Enhanced Erosion–Corrosion Resistance of Tungsten by Carburizing Using Spark Plasma Sintering Technique

The biggest obstacle for the application of tungsten as the target materials in the spallation neutron source is its serious corrosion in the coolant of flowing water. For this reason, W–Cr–C clad tungsten was developed by tungsten carburizing in a spark plasma sintering device, with superior corrosion resistance in the static immersion and electrochemical corrosion test. This work focused on its erosion and corrosion performance in a flowing water system, based upon test parameters simulated under the service conditions. W–Cr–C clad tungsten showed superior corrosion resistance to that of bare tungsten due to the corrosion form changing from the intergranular corrosion of bare tungsten to pitting corrosion of W–Cr–C coating. The corrosion rate of tungsten was as high as tenfold that of the coated sample at 20 °C, and at most fourfold at 60 °C after testing for 360 h. Effects of water velocity and temperature on pitting and intergranular corrosion were investigated in detail and their corresponding corrosion mechanisms were analyzed and discussed

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Investigation on the Optimized Binary and Ternary Gallium Alloy as Thermal Interface Materials This work presents an experimental study to enhance the thermal contact conductance of high performance thermal interface materials (TIMs) using gallium alloy. In this experiment, the gallium alloy-based TIMs are synthesized by a micro-oxidation reaction method, which consists of gallium oxides (Ga 2 O 3 ) dispersed uniformly in gallium alloys. An experimental apparatus is designed to measure the thermal resistance across the gallium alloy-based TIMs under steady-state conditions. The existence of Ga 2 O 3 can effectively improve the wettability of gallium alloys with other materials. For example, they have a better wettability with copper and anodic coloring 6063 aluminum-alloy without any extrusion between the interface layers. Gallium binary alloy-based TIMs (GBTIM) or ternary alloy based-TIMs (GTTIM) are found to increase the operational temperature range comparing with that of the conventional thermal greases. The measured highest thermal conductivity is as high as 19.2 Wm À1 K À1 for GBTIM at room temperature. The wide operational temperature, better wettability, and higher thermal conductivity make gallium alloy-based TIMs promising for a wider application as TIMs in electronic packaging areas. The measured resistance is found to be as low as 2.2 mm 2 KW À1 for GBTIM with a pressure of 0.05 MPa, which is much lower than that of the best commercialized thermal greases. In view of controlling pollution and raw materials wasting, the gallium alloy-based TIMs can be cleaned by 30% NaOH solution, and the pure gallium alloys are recycled, which can satisfy industrial production requirements effectively

Measurement of Strain-Amplitude Dependent Internal Friction with Torsion Pendulum and Vibration Reed Methods

<div><p>In the traditional standard of internal friction measurement the torsion pendulum and vibration reed were preferentially recommended where the issue of strain amplitude dependence of internal friction was not concerned. To more precisely measure the internal friction and modulus at various strain amplitude, in this paper the strain amplitude dependence of internal friction and modulus is considered by analyzing the stress distribution in the sample in different internal friction measurement methods. The formulas for the measurement of internal friction and modulus versus strain-amplitude are obtained by re-deriving the principal equations for internal friction and modulus measurements by torsion pendulum and vibration reed methods from the basic definition of internal friction. This provides a new standard for precise measurement of internal friction at different strain-amplitude in the cases of high strain-amplitude excitation or high damping materials where amplitude dependent effects always appear.</p></div

Design, Fabrication, and Properties of High Damping Metal Matrix Composites—A Review

Nowadays it is commonly considered that high damping materials which have both the good mechanical properties as structural materials and the high damping capacity for vibration damping are the most direct vibration damping solution. In metals and alloys however, exhibiting simultaneously high damping capacity and good mechanical properties has been noted to be normally incompatible because the microscopic mechanisms responsible for internal friction (namely damping capacity) are dependent upon the parameters that control mechanical strength. To achieve a compromise, one of the most important methods is to develop two-phase composites, in which each phase plays a specific role: damping or mechanical strength. In this review, we have summarized the development of the design concept of high damping composite materials and the investigation of their fabrication and properties, including mechanical and damping properties, and suggested a new design concept of high damping composite materials where the hard ceramic additives exhibit high damping capacity at room temperature owing to the stress-induced reorientation of high density point defects in the ceramic phases and the high damping capacity of the composite comes mainly from the ceramic phases

Li2ZrO3-Coated Monocrystalline LiAl0.06Mn1.94O4 Particles as Cathode Materials for Lithium-Ion Batteries

Li2ZrO3-coated and Al-doped micro-sized monocrystalline LiMn2O4 powder is synthesized through solid-state reaction, and the electrochemical performance is investigated as cathode materials for lithium-ion batteries. It is found that Li2ZrO3-coated LiAl0.06Mn1.94O4 delivers a discharge capacity of 110.90 mAhg&minus;1 with 94% capacity retention after 200 cycles at room temperature and a discharge capacity of 104.4 mAhg&minus;1 with a capacity retention of 87.8% after 100 cycles at 55 &deg;C. Moreover, Li2ZrO3-coated LiAl0.06Mn1.94O4 could retain 87.5% of its initial capacity at 5C rate. This superior cycling and rate performance can be greatly contributed to the synergistic effect of Al-doping and Li2ZrO3-coating