基于TaCl5的Ta2O2气凝胶制备工艺

主要介绍了以TaCl5为前驱体,低分子醇类为溶剂,分别采用环氧丙烷和环氧氯丙烷作为凝胶促进剂制备Ta2O2湿凝胶,湿凝胶经过CO2超临界干燥而获得白色Ta2O2气凝胶。透射电镜图谱表明气凝胶是由粒度为10～20 nm的颗粒堆积而成。N2等温吸附-脱附分析表明,气凝胶的比表面积为800～900 m2/g。     

基于PC-SAFT的CO2混合工质相平衡计算

统计缔合流体理论(PC-SAFT)能够应用于CO₂动力循环中CO₂混合工质物性的预测。PC-SAFT状态方程在计算CO₂混合工质气液相平衡时,其收敛性较差。本文介绍一种利用基于基团贡献法的蒸气压估算方法为PC-SAFT状态方程提供初值,从基团角度来预测CO₂混合工质气液平衡的方法。该方法在很多情况下的准确度高于Refprop 9.0计算结果,尤其在较高的CO₂比例下。对于温度滑移较大的CO₂混合工质计算中,该方法不会计算出Refprop 9.0中不平滑的尖点,避免了在一些情况下出现反常的计算结果,是一种稳定可靠的计算方法。     

Sm2(Fe,M)17C1.5(M=Ga,Si)化合物的形成和磁性

用电弧炉熔炼方法制备了Ｓｍ₂Ｆｅ_17-xＭ_xＣ_1.5（Ｍ＝Ｇａ，Ｓｉ）化合物，研究了它们的形成、结构与磁性。实验结果表明，用Ｇａ替代Ｆｅ，当２≤ｘ≤６时，可形成Ｔｈ₂Ｚｎ₁₇型单相化合物，而Ｓｉ的替代仅在ｘ＝２时为单相结构。居里温度随Ｇａ含量的增加从ｘ＝２时的６３３Ｋ下降到ｘ＝６时的３５１Ｋ，Ｓｍ₂Ｆｅ₁₅Ｓｉ₂关键词：     

高压下CO2稀释的CO/H2/Air火焰贫可燃极限处的辐射重吸收效应的数值研究

本文分别采用考虑辐射重吸收的谱带辐射（SNBCK）模型及未考虑辐射重吸收的光学薄辐射（OPT）模型,对0.1～4 MPa,CO₂稀释比为0%和20%的一维预混层流合成气/空气火焰进行数值分析,研究辐射重吸收效应对可燃极限及极限处的火焰传播速度和温度的影响。结果表明,辐射重吸收效应能有效拓宽贫可燃极限,提高燃料中CO₂比例或提高CO/H₂比例都会加剧上述效果。辐射重吸收效应随压力增大而逐渐增强,并造成可燃极限处最大火焰温度随压力先增加后减小,在1 MPa左右达到峰值。     

微生物碳捕获电池阴极室CO2捕获速率的计算

本文对含有Botryococcus Braunii UTEX 572的微生物碳捕获电池阴极室内的光合有效辐射（Photosyntheticallyactive radiation,PAR）分布建立数学模型。采用离散坐标法（Discrete Ordinate Method,DOM）求解一维稳态辐射传递方程（Radiative transfer equation.RTE）,使用SMARTS（the Simple Model for Atmospheric Transmission of Sunshine）模式对边界条件进行计算。在所建模型基础上,对400～800 nm波长范围的阴极室内PAR分布情况进行计算,并结合Botry-ococcusBraunii UTEX 572的生长动力学对CO₂的局部吸收速率进行研究。同时对不同散射处理方法,气泡含量以及藻类浓度对CO₂捕获速率的影响进行对比,为改善光在微生物碳捕获燃料电池阴极室的分布和阴极室优化设计提供依据。     

基于TaCl5的Ta2O2气凝胶制备工艺

 主要介绍了以TaCl₅为前驱体,低分子醇类为溶剂,分别采用环氧丙烷和环氧氯丙烷作为凝胶促进剂制备Ta₂O₂湿凝胶,湿凝胶经过CO₂超临界干燥而获得白色Ta₂O₂气凝胶。透射电镜图谱表明气凝胶是由粒度为10～20 nm的颗粒堆积而成。N₂等温吸附-脱附分析表明,气凝胶的比表面积为800～900 m²/g。     

金属醇盐法制备Ta2O5气凝胶

以乙醇钽为前驱物,采用金属醇盐溶胶-凝胶技术,获得了Ta2O5湿凝胶,分析了不同条件下的溶胶-凝胶过程,并初步探讨了凝胶过程机理。Ta2O5的溶胶-凝胶过程主要受到水量、催化剂用量及钽源浓度等因素的影响：体系在强酸性条件下凝胶,且随着酸性的增强,体系凝胶时间明显缩短;当水量较少时,凝胶时间随水量的增加而增加,但当水量增加到一定程度时,体系凝胶时间基本不变;实验证明,通过增大溶剂用量,体系凝胶时间延长,气凝胶理论密度降低。通过对溶胶-凝胶过程的控制,结合超临界干燥技术,获得了密度低至44 mg/cm3的Ta2O5气凝胶样品。     

V2CO2MXene从CO2/N2混合气体中选择性吸附CO2的第一性原理计算

二氧化碳作为温室气体中最重要的组成部分,其含量的变化将直接影响全球气候变化,在燃烧后气体中选择性捕获CO₂,对减缓因CO₂浓度过高引发的环境问题具有十分重要的意义.本文采用第一性原理计算的方法,研究了V₂CO₂ MXene材料对CO₂的选择性吸附性能.首先研究了不同官能团V₂CT_X MXene材料的结构和性质,发现V₂CO₂具有良好的稳定性.后研究了V₂CO₂对CO₂的吸附行为,结果表明,当CO₂被水平吸附时,V₂CO₂对CO₂气体分子的吸附能力较强且均满足在高性能吸附剂表面吸附CO₂的理想值(-0.42 eV-0.82 eV),可以适用于探测/捕获CO₂气体分子.此外,进一步研究了相同条件下V<...     

MgF2单晶的THz光谱研究

利用THz时域光谱技术对MgF₂晶体(样品1)和MgF₂：Co晶体(样品2)在0.5—2.5 THz的吸收特性进行了研究.在0.5—2.5 THz波段，样品1吸收系数α(ν)随频率ν增加而增大，最大值为24 cm^-1.样品2的吸收系数比样品1大得多，Co掺杂使晶格吸收带边向低频移动，而且样品2在1.9 THz有吸收峰，吸收系数达到70 cm^-1，由此求出F^--Co²⁺离子键伸缩振动的键力常数K为3.40×10^-2　N/cm.这一结果表明，THz光谱分析有可能成为研究晶体化学键的一种重要手段.利用光学常数之间的关系计算了两个样品在0.5—2.5 THz的介电函数的实部ε₁(ν)，得到样品1的ε₁(ν)值在4.67至4.73之间，样品2的ε₁(ν)值在4.62至5.01之间. 关键词： THz辐射 光谱 2晶体')" href="#">MgF₂晶体     

铁掺杂TiO2/膨润土光催化剂的制备及表征

以溶胶-凝胶法制备了过渡金属铁掺杂的Fe-TiO2/膨润土复合光催化剂,通过XRD、FTIR技术对该系列催化剂的结构进行了表征,并以亚甲基蓝染料废水为模型,考察了紫外光和日光下铁掺杂量对催化剂性能的影响。结果表明,催化剂中有锐钛矿型TiO2生成,铁掺杂TiO2进入了膨润土的蒙脱石层间,改变了蒙脱石层间的有序性,生成了Ti—O—Si键,实现了TiO2粒子与膨润土的复合;适量Fe3+的掺杂降低了TiO2粒子的粒径,并且部分Fe3+还可能进入了TiO2的晶格,形成了缺陷位,拓宽了TiO2的光谱利用范围,提高了光催化活性。     

Entanglement in the supermolecular dimer [Mn4]2

This paper investigates the entanglement in the supermolecular dimer [Mn4]2 consisting of a pair of single molecular magnets with antiferromagnetic exchange-coupllng J. The conventional yon Neumann entropy as a function of the exchange-coupling is calculated explicitly for all eigenstates with the quantum number range from M = M1 ＋ M2 = -9 to 0. It is shown that the yon Neumann entropy is not a monotonic function of the coupling strength. However, it is significant that the entropy of entanglement has the maximum values and the minimum values for most eigenstates, which is extremely useful in the quantum computing. It also presents the time-evolution of entanglement from various initial states. The results are useful in the design of devices based on the entanglement of two molecular magnets.     

O2/CO2气氛下循环流化床煤燃烧SO2排放

在热输入功率50 kW的循环流化床O₂/CO₂燃烧试验装置上研究燃煤SO₂排放特性及石灰石脱硫机理。结果发现,未添加石灰石时,O₂/CO₂气氛下SO₂排放量比相同O₂浓度的空气气氛下低;随着O₂浓度的升高,排放量升高。相同钙硫摩尔比下,O₂/CO₂气氛下石灰石的脱硫机理以直接脱硫为主,脱硫效率比空气气氛下高;随着O₂浓度的增加,石灰石脱硫效率提高。     

Mg2(BH4)2(NH2)2脱氢机理的理论研究

对Mg₂(BH₄)₂(NH₂)₂的脱氢机理展开系统的理论研究发现相对于分子内的脱氢过程,分子间的脱氢过程在热力学和动力学方面都是比较有利的. Mg₂(BH₄)₂(NH₂)₂脱氢过程的第一步是BH₄^-中的B-H^δ-和NH2-中     

The effect of pressure on the spin density wave transition in the layered cobaltites [Ca2CoO3]0.62[CoO2] and [Ca2Co4/3Cu2/3O4]0.62[CoO2]

In order to investigate the pressure effect on the magnetism in the layered cobaltites, positive muon spin rotation and relaxation μ⁺SR experiments have been carried out up to 1.3 GPa using c-aligned polycrystalline samples of [Ca₂CoO₃]_0.62[CoO₂] and [Ca₂Co_4/3Cu_2/3O₄]_0.62[CoO₂]. A transverse field μ⁺SR experiment indicates that the transition temperature to an incommensurate spin density wave IC-SDW state is independent of hydrostatic pressure up to 1.3 GPa for the both compounds. Furthermore, there are no changes in the spontanious muon precession frequency in zero field at 5 K even under 1.3 GPa. These results strongly suggest that the IC-SDW exists not in the rocksalt-type block ([Ca₂CoO₃] and/or [Ca₂Co_4/3Cu_2/3O₄]) but in the CoO₂ plane.     

EPR lineshape in ethylenediammonium chloromanganate (II), [C2H10N2] [MnCl4]

The EPR line shape has been measured on a single crystal of ethylene diammonium chloromanganate (II) as a function of field orientation with respect to the expected two dimensional network of manganese ions. The angular variation of the linewidth may be described by the expression δH= α + β(3 cos²δ ? 1)² with α = 20 and β = 4, and the lineshape may be described by I(H ? H₀) ? F [exp (? At ? Bt ln ($\text{t}\text{t}{}_0\text{)]}$ (where F refers to the Fourier transform of the bracketed function) with $\text{|}\text{B}\text{A}\text{| = 1.9 ± 0.8}$.     

Optically pumped submillimeter laser lines from CH2F2 and CD2Cl2 using a12C18O2 CW laser

Thirty-nine new submillimetre laser lines in CH₂F₂ and twelve in CD₂Cl₂ have been obtained in a Fabry-Perot FIR resonator by optically pumping with a CW¹²C¹⁸O₂ laser. The wavelength range obtained for CH₂F₂ is 126m to 1091m and for CD₂Cl₂ 212m to 774m. The wavelength measurements are accurate to within 5.10^–3. The relative polarisations of the pump laser and the FIR laser output were also determined. Tentative assignments of the IR and FIR transitions were made using existing microwave data.     

The effect of hydrostatic pressure on the ferroelectric phase transition in [NH2(CH3)2]3[Sb2Cl9]

The effect of hydrostatic pressure on the ferroelectric phase transition temperature in [NH₂(CH₃)₂]₃[Sb₂Cl₉] (DMACA) has been studied by electric permittivity measurements at pressures up to 400 MPa. The pressure-temperature phase diagram is given. The phase transition temperature (T_c) increases with increasing pressure up to 150 MPa, passes through a maximum and then decreases with a further increase of pressure. The unexpected nonlinear decrease in T_c with pressure increasing above 150 MPa suggests that the mechanism of ferroelectric phase transition in DMACA is different from hitherto assumed.     

Emission features of Ho ion in Nb2O5, Ta2O5 and La2O3 mixed Li2O-ZrO2-SiO2 glasses

Li₂O-ZrO₂-SiO₂: Ho³⁺ glasses mixed with three interesting d-block elemental oxides, viz., Nb₂O₅, Ta₂O₅ and La₂O₃, were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature. The luminescence spectra of Nb₂O₅ and Ta₂O₅ mixed Li₂O-ZrO₂-SiO₂ glasses (free of Ho³⁺ ions) have also exhibited broad emission band in the blue region. This band is attributed to radiative recombination of self-trapped excitons (STEs) localized on substitutionally positioned octahedral Ta⁵⁺ and Nb⁵⁺ ions in the glass network. The Judd-Ofelt theory was successfully applied to characterize Ho³⁺ spectra of all the three glasses. From this theory various radiative properties, like transition probability A, branching ratio β_r and the radiative lifetime τ_r, for ⁵S₂ emission levels in the spectra of these glasses have been evaluated. The radiative lifetime for ⁵S₂ level of Ho³⁺ ions has also been measured and quantum efficiencies were estimated. Among the three glasses studied the La₂O₃ mixed glass exhibited the highest quantum efficiency. The reasons for such higher value have been discussed based on the relationship between the structural modifications taking place around the Ho³⁺ ions.     

Effect of O-vacancy defects on the Schottky barrier heights in Ni/SiO2 and Ni/HfO2 interfaces

We perform first-principles density functional calculations to study the electronic structure of Ni/HfO₂ and Ni/SiO₂ interfaces and the effect of O-vacancy (V_O) defects on the Schottky barrier height and the effective work function. We generate two interface models in which Ni is placed on O-terminated HfO₂ (1 0 0) and α-quartz (1 0 0) surfaces. As the concentration of V_O defects at the interface increases, the p-type Schottky barrier height tends to increase in the Ni/HfO₂ interface, due to the reduction of interface dipoles, whereas it is less affected in the Ni/SiO₂ interface.     

Metal carbide-induced negative flatband voltage shift in TaCx and HfCx/HfO2 gate stacks

We systematically investigated the role of the top interface for TaC_x and HfC_x/HfO₂ gate stacks on the effective work function (Φ_m,eff) shift by inserting a SiN layer at the gate/HfO₂ top interface or HfO₂/SiO₂ bottom interface. We found that Φ_m,eff of the TaN gate electrode on HfO₂ was larger than that on SiO₂ because of the HfO₂/SiO₂-bottom-interface dipole. On the other hand, we found that Φ_m,eff values of the TaC_x and HfC_x gate electrodes on HfO₂ agree with Φ_m,eff on SiO₂. This is because the potential offset of the opposite direction with respect to the bottom interface dipole appears at the metal carbide/HfO₂ interface. It is thus concluded that the top interface in the metal carbide/HfO₂ gate stacks causes the negative Φ_m,eff shift.