NO在Ru(100)和Cs/Ru(100)表面上吸附的ARUPS研究

150K的低温下，NO在清洁的Ru表面的吸附，HeⅡ-ARUPS显示在Ef以下9．3eV（5σ＋1π）和14．6eV（4σ）处有两个峰，表明NO在Ru表面上是分子吸附。NO－4σ峰强度随HeⅡ光入射角的变化说明NO分子是倾斜地吸附在Ru表面上，其倾斜趋向于原于间距较大的〈0001〉力位。对于NO在Cs／Ru表面的吸附，ARUPS测得在Ef以下6．2，9．2，11．1，12．4和14．9eV处有五个峰，与N2O气侧的UPS谱比较，认定它们是N2O，NO共存的结果，表明NO在CS／Ru表面上分解后可形成N2O分子的吸附。     

双层石墨烯掺杂Pd对CO和NO的气敏特性研究

采用基于密度泛函理论的第一性原理计算方法,研究了AA堆叠型双层石墨烯掺杂Pd原子(Pd/BG)后对气体分子CO和NO的气敏特性和吸附机理.结果表明,Pd原子的掺杂改变了双层石墨烯的电子性质和局部几何结构.Pd原子替代双层石墨烯的一个碳原子后,杂质原子突出层外区域(Po)和突入层间区域(Pi)都可以形成稳定结构,但是突出(Po)构型更有利于气体分子的吸附.对于Po构型,CO和NO吸附在Pd/BG上的最稳定结构是不同的,CO分子与石墨烯表面呈一定夹角,而NO分子近似垂直于石墨烯表面.Pd/BG对NO分子的吸附强于CO分子.气体分子在Po构型上属于化学吸附,而在Pi构型上属于物理吸附.Pd/BG吸附CO和NO气体分子后具有不同的电子性质.Pd/BG体系为半导体性质,在吸附CO气体分子后,转变为金属性,系统无磁性;而在吸附NO气体分子后变为金属性且具有较大磁矩.这种电子性质的变化能够阐明气体分子吸附的敏感程度.研究结果能够为石墨烯基的气体传感器或者探测器提供理论基础和实验指导.     

MXene负载的锇单原子催化剂Os1/Ti2CS2催化低温CO氧化反应的理论研究(英文)

本文报道了一种对CO氧化反应具有低温催化活性的新型硫功能化MXene-Ti₂C (Ti₂CS₂)负载的锇金属单原子催化剂Os₁/Ti₂CS₂.通过密度泛函理论计算,从一系列过渡金属(M=Fe, Co, Ni, Cu; Ru, Rh, Pd,Ag; Os, Ir, Pt, Au)中筛选出最稳定的锇金属单原子催化剂.计算结果表明, Os1/Ti₂CS₂有利于O2和CO的共吸附,且O₂分子的吸附能略高于CO分子.此外,由于O2+2CO能稳定地共吸附在Os₁单原子上, CO氧化反应可能通过三分子反应机理进行.因此,我们研究了CO在Os₁/Ti₂CS₂单原子催化剂上发生氧化反应的四种不同的催化机理:Langmuir-Hinshelwood (L–H)、Eley Rideal (E–R)、termolecular L...     

用于分离CH4/CO2的分子筛型PAN-ACF的制备和性能

以聚丙烯腈基预氧纤维毡（PAN－OF）为原料，经过空气氧化和CO2活化制备出对CO2／CH4具有较好筛分性能的分子筛型聚丙烯腈基活性碳纤维毡（PAN－ACF），采用电子天平，变压吸附（PSA）技术，XPS分析表征了分子筛型PAN－ACF的吸附性能和表面结构，结果表明，所制PAN－ACF样品对CO2／CH4吸附的选择性为7－11，当吸附压力为0.15MPa时，所产CH4的浓度达到99．9％，随着吸附的压力升高甲烷气的浓度下降，XPS结果表明经该法处理的样品，其类石墨微晶间以sp^3杂化碳氧单键相联，并出现腈类及酰胺类基团。     

硝基甲烷在Cu(111)表面吸附的LEED、AES和UPS研究

本文介绍了在低温下运用LEED、AES和UPS研究硝基甲烷在Cu(111)表面的吸附成键和取向。AES和UPS的结果显示了硝基甲烷是以分子形式吸附在Cu(111)表面。随着硝基甲烷暴露量达2L时,与清洁铜表面相比功函数变化有最小值-0.75eV左右。暴露量再增大,功率数略增加,其变化值为-0.5eV。紫外光电子谱表明硝基甲烷是通过其前线轨道氧的2p电子与铜表面的d电子相互作用而产生吸附作用。     

CO和K在W(100)面上共吸附的HREELS研究

用高分辨电子能量损耗谱(HREELS)对CO和K在W(100)面的共吸附进行了研究。发现在有K沉积的W(100)面上,代表CO分子在顶位吸附时碳氧伸缩振动频率的损耗峰由255meV向低频率方向移动,该峰在CO饱和吸附时的强度随K的覆盖度增加而减小。在有K和CO的W(100)面上,观察到了一个与K覆盖度大小有关的新的能量损耗峰,其位置在100meV左右,在CO暴露过程中,它比255meV处的损耗峰更早出现。它联系着一种CO受K影响的能量更抵的吸附状态。我们归之为“斜躺”的CO分子振动频率。当K的覆盖度增大到0.06后,CO和K在180～220meV之间形成了两个能量损耗峰,它们与CO分解后在表面形成K—O复合物的振动模式相关。     

金属催化剂对CO气敏薄膜特性影响的密度泛函法分析

根据密度泛函理论,采用总体能量平面波赝势方法,计算了CO气体敏感薄膜中几种常用金属催化剂(Pt,Pd,Cu,Ag)的能量最低晶面,并对CO在这些晶面上的吸附特性进行了研究.从结合能、C-O键长、轨道布居、态密度等方面比较了C与金属成键强度及CO分子被活化程度.计算结果发现,CO在金属表面的吸附强度及金属对CO催化效果强弱的顺序是:Pt＞Pd＞Cu＞Ag.得出结论:对于CO气体传感器,Pt是通过金属催化剂添加提高灵敏度的最佳选择.     

静电纺丝法制备LaMnO3微／纳米纤维

以聚乙烯吡咯烷酮（PVP）为络合剂与Mn（CH3COO）2和La（NO3）3·6H2O反应制得前驱体，用静电纺丝法制备了PVP／Mn（CH3COO）2·La（N03）3纤维，经煅烧得到具有高比表面积的LaMnO3微／纳米纤维。并采用红外光谱（IR）、X射线衍射（XRD）、扫描电镜（SEM）等现代分析手段对所制备的纤维进行了表征。结果表明：焙烧后纤维的直径明显减小，在150-300nm之间：PVP特征吸收峰消失，新生成的M-O吸收峰随着焙烧温度的升高变强；XRD分析出现相应氧化物的特征峰，说明有LaMnO3的生成。     

NO在Ru（1010）和Cs／Ru（1010）表面上吸附的ARUPS研究

１５０Ｋ的低温下，ＮＯ在清洁的Ｒｕ（１０１０）表面的吸附，Ｈｅ－Ⅱ－ＡＲＵＰＳ显示在Ｅｆ以下９．３ｅＶ（σ＋１π）和１４．６ｅＶ（４σ）处有两个峰，表明ＮＯ在Ｒｕ（１０１０）表面上是分子吸附。     

聚丙烯酰二乙烯三胺二氧化碳吸附树脂的制备及性能

以丙烯酸甲酯和二乙烯基苯悬浮共聚,制备了交联度分别为5%、7%、9%的大孔交联聚丙烯酸甲酯(PMA),通过与二乙烯三胺的胺解反应得到了大孔交联聚丙烯酰二乙烯三胺(PAM)吸附树脂;通过红外光谱(FT-IR)对树脂的结构进行了表征;系统考察了静态吸附法下PAM树脂对CO2的吸附性能以及作为CO2吸附材料的循环使用性能。结果表明,在室温下交联度为5%的PAM树脂具有较高的CO2吸附量,达143.1 mg/g吸附剂,CO2吸附量随胺基数量增加而增大,且PAM树脂具有良好的循环使用稳定性。     

Nitric oxide adsorption and desorption on alumina supported palladium

The adsorption properties of nitric oxide (NO) on alumina supported palladium were studied by a simultaneous thermogravimetric-analysis and differential-scanning-calorimetry (TGA-DSC) in a temperature ranges between 220 and 470 K. Upon adsorption, NO molecules on both Pd/Al2O3 and Pd/NaOH-Al2O3 samples were molecularly adsorbed between 220 and 300 K. Some NO molecules were strongly adsorbed on Pd/NaOH-Al2O3 and possessed a higher enthalpy of adsorption [approximately 140 kJ (mol NO)(-1)] than Pd/Al2O3 [approximately 114 kJ (mol NO)(-1)]. Upon heating above 320 K, the adsorbed NO molecule on these palladium surface was dissociated. In addition, a temperature programmed desorption and mass spectrometer (TPD-MS) study in a temperature range between 300 and 1100 K further indicated that some strongly adsorbed NO molecules may stay on basic sites (*b) and Pd-NaOH interface sites (*i) to enhance the decomposition of NO.     

Characterization of bimetallic Au-Pt(111) surfaces

Structural and electronic properties of ultrathin Au films deposited on Pt(111) and annealed at different temperatures have been studied by ultraviolet photoelectron spectroscopy (UPS), photoemission of adsorbed xenon (PAX) and low energy electron diffraction (LEED). The LEED measurements indicate an initial pseudomorphic growth of the Au films. The UPS and PAX experiments show a strong temperature dependence of the surface morphology. The surface covered with Au at 150 K is quite rough but smoothens significantly above room temperature. At a temperature of 750 K intermixing and the formation of an Au-Pt surface alloy start at the interface. The electronic properties of this surface alloy seem to be nearly independent from the originally deposited Au amount in the investigated range of 1-10 monolayers. The removal of Au from the surface regions has also been verified by scanning tunneling microscopy. Adsorption experiments with CO as a titration agent show a significantly lower affinity of the Au-Pt surface alloy in comparison with the clean Pt surface.     

Preparation of Cu-TiN alloy by external nitridation in combination with mechanical alloying

A copper alloy dispersion strengthened by TiN was prepared by external nitridation in combination with mechanical alloying. After mechanical alloying pure Cu and Ti powders, a Cu-3wt.%Ti solid solution was formed. These powders were nitrided at 1073 K, resulting in a TiN layer on the surface of the copper powders. Further mechanical alloying was very efficient in breaking down the TiN surface layers. A very fine uniform distribution of nanosized TiN was obtained. The resulting copper alloy had a grain size of about 150 nm in diameter after annealing at 1173 K in vacuum for 5.4 ks, and showed a very high room temperature hardness value of 251 kg mm⁻² which was independent of annealing temperature below 1173 K.     

Heat Capacity of 1D Molecular Chains

The heat capacity of 1D chains of nitrogen and methane molecules (adsorbed in the outer grooves of bundles of closed-cap single-walled carbon nanotubes) has been studied in the temperature ranges 2–40 and 2–60 K, respectively. The temperature dependence of the heat capacity of 1D chains of nitrogen molecules below 3 K is close to a linear. It was found that the rotational heat capacity of methane molecules is a significant part of the total heat capacity of the chains throughout the whole investigated temperature range, whereas in the case of nitrogen, the librations are significant only above 15 K. The dependence of the heat capacity for methane below 10 K indicates the presence of a Schottky anomaly caused by the tunneling between the lowest energy levels of the \(\hbox {CH}_{4}\) molecule rotational spectra. Characteristic features observed in the temperature dependence of the heat capacity of 1D methane crystals are also discussed.     

GaN nanodiscs embedded in nanowires as optochemical transducers

The photoluminescence (PL) response of GaN/AlGaN nanowire heterostructures (NWHs) to hydrogen and oxygen between room temperature and 300?°C is reported. Exposure of Pt-coated NWHs to H2 leads to an increase of the PL intensity attributed to the suppression of surface recombination by local dipole fields of adsorbed atomic hydrogen. When exposed to O2, uncoated NWHs show a decrease in PL intensity that is assigned to enhanced non-radiative recombination. The detection limits are below 5 ppm at 150?°C.     

The changes in work function of group Ib and VIII metals on xenon adsorption,determined by field electron and photoelectron emission

The surface potentials of xenon on Ni, Pd, Pt, Rh, Ir, Ru, Fe, Cu, Ag and Au films have been determined by photoelectron emission as a function of the temperature of previous annealing. On Pd, Ir, Rh, Ru and Ag films, vapour- quenched at 78 K, the surface potential does not change significantly up to an annealing temperature of 400 K, but on Au and Ni it decreases with annealing. From measurements with a field emission microscope equipped with a probe-hole assembly it is found that the xenon surface potential is face specific. On Ir the largest surface potentials are found on the (111) and (100) tip regions. The variation with annealing temperature of the surface potential on a polycrystalline film may be attributed to the change in the contribution of the various crystal faces on the film surface.     

In situ high-pressure and high-temperature experiments on n-heptane

The Raman spectroscopy of n-heptane was investigated in a moissanite anvil cell at ambient temperatures and a diamond anvil cell under pressures of up to ~2000 MPa and at temperature range from 298 to 588 K. The results show that at room temperature the vibration modes, assigned to the symmetric and antisymmetric stretching of CH(3) and CH(2) stretching, shifted to higher frequency according to quasi-linearity with increasing pressure, and a liquid-solid phase transition occurred at near 1150 MPa. The high-temperature solidus line of n-heptane follows a quadratic function of P = 0.00737T(2) + 5.27977T - 1195.76556. Upon phase change, fitting the experimental data obtained in the temperature range of 183～412 K to the Clausius-Clapeyron equation allows one to define the thermodynamic parameters of n-heptane of dP/dT = 0.01474T + 5.27977.     

二元Al-Li合金的低温力学性能

本文研究了纯 Al,Al-ILi 和 Al-2.5Li 合金力学性能与实验温度的关系。结果表明,这些合金在低温下有很显著的增强增韧现象,但屈服强度变化较小,加工硬化能力显著提高;时效温度与 Al-2.5Li 合金低温力学性能改善无关,低温断裂前比室温时需经历更大的形变。     

Forming interface in Pd/Fe/GaAs/InGaAs structure for optical detector of free-electron spin

Conditions necessary for the formation of a Fe/GaAs interface have been established and the electrical, magnetic, and optical properties of Pd/Fe/GaAs heterostructures with InGaAs quantum wells have been studied. The possibility of obtaining an epitaxial layer of Fe on GaAs(001) surface at room temperature is demonstrated. The magnetization curve of Fe layer exhibits hysteresis with an easy axis in plane of the sample. Iron exhibits surface segregation by diffusion through a 4-nm-thick Pd layer. The properties of obtained Pd/Fe/GaAs/InGaAs structures show evidence for their possible use in optical detectors of free-electron spin.