The effects of boundaries such as grain boundaries and phase boundaries on low-field magnetoresistance (LFMR) have been investigated in single-phase lanthanum strontium manganates, in this case La0.7Sr0.3MnO3 (LSMO) and LSMO: zinc oxide (ZnO) nanocomposite thin films. In the pure LSMO films with similar grain size, it is found that the LFMR increases as the grain misorientation factor (β) increases. The LFMR in the nanocomposite films is greatly enhanced, as compared with single-phase films, due to the reduced grain size, and increased phase boundary (PB) and β effects. The composition study shows that the LFMR can be dramatically enhanced when the secondary phase content approaches the percolation threshold. The increased β and secondary phase concentration reduce the cross-section of electron conduction paths and favor the formation of the quasi-one-dimensional transport channels. Our results demonstrate that the reduction of cross-section of the electron conduction paths by tuning the grain orientation and secondary phase composition is necessary for enhancing LFMR effect.

This work reports the gold-coated self-organized silicon nanopyramidal array prepared by a wet etching and magnetron sputtering process at room temperature. Scanning electron microscopy was used to detect the morphology of gold films. The surface-enhanced Raman scattering (SERS) spectra of the rhodamine 6G (R6G) molecules adsorbed on a nanoscale gold film were recorded. Experimental results show the relationships between gold film thickness and SERS intensity. A full three-dimensional finite difference time domain calculations were carried out, which compare the experimental results and show agreement with ratios of the SERS enhancement for the different thicknesses of gold films. Furthermore, numerical simulations of the array were conducted for both a real gold metal coating and a perfect electrical conductor to determine whether the SERS enhancement was due to diffraction or plasmonic effects. The sample with the fast fabrication process used in this work could provide a new way to obtain a uniform enhancement and low cost SERS substrate.

Changes in the colloid-chemical and photocatalytic properties of titania nanoparticles by attrition milling in the presence of glycine (Gly) and subsequent heat treatment were examined. By milling at 1500 rpm for 6 h, the average particle size was decreased from 123 to 85 nm, with simultaneous decrease in the specific surface area from 35.1 to 23.5 m2/g. Interfacial reactions between titania and Gly were confirmed by Fourier transform infrared spectroscopy, from the blue shift of the COO− related vibrational bands by 25 cm−1, relative to the same band from the pristine Gly. The bimodal N1s x-ray photoelectron spectroscopy peak similar to that from the reported titania—amino acid complex is another indication of the complex formation with the participation of nitrogen. When the dispersion was dried and calcined at 500 °C in air, the powder exhibited pale yellow color. Diffuse reflectance spectroscopy showed significant visible light absorption, suggesting nitrogen incorporation into titania. The fired product showed high photocatalytic antibacterial activity by irradiation of blue light centered at around 440 nm, using Escherichia coli as a specimen of bacterial species. Thus, the present Gly-modified titania nanoparticles could be used for eliminating indoor bacteria under soft blue illumination. The series of interfacial chemical processes involved are also discussed.

Zn1.98Mn0.02P2O7 was synthesized by the wet chemical route. The purity of the phase and the oxidation state of manganese ion were investigated by x-ray diffraction (XRD) and electron paramagnetic resonance (EPR). Structural phase transition in α-Zn2P2O7 was investigated by high-temperature XRD (HTXRD), differential scanning calorimetry (DSC), and EPR studies. There is a distinct signature of phase transitions between 390 and 400 K in our powder sample by EPR and HTXRD. There was a sharp reduction in the volume of unit cell, while going from alpha to beta phase; with discontinuity in 405 K, which confirmed the transition to be of first order. Similarly, the effect of temperature on zero-field splitting parameter (D) also showed that there is a sudden jump (discontinuity) in the value at around 400 K (phase transition temperature) confirming the transition to be of first order. DSC studies corroborated these findings.

We report the mechanical behavior of vertically aligned carbon nanotube films, grown on Si substrates using atmospheric pressure chemical vapor deposition, subjected to in situ large displacement (up to 70 μm) flat-punch indentations. We observed three distinct regimes in their indentation stress–strain curves: (i) a short elastic regime, followed by (ii) a sudden instability, which resulted in a substantial rapid displacement burst manifested by an instantaneous vertical shearing of the material directly underneath the indenter tip by as much as 30 μm, and (iii) a positively sloped plateau for displacements between 10 and 70 μm. In situ nanomechanical indentation experiments revealed that the shear strain was accommodated by an array of coiled carbon nanotube “microrollers,” providing a low-friction path for the vertical displacement. Mechanical response and concurrent deformation morphologies are discussed in the foam-like deformation framework with a particular emphasis on boundary conditions.

Decoupled growth often occurs in the nonfacetted–facetted eutectic systems. And it is generally considered that the nonfacetted solid solution acts as the leading phase in the decoupled growth. In this work, Fe40Ni40P14B6 eutectic alloys were systematically studied via solidification of undercooled melts and crystallization of amorphous alloys. Upon solidification of melts subjected to different undercoolings, as the undercooling increases, the growth mechanism develops from cooperative growth to decoupled growth. Upon crystallization of amorphous alloys, the partially crystallized sample consists only of strongly faulted intermetallic (Fe,Ni)3(P,B) with chemical composition deviating from stoichiometry. Formation of supersaturated solid solution γ(Fe, Ni) in the solidification and supersaturated intermetallic (Fe,Ni)3(P,B) in the amorphous crystallization indicates that decoupled growth results from solute trapping and disorder trapping in rapid growth of solid solution and intermetallic, respectively. Further application of rapidly quenched experiments and theoretical analysis declare that the decoupled growth results from a competition between the growth of γ(Fe, Ni) and (Fe,Ni)3(P,B), which are controlled by solute trapping and disorder trapping, respectively.

A kinetic model of crystallization based on two-dimensional nucleation and growth of plate-like crystals with constant thickness is analyzed. It is shown that plate thickness required for nucleation is limited. The lower limit is determined by zero Gibbs’ free energy of transition, the upper one corresponds to the conditions when the critical cluster volume of nucleation is equal to two elementary kinetic units. Effects of plate thickness on crystallization kinetics are discussed. In the lower temperature range, creation of thicker plates is preferred. For a given plate thickness, frequency of the phase transition decreases with increasing temperature. Numerical calculations for α-polypropylene concern kinetics of primary nucleation and global phase transition in a system of one or several fractions of plate-like kinetic elements.

A mixture of pure Ni powder and pure W powder with a nominal composition Ni–15 at.% W was subjected to ball milling in a planetary mill and in a shaker mill. The microstructural evolution upon milling and upon subsequent annealing in the temperature range from 25 to 800 °C was investigated using ex situ and in situ x-ray diffraction integral breadth (single-line and Williamson–Hall) methods and whole powder pattern modeling as well as scanning electron microscopy, transmission electron microscopy, and differential scanning calorimetry. A nanocrystalline Ni(W) solid solution phase develops upon ball milling, with a higher W content by milling in the shaker mill as compared to the planetary mill. Grain coarsening studies indicated a very high stability of the nanocrystalline state, up to almost about 500 °C. Results of annealing at higher temperatures showed that, while the dissolved W content increased in the Ni matrix, a high stability against grain coarsening occurs, which can be ascribed to the presence of (segregated) W atoms at the grain boundaries.

Patterned porous films prepared by the breath figure method have received considerable interests because of the potential applications. This paper reports a top–down method to fabricate functional patterned films. Cross-linked polystyrene microspheres were synthesized by a two-stage dispersion polymerization using divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA) as cross-linkers, which provide free vinyl groups on the microspheres surface. The amounts of residual vinyl groups were determined by potentiometric titration. Glucose was then bound to the microspheres via thiol–ene reaction, which was confirmed by x-ray photoelectron spectroscopy and water contact angle measurements. Results indicate that vinyl groups of EGDMA show relatively higher reactivity than that of DVB. Microspheres with glucose were assembled into the pores of honeycomb films prepared by the breath figure method, forming functional arrays for recognizing a lectin, Con A. This top–down method is useful in preparing patterned films with various functional moieties, which may act as a platform, such as, for investigating carbohydrate–lectin interactions and for sensing.

To clarify the underlying mechanism of formation and growth of aluminum coating, the interface microstructures of as-prepared aluminum coating iron were investigated using various experimental methods. The liquid Al–Si, Al–Ge alloys were chosen as the dipping baths. In both cases, the total thickness of the reaction layer is controlled mainly by the well-known diffusion growth of η-Al5Fe2. The melt environment of the Al bath plays a decisive role in the formation and growth of the diffusion layer. The results show that Ge atoms could also decelerate reaction layer growth like Si atoms, which mainly restrain the diffusion of Al atoms. Meanwhile, Ge element represents an abnormal concentration gradient in the η-Al5Fe2 phase. The diverse growth behavior of the diffusion layer is attributed to the strong controlling role of the alloying element in Al baths based on the atomic diffusion and activity analysis.

Confined synthesis of three-dimensionally ordered mesoporous-imprinted (3DOm-i) zeolites within three-dimensionally ordered mesoporous (3DOm) carbons prepared from silica colloidal crystals was achieved through multiple hydrothermal (MHT) synthesis and steam-assisted crystallization (SAC). The transition of ordered mesoporous structures, starting from silica colloidal crystal to resulting 3DOm-i zeolites including the intermediate 3DOm carbon templates, and the correlations among the confined synthesis methods, crystal growth nature of different zeolites, and the sintering of the templates were studied. An imperfect replication was found in 3DOm-i zeolite when it compared to silica colloidal crystals regardless the synthesis methods (MHT or SAC), which might be originated from combination effects of sintering of the silica colloidal crystals and partial filling of cavities of the 3DOm carbon template during the confined synthesis, and the degree of the structure replication was notably influenced by microstructures of zeolite as well. A thorough investigation of the growth development of 3DOm-i BEA zeolites with various Si/Al ratios ranging from 14 to 27 through the MHT method confirmed that the crystallization takes place in the carbon template by a cage-to-cage propagation growth process.

Grain refinement strengthening in low carbon ferrite–cementite steel was investigated using the estimated true stress (σ)–true strain (ε) relationship up to the plastic deformation limit, i.e., just before fracture. Static and stepwise tensile tests were performed using ferrite–cementite (FC) steels with ferrite grain sizes in the range 0.5–34 μm, and the σ–ε relationships up to the plastic deformation limit were estimated by using the Bridgman equation. In the nominal stress–strain curves, the lower yield stress and tensile strength increased and the uniform and total elongations decreased with a decrease in the ferrite grain size. It was found from the σ–ε relationships of the FC steels that grain refinement strengthening up to 0.8 μm can improve σ and ε at the plastic deformation limit. From the scanning electron microscopy observations of the cross-sectional planes parallel to the tensile direction for the FC steels, voids were observed at the interface between ferrite and cementite in the case where the thickness of elongated ferrite came close to the size of the dispersed cementite.

This paper examines the onset and progression of dynamic recrystallization (DRX) phenomena under shear deformation conditions characterized by strains >1 and strain rates >102/s by purposing large strain machining (LSM) as a test of microstructure response. To accomplish this, samples are created using LSM while characterizing the deformation using digital image correlation and infrared thermography. Microstructural consequences resulting from the characterized thermomechanical conditions are examined using electron backscattered diffraction. The progression of DRX is measured by identifying the threshold of grain orientation spread demarcating the onset of recrystallization and utilizing this threshold to segregate the microstructure and quantify the extent of DRX. A model for the onset of DRX as a function of thermomechanics of deformation is presented. This characterization can help understand surface microstructures resulting from shear-based manufacturing processes, such as turning, milling, shaping, etc., that are created under analogous thermomechanical conditions.

The crushing strength or compression strength is a fundamental mechanical property for reticulated ceramic foams. There are essential influencing variables such as the rate of the applied load, the size of the applied load area, the sample size, and the strut homogeneity of the samples. In this work, the impact of the variation of the testing parameters on the crushing strength measurement was evaluated with the help of industrially produced ceramic foams made of Al2O3, ZrO2, SiC, and fused silica. The results indicate that the rate of the applied load has no significant influence on the crushing strength of the ceramic foams. Whereas the size of the applied load area and the sample size have an evident influence. The experimental results were compared with the minimum principal stress distribution calculated with FEM.

The use of MgO nanoparticle (NP) loaded poly(methylsilsesquioxane) (PMSQ) as a low temperature processable composite dielectric has been investigated. The composite dielectrics have been synthesized using facile ultrasonic mixing of trimethoxymethylsilane (MTS), butanol (n-BuOH) and deionized water at 60 °C, with MgO loadings from 0.096 up to 0.39 wt% of the initial solution. Thin films of the composite materials produced have shown an increase in dielectric constant from 2.8 for raw PMSQ up to 3.4 for the 0.39 wt% loaded PMSQ + MgO NP composites at frequencies up to 2 MHz, comparable to 3.9 for SiO2. The composite dielectric materials have shown suitability as a dielectric material for a P3HT OFET, with the performance comparable to a standard SiO2 dielectric control sample.

SiC nanowires (NWs) designed from selected bulk polytypes are investigated using quantum mechanics-based simulations (both ab initio and semiempirical methods), and their structure–property relationships examined vis-à-vis their size, shape, and orientation. It is found that 2H–SiC NWs of hexagonal morphology oriented along the <0001> direction are the most stable ones compared to NWs designed using other bulk polytypes (e.g., 3C, 4H, or 6H) and other morphologies (round, square, rhombus, etc.) for diameters with 1 nm < d < 14 nm. Based on the electronic density calculations, it is found that 2H–SiC <0001> NWs exhibit semiconductor-like characteristics (akin to their bulk counterparts), even when their diameters approach 1 nm. On the other hand, SiC NWs designed from 3C, 4H, and 6H bulk polytypes, regardless of their morphology, exhibit gapless features for diameters less than 3.5 nm. Undoubtedly, these novel properties of SiC NWs can be exploited in the fabrication of nanoscale devices.

The structural, electronic, and magnetic properties of quasi-one-dimensional MoS2nanowires (NWs), passivated by extra sulfur, have been determined using ab initio density functional theory. The nanostructures were simulated using several different models based on experimental electron microscopy images and theoretical literature. It is found that independently of the geometrical details and the coverage of extra sulfur at the Mo edge, quasi-one-dimensional metallic states are predominant in all the low-energy model structures despite their reduced dimensionality. These metallic states are localized mainly at the edges. However, the electronic and magnetic character of the NWs does not depend only on the S saturation but also on the symmetry configuration of the S edge atoms. Our results show that for the same S saturation, the magnetization can be decreased by increasing the pairing of the S and Mo edge atoms. In spite of the observed pairing of S dimers at the Mo edge, the NWs do not experience a Peierls-like metal–insulator transition.

Copper nanoparticles (Cu-NPs) were prepared in virgin coconut oil (VCO) using a laser ablation technique. A copper plate immersed in VCO was irradiated by an Nd:YAG laser at wave lengths of 532 nm for 5, 10, 20, and 30 min. By increasing the ablation time from 5 to 30 min, the particle size inside the nanofluid decreased from 11 to 4 nm and the concentration, refractive index, and the volume fraction of copper nanofluid increased. The Cu-NPs were capped with oxygen from hydroxyl groups of the VCO, as verified by Fourier transform infrared spectroscopy. The refractive indices, obtained by analysis of the surface plasmon resonance signals increased from 1.44371 + 0.0034i to 1.44387 + 0.0142i, and special self-phase modulation due to nonlinearity effect was investigated.