Scanning tunneling microscopy measurements of the initial erosion of graphite by hyperthermal atomic oxygen and neon

Highly ordered pyrolitic graphite (HOPG) was bombarded by low-energy (30eV) O⁺ and Ne⁺ at fluxes in the range of 10¹⁵–10¹⁶ ions cm⁻². The initial erosion of a few monolayers was studied with the aid of scanning tunneling microscopy (STM). Damage consisting of hillocks was observed for both O⁺ and Ne⁺, and the damage density increased with dose. O⁺-bombarded surfaces exhibited partial exfoliation of one to two monoatomic layers (propably as a result of chemical erosion), which was absent for Ne⁺ bombardment. Surface reconstruction of damaged areas was observed. The present work is the first step in an STM study of the effects of atomic oxygen erosion of graphite/epoxy composites in space.     

Desorption mass spectrometry of olestra

Field desorption (FD), fast atom bombardment (FAB) and plasma desorption (PD) mass spectrometry have been used for the characterization of olestra, a mixture of octa-, hepta- and hexaesters of sucrose formed by reaction of sucrose with long-chain fatty acids (C₁₂–C₁₈). Most previous applications of desorption ionization mass spectrometry have involved polar compounds; however, the relatively low-polarity olestra is also amenable to these techniques with proper sample preparation. Field desorption provides molecular weight information, but the transience of the signals limits the usefulness for observing fragmentation and measuring ester distributions. In addition, FD may not be sensitive enough to allow characterization of fractions isolated from analytical high-performance liquid chromatography (HPLC) columns. Fast atom bombardment produces longer-lasting signals, which permit characterization of components over a wide mass range. However, signal-to-noise fluctuates substantially, depending on analyte solubility in the matrix, making the characterization of partial esters collected from HPLC uncertain and difficult. Plasma desorption mass spectrometry is the easiest and most sensitive technique for olestra characterization but provides the lowest mass resolution. Because it requires no more than a few μg of material, it is effective for the characterization of HPLC fractions. Furthermore, it is the only method, of the three investigated, that allows detection of intact dimeric species having molecular masses in the 3,000 to 5,000 dalton range.     

Steel surface treatment by a dual process of ion nitriding and thermal shock

Samples of AISI 4140 steel were surface treated under two different processes: ion nitriding and high energy pulsed plasma irradiation. Ion nitriding was performed with a 100 Hz square wave glow discharge, in an atmosphere of an 80% N₂ and 20% H₂ mixture, under a total pressure of 5.6 mbar. Pulsed plasma irradiation consisted in the surface irradiation with a predetermined number of pulses of high energy and short duration argon plasmas, accelerated in a Z-Pinch experiment. Each pulse can induce high temperatures in a short time (<200 ns), followed by an also fast (∼10 μs) cooling down. The samples, ion nitrided and post-irradiated with pulsed plasmas showed important surface property improvements with respect to samples subjected only to ion nitriding. Those improvements consisted of an increase in the thickness of the hardened layer, and in a reduction of the micro-hardness gradient. These results show a complex surface layer structure that improves the support base for loads, reducing the probability of surface layer loosening.     

离子束轰击形成表面非晶态合金

近期发展起来的离子束材料改性技术,利用离子束轰击固体不但可以改变材料表面成     

A generalized model for radiation-induced amorphization and crystallization of U3Si and U3Si2 and recrystallization of UO2

A rate-theory model of radiation-induced amorphization and crystallization of U₃Si during ion irradiation has been generalized to include U₃Si₂ and UO₂. The generalized model has been applied to ion-irradiation and in-reactor experiments on U₃Si and U₃Si₂ and provides an interpretation for the amorphization curve (dose required to amorphize the material as a function of temperature), for the ion-radiation-induced nanoscale polycrystallization of these materials at temperatures above the critical temperature for amorphization, as well as for the role of the small crystallites in retarding amorphization. An alternative mechanism for the evolution of recrystallization nuclei is described for a model of irradiation-induced recrystallization of UO₂ wherein the stored energy in the UO₂ is concentrated in a network of sinklike nuclei that diminish with dose due to interaction with radiation-produced defects. The sinklike nuclei are identified as cellular dislocation structures that evolve relatively early in the irradiation period. The complicated kinetics involved in the formation of a cellular dislocation network are approximated by the formation and growth of subgrains due to the interaction of shock waves produced by fission-induced damage to the UO₂.     

Formation and annealing behavior of defect clusters in electron or He-ion irradiated Ti-rich Ti–Al alloys

In order to clarify the effect of He atoms on the formation and annealing behavior of defect clusters in Ti–Al alloys, a Ti–47 at.% Al intermetallic compound has been irradiated with electrons and He-ions. Helium-ion irradiation enhances the nucleation of defect clusters, especially of interstitial loops, at temperatures from 623 to 773 K in both γ-TiAl and ₂-Ti₃Al grains of the sample. However, there is little difference between the annealing temperature ranges of defect clusters in TiAl grains formed by He-ion or electron irradiation at 623 K. The dot-shaped clusters and interstitial loops grow scarcely during annealing, but are annihilated by annealing up to 923 K. Cavities are formed after irradiation with He-ions below 10 dpa at 773 K, but no cavities are formed by electron irradiation up to 30 dpa. The cavities in γ-TiAl and ₂-Ti₃Al grains survive after annealing even at 1053 K for 1.8 ks, keeping their density and diameter to be nearly the same as those in the as-irradiated grains.     

盐酸雷诺希芬的电子电离质谱和快原子轰击电离(-)质谱研究

盐酸雷诺希芬是一种用于治疗骨质疏松症的药物 ,采用 EI-MS、FAB( -) -MS两种质谱技术分别对其的结构和裂解途径进行了研究。采用 FAB( -) -MS,获得 m/z5 1 0 [M+HCl+H]-、m/z5 0 9[M+HCl]-、m/z473 [M]和 m/z472 [M-H]质谱峰 ;采用 EIMS,获得 m/z473 [M]+ 、m/z474[M+H]+ 。因此 ,分子离子m/z 473 [M]+ 与分子式 C2 8H2 7NO4S相符。并解释了其中的主要特征子离子 ,并对其结构进行了确证。     

盐酸雷诺希芬的电子电离质谱和快原子轰击电离(-)质谱研究

盐酸雷诺希芬是一种用于治疗骨质疏松症的药物,采用EI-MS、FAB(-)-MS两种质谱技术分别对其的结构和裂解途径进行了研究.采用FAB(-)-MS,获得m/z 510[M HCl H]-、m/z 509[M HCl]-、m/z 473[M]和m/z 472[M-H]质谱峰;采用EIMS,获得m/z 473[M] 、m/z 474[M H] .因此,分子离子m/z 473[M] 与分子式C28H27NO4S相符.并解释了其中的主要特征子离子,并对其结构进行了确证.     

氩离子轰击感生Ni2Al3和NiAl3成分变化的TEM/EDS研究

在能量为3，5和7keV的氩离了轰击下，对激冷Ni-50%Al(质量分数）合金薄膜进行减薄，用配备有超薄窗口能谱仪的高分辨电镜观察分析了减薄后样品中两种合金相Ni2Al3和NiAl3的结构和成分变化。结果表明，在离子轰击下，合金相Ni2Al3和NiAl3的成分均有变化，Ni含量明显高于合金相化学配比。随着离子能量的降低，轰击后合金相中Ni含量增加。在3keV氩离子轰击下两个相的含Ni量均高达87％（原子分数）左右，在离子轰击过程中初始的NiAl3相点阵结构未发生明显变化，而Ni2Al3的初如结构在3和5keV氩离子轰击减薄后部分转变为体心立方结构。     

Quasi-Ordered Nanoforests with Hybrid Plasmon Resonances for Broadband Absorption and Photodetection

With the continuing development of green energy technology, solar energy is the most widely distributed and easily utilized form of energy in nature. High-absorption absorbers over a wide spectrum range are beneficial for solar energy harvest. Herein, a fast and efficient method is developed to fabricate a broadband absorber consisting of quasi-ordered nanoforests and metal nanoparticles using a simple plasma bombardment process on a 4-inch silicon wafer, offering high throughputs that can meet practical application demands. The absorber exhibits high absorption exceeding 90% from 300 to 2500 nm, good absorption stability with negligible disturbance from the polarization and the incident angle of light. This effective absorption behavior can be ascribed to multilevel hybridization of the plasmon resonances in the hybrid structures and cavity mode resonances inside the nanoforests. Furthermore, the absorber is integrated onto a thermopile for photodetection with largely enhanced photoresponse from 532 to 2200 nm. The photoinduced voltage of the devices shows a large increment of 433% at 100 mW cm⁻² light power density, in comparison with a contrast pristine thermopile. It is expected that such a broadband absorber holds great potential for multiple applications, including solar steam generation, photodetection, and solar cells.