Small Amounts Of Oxides Research Articles

Printable tiny thermocouple by liquid metal gallium and its matching metal

Direct printing of thermocouples by the liquid metal was proposed. The fabricated temperature sensor composed of gallium and its matching metal exhibited excellent linear dependence between thermoelectric voltage and temperature within the range from 0 to 200 °C. Further, it was disclosed that liquid metals with high purity could be used for high precision thermocouples with tiny size, which were quite convenient to be used in micro channel measurement due to their fluidity in making sensors; while liquid metals with a small amount of oxides were handy for depositing on the substrate by “hand-written” style, with thin film thickness of approximately 50 μm.

Supersaturated Ni-10 wt% Ti Alloys Fabricated by Mechanical Alloying and Plasma Spraying

A supersaturated Ni-10Ti alloy powder was produced from Ni and Ti elemental powders by solid state synthesis utilizing high energy mechanical alloying with times up to 5 h. Then, the milled powders were deposited on AISI 304 stainless steel substrate using air plasma spraying (APS) process. The microstructure and phase composition of the products were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The results indicated that the coatings contain Ni–Ti supersaturated solid solution and small amounts of oxides. The microhardness value for the deposited layer was comparable to that of as-milled powder. Further investigation showed that the corrosion performance of Ni-10Ti coating was comparable to that of AISI 304 stainless steel substrate.

Performance study of a water ramjet engine

A performance study of a water ramjet engine is described. The engine is powered by the reaction of a magnesium-based propellant and ingested water. In this study, a solid propellant, which consisted of a large percentage of magnesium, a binder and a small amount of oxidant, was used as a hydro reactive fuel. Cold water was injected into the combustion chamber as a main oxidant. A scaled-down experimental engine was tested in a direct-connect ground testing system to characterize the factors influencing the engine performance. The results show that the increasing of total water/fuel ratio, an addition of secondary water intake along the combustion chamber, a larger magnesium content in the solid propellant, a smaller primary water injection angle towards the coming main flow, and a higher primary injection pressure were all able to promote the engine performance. The maximum engine performance was obtained in test 08, and with all tests, an appropriate set of parameters and conditions for the optimum engine performance were determined

ChemInform Abstract: Vibrational Spectra of Niobium(V) Fluoro and Oxo Fluoro Complexes Formed in Alkali-Metal Fluoride Melts.

Raman spectra of the molten system LiF-NaF-KF-K 2 NbF 7 at 650°C indicate the presence of NbF 7 2− ions. With the addition of small amounts of oxide, vibrational frequences due to a NbOF n (n-3)− species are observed at 921 (p), 583 (p) and 307 cm −1 (dp) for oxide to niobium(V) mole ratios up to approximately 2. Infrared spectra of solidified melts support the existence of a niobium-oxygen double bond in this complex. The vibrational spectrum is in accord with the band pattern of monomeric NbOF 5 2− with a C 4v symmetry

An X-ray photoelectron study of the (Ca2.5Th0.5)Zr2Fe3O12, (Ca1.5GdTh0.5)(ZrFe)Fe3O12, and (Ca2.5Ce0.5)Zr2Fe3O12 ceramics with a garnet structure

X-ray photoelectron spectroscopy (XPS) was for the first time applied to examination of the (Ca2.5Th0.5)Zr2Fe3O12 (I), (Ca1.5GdTh0.5)(ZrFe)Fe3O12 (II), and (Ca2.5Ce0.5)Zr2Fe3O12 (III) ceramics with a garnet structure. The component ratio in the initial charge was set so as to obtain phases with a garnet structure, promising as matrices for immobilization of long-lived actinides. Gadolinium was introduced as a neutron absorber and a simulator of trivalent actinides, Am and Cm. Ceramics I and III are comprised primarily of a phase with a garnet structure and contain a small amount of oxides with the perovskite and fluorite structures; ceramics II consists entirely of a phase with a garnet structure. The oxidation states of the metal ions in the ceramics, as well as the Me-O interatomic distances in the phase structure, were determined by XPS. To this end, both traditional characteristics (line intensities and energy positions) of the X-ray photoelectron spectra of inner electrons and the fine-structure characteristics of the spectra of the valence and inner electrons were used. A change of the composition of the surface of ceramics II and III upon treatment with 0.01 HCl solution at 150°C and the saturated vapor pressure for 30 days was examined.

The Mechanism of Direct Heme Transfer from the Streptococcal Cell Surface Protein Shp to HtsA of the HtsABC Transporter

The heme-binding proteins Shp and HtsA are part of the heme acquisition machinery found in Streptococcus pyogenes. The hexacoordinate heme (Fe(II)-protoporphyrin IX) or hemochrome form of holoShp (hemoShp) is stable in air in Tris-HCl buffer, pH 8.0, binds to apoHtsA with a K(d) of 120 +/- 18 microm, and transfers its heme to apoHtsA with a rate constant of 28 +/- 6s(-1) at 25 degrees C, pH 8.0. The hemoHtsA product then autoxidizes to the hexacoordinate hemin (Fe(III)-protoporphyrin IX) or hemichrome form (hemiHtsA) with an apparent rate constant of 0.017 +/- 0.002 s(-1). HemiShp also rapidly transfers hemin to apoHtsA through a hemiShp.apoHtsA complex (K(d) = 48 +/- 7 microM) at a rate approximately 40,000 times greater than the rate of simple hemin dissociation from hemiShp into solvent (k(transfer) = 43 +/- 3s(-1) versus k(-hemin) = 0.0003 +/- 0.00006 s(-1)). The rate constants for hemin binding to and dissociation from HtsA (k'(hemin) approximately 80 microm(-1) s(-1), k(-hemin) = 0.0026 +/- 0.0002 s(-1)) are 50- and 10-fold greater than the corresponding rate constants for Shp (k(hemin) approximately 1.6 microM(-1) s(-1), k(-hemin) = 0.0003 s(-1)), which implies that HtsA has a more accessible active site. However, the affinity of apoHtsA for hemin (k(hemin) approximately 31,000 microm(-1)) is roughly 5-fold greater than that of apoShp (k(hemin) approximately 5,300 microM(-1)), accounting for the net transfer from Shp to HstA. These results support a direct, rapid, and affinity-driven mechanism of heme and hemin transfer from the cell surface receptor Shp to the ATP-binding cassette transporter system.

Morphological study of supported thin Pd and Pd–25Ag membranes upon hydrogen permeation

Morphological change of Pd and Pd–25Ag membranes supported by V–15Ni alloy upon hydrogen permeation was investigated in the temperature range 423–673 K. The supported Pd–25Ag membrane exhibited higher resistance to hydrogen-induced cracking and grain growth than the supported Pd membrane. Long-term permeation of Pd–25Ag/V–15Ni composite membrane was carried out at 573 and 673 K for 200 h. There was no strong metallic interdiffusion between the Pd–25Ag membrane and the V–15Ni support after the long-term permeation at 573 K but small amounts of oxide had formed on the surface of Pd–25Ag membrane. Whisker and fissure-oxide morphologies were dominant on the exit and entrance side of the Pd–25Ag/V–15Ni composite membrane, respectively, accompanied by severe metallic interdiffusion after the long-term permeation at 673 K. AES and FE-SEM results revealed that metallic interdiffusion and selective oxidation of vanadium were responsible for the deterioration of Pd–25Ag membrane at 673 K. Hydrogenation–dehydrogenation of Pd and Pd–25Ag membranes supported by stainless steel and V–15Ni alloy were in situ examined by an optical microscope. The formation of hydride was uniform in the Pd/V–15Ni sample but localized in the Pd–25Ag/V–15Ni sample, suggesting that the hydrogen transfer through interface was strongly dependent on the composition of Pd alloy membranes. As for the stainless steel supported samples, both Pd and Pd–25Ag membranes had fractured.

Synthesis and Properties of Oligodeoxynucleotide Analogs with Bis(methylene) Sulfone Bridges

AbstractA convergent, solution‐phase synthesis was developed for the bis(methylene) sulfone‐bridged oligodeoxynucleotide analogs (SNA) 5′‐d(HOCH2‐Tso2Tso2Tso2Cso2Tso2Tso2Tso2T‐CH2SO$\rm{_{3}^{-}}$)‐3′ (35b) and 5′‐d(HOCH2‐Tso2Tso2Tso2Tso2Tso2Tso2Tso2T‐CH2SO$\rm{_{3}^{-}}$)‐3′ (34c) (SO2 corresponds to CH2SO2CH2 instead of OP(O)(O−)(O). In these, the phosphodiester linkages are replaced by non‐ionic bis(methylene) sulfone linkers. The general strategy involved convergent coupling of 3′,5′‐bishomo‐β‐D‐deoxyribonucleotide analogs functionalized at the 6′‐end (CH2C(5′)) as bromides or mesylates and at the CH2C(3′) position as thiols, with the resulting thioether being oxidized to the corresponding sulfone. A single charge was introduced at the terminal CH2C(3′) position of the octamers to increase their solubility in water. During the synthesis, it became apparent that the key intermediates generated secondary structures through either folding or aggregation in a variety of solvents. This generated unusual reactivity and was unique for very similar structures. For example, although the dimeric thiol d(BzOCH2‐Tso2C‐CH2SH) (14b) was a well‐behaved synthetic intermediate, the tetrameric thiol d(TrOCH2‐Tso2Tso2Tso2toC‐CH2SH) derived from the corresponding thioacetate was rapidly converted to a disulfide by very small amounts of oxidant (28→29, Scheme 6), while the analogous tetrameric thiol d(BzOCH2‐Tso2TsTso2T‐CH2SH) (26), differing only by a single heterocycle, was oxidized much more slowly (Bz=PhCO, Tr=Ph3C, to=2‐MeC6H4CO (at N4 of dc)). The sequence‐dependent reactivity, well known in many classes of natural products (including polypeptides), is not prominent in natural oligonucleotides. These results are discussed in light of the proposal that the repeating negative charge in nucleic acids is key to their ability to serve as genetic molecules, in particular, their capability to support Darwinian evolution. The ability of 5′‐d(HOCH2‐Tso2Tso2Tso2Cso2Tso2Tso2Tso2T‐CH2SO$\rm{_{3}^{-}}$)‐3′ (35b) to bind as a third strand to duplex DNA was also examined. No triple‐helix‐forming propensity was detected in this molecule.

Oxidation-Assisted Secondary Ion Mass Spectrometry Methodology to Quantify Mixed Alkylthiol Self-Assembled Monolayers on Gold: Applications to Competitive Chemical Adsorption

A novel ozone oxidation assisted secondary ion mass spectrometry (SIMS) methodology was developed. The method provides a direct and simple approach to quantify mixed alkylthiol self-assembled monolayers (SAMs) on gold with higher detection sensitivity. Ozone oxidation of alkylthiol SAMs on gold causes the rupture of thiol−gold covalent bonds and the conversion of alkanethiolate to alkyl sulfonate. With negative ion SIMS measurement, the secondary ion yields of alkyl sulfonate are much higher than those of any molecular ions which originate from covalently bound alkylthiols. Using the intensity of molecular ions originating from intact alkyl sulfonate molecules from oxidized mixed SAMs to quantify the original mixed SAMs on gold can improve detection sensitivity. In this paper, we report results on the optimization of conditions for ozone oxidation of mixed alkylthiol SAMs on gold. Optimization using a combination of X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry data demonstrated that a small amount of oxidation was sufficient to produce strong SIMS signals to quantify the composition of mixed alkylthiol SAMs on gold. We applied the optimized method to a case study of steric effects on competitive chemical adsorption of alkylthiols to gold. The results from the case study indicated that by conversion of alkanethiolate to alkyl sulfonate using ozone oxidation pretreatment, mixed SAMs on gold can be straightforwardly quantified by SIMS analysis. Further, steric effects controlling the relative adsorption probability and surface coverage of a component from a mixture can be quantified. The competitive adsorption probabilities with respect to 1-decanethiol are 0.2 for 1-butanethiol, 5 × 10-3 for 1-methyl-1-propanethiol, and 9 × 10-4 for 2-methyl-2-propanethiol. The molar concentration ratio that is needed to form 1:1 mixed short/long SAMs is 5:1 for 1-butanethiol/decanethiol, 200:1 for 1-methyl-1-propanethiol/decanethiol, and 1000:1 for 2-methyl-2-propanethiol/decanethiol.

Site-selective spectroscopy in dysprosium-doped chalcogenide glasses for 13-m optical-fiber amplifiers

Dy3+ -doped chalcogenide glasses are potential candidates for 1.3µm optical-fiber amplifiers. We describe spectroscopic characterization of Dy3+ -doped gallium lanthanum sulphide glasses with low and high oxide content. The spectroscopic investigations show that small amounts of oxide (1) in low-oxide-content sulphide glass create a second group of sites with a local environment different than that of the main sulphide sites. Dy3+ ions in the oxide site, which can constitute up to approximately one third of the total number of Dy3+ ions, experience a high-phonon-energy environment and do not show any 1.3µm emission and hence cannot provide gain for a potential 1.3µm optical-fiber amplifier in this material.

A fundamental model of platinum impregnation onto alumina

Refined forms of the revised physical adsorption Model (RPA) proposed by Agashe and Regalbuto (J. Coll. Interf. Sci. 185 (1997) 174) and a proton transfer model by Park and Regalbuto (J. Coll. Interf. Sci. 175 (1995) 239) were employed to model five sets of data of platinum (from chloroplatinic acid, CPA) adsorption over alumina found in the literature. Through a detailed individual consideration of ionic strength, which is the main cause of adsorption retardation at pH extremes, the results were further improved such that adsorption could be predicted a priori to a very reasonable degree without adjustable parameters. A comprehensive simulation of uptake as a function of initial platinum concentration, initial solution pH and the surface loading (amount of oxide surface per solution volume) shows that the model reflects all important features of adsorption typically seen in experimental studies and illustrates how it can be used to optimize the design of a catalyst impregnation. Over a range of low–moderate surface loadings corresponding to wet impregnation of relatively small amounts of oxide in excess solution, the diprotic chloroplatinic acid itself creates favorable electrostatic conditions and little or no pH adjustment is required to obtain full uptake of the available platinum from the solution (high “uptake efficiency”). At higher surface loadings corresponding to dry impregnation or pore volume filling that are more representative of industrial catalyst preparation recipes, however, the pH buffering effect of the oxide becomes so pronounced that additional acid is required to sufficiently charge the oxide surface and facilitate full platinum uptake. This offers a new interpretation of the often-cited necessity of excess hydrochloric acid in pellet impregnation at high surface loading, where a homogeneous metal distribution in the pellet is desired; the protons rather than the chloride ions may be the important factor. Furthermore, excessive amounts of platinum in solution (corresponding to an excess of a monolayer of Pt complexes at the surface) lead to self-inhibition based on high ionic strength in the solution and a dramatic drop in noble metal efficiency.

A novel polymer matrix method for synthesizing ZrO2 nanocrystals at moderate temperature

A novel polymer matrix method for synthesizing ZrO2 nanocrystals at moderate temperature

Thermal Functionalization of Hydrogen-Terminated Porous Silicon Surfaces with Terminal Alkenes and Aldehydes

AbstractH-terminated porous silicon (PSi) surfaces were chemically modified with terminal alkenes and aldehydes at high temperature to yield organic monolayers covalently attached to the surface through Si-C and Si-O-C bonds, respectively. Diffuse reflectance infrared Fouriertransform and X-ray photoelectron spectroscopies have been used to characterize the surfaces. Derivatized surfaces retain the PSi photoluminescence. Chemography was used to monitor the chemical changes of the PSi surface when exposed to 100% humidity in air. Organic monolayers linked through Si-C bonds are found to be highly resistant and have shown a better protection of the surface against corrosion compared to surfaces that are linked through Si-O-C bonds. The surface functionalized with ethyl undecylenate exhibits an even higher passivation of the surface through the presence of small amounts of oxide, which are induced by traces of water present in this chemical reagent, along with organic molecules attached to the surface.

PZT nanocomposites reinforced by small amount of oxides

Pb(Zr,Ti)O 3 (PZT) nanocomposites were prepared from high purity PZT powder and small amount (0·1–1·0 vol%) of oxides, i.e. Al 2O 3, MgO and ZrO 2. Effects of the additives on mechanical and piezoelectric properties of the nanocomposites were investigated. The fracture strength and hardness of PZT nanocomposites with 0·5 vol% Al 2O 3 or 0·1 vol% MgO additives were significantly improved. The reduced grain size of the nanocomposites is considered to be responsible for the excellent mechanical properties. Though the dielectric constants of the composites were decreased with an addition of Al 2O 3 or MgO, the planar electromechanical coupling factor, K p , of MgO-added composites was higher than that of Al 2O 3-added. As a consequence, the PZT/0·1 vol% MgO nanocomposite showed good mechanical and suitable piezoelectric properties. Addition of ZrO 2 had little effect on mechanical and electrical properties of the composites.

Adaptive Responses of Living Cells towards Low-Doses of Radiation : Induction of Endogenous Antioxidant System and Its Applicable Possibility for Treatment of Diseases

Bacteria and mammalian cells show an adaptive response to oxidative stress. Pre-treatment with small amounts of oxidant induces resistance to the subsequent, otherwise lethal, doses of oxidant. Previous studies have shown that this adaptive response involves the induction of superoxide dismutase (SOD), glutathione peroxidase (GPX), metallothionein, heat shock proteins, and other factors. The toxicity of ionizing radiation, particularly at low doses, to living cells, is thought to be due to reactive oxygen species (ROS) formation. Thus, adaptive responses to low doses of ionizing radiation and to oxidants are likely to be similar. In this paper, the induction of endogenous glutathione (GSH) together with antioxidant enzymes induced by low-dose radiation was reviewed. Futhermore, the applicable possibility of this efficacy for the prevention of and / or therapy of various reactive oxygen species (ROS)-related diseases including Parkinson's diseases, aging, and diabetes, was discussed.

Synthesis, cure analysis, and composite properties of allylated cyclopentadiene resins

AbstractAllylated cyclopentadiene was synthesized through the phase transfer reaction of cyclopentadiene and allyl chloride in the presence of a strong base. The reaction yielded a mixture of isomers with 2 to 6 allyl groups per cyclopentadiene ring. Variations in reactant ratios changed product ratios only slightly; however, lower ratios of allyl chloride to cyclopentadiene (4:1 and 2:1) produced lower substituted products. DSC analysis of the ACP showed thermal cure without added catalyst. The total enthalpy of cure was ∼750 J/g with a peak energy at 310°C. FTIR analysis of the thermal cure showed the predominate cure mechanisms to be ene reactions and polyadditions of allyl groups with a small amount of oxidation. Partial curing (B‐staging) of ACP was conducted thermally at 180 and 200°C. An increase in viscosity with time was found in each case with gelation occurring at ∼15 h and 3 h, respectively. ACP resin was also cured using various concentrations of peroxide and BF30 dibutyl etherate catalysts. In all cases gelled materials were formed. ACP/carbon fiber and ACP/glass fiber composites gave flexural moduli of 165 and 42 GPa, respectively. Flexural strength values were found to be 956 MPa for ACP/carbon and 681 MPa for ACP/glass. Treatment of ACP/carbon fiber composites in boiling water or refluxing toluene had no significant effect on their mechanical properties.

Surface oxide layers and the wetting temperature of alkali metals

It is now well known that at low temperatures liquid helium does not wet unoxidised caesium and rubidium surfaces. Recent experiments on rubidium have shown the unexpected result that its wetting temperature is considerably increased by a small amount of oxidation and it was suggested that this corresponds to a decrease in the electronic work function. We propose an idealised model for the interaction of helium with the surface of an oxidised alkali metal and find that it predicts that such a surface could indeed have a higher wetting temperature than the pure metal.

Sliding behavior of Pb-Sn alloys

A series of sliding tests of Pb-Sn alloy disks sliding against 52100 steel balls has been conducted in vacuum, air, Ar-5%H 2, nitrogen and with a lubricant. The wear tracks and the near-surface material have been characterized by optical microscopy, microhardness, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The friction coefficient is similar for a wide range of composition, from pure Pb to pure Sn. In vacuum, mineral oil, nitrogen and Ar 5%H 2, sliding is smooth and friction is low. The original lamellar structure of the eutectic alloy is unstable during sliding. The lamellae bend towards the sliding direction and break down during early stages of sliding, and the structure eventually becomes coarsened and equiaxed. The material near the surface work-softens and a negative hardness gradient is produced. In air, the friction coefficient and friction fluctuations are larger and two layers develop on the surface. The outer layer has a very fine grain size, while the underlying layer, between the fine-grained layer and the lamellar structure, is coarsened and equiaxed and is similar to that produced in vacuum. The fine-grained layer is a little harder, so the hardness gradient at the surface is positive. Small amounts of oxides, SnO 2 and SnO, have been found in this layer. Material transfer from the ball to the disk is not detected in any of these tests. However, material is transferred from the disk to the ball for sliding in both vacuum and air. Wear debris appeared only for the case of sliding in air. The results may be helpful in understanding the sliding behavior of soft bearing materials such as Babbitts. The results also suggest simple guidelines for the design of materials having low friction and smooth sliding at elevated temperatures.

Titanium Carbide Films Deposited by Laser Reactive Ablation

ABSTRACTTitanium carbide films were deposited on silicon wafers by laser reactive ablation. A pure titanium target placed inside a methane (CH4) atmosphere was irradiated by a XeCl excimer laser with a fluence of 5 J/cm2 and a repetition rate of 8 Hz. Experiments were performed at different values of the ambient pressure in order to investigate the influence of the deposition parameters on the film properties. Results show that at low pressure values (p< 10-5 mbar) the deposited layers are mainly constituted of metallic titanium whereas for pressure ranging from 10-5 to 10-1 mbar they are formed of titanium carbide (TiC) with small amount of oxides. The stoichiometry and thickness of the titanium carbide films can be controlled by the partial pressure of the atmosphere and the number of laser pulses, respectively.

High temperature sulfidation-oxidation of stainless steels

The alloys 153MA, 253MA and 353MA, Type 310S stainless steel, Type 309S stainless steel and IN601 were all exposed at 900 °C to a complex gas mixture of CO/CO2/SO2/N2, corresponding to a sulfur partial pressure of 1.3 x 10-3 atm and oxygen partial pressure of 3.2 x 10-l4 atm. The corrosion kinetics were parabolic in all cases. The rate for IN601 was unacceptably high due to extensive liquid sulfide formation. The other materials all formed solid external scales as well as undergoing some interna1 corrosion. The rates for all three MA alloys were less than those of the two conventional stainless steels. The corrosion behaviour of all the materials was dominated by sulfide formation as only relatively small amounts of oxides were formed. The same materials were exposed at 800 °C to a gas mixture corresponding to a sulfur partial pressure of 1.7 x 10-3 atm and an oxygen partial pressure of 4.9 x 10-l6 atm. No liquids were formed, and the corrosion products consisted of an outer scale layer of (Fe, Ni)l-xS, and an inner layer containing mixtures of sulfides and oxides. Reaction kinetics were again parabolic. The rates were rather similar, with IN601 reacting fastest, and 353MA slowest.