Reduction In Crystallite Size Research Articles

The novel Carbon Nanotube-assisted development of highly porous CaZrO3-CaO xerogel with boosted sorption activity towards high-temperature cyclic CO2 capture

Herein, for the first time, we employed three minor concentrations of Carbon Nanotubes (CNT), 2.5, 5, and 10 wt.%, as an auxiliary additive to boost the textural and structural features and CO2 capture potential of sol–gel-derived CaZrO3-CaO adsorbents. The corresponding xerogels were developed with 15/1 and 30/1 Ca/Zr molar ratios to minimize the required amount of prohibitive Zr-based precursor. For both types of CaZrO3-CaO xerogels, 5 wt.% of CNT was recognized as the most efficient amount. In addition to 15.84 and 33.1% reduction in CaO crystallite sizes, 50.57 and 90.55% increments in pore volume values were reported for CaO-based adsorbents developed with 15/1 and 30/1 Ca/Zr molar ratios, respectively. Over 15 cycles under harsh CO2 capture conditions, the total amount of captured CO2 for both abovementioned types of CaO-CaZrO3 xerogels raised from 2.01 and 1.96 to 2.92 and 3.01 g CO2/g adsorbent, sequentially. CaZrO3-promoted CaO nanoadsorbents merged with 5 wt.% CNT showed the ultimate CO2 capture capacity of 0.164 and 0.149 g CO2/g adsorbent for xerogel prepared with 15/1 and 30/1 M ratios of Ca/Zr, respectively. Even though the xerogel containing a Ca/Zr molar ratio of 15/1 showed the best sorption durability and ultimate capture capacity, CNT more significantly affects the CaO-based xerogel developed with a Ca/Zr molar ratio of 30/1. It can be deduced that the low content of CNT notably contributes to develop highly efficient and fluffy-like promoted xerogels containing minor concentrations of CaZrO3 species.

Enhanced optoelectrical performance of ultraviolet detectors based on self-assembled porous zinc oxide nanostructures

A templated self-assembly technique was utilized in the present study to grow porous zinc oxide nanostructures. The nanostructures were formed by the electrochemical deposition of ZnO through the interstitial spaces between polymer microsphere templates. After the deposition, polymer microspheres were removed by dissolving in chloroform solvent, leaving porous ZnO nanostructures. This technique is benefited from facile controllability of the pore morphology and size by varying the diameter of microspheres. X-ray diffraction analysis showed a dominant peak corresponding to the hexagonal ZnO structure. Moreover, no significant structural strain was observed after the removal of spheres unlike the other synthesis methods of porous materials. The improved photoluminescence (PL) properties revealed an enhancement in the light capturing capability of the systems due to the multiple scattering of light in the pore walls. The porous sample showed a PL blue-shift compared to the flat one, indicating a reduction in crystallite size of ZnO nanostructures. To assess the photonic applications of synthesized porous ZnO substrates, a metal-semiconductor-metal photodetector was developed via the metallization of ZnO nanostructures, and their optoelectrical properties were tested under UV radiation. The results showed an improvement in photosensitivity and quantum efficiency of devices based on porous ZnO substrates which can be assigned to the larger exposed area and elevated rates of electron-hole generation in this sample.

Manufacturing Bulk Nanocrystalline Al-3Mg Components Using Cryomilling and Spark Plasma Sintering.

In the current study, pure aluminum (Al) powders were cryomilled with and without 3 wt.% pure magnesium (Mg) dopant for varying durations followed by spark plasma sintering (SPS) of powders to prepare bulk components with superior mechanical properties. The crystallite sizes were determined for powders and the bulk components by analyzing the X-ray diffraction (XRD) spectrum. The calculations indicated a reduction in crystallite size with the increase in the cryomilling duration. The results also showed a more significant decrease in the crystallite sizes for Al-3Mg samples than that of pure Al. The changes in the surface morphology of powders were characterized using scanning electron microscopy (SEM). The elemental mapping analysis at nanoscale was carried out using Energy-dispersive X-ray spectroscopy (EDX) in Scanning transmission electron microscopy (STEM). The mechanical properties of the bulk components were assessed using a Vickers Microhardness tester. The test results demonstrated an improvement in the hardness of Mg-doped components. Higher hardness values were also reported with an increase in the cryomilling duration. This article discusses the mechanisms for the reduction in crystallite size for pure Al and Al-3Mg and its subsequent impact on improving mechanical properties.

GaN nanostructure for hydrogen gas sensor

The growth of heterostructure of n-type GaN/AlN/Si(111) is carried out using the molecular beam epitaxy (MBE) Veeco model Gen II system. The surface morphology of the as-grown GaN sample showed pits on the GaN surface in a ratio small than those found by other research groups. Porous GaN samples were synthesized by an electrochemical etching technique combined with increasing the current density to 75 mA/cm2. The formation of pore structures are of different sizes, the etched surface became hexagonal, and pore structures are confined to a smaller size. The PL results showed greater blue shift luminescence in comparison to results found by other research groups. The reduction in crystallite size is confirmed by an increase in the broadening of XRD spectra. Raman spectra also displayed a strong band at 522 cm−1 from the Si(1 1 1) substrate, and a small band at 301 cm−1. These are due to the acoustic phonons of Si. Two Raman active optical phonons are assigned to h-GaN at 139 cm−1 and 568 cm−1, due to E2 (low) and E2 (high) respectively. The sensitivity of the gas sensor is increased as a function of the hydrogen flow rate and they became much higher compared to the as-grown sample.

Grain size effect on electrical properties of Ag6PS5I-based ceramic materials

Micro- and nanocrystalline powders were prepared by grinding of pre-synthesized Ag6PS5I in an agate mortar and a planetary ball mill, which were further investigated using XRD and SEM methods. Appropriate ceramic materials in the form of disks with a relative density of (91…94) ± 1% of the theoretical one were made using the cold pressing method for the obtained powders with subsequent annealing at the temperature 923 K. The values of the ionic and electron components of the total electrical conductivity were obtained analyzing the corresponding frequency dependences of the total electrical conductivity on the Nyquist plots using electrode equivalent circuits. It has been ascertained that reduction of crystallite sizes in Ag6PS5I-based ceramic materials leads to a slight increase in ionic conductivity and a significant increase in the electronic one, resulting in a decrease of the ratio between them.

Construction of zinc-cobalt alloy film by supercritical-CO2 electrodeposition pathway: Evaluation of electrochemical robustness

• Zn-Co alloy film was prepared by supercritical-CO 2 electrodeposition pathway. • The higher incorporation of cobalt significantly improves the corrosion resistance. • Cobalt act as an inhibitor in the alloy coating. • The inhibition of coating is 27.6 % increase in the supercritical-CO 2 process. Supercritical-CO 2 (SC-CO 2 ) approach to the electrodeposition process has received significant attention due to its advantages, such as low surface tension, high diffusivity, and permeability. These properties can even replace the role of toxic additives and surfactants. Here in, we demonstrated the green fabrication of zinc-cobalt (Zn-Co) alloy film by SC-CO 2 electrodeposition process and explored its electrochemical performance. The prepared films were characterized by various micro-and spectroscopic analyses. Based on the results, the SC-CO 2 method prepared films show a compact structure with reduced crystallite size and 27.6 % improved corrosion resistance than the conventional method.

The synergistic role of Ni-Co bimetallic catalyst for H2-rich syngas production via glycerol dry reforming

A by-product of biodiesel manufacturing, glycerol, is known for its potential to generate syngas via the glycerol dry reforming (GDR) reaction. This study evaluates monometallic and bimetallic Nickel–Cobalt (Ni–Co) (with 15%Co, 3%Ni–12%Co, 4.5%Ni-10.5%Co, 7.5%Ni-7.5%Co, 10.5%Ni-4.5%Co and 15%Ni loading) on Alumina (Al2O3) support extracted from aluminium dross. The catalysts were prepared using an ultrasonic-assisted impregnation process and used in GDR at temperatures ranging from 873 to 1173 K at stoichiometric feed ratio. Analyses result showed that the diluting impact of Ni–Co bimetallic precursors resulted in a reduction of metal crystallite size and improved H2 and CO2 uptake. The conversion of glycerol and product yield were in the order of 3%Ni–12%Co/Al2O3 > 4.5%Ni-10.5%Co/Al2O3 > 7.5%Ni-7.5%Co/Al2O3 > 10.5%Ni-4.5%Co/Al2O3 > 15%Co/Al2O3 > 15%Ni/Al2O3, with 3%Ni–12%Co/Al2O3 having values of 75.6%, 64.7% and 44.8%, for glycerol conversion, H2 and CO yield respectively. All catalysts achieved product ratios ranging from 1.20 to 1.44. The high oxygen vacancies in Ni–Co bimetallic catalysts aided the reduction of carbon formation. Enhanced Ni–Co particles dispersion on Al2O3 support reduced the agglomeration of metal particles, thus, creating smaller crystallite size. The changes in binding energy peaks of Ni and Co were indicative of strong electronic interaction which created Ni–Co bimetallic alloys. 3%Ni–12%Co was regarded as the best catalyst for this study since it was effective in enhancing the conversion of glycerol and product yield.

Sharp luminescence system in titanium dioxide with zero-phonon transition at 1.573 eV

In this paper, we discuss near-IR steady-state and time-resolved low-temperature (5 K) luminescence of crystalline titanium dioxide (TiO2) powders with different particle sizes. Upon optical excitation with quantum energy close to 3.1 eV, the near-IR luminescence of all the powders reveals a very similar characteristic spectrum, which includes a narrow 1.573 eV line, a set of wider peaks in 1.565–1.545 eV range, and a broad band at ∼1.42 eV. The spectrum remains unchanged when using different excitation quanta, thus indicating that all components are governed by the same luminescence system. It is also confirmed by identic two-exponential luminescence decays with characteristic decay times 70 μs and 400 μs observed for all parts of the spectrum. The properties of the luminescent system are not sensitive to the crystallite size reduction to 10 nm, and its intensity sharply increases after annealing converting the anatase phase into rutile. A comparison of the spectrum with TiO2 phonon density of states indicates that 1.573 eV peak is a zero-phonon transition, and 1.545–1.565 eV structure is due to interaction with bulk phonons of rutile phase. The band at 1.42 eV seems to be due to non-adiabatic electron-phonon coupling. The data obtained clearly indicates that the luminescent system is governed by inner shells of transition elements located in rutile lattice. This transition element can be vanadium as it follows from ICP-MS data and theoretical modeling. The detected luminescent system provides a convenient optical marker of TiO2, including nanoform, and thus can be useful for some applications related to medicine, biology, as well as the food industry.

ZnO nanoparticles and compositional dependence of structural, thermal, mechanical and electrical properties of eutectic SAC355 lead-free solder

Purpose This paper aims to summarise the effects of ZnO nanoparticles (0.1, 0.3, 0.5, 0.7 and 1.0 Wt.%) on the structure, mechanical, electrical and thermal stability of Sn–3.5Ag–0.5Cu (SAC355) solder alloys for high-performance applications. Design/methodology/approach The phase identification and morphology of the solders were studied using X-ray diffraction and scanning electron microscopy. Thermal parameters were investigated using differential scanning calorimetry. The elastic parameters such as Young's modulus (E) and internal friction (Q−1) were investigated using the dynamic resonance technique, whereas the Vickers hardness (Hv) and creep indentation (n) were examined using a Vickers microhardness tester. Findings Microstructural analysis revealed that ZnO nanoparticles (NPs) were distributed uniformly throughout the Sn matrix. Furthermore, addition of 0.1, 0.3 and 0.7 Wt.% of ZnO NPs to the eutectic (SAC355) prevented crystallite size reduction, which increased the strength of the solder alloy. Mechanical parameters such as Young's modulus improved significantly at 0.1, 0.3 and 0.7 Wt.% ZnO NP contents compared to the ZnO-free alloy. This variation can be understood by considering the plastic deformation. The Vickers hardness value (Hv) increased to its maximum as the ZnO NP content increased to 0.5. A stress exponent value (n) of approximately two in most composite solder alloys suggested that grain boundary sliding was the dominant mechanism in this system. The electrical resistance (ρ) increased its maximum value at 0.5 Wt.% ZnO NPs content. The addition of ZnO NPs to plain (SAC355) solder alloys increased the melting temperature (Tm) by a few degrees. Originality/value Development of eutectic (SAC355) lead-free solder doped with ZnO NPs use for electronic packaging.

Enhanced bacterial inhibition and photocatalyzed degradation of industrial contaminants by polyethylene glycol capped PbWO4 nanoparticles

Lead tungstate nanoparticles (PbWO4 NPs) and PEG capped PbWO4 nanoparticles (PEG/PbWO4 NPs) were synthesized by co-precipitation technique. Vibrational, structural, optical and morphological properties of the as-prepared nanoparticles were observed by FTIR, XRD, UV-vis and SEM techniques. These nanoparticles show a tetragonal stolzite crystalline structure. The quantum confinement of nanoparticles was confirmed by UV-vis spectrum. Since polymeric modifying agent, polyethylene glycol (PEG) performs as a stabilizer and also helped to unite the surface of the PbWO4 NPs. FTIR established the functional groups in PEG united with the PbWO4 NPs and reduction took place in the reaction medium. The adsorbed PEG onto the PbWO4 NPs initiated the negative charge onto the particle surface and thus repelled the particles away from one another, hindering them from aggregation. The formation of quasi-octahedrons was confirmed from SEM images. The consequences of the antimicrobial study prove that the better capability of PEG/PbWO4 NPs to inhibit the growth of Staphylococcus aureus, Pseudomonas aeruginosa, and Aspergillus niger. This study signified that PEG is an effective surfactant for morphology control, reduction of crystallite size, photocatalytic degradation of methyl orange and antimicrobial activity of PbWO4, maybe because of the steric impediment it grants.

The effect of Zr (IV) doping on TiO2 thin film structure and optical characteristics

Dense thin films of TiO2 and TiO2 doped with Zr4+ were spin coated on glass substrate and annealed at 450 °C. The optical characteristics and crystalline structure were studied using UV–vis, PL, XRD, and SEM. X-ray investigation proved that an anatase phase was formed in all Zr-doped samples (0, 0.5, 1, 5, and 10 %). Zr-doping changes the band gap energy from Eg = 3.48 eV (undoped) to 3.57 eV (1 % doping), along with the large size of Zr4+ results in slight lattice enlargement. Increasing Zr-doping beyond 1.0 % is associated with decreasing the band gap due to amorphization of TiO2. The anatase crystallites growth is stalled with increasing doping; from 23.5 nm to 10.43 nm and micro-strain increases with increasing doping concentration. The changes in optical properties, crystal growth and structure properties are due to lattice strain created by the collective effect of Zr-doping and reduction in crystallite size. Zr-doped TiO2 nanoparticles exhibited typical photoluminescence (PL) matching to the visible spectrum region when excited at 275 nm. The produced thin films had a lower rate of electron–hole recombination than TiO2 that was not doped.

Steam-modified sol-gel method for TiO2-based nanosized particles

TiO 2 -based nanoparticles were synthesized using a steam-modified sol–gel method. Water, acting as the reactant was sprayed as steam into an organic solvent containing a precursor. Each droplet of water acted as a small volume of reactant in the hydrolysis reaction. Titanium isopropoxide was used as a metal alkoxide precursor to synthesize TiO 2 and CeO 2 /TiO 2 . The crystallite size reduction of the particles obtained by this steam-modified sol–gel method was confirmed by peak broadening, and the crystallite size was calculated using Rietveld refinement. The crystal sizes observed via transmission electron microscopy (TEM) imaging agreed with results obtained from Rietveld refinement. The particle size of TiO 2 synthesized using the water method was 31.4 nm, that of TiO 2 synthesized using the steam method was 8.62 nm, CeO 2 /TiO 2 synthesized using the water method was 13.58 nm, and that of CeO 2 /TiO 2 synthesized using the steam method was 7.21 nm. Scattering signals of TiO 2 water and CeO 2 /TiO 2 water were not observed; TiO 2 synthesized with the steam method showed a size distribution centered at 8.55 nm when measured by small-angle X-ray scattering (SAXS), whereas CeO 2 /TiO 2 synthesized using the steam method showed a particle-size average of 7.16 nm. The size measured by SAXS was similar to the size results obtained by Rietveld refinement and the particle-size analysis using TEM imaging. Each particle formed through steam hydrolysis comprised one crystal, indicating that each particle was a complete crystal. The change in the electronic structure with different water addition processes was confirmed by X-ray absorption near edge structure (XANES).

Defect mediated structural, optical, electrical and mechanical properties of mechano-synthesized PbTe nanostructure as a superior thermoelectric material: Correlation among electrical, mechanical and optical properties

This work reports on the formation of anti-site defects in mechanically alloyed PbTe samples and their anomalous effects on the optical and electrical properties of the sample. PbTe nanoparticles have been synthesised by mechanical alloying of the elemental Pb and Te powders mixed in stoichiometric ratio under an inert (Ar) atmosphere for different time durations. The structural and microstructural characterisations have been carried out by analysing X-ray diffraction (XRD) patterns, field-emission scanning electron microscope (FESEM), and high-resolution transmission electron microscope (HRTEM) images. The elemental composition has been revealed from the energy-dispersive X-Ray (EDX) spectrum. The phase pure cubic PbTe is formed within just 30 min of milling. The Rietveld analysis of XRD patterns, FESEM, and HRTEM images revealed the crystallite size reduction and the increase in r.m.s. lattice strain with the increase in milling durations. Inclusions of more and more anti-site defects of type [PbTe] with increasing milling time are reflected in the expansion of the cubic lattice parameter with milling durations. Fourier-transform infrared (FTIR) spectrum reveals that PbTe is a narrow bandgap semiconductor, and the bandgap shows a redshift with increased milling time and reduced crystallite size. This anomalous behaviour of the optical bandgap with reduced particle size is well explained by Urbach tailing due to increased defects in the more extended milled sample. The positions of the conduction and valence bands in the milled PbTe samples are determined for different milling times. The DC conductivity study also shows anomalous behaviour; electrical conductivity increases with particle size reduction in more extended milling time samples. It is resolved by considering that the carrier concentration increases with a longer milling time due to induced anti-site defects while milling. It results in bandgap reduction with milling durations and shows the predominant effect of electronic conductivity over ionic conductivity. The conduction mechanism is explained as per the Pertritz model, and the dependence of activation energies on particle size and temperature has been explained in detail. The Vickers hardness of the milled samples is determined, and its variation with grain size is explained with the Hall-Petch relation. The improved electrical conductivity with increased milling is also manifested in the measured hardness values.

Shockwave impact on the stability of anatase titania nanoparticles

The stability of anatase titania nanoparticles was investigated under exposure to repeated loading of shockwaves produced in a diaphragm-driven high-pressure shock tube. The titania samples were exposed to 20 shocks with pressure, temperature, and steady exposure time in the range of 20.5 – 26 bar, 1399 – 2101 K, and 1.74 – 1.83 ms, respectively. The crystal structure and surface morphology were analyzed before and after the shockwave treatment using various characterization techniques. After repeated shock exposure, there was reduction in crystallite size by ~ 40%, modification in the surface charge, and an increase in the hydroxyl groups in titania. The onset of phase transformation from anatase to rutile was observed after 20 shocks. This work gives insights into the structural changes induced by shockwaves in anatase nanoparticles which can help improve their performance as a catalytic support in heterogeneous catalysis.

Existence of Ti3+ and dislocation on nanoporous CdO–TiO2 heterostructure applicable for degrading chlorophenol pollutant

This study addresses the significance of wastewater recuperation by a simple and facile treatment process known as photocatalyst technology using visible light. Titanium di-oxide (TiO2) is the most promising photocatalyst ever since longing decades, has good activity under UV light, owing to its small band gap. Hence, TiO2 has been modified with metal oxides for the positive response against visible light. Since this is an efficient process, the novelty has been made on nanometal oxide CdO (cadmium oxide) combined with TiO2 to acquire the best efficiency of degrading organic chlorophenol contaminant. Initially, the composites were synthesized by sol-gel and thermal decomposition methods and investigated for their various outstanding properties. The characterized outcomes have exhibited heterostructures with reduced crystallite size from the X-ray diffraction studies. Then, the determination of nanoporous feature was recognized through HR-TEM analysis which was also detected with some dislocations. The EDX spectrum was identified the perfect elemental composition. The nitrogen adsorption-desorption equilibrium was attained that offers many pores measured with high surface area. The XPS result convinced that Ti3+ was accessible along with TIO2/CdO composite. Further the absorption towards higher wavelength was obtained from UV–vis spectra. Finally, for the photocatalytic application of chlorophenol, the composite shows higher percentage of degrading efficiencies than the pristine TiO2. The photocatalytic mechanism was discussed in detail.

Synthesis and Characterization of Zinc Oxide Nanoparticles Using Thermophilic Bacteria Isolated from Arid Region of Rajasthan

AbstractFour bacterial strains were used for biosynthesis of zinc oxide (ZnO) nanoparticles (NPs), namely Bacillus tropicus SHJP5, Bacillus tropicus LKJP6, Aeribacillus composti SJP25, and Aeribacillus pallidus SJP28. The synthesized nanoparticles were characterized using UV‐Visible spectroscopy (UV‐Vis), Fourier transform infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Photoluminescence spectroscopy (PL), Thermogravimetric analysis (TGA), and X‐ray diffraction (XRD). The XRD pattern of NPs (bio‐synthesized) shows the polycrystalline hexagonal wurtzite structure with the three major planes (100), (002), and (001). The average crystallite size determined by the Debye‐Scherrer equation is between 8–54 nm. A reduction in crystallite size of as‐prepared nanoparticles was observed in the presence of bacterial strains. The FTIR analysis reveals the amide, carboxyl, and hydroxyl groups found on the surface of biosynthesized ZnO NPs. These groups behave as reducing and stabilizing agents. The UV‐Vis spectra reveal the absorption bands for control, SHJP5, LKJP6, SJP25, and SJP28 at 373, 363, 382, 358, and 380 nm respectively. The corresponding energy band gap was found to be 3.324, 3.415, 3.246, 3.463, and 3.263 eV respectively, with the decreasing size of the nanoparticles produced by bacterial strains. The FESEM analysis confirms the hexagonal structure of bio‐synthesized ZnO NPs. The nanoparticles have a uniform distribution of spherical shape except for the strain Aeribacillus pallidus LKJP6 which exhibits uniform and thin nanorods. Minimum inhibitory concentration (MIC) tests against E. coli (7.1 mg/ml) and S. aureus (3.2 mg/ml) verified the antibacterial activity of produced ZnO NPs. The use of isolated strains for the extracellular manufacture of ZnO NPs is encouraged in this work. To the best of our knowledge, this might be the first study that has been presented that shows the structural, optical, and surface morphology of a thermophilic bacterium, Bacillus tropicus SHJP5, Bacillus tropicus LKJP6, Aeribacillus composti SJP25, and Aeribacillus pallidus SJP28 for the biosynthesis of ZnO NPs in particular.

Synergistic effect of Urea and Potassium Sulphate during hydrothermal synthesis of NiO nanospheres with reduced crystallite size and enhanced electrical conductivity

Nickel oxide (NiO) nanoparticles (NPs) have been synthesized using a high-yield, efficient hydrothermal technique. Investigations have been done to study the effect of the alkaline environment provided by Urea and Potassium Sulphate on the structural, optical and electrochromic properties of NiO nanoparticles. Hydrolysis of Urea provides an alkaline environment that controls the formation of NiO precipitate. SO42- ions in Potassium Sulphate create active sites on the surface of Ni(OH)2 leading to better absorption of Ni2+ and OH– ions. Present study shows that Urea and Potassium Sulphate act synergistically as structure directing/ complexing agents in the formation of NiO nanoparticles. FESEM studies of the NiO particles depict a spherical morphology with an average crystallite size of 7 to 11 nm as calculated using XRD. The process of charge transfer in electrodes, diffusion of molecules and ions within the electrolyte and adsorption of ions on an electrode surface has been explored using Cyclic Voltammetry and Electrochemical Impedance Spectroscopy. The carrier lifetime has been observed as 5–7 μs, upon fitting the exponential decay curve of TRPL. So, lower charge transfer resistance, higher carrier lifetime and uniformly distributed nanoparticles are indicative of the material to offer better electrical conductivity for enhanced performance in solar cells and electrochromic applications.

Evolution of electrical, superconducting, crystallinity and structural features with aliovalent Nd/Sr replacement in Bi-2223 ceramics

This paper blazes the trail for the understanding of fundamental characteristic features for Bi-2223 ceramic with aliovalent Nd/Sr replacement in Bi1.8Pb0.35Sr1.9-yNdyCa2.2Cu3Ox superconducting matrix (0.00 ≤ y ≤ 0.10). Full characterization of superconductors is performed by conventional experimental methods, viz. X-ray diffraction (XRD), dc electrical resistivity based on temperature (ρ-T), electron dispersive X-ray (EDX) and scanning electron microscopy (SEM) examinations. Measurement results display that the trivalent Nd+3 ions may partially be substituted by Sr+2 impurities in the Bi-2223 crystal structure. EDX results illustrate that the local elemental composition distributions of Nd atoms increase systematically depending on substitution level. However, it is noted that the replacement mechanism damages seriously fundamental electrical, superconducting, crystallinity and structural features. Dc electrical findings present that the superconducting and electrical properties reduce remarkably with the increment of aliovalent Nd/Sr substitution due to deviation in the mobile holes, inhomogeneities of oxidation states in the copper-oxide layers, and formation of new internal and microscopic problems in the crystal system, confirmed by SEM examination. Besides, the characteristic transition temperatures diminish harshly from 116.59 K to 108.74 K for onset and 108.40 K until 78.81 K for offset transition temperature. The dramatic decrements stem from the degradation in bipolaron formations in the superconducting clusters, phonon modes and especially the gap coefficient. Similarly, the presence of Nd impurity damages the amplitude of pairing wave function. In fact, at maximum replacement level the ceramic compound exhibits a slight trace of pseudo-critical transition. The XRD results indicate that both the appearance or disappearance of characteristic diffraction peaks and the reduction of average crystallite size and c lattice cell constant confirm the reduction of high-Tc superconducting phase due to the suppression in the structural quality. The SEM pictures indicate that the appearances of surface morphology and crystallinity quality remarkably deteriorate depending on Nd/Sr replacement level as a consequence of non-uniform grain alignment distributions, structural problems, microvoids, internal defects, porosity, misoriented grain coalescences and microcrystals in the superconducting system. Additionally, the negative effect of Nd/Sr substitution is extensively discussed on the activation energy for the crystallization, thermodynamic stability, reaction kinetics, surface nucleation and growth mechanisms for the first time.

Effects of silica nanoparticles addition on formation of oxide layers on Al[sbnd]Si alloy by plasma electrolytic oxidation: The origin of stishovite under ambient conditions

The effects of different amorphous silica nanoparticles (NPs) with average particle size of 48 nm – n−SiO2(48) and 100 nm – n−SiO2(100) added to the electrolyte under plasma-electrolytic oxidation (PEO) of AlSi alloy 361.0 (9.8 wt. % Si) on the oxide layers structure, phase composition and properties were investigated. Unexpected formation of high pressure (HP) SiO2-phase – stishovite was detected in the oxide layers formed using n−SiO2(48) under ambient conditions. This HP-phase was not detected while using n−SiO2(100) and the electrolyte without nanoparticles. It was found that the addition of the n−SiO2 resulted in significant increase in the oxidizability, and, accordingly, in the thickness of the PEO-formed oxide layers, their wear resistance (by ~1.5 times) and thermal resistivity (by ~4 times) as compared to the oxide layers obtained without NPs. It also resulted in crystallite size reduction and an increase of the amorphous phase fraction, both effects are more pronounced while using n−SiO2(48) despite the equal initial concentrations of the nanopowders in the electrolyte (3 g/l). To explain these effects, a novel approach to the NPs/oxide layer interaction and the corresponding quantitative model were introduced. The interaction was considered as the colliding with the rigid oxide layer surface of rapidly moving charged NPs accelerated by electric field in the vapour-gas bubbles (VGB) formed in porous channels prior micro-arc discharge. During elastic/inelastic collision, the particle kinetic energy transforms to compressive strain energy, heating of the particle and/or to kinetic energy of the bounced off particle providing different interaction scenarios depending on the particle size. The developed model makes it possible to predict the HP SiO2-phase formation, an increase in the fraction of amorphous phases and reduction in the crystallite size in the PEO-formed layers in the presence of NPs, which can result in improvement of protective and mechanical properties of the layer.

Ultrahigh-energy-density dielectric materials from ferroelectric polymer/glucose all-organic composites with a cross-linking network of hydrogen bonds

Polymer dielectrics have been widely used for capacitive energy storage. However, the volumetric energy density of polymer dielectrics is generally low, which falls short of the need for high-power and compact-size electronic devices and electrical systems. Here, a scalable all-organic composite based on a ferroelectric polymer incorporated with an abundant, cost-effective organic molecule, i.e., glucose is reported, exhibiting record dischargeable energy density (37.7 J/cm3) that outperforms the state-of-the-art dielectric polymer composites. The glucose molecules rich in hydroxyl groups are found to facilitate the formation of a physically cross-linking network of hydrogen bonds within the polymer matrix, which is responsible for the remarkable performance improvement. Both simulation and experimental results show that the hydrogen bonds serve as the trapping sites of charge carriers and suppress conduction loss. The hydrogen bond network is also found to account for the increased crystallinity, reduced crystallite size, and stabilized γ phase in the polymer, which leads to enhanced electric displacement and reduced hysteresis loss. In combining the advantages of extraordinary energy storage performance, abundant raw materials, ease of preparation, this approach is viable for large-scale production of polymer-based high-energy-density dielectric materials.