Al-W Alloy Research Articles

Barnacle carapace-chitosan supported highly-efficient nano Al-W alloy electrocatalyst for sustainable bio-glycerol valorization: Environmental impact and cost analyses

For the first time, highly efficient, corrosion resistant, and chemically stable rock barnacle carapace-derived chitosan (CH) supported non-noble nano aluminum-tungsten bimetallic-alloy based bifunctional electrocatalyst has been developed for waste pork lard-derived glycerol (WPLG) electrolysis in NaOH medium, ascertaining sustainability. An indirect bio-glycerol oxidation mechanism has been well executed to produce industrially important glyceric acid (6.65 mmol cm−2 h−1, 79.92% selectivity, ∼90% FE%) and formic acid (1.67 mmol cm−2 h−1, 18.07% selectivity) at the anode at ambient temperature and pressure. However, among the various prepared unsupported and supported nanocomposite electrocatalysts, the optimal aluminum-tungsten alloy anchored over chitosan renovated carbon nanotube (Al:W = 1:2 mole/mole) electrode rendered the lowest onset potential (0.95 V vs. RHE) and highest peak current density (119.61 mA cm−2) for the WPLG electrooxidation at the anode, coupled with H2 generation (28.55 ml cm−2 h−1) in the cathode in a membrane free electrochemical-cell by replacing sluggish oxygen evolution reaction. Comparing the electricity consumption for H2 production from various prepared catalysts, the supported optimum catalyst consumed 9.3% less energy (only 2.9 kWh/m3 H2) and 67.91% less corrosion current density as compared to the unsupported Al/W electrocatalyst, exhibiting excellent stability and durability (>200 cycles) due to good alloy-support interaction. Finally, a comprehensive life cycle impact assessment and life cycle costing of the overall WPLG electrolysis demonstrated 12.29% lower global warming potential (GWP100) while saving 11.03% of the cost compared to commercial glycerol electrolysis, which could procreate an effective approach toward inexpensive catalyst fabrication and its subsequent application for sustainable glycerol electrolysis.

Spatial phase structure and oxidation process of Al-W alloy powder with high sphericity

• The Al-30W alloy powder was prepared by thermit reduction and gas atomization. • The Al-30W alloy powder particles presented unique spatial phase structures. • The spatial phase structures of the Al-30W alloy powder changed with temperature. • The Al-30W alloy powder had excellent thermal reactivity and oxidation integrity. • The oxidation product WO 3 of the Al-30W alloy powder volatilized in gaseous form. In this study, Al-30W (wt.%) alloy powder was prepared by Aluminothermic reduction and high-temperature gas atomization. We then studied the phase composition, surface morphology, spatial phase structure, and thermal oxidation process using XRD, SEM/EDS, TEM, DSC, and DTA/TG analysis. The results showed that the Al-30W alloy powder exhibited high sphericity, and the interior presented a special spatial phase structure in which the Al/W amorphous alloy phase and the metastable Al/W intermetallic compound phase were distributed in the pure Al matrix. When the Al-30W alloy powder was stabilized in a vacuum tube furnace, the spatial phase structure of the alloy powder changed, and a small amount of pure Al was embedded in the Al 12 W matrix. The resulting Al-30W alloy powder products, treated in air at different temperatures, were collected in situ and characterized. The results presented that with an increase in temperature, the types and morphologies of the Al/W intermetallic compounds in the Al-30W alloy powder changed. Furthermore, the Al-30W alloy powder began to undergo intense oxidation reactions at about 900 °C, accompanied by a concentrated energy release and rapid weight gain. The volatilization of WO 3 produced in the oxidation process promoted the complete oxidation of the Al-30W alloy powder, and the Al-30W alloy powder was completely oxidized at 1300 °C. At this stage, all W atoms were transformed into gaseous WO 3 , and only a large number of small Al 2 O 3 fragments remained in the oxidation product. Thus, the Al-30W alloy powder exhibited excellent thermal reactivity and oxidation integrity, and may offer excellent application prospects in the field of energetic materials.

Electrodeposition and characterisation of Al-W alloy films from ionic liquid

Al–W alloy films were prepared by electrodeposition using anhydrous 1-ethyl-3-methylimidazolium chloride (EMIMCl) ionic-liquid solution with aluminium chloride in a ratio of 1:1.5. As a commercially available tungsten precursor, tungsten hexachloride was used. The metal is dissolved in the ionic liquid at concentrations up to 0.06 mol/l. The deposition took place outside the glove box with a continuous argon stream over the electrolyte at a temperature of 60 °C with a current density of 1 A/m2. Resulting alloys show a tungsten content higher than 20 wt% (3.5 at%). The phase composition of Al-W alloys was observed by X-ray diffraction (XRD), and the chemical composition was characterised by scanning electron microscopy (SEM) and inductively-coupled plasma optical emission spectroscopy (ICP-OES).

Processing Map of Powder Metallurgy Al-W Alloys at Elevated Temperatures

An Al-0.71 wt.% W alloy was prepared via powder metallurgy (PM) using a room-temperature pressing process and a subsequent hot-pressing process. Studies of the deformation behavior of the PM Al-W alloy were conducted using hot-compression tests in the temperature range from 420 to 570 °C and a strain rate range from 0.001 to 5 s−1. After the stress-strain data were acquired as a function of temperature and strain rate, processing maps that depict the variation in the power dissipation efficiency were constructed and interpreted via the dynamic materials model. The optimum temperature and strain rate combination for PM billet conditioning were demonstrated to be 560-570 °C and 0.001 s−1, respectively. Additionally, a secondary metal working process with a higher production efficiency on the PM billet was conducted at a higher strain rate from 0.01 to 0.1 s−1 and at a low temperature from 500 to 540 °C. The PM Al-W alloy was successfully extruded at 540 °C with a ram speed of 2 mm min−1 and an extrusion ratio of 5:1. The ultimate tensile strength and elongation of the test sample taken from the 15-mm-diameter as-extruded rods were 478 MPa and 15.4%, respectively.

Electrodeposition of Al-W Alloy Films in a 1-Ethyl-3-methyl-imidazolium Chloride-AlCl3 Ionic Liquid Containing W6Cl12

The electrodeposition of Al-W alloy films in a Lewis acidic 1-ethyl-3-methyl-imidazolium chloride (EMIC)-AlCl3 ionic liquid using W6Cl12 as the W ion source was investigated. W6Cl12 dissolved in the ionic liquid at a higher concentration than other W ion sources used in previous studies. Potentiostatic electrodeposition was performed in a bath containing W6Cl12 at a concentration of 49 mM. Dense Al-W alloy films containing up to 12 at.% W were electrodeposited at potentials more negative than 0 V vs. Al/Al(III). The deposition current density at >0 V was lower than 0.3 mA cm−2, while that for Al-W alloy films was higher and reached 38 mA cm−2 at −0.5 V. The deposition of W was induced by the deposition of Al. At lower W concentrations, the Al-W alloy films were composed of a super-saturated solid solution, and in the W content range of 9–12 at.% they comprised an amorphous phase. Potentiodynamic polarization and nano-indentation showed that the Al-W alloy films containing 10–12 at.% W exhibited high pitting corrosion resistance, high hardness, and low Young's modulus.

Mechanical Properties of Electrodeposited Al-W Alloy Films and the Effects of Subsequent Heat Treatment

Due to their high oxidation and corrosion resistance, Al coatings are effective in extending the lifetimes of other metallic materials. However, the low mechanical strength of Al can limit its adoption for certain applications. Alloying Al with other transition metals, which improves the mechanical properties, can be a possible solution to this problem. Electrodeposition is a simple method of forming Al-base alloy films from ionic liquids represented by EMIC-AlCl3. Among the Al-base alloys, Al-W alloy is of significant interest since it is expected to exhibit excellent mechanical properties. The electrodeposition of Al-W alloys from EMIC-AlCl3 baths containing K3W2Cl9 was reported previously[1]. However, Al-W alloys electrodeposited from this system had a powdery morphology when the W content was >7 at.%, and the mechanical properties have not been investigated. In this study, we report the electrodeposition of Al-W alloy films from EMIC-AlCl3 baths containing WCl2. Nano-indentation tests were undertaken to determine the hardness and Young’s modulus of the Al-W alloy films. The effects of heat treatment on the mechanical properties were also examined. It was possible to electrodeposit Al-W alloy films containing up to 12 at.% W. XRD patterns showed that these films were fcc solid solution at low W contents, and were amorphous at 12 at.% W. The hardness increased from 1.8 GPa with increasing W content. The film containing 12 at.% W showed the highest hardness value of 4.6 GPa, which is close to that of pure bulk W. The Young’s modulus also increased from 97 to 168 GPa with increasing W content in the solid solution range, followed by a sudden decrease to 89 GPa at 12 at.% W. This value is close to that of pure bulk Al. The low Young’s modulus of Al-12 at.% W alloy is attributed to its amorphous structure. Heat treatment at 300-400°C for 3 h was carried out. After the heat treatment at 400°C, Al-W intermetallic compounds were detectable by XRD, and both the hardness and Young’s modulus increased. These results show that Al-W alloy films with excellent mechanical properties can be obtained from EMIC-AlCl3-WCl2baths. In particular, amorphous Al-12 at.% W films displayed interesting properties, including hardness values as high as that of W and Young’s modulus values as low as that of Al. The hardness and Young’s modulus of Al-W films can be controlled by modifying the W content and conducting subsequent heat-treatment. [1] T. Tsuda et al., Journal of the Electrochemical Society 161, D405-D412 (2014)

Electrodeposition of Al-W Alloys in AlCl3-NaCl-KCl Molten Salt Containing WCl4

Introduction Aluminum and aluminum alloys are widely used in a variety of industrial products like cars and electric appliances due to the lightweight and excellent electrical and thermal conductivity. Furthermore, aluminum oxide which is very thin and chemically stable forms on the surface. The oxide film contributes the corrosion resistant property of the surface. However, in the presence of halogen ions (ex. Cl-, F-, I- and Br- ions), corrosion takes place for the oxide surface. Al‐transition metal alloys have better corrosion resistance for chloride solution. Al-W alloys especially show the good corrosion resistance for pitting corrosion of the surface. Al-W alloys are also expected the increase of the hardness compared with pure Al. One of the available method to obtain Al alloys is an electrodeposition. Tsuda et al. previously reported the electrodeposition of Al-W alloy in the Lewis acidic AlCl3-[EtMeIm]Cl room temperature ionic liquid1). When higher temperature molten salts are used for electrodeposition of Al-W alloys, rapid electrodeposition may be achieved. AlCl3-NaCl-KCl molten salt is useful melt because the eutectic point of this system is 366 K at the composition of AlCl3 : NaCl : KCl = 61 : 26 : 13 (molar ratio). In this study, we report the mechanism of electrodeposition of Al-W alloys in the AlCl3-NaCl-KCl melt and discuss the relationship between the composition of the electrodeposit and the electrolysis potential. Experimental Electrodeposition of Al-W alloys was carried out in AlCl3-NaCl-KCl melt containing 10 mM WCl4 at 423 K. The electrochemical cell was used three-electrode system. A glassy carbon plate or a pure copper plate was used as working electrode at the voltammogram measurements or constant current electrolysis, respectively. An aluminum plate or a tungsten plate was used as counter electrode. Pure aluminum wire placed in a Pyrex glass tube filled with the AlCl3-NaCl-KCl melt was used as a reference electrode. All electrochemical measurements were performed under air atmosphere. The composition, surface morphology and identification of the electrodeposits were used X-ray fluorescence spectrometer (XRF), scanning electron microscope (SEM) and X-ray diffraction (XRD) instrument. Results and discussion A voltammogram was measured between 1.5 V and -0.2 V vs. Al/Al (III) at a sweep rate of 0.01 Vs-1 on a glassy carbon electrode in the AlCl3-NaCl-KCl melt with or without WCl4. In the melt without WCl4, the voltammogram showed a cathodic current at lower than -0.03 V with steep increase. An anodic current was observed from -0.02 V in the reverse scan. The cathodic and anodic currents correspond to the Al deposition and dissolution reactions, respectively. In the melt containing WCl4, two small cathodic currents were observed from 1.05 V and 0.45 V in the cathodic scan. The two cathodic currents correspond to a reduction of tungsten ions. When the potential is reversed at -0.2 V, an anodic current appeared from 0 V. The anodic current corresponds to dissolution of Al and Al-W alloy formed by the previous cathodic scan. In the results, the reduction steps of W ions lower than 1.05 V may occur from W (IV) to W (III), and from W (III) to W (0) below 0.45 V. To examine the relation between the electrolysis potential and the composition of the electrodeposits, constant potential electrolysis of Al-W alloys was carried out on Cu substrate at the potential range from -0.05 V to 0.4 V with electric charge of -30 Ccm-2(theoretical film thickness, 10 μm). The results suggested that when the electrolysis potential becomes higher, the W content in the electrodeposits increases. SEM images of the Al-W alloy prepared at -0.05 V and -0.025 V showed size of particle of about 5 μm, and cover the entire surface uniformly. On the other hand, it was found that a relatively small electrodeposit was formed on the substrate at higher than 0 V. The results of XRD showed the peaks corresponding to Al when the W content is less than 1 at%. When the W content is higher than 19 at%, Al peaks disappeared. However, broad peak showing the presence of an amorphous phase of W was observed at 0.4 V. Reference 1) Tetsuya Tsuda et al, J. Electrochem.Soc. 161, D405 (2014). Acknowledgment This paper is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Electrodeposition of Al-W Alloy Films from Ionic Liquid and Evaluation of Their Corrosion Resistance and Mechanical Properties

Introduction The many useful characteristics of Al, particularly its high oxidation and corrosion resistance, make Al coatings effective in extending the lives of metallic materials. However, if Al is exposed to an environment where chloride ions are present (like seawater), the Al passivation layer is destroyed locally, followed by the creation of small holes on the surface. This form of corrosion is called pitting corrosion, and Al–transition metal alloys are known to exhibit a resistance to pitting corrosion. In particular, sputtered Al–W alloy films are reported to show outstanding pitting corrosion resistance [1-3]. Establishing a method for electrodeposition of Al–W films is of importance for industrial applications, because electrodeposition has advantages over other film formation processes including simple equipment, high film formation speed, and applicability in the case of complex surface shapes. Tsuda et al. reported the electrodeposition of Al–W alloys with a high W content from the 1-ethyl-3-methylimidazolium chloride(EMIC)–AlCl3 ionic liquid containing K3W2Cl9 [4]. However, these Al–W alloys had a powdery morphology when the W content was higher than 3 at%, and did not show significant pitting corrosion resistance. In this study, we formed smooth, dense and adherent Al–W alloy coatings by electrodeposition from the EMIC–AlCl3 ionic liquid with the addition of WCl2, and we investigated the pitting corrosion resistance of the resulting coatings. Furthermore, we evaluated the mechanical properties of the Al–W alloy coatings. Experimental The electrolytic bath was prepared by mixing EMIC with anhydrous AlCl3, and tungsten(II) chloride. The tungsten(II) chloride was prepared by reduction of tungsten(VI) chloride by bismuth. The electrodeposition of Al–W films was conducted under galvanostatic conditions using Cu and Al plates as the cathode and anode, respectively. The bath temperature was 80°C. All electrodeposition experiments were conducted in an argon-filled glove box. The electrodeposited films were analyzed by SEM, EDX, and XRD. Partial current density and current efficiency were determined by ICP-AES. The water content of the electrolytic bath was measured by the coulometric Karl Fischer method. Pitting corrosion potentials were determined by linear sweep voltammetry in a deaerated 3.5 wt% NaCl aqueous solution at room temperature. The mechanical properties of Al–W films were analyzed by the nano-indentation method. Results and Discussion The electrodeposited Al–W films were gray and had a rather smooth appearance. Surface and cross-sectional SEM observation showed that these films were composed of dense globular grains, which is characteristic of amorphous deposit. The average grain size was less than 3 μm. At a fixed concentration of tungsten (II) chloride in the bath, the W content of the films was, typically 15–16 at%, independent of the current density. XRD measurements detected no diffraction peaks from these Al–W films, indicating that the films were amorphous. The current efficiency for the Al–W electrodeposition estimated by ICP-AES was less than 87%, which was lower than that for pure Al electrodeposition. Further, the water content was found to be higher in the electrolytic bath with tungsten(II) chloride than in the bath without it. Therefore, the current loss is attributed to the reduction of water. The pitting corrosion potential of the Al–W alloy film was more positive by >800 mV than that of pure Al, indicating that the Al–W films have a high resistance to the pitting corrosion. Nano-indentation showed that the amorphous Al–W alloy films had high hardness and low elastic modulus compared to a pure Al film. As the alloy films were amorphous, the films contained no grain boundaries and dislocations, and this should be responsible for the excellent hardness and elastic modulus. Conclusion Smooth, dense, and adherent Al–16 at% W alloy films were obtained by electrodeposition. The Al–W alloy films exhibited excellent pitting corrosion resistance and mechanical properties compared with pure Al films. These results sufficiently demonstrate the potential applications of the electrodeposited Al–W alloy as a surface protective material.

Microstructural stability and tensile properties of a Ti-containing single-crystal Co–Ni–Al–W-base alloy

Microstructural stability and tensile properties of a Ti-containing single-crystal Co–Ni–Al–W-alloy with low tungsten content have been investigated. The alloy possesses relatively lower density and higher γ′ solvus temperature compared to some high-tungsten-content Co–Al–W-base alloys. After aging at 900–1000°C for 400 h, the alloy maintains the stable γ/γ′ two-phase microstructure without the presence of secondary phases. In the low and medium temperature range (R.T.–800°C), the alloy exhibits superior tensile strength compared to the reported single-crystal Co–Al–W-base alloys, while above 800°C, the yield stress decreases rapidly with temperature increasing. The major deformation mechanisms of the alloy consist of shearing of the γ′ precipitates by pairs of a/2〈110〉-type dislocations from room temperature to 800°C and bypassing of the γ′ precipitates by a/2〈110〉-type matrix dislocations above 900°C. At 900°C, it shows a transition from the γ′ shearing to bypassing.

Pressing Process of Al-W Alloy Powder and Constitutive Model the Pressed Billet at Elevated Temperatures

Al-W alloy billets were produced by powder pressing at room temperature and subsequent hot pressing. Quantities of billets were compressed at constant strain rate and temperature with 60% height reduction on Gleeble-3800 thermal simulation testing machine to study the plastic flow behaviors of the test alloy. The temperature of the compression processes ranged from 450 to 570oC. The strain rate was varied between 0.001 and 1s−1. The regularity of flow stress for the test alloy varied at elevated temperatures was studied. The activation energy during hot deformation is 757.943 kJ/mol by calculated, and the Arrhenius constitutive relation model was established. Keywords: Al-W alloy, powder metallurgy, thermal simulation, constitutive model

Electrodeposition of Al-W-Mn Alloy from Lewis Acidic AlCl3−1-Ethyl-3-Methylimidazolium Chloride Ionic Liquid

The electrodeposition of non-equilibrium ternary Al-W-Mn alloys was investigated in the Lewis acidic 66.7-33.3 mol % aluminum chloride–1-ethyl-3-methylimidazolium chloride (AlCl3–[C2mim]Cl) ionic liquid (IL) with K3[W2Cl9] and MnCl2 to improve the properties of binary Al-W alloy electrodeposits. The Al-W-Mn alloys were electrochemically deposited on Cu substrates. The W content in the Al-W-Mn alloys monotonically decreased with increasing the applied current density independently of the K3[W2Cl9] and MnCl2 concentration in the IL solution. The Mn content in the ternary alloys was significantly affected by the electrodeposition condition. The XRD and EDS analyses revealed that the Al-W-Mn alloys prepared in this research have non-equilibrium solid solution and amorphous phases without chloride contamination. The surface morphology was improved by adding Mn to the Al-W alloy, and the pitting potential of the Al-W-Mn alloy surpassed that for the electrodeposited Al-W and Al-Mn binary alloy systems.

Constitutive Relationship Model of Al-W Alloy Using Artificial Neural Network

Isothermal compression experiment of Al-W alloy was carried out using Gleeble1500 thermodynamic simulator within a temperature range of 420°C-570°C and a strain rate range of 0.001s-1-1s-1。And the constitutive relationship model for this alloy was successfully developed using BP neural network. In the proposed model, the input variables are strain, strain rate and deformation temperature while the flow stress is the output variable. The results show that absolute maximum error between predicted and experimental values of flow stress is less than 10.0Mpa, the correlation coefficient is 0.993. It was found that the established constitutive relationship model could provide a good representation of the test data and describe the whole deforming process better compared with the traditional method.

Electrodeposition of Al-W-Mn Alloy from Lewis Acidic AlCl3−1-Ethyl-3-Methylimidazolium Chloride Ionic Liquid

It is well-known that Al-W alloy prepared by non-equilibrium alloying methods, e.g., RF sputtering deposition, show the most superior chloride-induced pitting corrosion potential among Al-transition metal binary alloys. If the W content exceeds 10 atomic percent (at %), the pitting potential is capable of extending the passive region more than 2600 mV against pure Al.1 Recently we have established the electrodeposition process of the binary Al-W alloy from the Lewis acidic 66.7-33.3 percent mole fraction (mol %) AlCl3–[C2mim]Cl ionic liquid.2 Depending on the electrodeposition conditions, it was possible to prepare Al-W alloys with W content approaching 96 at %. However, Al-W alloys with a high chloride pitting potential comparable to those produced by other non-equilibrium methods were not obtained because of their powdery morphology and fragile nature. Current challenge faced by Al-W alloy electrodeposition is to find out a new approach to form a smooth and dense layer onto a metal substrate possibly leading to higher chloride-induced pitting potential. In this study, we examined ternary Al-W-Mn alloy electrodeposition from the Lewis acidic 66.7-33.3 mol % AlCl3–[C2mim]Cl with both K3[W2Cl9] and MnCl2 because the addition of Mn to binary Al-transition metal alloys often gives a favorable chloride pitting potential.3 The procedures used for the preparation and purification of the AlCl3−[C2mim]Cl IL were identical to those described in previous articles.2-4 All the electrochemical experiments were conducted using a three-electrode cell. A Teflon® sheathed platinum rotating disk electrode was employed for the working electrode. A coil of 1.00 mm diameter aluminum wire was used for the counter electrode. The reference electrode was an aluminum wire immersed in a neat 66.7-33.3 mol % AlCl3–[C2mim]Cl, but was separated from the bulk IL by porosity E glass frits. All experiments were carried out in an Ar gas-filled glove box with O2 and H2O < 1 ppm. Alloy samples were deposited from the 66.7-33.3 m/o AlCl3−[C2mim]Cl with K3[W2Cl9] and MnCl2 onto Teflon®-sheathed 2.0-mm-diameter copper cylinder electrodes.Cyclic voltammograms were recorded at a Pt stationary disk electrode in the 66.7 mol % AlCl3–[C2mim]Cl before and after addition of K3[W2Cl9] and/or MnCl2 (Figure 1). In the neat melt, Al deposition/stripping occurred at 0 V vs. Al(III)/Al by the electrochemical reactions of the [Al2Cl7]-. After addition of K3[W2Cl9] or MnCl2 to the neat IL, the Al deposition/stripping behavior altered as reported in previous articles.2,3 Interestingly the electrochemical behavior varied significantly after addition of both K3[W2Cl9] and MnCl2. Three unknown oxidation peaks related to Al alloy stripping appeared. The main oxidation peak observed at ca. 0.73 V was more positive than those in the K3[W2Cl9] or the MnCl2 solutions. Based on this, the Al-W-Mn alloy was prepared on Cu substrates rotated at a fixed rate of 1000 rpm by a dc galvanostatic method at 353 K. As is the case for binary Al-W alloy electrodeposition in the 66.7 mol % AlCl3–[C2mim]Cl,2 the W content in the ternary Al-W-Mn alloys decreased with increasing the applied current density independently of the K3[W2Cl9] and MnCl2 concentration in the IL. The Mn content greatly varied with the solution composition and the applied current density. X-ray diffraction patterns of the samples are shown in Figure 2. As we expected, XRD pattern for Al92.1W0.2Mn7.7 suggested an amorphous phase formation, which is usually signaled by the disappearance of the fcc Al reflections and the development of a broad reflection centered at about 2θ = 41°, due to the high Mn content. Surprisingly the pattern for Al88.6W3.6Mn7.8 did not show the broad reflection while the Mn content in these two samples is about the same. It is difficult to explain this unexpected result; however, there is no doubt that W atoms in the alloys prevent an amorphous phase formation in Al-W-Mn alloy system. This result is very similar to the fact found during the electrodeposition of Al-Mo-Ti alloy.4 The chloride-induced pitting potential of the Al-W-Mn alloys produced in this study exceeded that for Al-W and Al-Mn binary alloy electrodeposits. Thus, the Mn addition to Al-W alloy electrodeposits is a highly effective approach in the improvement of surface morphology and chloride-induced pitting potential.

Al-W Alloy Deposition from Lewis Acidic Room-Temperature Chloroaluminate Ionic Liquid

The electrochemistry of binuclear tungsten salt, K3[W2Cl9], was examined in the Lewis acidic 66.7-33.3 mole percent (m/o) aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl3-[EtMeIm]Cl) room-temperature ionic liquid as it pertains to the electrodeposition of the Al-W alloy. We revealed that Al-W alloy without chloride contamination can be electrodeposited from the 66.7 m/o AlCl3−[EtMeIm]Cl with the K3[W2Cl9]. Interestingly Al-W alloy having an amorphous phase as well as W-rich Al alloy over 96 atomic present (a/o) W were successfully produced. However the Al-W alloy became covered with powdery deposits with increasing the W content in the alloy. The resulting Al-W alloy showed a favorable chloride-induced pitting potential comparable to that produced by a usual sputtering method if the W content was less than ca. 3 a/o W.

Mechanical Properties of Bulk Nanocrystalline Aluminum-Tungsten Alloys

The Al-W alloy powders containing up to 4 at. pct W particles in a nanocrystalline Al matrix were synthesized by ball milling and then hot compacted (HC) at 573 K or cold compacted using high-pressure torsion (HPT). Hardness measurements were made to determine the effects on mechanical properties. Based on existing models, the hardening effect of W particles in HC samples was attributed to Orowan-particle strengthening. Composite-type strengthening due to large W particles appeared to be negligible. Both the compressive strain and shear strain in high pressure torsion added to the strengthening effects without producing a change in the grain size.

Suppression of Resistance Increase in Annealed Al/W Interconnects by Capacitively Coupled Plasma Nitridation on W Surface

The suppression of the resistance increase in annealed Al/chemical vapor deposition (CVD)-W interconnects has been achieved by exposing the W surface to N2 plasma before Al deposition. The N2 plasma was generated in a capacitively coupled parallel-plate reactor. This process forms a thin WNx layer at the interface between the Al and the W layer. The WNx layer prevents Al-W alloy formation during annealing at 450°C. With this N2 plasma treatment, the resistance increase after annealing at 450°C is suppressed to only 10% compared to 140–180% in samples without the N2 plasma treatment. The N/W ratio and the thickness of the WNx layer are about 1.1 and 4 nm, respectively. The WNx layer formed in our experiment is found to be thicker and have a higher N concentration than the WNx layer formed by electron cyclotron resonance (ECR) plasma nitridation. This is probably due to the large self-bias voltage of the N2 plasma generated in a capacitively coupled parallel-plate reactor.

Oxidation behavior of Al-W alloy films deposited on Cu as a passivation layer

The oxidation behavior of Al-W alloy films (500 Å) deposited on Cu as a passivation layer to protect Cu from oxidation has been examined by Auger electron spectroscopy and X-ray photoelectron spectroscopy. The preferential oxidation of Al in the Al-W alloy protects underlying W and Cu from oxidation, and simultaneously, Cu is rejected by the formation of Al 2O 3 within the system, resulting in a successful separation of Cu from the surface oxidized layer due to the oxidation even after heating at 500 °C for 1 h in air.

Direct observation of the anodic film on a sputter-deposited amorphous Al-W alloy

Abstract The formation of barrier-type anodic films on sputter-deposited amorphous Al-30W (at.%) alloy has been studied for the first time to elucidate ionic transport mechanisms across the film and associated interfaces. The film, grown with high Faradaic efficiency at 50 Am−2 to 150 V in aqueous 0.01 m ammonium pentaborate electrolyte at 293 K, comprises two main layers of relatively uniform composition and with flat, parallel and sharp interfaces: An outer layer, representing about 15% of the film thickness and composed of tungsten-free anodic alumina, and an inner layer containing both aluminium and tungsten in an amorphous structure based on groupings of Al2O3 and WO3. The two layers form as a consequence of the slower migration of tungsten species in the film compared with that of A13 + ions. The inner layer has, as expected on compositional grounds, a lower ionic resistivity than the outer layer; yet, contrary to predictions, film formation proceeds in a uniform manner, i.e. without current channelling. Aluminium and tungsten are incorporated into the film at the alloy-film interface in their alloying proportions within the limitations of the measurements.

Resolution Test for the Sem

Many experiments have been proposed for testing resolution in the scanning electron microscope but no standard has been universally accepted.Many investigators have used the smallest separation between two arms of a 50-50% Al-W alloy dendrite as being a measure of resolution but, like other tests, criticism has persisted due to the difference in vertical height between the arms. During the course of our investigations of anodically formed oxides on Zircaloy-2 (a dilute Zr alloy containing 0.05% Ni, 0.1% Fe, 0.1% Cr and 1.5% Sn) a rapid measure of instrument performance was found. The SEM results presented here were obtained on a Coates and Welter CWIKSCAN Model 106A.