Addition Of Tungsten Research Articles

Microstructure and tempering softening mechanism of modified H13 steel with the addition of Tungsten, Molybdenum, and lowering of Chromium

The rapid development in the advanced manufacturing industry asks for better tempering softening resistance (TSR) of Hot work die steels. In this work, a modified H13 steel (CXN03 steel) with additional tungsten, molybdenum, and lowering chromium was prepared. The TSR of CXN03 is significantly better than H13. After quenching at 1040 °C, the hardness and strength of H13 were larger than those of CXN03. However, the hardness and strength of CXN03 exceeded those of H13 after 2 h tempering at 600 °C. A mathematical model was utilized to correlate microstructural characteristics with yield strength during tempering. The calculated results indicated that the superior tempering softening resistance of CXN03 steel mainly results from the excellent stability of dispersive nano-sized M2C, which could prevent dislocation recovery. Recrystallization softening was observed in H13 but not in CXN03. The recrystallization of H13 is driven by dislocation movement, and the rearrangement of dislocations contributed to the formation of sub-boundaries. These sub-boundaries could divide martensite lath as well as form sub-grains. As the tempering time increased, sub-boundaries transformed into high-angle grain boundaries by absorbing the vicinal dislocations. Therefore, martensite lath collapsed, and massive recrystallized grains occurred. The massive stable M2C in CXN03 hindered the dislocation rearrangement, thus preventing the recrystallization.

Understanding the Catalytic Deactivation upon Hydrothermal Aging at 850 °C of WO3/Fe-Cu-ZSM-5 Catalyst for Selective Catalytic Reduction of NO by NH3

A WO3/Fe-Cu-ZSM-5 catalyst was prepared using the solid state ion exchange method (SSIE) and its performance for the Selective Catalytic Reduction of NO with NH3 (NH3-SCR of NO) was investigated. The study shows that the tungsten addition can slightly improve the high temperature catalytic activity of Fe-Cu-ZSM-5. The influence of hydrothermal aging at 850 °C for 5 h on the structural and textural properties of WO3/Fe-Cu-ZSM-5 was also studied in this paper. The XRD and FE-SEM measurements did not indicate a breakdown of the zeolite structure upon steam treatment for both aged catalysts. The aged W-base catalyst demonstrates a lower deactivation and better catalytic activity for NO reduction than the bimetallic catalyst after hydrothermal aging despite the lower acidic properties as shown by FTIR-Pyr spectroscopy owing to the presence of tungsten oxide crystallites. The “severe” stage of aging occurring in the absence of W led to the formation of copper oxide agglomerates detected using STEM and H2-TPR techniques being responsible for the deterioration of SCR activity of the aged Fe-Cu-ZSM-5.

Effect of Tungsten Addition on Continuous Cooling Transformation and Precipitation Behavior of a High Titanium Microalloyed Steel

Effects of tungsten addition on the continuous cooling transformation (CCT) characteristics and precipitation behavior of a high titanium microalloyed steel were investigated by dilatometry, optical microscopy, scanning and transmission electron microscopy, and hardness measurements. The results showed that the ranges of transformation products were moved to the right side of the CCT diagram when the 0.4% W was added. Accordingly, the following observations were made: (i) the ferrite phase transformation was shifted to the side of lower cooling rates and reduced temperatures; (ii) the bainite phase transformation region ran throughout the whole cooling rate range studied. Addition of W had a positive effect on the particle size refinement and number density increase of the precipitates. At the low cooling rates, in the range of <14 °C/s, W addition shifted the precipitation hardening peak to the low cooling rate side as the ferrite transformation induced stronger precipitation strengthening than the bainite one. Furthermore, the effect of W addition on phase transformation strengthening was obvious (increase in hardness: ~40Hv) at the high cooling rate range, over 14 °C/s.

The effect of Ta, W, and Re additions on the tensile-deformation behavior of model Ni-based single-crystal superalloys at intermediate temperature

The influence of refractory additions on tensile deformation behavior has been studied at an intermediate temperature (760°C) using scanning and transmission electron microscopy. Tensile experiments revealed that elemental additions of tantalum (Ta), tungsten (W), and rhenium (Re) could improve the yield strength (YS) of the model alloys with an order of YS(Ni–Al–W) > YS(Ni–Al–Ta) > YS(Ni–Al-Re) > YS(Ni–Al). During the plastic deformation of model alloys at the intermediate temperature, the deformation via Orowan bypassing and shear could be activated synergistically. The changes of anti-phase boundary (APB) energies on {001} and {111} planes are related to the cross-slip driving force, critical resolved shear stress and stage II work hardening rate in γ' precipitates. The effects of γ' size and refractory additions (Ta, W, and Re) on the yield strength of model alloys at intermediate temperature are also discussed, which can provide qualitative reference for alloy design.

Effects of cerium and tungsten addition on acid–base properties of spindle-like α-Fe2O3 in low-temperature SCR of NOx with NH3

Low-temperature selective catalytic reduction (SCR) is important for the elimination of NOx from stationary sources. In the present study, the loading of Ce and W on α-Fe2O3 was achieved through the integration of single-mode microwave and incipient wetness impregnation (IWI) methods. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images reveal that the structure of α-Fe2O3 is spindle-like, and the structure remains unchanged after the introduction of Ce and/or W. The results of NH3-SCR investigation demonstrate that NOx conversion over Ce–W/α-Fe2O3 is more than 85% at 300 °C, which is much higher than that over Ce/α-Fe2O3 and α-Fe2O3. Our studies illustrate that the addition of Ce can significantly increase the amount of surface oxygen vacancies as well as sites of moderate basicity. On the other hand, the addition of W can obviously decrease the amount of basic sites and increase the number of Brønsted acid sites. The synergistic effect of Ce and W addition on balancing acidity/basicity properties accounts for the high activity of Ce20W10/α-Fe2O3 for NOx removal at low temperatures. The study provides insight into the relationship between acidity/basicity properties and catalytic performance of Ce–W/α-Fe2O3 catalysts, which is beneficial to the design of high-performance NH3-SCR catalyst for NOx removal at low temperatures.

Effect of Boron and Tungsten Addition on Superplasticity and Grain Growth in Electrodeposited Nickel Alloys

Effect of Boron and Tungsten Addition on Superplasticity and Grain Growth in Electrodeposited Nickel Alloys

The Effect of Tungsten Addition on Steam Oxidation Behavior of the Fe-20Cr-35Ni (at％) Alloy at 1073 K

The Effect of Tungsten Addition on Steam Oxidation Behavior of the Fe-20Cr-35Ni (at％) Alloy at 1073 K

New Low-Temperature Method of Synthesis of Boron Carbide Matrix Ceramics Ultra-Dispersive Powders and their Spark Plasma Sintering

The ultra-dispersive powders of pre-ceramic precursors for boron carbide based composites were obtained by relatively low-temperature (at 200 – 1000 °C) synthesis from liquid charges containing available compounds such as salts and oxides. Boron carbide matrix ceramics were compacted by their reactive spark plasma sintering (SPS) at 1500 – 1700 °C. It is noted that the X-ray diffraction (XRD) peaks corresponding (m)ZrO2 and WC phases presented in the synthetic pre-ceramic precursors disappear after the SPS is conducted at 1500 °C. It is established that the addition of tungsten and cobalt compounds promotes both the low-temperature synthesis of ceramic components and sintering processes of their powders. Energy dispersive X-ray (EDX) analysis showed that the ceramics contain a small amount of Co (0.8 – 2 wt.%). The density of samples of cobalt-containing ceramics B4C–ZrB2–W2B5–Co is higher compared to that of cobalt-free ceramics B4C–ZrB2–W2B5.

Plasma-enhanced sol-gel fabrication of CoWNiAl2O4 nanocatalyst used in oxidative conversion of greenhouse CH4/CO2 gas mixture to H2/CO

Design of nanocatalysts with promoted anti-coke ability, high catalytic activity and stable performance during oxidative conversion of CH4/CO2 mixture to syngas was the purpose of this study. First, NiAl2O4, WNiAl2O4 and CoWNiAl2O4 nanocatalysts were fabricated using sol-gel technique. Then, plasma treatment was utilized for enhancement of CoWNiAl2O4. The fresh samples were characterized by XRD, FESEM, EDX, BET, TEM and FTIR analyses. Through the 48 h time on stream performance, methane conversion was dropped by 13% and coke deposition of 17.3% occurred during the stability test of NiAl2O4. Addition of tungsten into NiAl2O4, due to its ability in upgrading the rate of coke gasification, caused quite stable performance. In contrast, lower catalytic activity was found for WNiAl2O4 as a result of active sites coverage. It was made an effort to compensate the reduction of catalytic activity by cobalt addition. Smaller particle size and uniform dispersion were achieved for cobalt promoted nanocatalysts. Therefore, catalytic activity was ascended. However, for sol-gel prepared CoWNiAl2O4 high efficiency was found, but higher amount of deposited coke and deactivation were detected. The novel synthesis method i.e. hybrid sol-gel plasma alongside the cobalt and tungsten promoters caused a well-designed nanocatalyst. Promoted dispersion of active phases, finer particle size, stronger metal-support interaction and high surface area were achieved for plasma-enhanced sol-gel fabricated CoWNiAl2O4. Due to these tremendous properties, XCH4= 92% was obtained for this sample at 850 °C. A well-maintained structure and excellent dispersion were gained after 48 h TOS, as evidenced by FESEM and EDX images of used nanocatalysts.

Modulating local environment of Ni with W for synthesis of carbon nanotubes and hydrogen from plastics

The strategy of thermochemical conversion of plastic waste into carbon nanotubes (CNTs) and hydrogen makes both environmental and economic sense. Exploring high-performance catalysts is an essential prerequisite of converting plastics by pyrolysis and in-line catalysis technology. To improve the catalytic performance of Ni–Mg system, high-valency and refractory tungsten as a promoter was introduced. A series of W–Ni–Mg oxides with various W/Ni atomic ratios (0, 1/15, 1/7, 1/3) were synthesized and their catalytic performances were evaluated. The sample with W/Ni atomic ratio of 1/7 exhibited the mixed phase of MgNiO2 and MgWO4 and showed the highest yields of CNTs and hydrogen. Furthermore, the effect of tungsten on the modulating the local coordination and electronic structure of active Ni was explored. The addition of tungsten facilitated the reduction of Ni and maintained it as solid state, not traditional quasi-liquid state, to alleviate the aggregation and migration of Ni nanoparticles. Thus, the CNT growth over W–Ni–Mg oxide sample predominantly followed vapor−solid−solid mechanism, while vapor−liquid−solid mechanism could still occur as the secondary growth of CNTs.

Tuning the energy bandgap and nonlinear absorption coefficients of WOx/ ZrO2 nanocomposite thin films with the role of weight and doping concentration

The structural, linear and nonlinear optical properties of PMMA/ZrO2 and PMMA/WZrO2 nanocomposites thin films were investigated. Tungstated zirconia nanoparticles were synthesized with different tungsten concentrations (3, 20 and 37% w/w) via solvothermal reflux method. To investigate the effect of weight and doping concentration, thin films with different tungsten ratio (undoped, %3, %20 and %37 W doped) were prepared and also weight percentage of the investigated samples in polymer (10 and 20 wt%) were changed for each doping ratio. The samples were examined using XRD, TEM, XPS and EDX analysis. The linear and nonlinear optical properties were studied by UV–Visible spectrophotometry and Z scan technique. The linear spectra were used to calculate the energy band gap. The fluorescence peak at 375 nm for undoped and doped ZrO2 nanocomposites are assigned to the presence of oxygen vacancies in the nanostructures. A theoretical model including one photon, two photon and free carrier absorptions and their saturations were used to analyze the experimental data. The linear absorption of all samples increased with increasing weight percentage of the films. The films which have a low tungsten ratio (%3 W) showed minimal absorption. The band gap decreased with addition of tungsten and the increasing nanoparticle weight concentration. OA Z-scan experiment results indicated that the addition of the tungsten to PMMA/ZrO2 reduced the nonlinear absorption performance.

Effectiveness of tungsten addition on the performance of electroplated nickel diffusion barriers for copper metallization on textured silicon

In this work, the nickel-tungsten alloy is used as the diffusion barrier for copper metallization on textured silicon. Nickel silicides formed as the seed layer for the nickel-tungsten alloy. Then, copper metallization was performed by an electroplating method to create the Cu/NiW/NiSiy/Si structure. The Cu/NiW/NiSiy/Si samples were annealed at various temperatures for 10 minutes in an annealing furnace under Ar/H2 atmospheres. The annealed Cu/NiW/NiSiy/Si samples were characterized by X-ray diffraction, scanning electron microscopy, and scanning transmission electron microscopy. For the Cu/NiW/NiSiy/Si samples with NiW thicknesses of 300 nm and 350 nm, the Cu3Si phase developed at annealing temperatures of 500 °C and 600 °C, respectively. The NiW layer is a better diffusion barrier against copper than the Ni layer.

Polyethylene composite with boron and tungsten additives for mixed radiation shielding

Mixed neutron and gamma radiations are common in many nuclear applications. Several materials can be combined to obtain a composite material that is better for mixed radiation than the individual component materials. The aim of this paper is to investigate the shielding effectiveness of a polyethylene (PE)-based composite with boron and tungsten additives. Several compositions are tested to shield against a 252Cf fission neutron source using an attenuation experiment. The composite is also manufactured using the melt-mixing method of component raw materials. Comparisons are made between the different compositions and the experimental results. Results suggest that the PE composite with 16%wt boron and 16%wt tungsten show the best mixed radiation attenuation as compared to pure PE, PE composite with 25%wt boron, and PE composite with 25%wt tungsten.

The Effect of Tantalum, Tungsten, and Rhenium Additions on the Tensile-Deformation Behavior of Model Nickel-Based Single-Crystal Superalloys at Intermediate Temperature

The Effect of Tantalum, Tungsten, and Rhenium Additions on the Tensile-Deformation Behavior of Model Nickel-Based Single-Crystal Superalloys at Intermediate Temperature

Mechanism of Action of the Tungsten Dopant in LiNiO2 Positive Electrode Materials

AbstractThe addition of tungsten has been reported to greatly improve the capacity retention of Ni‐rich layered oxide cathode materials in lithium‐ion batteries. In this work, Ni(OH)2 precursors, coated with WO3 and also W‐containing precursors prepared by co‐precipitation followed by heat treatment with LiOH·H2O, are studied. Structural analysi s and electron microscopy show that W is incorporated as amorphous LixWyOz phases concentrated in all the grain boundaries between the primary particles of LiNiO2 (LNO) and on the surface of the secondary particles. Tungsten does not substitute for Ni or Li in the LNO lattice no matter how W is added at the precursor synthesis stage. Scanning electron microscopy (SEM) images show that adding W greatly suppresses primary particle growth during synthesis. In agreement with previous literature reports, cycling test results show that 1% W added to LNO can greatly improve charge–discharge capacity retention while also delivering a high specific capacity. The LixWyOz amorphous phases act as coating layer on both the primary and secondary particles, restrict primary particle growth during synthesis and increase the resistance of the secondary particles to microcracking.

Tungsten Infused Grain Boundaries Enabling Universal Performance Enhancement of Co-Free Ni-Rich Cathode Materials

Ni-rich cathode materials suffer from poor capacity retention due to micro-cracking and interfacial reactivity with electrolyte. Addition of tungsten (W) to some Ni-rich materials can improve capacity retention. Here, a WO3 surface coating is applied on Ni-rich hydroxide precursors before heating with lithium hydroxide. After heating in oxygen, Ni-rich materials with any of the commonly used dopants (magnesium, aluminum, manganese, etc.) show a “universal” improvement in capacity retention. Experimental characterization and theoretical modelling showed W was concentrated in the grain boundaries between the primary grains of secondary particles of the layered oxides, and W is incorporated in amorphous LixWyOz phases rather than as a substituent in the LiNiO2 lattice. This self-infusion of W in the grain boundaries during synthesis also significantly restricts primary crystallite grain growth. Along with smaller primary grain size, the LixWyOz phases in the grain boundaries lead to improved resistance to microcracking and reduced surface or interfacial reactivity. Improving the intrinsic properties of primary grains through doping of Mg, Al, or Mn and reinforcing the secondary particle structure mechanically and chemically using W or a similar element, M, that forms LixMOy phases and does not substitute into LiNiO2 is a universal strategy to improve polycrystalline Ni-rich materials.

Excellent low-temperature NH3-SCR of NO activity and resistance to H2O and SO2 over WaCeOx (a = 0.06, 0.12, 0.18, 0.24) catalysts: Key role of acidity derived from tungsten addition

Bimetallic WaCeOx (a = 0.06, 0.12, 0.18, 0.24) catalysts were synthesized for selective catalytic reduction of NOx with NH3 (NH3-SCR). The influences of W on structure, activity and surface properties were investigated by XRF, XRD, Raman, TEM, N2 adsorption-desorption, H2-TPR, O2/NH3/SO2-TPD, XPS, and in-situ DRIFTS. The characterization results show that the W/Ce ratio has a great effect on the NH3-SCR activity. The different catalytic activities of WaCeOx are mainly attributed to the acidity change, especially the increase of B-acid content plays a major role in enhancing low temperature activity. W0.18CeOx exhibits excellent low-temperature NH3-SCR activity, SO2/H2O resistance and N2 selectivity with a broad activity window (190–490 °C) with 5%H2O. Moreover, good activity window (235–460 °C) can be maintained even the catalyst treated with 5% H2O at 800 °C for 12 h, showing especial hydrothermal stability. Thus, it can be summarized that W0.18CeOx is regarded as outstanding catalyst for low-temperature NH3-SCR of NO.

Effect of alloy elements on iridium shear modulus by Ab initio analysis.

The effect of the addition of rhodium (Rh), rhenium (Re), tungsten (W), gold (Au), and platinum (Pt) on the shear modulus of face-centered cubic iridium (Ir) was investigated using an ab initio method. The shear modulus was calculated using the second derivative of the strain energy with respect to strain. It was found that both the bulk modulus (G) and the ratio (G/B) between bulk and shear modulus decreased with the addition of elements to the Ir, which meant that all five of these alloy elements lowered the brittleness of the bulk Ir. The decreased shear modulus was the main factor for the lowered brittleness. And the decreasing order of shear modulus in the [112] and [100] crystalline directions was Ir > Rh > Pt > W = Au > Re and Ir > W > Rh > Pt > Au > Re respectively. The reason for the order was both the atomic distance and the bond strength between alloy atoms and Ir atoms. The larger bond strength meant the larger shear modulus, and the smaller atomic distance meant the smaller shear modulus.

Experimental Investigation of Material Properties in FSW Dissimilar Aluminum-Steel Lap Joints

The friction stir lap welding of AA5083 H111 aluminum alloy and S355J2 grade DH36 structural steel was investigated. A polycrystalline cubic boron nitride with tungsten and rhenium additives tool was used. According to visual inspection, radiographic examination, and tensile test, it was observed that the best results were obtained for rotation speeds of about 700–800 rpm, with a feed speed ranging between 1.3 and 1.9 mm/s. From the fatigue tests, it is possible to state that there was a preferential propagation of cracks in the part of the aluminum alloy base material. Furthermore, a different response to fatigue stress for samples extracted from the same weld at different positions was observed, which introduces an overall variability in weld behavior along the welding direction. The specimens obtained in the second part of the weld endured a larger number of cycles before reaching failure, which can be related to progressively varying thermal conditions, dissipation behavior, and better metal coupling as the tool travels along the welding line.

Influence of W Addition on Microstructure and Resistance to Brittle Cracking of TiB2 Coatings Deposited by DCMS.

The aim of this work was to determine the influence of the tungsten addition to TiB2 coatings on their microstructure and brittle cracking resistance. Four coatings of different compositions (0, 7, 15, and 20 at.% of W) were deposited by magnetron sputtering from TiB2 and W targets. The coatings were investigated by the following methods: X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). All coatings had a homogeneous columnar structure with decreasing column width as the tungsten content increased. XRD and XPS analysis showed the presence of TiB2 and nonstoichiometric TiBx phases with an excess or deficiency of boron depending on composition. The crystalline size decreased from 27 nm to 10 nm with increasing W content. The brittle cracking resistance improved with increasing content of TiBx phase with deficiency of B and decreasing crystalline size.