Effect Of Active Elements Research Articles

The effect of active elements on the microstructure and properties of graphite and copper-brazed joints

The effect of active elements on the microstructure and properties of graphite and copper-brazed joints

Effects of active elements (Si, Cu, Zn, Mg) on the interfacial properties of Fe/Fe2Al5: A first-principles study

Active elements play a crucial role in enhancing the interfacial bonding between matrix and intermetallic in Fe-based materials. In this paper, alloying elements (Si, Cu, Zn, Mg) were innovatively added to study the influence on the strength of Fe/Al alloy with the help of first-principles calculation. The first-principles calculation was used to understand the interface strengthening mechanism at the electronic level. The results show that Al(Fe-Fe)-TOP Fe2Al5(0−20)/Fe(110) is an ideal interface configuration for the following studies. The doping atoms are more inclined to replace the Al atoms at the interface. When replacing Al atom, alloying element Cu, Mg and Zn can significantly improve the bonding strength of Fe2Al5(0−20)/Fe(110) interface, and the effect of Si is weak that can be neglected. Furthermore, the analyses of electronic structure show that the Fe-Al and Fe-Mg bonds are metallic bonds with covalency. The Fe-Si bonds are mainly ionic bonds. There are obvious charge transfer between Cu, Zn and Fe atoms, and the Fe-Cu and Fe-Zn bonds are strong metal bonds. The bonding strength between atoms may be linked to the number of valence electrons they possess. These results provide important insights into enhancing the interfacial adhesion strength of the Fe/Fe2Al5 system in Fe/Al alloys by adding active elements.

The effects of active elements on adhesion strength of SiC/Cu interface in SiC reinforced Cu-based composite: A first-principles investigation

Application of SiC reinforced Cu-based composites has been greatly limited by the weak interfacial bonding strength between SiC and Cu matrix. In this work, the active elements (Fe, W, Zr and Ti) were introduced to enhance the adhesion strength of SiC/Cu interface, and the strengthening mechanism was revealed by using the first-principles calculations at the atomic level. The results show that the C-terminated SiC(111)/Cu(111) interface with fcc stacking sequence (C-fcc-Cu) has the largest adhesion strength, which is primarily contributed by the strong hybridizations between interfacial C-p, Si-p and Cu-d orbitals. Interestingly, the addition of those active dopants can significantly improve the work of adhesion and enhance the interfacial bonding strength of C-fcc-Cu interface. More importantly, Zr and Ti atoms are prone to segregate to interface and then combine with interfacial C atoms to form new compounds (ZrC and TiC), which could act as interfacial binders to enhance interfacial atoms interactions. The corresponding strengthening micro-mechanism was determined by the analysis of electronic properties. The Fe, W, Zr and Ti dopants can enhance the electron concentration at interface and improve the electron transfer, orbital hybridizations between dopants and C atoms.

Effects of active elements on adhesion of the Al2O3/Fe interface: A first principles calculation

The poor wettability of alumina surface greatly limits the interface binding between alumina and iron in alumina reinforced iron matrix composites. In this work, the active elements (Ti and Ni) additives are introduced into the interface to enhance the adhesion of the interface, and the activation mechanism is studied. Through the analysis of the embedding ability of activating elements Ti or Ni in Al2O3/Fe interface and their influence on adhesion of interfaces, it is revealed that Ti is prone to segregation at the interface and has a great improvement on the strength and stability of interface binding. However, Ni hardly enhances interface interaction and even causes interface deterioration. Electron structures analysis shows that 4 s, 3p, 3d coupling of Ti results in more electrons involved in the interface interaction, and the formation of Ti-Fe and Ti-O bonds essentially determines the increase of the work of adhesion. The activation mechanism of Ti and Ni well explains the experimentally reported different existence forms and action modes of Ti and Ni.

Voltage-Mode Four-Phase Sinusoidal Generator and Its Useful Extensions

This paper introduces a new voltage-mode second-order sinusoidal generator circuit with four active elements and six passive elements, including grounded capacitors. The frequency and condition of oscillation can be independently controlled. The effect of active element’s nonidealities and parasitic effects is also studied; the proposed topology is good in absorbing several parasitic elements involved with the active elements. The circuit is advantageous for generating high frequency signals which is demonstrated for 25 MHz outputs. Several circuit extensions are also given which makes the new proposal useful for real circuit adoption. The proposed theory is validated through simulation results.

Hot Corrosion of Cobalt-Based Alloy with (Na, K)<sub>2</sub>SO<sub>4</sub> Coating at 900 °C

The hot corrosion behavior of pure Co, Co-10Cr and Co-10Cr-5Al alloys coated with (4～4.5) mg/cm2 (Na, K)2SO4 deposits has been studied at 900 °C in air by thermogravimetry and SEM/EDX analysis. The results show that hot corrosion rate of Co-10Cr alloy was obviously higher than that of Co-10Cr-5Al alloy and hot corrosion rate of pure Co was between those of the two cobalt-based alloys. Both alloys produced complex corrosion scales, containing an outermost layer of pure cobalt oxide and an inner layer where the oxides of both alloy components were simultaneously present on the Co-10Cr alloy, while a middle layer containing CoO and Cr2O3 and an inner layer of Al2O3 with a few aluminum sulfides appeared on the Co-10Cr-5Al alloy. The results were interpreted by taking into account the effect of active element and hot corrosion mechanism.

The effect of 3-methyl 1-pentyn 3-ol on the corrosion of Al-Si-Cu alloys in acid solutions by using SEM, EDX and AAS

In this study, the effect of alloying elements on the corrosion of Al-Si-Cu alloys in H2SO4 and HCl media content 3-methyl-1pentyn-3-ol (3mlp3ol) is investigated by using SEM, EDX, AAS. The effect of active elements and 3-methyl-1-pentyn-3-ol (inhibitor) on the corrosion of alloys is determined using SEM, EDX and AAS results. Experimental results which indicated active alloying elements are Cu, Zn, Mg for Al-Si-Cu alloys in the studied solutions.

Effect of Active Elements on the Oxidation Behavior of a FeCrAl Alloy Produced by Co-Rolling and Annealing

Abstract The choice of a metal alloy for supporting catalytic converter bodies depends on the mechanical, thermal, and chemical resistance of the alloy under operative conditions. The demand for providing a more efficient conversion instigated the development of improved substrate technologies. In this paper, a thin foil of FeCrAl alloy was produced by diffusion alloying of aluminum clad ferritic stainless steel containing very small amounts of active elements (Hf, Y, Zr). The effect of the active elements on the oxidation behavior of such an alloy has been evaluated. Isothermal tests carried out in air at 900°C, 1000°C, and 1100°C showed kinetics representing a very protective behavior. The oxide scale always appeared very flat and adherent to the substrate. The beneficial effect of active elements on scale protectiveness was apparent also during cyclic oxidation tests carried out in air over the 800–1000°C temperature range. Breakaway oxidation was never observed. Active elements are believed to limit diffusion processes through the scale, and this leads to the formation of a flat and adherent alumina scale that can withstand additional stress due to the thermal expansion mismatch between the oxide and the metal.

Interfacial Microstructures and Bonding Strength between Aluminum Nitride and Silver Brazing Filler Metals Containing Various Active Elements

Effect of active element on interfacial microstructures and bonding strength of brazed AlN/AlN joints has been investigated and compared with the case of brazed Si3N4/Si3N4 joints. Brazing was carried out at 1173 to 1473 K for 3.6 ks in a vacuum using Ag-Cu filler metals containing Ti, Zr, V and Nb as an active element. The obtained joint had no defects such as un-bonded areas, regardless of active element and bonding temperature. Four kinds of active elements were divided into two groups by shear tests and microstructural observations. One was Ti and Zr, and the other was V and Nb. The bonding strength of the former was higher than that of the latter. In particular, the joint with Ti addition showed an excellent strength of about 200 MPa. Main fracture position in the joints with Ti and Zr additions was within the AlN, while most joints with V and Nb additions broke at the interface between the active filler metal and the AlN. In the former, TiN and ZrN layers consisting of fine grains were observed adjacent to the AlN. On the other hand, the joint with Nb addition had roundish grains of Nb2N in similar locations. It was considered that the existence of fine grains contributed to the enhancement of bonding strength due to the increase of contact area and to the formation of complicated interface. These tendencies were essentially consistent with those of the brazed Si3N4/Si3N4 joints.

Effects of active elements on oxide removal by a vacuum arc

The effects of alkali metal elements on the action of a vacuum arc were studied in the context of metal surface cleaning or removal of oxide on the surface. Compounds containing these elements were applied in an aqueous solution to the work-piece surface. This application significantly reduced surface roughness and increased the cleaning rate (oxide removal rate). Surface roughness was reduced by as much as 2.5 times not using these compounds, and the cleaning rate increased by 1.8 times.

Diffusion and growth mechanism of Al 2O 3 scales on ferritic Fe-Cr-Al alloys

In order to determine the growth mechanism of α alumina scales, cationic and anionic diffusion studies have been performed on scales developed on three alumina former Fe-Cr-Al alloys. Two of them were classically elaborated and differed by the presence or not of implanted yttrium. The third one is an ODS alloy, the MA 956. First, the oxidation behaviour in oxygen was characterised in a temperature range 1000–1200°C, with morphological studies and analyses of the scales. Then, anionic self diffusion coefficients were determined by isotopic exchange 16O– 18O, cationic self diffusion was simulated by Cr diffusion and the penetration profiles were determined by SIMS. These profiles were analysed considering two domains: the first one relative to effective diffusion and the second to grain boundary diffusion. The f values, fractions of sites associated with the grain boundaries were modified by considering the roughness of the scales. The anionic and cationic self-diffusion coefficients are compared with those extrapolated from massive aluminas and the experimental parabolic oxidation constants are compared with those calculated with diffusionnal data. The results obtained are discussed by taking into account the differences in the scale morphology which looks like an important parameter. Then, the effect of active elements on the morphology and on the transport and mechanical properties is commented.

Effect of active elements of lubricating-cooling liquids on embrittlement of iron-based alloys

Effect of active elements of lubricating-cooling liquids on embrittlement of iron-based alloys