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As a promising hydrogen storage material, the practical application of magnesium is obstructed by the stable thermodynamics and sluggish kinetics. In this paper, three kinds of NiTiO3 catalysts with different mole ratio of Ni to Ti were successfully synthesized and doped into nanocrystalline Mg to improve its hydrogen storage properties. Experimental results indicated that all the Mg-NiTiO3 composites showed prominent hydrogen storage performance. Especially, the Mg-NiTiO3/TiO2 composite could take up hydrogen at room temperature and the apparent activation energy for hydrogen absorption was dramatically decreased from 69.8 ± 1.2 (nanocrystalline Mg) kJ/mol to 34.2 ± 0.2 kJ/mol. In addition, the hydrogenated sample began to release hydrogen at about 193.2 °C and eventually desorbed 6.6 wt% H2. The desorption enthalpy of the hydrogenated Mg-NiTiO3-C was estimated to be 78.6 ± 0.8 kJ/mol, 5.3 kJ/mol lower compared to 83.9 ± 0.7 kJ/mol of nanocrystalline Mg. Besides, the sample revealed splendid cyclic stability during 20 cycles. No obvious recession occurred in the absorption and desorption kinetics and only 0.3 wt% hydrogen capacity degradation was observed. Further structural analysis demonstrates that nanosizing and catalyst doping led to a synergistic effect on the enhanced hydrogen storage performance of Mg-NiTiO3-C composite, which might serve as a reference for future design of highly effective hydrogen storage materials.

Catalysis today 376, S0920586121002856 (1-10) (2021). doi:10.1016/j.cattod.2021.06.018, The objective of this research was to investigate how the photocatalytic activity of pure TiO$_2$ can be improved bySnO$_2$ modification. Different molar ratios of tin to titanium were prepared. The correlation between tin concentration and structural properties was investigated to explain the mechanism of photocatalytic efficiency and to optimize the synthesis conditions to obtain enhanced activity of the SnO$_2$-modified TiO$_2$ photocatalysts under UV-irradiation. The SnO$_2$-modified TiO$_2$ photocatalysts were prepared by a low-temperature sol-gel method based on organic tin and titanium precursors. The precursors underwent sol-gel reactions separately to form SnO$_2$-TiO$_2$ sol. The sol-gels were deposited on a glass substrate by a dip-coating technique and dried at 150 °C to obtain the photocatalysts in the form of a thin film. To test the thermal stability of the material, an additional set of photocatalysts was prepared by calcining the dried samples in air at 500 °C. The photocatalytic activity of the samples was determined by measuring the degradation rate of an azo dye. An increase of up to 30% in thephotocatalytic activity of the air-dried samples was obtained when the TiO$_2$ was modified with the SnO$_2$ in a concentration range of 0.1–1 mol.%. At higher SnO$_2$ loadings, the photocatalytic activity of the photocatalystwas reduced compared to the unmodified TiO$_2$. The calcined samples showed an overall reduced photocatalyticactivity compared to the air-dried samples. Various characterization techniques (UV-Vis, XRD, N2-physisorption,TEM, EDX, SEM, XAS and photoelectrochemical characterization) were used to explain the mechanism for the enhanced and hindered photocatalytic performances of the SnO$_2$-modified TiO$_2$ photocatalysts. The results showed that the nanocrystalline cassiterite SnO$_2$ is attached to the TiO$_2$ nanocrystallites through the Sn-O-Ti bonds. In this way, the coupling of two semiconductors, SnO$_2$ and TiO$_2$, was demonstrated. Compared to single-phase photocatalysts, the coupling of semiconductors has a beneficial effect on the separation of charge carriers, which prolongs their lifetime for accessibility to participate in the redox reactions. The maximum increase in activity of the thin films was achieved in the low concentration range (0.1–1 mol.%), which means that an optimal ratio and contact of the two phases is achieved for the given physical parameters such as particle size, shape and specific surface area of the catalyst., Published by Elsevier, Amsterdam

The unclear miscibility of CuNi alloys was investigated with atom probe tomography (APT). Multilayered thin film samples were prepared by ion beam sputtering (IBS) and focused ion beam (FIB) shaping. Long-term isothermal annealing treatments in a UHV furnace were conducted at temperatures of 573, 623, and 673 K to investigate the mixing process. The effective interdiffusion coefficient of the nanocrystalline microstructure (including defect diffusion) was determined to be Deff = 1.86 × 10−10 m2/s × exp(−164 kJ/mol/RT) by fitting periodic composition profiles through a Fourier series. In nonequilibrium states, microstructural defects like grain boundaries and precipitates were observed. While at the two higher temperatures total mixing is observed, a clear experimental evidence is found for a miscibility gap at 573 K with the boundary concentrations of 26 and 66 at%. These two compositions are used in a subregular solution model to reconstruct the phase miscibility gap. So, the critical temperature TC of the miscibility gap is found to be 608 K at a concentration of 45 at% Ni.

[EN] Metal-Organic Frameworks (MOFs) are extensively used in different applications, including heterogeneous catalysis given the fact that practically any center can be designed on demand and is accessible for reactants. Just like any other microporous catalysts, the limited diffusion of reactants and products is an endemic drawback also in MOFs. To face it, the use of nanocrystalline MOFs is a proven alternative, which in addition is often accompanied by improvements in sustainability of synthesis procedure (room temperature, water as solvent, etc.). This work goes further adding surfactant-induced mesoporosity to the nanocrystallinity of these materials. As a proof of concept, the nanocrystalline NH-MIL-53(Al) and CTA (cetyltrimethylammonium) were selected as the sustainably-prepared nanocrystalline MOF and a cationic surfactant, respectively. The MOF system is formed by massive and practically instantaneous precipitation entrapping the surfactant, which generates mesopores in the aggregates. The simple washing with ethanol at room temperature leads to a nanocrystalline NH-MIL-53(Al) material containing outstanding intercrystalline mesoporosity. The so-obtaining hierarchically-porous NH-MIL-53(Al) is able to effectively remove bisphenol A (BPA) from aqueous solution (more than 90% of a 25 ppm BPA aqueous solution in just 10 min at room temperature), duplicating the performance given by its counterpart nanocrystalline NH-MIL-53(Al) prepared in the absence of surfactant., This work has been financed by the Spanish State Research Agency (Agencia Estatal de Investigación AEI) and the European Regional Development Fund (Fondo Europeo de Desarrollo Regional, FEDER) through the Project MAT2016-77496-R and CSIC (2019AEP076). M.A. M. acknowledges Spanish MINECO for Ph.D. student contract BES-2017-082077. N.R.H. acknowledges CSIC for the I-COOPA-2019 (COOPA20376) grant and M.S.S the I-COOPA-2018 (COOPA20271) project

3D electrodes have shown extraordinary promise for electrochemical energy storage devices in wearable electronics. However, it is still a significant challenge to rationally design 3D electrode that has the characteristics of lightweight, flexibility, low cost, high performance and miniaturization. In this work, we present a novel design of 3D electrode by directly growing the nanocrystalline TiO2 film on carbonized eggshell membrane. The unique architecture can supply not only a continuous electron transport pathway through an interconnected carbon fibrous network but also an efficient electrolyte flux via an interpenetrating porous network. Besides, nanocrystalline TiO2 film on carbonized eggshell membrane offers a short ion diffusion path in the solid-phase, leading to a rapid kinetic of electrochemical reaction. When tested as an anode for Li-ion battery, TiO2 film in 3D electrode demonstrated excellent electrochemical performance with a large reversible capacity, excellent rate capacity and long life cycling property.

The strength of polycrystalline metals increases with decreasing grain size, following the classical Hall-Petch relationship. However, this relationship fails when softening occurs at very small grain sizes (typically less than 10 to 20 nm), which limits the development of ultrahigh-strength materials. In this work, using columnar-grained nanocrystalline Cu-Ag ‘samples’, molecular dynamics simulations were performed to investigate the softening mechanism and explore the strengthening strategies (e.g., formation of solid solution or grain boundary (GB) segregation) in extremely fine nanograined metals. Accordingly, the softening of pure metals is induced by atomic sliding in the GB layer, rather than dislocation activities in the grain interior, although both occur during deformation. The solid solution lowers the stacking fault energy and increases the GB energy, which leads to the softening of NC metals. GB segregation stabilizes GB structures, which causes a notable improvement in strength, and this improvement can be further enhanced by optimizing the solute concentration and GB excess. This work deepens the understanding of the softening mechanism due to atomic sliding in the GB layer and the strengthening mechanism arising from tailoring the GB stability of immiscible alloys and provides insights into the design of ultrahigh-strength materials.

Nanocrystalline copper ferrite shows distinct photocatalytic properties, but it suffers from a high recombination rate of photogenerated electrons (e−) and holes (h+) due to its narrow bandgap. Herein, Al3+ doping is shown to reduce the (e−/h+) recombination rate and improve the charge carriers’ availability in doped CuFe2−xAlxO4 (0 ≤ x ≤ 1) nanoparticles produced by a solid-state, mechanochemical process. CuFe2−xAlxO4 (0 ≤ x ≤ 1) nanoparticles exhibit the growth of a nanocrystalline cubic spinel lattice when annealed at 1000 °C. The lattice parameter is reduced by Al3+ doping due to the smaller ionic radius of Al3+ ions substituting bigger Fe3+ ions. However, a higher degree of sintering and greater crystallite size are observed for Al3+ doped samples. The surface morphology and topography also reveal an increase in the particle size, but significantly narrow size distribution and greater homogeneity. The effect of Al3+ doping on the optical properties of CuFe2−xAlxO4 (0 ≤ x ≤ 1) nanoparticles is demonstrated by a decrease in the photoluminescence signal that is attributed to the lower rate of (e−/h+) recombination. Thus, Al3+ doping increases transition time and improves the availability of charge carriers for potential photocatalytic applications.

Developing novel magnetocaloric materials is of great significance for the applications of magnetic refrigeration. In this study, we designed a heterogeneous rare-earth-based high-entropy alloy (HEA) comprising amorphous matrix, local crystal-like cluster and nanocrystalline dihydride with average size of 7.5 nm through isothermal hydrogenation. This heterogeneous structure can significantly tune the magnetocaloric effect of alloy. After hydrogenation, the predominant exchange interaction transforms from ferromagnetic to antiferromagnetic with the disappearance of spin-glass-like behavior, and a complete second-order magnetic transition is obtained. Compared with the Gd20Tb18Dy18Co20Al24 high-entropy metallic glass with a small number of nanocrystals, the maximum magnetic entropy change of the hydrogen-containing HEA is increased from 8.8 to 13.6 J kg−1 K−1 under applied magnetic field change of 5 T accompanying unobvious hysteresis and decreased magnetic transition temperature from 59 to 8 K, which is more promising as magnetic refrigerant at cryogenic temperature. This work provides a novel concept of designing heterogeneous structure in terms of special cluster and preferential nanocrystalline to modulate the properties of metallic glasses.

To endow Ti-based orthopedic implants with strong bactericidal activity, a ZnO nanorods-patterned coating (namely ZNR) was fabricated on Ti utilizing a catalyst- and template-free method of micro-arc oxidation (MAO) and hydrothermal treatment (HT). The coating comprises an outer layer of ZnO nanorods and a partially crystallized inner layer with nanocrystalline TiO2 and Zn2TiO4 embedded amorphous matrix containing Ti, O and Zn. During HT, Zn2+ ions contained in amorphous matrix of the as-MAOed layer migrate to surface and react with OH− in hydrothermal solution to form ZnO nuclei growing in length at expense of the migrated Zn2+. ZNR exhibits intense bactericidal activity against the adhered and planktonic S. aureus in vitro and in vivo. The crucial contributors to kill the adhered bacteria are ZnO nanorods derived mechano-penetration and released reactive oxygen species (ROS). Within 30 min of S. aureus incubation, ROS is the predominant bactericidal contributor with quantitative contribution value of ∼20%, which transforms into mechano-penetration with prolonging time to reach quantitative contribution value of ∼96% at 24 h. In addition, the bactericidal contributor against the planktonic bacteria of ZNR is relied on the released Zn2+. This work discloses an in-depth bactericidal mechanism of ZnO nanorods., Graphical abstract Image 1, Highlights (1) A templates and catalysts-free method is used to fabricate ZnO nanorods on Ti (2) ZnO nanorods-arrayed coating shows intense broad-spectrum bactericidal activity (3) Main bactericidal contributor of ZnO nanorods to adhered bacteria is mechano-puncture (4) Main bactericidal contributor of ZnO nanorods to planktonic bacteria is released Zn2+

Structure, magnetic properties and ductile of melt-spun Fe83-xSi4B13-yCyCux (x = 0–1.7; y = 0–8) alloys were investigated. The addition of 1.7 at.% Cu in a Fe83Si4B13 amorphous alloy generates abundant α-Fe crystals by providing nucleation sites, and further C doping promotes the growth of the crystals by suitable turning amorphous-forming ability, hence they increase saturation magnetic flux density (Bs) and slightly worse magnetic softness of the as-spun alloys. The as-spun Fe81.3Si4B7C6Cu1.7 alloy possesses a combined structure of a fully amorphous layer in wheel side surface and predominating nanocrystalline structure with gradually enlarged α-Fe crystal, whose average size and volume fraction are determined as about 12 nm and 32%, respectively, therefore superior soft magnetic properties and ductile with a high Bs of 1.74 T, coercivity (Hc) of 32.7 A/m, effective permeability (μe, at 1 kHz) of 3200 and high relatively strain at fracture (ef) of 3.61% can be achieved directly in this alloy by only using melt-spinning. The annealing at 578 K releases internal stress, promotes the growth of the α-Fe crystals and remains the amorphous layer of the Fe81.3Si4B7C6Cu1.7 alloy, then improves the soft magnetic properties and maintains the superior ductile with increasing the Bs and μe to 1.80 T and 14,100, respectively, lowering the Hc to 9.4 A/m and slightly reducing the ef to 2.39%. The combination of superior soft magnetic properties and ductile and simplified synthesis process entitles the Fe-Si-B-C Cu nanocrystalline alloys great potentials in high performance electromagnetic applications.

The Y, F, and Ag tridoped TiO2/SnO2 composite nanocrystalline film (YFAg–TS) with prominent photocatalytic performance was prepared by the modified sol–gel method and was characterized by utilizing X-ray diffraction (XRD), differential thermal and thermogravimetric (DTA–TG) analysis, scanning tunneling microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) method, ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), and photoluminescence (PL). The XRD and DTA–TG results expose that the YFAg–TS catalyst is a mixed phase consisting of anatase, rutile, and chlorargyrite, which is beneficial to improving the photocatalytic performance of TiO2. The SEM, TEM, and BET results disclose that the YFAg–TS film has smaller nanoparticles, higher surface area, and narrower pore size compared with pure TiO2 film. The XRD and TEM results exhibit that a part of yttrium can enter the TiO2 lattice to induce lattice distortion. The XPS results confirm the presence of Y3+ state in the YFAg–TS sample, and Y3+ ions can act as the trapping site of electrons to expedite the separation of electrons and holes. The UV–vis DRS results reveal that the YFAg–TS film has an obvious absorption edge shift and a narrower bandgap (2.70 eV) compared with pure TiO2 film. The PL results show that the YFAg–TS film has the highest photogenerated electrons and holes separation efficiency and charges transfer efficiency among all samples. The photocatalytic activity of the YFAg–TS is assessed by monitoring the degradation of methyl green and formaldehyde solution. The results manifest that the YFAg–TS film has high stability and excellent photocatalytic performance. The possible synergistic photocatalytic mechanism of YFAg–TS films has been discussed in this paper.

Grain refinement to the nanocrystalline regime is the most effective way to strengthen materials but this often deteriorates the grain-size thermal stability and plasticity. Here we manufactured a nanocrystalline face centred cubic CrCoNi medium entropy alloy with columnar grains via magnetron sputtering. Compression of CrCoNi pillars with diameters of ∼ 1 µm revealed a record high yield strength of ∼5 GPa for pillars with face centred cubic structures and engineering plastic strain of > 30%. The alloy possessed an outstanding grain-size thermal stability even at 1073 K. Both nanocrystalline grain size and a high density of nanotwins/stacking faults are critical to the exceptional yield strength. Deformation twinning, grains refinement during deformation, grain boundary sliding and random grain orientation all contribute to the large plasticity. The outstanding thermal stability is attributed to the sluggish diffusion effect and the low energy of twin boundaries.

Thin film of WO3 has been deposited on conductive fluorine tin oxide substrate using the hydrothermal technique. The film's microstructural, morphological and optical properties have been identified using X-ray diffraction, atomic force microscope, and spectrophotometer. The obtained results have confirmed the nanocrystalline structure of the as-received WO3 thin film with crystallite size ≈63.4 nm. Analysis of the absorption coefficient using Tauc's model shows the possibility of direct and/or indirect allowed transition with energy gaps 3.95 and/or 3.45 eV, respectively. The refractive index has been determined by different methods showing the average value (2.2 and 2.3 corresponding to the direct and indirect transitions, respectively). The nonlinear refractive index and third-order nonlinear optical susceptibility have been determined, showing the high polarizability of WO3/FTO with radiation to be promising for different optical devices and applications.

This study coated the surface of irregularly shaped 5-μm boron particles with TiO2 nanoparticles to improve the ignition performance of the boron. A simple and inexpensive chemical method was used to coat the surface of boron with TiO2. Five different samples of boron coated with TiO2 nanoparticles were obtained by varying the concentration of Ti precursor. Surface structures were analyzed using different characterization techniques, which showed the formation of nanocrystalline TiO2 nanoparticles over the boron surface. The nanoparticles of TiO2 were well dispersed over the boron surface, and exhibited strong interfacial contact with the boron. The oxidation of boron and boron coated with TiO2 was analyzed by thermogravimetric technique in an air atmosphere from room temperature to 1000 °C. Results revealed that the oxidation of boron started at a temperature approximately 162 °C lower after coating with TiO2. The ignition behavior of the boron and boron coated with TiO2 particles was studied using a shock tube. The results of the shock tube experiments demonstrated the TiO2 coated boron had a shorter ignition delay time than the bare boron. An approximate 35% reduction was observed in the ignition delay time of boron after coating with TiO2 nanoparticles, showing its potential value in high energy density fuels.

Although the optical properties of nanocrystalline cesium tungsten bronze have been widely studied, there is a lack of research on the effect of particle size on its optical properties. In order to further investigate size and shape effect on the NIR shielding performance, cesium tungsten bronze nanoparticles with different sizes and morphologies were prepared by two methods. The size of irregular shaped samples prepared by solvothermal method is tens of nanometers, while the size of hexagonal prism shaped samples prepared by solid state reaction method is hundreds of nanometers. The element spectrums shows that there are more oxygen vacancies in large particles than in small particles. The NIR shielding performance of large particles far lower than that of small particles, indicating that the influence of shape and size on optical properties is more obvious than that of oxygen vacancy. Theoretical calculation on hexagonal prism shaped particles exhibits that the NIR extinction of large aspect ratio is better at longer wavelength and small aspect ratio is better at shorter wavelength.

Here, the up-and down-conversion emissions enhancement in Er3+/Yb3+/Li+ co-doped Y4O(OH)9NO3 and Y2O3 nanoparticles was studied in function of the calcination temperature. Tri-doped Y4O(OH)9NO3 nanophosphors were synthesized by the hydrothermal method and then calcined to yield Y2O3 nanocrystalline structures. The phase evolution from Y4O(OH)9NO3 to Y2O3 was investigated by XRD analysis, and the quantification of Li + species in the nanoparticles lattice was done by FTIR. Both techniques allow explaining the photoluminescence enhancement in terms of the calcination temperature required to achieve optimum lithium incorporation. SEM analysis was used to monitor changes in the morphology with the thermal treatment temperature. The resulting photoluminescence emission spectra of the Er3+/Yb3+ doped Y4O(OH)9NO3 and Y2O3 nanocrystals were composed of emission bands associated with the Er3+ 2H11/2, 4S3/2 → 4I15/2 (green), 4F9/2 → 4I15/2 (red), and 4I13/2 → 4I15/2 (infrared) intraelectronic transitions, and its relative contribution was found to be sensitive to the calcination temperature. Thus, tunable color emission from yellowish-orange to yellow-green light with a color temperature of 2581–4433 K upon 980 nm excitation, respectively, was observed.

We report nearly full densification of polycrystalline rhombohedral beta (β)-boron without the addition of sintering aids via spark plasma sintering (SPS). The analytical aberration corrected transmission electron microscope observations have revealed in-situ growth of nanocrystalline boron-rich oxide precipitates that contain approximately 4 at.% of oxygen and beget the densification of β-boron. Further electron energy loss spectroscopy and diffraction analysis confirmed that the newly formed boron-rich oxide (nominally B96O4) structure with B-O σ-bonding belongs to space group R 3 ¯ m . Depth sensitive nanoindentation showed boron-rich oxide phase has a hardness of about 41 ± 2 GPa, which is 10% higher than that of β-boron matrix. The estimated hardness and fracture toughness of β-boron were approximately 31 GPa and 2.2 MPa m1/2, respectively, using Vickers microindentation, which falls in the range of those commercially used boron carbides. These results suggest that the enhanced densification and mechanical properties arise from the newly formed boron-rich oxide in β-boron during SPS experiments.

Ga2O3 films were deposited on Si substrates through radio-frequency magnetron sputtering at room temperature and were annealed in situ in a high-vacuum environment. The as-deposited Ga2O3 film exhibited an island-like surface morphology and had an amorphous microstructure, with a few nanocrystalline grains embedded in it. After high-temperature in situ annealing, the films recrystallized and exhibited coalesced surfaces. Because of the thermally driven diffusion of Ga, the interfacial layer between Si and Ga2O3 was composed of SiGaOx. Compared with ex situ annealing in air, in situ annealing in high vacuum is more advantageous because it enhances surface mobility and improves the crystallinity of the Ga2O3 films. The higher oxygen vacancy concentration of in situ annealed films revealed that oxygen atoms were easily released from the Ga2O3 lattice during high-vacuum annealing. Photoluminescence (PL) spectra exhibited four emission peaks centered in ultraviolet, blue, and green regions, and the peak intensities were significantly enhanced by thermal annealing at >600 °C. This work elucidates the effect of the in situ annealing treatment on the recrystallization behavior, interfacial microstructure, oxygen vacancy concentration, and PL performance of the Ga2O3 films, making it significant and instructional for the further development of Ga2O3-based devices.

Nanocrystalline metals often display a high strength up to the gigapascal level, yet they suffer from poor plasticity. Previous studies have shown that the development of hetero-sized grains can efficiently overcome the strength-ductility trade-off of nanocrystalline metals. However, whether this strategy can lead to the fabrication of nanocrystalline nanowires exhibiting both high strength and superplasticity is unclear, similar to the atomistic deformation mechanism. In this paper, we show that ultra-small nanocrystalline Au nanowires comprising grains in both the Hall–Petch and inverse Hall–Petch grain-size regions can exhibit extremely high uniform elongation (236%) and high strength (2.34 gigapascals) at room temperature. In situ atomic-scale observations revealed that the plastic deformation underwent two stages. In the first stage, the super-elongation ability originated from the intergrain plasticity of small grains via mechanisms such as grain boundary migration and grain rotation. This intergrain plasticity caused the grains in the heterogeneous-structured nanowires to grow very large. In the second stage, the super-elongation ability originated from intragrain plasticity accompanied by the diffusion of surface atoms. Our results show that the hetero-grain-sized nanocrystalline nanowires, comprising grains with sizes both in the strongest Hall–Petch effect region and the inverse Hall–Petch effect region, were simultaneously ultra-strong and ductile. They displayed neither a strength-ductility trade-off nor plastic instability.

A novel hot extrusion method to fabricate anisotropic nanocrystalline SmCo5 magnet was investigated. The results indicate that the hot-extruded (HE) SmCo5 magnet obtains a strong c-axis texture in perpendicular to the extrusion direction, but the texture strength is clearly different in different regions. The deformation degree plays a key role in the formation of c-axis crystallographic texture and magnetic anisotropy. In surface region of the HE magnet, the deformation degree of grains is the biggest, and the c-axis texture and remanence are the strongest. Furthermore, deformation mechanism of the HE SmCo5 magnet was preliminarily discussed.

In the present work, nanostructured hydroxyapatite (HA)-containing coating was prepared on a Ti surface by ultrasonic mechanical coating and armoring (UMCA). A Ti plate was pre-coated with HA slurry, followed by UMCA, which was achieved by high-frequency ZrO2 ball bombardment. The UMCA process comprised several cycles of pre-coating and ball bombardment, providing high amounts of HA and good coating adhesion. The coating mainly consisted of nano-HA particles (less than 10 nm) and a small amount of Ti. Furthermore, the deformation structures of the Ti surface region were characterized in a nanocrystalline layer with a grain size of 50–200 nm. Additionally, the coating exhibited improved bioactivity and corrosion resistance in Hanks’ balanced salt solution than the Ti surface. Furthermore, the in vitro cytotoxicity test assessed that the HA-containing coating was non-cytotoxic.

Soft magnetic powder cores are attractive due to their loss at medium frequency. However, the performance of electrical equipment is affected by temperature increase by the heat of core losses. In this paper, the magnetic properties of nanocrystalline powder core, amorphous powder core, X-Flux (Fe-Si), Sendust (Fe-Si-Al), and ferrite are measured and compared in the range of 25 °C to 125 °C from 20 kHz to 100 kHz. The discussed magnetic properties include the temperature dependent coercive field, initial permeability, inductance factor, saturation flux density, and core loss. The results show that magnetic properties depend on temperature and frequency. In comparison, the nanocrystalline powder core has the best temperature stability and relatively low core loss among the five materials, so it can be well used at broad temperature and medium frequency.

ZnAl2O4 nanocrystalline particles were prepared using the solution combustion method using a new combustion fuel, Leucine. The prepared samples' structural, microstructural–elemental composition, and optical characteristics were investigated using XRD, SEM-EDS, and UV–Visible spectroscopy. As-synthesized ZnAl2O4 nanoparticles are polycrystalline, with no secondary phases, and crystallized in a cubic - spinel structure. The polycrystalline nature of the prepared sample is due to the exothermicity of fuel and oxidizer, which demonstrate that the fuel utilized (Leucine) provided adequate energy for the production of nanoparticles in their as-synthesized form, as supported by adiabatic temperature through thermodynamic calculations. The thermodynamic calculations also include a universal method to estimate the specific heat capacity at constant pressure. Furthermore, even after 2 h of calcination at 600 °C, ZnAl2O4 exhibits a single phase with no secondary phases, indicating the material stability and single-phase nature. The crystallinity of ZnAl2O4 nanoparticles was observed to increase with increasing annealing temperature. SEM micrographs of as-synthesized samples exhibit the formation of dense particles, voids, and pores in the as-synthesized sample. In addition, tiny aggregates were detected on the surface of more prominent clusters, which reduced as the calcination progressed. In addition, calcined samples exhibit a greater optical reflectance than as-synthesized samples. Tauc's graphs were used to compute the optical energy bandgap. The calculated energy band gap is redshifted to that of the bulk material. The bandgap energy decreases upon calcination, suggesting that the prepared materials have a larger crystallite size or more crystallinity. Correlations were found between the Tad, and the structural and optical properties of the prepared samples. The findings suggest that Leucine could be used as a novel combustion fuel to produce crystalline ZnAl2O4 nanoparticles in their as-synthesis form.

The electrodeposition technique was used to synthesize copper-doped ZrO2 thin film. Different characterization technique such as vibrating sample magnetometry, UV–visible spectroscopy, scanning electron microscope, and X-ray diffractometry were used to study the magnetic, optical, surface morphology, and structural properties of the thin films. The Uniform nanocrystalline grains without cracks, and of various sizes were obtained. The optical studies showed a decrease in energy band gap from 4.1 eV to 3.9 eV. The magnetic studies revealed that the doped samples have unique ferromagnetic ordering, this could be due to the increase in grain size. The 2% and 4% doped samples are saturated around 4.51 × 10−4 emu/g and 4.70 × 10−4 emu/g at coercive field of 274.54 and 274.96 respectively.

The nanocrystalline alloys are gradually used as shielding materials in wireless power transfer (WPT) systems with the development of high-power-density. In this paper, the system properties of WPT using ferrite and four types of nanocrystalline cores are simulated by three-dimensional (3-D) finite element analysis (FEA). Based on this, a novel shielding pad composed of nanocrystalline alloy and ferrite is designed to improve the WPT system properties. The WPT systems are preliminarily compared by 3-D FEA when the different nanocrystalline alloys are used in the novel shielding pad. The experimental WPT system for 85 kHz, 1.5 kW with a 24 cm air gap between the primary and secondary coils is built to validate the simulation. The results show that significantly greater shielding can be realized for the novel pad at the price of a slight decrease of transmission efficiency than conventional ferrite core.

Synthesis of nanostructured carbon allotropes using CO2 as a cheap carbon source is challenging and usually limited by high temperature activation. Herein, formation of 3D nanostructured carbon allotropes including nano-graphene and single crystalline nanodiamond films is feasible at room temperature on various single crystal metals (e.g., Bi, Ag, Zn, and Co) that were formed under the dynamic CO2 electrochemical reduction reaction environment at relatively low applied potential (−1.1 to −1.6 V vs. Ag/AgCl). The nanocrystalline carbon was obtained as the major products from CO2 (≥96% selectivity, ∼1 μm thickness) without any liquid products. Upon applying the negative potential, nanoclustering of the self-limiting ultrathin metal oxide layers of metal particles on the highly conductive substrate could lead to formation of negatively charged metal clusters, which were well stabilized by the ternary electrolyte system containing [BMIm]+[BF4]-/propylene carbonate/water. This system allows the reduction of CO2 into single atoms C∗ and the subsequently electrocrystallization of C∗ into carbon allotropes on the crystallographic planes of the single crystal metals formed as the building blocks. The CO2-derived Ag–C/epoxy composites show promising thermal conductivity. The results present a breakthrough advancement in the growth of nanostructured carbon allotropes from CO2 by the viable negative CO2 emission approach.

Dual-emitting manganese ions singly doped 5ZnO-(5–2.5x)Ga2O3-2.5 xAl2O3–90SiO2 glass-ceramic (GCs) samples, containing the alloyed Zn(Ga, Al)2O4 nanocrystals with a size of about 5 nm, were successfully prepared by a sol-gel method under different heat treatment temperatures, demonstrating an excellent white light emission. We found that the formation of the ZnGa2O4 nanocrystals began at 650 °C (absence of Al2O3, x = 0) while that of the ZnAl2O4 crystals required a higher temperature of about 900 °C (presence of Al2O3, x = 2) in SiO2 glasses. A nanostructured Zn(Ga, Al)2O4:Mn2+, Mn4+ in the glass-ceramic was synthesized by Al3+ replacing part of Ga3+. The doping of Al3+ has effectively contributed to the existence of Mn2+, thus realizing the regulation of the valence state of manganese ions. The glass ceramic samples showed red emission arrived from the 2Eg → 4A2g transitions of Mn4+, green emission originated from the 4T1→6A1 transition of Mn2+, and blue emission derived from the self-activation center of ZnGa2O4 nanocrystalline. In particular, the 0.1%Mn doped the 5ZnO-(5–2.5x)Ga2O3-2.5xAl2O3–90SiO2 glass-ceramic samples can provide white color emission depending on the Al doping concentration (x), x = 0.4–0.9 and the annealing temperature, 650–900 °C.

A diamond film was synthesized by chemical vapor deposition, where a hot graphite plate was used to thermally activate methane and hydrogen. The effect of parameters on the diamond films grown, such as pressure ranging from 40 to 100 torr, methane concentration in hydrogen varying from 0.5 to 2 vol %, and substrate temperatures from 1020 to 1140 °C, were studied. Diamond films with nanocrystalline to polycrystalline crystal sizes were obtained. A maximum growth rate of 0.8 μm/h was obtained, and the quality is comparable to diamond films synthesized by the hot metal filament chemical vapor deposition method. In contrast to the hot filament method, this method does not use a metallic filament as thermal activator. Therefore, the diamond films contain no metal contaminants and thus can be used for electronic and biomedical applications. The absence of metal contaminants was confirmed using different methods.

It is challenging to develop a material that combines good mechanical properties and high translucency since these properties are generally not coincident in one material. In this study, we prepared ZrO2-SiO2 nanocrystalline glass-ceramics that combines the above two types of properties. Raw powder with 55 mol%, 65 mol%, and 75 mol% ZrO2 and each with 5 mol% yttrium as a dopant was prepared by sol-gel method, followed by spark plasma sintering to obtain dense glass-ceramics. XRD results demonstrated that the glass-ceramics with 65 mol% and 75 mol% ZrO2 were composed of tetragonal-ZrO2, whereas, that with 55 mol% ZrO2 was composed of cubic-ZrO2. The as-sintered glass-ceramics showed black/brown discoloration, but they obtained high translucency after thermal treatment. X-ray energy-dispersive spectrometry (EDS) results in scanning electron transmission microscopy (STEM) mode demonstrated yttrium dopants were predominately distributed in ZrO2 nanocrystallites. The glass-ceramics with 65 mol% ZrO2 had the highest flexural strength, achieving an average value of 673 MPa. The glass-ceramics with different compositions sintered at different temperatures showed fracture toughness values ranging from 5.25 MPa m1/2 to 6.69 MPa m1/2. The strong and translucent ZrO2-SiO2 nanocrystalline glass-ceramics showing great protentional to be used in many fields.

From the perspective of high-temperature applications, materials with excellent high-temperature mechanical properties are always desirable. The present work demonstrates that the binder-free nanopolycrystalline WC ceramic with an average grain size of 103 nm obtained by high-pressure and high-temperature sintering exhibits excellent mechanical properties at both room temperature and high temperature up to 1000 °C. Specifically, the binder-free nanopolycrystalline WC ceramic still maintains a considerably high Vicker hardness HV of 23.4 GPa at 1000 °C, which is only 22% lower than the room temperature HV. This outstanding thermo-mechanical stability is superior to that of typical technical ceramics, e.g. SiC, Si3N4, Al2O3, etc. Nanocrystalline grains with many dislocations, numerous low-energy, highly stable Σ2 grain boundaries, and a relatively low thermal expansion coefficient, are responsible for the observed outstanding high-temperature mechanical properties.

In this work, we investigated the influence of Chromium (Cr) concentration 1.5 wt%Cr- 3.5 wt%Cr on the properties of zinc oxide (ZnO) thin films deposited by Dip-Coating technique. The structural, morphological and electrical properties of the obtained thin films are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and by electrical measurements for testing solar cell performances. It was found that the doped films become more amorphous by increasing Cr concentrations. As a result, the surface morphology of ZnO thin films exhibits the formation of different structures of: nanofibers, nanofibrils and nanorods clearly distributed inside ZnO cells. Moreover, it was also observed that the n-type ZnO is inverted to p-type for 1.5 and 2.5 wt%Cr. The most suitable electrical parameters for this study were obtained for 1.5 wt%Cr doped ZnO solar cells and for 2.5 wt%Cr doped ZnO with an efficiency of 24.32% and 22.43%, respectively.

This report demonstrates high temperature sealing tendency of alumino-silicate glasses (ASG) on the system SiO2-MgO-Al2O3-B2O3-K2O-MgF2 doped with silver (Ag) and gold (Au) nanoparticles. Density of the melt-quenched (1550 °C) glasses were in 2.51–2.55 g.cm−3. The glasses were heat-treated at 900 ± 10 °C over which the opaque glass-ceramics were obtained with major crystalline phase (XRD) fluorophlogopite mica [KMg3(AlSi3O10)F2] with secondary phase norbergite (Mg2SiO4.MgF2). FESEM study indicated the development of Rod-like and rock-like crystallite particles (size ∼1–4 µm) randomly dispersed in mother glass–ceramic which was restructured into nanocrystalline morphology (crystallite size ∼100–400 nm) with the aid of Ag- or Au- nanoparticles. The significant change in microstructure influenced the corresponding density (2.51–2.55 g.cm−3) and thermal expansion characteristics. Coefficient of thermal expansion (CTE) for ASG was estimated to be 9.96 ± 0.10×10−6/K (50–800 °C), which increased to 10.46–11.01×10−6/K when doped with Ag- or Au- content. Such wide CTE (11.01 ± 0.11×10−6/K) value matches well with the CTE of ceramic/metallic materials used for high temperature application thus Ag- doped SiO2-MgO-Al2O3-B2O3-K2O-MgF2 glass can be a suitable for high temperature sealing application (like SOFC).

The present work reports the structural, morphological, and optical analysis of rare earth metal ion (Nd3+) doped Titanium Dioxide Nanoparticles. Titanium Dioxide doped with Neodymium ions (1 wt% and 4 wt%) have been studied by X-ray diffraction (XRD) Aanlysis, High Resolution Transmission Electron Microscopy (HR-TEM) analysis, Energy Dispersive X-ray Analysis (EDAX), Ultraviolet–visible (UV–Vis) spectroscopic analysis. The powder X-ray diffraction patterns ensured the nanocrystalline anatase formation of all the samples. The morphology and particle size of the TiO2 host matrix were confirmed by High Resolution Transmission emission electron microscopy (HR-TEM). The particle size trend obtained from HR- TEM images is acceptable with the crystal size obtained from XRD results. Ultraviolet–visible measurements were carried out to investigate the optical properties of our powdered titania. The dye sensitized solar cells were fabricated with these as-synthesized materials as the photoanode and the J-V measurement shows improved high open circuit voltage, short circuit current and high efficiency achieved.

AlN ceramic was successfully wetted and then joined with nonactive Sn9Zn eutectic solder assisted by ultrasonication in air. The effect of ultrasonic time on the formation of joint was studied. Results indicated that the defect-free joint can be obtained at an ultrasonic time of 5 s. Two regions, namely, AlN/Sn (s,_s) and AlN/Zn (s,_s), were found in the bonding interface. Zn and O accumulated in the AlN/Sn (s,_s) interface. An amorphous and nanocrystalline layer of ZnO formed in the hard-wet AlN surface. And Zn (s,_s) directly bonded with AlN. The low temperature and fast bonding of the AlN was attributed to the high pressure and temperature caused by cavitation effect. The shear strength of the joint increased from 10.6 MPa to 30.7 MPa when the ultrasonic treatment time increased from 5 s to 150 s. With the prolongation of ultrasonic time, more AlN ceramic particles entered the solder and acted as the reinforcing phase.

Utilizing eggshells to synthesize a value added product like nanocrystalline hydroxyapatite (HA) has received a lot of attention from researchers since they are composed of CaCO3 with biologically essential trace elements such as Mg, Si, etc. Different biomedical applications need HA with appropriate nanoscale characteristics like crystallinity, particle size, morphology, surface area, mesoporous nature, etc. The same can be achieved by tuning the reaction parameters, choosing a suitable mode of preparation and utilizing organic modifiers. Here, we report the rapid synthesis of eggshell derived HA in the presence different organic modifiers using a custom built microwave reactor employing the previously optimized parameters. The synthesis process is relatively rapid and gets completed in 5 min. The absence of an organic modifier yielded inhomogeneous size nanorods in the range of 40 – 600 nm. Ethylenediaminetetraacetic acid (EDTA) assisted synthesis resulted in a flower like 1.67 ± 0.12 μm sized HA. Whereas polyethylene glycol 6000 (PEG) and cetyltrimethylammonium bromide (CTAB) assisted synthesis produced aggregated nanorods of length 31 ± 8 and 68 ± 20 nm, respectively. While the synthesis with trisodium citrate dihydrate (TSC) resulted in needles of HA with typical length of 32 ± 8 nm. Presence of Na, Mg and Si trace elements are confirmed from the composition analysis. All the samples are found to be mesoporous in nature. The in vitro cell culture experiment carried out using fibroblast NIH 3T3 cell line clearly revealed equal or higher cell viability for the samples synthesized in presence of organic modifiers as compared to sample produced without organic modifier. Thus, from the present study we find that the synthesis of eggshell derived HA using different organic modifiers via a custom built microwave reactor can be a potential approach for the rapid preparation of precursor materials with suitable nanoscale characteristics for developing bone fillers, drug/protein delivery carriers, tissue engineering scaffolds, etc.

Aiming to gain insight on the hydrogen storage properties of Mg-based alloys, partial hydrogenation and hydrogen pressure related de-/hydrogenation kinetics of Mg–Ni–La alloys have been investigated. The results indicate that the phase boundaries, such as Mg/Mg2Ni and Mg/Mg17La2, distributed within the eutectics can act as preferential nucleation sites for β-MgH2 and apparently promote the hydrogenation process. For bulk alloy, it is observed that the hydrogenation region gradually grows from the fine Mg–Ni–La eutectic to primary Mg region with the extension of reaction time. After high-energy ball milling, the nanocrystalline powders with crystallite size of 12∼20 nm exhibit ameliorated hydrogen absorption/desorption performance, which can absorb 2.58 wt% H2 at 368 K within 50 min and begin to desorb hydrogen from ∼508 K. On the other side, variation of hydrogen pressure induced driving force significantly affects the reaction kinetics. As the hydrogenation/dehydrogenation driving forces increase, the hydrogen absorption/desorption kinetics is markedly accelerated. The dehydrogenation mechanisms have also been revealed by fitting different theoretical kinetics models, which demonstrate that the rate-limiting steps change obviously with the variation of driving forces.

A study of the structural, Raman scattering and thermodynamic properties of a nanocrystalline ceramic rare earth oxide Yb2O3 and its bulk counterpart is reported. The nanosized sample was obtained by mechanical milling of bulk Yb2O3 (99.998%, high purity powder). The Rietveld analysis of the X-ray diffraction data indicates the presence of nanoparticles with a mean grain size of 12 ± 1 nm after 75 h of milling time. The crystallographic structure within nanoparticles is cubic Ia-3 and the lattice parameter a = 10.455 ± 0.002 A. The nanocrystalline structure is confirmed by the evaluation of transmission electron microscopy images, showing a size distribution with a mean size DTEM = 8 ± 2 nm. Measurements of the specific heat (2 K–300 K) reveal an excess contribution respect to the unmilled (bulk) compound in the high temperature region above 70 K. At lower temperatures the results are consistent with a drastic change of the antiferromagnetic contribution (ordered below TN = 2.2 K) as a result of the magnetic disorder arising from the size reduction process. The specific heat above TN for the bulk and nanocrystalline samples are explained by the interplay among the phonon contribution, crystalline field and the presence of anharmonic effects. In the nanocrystalline state, broadening and shifts of the contribution of phonon modes to the Raman spectra, and a further reinforcement of the anharmonic contribution are found.