitrary geometry. Results show that the proposed method performs well, maintaining a good mesh quality after each parameter update. The Markov chains converge and statistical descriptions of the inferred parameters are obtained. [ABSTRACT FROM AUTHOR]

In this paper, space–time finite element method is developed for the dynamic fracture analysis of dam–reservoir (DR) system which is supported on a perfectly rigid foundation. In this method, an auxiliary variable q representing the first-order time derivative of hydrodynamic pressure is treated as the primary unknown for the reservoir domain. Similarly, velocity v is the primary unknown for the solid domain. A three point Gauss–Lobatto quadrature rule is employed for computing time integral of those terms which contain stress term. Further, a partitioned method based on a block-iterative scheme is employed to incorporate the material nonlinearity of the concrete and to enforce the coupling between the two domains in a single iteration loop. A co-axially rotating crack model with exponential strain softening rule is employed to model the fracture of the concrete. Afterwards, numerical performance of the proposed scheme is demonstrated by analyzing two situations of dynamic fracture of Koyna concrete gravity dam. • Single iteration-loop to handle material-nonlinearity and dam-reservoir coupling • Each of dam- and reservoir-domain is represented by a single primary variable • Secondary unknowns, pressure and displacement remain continuous in time • Base cracks have less impact on the initial response of Koyna dam • Neck area near downstream face of the dam is most vulnerable regime of Koyna dam • Dam-reservoir interactions amplify response of Koyna dam • Cracking of concrete elongates the vibration period of the dam [ABSTRACT FROM AUTHOR]

Vacancy activated BN is able to spontaneously reduce various metal ions (Ag, Pt, Au, Cu, Fe) without any reducing agents to form metal-BN heterostructures. It further allows the activated BN as the catalyst support for Pt based single atom catalysis, such as hydrogen evolution reaction. [Display omitted] Hexagonal boron nitride (hBN) has long been considered chemically inert due to its wide bandgap and robust covalent bonds. Its inertness hinders hBN from functionalization for energy conversion applications. A question arising is whether it is possible to make hBN chemically reactive. Here, we report cryomilling in liquid N 2 , as an effective strategy to activate the chemical reactivity of hBN by engineering different vacancies to produce defective-BN (d-BN). The local reactivity of the vacancies is probed by photoluminescence (PL) emissions and electron spin resonance spectroscopy (ESR). Density functional theory calculations reveal that the formation of different vacancies with/without oxygen cause the creation of mid-gap states that are responsible for the PL emissions in the visible region. These vacancies also generate localized free radicals which are both theoretically and experimentally confirmed by spin density calculations and ESR. Due to the vacancy induced free radicals and Fermi level shifts, d-BN can be controllably functionalized with single metal atoms by the spontaneous reduction of metal cations; mono-metallic or bi-metallic clusters can also be effectively reduced. As a proof of concept, the surface-bound metal nanostructures, especially substrate confined single metal atoms, exhibit improved hydrogen evolution catalytic performance, and can be further used for sensing, and quantum information. [ABSTRACT FROM AUTHOR]

Interfaces are often crucial determinants of the physicochemical properties of a material. As a result, the rational production and engineering of heterogeneities, and the resulting interfaces, can enhance the functionality of a material system. This is especially true of two dimensional (2D) materials, which are only a few atoms thick and thus sensitive to small perturbations of their surroundings. As a result, 2D materials and their heterostructures have been recently modified to function as catalysts, photodetectors, chemical sensors, memory, logic devices, single photon emitters, and more. In this review, we summarize the current understanding of functional interfaces in few-layered chalcogenide 2D systems, and address the following topics: The classification of interfaces by dimensionality and electronic structure, methods of creating 2D interfaces, characterization techniques and related challenges, applications of interfacial engineering in 2D systems, and finally a perspective on the future of this rapidly advancing field of study. [ABSTRACT FROM AUTHOR]

Activated Carbon (AC) with high specific surface area and elevated porosity was synthesized from babassu mesocarp by hydrothermal carbonization, followed by KOH activation-coupled pyrolysis and subjected to heat-treatment at three different temperatures to generate AC-1100, AC-1400 and AC-2200. Raman spectroscopy, X-Ray diffraction (XRD), transmission electron microscopy (TEM) and N 2 adsorption-desorption were used to characterize structurally the synthesized materials and electrochemical studies to evaluate the capacitance properties. The Raman spectra showed sharpening of graphitic bands and decrease in intensities of amorphous bands with the increase of treatment temperature. AC-2200 showed a significant decrease of I D /I G due to the crystal growth in ab plane and drastic increase of I 2D /I G due to graphitic ordering in c direction, further proven by sharpening of characteristic XRD peaks and visualization of few-layer well-formed graphite micro-crystals by TEM. Although gradual heat treatment resulted in an increase in sample crystallinity, the surface area and porosity decreased, leaving AC-2200 practically non-porous. These changes were reflected in their electrochemical properties as AC-1400 showed highest double layer capacitance owing to an optimization between structural ordering and retention of porosity, while the capacitance, as well as the resistance, of AC-2200, decreases dramatically due to loss of pores and increased crystallinity brought in by graphitization. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Hydrogen peroxide (H 2 O 2) is an alternative oxidant and green method for the purification and functionalization of carbon nanotubes (CNTs), which works more efficiently in combination with UV radiation. In this paper, we investigated and monitored the oxidation mechanism of ethanol-synthesized and standard multi-walled carbon nanotubes. Characterization was carried out by high-resolution transmission electron microscopy (HRTEM), X-ray photo electron spectroscopy (XPS), acid/base titrations, thermo-gravimetric analysis (TGA) and Raman spectroscopy. Interestingly, we found a close correlation between oxidation time and the nature of the nanotubes. For the first time, a unique cyclic peeling of layers within MWNTs, termed "onion effect" was found. In this process, the degree of crystallinity of the outer layers significantly changed for the different peeling stages. We explain the process and how the number of layers within nanotubes gradually decreases when reaching critical acid concentrations. This method now allows the synthesis of MWCNTs with specific numbers of walls, diameter and controlled degree of crystallinity that could be effectively used for applications in biology and composites. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract The influence of physical and chemical surface properties on the adsorption of nitrobenzene, a major organic contaminant in wastewater, was investigated using a wide range of graphene-based materials. These included carbon blacks and activated carbons as well as nanostructured materials such as graphitic nanoribbons (GNRs) and graphene-like structures derived from rice husk (RHC). The surface of GNRs was also modified by oxidation with hydrogen peroxide under UV irradiation (yielding Ox-GNRs). For the understanding of the importance of electrostatic and dispersive interactions, the uptake of nitrobenzene was measured in solutions at controlled pH conditions. The Langmuir and Freundlich parameters were found to be dependent on both surface physics and chemistry. To elucidate this influence, the adsorption of H 2 O/D 2 O was performed on selected samples. The edge surfaces of nanoporous carbons appear to exert dominant interactions with polar molecules such as nitrobenzene. At the same time, while the presence of micropores is the most important factor for adsorption at low concentration, the meso- and macropores become more important at higher nitrobenzene concentrations. The novelty of this study resides in the use of complementary techniques to understand the adsorption on traditional carbon materials as a guide for the optimization of novel, graphene-like nanostructured adsorbents. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Earthquake and tsunami impose great threats on the stability of a breakwater. Foundation of the breakwater is weakened by these forces, and it may result in collapse of the breakwater. Lateral flow of seabed soils take place beneath the breakwater, and excess pore water pressure is generated in the foundation by an earthquake that precedes tsunami. These factors may lead to excessive settlement and horizontal displacement of the breakwater. Tsunami introduces additional instability to the deformed breakwater. Due to water level difference between seaside and harborside of the breakwater during a tsunami, seepage occurs through its foundation, and it may cause pipping of seabed soils. Tsunami induced scouring of mound is also a big problem for the stability of the breakwater foundation. Finally, these result in failure of the breakwater foundation. Due to failure of its foundation, the breakwater may collapse and cannot block the tsunami. It results in entering of the tsunami in coastal areas. In order to make a breakwater resilient against earthquake and tsunami induced damage, reinforcing countermeasures were developed for foundation of a breakwater. Geogrid, gabions and sheet piles were used for reinforcing a foundation model. The effectiveness of the model is evaluated through physical modeling for mitigating the earthquake and tsunami induced damage. Shaking table tests were performed to determine the effectiveness of the reinforced model under different earthquake loadings. Tsunami overflow test was conducted on the same deformed model in order to see the effects of tsunami on the model. Comparisons were made between the unreinforced and reinforced foundations, and it was observed during the tests that the reinforced foundation performed well in reducing the damage of the breakwater brought by the earthquake and tsunami. Overall, this study is useful for practice engineering, and the reinforced foundation model can be adopted for designing a breakwater foundation to reduce damage triggered by an earthquake and tsunami in the future. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of water is a renewable way to produce clean hydrogen energy. In order to overcome the high-cost and shortage of noble metals, transition metal compounds involving earth-abundant elements, such as MoS 2 and WS 2 , have been proposed as novel catalysts for hydrogen evolution reaction (HER). Efforts have been made to increase the intrinsic catalytic activity of transition metal dichalcogenides (TMDCs), while alloying same- group elements has not been vastly investigated. Moreover, besides the catalytic activity, the design of free-standing catalytic electrodes is also critical for HER. In this work, we synthesize pyrolytic carbon film with Mo x W 1- x S 2 nanoflakes embedded as a free-standing flexible electrodes for HER catalysis. The pyrolytic carbon acts as conductive and flexible matrix for TMDC alloys with controlled composition, resulting in remarkably enhanced HER activity. The highest HER activity was observed for Mo 0.37 W 0.63 S 2 /C samples with an overpotential of 0.137 V at geometric current densities of j geo  = 10 mA cm −2 and a Tafel slope of 53 mV dec −1 . These results now provide low-cost viable alternatives for the design and construction of catalysts based on alloyed TMDCs. [ABSTRACT FROM AUTHOR]

A wide variety of synthetic carbon allotropes embrace tremendous potential for energy storage applications. There have been number of reports on the synthesis of carbonaceous anode materials with lithium (Li) storage capacity larger than the theoretical limit for graphite (372 mAh/g, corresponding to LiC 6 ). However, besides the performance, available resources and cost efficiency are obstacles that could hinder their exploitation. Here we present carbon-rich Precambrian rock “shungite” as a natural resource for a Li-ion battery anode. It is found that upon structural modification the energy density of fully lithiated “shungite” can exceed the density of graphite, becoming comparable to non-graphitizable (“hard”) carbon. High-resolution transmission electron microscopy (HRTEM) studies of modified “shungite” suggest that it consist of spatially arranged fractals of bended, curved, mono- or stacked graphene layers. By analyzing the features of 7 Li Nuclear Magnetic Resonance (NMR) spectra of fully lithiated “shungite” we conclude that the enhanced storage capacity is mainly due to the presence of open edge few layered graphene flakes. We thus suggest carbon-rich “shungite” as an alternative and effective natural resource for Li-ion battery electrodes. [ABSTRACT FROM AUTHOR]

The interaction of the noble atoms (Ar and Xe) with single-walled carbon nanotube (SWCNT) bundles are investigated using Raman spectroscopy in conjunction with computational modeling known as ReaxFF force field. SWCNT bundles were deposited on transmission electron microscopy (TEM) grids, and different noble gases were adsorbed onto the nanotubes at 20 K. Raman spectra acquired show significant frequency blueshifts of the radial breathing mode (RBM), G- and G′(or 2D)-bands due to gas solidification within the external groove sites (free spaces between the tubes in the bundle) and external surfaces of the bundles. This solid shell formed by the adsorbed gases contributes with a hydrostatic pressure to the system. We show from Raman measurements that the frequencies found after gas adsorption exhibit almost the same shifts indicating that the interactions between SWCNTs bundles and the gases (Ar or Xe) are nearly identical. [ABSTRACT FROM AUTHOR]

Hexaniobate nanosheets derived from the parent compound K 4 Nb 6 O 17 have been decorated with CeO 2 nanoparticles by ion exchange with aqueous cerium (IV) solution. Very homogeneous CeO 2 nanoparticle decoration of the hexaniobate sheets can be achieved by this method and the resulting composites may absorb visible light. HRTEM images show that ∼3.0 nm diameter CeO 2 nanoparticles adhere to hexaniobate nanosheets that are exfoliated and then restacked prior to Ce deposition. The interfacial interaction between CeO 2 nanoparticles and nanosheets would be due to an electrostatic attraction mechanism. Raman and XRD measurements have given strong evidence that CeO 2 nanoparticles have fluorite structure. EDS, FTIR and XPS results suggest almost complete exchange of TBA + and K + by Ce 4+ . Cerium ion exchange on the acid exchanged parent compound, H 2.9 K 1.1 Nb 6 O 17 , revealed that the extent of Ce ion exchange is much greater in case of nanosheets, which may be rationalized by the larger surface area available after exfoliation. XPS measurements show that the ratio of Ce 4+ /Ce 3+ is around 4.4, in agreement with the formation of fluorite structure (CeO 2 ). Thus, these CeO 2 nanoparticle/nanosheet composites may be useful for catalytic processes. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) wasprepared from babassu mesocarp, an abundant biomass inBrazil. Thermal pretreatments, including hydrothermal carbonization and pyrolysis at different temperatures were applied along with potassium hydroxide activation, in synthesizing ACs with varying structure, electronic and surface properties. A thorough characterization of the ACs revealed their low structural order and high specific surface area, containing micropores and mesopores. Furthermore, negatively charged surface oxygen functional groups make them potential candidates as adsorbents for cationic chemical species. A detailed study of adsorption of methylene blue cationic dye was carried out by varying time, initial concentration, pH and ionic strength of the dye solution, which showed that the chief driving force of this adsorption is the Coulombic interaction on the surface, followed by diffusion throughout the pores. These ACsshowed fast and efficient dye uptake – the best sample showedequilibrium adsorption capacity of 388 mg g−1for methylene blueand 220 mg g−1 for another cationic dye crystal violetduring 6 h –and thereby can be used as renewable and sustainable adsorbents. [Display omitted] • Brazilian babassu coconut biomass wasused to generate activated carbon (AC). • Hydrothermal carbonization was used, following chemical activation with KOH. • Methylene blue (MB) dye was used to examine the adsorption properties of AC. • Efficient MB uptake was observed, owing to the active surface and porosity of AC. • Synthesis parameters were varied to obtain the best possible adsorbent AC material. [ABSTRACT FROM AUTHOR]

We report the study of the growth of CeO 2 nanoparticles on the external walls and Ce 4+ intercalation within the titanate nanotubes. The materials were fully characterized by multiple techniques, such as: Raman spectroscopy, infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The ion exchange processes in the titanate nanotubes were carried out using different concentrations of Ce 4+ in aqueous solution. Our results indicate that the growth of CeO 2 nanoparticles grown mediated by the hydrolysis in the colloidal species of Ce and the attachment onto the titanate nanotubes happened and get it strongly anchored to the titanate nanotube surface by a simple electrostatic interaction between the nanoparticles and titanate nanotubes, which can explain the small size and even distribution of nanoparticles on titanate supports. It was demonstrated that it is possible to control the amount and size of CeO 2 nanoparticles onto the nanotube surface, the species of the Ce ions intercalated between the layers of titanate nanotubes, and the materials could be tuned for using in specific catalysis in according with the amount of CeO 2 nanoparticles, their oxygen vacancies/defects and the types of Ce species (Ce 4+ or Ce 3+ ) present into the nanotubes. [ABSTRACT FROM AUTHOR]

Abstract: In steep and rocky terrains, their rough surfaces make it difficult to create landslide inventories even with detailed maps/images produced from airborne LiDAR data. To provide objective clues in locating deep-seated landslides, the surface textures of a 5 km2 steepland area in Japan was investigated using the eigenvalue ratio and slope filters calculated from a very high resolution LiDAR-derived DEM. The range of filter values was determined for each of a number of surface features mapped in the field and these included: cracked bedrock outcrops, coarse colluvial deposits, gently undulating surfaces, and smooth surfaces. Recently active slides commonly contained patches of ground in which deposition and erosion occurred together near the erosion front, or where cracked bedrock outcrops and coarse colluvial deposits coexisted under a gently undulating surface. The characteristic eigenvalue and slope filter values representing this sliding process were applied to maps of the DEM derived filter values to extract potential sites of recent landslide activity. In addition, the relationships between the filter values of deep-seated landslides at various stages of evolution within the field mapped area were extended to the entire study area, to assess the contribution that landslide evolution makes to change in the landscape as a whole. While landslide components made up the steepest as well as the gentlest parts of the landscape depending on their evolutionary stage, landslides were constantly coarsened and steepened by progressive erosion, probably initiated by river bank erosion at the foot of slopes. [Copyright &y& Elsevier]