(Information source: China Rare Earth website)

The "Top 10 Science and Technology News of China's Rare Earths in 2018", sponsored by the China Rare Earth Society and Baotou Rare Earth Research Institute, hosted by the "China Rare Earth" website, and co organized by media such as Rare Earth Information and Rare Earth, has been announced recently. The selection results will be published on the website of the China Rare Earth Society, China Rare Earth website, and Rare Earth Information magazine. The top ten science and technology news selected this time were selected from over 100 rare earth science and technology news articles of 2018, which underwent two stages of initial review and expert evaluation.

1. Realizing mW level mid infrared laser output using rare earth single crystal fibers

Single crystal fiber is a new and efficient laser gain medium that can effectively overcome bottleneck problems such as thermal effects caused by bulk crystals and glass fibers. It will have significant application value in the field of high-power all solid state fiber lasers in the future. On the basis of years of rare earth crystal design and growth technology development, the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, has achieved mW level mid infrared laser output. This achievement constructs a complete innovative chain from basic theoretical research on rare earth crystals and new crystal structure design, to optimization of micro pull-down growth technology and single crystal fiber laser output. This marks another original breakthrough in the downstream application field of high value-added rare earth resources in China.

Researcher Xue Dongfeng, director of the State Key Laboratory of Rare Earth Resources Utilization, first defined the definition of "rare earth crystal", constructed a micro pull-down rare earth single crystal fiber growth model from two aspects of crystallization thermodynamics and dynamics, and used the theoretical model to obtain the key parameters in the growth of rare earth single crystal fiber. In order to further clarify the chemical bonding mode at the growth interface, an orbital hybridization model is established to study the bonding behavior of rare earth ions, quantitatively correlate the coordination number, coordination structure, and outer orbital hybridization mode of rare earth ions, and use it to quantitatively calculate the growth rate of rare earth single crystal fibers. This work innovatively utilizes the chemical bonding mode at the growth interface to solve the cross scale problem between the microstructure composition and the bulk material of rare earth single crystal fibers. It is used for the directional design of multi-scale rare earth single crystal fiber growth schemes, and successfully grows a series of single crystal fibers with a diameter of 0.5-3 mm, including rare earth aluminates, galliates, silicates, etc., achieving mW level mid infrared laser output.

2. In situ construction of rare earth upconversion nanocrystals with hollow core-shell structure achieved by electron beam etching

Due to the upconversion luminescence properties of rare earth nanocrystals, which convert near-infrared light into short wavelength visible ultraviolet light, and the high specific surface area and rich tunable pore structure of hollow core-shell structured nanocrystals, they have broad application prospects in biosensing and imaging, drug release, and medical diagnosis and treatment. The synthesis of hollow core-shell structure upconversion nanocrystals is mainly achieved through the hard template method. However, the hard template method requires the upconversion nanocrystals to be first coated with silica or polymer, and then removed by selective corrosion or high-temperature calcination. Its synthesis process is complex and cannot achieve in-situ construction of hollow core-shell structure nanocrystals on the substrate, greatly limiting its application range.

The epitaxial growth of uniformly coated homogeneous shells on the surface of rare earth upconversion nanocrystals is often considered an effective strategy to reduce the surface defect density of the original nanocrystals and improve the upconversion luminescence efficiency. However, there is still a lack of in-depth experimental research on the fundamental issues of the conversion of nanocrystalline core-shell interface structure, especially whether interface defects are significantly suppressed, for homogeneous coated core-shell structures. Supported by the Science Fund for Distinguished Young Scholars of the National Natural Science Foundation of China, the "973" Program of the Ministry of Science and Technology, the Chinese Academy of Sciences strategic leading science and technology project and the international innovation team, Chen Xueyuan Research Group and Wang Yuansheng Research Group of the Key Laboratory for Functional Nanostructure Design and Assembly of Fujian Institute of Physical Structure, Chinese Academy of Sciences cooperated to find that there are still a lot of crystal defects at the interface between the core and shell of homogeneous coated core-shell structure nanocrystals through electron beam irradiation of rare earth upconversion nanocrystals, and the concentration of the interface defects is even higher than the concentration of the bulk defects in the core. On this basis, by utilizing this interface defect control and electron beam etching, the in-situ construction of hollow core-shell structure rare earth upconversion nanocrystals on a carbon film substrate was achieved for the first time. Under electron beam irradiation at a certain power density, the core-shell structure rare earth upconversion nanocrystals pre deposited on a carbon film substrate rapidly transform from solid spheres to hollow core-shell structures, and the entire process can be completed within 30 seconds, while the hollow core-shell structure nanocrystals still maintain their original crystal structure. Through in situ transmission electron microscopy observation of the transformation process of nanocrystals from solid to hollow core-shell structure, combined with theoretical model analysis, researchers further revealed the micro mechanism of the formation of this hollow core-shell structure: when the nanocrystals are irradiated by high-energy electron beams, Ln (rare earth atoms), F, and Na atoms in the nanocrystals gain kinetic energy during electron collision, break free from lattice constraints, and undergo atomic migration or sputtering, thereby forming pores in the nanocrystals. Due to the presence of numerous defects at the core-shell interface in nanocrystals with core-shell structure, the probability of lattice atoms breaking free from lattice constraints and undergoing atomic migration or sputtering significantly increases when irradiated by an electron beam. Therefore, a spherically symmetric hollow structure is preferentially and rapidly formed at and near this interface, ultimately achieving the transformation of nanocrystals from solid to hollow core-shell structure. The results of this study indicate that interface defect control based on core-shell structured nanocrystals using electron beam atomic scale etching of nanocrystals is an effective method for in-situ construction of hollow core-shell structured rare earth upconversion nanocrystals. This method will provide new ideas for in-situ construction of special structured functional nanocrystals in the field of nanodevice applications.

3. Progress in Resource saving High Performance Rare Earth Permanent Magnet Materials

On October 12, 2018, the National Key Basic Research and Development Program (973 Program) - "Design and Controllable Preparation of Resource saving High Performance Rare Earth Permanent Magnet Materials" project, led by Academician Shen Baogen, successfully passed the acceptance of the expert group of the Ministry of Science and Technology. This project consists of three sub projects: "Scientific Basic Research on Preparation Technology of High Performance Rare Earth Permanent Magnet Materials", "Mechanism Research on High Light Rare Earth Content and High Performance Rare Earth Permanent Magnet Materials", and "Design and Exploration of New High Performance Rare Earth Permanent Magnet Materials". They are respectively led by Professor Zhu Minggang, Academician Shen Baogen, and Researcher Rao Guanghui.

This project has made breakthroughs in the research of high performance and corrosion resistance of high abundance rare earth permanent magnet materials. When the Ce substitution amount is 35% of the total rare earth content, its magnetic energy product exceeds 40MGOe (laboratory level); When Ce accounts for 50% of the total rare earth content in the magnet, its intrinsic coercivity reaches 10.8KOe; Obtained multiple innovative inventions such as "high corrosion resistance multi hard magnetic main phase Ce permanent magnets" and key industrial technologies, and prepared high-performance cerium magnets with comprehensive performance (BH) max+Hjc>63 dual main phase sintered magnets; It was found that magnets with high Ce content exhibited galvanic corrosion phenomenon where the main phase was corroded while the magnetic phase was not corroded. Through the implementation and technological promotion of the project, the national production of cerium (or cerium containing) magnets will be promoted from 800 tons at the beginning of the project to over 30000 tons, accounting for one-fifth of the total production of rare earth permanent magnets.

The intrinsic magnetism of mixed rare earth iron boron was studied, and it was demonstrated that Ce contributes to saturation magnetization. It was found that co substitution of La and Ce facilitates the migration of Ce's valence state to+3 valence, and MMFeB has the necessary conditions for preparing permanent magnets; Revealed the exchange coupling effect and coercivity mechanism of rapidly quenched MM-Fe-B permanent magnet materials.

The phase equilibrium of La Fe-B, Ce Fe-B ternary systems and Nd2Fe14B-RE2Fe14B pseudobinary alloy systems were determined for the first time. The thermodynamic parameters of the phase equilibrium and thermochemical experimental data of the rare earth RE-Fe system were obtained for the first time, and the phase diagram thermodynamic database of the rare earth RE-Fe-B multi-component alloy system was constructed. This provides an important thermodynamic basis for studying the structure-activity relationship between the composition, microstructure, and magnetic properties of rare earth permanent magnet alloys.

4. Industrialization of Rare Earth Based SCR Catalysts for Diesel Vehicles

On February 24, 2016, Baotou Rare Earth Research Institute and Hebei Huate Automotive Parts Co., Ltd. jointly began the research and development of SCR catalysts for diesel vehicles. In January 2018, the rare earth based SCR catalyst passed the bench test conducted by the China Automotive Technology Research Center, and its performance met and exceeded the National V emission requirements; In the whole vehicle PEMS test (including urban and non urban roads), the effective window pass rate of foreign brand vanadium based catalysts is 90% -92%, while the pass rate of rare earth based SCR catalysts is 100%. Through various test results, it can be seen that rare earth based SCR catalysts have successfully taken off the "crown" of diesel vehicle based rare earth based denitrification catalysts with independent intellectual property rights. This technology has broken the technological barriers of multinational enterprises in China.

The powder synthesis pilot line for rare earth based SCR catalysts was successfully completed at the end of September 2018, with a production scale of 2.5-3 tons of powder per month. In the same year, Northern Rare Earth, Hebei Huate, and Beijing Kaides jointly established Northern Rare Earth Huakai High tech (Hebei) Co., Ltd. to jointly build a rare earth based SCR catalyst and post-treatment system project for diesel engines. The plan is to build a demonstration line for annual production of 100 tons of SCR catalyst powder (50000 sets/year) in 2019, and a production line for annual production of 1000 tons of SCR catalyst powder (250000 sets/year) in 2022. It is expected to achieve sales of 5 million liters of SCR catalyst and 2 million liters of DPF catalyst by 2023, with sales reaching 381 million yuan.

During the rapid advancement from National V to National VI, catalysts containing light rare earth compounds such as lanthanum and cerium with special pore structures were synthesized, successfully breaking through the coating process of National VI catalysts. At present, the performance of rare earth based SCR catalysts has fully met the national VI emission standards.

5. Breakthrough Progress in Precise Photon Dynamics Control of Rare Earth Upconversion Nanomaterials

Kong Xianggui and Liu Xiaomin, researchers of the Changchun Institute of Optics, Precision Mechanics and Physics of the Chinese Academy of Sciences, innovatively combined the controllable "ion nano zoning doping" technology and the delayed excitation control method of rare earth ions with the Monte Carlo simulation method, and for the first time in the world, they clearly described the dynamic process of photon energy absorption, migration, transmission and recombination in the multi nanometer layer region, vividly depicted the dynamic images of rapid single transient migration and "wandering" randomness of photon energy, realized the precise control of the photon dynamics process, and defined the direction for solving the challenging problem of low photon up conversion efficiency.

6. Achievements in the application of rare earth electronic slurries

The performance of rare earth electronic slurries is far superior to traditional electronic slurries. It has the characteristics of intelligence, far-infrared, efficient environmental protection, and green energy conservation, and its electrical, thermal, magnetic, chemical, and mechanical properties are unparalleled.

Based on previous research results, Guangdong Tianchen Electronic Technology Co., Ltd. has further upgraded and applied the formulation technology of rare earth electronic slurries, and developed a patented product for PTCR rare earth thick film circuit controllable electric heating elements. This technology has successively obtained domestic invention patents, US patents, Japanese patents, and EU patents. The key technology involved in this intelligent chip heat source is mainly composed of a variety of high thermal conductivity substrate materials, which are professionally used in the field of electric heat sources. The thermal performance is stable, and it is still in the early stage of research and development internationally. In 2018, the modular combination intelligent collector system was successfully developed and applied to the intelligent gallbladder free electric boiler series. It has fast heating, high thermal efficiency, energy conservation, safety, environmental protection, comfort, compact size, and easy installation. It is widely used in fields such as solar energy, wind energy, lithium-ion batteries, smart household appliances, industry, automobiles, energy, electricity, military, and various new energy fields.

7. Progress in Research on Extremely Low Field Magnetic Resonance

The team led by Dong Hui, a doctor from the Center for Excellence and Innovation in Superconducting Electronics of the Chinese Academy of Sciences and the State Key Laboratory of Information Functional Materials of the Shanghai Institute of Microsystems and Information Technology of the Chinese Academy of Sciences, cooperated with the project of Krause, a professor from the Ulrich Research Center in Germany, to suppress power frequency noise interference within ± 500Hz bandwidth in extremely low field magnetic resonance imaging (ULF-MRI) images by more than 85%, solve the problem of inherent power frequency noise interference in unshielded or simply shielded ULF-MRI images, and take a solid step towards realizing low-cost mobile MRI systems.

Magnetic resonance imaging (MRI) technology has become an indispensable means of clinical medical diagnosis. At present, the typical field strengths of mainstream clinical MRI systems are 1.5 and 3.0 Tesla, which are expensive and have strict requirements for the usage environment. The working field strength of ULF-MRI is four orders of magnitude lower than that of traditional MRI. It has the characteristics of simple system, low cost, insensitivity to metals, and can obtain the intrinsic T1 contrast between tumors and normal tissues without the need for contrast agents. In recent years, it has received widespread attention and research. However, power frequency harmonic noise from the power grid can introduce band artifacts in ULF-MRI images. These artifacts will cross the sample image, seriously damaging the imaging quality and affecting the signal-to-noise ratio. This study uses an ultra sensitive magnetic sensor, a superconducting quantum interferometer (SQUID), as a signal detection probe. Based on the spatial correlation of power frequency harmonic noise, a dynamic suppression method for ULF-MRI power frequency harmonic interference is proposed from the perspective of sensor hardware configuration and denoising algorithm design. The proposal of this method helps to reduce the system's requirements for environmental magnetic fields, laying a solid foundation for subsequent research on low-cost mobile MRI systems that can be used for daily routine examinations. This method has potential applications in fields such as ground magnetic resonance imaging and hyperpolarization magnetic resonance imaging using traditional coil detection.

8. Successful development of multifunctional solid-state quantum memory with multiple degrees of freedom multiplexing

Guo Guangcan, an academician of the CAS Member and a professor of the University of Science and Technology of China, has made new progress in the field of quantum storage, developed a multi degree of freedom parallel multiplexed solid-state quantum memory, realized the multiplexed quantum storage across three degrees of freedom for the first time in the world, and demonstrated the arbitrary photon pulse operation function of time and frequency degrees of freedom.

Due to the insurmountable fiber optic channel loss, the current ground secure quantum communication distance is limited to the order of one hundred kilometers. The quantum relay scheme based on quantum memory can effectively overcome channel loss and expand the working distance of quantum communication, so quantum memory is the core device for future long-range quantum communication and quantum networks. The key indicator for the practicality of quantum networks is communication speed, and multi-mode multiplexing quantum memory can greatly improve the communication speed of quantum networks. For classic storage devices such as hard drives or USB drives, each storage unit can only store one bit at a time. For quantum memory, due to its quantum coherence, one storage unit can store a large number of quantum bits at once, which is the concept of multiplexing. In principle, all degrees of freedom of quantum memory can be reused.

In recent years, Li Chuanfeng's research team has been committed to experimental research on multiplexing quantum storage based on rare earth doped crystals. In 2015, the spatial degree of freedom of photons was first utilized to achieve multiplexing quantum storage, with a storage dimension of 51 dimensions, maintaining the highest level of solid-state quantum storage dimension to date. When multiplexing, each dimension can be treated as a mode, resulting in 51 spatial degrees of freedom. In the same year, utilizing the temporal freedom of photons, deterministic single photon quantum storage of 100 modes was achieved, maintaining the highest number of modes in solid-state quantum storage to date.

In order to further enhance the reuse capability of quantum memory, the research team innovatively adopted a multi degree of freedom parallel reuse storage scheme. For example, if there are M storage modes in the first degree of freedom, N modes in the second degree of freedom, and P modes in the third degree of freedom, the total number of reuse modes in a quantum memory is the product of the number of modes in each degree of freedom, i.e. M * N * P. The research group chose the time, space, and frequency degrees of freedom of photons for parallel multiplexing, and took the lead in achieving multiplexing quantum storage across these three degrees of freedom internationally. Two time modes, two frequency modes, and three spatial modes were used in the experiment, with a total of 2 * 2 * 3=12 modes. The experimental results demonstrate the feasibility of multi degree of freedom parallel multiplexing quantum storage. This new method of increasing the number of quantum storage modes will have important applications in the research of quantum networks and quantum flash drives.

In the long range quantum communication with multi-mode multiplexing, the working modes of two relay nodes may be different. In order to perform further entanglement swapping, different relay nodes must change their working modes to the same mode, which requires the mode transformation function. The research group cleverly designed storage schemes and devices, demonstrating that their multi degree of freedom multiplexed quantum memory has arbitrary mode transformation capabilities in both time and frequency degrees of freedom.

The research team further demonstrated that their memory can achieve arbitrary pulse operations in both time and frequency degrees of freedom, with representative operations including pulse sorting, beam splitting, frequency division, cross frequency photon combining, and narrowband filtering. The experimental results show that during all these operations, the three-dimensional spatial quantum states carried by photons maintain approximately 89% fidelity. This storage device can perform all the operations required for Knell Laframme Milburn type quantum computing, so this achievement is expected to have more applications in fields such as linear optical quantum computing.

9. The first permanent magnet direct drive electric locomotive in China has been taken offline

On November 1, 2018, a high-power AC transmission electric locomotive with completely independent intellectual property rights was officially launched by CRRC Datong Company. This is the first high-power AC transmission electric locomotive in China to adopt permanent magnet and direct drive technology.

Permanent magnet direct drive electric locomotives are a new breakthrough in the field of AC electric locomotives in China, following the "fast passenger electric locomotives" and "heavy-duty electric locomotives". The total efficiency of locomotives will increase by more than 3%, saving 200 kWh of electricity per hour. They also have significant features such as low maintenance costs, green environmental protection, and silence. At the same time, the permanent magnet direct drive electric locomotive adopts direct drive wheelset technology, eliminates the traditional transmission gearbox, has a simple structure, effectively reduces mechanical energy consumption losses, and the maintenance cycle of the drive system components is about 2 million kilometers, saving users a lot of maintenance costs. The comprehensive economic benefits of the product are significant.

10. Isotropic heat-resistant adhesive magnetic powder has won multiple awards such as the China Patent Award

In 2018, the isotropic and heat-resistant rare earth bonding magnetic powder preparation technology and products developed by Youyan Rare Earth successively won the 20th China Patent Excellence Award, the 5th Beijing Invention Patent Second Prize, and the China Rare Earth Science and Technology Progress Second Prize.

Rare earth bonded magnetic materials are particularly suitable for the application of micro motors due to their high magnetic performance, high degree of shape freedom, and net final shape, making motors more energy-efficient and efficient. With the rapid development of downstream applications such as new energy vehicles, energy-saving appliances, and intelligent robots, there is an urgent need for isotropic adhesive magnetic powders with high comprehensive magnetic performance and high thermal stability.

Based on this, Youyan Rare Earth has successfully developed a key preparation technology for isotropic and heat-resistant rare earth bonded magnetic powders, solving the thermal stability problem of existing nanocrystalline bonded magnetic powders in complex service environments, and achieving the simultaneous improvement of comprehensive magnetic properties and thermal stability of magnetic powders. At present, the company has successfully developed more than ten high-performance isotropic rare earth bonded magnetic powder grades, and has an annual production line of 1000 tons of rare earth bonded magnetic powder. The products are supplied in bulk to high-end bonded magnet production customers at home and abroad.