Chemical degradation of the side-chain of perfluorosulfonic acid (PFSA) membranes by hydroxyl radicals (•OH) is examined with electronic structure calculations. The energetics associated with homolytic bond cleavage and for the sequence of reactions involved in the degradation was determined. Results show that the degradation of side-chain begins with the cleavage of the C–S bond. The sequence of reactions of the side-chain with •OH indicates scission of the backbone yielding reactive end-groups. The kinetics of the C–S bond cleavage was studied via: (i) reaction of anionic fragment with a •OH; and (ii) decomposition of fragment radical. The activation energy for the second pathway was calculated to be ∼11 kcal/mol lower requiring a change in symmetry of the molecular geometry of the sulfonate group from trigonal pyramidal to trigonal planar. This suggests that although the C–S bond may be the weakest in the side chain of a PFSA ionomer, its cleavage is kinetically hindered.

Most instrumented indentation theoretical studies and models consider bulk sample geometry, which implies no influence on the indentation response. In the particular case of thin samples, our previous studies have shown that the thickness has an influence on the experimental device behavior as well as on the sample and material response. This work is a numerical and experimental illustration of this particularity. Spherical macroindentation tests are performed on AISI 1095 steel samples of thicknesses varying from 0.55 to 10 mm. Experimental and numerical results are compared. Experimental limitations are investigated, and solutions to obtain results that are independent of the sample thickness and curvature are proposed. We show that the proposed solution leads to a reliable identification of the material mechanical properties of thin and moderately bent samples.

Atomic structures of the Zr48Cu45Al7 as-prepared and annealed metallic glasses (MGs) were investigated by performing the reverse Monte Carlo simulation on the synchrotron radiation-based experiments. It was found that although the annealed sample remains completely amorphous, the volumes of the Al-centered clusters evidently expand, which is attributed to the relatively longer Al–Zr bonds. As a result, the role of Al atoms as the glue atoms to connect and fix the Zr- and Cu-centered large clusters is accordingly weakened, which leads to the ease of the rearrangement of atoms and clusters in the glass state. This study provides an insight into the microstructures of MGs, which extends understanding of the structural evolution in the glass alloys during annealing prior to the precipitation of nanocrystals.

Most CuIn(SexS1−x)2 (CISS) thin films are deposited via conventional two-stage process. However, a significant problem related to the conventional two-stage process is the separation of CuInSe2 and CuInS2 phases. In this article, single-phase CISS thin films have been successfully prepared by selenizing sulfides of copper and indium. The mixed sulfides of Cu–In precursors were synthesized by coprecipitation method and then partly reduced. The inks containing partly reduced powders and organic binders were deposited onto glass substrate using a spin-coating technique. After coating, the precursor films were selenized to get CISS. X-ray diffraction and energy dispersive x-ray spectroscopy data show that the single (112) peak position changed with the variation of Se/S ratio. The absorption energy Egchanges linearly with Se/(Se + S) calculated by ultraviolet–vis absorption spectra. Those results confirm the formation of single-phase CISS with homogenous composition.

Plasticity initiation behavior that appears as a pop-in phenomenon on a loading process during indentation-induced deformation was investigated to reveal the effects of lattice defects such as grain boundary and solute element for various metallic materials including Fe alloys through instrumented nanoindentation techniques. The critical load Pc of pop-in on a loading process is lower in the vicinity of the grain boundary than in the grain interior, but the relative hardness of the boundary is equal to or greater than that in grain interior. In-solution Si produces a larger increase in the Pc for both the grain boundary and the grain interior in the Fe–Si alloy than in the interstitial-free steel. The maximum shear stress corresponding to the Pc underneath the indenter is directly proportional to the shear modulus in single crystals with various crystallographic structures. Microstructural effects on the Pc are considered based on some dislocation models.

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.

The residual stress in Al–Cu–Fe–B quasicrystalline thin films has been characterized by x-ray diffraction and the curvature method. Films with thicknesses in a range from 0.55 to 2.6 μm were deposited using magnetron sputtering on Si(100) substrates maintained at a temperature of 560 °C. It is found that the tensile stress in uncracked films as determined by the curvature method is close to that measured by a modified sin2ψ method using main diffraction peaks of the icosahedral structure and corresponds approximately to 1.1 GPa. This value is close to that of the thermal stress estimated from the mismatch between thermal expansion coefficients of the film and substrate, suggesting that thermal stress is the main source of residual stress. Increasing film thickness results in the development of cracks and partial delamination of the film, accompanied by the sudden decrease of the stress. The fracture toughness of the quasicrystalline films is estimated between 1.5 and 1.9 MPa.

The hardening effect caused by the relaxation of nonequilibrium grain boundary structure has been explored in nanocrystalline Ni–W alloys. First, the kinetics of relaxation hardening are studied, showing that higher annealing temperatures result in faster, more pronounced strengthening. Based on the temperature dependence of relaxation strengthening kinetics, triple junction diffusion is suggested as a plausible kinetic rate limiter for the removal of excess grain boundary defects in these materials. Second, the magnitude of relaxation strengthening is explored over a wide range of grain sizes spanning the Hall–Petch breakdown, with an apparent maximum hardening effect found at a grain size below 10 nm. The apparent activation volume for plastic deformation is unaffected by annealing for grain sizes down to ∼10 nm, but increases with annealing for the finest grain sizes, suggesting a change in the dominant deformation mechanism for these structures.

Nd-doped LaVO4 crystals with the concentration up to 0.94 at.% were successfully grown by the Czochralski method. X-ray powder diffraction measurement reveals that this crystal belongs to a monoclinic space group P21/n. Refractive indices of Nd:LaVO4 have been measured with two right angle prisms for the first time to our knowledge and show that they are anisotropic. Its absorption and fluorescence spectra are also investigated. With the Judd–Ofelt theory, the optical parameters calculated are Ω2 = 2.142 × 10−20 cm2, Ω4 = 3.704 × 10−20 cm2, and Ω6 = 2.948 × 10−20 cm2. By these parameters, the absorption oscillator strengths, line strengths, transition probabilities, fluorescence branch ratios, radiative lifetime, and integrated emission cross section are also derived and compared with familiar vanadates, which show that Nd:LaVO4 is a atypical material and has potential applications in the lasers, especially in the pulsed lasers.

Asphalt bitumens are complex colloidal systems of high viscosity and complex behavior, which are mainly used for making asphalt concrete for road surfaces. Thermal and rheological characterizations are needed to understand their complex behavior, particularly at the processing stage. Prediction of properties at short and long observation times is usually performed through time-temperature superposition (TTS) models, which make use of some calculated shift factors. The influence of crystallization-like transformation processes on the validity of these shift factors is investigated here by temperature-modulated differential scanning calorimetry (TMDSC). Four asphalt emulsions are considered in this work, each one with a specific transformation behavior. The structure-properties relationships are explained on the basis of the transformation profiles and rheological data.

Protocols are developed to assess viscoelastic moduli from unloading slopes in Berkovich nanoindentation across four orders of magnitude in time scale (0.01–100 s unloading time). Measured viscoelastic moduli of glassy polymers poly(methyl methacrylate), polystyrene, and polycarbonate follow the same trends with frequency (1/unloading time) as viscoelastic moduli generated from dynamic mechanical analysis and broadband viscoelastic spectroscopy but are 18–50% higher. Included in the developed protocols is an experimental method based on measured indent area to remove from consideration indents for which viscoplastic deformation takes place during unloading. Ancillary measurements of indent area and depth reveal no detectable (∼1%) change in area between 200 s and 4.9 days following removal of indenter.

The use of Mg-Al-Ca alloys is limited mainly due to the hot crack defect. The exact mechanism of hot crack formation is not yet clearly understood. In this article, the hot crack mechanism is established from the present first-principles calculations based on the density functional theory and density functional perturbation theory . The thermal expansion behavior of Mg and the critical compounds Mg2Ca and Al2Ca in Mg-Al-Ca alloys is calculated. According to the present calculations, Mg2Ca is almost equal to Mg in thermal expansion, whereas the same in Al2Ca is much too lower. Al2Ca improves the creep resistance of Mg-Al-Ca alloys due to its high thermal stability, but it also accounts for the hot crack defect due to very small thermal expansion.

Large quasicrystals up to ∼10 μm in size with a volume fraction of ∼30% have been identified in a nitrogen gas-atomized marginal glass-forming alloy Al85Ni5Y6Co2Fe2 by detailed transmission electron microscopy. The formation of the large quasicrystal (Q) phase is discussed through the configuration of the valence electrons of its constituent elements, and the thermodynamic and kinetic factors associated with the solidification of this marginal glass-forming alloy during gas atomization. The finding leads to an important inference that marginal glass-forming alloys could be ideal systems for the formation of bulk quasicrystals under appropriate kinetic conditions. The Q phase is stable up to ∼500 °C and decomposes thereafter. The activation energy for the decomposition of the Q phase is similar to the self-diffusion of Al. Two new intermetallic phases associated with the formation and decomposition of the Q phase have also been identified and characterized.

Yttria-stabilized zirconia (YSZ)/Al2O3 multilayers deposited on Pt foil were studied by differential scanning calorimetry. Observed thermal effects were interpreted using additional evidence from x-ray diffraction and transmission electron microscopy. The crystallization temperature of YSZ increases from 344 to 404 °C as the layer thickness decreases from 15 to 4 nm. The enthalpy of crystallization becomes more exothermic with decreasing thickness, and it was measured to be −26 kJ/mol YSZ for 4-nm-thick layers and −12 kJ/mol for 15-nm-thick layers. The latter value is consistent with the reported crystallization enthalpy for YSZ powder of the same composition prepared by precipitation from aqueous solution. The more exothermic crystallization enthalpies for thinner films are indicative of a decrease in their degree of crystallinity. The 2–6-nm-thick Al2O3 layers remain amorphous when heated to 1000 °C. The described methodology enables thermal analysis of oxide thin films using commercial instruments.

Gold nanoparticles (AuNPs) were biosynthesized using Bacillus megaterium, a common soil bacterium. Transmission electron microscopy images revealed that well-developed, spherical, homogeneous nanoparticles are formed extracellularly in reactions containing aqueous chloroaurate ions and conditioned medium at pH 4. Atomic force microscopy measurements showed that adhesion forces between biosynthesized AuNPs and breast cancer cells were almost six times greater than adhesion forces between biosynthesized AuNPs and normal breast cells. Furthermore, adhesion forces of biosynthesized AuNPs to breast cancer cells were three times greater than adhesion forces between chemically synthesized AuNPs and the same breast cancer cells. Finally, adhesion forces between biosynthesized AuNPs conjugated to breast-specific antibodies (AuNP-Ab conjugates), and breast cancer cells were almost five times greater than adhesion forces between unconjugated AuNPs and breast cancer cells. The implications of the results are discussed for the development of nanostructures for the targeted detection and treatment of breast cancer.

Solid polymer electrolytes (SPEs) with poly(vinylidene fluoride-hexafluoropropylene) [P(VdF-HFP)] as polymer host, doped with magnesium trifluoromethanesulfonate (MgTf) and 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIMTf) have been synthesized via solution casting method. This P(VdF-HFP)/MgTf/BMIMTf-based SPE achieves ∼3 × 10−3 and ∼7 × 10−3 S·cm−1 at 30 and 80 °C, respectively, with 75 part by weight (pbw) of BMIMTf. At the same time, they are also examined by means of frequency-dependent conductivity, dielectric permittivity, and dielectric modulus studies. Scanning electron microscopy reveals drastic morphological changes on SPE with small amount of BMIMTf. Even though it gradually changes back to its undoped state with higher concentration, it appears to be swollen. Examination on relationship between ionic conductivity and crystallinity by differential scanning calorimetry technique shows inconsistency at concentration higher than 75 pbw. This observation is related to greater ion–ion interaction due to excessive BMIMTf. Photoluminescence is also used to detect structural alterations in the local environment of SPE.

Concentrated electric field is crucial in generation of needleless electrospinning; the electric field profile together with electric field intensity of the spinneret directly affect the needleless electrospinning performance. Understanding the electric field of different spinnerets would definitely benefit the design and optimization of needleless electrospinning. Three-dimensional (3D) finite element analysis has been used to analyze the electric field profile and electric field intensity of different spinnerets for needleless electrospinning by using the simulation software COMSOL Multiphysics 3.5a. It has been found that evolution of the spinneret of needleless electrospinning from cylinder to multiple disks and then to multiple rings results in stronger and more concentrated electric field. The analysis based on 3D simulation of the electric field could benefit further development of needleless electrospinning in which the production rate and quality of as-spun nanofibers are of great importance.

The covalent attachment of cysteamine-functionalized polyaniline (PANI–NH2) nanofibers onto graphene oxide (GO) sheets in an aqueous medium is investigated for the first time. The functionalized PANI is covalently attached onto the GO surface by simple amidation in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide. The technique can be conveniently scaled up for bulk production. The hybrid nanomaterial is easily synthesized, has good thermal stability, and disperses well in a solvent. Characterization techniques (Fourier transform infrared spectroscopy, thermogravimetry analysis, field emission scanning electron microscopy, and transmission electron microscopy) indicate the successful binding of the functionalized PANI nanofibers onto GO.

Controllable degradation of scaffolds plays an important role in tissue engineering applications. Here, we describe a biomimetic approach to control chitosan scaffold degradation by incorporating lysozyme-loaded poly(D,L-lactic-co-glycolic acid) microspheres in 3D chitosan scaffolds. In vitro degradation tests reveal that the degradation rate increased when the mass ratio of microspheres-to-chitosan increased whereas the contrast group showed a visible turning point at 28d. In vivo degradation rate was much faster than that in vitro, and the relationship between in vitro degradation and in vivo degradation was correlative. Finally, for determining the primary biocompatibility of the combined scaffolds, studies such as cytotoxicity assay, cell attachment study and histological evaluation were carried out. It is concluded that the combination method of enzyme and scaffold is suitable for chitosan scaffold degradation; it also demonstrates an alternative strategy for other biomaterials used in tissue engineering.

The thermal dilation experiment and the martensite transformation features of modified high Cr ferritic heat-resistant steel upon continuous cooling were explored at various cooling rates. The “spread” martensite transformation model was introduced to investigate the influence of the cooling rate applied on the martensite transformation behaviors. The martensite fraction, martensite formation rate, and the density of martensite laths were obtained as a function of cooling rate. Both the onset and offset temperatures of the martensite transformation decrease with the increase of cooling rate, and the martensite formation rate bursts at the beginning of transformation and then reaches a peak rapidly. The fitted data based on the proposed kinetic model indicated that the aspect ratio of martensite lath decreases, instead the density of martensite laths increases, with the increase of cooling rate.