Simulations of the surfaces of soda lime aluminoborosilicate glasses exposed to water

Molecular dynamics simulations of 7 compositionally different sodium calcium alumino‐borosilicate glasses showed formation of ⁴B and ⁵Al more consistent with experimental data without compromising the other structural features that match experimental results observed in recent simulations of these glasses. Analysis of the dry surfaces of these glasses show a lack of ⁴B in the top 5‐6 Å of the surface in comparison to the bulk concentration for all glasses and no ⁵Al. Upon exposure to water, the simulations show that the ³B in the top 5‐6 Å of the glasses are preferentially attacked, decreasing the number of B bonds to O originally from the glass, indicating a change in the glass network. Inclusion of all B–O bonds in the top 5‐6 Å (i.e., including O from water) shows a decrease in ³B but an increase in ⁴B that is consistent with NEXAFS analysis, which the simulations show are hydroxylated. There is an increase in the concentration of ³Al in the dry surface in comparison to the bulk, but exposure to water converts almost all of these ³Al to ⁴Al. Hydroxyl concentrations vary from 2.6/nm² to 4.1/nm², with SiOH and BOH dominating these surface hydroxyls. Upon exposure to water, network linkages to B are preferentially ruptured. This, and the preferential loss of the nonbridging oxygen sites attached to Na, provide atomistic evidence of the initial stages of removal of B and Na from glass surfaces exposed to water.     

Adhesion Between Plasma-Treated Polypropylene Films and Thin Aluminum Films

Polypropylene (PP) film was treated with radio-frequency-induced oxygen plasma, followed by the vacuum deposition of aluminum (Al) thin film, and the peel strength of the Al deposited PP film (Al/PP) was examined. The peel strength of plasma-treated PP film varied widely in the range of 6.7 to 157 N/m depending upon the plasma treatment conditions, whereas that of the untreated PP was 5.2 N/m. The peel strength was minimized at oxygen pressure near 13.3 Pa (0.1 Torr), and decreased with increasing discharge power. The peel strength rapidly increased at the initial stage of plasma treatment (∼ several seconds), decreased at the second stage, and slightly increased again at the third stage. A good agreement was found between the peel strength of Al/PP and the amounts of oxygen introduced onto the PP surface at the initial stage. A short-time treatment was very effective to improve the adhesion of Al/PP. At the end of the second stage, a large amount of carbon was detected by XPS on the Al layer of the peeled interface of Al/PP, which gave a minimum peel strength. Cohesive failure of PP film might have occurred. SEM photograph showed that PP surface was etched by oxygen plasma at the thrid stage. These peel behaviors of Al/PP were explained by the chemical and physical changes of the PP surface caused by oxygen plasma treatment: (1) introduction of O-functional groups onto the PP surface at the initial stage, (2) formation of weak booundary layers resulting from the partial scission of PP molecules at the second stage, and (3) plasma etching of the PP surface at the third stage.     

Structure and composition of surface depletion layers in poled aluminosilicate glasses

Thermal poling processes can be used to form modified surface layers on glass that, under ion-blocking electrode conditions, are depleted of virtually all network-modifying cations relative to the network-forming species. During this process, many outstanding questions remain as to the structure of these layers and how it may vary between glasses of different “parent” composition, with important implications for resultant surface properties and industrial applications of this technology. This phenomenon of depleting modifiers is particularly difficult to rationalize in aluminosilicate glass compositions, where—in the parent glass—aluminum ions are predominantly present as cation-charge-compensated [AlO4]⁻ tetrahedra prior to poling. Here, we present results of a detailed investigation into the surface depletion layers formed across a wide range of ternary sodium aluminosilicate (NAS) glasses, applying a host of surface-sensitive spectroscopy methods to directly interrogate the resulting composition and structure within the Na-depleted, anode-side surface layers. The desired depletion layers were successfully formed on all of the NAS glasses attempted, all showing (a) near-complete depletion of alkali within 300-500 nm-thick layers on the anode-side surfaces, (b) thin zones of Al depletion with the Na-depleted layer, and (c) the absence of injected H⁺ ions that could serve as an alternative charge-compensation mechanism. These data essentially confirmed a true binary Al₂O₃–SiO₂ composition inside the depletion layers. However, no significant structural dependence was found as a function of parent glass, where initial compositions ranged from peralkaline to charge-balanced. Importantly, TEM imaging showed the depletion layers to be fully amorphous and homogeneous (not phase-separated) at the nanoscale, despite final compositions in the range of 5-33 mol% Al₂O₃—a composition space notoriously prone to phase-separation if prepared by conventional melting. Within the depletion layers, ELNES and TEY-XANES evidence is shown for retention of Al in a 4-coordinated state, along with XPS data indicating elimination of non-bridging oxygen. Taken as a whole, our results indicate a highly-connected aluminosilicate network, most likely with a relatively high concentration of 3-coordinated oxygen—or O “triclusters”—as a plausible means of charge-compensating 4-coordinated Al in the absence of Na⁺ or H⁺. The combined results of this work provide convincing new evidence for unique glass structures within the depletion layers not achievable through analogous melt pathways, with important implications for surface properties.     

Evaluation of citric acid added cleaning solution for removal of metallic contaminants on Si wafer surface

We have investigated cleaning solutions based on citric acid (CA) to remove metallic contaminants from the silicon wafer surface. Silicon wafers were intentionally contaminated with Fe, Ca, Zn, Na, Al and Cu standard solution by spin coating method and cleaned in various CA-added cleaning solutions. The concentration of metallic contaminants on the silicon wafer surface before and after cleaning was analyzed by vapor phase decomposition/inductively coupled plasma-mass spectrometry (VPD/ICP-MS). And the surface micro-roughness was also measured by atomic force microscopy (AFM) to evaluate the effect of cleaning solutions. It was found that acidic CA/H₂O solution has the ability to remove metallic contaminants from silicon surfaces. Fe, Ca, Zn and Na on silicon surface were decreased from the order of 10¹² atoms/cm² to the order of 10⁹ atoms/cm² even at low CA concentration, low temperature of CA solution and with short immersion time. CA was also effective in alkali cleaning solution. Fe, Ca, Zn, Na and Cu were reduced down to the order of 10⁹ atoms/cm² in CA added with NH₄OH/H₂O₂/H₂O solution without degradation of surface micro-roughness.     

Na2SiO3电解液体系中CaCl2/MgCl2加入量对Ti6Al4V合金微弧氧化膜层特性的影响

本文以Na2SiO3为基础电解液体系,加入一定量的CaCl2及MgCl2,对Ti6Al4V合金表面进行微弧氧化,研究CaCl2及MgCl2的加入对Ti6Al4V合金表面微弧氧化膜形成过程及其特性的影响规律。试验结果表明:CaCl2及MgCl2加入量从0.05g/L增加到0.35 g/L的过程中,正向起弧电压分别从350V增加至358V、330V增加至369V。SEM形貌分析显示,随着电解液中CaCl2的加入量增加,氧化膜层表面的孔洞减少,膜层表面出现直径约为5μm的颗粒状陶瓷,膜层变得疏松;MgCl2的加入量增加,氧化膜表面孔洞减少。EDS分析结果显示加入CaCl2、MgCl2的电解液中获得的膜层组成元素分别是Ti、Na、Al、Si、P、O,与基础电解液体系相比较,Ca元素有所增加,Mg元素变化不明显。XRD分析结果表明,CaCl2加入到电解液中出现了更多的金红石相TiO2的衍射峰;MgCl2加入电解液中之后,锐钛矿相TiO2有所增加。     

Partial Oxidation and Dry Reforming of Methane Over Ca/Ni/K(Na) Catalysts

Partial oxidation and dry reforming of methane to synthesis gas over Ca/Ni/K(Na) catalysts have been studied. Effects of temperature, pressure, and oxygen/methane ratios on catalytic activity, selectivity, and carbon formation have been determined. Also reforming of ¹³CH₄ in the presence of CO₂ and Temperature-Programmed Oxidation (TPO) of deposited carbon after the reaction indicated that both methane and CO₂ contribute to carbon formation. The TPO of deposited carbon on Ca/Ni/K catalyst showed that the catalyst consumed a significant amount of oxygen, only a fraction of which was consumed by carbon species on the surface, indicating that the surface oxygen plays a significant role in oxidizing and removing carbon species from the catalyst surfaces     

Protective Effect of N-Acetylserotonin against Acute Hepatic Ischemia-Reperfusion Injury in Mice

The purpose of this study was to investigate the possible protective effect of N-acetylserotonin (NAS) against acute hepatic ischemia-reperfusion (I/R) injury in mice. Adult male mice were randomly divided into three groups: sham, I/R, and I/R + NAS. The hepatic I/R injury model was generated by clamping the hepatic artery, portal vein, and common bile duct with a microvascular bulldog clamp for 30 min, and then removing the clamp and allowing reperfusion for 6 h. Morphologic changes and hepatocyte apoptosis were evaluated by hematoxylin-eosin (HE) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, respectively. Activated caspase-3 expression was evaluated by immunohistochemistry and Western blot. The activation of aspartate aminotransferase (AST), malondialdehyde (MDA), and superoxide dismutase (SOD) was evaluated by enzyme-linked immunosorbent assay (ELISA). The data show that NAS rescued hepatocyte morphological damage and dysfunction, decreased the number of apoptotic hepatocytes, and reduced caspase-3 activation. Our work demonstrates that NAS ameliorates hepatic IR injury.     

Effect of Surface and Oxygen Coverage on Ethylene Epoxidation

Ethylene epoxidation was studied as a function of oxygen coverage; for three different surfaces (111), (100) and (110) of three different IB metals using periodical DFT calculations. Oxygen coverage dependence was tested for 11, 25 and 33?% surface oxygen on Ag(111) surface. Calculations showed that increasing oxygen amount increased the exothermicity of the reaction while lowering the activation barriers. At studied oxygen ratios ethylene oxide and acetaldehyde formations proceed through OMC intermediate. In agreement with earlier studies, predicted selectivity is independent of surface structure. Generally the activation barriers for aldehyde formation are lower than those for epoxide formation on the studied surfaces. On copper surfaces the high stability of the precursor intermediates caused high activation barriers for the product formations. Also, epoxide formation is endothermic with respect to pre-oxygenated copper surfaces. On the other hand gold surfaces showed the smallest activation barriers for the product formations. Ag surfaces did not show conclusive differences for the activation barriers for epoxide versus aldehyde formation, which is in agreement with the ~50?% EO selectivity of the un-promoted metallic silver.     

An XPS study of argon ion beam and oxygen RIE modified BPDA-PDA polyimide as related to adhesion

Modification of polymer surfaces by changing the chemical structure, surface energy, and bonding characteristics has considerable technological importance in the area of adhesion. Reactive ion etching (RIE) and ion beam (IB) bombardment were employed to modify the surfaces of fully imidized 3,3',4,4'-biphenyl tetracarboxylic acid dianhydride-p-diaminophenyl (BPDA-PDA)-based polyimide (PI) films. These modification techniques affect only a shallow surface region, approximately 10-20 nm, and the bulk properties of the polymer are unaffected. The angle-resolved X-ray photoelectron spectroscopy (XPS) technique was used to characterize the PI surfaces modified by argon IB bombardment or oxygen RIE treatment. On the argon ion-bombarded surfaces, the XPS spectra indicate that the carbonyl and imide groups are decreased. Oxygen RIE treatment resulted in an increase in the atomic concentration of oxygen. To understand the surface aging effect, the freshly modified PI surfaces were exposed to laboratory air for 1 and 2 days. The changes in composition as a function of the depth of the modified surface region right after treatment and after aging were determined by the angle-resolved XPS technique (ARXPS). Contact angle measurements were used to determine the polar and dispersion components, the sum of which is the surface free energy. The polar component of the surface free energy shows the greatest change, with an increase of 8.0-9.4 times for both the oxygen RIE and ion beam treatments as compared with the as-cured PI surface. Aging of these modified surfaces resulted in a decrease of surface free energy as compared with the just-modified surfaces. In the case of oxygen RIE treatment, the dispersion component of the surface free energy showed little or no change from the as-cured sample. Adhesion of chromium/copper/chromium (Cr/Cu/Cr) films on PI was determined by peel strength measurements. Significant increases in peel strength, by a factor of 10-80, were shown for the modified surfaces. A good correlation between the peel strength and the experimentally determined polar component of surface energy was shown.     

Ionic Conductivity in Sodium–Alkaline Earth–Aluminosilicate Glasses

The effect of alkaline‐earth ions on Na transport in aluminosilicate glasses was studied by measuring ionic conductivity for a systematic compositional series of Na₂O–RO–Al₂O₃–SiO₂ glasses (R=Mg, Ca, Sr, Ba). The Na transport in aluminosilicate glass could be affected by compositional changes in aluminum coordination and nonbridging oxygen as well as physical properties such as dielectric constant, shear modulus, and ionic packing factor. Through careful experimental designs and measurements, the main determinants among these parameters were identified. ²⁷Al MAS‐NMR indicated that all aluminum species contained in these glasses are four‐coordinated. The activation energy for ion conductivity decreased with increasing aluminum content and decreasing ionic radii of the alkaline‐earth ion in the region where [Al] < [Na]. When the aluminum content exceeded the sodium content ([Al] > [Na]), the composition dependence of the activation energy depended on the specific alkaline earth. These results are explained based on variations in free volume and dielectric constant caused by structural changes around the AlO₄ charge compensation sites. These structure changes occur in response to the smaller size and higher field strength of the alkaline‐earth ions, and are most prevalent in the compositions which require bridging of two AlO₄ sites by the alkaline‐earth ion for charge compensation.     

Electrochemical behaviour of Ni + Al alloy as an alternative material for molten carbonate fuel cell cathodes

This paper presents an investigation of the performance and stability for oxygen reduction on in situ oxidized Ni alloys, specially focused on 95 at % Ni + 5 at % Al and 85 at % Ni + 15 at % Al alloy electrodes in Li/Na carbonate eutectic. Test specimens of the alloys were prepared as thin film electrodes sputtered onto Au substrates. In situ oxidation of alloy electrodes and electrochemical measurements for oxygen reduction on the electrodes were performed in the free-volume melt at 923 K. It was found that the in situ oxidized Ni + Al alloys exhibit higher performance for the oxygen reduction than the NiO without Al. Electrochemical fractal analysis (EFA) revealed higher oxide film stability of the Ni + Al alloys in comparison to NiO electrodes. The surface morphology of the alloy specimen after oxidation was investigated with SEM and AFM.     

钠离子对合成愈创木酚催化剂的影响

在微型固定床连续流动反应装置上评价催化剂,研究了碱金属离子对合成愈创木酚催化剂AlPTiSbO性能的影响,结果显示碱金属离子对催化剂有较大的影响。优化了催化剂中钠离子的含量,发现最佳的钠铝原子比为0．045。在此催化剂上,280℃,常压下,愈创木酚的选择性为98％,邻苯二酚的转化率达到92％,催化剂稳定性也明显增加。采用BET,XRD,XPS和NH3-TPD等技术对催化剂进行了表征。结果显示,添加钠离子后,催化剂的比表面积有所增加;催化剂中磷酸盐（钠）含量增加;催化剂的表面酸强度降低。     

Surface composition of carbon fibers subjected to oxidation in nitric acid followed by oxygen plasma

Type II, PAN-based carbon fibers (unsized and commercially treated) have been exposed to nitric acid and oxygen plasma individually and also to combined nitric acid/oxygen plasma treatments and the surface compositions have been determined using angle-resolved X-ray photoelectron spectroscopy (ARXPS) and ion scattering spectroscopy (ISS). Most of the oxygen on the as-received carbon fibers resides within the outermost 10-15 Å of the surface. Fiber exposure to nitric acid at 115°C for 20-90 min enhances the oxygen surface concentration to a point of saturation and the oxygen depth distribution is increased and becomes more uniform within the maximum XPS sampling depth (~60-100 Å). In addition, the fiber surface area is believed to be increased. After treating fibers to various degrees in nitric acid, subsequent exposure to oxygen plasma yields an additional increase in the surface oxygen content, particularly in the outermost fiber layers (10-15 Å). Under the conditions of the investigation, the maximum amount of surface oxidation occurs after sequential fiber exposure to nitric acid at 25°C for 30 s and oxygen plasma. As the extent of initial nitric acid treatment is increased, the synergism with subsequent plasma oxidation decreases, and the oxygen concentration becomes more uniform within the outer layers of the oxidized fibers. Overall, the data are consistent with a proposed oxidation mechanism in which oxygen plasma acts to enhance the surface density of oxygen on roughened and pitted nitric acid-oxidized fiber surfaces. As the duration of nitric acid exposure is increased, it is hypothesized that subsequent exposure to oxygen plasma smoothes the fiber surfaces but the surface density of oxygen remains essentially constant.     

Na2O-Al2O3-Fe2O3系烧结过程中铝、铁的反应行为

以Al2O3, Fe2O3和Na2CO3为原料,对Na2O-Al2O3-Fe2O3系烧结过程中的反应行为进行了详细研究. 基于溶出率与时间、温度的关系,证明Na2O×Al2O3和Na2O×Fe2O3的生成反应动力学都服从Zhuralev-Lesokin-Tempelman模型,表观活化能分别为186.59和80.92 kJ/mol,表明Na2O×Fe2O3比Na2O×Al2O3在动力学上更易形成;Al2O3易与Na2O×Fe2O3反应形成Na2O×Al2O3和Fe2O3,在1273 K烧结30 min,所得熟料Al2O3溶出率达98.51%;Fe2O3对Na2O×Al2O3的形成有双重作用,在1273 K下可加速Na2O×Al2O3的形成,超过1323 K,促使Na2O×Al2O3分解成Na2O和b-Al2O3,且随着温度升高或时间延长,分解程度增高,从而导致熟料中Al2O3溶出率显著降低.     

Use of seydişehir alumina as a support for CO oxidation catalysts

An Al 2 O 3 sample obtained from Seydi y ehir Eti Alüminyum A. z was treated and characterized for its potential use as a catalyst support. Atomic absorption spectroscopy and flame photometry characterization revealed the presence of 95.52% Al 2 O 3 , 4.44% Na 2 O, and 0.043% Fe 2 O 3 in the original sample. Both n -Al 2 O 3 and f -Al 2 O 3 phases were identified in the crystalline structure by X-ray diffraction analysis. However, f -Al 2 O 3 was found to be the phase in abundance. The BET surface area of the original sample was found to be 40.85 m 2 /g. The original sample was treated in various concentrations of hydrochloric acid to remove Na 2 O impurity. The acid concentration was optimized for the Na 2 O removal efficiency and surface area enhancement. The optimum HCl concentration was found to be 1 M. 1 Pt/Al 2 O 3 catalysts prepared from these supports and a reference support (Johnson Matthey n -Al 2 O 3 ) were tested for CO oxidation reactions. Catalysts prepared fromSeydis¸ehir alumina showed reasonable activity for the CO oxidation reaction.     

Thermal Behavior of Silver in Ion-Exchanged Soda-Lime Glasses

The refractive index and the nonlinear optical properties of sodium silicate glass can be easily tailored by replacing the sodium with silver. However, the thermal responses of silver and the corresponding modifications of the silica (SiO₂) network in ion-exchanged glass under heating are still not clear. X-ray photoelectron spectroscopy has been used to study the in-situ behavior of silver and SiO₂networks on the surfaces of silver-ion-exchanged-content soda-lime glasses during heating and cooling processes under ultrahigh vacuum. Temperature-dependent concentration changes and oxidation states have been monitored. The results show that silver diffuses toward the surface, precipitates, and crystallizes during heating, and the total silver surface concentration is slowly increased during cooling. The concentration changes and binding-energy shifts of oxidized and neutral silver atoms, a new nonbridging oxygen species (NBO*), and a new silicon species (Si[a]) have been applied to deduce a disappropriation reaction mechanism of the Ag+ ion on the surface during annealing. The SiO2 network is modified at temperatures of <350°C to accommodate more silver on the surface and to balance the extra charge that is carried by the Ag+ ion. The fact that the SiO2 network polymerizes during annealing has been deduced from the results of the higher binding energies of Si 2_p and O 1s after annealing. This observation is of importance in optimizing the distribution of the ion-exchanged silver and in the formation of silver-metal colloids in glass networks.     

Kinetics and mechanism of the oxygen electroreduction reaction on faceted platinum electrodes in trifluoromethanesulfonic acid solutions

The kinetics of the oxygen electroreduction reaction (OERR) were investigated on (1 1 1)-type and (1 0 0)-type faceted, and polycrystalline platinum electrodes in aqueous (0.05–1.0)m trifluoromethanesulfonic acid (TFMSA) using the rotating disc and ring-disc electrode techniques at 25°C. Reaction orders with respect to oxygen close to either 1/2 or 1 were found, depending on the TFMSA concentration and platinum surface morphology. At all TFMSA concentrations the formation of H₂O₂ was enhanced at (1 0 0)-type platinum surfaces. The difference in the electrocatalytic activity of platinum surfaces can be explained through data derived from the OERR formalism proposed by Damjanovicet al. The rate of the direct O₂ to H₂O electroreduction reaction increased steadily with the cathodic overvoltage irrespective of the platinum surface morphology, whereas a maximum H₂O₂ formation rate was found at about 0.5 V, depending on the TFMSA concentration. The H₂O₂ decomposition rate on (1 0 0)-type platinum electrode yielding H₂O approached zero within a certain potential range.     

Molecularly Resolved Studies of the Reaction of Pyridine and Dimethylamine with Oxygen at a Cu(110) Surface

Pyridine and dimethylamine have been studied at clean and oxidised Cu(110) surfaces as model systems for the interaction of amines with heterogeneous catalysts using scanning tunnelling microscopy and X-ray photoelectron spectroscopy. Both molecules interact strongly with sub monolayer concentrations of chemisorbed oxygen causing a change from the well known p(2×1)O(a) islands to a (3×1) structure. XPS shows a 1:1 correspondence between the concentration of surface oxygen and that of chemisorbed pyridine but the stoichiometry of the dimethylamine/oxygen system could not be directly measured because of a slow reaction which results in the desorption of oxygen as water and the formation of a chemisorbed amide. The amide also decomposes at room temperature and desorbs leaving a clean surface. However, the 2:1 stoichiometry of the dimethylamine/oxygen reaction suggests a 1:1 dimethylamine:oxygen ratio in the (3×1) structure. The results of the study are interpreted in terms of an amine–oxygen complex, which may provide a general model for the interaction of amines with oxygen at metal surfaces.     

Effect of Atmospheric Plasma Treatment on Carbon Fiber/Epoxy Interfacial Adhesion

In this work the effect of atmospheric plasma treatment on carbon fiber has been studied. The carbon fibers were treated for 1, 3 and 5 min with a He/O₂ dielectric barrier discharge atmospheric pressure plasma. The fiber surface morphology, surface chemical composition and interfacial shear strength between the carbon fiber and epoxy resin were investigated using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and the single fiber composite fragmentation test. Compared to untreated carbon fibers, the plasma treated fiber surfaces exhibited surface morphological and surface composition changes. The fiber surfaces were found to be roughened, the oxygen content on the fiber surfaces increased, and the interfacial shear strength (IFSS) improved after the atmospheric pressure plasma treatment. The fiber strength showed no significant changes after the plasma treatment.     

Chemical and morphological analyses of zinc powders for alkaline batteries

Zinc powders containing Bi, In and either Mg or Al were analyzed to determine chemical and morphological differences. Morphology and chemistry may influence the reactivity of Zn powders in the basic environment found inside alkaline batteries. Increased reactivity leads to increased Zn corrosion, increased hydrogen gas evolution, and possibly leakage of the battery electrolyte. The surface chemistry of the powders was examined using Auger electron spectroscopy, X-ray photoelectron spectroscopy, and atomic absorption spectroscopy to check for surface ZnO. Powder chemistry was measured using an electron probe micro analyzer equipped with an energy dispersive X-ray analyzer. Inert gas fusion determined the bulk oxygen content. Morphology studies included powder sieving for size determination, examining loose powders with a scanning electron microscope (SEM), and determining surface areas via Brunauer, Emmet, and Teller (BET) analyses. SEM images showed differences in powder shapes and surface conditions between passed and failed powders. Powders exhibiting smooth surfaces and regular shapes were more likely to pass gas testing. However, pass/fail gas test results could not be correlated to powder chemistry, powder size, or surface area. Powder roughness and irregularity may indicate an increase in the number of active sites such as peaks and barbs versus particles with smooth surfaces.