Transmission electron microscopy (polycrystalline electron diffraction, nanoelectron diffraction, and energy dispersive x-ray spectroscopy) was used to determine the dispersion of crystal phase and Nb dopants in mixed-phase (anatase and rutile) Ti1−xNbyO2 thin films prepared by reactive sputtering. When co-sputtering mixed-phase TiO2 with a dopant, it is unclear how the crystal phases are distributed within thin film structures, what the dominant interfaces are, and how the dopant is distributed within the crystal phases. In the Ti1−xNbyO2 films, anatase and rutile grains were found to be homogeneously dispersed indicating that anatase/rutile interfaces are the dominant interfaces. Anatase/rutile interfaces are a critical feature of mixed-phase materials which impart high reactivity to the composite. Nb homogeneously dispersed at low concentrations, but at high concentrations, Nb segregated in the rutile phase. There is an apparent threshold beyond which Nb segregates according to its higher solubility in rutile due to a better lattice fit.

Unbalanced magnetron sputtering (UBMS) is suitable for the preparation of hard and hydrogen-free diamond-like carbon (DLC) films. Since those films generally suffer from internal stresses and bad adhesion, the addition of a methane source offers two advantages: (i) the control of the film properties by variation of the hydrogen content and (ii) a pretreatment of methane plasma source ion implantation (PSII), which results in a gradient carbon layer within the substrates, ensuring the adhesion of the subsequently deposited DLC films. PSII and UBMS were combined to prepare DLC films on stainless steel substrates and silicon wafers. Different amounts of methane were added to the working gas, argon, to investigate the effect of the hydrogen content on the film properties, i.e., hardness, adhesion, and friction coefficient. Composition and chemical structure of the films were investigated by depth profiling (secondary-ion mass spectrometry) and Raman spectroscopy. Smooth adhesive films could be obtained with the lowest friction coefficient for small additions of methane as a hydrogen source during the sputtering process.

Ni-based under-bump metallization (UBM) has attracted wide attention due to its low reaction rate with Sn, compared with Cu and Cu alloy. In this study, the interfacial reactions between eutectic Sn–3.5Ag solder and Ni-based UBM, including electroplated Ni (EP-Ni) and electroless Ni (EL-Ni) are investigated. Morphology and growth kinetics of Ni3Sn4 intermetallic compounds are studied at different reflow temperatures and durations. The growth rate and the growth activation energy of Ni3Sn4 were measured for the two sets of samples. The activation energies are measured to be 25 kJ/mol and 38 kJ/mol for the Ni3Sn4 growth on EP-Ni and EL-Ni, respectively. The Ni3Sn4 on EP-Ni UBMs shows a slower growth rate and the Ni3Sn4/solder interface is void free even after 20-min reflow at 240 °C. On the other hand, the interface of Ni3Sn4/EL-Ni has a lot of microvoids after reflowing at 240 °C for 20 min.

This study investigated the performance of membrane electrode assembly (MEA) fabricated with various loadings of platinum catalyst on carbon nanotubes (CNTs) and sulfonated membrane at constant conditions of duration, temperature and pressure. The fabricated MEA was tested in a single proton exchange membrane (PEM) fuel cell unit using hydrogen and oxygen as fuel and oxidant gases respectively. The results obtained show that the performance of the MEA in the cell improves with increase in loading of the catalyst on the electrodes. The results obtained on kinetics of the fuel cell indicate that the MEA samples fabricated with 30 and 40 wt% Pt catalyst electrodes conform to the Tafel equation whereas the remaining MEA fabricated with 10 and 20 wt% catalyst samples do not obey the Tafel equation due to large values of their overpotential. Hirschenhofer and Tafel equations were used to model the performance of the catalyst electrodes in the cell and the simulated voltage obtained from the former showed better conformity with the experimental voltage than the latter.

The effects of temperature and alloying elements on deformation in the high-strain-rate regime were investigated by testing fine-grained magnesium alloys with an average grain size of 2 ∼ 3 μm by a nanoindentation technique. The dynamic hardness measurements aligned well with existing quasistatic data, together spanning a wide range of strain rates, 10−3 ∼ 150/s. The high-rate hardness was influenced by various alloying elements (Al, Li, Y and Zn) to different degrees, consistent with expectations based on solid solution strengthening. Transmission electron microscopy observations of the indented region revealed no evidence for deformation twins for any alloying elements, despite the high strain-rate. The activation energy for deformation in the present alloys was found to be 85 ∼ 300 kJ/mol within the temperature range of 298 ∼ 373 K, corresponding to a dominant deformation mechanism of dislocation glide.

Nanostructured Al–Mn alloys are proposed as high-strength low-density materials, which can be electroformed (i.e., produced electrolytically and removed from the substrate) from ionic liquid. A variety of current waveforms, including direct current (DC) and pulsed current (PC), are used to electrodeposit nanostructured Al–Mn alloys, with some PC methods producing significant improvements in film ductility. Transmission electron microscopy observations point to a number of structural advantages induced by PC that apparently ductilize the Al–Mn alloys: (i) grain refinement to the nanocrystalline range without the introduction of a competing amorphous phase, (ii) unimodal nanocrystalline grain size distribution, and (iii) more homogeneous structure. The significant increase in apparent ductility in the PC alloys is also apparently related to stress- or deformation-induced grain growth, which leads to alloys with unique combinations of specific hardness and film ductility.

Nanowires have attracted tremendous research interests due to their potential applications. Their mechanical properties are critical for the reliability and durability of the nanowire-based devices. Compared to many other characterization techniques, the lateral probing of a nanowire using nanoindentation has the advantage of relatively simple sample preparation. However, the data analysis is difficult due to the complex contact mechanics. In all previous studies, some questionable approximations have been made to proceed with data analysis. In this study, a quantitative physical picture of nanowire lateral probing is proposed, which we believe is the first time in the literature. Three-dimensional finite element analysis (FEA) is performed and compared to a double-contact analytical model in which the two contacts, namely contact 1 (indenter/nanowire) and contact 2 (nanowire/substrate), are considered. Both the FEA and analytical models are for a specific case: an elastic spherical indention of a GaN nanowire on a Si substrate. We find that contact 1 cannot be well approximated by a Hertzian elliptical contact as assumed in many studies. We also find a large contact deformation at contact 2, which has been ignored in almost all previous studies. Finally, the adhesion condition and nanowire-receding at contact 2 are found to have insignificant effects on the data analysis.

As anhydrous proton conductive membranes, sulfonated polysulfone (SPSU) and 1H-1,2,3-benzotriazole (BTri) hybrid membranes were prepared. The sulfonation of polysulfone was performed with trimethylsilyl chlorosulfonate, and high degree of sulfonation (134%) was obtained. The polymer electrolyte membranes, SPSU–BTriX, were prepared by blending of 1H-1,2,3-benzotriazole in SPSU. FTIR confirmed the sulfonation of PSU and the ionic interaction between sulfonic acid and benzotriazole units. Thermogravimetric analysis (TGA) analysis showed that the polymer electrolyte membranes are thermally stable up to approximately 200 °C. Scanning electron microscopy analysis indicated the homogeneity of the membranes. The maximum proton conductivity has been measured for SPSU–BTri2 as 3.6 × 10−3S/cm at 150 °C.

The addition of Al to a Mg–10Gd alloy was found to lead to substantial grain size reduction during casting at concentrations between 0.8% and 1.3%. At these concentrations, Al2Gd particles were found at the center of grains, and the orientation relationship $[112]_{{\rm{Al}}_{\rm{2}} {\rm{Gd}}} \,{\rm{‖}}\,[2\bar 1\bar 10]_{{\rm{\alpha - Mg}}} ,\,(1\bar 10)_{{\rm{Al}}_{\rm{2}} {\rm{Gd}}} \,{\rm{‖}}\,(0\bar 110)_{{\rm{\alpha - Mg}}} $ was found reproducibly between Al2Gd and α-Mg, indicating that these are the heterogeneous nucleant particles that form in situ at these Al contents. Most of these nuclei were between 2 and 7 μm in size. Furthermore, little grain coarsening was observed during solution treatment, particularly compared with an alloy grain refined by Zr particles where substantial coarsening occurred. This appears to be because Al2Gd particles restrict grain boundary motion during solution treatment.

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 performance of materials exposed to high doses of neutron radiation is currently of great interest for the development of nuclear fusion energy production. An Fe12%Cr alloy was subjected to high-dose (6 dpa) radiation with 2MeV Fe+ ions to simulate the damage structures caused by neutron radiation, resulting in a damage layer ∼0.7 μm in depth from the surface. Spherical nanoindentation, using indenters with radii of 5, 10, and 20 μm, was used to determine reliable values for the initial yield pressure, the evolution of plastic deformation and the elastic modulus of this material, in the irradiated and unirradiated condition. The results showed that the initial yield pressure within the damage layer can be determined and was approximately a factor of two higher than that of the same material in the unirradiated condition. The irradiated material appeared to display strain softening following yield.

Deposition of ibuprofen (IBU) into ordered mesoporous silica SBA-15 was carried out to prepare controlled release nanodrug using supercritical carbon dioxide (scCO2) as solvent at 17 MPa and 310.15 K. The maximum drug loading of IBU/SBA-15 was as high as 41.96%. The characterization of the obtained materials was performed using x-ray diffractometry (XRD), scanning electron microscopy (SEM), and nitrogen (N2) adsorption-desorption isotherms; the results indicate that most adsorbed drugs were inside the nanoscale channels. The in vitro study shows that the time of complete (100%) release significantly decreases as drug-loading decreases. The interesting aspect is that the samples with similar drug loading display different release rates, which may be due to differences in the drug quantity adsorbed inside the pores. In addition, the modified Noyes-Whitney equation was used to model the release kinetics for all the samples and a good agreement was obtained between the model representation and experimental data. In addition, the solubility of IBU in scCO2was tested through a high-pressure view cell at the temperature range of 298.15–320.15 K and pressure range of 7–17 MPa. The experimental solubility data were well correlated using Chrastil’s equation as well as Mendez-Santiago and Teja’s equation.

Elemental enrichment behavior on the surface of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) was investigated in order to understand potential degradation mechanism of solid oxide fuel cell cathodes. Surface morphological changes were examined using scanning electron microscopy after heat treatment in the temperature range of 600–900 °C. Submicron-sized precipitates were formed on grain surfaces after heat treatment. Their shapes appeared to be aligned along the surface orientations of the underlying grains. Auger electron spectroscopy and transmission electron microscopy characterization revealed that the precipitate was strontium (Sr)-oxygen (O) based. The formation of Sr–O precipitates was found to increase with increasing temperature and oxygen partial pressure. A defect chemistry model is presented based on the observed phenomena.

This paper shows a comparison between different nanostructured oxides, obtained by polymeric precursor method, regarding their activity for biodiesel conversion from oil–methanol mixtures. The basicity/acidity and surface area (SA) of the oxides were taken in account to analyze the catalytic activity in the transesterification reaction. The temperature dependence for the heterogeneous catalysts was analyzed, where only CaO showed activities at 70 °C (∼98% of conversion), while the other oxides, SnO2, ZnO, TiO2, CaTiO3, were observed active only at 150 °C for the reaction parameters adopted. The results revealed that the highest activity observed is not associated to SA only but mainly with the surface basicity. This suggest that, for oxides synthesized by the polymeric precursor method, the surface basicity surpasses the particle size effects in catalysis in a way to promote the transesterification reaction.

Tetra(4-dihydroxyborylphenyl)germanium as the tetrahedral units and 1,2,4,5-tetrahydroxybenzene as linkers were selected to form a crystalline porous aromatic framework, CPAF-13, with the planar five-membered BO2C2 ring in its structure by a dehydration reaction. The crystallinity of CPAF-13 was confirmed by x-ray diffraction analysis. The Ar sorption measurement on activated CPAF-13 results in a surface area of 417 m2/g, using Brunauer Emmett Teller model. CPAF-13 also shows a considerable adsorption capacity of H2.

The migration mechanism and the minimum energy path of vacancies, interstitials, and an interstitial–vacancy pair in zinc oxide have been studied by the dimer method. The in-plane and out-of-plane migrations of zinc and oxygen vacancies are anisotropic. The kick-out mechanism is energetically preferred to zinc and oxygen interstitials that can easily migrate through the ZnO crystal lattice. In addition, the migration process of an interstitial–vacancy pair as a complex of an octahedral oxygen interstitial and a zinc vacancy is dominated by an oxygen interstitial/zinc vacancy successive migration. The energy barriers indicate that the existence of oxygen interstitial in the defect pair can promote the mobility of zinc vacancy, whereas the migration of oxygen interstitial is slowed down due to the presence of zinc vacancy. In the end, we show a possible migration path of the interstitial–vacancy pair that can be dissociated through a set of displacement movements.

There is high scientific and technological interest to develop photocatalytic coatings on stainless steels surface to remove fouling under light radiation. In this study, a novel method is described to prepare photocleanable stainless steel by anodization to form aligned nanopore arrays (NPAs) on the surface in ethylene glycol containing perchloric acid. Perchloric acid concentration, applied voltage and anodization time of anodization process were investigated. The NPAs are mainly composed of iron (III) oxide and chromium (III) oxide. This photocleanable stainless steel has remarkable visible-light photocatalytic activities, which show potential applications particularly for outdoor purpose. Moreover, the stainless steel surface remains highly polished and exhibits good corrosion resistance after anodization.

We prepared hybrid aluminum oxide (Al2O3)/polymethyl methacrylate (PMMA) composites with tunable lamellae, produced through a two-step synthetic method: fabrication of inorganic scaffolds via ice-templating, followed by organic infiltration polymerization as a substitute for the sublimed ice. The final lamellar hybrid products show anisotropic physical properties. The thermal conductivity in both principal directions was determined for three different samples as a function of temperature (∼3 K–300 K). Typical room temperature thermal conductivities are in the range of 0.5–2.5 W/(m K), depending on the composition and direction. Across the lamellae, the thermal conductivity is well modeled by a linear series of thermal resistors, and along the lamellae it is well represented by parallel thermal resistors of continuous slabs of PMMA and ∼200-μm long slabs of Al2O3, joined by PMMA. From the thermal conductivity perspective, the Al2O3/PMMA composite is a nacre mimic.

Yellow-emitting long afterglow phosphors Sr3−xSiO5, xMF2: Eu2+, Dy3+ (0 ≤ x ≤ 0.15, M: Ba, Sr, Ca) have been prepared by high-temperature solid-state reaction method followed with rapid cooling process. Photoluminescence measurement reveals that the main emission of the phosphors locates at 575 nm, corresponding to the 4f65d1–4f7 transition of Eu2+. The introduction of alkaline earth metal fluoride effectively enhances the luminescence intensity and prolongs the afterglow time. Especially, the afterglow of the Sr2.95SiO5, 0.05BaF2: Eu2+, Dy3+ phosphor can last for 12 h. Thermal luminescence measurement shows that the trap density of Sr3SiO5: Eu2+, Dy3+ phosphor can be adjusted by adding different alkaline earth metal fluorides, which offers a feasible way to improve the afterglow properties of silicate phosphors.

The relationship between hardness and flow stress in glassy polymers is examined. Materials studied include poly(methylmethacrylate), polystyrene, and polycarbonate. Properties are strongly rate dependent, so broadband nanoindentation creep (BNC) is used to measure hardness across a broad range of indentation strain rates (10−4 to 10 s−1). Molybdenum (Mo) is also studied to serve as a “control” whose rate-dependent hardness properties have been measured previously and whose flow stress, unlike the polymers, is pressure insensitive. The BNC hardness data are converted to uniaxial flow stress using two methods based on the usual Tabor–Marsh–Johnson correlation. With both methods the resulting BNC-derived uniaxial flow stress data agree closely with literature compression uniaxial flow stress data for all materials. For the polymers, the BNC hardness data depend on initial rate of loading, indicating that the measured properties are path dependent. Path dependence is not detected in Mo.