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在Ni70Mn25Co5-C体系中添加含氢化合物Fe(C5H5)2作为新型氢源, 利用温度梯度法, 在压力为5.5-6.0 GPa、温度为1280-1400 ℃的条件下, 成功合成出氢掺杂的宝石级金刚石大单晶. 通过傅里叶显微红外光谱发现, 随着Fe(C5H5)2添加量的增加, 合成晶体中与氢相关的对应于sp3杂化C-H键的对称伸缩振动和反对称伸缩振动的红外特征峰2850和2920 cm-1逐渐增强, 而晶体中氮含量却逐渐减少. 通过合成晶体的拉曼光谱分析发现, 金刚石的拉曼峰伴随Fe(C5H5)2的添加向高频偏移, 这表明氢的进入在金刚石内部产生了压应力. 观察扫描电子显微镜图像发现, 在低含量Fe(C5H5)2添加时晶体表面平滑, 而高含量添加时晶体表面缺陷增多, 且呈现出气孔状. 使用新的添加剂Fe(C5H5)2作为氢源, 合成出含氢宝石级金刚石单晶, 丰富了金刚石单晶中对氢的研究内容, 也可为理解天然金刚石的形成机理提供帮助. 相似文献
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采用密度泛函理论中的广义梯度近似, 对X@C20F20(X=He, Ne, Ar, Kr)几何结构和电子结构进行了计算研究. 几何结构优化发现: 惰性气体原子X内掺到C20F20笼后, 均稳定于碳笼中心, 随着内掺X原子序数的增大, X原子对C20F20笼的影响越来越大. 能隙、内掺能和振动频率计算表明: 内掺X原子使得C20F20的稳定性得到了显著提升, X@C20F20(X=He, Ne, Ar, Kr)都具有良好的稳定性, 并且随着X原子序数的增大, 其稳定性也基本呈现逐渐增强的趋势. 电子结构研究发现: X原子对X@C20F20费米能级附近的占据轨道基本没有贡献, 而对其未占据轨道贡献较大. 计算还发现: 在X@C20F20中, He 和Kr分别从C20F20的C 笼上获得了0.126和0.271个电子, 而Ne和Ar却分别向C笼转移了0.060和0.012个电子. 由此可见: X原子与C原子之间都发生了电荷转移, C笼上的C原子与惰性气体原子X间形成了一定的离子键. 相似文献
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The adsorption and thermal decomposition of perfluorodimethyl ether, (CF3)2O, on a high-surface-area Al2O3 surface was investigated by FTIR under both vacuum and pressure conditions. IR spectra in the 4000-1050 cm−1 range were collected and the spectral assignments were assisted by quantum chemical ab initio calculations. The spectral evidence indicated that (CF3)2O decomposed to form adsorbed fluoroformate, FCOO (ads). Increases of temperature (up to 525 K) caused the FCOO (ads) to convert to hydrogen formate, HCOO (ads). Surface hydroxyl groups participated in the decomposition of (CF3)2O and the conversion of FCOO (ads) to HCOO (ads). A decomposition mechanism is proposed. 相似文献
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大气臭氧层因吸收太阳紫外光, 是人类必不可少的保护伞. 氟利昂在太阳光辐射下解离生成破坏臭氧的游离态氯原子, 是破坏大气臭氧层的主要元凶之一. 本文利用飞行时间质谱技术和离子速度成像技术研究了氟利昂F113(三氟三氯乙烷)分子在800 nm 飞秒光作用下的多光子电离解离动力学. 利用飞行时间质谱探测技术, 得到了三氟三氯乙烷在该波长飞秒激光作用下发生多光子电离解离产生的碎片质谱. 通过荷质比对碎片质谱进行了详细的标定和分析. 在质谱上未发现母体离子, 所有观察到的离子都是由于激光脉冲作用下产生的碎片. 三个最主要的碎片离子是CFCl2+, CF2Cl+, C2F3Cl2+. 通过飞行时间质谱标定, 发现并归属了多个解离通道. 三个主要的解离机理分别为: 1) C-Cl键断裂直接生产氯自由基的通道C2F3Cl3+→C2F3Cl2++Cl; 2) C--C键断裂C2F3Cl3+→CFCl2++CF2Cl; 3) C--C键断裂C2F3Cl3+→CF2Cl++CFCl2. 利用离子速度成像技术对这三个主要通道产生的碎片离子进行成像, 得到了C2F3Cl2+, CFCl2+和CF2Cl+离子的速度影像. 由C--Cl键断裂产生的碎片离子C2F3Cl2^{+}的速度分布由两个高斯分布曲线拟合, 而由C--C键断裂产生的碎片离子CFCl2+和CF2Cl+可以用一个高斯曲线拟合. 通过影像分析得到了解离碎片的平动能分布和角向分布各向异性参数等详尽的动力学信息. 结合高精度密度泛函理论计算对解离动力学进行了进一步的分析和讨论.深入认识氟利昂的解离动力学可为进一步控制破坏臭氧层提供理论参考和实验依据. 相似文献
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Sasagawa T. Kawahara A. Obara M. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1989,17(1):1-5
The ArF-laser (193-nm)-induced discharge interruption is comparatively described in a mixture of C2H3Cl/CF 4/CH4, CF4/CH4, and C2 H3Cl/He using a hollow-cathode-type discharge tube. The unfocused ArF laser (typically 27 mJ/cm2 and 10 ns duration) illuminated both the negative glow inside the hollow cathode and the column between the two electrodes. With a 1.8-torr mixture of C2 H3Cl/CF4, the discharge current of 1 mA was decreased rapidly with a current-decay time constant of 1 μs and a current-decay rate of 1 kA/s. With a 1.5-torr mixture of CF4/CH4, 2.2 μs and 450 A/s were obtained. With a 1.5-torr mixture of CH2H3Cl/He, a time constant of over 3 μs and a rate of less than 300 A/s were obtained. An analysis of the discharge interruption induced by ArF-laser irradiation is given in terms of photon-plasma kinetics. The current peak induced by ArF irradiation is also explained for a mixture of C2H3 Cl/He in terms of photoionization and photodetachment processes 相似文献
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Robert J. Levis Lisa A. Delouise Eric J. White Nicholas Winograd 《Surface science》1990,230(1-3):35-46
The adsorption and thermal decomposition of C2H2 on Rh{111} is compared to the atomically stepped Rh{331} surface over a temperature range of 300 to 800 K. Using X-ray photoelectron spectroscopy (XPS) we find that the C 1s spectra as a function of C2H4 exposure exhibit a shift in binding energy (Eb) from 283.5 eV at 1 L C2H4 exposure on both surfaces to 283.8 eV on Rh{33 and to 284.1 eV on Rh{111} at saturation coverage (4 L). Careful analysis of the C 1s Eb value and full width at half maximum as a function of surface temperature after a 10 L exposure of C2H4 at 300 K reveals that a species consistent with a C2H adsorbate composition is formed between 400 and 450 K on Rh{111}. This species is also observed on Rh{331} although at the lower temperature of 375 K. Computer peak deconvolution of the C 1s spectra between 500 and 700 K suggests that a CHads or Cads surface fragment is formed and increases in concentration at the expense of the C2H species as the surface temperature increases. Above 750 K a graphite overlayer is formed on both surfaces. This overlayer, however, exhibits a low degree of carbon π-character bonding on Rh{331}. The adsorption and decomposition mechanisms suggest that the 300 K C2H4 adsorbate on Rh{331} is ethylidyne and that the stepped surface is more thermally reactive than the flat Rh{111} surface. 相似文献
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Ultrasonic irradiation of solutions containing volatile organometallic complexes results in intense emission from excited-state metal atoms. We have determined the effect of dissolved gases (Xe, Kr, Ar, Ne, He, CF4, C2F6, CO, N2) on the intensity of the sonoluminescence resulting from ultrasonic irradiation of silicone oil solutions of Cr(CO)6. This provides a well-defined, spectrally resolved probe of sonoluminescence with emission resulting from a single species, the chromium atom excited states. As predicted by the hot-spot, thermal mechanisms of sonoluminescence, the intensity of excited-state Cr emission decreases with increasing thermal conductivity of the noble gases. The intensity of sonoluminescence increases with increasing γ (i.e. Cp/Cv), which is also in accord with a thermal mechanism. Sonoluminescence is substantially diminished by the addition of even small amounts (≈ 1%) of CF4 or C2F6, even though they are capable of supporting electrical discharge. This is in agreement with a thermal mechanism, but is in direct conflict with electrical theories of sonoluminescence. 相似文献
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Quantitative adsorption studies, temperature programmed desorption (TPD) and Auger spectroscopy have been used to study the interaction of C2Cl4 with Fe(110) at 90 and 325 K. At 90 K, multilayer C2Cl4 adsorption occurs. The following desorption products are observed in the temperature range of 90–1050 K: C2Cl4 from the multilayer and the monolayer, FeCl2, and a high mass iron chloride species with mass spectrometer cracking products FeCl+2, FeCl+, and Fe+. Irreversible dissociative C2Cl4 adsorption occurs at 325 K and the only desorption product which is observed is the high mass iron chloride species. Auger spectroscopy shows that surface carbon from C2Cl4 starts to diffuse into the bulk of the crystal at ˜ 480 K while small coverages of chlorine remain on the surface of the crystal even after heating to 1050 K. Comparison of the behavior of C2Cl4 and CCl4 on Fe(110) indicates that radical products (·CCl3 and :CCl2) observed to be produced from CCl4 adsorption are not produced from C2Cl4 adsorption. This difference is probably due to the enhanced surface reactivity of the C=C bond in C2Cl4. A special reactivity of iron defect sites for C2Cl4 is observed through the production of associated FeCl2 species which desorb via zero-order kinetics with an activation energy of 44.8 ± 8.5 kcal/mol, the sublimation enthalpy of FeCl2. 相似文献
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The interaction of CO2 with Cs-promoted Fe(110) at 85 K as well as temperature-dependent reactions between 100 and 700 K have been studied by means of ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). Several surface species could be detected at 85 K, i.e. carbon monoxide (CO), carbonate (COn−3), physisorbed linear carbon dioxide (COlin2) and very small amounts of oxidic oxygen (Oox). An oxalate species (C2Om−4) could not be identified definitively, but from comparison with the literature there is evidence that C2Om−4 is present. Increasing the temperature after saturation with CO2 leads to a complicated reaction behaviour. CO2 either desorbs or dissociates into CO and COn−3 or forms C2Om−4 at temperatures between 85 and 160 K. Above 160 K C2Om−4, decomposes in parallel reactions into CO2, COn−3 and CO. Above 320 K, adsorbed CO either desorbs into the gas phase or dissociates into C and O. In the temperature region between 500 and 700 K a recombination of C and O to CO and the desorption of Cs take place. As in the case of Fe(110)/K+CO2, at high alkali coverages two carbonate species could be detected which dissociate upon heating at different temperatures. The system Fe(110)/Cs+CO2 is proved to be very similar to the system Fe(110)/K+CO2. 相似文献
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The interaction between C60 molecules and the Si(100) surface and the preparation of silicon-carbide thin films by thermal reaction of C60 molecules with the Si(100) surface have been investigated using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, reflection high-energy electron diffraction and atomic force microscopy measurements. The effects of annealing temperature and C60 coverage on the SiC formation will be discussed. It is found that the C60 molecules bond covalently with silicon, and the number of bonds increase upon increasing the annealing temperature. Annealing at T≥830°C entails the formation of stoichiometric silicon carbide clusters that coalesce to form a continuous SiC layer when the C60 coverage is greater than one monolayer. Deep pits acting as silicon diffusion channels are present with dimensions that increase with the amounts of C60.
The interaction of C60 with the SiC surface was also investigated. It is found that a similar covalent interaction is present in the two systems C60/Si and C60/SiC. 相似文献
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The tunneling magnetoresistance (TMR) of samples containing well-defined Co clusters (≈4.5 nm mean diameter) embedded in C2H2 matrices essentially is independent of Co-cluster volume fraction vCo and reveals a value of about 26% at T=2 K. This result is in contrast to that obtained for Co clusters embedded in C2H4 matrices (Phys. Rev. B 67 (2003) 094433). In the latter system the TMR strongly decreased with increasing vCo indicating different possible orientation of the C2H4 molecule sandwiched between the Co clusters. We, therefore, conclude that the C2H2 molecules are sandwiched in a rather well-defined orientation between the Co clusters. They probably form double layers of C2H2 molecules with the C–C bond axis parallel to the Co cluster surface. 相似文献
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采用传统固相烧结法成功制备出磷灰石结构材料Ca8LnNa(PO4)6F2(Ln=La,Nd和Sm),并通过常规X射线衍射(X-ray diffraction,XRD)进行表征确定三种样品都为单一相。在室温条件下用800 keVKr2+对三种样品进行辐照实验,辐照后的样品利用掠入射X射线衍射(grazing incidence X-ray diffraction,GIXRD)进行表征获取其表面辐照损伤层的结构信息。发现在实验辐照剂量范围内(1.0×1014~7.0×1014cm-2)三种样品都发生了从晶体结构到非晶结构的转变,不过三种样品的抗辐照非晶性能却有差异,抗辐照非晶能力大小关系是Ca8LaNa(PO4)6F2 > Ca8NdNa(PO4)6F2 > Ca8SmNa(PO4)6F2。这是由于在Ca8LnNa(PO4)6F2中,当镧系核素半径越小时,将有更大概率占据Ca(2)位置与F形成比Ca-F更弱的离子键。因此,镧系核素半径越小,辐照下将有更多的点缺陷保留下来,更容易发生非晶相变。 相似文献
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Photoemission studies reveal the existences of metallic Rb4C60 and Rb5C60 surface phases on the top layer of C60 single crystal. After Rb3C60 thin film with thickness of nanometers has formed on the (1 1 1) surface layers of the C60 single crystal, the excess deposition of Rb atoms do not induce the bulk-like face-centered cubic to body-centered tetragonal or body-centered cubic structure transitions at room temperature. The large size of C60 molecule offers the surface vacancies for the formation of Rb4C60 and Rb5C60 monolayer that is further verified by Rb 3d core-level photoemission measurements. Valence band photoemission results exhibit the surface phases are metallic. 相似文献
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Josep M. Ricart Marie P. Habas Anna Clotet Daniel Curulla Francesc Illas 《Surface science》2000,460(1-3):170-181
The adsorption of CO2 on the clean and potassium-precovered Pt(111) surface has been studied by means of the cluster model approach within the hybrid B3LYP density functional theory-based method. On the clean surface, CO2 is undistorted and weakly bound. The equilibrium position of this physisorbed species appears at a rather large distance from the surface. However, when coadsorbed K atoms are included in the model, a chemisorbed, bent CO2 species on top of a surface Pt atom is found. The presence of the coadsorbed K is found to be necessary to promote CO2 chemisorption and activation, the key step in activating the CO2 molecule being a direct interaction with the coadsorbate. In addition, the calculated vibrational frequencies for this chemisorbed species are in agreement with available experimental data. 相似文献
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John W. Peck Daniel I. Mahon David E. Beck Barbara Bansenaur Bruce E. Koel 《Surface science》1998,410(2-3):214-227
The adsorption and reaction of methyl nitrite (CH3ONO, CD3ONO) on Pt(111) was studied using HREELS, UPS, TPD, AES, and LEED. Adsorption of methyl nitrite on Pt(111) at 105 K forms a chemisorbed monolayer with a coverage of 0.25 ML, a physisorbed second layer with the same coverage that desorbs at 134 K, and a condensed multilayer that desorbs at 117 K. The Pt(111) surface is very reactive towards chemisorbed methyl nitrite; adsorption in the monolayer is completely irreversible. CH3ONO dissociates to form NO and an intermediate which subsequently decomposes to yield CO and H2 at low coverages and methanol for CH3ONO coverages above one-half monolayer. We propose that a methoxy intermediate is formed. At least some C–O bond breaking occurs during decomposition to leave carbon on the surface after TPD. UPS and HREELS show that some methyl nitrite decomposition occurs below 110 K and all of the methyl nitrite in the monolayer is decomposed by 165 K. Intermediates from methyl nitrite decomposition are also relatively unstable on the Pt(111) surface since coadsorbed NO, CO and H are formed below 225 K. 相似文献
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R.V. Shpanchenko M.G. Rozova A.M. Abakumov E.I. Ardashnikova M.L. Kovba S.N. Putilin E.V. Antipov O.I. Lebedev G. Van Tendeloo 《Physica C: Superconductivity and its Applications》1997,280(4):3652-280
Bulk superconductivity with Tc up to 94 K has been induced by fluorination of non-superconducting YBa2Cu3O6.11 using XeF2 as a fluorination agent. Strong changes on X-ray patterns were found after fluorination of reduced YBCO. High resolution electron microscopy of superconducting samples showed the presence of a new phase with c ≈ 13 Å which exists as noticeable areas included within a matrix of the 123 structure or which occurs as isolated defects with a limited extension. All fluorinated compounds exhibited a strong disorder along the c-direction resulting in a ‘loss’ of c-parameter on X-ray patterns. The present results demonstrate that fluorine indeed enters the YBCO structure with a significant structural rearrangement for the high level of fluorination. The structure of the fully fluorinated YBa2Cu3O6F2 phase, possibly responsible for superconductivity, has been deduced from high resolution electron microscopy. 相似文献
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We have studied the ultraviolet laser induced desorption of NO/Cr2O3(0001), K/Cr2O3(0001) and the coadsorbate system NO/K/Cr2O3(0001) using resonance enhanced multiphoton ionization spectroscopy for state selective detection of the desorbing species after excitation with nanosecond laser pulses. The goal of our experiments was to study the influence of surface electronic modifications via alkali adsorption on the photodynamics of a simple molecule. The photochemistry of the isolated and the coadsorbate systems is strongly dependent on the coverage of the diverse components. In this paper we shall mainly focus on data for the low coverage regime of potassium. From the two adsorbate species of NO, a chemisorbed and a physisorbed species, we present data of the chemisorbed species. The velocity distributions show a strong dependence on the excitation energy which we interpret on the basis of electron energy loss spectra as being due to surface charge transfer states. This is corroborated with our coadsorption experiments with low coverages of potassium which alter the velocity distributions. 相似文献