Quantum Capacitance: A Perspective from Physics to Nanoelectronics

All materials (including conductors) possess the so-called quantum capacitance, which is present in series with the traditional geometric (electrostatic) capacitance. It is usually a large positive quantity and therefore irrelevant for most materials except for nanostructures. Quantum capacitance has been found to reduce the overall capacitance of nanostructures compared with what is predicted by classical electrostatics. One of many tantalizing recent physical revelations about quantum capacitance is that it can posses a negative value, hence, allowing for the possibility of enhancing (sometimes dramatically) the overall capacitance in some particular material systems—beyond the scaling predicted by classical electrostatics. We provide here a short overview of this subject and review some recent developments.     

低地轨道环境中的原子氧对空间材料的侵蚀与防护涂层

介绍了由于原子氧(AO)侵蚀引起的空间材料降变机制 和地面AO模拟技术发展的现状.重点讨论了抗AO侵蚀涂层的性能、材料种类及不同涂层对AO 侵蚀的防护效果.同时分析了该领域未来研究的方向及发展趋势.     

OLEDs based on some mixed-ligand terbium carboxylates and zinc complexes with tetradentate Schiff bases: Mechanisms of electroluminescence degradation

Mixed-ligand terbium carboxylates—Tb(Carb)₃(TPPO)₂ (HCarb = HSal (salicylic acid), Hpobz (2-phenoxybenzoic acid); TPPO = triphenylphosphine oxide) and zinc complexes with tetradentate Schiff bases—ZnSB (H₂SB = H₂SAL1, H₂SAL2 (derivatives of salicylic aldehyde); H₂MO1, H₂MO2 (derivatives of o-vanillin)) were used as electroluminescent (EL) layers in organic light emitting diodes (OLEDs). These devices have undergone reversible and irreversible mechanisms of EL degradation. The reversible one is mainly associated with charge carrier trap filling. At the same time several mechanisms of irreversible degradation were observed under UV light irradiation, heating and ageing in ambient conditions. The degradation mechanisms of OLEDs under heating from 293 K to 320 K were related to the changes in the interface regions. The initial degradation was eliminated by (1) an application of alternating bias voltage; (2) a decrease of the substrate temperature and the velocity of the thermal evaporation of materials. The degradation of OLEDs was not observed under low UV irradiation that is promising for OLEDs operation under day light.     

Physical properties of CVD-grown Se—carbon films

A novel chemical vapor deposition (CVD) approach based on the thermal decomposition of an aromatic hydrocarbon in the presence of Se vapor is used to grow films of layered Se—carbon compounds. In principle, this technique can produce a wide variety of new carbon-based materials, for example, graphite intercalation compounds (GICs) which, for kinetic reasons, cannot be made if the intercalant vapor has to diffuse large distances into a pre-existing graphitic host. In particular, homogeneous oriented submicron films of either pure stage-3 (Se₂₄C) or mixed-stage Se—carbon layer compounds have been successfully grown on Ni substrates in evacuated sealed quartz tubes. X-ray diffraction, X-ray photoelectron spectroscopy, Raman scattering and the c-axis electrical transport measurements are discussed in terms of both covalent Se—carbon bonding and an ionic model assuming the formation of an acceptor-type Se—GIC with electron transfer from carbon to Se. Our CVD-grown Se—carbon films exhibit the largest thermoelectric power reported in the open literature among carbon-based compounds. However, the value is at least a factor of 10 less than reported for these materials in patents by Sharp Corp.     

Modeling of the anisotropic elastic properties of plasma-sprayed coatings in relation to their microstructure

The transversely isotropic elastic moduli of plasma-sprayed coatings are calculated in terms of microstructural parameters. The dominant features of the porous space are identified as strongly oblate pores, that tend to be either parallel or normal to the substrate. “Irregularities” in the porous space geometry—the scatter in pore orientations and the difference between pore aspect ratios of the two pore systems—are shown to have a pronounced effect on the effective moduli. They may be responsible for the “inverse” anisotropy (Young’s modulus in the direction normal to the substrate being higher than the one in the transverse direction) and for the relatively high values of Poisson’s ratio in the plane of isotropy. The analysis utilizes results of Kachanov et al. (Appl. Mech. Rev., 1994, 47, 151) on materials with pores of diverse shapes and orientations.     

Mikrobielle Werkstoffzerstörung – Grundlagen: Mikrobielle Schädigungsmechanismen

Microbial deterioration of materials – fundamentals: Microbial destruction mechanisms Generally, all kinds of microorganisms – bacteria and cyanobacteria, algae, fungi, and lichens – are able to attack and degrade materials. The deterioration is caused by the excretion of metabolic intermediates and/or endproducts as well as exoenzymes. Depending on the use of a material, a discoloring of a resin or a total destruction of a material, may result in a serious microbiologically influenced corrosion damage. Although many microorganisms are known to participate in these processes, the ways of action may be summarized by seven main categories:

• 1) attack by mineral acids like sulfuric, nitric, carbonic acid → hydrolysis of materials
• 2) attack by organic acids like acetic, citric, oxalic, gluconic, and other acids → hydrolysis of materials and chelatization of cations
• 3) saltstress because of reactionproducts of 1) and 2) → retaining water in porous materials causes increased susceptibility against freeze-thaw attack and further crystallisation → swelling attack
• 4) production of noxious, compounds like hydrogen sulfide, nitrogen oxides → production of mineral acids or precipitation of metal sulfides
• 5) effect of biofilm → exopolymers cause localized corrosion cells as well as retainment of water in porous materials (s. above); in addition hydrophobic effects on surfaces
• 6) attack by exoenzymes → cleavage of insoluble organic compounds to small, water soluble molecules
• 7) production of wetting agents → increased solubility of hydrophobic substances

Usually, the deterioration of a material is caused by a combined action of the above mentioned factors. However, chemical methods often fail to detect the mechanisms properly because some compounds may be subject to a metabolic turnover (organic acids, nitrogen compounds etc.). Microbiological analyses are necessary for clearing up the mechanism of attack.     

A Study of the Adsorption–Structural Parameters and Photoactivity of TiO2/Kaolinite Composite

Protection of Metals and Physical Chemistry of Surfaces - The TiO2/kaolinite material—a filler for construction materials with the function of passive degradation of household organic...     

Gradients in elastic modulus for improved contact-damage resistance. part ii: the silicon nitride–silicon carbide system

In an effort to create elastic-modulus (E) graded materials for contact-damage resistance—free of substantial amounts of glass—silicon nitride (Si₃N₄)-silicon carbide (SiC) graded materials were processed. The structure of these graded materials is such that Si₃N₄ (E=300 GPa) is at the contact surface and SiC (E=400 GPa) is in the interior, with a stepwise gradient in composition existing between the two over a depth of 1.6 mm. A pressureless, liquid-phase co-sintering method, in conjunction with a powder-layering technique, was used to achieve this structure. The liquid phase used was yttrium aluminum garnet (YAG). Under spherical indentation, cone-cracks did not form in the graded material, but some inelastic shear deformation was observed. Cone cracks formed in both the monolithic Si₃N₄ and the monolithic SiC end member materials under identical indentation conditions. Finite element analysis (FEA) of the stresses associated with indentation revealed that the maximum principal tensile stresses outside the Hertzian contact circle, which drive the classical cone-cracks, are reduced by approximately 12% in the graded material relative to the monolithic silicon nitride case. This reduction is significantly lower than what was calculated for the Si₃N₄-glass case (Part I), owing to the shallower, linear E-gradient over a 1.6 mm depth in Si₃N₄-SiC, as compared with the power-law, steeper E-gradient over 0.4 mm depth in the Si₃N₄-glass. It appears that, in addition to the E-gradient, the inelastic deformation contributes to the suppression of cone cracks in the Si₃N₄-SiC graded material. It is suggested that compressive residual stresses may be present in the Si₃N₄-SiC graded material, which are also likely to aid in the suppression of cone-cracks.     

Molten glass corrosion resistance of MoxRuySiz compounds at 1350 °C in an alkali borosilicate glass

Corrosion of Mo-silicides and Mo_xRu_ySi_z compounds in molten glass is studied by electrochemical techniques at 1350 °C, metallographic observations (SEM) and chemical analysis (EPMA). The open circuit potential measurements (free-potential) enabled the determination of the reactions responsible for the degradation of the materials.The degradation of Mo-silicide occurs through selective oxidation of Si. Mo_xRu_ySi_z compounds were subjected to reactions leading to the successive oxidation of silicon and molybdenum. The progressive depletion of Si and Mo resulted in the more or less quick formation of a thick, porous and low adherent Ru-layer. Therefore, Ru-additions had no positive effect on the molten glass corrosion resistance of MoSi₂-based materials and should even accelerate the degradation kinetics of the later through galvanic coupling.     

Corrosion Resistance of an Electron Beam Refined 26% Cr– 1% Mo Ferritic Stainless Steel

Abstract

A high purity iron—26% chromium—1% molybdenum alloy which has recently been made available in commercial quantities has outstanding resistance to attack in a wide variety of chloride-ion-containing environments and organic acids. The material is resistant to stress-corrosion cracking in boiling magnesium chloride, and its low carbon and nitrogen content makes it highly resistant to intergranular attack.     

Immunological Response to Biodegradable Magnesium Implants

The use of biodegradable magnesium implants in pediatric trauma surgery would render surgical interventions for implant removal after tissue healing unnecessary, thereby preventing stress to the children and reducing therapy costs. In this study, we report on the immunological response to biodegradable magnesium implants—as an important aspect in evaluating biocompatibility—tested in a growing rat model. The focus of this study was to investigate the response of the innate immune system to either fast or slow degrading magnesium pins, which were implanted into the femoral bones of 5-week-old rats. The main alloying element of the fast-degrading alloy (ZX50) was Zn, while it was Y in the slow-degrading implant (WZ21). Our results demonstrate that degrading magnesium implants beneficially influence the immune system, especially in the first postoperative weeks but also during tissue healing and early bone remodeling. However, rodents with WZ21 pins showed a slightly decreased phagocytic ability during bone remodeling when the degradation rate reached its maximum. This may be due to the high release rate of the rare earth-element yttrium, which is potentially toxic. From our results we conclude that magnesium implants have a beneficial effect on the innate immune system but that there are some concerns regarding the use of yttrium-alloyed magnesium implants, especially in pediatric patients.     

ZWZY5配方设计系统在耐磨堆焊焊条研究中的应用

ＺＷＺＹ５配方设计系统具有拟正交试验配方方案、进行正交回归设计、最优化计算、建立焊接材料性能指标回归方程,求得最优化配方,预报焊接材料性能,求解多元非线性回归方程,从而获得某一已知性能指标的多个焊接材料配方等功能。将其用于配方设计十分简便、快速而准确,从根本上克服了传统配方设计方法的盲目性。作者将ＺＷＺＹ５配方设计系统应用于耐磨堆焊电焊条的研制,取得十分满意的结果,研制成功了综合性能优良的“堆５１     

The QSL reactor for lead and its prospects for Ni,Cu and Fe

In 1960, the author stated: “The dead hands of nitrogen have been lifted from oxidation reactions which utilize the oxygen in air…. Greatly improved reverberatory and rotary furnace designs will be employed for utilization of tonnage oxygen in continuous autogenous smelting and converting…. The institutions of higher education, founts of trained manpower and virgin scientific knowledge, need and deserve generous support from their mining industry beneficiaries.”⁶⁶ This case history demonstrates the rewards obtainable by such cooperation. Much-increased American academia-industry-government teamwork research and development is imperative, with overall modernization of metal making—including scrap recycling—as the objective. The Q-S continuous oxygen converter has come a long way since it appeared on the cover of the August 1974 Journal of Metals, and the saga reflects the U.S. Army Engineers’ motto: “Essayons.” (“Let us try”).     

CYCLIC DEFORMATION OF COARSE GRAINED POLYCRYSTALLINE PURE Ai——Ⅰ.SLIP CHARACTERISTICS

Comparing with ordinary ploycrystalline materials sized to μm grade,the slip morphology ofthe coarse grained polycrystalline pure Al is characterized by:(1)several slip domains occurin a grain,and in same domain,several slip systems operate at same time or one after anotherintensely,a beautiful and neat slip pattern is forming on the specimen surface;(2)for highΣ-value coincident and random grain boundaries,the grain boundary affecting zone(GBAZ),bout 50—120μm wide,is favourable site to form intergranular crack at early fa-tigue life easily,and migration or slide of the boundaries were often observed.While lowΣ-value near-coincident grain boundaries show a higher degree of slip continuity and straincompatibility than high Σ-value ones.Intergranular crack is not easily nucleated at lowΣ-value near-coincident boundaries;and(3)due to suppression of grain boundary slip attriple grain boundary node,the high Σ-value and random grain boundary among the threeboundaries of tricrystal crack easily during cyclic deformation.     

Factors influencing the performance of a Cr-Ni-Fe alloy exposed to sulfidising/oxidising/carburising environments at 800°C

Studies concerned with the corrosive degradation of engineering alloys exposed to multi-reactant gaseous environments containing sulphur, oxygen and carbon-bearing species have intensified during the past decade. In particular, the attack experienced by materials exposed in coal conversion plants has become one of the major areas of concern. These process atmospheres are generally characterised by low oxygen activities and high sulphur and carbon activities and sulphidation can therefore pose significant problems in the design and operation of such plant. This paper presents the results of studies carried out on a laboratory cast austenitic 25 Cr-35 Ni-Fe “model” alloy exposed to a range of H₂-CO-H₂O gas mixtures containing H₂S additions such that the oxygen and carbon activities remain constant (pO₂ = 10^?21 bar, a_c = 0.3) whilst the sulphur activity is varied systematically within the range, pS₂ = 10^?9 to 10^?7 bar at 800°C. Tests have also been carried out in an equivalent sulphur-free atmosphere for reference purposes. The influence of surface condition upon corrosion behaviour has received some attention by comparing the results obtained on ground samples with those obtained on work-free electropolished specimens. The kinetics and mechanisms by which this alloy corrodes have been established for exposure periods ranging from 5 min to 5000 h. These studies provide a clear understanding of the factors which can lead to catastrophic sulphidation attack in these types of environment and they also establish the critical dependence of long-term corrosion resistance upon the sulphur activity of the atmosphere.     

From Electronic Structure to Thermodynamics of Actinide-Based Alloys

In this brief review, we show that thermodynamic modeling of complex multicomponent actinide-based alloys is crucial for fuel development and for predicting the impact of evolving fuel chemistry with time on materials performance. With input from energetics and equilibrium properties of alloys from ab initio electronic-structure calculations, within the framework of density-functional theory, the CALPHAD methodology is a viable approach to thermodynamic assessment for this class of materials. Despite the limited availability of experimental thermodynamic data, this approach can predict important features in the phase diagram and, perhaps more importantly, guide and motivate further experiments for validating the methodology and the data for subsequent modeling of materials performance on a higher level.     

Oligomers and isomers: new horizons in poly-anilines

The extraordinarily important potential role of isomers in determining the electronic, magnetic, optical, structural and mechanical properties of poly-anilines, including polyaniline is presented. It is based on a summary of known types of isomers—positional, cis/trans, rotational—and isomerism processes, some of which occur relatively slowly even at room temperature in solution. Possible general approaches for determining the intrinsic properties of polyaniline by isolating the polymer preferably in one isomeric form or as a mixture containing a smaller than usual number of different isomers, are outlined.     

High temperature interaction of Al/Si-modified Fe-Cr alloys with KCl

The corrosion behaviour of pure iron, pure chromium, and aluminium/silicon alloyed Fe-Cr materials was investigated at 650 °C in air accompanied by gaseous or solid KCl salt. The corrosion rates of these materials with KCl salt are high and they are strongly affected by the salt amount, the types of the alloying elements and the concentration of chromium. The dominant degradation mechanism for the chromia-forming alloys by KCl attack is the preferential formation of potassium chromate over the conventionally protective chromia, characterized by typical features of bubbles, cracks, volatility and severe spallation for the corrosion products. A detrimental effect of chromium is confirmed. Al-alloying addition to Fe-Cr alloys is beneficial by enhancing the corrosion resistance. Silicon is more effective in promoting the corrosion resistance of Fe-Cr alloys by forming a stable and dense oxide layer in the inner zone which suppresses the rapid growth of iron oxides.     

Zweckmäßige Apparatekonstruktionen aus Kunstkohle und Elektrographit und deren Einsatzgebiete

Suitable apparatus designs of synthetic carbon and electro-graphite, and their applications Production and properties of synthetic carbon and electrographite ane described. Through impregnation of the intrinsically porous materials, one obtains apparatus materials of high corrosion resistance with a wide field of applications. The quality of these materials is largely governed by the type of impregnating agent and by the impregnation method. The properties of the carbon materials must be taken into account in the structural design. Numerous types of graphite equipment have been developed. The advantages and disadvantages of certain designs for specific spheres of application are discussed. In conclusion, some general advice is given concerning transport, servicing and repairs.     

Photoluminescence behavior and visible light photocatalytic activity of ZnO,ZnO/ZnS and ZnO/ZnS/α-Fe2O3 nanocomposites

In order to achieve effective, economic, and easily achievable photocatalyst for the degradation of dye methyl orange (MeO), ZnO, ZnO/ZnS and ZnO/ZnS/α-Fe₂O₃ nanocomposites were prepared by simple chemical synthetic route in the aqueous medium. Phase, crystallinity, surface structure and surface behavior of the synthesized materials were determined by X-ray diffraction (XRD) and Brunauer–Emmett–Teller analysis (BET) techniques. XRD study established formation of good crystalline ZnO, ZnO/ZnS and ZnO/ZnS/α-Fe₂O₃ nanomaterials. By using intensity of constituent peaks in the XRD pattern, the compositions of nanocomposites were determined. From the BET analysis, the prepared materials show mesoporous behavior, type IV curves along with H4 hysteresis. The ZnO/ZnS/α-Fe₂O₃ composite shows the largest surface area among three materials. From the UV–visible spectra, the band gap energy of the materials was determined. Photoluminescence spectra (PL) were used to determine the emission behavior and surface defects in the materials. In PL spectra, the intensity of UV peak of ZnO/ZnS is lowered than that of ZnO while in case of ZnO/ZnS/α-Fe₂O₃, the intensity further decreased. The visible emission spectra of ZnO/ZnS increased compared with ZnO while in ZnO/ZnS/α-Fe₂O₃ it is further increased compared with ZnO/ZnS. The as-synthesized materials were used as photocatalysts for the degradation of dye MeO. The photo-degradation data revealed that the ZnO/ZnS/α-Fe₂O₃ is the best photocatalyst among three specimens for the degradation of dye MeO. The decrease of intensity of UV emission peak and the increase of intensity of visible emission cause the decrease of recombination of electrons and holes which are ultimately responsible for the highest photocatalytic activity of ZnO/ZnS/α-Fe₂O₃.