The structure of Cu- and Cd-UPD-layers on a stepped Pt(533) single crystal surface studied by grazing incidence XAFS, XRD and XPS

Small two-dimensional clusters and linear nanostructures of copper and cadmium were prepared electrochemically on the stepped surface of a (533) Pt single crystal. The deposition was performed under potentiostatic conditions in a solution of 0.001 M CuSO₄ or 0.005 M CdSO₄ in H₂SO₄ in the potential range of under potential deposition (UPD). The surface was examined with X-ray photoelectron spectroscopy (XPS) for quantification of the deposited amount. Grazing incidence X-ray absorption fine structure (GIXAFS) and grazing incidence X-ray diffraction (GIXRD) were used for determination of the adsorbate structure. The X-ray absorption and X-ray diffraction experiments were performed in-situ within the electrolyte at X-ray beam lines at HASYlab (DESY, Hamburg). Combining the results of the different methods, it was possible to reveal the structures of the metal adsorbates at several characteristic potentials in the UPD range.     

The oxidation of carbon monoxide on Rh(100) under steady state conditions: An FT-IR study

The steady-state oxidation of CO on clean Rh(100) at low pressures has been investigated using in-situ infrared spectroscopy and mass spectrometry. The results show that at a fixed CO pressure, the temperature at which the CO₂ formation rate maximizes decreases as a function of increasing O₂ pressure. Vibrational data indicate that this maximum rate coincides with a CO coverage of less than 0.01 monolayers.     

Studies on the surface free energy and surface structure of PTFE film treated with low temperature plasma

The surface free energy and surface structure of poly(tetrafluoroethylene) (PTFE) film treated with low temperature plasma in O₂, Ar, He, H₂, NH₃, and CH₄ gases are studied. The contact angles of the samples were measured, and the critical surface tension γ_c (Zisman) and γ_c (max) were determined on the basis of the Zisman's plots. Furthermore, the values of nonpolar dispersion force γ^a_s, dipole force γ^b_s, and hydrogen bonding force γ^c_s to the surface tensions for the plasma-treated samples were evaluated by the extended Fowkes equation. Mainly because of the contribution of polar force, the surface free energy and surface wettability of PTFE film which was treated with H₂, He, NH₃, Ar, and CH₄ for a short time increased greatly. Electron spectroscopy for chemical analysis (ESCA) shows that the reason was the decrease of fluorine and the increase of oxygen or nitrogen polar functional group on the surface of PTFE. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1733–1739, 1997     

A study on the crystal structure of palm oil-based whipping cream

The crystal structure of palm oil-based whipping cream was studied. Various proportions of refined, bleached, and deodorized palm oil (RBDPO) and palm kernel oil (RBDPKO) were prepared and their crystal structure and thermal profile were observed by an X-ray diffractometer and a differential scanning calorimeter, respectively. The results showed that all blends possessed a stable and shiny β′ polymorph at 25°C, which showed that RBDPO and RBDPKO were appropriate for producing a nondairy whipping cream. Some eutectic effect was observed in some blends, which was attributed to the complex combination of TAG in RBDPO and RBDPKO.     

Hydrogen evolution during the oxidation of formaldehyde on Au:: The influence of single crystal structure and Tl-upd

Hydrogen evolution during formaldehyde oxidation in alkaline solution has been monitored by Differential Electrochemical Mass Spectrometry on Au(111) and polycrystalline gold. The current efficiency for hydrogen evolution increases with higher concentration and is in the same range on both, polycrystalline Au and Au(111) electrode. The onset potentials and half-wave potentials are higher on Au(111). Reaction orders for the faradaic current on the bare gold electrodes have been determined as 0.21 for higher and 0.76 for lower concentrations. Reaction orders for hydrogen evolution during formaldehyde oxidation are 1.4 times higher in each case. Tafel slopes in the range of 140–160 mV are found. This signifies that the first reaction step involving the formation of adsorbed hydrogen is largely determining the overall reaction rate. In the presence of thallium adlayers hydrogen evolution from formaldehyde oxidation is largely suppressed. On the thallium modified polycrystalline Au, formaldehyde oxidation is shifted for 100 mV to higher potentials where Tl is partially desorbed and hydroxide is coadsorbed on the modified surface. On thallium modified Au(111), a similar process takes place, but in the same potential region as the onset of formaldehyde oxidation on the bare surface and therefore the formaldehyde oxidation is only slightly shifted. Tafel slopes are decreased to 80 mV/dec in the presence of thallium. In the presence of adsorbed thallium, the first reaction step is in equilibrium, the coverage with adsorbed hydrogen is smaller and its recombination to H₂ is largely suppressed.     

化学复合镀对LaMg2Ni6Mn3合金表面结构及电化学性能的影响

分别对AB3型贮氢合金(LaMg2Ni6Mn3)进行化学镀铜、化学镀镍及复合化学镀铜--镍合金.化学镀铜--镍合金后,最大放电容量由319 mA-h/g增大到390 mA-h/g,合金的容量衰减率从20%降至1%.X射线衍射结果显示,CuNi4O相和Mg2Ni3O相是导致合金最大放电容量增大以及循环稳定性增强的因素.扫...     

The substituent effects on the structure and surface morphology of polyaniline

In this work, poly(2‐fluoroaniline), poly(2‐chloroaniline), poly(2‐methylaniline), and poly(N‐ethylaniline) were prepared by a self‐assembly method using an oxidizing system consisting of a dopant anion, p‐toluene sulfonate with ammonium peroxydisulfate. The effects of substituents on the surface morphology, conductivity, molecular weight, spectral and thermal properties of the polymers were studied. SEM results revealed that the surface morphology of the resulting polymers changed from nanofiber to spherical structure by changing the substituent on the aniline monomers. The structure and properties of these conducting films were characterized by FTIR, UV‐vis, elemental analysis, TGA, conductivity, and cyclic voltammetry. The polymer films show electroactivity in monomer free solution. Molecular weight of the polymers was determined by gel permeation chromatography. The dry electrical conductivity values of the substituted‐polyanilines were found to be lower than that of PANI. The results revealed that the molecular structures of the polymers were similar to those of the emeraldine form of polyaniline. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The effects of Ni-addition on the crystal structure,thermal properties and morphology of Mg-based hydroxyapatites synthesized by a wet chemical method

Four Mg-based hydroxyapatites (HAps) doped with Ni at various amounts of 0, 0.6, 1.2 and 1.8?at% were prepared at the temperature of 870?°C by a wet chemical synthesis. The crystallite size, lattice parameters and crystallinity percent dramatically decreased with adding of Ni. The amount of HAp phase for all the Ni-containing samples is smaller than that of the Ni-free MgHAp. Furthermore, the lattice strain, stress and anisotropic energy density values were affected by the amount of Ni. The differential thermal analysis (DTA) measurements taken in the temperature range from 25 to 1000?°C showed that all the samples are thermally stable. No significant change in the morphology was observed. It was observed that the gradual introduction of Ni caused the Ca-deficiency.     

Tunable self-assembly of one-dimensional nanostructures with orthogonal directions

High-temperature exposure of a Mo(110) surface to borazine (HBNH)₃ leads to the formation of two distinctly different self-assembling nanostructures. Depending on the substrate temperature during preparation, either well-aligned, ultra-thin boron nanowires or a single-layer stripe structure of hexagonal boron nitride forms. Both structures show one-dimensional (1D) characteristics, but in directions perpendicular to each other. It is also possible to grow the two phases in coexistence. The relative weights are controlled by the sample temperature during preparation.     

Strong metal-support interaction in the Pt-Na0.7WO3 system: A study by low energy ion scattering spectroscopy and other surface sensitive techniques

The system formed of platinum deposited on the (100) surface of a Na_0.7WO₃ single crystal was studied by low energy He⁺ ion scattering and other surface sensitive techniques. After Pt deposition, flashing at or over approximately 500 K leads to the blocking of the Pt adsorptive sites by sodium oxide and to the consequent suppression of the capability to chemisorb CO at room temperature.     

Probing crystal structure and site-selective photo-physical properties of various Eu3+-doped niobates

Niobates of the formula Ba₂LaNbO₆ and BaLaM²⁺NbO₆ (M²⁺ = Mg, Ca) were synthesized by the conventional solid state route. Size dependence of M-cation on the bulk crystal structure of BaLaM²⁺NbO₆ was studied and compared with the Ba₂LaNbO₆ compound. X-ray diffraction study confirmed that BaLaMgNbO₆ compound has the rhombohedral () crystal structure as compared to the monoclinic (I2/m) in BaLaCaNbO₆ and Ba₂LaNbO₆. The change in the local structure of La cation among these compounds was investigated by carrying out Photoluminescence study on 2 atom% Eu³⁺-doped samples. PL study of BaLaMgNbO₆:Eu³⁺ sample indicates Eu³⁺ ions occupying the distorted 12-coordinated A-site, while in Ba₂LaNbO₆: Eu³⁺, Eu³⁺ is present at highly symmetric octahedral B-site. Upon excitation, the light emission of these compounds changes from reddish-orange to red to purple in the order Ba₂LaNbO₆:Eu → BaLaCaNbO₆:Eu → BaLaMgNbO₆:Eu³⁺, due to change in Eu³⁺-ions site occupancy. Lifetime study also confirmed the presence of two different Eu³⁺ components at two different lattice sites and their respective emission spectra were isolated by time resoled emission spectroscopy. Furthermore, this site selective lattice occupancy of Eu³⁺ ions also gave various new insights about its radiative and nonradiative properties at different lattice sites. This works presents a complete structural understanding of BaLaMNbO₆-based matrices and their versatile phosphor characteristics when doped with Eu³⁺ ion.     

The magnetic,thermal transport properties,magnetothermal effect and critical behavior of Co3Sn2S2 single crystal

Through the magnetic/thermal transport measurements combined with the analyses of magnetocaloric effect and critical behavior of Co₃Sn₂S₂ single crystal, the main results we obtained are as follows: in the case of the magnetic field H//c-axis, Co₃Sn₂S₂ exhibits the phase-separation state below T_c in the low-field region (H < 500 Oe). T_c increases slightly from 174 to 177 K with an increase in H from 100 to 10 kOe. The second-order magnetic phase transition near T_c and the itinerant ferromagnetism below T_c are identified. The magnetization below T_c matches well with the three-dimensional Ising model, instead of the mean-field model. In the case of H//ab, T_c changes between 175 and 178 K with varying H. Noticeably, M above T_c exhibits a small positive value, instead of the null M as commonly expected in the paramagnetic region. An extra phase transition below 166 K is observed. The magnetic transition near T_c seems not to be the second-order phase transition. All results show a significant characteristic of anisotropic magnetic phase transition for the Co₃Sn₂S₂ single crystal. They support mutually those in previous reports, moreover, some new phenomena are also observed. They also provide the experimental evidences for the deep insight into the magnetic phase–transition behavior of Co₃Sn₂S₂.     

Mechanisms of nucleation and crystal growth in a nascent isotactic polypropylene/poly (ethylene-co-octene) in-reactor alloy investigated by temperature-resolved synchrotron SAXS and DSC methods

The nucleation and lamellar growth mechanisms of nascent isotactic polypropylene/poly(ethylene-co-octene) (N-iPP/PEOc) in-reactor alloy were investigated with temperature-resolved synchrotron small angle X-ray scattering (SAXS), differential scanning calorimeter (DSC) and polarized optical microscopy (POM) methods. We have observed two crystallization peaks (fractionated crystallization behavior) during cooling process in N-iPP/PEOc in-reactor alloy. We also determined that the crystallinities from that two crystallization peaks were dependent on liquid-liquid phase separation (LLPS) time with t^0.10 and t^−0.28, respectively. It was explained that the fractionated crystallization behavior in the N-iPP/PEOc in-reactor alloy system was caused by crystal nucleation occurring in the iPP rich domain by heterogeneous nucleation and at interface of iPP and PEOc rich domains by the fluctuation assisted nucleation. The fluctuation assisted nucleation only occurred at interface of iPP and PEOc domains by concentration fluctuation through the coupling of liquid-liquid spinodal decomposition and the cross-over to crystal nucleation process. Both lamellar crystals formations from heterogeneous and fluctuation assisted nucleation in N-iPP/PEOc were probed by temperature-resolved SAXS during cooling process. Our results provide the physical model for the multiple nucleation and crystal growth mechanisms in the multi-component, multi-phase polymer systems such as in-reactor alloy or blend.     

The effect of thermal annealing on the adherence of Al2O3 films deposited by LP-MOCVD on several high alloy steels

Thin alumina films, deposited at 280°C on several high alloy steels by low-pressure metal-organic chemical vapor deposition (LP-MOCVD), were annealed at 0.17 kPa in a nitrogen atmosphere for 2, 4, and 17 h at 600 and 800°C. Film adhesion was studied by scanning scratch testing (SST) and Auger electron spectroscopy (AES). The best adhesion properties were obtained with commercial oxide dispersion-strengthened (ODS) high-temperature alloys, especially PM 3030. Among the 'normally' high alloy stainless steels, type AISI-321 showed the best adhesion. The other stainless steel-alumina combinations exhibited a reduced critical load, L_c, after thermal treatment. Alumina on ODS alloys exhibited an increased adhesion. AES studies revealed that this increase could be explained by: (1) the presence of sulfur-trapping elements, preventing segregation of sulfur at the interface; and (2) titanium and carbon enrichment at the interface, resulting in an anchoring effect between the oxide and the substrate.     

Surface structure and the instability of the formate overlayer at a Pb(110) surface

A combination of photoelectron and vibrational spectroscopies has established that a high energy formate species generated at a Pb(110)-surface is tilted with respect to the surface normal and decomposes spontaneously through H-bonding interactions with HCOOH(g) at 295 K.We are grateful to SERC for their support while BA was in receipt of a Turkish Government Scholarship.     

The influence of starting materials on the structure of ultrafine carbon powders

The primary ultrafine carbon powders were prepared by sol–gel supercritical fluid drying method using different starting materials. After heat-treatment at 1100 and 2600°C, respectively, the ultrafine carbon powders were obtained. The properties of primary ultrafine carbon powders and their annealed products were characterized by TEM, XRD, Raman spectra and nitrogen adsorption. The results reveal that starting materials have influence on the structure of ultrafine carbon powders.     

Effect of NA-light radiation on the optical gap and crystal structure of AgNO3-diffused PVDF sensor

A casting method was used to prepare polyvinylidene fluoride (PVDF) and 1 wt % MnCl₂-filled PVDF films. AgNO₃ was allowed to diffuse through the filled films. The 3 types of the prepared films were irradiated by Na light with various doses. The post-irradiation and relaxation effects were investigated using ultraviolet–visible spectroscopy, X-ray analysis, and optical microscopy. The results were interpreted on the bases of a theoretical model previously suggested for a build-up and decay of radiation-induced conductivity associated with the transition of charge carriers in the presence of a uniform trap distribution. Various structures were proposed for the diffused AgNO₃ before and after irradiation. It was found that the induced change in optical gap, due to 5-min irradiation time for the AgNO₃ diffused films, exhibits no relaxation phenomenon. Accordingly, this film can be used in photorecording applications. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1759–1767, 1998     

Nickel interlayer on the microstructure and property of TC6 to copper alloy diffusion bonding

In the present study, diffusion bonding of two dissimilar materials TC6 and copper alloy was investigated in vacuum chamber by directly bonding and using Ni foil as interlayer. Interface quality of the joints was evaluated by mechanical property and microstructure. The maximum shear strength of directly bonding was found to be 64 MPa for the speciemen bonded at 850 °C, 5 MPa for 30 min; and the maximum shear strength with Ni foil interlayer was 113 MPa under the same bonding parameters. The bonding interfaces and fracture surfaces were analyzed by energy disperse spectrometer, scanning electron microscopy and X-ray diffraction. The results show that the diffusion region of directly bonding specimen generated several IMCs (Ti₂Cu and Ti₅CuSn₃, etc.). Fracture morphology showed that brittle fracture present at the Ti₅CuSn₃ IMCs, which was the weak point of the joint. While the diffusion zone of the specimen with Ni foil interlayer consists of various phase including Ti₂Ni, TiNi, TiNi₃ at TC6 side, and Cu-Ni solid solution at ZQSn11-4-3 side, and fracture surface of joint present a mixture of brittle and ductile characteristics, and fracture initiated at the TiNi₃/Ni interface.     

The effect of synthesis conditions on the phase composition and structure of thorium bearing murataite ceramics

Samples of thorium-bearing ceramic with a target composition (wt%) 5 Al₂O₃, 10 CaO, 55 TiO₂, 10 MnO, 5 Fe₂O₃, 5 ZrO₂, 10 ThO₂ were produced by melting in glassy carbon crucibles in a resistive furnace and by cold crucible inductive melting (CCIM) at a vibration power of 10 kW and operation frequency of 5.28 MHz. All the samples contained 85–95 vol% murataite polytypes with 5- (5C), 8- (8C), and 3-fold (3C) elementary fluorite unit cell composing core, intermediate zone and rim of the grains, respectively, and minor crichtonite, perovskite, pyrochlore, rutile, etc. A feature of the ceramics obtained by melting in glassy carbon crucibles is formation of Fe (II) titanate whereas the inductive-melted ceramics contained traces of vitreous phase due to melt contamination with a cold crucible putty material. Melting rate in the cold crucible of up to 350 kg/(m² × h) has been achieved. The ceramics obtained have excellent chemical durability.