Ultra-precision machining of cerium-lanthanum alloy with atmosphere control in an auxiliary device

Cerium–lanthanum alloys are the main component of nickel–metal hydride batteries,and they are thus an important material in the greenenergy industry.However,these alloys have very strong chemical activity,and their surfaces are easily oxidized,leading to great difficulties in their application.To improve the corrosion resistance of cerium–lanthanum alloys,it is necessary to obtain a nanoscale surface with low roughness.However,these alloys can easily succumb to spontaneous combustion during machining.Currently,to inhibit the occurrence of fire,machining of this alloy in ambient air needs to be conducted at very low cutting speeds while spraying the workpiece with a large amount of cutting fluid.However,this is inefficient,and only a very limited range of parameters can be optimized at low cutting speeds;this restricts the optimization of other cutting parameters.To achieve ultraprecision machining of cerium–lanthanum alloys,in this work,an auxiliary machining device was developed,and its effectiveness was verified.The results show that the developed device can improve the cutting speed and obtain a machined surface with low roughness.The device can also improve the machining efficiency and completely prevent the occurrence of spontaneous combustion.It was found that the formation of a build-up of swarf on the cutting tool is eliminated with high-speed cutting,and the surface roughness(Sa)can reach 5.64 nm within the selected parameters.Finally,the oxidation processes of the cerium–lanthanum alloy and its swarf were studied,and the process of the generation of oxidative products in the swarf was elucidated.The results revealed that most of the intermediate oxidative products in the swarf were Ce^(3+),there were major oxygen vacancies in the swarf,and the final oxidative product was Ce^(4+).

INFLUENCE OF LANTHANUM ON THE STRUCTURE AND MECHANICAL PROPERTIES OF ALUMINUMSILICON EUTECTIC ALLOY

This paper deals with the characteristics of silicon modification with lanthanum of Al-Si eutectic alloy in sand mold and metal mold with optical microscopy,scanning electron microscopy,electron microprobe and X-ray diffractometer.It is found that the amount of lanthanum,liquid alloy condition,holding time and stir- ring liquid influence the modification of silicon.The modification of silicon with lanthanum is of long effectiveness and has a“incubation time”.The modification can improve the ductility(δ_s)and tensile strength (σ_b)of the alloy,but their maximum values are not corresponding to the same amount of lanthanum.

Electrochemical formation of La-Al intermetallic compounds in fluoride melts

The electrochemical formation of La-Al alloys in LiF-CaF_(2)molten salt on a molybdenum electrode at 1123 K was investigated by electrochemical techniques,such as cyclic voltammetry,square-wave voltammetry and open-circuit chronopotentiometry.The formation signals of four types of Al-La intermetallic compounds were observed.The Al-La alloy was obtained through galvanostatic electrolysis at 2.5 A·cm^(-2)for 3 h.The phase composition and microstructure of the electrolytic products were analysed by X-ray diffraction(XRD)and scanning electron microscopy with energy-dispersive spectroscopy(EDS).XRD results show that the phase compositions of the alloys are Al_(11)La_(3)and Al,and EDS results reveal 26.7 at%La in the alloy.

Effects of Ce^(3+) energy level structure on absorption and luminescence properties of Ce-doped YAlO_3,Y_3Al_5O_(12),and LaAlO_3 single crystals

We investigate the spectra and scintillation properties of Ce：YAlO3, Ce：Y3Al5O12, and Ce：LaAlO3. For Ce：YAlO3, the excitation spectrum is very similar with the absorption spectrum; for Ce： Y3Al5O12 and Ce：LaAlO3, the excitation spectra are different from the absorption spectra. Further, Ce：YAlO33 has better scintillation performance than Ce： Y3Al5O12; whereas Ce：LaAlO3 has not demonstrated scintillation performance to date. We also provide reasonable explanations for these experimental phenomena from the viewpoint of energy level structure.