Influence Of Pt Research Articles

Control of perpendicular magnetic anisotropy and spin pumping damping in MgO/CoFeB/ Ta/Pt structures

The perpendicular magnetic anisotropy (PMA) and spin pumping induced magnetic damping of CoFeB films can be significantly tuned by the adjacent nonmagnetic layer (Ta or Pt). For the CoFeB/Pt(tPt) structure, both PMA strength and magnetic damping increase with tPt, due to the enhanced interfacial orbital hybridization and spin pumping effects, respectively. By inserting a thin Ta interlayer between CoFeB and Pt, the magnetic easy axis immediately turns into in-plane direction. Meanwhile, time-resolved magneto-optical Kerr effect measurement shows an obvious reduction in the magnetic damping, which can be explained as the increase of spin current backflow and the decrease of interfacial spin-mixing conductivity. As the Ta interlayer thickness (tTa) increases, the effective damping parameter αs measured at saturation field initially decreases and eventually reaches a constant value of 0.027. The αs value at tTa > 5 nm does not change regardless of the top Pt layer, implying the influence of Pt is completely isolated and the spin diffusion length of Ta is around 5 nm. Our findings provide more insights into the control of PMA strength and spin pumping contribution to magnetic damping.

Ceria-supported small Pt and Pt3Sn nanoparticles for NOx-assisted soot oxidation

Introduced herein are small Pt and Pt3Sn nanoparticles, stabilized with organosilane or organostannane and impregnated on ceria support, as active sites for NOx-assisted soot oxidation reaction. The catalysts have been tested with four reactions: CO oxidation, NO oxidation, NOx-free soot oxidation and finally NOx-assisted soot oxidation. Our Pt nanoparticles reportedly possess remarkable catalytic activities in CO oxidation, as they actively convert CO at 50°C, while the alloy Pt3Sn nanoparticles are active at higher temperature. The Pt nanoparticles also mediate more actively NO oxidation than their alloy counterpart, leading to more NO2 production beneficial for soot oxidation. The influence of Pt and Pt3Sn active sites on the catalytic activity during NOx-free soot oxidation becomes less prominent than the morphology, due to the high dependency of the reaction on catalyst structure. The presence of Sn, nevertheless, induces lower oxidation reaction temperature. Finally, in the presence of NOx, the metal active sites undoubtedly boost the catalytic activity of soot oxidation. Pt/CeO2-NC (NC stands for “nanocubes”), reported herein as our most achieving catalyst, demonstrates a remarkable activity, lowering the oxidation temperature at about 80°C, thanks to the synergy of the active metal nanoparticles and reactive ceria nanocubes. Surprisingly, the catalytic activity of the alloy counterpart (Pt3Sn/CeO2-NC) is close to Pt/CeO2-NC, indicating the potential of the catalyst as an alternative to reducing the employment of precious metal in automotive catalysis. The thermally aged Pt catalysts have demonstrated good resistance to sintering, thanks to the outer protection by silica patches. However, the catalytic activities of the aged Pt3Sn catalysts rely heavily on support morphology.

Simultaneous achievement of high perpendicular exchange bias and low coercivity by controlling ferromagnetic/antiferromagnetic interfacial magnetic anisotropy

This study investigates the influence of Pt and Au spacer layers on the perpendicular exchange bias field and coercivity of Pt/Co/(Pt or Au)/Cr2O3/Pt films. When using a Pt-spacer, the perpendicular exchange bias was highly degraded to less than 0.1 erg/cm2, which was about half that of the Au-spacer system. The Au spacer also suppressed the enhancement in coercivity that usually occurs at around room temperature when using Pt. It is suggested that this difference in exchange bias field is due to in-plane interfacial magnetic anisotropy at the Pt/Cr2O3 interface, which cants the interfacial Cr spin from the surface normal and results in degradation in the perpendicular exchange bias.

Influence of Superfine Materials on the Vegetative Reproduction of Black Currant

We studied the influence of superfine materials on the rooting ability and development of softwood cuttings of Ribes nigrum. The inhibiting effect of the soil amended with ZnO and Pt nanoparticles at the concentration of 5 mg/kg of substrate on the rhizogenesis of black currant cuttings was stated. On adding the suspension of ZnO nanoparticles the rooting ability of cuttings decreased by 32.3 %, and under the influence of Pt nanoparticles – by 41.4 %. The decrease in the morphometric parameters of development of the cuttings’ above-ground part and roots (growth amount, number of cratches and leaves, number of roots and their length) was observed. The change in the biochemical composition of leaves in the cuttings was stated. In the replication with zinc oxide the concentration of chlorophyll in leaves significantly decreased by 21.8 %. Under the influence of Pt the concentration of flavonoids in leaves increased by 48.8 %.

Methanation of CO2 on Ni/γ-Al2O3: Influence of Pt, Pd or Rh promotion

Methanation of carbon dioxide was carried out in a plug flow reactor (CO2:H2=1:4, GHSV=5700h−1) over a series of noble metal promoted Ni/γ-Al2O3 catalysts, prepared by the co-impregnation method: Ni(10wt.%)-Pt(0.5wt.%)/γ-Al2O3, Ni(10wt.%)-Pd(0.5wt.%)/γ-Al2O3, and Ni(10wt.%)-Rh(0.5wt.%)/γ-Al2O3. Characterization of catalysts was performed by N2 adsorption–desorption isotherms at −196°C (BET), X-ray powder diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption of H2 (H2-TPD), and CO2 (CO2-TPD). Promotion by noble metals resulted in better reducibility of NiO (Ni-Rh>Ni-Pt>Ni-Pd>Ni), enhanced metal dispersion and H2 chemisorption capacity (Ni-Pt>Ni-Rh>Ni-Pd>Ni), with no significant influence upon the support intrinsic activity given by the CO2 adsorption capacity. Catalytic activity of the promoted catalysts compared to the unpromoted one was performed by temperature programmed reactions (TPRea, 30–300°C) and stability tests at 250°C, under atmospheric pressure, and was evaluated in relation with the structural and functional properties of the catalysts. Promotion by Pt and Pd of Ni/γ-Al2O3 resulted in enhanced CO2 conversion and CH4 selectivity values in the 180–270°C domain, while Ni-Rh/γ-Al2O3 was inferior to Ni/γ-Al2O3. Considering the stability, all catalysts show stable catalytic performance over the investigated time range, with CH4 selectivity values above 90%. Ni-Pd/γ-Al2O3 is the most efficient catalyst, with stable CO2 conversion of 74.6% and CH4 selectivity of 96.6% at 250°C, in addition to the maximum values of 90.5% and 98.7%, respectively, at 300°C, obtained during temperature programmed reaction runs.

Influence of Pt Nanoparticle Induced Defects and Surface Coverage in Determining Asymmetric Programming/Erasing Signatures for Nanocrystal Embedded Nonvolatile Memory Applications

Metal nanocrystal embedded nonvolatile memory (NVM) devices have attracted significant attention over the past two decades as promising alternatives to conventional floating gate memory devices. This study explores the applicability of sub‐2 nm Pt nanoparticle (NP) embedded in ALD Al2O3 as charge storage nodes in Si‐based NVM devices. The influence of Pt NP‐induced border traps within Al2O3 near the Si surface and their surface coverage dependent pinning of Pt NP work function are explored as part of this study. The pinning of the nanocrystal memories induced by a high density of dangling bonds near the Pt NP/Al2O3 interface skews the expected charging/discharging characteristics with electron programming favored over holes. The degree of this pinning has been probed utilizing C–V measurements and has been dependent on the density of Al2O3 dangling bonds near the Pt NP surface. This density of dangling bonds acting as border traps has been observed as an increasing function of the Pt NP surface percent coverage. Gaining adequate understanding the location, energy, and positioning of the energy levels of these defects at the metal/high‐k interface relative to Si band gap can help overcome poor retention and leakage issues that typically compromise the performance of new generation memory devices.

Influence of Pt and Pd Modification on the Visible Light Photocatalytic Activity of N-Doped Titania Photocatalysts.

Pd and Pt modified N-doped titania nanoparticle powders were prepared by a facile sol-gel method. Nitrogen doping and metal modification were carried out simultaneously during the preparation pro- cess. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and X-ray photoelectron spectroscopy (XPS). The visible light photocatalytic activities of the as prepared samples were evaluated by analyzing their effect on the photocatalytic decomposition of methyl orange (MO). The chemical state of the metal is the key factor determining the performance of metal modified N-doped titania. The Pd used to modify the N-doped titania (Pd-NT) in our study was of the PdOx(x≤2) species, which increased the absorbance in the visible light region, decreased the recombination of photo-generated electron-hole pairs, and resulted in a significant enhancement in the visible light photocatalytic activity. The Pt species used to modify the N-doped titania (Pt-NT) was mainly in the metallic state, which resulted in a decrease in the absorbance in the visible light region, and an increase in the recombination of photo-generated electron-hole pairs. Pt modification led to a deterioration in the visible light photocatalytic activity of the material.

(N7)-Platination and its effect on (N1)H-acidification in nucleoside phosphate derivatives

Pt(II) coordination, like of cis-(NH3)2Pt(II), affects the acid-base properties of guanosine derivatives. The acidity constants of such complexes are calculated by curve-fitting procedures using published 1H NMR shift data measured in aqueous solution (D2O) in dependence on pH (pD). Comparison of the pKa values of the ligands with those of the Pt(II) complexes reveals the expected behavior for (N7)-platination, i.e., (N1)H sites are acidified due to charge repulsion. These effects of Pt(II) are compared with those of Ni2+ and Cd2+, allowing predictions for the acidification of Zn2+. Studied are the cis-(NH3)2Pt(II) complexes of inosylyl(3′→5′)inosine, guanylyl(3′→5′)guanine (GpG)−, its 2′-deoxy relative d(GpG)−, and its phosphorylated derivative d(pGpG)3−. The Pt(II) effect is mostly rather symmetrical, like with d(CpGpG)2−, but it can also be quite asymmetrical, like with d(CpCpGpG)3− or in the cyclohexylamine-substituted Cisplatin complex of d(GpG)−. Potential consequences for base pairing between the platinated guanine and the complementary cytosine are discussed. It is proposed that partial deprotonation of dG under the influence of Pt(II) at physiological pH leads in water to a marked reduction in pairs with intact Watson–Crick hydrogen bonds, thereby adding to the well established thermal destabilization of double-stranded DNA by G,G intrastrand cross-links of Cisplatin.

Platinum Thin‐Film Electrodes Prepared by a Cost‐Effective Chemical Vapor Deposition Technique

Thin‐film growth of metallic platinum by aerosol‐assisted chemical vapor deposition (AA‐CVD) is an attractive alternative to the application of vacuum‐based methods. This versatile and scalable technique allows gas phase deposition of thin‐films from nebulized precursor solutions in a simple, open setup at moderate temperatures between 400 and 600°C. We discuss the film growth mechanisms on silicon and zirconia substrates in terms of microstructure, surface coverage, sheet resistance, and thermal stability. Furthermore, the positive influence of Pt thin‐films deposited by AA‐CVD on the area specific resistance (ASR) of symmetric Pt/YSZ/Pt cells in air is presented.

Effect of Pt and CeO2 on Growth of Y-123/nano-Y2O3 Single Grain Superconductors

The top seeded melt growth (TSMG) process is used widely to grow single grain, bulk superconductors for high field engineering applications. Within the TSMG process, the flux pinning ability of a single-grain bulk superconductor can be improved effectively by reducing the size of starting precursor powders prior to melt processing. This paper investigates the preparation of Y-123/nano-Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> single-grain samples based on TSMG process. A large number of microcracks and significant inhomogeneity were found in samples containing Pt and CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> additives, respectfully. This reduces the performance of samples made from nano Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> starring powders. A pretreatment of the starting powders was developed to decrease microcracks and improve the homogeneity of Y-123/nano-Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> single grain samples. The influence of Pt and CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> doping on the superconducting properties of the fully processed single grain were also investigated in detail. The Y-123/nano-Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> based samples exhibit features that are rarely seen in conventional YBCO single grain, bulk superconductors.

Kinetics of optically excited charge carriers at the GaN surface: Influence of catalytic Pt nanostructures

In this work, we use GaN with different deposited Pt nanostructures as a controllable model system to investigate the kinetics of photo-generated charge carriers in hybrid photocatalysts. We combine conductance and contact potential difference measurements to investigate the influence of Pt on the processes involved in the capture and decay of photo-generated charge carriers at and close to the GaN surface. We found that in the presence of Pt nanostructures the photo-excitation processes are similar to those found in Pt free GaN. However, in GaN with Pt nanostructures, photo-generated holes are preferentially trapped in surface states of the GaN covered with Pt and/or in electronic states of the Pt and lead to an accumulation of positive charge there, whereas negative charge is accumulated in localized states in a shallow defect band of the GaN covered with Pt. This preferential accumulation of photo-generated electrons close to the surface is responsible for a dramatic acceleration of the turn-off charge transfer kinetics and a stronger dependence of the surface photovoltage on light intensity when compared to a Pt free GaN surface. Our study shows that in hybrid photocatalysts, the metal nanostructures induce a spatially inhomogeneous surface band bending of the semiconductor that promotes a lateral drift of photogenerated charges towards the catalytic nanostructures.

Precise determination of dissolved platinum in seawater of the Japan Sea, Sea of Okhotsk and western North Pacific Ocean

Platinum is among the least abundant elements in the earth's crust and is now widely used in various products such as catalytic converters in automobiles and anticancer drugs. Consequently, the concentration of Pt in urban aquatic environments is increasing. However, little is known about the distributions and geochemical cycles of Pt in the ocean owing to its low concentrations in seawater (<0.2pmol/L). In this study, we report an improved analytical method for determining sub-picomolar levels of Pt in seawater, and reveal the distributions of Pt in the Japan Sea, Sea of Okhotsk, and western North Pacific Ocean.For determining sub-picomolar levels of Pt in seawater, we used isotope-dilution ICP-MS (Inductively Coupled Plasma Mass Spectrometry) after column preconcentration with an anion exchange resin. This method facilitated highly accurate analysis of Pt in seawater using small sample volumes (~1L). The detection limit and procedural blank value for this method were 0.015 and approximately 0.01pmol/L, respectively. We obtained conservative vertical distributions, with nearly constant Pt concentrations between 0.19 and 0.25pmol/L in the Japan Sea, Sea of Okhotsk, and western North Pacific Ocean. Judging from the constant dissolved Pt profiles, little anthropogenic influence of Pt is apparent in the open oceans at the present time.

Micromechanisms of fracture and strengthening in free-standing Pt-aluminide bond coats under tensile loading

Free-standing Pt-aluminide (PtAl) bond coats exhibit a linear stress–strain response under tensile loading and undergo brittle cleavage fracture at temperatures below the brittle-to-ductile transition temperature (BDTT). Above the BDTT, these coatings show yielding and fail in a ductile manner. In this paper, the various micromechanisms affecting the tensile fracture stress (FS) below the BDTT and yield strength (YS) above the BDTT in a PtAl bond coat have been ascertained and quantified at various temperatures. The micromechanisms have been identified by carrying out microtensile testing of stand-alone PtAl coating specimens containing different levels of Pt at temperatures between room temperature and 1100°C and correlation of the corresponding fracture mechanisms with the deformation substructure in the coating. An important aspect of the influence of Pt on the tensile behavior, slip characteristics, FS/YS and BDTT in the PtAl coating has also been examined. The addition of Pt enhances the FS of the coating by Pt solid solution strengthening and imparts a concomitant increase in fracture toughness and yet causes a significant increase in the BDTT of the coating.

Pt-promoted α-Al2O3-supported Ni catalysts: Effect of preparation conditions on oxi-reduction and catalytic properties for hydrogen production by steam reforming of methane

The effect of Pt addition on the oxi-reduction properties of α-Al2O3-supported Ni catalysts, with different degrees of interaction between NiO and the α-Al2O3 support, was studied using atmospheres of H2, H2/H2O, and CH4/H2O. The effect of Pt promotion on the reduction of NiO with H2 was significant for NiO species that interacted more strongly with the alumina surface, but was much lower when a NiAl2O4-like bulk phase was formed. For samples activated with H2, although metal dispersion decreased with increasing Pt content, the activity was maintained constant by the presence of Pt sites. For samples activated with a CH4/H2O mixture, the activity increased with increasing Pt content, due to the higher reducibility of Ni in the Pt-promoted catalysts. The Pt promotion effect was stable; there was no important decrease in the influence of Pt on NiO reduction, even after high temperature re-oxidation of the catalysts.

Characterization of 3R martensite in a Ni–40Al–15Pt bulk alloy

As Pt promotes the reversible martensite transformation, the aim of this study was to assess the influence of Pt on the crystallography of (β′) martensite, in terms of ordering adapted, twinning and stacking faults. The focused ion beam (FIB) milling process was used to prepare transmission electron microscopy (TEM) samples of the NiAlPt bulk alloys, whereby 3R, L10 ordering of the martensite was confirmed. The addition of Pt, coupled with high temperature oxidation resulted in more stacking faults, due to greater Pt diffusion and subsequent enrichment in martensite. For Pt diffusion the temperature must be in excess of 900°C, both for isothermal and cyclic oxidation. When the favorable temperature environment is achieved Pt can diffuse preferentially allowing for promotion of the transformation to martensite.

Influence of Pt on Oxidation Behavior of CoNiCrAlY Alloy

The microstructure, hardness and isothermal oxidation behavior of CoNiCrAlY alloy modified by addition of 3 wt% and 5 wt% Pt were investigated using scanning electron microscopy, Vickers hardness tester, X-ray diffraction and energy dispersive spectroscopy analysis. The results reveal that Pt has a significant influence on the microstructure of the experimental alloy by formation of β-(Ni,Pt)Al phase. Addition of Pt can slightly increase the hardness of the experimental alloys. Pt will accelerate the phase transformation of alumina from metastable θ-Al2O3 to stable αAl2O3, which is the main reason for the lowering oxidation rate and the formation of a protective oxide scale on the Pt-containing alloys. Furthermore, adding of Pt can improve the Al transport, which suppresses the consumption of βphase and eliminates the internal oxidation.

Influence of Pt as Mn diffusion barrier on the distribution of blocking temperature in Co/(Pt)/IrMn exchange biased layers

Many spintronic devices such as thermally-assisted magnetic random access memories take advantage of the ferromagnetic(F)/antiferromagnetic(AF) interaction to pin the magnetization of a reference layer. However, they suffer from detrimental blocking temperatures distributions from memory cell to memory cell. A low-temperature contribution to the distribution was ascribed to spin-glass like regions which are randomly spread over the film. We report on an attempt to reduce the amount of these spin-glass like regions due to interdiffusion of species by adding a diffusion barrier at the F/AF interface.

Effect of Pt: Pd atomic ratio in Pt–Pd/C electrocatalyst-coated membrane on the electrocatalytic activity of ORR in PEM fuel cells

The influence of Pt: Pd atomic ratios (1:2–1:8) on a carbon support upon its suitability as a cathode for a proton exchange membrane (PEM) fuel cell was evaluated at a constant membrane electrocatalyst loading of 0.15 mg/cm2. The results clearly demonstrated that the different Pt: Pd atomic ratios had a significant effect on both the electrocatalyst activity and also on the performance in a H2/O2 fuel cell. Decreasing the Pt: Pd atomic ratio led to an increase in the particle size of the electrocatalyst but a decrease in the particle dispersion and electrochemical surface area (ESA). With respect to the performance in a PEM fuel cell, decreasing the Pt: Pd atomic ratio led to a decreased exchange current density (j0), electrocatalytic activity and also mass activity (MA), but to an increased total resistance (R) of the cell. The maximum activity of the oxygen reduction reaction (ORR) and the peak power (492 mW/cm2) were obtained with an electrocatalyst with a Pt: Pd atomic ratio of 1:2. Finally, the rotating disk electrode (RDE) analysis showed that the mechanism of oxygen reduction on the prepared Pt–Pd/C electrocatalyst involved a four-electron pathway with high oxygen permeability in the Nafion film.

Barrier heights, polarization switching, and electrical fatigue in Pb(Zr,Ti)O3 ceramics with different electrodes

The influence of Pt, tin-doped In2O3, and RuO2 electrodes on the electrical fatigue of bulk ceramic Pb(Zr,Ti)O3 (PZT) has been studied. Schottky barrier heights at the ferroelectric/electrode interfaces vary by more than one electronvolt for different electrode materials and do not depend on crystallographic orientation of the interface. Despite different barrier heights, hysteresis loops of polarization, strain, permittivity, and piezoelectric constant and the switching kinetics are identical for all electrodes. A 20% reduction in polarization after 106 bipolar cycles is observed for all the samples. In contrast to PZT thin films, the loss of remanent polarization with bipolar switching cycles does not significantly depend on the electrode material.

The influence of Pt redistribution on Ni1−xPtxSi growth properties

We have studied the influence of Pt on the growth of Ni silicide thin films by examining the Pt redistribution during silicide growth. Three different initial Pt configurations were investigated, i.e., a Pt alloy (Ni+Pt/⟨Si⟩), a Pt capping layer (Pt/Ni/⟨Si⟩) and a Pt interlayer (Ni/Pt/⟨Si⟩), all containing 7 at. % Pt relative to the Ni content. The Pt redistribution was probed using in situ real-time Rutherford backscattering spectrometry (RBS) whereas the phase sequence was monitored during the solid phase reaction (SPR) using in situ real-time x-ray diffraction. We found that the capping layer and alloy exhibit a SPR comparable to the pure Ni/⟨Si⟩ system, whereas Pt added as an interlayer has a much more drastic influence on the Ni silicide phase sequence. Nevertheless, for all initial sample configurations, Pt redistributes in an erratic way. This phenomenon can be assigned to the low solubility of Pt in Ni2Si compared to NiSi and the high mobility of Pt in Ni2Si compared to pure Ni. Real-time RBS further revealed that the crucial issue determining the growth properties of each silicide phase is the Pt concentration at the Si interface during the initial stages of phase formation. The formation of areas rich in Pt reduce the Ni silicide growth kinetics which influences the phase sequence and properties of the silicides.