Shengqi Xi

Solid-state synthesis reaction between Al and Cu powders during ball milling

Abstract The solid-state synthesis reaction between Al and Cu during high energy ball milling has been studied. The most important effect of ball milling is that the grain size of the constituents decreased to the nanometer range and the constituents dissolved at the nanograin boundaries. This provides feasible conditions for the solid state synthesis reactions. The milling conditions have a sensitive effect on the process of this reaction. Only Cu9Al4 compound was formed for the AlxCu1−x (x = 0.3–0.7) alloys during ball milling.

The effects of carbon coating on nanoripples induced by focused ion beam

The morphology and topography of self-assembled nanoripple structures on LaAlO3 (100) surface with and without carbon coating were characterized using focused ion beam (FIB)/scanning electron microscope, as well as ex situ atomic force microscopy and transmission electron microscopy. When the surface was not covered by carbon coating and had low roughness, well-ordered and highly uniform nanoripples self-assembled on the surface bombarded by FIB. In contrast, disordered nanoripples formed after carbon coating. The deposited carbon significantly influences the morphology of surface nanoripples due to its effect on the surface roughness that affect the dynamic competition between the roughening and smoothing processes. This discovery suggests a means for fabricating well-ordered and highly uniform nanoripples for nanoscale devices application.

Research on temperature rise of powder during high energy ball milling

Abstract The temperature rise of powder accompanying with heavy plastic deformation during ball milling is expected to play an important role in determining the kinetics of synthesising and the properties of the final products. In this paper, temperature rise of powder during milling was estimated by using a microforging model. Relationships between the temperature rise and the deformation work of powder and between the temperature rise of mill container and the consumed power during ball milling have been found out. The results show that the temperature rise of mill container increased rapidly with the increased milling speed, and the temperature rise of powder increased with increasing milling speed and the weight ratio of ball to powder. The temperature of mill container calculated was in accordance with tested temperature of the mill container. The maximum temperature rise of powder ΔT max is not above 125 K under the maximum milling intensity.

Synthesising amorphous Cr–Mo alloy via mechanical alloying of immiscible Cr and Mo elements

Abstract In the present study, the amorphous Cr–Mo alloy was synthesised by mechanical alloying of immiscible Cr and Mo elements (Cr-35at.%Mo powders) at a temperature of ∼260 K under Ar atmosphere. The X-ray diffraction and transmission electron microscopy analysis showed that there was a transition between the Cr(Mo) solid solution and amorphous Cr–Mo phase during mechanical alloying. With increasing milling time, the initially formed Cr(Mo) solid solution transformed to the amorphous Cr–Mo alloy, which then transformed to Cr(Mo) solid solution once more. The underlying reason for this transition is likely the metastable nature of these two phase, i.e., solid solution and amorphous alloy.

Phase Transformation of Cu-Mo-C Powder during Mechanical Alloying and Annealing Process

The allotropes of graphite and activated carbon were mixed with Cu and Mo powder, respectively. And the two groups of mixtures were high-energy milled and annealed. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and DSC/TG were used to investigate the phase transformation during the milling and sintering process. For both groups of powder milled, Mo was hard to dissolve in Cu, and C mainly congregated in the surface of Cu powder. When Cu-Mo-graphite powder as milled was annealed, Mo2C was formed. In comparison to Cu-Mo-graphite alloyed powder, Cu-Mo-activated carbon powder partially formed Cu oxide and Mo oxide with higher binding energy during milling process, which caused higher reduction temperature of Cu oxide and reaction temperature of Mo2C.This template explains and demonstrates how to prepare your camera-ready paper for Trans Tech Publications. The best is to read these instructions and follow the outline of this text.

Effect of metastable Cr(Mo)s/Cr(Mo)a powders on mechanical alloying the immiscible Cu–Mo–Cr system

Abstract Metastable-state alloy powders are usually synthesised by milling and occur as products of mechanical alloying (MA), but they are rarely used as starting materials for other MA processes. In this work, metastable-state alloy powders, including supersaturated solid-solution Cr(Mo)s and amorphous Cr(Mo)a were prepared in advance. Then, the Cr(Mo)s/Cr(Mo)a powder mixture was mechanically alloyed with elemental Cu to form Cu–Mo–Cr alloy. The effects of the metastable-state powder Cr(Mo)s/Cr(Mo)a on MA of the immiscible Cu–Mo–Cr system were evaluated. Phases and microstructures of the milled powders were analysed by XRD and TEM, respectively. The results show that amorphous Cu-60wt.%Cr(Mo) and supersaturated solid-solution Cu-20wt.%Cr(Mo) alloy powders can be synthesised by MA. It is concluded that MA of the Cu–Mo–Cr ternary alloy system is significantly promoted when elemental Cu powder is milled with metastable-state alloy powder Cr(Mo)s/Cr(Mo)a. Furthermore, the promoting effect of amorphous Cr(Mo)a on MA the Cu–Mo–Cr alloy system is much greater than that of supersaturated solid-solution Cr(Mo)s, during the milling process.

One‐step synthesis of self‐standing Ni₃S₂/Ni₂P heteronanorods on nickel foam for efficient electrocatalytic hydrogen evolution over a wide pH range

The development of efficient, stable and low‐cost electrocatalysts for hydrogen evolution reaction (HER) through a facile strategy is undoubtedly vital to realize sustainable production of H2 in water splitting but still challenging. Herein, we present a one‐step approach, a simultaneous phosphorization and sulfurization thermal treatment of NF at low temperature, to direct grow Ni‐S−P heteronanorod arrays consisting of Ni3S2 and Ni2P on nickel foam (Ni‐S−P NRs/NF). Due to the direct growth, one‐dimensional structure and good conductivity of the catalyst hybrid, as well as the synergistic effect between Ni3S2 and Ni2P, the resultant Ni‐S−P NRs/NF exhibited excellent HER electrocatalytic activity over a wide pH range. Ni‐S−P NRs/NF shows an overpotential of 180, 148 and 292 mV to reach the current density of 100 mA cm−2 in 1.0 M KOH, 0.5 M H2SO4 and 1.0 M PBS solution, respectively. DFT theoretical calculations was further confirmed that the superior pH‐universal HER activity of Ni‐S−P NRs/NF is originated from the thermo‐neutral hydrogen adsorption free energy and the enhanced adsorption of water molecular by the Ni3S2/Ni2P heterostructure.

Preparation and Photocatalytic Activity of Yellow Titania

Titania powder was prepared by a sol-gel method and heat-treatment (HT). The morphology and structure of the titania powder were characterized by X-ray diffraction (XRD), differential thermal analysis, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of powder was investigated using methyl orange as target compound. Colour changing of powder was due to colour centers form. Under visible light, yellow powder showed the better photocatalytic activity than P25 powder and its visible light response was expanded. Preparation of yellow powder lowered conventional calcinations temperature obviously.