The high-density tungsten bronze (TB) Sr2-xCaxNaNb5O15 (SCNN, 0.05 ≤ x ≤ 030) lead-free ceramics were prepared by two-step solid-state reaction method. With increasing Ca2+ substitution, the crystal structure of SCNN ceramics slightly distorted from the TB tetragonal phase and became orthorhombic phase at room temperature. The smaller ionic radius of Ca2+ (1.34Å) compared with that of Sr2+ (1.44Å) contributed to the shrinkage of the crystal structure. Dielectric spectra of all compositions displayed two phase transitions: the ferroelastic orthorhombic to ferroelectric tetragonal phase transition (Te) at lower temperatures, and the ferroelectric to paraelectric phase transition (Tc) at higher temperatures. With increasing Ca2+ substitution, Te and Tc shifted towards higher temperature regions, while the maximum values of dielectric constant (εme and εm), Pr, Ec and d33 increased at first and then decreased. The ceramics with most homogeneous microstructure and highest density were obtained at x = 0.15, resulting in optimized properties.

Polycrystalline randomly oriented CaMnO3 films were successfully deposited on sapphire substrates by soft chemistry methods. The precursor solutions were obtained from a mixture of metal acetates dissolved in acids. The Seebeck coefficient and the electrical resistivity were measured in the temperature range of 300 K < T < 1000 K. Modifications of thermal annealing procedures during the deposition of precursor layers resulted in different power factor values. Thermal annealing of CaMnO3 films at 900 °C for 48 h after four-layer depositions (route A) resulted in a pure perovskite phase with higher power factor and electrical resistivity than four-layer depositions of films annealed layer by layer at 900 °C for 48 h (route B). The studied films have negative Seebeck coefficients indicative of n-type conduction and electrical resistivities showing semiconducting behavior.

Ag nanoparticles were prepared via a wet chemical reduction method and treated with tetraethoxysilane (TEOS) to form an insulating SiO2 layer on the surface (Ag@SiO2). The Ag@SiO2 nanoparticles were introduced in to the BaTiO3/poly (vinylidene fluoride) matrix to prepare the three-phase Ag@SiO2/BaTiO3/poly (vinylidene fluoride) composite, and the dielectric behavior of the composite was investigated. The results showed that the typical “conductor/polymer” percolation effect was not observed in the composite as a result of the SiO2 layer, which prevented Ag particles from contacting with each other directly and restricted the movement of electrons under external field. The high dielectric constant of 723 and a relatively low loss of 0.82 were achieved at 100 Hz with 40 vol% Ag@SiO2 and 20 vol% BaTiO3, respectively. The microcapacitor network model and “Maxwell-Wagner-Sillars” (MWS) effect were used to investigate dielectric properties of the three-phase composite.

Li+ for Na+ ion-exchange-induced phase separation in borosilicate glass was investigated. A glass with a composition, 70SiO2·15B2O3·15Na2O, was prepared. The glass was transparent, and macroscopically no phase separation was observed because the immiscibility temperature for the composition was lower than the glass transition temperature. Substitution of Li+ for Na+ at the surface domain of the glass induced phase separation in the domain and subsequent heat treatment evolved interconnected silica-rich and alkali borate-rich phases through the phase separation. However, the parts in which ion exchange did not occur kept homogeneous and transparent. This phenomenon is explainable by the fact that the immiscibility temperature for the Li+-substituted composition of the original glass elevated up to a temperature higher than the ion exchange and heat treatment temperatures. The borate-rich phases leached by acid treatment for the phase-separated glass. Through these processes, we obtained monolithic glasses consisting of porous domains, and homogeneous and transparent parts.

Surface-functionalized magnetic nanoparticles were prepared by a facile one-pot solvothermal method in ethylene glycol solution. Zeta value, size, and magnetic properties could be well tuned by introducing different functional group molecules. Characterizations, including transmission electronic microscopy, scanning electronic microscopy, thermogravimetric analysis, x-ray powder diffraction and vibrating sample magnetometer, and Fourier transform infrared spectrophotometer demonstrated the efficiency of this simple and general synthesis strategy. The hydrophilic magnetic nanoparticles with various surface functional groups and zeta values were evidenced as excellent candidates for bioseparation by extracting DNA molecules from a model mixture of cell fractures.

Using the thermal oxidation of iron, we show that the growth morphologies of one-dimensional nanostructures of hematite (α-Fe2O3) can be tuned by varying the oxygen gas pressure. It is found that the oxidation at the oxygen gas pressures of ∼0.1 Torr is dominated by the growth of hematite nanobelts, whereas oxidation at pressure near 200 Torr is dominated by the growth of hematite nanowires. Detailed transmission electron microscopy study shows that both the nanobelts and nanowires grow along the direction with a bicrystal structure. It is shown that nanowires are rooted on Fe2O3 grains, whereas nanobelts are originated from the boundaries of Fe2O3 grains. Our results show that oxygen gas pressure can be used to manipulate the Fe2O3/Fe3O4 interfacial reaction, thereby tailoring the oxide growth morphologies via the stress-driven diffusion.

The surface enthalpy of yttria-stabilized hafnia (YSH) (YxHf1 − xO2 − x/2) with different compositions was directly measured by a combination of high-temperature oxide-melt solution calorimetry and water adsorption calorimetry. The surface enthalpies for hydrated surfaces are 0.27 ± 0.06 J/m2 for x = 0.1, 0.77 ± 0.09 J/m2 for x = 0.17, and 1.30 ± 0.09 J/m2 for x = 0.24; and those for anhydrous surfaces are 0.51 ± 0.06, 1.08 ± 0.13, and 1.76 ± 0.09 J/m2 respectively. The enthalpies of both hydrated and anhydrous surfaces increase approximately linearly (R2 > 0.93) with increasing yttrium concentration. The surface enthalpies of Y0.1Hf0.9O1.95 were used to approximate those for pure anhydrous cubic hafnia. Combining the data relating to surface energies for monoclinic hafnia from our previous work and estimated data for tetragonal hafnia, a tentative stability map of HfO2 polymorphs as a function of surface area (SA) was constructed.

The photoelectrical properties of highly ordered TiO2 nanotube (TNT) arrays have been systematically and quantitatively studied and found to be closely related to their geometric and crystal structures. The geometric characteristics, including the nanotube diameter and length, were modified by adjusting the anodization potentials and durations, while the crystal structure was modified by thermal annealing at different temperatures. The nanotube array samples with the mixed crystalline phases possess higher photoconversion efficiency than those with the single anatase or rutile phase. The optimal content of rutile phase is about twice of that of anatase phase. In terms of the influence of the geometric structure, the TNT arrays with larger inner diameters and longer tube lengths have better photoelectrical properties. A geometric roughness factor has been applied to describe the combinative effect of the geometric characteristics. The TNT sample with the geometric roughness factor of 125.32 shows the superior photoconversion efficiency of 13.2%. The underlying mechanism has also been discussed in detail.

A nanoparticle catalyst of PtRuAu/C was synthesized by including an Au precursor in the radiolytic process for preparing a PtRu/C catalyst. Their methanol oxidation activity and electrochemical durability were measured by linear sweep voltammetry before and after potential cycling treatment. PtRuAu/C had a significantly higher durability than PtRu/C while maintaining a comparable high activity. The morphology and substructure of the nanoparticles were investigated by energy-dispersive x-ray spectroscopy, x-ray diffraction, and x-ray absorption fine structure spectroscopy. Metallic nanoparticles with diameters of about 2 nm were obtained; they probably had Pt-core/PtRu-shell structures. Transmission electron microscopy observations after potential cycling revealed that 2-nm-diameter nanoparticles containing Au did not coarsen, whereas nanoparticles without Au coarsened significantly to 3.7 nm. Some crystal defaults were observed in the coarsened particles, implying that the coarsening was caused by Ostwald ripening. The Au addition to catalyst particles consisting of PtRu inhibits coarsening and consequently improves the electrochemical durability.

Graphene and carbon nanotubes (CNTs) are fascinating materials, both scientifically and technologically, due to their exceptional properties and potential use in applications ranging from high-frequency electronics to energy storage devices. This manuscript introduces a hybrid structure consisting of graphitic foliates grown along the length of aligned multiwalled CNTs. The foliate density and layer thickness vary as a function of deposition conditions, and a model is proposed for their nucleation and growth. The hybrid structures were studied using electron microscopy and Raman spectroscopy. The foliates consist of edges that approach the dimensions of graphene and provide enhanced charge storage capacity. Electrochemical impedance spectroscopy indicated that the weight-specific capacitance for the graphenated CNTs was 5.4× that of similar CNTs without the graphitic foliates. Pulsed charge injection measurements demonstrated a 7.3× increase in capacitance per unit area. These data suggest that this unique structure integrates the high surface charge density of the graphene edges with the high longitudinal conductivity of the CNTs and may have significant impact in charge storage and related applications.

Electrochemical oxidation of graphite in mixed solutions of H2SO4–H3BO3 with various mass ratios was investigated. The potential correction to concentration in the formation of graphite intercalation compound II stage in the system graphite–H2SO4–H3BO3 was determined and compared with other systems. Boric acid was shown not to be co-intercalated with sulfuric acid into graphite matrix, but to be distributed on the surface of expandable graphite (EXP). The amount of boric acid on EXP depends on concentration of H3BO3 in electrolyte and it ranges from 3.7 to 11.0 wt%. Content of boric oxide formed after thermoshocking is equal to 3–9 wt% in exfoliated graphite (EG). Modification resulted in reducing specific surface area of EG. As the pores in modified EG were blocked by boric oxide, the temperature of oxidation of the EG and graphite foil increased by 200 °C.

The copper precipitation associated with austenite–ferrite transformation in a continuously cooled multicomponent steel was examined by atom probe tomography. During continuous cooling, carbon and austenite stabilizers such as nickel, manganese, and copper were prone to diffuse into the untransformed austenite and changed the solute enrichment in austenite and its decomposition process. The redistribution of alloying elements between newly formed ferrite and untransformed austenite led to the appearance of a variety of structural components of ferrite, bainite, martensite, and/or retained austenite in the microstructure. The solutes partitioning behaviors at the migrating ferrite/austenite heterophase interface had a great effect on the nature of copper precipitation. At a cooling rate of 0.1 °C/s, the transition bcc copper precipitate was considered to first nucleate by interphase precipitation and then grow after being embedded within ferrite. The situation of the actual nucleation of carbide in ferrite had a significant effect on the size and composition of copper precipitates, as well as the segregation behaviors of nickel and manganese at copper/matrix heterophase interface.

Thin films of Ni-49 at.%Ti were deposited by DC magnetron sputtering on silicon substrates at 300 °C. The as-deposited amorphous films were annealed at a vacuum of 10−6 mbar at various temperatures between 300 and 650 °C to study the effect of annealing on microstructure and mechanical properties. The as-deposited films showed partial crystallization on annealing at 500 °C. At 500 °C, a distinct oxidation layer, rich in titanium but depleted in Ni, was seen on the film surface. A gradual increase in thickness and number of layers of various oxide stoichiometries as well as growth of triangular shaped reaction zones were seen with increase in annealing temperature up to 650 °C. Nanoindentation studies showed that the film hardness values increase with increase in annealing temperature up to 600 °C and subsequently decrease at 650 °C. The results were explained on the basis of the change in microstructure as a result of oxidation on annealing.

Amorphous ribbons of Co69Fe7Si14B10-xZrx (x = 0, 2.5, 5, 7.5 and 10) alloys have been prepared and their structure, soft magnetic and magnetoimpedance (MI) properties have been investigated. Glass forming ability (GFA) of these alloys was calculated using GFA parameter (α = Tx/Tl) and verified by experimental results. Saturation magnetization of the amorphous ribbon decreases on replacement of B by Zr which reveals Zr has more pronounced effect in decreasing saturation magnetization. However, improvement of other soft magnetic properties (coercivity and permeability) leads to considerable increase in MI properties. Annealing leads to crystallization of Co2Si, Co2B, Co2Zr and CoSi phases causing deterioration of soft magnetic and MI properties due to the magnetic hardness of the secondary phase which arises due to the presence of magnetocrystalline anisotropy.

The aim of this study was the development of biocomposite scaffolds (membranes and matrices) based on natural polymers used for bone tissue engineering. The novelty featured in this paper is the use of phosphorylated dextran (PDex) as natural component in collagen-based biocomposites. The PDex both in acid form and as mixed salts of Mg–Na, Zn–Na, Ca-Na was characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy, potentiometric and conductometric titration and energy dispersive x-ray spectroscopy (EDX) analysis. The biocomposite scaffolds were obtained by freeze-drying as matrices and by free-drying as membranes with specific microporous morphological structures that depended on drying process of collagen gels with PDex. The biocomposites were physical–chemical characterized by differential scanning calorimetry (DSC) and, water and water vapor absorption. The biocompatibility was evaluated in vitro with human osteosarcoma MG 63 cell lines. The results showed that biocompatibility was improved by the use of PDex as mixed salts of Mg–Na, Zn–Na, Ca-Na in collagen biocomposites.