Y.J. Huang

Bulk metallic glasses: Smaller is softer

The authors report on the dramatic effect of sample size on the plastic deformation capability of a Ti-based bulk metallic glass. Compared with the larger one, the smaller size glassy alloy with the same chemical composition exhibits significantly enhanced plasticity, suggesting a “smaller is softer” trend of metallic glasses. The phenomenon is attributed to the fact that the smaller size alloy, which experienced a faster cooling rate during solidification, contains a larger amount of heats of relaxation and crystallization, favoring the preferential nucleation of shear bands and thus allowing enhanced plasticity upon compressive loading.

Plasticity of a TiCu-based bulk metallic glass: Effect of cooling rate

Compressive deformation was experimentally investigated for Ti 41.5 Cu 42.5 Zr 2.5 Hf 5 Ni 7.5 Si 1 bulk metallic glass (BMG) fabricated at different cooling rates. It was found that the ductility of the BMG alloy increased with increasing of the cooling rate in solidification. The alloy with a monolithic amorphous structure exhibited a large ductility, up to 12%. The effect of cooling rate on the ductility of the BMG alloy is interpreted in terms of the variation in amorphous nature and free volume of the as-cast materials.

Atomic-scale bonding of bulk metallic glass to crystalline aluminum

A Ti40Zr25Cu12Ni3Be20 bulk metallic glass (BMG) was welded to a crystalline aluminum by the parallel plate explosive welding method. Experimental evidence and numerical simulation show that atomic-scale bonding between the BMG and the crystalline aluminum can be achieved, and the weldment on the BMG side can retain its amorphous state without any indication of crystallization in the welding process. Nanoindentation tests reveal that the interface of the explosive joints exhibits a significant increase in hardness compared to the matrix on its two sides. The joining of BMG and crystalline materials opens a window to the applications of BMGs in engineering.

Ultralong Rutile TiO2 Nanowire Arrays for Highly Efficient Dye-Sensitized Solar Cells.

Vertically aligned rutile TiO2 nanowire arrays (NWAs) with lengths of ∼44 μm have been successfully synthesized on transparent, conductive fluorine-doped tin oxide (FTO) glass by a facile one-step solvothermal method. The length and wire-to-wire distance of NWAs can be controlled by adjusting the ethanol content in the reaction solution. By employing optimized rutile TiO2 NWAs for dye-sensitized solar cells (DSCs), a remarkable power conversion efficiency (PCE) of 8.9% is achieved. Moreover, in combination with a light-scattering layer, the performance of a rutile TiO2 NWAs based DSC can be further enhanced, reaching an impressive PCE of 9.6%, which is the highest efficiency for rutile TiO2 NWA based DSCs so far.

Zinc-doped SnO2 nanocrystals as photoanode materials for highly efficient dye-sensitized solar cells

Zn-doped SnO2 nanocrystals were successfully synthesized by a simple hydrothermal method. It is found that Zn doping into SnO2 can induce a negative shift in the flat-band potential (VFB) and increase the isoelectric point. As a result, dye-sensitized solar cells (DSCs) based on Zn-doped SnO2 nanocrystal photoanodes exhibit longer electron lifetimes and higher dye loading compared to undoped SnO2 based DSCs. The overall power conversion efficiency (η) of the optimized Zn-doped SnO2 based DSC reaches 4.18% and increases to 7.70% after the TiCl4 treatment. More importantly, a remarkable η of 8.23% is achieved for DSCs based on a high-quality double-layer SnO2 photoanode with the TiCl4 treatment, to the best of our knowledge, which is so far the best reported efficiency for DSCs based on SnO2 photoanodes.

One-pot synthesis of hierarchical SnO2 hollow nanospindles self-assembled from nanorods and their lithium storage properties

Novel hierarchical SnO2 hollow nanospindles self-assembled from nanorods have been successfully synthesized via a templating approach under hydrothermal conditions. The influence of the reactant concentration on SnO2 products is investigated in detail. It is found that the interplay of the acidic etching of Fe2O3 templates and controlled hydrolysis of SnCl2 is significant for the formation of the hierarchical SnO2 hollow nanostructures. The evolution process and formation mechanism of the hollow structures with nanorods are analyzed from the angle of nucleation and morphology. Moreover, the electrochemical properties of the hollow structures are also studied by charge–discharge cycling, the result displays that the hierarchical SnO2 hollow nanostructure exhibits much better lithium storage properties with higher reversible capacities and enhanced cyclic capacity retention than the commercial SnO2 nanoparticles.

Heterostructured TiO2/MgO nanowire arrays for self-powered UV photodetectors

Heterostructured TiO2/MgO nanowire arrays (NWAs) were grown vertically on fluorine-doped tin oxide (FTO) glass by a simple solvothermal method. A photoelectrochemical self-powered UV photodetector (UVPD) was fabricated using the heterostructured TiO2/MgO nanowire arrays (NWAs) as the photoanode. The TiO2/MgO NWAs based UVPDs shows a higher photocurrent density (J) and open-circuit voltage (Voc) with respect to the UVPD with bare TiO2 NWAs under UV light irradiance. The intrinsic role of the MgO shell layer on the J and Voc varitions of UVPDs is investigated in detail. An impressive responsivity of 0.233 A W−1 was achieved for the UVPD with TiO2/MgO NWAs, which is the highest responsivity for photoelectrochemical self-powered UVPDs based on various TiO2 nanostructured photoanodes so far. Moreover, this UVPD also exhibits a high on/off ratio, fast response time, excellent visible-blind characteristic and linear optical signal response.

A high-performance self-powered UV photodetector based on SnO2 mesoporous spheres @ TiO2

A novel self-powered UV photodetector (UVPD) based on the photoelectrochemical cell (PECC) has been constructed using the TiO2 coated SnO2 mesoporous spheres (SnO2-MS@TiO2). This self-powered UVPD displays a higher photocurrent density compared to the UVPD with the pure SnO2-MS. By means of external quantum efficiency (EQE), UV-vis absorption, and electrochemical impedance measurements, we scrutinize the intrinsic role of the TiO2 coating layer on the photocurrent enhancement. Under UV irradiation, this UVPD exhibits a high on/off ratio of 11519, a fast rise time of 0.007 s and decay time of 0.006 s, together with the excellent visible-blind characteristic and linear optical signal response. The self-powered photodetector is a promising candidate for application in high-sensitivity and high-speed UVPDs.

Refractive index and strain sensor made of S-tapered photonic crystal fiber

An experimental investigation on an S-tapered photonic crystal fiber interferometer is presented in this paper. The sensor exhibits highly surrounding refractive index sensitive, which is 4.7 × 10−3 RIU (refractive index unit) in 1.33–1.39 and 1.45 × 10−3 RIU in 1.39–1.44 commensurable with general sensors. Attribute to the S-shape’s distortion, red shifts are measured in axial strain test. In addition, insensitivity (4.3 pm/°C) in low temperature and sensitivity (22.4 pm/°C) in high temperature are confirmed by experiments. These properties combined with a simple fabrication process and a durable structure.

Application of 3A molecular sieve layer in dye-sensitized solar cells

3A molecular sieve layer was used as dehydration and electronic-insulation layer on the TiO2 electrode of dye-sensitized solar cells. This layer diminished the effect of water in electrolyte efficiently and enhanced the performance of cells. The conversion efficiency increased from 9.58% to 10.2%. The good moisture resistance of cells was attributed to the three-dimensional interconnecting structure of 3A molecular sieve with strong adsorption of water molecule. While the performance enhancement benefited from the suppression of the charge recombination of electronic-insulation layer and scattering effect of large particles.