氘在低活化铁素体/马氏体钢相关再沉积层中的热脱附行为

采用直流磁控溅射法,在氩气和氘气混合气氛下溅射金属靶制备铁、铬及钨与氘的共沉积层,模拟核聚变装置中燃料等离子体作用下低活化铁素体/马氏体(RAFM)钢第一壁材料表面再沉积层。分别考察了在磁控溅射腔室及直线等离子体模拟装置两种平台下,氘等离子体辐照对RAFM钢相关再沉积层中氘热脱附与滞留行为的影响。研究结果表明:氘与金属共沉积的RAFM钢相关涂层中,氘热脱附行为因受材料本身的组分和结构影响而存在差异;不同的氘等离子体辐照环境对氘在共沉积涂层中捕获形式的影响不同;总体而言,两种氘等离子体辐照后,均有大量氘滞留在RAFM钢相关再沉积层中,且氘总滞留量随氘等离子体辐照通量的增大而增大;铁基和钨基涂层中的氘滞留总量相当,均比铬基的低出1-2个数量级。     

Albumin-bound MRI contrast agents: the dilemma of the rotational correlation time

Human serum albumin (HSA) binds numerous molecules, among which are suitably designed MRI contrast agents. The rotational tumbling of the protein is thus one of the parameters likely to affect the in vivo relaxivity of these agents. Literature unveils discrepancies about the value of the rotational correlation time (τ_R) of HSA. In the present work, the τ_R of this protein has been determined by studying the deuterium relaxation rate of small molecules known for their strong binding to HSA (warfarin and 4-hydroxycoumarin). Values of approx. 20–22 ns are obtained at 310 K in a 4% HSA solution and are in good agreement with the theoretical predictions.     

Biosynthesis of (3<Emphasis Type="Italic">Z</Emphasis>,6<Emphasis Type="Italic">Z</Emphasis>,9<Emphasis Type="Italic">Z</Emphasis>)-3,6,9-Octadecatriene: The Main Component of the Pheromone Blend of <Emphasis Type="Italic">Erannis bajaria</Emphasis>

The hydrocarbons (3Z,6Z,9Z)-3,6,9-octadecatriene (3Z,6Z,9Z-18:H) and (3Z,6Z,9Z)-3,6,9-nonadecatriene (3Z,6Z,9Z-19:H) constitute the pheromone of the winter moth, Erannis bajaria. These compounds belong to a large group of lepidopteran pheromones which consist of unsaturated hydrocarbons and their corresponding oxygenated derivatives. The biosynthesis of such hydrocarbons with an odd number of carbons in the chain is well understood. In contrast, knowledge about the biosynthesis of even numbered derivatives is lacking. We investigated the biosynthesis of 3Z,6Z,9Z-18:H by applying deuterium-labeled precursors to females of E. bajaria followed by gas chromatography–mass spectrometry analysis of extracts of the pheromone gland. A mixture of deuterium-labeled [17,17,18,18-²H₄]-3Z,6Z,9Z-18:H and the unlabeled 3Z,6Z,9Z-18:H was obtained after topical application and injection of (10Z,13Z,16Z)-[2,2,3,3-²H₄]-10,13,16-nonadecatrienoic acid ([2,2,3,3-²H₄]-10Z,13Z,16Z-19:acid) or (11Z,14Z,17Z)-[3,3,4,4-²H₄]-11,14,17-icosatrienoic acid ([3,3,4,4-²H₄]-11Z,14Z,17Z-20:acid). These results are consistent with a biosynthetic pathway that starts with α-linolenic acid (9Z,12Z,15Z-18:acid). Chain elongation leads to 11Z,14Z,17Z-20:acid, which is shortened by α-oxidation as the key step to yield 10Z,13Z,16Z-19:acid. This acid can be finally reduced to an aldehyde and decarbonylated or decarboxylated to furnish the pheromone component 3Z,6Z,9Z-18:H. A similar transformation of 11Z,14Z,17Z-20:acid yields the second pheromone component, 3Z,6Z,9Z-19:H.     

Deuterium retention of boron-titanium and reduction of deuterium retention after helium ion irradiations

Deuterium ion irradiations with an ion with energy of 1.7 keV were conducted for boron-titanium (B-Ti) film prepared by electron beam evaporation and hot pressed titanium-boride, TiB₂. The amount of retained deuterium was measured for these materials using a technique of thermal desorption spectroscopy. The amount of deuterium retained in TiB₂ was comparable with that in B-Ti. Desorption peaks of deuterium in B-Ti were 470 K and 620 K, corresponding to a desorption in the low temperature regime observed in boron (B) and a desorption in titanium (Ti), respectively. The desorption peaks in TiB₂ were 620 K and 750 K, which correspond to the desorption in Ti and that in the high temperature regime in B, respectively. The desorption temperature in B-Ti was approximately 100 K lower than that in TiB₂. This difference is discussed based upon chemical bindings and amorphous/crystal structures of B-Ti and TiB₂. Irradiation of helium ion with energy of 5 keV was conducted for B-Ti after the deuterium ion irradiation. The amount of retained deuterium decreased and the desorption temperature shifted to the lower temperature regime, as the helium ion fluence increased. The shift to the low temperature regime is due to the enhancement of amorphous structure of B in B-Ti.     

The steady-state and dynamic simulation of cascade distillation system for the production of oxygen-18 isotope from water

Accurate simulation of water distillation system for oxygen-18(18O) isotope separation is necessary to guide industrial practice, since both deuterium(D) and oxygen-18 isotope get enriched and interfere with each other. In the present work, steady-state and dynamic distillation models are established based on a classic method and a cascade distillation system with 5 towers is introduced to test the models. The theoretical expressions of separation factor αH/Dfor protium/deuterium and separation factor α~(16)O/~(18) O.for oxygen-16/oxygen-18 were derived,with the existence of deuterium and oxygen-18, respectively. The results of the steady-state simulation by the classical method proposed in the present work agreed well with the results of the lumping method. The dynamic process could be divided into 5 stages. Impressively, a peak value of product withdraw was observed before the final steady state, which was resulted from the change of ~(16)O/~(18) O separation factor and isotope distribution. An interesting low concentration zone in the towers of T2–T5 existed at the beginning of the dynamic process and it required industrial evidence.     

Deuterated Diamond Like Carbon films (DDLC): Mechanical properties in relation with microstructure

The aim of this work is to study the mechanical properties of Deuterated Diamond Like Carbon (DDLC) in comparison with Diamond Like Carbon (DLC), to clarify the influence of hydrogen in amorphous carbon thin film (a-C:H) of DLC type. For this purpose we substitute hydrogen (H) in the film by its isotope deuterium (D) by replacing CH₄ by CD₄ and their mixture 1:1 in the plasma. To investigate the deuterium role in the film structure, both hydrogenated and deuterated carbon films are deposited onto silicon wafer and glass substrates using a radio frequency PECVD device. All the amorphous carbon thin films are prepared with a negative self-bias voltage in the range of 50 V to 600 V. We obtain thus a wide variation of chemical composition. Single layer is produced with a constant thickness of 200 nm, controlled by X-ray reflectivity. The effects of deposition parameters on mechanical and adhesion properties of the DLC films are investigated using nano-hardness and nano-scratch tests. Chemical compositions are determined by ions and electrons spectroscopies (RBS, ERDA, XPS). We find, among other results, that replacing hydrogen by deuterium in amorphous carbon structure enhanced hardness properties for low self-bias voltage.     

Energy distributions and radiation emissions in an inertial electrostatic confinement (IEC) device under low and moderate magnetic fields

The energy distributions and electromagnetic emissions of deuterium ions and electrons in an inertial electrostatic confinement (IEC) unit are reported for low and moderate magnetic field cases. The IEC device has a central wire system inside the grid system of the chamber for the production of the azimuthal magnetic field. The real-time simulations are performed by time integration method by using a finite difference method (FDM) for the physical geometry of device. It is observed that the field induces helical trajectories on the particles especially at the central region where the magnetic force is maximized in a fully ionized Deuterium media. The results prove that the particles have rich dynamics in terms of their trajectories. The effect of negative potential and particle–particle interaction play important roles to determine the trajectories even for low number of ions and electrons. Ion temperatures are calculated as T_i = 6.9 keV after 6 μs for low field case and T_i = 1.517 MeV after 22 μs for medium field case.     

The theoretical study of the deuterium enrichment of H-D gas mixture in continuous-type thermal-diffusion columns

The separation equations for enrichment of deuterium in H-D (Hydrogen-Deuterium) gas mixture by continuous-type thermal diffusion columns were developed theoretically. The transport equation modeling treats the enriching and stripping sections separately for each component of H₂-HD-D₂ system to estimate the concentration between the bottom and top ends of the thermal diffusion column. The empirical expressions of the transport coefficients were determined with the previous experimental data (Arita et al., 1998) correlating in the exponential form in terms of operating pressure. The theoretical predictions of the degree of separation and separation factor for recovery of deuterium from H-D gas mixture are in good agreement with the experimental results.     

Helium and hydrogen interaction in tungsten simultaneously irradiated by He+-H2+ at high temperature

Tungsten (W) is one of the most promising candidates for plasma facing materials in the fusion reactor. Helium (He) in W can influence the retention of hydrogen isotopes. In the present study, W targets were simultaneously irradiated by He⁺-H₂⁺ or He⁺-D₂⁺ ion beams with the energies of 1 keV or 3 keV, at fixed temperatures in a range of room temperature (R.T.) to 1073 K. Mechanisms of He and hydrogen interaction in W were discussed, especially from the point of He retention, which was characterized by the high-temperature thermal desorption spectroscopy (TDS) and glow-discharge optical emission spectroscopy (GD-OES) measurements. It is found that He desorption shifts to a lower temperature range for the W simultaneously irradiated by 3 keV He⁺-1 keV H₂⁺ at 573 K, under He⁺ fluence up to 1 × 10²² He⁺m⁻². Transmission electron microscope (TEM) observation and annealing treatment at the temperature of 873–1073 K show that the increased He uptake is caused by the formation of dislocation. Enhanced retention amounts for the hydrogen isotopes were also confirmed. Amounts of the dislocation loops introduced by the H₂⁺-only irradiation can be reduced by annealing treatment at 873 K, while that introduced by He⁺ irradiation are quite stable, which grows larger at elevated temperatures. With an increase of H₂⁺ energy, Helium uptakes at both weak trapping sites and bubbles are increased, while the amounts of hydrogen retention are decreased. It suggests that hydrogen ion has a significant influence on the He trapping sites at the irradiation temperature up to 573 K, while the hydrogen retention is determined by the distribution of He bubbles and dislocation loops.     

Structural and nanostructural behavior of deuterium implanted Highly Ordered Pyrolytic Graphite investigated by combined High Resolution Transmission Electron Microscopy,Scanning Electron Microscopy and Raman microspectrometry

This work aims at studying the impact of D⁺ ion implantation and thermal annealing on the organization of Highly Ordered Pyrolytic Graphite (HOPG). Raman microspectrometry, High Resolution Transmission Electron Microscopy (HRTEM) and Scanning Electron Microscopy (SEM) were used to characterize the multiscale organization of HOPG. For the first time, HRTEM images were processed, allowing a better estimation of structural parameters such as size of the graphene layers, mean interlayer spacing, distribution of the relative orientations of the graphene layers, defined as the spatial orientation of the stacked layers. Ion implantation induces a strong disordering of the HOPG reflected by a decrease of the length of graphene layers, and an increase of both angular dispersion and interlayer distance and a significant decrease of the Basic Structural Unit (BSU) diameter. Thermal annealing up to 1000 °C leads to partial reordering of the HOPG, with increase of the mean length of the graphene layers, decrease of their angular dispersion and interlayer distance and larger and increasingly parallel oriented BSUs. Even if the conservation of the lamellar nanostructure favors reordering, the latter is only partial since annealing temperature is far from 2000 °C, temperature above which stiff and perfect layers may be obtained.