Mesoporous TiO2 Nanofiber as Highly Efficient Sulfur Host for Advanced Lithium–Sulfur Batteries

Currently, lithium–sulfur batteries su er from several critical limitations that hinder their practical application, such as the large volumetric expansion of electrode, poor conductivity and lower sulfur utilization. In this work, TiO2 nanofibers with mesoporous structure have been synthesized by electrospinning and heat treating. As the host material of cathode for Li–S battery, the as prepared samples with novelty structure could enhance the conductivity of cathode composite, promote the utilization of sulfur, and relieve volume expansion for improving the electrochemical property. The initial discharge capacity of TiO2/S composite cathode is 703 mAh/g and the capacity remained at 652 mAh/g after 200 cycles at 0.1 C, whose the capacity retention remains is at 92.7%, demonstrating great prospect for application in high-performance Li–S batteries.

Joining of Zirconia and Ti-6Al-4V Using a Ti-based Amorphous Filler

Polycrystalline ZrO2-3 mol.%Y2O3 was brazed to Ti-6Al-4V by using a Ti47Zr28Cu14Ni11（at.%） amorphous ribbon at 1123–1273 K in a high vacuum. The influences of brazing temperature on the microstructure and shear strength of the joints were investigated. The interfacial microstructures can be described as ZrO2/TiO＋TiO2＋Cu2Ti4O＋Ni2Ti4O/α-Ti＋（Ti,Zr）2（Cu,Ni） eutectic/acicular Widmanst¨aten structure/Ti–6Al–4V alloy. With the increase in the brazing temperature, the thickness of the TiO＋TiO2＋Cu2Ti4O＋Ni2Ti4O layer reduced, the content of the α-Ti＋（Ti,Zr）2（Cu,Ni） eutectic phase decreased, while that of the coarse α-Ti phase gradually increased. The shear strength of the joints did not show a close relationship with the thickness of the TiO＋TiO2＋Cu2Ti4O＋Ni2Ti4O layer. However, when the coarse （Ti,Zr）2（Cu,Ni） phase was non-uniformly distributed in the α-Ti phase, or when α-Ti solely situated at the center of the joint, forming a coarse block or even connecting into a continuous strip, the shear strength greatly decreased.

Effect of parameters on interface of the brazed ZrO_2 ceramic and Ti-6Al-4V joint using Ti-based amorphous filler

A commercially available Ti47Zr2sCu14Nin （at. pct） amorphous filler foil was used to join ZrO2 ceramic and Ti-6A1-4V alloy. According to experimental observations, the interface microstructure accounts for the mechanical properties of the joints. The effects of brazing conditions and parameters on the joint properties were investigated. The joint shear strength showed the highest value of about 108 MPa and did not monotonously increase with the brazing time increasing. It was shown that decreasing of brazing cooling rate and appropriate filler foil thickness gave higher joint strength.