H~+,N~+和Ar~+离子束辐射诱导碳纳米结构的变化(英文)

在室温和高温下,以不同辐射剂量的H+、N+和Ar+离子辐照多壁碳纳米管和无定形碳纳米线。利用透射电镜和拉曼光谱研究多壁碳纳米管和无定形碳纳米线的结构变化及损伤。以70keV N+离子束辐射多壁碳纳米管在室温下可形成无定形碳纳米线。1000K下70keV的H+离子束照射导致无定形碳纳米线向金刚石结构转变。离子辐照多壁碳纳米管的有序程度足够高,70keV的N+和Ar+离子能够引起碳从多壁碳纳米管的剥落。离子辐射能够为缺陷的转化提供必需的动力学驱动力。     

Microstructure and characterization of phases in TIG welded joints of Zircaloy-4 and stainless steel 304L

Tungsten inert gas (TIG) welded joints between Zircaloy-4 and stainless steel 304L have been studied by scanning electron microscope (SEM) having energy dispersive system (EDS) as an attachment. Intermetallic compound Zr(Cr, Fe)₂ and Zr₂Fe–Zr₂Ni eutectic phase have been observed in the molten zone. The surface area occupied by intermetallic compound Zr(Cr, Fe)₂ is about twice compared to Zr₂Fe–Zr₂Ni eutectic phase. The shape of the intermetallic compound is rod like. The phases were also identified by using X-ray diffraction (XRD) technique. EDS and XRD results are quite in agreement.     

Adsorption of dyes from aqueous solutions on activated charcoal

Adsorption of industrially important dyes namely bromophenol blue, alizarine red-S, methyl blue, methylene blue, eriochrome black-T, malachite green, phenol red and methyl violet from aqueous media on activated charcoal has been investigated. The effect of shaking time, pH and temperature on the adsorption behaviour of these dyes has been studied. It was noted that adsorption of all the dyes on activated charcoal decreases with an increase in the pH and the temperature. The adsorption isotherms at different temperatures were found to be of L-type. Adsorption data was fitted to Freundlich, BET and Langmuir isotherms and various adsorption parameters have been calculated. The thermodynamic parameters such as DeltaG, DeltaH and DeltaS were calculated from the slopes and intercepts of the linear variation of lnK against 1/T, where K is the adsorption coefficient obtained from Langmuir equation, was used. The calculated values for the heat of adsorption and the free energy indicate that adsorption of dyes is favored at low temperatures and the dyes are chemisorbed on activated charcoal.     

Hybrid biosorbent: An innovative matrix to enhance the biosorption of Cd(II) from aqueous solution

To enhance the metal removing capacity of a fungus biosorbent, a new idea of producing a hybrid biosorbent (HB) matrix by combining two different biosorbents using a simple and low-cost immobilization technique was tested for the sorption of Cd(II). The two biosorbents, used as the building block for the production of HB matrix, were the fungal biomass of Phanerochaete chrysosporium (B1) and fibrous network of papaya wood (B2). Maximum independent biosorption capacity of B1 and B2 was noted, respectively, to be 71.36 and 17.62 mgCd(II)g(-1) biosorbent. However, when two biosorbents were hybridized to form HB matrix, the combined biosorption capacity (141.63 mgCd(II)g(-1) biosorbent) was increased by 98.47, 703.80%, respectively, as compared to the ability of B1 and B2 when used alone, and by 59.17% than the sum of separate individual abilities of biosorbents B1 and B2. The kinetics of equilibrium was fast, approximately 88% of Cd(II) biosorption taking place within 30 min. Biosorption kinetics and equilibria followed the pseudo-second order kinetics and Langmuir adsorption isotherms model. HB matrix was also shown to be highly effective in removing Cd(II) from aqueous solution in a continuous flow fixed-bed column bioreactor, both in batch and repeated cycles.     

Adaptive beam shaping by controlled thermal lensing in optical elements

We describe an adaptive optical system for use as a tunable focusing element. The system provides adaptive beam shaping via controlled thermal lensing in the optical elements. The system is agile, remotely controllable, touch free, and vacuum compatible; it offers a wide dynamic range, aberration-free focal length tuning, and can provide both positive and negative lensing effects. Focusing is obtained through dynamic heating of an optical element by an external pump beam. The system is especially suitable for use in interferometric gravitational wave interferometers employing high laser power, allowing for in situ control of the laser modal properties and compensation for thermal lensing of the primary laser. Using CO(2) laser heating of fused-silica substrates, we demonstrate a focal length variable from infinity to 4.0 m, with a slope of 0.082 diopter/W of absorbed heat. For on-axis operation, no higher-order modes are introduced by the adaptive optical element. Theoretical modeling of the induced optical path change and predicted thermal lens agrees well with measurement.