共查询到20条相似文献,搜索用时 31 毫秒
1.
M. Tang P. Lu J.A. Valdez K.E. Sickafus 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2006,250(1-2):142-147
Polycrystalline pellets of the rare-earth sesquioxide Dy2O3 with cubic C-type rare-earth structure were irradiated with 300 keV Kr2+ ions at fluences up to 5 × 1020 Kr/m2 at cryogenic temperature. Irradiation-induced microstructural evolution is characterized using grazing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM). In previous work, we found a phase transformation from a cubic, C-type to a monoclinic, B-type (C2/m) rare-earth structure in Dy2O3 during Kr2+ ion irradiation at a fluence of less than 1 × 1020 Kr/m2. In this study, we find that the crystal structure of the top and middle regions of the implanted layer transform to a hexagonal, H-type (P63/mmc) rare-earth structure when the irradiation fluence is increased to 5 × 1020 Kr/m2; the bottom of the implanted layer, on the other hand, remains in a monoclinic phase. The irradiation dose dependence of the C-to-B-to-H phase transformation observed in Dy2O3 appears to be closely related to the temperature and pressure dependence of the phases observed in the phase diagram. These transformations are also accompanied by a decrease in molecular volume (or density increase) of approximately 9% and 8%, respectively, which is an unusual radiation damage behavior. 相似文献
2.
Zilu ZHAO 《等离子体科学和技术》2018,20(11):115403
In this paper, volume barrier discharge with different gap distances is added on the discharge border of high-voltage electrode of annular surface barrier discharge for generating volume added surface barrier discharge (V-SBD) excited by bipolar nanosecond high-voltage pulse power in atmospheric air. The excited V-SBDs consist of surface barrier discharge (d=0 mm) and volume added surface barrier discharges (d=2 mm and 3 mm). The optical emission spectra are recorded for calculating emission intensities of N2 (C 3Ⅱu →B3Πg ) and N2+ (B 2Σu+ → X 2Σg+ ), and simulating rotational and vibrational temperatures. The influences of gap distance of V-SBD on emission intensity and plasma temperature are also investigated and analyzed. The results show that d=0 mm structure can excite the largest emission intensity of N 2 (C 3 Πu →B 3Πg ), while the existence of volume barrier discharge can delay the occurrence of the peak value of the emission intensity ratio of N2+ (B 2Σu+ → X 2Σg+ )/N 2(C3Πu →B3Πg ) during the rising period of the applied voltage pulse and weaken it during the end period. The increasing factor of emission intensity is effected by the pulse repetition rate. The d=3 mm structure has the highest threshold voltage while it can maintain more emission intensity of N2(C3 Π u →B 3Πg ) than that of d=2 mm structure. The structure of d=2 mm can maintain more increasing factor than that of the d=3 mm structure with varying pulse repetition rate. Besides, the rotational temperatures of three V-SBD structures are slightly affected when the gap distance and pulse repetition rate vary. The vibrational temperatures have decaying tendencies of all three structures with the increasing pulse repetition rate. 相似文献
3.
采用三重四级杆质谱模拟并分析微观含铀分子化学键断裂形成新的物质的过程以探讨单质铀的产生机理。结果表明,含铀分子在质谱中离子化后经碰撞诱导解离可生成U+。研究还发现,硝酸铀酰溶液通过电喷雾可形成UO+2(m/z 270)、UO2OH+(m/z 287)、UO2H2OOH+(m/z 305)、UO2NO+3(m/z 332)、UO2(H2O)3NO+3(m/z 386)及双聚铀酰离子[(UO2NO3H2O)2NO3]+(m/z 762),在具有一定动能N2的碰撞下它们均可产生游离的U+。通过模拟实验推测,天然单质铀形成的微观机理为:在漫长地质年代中放射性核素持续衰变产生的能量粒子撞击含铀分子使其化学键断裂生成游离铀离子,在封闭或强还原性等特殊地质条件下形成单质铀并被保存下来。 相似文献
4.
新型铯选择性吸附剂的合成及性能 总被引:1,自引:0,他引:1
在金属镍粉表面原位合成了与金属基体紧密结合的亚铁氰化镍钾(KNiFC/Ni)吸附剂。经分析,其表面为面心立方晶系的亚铁氰化镍钾(KNiFC),厚度约为40~80nm,晶格参数为0.996 0nm,化学组成可表示为K1.4Ni1.3Fe(CN)6。结果表明:该吸附剂不水解,对137 Cs具有较高的吸附容量,非常快的吸附速率,很高的选择性,Cs的吸附分配系数(Kd)可达105 mL/g,即使在1.0mol/L NaNO3溶液中,Kd值也大于103 mL/g;该吸附剂吸附137 Cs为典型的离子交换机制,NH+4由于具有和Cs+相近的离子半径所以竞争最为强烈。本吸附剂有望用于含铯废液的处理及137 Cs的分离或提取。 相似文献
5.
铀在生物体内的化学形态及分布是评价铀毒性的基础。文章通过尾静脉注射给药方式研究螯合剂对染铀小鼠体内铀分布的影响。通过建立包含主要体液金属离子、小分子配体及UO22+与螯合剂的热力学平衡模型,采用数值模拟方法研究UO22+在血液中的形态。实验结果表明:DTPA易与UO22+形成[(UO2)2(OH)DTPA]2-,对小鼠血液中的UO22+有明显的促排作用,但在促排的同时对小鼠的肾脏和骨骼有损伤;抗坏血酸对小鼠体内各组织器官的铀促排几乎无作用,但形成的[(UO2)2(OH)Ascorbate]2+会阻碍肾脏中U(Ⅵ)的代谢;NTA对小鼠体内各组织器官铀的促排作用小,并会促使体内出现固相(UO2)3(PO4)2·4H2O,对骨骼有较强的损伤作用,不适合作为铀的促排剂。 相似文献
6.
R. Schulz T. Bachmann E. Glaser P. Gaiduk 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1996,120(1-4):203-206
To investigate the nonlinear dose dependence of the thickness of the recrystallized layer during ion beam induced epitaxial recrystallization at amorphous/crystalline interfaces GaAs samples were irradiated with 1.0 MeV Ar+, 1.6 MeV Ar+ or 2.5 MeV Kr+ ions using a dose rate of 1.4 × 1012 cm−2 s−1 at temperatures between 50°C and 180°C. It has been found that the thickness of the recrystallized layer reaches a maximum value at Tmax = 90°C and 135°C for the Ar+ and Kr+ implantations, respectively. This means that the crystallization rate deviates from an Arrhenius dependence due to ion beam induced nucleation and growth within the remaining amorphous layer. The size of the crystallites depends on the implantation dose. This nucleation and growth of the crystallites disturbes and at least blocks the interface movement because the remaining surface layer becomes polycrystalline. Choosing temperatures sufficiently below Tmax the thickness of the recrystallized layer increases linearly with the implantation dose indicating that the irradiation temperature is too low for ion induced nucleation. 相似文献
7.
S. Y. Kim M. Harada H. Tomiyasu Y. Ikeda Y. Y. Park 《Progress in Nuclear Energy》2000,37(1-4):399-404
The structural and kinetic studies of U(VI) complex with benzamidoxime(Hba) as ligand in CD3COCD3 have been studied by means of 1H and 13C NMR. The Hba molecule was found to coordinate to UO22+ in the form of anionic benzamidoximate (ba), and the number of ba coordinated to UO22+ was determined to be 3 by analyzing the chemical shift of 13C NMR signal for Hba in the presence of UO22+. The exchange rate constants(kex) of ba in [UO2(ba)3] were determined by the NMR line-broadening method. The kinetic parameters were obtained as follows: kex(25°C) = 3.1 × 103s−1, ΔH≠ = 35.8 ± 3.5 KJ mol−1, and ΔS≠ = −65 ± 13.7 J K−1 mol−1. The UV-visible absorption spectra of solutions containing UO22+ and Hba were also measured. The molar extinction coefficient of the complex was found to be extremely large compared with those of UO2(L)52+ (L = unidentate oxygen donor ligands) complexes. This is due to the strong electron withdrawing of UO22+ from Hba and suggests that an interaction between UO22+ and Hba is very strong. Such a high affinity of monomeric amidoxime to UO22+ reasonably explains the high adsorptibility of amidoxime resin to U(VI) species, and is considered to result in the high recovery of U(VI) species from sea water using amidoxime resin. 相似文献
8.
9.
A. Meldrum L. A. Boatner W. J. Weber R. C. Ewing 《Journal of Nuclear Materials》2002,300(2-3):242-254
Single crystals of the ABO3 phases CaTiO3, SrTiO3, BaTiO3, LiNbO3, KNbO3, LiTaO3, and KTaO3 were irradiated by 800 keV Kr+, Xe+, or Ne+ ions over the temperature range from 20 to 1100 K. The critical amorphization temperature, Tc, above which radiation-induced amorphization does not occur varied from approximately 450 K for the titanate compositions to more than 850 K for the tantalates. While the absolute ranking of increasing critical amorphization temperatures could not be explained by any simple physical parameter associated with the ABO3 oxides, within each chemical group defined by the B-site cation (i.e., within the titanates, niobates, and tantalates), Tc tends to increase with increasing mass of the A-site cation. Tc was lower for the Ne+ irradiations as compared to Kr+, but it was approximately the same for the irradiations with Kr+ or Xe+. Thermal recrystallization experiments were performed on the ion-beam-amorphized thin sections in situ in the transmission electron microscope (TEM). In the high vacuum environment of the microscope, the titanates recrystallized epitaxially from the thick areas of the TEM specimens at temperatures of 800–850 K. The niobates and tantalates did not recrystallize epitaxially, but instead, new crystals nucleated and grew in the amorphous region in the temperature range 825–925 K. These new crystallites apparently retain some ‘memory' of the original crystal orientation prior to ion-beam amorphization. 相似文献
10.
A.M.P. Hussain A. Kumar D. Saikia F. Singh D.K. Avasthi 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2005,240(4):871-880
Conducting polymer polypyrrole thin films doped with LiCF3SO3, [CH3(CH2)3]4NBF4 and [CH3(CH2)3]4NPF6 have been electrodeposited potentiodynamically on ITO coated glass substrate. The polymer films are irradiated with 160 MeV Ni12+ ions at three different fluences of 5 × 1010, 5 × 1011 and 3 × 1012 ions cm−2. An increase in dc conductivity of polypyrrole films from 100 S/cm to 170 S/cm after irradiation with highest fluence is observed in four-probe measurement. X-ray diffractogram shows increase in the crystallinity of the polypyrrole films upon SHI irradiation, which goes on increasing with the increase in fluence. Absorption intensity increase in the higher wavelength region is observed in the UV–Vis spectra. The SEM studies show that the cauliflower like flaky microstructure of the surface of polypyrrole films turns globular upon SHI irradiation at fluence 5 × 1011 ions cm−2 and becomes smooth and dense at the highest fluence used. The cyclic voltammetry studies exhibit that the redox properties of the polypyrrole films do not change much on SHI irradiation. 相似文献
11.
The complex nature of laser-material interaction causes non-stoichiometric ablation of alloy samples.This is attributed to matrix effect, which reduces analyzing capability. To address this issue, the analytical performance of three different normalization methods, namely normalization with background, internal normalization and three point smoothing techniques at different parameter settings is studied for quantification of Ag and Zn by Laser induced breakdown spectroscopy(LIBS).The LIBS spectra of five known concentration of silver zinc binary composites have been investigated at various laser irradiances(LIs). Calibration curves for both Ag(I) line(4d~(10)5s~2S_(1/2)→4d~(10)5p~2P_(1/2) at 338.28 nm) and Zn(I) line(4s5s~3S_1→4s4p~3P_2 at 481.053 nm) have been determined at LI of 5.86?×?10~(10)W cm~(-2). Slopes of these calibration curves provide the valuation of matrix effect in the Ag–Zn composites. With careful sample preparation and normalization after smoothing at optimum parameter setting(OPS), the minimization of sample matrix effect has been successfully achieved. A good linearity has been obtained in Ag and Zn calibration curve at OPS when normalized the whole area of spectrum after smoothing and the obtained coefficients of determination values were R~2?=?0.995 and 0.998 closer to 1. The results of matrix effect have been further verified by analysis of plasma parameters. Both plasma parameters showed no change with varying concentration at OPS. However, at high concentration of Ag, the observed significant changes in both plasma parameters at common parameter setting PS-1 and PS-2 were the gesture of matrix effect. In our case, the better analytical results were obtained at smoothing function with optimized parameter setting that indicates it is more efficient than normalization with background and internal normalization method. 相似文献
12.
最近发现的全硼富勒烯(硼球烯,D2d B-/040),开启了硼球烯化学研究的新篇章。类似于富勒烯,金属掺杂也是硼球烯修饰和功能化重要途径。本工作采用密度泛函理论预测了一系列锕系金属掺杂硼球烯[An@B39]n+(An=U,n=3;An=Cm,n=2)。理论计算表明,这些硼球烯均为稳定的金属内嵌硼球烯,其中[U@B39]3+的能量最低,结构具有C3对称性,而[Cm@B39]2+为C1结构。成键性质分析表明,[U@B39]3+和[Cm@B39]2+均存在σ和π离域键。另外[An@B39]n+中U-B键的共价相互作用强于Cm-B键,且[U@B39]3+较[Cm@B39]2+更稳定。因此,An-B键的共价特征对于这些锕系金属内嵌硼球烯的形成是必不可少的。本工作扩展了硼球烯体系,并为新型稳定金属内嵌硼球烯的设计提供了理论线索。 相似文献
13.
Structural study on uranyl ion in 1-butyl-3-methylimidazolium nonafluorobutanesulfonate ionic liquid
The structure of uranyl ion in 1-butyl-3-methylimidazolium nonafluorobutanesulfonate ionic liquid (BMINfO) has been studied with 1H- and 35Cl-NMR, Raman, and UV-visible spectroscopy. In the 1H-NMR spectrum of the BMINfO solution prepared by dissolving UO2(ClO4)2·5 6H2O, the signal of H2O coordinated to UO22+ was observed at 6.64 ppm at 50°C (free H2O in BMINfO: 3.1 ppm at 50°C), suggesting that the uranyl species exists as the aquo complex, [UO2(H2O)n]2+. The signal of the coordinated H2O disappears with heating at 120°C for 3 h under vacuum. This indicates the dehydration from [UO2(H2O)n]2+. On the other hand, the 35Cl-NMR signal of ClO4− as the counter anion of UO22+ was observed at 1011 ppm (vs. Cl− in D2O) regardless of heating. This indicates that no ClO4− ion is in the first coordination sphere of UO22+. Furthermore, the UV-visible absorption spectra showed that the characteristic absorption bands due to UO22+ were sharpened with the dehydration. This means the simplification of the structure around UO22+. These results described above suggest that UO22+ in BMINfO has no ligand in its equatorial plane after the dehydration, i.e. UO22+ exists as a bare cation in this system. 相似文献
14.
To develop the non-invasiveand diagnostic agents for Alzheimer’s disease (AD), 99Tcm(CO)3+-L(L: (E)-2-(4-((4-(dimethylamino)phenyl)diazenyl)phenylamino)acetic acid, adiphenyldiazene derivative) was prepared,radiochemical purity was above 95%. Initialautoradiography results suggested that 99Tcm(CO)3+-Lshowed selective binding to the Aβ plaque-like structures in the brain section from theAD transgenic mice (Tg C57, APP, PS1 12-month-old), further, 99Tcm(CO)3+-Lshowed the same binding sites with fluorescence stained by Re(CO)3+-L.Biodistribution of 99Tcm(CO)3+-L innormal mice demonstrated low uptake in brain (5 min: (0.52 ±0.11)% ID/g)whilst slow clearance from the brain tissues at 120 min post-injection (0.28 ± 0.04)%ID/g. The corresponding Re analogue was alsosynthesized, and the nature of its lowest electronically excited state wasdetermined by studies of the UV-vis absorption and fluorescence emissionproperties at room temperature. In addition, the fluorescent staining of the Re-complexwas performed in comparison to Thioflavin-T and autoradiography results of 99Tcm(CO)3+-L.In conclusion, these results are encouraging for further exploration of 99Tcm(CO)3+-Las a SPECT imaging agent for Aβplaques in the AD brain. 相似文献
15.
Bing QI 《等离子体科学和技术》2019,21(8):85402-52
In this study, the density of metastable He2* in an atmospheric-pressure plasma jet operating in helium with 0.001% nitrogen has been measured using an auxiliary measuring electrode technique. In the glow discharge mode, waveforms from two grounding electrodes, including one main discharge electrode and one auxiliary electrode, are captured. The isolated current peak formed by Penning ionization in waveforms from the auxiliary measuring electrode is identified to calculate the density of metastable He2*. In our discharge environment, the helium metastable densities along the jet axis direction are between 2.26× 1013 and 1.74× 1013 cm-3, which is in good agreement with the results measured by other techniques. This measurement technique can be conveniently applied to the diagnosis of metastableHe2* in an atmospheric-pressure plasma jet array. 相似文献
16.
In this study, we confirm a tetrahedral structure for a Co2+ complex in supercritical water instead of the octahedral structure in normal water. The absorption spectra of Ru2+ complexes were observed for only stable species such as [Ru(phen)3]2+ in supercritical water. The photochemistry of uranyl(VI)-tributylphosphate(TBP) complex in supercritical carbon dioxide(scCo2) was studied in the pressure range of 8-40 MPa and from 289 to 336K. In order to examine the hydrogen-bond structures and molecular motions of supercritical water and non-aqueous solvents, their 1H spin-lattice relaxation times were measured under sub- and supercritical conditions by using high-pressure NMR. NiMo/Al2O3 was chosen as a catalyst because of its catalytic activity for hydrocracking aromatic structures. 相似文献
17.
UV-pulsed laser cavity ringdown spectroscopy of the hydroxyl radical OH(A–X)(0–0)band in the wavelength range of 306–310 nm was employed to determine absolute number densities of OH in the atmospheric helium plasma jets generated by a 2.45 GHz microwave plasma source.The effect of the addition of molecular gases N_2 and O_2 to He plasma jets on OH generation was studied.Optical emission spectroscopy was simultaneously employed to monitor reactive plasma species.Stark broadening of the hydrogen Balmer emission line(H_β)was used to estimate the electron density nein the jets.For both He/N_2 and He/O_2 jets, newas estimated to be on the order of 10~(15)cm~(-3).The effects of plasma power and gas flow rate were also studied.With increase in N_2 and O_2 flow rates, netended to decrease.Gas temperature in the He/O_2 plasma jets was elevated compared to the temperatures in the pure He and He/N_2 plasma jets.The highest OH densities in the He/N_2 and He/O_2 plasma jets were determined to be 1.0?×10~(16)molecules/cm~3 at x?=?4 mm(from the jet orifice)and 1.8?×?10~(16)molecules/cm~3 at x=3 mm, respectively.Electron impact dissociation of water and water ion dissociative recombination were the dominant reaction pathways, respectively, for OH formation within the jet column and in the downstream and far downstream regions.The presence of strong emissions of the N_2~+ bands in both He/N_2 and He/O_2 plasma jets, as against the absence of the N_2~+ emissions in the Ar plasma jets, suggests that the Penning ionization process is a key reaction channel leading to the formation of N_2~+ in these He plasma jets. 相似文献
18.
为研究铀矿区地下水化学性质对铀的存在形式的影响,本文以赣杭构造带某铀矿区地下水为研究对象,在对9个典型采样点地下水化学成分分析的基础上,采用数理统计软件SPSS 18.0和地球化学模拟软件PHREEQC及llnl.dat数据库,探究了研究区内地下水水化学特征及U的存在形式。结果表明:本研究区地下水水化学类型以HCO_(3)-Na与HCO_(3)-Na·Ca为主,U含量与Ca^(2+)和Mg^(2+)浓度体现出较强正相关性,与SO_(4)^(2-)的相关性次之;地下水中U元素主要以六价为主,几乎占100%,主要存在形式依次为UO_(2)(CO_(3))_(2)^(2-)、UO_(2)(CO_(3))_(3)^(4-)、UO_(2)CO_(3)、UO_(2)(OH)2、UO_(2)(OH)_(3)^(-)、UO_(2)OH^(+)等6种,其中UO_(2)(CO_(3))_(2)^(2-)占绝对优势,整体以碳酸铀酰形式为主,这也与研究区地下水酸碱性相对应。 相似文献
19.
Wolfgang Bolse Thomas Weber Wolfgang Lohmann 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1990,50(1-4):416-419
The ion mixing of Ti-steel bilayers with N+, Ar+, Ti+, Kr+ and Xe+ ions was investigated by means of Rutherford backscattering spectroscopy (RBS). The mixing rates exhibit a linear scaling with the deposited damage energy fD. No correlation between the properties of the mixing ion and the mixing efficiency was found. The results are compared with the predictions of ballistic and thermal-spike models. 相似文献
20.
为了解铀酰离子在北山地下水中的吸附、扩散和迁移行为,利用地球化学计算软件PHREEQC,采用由OECD/NEA发布的最新铀的热力学数据,计算了铀在我国高放废物地质处置库重点研究区甘肃北山地下水中的种态分布,并分析了围岩中存在的方解石对铀溶解度的影响。计算结果表明,在北山地下水组成不变的前提下,在偏酸性条件下,铀主要以UO2F+、UO2SO4、UO22+、UO2F2和UO2(SO4)22-的形式存在,而在中性至弱碱性条件下,主要以 UO2(CO3)4-3、UO2(CO3)22-、UO2(OH)3-和UO2(OH)42-的形式存在。我国计划建造的高放废物处置库的设计深度为地下500~1000m,其水岩体系一般呈弱碱性。在这样的弱碱性水岩体系中,以阴离子形式存在的铀酰配合物具有较强的可移动性。当地下水的pH=7.56时,在Eh<24mV的条件下,铀主要以沥青铀矿的形式存在,而在更高的Eh条件下,则主要以UO22+与CO32-和OH-形成的阴离子配合物的形式存在。当地下水与空气接触时,O2的存在会使Eh升高,此时铀的主要存在种态为UO22+及其各种配合物。当围岩体系中存在方解石时,在pH<8.0的条件下,铀在地下水中的溶解度会显著提高,而在更高pH条件下,方解石对铀的溶解度无明显影响。 相似文献