CO2/O2环境下L320钢在不同流速下的腐蚀行为研究

为了确定L320钢在CO₂/O₂环境中不同流速下的腐蚀行为,通过多相流瞬态模拟仿真软件,模拟目标管道的流动状态,确定室内模拟试验的流速范围,选择L320钢进行CO₂/O₂共存体系下不同流速的高温高压动态反应釜试验,采用扫描电镜、X射线衍射仪对腐蚀产物进行微观形貌表征和成分分析。结果表明:温度和压力随着里程的增加呈现下降的趋势;管道气体流速和壁面剪切力随着里程的增加呈现逐渐上升的趋势。基于Pearson相关系数法,确定了流速是影响腐蚀速率的主控因素。随着流速的增加,L320在CO₂/O₂共存条件下的均匀腐蚀速率逐渐增大。CO₂/O₂共存体系的腐蚀产物为Fe 2 O₃、FeOOH、Fe(OH)3、Fe 3 O 4、FeCO₃等。研究结论可为不同流速下的L320钢在CO₂/O₂共存环境中的防护提供借鉴。     

A wireless, passive carbon nanotube-based gas sensor

A gas sensor, comprised of a gas-responsive multiwall carbon nanotube (MWNT)-silicon dioxide (SiO₂) composite layer deposited on a planar inductor-capacitor resonant circuit is presented here for the monitoring of carbon dioxide (CO₂), oxygen (O ₂), and ammonia (NH₃). The absorption of different gases in the MWNT-SiO₂ layer changes the permittivity and conductivity of the material and consequently alters the resonant frequency of the sensor. By tracking the frequency spectrum of the sensor with a loop antenna, humidity, temperature, as well as CO₂ , O₂ and NH₃ concentrations can be determined, enabling applications such as remotely monitoring conditions inside opaque, sealed containers. Experimental results show the sensor response to CO₂ and O₂ is both linear and reversible. Both irreversible and reversible responses are observed in response to NH₃, indicating both physisorption and chemisorption of NH₃ by the carbon nanotubes. A sensor array, comprised of an uncoated, SiO₂ coated, and MWNT-SiO₂ coated sensor, enables CO₂ measurement to be automatically calibrated for operation in a variable humidity and temperature environment     

新型紫外非线性光学晶体KNa5Ca5(CO3)8的合成、表征及性能的研究

采用水热法合成出一种新型碳酸盐非线性光学晶体材料KNa₅Ca₅(CO₃)₈, 该晶体属于六方晶系, 空间群为P63mc, 晶胞参数为a=b=1.00786(4) nm, c=1.26256(8) nm, Z=2。其晶体结构可以看作是由站立的[CO₃]基团连接相邻的两个[CaCO₃]_∞层, 从而沿[010]方向形成了四种不同类型的孔洞, 在这些孔洞中填充着K、Na 和[Na_0.67Ca_0.33]原子。KNa₅Ca₅(CO₃)₈晶体的粉末倍频效应为KDP的1.2倍, 且能够在可见光区实现相位匹配。紫外-可见-近红外漫反射光谱测试结果表明其晶体具有较大的光学带隙, 大概为5.95 eV, 是具有潜在应用前景的紫外非线性光学晶体材料。此外, 第一性原理的计算结果表明, 晶体的非线性系数主要来源于CO₃基团。     

Effects of p(O2) and p(CO2) on epitaxial growth of BaTiO3 thin films on MgO(100) substrates by using metal organic acid salts

BaTiO₃ thin films were prepared by using metal organic acid salts on MgO(100) substrates, which have large lattice-misfit with BaTiO₃. Amorphous films prefired at 470°C were crystallized to BaTiO₃ phase by heat treatment at higher temperature. Crystallinity and in-plane alignment of the prepared films were found to depend on the heat-treatment conditions. BaTiO₃ films with high crystallinity but poor (100)-orientation were obtained in air at higher than 1200°C. Whereas, (100)-oriented epitaxial BaTiO₃ film was fabricated by annealing at 900°C under low oxygen partial pressure (p(O₂)). Low carbon dioxide partial pressure (p(CO₂)) is also found to be essential for preparation of epitaxial BaTiO₃ films on MgO substrates by using metal organic acid salts.     

Experimental investigation of a CO2 automotive air conditioner

In this study, a CO₂ automotive air conditioner prototype was designed and constructed. The compressor was of swash plate design; the gas cooler and evaporator were made of fin-tubes; a manual expansion valve and an internal heat exchanger accumulator were used. The lubricant, the CO₂ charge, the evaporator outlet pressure, the compressor speed, the air inlet temperature and flow rate of the gas cooler and the air flow rate of the evaporator were varied and the performance of the prototype was experimentally investigated in detail. The cooling capacity, compressor power consumption, CO₂ mass flow rate, and COP value were analyzed. The experimental results showed that the CO₂ system performance was greatly affected by different lubricants; the CO₂ system performance was sensitive to the mass charge; the high side pressure affected the system performance greatly and a high side pressure controller was needed.     

ZIF-67@PDA/含氟聚酰亚胺混合基质膜的制备及其气体分离性能

金属有机框架材料(MOF)/聚合物混合基质膜(MMMs)通过结合MOF的分子筛效应和聚合物基质成本较低、加工性能好、机械强度高的特征,使其在气体分离领域展现出巨大的应用前景。然而由于MOF在聚合物基体中存在分散性差问题,极大地限制了其应用。采用溶剂热法合成金属框架材料ZIF-67,并通过溶液氧化法在ZIF-67表面修饰聚多巴胺(PDA)层制备ZIF-67@PDA纳米多孔材料。以4,4’-二氨基二苯醚-2,2’-双(3,4-二羧酸)六氟丙烷二酐(ODA-6 FDA)型含氟聚酰亚胺(FPI)为基体、ZIF-67和ZIF-67@PDA为填料,制备不同质量分数的ZIF-67/FPI和ZIF-67@PDA/FPI。通过FTIR、WAXD、TGA、SEM、比表面和孔径分布分析仪、气体渗透仪等测试对MMMs的结构和性能进行表征并测试了N₂、O₂、CO₂、He 4种气体的渗透性。结果表明：经聚多巴胺修饰后的纳米微孔材料ZIF-67在聚合物基体中能均匀分散并为气体分子的通过提供快速通道,且表现出良好的热稳定性。ZIF-67@PDA对CO<...     

Influence of substrate properties on the growth of titanium films: part III

The growth of thin Ti-oxide films (12 nm) on alumina substrate films formed by reactive evaporation of Ti in an oxygen atmosphere was studied by in situ internal stress measurements under ultra high vacuum conditions and transmission electron microscopy. Oxygen pressure and substrate temperatures were the varied parameters of the reactive evaporation. These Ti-oxide-films with different oxygen content (O₂/Ti-films) were then used as substrate films for the deposition of a clean titanium film. The growth stress of the titanium film on the as-deposited O₂/Ti-substrate films is comparable with that previously found for H₂O/Ti-substrates and indicates island growth and the formation of polycrystalline titanium films. Annealing (400°C, 20 min) of the as-deposited – amorphous – O₂/Ti-films gives rise to the formation of crystalline TiO₂. The amount of TiO₂ formed during annealing is strongly dependent on the oxygen content of the O₂/Ti-film. The oxygen content, in return, is dependent on oxygen partial pressure and substrate temperature during O₂/Ti-film deposition. The corresponding changes in the substrate film properties (oxygen content, crystallinity, etc.) are reflected in significant changes in the growth stress of the titanium film. The stress vs. thickness curve of these titanium films appears to indicate a superposition of the growth stress of two different growth modes, i.e. growth of a polycrystalline film with island growth on the as-deposited, amorphous oxide substrate and epitaxial growth of a quasi single crystalline film on the crystalline TiO₂-substrate.     

MBE growth and characterization of buried silicon oxide films on Si(100)

Silicon molecular beam epitaxy (Si-MBE) has been used to produce silicon oxide (SiO_x) films by evaporating Si on a heated Si(100) substrate in an ultra high vacuum system with an O₂ pressure of 10⁻⁶ to 10⁻⁴ mbar. Then the SiO_x films were overgrown with pure Si. The influence of the substrate temperature, the O₂ pressure and the Si deposition rate on the oxygen content in the SiO_x films and on the crystalline quality of the Si top-layer was investigated by Rutherford backscattering spectrometry and ion channeling. Epitaxial growth of the Si top-layer was observed up to a maximum concentration of ≈20 at.% oxygen content in the SiO_x film. Cross-sectional transmission electron microscopy shows that the structure of the SiO_x film changes duringa subsequent annealing procedure. Electron energy loss spectrometry proves that amorphous SiO₂ is formed and the development of holes indicates that the density of the as-grown SiO_x film is much lower than that of SiO₂. The specific for the as-grown SiO_x films was determined by I–V measurements.     

焙烧温度对CO2-CH4重整制合成气NiO/γ-Al2O3催化剂性能的影响

采用水解-沉积法, 在不同焙烧温度下制备了cat-500、cat-600、cat-700和cat-800系列NiO/γ-Al₂O₃催化剂。XRD和H₂-TPR分析表明, 焙烧温度高于700 ℃, 活性组分与载体具有强烈的金属-载体相互作用(SMSI), 具体表现为活性组分前驱体以尖晶石NiAl₂O₄的形式存在。反应后催化剂的XRD、TG-DTG、TPH等表征结果表明, cat-700和cat-800试样的Ni晶粒尺寸分别为9.8和8.7 nm, 小于cat-500和cat-600试样(分别为15.7和13.6 nm), 分散性更好; 且催化剂表面积炭为丝状碳, 其不会导致催化剂失活, 但大量积累会引起床层压降升高, 影响催化剂的反应性能。cat-800试样110 h寿命试验表明, 高温焙烧制备的Ni基催化剂活性和稳定性均较高, CO₂转化率达95%左右, 失活速率仅为0.0536%/h。     

Laser Pyrolysis of Hydrocarbons in Synthesis of Soot Containing Fullerenes

Using a high power CW CO₂ laser, the pyrolysis in a flow reactor of different hydrocarbons/oxidizer mixtures with/without sensitizer lead to soots containing weightable quantities of fullerenes which were identified by FTIR spectroscopy, high performance liquid chromatography (HPLC) and time-of-flight mass spectrometry. The C₆₀ and C₇₀ quantification was done by HPLC. The FTIR spectroscopy of toluene extracts from the soots and of exhaust gases allowed to discuss some aspects concerning the influence of sensitizer (SF₆) addition as well as of the oxidiser (O₂/N₂O) on the fullerene production in laser pyrolysis of benzene-based mixtures.     

DBD转化CO2的研究现状及进展

为了更高效地进行CO₂的转化利用,许多学者开展了多种CO₂转化方法的研究。介电阻挡放电（dielectric barrier discharge,DBD）能在低温常压的环境下还原CO₂,是CO₂转化利用的重要方法之一。为了设计出更好的DBD反应器、更佳的反应条件和催化剂,总结了近年来DBD转化CO₂的相关研究。通过分析不同研究中过程参数、稀释性气体和催化剂等因素对CO₂转化量和能量效率的影响,发现催化剂能大幅度提高DBD转化CO₂的反应效率,并介绍了DBD中一些常用的催化剂。最后简要分析了此类研究的可能发展趋势。     

Anode mode in cathodic arc deposition apparatus with various cathodes and ambient gases

The anode mode of a vacuum arc in a cathodic arc deposition apparatus was observed as a function of ambient gas pressure ranging from 0.01 to 300 Pa. The chamber (400 mm in diameter and 600 mm in length) made of stainless steel (SUS304) acted as the anode. The arc was operated at a relatively low constant current of 50 A. The cathode materials used were Al, Ti, Fe, Ni, and Cu, and ambient gases were He, Ne, Ar, H₂, N₂, O₂, and CH₄. The principal results are as follows. (1) As the pressure was increased, the anode mode changed from diffuse-arc to footpoint to plane luminous to anode-spot mode. (2) The anode mode and resultant arc voltage increase were strongly dependent on gas species, and weakly on the cathode material. (3) Comparing diatomic and polyatomic (H₂, N₂, O₂, and CH₄) with mono-atomic molecule gases (He, Ne, and Ar), the onset pressure of the anode mode transition in the former was lower, the arc voltage higher, and the footpoints more numerous, smaller, and clearer. Both the dependence of the ambient pressure and the influence of the cathode materials and gas species on the anode mode changes were explained by the ion deficiency theory.     

Effects of oxygen on multiwall carbon nanotubes growth by PECVD

Multiwall carbon nanotubes (MWCNTs) were grown by dielectric barrier discharge (DBD)-type plasma enhanced chemical vapor deposition (PECVD) method in downstream. The temperature was 973 K and the compositions of gases were methane, hydrogen and oxygen in the total pressure of 0.05 MPa. The effect of O₂ concentration in the mixture on the configuration of carbon nanotubes (CNTs) was investigated in detail. Results from scanning electron microscope (SEM) and transmission electron microscope (TEM) showed that CNTs grown in CH₄/H₂ (38.6%/61.4%, volume) mixture have many defects and contained disordered graphitic materials. With the addition of appropriate amount of O₂ (∼ 0.67%), high-purity CNTs could be obtained. However, no CNT, even no carbon matrix existed under the condition of an excessive oxygen concentration (> 1.0%, volume) in the mixture. In order to understand the role of O₂ during CNTs growth, optical emission spectroscopy (OES) was in-situ employed and the results predicted that the improvement of CNTs quality in O₂ addition was attributed to the effect of OH oxidation from the reaction of atomic oxygen with hydrogen in the plasma.     

Comparative study of Li[Ni1/3Co1/3Mn1/3]O2 cathode material synthesized via different synthetic routes for asymmetric electrochemical capacitor applications

Layered Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode materials were synthesized by different synthesis routes using carbonate and hydroxide co-precipitation methods. Physical properties of the prepared Li[Ni_1/3Co_1/3Mn_1/3]O₂ varied depending on the synthesis method employed. These materials were applied as a positive electrode to an asymmetric electrochemical capacitor with activated carbon as the negative electrode and the electrochemical properties of the capacitor were studied. Li[Ni_1/3Co_1/3Mn_1/3]O₂ prepared by the carbonate co-precipitation exhibited higher capacitance and better rate capability with stable cycling retention over 500 cycles than Li[Ni_1/3Co_1/3Mn_1/3]O₂ prepared by the hydroxide co-precipitation. The asymmetric electrochemical capacitor (AEC) cell (AC/Li[Ni_1/3Co_1/3Mn_1/3]O₂) had a voltage slope from 0.2 to 2.2 V and delivered a capacity of 60 F g⁻¹ with a capacity retention of 88.4% during 500 cycles based on the overall active materials weight. The leakage current was largely decreased for the asymmetric electrochemical capacitor and the maintained voltage was 84.4% during 3 days.     

氧化石墨烯/聚氨酯杂化膜的原位聚合构建及气体渗透性

采用Hummers法制备了3种不同氧化程度的氧化石墨烯(GO),通过聚氨酯(PU)单体(4,4’-二异氰酸苯酯(MDI)和1,4-丁二醇(BDO))与GO的原位聚合构建了GO/PU杂化膜。利用XRD、Raman、FTIR和TEM等表征了GO的结构;探讨了GO填充量对GO/PU杂化膜的形貌和CO2、N2渗透性的影响。结果表明:3种不同氧化程度的GO均呈完全剥离状态,为半透明片状结构;随着氧化程度的增加,拉曼D峰与G峰的相对强度比分别为0.947、1.103和1.245;GO的氧化程度对GO在溶剂和杂化膜中的分散性有较大影响,氧化程度越高,分散性越好。GO/PU杂化膜的CO2、N2渗透系数及CO2/N2渗透选择因子均随GO填充量的增加先增大后减小;当中等氧化程度的GO(M-GO)与(MDI+BDO)的质量比为1.0%时,M-GO/PU杂化膜的CO2渗透系数为63.6×10-13 cm3(STP)/(cm·Pa·s),其中STP表示标准温度及压力,CO2/N2渗透选择因子可达48.5;填充适量的GO能显著提高GO/PU杂化膜的CO2渗透性及CO2/N2渗透选择性。     

TiO2(B)表面修饰富锂层状氧化物Li(Li0.17Ni0.2Mn0.58Co0.05)O2正极材料

采用喷雾干燥法和沉淀法, 制备了表面修饰TiO₂(B) (2wt%、4wt%、6wt%和8wt%)的富锂层状氧化物Li(Li_0.17Ni_0.2Mn_0.58Co_0.05)O₂正极材料。X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)结构测试分析结果表明, 修饰TiO₂(B)后样品的体相结构仍然保持初始样品的层状结构, 仅氧化物颗粒表面附着有少量TiO₂(B)纳米晶。示差扫描量热测试(DSC)表明, 与初始样品比较, 修饰TiO₂(B)后样品的热稳定性得到明显改善。在2.0~4.8 V范围内进行恒流电化学性能测试。研究显示, 在0.1C(1C=300 mA/g)倍率下, 修饰4wt%TiO₂(B)样品的首次放电比容量可达296.4 mAh/g, 首次库伦效率则由初始样品的77.7%提升到修饰TiO₂(B)后样品的84.3%, 100周循环后电极容量保持率由初始样品的69.5%提升到修饰TiO₂(B)后样品的80.2%。即使在阶梯倍率的2C倍率下, 修饰4wt%TiO₂(B)的样品仍具有较高的电化学容量(166.5 mAh/g)。以上研究结果表明, 表面修饰TiO₂(B)纳米晶可以显著改善富锂层状氧化物Li(Li_0.17Ni_0.2Mn_0.58Co_0.05)O₂的热稳定性和电化学性能。     

Marangoni convection and weld shape variations in Ar–O2 and Ar–CO2 shielded GTA welding

Increasing the oxygen or the carbon dioxide concentration in the argon-based shielding gas leads to an increase in the weld metal oxygen content when the oxygen or carbon dioxide concentration is to be lower than 0.6 vol.% in the shielding gas. However, when the O₂ or CO₂ concentration is higher than 0.6 vol.% in the Ar-based shielding gas, the weld metal oxygen is maintained around 200 ppm–250 ppm. An inward Marangoni convection mode in the weld pool occurs when the weld metal oxygen content is more than 100 ppm. When it is lower than 100 ppm, the Marangoni convection would change to the outward direction and the weld shape varies from a deep narrow to a shallow wide shape. The effective ranges of O₂ and CO₂ concentrations for deep penetration are same. A heavy layer of oxides is formed when the O₂ or CO₂ concentration in the shielding gas is more than 0.6 vol.%. Based on the thermodynamic calculation of the equilibrium reactions of Fe, Si, Cr and Mn with oxygen in liquid iron for the oxide products, FeO, SiO₂, Cr₂O₃ and MnO and the experimental oxygen content in the weld metal, Cr₂O₃ and SiO₂ oxides are possibly formed at the periphery area of the liquid pool surface under the arc column during the welding process. One model is proposed to illustrate the role of the oxide layer on the Marangoni convection on the pool surface at elevated temperature. The heavy oxide layer inhibited the fluid flow induced by the Marangoni convection and also became a barrier for the oxygen absorption into the molten weld pool.     

Preparation of strontium titanate thin films by mirror-confinement-type electron cyclotron resonance plasma sputtering

Using mirror-confinement-type electron cyclotron resonance (ECR) plasma sputtering method, strontium titanate (SrTiO₃) thin films have been prepared on Si and Pt/Ti/SiO₂/Si substrates at a low substrate temperature (below 450 K) in a low pressure (2.7×10⁻² Pa) environment of pure Ar and Ar/O₂ mixture. Prepared film surfaces were very smooth regardless of high deposition rate (8.5 nm/min). The composition ratio Sr/Ti of Sr to Ti in the films varied with the distance between the target and the substrate. All as-deposited films on Si substrates were found to be amorphous and were crystallized by post-deposition annealing using an electric furnace at 650 K, i.e. approximately 250 K lower than annealing for films obtained by conventional RF magnetron sputtering. Post-deposition annealing of these films using millimeter-wave radiation decreased the crystallization temperature to a value of 550 K. Furthermore, all as-deposited films on Pt/Ti/SiO₂/Si substrates by a plasma of Ar and O₂ gas mixture were found to be crystallized regardless of no substrate heating.     

单相双稀土改性SrZrO3热障涂层的热物理性能

由于SrO和ZrO₂的蒸气压不同, 造成等离子喷涂SrZrO₃涂层组分偏离原始粉末化学计量比, 从而导致制备态涂层中出现第二相ZrO₂。为了获得高相稳定性的单相涂层, 实验采用固相合成法合成并经过喷雾造粒制备了双稀土改性Sr过量SrZrO₃(Sr_1.1(Zr_0.9Yb_0.05Gd_0.05)O_3.05)热喷涂粉末, 采用大气等离子喷涂方法制备了相应的涂层, 研究了单相双稀土改性SrZrO₃热障涂层的热物理性能及其热循环寿命。研究结果表明, 制备态Sr_1.1(Zr_0.9Yb_0.05Gd_0.05)O_3.05涂层中无第二相产生, 1600 ℃热处理360 h后Sr_1.1(Zr_0.9Yb_0.05Gd_0.05)O_3.05保持单相SrZrO₃结构, 高温相稳定性良好。Sr_1.1(Zr_0.9Yb_0.05Gd_0.05)O_3.05涂层的烧结系数为7.27×10 ^-6 s ^-1, 热处理360 h后该涂层的热膨胀系数为(9.0~11.0)×10 ^-6 K ^-1 (200~1400 ℃), 热导率为2.83 W/(m?K) (1000 ℃)。Sr_1.1(Zr_0.9Yb_0.05Gd_0.05)O_3.05/YSZ双层涂层的火焰循环次数为1000次, 失效区域主要发生在Sr_1.1(Zr_0.9Yb_0.05Gd_0.05)O_3.05陶瓷层内。在喷涂粉末中增加SrO的含量能够弥补在大气等离子喷涂过程中Sr元素过量挥发的问题, 成功制备了单相双稀土改性Sr_1.1(Zr_0.9Yb_0.05Gd_0.05)O_3.05热障涂层。双稀土掺杂能够明显提高涂层的热膨胀系数, 且单相双稀土改性Sr_1.1(Zr_0.9Yb_0.05Gd_0.05)O_3.05涂层的抗烧结性能明显优于SrZrO₃涂层, 但单相Sr_1.1(Zr_0.9Yb_0.05Gd_0.05)O_3.05涂层热导率比含有第二相的SrZrO₃涂层高。     

Investigation of Iron-Fullerene Mixture Plasmas in ECR Discharge

Fullerene+iron (C₆₀+Fe) mixture plasmas were produced and studied in the ECR ion source of ATOMKI. The two main components of the plasma were obtained by different filament ovens. In this series of measurements we concentrated on the maximum ratio of C₅₈ (damaged fullerene) in the plasma. C₅₈ is less stable than C₆₀ and the probability to form new materials is higher. Using this method we produced molecules of mass M=752 both in single- and double-charged states with beam intensities of 8 · 10^-10A and 2 · 10^-10A, respectively. We identified this beam as a mixture of FeC₅₈, O₂C₆₀ and CO₂C₅₉, while the experiment did not give information on the exact location of the iron and oxygen in the carbon ball.