Applications of polymer thin films include functional coatings, flexible electronics, membranes and energy conversion. The physical properties of polymer films of nanoscale thicknesses typically differ from the bulk, due largely to entropic effects and to enthalpic interactions between the macromolecules and the external interfaces. Studies of the size-dependent physical properties of macromolecules have largely been devoted to linear chain polymers. In this Prospective, we review recent experiments and simulations that describe the structure and fascinating physical properties, from wetting to the glass transition, of star-shaped macromolecules. The properties of these molecules would render them more useful than their linear chain analogs, for some specific applications.

The Seebeck coefficient is an important parameter of thermoelectric materials, which is routinely measured by commercial or home-made equipment based on different methods. However, due to various temperature offsets in the measurement, the determination of temperature gradient can be inaccurate, leading to a large uncertainty in Seebeck coefficient. To elucidate the influence of the inaccurate temperature gradient on the determination of Seebeck coefficient, an error analysis has been performed on a commercial system. Several potential factors that may affect the establishment of temperature gradient were discussed in detail. A comparison between the single point method and the slope method was made to verify which is more accurate to calculate the Seebeck coefficient from the raw measurement data. It is suggested that the slope method is more preferable and the single point method can also be accurate enough when a relatively large temperature gradient is adopted.

The effect of Dy-doping on the dielectric nonlinearity was investigated in Mn and V-doped BaTiO3 multilayer ceramic capacitors under the same grain size condition, which was described by the Preisach model utilizing the first order reversal curve (FORC) distribution. The dielectric constants in both low and high field region could be enhanced by the Dy-doping, and it was associated with the increase of both reversible and irreversible FORC distributions near zero bias, whereas there was little variation in the saturation polarization that scales to the magnitude of spontaneous polarization. These results demonstrate that both reversible and irreversible domain wall motions are enhanced by Dy-donor incorporation in BaTiO3 resulting in softening of the dielectrics and increase of dielectric constants, which is supposed to be caused by the decrease of the pinning sources such as defect dipoles formed by the oxygen vacancies and their interaction with the domain walls.

In this work, the correlation between the number of nonbridging oxygen (NBO) atoms and the thermal and optical properties of TeO2–Li2O–MoO3 glasses was studied. Samples containing (100 − x)TeO2–x(Li2O–MoO3) with x = 10, 15, 20, and 25 mol% were investigated by Raman and Fourier transform infrared (FTIR) spectroscopies. From the optical absorption measurements, the band gap energies were determined. The Raman and FTIR results showed that with increasing x, the TeO4 units transform into TeO3+1 units and then into TeO3 units, while the Mo coordination changes from 4 → 6. This transformation corresponds to a decrease in the total number of NBO with increasing x in this glass matrix. The decrease in the NBO is also confirmed by the increase in band gap energies and the decrease in the optical basicity, indicating a more polymerized network with increasing x.

Multifunctionalized nanoparticles have a great attention owing to their unique advantages as ideal tools for gene/drug delivery, bioimaging, labeling, or intracellular tracking in biomedical applications. In the present work, azole functional Poly(glycidyl methacrylate) (PGMA) grafted hollow silica sphere (HSS) nanoparticles synthesized and characterized as biomaterials. For the preparation of HSS particles, a two-step method based on the sol–gel process was used in this study. HSS grafted with PGMA by free radical polymerization of (glycidyl methacrylate) (GMA) and HSPGMA (PGMA grafted HSS) modified with 5-aminotetrazole (ATet), 3-amino-1,2,4-triazole (ATri), and 1H-1,2,4-triazole (Tri) to obtain 1,2,4-triazole functional PGMA grafted HSS (HSPGMA-Tri), 5-aminotetrazole functional PGMA grafted HSS (HSPGMA-Tet) and 5-Amino-Triazole functional PGMA grafted HSS (HSPGMA-ATri) molecules via ring opening of the epoxide ring. Azole functional PGMA grafted HSS composites were doped with phosphoric acid. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) analyses were confirmed the grafting and modification of HSS. TGA and DSC were used to examine the thermal stability and homogeneity of the materials.

A series of (HfN)1−x (TaN)x , ceramics with x representing the starting powder blend compositions of 0.0, 18.8, 28.1, and 46.7 at.%, have been fabricated by vacuum plasma spraying. During the plasma spraying, the mixture lost approximately 25 at.% nitrogen facilitating the precipitation of metallic and metal-rich nitride phases. These specimens underwent static air oxidation exposure up to 1700 °C. In general, it was found that the addition of tantalum nitrides to the hafnium nitrides resulted in poorer oxidation behavior. However, the 18.8 at.% specimen deviated from this trend and had the lowest observed mass change. This specimen formed a dark-colored oxide scale, indexed as Hf6Ta2O17, which acted as a passivation layer. Within the scale, hafnium oxynitride phases were observed. A transformation pathway in forming these rhombohedral oxynitride phases is proposed by the filling in of oxygen in the light element interstitial locations of the rhombohedral ε-Hf3N2 and ζ-Hf4N3 structures.

The development of high performance Al–Cu based alloys generally depends on the strict control of the Fe content. However, with the increasing use of recycled aluminum alloys, it is necessary to increase the tolerance for the Fe content in Al–Cu cast alloys for the purpose of low cost, energy saving, and environment protection. In this study, the formation of Fe-rich intermetallics and their effect on the tensile properties of squeeze-cast Al–5.0 wt% Cu–0.6 wt% Mn alloys with an Fe content of up to 1.5 wt% have been investigated. The full formation sequence of squeeze-cast Al–5.0 wt% Cu–0.6 wt% Mn alloys with different Fe contents has been established. The results were also compared with the corresponding results obtained for Al–5.0Cu–0.6Mn alloys prepared by gravity die casting. It is found that the Fe-rich intermetallic compounds mainly consist of α-Fe and β-Fe in alloys with a low Fe content, changing into Al6(FeMn) and Al3(FeMn) for alloys with a high Fe content. The applied pressure promotes the formation of the Fe-rich intermetallics α-Fe/Al6(FeMn) and prevents the precipitation of needle-like β-Fe/Al3(FeMn). The elongation of the alloys gradually decreases with the Fe content, and a maximum value for both the ultimate mechanical strength and the yield strength was found for the alloys with 0.5 wt% Fe. The tensile properties of alloys with a different Fe content significantly increased as the applied pressure was increased from 0 to 75 MPa, especially the elongation.

The effect of current direction (CD) on the microstructural evolution and mechanical properties of a Cu–Zn binary phase (α + β) alloy during the primary process of phase transformation induced by electric current pulses (ECP) treatment was investigated. To clarify the effect of CD, the samples were prepared with different angles between the CD and rolling direction (RD) from 0° to 90°. Results showed that not only the microstructural evolution but also the corresponding mechanical properties all had a saddle point in the sample with the angle 45°. Analyzed from the mechanical properties, it could be found that the anisotropic of the materials becomes stronger due to the application of ECP. An important finding is that by changing the angles between the CD and the RD, a novel and effective approach to control the phase transformation process could be provided.

A series of zeolite–zeolite composites were prepared by a two-step hydrothermal crystallization procedure in which the mixture of presynthesized ZSM-5 zeolite acts as nutrients for the growth of postsynthesized Y zeolite, and the as-synthesized products are denoted as MFI–FAU. The structural, crystalline, and textural properties of the as-synthesized materials, as well as the references Y, ZSM-5, and a corresponding physical mixture composed of Y and ZSM-5 zeolite, were characterized by x-ray powder diffraction (XRD), Fourier transform infrared spectrum (FTIR), temperature-programmed desorption of ammonia, N2 adsorption–desorption, scanning electron microscopy, energy-dispersive spectrometry, and Thermogravimetry. The results show that the ratio of Y to ZSM-5 in the composite can be adjusted by controlling the hydrothermal treatment time of the second-step synthesis. Steric hindrance provoked by the concurrently growing crystals offers the postsynthesized Y zeolite phase, a relatively smaller size. A hierarchical pores system, which results from the extraction of silicon species from ZSM-5 and the polycrystalline accumulation of Y zeolite, has been created in the zeolite–zeolite composite. Catalytic performances of the zeolite–zeolite composite catalysts as well as the references catalysts were investigated during the catalytic cracking of isopropylbenzene. As compared with the corresponding physical mixture, the composite catalysts display the excellent catalytic performances with a higher conversion of isopropylbenzene as well as a longer catalytic life because of the introduced hierarchical pores system and the formation of special composite structure.

We theoretically investigated the structural and thermoelectric properties of Mg2Si with Al and Sb (Na and B) as n-type (p-type) impurities. Supercell calculations involving relaxation of the atomic positions using an ab initio pseudo-potential method were performed. The formation energies, Eform,i, for the i = Mg, Si, and 4b sites, and consequently, the energetically preferred sites occupied by the impurities, were discussed. The calculated Eform,i were used to estimate the impurity-site occupancy probabilities, pi(T), based on the canonical distribution in the equilibrium state, i.e., pi(T) ∝ exp(−Eform,i/kBT) (Boltzmann constant: kB, temperature: T), and the resultant effects on the carrier concentration. Next, an all-electron full-potential linearized augmented-plane-wave calculation was performed based on the optimized structures, and the temperature dependence of the thermoelectromotive force (the Seebeck coefficient) was evaluated using the Boltzmann transport equation. The calculated and experimental results for n-type doped systems were compared.

We are reporting on stress engineering utilizing AlN/GaN superlattices (SLs) for epitaxy of GaN layers on 200 mm silicon substrates carried out in Veeco's Propel™ rotating disk, single wafer metal organic chemical vapor deposition (MOCVD) reactor. The Turbodisc® reactor is designed to have homogeneous alkyl/hydride flow distribution and uniform temperature profile, which translate into excellent uniformity and concentric symmetry in epilayer thickness and alloy composition. This feature results in uniform and controllable stress in epilayers across large-size substrates. Crack-free 2 μm GaN layers were grown on 200 mm Si using uniformly strained AlN/GaN SLs with periods of 3–5 and 10–30 nm, respectively. Compressive and tensile stress can be precisely adjusted by changing the thickness of the AlN and GaN layers in the SLs, resulting in controllable wafer curvature/bow after cool down. For a fixed period thickness structure, the effects of growth conditions, such as growth rate of GaN, AlN V/III ratio, and growth temperature, on wafer stress were investigated.

The Mn-doped ZrO2/TiO2 nanostructured photocatalysts had been prepared by the simple hydrothermal method. The morphologies and structures of the as-prepared photo-catalyst were characterized by transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and electron paramagnetic resonance. The resultant nanostructured photocatalysts exhibited high photocatalytic activity under ultraviolet (UV) light irradiation, attributing to the improvement of the photo-absorption property and the separation efficiency of photo-generated electrons and holes. The hydroxyl radicals (•OH), superoxide radical (•O2−), and holes (h+) are the main active species in aqueous solution under UV light irradiation.

We investigated how coherent interfaces, between face centered cubic (fcc)/hexagonal close packed (hcp) systems, affect large strain deformation and fracture modes in hcp zircaloy aggregates with fcc hydrides. We derived 36 unique transformations related to coherent interfaces between fcc and hcp systems. We then used these orientation relations (ORs) with a dislocation-density crystalline plasticity formulation, a nonlinear finite-element, and a fracture approach that account for crack nucleation and propagation. We investigated how these ORs affect crack nucleation and propagation, dislocation density and inelastic slip evolution, stress accumulation, lattice rotation, and adiabatic heating. The predictions indicate that the physical representation of ORs affects local deformation and fracture behavior and are, therefore, essential for the accurate predictions of behavior at different physical scales in heterogeneous crystalline systems.