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Multilayer graphene (MLG) samples fabricated via chemical vapor deposition on Ni substrates were evaluated for their microstructure and mechanical properties and compared against those on a single-layer graphene lamella deposited on a Cu substrate. Electron microscopy shows that the deposition of MLG is not always uniform, and the number of lamellae vary from location to location. Furthermore, with the increase in number of lamellae, more defects evolved, and the layers no longer stayed parallel to the substrate surface. X-ray diffraction and Raman spectroscopy confirmed that the deposited graphene was not completely crystalline and contained amorphous regions and other defects. This nanocomposite showed an increase in nanoindentation hardness and elastic modulus at low indentation depths compared to a Ni film with no depositions. Overall, it was found that the deposited samples did not possess any graphenic qualities, but rather those of highly oriented pyrolytic graphite in the best case and turbostratic graphite in the worst case. [ABSTRACT FROM AUTHOR]

Nature-inspired hydrophobic coatings have caught great attention due to their repellency to corrosive mediums and less interaction between substrate and chemical species. Aluminum is considered one of the metals having superior properties against corrosion due to passive film formation. It can further be enhanced by the formation of a hierarchical structure through 2nd step anodization. In previous studies, carbon infiltrated in anodized alumina pores through CVD method (chemical vapor deposition) was quite an expensive and complex method. The fabrication of anti-corrosion coating with a simple and cost-effective method will broaden the aluminum alloy applications in the chemical, petrochemical, and aerospace industries, etc. In this research, pyrolytic carbon is infiltrated in porous alumina through pyrolysis at three different temperatures for 30 min under a controlled environment by using flaxseed oil as a source of carbon. The surface morphology along with chemical composition and wetting angle were studied through SEM (Scanning Electron Microscope), EDX (Energy Dispersive X-ray Spectroscopy), and Sessile drop method. It was found that both low surface energy and high roughness participate in increasing the wetting angle. Nanocomposite coating having maximum carbon content has a maximum wetting angle with inorganic liquid. Based on the electrochemical behavior determined by Tafel and EIS (Electrochemical Impedance Spectroscopy) analysis, the hydrophobic coating containing 57.5% carbon content having a contact angle of 95° exhibits maximum corrosion resistance of around 28,000 kohm as compared to anodized aluminum having minimum corrosion resistance of around 4.26 kohm. The results and the cost-effective method could be beneficial in aircraft parts as well as in aeronautical applications. [ABSTRACT FROM AUTHOR]

The main purpose of these studies was to obtain carbon–carbon composites with a core built of carbon fibers and a matrix in the form of pyrolytic carbon (PyC), obtained by using the chemical vapor deposition (CVD) method with direct electrical heating of a bundle of carbon fibers as a potential electrode material for nerve tissue stimulation. The methods used for the synthesis of PyC proposed in this paper allow us, with the appropriate selection of parameters, to obtain reproducible composites in the form of rods with diameters of about 300 µm in 120 s (CF_PyC_120). To evaluate the materials, various methods such as scanning electron microscopy (SEM), scanning transmission electron microscope (STEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and tensiometer techniques were used to study their microstructural, structural, chemical composition, surface morphology, and surface wettability. Assessing their applicability for contact with nervous tissue cells, the evaluation of cytotoxicity and biocompatibility using the SH-SY5Y human neuroblastoma cell line was performed. Viability and cytotoxicity tests (WST-1 and LDH release) along with cell morphology examination demonstrated that the CF_PyC_120 composites showed high biocompatibility compared to the reference sample (Pt wire), and the best adhesion of cells to the surface among all tested materials. [ABSTRACT FROM AUTHOR]

To improve the ablation resistance of C/C composites, tungsten (W) coating is applied by chemical vapor deposition (CVD) technology on C/C composites. Results show that the coatings are dense, with a thickness of about 400 µm. After heat treatment at a temperature of 1500 °C for 1 h, the main component of coating is W2C. Additionally, a dense WC layer forms on the surface of pyrolytic carbon (PyC). The sample subjected to heat treatment remains relatively intact after ablation at 3000 °C for 60 s, with a mass and linear ablation rate of 1.83 + 10-5 g s-1 and 3.03 × 10-5 cm s-1, respectively. The high-temperature stability of WC formed on PyC and the filling of fiber gaps to prevent oxygen penetration are the main reasons for the improved ablation resistance of W-coated C/C composites. [ABSTRACT FROM AUTHOR]

In this work, the coating and the matrix are connected as a whole by the continuous fibers. To achieve this goal, the C/C composite with carbon fibers in its surface region is prepared by the directional deposition of pyrolytic carbon (PyC). Compared with the conventional C/C composite that has a porous structure in the whole bulk, the as-prepared composite has a higher efficiency of polymer infiltration and pyrolysis (PIP) process (an improvement of about 88%). The carbon fiber network would provide the thermal channels for the coating during the ablation, which would reduce the ablation temperature (a decrease of about 180 °C) and thermal gradient in the coating, and then the thermal stress would decrease during the ablation, showing the good anti-ablation performance (the linear ablation rate of which is about 68.4% and 39.7% lower than pure C/C composite and conventional C/C-ZrC composite). [ABSTRACT FROM AUTHOR]

[Display omitted] • A macroscopic amount of boron-enriched pyrolytic carbon is fabricated by the high-temperature low-pressure CVD process. • A two-phase crystalline system consisting of intertwined graphene layers nterspersed with boron carbide provids high microhardness of the material. • Tree-like dendritic structures are formed by adding into reactor a small amount of oxygen-containing compounds. • Vertical orientation of the graphite substrate planes allows comparative studying the material depending on the boron content. In this paper we report the synthesis and characterization of the boron-enriched pyrolytic carbon (B-PyC). In the research we aimed to propose a material demonstrating high strength characteristics and heat resistance, durability, chemical inertness and biocompatibility. The material has been synthesized by high temperature low pressure CVD method. The synthesis is carried out on the inner surface of a vertically oriented hollow graphite hexagonal prism heated to the temperatures 1450–1570 °C. Controlled low-density flows of nitrogen, boron trichloride and carbonaceous gas react in this zone producing B-PyC film deposited on the vertical graphite plates. Morphology, mechanical and physical properties of this material was investigated using X-ray diffraction, scanning and transmission electron microscopy, mechanical testing instrumentations, thermogravimetric and thermal analysis. It was found that during the synthesis a two-phase crystalline system is organized comprising fragments of graphene layers (pyrolytic carbon) and boron carbide B 4 C. Such a structure provides high mechanical properties of the material and their stability in a wide temperature range, heat resistance, chemical inertia and biocompatibility. Depending on the synthesis conditions, the micro hardness may vary in a wide range including the range 100–140 HV the most attractive for traumatology and cardiac surgery as well as for a variety of engineering applications. [ABSTRACT FROM AUTHOR]

Condensed particles in the internal flow field of a solid rocket motor can cause serious erosion to thermal insulations under overload flight condition. Multi-walled carbon nanotubes (MWCNTs) can improve erosion resistance of insulations but at the cost of reduced thermal insulation performance. In this study, MWCNTs were precoated with pyrolytic carbon via chemical vapor deposition to reduce their thermal conductivity. Further, ethylene propylene diene monomer insulations reinforced with different contents of MWCNTs and precoated MWCNTs were prepared. Moreover, their ablation performances under simulated overload ablation conditions were tested and compared. Experimental results show that precoated MWCNTs can not only improve thermal insulation performance but also significantly increase particle erosion resistance of ethylene propylene diene monomer insulation materials. Charring ablation rate of the formula with 10phr precoated MWCNTs is 44.3% lower than that of basic formula and 41.6% lower than that of the formula with 3phr MWCNTs which has the same pure MWCNTs content. The char layers of MWCNTs reinforced formulas are more complete than basic formula, indicating that MWCNTs can improve char layer structure under particle erosion condition. The precoated MWCNTs can also promote the CVD reaction of pyrolysis gas in char layers during ablation, decreasing the porosity of char layers, which can increase the particle erosion resistance of insulation. • Particle resistance of EPDM insulation was studied with the overload simulation SRM; • EPDM insulation with less quantity of precoated MWCNTs retain good particle resistances; • Precoated MWCNTs can promote CVD reaction of pyrolysis gas within char layers. [ABSTRACT FROM AUTHOR]

The synthesis of carbon onions in the laboratory by various methods is common; however, naturally occurring carbon onions have only been found in a few geological samples on Earth. This study used high-resolution transmission electron microscopy to identify natural carbon onions in seven intrusion-affected coal samples collected from Permian coal-bearing strata in the Yongan Coalfield, Fujian Province, South China. This study identified the largest natural carbon onions ever recorded on Earth; their outer diameter was ∼55 nm. Granite porphyry intrusions and quartz hydrothermal veins are abundant in the Permian coal-bearing strata in this coalfield. All samples collected were tectonically deformed coals with highly developed structural fractures, friction mirror planes, and maximum vitrinite reflectance values of 4.0–9.5%. Natural carbon onions observed in the coal samples had single or multiple cores, with 24–46 graphitic shells characterized by outer diameters of 24–55 nm. The maximum vitrinite reflectance, outer diameter, and graphitic shell number of carbon onions in the intrusion-affected coal were positively correlated, indicating that the carbon onions were secondary products formed during coal metamorphism owing to magmatic intrusion. Our results suggest that carbon onions in intrusion-affected coal are synthesized by chemical vapor deposition. We speculate that natural carbon onions exist mainly in fractures or cavities, similar to vapor-deposited pyrolytic carbon, which is the leading cause of the uneven distribution of carbon onions in intrusion-affected coals in the study area. [ABSTRACT FROM AUTHOR]

Carbon-based materials (CBMs) such as graphene, carbon nanotubes (CNT), highly ordered pyrolytic graphite (HOPG), and pyrolytic carbon (PyC) have received a great deal of attention in recent years due to their unique electronic, optical, thermal, and mechanical properties. CBMs have been grown using a variety of processes, including mechanical exfoliation, pulsed laser deposition (PLD), and chemical vapor deposition (CVD). Mechanical exfoliation creates materials that are irregularly formed and tiny in size. On the other hand, the practicality of the PLD approach for large-area high-quality CMB deposition is quite difficult. Thus, CVD is considered as the most effective method for growing CBMs. In this paper, a novel pulsed laser-assisted chemical vapor deposition (LCVD) technique was explored to determine ways to reduce the energy requirements to produce high quality CBMs. Different growth parameters, such as gas flow rate, temperature, laser energy, and deposition time were considered and studied thoroughly to analyze the growth pattern. CBMs are grown on Si and Cu substrates, where we find better quality CBM films on Cu as it aids the surface solubility of carbon. Raman spectroscopy confirms the presence of high-quality PyC which is grown at a temperature of 750 °C, CH4 gas flow rate of 20 sccm, a laser frequency of 10 Hz, and an energy density of 0.116 J/cm2 per pulse. It is found that the local pulsed-laser bombardment helps in breaking the carbon-hydrogen bonds of CH4 at a much lower substrate temperature than its thermal decomposition temperature. There is no significant change in the 2D peak intensity in the Raman spectrum with the further increase in temperature which is the indicator of the number of the graphene layer. The intertwined graphene flakes of the PyC are observed due to the surface roughness, which is responsible for the quenching in the Raman 2D signal. These results will provide the platform to fabricate a large area single layer of graphene, including the other 2D materials, on different substrates using the LCVD technique. [ABSTRACT FROM AUTHOR]

SiC/SiO 2 nanowires (NWs) were successfully synthesized via a simple chemical vapor deposition method at 1200 °C under an argon atmosphere by using phenolic resin (PF) and silicon (Si) and then catalyzed by copper citrate. The obtained SiC/SiO 2 NWs as-calcined at 1200 °C had a chain-bead structure, and the SiC nanowire was wrapped by amorphous SiO 2 nanospheres: The diameter of the SiO 2 bead was in the range of 175–250 nm; the length of the SiC chain was 375–500 nm, and the diameter was 83 nm. The copper phase derived from copper citrate could dissolve with Si to form a Cu/Si alloy, and it could reduce the melting point of the Si particle and generate higher amount of SiO. The growth mechanism of the Cu-catalyzed SiC/SiO 2 NWs was vapor-solid (V–S). The strength and oxidation resistance of the PF pyrolysis carbons were reinforced by SiC/SiO 2 NWs. The cold crushing strength (CCS) of the PF pyrolysis carbons calcined at 1200 °C and 1300 °C increased from 0.08 MPa to 0.64 MPa and 0.36 MPa to 1.81 MPa, respectively. The starting and ending temperatures of weight loss temperatures of PF pyrolysis carbons were delayed from 513 °C and 678 °C to 568 °C and 723 °C, respectively. The enhancements in the mechanical properties and oxidation resistance properties of the PF pyrolysis carbons were because the C–SiC bonding phase of the PF resisted external stress and oxygen effectively. [ABSTRACT FROM AUTHOR]

Kelvin Probe Force Microscopy is a method to assess the contact potential difference between a sample and the probe tip. It remains a relative tool unless a reference standard with a known work function is applied, typically bulk gold or cleaved highly oriented pyrolytic graphite. In this report, we suggest a verifiable, two-dimensional standard in the form of a photolithographically patterned, wire-bonded structure manufactured in the technology of transfer-free p-type hydrogen-intercalated quasi-free-standing epitaxial Chemical Vapor Deposition graphene on semi-insulating high-purity nominally on-axis 4H-SiC(0001). The particular structure has its hole density p S = 1.61 × 1013 cm−2 measured through a classical Hall effect, its number of the graphene layers N = 1.74 extracted from the distribution of the ellipsometric angle Ψ , measured at the angle of incidence AOI = 50 ° and the wavelength λ = 490 nm, and its work function ϕ G R = 4.79 eV postulated by a Density Functional Theory model for the specific p S and N. Following the algorithm, the contact potential difference between the structure and a silicon tip, verified at Δ V G R − Si = 0. 64 V , ought to be associated with ϕ G R = 4.79 eV and applied as a precise reference value to calculate the work function of an arbitrary material. [Display omitted] • QFS graphene on SiC as a KPFM reference standard. • Electrically verifiable and updatable. • A likely complement to HOPG and bulk gold. [ABSTRACT FROM AUTHOR]

The study investigated the morphology, microstructure, structure, texture, and mechanical properties of heat-treated at 1600 °C and 2000 °C pyrolytic carbon (PyC) deposited from methane using various methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy, and ultrasonic dynamic measurements of Young's modulus. The PyC was synthesised at 1100 °C using a chemical vapour deposition (CVD) method with direct electrical heating of the two types of carbon fibres (CFs). The results showed that the PyC had a low- and medium-texture (LT and MT PyC). Analysis of the graphitization trajectory allowed the determination of structural changes in the material as a function of temperature, including the growth of crystallites and an increase in the crystallinity proportion without the significant rearrangement within PyC. The crystallite size and the number of interstitial defects has increased with temperature that controlled mechanical properties. Therefore, based on the results obtained, the most suitable composites for further research in the context of electrodes for stimulation of nervous tissue were obtained at the temperature of their synthesis, i.e. at 1100 °C. [Display omitted] • The matrix area distinguished low-textural (LT) and medium-textural (MT) PyC. • The surface can be significant during the deposition only of initial PyC layers. • Amorphous forms may evolve towards turbostratic ones. • Thermodynamically, the organising process may occur but is kinetically limited. • The mechanism of the graphitization trajectory was the formed domains growth. [ABSTRACT FROM AUTHOR]

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Thermal annealing of chemical vapor deposition (CVD)-grown carbon nanotubes (CNTs) is a practical method for reducing defects in CNTs, which is essential for promoting applications of CNTs in nanoscale or microscale materials. However, the increase in annealing temperature fails to bring noticeable improvements in the tensile properties of CNTs, implying the negative influence of carbon sublimation on the defect healing process. Here we propose a two-step annealing strategy for improving the microstructure and tensile properties of CVD-grown CNTs. This has been achieved through the epitaxial growth of pyrolytic carbon thin layers at the CNT surface and then followed by graphitization treatment at 2200 °C for 1 h. Tensile performances of two-step annealed CNTs have been investigated by in situ tests in a scanning electron microscope. The results show that the average Young's modulus and fracture strength of two-step annealed CNTs are improved approximately by 35% and 10%, respectively, compared to those of one-step annealed CNTs. Such an enhancement can be ascribed to the well-aligned CNT walls with fewer structural defects, supported by the characterization results from transmission electron microscope, X-ray diffraction and Raman spectroscopy. The two-step annealing strategy developed in this study for improving the mechanical properties of CNTs is expected to be applicable to a practical fabrication process. [ABSTRACT FROM AUTHOR]

Performance degradation always occurs in carbon fibers/carbon nanotubes (CFs/CNTs) multi-scale reinforced composites prepared by chemical vapor deposition (CVD) method. In this study, pyrolytic carbon (PyC) interlayers are introduced to overcome this problem, and the mechanism is studied in detail. The multi-scale reinforcements are combined with lithium aluminosilicate (LAS) glass-ceramic into ceramic matrix composites by slurry impregnation and hot pressing sintering. The results show that the PyC interlayers can protect the CFs from corrosion of the catalyst at high temperature, improve stress transfers and promote the synergy between various components. The CNTs and LAS matrix form a transition area, which causes deflection and shunting when cracks propagate. These factors have greatly increased the crack extension energy, so the mechanical properties have been greatly improved. The flexural strength, fracture toughness and work of fracture reach 602 ± 55 MPa, 10.7 ± 2 MPa m1/2, 4.6 ± 0.7 kJ m−2, respectively, which are 42.3%, 42.6% and 76.9% higher than CF/LAS. This work expands the study of the CFs/CNTs multi-scale reinforcements and the LAS composites, and provides a useful reference for the related research. [Display omitted] [ABSTRACT FROM AUTHOR]

The paper presents the analysis of the electromagnetic response of three-dimensional carbon-based porous structures (carbon foam) in the microwave (26–37 GHz) and terahertz (0.1–1 THz) frequency ranges obtained by chemical vapor deposition using nickel foam as a substrate. Raman spectroscopy and scanning electron microscopy provide the structural investigations of the obtained carbon films based on a nickel frame. It is shown that due to the nickel catalytic properties, the carbon film represents a sandwich structure in the given synthesis conditions, which consists of multilayer graphene and pyrolytic carbon. According to the analysis of the frequency dependences of reflectance and transmittance of carbon foam with a thickness of 1.6 mm and 300–400 μm pore size, these materials provide a 60% absorption in the microwave range and 100% absorption in the terahertz frequency range. Such thin films used as a carbon skeleton in a combination with flexible polymers can be applied as effective flexible absorbers of radiofrequency radiation. [ABSTRACT FROM AUTHOR]

Wafer-scale single-crystal graphene with strong antioxidation is fundamentally important for their applications in electronics and optoelectronics. Although significant progress has been achieved in the chemical vapor deposition (CVD) growth of graphene, the production of wafer-scale graphene with high crystalline and excellent oxidation resistance still remains a challenge. Here, we report the epitaxial growth of 6-inch single-crystal graphene on twinned Pt (111) films with in-plane rotation of 60°(T-Pt) by ambient-pressure CVD. Our results show that the CVD-grown graphene on T-Pt exhibits fast growth rate and ultrahigh stability under the high-temperature air condition (>500 °C). The density functional theory (DFT) calculations reveal that the twinned Pt(111) surface does not change the preferential orientation of graphene nucleation, leading to highly aligned graphene domains on the T-Pt substrate. Moreover, the edge growth of graphene cannot be limited by the Pt twin boundaries (TBs), which is responsible for the fast growth of graphene single crystals. This work provides a reliable route to produce wafer-size single-crystal graphene monolayers with excellent oxidation resistance and clarifies the oriented growth mechanism of graphene domains on twinned Pt substrate. Here, we report an oriented multi-nuclei growth strategy toward 6-inch single-crystal graphene on twinned Pt (111) films with in-plane rotation of 60° (T-Pt) by ambient-pressure chemical vapor deposition. The graphene on Pt grows fast and has better oxidation resistance than graphene on Cu substrate. The density functional theory (DFT) calculations reveal that Pt-twinned structure does not change the preferential orientation of graphene nuclei, resulting in highly oriented graphene domains on the T-Pt substrate. This work provides a reliable approach to produce wafer-size single-crystal graphene monolayers with excellent oxidation resistance and clarifies the oriented growth mechanism of graphene domains on T-Pt substrate. [Display omitted] [ABSTRACT FROM AUTHOR]

Heart valve problems affect more than 100 million people worldwide. According to statistics, around 55% of valvular diseases are treated by a mechanical prosthesis. The first heart valve replaced model was the caged-ball valve, more than 50 models of heart valves designed by different companies. Each design has different aspects such as valve geometry, leaflets design, materials used for model manufacturing, coating techniques, and coating materials. Depending on the patient's need and condition, the native heart valve either replaced by a biological or mechanical heart valve. Biological valves are made of living tissues whereas mechanical valves manufactured by the biomaterials, which are biocompatible and do not causes any reaction inside the body. The prototype discussed in this paper provides good hemocompatibility, because of the biomaterial used in this prototype manufacturing. It will reduce tissue ingr owth, due to the enhanced leaflet ear of the orifice ring. Moreover, it will cause less thrombotic effects into the host due to greater contact angel of graphite and smooth surface of graphite after pyrolytic coating. The significant evolution of mechanical valve designs consists of valve geometry, coating technique, and materials. In this research, the 3D-CAD model of Bileaflet Mechanical Mitral Heart Valve was designed using SOLID WORKS 2016 and fabricated by 5- axis Computer Numeric Control (CNC) machine. Graphite was used for the fabrication of prototype and Pyrolytic Carbon (PyC) coating was performed with Chemical Vapor deposition (CVD) technique. Scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) were used to determine the effects of CVD on surface topography and chemical structure of graphite model before and after coating. Furthermore, hemocompatibility of graphite and PyC analyzed through in-vitro hemolytic activity. The Characterization results showed that the Bileaflet Mechanical Mitral Heart valve prototype after PyC coating provides a smooth surface with improved hemocompatibility and less adhesion. Besides, the Mechanical Heart valves showed no hemolysis during the hemolytic activity. By virtue of its smooth and nonporous surface, it is antithrombotic and provides good hemodynamics. The advance long leaflet ear design reduces the tissue ingrowth around the orifice which will further limit the leaflets movement. [ABSTRACT FROM AUTHOR]

To improve the reliability, especially the toughness, of the reaction bonded silicon carbide (RBSC) ceramics, silicon carbide whiskers coated with pyrolytic carbon layer (PyC-SiC w) by chemical vapor deposition (CVD) were introduced into the RBSC ceramics to fabricate the SiC w /RBSC composites in this study. The microstructures and properties of the PyC-SiC w /RBSC composites under different mass fraction of nano carbon black and PyC-SiC w were investigated methodically. As a result, a bending strength of 550 MPa was achieved for the composites with 25 wt% nano carbon black, and the residual silicon decreased to 11.01 vol% from 26.58 vol% compared with the composite of 15 vol% nano carbon black. The fracture toughness of the composites reinforced with 10 wt% PyC-SiC w , reached a high value of 5.28 MPa m1/2, which increased by 39% compared to the RBSC composites with 10 wt% SiC w. The residual Si in the composites deceased below to 7 vol%, resulting from the combined actively reaction of nano carbon black and PyC with more Si. SEM and TEM results illustrated that the SiC w were protected by PyC coating. A thin SiC layer formed of outer surface of whiskers can provide a suitable whisker-matrix interface, which is in favor of crack deflection, SiC w bridging and pullout to improve the bending strength and toughness of the SiC w /RBSC composites. [ABSTRACT FROM AUTHOR]

Multi-scale reinforcement strategies have been widely integrated in the preparation of high-performance composites for high strength and functionality, but it is challenging to achieve the microstructurally adjustable and the feasible design of modulus matching between the matrix and the nano-reinforcements. Herein, we integrated the preparation of graphene nano-reinforcements with pyrolytic carbon matrix by a one-step oxygen controllable chemical vapor deposition (OCCVD) process and designed a multi-step gradient of the modulus carbon composite. Furthermore, the microstructure morphology and the deep molecular insights under different oxygen contents were obtained by simulating the OCCVD process based on reactive molecular dynamics. Additionally, the modulus and fracture strength of different carbon structures were acquired by corresponding mechanical simulations. On this basis, the experimentally designed and prepared multiscale carbon/carbon composites simultaneously exhibited excellent flexural mechanical properties and matrix deformation capacity compared with the conventional carbon/carbon composites. The interpenetrating structural features of the prepared composites promote a high level of interfacial shear resistance, resulting in significantly enhanced load transfer strengthening as well as crack-bridging toughening. Our method provides new insights into the chemical vapor deposition process and a new way of thinking about the fabrication of high specific strength composites with great simplicity and versatility. [Display omitted] [ABSTRACT FROM AUTHOR]

Tensile properties of silicon carbide (SiC) ceramics were improved by introducing a two-dimensional carbon nanotube film (CNT f) with excellent mechanical properties. CNT f was first assembled by floating catalyst chemical vapor deposition (CCVD); then CNT f with the pyrolytic carbon interfacial layer (CNT f /PyC) was prepared by chemical vapor infiltration (CVI). Afterwards, SiC was infiltrated into the CNT f and CNT f /PyC preforms by the CVI process, to prevent the uneven dispersion and agglomeration of CNT and damage caused by high temperature sintering. Two composites (CNT f /SiC, CNT f /PyC/SiC) were ultimately prepared, and their microstructures and tensile properties were studied. The results show that the tensile strengths of CNT f /PyC, CNT f /SiC and CNT f /PyC/SiC are 716 ± 60, 153 ± 11, and 155 ± 12 MPa, respectively, which illustrates that SiC ceramic reinforced by CNT f exhibits excellent tensile properties. Besides, the porosities of CNT f /SiC and CNT f /PyC/SiC are 17.4% and 22.6%, respectively. CNT f /PyC/SiC shows higher porosity but better tensile properties, indicating that the PyC interfacial layer enhances the tensile properties of CNT f /SiC composite. In addition, the strengthening and toughening mechanisms are also discussed. [ABSTRACT FROM AUTHOR]

This study reports the direct writing of low-resistance graphite film strip of 25 μm width and ∼65 nm height on nickel substrates by laser-assisted chemical vapor deposition (LCVD). Raman spectra of the LCVD graphite showed no D-band, confirming that it had little defects. The G-band was nearly constant but the 2D-band showed variations in shape and intensity. A detailed analysis of the 2D-band revealed that the LCVD graphite is a mixture of highly ordered graphite and turbostratic graphite. An observation of the stacking feature by transmission electron microscope further confirmed that the layers close to substrate was closely packed, whereas the layer interspacing gradually increased with distance, transforming into turbostratic graphite. The resistivity of LCVD graphite estimated from the sheet resistance measured by the 4-point method was 2.45 × 10−5 Ω m. Image 1 [ABSTRACT FROM AUTHOR]

In this work, carbon nanotubes (CNTs) were introduced on the pyrolytic carbon (PyC) interface via chemical vapor deposition (CVD) in order to improve the thermal conductivity and mechanical properties of SiC f / SiC composites. The results showed that three major parameters of CVD (a.k.a the deposition temperature, volume fraction of C 2 H 4 and deposition duration) strongly affected the nature of CNTs, as well as the thermal conductivity and mechanical properties of SiC f / SiC composites. The optimal parameters of CVD were found to be 800 °C, 15 vol% C 2 H 4 and 10-30 min. The thermal conductivity and mechanical properties of SiC f / SiC composites were enhanced by the addition of CNTs. However, the excessive deposition of CNTs provoked the formation of pores in the matrix, resulting in the reduction of the thermal conductivity and mechanical properties. The deposition of 5.8 vol % CNTs (corresponding to 20 min CVD deposition) was found to be the best condition to improve the thermal conductivity and mechanical properties of SiC f / SiC. [ABSTRACT FROM AUTHOR]

The generation IV nuclear reactors Tri-structural isotropic (TRISO) fuel suffer failure due to internal pressure generation, corrosion by fission products and kernel migration under temperature gradient. An innovative fuel particle design was conceptualized and realized for the first time in literature by embedding multi-wall carbon nanotube (MWCNT) into porous buffer pyrolytic carbon layer (B.PyC) of TRISO particle to address above issues. MWCNT embedded in B.PyC was obtained by sequential coating using novel chemical vapor deposition reactor. Scanning electron microscopy shows ~15 μm uniformly dispersed MWCNT into B.PyC layer. Transmission electron microscopy and Raman Spectroscopy analysis of the deposited CNT revealed to be multi walled with good crystalline. Results of small angle scattering technique of the composite layer using X-ray and neutrons (SAXS/SANS) reveal better pore structure and could pave new vistas for TRISO fuel development. Intrinsic MWCNT features offer immense potential to mitigate various shortcoming of TRISO particle during actual Generation IV nuclear reactor operation. [ABSTRACT FROM AUTHOR]

Fundamental charge‐transfer dynamics for technologically relevant carbons, such as disordered "hard" carbons, can be studied by designing planar mimics. We fabricate thin films of "pyrolytic carbon" (pyC) by decomposition of benzene at 1000 °C and examine the physical and electrochemical properties of the native pyC film, as well as variants after heteroatom doping, plasma oxidation, and metal nanoparticle modification. The pyC films are optically reflective at the macroscale, relatively planar (1–3 nm RMS roughness by atomic force microscopy) and disordered (via Raman scattering). Thiophenyl‐doped pyC films (0.6–1.7 atom % sulfur) suitably mimic the disorder, chemical state (X‐ray photoelectron spectroscopy), and work function (Kelvin probe) of a workhorse carbon black, Vulcan XC‐72. Using ferri/ferrocyanide as a redox probe, we find that oxygen functionalities enhance the heterogeneous electron‐transfer rate constant up to 3×, while high levels of sulfur dopants decrease the rate 2×. We also explore thiophenyl‐directed adsorption of Au nanoparticles and show that hydrogen evolution at 0.1 mA cm−2 occurs ∼95 mV more positive at <1 % Au@pyC∼S than at pyC∼S. [ABSTRACT FROM AUTHOR]

Single crystal graphite is an extremely useful substrate to grow functional single crystalline films for future electronic and optoelectronic device applications. Due to weak van der Waals interaction, it allows one to grow high quality epitaxial films without the restriction of lattice matching and the films are relaxed at the interface without generating a high density of misfit induced defects even with very large lattice mismatch systems. However, the sizes of single crystalline graphite substrates are typically very small when cleaved from the natural graphite or exfoliated from the commercial highly oriented graphite. In this study we grew large scale single crystalline AB-stacking graphite films by chemical vapor deposition of graphite on wafer size, single crystalline Ni(111) films that were epitaxially grown by magnetron sputtering on spinel (MgAl2O4(111)) substrates. Our results show that smooth, single crystalline graphite films can be achieved at temperatures below 925 °C. Growth temperatures higher than 1000 °C promotes much rougher and thicker graphite films resulted from the inhomogeneous graphite segregation and precipitation processes in the Ni film. These large single crystalline graphite films may serve as substrates to grow functional semiconductor films for electronic and optoelectronic device applications. [ABSTRACT FROM AUTHOR]

A novel sliding contact material of pyrolytic carbon (PyC)-coated copper foam/carbon composite was fabricated by a chemical vapor deposition (CVD) technology, followed by several densifying processes of furan resin impregnation and carbonization. Microstructure, electrical and thermal conductivities and current-carrying tribological performance were investigated. The results show PyC crystallites are evenly arranged on the copper foam surface after the CVD process. Because interface wettability between the copper foam and resin carbon matrix is improved by the PyC layer, the composite has a dense structure and a good interface bonding. The composite has obviously more advantages than the carbon-based pantograph strips in the density, electrical and thermal conductivities, due to the copper foam with three-dimensional structure. Friction and wear behaviors were investigated using a current-carrying friction tester. As the electrical current increases, wear rate and wear surface temperature continually increase, and friction coefficient changes from wildly fluctuating to stable. The high electrical current causes high temperature of wear surface and severe wear of oxidization and arc erosion. Copper oxide particles can improve wear surface roughness and change the sliding friction to the rolling friction between the friction couples. In addition, two physical models are schematically illustrated to understand wear mechanism during the current-carrying friction tests. [ABSTRACT FROM AUTHOR]

Understanding the deposition process of pyrolytic carbon is essential in controlling its microstructure and consequent macroscale performance. Herein, using molecule dynamics (MD) simulations with the ReaxFF potential, we revealed the initial formation process of pyrolytic carbon near the simplified surface of carbon fiber. Three stages were identified in the deposition process, where polycyclic aromatic hydrocarbons (PAHs) formed from precursor gas at first, followed by the deposition and assembly process of PAHs and subsequently the continuous chemisorption of light carbon species. The impacts of temperature, gas density and surface defects were investigated separately. Our results suggest that PAHs would be the main source of the deposition under high gas density and surface defects would promote the deposition prominently. Comparing formed pyrolytic carbon structures under different conditions, we also found that PAHs would produce more defects and interlayer connections while the growth from light carbon species would achieve a more intact in-plane architecture. Moreover, the potential relations between our simulated structures and previous experimental observations were discussed to explore the initial formation mechanism of pyrolytic carbon in actual deposition process. The MD simulation data and insights obtained here might be significant for understanding the deposition process of pyrolytic carbon at atomistic scale. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Radially aligned porous carbon nanotube arrays have been verified to effectively utilize the excellent performance of carbon nanotubes. Present work focuses on growing such unique structure on pyrolytic carbon coated carbon fibers by chemical vapor deposition. Results showed that high-quality and straight carbon nanotubes grow in radial morphology with diameter of about 150 nm and length ranging from 20 to 30 μm. The catalyst (cementite crystal phase) is located at the middle part of carbon nanotubes and the inner cavity is gradually collapsed. Weibull strength distribution indicated that after the growth of carbon nanotubes, both strength and strength stability of pyrolytic carbon coated carbon fibers are improved. Our work provides a great candidate for potential applications in the field of composite. Graphical abstract Image 1 Highlights • Radially aligned porous carbon nanotube arrays are successfully grown on pyrolytic carbon coated carbon fibers. • Structure of as-deposited carbon nantube arrays is characterized in detail. • Both strength and strength stability of pyrolytic carbon coated carbon fibers are improved. [ABSTRACT FROM AUTHOR]

Abstract Controlling the shape of metal nanoparticles is generally accomplished using shape-directing agents. Particle synthesis without shape-directing agents and shape control have attracted strong interest given the side effects of the shape-directing agents. Here, the potential of graphene in the deposition of metallic nanoparticles with different morphologies without using shape-directing agents was investigated. Doping graphene with nitrogen via plasma treatment enhanced the metal reduction. The nitrogen content was varied by changing the plasma treatment time. Nitrogen doping mainly occurred at boundary-like defects and involved pyrrolic nitrogen as the major chemical configuration. Graphene grown on copper substrate grown via chemical vapor deposition was used to deposit spherical silver nanoparticles throughout the graphene along with microparticles that were randomly distributed on the surface. Transition of microparticles of silver from dendrites to well-defined platelets morphologies was observed with nitrogen-doped graphene after 10 min of nitrogen plasma exposure. The number density of silver particles was controlled by varying the plasma treatment time. Surface-enhanced Raman scattering activity of these silver particles grown on graphene using copper substrates was assessed using a Rhodamine 6G Raman probe in the concentration range of 10 nM to 1 mM. Graphical abstract Image 1 Highlights • Silver deposition on graphene without shape directing agents was investigated. • Nitrogen doped graphene controlled the growth of silver morphology. • Triangular, rod, and diamond-shaped micro particles were randomly deposited. • Nitrogen enabled homogenous deposition of silver nanoparticles on graphene. • Surface enhanced raman scattering of R6G was assessed in the range of 10 nM to1 mM. [ABSTRACT FROM AUTHOR]

We studied X-ray absorption of multiwall carbon nanotube (MWCNT) produced by the chemical vapor deposition method using ethanol and benzene precursors at 1473 K with X-ray absorption fine structure in order to obtain a new designing direction for X-ray shielding fabrics. Acid oxidation and thermal annealing further treated the MWCNTs. The energy dependence of X-ray absorptivity of MWCNTs was efficiently used to remove the effect of the metallic impurity contribution, to elucidate the relationship between X-ray mass attenuation coefficient and the structure of MWCNT. The thermal annealing treatment at 2773 K was the most effective method to increase the crystallinity and to remove the impurities of MWCNTs. The acid and oxidation treated MWCNT induced not only the surface structure difference between MWCNT and highly oriented pyrolytic graphite (HOPG) but also the addition of surface oxygen related functional groups from those treatments, which influence the mass attenuation coefficient (μ / ρ). The X-ray absorptivity of heat treated E-MWCNT and B-MWCNT at 2773 K was close to that of HOPG indicating that those MWCNTs have a well-ordered crystal structure, quite similar to HOPG. On the other hand, E-MWCNT having a less-crystalline surface structure showed larger X-ray absorptivity than HOPG by about 9%. Image 1 [ABSTRACT FROM AUTHOR]

Highlights • The structural, chemical features and thickness of the PyC coating were strongly dependent on the deposition time. • The larger the thickness of PyC coating, the bigger roughness of the coating surface. • PyC coated fibers with thicker coating show a higher dispersion of the tensile strength. • After the PyC coating, the fibers stiffness increased together with the decreasing of their tensile strength. Abstract Nanostructured uniform pyrolytic carbon (PyC) coatings with different thicknesses were prepared on surface of T700 carbon fiber by chemical vapor deposition (CVD). The effect of coating on tensile strengths of the carbon fibers was studied by tow tensile strength test. The morphological change, roughness, microstructures, and thermal stability of carbon fibers with PyC coating (PyC-C f) were investigated by SEM, AFM, XRD, Raman, and Tg. It was found that with increase of the deposition time, the thickness of coating varied from 100 to 320 nm with increase in coating surface roughness. The coating adhered well with the carbon fiber substrates and the coating thickness is uniform. The oxidation resistance of PyC-C f was significantly higher than uncoated carbon fibers. However, the fiber became brittle after the coating and the coating is very sensitive to tensile stresses, which decreased the tensile strength of the fiber tows. The tensile strength measurement revealed that the carbon fiber with a 100 nm thickness of PyC coating maintained ∼69.4% of its original strength, and the 320 nm thickness of PyC-coated fibers showed the lowest strength because of the embrittlement caused by the PyC coating. [ABSTRACT FROM AUTHOR]

A pulsed-dc discharge method for plasma chemical vapor deposition (CVD) was developed using a constructed versatile pulsed-dc generator and a vacuum discharge chamber. Argon (Ar) gas discharge experiments were performed under a variety of discharge conditions, and plasma conditions were evaluated using optical emission spectroscopy. The developed system can perform glow discharge by employing nearly rectangular, unipolar, and high-voltage negative pulses with a wide variation of voltage amplitudes and a set discharge current, pulse repetition rate, and duty cycle. Plasma conditions could also be tuned by varying the pulse parameters. A preliminary test of the deposition of diamond-like carbon (DLC) films on silicon (Si) substrates and ultrathin pyrolytic carbon (PyC) films on nanothickness metal-catalyzed glass substrates was performed with acetylene (C2H2) by selecting some typical deposition conditions based on the gas discharge experiments. The deposited films were characterized via Raman spectroscopy. The characteristic properties of DLC and PyC films were achieved. The DLC films demonstrated conventional hard insulating properties while the ultrathin PyC films exhibited conductive and semitransparent properties. These results revealed that the developed pulsed-dc discharge system for plasma CVD is applicable for the synthesis of insulating hard as well as soft conducting carbon thin films. [ABSTRACT FROM AUTHOR]

Van der Waals (vdW) heterostructures composed of different two-dimensional (2D) materials are at the center of many novel devices. To prepare vdW heterostructures which are of the highest quality and suitable for applications, chemical vapour deposition (CVD) can be used to grow the 2D materials directly on top of each other and thus build the vdW heterostructure in a bottom-up fashion. However, obtaining layers of uniform quality by precisely controlling their growth poses a severe challenge. The aim of our work is to understand the growth mechanisms and we have chosen MoS 2 layers on highly oriented pyrolytic graphite (HOPG) as a model system for the MoS 2 -graphene interface. In our model system we observe, that MoS 2 layers do not grow on the HOPG terraces but are more likely to grow at HOPG edges, one-dimensional defects, which obviously acts as growth seeds. In graphene however, step edges are absent and the ever-improving quality of commercially available CVD graphene yields less and less defects per unit area. While this is clearly an advantage for most devices, in the light of our findings it constitutes a major disadvantage for the bottom-up preparation of vdW heterostructures. To overcome this obstacle we artificially introduce defects into the HOPG surface by highly charged ion irradiation. In this way we induce an easily controllable number of quasi zero-dimensional defects before the chemical vapour deposition of MoS 2 takes place. We show that this treatment results in MoS 2 island growth on top HOPG terraces. [ABSTRACT FROM AUTHOR]

Abstract: Carbon spheres of nanometric dimension are known since the first studies on the synthesis of fullerenes. Their shape originates from the curvature of a carbon sheet similar to fullerenes, but with numerous graphitic rings that regulate the inside structure and the formation of open edges at the surface. This paper focuses on the structural and electronic characterization of carbon spheres obtained from a chemical vapor deposition synthesis process. Two different sets of samples are analyzed in detail, in particular, electron microscopies and Raman spectroscopy help understanding the morphology and the graphitic‐sp2 arrangement of the carbon atoms in the architectures. In addition, the iron catalyst used during the reaction process confers the carbon spheres a ferromagnetic response at room temperature. Therefore, both the structural properties of the samples and the active contribution of iron mark the difference in the measured photoresponse as well as in the electrochemical behavior. The X‐ray photoelectron spectroscopy study addresses these points by giving information on the composition and the iron chemical state in the assembly. The collected results underline the advantages offered by this nanomaterial for sustainable applications. [ABSTRACT FROM AUTHOR]

Pyrolytic boron nitride (PBN) plates were synthesized by chemical vapor deposition (CVD) with temperatures of 900–1900 °C and total pressures of 50–1000 Pa on graphite by using borazine as the precursor. The effects of temperature and pressure on the micromorphology and crystal structure of the PBN were investigated. The as-deposited PBN possessed three typical types of micromorphologies depending on the deposition condition. PBN with dense and laminated structure (Type A) were deposited at temperatures of 1150–1900 °C with relative low pressures of 50–200 Pa, and PBN with porous and isotropic structure (Type C) was deposited at temperatures above 1100 °C with higher pressures above 250 Pa. PBN with dense and glass-like fracture structure (Type B) was obtained at the other range of the deposition condition. The interlayer spacing ( d (002) ) and the preferred orientation ( PO ) of the crystallite were calculated by using XRD data of the PBN plates. The degree of the preferred orientation tended to be higher with the increase of temperature and decrease of pressure, and higher temperature led to smaller value of d (002). The crystal growth mechanism of the three types of PBN was discussed. [ABSTRACT FROM AUTHOR]

Optical properties of mono-graphene fabricated by chemical vapor deposition (CVD) and highly oriented pyrolytic graphite (HOPG) are comparatively studied by Mueller matrix ellipsometry (MME) over an ultra-wide energy range of 0.73–6.42 eV. A multilayer stacking model is constructed to describe the CVD mono-graphene, in which the roughness of the glass substrate and the water adsorption on the graphene are considered. We introduce a uniaxial anisotropic dielectric model to parameterize the optical constants of both the graphene and the HOPG. With the established models, broadband optical constants of the graphene and the HOPG are determined from the Mueller matrix spectra based on a point-by-point method and a non-linear regression method, respectively. Two significant absorption peaks at 4.75 eV and 6.31 eV are observed in the extinction coefficient spectra of the mono-graphene, which can be attributed to the von-Hove singularity (i.e., the π-to-π ∗ exciton transition) near the M point and the σ-to-σ ∗ exciton transition near the Γ point of the Brillouin zone, respectively. Comparatively, only a major absorption peak at 4.96 eV appears in the ordinary extinction coefficient spectra of the HOPG, which is mainly formed by the π-to-π ∗ interband transition. [ABSTRACT FROM AUTHOR]

The application of graphene as a two-dimensional nano-material has gained wide interest in different research areas, but its use is still novel for scientists. There has been continuous progress in the development of different synthesis methods to readily produce graphene at a lower cost. Chemical vapor deposition (CVD) is a powerful process to produce graphene, and it is accompanied by other methods. The present article provides a detailed review of the synthesis of graphene by a CVD process at temperatures below 1000 °C (LTCVD). In this work, challenges related to the use of plasma-assisted CVD, different carbon precursors, and catalysts are discussed. [ABSTRACT FROM AUTHOR]

Efficient generation of reactive oxygen species (high concentrations of 1 O 2 and OH) was successfully performed using a radical vapor reactor (RVR) at ordinary temperature and atmospheric pressure without using any chemical reagent. In this study, we successfully introduced modified functional groups onto highly oriented pyrolytic graphite (HOPG) by a sustainable process using an RVR. Although the introduction of a functional group onto HOPG is difficult because of the presence of strong C C bonds in HOPG, the RVR can easily modify it because reactive oxygen species have high energy and high reactivity. Moreover, the RVR process does not require any chemical reagent; it also does not produce any exhaust, except for air and water. The RVR-treated HOPG was analyzed by contact angle measurement (CAM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM), and scanning tunneling microscopy (STM). These analyses revealed that the HOPG surface became hydrophilic and it showed different physical property owing to the modification caused by the introduced oxygen element. [ABSTRACT FROM AUTHOR]

The properties and synthesis procedures of the nanometrically thin pyrolyzed photoresist films (PPF) and the pyrolytic carbon films (PCF) were compared, and a number of similarities were found. Closer examination showed that the optical properties of these films are almost identical; however, the DC resistance of PPF is about three times higher than that of PCF. Moreover, we observed that the wettability of amorphous PPF and PCF was almost comparable to crystalline graphite. Potential applications executed by utilizing the small difference in the synthesis procedure of these two materials are suggested. [ABSTRACT FROM AUTHOR]

Carbon coated aligned multi-walled carbon nanotube (AMWCNT/C) sheets were used for studying the controlled radial growth of MWCNTs. Pyrolytic carbon (PyC) was deposited on the surface of nanotubes using multiple cycles of chemical vapor infiltration. Morphological and structural characterization showed that when graphitization was done in one step, after the deposition of multiple cycles of PyC, the presence of a large amount of disordered carbon on the surface of nanotubes led to a poorly graphitized coating structure that did not resembled nanotube walls anymore. Graphitization of the AMWCNT/C sheets after each deposition cycle prevented the development of disordered carbon during the subsequent PyC deposition cycles. Using the cyclic-graphitization method, thick PyC coating layers were successfully graphitized into a crystalline structure that could not be differentiated from the original nanotube walls. TEM observation and X-ray data confirmed radial growth of nanotubes, while spectra collected from Raman spectroscopy revealed that radially grown CNTs had the same quality as graphitized pristine nanotubes. The focus of this study was to compare the effect of cyclic graphitization with a one-step graphitization method to gain insight on the necessary parameters needed to radially grow high quality CNTs. [ABSTRACT FROM AUTHOR]

• Si 3 N 4nws @PyC nls -HA-C composites with multilayer core–shell structures were designed to imitate the natural bone structure. • In-vitro, Si 3 N 4nws @PyC nls -HA-C exhibited a cell proliferation rate of 157.7%, showing excellent bioactivity. • In-vivo, the Si 3 N 4nws @PyC nls -HA-C demonstrated outstanding histocompatibility. To further optimize the structure of bone tissue engineering composites, silicon nitride nanowires-pyrolytic carbon-hydroxyapatite-carbon matrix (Si 3 N 4nws @PyC nls -HA-C) composites with multilayer core–shell structures are synthesized by chemical vapor deposition (CVD), pulsed electrodeposition (PED), and chemical vapor infiltration (CVI) methods. The microstructure, in-vitro bioactivity, and in-vivo histocompatibility of Si 3 N 4nws @PyC nls -HA-C (SPHC) composites are evaluated. In-vitro, the SPHC exhibited a cell proliferation rate of 157.7% and demonstrated outstanding protein adsorption. In-vivo, the SPHC demonstrated excellent histocompatibility. Therefore, the SPHC composites can serve as an alternative suitable biomaterial for bone tissue engineering. [ABSTRACT FROM AUTHOR]

The unique structural properties of vertically aligned graphene sheets or Carbon Nanowalls (CNWs) have attracted great interests for their potential for various applications in microelectronic devices, energy storage, and catalyst support materials. During the handling or operation of the devices, tension and/or pressure are often needed. Under such conditions, CNWs must undergo compression and stress. Therefore, the deformation mechanism and evolution behavior of the CNW structures under load play a critical role in the performance and reliability of the devices. In this study, the mechanical properties of a typical maze-like CNW structure synthesized by a Radial Injection Plasma Enhanced Chemical Vapor Deposition (RI-PECVD) technique were analyzed by employing the nanoindentation method. The measured compressive strength of the CNW structure was 50 MPa with an average modulus E value of ∼28 GPa, which is significantly higher than that of pyrolytic graphite and other graphene-based materials such as 3D graphene-derived carbon, commercial graphene, and reduced graphene oxide films. An elastoplastic behavior of a soft material was observed in high-resolution microscopy and a mechanism of deformation for CNWs is elucidated. [Display omitted] • The mechanical properties of a typical maze-like CNW structure are systematically investigated using a nanoindentation method. • The maze-like CNWs sample exhibits a modulus value of 28 GPa, which is significantly higher than other graphene-based materials. • A possible deformation mechanism of the CNW is proposed, indicating that soft edges and a hard body of the CNW structure perform an elastoplastic deformation behavior. [ABSTRACT FROM AUTHOR]

Heterostructures of 2D materials are expected to become building blocks of next generation nanoelectronic devices. Therefore, the detailed understanding of their interfaces is of particular importance. In order to gain information on the properties of the graphene – MoS 2 system, we have investigated MoS 2 sheets grown by chemical vapour deposition (CVD) on highly ordered pyrolytic graphite (HOPG) as a model system with atomically clean interface. The results are compared with results reported recently for MoS 2 grown on epitaxial graphene on SiC. Our STM study revealed that the crystallographic orientation of MoS 2 sheets is determined by the orientation of the underlying graphite lattice. This epitaxial orientation preference is so strong that the MoS 2 flakes could be moved on HOPG with the STM tip over large distances without rotation. The electronic properties of the MoS 2 flakes have been investigated using tunneling spectroscopy. A significant modification of the electronic structure has been revealed at flake edges and grain boundaries. These features are expected to have an important influence on the performance of nanoelectronic devices. We have also demonstrated the ability of the STM to define MoS 2 nanoribbons down to 12 nm width, which can be used as building blocks for future nanoelectronic devices. [ABSTRACT FROM AUTHOR]

To improve the mechanical properties of carbon-bonded carbon fiber (CBCF) composites, they are firstly fabricated by chemical vapor deposited (CVD) pyrolytic carbon (PyC) coating layer on the carbon fiber surface, and then modified by zirconium boride (ZrB 2 ) using three cycles of precursor infiltration and pyrolysis (PIP) process. The effects of different PyC interface thickness on the microstructure and mechanical properties of ZrB 2 modified PyC coated CBCF (PyC–CBCF/ZrB 2 ) composites were studied and characterized. As the PyC thickness increased from 0.5 to 3.6 μm, the flexural properties of PyC–CBCF/ZrB 2 composites are noticeably enhanced in x / y and z direction, respectively. Mechanical enhancements for PyC–CBCF/ZrB 2 composites are mainly attributed to the effective interface bonding between carbon fiber and PyC, crack deflection and branching within the laminar PyC layer and carbon fiber pullout from PyC interface coating. [ABSTRACT FROM AUTHOR]

The definition of the term “pyrolytic carbon” is given. Types of microstructures of pyrolytic carbon and development of their classification are presented. Various structures and modes of occurrence of pyrolytic carbon deposits in relation to the conditions of their formation, in nature as well as final effects or by-products of laboratory and industrial processes, are presented based on the literature and the authors' own research. [ABSTRACT FROM AUTHOR]

Carbon materials have been extensively investigated due to their diversity, favorable properties, and active applications including electroanalytical chemistry. This critical review discusses new synthetic methods, novel carbon materials, new properties and electroanalytical applications of carbon materials particularly related to the preparation as well as bioanalytical and environmental applications of highly oriented pyrolytic graphite, graphene, carbon nanotubes, various carbon films (e.g. pyrolyzed carbon films, boron-doped diamond films and diamond-like carbon films) and screen printing carbon electrodes. Future perspectives in the field have also been discussed (366 references). [ABSTRACT FROM AUTHOR]

SiC/C–SiC composites were fabricated via a chemical vapor infiltration (CVI) method using porous SiC/C composites as preform. The influences of the SiC/C preform densities on the mechanical, microstructure and electromagnetic interference shielding properties (EMI) of the SiC/C–SiC composites have been studied. Results show that the SiC/C–SiC composites densities increase with increasing the SiC/C preform densities. When the SiC/C preform density is 1.21 g/cm 3 , the flexural strength, shear strength and toughness of the corresponding SiC/C–SiC composite can reach 220 MPa, 20.98 MPa and 10.21 MPa m 1/2 , respectively. The surface reflection (SE R ) and the internal absorption (SE A ) both increase with increasing the SiC/C preform densities. The enhancement of the EMI is mainly attributed to the formation of conductive networks by the continuous pyrolytic carbon (PyC) matrix and the surface reflection is the dominant shielding mechanism. [ABSTRACT FROM AUTHOR]