ZrC-SiC-MoSi2涂覆C/C-SiC-ZrC陶瓷基复合材料在氧乙炔焰下的烧蚀行为及机理(英文)

为进一步提高C/C复合材料在不同烧蚀环境下的烧蚀性能,采用浆料刷涂法在C/C-SiC-ZrC陶瓷基复合材料上制备Zr含量分别为34%和60%(质量分数)的ZrC-SiC-MoSi₂涂层,并且利用氧乙炔焰研究涂层C/C-SiC-ZrC复合材料在3种不同氧气及乙炔流量下的烧蚀行为。结果表明：随着Zr含量的增加,涂层内部的ZrC和SiC颗粒尺寸明显减小,且颗粒分布更加均匀。Zr含量为60%的涂层线烧蚀率随氧气和乙炔流量的增加而增加,而Zr含量为34%的涂层线烧蚀率随氧气和乙炔流量的增加,先增加后降低。此外,详细讨论ZrC-SiC-MoSi₂涂层在不同条件下的烧蚀机理。随着氧气和乙炔流量的增加,主要的烧蚀机制由氧化变为氧化和蒸发的结合作用,最后变为氧化、蒸发及剥蚀的结合作用。     

Properties of hydrogenated amorphous carbon films deposited by PECVD and modified by SF6 plasma

Hydrogenated amorphous carbon (a-C:H) films were grown at room temperature on glass and polished silicon substrates using RF-PECVD (Radio-Frequency Plasma Enhanced Chemical Vapor Deposition). Plasmas composed by 30% of acetylene and 70% of argon were excited by the application of RF signal to the sample holder with power ranging from 5 to 125 W. After deposition, the films were submitted to SF₆-plasma treatment for 5 minutes. SF₆ plasmas were generated at a pressure of 13.3 Pa by a RF power supply operating at 13.56 MHz with the output fixed at 70 W. The resulting films were characterized in terms of their molecular structure, chemical composition, surface morphology, thickness, contact angle, and surface free energy. During the SF₆ plasma treatment, fluorine species were incorporated in the film structure causing chemical alterations. The interaction of chemical species generated in the SF₆ plasmas with surface species was responsible for the decrease of the film thickness and surface energy, and for the increase of the film roughness and hydrophobicity.     

Doping of poly(acetylene) to the metallic state using thionyl chloride

SOCl₂ has been found to be an effective oxidant for poly(acetylene), increasing the electrical conductivity by several orders of magnitude. The oxidized (CH)_x sites are thought to be compensated with chloride ion liberated by reduction of SOCl₂. The use of poly(acetylene) as a current collector in lithium/oxyhalide cells is reported elsewhere [14].     

The inhibition of Ni corrosion in H2SO4 solutions containing simple non-saturated substances

The inhibition of Ni electrodissolution in H₂SO₄ solutions containing carbon monoxide, ethylene or acetylene was investigated after adsorption equilibrium at room temperature. The interaction of these molecules with Ni was followed by the anodic stripping of adsorbed residues. The Ni electrodissolution inhibitory effect caused by the different adsorbates increases in the following order: ethylene < carbon monoxide < acetylene. Anodic stripping curves were simulated by applying a numerical method, such as Runge-Kutta's, and the different voltammetric contributions calculated by numeric deconvolution. These analyses provide a further insight into the mechanism of the Ni electrodissolution in acid containing carbon monoxide, ethylene or acetylene.     

Effects of Laser Surface Modification of Nimonic with Aluminum on Oxidation Behavior

Using a high-power CO₂ laser, aluminum-surface alloying was carried out on a nickel-base superalloy (Nimonic 80A) with the aim of improving its oxidation resistance. After the treatment, scanning-electron microscopy (SEM) studies show the alloy area to have a two-phase structure of Ni solid solution and Ni₃Al intermetallic. These layers were subsequently subjected to a laser-remelting treatment with different beam-scanning speeds in order to homogenize their structure. Metallographic studies indicate the formation of a single dendritic phase rather than the two-phase structure present in the unmelted alloyed tracks and a decrease in the aluminum content throughout the laser track. To establish their oxidation behavior at high temperatures, the alloyed layers and remelted alloyed layers were oxidized at 1273 K for varying times, between 24 and 300 hr, comparing their behavior with that of untreated specimens. The results indicate the formation of a protective alumina layer on the alloyed specimens. The oxidation behavior differs, depending on the scanning rate (of the laser beam over the specimen surface) during remelting. Oxidation of the remelted specimens at the maximum rates studied (500 mm/min) leads to the formation of protective oxides on the superalloy. However, when remelting takes place at lower rates (100 and 300 mm/min), the amount of aluminum present is insufficient to develop a continuous protective-oxide layer.     

添加剂对锌电极性能的影响(英文)

为了改善镍锌电池的性能,同时研究电极中添加剂对锌电极性能的影响,选用正交设计对影响锌电极的4个因素(乙炔黑、Bi2O3、PbO、包覆La(OH)3的Ca[Zn(OH)3]2·2H2O)选择3个水平进行测试。对没有任何添加剂的氧化锌在20%KOH电解液中进行充放电循环实验,研究添加剂的作用。为了更好地解释锌电极放电容量衰减的原因,对正交实验的最差样品和最优样品放电产物所含的Zn和Ca的比例进行分析。通过表征,得出了在该实验条件下的电极添加剂的最优配比方案为:在5g样品中,乙炔黑0.02g,Bi2O3 0.5g,PbO 0.3 g,包覆La(OH)3的Ca[Zn(OH)3]2·2H2O)0.2g。     

Physical properties of the GaPd2 intermetallic catalyst in bulk and nanoparticle morphology

Intermetallic compound GaPd₂ is a highly selective catalyst material for the semi-hydrogenation of acetylene. We have determined anisotropic electronic, thermal and magnetic properties of a GaPd₂ monocrystal along three orthogonal orthorhombic directions of the structure. By using ⁶⁹Ga and ⁷¹Ga NMR spectroscopy, we have determined the electric-field-gradient tensor at the Ga site in the unit cell and the Knight shift, which yields the electronic density of states (DOS) at the Fermi energy ε_F. The DOS at ε_F was determined independently also from the specific heat. To see the change of electronic properties of the GaPd₂ phase on going from the bulk material to the nanoparticles morphology, we have synthesized GaPd₂/SiO₂ supported nanoparticles and determined their electronic DOS at ε_F from the ⁷¹Ga NMR spin-lattice relaxation rate. The electronic DOS of the GaPd₂ was also studied theoretically from first principles. All results are compared to the chemically related compound GaPd. The active–site-isolation concept for an increased catalytic selectivity is discussed in relation to the GaPd₂ and GaPd structures.     

The Effect of the Topography and Chemical Composition of the Surface Layers of FeCuNbBSi Amorphous Alloys on Their Electrochemical Behavior

The effect of topography and chemical composition of the surface layers of amorphous Fe_76.1Cu_1.0Nb_3.0Si_13.8B_6.1 alloys on their electrochemical behavior was investigated in a neutral borate buffer solution and 1 M H₂SO₄ solution, both in the initial state and after thermal treatment. It is shown that the formation of a dense oxide film in the process of quenching and annealing results in a self-passivation of the surface of bands in the buffer solution. In the sulfuric acid solution, the electrochemical behavior of the alloys is determined by the structural–phase state of the surface. The protective properties of the passive film are improved with the diminution of grains forming in the course of heat treatment on the surface and in the amorphous matrix of alloys during crystallization, as well as by enhancing the surface homogeneity. It is ascertained that the passivation process in both of solutions occurs easier with an increase in the concentration of silicon in the surface layers of ultra-rapidly quenched bands.     

Formation of molybdenum boride cermet coating by the detonation spray process

The effects of the powder particle size and the acetylene/oxygen gas flow ratio during the detonation spray process on the amount of molybdenum phase, porosity, and hardness of the coatings using MoB powder were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The results show that the presence of metallic molybdenum in the coating results from decomposition of MoB powder during thermal spray. The compositions of the coatings are metallic Mo, MoB, and Mo₂B, which are different from the phases of the original powder. The amount of molybdenum phase increases monotonously with the oxygen/acetylene ratio, but the increasing rate for the fine powder is faster than that for the coarse powder. The porosity and hardness of the coating are related to the amount of molybdenum phase. The phase constitution of the coating is discussed.     

AISI 316L奥氏体不锈钢低温离子-气体渗碳工艺优化

目的将低温离子-气体乙炔渗碳应用于AISI 316L奥氏体不锈钢表面硬化处理,同时探讨其硬化处理的最优工艺参数及优化效果。方法采用离子轰击去除不锈钢表面钝化膜并活化其表面,再进行低温气体乙炔渗碳,实验过程使用脉冲式供气循环处理方式。进行温度梯度实验,寻找渗碳处理的临界温度。并采用正交试验法设计3因素3水平共9组实验,分析气体比例、离子轰击时间、保温压强3个因素对渗碳层硬度和厚度产生的影响,以期得到不锈钢低温离子-气体乙炔渗碳优化工艺。通过对经过最优化工艺处理过后的不锈钢硬化层组织、成分、厚度、硬度、耐磨性、耐蚀性能的研究分析,验证此工艺对AISI 316L奥氏体不锈钢硬化处理的适用性。结果处理温度为540℃时渗碳层有碳的铬化物析出;离子轰击时间对渗碳层硬度影响最大,保温压强对硬化层厚度影响最明显。在硬化处理温度为520℃,V(H2)∶V(C2H2)=1∶1,渗碳压强为-0.02 MPa,离子轰击时间为20 min时,316L奥氏体不锈钢离子-气体乙炔渗碳效果最优。经优化工艺处理后不锈钢硬化层厚度达到30μm左右,表面硬度达到838HV0.05,耐蚀性和耐磨性能等都显著提高。结论低温离子-气体乙炔渗碳硬化处理适用于AISI 316L奥氏体不锈钢,其处理最合适温度为520℃。经优化工艺处理后的不锈钢具有较高的硬度、厚度,良好的硬度梯度,高耐蚀性能及高耐磨性能。     

Mechanical and tribological properties of the High Target Utilization Sputtering W-C coatings on different substrates

The effects of three types of substrates (Si, bearing steel, and WC-Co) and acetylene addition (0–3.2 vol.% in Ar atmosphere) on the topography, structure, composition, nanohardness and tribological behavior of the High Target Utilization Sputtering W-C coatings were investigated. The results showed that the substrates affected mostly the coating topography, roughness and nanohardness whereas the composition, indentation moduli and coefficients of friction were influenced only by the increase of free carbon content from acetylene addition. Up to ~ 5 GPa difference in the hardness of the W-C coatings on Si substrates compared to that on steel was obtained. Simultaneously, methodological problems with the hardness measurements were identified on WC-Co substrate which has the hardness close to that of the coatings. The average values of the coefficient of friction were around 0.3 and slightly decreased at higher carbon contents but the influence of the substrates was small.     

The effect of Cr2O3 addition on crystallization and properties of La2O3-containing diopside glass-ceramics

We report on the effect of La₂O₃ and Cr₂O₃ on the structural, thermal and crystallization behavior of diopside-based glasses and on the processing, microstructure and properties of the sintered glass-ceramics (GCs). The structural features and thermal behavior of the glasses were investigated by Fourier transform infrared spectroscopy, density measurements, dilatometry and differential thermal analysis. The sintering, crystallization, microstructure and properties of the GCs were investigated under different heat treatment conditions (800–1000 °C; 1–300 h). The good matching of thermal expansion coefficients and the strong, but not reactive, adhesion to yttria-stabilized zirconia and Crofer 22 APU alloy, in conjunction with a low level of electrical conductivity, indicates that the investigated GCs are suitable candidates for further experimentation as solid oxide fuel cell sealants.     

Multiphase and microstructure effects on the hydrogen absorption/desorption behavior of a Ti–22Al–27Nb alloy

The hydrogen absorption/desorption behavior of hydride-forming alloys depends on their microstructure. We investigated multiphase effects on the hydrogen absorption/desorption behavior at 100°C of a ternary alloy [Ti–22Al–27Nb (at.%)] whose microstructure consists of β (bcc) [or its ordered phase β₀ (B2)] and/or O (orthorhombic, based on Ti₂AlNb) phases. On exposing β₀ single-phase specimens to hydrogen, β hydride (B2) is easily formed. However, further hydriding to γ hydride (bct) does not easily occur. When the O phase exists in the β matrix phase, the β→γ hydride transformation occurs and the reversible absorption/desorption of hydrogen between β and γ hydrides is observed. Roles of the O phase in the reversible hydrogen absorption/desorption behavior are discussed on the basis of the crystal structure correlation between the β phase, O phase and γ hydride phase and the ordering of hydrogen atoms in these phases.     

Effect of the Molecule Structure of Acetylene Compounds on the Kinetics of the Electrode Reactions of Iron in Hydrochloric and Sulfuric Acids

The electrochemical interaction of acetylene compounds, both with and without -hydrogen, with iron in hydrochloric and sulfuric acids was investigated by potentiostatic voltammetry on a rotating disk electrode and capacitance measurements on a stationary electrode. The tendency of acetylene compounds to electrochemical reduction correlates with their ability to polymerize on iron in acidic solutions. The presence of -hydrogen atom determines the ability of an acetylene compound to polymerize on iron, thus inducing the secondary inhibition. The compound containing no -hydrogen manifests only adsorption mechanism.     

Investigation of the main influencing parameters on the degassing behavior of titanium carbonitrides using mass spectrometry

It is well known that titanium carbonitrides (Ti(C,N)) release carbon monoxide (CO) and nitrogen (N₂) upon heat treatment, which can influence further processing such as sintering. Thus a deeper understanding concerning the driving forces of the degassing behavior could facilitate the development of further processing steps. Therefore, the focus of this study was put on determining the main influencing factors of the degassing behavior of titanium carbonitrides during heat treatment. For this purpose, an application-oriented characterization method by modifying an evolving gas analysis device (EGA) was developed. Quadrupol mass spectrometry (MS) was applied to monitor the gas evolution as a function of temperature under vacuum. The evolving CO and N₂ were transported to the mass spectrometer using a helium carrier gas flow. Thermogravimetric analysis was deployed to complement the mass spectrometry data and to further elaborate on the outgassing behavior of the different sample species.Titanium carbonitride powders with different C/N/O ratios, grain size as well as free carbon content blended with typical binder metals (Co, Ni and Co + Ni) were investigated regarding their degassing behavior. The different C/N/O ratios influenced decisively the CO as well as the N₂ outgassing in terms of quantity and temperature range. Consequently, a unique outgassing pattern, a “finger print”, was identified for each titanium carbonitride powder type. An altered grain size on the other hand, did not lead to a changed gas evolution. However, the content of free carbon was influencing the CO and the N₂ outgassing significantly. The binder type, by contrast, was influencing the N₂ evolution to a higher degree than the CO evolution.     

Ferroelasticity and hysteresis in LaCoO3 based perovskites

Perovskite-type ABO₃ (where A=La, Ca; B=Co) ceramics are very promising materials for oxygen separation membrane and solid oxide fuel cells applications. However, their mechanical behavior has not yet been adequately studied. We studied the mechanical performance of perovskite ceramics using a combination of microindentation, compression, and bending. Our work demonstrated ferroelastic hysteretic behavior during indentation and compression loading in LaCoO₃ based perovskites. This behavior can be caused by domain reorientation and/or phase transformation. Domain switching under the compression loading in LaCoO₃ based perovskites has been demonstrated by XRD. Nonlinearity during fracture toughness measurements was observed in the dense La_0.8Ca_0.2CoO₃ perovskite. Such nonlinearity can be assigned to the domain switching or the phase transformation during crack propagation. This might be a reason of a higher fracture toughness of this material compared to non-ferroelastic composition.     

Influence of an O2 Type Oxidizing Environment on SiCf/SiC Composites: Properties/Microstructure Relationship

Ceramic matrix composites have been identified as a potential material of core structure for the fourth generation of fission nuclear reactors. Regarding their excellent mechanical behavior in very harsh conditions (high temperature and high irradiation flux), the CVI–SiC_f/SiC composites with pyrocarbon interlayer are of prime interest for the fuel cladding in the gas-cooled fast reactor. Although the working atmosphere is helium in these advanced reactors, the presence of oxidizing impurities could have a significant role on the mechanical behavior of materials subjected to long-term exposures. Within this framework, this study was intended to investigate the influence of oxidation on the SiC_f/SiC composites mechanical properties. Different pre-damage states were intentionally introduced by mechanical tensile tests on plate specimens before performing an oxidation treatment of 1,000 h at 1,000 °C under helium with 10 ppm of O₂. The degradation of the composite was determined from the mechanical behavior of post-exposure specimens. Results were correlated both with microstructural observations of the damage and with characterizations of the generated oxides at the surface of the composites. The most severe decline of mechanical properties occurs for the higher predamaged loadings. Indeed in this case, the silica formed during the oxidation of SiC is not in sufficient quantities to fill the cracks.     

Synthesis and properties of novel triphenylamine polymers containing ethynyl and aromatic moieties

Novel polymers composed of TPA (triphenylamine), ethynyl and aromatic units in the main chain were synthesized. These polymers are structurally rigid due to aromatic and acetylene moieties and show high T_g and thermal stability. The polymers 3a and 4 are cross-linked on annealing at ∼220°C and they can be potentially used as a hole-transporting material for multi-layer devices with spin-coating.     

Untersuchungen zur passivierenden Wirkung organischer Oxidationsmittel auf Eisen in neutralen und schwach sauren Lösungen — 1. Mitteilung: C-Nitrosoverbindungen und Chione

Investigations into the passivating effect of organic oxidizing substances on iron in neutral and weakly acided solution I. Communication: C-nitrosocompounds and quinones Using potential/time curves the authors have found that in solutions containing 0.1 M sodium sulphate and 0.1 M KH₂? PO₄/K₂HPO₄ certain oxidizing media have rather a pronounced passivating effect. The inhibiting action of p-nitrosodimethylaniline and p-nitrosophenol comes to bear in a comparatively broad pH range while potassium quinone monosulfonate and acetylene quinone are passivators in neutral solutions only and quinone as such has a good effect only in additated solutions buffered to pH 5.2 to 6.3 α-nitroso-β-naphthol on the other hand forms a surface layer inhibiting corrosion.     

Effect of rare earth and calcium treatments on the mechanical,physical, and electrochemical properties of a 16Mn steel

Two treatment methods, namely Ca-Si injection into the ladle and rare earth (RE) additions to the mold, were investigated for their effectiveness in controlling the microstructure, particularly sulfide inclusions, and hence the properties of a 16Mn plain-carbon steel. A combined Ca + RE treatment increased the critical crack opening displacement in the transverse direction of sheet material to that in the rolling direction. The combined treatment also improved the resistance to stress-corrosion cracking (SCC) in a boiling 20 wt.% NH₄NO₃ solution. Too large a RE addition, ultimately lowers SCC resistance. The RE additions retarded austenite grain growth, whereas the Ca-only addition accelerated grain growth. The changes in fracture behavior, SCC resistance, and austenite grain growth behavior are explained in terms of the segregation of the RE to the grain boundaries and the subsequent changes in the electrochemical and mechanical properties of the grain boundaries relative to the grain interiors. A combined treatment of injecting 3.4 kg Ca-Si per ton of steel into the molten steel and adding 0.03 wt.% RE to the mold yielded optimum properties.