Zhixiong Wu

Bulk modulus of ternary chalcopyrite AIBIIIC2VI and AIIBIVC2V semiconductors

We report the first observation of superconductivity in a bulk Pr1-xCaxBa2Cu3O7-delta (0.4 less than or equal to x less than or equal to 0.6) system synthesized under high pressure with different oxygen environments. The highest T-c of 98 K was observed for the oxygen-deficient tetragonal Pr0.5Ca0.5Ba2Cu3O7-delta sample. Our results unambiguously demonstrate that Pr has a mixed valency greater than 3+. We conclude that hole depletion is the primary cause of the suppression of superconductivity by Pr in PrBa2Cu3O7, eliminating the hypothesis based upon pair-breaking

Preparation and thermal properties of epoxy composites filled with negative thermal expansion nanoparticles modified by a plasma treatment

Epoxy composites filled with negative thermal expansion nanoparticles, Mn3(Cu0.6Si 0.15Ge0.25)N, modified by a plasma treatment were prepared. Thermal expansion properties and thermal conductivities of the Mn3(Cu 0.6Si0.15Ge0.25)N/ epoxy composites were investigated within the temperature range of 77—300 K. Compared to neat epoxy resin, Mn3(Cu0.6Si0.15Ge0.25)N/epoxy composites show remarkably lower coefficient of thermal expansions (CTEs) and higher thermal conductivities. Especially for the composite with 32 vol.% of Mn3(Cu0.6Si0.15Ge0.25)N, the reduction of CTE value up to 42% in the temperature range of 77—195 K, and the thermal conductivities are 2.8 and 4 times as large as those of the neat epoxy resin at 298 and 77 K, respectively.Epoxy composites filled with negative thermal expansion nanoparticles, Mn3(Cu0.6Si 0.15Ge0.25)N, modified by a plasma treatment were prepared. Thermal expansion properties and thermal conductivities of the Mn3(Cu 0.6Si0.15Ge0.25)N/ epoxy composites were investigated within the temperature range of 77—300 K. Compared to neat epoxy resin, Mn3(Cu0.6Si0.15Ge0.25)N/epoxy composites show remarkably lower coefficient of thermal expansions (CTEs) and higher thermal conductivities. Especially for the composite with 32 vol.% of Mn3(Cu0.6Si0.15Ge0.25)N, the reduction of CTE value up to 42% in the temperature range of 77—195 K, and the thermal conductivities are 2.8 and 4 times as large as those of the neat epoxy resin at 298 and 77 K, respectively.

Preparation and Property Study of Graphene Oxide Reinforced Epoxy Resin Insulation Nanocomposites with High Heat Conductivity

In this paper, graphene oxide reinforced epoxy resin nanocomposites were successfully prepared. Compared with unmodified epoxy resin, the heat conductivity of the graphene oxide reinforced epoxy resin nanocomposites had been improved while keeping the insulation performance. The tensile strength was investigated at both room temperature (300 K) and liquid nitrogen temperature (77 K). And the fracture surfaces were examined by scanning electron microscopy (SEM). Results showed that the materials had excellent mechanical properties, which could be advantages for the applications as insulating layer in low temperature superconducting magnets.

Mechanical Characterizations of Structural Materials for Large Superconducting Magnets at Low Temperatures

In the past decades, China was involved in several large superconducting magnet tasks. These magnets require cryogenic structural materials as reinforcement. Within this context, mechanical characterization of these materials at cryogenic temperature obtained with specimens from readily available components is a prerequisite for a safe engineering design. In China, almost all cryogenic mechanical measurements of structural materials dealing with large superconducting magnets have been conducted at the Center of Cryogenic Materials and Applied Superconductivity, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. This paper shows the recent mechanical measurement results with toroidal-field coils, poloidal-field coils, correction coils, feeders, magnet supports, a full-size conductor, and insulation materials for the International Thermonuclear Experimental Reactor task.

Properties of radiation stable insulation composites for fusion magnet

High field superconducting magnets made of Nb3Al will be a suitable candidate for future fusion device which can provide magnetic field over 15T without critical current degradation caused by strain. The higher magnetic field and the larger current will produce a huge electromagnetic force. Therefore, it is necessary to develop high strength cryogenic structural materials and electrical insulation materials with excellent performance. On the other hand, superconducting magnets in fusion devices will experience significant nuclear radiation exposure during service. While typical structural materials like stainless steel and titanium have proven their ability to withstand these conditions, electrical insulation materials used in these coils have not fared as well. In fact, recent investigations have shown that electrical insulation breakdown is a limiting factor in the performance of high field magnets. The insulation materials used in the high field fusion magnets should be characterized by excellent mechanical properties, high radiation resistivity and good thermal conductivity. To meet these objectives, we designed various insulation materials based on epoxy resins and cyanate ester resins and investigated their processing characteristic and mechanical properties before and after irradiation at low temperature. In this paper, the recent progress of the radiation stable insulation composites for high field fusion magnet is presented. The materials have been irradiated by 60Co ?-ray irradiation in air at ambient temperature with a dose rate of 300 Gy/min. The total doses of 1 MGy, 5 MGy and 10 MGy were selected to the test specimens.

Evaluation of the cryogenic mechanical properties of the insulation material for ITER Feeder superconducting joint

The Glass-fiber reinforced plastic (GFRP) fabricated by the vacuum bag process was selected as the high voltage electrical insulation and mechanical support for the superconducting joints and the current leads for the ITER Feeder system. To evaluate the cryogenic mechanical properties of the GFRP, the mechanical properties such as the short beam strength (SBS), the tensile strength and the fatigue fracture strength after 30,000 cycles, were measured at 77K in this study. The results demonstrated that the GFRP met the design requirements of ITER.

Mechanical properties of AA5083 in different tempers at low temperatures

Aluminium alloy 5083 was chosen for use in the critical cryogenic applications of shipboard transportation of liquefied natural gas (LNG). In the present work, the tensile, Charpy impact, bend and fatigue crack propagation behaviours of aluminium alloy 5083 in temper O, H112, and H32 were investigated both at room and cryogenic temperatures.

Mechanical behaviors of hyberbranched epoxy toughened bisphenol F epoxy resin for cryogenic applications

Epoxy resins have been widely employed in cryogenic engineering fields. In this work, bisphenol F epoxy resin was modified by an aromatic polyester hyperbranched epoxy resin (HTDE-2). Mechanical behaviors of the modified epoxy resins in terms of tensile properties and impact property were studied at both room and cryogenic temperatures. Moreover, the toughening mechanism was discussed by fracture surface morphology analysis. The results demonstrated that, the mechanical properties of composites initially increased until reaches the maximum value with increasing the mass content of the HTDE-2, and then decreased at both room temperature (RT) and 77K. Especially, the impact strength at 77 K was improved 40.7% compared with the pure epoxy matrix when 10 wt% HTDE-2 was introduced. The findings suggest that the HTDE-2 will be an effective toughener for the brittle bisphenol F epoxy resin for cryogenic applications.