Influence of rare earth addition on the properties of AA6351 hybrid composites

Nowadays, the effect of the rare earth addition on the performance of aluminium matrix composites is a major interest for many researchers. The present research work emphasis is on the study of the effect of praseodymium oxide (rare earth element) addition on the performance of AA6351 hybrid composites. Silicon carbide and rice husk ash in the weight proportions of 6:2 were ball-milled with various weight percentages (0.4%, 0.8%, and 1.2%) of praseodymium oxide to have a consistent microstructure and combined density equivalent to the AA6351 matrix alloy. Further, AA6351 hybrid composites with the ball-milled reinforcement of silicon carbide, rice husk ash, and praseodymium oxide were produced using stir-casting technique. Physical, microstructural, mechanical, and tribological characterization were done to study the impact of praseodymium oxide addition on the developed hybrid composites. An increment of 2.61% in the density, 49.40% in the microhardness, and 19.78% in the ultimate tensile strength was recorded with the incorporation of 1.2 weight percentage of praseodymium oxide in the AA6351 hybrid composites. The wear rate of the developed composites also improved by 32.92% with the addition of praseodymium oxide. The results exhibited a remarkable improvement in the performance of the AA6351 hybrid composites with the addition of rare earth element.

Japan’s Rare Earth Strategy and Price Volatility on Tobacco Cultivation: How Demand Management Worked?

The two major light rare earth elements (REES) involved in Japan’s rare earth strategy: Cerium Oxide and Praseodymium Oxide, whether the price is affected by the demand management capability of the Japanese tobacco cultivation industry is the problems to be solved in this paper. For this aim, the monthly data from April 2008 to June 2017 was used to construct a model which takes into account the financial factors and demand factors for the two product by nonlinear methods, and use MSVAR model with regime-switching characteristic. The results are as follows. In general, different products have different price volatility characteristics. Even if the number of the regime is the same, the volatility connotation is different. Firstly, Cerium Oxide in the violent fluctuation regime has financial properties, and the financial properties of Praseodymium Oxide are reflected in three regime stages. Secondly, Japan’s industry factors have a significant change in the relationship between Cerium Oxide and Praseodymium Oxide to a certain extent. Among them, Information technology and tobacco cultivation Industrials as direct influencing factors have a counter-regulatory effect on the two product at certain price fluctuations, which reflects the direct demand management capabilities of Japanese companies, and Utilities and Telecommunication have a counter-regulation effect on Cerium Oxide and Praseodymium Oxide at certain price fluctuations, which reflects the indirect demand management ability of Japanese companies.

Impact of Praseodymia Additions and Firing Conditions on Structural and Electrical Transport Properties of 5 mol.% Yttria Partially Stabilized Zirconia (5YSZ)

Ceramics samples with the nominal composition [(ZrO2)0.95(Y2O3)0.05]1-x[PrOy]x and praseodymia contents of x = 0.05–0.15 were prepared by the direct firing of compacted 5YSZ + PrOy mixtures at 1450–1550 °C for 1–9 h and characterized for prospective applicability in reversible solid oxide cells. XRD and SEM/EDS analysis revealed that the dissolution of praseodymium oxide in 5YSZ occurs via the formation of pyrochlore-type Pr2Zr2O7 intermediate. Increasing PrOy additions results in a larger fraction of low-conducting pyrochlore phase and larger porosity, which limit the total electrical conductivity to 2.0–4.6 S/m at 900 °C and 0.28–0.68 S/m at 700 °C in air. A longer time and higher temperature of firing promotes the phase and microstructural homogenization of the ceramics but with comparatively low effect on density and conductivity. High-temperature processing leads to the prevailing 3+ oxidation state of praseodymium cations in fluorite and pyrochlore structures. The fraction of Pr4+ at 600–1000 °C in air is ≤2% and is nearly independent of temperature. 5YSZ ceramics with praseodymia additions remain predominantly oxygen ionic conductors, with p-type electronic contribution increasing with Pr content but not exceeding 2% for x = 0.15 at 700–900 °C. The average thermal expansion coefficients of prepared ceramics are in the range of 10.4–10.7 ppm/K.

Promotional Effects of Rare-Earth Praseodymium (Pr) Modification over MCM-41 for Methyl Mercaptan Catalytic Decomposition

Praseodymium (Pr)-promoted MCM-41 catalyst was investigated for the catalytic decomposition of methyl mercaptan (CH3SH). Various characterization techniques, such as X-ray diffraction (XRD), N2 adsorption–desorption, temperature-programmed desorption of ammonia (NH3-TPD) and carbon dioxide (CO2-TPD), hydrogen temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectrometer (XPS), were carried out to analyze the physicochemical properties of material. XPS characterization results showed that praseodymium was presented on the modified catalyst in the form of praseodymium oxide species, which can react with coke deposit to prolong the catalytic stability until 120 h. Meanwhile, the strong acid sites were proved to be the main active center over the 10% Pr/MCM-41 catalyst by NH3-TPD results during the catalytic elimination of methyl mercaptan. The possible reaction mechanism was proposed by analyzing the product distribution results. The final products were mainly small-molecule products, such as methane (CH4) and hydrogen sulfide (H2S). Dimethyl sulfide (CH3SCH3) was a reaction intermediate during the reaction. Therefore, this work contributes to the understanding of the reaction process of catalytic decomposition methyl mercaptan and the design of anti-carbon deposition catalysts.

Evaluation of the Pr + O → PrO+ + e− chemi-ionization reaction enthalpy and praseodymium oxide, carbide, dioxide, and carbonyl cation bond energies

Guided ion beam tandem mass spectrometry was used to measure the kinetic energy dependent product ion cross sections for reactions of the lanthanide metal praseodymium cation (Pr+) with O2, CO2, and CO and reactions of PrO+ with CO, O2, and Xe.