Training of the Ni-Mn-Fe-Ga ferromagnetic shape-memory alloys by cycling in a high magnetic field

The temperature and magnetic field dependencies of Ni-Mn-Ga polycrystals deformation are investigated. Ingots were prepared by arc-melting in argon atmosphere and further annealing. A training procedure (cycling across the martensitic transition point) for the two-way shape-memory effect was performed with Ni$_{2.16}$Fe$_{0.04}$Mn$_{0.80}$Ga samples. Changes in sample deformations were noticed with changing the magnetic field at a constant temperature. The first cycle deformation increment as compared with the initial value (in the austenitic state at zero field) in the course of the martensitic transition was 0.29%, and 0.41% and 0.48% for the second and third cycles, respectively.Comment: Presented at the Second Moscow International Symposium on Magnetism (Moscow-2002

An efficient control of Curie temperature TCT_C in Ni-Mn-Ga alloys

We have studied the influence of alloying with a fourth element on the temperature of ferromagnetic ordering $T_C$ in Ni-Mn-Ga Heusler alloys. It is found that $T_C$ increases or decreases, depending on the substitution. The increase of $T_C$ is observed when Ni is substituted by either Fe or Co. On the contrary, the substitution of Mn for V or Ga for In strongly reduces $T_C$.Comment: presented at ICM-200

The magnetic field influence on magnetostructural phase transition in Ni2.19Mn0.81Ga

Magnetic properties of a polycrystalline alloy Ni$_{2.19}$Mn$_{0.81}$Ga, which undergoes a first-order magnetostructural phase transition from cubic paramagnetic to tetragonal ferromagnetic phase, are studied. Hysteretic behavior of isothermal magnetization $M(H)$ has been observed in a temperature interval of the magnetostructural transition in magnetic fields from 20 to 100 kOe. Temperature dependencies of magnetization $M$, measured in magnetic fields $H = 400$ and 60 kOe, indicate that the temperature of the magnetostructural transition increases with increasing magnetic field.Comment: Presented at the Second Moscow International Symposium on Magnetism (Moscow-2002

Magnetic properties of Ni2.18Mn0.82Ga Heusler alloys with a coupled magnetostructural transition

Polycrystalline Ni2.18Mn0.82Ga Heusler alloys with a coupled magnetostructural transition are studied by differential scanning calorimetry, magnetic and resistivity measurements. Coupling of the magnetic and structural subsystems results in unusual magnetic features of the alloy. These uncommon magnetic properties of Ni2.18Mn0.82Ga are attributed to the first-order structural transition from a tetragonal ferromagnetic to a cubic paramagnetic phase.Comment: 4 pages, 4 figures, revtex

ANALYSIS OF KEY TRENDS OF THE INTERNATIONAL COAL MARKET (ON THE EXAMPLE OF THE COUNTRIES OF NORTH-EASTERN ASIA)

The article provides an analysis of key trends in the international market, using the example of the countries of Northeast Asia. In 2019, the world coal market amounted to 1,424.5 million tons, of which 78.1% are energy grades to produce electricity and heat, and 21.9% are in metallurgy, the reserves of which are significantly less. The import coal market of the countries of Northeast Asia in 2019 was already 680 million tons, covering 48% of the entire world coal market. The paper provides an overview of the key importers and exporters of coal in the world, the quantitative and qualitative characteristics of the supplied raw materials, and analyzes the key factors affecting the pricing of coal. In the conclusions, the main trends in the international coal market of the countries of Northeast Asia are presented, including "geographical" — the shift of the center of world trade from Europe to Asia, and "types and quality of imported coal" — an increase in the share of high-quality premium energy and coking (metallurgical). Trends can be clearly seen in the countries of Northeast Asia, which actively use coal, and are making efforts to decarbonize their national economies, while intensifying inter-fuel competition with other primary energy sources.</jats:p

Factors of development and introduction of clean coal-mining technologies in the world economy

Despite the route lined out since the turn of the 21st century toward the use of renewable energy sources, as of today and for the nearest decades, the fossil energy resources represent the critical part in the world economy. Fossil fuels will keep prevailing in the energy budget of the most countries in 2020 according to the long-term forecasts of the International Energy Agency and by estimates of the other authoritative sources. In the electric energy production, the contribution of coal in 2020 is the largest worldwide and continues growing owing to high-level consumptions in China, India, developing countries in Southeastern Asia, as well as in the mature economies of Japan and Australia. The huge own reserves of coal provide the developing economies with relatively cheap and reliable source of energy, the underside of which is the increased environmental damage. It is critical to develop and investigate approaches to minimization of technological environmental impact at the preserved balance between the economic advance, social welfare and environmental conservation. In the coal-powered energy generation, such approach is application of clean mining technologies. In order to identify application features of such technologies in modern conditions and in the future, it is necessary to review the historical background of economically efficient solutions, the engineering capabilities and the global market conditions in terms of the United States of America as the top coal producer and consumer among the mature economies possessing the advanced coal mining technologies. The outcome of the review is also helpful in the analysis of economic efficiency of clean technologies to be introduced in the coal industry in Russia. Thus, the aim of this article is to examine development and introduction of clean coal technologies in terms of the U.S.A. for tracing promising trends in the conditions of a global economic system.</jats:p