Textured epitaxial HfO2 thin films of monoclinic structure were grown on r-cut Al2O3 by atomic layer deposition from HfCl4 and H2O at temperatures 450–750 °C. The film-to-substrate out-of-plane orientation was determined to have a single (001)HfO2//(1$\bar 1$02)α-Al2O3 relationship. The in-plane orientation showed the existence of two possible relationships: [100]HfO2//[110]α-Al2O3 and [$\bar 1$00]HfO2//[110]α-Al2O3. In films deposited at 400 °C traces of (010) growth plane were observed in addition to the preferential (001) growth. The lattice of HfO2 was compressed in the surface plane and expanded in the surface normal direction. The strain was highest in the films grown at 450–550 °C. With the increase of deposition temperature to 750 °C, the strain decreased. The strain relaxation in films deposited at 750 °C was in correlation with marked surface roughening in the initial stage of deposition at this temperature. The roughness of the epitaxial films was lower than that of polycrystalline films with comparable thickness deposited on Si(100) and SiO2 substrates.

A new type of cross-linked poly(vinyl alcohol) (PVA)-sulfosuccinic acid (SSA) polymers were synthesized by varying the amount of SSA and then blending with 3-amino-1,2,4-triazole (ATri) and 1H-1,2,4-triazole (Tri) at different stoichiometric ratios to obtain proton conductive membranes in anhydrous state. The proton conductivities of membranes were investigated as a function of azole composition, SSA composition, and operating temperature. The final structures of the copolymers were confirmed by Fourier transform infrared spectra. The resultant hybrid membranes are transparent, flexible, and showed good thermal stability up to approximately 200 °C. Differential scanning calorimetry results illustrated the homogeneity of the materials. The cross-linking of the structure was confirmed by the alteration of solubility of the membranes. Methanol permeability measurements showed that the composite membranes have lower methanol permeability compared to Nafion 112. The proton conductivity of the membranes continuously increased with increasing SO3H content and 3-amino-1,2,4-triazole (ATri) content. A maximum proton conductivity of 7.26 × 10−3 S/cm was achieved for ATri-3 at 140 °C under anhydrous conditions. Incorporation of ATri unit (according to Tri unit) significantly increased the proton conductivity of the membranes, probably due to the ion transport channel or network structures formed in the membranes.

Electrical properties of ZrO2 formed by simultaneous oxidation and nitridation of sputtered Zr thin films on Si have been systematically investigated. Various oxidation/nitridation temperatures (500, 700, 900, and 1100 °C) have been carried out in N2O ambient for an extended time of 20 min. Results indicated that the sample oxidized and nitrided at 700 °C possessed the highest effective dielectric constant of 18.22 and electrical breakdown field of 10.7 MV/cm at a current density of 10−6 A/cm2. This is attributed to the lowest effective oxide charge, interface-trap density, and total interface-trap density. The Fowler–Nordheim tunneling mechanism has been investigated for all samples and the highest value of barrier height extracted between the conduction band edges of oxide and semiconductor was 1.22 eV.

Fine-sized powders of BaSi3Al3O4N5:Eu2+ phosphors with high stability and improved photoluminescence properties were successfully synthesized by the traditional solid-state reaction method under a reductive atmosphere using BaF2-fluxing additives in the raw powder mixture. The produced phosphors had strong blue emission under excitation in ultraviolet (UV) and vacuum ultraviolet (VUV) light, due to the 4f 5d–4f7 transition of Eu2+ ions. X-ray diffraction, scanning electron microscopy, XANES, and the photoluminescence (PL) spectra under UV and VUV were used to characterize the as-received samples. The experimental results showed that the addition of BaF2 flux improved the crystalline regime and the PL properties of the produced phosphors. Most significantly, it allowed control of the particle size and particle size distribution in the final powders but did not jeopardize the high thermal and chemical stability of the phosphors produced. With the modification of the BaF2 flux, the blue-emitting BaSi3Al3O4N5:Eu2+ phosphors will show excellent packing and coating properties and could be a good candidate for the light-emitting diodes and plasma display panels.

Zeolite-based supports for inorganic membranes intended for gas separation have the potential to increase the resistance to thermal shock-induced cracking compared with ceramic or metallic substrates. We have studied the effect of exposure at 90 °C of hierarchically porous silicalite-I substrates to aqueous solutions at pH 2.0, 10.6, and 13.0 for periods up to 168 h. Silicalite-I supports were produced in binder-free form by pulsed current processing and using clay-binders by conventional thermal treatment. Long-term (168 h) acid and alkali treatment of the silicalite-I substrates results in a slight removal of silicon (in acid) and aluminum (in alkali) and does not affect the specific surface area and the crystalline microporous structural features but broadens the size distribution of the macropores. The mechanical strength remains unchanged after exposure to both alkaline and acidic solutions and the binder-free substrates display more than 20 times higher strength than the binder-containing materials.

Natural fiber composites are becoming more attractive for applications as energy absorbers in the automotive industry despite their high moisture absorption characteristics. The main objective of this paper is to study the impact strength and moisture absorption properties of long fiber and short fiber hybrid composites using a kenaf/polyethylene terephthalate fiber reinforced in the polyoxymethylene matrix. The results obtained from the impact test gave 10.8 J/cm for the longer fiber hybrid composites, which is higher compared to 8.0 J/cm obtained for the short fiber hybrid composites due to less fiber pullout from the matrix. A moisture content of 0.92% and percentage water absorption of 6.77% were obtained for the long fiber composite due to poor interfacial adhesion between the fiber and the matrix. A high void content of 0.52% and porosity of 1.21% also accounted for high water and moisture absorption of the long fiber hybrid composite.

In this paper, we demonstrate a thin film Cu–Ni–Nb alloy deposited directly on silicon, without a designated barrier, showing very high thermal stability at a temperature up to 700 °C for 1 h. Thin [Nb–Ni12]Cux films were sputter deposited and annealed, and their material and electrical properties were studied. The results can be explained by the “cluster-plus-glue atom” model for stable solid solutions, where [Nb–Ni12] cuboctahedral clusters are embedded in a Cu matrix. In this model, the clusters are congruent with the Cu minimizing atomic interactions allowing a good stability. The properties of the films were found to be affected by the Ni/Nb ratios. Especially, the (Nb1.2/13.2Ni12/13.2)0.3Cu99.7 film annealed at 500 °C for 1 h had the lowest electrical resistivity of about 2.7 μΩ cm. And even after 40 h annealing at 500 °C, it maintained a low resistivity of about 2.8 μΩ cm, demonstrating extremely high stabilities against silicide formation.

Highly efficient polytype 4H silicon carbide (4H-SiC) p–n diodes for ultraviolet (UV) light detection have been fabricated, characterized, and exposed to high-intensity mercury lamp irradiation (up to 17 mW/cm2). The behavior of the photocurrent response under UV light irradiation using a low-pressure mercury UV-C lamp (4 mW/cm²) and a medium-pressure mercury discharge lamp (17 mW/cm²) has been studied. We report on long-term UV photoaging tests performed for up to 22 mo. Results demonstrate the robustness of SiC photodiodes against UV radiation. The devices under test showed an initial burn-in effect, i.e., the photocurrent response dropped by less than 5% within the first 40 h of artificial UV aging. Such burn-in effect under UV stress was also observed for previously available polytype 6H silicon carbide (6H–SiC) p–n photodetectors. After burn-in, no measurable degradation has been detected, which makes the devices excellent candidates for high irradiance UV detector applications.

A novel Ba2MgMoO6:Eu3+ orange-red phosphor was synthesized by the Pechini method and characterized by x-ray diffraction. Photoluminescence properties of BaMgMoO6:Eu3+ phosphors have been represented in the excitation and emission spectra. The charge transfer (CT) band of Ba2MgMoO6 host is situated at near-ultraviolet (UV) region, whose central wave length and bandwidth are 394 and 80 nm, respectively. And it matches well the emission wave length from near-UV light emitting diodes (LEDs). The most intensive emission of 5D0 → 7F1 (598 nm) of Eu3+ in Ba2MgMoO6:Eu3+ is much narrow with a full width at half-maximum less than 2 nm under excitation with either CT band or 394 nm. And a low concentration quenching occurs in Ba2MgMoO6:Eu3+, and the optimal doping concentration is about 0.05. The mechanism of charge and energy transfer from Ba2MgMoO6 host to Eu3+ is proposed and analyzed on the basis of its crystal structure. In a word, Ba2MgMoO6:Eu3+ may be a promising orange-red component for near UV white LEDs.

Under the strategies of doping to extend the absorptive response region of a semiconductor and fabricating a mesoporous structure with large specific surface area to enhance the photocatalytic property, an efficient visible-light-driven photocatalyst of bismuth-doped titanium dioxide (Bi/TiO2) was prepared via a facile sol-gel route. The resulting materials were characterized by powder x-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TG), UV–vis diffuse reflectance spectrum (DRS), and N2 adsorption–desorption measurements (BET). The photocatalytic performances of as-synthesized particles were monitored by degradation of 2,4-dichlorophenol (2,4-DCP) in transparent aqueous solutions under visible light illumination. The results revealed that mesoporous PEG-modified Bi-doped TiO2 exhibited much higher photocatalytic activities than Bi-doped TiO2 without modification, and noticeably the optimized doping level was increased from 2 to 4 mol%. The visible-light photocatalytic activity enhancement of PEG-modified Bi-doped TiO2 could be attributed to appropriate proportional mixed crystal phase, large surface area, porosity, mesoporous network with interconnected small nanocrystals, and its strong absorption in the visible region.

We investigate the size-dependent carrier dynamics and activation energy in cadmium telluride/zinc telluride (CdTe/ZnTe) quantum dots (QDs) grown on silicon (Si) substrates. Photoluminescence (PL) spectra show that the excitonic peak corresponding to transitions from the ground electronic subband to the ground heavy-hole band in CdTe/ZnTe QDs shifts to a lower energy level with increasing CdTe thickness, owing to an increase in the size of the CdTe QDs. Time-resolved PL measurements performed to study the carrier dynamics reveal a longer exciton lifetime for CdTe/ZnTe QDs with increasing CdTe thickness on account of the reduction of the exciton oscillator strength resulting from a strong built-in electric field in the larger QDs. The activation energy of the electrons confined in the CdTe/ZnTe QDs, as obtained from the temperature-dependent PL spectra, increases with increasing CdTe thickness. These results indicate that the carrier dynamics and activation energy of CdTe/ZnTe QDs are affected by the size of the CdTe QDs.

We used miniemulsion to synthesize novel water-soluble dispersion of nanocapsules with a polyaniline (PANI) shell and luminescent ultrasmall Si nanoparticle core with diameters of 50–300 nm. The capsules are functionalized with aromatic sulfonic acid. The capsules may be reconstituted in thin films or structured surfaces. The stability of the luminescence and dispersion of the capsules is studied under a wide range of pH conditions. The multiplicity of nanoparticles in the core provides highly amplified and reproducible signal for luminescence-based imaging using standard fluorescence microscopy, while the PANI shell allows a variety of routes for functionalization as well as electrical interrogation, which enables a wide range of biosensing/imaging applications.

Incorporation of porosity into a monolithic material decreases the effective thermal conductivity. Porous ceramics were prepared by different methods to achieve pore volume fractions from 4 to 95%. A toolbox of analytical relations is proposed to describe the effective thermal conductivity as a function of solid phase thermal conductivity, pore thermal conductivity, and pore volume fraction (νp). For νp < 0.65, the Maxwell–Eucken relation for closed porosity and Landauer relation for open porosity give good agreement to experimental data on tin oxide, alumina, and zirconia ceramics. For νp > 0.65, the thermal conductivity of kaolin-based foams and calcium aluminate foams was well described by the Hashin Shtrikman upper bound and Russell’s relation. Finally, numerical simulation on artificially generated microstructures yields accurate predictions of thermal conductivity when fine detail of the spatial distribution of the phases needs to be accounted for, as demonstrated with a bio-aggregate material.

All-oxide ultraviolet (UV) photosensors based on NiO/ZnO nanowire heterostructure were fabricated on corning glass substrates. The p-type NiO layers were directly deposited on the ZnO nanowire arrays grown on the AZO bottom electrode/glass for the formation of a p–n diode, followed by the growth of the ITO top electrode layer for the electrical interconnection of nanostructures. The fabricated device structure showed a transmittance value of about 60% in the visible region, resulting in semitransparent properties. The current–voltage (I–V) characteristics of the fabricated p–n heterostructure showed a typical rectifying behavior with a current rise at about 4 V and an I(forward)/I(reverse) ratio of about 11.3 at 8 V. In addition, the ITO/p-NiO/n-ZnO/AZO structure responded at a wave-length position of 370 nm in reverse bias, together with weak photoresponse in the visible region. An UV sensor based on the all-oxide ZnO nanowire absorber exhibited improved photoresponse compared to the device based on a ZnO thin film.

A new strategy using hyperbranched poly(amidoamine)s to functionalize CdTe quantum dots (QDs) has been described. Hyperbranched poly(amidoamine)s with amine terminals (HP-EDAMA1) were synthesized by one-pot polymerization via the coupled-monomer method and subsequently used to functionalize preformed CdTe QDs. Quite different from previous studies in which the photoluminescence of QDs was quenched by further functionalization with tailored ligands, the quantum yield of CdTe/HP-EDAMA1 nanocomposites was 2 times that of pure CdTe QDs without modification. With this versatile method, the photoluminescence quenching of QDs in the modification process by matrix materials can be effectively solved and new QDs/hyperbranched polymer nanocomposites with potential applications in biomedicine might be offered.

Sol–gel-derived aluminum (Al)-doped zinc oxide thin films have been deposited on silicon (Si) wafers and microslide glass substrates using the spin coating technique. The atomic ratio of Al:Zn in the films is 0.05, 0.1, 0.2, and 0.3. The films have been characterized using different techniques, i.e., x-ray diffraction, Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy, UV-visible-near infrared spectrophotometry, spectroscopic ellipsometry, and the four-probe method. The films have exhibited excellent optical transmittance (∼90%). The refractive indices of the films are in the range between 1.47 and 1.53. The thickness of the films is in the range of 103–115 nm. The films have demonstrated reflectivity of about 3% at a wave length of 600 nm. The reflectivity, transmittance, refractive index, and thickness values of the films show that the films are promising candidates for utility as antireflection coatings in silicon solar cells.

We report on the successful synthesis of a graphene–carbon nanotube (CNT) hybrid architecture by a parallel chemical vapor deposition (CVD) of the two carbon allotropes. The carbon hybrid is a three-dimensional (3D) nanostructure with tuneable architecture comprising vertically grown CNTs as pillars and a large-area graphene plane as the floor. The formation of CNTs and graphene occurs simultaneously in a single CVD growth that we describe as a synchronous synthesis method. Unique nature of the fabrication approach contributes significantly to the quality and composure of final nanohybrid. Detailed characterization elucidates the cohesive structure and robust contact between the graphene floor and the CNTs in the hybrid structure. The functionality of the synthesized graphene hybrid structure has been demonstrated by its incorporation into a supercapacitor cell. Our fabrication approach provides an attractive pathway for the fabrication of novel 3D hybrid nanostructures and efficient device integration.

The microstructure evolution and diffusion of silicon during heat-treatment and plastic deformation process were studied on the clad plates of Al–Mn/Al–Si aluminum composite fabricated by continuous casting. The results show that when the clad slab is homogenized and hot rolled, silicon diffuses across the interface from the Al–Si alloy (4004) side to the Al–Mn alloy (3003) side and dissolves into the 3003 matrix forming a solid solution. However, after deformation by cold-rolling, the increased driving force for precipitation of the solute elements in the core alloy side along with the abundant defects introduced by the severe deformation promotes the precipitation. Some Mg2Si particles precipitate from the solid solutions to form a transition region close to the interface of the two components. The presented transition area not only benefits the microstructure of the clad sheet but also improves the distribution of the microhardness across the interface, a tendency of gradient transition.

A new acentric protonated garnet Li6−xHxCaLa2Nb2O12 has been synthesized and structurally characterized from Rietveld refinement of high-resolution neutron diffraction data. This phase can be prepared by Li+/H+ exchange on the mother garnet Li6CaLa2Nb2O12 in acetic acid heated at reflux for 4 days, conditions determined after several tests varying acid solution, time, and temperature. Li6−xHxCaLa2Nb2O12 crystallizes in the noncentrosymmetric cubic space group I$\overline 4$3d (no. 220) with the cell parameter a = 12.8040(3) Å. The noncentrosymmetry has been confirmed from unambiguous results obtained by second harmonic generation test as well as from transmission electron microscopy study (selected area electron diffraction). The Li+/H+ exchange corresponds to a topotactic reaction since this new protonated phase is built from the garnet framework [CaLa2Nb2O12]6− like its mother form Li6CaLa2Nb2O12 with lithium and proton cations distributed on different sites.