To produce metal-diamond composite materials with high thermal conductivity, it is important for a high-quality carbide interface to exist between the metal matrix and diamond. The addition of ...carbide-forming elements to the matrix positively influences the interfacial thermal conductance (ITC), and is an effective method for improving the bulk thermal conductivity of composite materials. Diamond powder was mixed with Cu0.65Cr alloy powder, using a 1:1 volume ratio. The pulse plasma sintering (PPS) parameters were optimized to control the carbide interface between the diamond and matrix. The microstructures and phase compositions of the fabricated materials were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The interfacial layer was characterized using SEM and focused ion beam (FIB) techniques. The residual Cr content of the matrix was estimated, to determine its influence on the thermal properties of the matrix. To calculate the ITC, differential effective medium (DEM) and Hasselman-Johnson (H–J) models were used. The highest thermal conductivity of 687Wm−1K−1 was achieved by a composite material that was fabricated at 850°C over a period of 10min, which had an 81-nm-thick interfacial carbide layer. An ITCDEM value of 5·107Wm−2K−1 was obtained.
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•Cu0.65Cr/50vol.% diamond composites were fabricated via pulse plasma sintering.•Varying sintering parameters were applied to optimize the fabrication process.•Cr3C2 carbide formed at the matrix/diamond interface.•The sample fabricated at 850°C in 10min possessed the maximum thermal conductivity of 687W m−1K−1.•The optimum thickness range of the interfacial carbide layer was estimated.
The unique optical properties of zinc oxide nanocrystals (ZnO NCs) are strongly dependent on both the properties and the composition of the inorganic core-organic ligand interface. Developing a novel ...organometallic self-supporting approach, we report on the synthesis and characterization of ZnO nanocrystals coated by chiral monoanionic aminoalcoholate ligands. The resulting ZnO NCs are both chiroptically active and possess size dependent optical properties. The size and in consequence the emission color of the ZnO NCs could be simply adjusted by the characteristic of the aminoalcohol used.
We present a facile and green approach to produce crystalline TiO2 nanoparticles on a surface of different carbonaceous materials derived from lignocellulosic biomass such as STARBON‐800® obtained by ...carbonization at 800 °C and biochar‐SWP700 (Soft Wood Pellets (SWP) obtained by pyrolysis at 700 °C) via novel low‐temperature ultrasound‐promoted green methodology coupled with citric acid as a cross‐linking agent. In comparison to other methods, the developed method has several significant benefits such as simplicity, great ability to get crystalline TiO2 particles (elimination of high‐temperature treatment (material calcination at >300 °C) needed in the conventional sol‐gel method, which is extremely important in transforming amorphous TiO2 into a photoactive crystalline phase) elimination of risky chemicals and oxidizing agent, and also ability to change some parameters (e. g. ultrasound intensity). Prepared materials were characterized by XRD, DR UV−vis, N2 physisorption, HR‐XPS, XRF, HR‐TEM, FT‐IR and subsequently tested for their photocatalytic activities both in photocatalytic phenol degradation (in water) and oxidation of methanol (in air) under UV and visible light irradiation.
The sweet sound of progress: Immobilization of TiO2 on lignocellulose‐based carbons via low‐temperature ultrasound‐promoted sol‐gel methodology and elimination of the high‐temperature treatment step required in the conventional sol‐gel method. The plausible mechanism for the formation of TiO2 on lignocellulosic carbon materials was deeply explored.
We present detailed Raman studies of graphene deposited on gallium nitride nanowires with different variations in height. Our results indicate that different density and height of nanowires impact ...graphene properties such as roughness, strain, and carrier concentration as well as density and type of induced defects. Tracing the manifestation of those interactions is important for the application of novel heterostructures. A detailed analysis of Raman spectra of graphene deposited on different nanowire substrates shows that bigger differences in nanowires height increase graphene strain, while a higher number of nanowires in contact with graphene locally reduces the strain. Moreover, the value of graphene carrier concentration is found to be correlated with the density of nanowires in contact with graphene. The lowest concentration of defects is observed for graphene deposited on nanowires with the lowest density. The contact between graphene and densely arranged nanowires leads to a large density of vacancies. On the other hand, grain boundaries are the main type of defects in graphene on rarely distributed nanowires. Our results also show modification of graphene carrier concentration and strain by different types of defects present in graphene. Therefore, the nanowire substrate is promising not only for strain and carrier concentration engineering but also for defect engineering.
•The self-terminating growth mode was performed in the presence of hydrogen and argon.•H2 atmosphere leads to reduction of C contamination by four orders of magnitude than Ar.•Growth under flow of ...hydrogen leads to smooth uniform surface of the BN layers.
Boron nitride films were grown on 2-inch sapphire substrates using the MOCVD technique. The growth was performed using a pulsed source injection mode with triethylborane (TEB) and ammonia (NH3) with a high V/III ratio, which corresponds to the self-terminated growth mode. Two different carrier gases, H2 and Ar, were used to investigate their influence on the growth mechanism, while all the other growth parameters were kept the same.
The BN films thus obtained were examined using XRR, SIMS, Raman spectroscopy, ATR spectroscopy, SEM and AFM. A difference was found in the surface roughness. The BN films grown in an H2 atmosphere had a surface roughness three times smoother than those grown in Ar.
However, the main difference was brought to light by SIMS measurements. The SIMS measurements revealed that growth under an H2 flow leads to a reduction in carbon concentration by more than four orders of magnitude. It was also shown that the boron distribution in the BN film grown under an H2 flow is very uniform. It is discussed that this mechanism is related to the reactions between TEB and NH3 in the presence of H2. The elimination of carbon by using hydrogen reveals its role in BN growth, which is indeed essential.
Hybrid materials based on inorganic nanocrystals with organic polymers feature peculiar and fascinating properties and various applications. However, there is still a need for simple synthesis ...procedures that provide precise control over the polymer/nanocrystal microstructure of these materials. Herein, a novel organometallic approach to polymer-coated ZnO nanocrystals was developed. The presented method merges the initial ring-opening polymerization of ϵ-caprolactone mediated by an organozinc alkoxide initiator and an air-promoted transformation of the resulting macromolecular organozinc species. This one-pot procedure results in quantum-sized ZnO crystals with a core diameter of ca 3 nm coated by poly(ϵ-caprolactone) covalently bonded to the surface. Overall, the ability to create well-defined hybrid composites should provide a unique ability to access various nanosystems.
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•One-pot organometallic procedure for preparing polymer-coated zinc oxide nanocrystals•Alkylzinc aminoalcoholate as an initiator for ring-opening polymerization of caprolactone•Macromolecular organozinc species as precursors for quantum-sized ZnO nanocrystals
Nanocomplex; Nanotechnology; Nanostructure
Silicon plates were installed above the inner and outer divertor of the JET with the ITER-like wall (ILW) after the second and third ILW campaigns to monitor dust generation and deposition with the ...aim to determine the morphology and content of individual particles and co-deposits, including deuterium content. Particular interest was in metal-based particles: Be, W, steel, Cu. Ex-situ examination after two ILW campaigns was performed by a set of microscopy and ion beam methods including micro-beam nuclear reaction analysis and particle-induced X-ray emission. Different categories of Be-rich particles were found: co-deposits peeled-off from plasma-facing components (PFC), complex multi-element spherical objects, and solid metal splashes and regular spherical droplets. The fuel content on the two latter categories was at the level of 1 × 10
at/cm
indicating that Be melting and splashing occurred in the very last phase of the second experimental campaign. The splashes adhere firmly to the substrate thus not posing risk of Be dust mobilisation. No tungsten droplets were detected. The only W-containing particles were fragments of tungsten coatings from the divertor tiles.
•A new, hybrid, glow discharge oxynitriding process of titanium is presented.•Oxynitrided TiO2+Ti2N+αTi(N) type layer has diffusive character.•Outer TiO2 (rutile) layer has nanocrystalline structure ...and decreased wettability.•Oxynitrided layer on titanium increases hardness, wear and corrosion resistance.•Nanocrystalline TiO2 exhibits better antithrombogenic properties than titanium.
The plasma oxynitriding process is a prospective method of producing titanium oxides as an integral part of a diffusive nitrided surface layer on titanium implants. This hybrid process, which combines glow discharge assisted nitriding and oxidizing, permits producing TiO2+Ti2N+αTi(N)-type diffusive surface layers. The oxynitrided surface layers improve the corrosion and wear resistance of the substrate material. Additionally, the nanocrystalline titanium oxide TiO2 (rutile) improves the biological properties of titanium and its alloys when in contact with blood, whereas the TiN+Ti2N+αTi(N) zone eliminates the effect of metalosis.
Using a nanostructured platform (a controlled‐shape nano‐oxide) and conventional wet impregnation techniques, powder‐type materials have been prepared in which atomically thin surface layers are ...deposited under very mild conditions. More importantly, an advanced methodology, combining energy dispersive X‐ray spectroscopy‐scanning transmission electron tomography (STEM‐EDX ET) and deep learning denoising techniques, has been developed for the 3D compositional characterization of these unique nanosystems. The complex case of LaOx‐coated CeO2 nanocubes is illustrated. For these, aberration corrected 2D STEM‐EDX evidence that ceria nanocubes become covered with a 2–4 atom‐thick layer of a La, Ce‐mixed oxide with spatially varying composition. However, STEM‐EDX ET reveals that this layer distributes unevenly, patching most of the available nanocube surface. The large flexibility and spread availability of the involved synthetic techniques enables, using the tools here developed, a wide exploration of the wealth of questions and applications of these intriguing, atomically thin, surface oxide phases.
An advanced methodology, combining energy dispersive X‐ray spectroscopy‐scanning transmission electron tomography (STEM‐EDX ET) and deep learning denoising techniques, has been developed for the 3D compositional characterization of ultra‐thin epitaxial layers on controlled‐shape nano‐oxides. The results evidence relevant information to determine key structural/morphological/compositional features of nanomaterials involving the epitaxial growth of ultrathin layers and components with close chemistries.
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