Structure and Performance Changes of Ni-Co-Al Shape Memory Alloys in Relation to Co/Al Atomic Ratio

As a potential ferromagnetic shape memory alloy, Ni-Co-Al has excellent mechanical properties, large ma gentic-field-induced strain and high martensitic transformation temperature. The relationship between microstructure and performance （mechanical and magnetic properties） of Ni-Co-Al with different Co/Al atomic ratios （RCo/Al） was investigated. Samples exhibit β and γ dual-phase structure. The γ phase grows coarse and the volume fraction of γ phase increases with the rise of RCo/Al. Besides, sample with high amount of γ phase content has smaller βgrains ow- ing to the pinning effect of γ phase. The martensite, transformed from β phase, is tetragonal L10 structure with a （111） twinning plane. The martensitic transformation temperature of samples ascends with increasing R co/Al owing to more Co embedded into the cell, which makes the valence electron concentration （e/a） of system rise. The satura- tion magnetization （Ms） of samples increases as Rco/Al rises because Co-rich 7 phase has excellent magnetic property. Meanwhile, both compressive and micro-hardness tests reveal that the samples containing more γ phase have excel- lent ductility due to the intrinsic good ductility nature of γ phase.

Effects of ceria/zirconia ratio on properties of mixed CeO_2-ZrO_2-Al_2O_3 compound

A series of CexZr0.50-xAl0.50O1.75(0.05≤x≤0.45) mixed oxides with different Ce/Zr ratio were prepared by co-precipitation method and characterized by means of X-ray diffraction(XRD),Brunauer-Emmet Teller method(BET),temperature-programmed reduction(H2-TPR) and oxygen pulsing technique.The XRD results showed that all samples kept the single CeO2 cubic fluorite structure after calcination at 600 and 1000 oC for 5 h.The results of BET revealed that CexZr0.50-xAl0.50O1.75 with Ce/Zr molar ratio 1/1 exhibited hi...

Organic Geochemistry of the Early Jurassic Oil Shale from the Shuanghu Area in Northern Tibet and the Early Toarcian Oceanic Anoxic Event

This paper presents new geological and geochemical data from the Shuanghu area in northern Tibet, which recorded the Early Toarcian Oceanic Anoxic Event. The stratigraphic succession in the Shuanghu area consists mostly of grey to dark-colored alternating oil shales, marls and mudstones. Ammonite beds are found at the top of the Shuanghu oil shale section, which are principally of early Toarcian age, roughly within the Harplocearas falciferrum Zone. Therefore, the oil shale strata at Shuanghu can be correlated with early Toarcian black shales distributing extensively in the European epicontinental seas that contain the records of an Oceanic Anoxic Event. Sedimentary organic matter of laminated shale anomalously rich in organic carbon across the Shuanghu area is characterized by high organic carbon contents, ranging from 1.8% to 26.1%. The carbon isotope curve displays the δ 13C values of the kerogen (δ 13Ckerogen) fluctuating from –26.22 to –23.53‰ PDB with a positive excursion close to 2.17‰, which, albeit significantly smaller, may also have been associated with other Early Toarcian Oceanic Anoxic Events (OAEs) in Europe. The organic atomic C/N ratios range between 6 and 43, and the curve of C/N ratios is consistent with that of the δ 13Ckerogen values. The biological assemblage, characterized by scarcity of benthic organisms and bloom of calcareous nannofossils (coccoliths), reveals high biological productivity in the surface water and an unfavorable environment for the benthic fauna in the bottom water during the Oceanic Anoxic Event. On the basis of organic geochemistry and characteristics of the biological assemblage, this study suggests that the carbon-isotope excursion is caused by the changes of sea level and productivity, and that the black shale deposition, especially oil shales, is related to the bloom and high productivity of coccoliths.

Microstructure and phase compositions of as-cast Mg–3.9Zn–0.6RE(Gd,Y) alloy with different Gd/Y ratios

Mg-Zn-RE （Gd, Y） alloys with different Gd/Y atomic ratios were prepared by conventional casting, and the microstructure of the alloys was studied by multiple means. Icosahedral quasicrystal phases are observed in all alloys. The different Gd/Y atomic ratios affect the micro- structures of the alloys irregularly. The alloy with more Gd has large dendritic structure and more complicated phase composition which are composed of I-phase lamellar eutectic, W-phase divorced eutectic, Mg-RE cuboid par- ticles and Mg-Zn binary phases. Other two alloys show similar microstructures and phase compositions with very thin lamellar eutectics which distribute along the inter- dendritic region, and the lamellar eutectics are formed by I-phase and Mg. The element contents of the I-phases and Mg-RE phases are partially controlled by the Gd/Y atomic ratio.

Microstructure and mechanical properties of Cr films deposited with different peak powers by high-power impulse magnetron sputtering

For high-power impulse magnetron sputtering(HIPIMS),the peak power applied to the target is of great importance for regulating the ionization degree of the metal target and ion/atom flux ratio.In this work,chromium(Cr)films were deposited on 316-L stainless steel substrates and silicon(100) wafers with different peak powers by HIPIMS.The relationship between peak target power and properties of Cr films was explored in detail.The resulting structure and mechanical properties of deposited Cr films were characterized by X-ray diffraction(XRD),transmission electron microscope(TEM),atomic force microscopy(AFM),indentation hardness and scratch tester.The results indicate that the ionization degree of metal target and ion/atom flux ratio increase with the increase in peak power but without the loss of deposition rate at the same time.At low ionization degree,the deposited Cr film has low compressive residual stress and low hardness but good adhesion strength.When the ionization degree of target metal increases with increasing peak power,Cr film exhibits finer size and smoother surface with improved hardness but decreased adhesion strength.

Intermetallic PdBi aerogels with improved catalytic performance for the degradation of organic pollutants in water

It is always highly pursued to develop efficient and durable catalysts for catalytic applications.Herein,intermetallic PdBi aerogels with tunable activity were prepared successfully via a surfactant-free spontaneous gelation process.The prepared PdBi aerogels have a three-dimensional high porous structure and plentiful active sites pervaded on the ultrathin interlinked nanowires network.These unique structures,as well as the synergistic effect between Pd and Bi,can accelerate mass and electron transfer,and improve the atom utilization ratio of Pd atoms to promote the catalytic efficiency.As a proofof-concept application,the optimized Pd_(2) Bi_(1) aerogels exhibit 4.2 and 6.2 times higher catalytic activity for the reduction of 4-nitrophenol(4-NP)and methylene blue(MB)than those of commercial Pd/C,respectively.With the introduction of non-noble metal of Bi,the cost of the resulted Pd Bi aerogels can be dropped signi ficantly while the catalytic capability of Pd Bi aerogel will be improved sharply.This strategy will bring good hints to rationally design fine catalysts for various applications.