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Synthesis and growth mechanism of aluminum nitride nanowires via a chloride-assisted chemical vapor reaction method
摘要： We report a large scaled fabrication of AlN nanowires via a chloride-assisted chemical vapor reaction technique at 1100°C in flowing N2 atmosphere using aluminum powders as starting materials. The as-obtained hexagonal AlN nanowires had the length of hundreds of microns and diameter of 20-100 nanometers, and indicated a single crystalline characteristic. The yield production was significantly increased with ammonium chloride and aluminum chloride addition because of the formation of intermediate gaseous AlCl and HCl. The addition of ammonium chloride and aluminum chloride also promoted the formation of ferric chloride, which served as the catalyst and further facilitated the growth of AlN nanowires. The vapor–liquid–solid and vapor–solid growth mechanism are proposed and discussed in details.
关键词： growth mechanism,ammonium chloride,nanowire,Aluminum nitride,chemical vapor reaction,aluminum chloride
更新于2025-09-09 09:28:46
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An insight into the polarization mechanism of rutile based oxides with a wide doping levels in the TiO2-CuO-TaO2.5 ternary system
摘要： Excellent dielectric properties have been found in some acceptor-donor co-doped rutile TiO2 type materials, but the polarization mechanism has long been debated. In present work, the polarization behaviors of single solid solutions Ti1-x(Cu0.333Ta0.667)xO2 (0 < x ≤ 0.465) samples are systematically investigated by establishing the ternary phase diagram of Ti1-xCu2x-2.5yTayO2 (0.05 ≤ x ≤ 1, 0 ≤ y ≤ 0.667). Basing on the obtained phase diagram and the analysis about microstructure, element valence and dielectric behaviors of rutile Ti1-x(Cu0.333Ta0.667)xO2 compositions with various doping levels (x = 0%, 5%, 18%, 33% and 45%), it is demonstrated the existence of multiple polarization mechanisms in this ternary dielectric system, i.e. free carrier nearest-neighbor-hopping polarization as well as internal barrier and surface barrier layer capacitor effect, contribute together to the overall dielectric behaviors. This work would provide guidance to achieve new electronics material with desired structures and properties.
关键词： Impedance spectrum,Polarization mechanism,High doping level,Ternary phase diagram
更新于2025-09-09 09:28:46
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Effects of different pH regulators on the color properties of attapulgite/BiVO4 hybrid pigment
摘要： Four different pH regulators including NaOH, Na2CO3, NaHCO3 and NH3·H2O were employed to prepare attapulgite doped bismuth yellow hybrid pigments by aqueous precipitation followed by an annealing process. Different hybrid pigments derived from different pH regulators had different color properties, and it might be related to the generated products in the process of adjusting pH, which further affected the phase compositions of the end hybrid pigments after being annealed. By contrast, the bismuth yellow hybrid pigments prepared using Na2CO3 as pH regulator exhibited the optimal color properties (L? = 76.81, a? = 4.64, b? = 81.16, C ? = 81.29, and h° = 86.73). Interestingly, attapulgite provided the carrier for BiVO4 nanoparticles to inhibit the agglomeration, and the doping elements to improve its color properties as well. The as-prepared hybrid pigments are expected to be served as an eco-friendly and low-cost yellow colorant to replace the traditional and toxic ones.
关键词： Coloration mechanism,pH regulators,BiVO4,Attapulgite,Comparative studies
更新于2025-09-09 09:28:46
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Perspectives of the Friction Mechanism of Hydrogenated Diamond-Like Carbon Film in Air by Varying Sliding Velocity
摘要： The purpose of the present work is to probe the friction mechanism of hydrogenated diamond-like carbon (H-DLC) ?lm in air by varying sliding velocity (25–1000 mm/s). Friction tests of Al2O3 ball against H-DLC ?lm were conducted with a rotational ball-on-disk tribometer. As the sliding velocity increases, both the friction coef?cient and the surface wear of H-DLC ?lm decrease, reach the minimum values, and then increase in the high sliding velocity region. Based on the observed results, three main friction mechanisms of H-DLC ?lm—namely graphitization mechanism, transfer layer mechanism, and passivation mechanism—are discussed. Raman analysis indicates that the graphitization of worn surface on the H-DLC ?lm has a negligible contribution to the variation of the friction coef?cient and the surface wear. The origin of the sliding velocity dependence is due to the synergistic interaction between the graphitized transfer layer formation and the surface passivation. The present study will not only enrich the understanding of friction mechanism of H-DLC ?lms in air, but will also help to promote their practical engineering applications.
关键词： transfer layer,sliding velocity,surface passivation,diamond-like carbon ?lm,friction mechanism
更新于2025-09-09 09:28:46
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Renewal Mechanism of UV-Ozone-Cleaning Process on Contaminated Screen-Printed Carbon Electrodes
摘要： Screen-printed carbon electrode (SPCE) has been extensively applied in electrochemical (EC) detection due to its excellent characteristics and low cost. However, SPCE is more likely to be contaminated that seriously affects the sensitivity and reproducibility of detection. In this paper, UV-ozone-cleaning process was utilized to solve this problem. Renewal mechanism of UV-ozone-cleaning on contaminated SPCE was ?rstly investigated in detail, in which the level of SPCE contamination was represented by interfacial impedance. Both scanning electron microscopy and X-ray photoelectron spectroscopy were employed to evaluate the surface morphology and chemical constituents of SPCE respectively. The results indicate that the signi?cant EC enhancement was mainly attributed to the removal of contaminants, the increase of both reaction area and surface oxygen functional groups. To further demonstrate the renewal effect, the determination of nicotinamide adenine dinucleotide was performed. Compared with the contaminated SPCE, the UV-ozone-cleaned SPCE exhibits better EC response that the anodic peak current increased by 6～28% and the sensitivity increased from 13.31 to 19.11 μA · mM?1. Moreover, the cleaned SPCE shows good reproducibility with the low standard deviation of peak current and oxidation potential.
关键词： screen-printed carbon electrode,electrochemical detection,contamination,renewal mechanism,UV-ozone-cleaning
更新于2025-09-09 09:28:46
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Design of graphitic carbon nitride supported Ag–Cu2O composites with hierarchical structures for enhanced photocatalytic properties
摘要： A novel ternary photocatalytic nanocomposite, Ag–Cu2O/C3N4, has been successfully synthesized via a facile two-step reduction procedure at room temperature, wherein Ag nanoparticles are directly growing on the surface of Cu2O supported by C3N4 nanosheets. The resulting ternary Ag–Cu2O/C3N4 photocatalyst exhibits enhanced photocatalytic activity towards methyl orange (MO) degradation compared with its conterparts (Cu2O, spherical Ag–Cu2O and Cu2O/C3N4), demonstrating a removal rate of MO up to 95.7% within 30 min. The enhanced photocatalytic activity can be ascribed to the following factors: 1) the surface plasmon resonance effect of Ag nanoparticles broadening the visible light response of Cu2O; 2) the introduction of C3N4 functioning not only as a fast electron delivery but also a fine stabilizer to prevent the Ag–Cu2O composite from agglomeration. Mechanism studies reveal that MO is cracked into smaller fragments and the h+ is the main reactive species participating in the photocatalytic process. Moreover, the Ag–Cu2O/C3N4 photocatalyst also shows high photodegradation ability for another two representative azo dyes, acid orange II and congo red. This study demonstrates the potential of Ag–Cu2O/C3N4 in the degradation of azo dyes and also provides a guide to design of Cu2O-based ternary photocatalysts for further wastewater remediation.
关键词： Wastewater remediation,Cuprous oxide,Photocatalysis,C3N4 nanosheets,Fragments,Mechanism
更新于2025-09-09 09:28:46
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[IEEE 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Greifswald, Germany (2018.9.23-2018.9.28)] 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Recent Progress in Vacuum Breakdown at Nanoscale: Experiment and Simulation
摘要： Vacuum breakdown at nanoscale are drawing more and more attractions due to the dramatic shrink of the feature size for the vacuum microelectronic devices in space environment and other fields, which demands a further exploring on the fundamental properties of vacuum breakdown at nanoscale. Hence, in the present paper, recent progress on experimental and simulation work are summarized and presented, involving the published work and our research work. The general methodology, typical experimental techniques and the influence factors are all investigated and summarized. Results show that the combination of scanning electron microscope(SEM), focused ion beam and piezoelectric-driven nanomanipulator demonstrates to be an effective and precise technique for the experimental study, which could be used in the range from 10nm to 500nm. Moreover, the factors of electrode materials types, gap distance, electrode geometries play various roles on the vacuum breakdown behaviors as well. In the aspect of simulation research, the analytical solution is found to be the most used method so far. Consequently, the summary of methodology, influence factors and potential mechanism on vacuum breakdown at nanoscale is very vital to help understand the underlying principle and then paves the way to the insulation evaluation and structure design of vacuum micro devices.
关键词： influence factors,vacuum breakdown,mechanism,methodology,nanoscale
更新于2025-09-09 09:28:46
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Formation of BiFeO3 Nanoparticles Using Impinging Jets Microreactor
摘要： The influence of the reactants mixing in an impinging jets microreactor of the formation of single-phase nanocrystals of bismuth orthoferrite has been studied. The 30–100 nm amorphous particles are formed under the impinging jets microreactor conditions, which are converted in bismuth orthoferrite with mean crystallite size 17 nm at 420°С.
关键词： impinging jets microreactor,phase formation mechanism,bismuth ferrite
更新于2025-09-09 09:28:46
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Significant Enhancement of Hydrogen-Sensing Properties of ZnO Nanofibers through NiO Loading
摘要： Metal oxide p-n heterojunction nano?bers (NFs) are among the most promising approaches to enhancing the ef?ciency of gas sensors. In this paper, we report the preparation of a series of p-NiO-loaded n-ZnO NFs, namely (1?x)ZnO-xNiO (x = 0.03, 0.05, 0.7, 0.1, and 0.15 wt%), for hydrogen gas sensing experiments. Samples were prepared through the electrospinning technique followed by a calcination process. The sensing experiments showed that the sample with 0.05 wt% NiO loading resulted in the highest sensing performance at an optimal sensing temperature of 200 ?C. The sensing mechanism is discussed in detail and contributions of the p-n heterojunctions, metallization of ZnO and catalytic effect of NiO on the sensing enhancements of an optimized gas sensor are analyzed. This study demonstrates the possibility of fabricating high-performance H2 sensors through the optimization of p-type metal oxide loading on the surfaces of n-type metal oxides.
关键词： ZnO,NiO loading,sensing mechanism,gas sensor,nano?ber,p-n heterojunction
更新于2025-09-09 09:28:46
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Structural, morphological, optical and dielectric properties of M <sup>3+</sup> /PVA/PEG SPE Films (M = La, Y, Fe or Ir)
摘要： Low band gap polymer complexes are promising due to its flexibility, and exhibiting electronic and optical properties of inorganic semiconductors. The effect of PEG on the physical properties of PVA was evaluated. Then, blend (PVA: PEG = 50:50) doped with rare earth (La or Y) and transition metal (Fe or Ir) chlorides to obtain solid polymer electrolyte films. XRD shows that adding PEG to PVA results in a new peak, 2θ = 23o with increased intensity as PEG ratio increases. However, doping with La3+, Fe3+ or Ir3+ eliminate this peak and decrease the crystallinity. SEM exhibits significant changes in the morphology of films. FTIR confirms miscibility between PVA & PEG and the complexation of the salts. The optical band gap (Eg) of PVA ~ 5.37 eV, decreased slightly by blending with PEG. While it decreased significantly to 2.64 eV and 2.78 eV after doping with Fe3+ or Ir3+. There are a consistency between Eg values obtained by Tauc's model and that obtained from the optical dielectric loss. The dielectric constant and loss, in temperature range 303–405 K & frequency range 1.0 kHz ‐ 5.0 MHz, indicate one or two relaxation peak(s) depending on the film composition. Accordingly, conduction mechanism varied between correlated barrier hopping and large polaron tunneling. The DC conductivity was strongly depend on the dielectric loss. The transition metal salts appear to be more effective than the rare earth ones in increasing σac of films to higher values that candidates them in semiconductors industry.
关键词： conduction mechanism,low band gap polymers,activation energy,PVA/PEG blend,rare earth metal complexation,solid polymer electrolyte
更新于2025-09-09 09:28:46