轻金属无渍液压油的研究

介绍了一种46#无渍液压油的制备过程,主要步骤包括无渍基础油的筛选、黏度指数改进剂的筛选以及无灰复合剂的筛选。该无渍液压油除满足铝箔轧机对液压油抗炮性、抗磨性等基础性能要求外,还具备挥发性好、无油渍残留等特点,在国内多家企业使用中反馈效果良好。

Three-dimensional porous graphene sponges assembled with the combination of surfactant and freeze-drying

With the combination of surfactant and freeze-drying, we have developed two kinds of graphene spongy structures. On the one hand, using foams of soap bubbles as templates, three-dimensional porous graphene sponges with rich hierarchical pores have been synthesized. Pores of the material contain three levels of length scales, including millimeter, micrometer and nanometer. The structure can be tuned by changing the freezing media, adjusting the stirring rate or adding functional additives. On the other hand, by direct freeze-drying of a graphene oxide/surfactant suspension, a porous framework with directionally aligned pores is prepared. The surfactant gives a better dispersion of graphene oxide sheets, resulting in a high specific surface area. Both of the obtained materials exhibit excellent absorption capacity and good compression performance, providing a broad range of possible applications, such as absorbents, storage media, and carriers.

Carbon nanotube-polypyrrole core-shell sponge and its application as highly compressible supercapacitor electrode

A carbon nanotube （CNT） sponge contains a three-dimensional conductive nano- tube network, and can be used as a porous electrode for various energy devices. We present here a rational strategy to fabricate a unique CNT@polypyrrole （PPy） core-shell sponge, and demonstrate its application as a highly compressible supercapacitor electrode with high performance. A PPy layer with optimal thickness was coated uniformly on individual CNTs and inter-CNT contact points by electrochemical deposition and crosslinking of pyrrole monomers, resulting in a core-shell configuration. The PPy coating significantly improves specific capacitance of the CNT sponge to above 300 F/g, and simultaneously reinforces the porous structure to achieve better strength and fully elastic structural recovery after compression. The CNT@PPy sponge can sustain 1,000 compression cycles at a strain of 50% while maintaining a stable capacitance （〉 90% of initial value）. Our CNT@PPy core-shell sponges with a highly porous network structure may serve as compressible, robust electrodes for supercapacitors and many other energy devices.

Microwave absorbing properties and magnetic properties of different carbon nanotubes

The microwave absorbing properties and magnetic properties of as-grown Fe-filled carbon nanotubes (CNTs), annealed Fe-filled CNTs, and multi-walled CNTs were studied. Vibrating sample magnetometer results showed that the annealed Fe-filled CNTs have the weakest coercivity and strongest saturation magnetization among the three types CNTs, due to the presence of more ferromagnetic α-Fe nanowires. After annealing, the values increased to 291.0 Oe and 28.0 emu/g and the samples showed excellent microwave absorbing properties. The reflection loss was over 5 dB between 11.6 GHz and 18 GHz with a maximum value of 10.8 dB for annealed Fe-filled CNTs (1.1 wt%)/epoxy composite.

Fabrication of large area hexagonal boron nitride thin films for bendable capacitors

Highly reliable and bendable dielectrics are desired in flexible or bendable electronic devices for future applications. Hexagonal boron nitride （h-BN） can be used as bendable dielectric due to its wide band gap. Here, we fabricate high quality h-BN films with controllable thickness by a low pressure chemical vapor deposition method. We demonstrate a parallel-plate capacitor using h-BN film as the dielectric. The h-BN capacitors are reliable with a high breakdown field strength of -9.0 MV/cm. Tunneling current across the h-BN film is inversely exponential to the thickness of dielectric, which makes the capacitance drop significantly. The h-BN capacitor shows a best specific capacitance of 6.8 F/cm^2, which is one order of magnitude higher than the calculated value.

Provenance of Uranium Mineralization of the Yuqia Area,Northwest China:Constraints from Detrital Zircon U-Pb Geochronology and Hf Isotopes

Many sandstone-type uranium mineralization sites have been identified along the northern margin of the Qaidam Basin in North China.Intense tectonism and multistage magmatism that occurred there have restricted the use of conventional techniques(petrogeochemistry)to deduce the sources of detritus and uranium in these sediments,and to further explore the sandstone-type uranium deposits.In this study,U-Pb geochronological and Hf isotopic analyses were conducted on detrital zircon grains collected from Jurassic to Paleogene sandstones exposed in the Yuqia area of the Qaidam Basin.The results indicate that the U-Pb ages of the analyzed zircon grains are clustered into four groups,285–229,498–401,999–806,and 2520–2305 Ma.Theε_(Hf)(t)of the analyzed zircon grains ranges from-21.9 to+10.5,with two-stage Hf model ages(T_(DM2))concentrated between 2.1 and 1.3 Ga.Based on paleocurrent studies and results of petrological,detrital zircon geochronology,and Hf isotopic analyses,the Jurassic sediments in the Yuqia area were likely derived from the tectonic belt along the northern margin of the Qaidam Basin,such as the Qilian Mountains and the Quanji Block.In contrast,the Paleogene sediments were probably sourced from the northern margin of the Qaidam Basin and the Qilian Mountains.The uranium and thorium content and Th/U value of the rock mass and sedimentary strata in the source area show that the Indosinian Early Paleozoic uranium-rich granites and the Middle Jurassic uranium-rich strata of the northern margin of the Qaidam tectonic belt in the source area provide dual uranium sources for the Yuqia sandstone-type uranium mineralization.Therefore,the study area appears to be favorable for sandstone-type uranium mineralization and may have potential for uranium prospecting.

Interconnected graphene/polymer micro-tube piping composites for liquid sensing

Detection and analysis of volatile organic compounds （VOCs） as pollutants in the atmosphere and liquids are of great significance because of the detrimental effects of VOCs. A polymer-coated graphene micro-tube piping （GMP） structure with a cross-linked and interconnected channel network was synthesized for liquid sensing. By virtue of their unique cross-linked and interconnected channel network configuration, polycrystalline conformation, and the support of a polymer layer, the resistivity of the 3D hollow micro-tubing GMPs was sensitive to strain, ensuring high sensitivity of the liquid sensor （R/Ro of -4 × 10^3% for pure acetone and R/Ro of -105% for 0.01 wt.% acetone solution）. Due to the capillary force, the interfaces of the 3D structures can speed up the penetration of solvents into the polymer, thus promote distinct selectivity within seconds and significantly decrease the response time. Owing to their good selectivity, high sensitivity, rapid response and flexibility, and the ease of use of the sensors and the simplicity of the fabrication processes, the GMP/polymer composites should be a good candidate for liquid sensing.

Graphene-CdSe Nanobelt Solar Cells with Tunable Configurations

We have combined two planar nanostructures, graphene and CdSe nanobelts, to construct Schottky junction solar cells with open-circuit voltages of about 0.5 V and cell efficiencies on the order of 0.1%. By covering transparent graphene or carbon nanotube （CNT） films on selected positions along macroscopically long CdSe nanobelts, we have demonstrated the fabrication of active solar cells with many different configurations and parallel connections from individual or multiple assembled nanobelts. The graphene-CdSe nanobelt solar cells reported here show a great flexibility in creating diverse device architectures, and might be scaled up for cell integration based on assembled nanobelt arrays and patterned graphene （or CNT） films.

Magnetic transitions in graphene derivatives

The magnetic transitions in graphene oxide （GO） have been investigated experimentally. Micron-sized GO flakes exhibit dominant diamagnetism accompanied by weak ferromagnetism at room temperature. However, when the lateral dimensions of GO flakes are reduced from micron-size to nano-size, a clear transition from dominant diamagnetism to ferromagnetism is observed. After reducing the GO chemically or thermally, the dominant magnetic properties are not altered markedly except for the gradual enhancement of ferromagnetic components. In contrast, at 2 K, significant paramagnetism is present in both the micron-sized and nano-sized GO sheets. The effects of different functional groups on magnetic transitions in graphene derivatives have been further investigated using on hydroxyl-, carboxyl-, amino- and thiol- functionalized graphene. The results reveal that significant diamagnetism with weak ferromagnetism is present at room temperature in all of these functionalized graphene derivatives and the ability of different functional groups to introduce magnetic moments follows the order -SH 〉 --OH 〉 -COOH, -NH2. Notably, at 5 K, diamagnetism, paramagnetism and ferromagnetism coexist in thiol-, hydroxyl- and carboxyl-functionalized graphene, while amino-graphene exhibits dominant paramagnetism, analogous to the low-temperature magnetism in GO. These results indicate that diamagnetism, paramagnetism and ferromagnetism can coexist in graphene derivatives and magnetic transitions among the three states can be achieved which depend on edge states, vacancies, chemical doping and the attached functional groups. The results obtained may help settle the current controversy about the magnetism of graphene-related materials.

CuI-Si Heterojunction Solar Cells with Carbon Nanotube Films as Flexible Top-Contact Electrodes

We report the fabrication of CuI-Si heterojunction solar cells with carbon nanotubes （CNTs） as a transparent electrode. A flexible CNT network was transferred onto tile top of a polycrystalline CuI layer, making a conformal coating with good contact with the underlying CuI. The solar cells showed power conversion efficiencies in the range of 6% to 10.5%, while the efficiency degradation was less than 10% after the device was stored in air for 8 days. Compared with conventional rigid electrodes such as indium tin oxide （ITO） glass, the flexibility of the CNT films ensures better contact with the active layers and removes the need for press-contact electrodes. Degraded cells can recover their original performance by acid doping of the CNT electrode. Our results suggest that CNT films are suitable electrical contacts for rough materials and structures with an uneven surface.