Addition Of Ru Research Articles

Microstructure and Formation Mechanism of β Eutectoid Decomposition in a γ‐TiAl Alloy with Ru Addition

A eutectoid decomposition of β→α + τ1 occurs during water quenching (WQ) and the corresponding formation mechanism in a γ‐TiAl alloy with Ru addition is studied. A novel morphology consisting of outer lamellar and inner net‐like eutectoid microstructure is observed. The α and τ1 products are determined to nucleate and grow with the same crystalline orientation in a eutectoid aggregation, respectively. No specific crystalline orientation is confirmed between α and τ1. The eutectoid reaction is found to be controlled by diffusion. Moreover, α and τ1 grow in a synchronous manner. The outer lamellar region absorbs Ti, but excludes both Ru and Al atoms to the center of the β matrix during the eutectoid reaction. Correspondingly, the high Ru and Al contents promote the sidewise growth of τ1 lamellae and result in the distinctions in microstructure with the outer lamellae.

Ni-Ru-MgO catalyst with high activity and stability for methanation of syngas and producer gas

A new catalyst composition comprised of Ni, Ru, and MgO was investigated with a focus on improving methanation performance for sub-stoichiometric H2/CO-ratio producer gas from biomass gasification. The catalyst was loaded on an alumina support by wet impregnation for testing the catalytic methanation activity for syngas (CO/H2) and producer gas (CO/CO2/H2) in a fixed-bed reactor. The optimum addition of promoters Ru and MgO to the main Ni catalyst was determined by maximizing the CO conversion and CH4 yield in the methanation reactions. The optimization experiments were conducted on a low-surface-area alumina support. With 10% Ni loading, the highest activity and stability was achieved with the addition of 1.5%MgO and 0.5–1.0% Ru as promoters. X-ray Photoelectron Spectroscopy (XPS) of Ni in pretreated Mg-Ni and Ni-Ru-Mg catalysts indicated the presence of approximately 30% of Ni in metallic state on the Al2O3 support. Bulk reduction, measured by TPR, was nearly 40% in the Mg-Ni-Ru catalysts. The MgO promoter enhanced the methanation activity, while the Ru component was mainly responsible for improvement in catalytic stability in the low H2/CO-ratio (1.82) feed gas. The effect of the presence of H2O in the feed gas showed no significant change in the methanation activity of the catalyst. The Ni-Ru-Mg catalyst showed much higher stability in comparison to a promoted Ni-based commercial catalyst. The CO in the low H2/CO-ratio feed gas was primarily responsible for catalyst deactivation due to coke formation. Experiments with high-surface-area commercial alumina supports with the Ni-Ru-Mg catalyst demonstrated CO conversion activity comparable to a commercial catalyst but eliminated deactivation due to coke formation at the low H2/CO-ratio producer gas commonly found in the gasification of biomass.

Influence of Ru on the thermomechanical fatigue deformation behavior of a single crystal superalloy

The deformation mechanisms of a single crystal nickel-base superalloy with and without Ru-doped have been investigated under out-of-phase thermomechanical fatigue. The Ru-doped alloy exhibits a thermomechanical fatigue life more than twice as high compared to the Ru-free alloy and a difference in thermomechanical fatigue behavior is also displayed. Microstructure studies by scanning electron microscopy and transmission electron microscopy revealed that the deformation mechanism of the Ru-free alloy in the initial stage is the movement of dislocations in the γ matrix. In the later stage of the thermomechanical fatigue test, large amounts of twins are formed in the material, and a large number of stacking faults and dislocations are sheared into the γ' precipitates. By comparing with the Ru-free alloy, the Ru-doped alloy has a higher matrix strength due to the solid solution strengthening effect of Ru, and is also prone to different deformation mechanisms. For example, the stacking faults are formed in the initial thermomechanical fatigue cycles and remain in the matrix throughout the entire thermomechanical fatigue process. The formation of twins, on the other hand, is suppressed by Ru addition. Such effects are believed to extend the thermomechanical fatigue life effectively.

Effect of Ru addition on γ/γ′ microstructural stability in a low-density CoNi based superalloy

The present work explores the effect of ruthenium (Ru) addition to the γ/γ′ strengthened Co-30Ni-10Al-5Mo-2Nb superalloy. A 2 at.% Ru increases the γ/γ′ microstructural stability at 900°C. XRD and APT revealed a reduction of γ/γ′ lattice misfit by ∼ 26% and segregation of Ru at γ/γ′ interface, respectively that contribute to the decrease of γ/γ′ interfacial energy. The temporal evolution of γ′ precipitates at 900°C shows the classical matrix diffusion controlled LSW mechanism with a coarsening rate constant (Kr) ∼ 6.03 nm3/s similar to the values for Co-Al-W based superalloys. Furthermore, Ru addition increases the degree of anomalous strengthening with a peak 0.2% proof stress (PS) value of ∼ 630 MPa at 770°C. The results show Ru as a promising alloying addition to increase the γ/γ′ microstructural stability at high temperatures for the low-density class of CoNi-based superalloys.

Effects of promoters on carburized fused iron catalysts in Fischer-Tropsch synthesis

The effects of K, Ru or La promoters on the structure, surface area, crystal phase, and catalytic behavior during FT synthesis of carburized and uncarburized fused Fe catalysts were studied by XRD, XPS, TPD, N2-physisorption and catalytic reaction evaluation techniques. Addition of K improved selectivity of C5+ products for both the carburized and uncarburized catalysts. Addition of Ru suppressed catalytic activity of the carburized catalyst, but had little influence on the uncarburized one. Addition of La led to the encapsulation of the iron carbide, which consequently severely inhibited the carburization and decreased the activity. While Ru and La promote the formation of light components due to their ability to promote hydrogen adsorption. The performance of the reaction in the experiment indicated that the U-K catalyst had the best product distribution, in which the methane selectivity was 4.04%, and the C5+ selectivity was 75.84%.

Upgrading syngas from wood gasification through steam reforming of tars over highly active Ni-perovskite catalysts at relatively low temperature

Tar formation during biomass gasification causes several operational problems, besides limiting the downstream application of the syngas produced. The development of an efficient catalyst for tar reforming at mild temperature is targeted. In this study, La-based perovskite (La0.6Sr0.4Co0.2Fe0.8O3-δ)-supported Ni materials have been synthesized through wetness impregnation (Ni/LSCF) and one-pot sol-gel method (Ni-LSCF). As-prepared catalysts have been characterized by N2 physisorption, XRD, TPR, H2-TPD and XPS. The impact of the synthesis path and the effect of Ru have been evaluated in steam reforming of toluene and phenol at low temperature (550 °C) under a model syngas. Regardless the tar model molecule, similar catalytic stability and activity toward tar reforming were attained for both Ni/LSCF and Ni-LSCF. However, a better catalytic performance toward WGS and higher resistance to coke formation were evidenced for Ni-LSCF than for Ni/LSCF. This better behavior has been mainly ascribed to the high Sr content at its surface, pointing out the key role of the basic elements at the catalytic surface in the activity and stability in steam reforming of tars. The addition of Ru led to an enhancement in the catalytic activity for toluene reforming, while no noticeable improvement was attained for phenol reforming.

Perovskites Doped with Small Amounts of Noble Metals for IT-SOFCs

Solid oxide fuel cells (SOFCs) have a great potential among the emerging energy conversion technologies because they can efficiently convert various types of fuel (hydrogen, methane, CO, biogas) into electrical energy in the 750-850 °C temperature range. The choice of electrodes remains a challenge because most metal oxides suffer from low chemical stability and low electrocatalytic activity toward oxygen reduction reaction (ORR) in the intermediate temperatures (IT) range (500-700 °C) [1]. In this view, perovskite oxides (ABO3) have shown excellent properties in terms of thermal stability, compatibility with other cell components, low production cost and, most importantly, great flexibility [1]. La0.6Sr0.4FeO3-δ, (LSF) perovskite oxide have been widely investigated for the high electrical conductivity and the electrochemical properties [2]. However, the main drawback is the poor activity towards ORR in the IT range, as most iron-based perovskite oxides [3]. The B-site doping with noble metal catalysts can sensitively improve the properties and make the compounds suitable for electrode application.The addition of small amounts of Ru or Pt into LSF structure can be an effective approach to improve the electrocatalytic properties [4,5]. Specifically, we synthesized B-site doped LSF powders with very low amounts (<5%mol) of Ru and Pt by using solution combustion synthesis (SCS) method. The synthesized powders were calcined at quite low temperature (750 °C) to get as high as possible surface area (>15 m2/g). All compounds showed a single perovskite phase. As reported in Fig. (a), the addition of Ru and Pt in the structure causes a progressive shift of the XRD peaks to lower 2θ angles indicating the perovskite lattice expansion due to the substitution of Fe4+/ Fe3+ sites with larger Ru and Pt ions.To assess the electrocatalytic activity, the compounds were investigated in oxidizing conditions using electrochemical impedance spectroscopy (EIS) analysis. Fig. (b) shows the Arrhenius plot of area specific resistance (ASR) values of LSFRu and LSFPt perovskite oxides. The ASR values were measured on LSFM/La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM)/LSFM (M=Ru, Pt) symmetric cells in the temperature range 550-800 °C. The insertion of a very low amount (1%mol) of Pt or Ru significantly reduces the polarization resistance, confirming the beneficial effect of noble metal ions on ORR activity. All these features suggest that very low Pt and Ru doping positively affects the structural and electrocatalytic properties valuably for cathodic applications.[1] Hwang J, Rao R.R. (2017). Science 358:751-756[2] Hansen KK, Mogensen M (2008). ECS Trans 13:153–160[3] Chavan SV, Singh RN (2013). J Mater Sci 48:6597–6604[4] Fan W, Sun Z. (2016) RSC Adv 6:34564[5]Shaoli G., Hongjing Wu, (2015),Catalysts, 5, 366-391 Figure 1

Microstructure, mechanical properties, and cutting performances of WC-Co cemented carbides with Ru additions

In this study, the microstructure, mechanical properties, and cutting performance of WC-8Co cemented carbide with different Ru additions were studied in detail. The results show that Ru can inhibit the abnormal growth of WC grains and the mean grain size of WC grains decreases. Ru can result in the lattice distortion of Co phases and promote the phase transition of Co from face-centered cubic (FCC) to hexagonal closepacked (HCP) as Ru can reduce the stacking fault energy of Co phases. The proportion of HCP Co phases increased from 14.4 to 39.6% with increasing Ru content. Meanwhile, among the five groups of cemented carbides with different Ru additions, cemented carbides with 1.5 wt% Ru exhibit the highest hardness of 1382 HV and transverse rupture strength (TRS) of 3790 MPa. The enhanced hardness and TRS were due to solid solution strengthening and phase transition of Co, respectively. The fracture toughness of cemented carbide was enhanced from 16 MPa m−1/2 with 0 wt% Ru to 19 MPa m−1/2 with 0.5 wt% Ru. Additionally, during the dry cutting of Ti–6Al–4V, the diffusion of Ti and Al elements is hindered. Therefore, the wear resistance of the tools is improved. The cutting lifetime of the cemented carbide tools with 0.5 wt% Ru increased three-fold compared to those without Ru addition.

The role of ruthenium on the acidity of mixed alumina and silica phases and its impact on activity for ethanol dehydration

AbstractRuthenium catalysts anchored on three distinct supports (γ‐Al2O3, γ‐χ‐Al2O3, and silica [SiO2]) are tested for ethanol dehydration at 250°C. The catalytic materials were characterized using X‐ray diffraction (XRD), N2 physisorption, ammonia temperature programmed desorption (NH3‐TPD), FTIR, UV‐Vis spectroscopy, in situ UV‐Vis spectroscopy, H2 temperature programmed reduction experiments (H2‐TPR), and thermogravimetric analysis (TGA) after reaction. The activity was correlated to the number of acid sites present in the support. However, the addition of Ru increased the activity for alumina supported catalysts. Product selectivity depends on the nature of the acid sites present on the catalytic material, with ruthenium playing a critical role on the acid properties of the catalysts.

Trimetallic Ni-Co-Ru catalyst for the dry reforming of methane: Effect of the Ni/Co ratio and the calcination temperature

This work studies the effect of Ni/Co ratio and calcination temperature on the performance of trimetallic Ni-Co-Ru catalysts supported on MgO-Al2O3. Higher activity was achieved with higher Ni/Co ratios, and the effect of calcination temperature on stability was small except for the bimetallic Co-Ru catalyst which showed different deactivation mechanisms at different calcination temperatures. A higher calcination temperature was generally associated with an increased coking rate due to elevated sintering, while a lower calcination temperature slightly improved the reducibility of the catalysts. Promoting the Ni-Co catalysts with Ru improved their stability and reducibility, but slightly compromised catalyst activity when calcined at high temperature. Coking rate was significantly reduced by Ru addition on the 7.5Ni 7.5Co sample. Excellent stability and the lowest coking rate were achieved at the expense of a slightly lowered activity with the 5Ni 10Co 0.25Ru catalyst calcined at 750 °C.

Influence of Ta/Al ratio on the microstructure and creep property of a Ru-containing Ni-based single-crystal superalloy

Two alloys with different Ta and Al contents were applied to study the influence of Ta/Al ratio on the microstructural evolution and creep deformation under high temperature. The increase of Ta/Al ratio made the γ/γ′ lattice misfit more negative and enhanced the volume fraction of γ′ phase, which produced cubic and small γ′ phase in the initial microstructures. These initial tiny γ′ phases impeded the dislocations movement and delayed the course of complete rafted γ′ phase during the origination of creep deformation, which prolonged the time of the primary creep stage. Moreover, the increase of Ta/Al ratio and addition of Ru produced the denser and stable dislocation networks, the high APB energy and better solution strengthening, which hindered the climbing and sliding of dislocations, and restrained the formation of superdislocations in the γ′ precipitate. The second creep stage was extended, and the minimum creep rate was reduced. Hence, the increase of whole creep life of the alloy containing high Ta/Al ratio was attributed to the prolongation of the primary and second creep stages, and the low minimum creep rate. The appearance of the topological inversion phenomenon during the tertiary creep stage was the primary cause for the sudden increase of the creep strain rate of the alloy containing low Ta/Al ratio. However, the high creep strain rate of the alloy containing high Ta/Al ratio during the tertiary creep stage was related to the occurrence and extending of the cracks near the voids. Both alloys would lose efficacy within 20 h–30 h.

Mid-Infrared Scattering in γ-Al2O3 Catalytic Powders.

The energy efficiency of heterogeneous catalytic processes may be improved by using mid-infrared light to excite gas-phase reactants during the reaction, since vibrational excitation of molecules has been shown to increase their reactivity at the gas-catalyst interface. A primary challenge for such light-enabled catalysis is the need to ensure close coupling between light-excited molecules and the catalyst throughout the reactor. Thus, it is imperative to understand how to couple infrared light efficiently to molecules near and inside catalytic material. Heterogenous catalysts are often nanoscale metal particles supported on high surface area, porous oxide materials and exhibit feature sizes across multiple scattering regimes with respect to the mid-infrared wavelength. These complex powders make a direct measurement of the scattering properties challenging. Here, we demonstrate that a combination of directional hemispherical measurements along with the in-line transmission measurement allow for a direct measurement of the scattered light signal. We implement this technique to study the scattering behavior of the catalytic support material γ-Al2O3 (with and without metal loading) between 1040 and 1220 cm-1. We first study how both the mean grain size affects the scattering behavior by comparing three different mean grain sizes spanning three orders of magnitude (2, 40, and 900 µm). Furthermore, we study how the addition of metal catalyst nanoparticles, Ru, or Cu, to the support material impacts the light scattering behavior of the powder. We find that the 40 µm grain size scatters the most (up to 97% at 1220 cm-1) and that the addition of metal nanoparticles narrows the scattering angle but does not decrease the scattering efficiency. The strong scattering of the 40 µm grains makes them the most ideal support material of those studied for the given spectrum because of their ability to distribute light within the reactor. Finally, we estimate that less than 100 mW of laser power is needed to cause significant excitation for testing mid-infrared catalysis in a Harrick Praying Mantis diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reactor, a magnitude easily available using commercial mid-infrared lasers. Our work also provides a mid-infrared foundation for a wide range of studies of light-enabled catalysis and can be extended to other wavelengths of light or to study the scattering behavior of other complex powders in other fields, including ceramics, biomaterials, and geology.

Ni-based catalyst over rice husk-derived silica for the CO2 methanation reaction: Effect of Ru addition

Amorphous, high purity and sulfur-free silica was obtained from rice husk, which was used as support in metal catalysts. Ni and Ni-Ru catalysts were synthesized by wet impregnation over SiO2. The metallic loading was varied keeping the Ru/Ni ratio equal to 0.1. The solids were characterized by different techniques such as XRD, FT-IR, N2 adsorption, XRF, HRTEM, EDX, Raman, TPR, H2-TPD and XPS. They were evaluated in the CO2 methanation reaction between 250 and 400 °C. The rice husk-derived silica allowed obtaining Ni-based catalysts more suitable for CO2 methanation than commercial fumed silica. The incorporation of low amounts of Ru into Ni-based catalysts decreased particle size and improved the reducibility of NiO as well as the H2 adsorption capacity. The catalysts were active and stable. The Ni5Ru solid resulted the most promising catalyst for the CO2 methanation reaction by achieving the highest methane production rate with the lowest metal loading.

Effect of Re and Ru on the phase stability and coarsening kinetics of L12 phase in a Ni29Co27Fe27Cr3Al7Ti7 high entropy alloy

The thermal stability of precipitates is a major concern for L12-type strengthening high entropy alloy at elevated temperatures. In this study, we systematically investigated the effect of Re and Ru on the phase stability an d coarsening kinetics of L12 precipitates in the Ni29Co27Fe27Cr3Al7Ti7 HEA. The L12 phase exhibited a high volume fraction of 40.29% in the explored HEA and remained a stable morphology during the long-term exposure. Re addition did not change the volume fraction of L12 phase, while Ru addition decreased it to 34.42%. Both Re and Ru facilitated the formation of L21 precipitates slightly. Minor Re significantly decreased the coarsening rate of L12 phase and minor Ru also retarded the coarsening of L12 phase to some degree, which were mainly ascribed to the sluggish diffusion of Re and Ru atoms. These findings provide a feasible strategy to improve the coarsening resistance of L12 precipitates in HEA system through sluggish atomic diffusion.

A hydrothermal synthesis of Ru-doped LiMn1.5Ni0.5O4 cathode materials for enhanced electrochemical performance.

An Ru-doped spinel-structured LiNi0.5Mn1.5O4 (LNMO) cathode has been prepared via a simple hydrothermal synthesis method. The as-prepared cathode is characterized via Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), laser particle size distribution analysis, X-ray photoelectron spectroscopy (XPS) and electrochemistry performance tests. The FTIR spectroscopy and XRD analyses show that the Ru-doped LNMO has a good crystallinity with a disordered Fd3̄m space group structure. The disordered structure in the cathode increased and the LixNi1−xO impurity phase decreased when Ru addition increased. SEM shows that all samples are octahedral particles with homogeneous sizes distribution, and the particle size analysis shows that the Ru-doped samples have smaller particle size. XPS confirms the existence of Ru ions in the sample, and reveals that the Ru induce to part of Mn4+ transfers to Mn3+ in the LNMO. The electrochemical property indicated that the Ru-doped cathode exhibits better electrochemical properties in terms of discharge capacity, cycle stability and rate performance. At a current density of 50 mA g−1, the discharge specific capacity of the Ru-4 sample is 140 mA h g−1, which is much higher than that of the other samples. It can be seen from the rate capacity curves that the Ru-doped samples exhibit high discharge specific capacity, particularly at high current density.

Theoretical Investigation into the Key Role of Ru in the Epoxidation of Propylene over Cu2O(111)

The copper-catalyzed propylene epoxidation reaction is an important process to produce PO (propylene oxide), and the addition of Ru can enhance its selectivity significantly, so it is worthy to exp...

AN AB INITIO INVESTIGATION OF THE EFFECT OF Co, Ru, W, Ta ON THE STABILITY AND ELECTRONIC PROPERTIES OF Ni–BASE SINGLE CRYSTAL SUPERALLOYS

A first principles calculation method was used to investigate the site preference of Co, Ru, W, Ta at the '/ interface in Ni-based single-crystal superalloys. The calculation results show that the addition of Co, Ru, W and Ta can decrease the total energy and the binding energy of '/ interface, which may result in an improved microstructure stability of Ni-based single-crystal superalloys. Cr atom prefers to occupy a Ni site in  phase, while Ru, W and Ta atoms prefer to occupy Al sites in ' phase. It is found that the electronic bonding mechanism of '/ interface with the doped alloying elements can be summarized as the combination of d-d hybridization between Co-3d, d-p hybridization among Ru-4d, W-5d, Ta-5d orbits located at Al4 site in ' phase and Al-3p orbits and the electron charge transfers from Cr, Ru, W and Ta to Ni sites. The enhanced chemical bondings between alloying atoms and their neighbor host atoms are considered to be the main strengthening mechanism of the alloying elements in '/ interface of Ni-based single-crystal superalloys.

Sliding Wear Behavior of Ti-6Al-1.5V-1Mo-0.5Zr-0.1C Alloy Modified with Small Additions of Ru and Different V and Mo Contents.

AbstractTitanium alloys have been successfully used in the energy industry due to their stability at high temperature service, good mechanical properties and corrosion resistance. The near-α Ti-6%Al-1.5%V-1.0%Mo-0.5%Zr-0.1%C alloy, has been successfully used in several parts for geothermal energy generation. Several studies have concluded that the wear behavior of Ti alloys is generally poor; however, the specific tribosystem must be analyzed. This work analyzes the additions of 0.3%Ru, and variations of the V and Mo contents on the wear performance of a Ti alloy. Different combinations of α+β and degrees of microstructural refinement were observed depending on the composition. Wear test were undertaken by using a dry sliding block-on-ring configuration under the ASTM G77 standard. Two different loads (7 and 25 N) were used against a M2 hardened steel ring as a counter face with a hardness of 790 HV. Results showed that for the 7N load, the wear behavior is related to the volume fraction and thickness of the α phase; on the other hand, for the 25N load tests, the wear losses are directly proportional to the bulk hardness of the alloys and the α plate thickness, for this condition, best wear performance was achieved by the alloy 3 which contains 1.0wt%V, 1.8wt% Mo and 0.25wt% Ru. From the experimental results of the present study, it has been found that the wear behavior is directly related to the microstructure, e.g. amount of phases, refinement degree, applied load, and, in a lesser extent to the bulk hardness.

Sliding wear characteristics of WC-VC-Co alloys with various Ru additions

Investigations were done on the sliding wear characteristics of the following four alloy series: 80WC-10VC-(10-x)Co-xRu (0 ≤ x ≤ 3, 89.6-x)WC-0.4VC-10Co-xRu (0 ≤ x ≤ 2, 89.2-x)WC-0.8VC-10Co-xRu (0 ≤ x ≤ 2) and 89.6WC-0.4VC-(10-x)Co-xRu (0 ≤ x ≤ 3) (wt%), using a CSM ball-on-disk tribometer. All alloys had WC grains less than 1 μm and mild wear. Increased binder volume fractions increased the wear of 80WC-10VC-(10-x)Co-xRu and 89.6WC-0.4VC-(10-x)Co-xRu (wt%) alloys. The opposite occurred for the (89.6-x)WC-0.4VC-10Co-xRu and (89.2-x)WC-0.8VC-10Co-xRu (wt%) alloys. A direct relationship was found between alloy wear rate and binder mean free path for the 80WC-10VC-(10-x)Co-xRu, 89.6WC-0.4VC-(10-x)Co-xRu and (89.6-x)WC-0.4VC-10Co-xRu (wt%) series. There was an inverse relationship between binder mean free path and wear rate for the (89.2-x)WC-0.8VC-10Co-xRu (wt%) alloys. Alloy wear rate increased with increased mean WC intercept length for all series. There was an inverse relationship between hardness and wear rate for all alloy series. Higher Ru and VC contents increased the wear resistance of the alloys by decreasing the WC grain size. However, VC had a more significant effect on sliding wear than Ru. The 80WC-10VC-(10-x)Co-xRu (wt%) alloys had the lowest wear rates. Higher VC contents could potentially improve the cutting properties. Since there was a limited range of compositions, the effect of Ru on the cutting potential could not be evaluated.

Role of Ru on the microstructure and property of novel Co–Ti–V Superalloy

Abstract