Substituent Influence of Yttria by Gadolinia on the Tetragonal Phase Stability for Y_2O_3-Ta_2O_5-ZrO_2 Ceramics at 1300℃

The influences of equimolar substitution of yttria by gadolinia on the phase constituent and stability for Y203- Ta2Os-Zr02 ceramics have been investigated. The ceramics with the Gd content lower than 8 tool% exhibit pure tetragonal phase as well as high tetragonal phase stability. However, the high Gd containing ceramics consist of t-Zr02, m-Zr02 and monoclinic GdTa04 and show complicated phase evolution behaviors. The fractions of monoclinic Zr02 and GdTa04 increase with increasing Gd content, indicating that the excessive substitution of Gd for Y results in a reduction in the tetragonal phase stability. In addition, the lower Gd containing ceramics show an almost invariable tetragonality, while the higher Gd containing ceramics reveal a composition-dependent tetragonality. Accordingly, an association of the tetragonal phase stability and tetragonality with the Gd concentration is established, which provides us a clue to understand the phase stability of these ceramics.

Effect of Acid Treatment on Electrocatalytic Performance of PtNi Catalyst

In this paper,we describe the synthesis of the AC-PtNi/G catalysts with graphene as the carrier,via the alcohol reduction and the sulfuric acid treatment.The prepared catalysts were microscopically characterized by X-ray diffractometry(XRD),X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM),electron spectroscopy(EDAX),and transmission electron micros-copy(TEM).We tested the electrochemical performance of the prepared catalysts using an electrochemical workstation and in situ infrared spectroscopy(FTIR).The results showed that the acid-treated AC-PtNi/G catalysts had a more uniform dispersion and with the increased of treatment time,the particle size of the catalyst became smaller.And the electrocatalytic performance of the AC-PtNi/G-48h catalyst treated with sulfuric acid for 48 h was significantly better than that of the untreated PtNi/G catalyst.Its electrochemically active surface area was 76.63 m^(2)/g,and the peak current density value for catalytic oxidation of ethanol was 1218.83 A/g,which was 10 times that of ordinary commercial Pt/C catalyst.The steady-state current density value of 1100 s was 358.77 A/g,and it has excellent anti-CO toxicity performance.It was determined that a sulfuric acid treatment controlled catalyst particle size and increased the electrocatalytic activity of the catalytic oxidation of ethanol.

Facile synthesis of transition metal carbide nanoparticles embedded in mesoporous carbon nanosheets for hydrogen evolution reaction

Transition metal carbides(TMC)modified by mesoporous carbon nanosheets(MCNSs)with high activity,fast elec-tron/ion transfer and long durability are considered as promising electrocatalysts for hydrogen evolution reaction(HER).