scholarly journals Sustainability Assessment of the Rare-Earth-Oxide Production Process and Comparison of Environmental Performance Improvements Based on Emergy Analysis

2021 ◽  
Vol 13 (23) ◽  
pp. 13205
Author(s):  
Jing An ◽  
Aitian Tao ◽  
He Yang ◽  
Ang Tian
Keyword(s):  
Rare Earth ◽  
Production Process ◽  
Sustainability Assessment ◽  
Rapid Development ◽  
Rare Earth Oxide ◽  
External Input ◽  
Environmental Benefits ◽  
Pollutant Emissions ◽  
Emergy Analysis ◽  
The Rare Earth

In recent years, the rapid development of the rare earth industry has had a serious impact on the environment. Some enterprises have taken measures to improve the production process. In order to explore the sustainability of this industry and these improvements’ environmental benefits, this paper combines emergy analysis and lifecycle assessment to evaluate and compare the production process of rare-earth oxides considering the three aspects of emergy flow, pollutant emissions, and emergy-based indicators. Changes in the emergy of pollutant emissions before and after improvement of the production process are discussed. The results show that the greatest inputs in the mining and beneficiation stage and smelting separation stage are labor force and service and non-renewable resources, respectively. These two production stages are highly dependent on external input and have weak competitiveness. Both stages place great pressure on the environment, so the bastnasite production process would be unsustainable in the long term. After the improvement, the environmental impact of the production process for bastnaesite changed significantly, indicating that the improvement effect of the wastewater treatment facilities and the change of fuel from coal to natural gas is remarkable.

Thermal Evolution and Electrical Properties of Rare-Earth Oxide Doped Zirconia

1988 ◽  
Vol 121 ◽  
Author(s):  
B. S. Chiou ◽  
M. Y. Lee ◽  
J. G. Duh
Keyword(s):  
Activation Energy ◽  
Rare Earth ◽  
Ionic Radius ◽  
Thermal Evolution ◽  
Rare Earth Oxide ◽  
Zirconia Ceramics ◽  
Wet Chemical ◽  
Ir Analysis ◽  
Lower Temperature ◽  
The Rare Earth

ABSTRACTSynthesized zirconia ceramics are prepared through the coprecipita-tion process. Application of the wet chemical approach is aimed at the achievement of highly sintered ceramics at lower temperature. The thermal evolution of the synthesized CeO2-ZrO2 powder is investigated with the aid of DTA and TGA measurement. The exothermic peaks on the DTA thermogram are futher identified by the IR analysis. The effect of CeO on the occurrence of the peaks is probed. For other rare-earth oxiae doped ceramics, such as Nd2O3. and Dy2O3. containing zirconia, the bulk and grain boundary resistances are evaluated by the impedance spectroscopy. The dependence of the associated activation energy in the rare-earth oxide doped zirconia is discussed with respect to the variation of the ionic radius of the rare earth constituent.

Nano Crystallite ZrO2, La2O3 and CeO2: Synthesis, Characterization and their Properties

2013 ◽  
Vol 209 ◽  
pp. 212-215
Author(s):  
A.K. Patel ◽  
A.R. Umatt ◽  
B.S. Chakrabarty
Keyword(s):  
Rare Earth ◽  
Surface Area ◽  
Gas Adsorption ◽  
Chemical Properties ◽  
Rare Earth Oxide ◽  
Combustion Method ◽  
Rare Earth Oxides ◽  
Precipitation Method ◽  
Reaction Conditions ◽  
The Rare Earth

It is well known that a minor addition of rare earth oxides can provide a beneficial effect towards various catalytic reactions. Use of rare earth oxide in different applications could improve commercial productivity in an affordable way. Among the rare earth oxides, ZrO2, La2O3 and CeO2 are very interesting due to their various characteristics showing a large range of applications in organic reactions. The changes in the molecular properties of materials at the nano scale level greatly enhance their physical properties as well as chemical properties and activity. Due to the extremely small size of the particles, an increased surface area is provided to the reactant enabling more molecules to react at the same time, thereby speeding up the process. In this work, the enhancement in the catalytic activity of these nano structured rare earth oxides has been studied under different reaction conditions. Nano crystalline ZrO2, La2O3 and CeO2 samples were synthesized using precipitation method and optimum reaction conditions have been established; whereas the corresponding bulk samples were synthesized by combustion method. The identification of phase and crystalline size of synthesized oxides have been done by X-ray diffraction, the band gape of these three oxides in both the forms has been analyzed by UV absorbance and surface area has been determined by gas adsorption analysis (BET). Moreover their different properties and the activity of nano crystallite oxides have also been compared with their bulk counterparts. Even the activity of ZrO2 is also compared with the rare earth oxides La2O3 and CeO2.

Pressure Dependence of the Resistivity of the Rare Earth Oxide Nitrides Eu1−x2+Lnx3+NxO1−x (Ln = Nd, Eu)

1979 ◽  
Vol 93 (1) ◽  
pp. K63-K66 ◽  
Author(s):  
B. Chevalier ◽  
G. Demazeau ◽  
J. Etourneau ◽  
P. Hagenmuller
Keyword(s):  
Rare Earth ◽  
Pressure Dependence ◽  
Rare Earth Oxide ◽  
The Rare Earth

scholarly journals Study of Cracking Mechanism and Wear Resistance in Laser Cladding Coating of Ni-based Alloy

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Zhenglei Yu ◽  
Lunxiang Li ◽  
Deqiang Zhang ◽  
Guangfeng Shi ◽  
Guang Yang ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Wear Resistance ◽  
Rare Earth ◽  
Fracture Mechanics ◽  
Composite Coating ◽  
Laser Cladding ◽  
Rare Earth Oxide ◽  
Cracking Mechanism ◽  
Crack Susceptibility ◽  
The Rare Earth

AbstractNickel-based alloy coatings were widely used for the remanufacturing of dies and moulds by laser cladding, but the crack sensitivity would be increase due to the higher strength and hardness, which reduced the wear resistance of Ni-based alloys. In this paper, Ni-based coatings with the addition of a plastic phase (an austenitic stainless net) were prepared using laser cladding technology, and the CeO2 was added in cladding layers. The cracking mechanism, microhardness, microstructure, phase composition, and wear properties were investigated. The relationship between thermal stress and the elastic and plastic fracture had been developed from the standpoint of fracture mechanics and thermal elastic fracture mechanics. The fracture criterion of the nickel-based coating was obtained, and the study has shown that the crack sensitivity could be reduced by decreasing the thermal expansion coefficient Δα. Thus, a new method was proposed, which the stainless steel nets were prefabricated on the substrate. It was found that the number of cracks reduced significantly with the addition of stainless steel net. When the stainless steel net with 14 mesh was added in Ni-based coatings, the average microhardness of nickel composite coating was 565 HV0.2, which was 2.6 times higher than that of the 45 steel substrate. Although the rare earth oxide 4 wt.% CeO2 and stainless steel net were added in the Ni-based coating reducing the microhardness (the average microhardness is 425 HV0.2), the wear resistance of it improved substantially. The wear volume of Ni-based composite coating was 0.56×10−5 mm3·N−1·m−1, which was 85.1% lower than that of 45 steel. The experiment results have shown that the Nickel-based composite coating is equipped with low crack sensitivity and high abrasive resistance with austenitic stainless net and the rare earth oxide 4 wt.% CeO2. This research offers an efficient solution to produce components with low crack susceptibility and high wear-resistance coatings fabricated by laser cladding.

Effect of Re Addition on the Ignition Resistance of Pure Magnesium

2014 ◽  
Vol 788 ◽  
pp. 88-92 ◽  
Author(s):  
Jian Ding ◽  
Zheng Fang ◽  
Lin Qin ◽  
Wei Min Zhao
Keyword(s):  
Rare Earth ◽  
Magnesium Alloy ◽  
Oxide Film ◽  
Rare Earth Elements ◽  
Oxidation Resistance ◽  
Rare Earth Oxide ◽  
Pure Magnesium ◽  
Ignition Point ◽  
The Rare Earth

This paper focus on the effect of rare earth elements addition on the oxidation resistance of pure magnesium. The results show that the ignition points of the Mg-RE alloys vary like “V” along with the increase of the rare earth elements. When the content of Y reaches 10wt%, the ignition point of magnesium alloy is 890K, about 40K higher than the ignition point of pure magnesium. After the addition of rare earth elements, dense oxide film forms on the surface of Mg-RE alloys. The outer oxidation film mainly consists of rare earth oxide.

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