Novel lignin-chitosan-PVA composite hydrogel for wound dressing.

We consider Bloch bound states in the radiation continuum in periodic arrays of dielectric spheres. It is demonstrated that the bound states are associated with phase singularities of the quasimode coupling strength. That makes the bound states topologically protected and, therefore, robust against any variation of parameters preserving the periodicity and rotational symmetry about the array axis. It is shown that under variation of parameters the bound states can only be destroyed by either annihilation of the topological charge or by migration to the sector of the parametric space where the second radiation channel is open.

Topological Bound States in the Continuum in Arrays of Dielectric Spheres

Characterization of microstructure and mechanical properties of laser melting deposited Ti–6.5Al–3.5Mo–1.5Zr–0.3Si titanium alloy

Progress on discontinuously reinforced titanium matrix composites

Isothermal compressions of near-alpha Ti60 alloy were carried out on a Gleeble-3800 simulator in the temperature range of 960-1110 degrees C and strain rate range of 0.001-10.0 s(-1). The high-temperature deformation behavior was characterized based on an analysis of the stress-strain behavior, kinetics and processing map. The flow stress behavior revealed greater flow softening in the two-phase field compared with that of single-phase field. In two-phase field, flow softening was caused by break-up and globularization of lamellar a as well as deformation heating during deformation. While in the single-phase field, flow softening was caused by dynamic recovery and recrystallization. Using hyperbolic-sine relationships for the flow stress data, the apparent activation energy was determined to be 653 kJ/mol and 183 kJ/mol for two-phase field and single-phase field, respectively. The processing map exhibited two instability fields: 960-980 degrees C at 0.3-10 s(-1) and 990-1110 degrees C at 0.58-10 s(-1). These fields should be avoided due to the flow localization during the deformation of Ti60 alloy. (C) 2011 Elsevier B.V. All rights reserved.

High-temperature deformation behavior of Ti60 titanium alloy

Hot working of Ti–6Al–3Mo–2Zr–0.3Si alloy with lamellar α + β starting structure using processing map

We investigate narrowband transmission filters based on subwavelength-grating reflectors at normal incidence. Computational results show that the filtering is realized through symmetry-protected mode coupling. The guided mode resonances introduced by the slab layer allow flexible control of the filter frequencies. The quality factor of the filters could exceed 106. Dielectric gratings can be used over the entire range of electromagnetic waves, owing to their scale-invariant operations. Owing to the high refraction index and low index dispersion of semiconductors in the infrared range, these filters can be applied over a broad range from near infrared to terahertz frequencies.

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Normal incidence filters using symmetry-protected modes in dielectric subwavelength gratings

A novel laminated Ti–TiBw/Ti composite containing Ti layers and TiBw/Ti composite layers were successfully fabricated by the reaction hot-pressing technique. The TiB whiskers and their network distribution structure play an effective role in microstructural evolution of the Ti matrix during the sintering and cooling processes. Interestingly, the morphology and size of grains in the laminated Ti–TiBw/Ti composites exhibit gradient distribution. The Ti layer comprises coarse lath-like grains while the TiBw/Ti composite layer contains two different sizes of equiaxed grains. A combination of high strength and ductility can be obtained by incorporating a low volume fraction of in-situ TiBw through the grain refinement mechanism and the laminated structure. The TiBw/Ti composite layer with high strain hardening rate delays localized necking of the Ti layer. The novel laminated structure of Ti–TiBw/Ti composite allocates stress and strain reasonably well and reveals a prolonged uniform plastic deformation capability.

Gradient grain distribution and enhanced properties of novel laminated Ti–TiBw/Ti composites by reaction hot-pressing

The use of DMSO-doped-poly (3,4-ethylenedioxythiophene):poly (4-styrenesulfonate) (PEDOT:PSS) thin films produced by spin coating as transparent electrodes for a liquid crystal terahertz (THz) phase shifter is reported. The transmittance of these newly proposed transparent electrodes is as high as ∼90%. The phase shifter provides continuous tunability, full electrical controllability, and low-voltage operation at THz frequencies. A maximum phase shift of 129.4° at 1.17 THz is achieved in a 500 μm-thick cell when the driving voltage is as low as 6.7 V (rms).

Electrically tunable liquid crystal terahertz phase shifter driven by transparent polymer electrodes

A range of laminated Ti–TiBw/Ti composites composed of Ti layer and TiBw/Ti composite layer with different volume fractions of TiB whisker (TiBw) were successfully fabricated by diffusion welding. TiBw reinforcement exhibits different morphologies, such as needle-like, self-joining, claw-like and cluster structures due to the increasing volume fractions of TiB. The elastic modulus and yield strength of the laminated composites with different volume fractions of TiB are consistent with the HT equation and shear lag model, respectively. The ultimate tensile strength of the laminated composites with 5 vol%, 8 vol%, 10 vol% and 12 vol% TiBw/Ti composite layer is 604 MPa, 689 MPa, 744 MPa and 789 MPa, along with tensile elongation of 19.7%, 14.1%, 10.4% and 5.5%, respectively. The fracture characteristics of the laminated composites reveal a ductile to brittle transition (DBT) behavior with the increase of TiB volume fraction: fractograph in TiBw/Ti composite layer changes from tortuous into flatter, and Ti layer changes from ductile fracture accompanying with many dimples into brittle fracture with many lath-like fracture morphologies, which are attributed to the decreasing size of plastic zone at the tunnel crack tip.

Xuan Cui

Papers

Hot working of Ti–6Al–3Mo–2Zr–0.3Si alloy with lamellar α + β starting structure using processing map

Normal incidence filters using symmetry-protected modes in dielectric subwavelength gratings

Gradient grain distribution and enhanced properties of novel laminated Ti–TiBw/Ti composites by reaction hot-pressing

Electrically tunable liquid crystal terahertz phase shifter driven by transparent polymer electrodes

Effects of reinforcement volume fraction on tensile behaviors of laminated Ti–TiBw/Ti composites