Effect Of Pt Content Research Articles

Performance of Pt-doped Ni/NiAlOx catalysts for phenanthrene hydrogenation saturation

Limited by the steric hindrance, hydrogenation of the final unsaturated ring in polycyclic aromatic hydrocarbons remains a challenge. In this work, a series of Pt-Ni/NiAlOx catalysts with different Pt doping amounts were synthesized by impregnation method to enhance the adsorption of aromatics, and phenanthrene was served as the model compound. The effects of Pt content on the structure and saturation performance of Pt-Ni/NiAlOx catalysts were systematically investigated. When the saturation reaction was performed at 300°C, 5 MPa and a weight hourly space velocity of 52 h−1, the selectivity of perhydrophenanthrene could be enhanced from 40% over Ni/NiAlOx catalysts to 67% over 0.5Pt-Ni/NiAlOx catalysts with 0.5%Pt loading. Meanwhile, the obvious reaction rate and turnover frequency were also improved from 1.53×10−3mol/(kg·s) and 14.64×10−3s−1 to 1.81×10−3mol/(kg·s) and 22.16×10−3s−1, respectively. This is related to the modified stability of metallic electron-deficient structure of Ni by Pt introduction in phenanthrene hydrogenation, which can promote the adsorption of aromatic hydrocarbons as well as the hydrogenation activity.

Micro Direct Methanol Fuel Cell Based on Reduced Graphene Oxide Composite Electrode.

The effect of an anode composite electrode on the performance of a micro direct methanol fuel cell (μDMFC) is analyzed from sample preparation configurations and discussed in detail, with a specific focus on the catalyst layer and the micro-porous layer on the anode composite electrode. This study investigates the effects of Pt content, Pt-Ru molar ratio, Nafion content, catalyst support, and preparation method in the catalyst layer, along with the carbon loading and polytetrafluoroethylene (PTFE) content in the micro-porous layer, on the performance of the anode composite electrode. The results show that the anode composite electrode delivers the best performance with 30% Pt content, a 1:1.5 Pt-Ru molar ratio, 10% Nafion content on reduced graphene oxide as the catalyst support. The synthesis is optimized with the impregnation reduction method using NaBH4 as the reducing agent, with the addition of 1.5 mg/cm2 carbon loading and 5% PTFE.

Reactive air brazing of Al2O3 ceramic with Ag-CuO-Pt composite fillers: Microstructure and joint properties

The effect of Pt content dispersed in Ag-CuO fillers on the interfacial microstructure and properties of Al2O3 ceramic joints brazed in air was investigated. Pt addition did not influence the variety of phases formed during reactive air brazing of Al2O3 joints. The position and morphology of CuO phase changed with Pt content which varied from 0 to 13.6 wt. %. Pt dissolved into Ag matrix completely. The typical interfacial sequence of brazed joints was Al2O3/CuAl2O4/CuO/Ag(s, s)/CuO/CuAl2O4/Al2O3. The addition of Pt to the Ag-CuO filler enhanced significantly the strength of Al2O3 joint from room temperature and up to 600℃. The joints brazed with Ag-CuO-9.0 wt. % Pt had the highest average strength at room temperature and at 600℃. The strength increased by 17 % and almost 100 %, respectively, compared with the Pt-free joint.

Effects of Pt Content on Room-Temperature Hydrogen Sensing Characteristics of Pt-SnO2 Nano-Composite Ceramics

A series of Pt-SnO2 nano-mixtures with 0, 0.25, 1 and 2.5 wt% Pt separately were prepared using SnO2 nanoparticles and H2PtCl6. Through pressing and sintering, Pt-SnO2 nano-composite ceramics with Pt nanoparticles well dispersed have been successfully prepared from the nano-mixtures. Their resistance is found to increase monotonously and greatly with increasing Pt content, which is increased by three orders of magnitude when Pt is increased from 0 to 2.5 wt%. All those samples with a Pt content show distinct responses to hydrogen at room temperature, while their hydrogen sensitivity and their recovery time both decease dramatically with increasing Pt content. These results strongly suggest that Pt as a catalyst promotes oxygen chemisorption on SnO2 and the reaction between hydrogen and oxygen at room temperature. Pt thus has catalytic effects on both hydrogen and oxygen, which leads to quite complicated effects of Pt content on the room-temperature hydrogen sensing behaviors of semiconducting metal oxides.

Effect of Pt content on initial TGO formation and available Al reserve of Pt-Al coatings during thermal cycling

Platinum aluminide coatings with different Pt content were fabricated. Their oxidation kinetics and the growth behavior of TGO were investigated. By analyzing the effect of Pt content on the oxidation rate constant and the surface roughness, we found that 13.92–18.52at.% Pt addition promoted the formation of TGO, and the coatings with ≤13.92at.% Pt addition showed relatively low surface roughness. However, the mechanically induced chemical failure occurred on the coating with high Pt content (≥26.96at.%) due to the decreased Al reserve. Our results indicated that the optimum Pt content was 13.92at.% and excessive Pt addition decreased Al supplement of coatings for TGO sustainable growth.

Hot corrosion behaviour of single-phase platinum-modified aluminide coatings: Effect of Pt content and pre-oxidation

Hot corrosion behaviour of nickel-based aluminide coatings with different thicknesses of initial Pt plating was evaluated in the Na2SO4/NaCl (75:25, wt./wt.) salt mixture at 900°C. Compared to plain aluminide, the Pt-modified coatings showed better hot corrosion resistance by hindering the outward diffusion of undesirable elements from the substrate alloy. Pre-oxidation was confirmed to be capable of preventing molten salt from accessing the alloy surface and reversibly dissolving the oxide scale. Oxide growth and dissolution, acting as two competitive processes, occurred simultaneously and had an important impact on the entire performance of the Pt-modified aluminide coatings in hot corrosion.

Effect of the platinum catalyst content on the tracking and erosion resistance of addition-cure liquid silicone rubber

An addition-cure liquid silicone rubber (ALSR) with ureido-containing MQ silicone resin (U-MTQ) was prepared by hydrosilylation with platinum catalyst (Pt). ALSR samples were characterized by thermogravimetric analysis (TGA) and thermogravimetry coupled with infrared spectroscopy (TG-FTIR), and the char layers of ALSR samples after inclined plate tracking and erosion test (IPT) were characterized by X-ray photoelectron spectroscopy (XPS). The effects of Pt content (5–100 ppm) on the curing characteristics, mechanical properties and tracking and erosion resistance of ALSR were investigated. It was found that the cure rate increased with increase of Pt content. When the Pt content was 10 ppm or 15 ppm, the ALSR had excellent tracking and erosion resistance, all specimens could pass the 4.5 kV level in IPT, and the erosion rate was only 0.13% and 0.15%, respectively. ALSR samples possessed optimum mechanical properties and thermal stability when the Pt content was 15 ppm. TG-FTIR results showed that ALSR generated less carbonyl compounds (CH2O) and cyclic oligomers but more methane (CH4) when the Pt content was 15 ppm. This demonstrated that there were lower levels of the oxidation of methyl groups and the main chain unzipping degradation of ALSR, and more homolysis of Si-CH3 during the degradation. The XPS results also showed that the macromolecular radicals would further cross-link to form a firm Si-C ceramic barrier to protect ALSR samples under Pt catalysis and high temperature, thus the tracking and erosion resistance of ALSR could be improved.

Effects of Pt content on the crystallinity and optical properties of Ag/Pt nanoboxes: from solid to single and polycrystalline mesoporous nanostructures

Synthetic methods to obtain hollow-like systems based on galvanic reaction are of wide importance due to the simplicity and efficiency of the method, yet due to fast and spontaneous reduction, the reaction for platinum-based structures is usually not well controlled. Systematic studies over the evolution of the galvanization process are still important in order to determine key feature on the structural transformation. On this paper, electron microscopy techniques were used to correlate the crystallinity of Ag/Pt nanoboxes of 78 nm in size with low and high-index facets surfaces from Ag nanocubes template. It was observed that 1.6 μmol addition of platinum precursor is enough to produce Ag/Pt nanoboxes. However, the crystallinity of the walls was tune from single crystal to polycrystalline by increasing the amount of platinum. More importantly, electron tomography reconstructions allow us to identify the concavities sides on the polycrystalline double-layer porous sample. Platinum content and nanostructure has been also associated to the optical properties were an extinction of the absorption band is observed after the solid template has been fully transformed to a nanobox. The final Ag/Pt porous/hollow nanoboxes with concave sides were tested on a model reaction for the reduction of 4-ntp to 4-amp.

The Effect of Pt Content on the Scale Development on β-NiAl at Very Early Oxidation Stages

Very early stages of development of the oxide scale formed in air at 1150° on unmodified and containing varying amounts of Pt (5, 10 and 15 at.%) β-NiAl intermetallic compound were studied. The scale morphology was observed using scanning electron microscopy, while photoluminescence spectroscopy was applied to determine its phase composition with spatial resolution down to 1 μm. It was found that the scales were non-uniform in terms of their morphology and, to a lesser extent, of their phase composition. Pt additions resulted in earlier development of the α-Al2O3 oxide, which, based also on recently reported literature experimental and modelling results, may be attributed to the increased rate of the scale evolution. The possible direct effect of Pt on the phase transformation of unstable aluminium oxides into α-Al2O3 still needs to be verified as the complementary or alternative explanation.

Carbon supported PdxPty nanoparticles for oxygen reduction. The effect of Pd:Pt ratio

Studies concentrated on the development of carbon supported PdxPty/C electrocatalysts for the oxygen reduction reaction (ORR). The application of the reverse ‘water-in-oil’ microemulsion method allowed to obtain a number of electrocatalysts with metal nanoparticles of ca. 5–6nm in size. Catalysts with the constant metal loading of 10wt% and various Pd:Pt atomic ratios were investigated. The textural features of the PdPt/C catalysts (surface area, morphology) as well as the PdPt phase (metal particle size, bulk composition) were characterized by a number of techniques. A particular attention was paid to the characterization of the surface properties of the PdPt particles using cyclic voltammetry technique. For all Pt contents (5 to 70 at%) a segregation of metal components (Pt, Pd) occurred leading to the Pt enrichment in the top layers. The observed Pt enrichment manifested especially strongly for PdPt catalysts with bulk Pt content below 20 at%. The surface fraction of Pt as high as 0.8 to 0.9 was attained regardless of nominal Pt content, starting from 30 at%. Among the catalysts, those with Pt content of 50 and 70 at% exhibited the highest activity towards ORR in terms of positively shifted half-wave potential, even surpassing that of Pt/C. Moreover, the obtained specific activity and turnover frequency values also suggested similar activities of catalysts with Pt content of 50 and 70 at%. A negligible formation of hydrogen peroxide on these two catalysts, indicated almost exclusively a desired four-electron process leading to water formation. The observed effect of Pt content on ORR activity is discussed in terms of surface properties of the PdPt nanoparticles.

Skelton isomerization of n-heptane under the effects of Pt content, particle size and reduction technique

A synthetic approach is developed to produce highly disperse, low loading (0.1- wt%, 0.3-wt% and 0.6- wt%) Pt nanoparticles incorporated montmorillonite (MMT) with average diameter of less than 4.0 nm using economical reduction processes. This was achieved by using formalin followed by chemical reduction with hydrogen to produce Pt nanoparticles incorporated MMT support. The physicochemical characterizations of the Pt nanoparticles incorporated MMT were performed by elemental analysis, FTIR, XRD, N2-adsorption and transmission electron microscopy. The results show that the Pt nanoparticles were uniformly distributed throughout the MMT support with Pt loading of less than 4.0 nm and the size of Pt is dependant on its loading. The catalytic activity for heptane isomerization reaction was evaluated over the prepared catalysts. At 0.1-wt% of Pt, the catalyst shows high activity for heptane isomerization, while at high Pt loading shoed high tendency to cracking. The preparation procedure is simple and favorable for a variety of metal nanoparticles syntheses for catalysis applications.

Effects of annealing on dielectric and ferroelectric properties in Pb(In1/2Nb1/2)O3–xPbTiO3(x≤0.30) ceramics

(1−x)Pb(In1/2Nb1/2)O3–xPbTiO3 (PIN–xPT, x=0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) ceramics were prepared by wolframite method and then annealed at 650°C for 24h. Effects of PT contents on the phase structure in these ceramics were analyzed by XRD. The samples with x≥0.15 were of single phase perovskite structure. The stability of perovskite phase structure for the samples with x≤0.10 was improved by using thermal annealing. Dielectric and ferroelectric properties of these samples were systematically investigated. It was found that the dielectric constants of the PIN–PT ceramics were increased within a wide temperature range and the phase transition temperatures shifted to low temperature after annealing. Hysteresis loops in PIN–xPT(x<0.20) ceramics had fake polarization and the peaks of electrical current appeared at the maximum applied field. The effects of PT content and annealing on dielectric and ferroelectric properties in PIN–PT ceramics are discussed.

Microstructure Analysis of Ti-xPt Alloys and the Effect of Pt Content on the Mechanical Properties and Corrosion Behavior of Ti Alloys.

The microstructure, mechanical properties, and corrosion behavior of binary Ti-xPt alloys containing 5, 10, 15 and 20 wt% Pt were investigated in order to develop new Ti-based dental materials possessing superior properties than those of commercially pure titanium (cp-Ti). All of the Ti-xPt (x = 5, 10, 15, 20) alloys showed hexagonal α-Ti structure with cubic Ti3Pt intermetallic phase. The mechanical properties and corrosion behavior of Ti-xPt alloys were sensitive to the Pt content. The addition of Pt contributed to hardening of cp-Ti and to improving its oxidation resistance. Electrochemical results showed that the Ti-xPt alloys exhibited superior corrosion resistance than that of cp-Ti.

Effect of Pt Content on TGO Growth in EB-PVD TBC Systems with Niptal Bondcoats

The oxidation behavior of Pt modified aluminide coating on the CMSX-4 Ni-base alloy plays major role to the EB-PVD TBC failure. The thermally growth oxide (TGO) is one of the most important factors to affect TBC lifetime. Two different Pt-content NiPtAl coatings in EB-PVD TBC systems were studied at 1100°C in air. The results indicated that cross-sections of oxide layer on the NiPtAl coatings within TBC in air were similar for the both bondcoats. The cracks could be found on the TBC/TGO/BC interfaces for the two bondcoats. The TGO morphologies of the low and high-Pt bondcoats on the side without TBC showed great different due to small PtAl particles size within high-Pt bondcoats. The irregular alumina on the both bondcoats was also showed on the sides with TBC compared to ones without TBC due to absence of the TBC. The TGO growth on the high-Pt bondcoats was faster than the low-Pt coatings during initial oxidation time. With the time increasing, the high-Pt content could suppress the TGO growth rate. Thinner TGO thickness could be obeserved on the both NiPtAl coatings due to the stress in TGO accumulation and oxide spallation.

One-Step Synthesis of Pt-Nanoparticles-Laden Graphene Crumples by Aerosol Spray Pyrolysis and Evaluation of Their Electrocatalytic Activity

Pt-nanoparticles-laden graphene (GR) crumples were directly synthesized from a colloidal mixture of aqueous chloroplatinic acid (H2PtCl6) and graphene oxide (GO) sheets via aerosol spray pyrolysis (ASP). Effects of Pt content in the Pt/GR composite and temperature of heating zone on the particle morphology, diffraction pattern, and specific surface area were investigated. The morphology of Pt/GR was the shape of a crumpled sheet of paper and the average size of the composite was around 1.3 μm in diameter. As Pt content increased from 2 to 20 wt%, higher numbers of Pt nanoparticles are observed on the GR at higher Pt content and the specific surface area of the composite also increased from 122 to 146 m2/g. Also, the intensity of the GR peak decreased, but that of the Pt peak increased. As temperature increased from 500°C to 900°C, an increase of the particle size of Pt due to sintering was observed. Electrocatalytic application of the Pt/GR composites was examined through methanol oxidation reaction. The ...

Activities of Pt/Sibunit-1562 catalysts in the ORR in PEMFC: Effect of Pt content and Pt load at cathode

In this paper, a systematic investigation was carried out of activities at 80 °C of Pt supported on Sibunit-1562 graphitized carbon in the electroreduction of oxygen in the polymer electrolyte fuel cell. Pt content in the Pt/Sibunit-1562 catalysts was 20, 40, and 60 wt.% and Pt load at the cathode was varied in the 200–6.25 μgPt cm−2 interval. The results were compared with the activity of commercial 20 wt.% Pt/Vulcan XC-72 catalyst. To optimize the transport properties of the cathode layer and maintain its thickness upon using Pt/Sibunit −1562 catalysts with varied Pt content and Pt loads a definite amount of Vulcan-XC-72 carbon support was added to the cathode catalytic inks. Higher activity of Pt/Sibunit-1562 catalysts was found as compared to that of commercial 20 wt.% Pt/Vulcan XC-72 with similar particle size of the active component.

Effect of Pt content on structure and magnetic properties of Fe100−xPtx films deposited on thermally oxidized Si substrates by rapid thermal annealing

Fe100-xPtx films with Pt contents (x) = 29–65 at.% were deposited directly onto thermally oxidized Si(100) substrate by dc magnetron sputtering. The films were then post-annealed at 700 °C for 3 min by rapid thermal annealing (RTA) at a high heating ramp rate of 100 °C/s. Experimental results show that Fe3Pt film displayed (111) preferred orientation and tended towards in-plane magnetic anisotropy when the Pt content was 29 at.%. When the Pt content was increased to 49 at.%, the FePt film inclined towards (001)-texture and perpendicular magnetic anisotropy. Its out-of-plane coercivity (Hc⊥), saturation magnetization (Ms) and out-of-plane squareness (S⊥) reached 1010 kA/m, 0.47 T and 0.8, respectively. These results reveal its significant potential as perpendicular magnetic recording media for high-density recording. Upon further increasing the Pt content to 65 at.%, the coercivity of the films decreased drastically to below 65 kA/m and tended towards in-plane magnetic anisotropy.

Effects of Pt Content on Mechanical Properties of Dy123 Bulks

Mechanical properties of Dy123 (DyBa2Cu3Ox) dense bulks which had few pores and those of conventional Dy123 bulks which had micro-pores were evaluated. While the dense bulks were fabricated by heating precursors in O2 atmosphere, the porous bulks were fabricated in air. Mechanical properties of the dense bulks were superior to those of the porous bulks. The average sizes of Dy2BaCuO5 particles dispersed in the bulks with 0.5 wt.% Pt were smaller than those dispersed in the bulks with 0.25 wt.% Pt. Bending strength values of the former bulks were higher than those of the latter bulks.

Study of brittle-to-ductile-transition in Pt-aluminide bond coat using micro-tensile testing method

The Brittle-to-ductile-transition-temperature (BDTT) of free-standing Pt-aluminide (PtAl) coating specimens, i.e. stand-alone coating specimens without any substrate, was determined by micro-tensile testing technique. The effect of Pt content, expressed in terms of the thickness of initial electro-deposited Pt layer, on the BDTT of the coating has been evaluated and an empirical correlation drawn. Increase in the electrodeposited Pt layer thickness from nil to 10 μm was found to cause an increase in the BDTT of the coating by about 100°C.

The effect of Pt content on γ–γ′ NiPtAl coatings

This study investigated the impact of Pt content on the coating composition and subsequent oxidation behavior of γ–γ′ NiPtAl diffusion coatings. Coatings were fabricated by vacuum annealing electroplated Pt on single-crystal and directionally-solidified superalloy substrates. Specimens with 7 and 12 µm thick layers of electroplated Pt were annealed at 1100 or 1175 °C. Coating compositions were characterized to evaluate the distribution of Pt and Al as a function of annealing temperature and Pt thickness. Selected coatings were evaluated in cyclic oxidation at 1100 and 1150 °C. Coatings with higher Pt contents showed improvements in spallation resistance, particularly at 1100 °C for a directionally-solidified superalloy substrate with higher Hf and S contents.