The Preparation of a Low-Cost, Structurally Simple Triboelectric Nanogenerator Based on Fullerene Carbon Soot-Doped Polydimethylsiloxane Composite Film.

Triboelectric nanogenerators (TENGs) have emerged as viable micro power sources for an array of applications. Since their inception in 2012, TENGs have been the subject of significant advancements in terms of structural design and the development of friction materials. Despite these advancements, the complexity of their structural designs and the use of costly friction materials hinder their practical application. This study introduces a simplified TENG model utilizing an economical composite film of fullerene carbon soot (FS)-doped polydimethylsiloxane (PDMS) (FS-TENG). It confirms the FS-TENG's ability to convert mechanical energy into electrical energy, as demonstrated through experimental validation. The generated electricity by the FS-TENG can power devices such as light-emitting diodes (LEDs), digital watches, kitchen timers, and sports stopwatches, highlighting its efficiency. This research enhances the development of TENGs featuring low-cost, streamlined structures for sustainable and autonomous energy sensing applications.

Phase transformation and strengthening of the gas-atomized FeCoCrNiMo0.5Al1.3 high-entropy alloy powder during annealing.

Phase evolution and strengthening of the FeNiCoCrMo0.5Al1.3 powder alloy produced via inert gas atomization and annealed in the temperature interval of 300-800 °C have been studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and microhardness testing. It was found that annealing at 300-600 °C leads to an increase of the element segregations between the several solid solutions with a rise of the lattice misfit (ε) to 1.5 % and microhardness growth to 1070 HV. It was assumed that elastic stress caused by the element partitioning is the main strengthening mechanism: microhardness rises linearly with misfit rise with dHV/dε = 43400 MPa. Sigma arises after the maximum elastic deformation (in 1.5 %) was reached. Formation of the dispersed coherent sigma phase in the annealing interval 600-800 °C results in the microhardness rise. Oxidation that began at 800 °C in 27 h is accompanied with FCC formation due to a depletion of the B2 in Al caused by Al2O3 formation. Estimation of the activation energy of the initial stage of the solid solution decomposition gives a very low value in 0.65eV, apparently caused by the high concentration of quenched vacancies. The activation energy of sigma formation approximately coincides with the activation energy of self-diffusion in BCC metals (about 2.60 eV).

Oxidation Behavior of FeNiCoCrMo0.5Al1.3 High-Entropy Alloy Powder.

One of the most promising applications of FeNiCoCrMoAl-based high-entropy alloy is the fabrication of protective coatings. In this work, gas-atomized powder of FeNiCoCrMo0.5Al1.3 composition was deposited via high-velocity oxygen fuel spraying. It was shown that in-flight oxidation of the powder influences the coating's phase composition and properties. Powder oxidation and phase transformations were studied under HVOF deposition, and during continuous heating and prolonged isothermal annealing at 800 °C. Optical and scanning electron microscopy observation, energy dispersive X-ray analysis, X-ray diffraction analysis, thermogravimetric analysis, differential thermal analysis, and microhardness tests were used for study. In a gas-atomized state, the powder consisted of BCC supersaturated solid solution. The high rate of heating and cooling and high oxygen concentration during spraying led to oxidation development prior to decomposition of the supersaturated solid solution. Depleted Al layers of BCC transferred to the FCC phase. An increase in the spraying distance resulted in an increase in α-Al2O3 content; however, higher oxide content does not result in a higher microhardness. In contrast, under annealing, the supersaturated BCC solid solution decomposition occurs earlier than pronounced oxidation, which leads to considerable strengthening to 910 HV.

2D Heterolayer-Structured MoSe2-Carbon with Fast Kinetics for Sodium-Ion Capacitors.

Two-dimensional (2D) layered MoSe2 has been demonstrated to be a promising electrode material for new energy storage systems. However, its nature of poor conductivity and the undesirable interlayer spacing hinder its further application. In this paper, a general and simple plasma-enhanced chemical vapor deposition method is proposed to produce 2D heterolayer-structured MoSe2-carbon (MoSe2/C) with carbon atoms inserted in the MoSe2 layers. After morphology optimization, when applying flat-type MoSe2/C-200 nanosheets with an enlarged interlayer spacing of 0.79 nm as the anode and activated carbon as the cathode, the assembled sodium-ion hybrid capacitors can reach a maximum energy/power density of 116.5 W h kg-1/107.5 W kg-1 and exhibit superior cycling durability (91.3% capacitance retention after 4000 cycles at 1 A g-1). The good electrochemical property can be ascribed to the enlarged interlayer spacing that can offer fast diffusion channels for Na ions, and the carbon layer sandwiched in the MoSe2 layer can not only enhance the electron transfer, accelerating the reaction kinetics, but also alleviate the volume change of MoSe2, ensuring the good stability of the electrode. The proposed approach can also be extended to other 2D transition metal chalcogenide (TMC) materials for constructing the TMC/C heterostructures for the application in energy storage systems.

Effect of Glass Filler Geometry on the Mechanical and Optical Properties of Highly Transparent Polymer Composite.

In this work, we studied the influence of the geometry and degree of filling of glass dispersed particles on the optical and mechanical properties of flexible high-transmission composites, based on thermoplastic polyurethane. Glass spheres, glass flake and milling glass fiber were used as fillers. Studies of mechanical properties have shown that the introduction of any filler leads to a decrease in tensile strength and an increase in the elastic modulus of the composite material, however, with the introduction of glass flakes and milling glass fiber, a significant increase in the yield strength of the material is observed. The optical properties of composites with glass spheres decrease exponentially with an increase in the volume fraction of the filler. With an increase in the concentration of glass flakes and milling glass fiber to 10 vol.%, a sharp decrease in transmission is observed. With a further increase in concentration, the orientation of the filler along the film occurs, due to which the transmission in the visible range increases to values close to those of a pure polymer.

Simulation of the Particle Transport Behaviors in Nanoporous Matter.

The transport behaviors of proton into nanoporous materials were investigated using different Monte Carlo simulation codes such as GEANT4, Deeper and SRIM. The results indicated that porous structure could enhance the proton scattering effects due to a higher specific surface area and more boundaries. The existence of voids can deepen and widen the proton distribution in the targets due to relatively lower apparent density. Thus, the incident protons would transport deeper and form a wider Bragg peak in the end of the range, as the target materials are in a higher porosity state and/or have a larger pore size. The existence of voids also causes the local inhomogeneity of proton/energy distribution in micro/nano scales. As compared, the commonly used SRIM code can only be used to estimate roughly the incident proton range in nanoporous materials, based on a homogeneous apparent density equivalence rule. Moreover, the estimated errors of the proton range tend to increase with the porosity. The Deeper code (designed for evaluation of radiation effects of nuclear materials) can be used to simulate the transport behaviors of protons or heavy ions in a real porous material with porosity smaller than 52.3% due to its modeling difficulty, while the GEANT4 code has shown advantages in that it is suitable and has been proven to simulate proton transportation in nanoporous materials with porosity in its full range of 0~100%. The GEANT4 simulation results are proved consistent with the experimental data, implying compatibility to deal with ion transportation into homogeneously nanoporous materials.

Microstructure Evolution of FeNiCoCrAl1.3Mo0.5 High Entropy Alloy during Powder Preparation, Laser Powder Bed Fusion, and Microplasma Spraying.

In the present study, powder of FeCoCrNiMo0.5Al1.3 HEA was manufactured by gas atomization process, and then used for laser powder bed fusion (L-PBF) and microplasma spraying (MPS) technologies. The processes of phase composition and microstructure transformation during above mentioned processes and subsequent heat treatment were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and differential thermal analysis (DTA) methods. It was found that gas atomization leads to a formation of dendrites of body centered cubic (BCC) supersaturated solid solution with insignificant Mo-rich segregations on the peripheries of the dendrites. Annealing leads to an increase of element segregations till to decomposition of the BCC solid solution and formation of σ-phase and B2 phase. Microstructure and phase composition of L-PBF sample are very similar to those of the powder. The MPS coating has a little fraction of face centered cubic (FCC) phase because of Al oxidation during spraying and formation of regions depleted in Al, in which FCC structure becomes more stable. Maximum hardness (950 HV) is achieved in the powder and L-PBF samples after annealing at 600 °C. Elastic modulus of the L-PBF sample, determined by nanoindentation, is 165 GPa, that is 12% lower than that of the cast alloy (186 GPa).

Tribological Properties of Al-Based Composites Reinforced with Fullerene Soot.

Aluminum-based composite materials reinforced with fullerene soot, which is a mixture of fullerene and amorphous carbon, are promising materials for friction and wear applications. Composite materials: aluminum with 2% fullerene soot (f.s) and Al with 2% f.s and 2% Cu were obtained via mechanical milling followed by hot pressing. The tribological properties (friction and wear) of the listed composites were investigated and compared with the results for pure aluminum obtained under similar conditions. It has been shown that the addition of fullerene soot reduces the friction coefficient by 25%. At additional alloying with copper, the friction coefficient decreased by 35% in comparison with pure aluminum and also lad to a decrease in friction fluctuations. The wear rate of composite Al with 2% f.s decreased twice in comparison with that of pure aluminum, and with additional alloying it decreased 2.5 times. The morphology of the wear surfaces was investigated by scanning electron microscopy (SEM). The influence of fullerene soot and additional alloying on the wear mechanism was shown.

The Effect of Fullerene Soot Nanoparticles on the Microstructure and Properties of Copper-Based Composites.

Copper-based composite materials strengthened with nanosized fullerene soot particles were produced by mechanical milling and hot pressing technology with a content of carbon up to 5 wt. %. The microstructure of the composite powders and the compacts prepared using them were examined by light microscopy, SEM, EDS, XRD, and XPS; hardness, heat conductivity, and tribological characteristics were measured. The interesting feature of the observed microstructure was a "marble" pattern formed by a white boundary net. The study shows homogeneous distribution of carbon inside the copper grains and its lower concentration in the grain boundaries. The effect was caused by a reaction of carbon with oxygen adsorbed by the copper particles surface. The maximal hardness of the material is 160 HB for the sample with 0.5 wt. % of fullerene soot; this material has the minimal friction coefficient (0.12) and wear in a dry friction condition. Heat conductivity of the material (Cu-0.5 wt. % C) is 288 W/m*K.

Conditions for Production of Composite Material Based on Aluminum and Carbon Nanofibers and Its Physic-Mechanical Properties.

Aluminum-based metallic matrix composites reinforced by carbon nanofibers (CNFs) are important precursors for development of new light and ultralight materials with enhanced properties and high specific characteristics. In the present work, powder metallurgy technique was applied for production of composites based on reinforcement of aluminum matrices by CNFs of different concentrations (0~2.5 wt%). CNFs were produced by chemical vapor deposition (CVD) and mechanical activation. We determined that in situ synthesis of carbon nanostructures with subsequent mechanic activation provides satisfactory distribution of nanofibers and homogeneous composite microstructure. Introduction of 1 vol% of flux (0.25 NaCl + 0.25 KCl + 0.5 CaF2) during mechanic activation helps to reduce the strength of the contacts between the particles. Additionally, better reinforcement of alumina particles and strengthening the bond between CNFs and aluminum are observed due to alumina film removal. Introduction of pure aluminum into mechanically alloyed powder provides the possibility to control composite durability, plasticity and thermal conductivity.

Single-walled carbon nanotubes coated with ZnO by atomic layer deposition.

The possibility of ZnO deposition on the surface of single-walled carbon nanotubes (SWCNTs) with the help of an atomic layer deposition (ALD) technique was successfully demonstrated. The utilization of pristine SWCNTs as a support resulted in a non-uniform deposition of ZnO in the form of nanoparticles. To achieve uniform ZnO coating, the SWCNTs first needed to be functionalized by treating the samples in a controlled ozone atmosphere. The uniformly ZnO coated SWCNTs were used to fabricate UV sensing devices. An UV irradiation of the ZnO coated samples turned them from hydrophobic to hydrophilic behaviour. Furthermore, thin films of the ZnO coated SWCNTs allowed us switch p-type field effect transistors made of pristine SWCNTs to have ambipolar characteristics.

Synthesis of ZnO tetrapods for flexible and transparent UV sensors.

ZnO tetrapods (ZnO-Ts) were synthesized in a vertical flow reactor by gas phase oxidation of Zn vapor in an air atmosphere. The morphology of the product was varied from nearly spherical nanoparticles to ZnO-Ts, together with the partial pressure of Zn and reaction temperature. MgO introduced during synthesis, increased the band gap, the optical transparency in the visible range, and also changed the ZnO-T structure. Fabricated flexible transparent UV sensors showed a 45-fold current increase under UV irradiation with an intensity of 30 µW cm(-2) at a wavelength of 365 nm and response time of 0.9 s.

Studies on mechanism of single-walled carbon nanotube formation.

We presented detailed studies of the formation of single-walled carbon nanotubes by an aerosol method based on the introduction of pre-formed catalyst particles into conditions leading to carbon nanotube synthesis. Carbon monoxide and iron nanoparticles were used as a carbon source and a catalyst, respectively. The vital role of etching agents such as CO2 and H2O in CNT formation was demonstrated on the basis of on-line Fourier-transform infrared spectroscopy measurements. Hydrogen was shown to participate in the reaction of carbon release and to prevent the oxidation of the catalyst particles and the hot wire. The addition of H2 and small amounts of CO2 and H2O led to an increase in the carbon nanotube lengths. The catalyst particle evaporation process inside the reactor was found to become significant at temperatures higher than 1100 degrees C. The carbon nanotube growth was found to occur at a temperature of around 900 degrees C in the heating section of the reactor by in situ sampling and the growth rate was calculated to exceed 1.1 microm/s. A detailed analysis of possible processes during carbon nanotube formation revealed heptagon transformation as a limiting stage. A mechanism for carbon nanotube formation was proposed.