查看更多>>摘要：? 2022 Elsevier B.V.Tungsten (W) incorporated diamond film was homoepitaxially grown on a mosaic diamond wafer by hot-filament chemical vapor deposition. The crystallinity of the W incorporated epilayer and the original mosaic diamond wafer was characterized by using high-resolution electron backscatter diffraction (HR-EBSD). From kernel average misorientation maps (KAM) derived from HR-EBSD measurements, it was found that the numerical value of KAM and the width of coalescence boundary region (CBR) of W incorporated epilayers were much smaller than those of original mosaic diamond wafers and not only in the CBR but also in the bulk area, the crystalline quality of the W incorporated epilayer is better than that of the original mosaic diamond wafers. It is suggested that the primal role for the W incorporation is strain reduction near threading dislocations during growth.
查看更多>>摘要：? 2022 Elsevier B.V.Diamond film sensors with large volumes that are synthesized by microwave plasma chemical vapor deposition (MPCVD) and contain perfectly aligned nitrogen-vacancy (NV) ensembles are promising material for achieving highly sensitive quantum magnetometers. The step-flow growth mode of MPCVD on diamond (111) surface is required to realize aligned NV center ensembles. However, it is difficult to control the growth mode on diamond (111) surface due to the presence of twins and the conventional growth rate of aligned NV center ensembles is lower than 0.5 μm/h. In this study, we achieved a high growth rate (6.6 μm/h) of diamond (111) film containing perfectly aligned NV ensembles with high contrast (30%) by applying high power density plasma (103 W/cm3) and precisely controlling the gas flow rate ratios of CH4/H2 and N2/CH4. The growth mode was controlled to realize step flow growth by inducing the hydrogen etching of the nucleation with decreasing the CH4/H2. It was considered that increasing the microwave power density produces a large amount of atomic hydrogen and carbon precursor, leading to a high growth rate of perfectly aligned NV center diamond film. By controlling the N2/CH4 ratio, the nitrogen density in the diamond film could be precisely controlled to obtain a high contrast. Moreover, we measured the quality of the obtained diamond sensor films using the ODMR spectra and Ramsey sequence. We confirmed a high Rabi contrast (approximately 30%) and no significant decrease in T2? due to the deterioration of the crystallinity of the diamond film was observed. This result is promising for building material technology for highly sensitive quantum sensors with large sensor volumes.
查看更多>>摘要：? 2022 Elsevier B.V.Ordinary diamond presents the disadvantages of poor self-sharpening and concentrated grinding stress when it is used as an abrasive. Moreover, this kind of diamond cannot be well wetted by the vitrified bond, resulting in a lower holding force of the binder to the abrasives (i.e., the diamond is easy to detach from the binder matrix during grinding). These comprehensive factors not only reduce the surface quality of the processed workpiece, but also hinder the processing efficiency. In order to solve these problems, a new type of porous diamond with high self-sharpening properties was prepared using a thermochemical corrosion method in this study. Our results showed a great improvement in pore volume and specific surface area of the porous diamond compared with ordinary diamond abrasive particles, and the holding force and wettability of vitrified bond to the porous diamond abrasive particles were also improved. Compared with ordinary diamond abrasive tools, porous diamond abrasive tools showed a 29.6% increase in grinding efficiency, a 15.5% decreased in grinding ratio, a 27.5% reduction in workpiece surface roughness, and the scratches on the silicon wafer surface were reduced and refined.
查看更多>>摘要：? 2022 Elsevier B.V.Novel trigonal BC11 is reported from extended carbon network diamond-like C12 hosting boron based on crystal chemistry rationale and geometry optimization onto ground state structure within the density function theory DFT. From charge density projections, while C12 is identified as a covalent tetrahedral carbon network, BC11 shows a stacking of C–C covalent substructure blocks separated by B–C ones with resulting metallic like global behavior. From the elastic constants, h-BC11 is identified as mechanically stable with large bulk B and shear G moduli: B(BC11) = 405 GPa; G(BC11) = 414 GPa versus diamond-like C12 characterized by higher magnitudes: B(C12) = 455 GPa and G(C12) = 552 GPa. Both were found dynamically stable from the phonons band structures which exhibit positive frequencies and highest ones at ω ~ 40 THz, close to diamond. Thermal properties reporting temperature change of the entropy and the heat capacity show close similarity with diamond. While large band gap insulating behavior characterizes C12, with EGap ~ 4.5 eV, the electronic band structure of BC11 is metallic with boron p-weighted bands crossing the Fermi level as also detailed with the electronic density of states DOS. The results let suggest that BC11 is a good model structure of heavily doped diamond.
查看更多>>摘要：? 2022 Elsevier B.V.Hydrogenated amorphous carbon coatings improve mechanical performance characteristics on a variety of substrates, resulting in widespread industry applications requiring a combination of high hardness, low coefficient of friction, wear resistance, elasticity, and adhesion. However, such a combination of properties is difficult to achieve. We investigated the structure, mechanical properties and scratch behavior in single-layered and multilayered amorphous carbon thin films made by plasma immersion ion implantation-based plasma enhanced chemical vapor deposition. The elastic modulus and hardness in single-layered films were improved up to 149 GPa and 17 GPa respectively by varying the applied bias voltage and pulse width. We observed a non-equivalent impact on mechanical properties and coating structure based on whether pulse width or frequency were varied in the duty cycle range of 1–12.5%. Mechanical properties were independent of pulse frequency within experimental uncertainty. All the single-layered films showed exceptional elastic recovery of ~70%. Film microstructures as measured by Raman microscopy showed that the maxima in modulus/hardness as a function of bias voltage correlated to films with the highest sp3 bonding fraction, highest sp2 disorder, and overall lowest disorder. The maxima in hardness and elastic modulus as a function of pulse width correlated with intermediate sp3 bonding fraction and highest overall disorder, but the sp2 disorder was nearly unchanged. Based on single-layer results, multilayers were developed. Nanoindentation and scratch testing showed that while multilayering preserved high hardness and improved friction behavior irrespective of the recipe, the scratch volume was strongly correlated to the hardness.
查看更多>>摘要：? 2022The transformation of various carbonaceous substances into ordered carbon nanostructures is a fundamental process in nanotechnology. Since this structural transformation is a common property of various methods for producing CNTs, understanding the mechanism of this process in the bulk of a plasma jet will be extremely important, since no substrates are used here. We present an experimental and numerical study of the synthesis of CNTs with and without external catalysts for the pyrolysis of soot, acetylene, and ethanol in a DC argon plasma at a pressure of 350 Torr. By combining various physical methods, including simultaneous thermal analysis, diffraction analysis, electron microscopy, and energy dispersive analysis, we will show that the aggregation state of the precursor significantly affects the structural and morphological properties of CNTs. Theoretical calculations under the assumption of local thermodynamic equilibrium made it possible to study the gas phase composition of a plasma flow in which the CNT precursor is nucleated. It was found that during the pyrolysis of soot (C), the condensation temperature of solid carbon is 3672 K, with the hydrogen in precursor (C2H2) it is lower and equals 3353 K, with the addition of oxygen (C2H5OH) its value becomes even <3141 K. At the lowest condensation temperature, the most thermally stable CNTs are formed.
查看更多>>摘要：? 2022A normally-off hydrogen-terminated diamond field effect transistor with an Er2O3/Al2O3 bilayer dielectric was fabricated. Dielectric materials Er2O3 and Al2O3 were deposited on H-diamond surface using radio frequency sputtering and atomic layer deposition, respectively. The threshold voltage of the device was ?0.49 V at VDS of ?20 V, which indicated a normally off characteristic, that could be attributed to the low work function of Er2O3 and the polar character of amorphous Er2O3. The maximum drain-source current for the hydrogen-terminated diamond field effect transistor with 6 μm gate length was ?16.1 mA/mm and the sheet carrier density integrated was 1.08 × 1013 cm?2. The maximum effective hole mobility was 110.47 cm2/V·s and the interfacial trapped charge density was 3.16 × 1012 eV?1 cm?2. This bilayer dielectric of Er2O3/Al2O3 provides an alternative plan for the fabrication of normally-off diamond device.
查看更多>>摘要：? 2022 Elsevier B.V.The update of optoelectronic technology requires that the optical window has the dual functions of optical transparency and electromagnetic shielding. A transparent electromagnetic shielding method based on graphene mesh structure is proposed. The optical transmittance of the graphene mesh was theoretically analyzed. Graphene mesh is fabricated by ordinary mask photolithography technology to arbitrarily adjust the structure and number of layers. It retains the same properties as the unpatterned graphene film. Through mesh structure design and layer number control, graphene mesh can be used to replace graphene film with uniform thickness. The average transmittance of the four-layer graphene mesh in the 3–5 μm band is 95.26%, and the average shielding efficiency in the 12–18 GHz band is 3.86 dB. It shows that the graphene mesh maintains high optical transmittance and has good electromagnetic shielding effectiveness.
查看更多>>摘要：? 2022 Elsevier B.V.The devastating repercussions of natural freezing rain phenomena on a variety of industrial facilities might be avoided if the surface-under-attack is designed to be superhydrophobic, thus, repelling the impacting supercooled droplets and remaining free of ice. Regrettably, in climate regions with negative temperatures and highly humid atmosphere, the supersaturated water vapor freezes within the micro- nanocavities of the non-wettable surface and droplet bouncing associated with superhydrophobicity could no longer be preserved. This article explores the possibility of fabricating superhydrophobic carbon soot coatings that would maintain droplet rebound even if their surface is covered with frost. By analyzing the droplet impact dynamics on two groups of frosted soot coatings, differing by morphology, roughness, surface chemistry and porosity, we show for the first time that the liquid meniscus impalement can be cancelled when the soot consists primarily of macropores and oxygen functional groups below 7 at. %. Such a surface configuration ensures minimum energy losses (qualitatively defined) right after the dynamic collision due to the sparsely inceptive ice bridges that normally enhance the heat transfer at the contact interface. The results reported herein could be a useful platform for developing universal icephobic surfaces applicable to harsh environments.
查看更多>>摘要：? 2022 Elsevier B.V.Defects engineering in electrode materials is popular in lithium?sulfur (Li-S) batteries. Generally, the defects can improve the adsorption and catalytic activity for polysulfides of materials. Herein, we synthesize zinc oxide (ZnO) samples with different concentration of Zn vacancies (ZnO-1 h, ZnO-2 h, ZnO-4 h). We find that the Zn vacancies in ZnO render high catalytic activity for fast kinetics of polysulfides, while the more Zn vacancies cause the worse adsorption of ZnO. When these samples combine with reduced oxide graphene (rGO) to load sulfur as sulfur cathodes (noted ZnO-2 h/rGO/S etc.), the ZnO-2h/rGO/S cathode exhibits the optimal performance because ZnO-2 h has the best catalytic activity and modest adsorption. Under electrolyte to sulfur (E/S) of 7.5 μL mgS?1, the ZnO-2 h/rGO/S cathode exhibits a higher initial capacity of 1369.7 mAh g?1 at 0.2C (1C = 1672 mA g?1) and better rate performance than ZnO/rGO/S. The density functional theory calculations reveal the higher conductivity but lower adsorption for polysulfides of ZnO with Zn vacancies (Zn1-xO) than ZnO. Further, the stronger catalytic activity of Zn1-xO can be explained by the increase of S-S length in Li2S4 absorbed on Zn1-xO. This paper exposes that the high catalysis is predominant than the strong adsorption for choosing electrode materials.
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