Oxygen variation in titanium powder and metal injection molding

The control of oxygen is paramount in achieving high-performance titanium(Ti)parts by powder metallurgy such as metal in-jection molding(MIM).In this study,we purposely selected the Ti and Ti-6Al-4V powders as the reference materials since these two are the most representative Ti materials in the industry.Herein,hydride-dehydride(HDH)Ti powders were pre-oxidized to examine the ef-fect of oxygen variation on the characteristics of oxide layer on the particle surface and its resultant color feature.The results indicate that the thickness and Ti oxide level(Ti^(0)→Ti^(4+))of the oxide layer on the HDH Ti powders increased as the oxygen content increased,lead-ing to the transition of color appearance from grey,brown to blue.This work aids in the powder feedstock selection at the initial stage in powder metallurgy.In addition,the development of oxygen content was comprehensively studied during the MIM process using the gas-atomized(GA)Ti-6Al-4V powders.Particularly,the oxygen variation in the form of oxide layer,the change of oxygen content in the powders,and the relevant parts were investigated during the processes of kneading,injection,debinding,and sintering.The oxygen vari-ation was mainly concentrated in the sintering stage,and the content increased with the increase of sintering temperature.The variation of oxygen content during the MIM process demonstrates the crucial role of powder feedstock and sintering stage in controlling oxygen con-tent.This work provides a piece of valuable information on oxygen detecting,control,and manipulation for the powder and processing in the industry of Ti and its alloys by powder metallurgy.

In-situ growth of flexible 3D hollow tubular Cu_(2)S nanorods on Cu foam for high electrochemical performance supercapacitor

For pursing high-performance supercapacitors,both of the design strategy and structural characteristic of electrode materials are crucial.Herein,we report the in-situ growth of flexible self-assembled 3D hollow tubular Cu_(2)S nanorods on Cu foam substrate(Cu_(2)S@Cu).The Cu substrate is simultaneously acted as a copper source and a collector,which reduces the contact resistance.Moreover,the highly ordered 3D unique structure increases the redox reactive sites and enhances the ion transmission effectively,resulting in greatly improved electrochemical performance.Based on the Cu_(2)S@Cu electrode,the supercapacitor exhibits high areal capacitance of 1000 mF cm^(-2) at a current density of 2 mA cm^(-2),and great cycle stability,maintaining 96.9% capacitance after 10,000 cycles.Furthermore,the supercapacitor also shows an excellent flexibility with no significant decrease in the twisting or bending state.The capacity retention rates are 99.8% and 86.1%,respectively,and finally recover to 99.3%,confirming its great potential in practical application for portable electronic devices.