Hybrid Nanocrystalline Research Articles

Decoupled dual‐channel loosely coupled transformer with hybrid nanocrystalline and ferrite core for current sharing of modular wireless power transfer system

AbstractCross‐coupling and current sharing are the main problems faced by modular wireless power transfer (WPT) systems for electric vehicle (EV) applications. In this study, a decoupled dual‐channel wireless power transfer loosely coupled transformer (LCT) with a hybrid core composed of nanocrystalline and ferrite is proposed for modular WPT systems, as well as WPT systems with specific hybrid topology or detuned compensation. Firstly, the requirements of the LCT for modular parallel dual‐channel WPT system and detuned compensation are discussed. For these requirements, the structure and corresponding optimization design method of the decoupled dual‐channel LCT with a hybrid core is then proposed, and an LCT is designed with this method for the case study. Furthermore, the LCT is analysed by the finite element method (FEM). It is revealed that the mutual inductances of the proposed LCT between transmitting and receiving coils can be symmetrical under misalignment in multiple directions, while the cross‐coupling is eliminated. Finally, the designed LCT is manufactured and verified in a modular parallel dual‐channel WPT system. The experimental results show that the current and power sharing is realized under misalignment in multiple directions.

The synthesis of high sinterability (Zr, Hf)C and SiC hybrid nanocrystalline particles by sol-gel method

Multi-phase UHTCs are favoured for their superior ablation resistance and mechanical properties. In this work, to improve the efficiency and decrease the sintering temperature and pressure, the (Zr, Hf)C and SiC hybrid nanocrystalline particles were prepared via the sol-gel method combining carbothermal reduction at 1600 °C. Utilizing their high sinterability, a relative density of 96.1% (Zr, Hf) C–SiC composite was obtained at the conditions of 1900 °C and 30 MPa using SPS technology. XPS and FT-IR results demonstrate that Zr, Hf, and Si were successfully trapped in the cross-linking structure of the precursors. Precursors of Zr, Hf, and Si reached a molecular-level mixture in the gel phase. SEM, XPS, and XRD characterization showed that the Si–C bond was formed preferentially, leading to the emergence of SiC whiskers and SiC wrapped (Zr, Hf)C with increasing temperature. And, the (Zr, Hf)C can be easily generated during solid solution reaction. Eventually, a nanoscale mixture of (Zr, Hf)C and SiC particles was successfully obtained at 1600 °C. The hardness and compressive strength of the (Zr, Hf)C–SiC composite were 12.94 GPa and 622 MPa, respectively. Comparing usual sintering processes (over 2000 °C and 35 MPa), the reason for the improved sinterability can be attributed to the high sintering activity of the (Zr, Hf)C and SiC hybrid particles, and the existence of the solid solution and nano-SiC.

Hybrid Nanocrystalline Ribbon Core and Flake Ribbon For High-Power Inductive Power Transfer Applications

Hybrid Nanocrystalline Ribbon Core and Flake Ribbon For High-Power Inductive Power Transfer Applications

Hybrid nanocrystalline ribbon core for 22kW automotive wireless charging

Hybrid nanocrystalline ribbon core for 22kW automotive wireless charging

On the tribological behavior of cobalt-based nanocomposite coatings containing ZnO@Graphene oxide core-shell nanoparticles

A hybrid nanocrystalline cobalt-based coating was prepared by cathode plasma electrolytic deposition (CPED). Zinc oxide and graphene oxide (GO) nanoparticles were mixed to form a core-shell structure through electrostatic self-assembly by using (3-aminopropyl)triethoxysilane (APTES) modifier. ZnO@GO nanoparticles were used as additives to improve wear and friction properties of deposited coatings. The concentration effect of core-shell ZnO@GO addition (0.1, 0.2 and 0.3 %wt) on the friction, wear, coating thickness and mechanical properties was investigated. The composition and microstructure of deposited coatings were studied by scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy and energy dispersive spectroscopy (EDS). Reciprocating sliding wear tests using a ball-on-plate configuration were carried out on a PLINT TE67 tribometer. AISI 52100 steel was used as ball and the coating deposited onto a AISI 304 stainless steel substrate was used as plate. Coatings were dense, nanocrystalline and uniform with a FCC metastable cobalt structure. Core-shell concentration above to 0.2 %wt resulted in a decrease of grain size and an increase of hardness and wear resistances. Nanoparticles act as nucleation sites for grain formation, decreasing grain sizes. Samples using 0.3% ZnO@GO displayed the lowest wear and friction coefficients. ZnO@GO nanoparticles enables the formation of a protective layer consisting of oxide and exfoliated GO on the top of worn surfaces.

Fabrication of hybrid nanocrystalline Al–Ti alloys by mechanical bonding through high-pressure torsion

This study demonstrates an approach of utilizing high-pressure torsion (HPT) to fabricate a novel hybrid material by the direct bonding of Al and Ti disks at room temperature under a compressive pressure of 6.0 GPa and with increasing numbers of HPT turns up to 50. Detailed structural observations revealed the formation of a multi-layered nanostructure in the edge regions of the disks with a grain size of ∼30 nm. X-ray diffraction (XRD) and selected area electron diffraction (SAED) confirmed the presence of three intermetallic compounds, AlTi, Al3Ti and Ti3Al, in the layered structures. Processing by HPT led to the formation of a hybrid nanocomposite with exceptional hardness (over 300 Hv) in the edge regions of the disks. Special emphasis was placed on understanding the evolution of hardness in the hybrid material. The investigation demonstrates a significant opportunity for using HPT processing to deepen the knowledge on diffusion bonding and mechanical joining technologies as well as for fabricating new and valuable hybrid nanomaterials.

Tuning nanostructure and mechanical property of Fe–Co–Ni–Cr–Mn high-entropy alloy thin films by substrate temperature

Improving the mechanical property of high-entropy alloys (HEAs) with face-centered cubic (fcc) structure is critical for their potential applications. In this study, the effects of substrate temperature, Tsub, on nanometer-sized structure and mechanical property of fcc-structured Fe–Co–Ni–Cr–Mn HEA thin films prepared by magnetron sputtering were systematically investigated. All films grow in a nanocolumnar manner and display a single fcc-structured solid solution phase with (111) preferential orientation in addition to the reduced amorphous phase fraction and increased average grain size with increasing Tsub. The top-surface cauliflower-like hierarchical microstructure with some voided boundaries for 293 K-film gradually disappears with increasing Tsub up to 573 K. For higher Tsub (673 K–773 K), the obvious grain growth occurs with significantly increased column size and roughness. The variations in normal hardness, H, and Young's modulus, Es, obtained from nanoindentation tests on the surface of Fe–Co–Ni–Cr–Mn HEA thin films experienced a process of first increasing and then decreasing with Tsub, with a maximum at Tsub = 573 K. The former increase is due to enhanced interfacial adhesion and the later decrease is ascribed to the weakened grain boundary strengthening caused by grain growth. The 573 K-film with a nanocomposite structure including hybrid nanocrystalline and amorphous phase exhibits the highest H (∼10.0 GPa) and Es (∼185.5 GPa) and is the strongest in terms of hardness among reported Fe–Co–Ni–Cr–Mn HEAs without post-treatment. In-situ micro-tensile tests alone the surface of Fe–Co–Ni–Cr–Mn HEA thin films uncovered the higher lateral yield strength (∼1.1 GPa), fracture strength (∼1.4 GPa), and Young's modulus (∼64.3 GPa) for 573 K-film than those of 293 K- and 773 K-films as well, consistent with nanoindentation results. Anisotropic mechanical responses normal to and along the surface were clearly found in Fe–Co–Ni–Cr–Mn HEA thin films, which are caused by the nanocolumnar morphology and the weakened columnar boundaries adhesion compared to the column itself.

A multifunctional ruthenium based dye for hybrid nanocrystalline titanium dioxide/poly(3-hexylthiophene) solar cells

This work reports the influence of a Ru based dye (RuC) on enhancing the performance of nanocrystalline titanium dioxide (TiO2)/Poly(3-hexylthiophene) (P3HT) solar cells. UV–Vis absorption spectra of TiO2/P3HT and TiO2/RuC/P3HT films reveal that the absorption spectrum of TiO2/P3HT is broadened in the UV region due to the addition of the RuC dye. With pumping laser at the wavelength corresponds to maximum absorption of P3HT, photoluminescence (PL) of TiO2/RuC/P3HT nanocomposite film was significantly quenched in comparison with PL of TiO2/P3HT film which confirms the efficient exciton dissociation in TiO2/RuC/P3HT. The insertion of the dye suppresses the dark current by two orders of magnitude in the cells while extends external quantum efficiency (EQE) spectra and hence increases the average short circuit current density (JSC) from 2.52 (±0.25) to 6.44 (±0.43) mA/cm−2, resulting in three fold power conversion efficiency (PCE) increment from 0.73 (±0.06) to 2.35 (±0.13) %, under 100 mW cm−1 (1 sun) illumination with AM 1.5 filter.

Synthesis of Hybrid Nanocrystalline Alloys by Mechanical Bonding through High‐Pressure Torsion

An overview of the mechanical bonding of dissimilar bulk engineering metals through high‐pressure torsion (HPT) processing at room temperature is described in this Review. A recently developed procedure of mechanical bonding involves the application of conventional HPT processing to alternately stacked two or more disks of dissimilar metals. A macroscale microstructural evolution involves the concept of making tribomaterials and, for some dissimilar metal combinations, microscale microstructural changes demonstrate the synthesis of metal matrix nanocomposites (MMNCs) through the nucleation of nanoscale intermetallic compounds within the nanostructured metal matrix. Further straining by HPT during mechanical bonding provides an opportunity to introduce limited amorphous phases and a bulk metastable state. The mechanically bonded nanostructured hybrid alloys exhibit an exceptionally high specific strength and an enhanced plasticity. These experimental findings suggest a potential for using mechanical bonding for simply and expeditiously fabricating a wide range of new alloy systems by HPT processing.

Laser Selective Photoactivation of Amorphous TiO2 Films to Anatase and/or Rutile Crystalline Phases

Titanium dioxide (TiO2) is a remarkable metal-oxide semiconductor with unique optoelectronic properties ideal for photovoltaics and photocatalytic conversion. The principal crystalline phases for TiO2 are anatase, rutile, and brookite. The combination of both anatase and rutile crystalline structures can positively impact the optoelectronic properties of TiO2 films. With standard sol–gel processing, high-temperature conversion generally yields one dominant phase and limits the combined use of anatase and rutile TiO2 for optoelectronic devices. We report on a singular route to controllably engineer hybrid nanocrystalline films of TiO2 at room temperature to synergistically exploit both anatase and rutile TiO2 phases. Relying on sol–gel chemistry, this approach starts from an amorphous film and uses photoinduced activation using a low-power laser to achieve specific spatially controlled pattern consisting of different TiO2 crystalline phases within the same film. While achieving remarkable precision, reprod...

Cellulose–Polyvinyl Alcohol–Nano-TiO2 Hybrid Nanocomposite: Thermal, Optical, and Antimicrobial Properties against Pathogenic Bacteria

ABSTRACTCellulose fiber-reinforced composite has received great attention due to the high strength, stiffness, biodegradability, and renewability of the excellent natural biomaterials. Cellulose nanofibers for the development of organic–inorganic hybrid composite is relatively new filed of research. Cellulose macro and nanofibers can be used as reinforcement in the hybrid composite because of improved mechanical, thermal, optical, electrical, morphological, and biological properties. The hybrid nanocomposites were synthesized by an in situ sol–gel process in the presence of coupling agent. The sol–gel process has definitely proven its potential by providing the synthesis of various functional organic–inorganic hybrid nanocomposites through an in situ sol–gel process. The hybrid nanocomposites have been prompted by the ability to control the morphology of final materials. The photoluminescence spectral studies indicate that the emission shifts toward higher wavelength (326–532 nm) accompanied by a reduction in impurity centers with increasing concentration of poly(vinyl alcohol)–TiO2 and hybrid nanocomposite. The final nanostructured TiO2 hybrid nanocomposites with particle size ranging from 0.32 to 20 nm were characterized by Field -emission transmission electron microscopy (FE-TEM) analysis. Furthermore, cellulose–poly(vinyl alcohol)–nano-TiO2 hybrid composite was characterized by Fourier transform infrared, X-ray diffraction, UV, Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), FE-SEM–EDX, Field-emission scanning electron microscopy (FE-SEM), and FE-TEM analysis. The different analysis results of the hybrid composite indicate the optical transparency, optical properties, Tg, crystallinity, thermal stability, and controlled morphology of hybrid nanocrystalline composites. Finally, the cellulose–poly(vinyl alcohol)—nano-TiO2 hybrid nanocomposites were tested against pathogens such as Gram-positive Bacteria Bacillus cereus and Gram-negative Escherichia coli for antimicrobial activity. These results show that the hybrid composite exhibited excellent antimicrobial properties against pathogens.

Improving the plasticity of thin cold-rolled steel sheet for cold stamping

Two methods of surface treatment are proposed to improve the technological plasticity of thin cold-rolled carbon-steel sheet: ionic bombardment by low-energy titanium atoms; and epilam coating. Both methods markedly increase the extensibility of the sheet (by a factor of 1.2–1.3), as estimated by the maximum crater depth without cracking in Erichsen tests (from the VG group to values exceeding those for the VOSV group, which corresponds to extremely complex extension, in State Standard GOST 9045–93). This is associated with change in the behavior of the sheet on deformation (with change in the properties of the material) as a result of two processes: the healing of surface defects; and the creation of hybrid nanocrystalline and submicrocrystalline structure in the surface layer. In epilam coating, only the first process occurs; in ionic bombardment, both are observed.

Effect of Au nanoparticles added in nanocrystalline TiO<SUB align="right">2 film on the photoelectrode of dye-sensitised solar cells

In this study, we used a citrate reduction method and electrophoretic deposition (EPD) to prepare hybrid nanocrystalline TiO2/Au films and applied it to the photoelectrode of dye-sensitised solar cell. The films and solar cells were investigated by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), I-V characteristics and electrochemical impedance spectroscopy (EIS) analyses. In the FE-SEM analysis, TiO2/Au hybrid layers have the porous structure that is advantageous in the dye-loading capacity. The results of EDX reveal that the TiO2/Au hybrid layer contains 0.28 wt% gold nanoparticles. X-ray diffraction patterns show that the TiO2/Au hybrid films contain TiO2 anatase and rutile phase, and Au peaks. Under sunlight simulator (AM 1.5 100 mW/cm2) illumination, the conversion efficiency of dye-sensitised solar cell with TiO2/Au hybrid layer is obviously higher than that of TiO2 film. In the analysis of electrochemical impedance spectroscopy (EIS), the total impedance of hybrid TiO2/Au photoelectrode is 98.9 Ω, which is lower than that of TiO2 film photoelectrode. These results indicate that TiO2/Au hybrid layer can increase the conductivity and reduce the recombination of charges in the photoelectrode, resulting in the increase in conversion efficiency for DSSCs.

Controlling Recombination Kinetics of Hybrid Nanocrystalline Titanium Dioxide/Polymer Solar Cells by Inserting an Alumina Layer at the Interface

Controlling Recombination Kinetics of Hybrid Nanocrystalline Titanium Dioxide/Polymer Solar Cells by Inserting an Alumina Layer at the Interface

Direct Growth of Nanocrystalline Graphene/Graphite Transparent Electrodes on Si/SiO2 for Metal‐Free Schottky Junction Photodetectors

Conventional methods to produce graphene/silicon Schottky junctions inevitably involve graphene transfer and metal deposition, which leads to the techniques being complicated, high‐cost, and environmentally unfriendly. It is possible to directly grow hybrid nanocrystalline graphene/graphite transparent electrodes from photoresist on quartz without any catalyst. Due to the source material being photoresist, nanographene/graphite patterns can easily be made on Si/SiO2 structures to form nanographene/silicon Schottky junctions via commercial photolithography and silicon techniques. The obtained Schottky junctions exhibit excellent properties with respect to photodetection, with photovoltage responsivity of 300 V W‐1 at a light power of 0.2 μW and photovoltage response time of less than 0.5 s. The devices also exhibit an excellent reliability with the photovoltage deviating less than 1% when cycled over 200 times.

Preparation and photovoltaic property of a new hybrid nanocrystalline SnO2/Polypyrrole p–n heterojunction

Hybrid photovoltaic structures based on transparent conductive SnO2 and electrically conductive polypyrrole (PPy) were prepared. Nanocrystalline SnO2 is considered an n-type barrier and window layer on p-type PPy layer in cell structures. The surface morphology and thickness of the layers were studied using scanning electron microscopy. The optical absorbance data showed an increase of absorbance in contrast with PPy and SnO2. There was a red shift in absorbance wavelengths and a decrease in band gaps for the prepared PV structures. To investigate the electrical properties of the obtained structures, current-voltage characteristic was measured. The best structure showed an open-circuit voltage of 0.170 V, a short-circuit current density of 0.017 mA/cm2, a fill factor of 0.36 and power conversion efficiency of 0.076.

Novel solution routes of synthesis of metal oxide and hybrid metal oxide nanocrystals

Novel solution routes covering a wide range of processes like hydrothermal, solvothermal and supercritical techniques have been described in detail with reference to the processing of a wide range of advanced inorganic nanocrystalline materials and organic-inorganic hybrid nanocrystalline materials. The significance of the thermochemical calculations, in situ surface modification and the experimental parameters has been discussed. One step in situ fabrication of advanced functional nanocrystalline materials by soft solution processing has also been discussed briefly. Synthesis of nanocrystals of metal oxides and hybrid nanocrystals and also processing several nanocomposites like carbon nanotubes: metal oxide, activated carbon: metal oxide, etc. has been reviewed in relation to various process parameters. The effect of doping, size, shape and quality on the properties of nanocrystalline materials has been discussed in relation to the photoluminescence and photocatalytic characteristics.

Role of Poly(Ethylenedioxythiophene)/Poly(Styrene Sulphonate) on the Performance of Nanocrystalline Titanium Dioxide/Poly(3-Hexylthiophene) Polymer Solar Cells

Hybrid nanocrystalline titanium dioxide (TiO2)/polymer solar cells draw intense interest due to the potential advantages of nanocrystalline TiO2. The poly(styrenesulfonate)-doped poly(ethylenedioxy thiophene) (PEDOT:PSS) layer spin-coated below the top electrode in these solar cells had shown enhanced performance in previous studies, which motivated to explore the dependence of the thickness of the PEDOT:PSS layer on its performance. This study focused on the characterization of solar cells fabricated with poly(3-hexylthiophene) (P3HT) polymer with a silver electrode and different PEDOT:PSS layer thicknesses, in the dark and under AM 1.5 stimulated illumination with the intensity varying from 10 to 100 mW/cm 2 . The variations in the photovoltaic parameters, particularly the open-circuit voltage, proved that the PEDOT:PSS layer significantly affects the photovoltaic parameters through the characteristic changes in the morphology as well as the electrical properties. Discussed herein is the possible influence wielded by the thickness of the PEDOT:PSS layer on different factors, such as the series and shunt resistances, the mode of recombination, the reduction of the energy barrier, and the diffusion of silver. The optimum power conversion efficiency was observed for the as-prepared devices with 50-nm-thick PEDOT layers. The optimum power conversion efficiency, however, shifted to that corresponding to the 80 nm thick PEDOT:PSS layer about 30 weeks after the fabrication. A sublinear variation of the short-circuit current density with the intensity was found in the aged cells with relatively lower PEDOT:PSS layer thicknesses, supporting the view of dominant recombination contributed from bimolecular recombination in the cells with lower PEDOT:PSS thicknesses. The significantly increased open-circuit voltage and the more stable current density in the aged devices are the main causes of the improved performance of the cells generally with above 60 nm thick PEDOT:PSS layers. These, along with the long-term stability found in the cells with reasonably thick PEDOT:PSS layers, may be a figure of merit, most probably attributable to the comparatively minimized diffusion of silver nanoparticles.

Failure mechanisms in metal/metal hybrid nanocrystalline microtruss materials

New types of hybrid nanocrystalline cellular materials can be created by electrodepositing ultra-high-strength nanocrystalline sleeves on microtruss cores. Electrodeposition creates an interconnected network of nanocrystalline tubes that controls the mechanical properties of the cellular hybrid. Although they have exceptional mechanical properties, the hierarchical structure of these materials means that there is a complex set of mechanisms involved during failure, including inelastic buckling of the composite nanocrystalline struts and nanocrystalline sleeve fracture. This study uses a combination of finite-element and experimental methods to investigate the effect of material and architectural failure on the compressive strength of nanocrystalline Ni-reinforced aluminum microtrusses.

Mechanical properties of hybrid nanocrystalline metal foams

Electrodeposition can be used to create new types of hybrid nanocrystalline cellular materials in which the interconnected network of nanocrystalline tubes controls the overall mechanical performance. The present study examines the mechanical performance and failure mechanisms that occur during the uniaxial compression of conventional open-cell Al foams that have been reinforced with electrodeposited nanocrystalline Ni. A composite cellular material approach was used to model the measured increase in compressive modulus and peak strength in terms of the predicted behaviour for a hollow-tube nanocrystalline Ni foam.