Zn In Cu Research Articles

Synergistic effect of bimetal in isoreticular Zn–Cu–1,3,5-benzenetricarboxylate on room temperature gaseous sulfides removal

Isoreticular bimetal M−Cu−BTC has considerable potential in improving the sulfides removal performance of Cu–BTC. Herein, three transition metals, namely, Zn2+, Ni2+ and Co2+, were assessed to fabricate M−Cu−BTC, a desirable isoreticular bimetal. Results demonstrated the feasibility of using Zn2+ to fabricate an isoreticular bimetallic Zn–Cu–BTC. The Zn2+ doping content of Zn–Cu–BTC was varied to investigate its influence on the hydrogen sulfide (H2S) and methyl sulfide (CH3SCH3) removal performance of Cu–BTC. The experimental results indicated that the sulfides removal performance of Zn–Cu–BTC increased and then decreased with increasing Zn doping content. The highest H2S and CH3SCH3 removal capacities of 84.3 and 93.9 mg S/g, respectively, were obtained when the Zn2+ doping content was 17%. The hybridisation of Zn and Cu in Zn–Cu–BTC induced a strong interaction between them. This interaction increased the binding energies of H2S and CH3SCH3 towards the Cu and Zn adsorption sites while weakening the bond order between Zn and Cu. The weakened bond order made the Zn–Cu bonds easier to form metal sulfides during desulfurization process, thereby synergistically enhancing sulphide removal.

Phase Formation and Diffusivity in the Ternary Cu-Zn-In System

Formation of the phases in Cu-Zn-In system was investigated by means of diffusion multiples annealed in isothermal conditions. The annealing of three different configurations of joints was performed at increasing temperatures (130, 350, 450 °C): below and above melting temperature of In and above Zn melting temperature. It was found that In revealed the ability for the preferential diffusion in Zn along the grain boundaries, forming the eutectic phase. In all applied temperatures, pure Cu was the barrier for the diffusion of In, while the diffusion of Zn proceeded easily, leading to the formation of binary CuZn phases; the phases from the Cu-In system were not found. The ternary Cu-Zn-In phases were formed at temperatures of 350 and 450 °C, at which the simultaneous diffusion of In and Zn in Cu took place, with participation of liquid In and Zn. The obtained results are the starting point for the calculation of the Cu-Zn-In phase diagram which remains unavailable, in spite of fact that all Cu-Zn, In-Zn and Cu-In binary diagrams are well known.

Improvement of hetero-interface engineering by partial substitution of Zn in Cu2ZnSnS4-based solar cells

This paper investigates the effects of partial substitution of zinc (Zn) in pure sulfide kesterite (Cu2ZnSnS4) by cadmium (Cd) and manganese (Mn) incorporation. Thin films of Cu2ZnSnS4 (CZTS), Cu2Zn1–xCdxSnS4 (CCZTS) and Cu2Zn1–xMnxSnS4(CMZTS) were produced chemically. A comparison of pure CZTS with CCZTS and CMZTS was performed to study the influence of Cd and Mn incorporation on the morphology, structure, optical and electronic properties of the films. The results show an improvement of the morphology and an adjustment of the band gap and valence band position by partial substitution of Zn with Cd and Mn. In addition, for the first time, the band alignment at the absorber/buffer hetero-interface is studied with partial Zn substitution. Band alignments at the absorber/buffer hetero-interface were estimated by XPS and UV/Visible measurements. The results show a cliff-like CBO for CZTS/CdS heterojunction, a spike-like CBO for CCZTS/CdS and a near flat-band CBO for CMZTS/CdS heterojunction.

Structural, optical and antibacterial investigation of La, Cu dual doped ZnO nanoparticles prepared by co-precipitation method

La, Cu dual doped ZnO with Cu = 0%-4% were prepared by co-precipitation route. The XRD pattern optimized the Cu content as 2% which restrict the secondary phase formation. The new phase at 38.7° corresponding to CuO (111) and the another phase at 42.3° related to Zn (101) came from un-reacted Zn2+ ions appeared in Cu = 4% doped sample. Zeta potential measurements confirms the stability of the particles. The blue shift of absorption edge and the energy gap from 3.66 eV to 3.99 eV by Cu doping was discussed by the shape of the particles, the distortion of the host lattice and generation of defect concentrations. The characteristic IR peaks around 470-489 cm-1 was related to the octahedral sites of Zn-O for Cu = 0 and 2% which is shifted to 616 cm-1 corresponding to the tetrahedral site at Cu = 4%. The shift in frequency was originated from the dissimilarity in the volume and bond lengths by the substitution of La and Cu in Zn-O. Based on the antibacterial report, it can be concluded that the Cu-doped Zn-La-O solid solution compose an effectual antimicrobial agent against pathogenic microorganisms. Cu = 4% doped sample possessed highest bacterial killing capacity because of the enhanced crystallite size and high density of oxygen vacancies which led the higher ROS values. Tuning of crystallite size and energy gap and the enhanced bactericial killing capacity by Cu addition is useful for opto-electronic device and medical applications.

Preparation and in vitro antibacterial properties of anodic coatings co-doped with Cu, Zn, and P on a Ti–6Al–4V alloy

In this study, copper (Cu) and zinc (Zn) as well as phosphorus (P) were co-doped into a Ti–6Al–4V titanium alloy via micro-arc oxidation (MAO). The entrance mechanisms of Cu and Zn into MAO coatings were investigated by an orthogonal experiment. The results show that Cu and Zn in Cu–Zn–P coatings separately exist mainly in the forms of Cu2O and Zn3(PO4)2. The Cu content in MAO coating increases with increasing EDTA-CuNa2 and KOH concentrations and decreasing phytic acid concentration but is nearly independent of EDTA-ZnNa2 concentration. The Zn content increases with increasing EDTA-ZnNa2 concentration and decreasing EDTA-CuNa2 concentration, indicating the competing effect between Cu and Zn for incorporation into Cu–Zn–P coatings. Compared with Zn ions, Cu ions do not readily enter anodic coatings due to their simultaneous involvement in coating formation on the anode and precipitation of metallic copper on the cathode. Cu–Zn–P coatings with appropriate amounts of Cu and Zn achieve excellent antibacterial ability against Escherichia coli (E.coli), Staphylococcus aureus (S.aureus), and Methicillin-resistant Staphylococcus aureus (MRSA). These antibacterial properties, in addition to excellent cytocompatibility, make Cu–Zn–P coatings as promising materials for orthopedic applications.

Effect of H2S on the corrosion-fouling behaviors of Cu-base surface

Based on the First-principles method of density functional theory (DFT), the adsorption of H2S on the primary growth surface (001)(111)(110) of Cu-base was investigated. The results demonstrate that the stable adsorption position of H2S on Cu(001)(111)(110) surface is t-parallel, b-H-down-c and h-H-down-c, respectively. And the corresponding adsorption energy is the minimum of −0.580 eV, −0.560 eV, −0.527 eV. After doping Zn in Cu, b-parallel, b-parallel and h-H-down-p are the stable adsorption position of H2S on Cu–Zn(001)(111)(110) surface. More chemical bonds form on adsorption sites of Cu and Cu–Zn substrate. Crystal structure of Cu doping Zn becomes unstable and easy to be corroded. Additionally, the experimental results reveals that copper shows better corrosion resistance of H2S than that of brass. Trends of fouling deposit curve of copper and brass are similar while the fouling is prone to deposit on the surface of brass after H2S corrosion. The consequences evidence that the fouling deposition can be influenced by the corrosive surface of materials and the fouling is prone to deposit on the corrosive pits and cracks. Furthermore, the crystal form of calcium carbonate on the surface of brass and copper after H2S corrosion is primarily aragonite and calcite. The corrosion products can promote the fouling adhesion.

Fabrication and characterization of novel biodegradable Zn-Mn-Cu alloys

Zn-Mn-Cu alloys with micro-alloying of Mn and Cu in Zn are developed as potential biodegradable metals. Although the as-cast alloys are very brittle, their ductilities are significantly improved through hot rolling. Among the as-cast and the as-hot-rolled alloys, as-hot-rolled Zn-0.35Mn-0.41 Cu alloy has the best comprehensive property. It has yield strength of 198.4±6.7MPa, tensile strength of 292.4±3.4MPa, elongation of 29.6±3.8% and corrosion rate of 0.050-0.062mma−1. A new ternary phase is characterized and determined to be MnCuZn18, which is embedded in MnZn13, resulting in a coarse cellular/dendritic MnZn13-MnCuZn18 compound structure in Zn-0.75 Mn-0.40Cu alloy. Such a coarse compound structure is detrimental for wrought alloy properties, which guides future design of Zn-Mn-Cu based alloys. The preliminary research indicates that Zn-Mn-Cu alloy system is a promising candidate for potential cardiovascular stent applications.

Simultaneous increase in strength and ductility by decreasing interface energy between Zn and Al phases in cast Al-Zn-Cu alloy

Cast-Al alloys that include a high amount of the second element in their matrix have comparatively high strength but low ductility because of the high volume fraction of strengthening phases or undesirable inclusions. Al–Zn alloys that have more than 30 wt% Zn have a tensile strength below 300 MPa, with elongation under 5% in the as-cast state. However, we found that after substitution of 2% Zn by Cu, the tensile strength of as-cast Al–Zn–Cu alloys was 25% higher and ductility was four times higher than for the corresponding Al–35% Zn alloy. Additionally, for the Al–43% Zn alloy with 2% Cu after 1 h solution treatment at 400 °C and water quenching, the tensile strength unexpectedly reached values close to 600 MPa. For the Al–33% Zn alloy with 2% Cu, the tensile strength was 500 MPa with 8% ductility. The unusual trends of the mechanical properties of Al–Zn alloys with Cu addition observed during processing from casting to the subsequent solution treatment were attributed to the precipitation of Zn in the Al matrix. The interface energy between the Zn particles and the Al matrix decreased when using a solution of Cu in Zn.

Comparative study on the wettability and interfacial structure in Sn–xZn/Cu and Sn/Cu–xZn system

Zn is the common used alloying element in Pb-free solder to depress the growth of interfacial intermetallic compound (IMC) in solder joints, but is also an oxidation preferred element to decrease the wettability of solder. This paper provides a potential replacement on the Zn-contained solder with small amount of Zn alloyed Cu substrate to avoid the deterioration on wettability but keep the depressing effect on growth of IMC through the comparative study on Sn–xZn/Cu and Sn/Cu–xZn. To systematically study the effect of Zn alloying, 0.2–0.8 wt% content of Zn was added into pure Sn solder and 2.29 and 4.89 wt% content of Zn was alloyed into Cu substrate. The wettability, interfacial reaction during soldering and interfacial IMC growth of Sn–xZn/Cu and Sn/Cu–xZn during isothermal aging were studied and compared with Sn/Cu system. Zn alloyed into Cu substrate exhibited a far better wettability than Zn alloyed into solder. Although there was no significant change on the composition, morphology and thickness of interfacial of IMC in Zn-contained system during soldering, Zn alloyed into Cu substrate or Sn solder obviously depressed the formation of Cu3Sn and the growth of IMC layers during isothermal aging compared with Sn/Cu system. The depressing effect and calculated activation energy on the growth of IMC increased with the content of Zn in Cu or in Sn, and can be attributed to the CuZn solid solution existed at the interface because it decreased the driving force on formation of Cu3Sn and the diffusion rate of Cu atoms. Compared Sn/Cu–xZn with Sn–xZn/Cu, Cu–4.89Zn substrate provided a similar depressing effect on IMC growth but an exceeding wettability compared with Sn–Zn solder, and can be offered as an alternative under bump metallurgy (UBM) in solder joints.

Effect of stacking fault energy on mechanical properties and strengthening mechanisms of brasses processed by cryorolling

In the present study, contribution of individual strengthening mechanisms has been analyzed to corroborate the improvement of the mechanical properties of cryorolled brasses of Cu–3.8% Zn and Cu–9.6%11Zn content is in weight % until unless stated. Zn compositions. The samples were cryorolled up to the maximum possible reduction in area after homogenized annealing (at 800°C for 4h). After the cryodeformation, a remarkable ~12 times improvement of yield strength (YS) was observed for both the alloys compared to that of the homogenized samples. The improvement of the YS is found to be much higher compared to that reported in our earlier work [Mater. Des 67 (2015) 637–643], although alloying content is much less in the present study. This is attributed to the change in rolling design, which allowed deformation of the samples under LN2 during rolling. The short time ageing (20min, 225–300°C) followed by cryorolling was found to enhance ductility without affecting the YS significantly. The solid solution strengthening by Zn in Cu leads to the decrease in the stacking fault energy which prevents the dynamic recovery and restricts the process of cross slip. Thereby, it helps to increase twining activity for further deformation. The TEM investigation confirmed that the formation of subgrains and nanotwins is responsible for the simultaneous improvement of strength and ductility. The analysis of different strengthening mechanisms revealed that the grain size refinement played the pivotal role in the improvement of the mechanical properties.

Presence of golden ratio relationships in Fe–Fe3C, Cu–Zn and Cu–Sn alloy systems

Iron–carbon, copper–zinc and copper–tin are the three most significant alloy systems. Iron–carbon system is commonly known for steels, copper–zinc for brasses and copper–tin for bronzes. This paper shows how eutectoid, peritectic, eutectic, cementite-intermetallic, maximum solubility of carbon in ferrite, maximum solubility of carbon in austenite points in Fe–Fe 3 C phase diagram are linked to one another through golden ratio relationships. This paper also shows the ratios between proportions of Cu and Zn at maximum solubility of Zn in Cu at 456 and 0°C and the ratio of proportions of Cu–Sn at e-Cu 3 Sn (IMC) in Cu–Zn and Cu–Sn phase diagrams, respectively, are related to golden ratio. It is predicted that the occurrence of these relationships at vital points in mentioned systems is in accordance with Constructal law of design in nature and golden ratio is the reason for uniqueness and usefulness of these points.

Electrodeposition of Compact and Porous Cu-Zn Alloy Electrodes and Their Use in the Cathodic Reduction of Nitrate

Compact and porous Cu-Zn alloys were electrodeposited from citrate baths. The latter deposits, consisting of a spongy material with a macroscopic interconnected porosity (pore diameter of tens of microns), were obtained at large current densities (−3 A cm−2) causing strong hydrogen evolution. Porous deposits with compositions between Cu62Zn38 and Cu91Zn9 were obtained by varying the ions concentrations in the deposition baths, with optimal morphology for the Cu70Zn30 composition. The lattice parameter of the samples, estimated from XRD data, showed in the explored range a linear dependence on composition, consistent with formation of a solid solution of Zn in Cu. The alloy materials were tested in nitrate reduction in alkali by voltammetry, chronoamperometry and constant potential electrolysis. Their performances were compared with those of similar (compact and porous) Cu electrodes. The nitrate reduction current decayed rapidly at compact Cu electrodes and was stable at the other electrodes, being the highest at porous Cu70Zn30. In all cases, the main product was ammonia.

Modifications in band gap and optical properties of Zn0.96−xNd0.04CuxO (x = 0, 0.05, 0.1 and 0.15) nanoparticles

Nd-doped and Nd, Cu co-doped ZnO nanoparticles (Zn0.96−xNd0.04CuxO, x = 0, 0.05, 0.1 and 0.15) were synthesized by sol–gel method. The structural and optical properties of the samples were investigated by X-ray diffraction (XRD) and UV–visible photo-spectrometer. The synthesized nanoparticles have different microstructure without changing a hexagonal wurtzite structure. CuO phase was noticed in XRD spectra at 38.73° after Cu = 5 % which was formed from remaining un-reacted Cu2+ ions. The average crystal size was gradually increased from Cu = 0 % (17 nm) to 15 % (17.6 nm) having lowest value (16.7 nm) at Cu = 5 %. The change in lattice parameters confirmed the substitution of Cu in Zn–Nd–O lattice. The observed constant c/a ratio revealed that there was no change in hexagonal wurtzite structure by Cu-doping. The energy dispersive X-ray spectra confirmed the presence of appropriate amount of Nd and Cu in Zn–O lattice. The optical absorption was increased gradually from Cu = 0–10 % and showed maximum at Cu = 10 % due to the presence of more nucleation centres and defect states. The defects related green band between 487 and 493 nm was due to the oxygen vacancies and intrinsic defects. The higher transmittance (≈ 90 %) noticed at Cu = 15 % leads to the industrial applications. The observed blue shift in energy gap from 3.49 eV (Cu = 0 %) to 3.65 eV (Cu = 10 %) and the red shift from Cu = 10 % (3.65 eV) to Cu = 15 % (3.61 eV) can be explained by the Burstein–Moss effect. Presence of chemical bonding was confirmed by Fourier transform infrared spectra.

Cu(In,Ga)S2 films prepared by two‐stage evaporation on ZnO coated substrates

AbstractWe have prepared Cu(In,Ga)S2 films with an almost homogeneous Ga depth distribution using the two‐stage multi‐source evaporation process on soda lime glass (SLG) substrates with one of three different kinds of back contact: Mo(1000nm), ZnO(500nm), and Mo(30nm)/ZnO(500nm), respectively. We have investigated the depth profiles of Zn and Na (diffused from SLG) in Cu(In,Ga)S2 films by secondary ion mass spectroscopy (SIMS) and compare them to those in films prepared by single stage co‐evaporation. The efficiencies are higher on Mo/ZnO than they are on ZnO. It was observed by SIMS that the amount of Zn in Cu(In,Ga)S2 on Mo/ZnO is lower than it is in Cu(In,Ga)S2 on ZnO. The obtained efficiencies are generally higher with two‐stage evaporation than with single stage co‐evaporation. The Na concentration in Cu(In,Ga)S2 prepared by two‐stage evaporation is two orders of magnitude higher than in single stage co‐evaporated films. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Preparation of wide gap Cu(In,Ga)S 2 films on ZnO coated substrates

We have prepared Cu(In,Ga)S 2 films at growth temperatures from 300 °C to 580 °C with a homogeneous gallium depth distribution (estimated band gap 1.67 eV) onto soda lime glass (SLG) substrates with one of three different kinds of back contact: Mo(1000 nm), ZnO(500 nm), and Mo(30 nm)/ZnO(500 nm), respectively. We have also investigated the depth profiles of Zn and Na (diffused from SLG) in Cu(In,Ga)S 2 films by secondary ion mass spectroscopy (SIMS). The efficiency of solar cells on Mo increases with increasing growth temperature. It is higher on Mo/ZnO than on ZnO, and increases from 350 °C to 450 °C, then decreases above 450 °C. It was observed by SIMS that the amount of Zn in Cu(In,Ga)S 2 on Mo/ZnO is lower than it is on ZnO up to 450 °C, and a large amount of Zn diffuses into absorbers over 450 °C, which contributes to decreasing efficiency. The amount of Na in the back contact increases with growth temperature. The depth distribution of Na in Cu(In,Ga)S 2 films on Mo is almost constant in the order of 10 17–10 18 cm − 3 , on ZnO and Mo/ZnO the Na concentration increases towards the surface and is in the range of 10 15–10 17 cm − 3 .

Methanol partial oxidation on Cu–Zn thin films grown on Ni(1 0 0) surface

Methanol partial oxidation on Cu–Zn thin films epitaxially grown on Ni(1 0 0) surface has been investigated in an ultra high vacuum (UHV) system combined with a high-pressure reaction cell. According to temperature programmed reaction (TPR) and temperature programmed desorption (TPD) in UHV, surface reaction between methanol and pre-adsorbed oxygen on epitaxially grown Cu thin films mainly produced H 2 and CO together with HCHO, although addition of Zn greatly suppressed the formation of HCHO. Annealing of the thin films at 420 K prior to admission of methanol and oxygen reactants dramatically accelerated reaction rate of CO 2 product and the maximum formation of H 2 and CO 2 was observed on the surface of 1 ML Cu with 0.25 ML Zn. On the contrary, the rate of methanol partial oxidation in the high-pressure reaction cell monotonously increased with the thickness of Cu films up to 3 ML. The addition of 0.25 ML Zn increased the reaction rate independent of Cu film thicknesses of 1–6 ML. Post-reaction surface analysis showed Cu agglomeration on the Ni substrate. Cu 2p X-ray photoelectron spectroscopy (XPS) and LMM Auger data reveal the presence of Cu + species in addition to metallic Cu atoms abundant in the films corresponding to the higher reactivity. It is proposed that the oxidation number of Cu is controlled by oxided Zn in Cu–Zn alloy.

Diffusion induced grain boundary migration in the Cu–Zn system

Diffusion induced grain boundary migration (DIGM) has been studied in the Cu–Zn system by exposing polycrystalline Cu to Zn vapor with a Cu-38wt.% Zn alloy as the source of Zn. The time and temperature dependence of the migration distance has been studied in the temperature range 350 to 600 °C. The composition-distance profile was obtained along the thickness of the sheet specimen to determine the diffusivity, k D b δ at each temperature. Similarly, the quantity of Zn was determined behind the migrated grain boundary to calculate the coherency strain energy and the total chemical free energy change. It was observed that a part of the total free energy change was used for volume diffusion ahead of the migrating grain boundary. The effective free energy change was calculated and it was observed that the fraction of the total free energy change used for volume diffusion increased as the transformation temperature increased. A plot of instantaneous rate of migration vs. composition behind the grain boundary has indicated that the coherency strain energy acts as the driving force for DIGM. The fine-grained layer followed a parabolic growth behavior. The diffusion coefficients calculated from the thickness of the fine-grained layer are of the same order of magnitude as those calculated from the rate of migration of the grain boundary. The diffusivity as well as the activation energy calculated from the k D b δ vs. 1 / T plot corresponds to that of grain boundary diffusion of Zn in Cu.

On the “Active spacer and stabilizer” role of Zn in Cu 1− xZn xFe 2O 4 in the selective mono-N-methylation of aniline: XPS and catalysis study

A systematic catalytic methylation study on ferrospinel materials led to the selective production of N-methylaniline (NMA) with Cu 1− x Zn x Fe 2O 4. Aniline methylation was carried out on Cu 1− x Zn x Fe 2O 4 with a feed composition of CH 3OH:PhNH 2:H 2O = 3:1:1 at 513–633 K. NMA was formed selectively on all of the catalyst compositions, with trace amounts of secondary products under most of the conditions. Cu 0.5Zn 0.5Fe 2O 4 composition showed high catalytic activity and stability up to 100 h. Although the Cu 2+ was responsible for methylation activity, Zn 2+ enhanced the overall stability of the catalyst system. XPS investigations revealed that the degree of Cu 2+ reduction decreased dramatically from x = 0.05 / 0.25 to 0.5/0.75 on spent catalysts. TPR studies indicated that the reducibility of Cu 2+ decreased from fully reducible at 523 K with Cu-rich compositions to partially reducible at 573 K on x = 0.5 . Stable activity observed on Cu 0.5Zn 0.5Fe 2O 4 can be attributed to the highly heterogeneous distribution of metal ions. This heterogeneous distribution indicates an important role of zinc, likely as an “active spacer cum stabilizer” that hinders the reduction of active Cu 2+ and contributes to prolonged activity.

Characteristic features of diffusion induced grain boundary migration for Σ9 [110] asymmetric tilt boundaries in the Cu(Zn) system

The characteristic features of diffusion induced grain boundary migration (DIGM) in the Cu(Zn) system were experimentally studied for [110] asymmetric tilt boundaries using Cu bicrystals annealed at 693 K for various times by a capsule zincification technique. The experiment was carried out for the boundaries with inclination angles of φ=0, 20, 35, 55, 65 and 90° and with a constant misorientation angle of θ=39° (Σ9). During annealing, the grain boundary migrates towards a crystal grain of larger coherency strain energy with higher probability due to DIGM. Taking elastic anisotropy of each crystal grain into consideration, the difference between the probabilities of grain boundary migration towards both side grains can be accounted for by the coherency strain model proposed by Hillert. The migration rate v of the moving boundary is almost constant regardless of the annealing time t between t=72 and 384 h (2.59×10 5 and 1.38×10 6 s). The value of v monotonically decreases with increasing inclination angle. This implies that the boundary diffusion coefficient of Zn in Cu is a monotone decreasing function of the inclination angle. The experimental results on the kinetics at the steady state stage were theoretically analyzed using the energy balance model proposed by Kajihara and Gust ( Scripta mater., 1998, 38, 1621. The analysis indicates that the effective driving force Δ ef G for the grain boundary migration is merely one-thirtieth of the chemical driving force, whereas it still remains three times greater than the minimum value corresponding to the coherency strain energy during DIGM under the present experimental conditions. The mobility of the moving boundary was evaluated to be M=3.77×10 −17 m 4/Js from the values of v and Δ ef G according to the relationship M= v/Δ ef G. This value of M is close to the results estimated by Yamamoto et al. ( Acta mater., 1999, 47, 1757) for the [100] twist and random boundaries in the Cu(Zn) system.

Quantitative analysis of observations on diffusion induced grain boundary migration for random boundaries in the Cu(Zn) system using a driving force model

Diffusion induced grain boundary migration (DIGM) in the Cu(Zn) system was experimentally studied by Li and Hillert using polycrystalline Cu specimens zincified with binary Cu–Zn alloys containing 3.9–30.5 wt% of Zn at temperatures between 573 and 773 K. Their experimental results have been quantitatively analyzed using the energy balance model proposed by Kajihara and Gust. The effective driving force Δ ef G for DIGM has been evaluated from the migration rate v of the moving boundary and the composition in the region alloyed with Zn behind the moving boundary, and then the mobility M of the moving boundary has been calculated using the relationship M= v/Δ ef G. According to the analysis, the grain boundary migration obeys the chemical driving force model proposed by Hillert and Purdy for the largest experimental values of v at 573 and 623 K. However, the chemical driving force is partially consumed by the volume diffusion of Zn in the Cu matrix ahead of the moving boundary for the other experimental values of v at 623–773 K. In such a case, the migration rate dependence of the effective driving force should be taken into consideration. The temperature dependence of the mobility gives a value of Q M =177 kJ/mol as the activation enthalpy for the grain boundary migration. This value is close to the activation enthalpy for volume diffusion of Zn in Cu, 191 kJ/mol. Consequently, the grain boundary migration is considered to be controlled by the solute drag effect due to the volume diffusion of Zn in the Cu matrix in the neighborhood of the moving boundary.