Reactive Wetting Research Articles

High-temperature interactions of liquid magnesium with a pure copper substrate

For the first time, experimental results of the high-temperature interaction of liquid magnesium with pure copper are presented. The investigation was performed using the sessile drop method and capillary purification procedure allowing both non-contact heating of the Mg/Cu couple and in situ cleaning of the Mg drop from a native oxide film. The test was done under isothermal conditions at 710 °C in a protective atmosphere, which was a mixture of Ar + 5 wt% H2.The images of the Mg/Cu couple collected during the high-temperature measurements were used to determine the time-dependent values of the contact angle (θ) formed between the liquid magnesium drop and the copper substrate.The solidified couple was subjected to detailed microstructural observations by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), both coupled with energy-dispersive X-ray spectroscopy (EDS).Under the applied measurement conditions, immediately after contact with the Cu substrate, the liquid Mg drop showed a very good wetting (θ0 ∼ 22°), followed by rapid spreading over the substrate, forming a final contact angle θf ∼ 11°. However, SEM/EDS analysis revealed that θf is an apparent angle due to the deep crater (∼200 μm) formed in the substrate under the Mg drop by the dissolution of Cu in liquid Mg.The comparative SEM/TEM/EDS analysis suggests that good wetting and rapid spreading in the Mg/Cu couple are dominated by the reactive wetting mechanism due to the dissolution of the Cu substrate in the liquid Mg drop and its saturation with a high amount of dissolved Cu. Consequently, the microstructure of the solidified drop was composed of large Cu-rich primary MgCu2 crystals surrounded with a two-phase eutectic mixture (MgCu2 + Mg2Cu) formed at the final stage of cooling. In addition, the MgCu2 phase was also nucleated and grown at the Mg/Cu interface to form a continuous layer.

Effect of Surface Roughness and Droplet Size on Solder Wetting Angles.

Reactive wetting is a process ubiquitous in modern electronic soldering processes. Nonetheless, the dependencies of reactive wetting angles on surface roughness and droplet size are not well understood but become increasingly important for reliable miniaturization of devices. In this study, advancing contact angles of the Sn(l)/Cu(s) reactive solder system are investigated and the aforementioned dependencies are evaluated. Several surface roughnesses and a large array of droplet sizes are measured. Clear size dependencies are observed for both smooth and rough substrates, yet interestingly, the trends are inverted. This inversion of the size dependence of the wetting angle is discussed on the basis of the triple line pinning phenomenon, Wenzel's wetting model, and the consumption of Sn by a solder reaction. Quantitative models are proposed, with which size dependencies on rough and smooth surfaces can be better understood. Triple line pinning barrier energies are calculated. Larger pinning barriers are determined for rougher substrates.

Study on Tungsten Metallization and Interfacial Bonding of Silicon Nitride High-Temperature Co-Fired Ceramic Substrates

For the first time, Si3N4 HTCC has been prepared using W as the metal phase by high-temperature co-firing (1830 °C/600 KPa/2 h) as a potential substrate candidate in electronic applications. It was discovered that the addition of Si3N4 to the W paste has a significant impact on thermal expansion coefficient matching and dissolution wetting. As the Si3N4 content increased from 0 to 27.23 vol%, the adhesion strength of W increased continuously from 2.83 kgf/mm2 to 7.04 kgf/mm2. The interfacial bonding of the Si3N4 ceramic and the conduction layer was discussed. SEM analysis confirmed that the interface between Si3N4 and W exhibited an interlocking structure. TEM, HRTEM and XRD indicated the formation of W2C and W5Si3 due to the interface reactions of W with residual carbon and Si3N4, respectively, which contributed to the reactive wetting and good adhesion strength between the interface. Suitable amounts of Si3N4 powder and great interfacial bonding were the main reasons for the tough interfacial matching between the Si3N4 ceramic and the conduction layer.

Continuous Hot‐Dip Galvanizing of Medium‐Manganese Third‐Generation Advanced High‐Strength Steels

The effects of process atmosphere oxygen partial pressure (pO2) on the preimmersion surface structures, interfacial reactive wetting products, and reactive wetting mechanisms of two prototype (0.15–0.20)C–(5.6–5.9)Mn–(0.4–1.9)Al–(1.1–1.5)Si–(0–0.6)Cr (wt%) third‐generation advanced high‐strength steels during continuous hot‐dip galvanizing are determined. In this study, the two‐stage thermal processing routes employed comprise an austenitization anneal followed by flash pickling and an intercritical anneal. All annealing treatments are conducted in a N2–5 vol% H2 process atmosphere with a controlled dew point. The substrates are austenitized at dew points of –30 or –10 °C, intercritically annealed at a dew point of –30, –10, or +5 °C, and then galvanized using a conventional 0.2 wt% Al (dissolved) bath. The preimmersion surfaces comprise a near‐pure Fe layer with dispersed nanoscaled oxide nodules. The primary reactive wetting mechanism is the direct wetting of the surface Fe, while oxide wetting, oxide cracking and liftoff, and oxide bridging by the liquid metal bath are secondary reactive wetting mechanisms. Zn ingress into the substrate via pores in the oxide network from selective dissolution during flash pickling is also noted. A well‐developed Fe2Al5–xZnx interfacial layer is observed for all metallic coating conditions. The resultant coatings show outstanding adherence after ASTM three‐point bend testing.

Wettability and Reactivity of Liquid Magnesium with a Pure Silver Substrate

For the first time, experimental data on the high-temperature interaction of liquid Mg with pure Ag are presented. The study was performed by the sessile drop method and capillary purification procedure. The test was carried out under isothermal conditions at 720 °C in a protective atmosphere of Ar + 5 wt.% H2. The solidified couple was subjected to detailed microstructural observations by scanning electron microscopy (SEM) coupled with energy-dispersive x-ray spectroscopy (EDS). Under the used conditions, immediately after contact with the Ag substrate, liquid Mg drop showed a good wetting (θ0 ~ 65°) followed by fast spreading over the substrate in subsecond time to form the final contact angle of θf ~ 31°.SEM/EDS analysis showed that θf is apparent because of a deep crater (200 μm) formed in the substrate under the drop by the dissolution of Ag in liquid Mg. SEM/EDS observations of complex structural transformations in the Mg/Ag couple due to high-temperature contact and subsequent cooling are in good agreement with the Ag-Mg phase diagram. Besides substrate dissolution, the interaction between liquid Mg and solid Ag at 720 °C is accompanied with the alloying of the Mg drop with Ag and the formation of a continuous layer of the β-AgMg phase at the Mg/Ag interface. During cooling, the chemical composition of the Mg(Ag) drop continuously changes, and this process is followed by the formation of the β-AgMg phase by secondary precipitation from Ag-saturated liquid, a partial transformation of the β-AgMg to ε′-Ag17Mg54 phase by peritectic reaction, followed by the solid-state transformation of the ε′-phase to the ε-AgMg3 phase, and finally, the solidification of residual liquid in the form of the two-phase eutectic mixture of AgMg4 + (Mg). The results obtained suggest that a very good wetting and fast spreading observed experimentally for the Mg/Ag couple is caused by high reactivity between liquid Mg and Ag substrate leading to the combined effect of two reactive wetting mechanisms, i.e. through dissolutive wetting and wetting through the formation of the interfacial reaction product (β-phase).

A reactive wetting strategy improves lithium metal reversibility

The cycling of lithium metal (Li0) anode is often accompanied by irregular lithium plating/stripping, leading to poor Li0 reversibility, and posing a grand challenge to constructing reliable Li0 batteries. Hereby, we report a reactive wetting strategy to enable conformal and highly reversible Li0 plating/stripping through a lithium-reactive substrate. The reactive wetting, smooth nucleation, and conformal growth behaviors of Li0 are visualized through in-situ transmission electron microscopy, ex-situ scanning electron microscope, and in-situ optical microscope characterizations. Based on the reactive wetting substrate, high average Coulombic efficiencies (99.0% at 0.5 mA cm−2 for 400 cycles) are realized for Li0 anodes. By pre-plating Li0 into the reactive wetting substrate as anodes and leveraging LiFePO4 as cathodes, high capacity retention (76.0% after 200 cycles in low N/P ratio conditions) is also achieved in the as-constructed Li0 full cells. This work establishes a fundamental understanding of reactive wetting dynamics of Li0 and provides a drop-in solution to improving Li0 reversibility.

Reactive Spreading Dynamics of Molten Polymer Liquids

Despite the key to the adhesion between polymers and a plethora of materials, our understanding of reactive wetting is still rudimentary. In the present work, we report the reactive wetting dynamics of molten maleic anhydride-grafted polypropylene (MA-g-PP) liquids modeled by molecular-kinetic theory (MKT). The dependencies of the contact line friction (ζ) and viscosity (η) were compared for reactive and nonreactive wetting polymer systems. Compared with linear dependencies of ζ and η for the nonreactive wetting systems, the reactive wetting system presented a nonlinear relationship. In the capillary regime, the chemistry-affected regime is followed by a regime that is nearly not affected by chemical reactions, which is identified by the linear MKT. The formation of a new interface and the resulting entanglements of polymer chains in the chemistry-affected regime contribute to the dependence of ζ on η in the capillary regime.

Dynamics of intermetallics formation in the Al/Ni reactive wetting system

Due to the complexity of interfacial reactions during reactive wetting process at high temperatures, the intrinsic mechanism behind the formation and growth of intermetallic compounds (IMCs) is still unclear. This study presents insight into the possible formation of Al/Ni IMCs in the Al (l)/Ni (s) wetting system at 1023.15 K using molecular dynamics (MD) simulation. The reactive wetting process has been broadly classified into three regimes based on the Al/Ni interphase condition: fast spreading (mostly non-reactive), crossover (dissolutive), and slow-spreading (reactive). It is found that the intermetallic phases are nucleated during the dissolutive phase; however, the stable IMCs are formed during the reactive stage and are mostly composed of AlNi and Al3Ni5. The growth of IMCs in the radial direction shows the same behavior as the contact radius of the droplet, which is a significant increase of both the droplet radius and IMCs growth in the radial direction before the droplet reaches its quasi-equilibrium base radius. Quasi-equilibrium droplet radius occurs when changes in droplet radius are negligible. In a quasi-equilibrium regime, no significant change in droplet radius and IMCs growth is observed. In contrast, the IMCs growth in the normal direction shows the opposite behavior: the thickness of IMCs increases significantly during the quasi-equilibrium regime.

Research on the corrosion behavior of low carbon mold flux on submerged nozzle refractory

AbstractIn this paper, the wetting and corrosion behavior between medium and low carbon mold flux and Al2O3‐ZrO2‐C nozzle refractory were studied through a high‐temperature wetting experiment. Combined with microstructure analysis, the corrosion mechanism of low carbon mold flux on nozzle slag line material was clarified. The results show that the wettability of low‐carbon mold flux and Al2O3‐ZrO2‐C nozzle refractory is better, compared with the traditional medium carbon mold flux, the contact angle between low‐carbon mold flux and Al2O3‐ZrO2‐C material is smaller and the mold flux spreads faster on the nozzle surface at the same temperature range. According to the microstructure analysis, the corrosion degree of low‐carbon protective slag on the ZrO2‐C material of the nozzle slag line is serious, and the corrosion depth is large. Due to the influence of carbon content, the wettability between low‐carbon mold flux and ZrO2‐C material of the nozzle slag line is better, which provides favorable kinetic conditions for the dissolution and penetration of low‐carbon mold flux into the nozzle. In addition, compared with medium carbon slag, the carbon concentration difference between low‐carbon mold flux and nozzle material is larger, resulting in greater diffusion driving force of carbon atoms, which affects the wetting, dissolution, and chemical reaction of the interface between the two phases.

Anti-phase boundary accelerated exsolution of nanoparticles in non-stoichiometric perovskite thin films

Exsolution of excess transition metal cations from a non-stoichiometric perovskite oxide has sparked interest as a facile route for the formation of stable nanoparticles on the oxide surface. However, the atomic-scale mechanism of this nanoparticle formation remains largely unknown. The present in situ scanning transmission electron microscopy combined with density functional theory calculation revealed that the anti-phase boundaries (APBs) characterized by the a/2 < 011> type lattice displacement accommodate the excess B-site cation (Ni) through the edge-sharing of BO6 octahedra in a non-stoichiometric ABO3 perovskite oxide (La0.2Sr0.7Ni0.1Ti0.9O3-δ) and provide the fast diffusion pathways for nanoparticle formation by exsolution. Moreover, the APBs further promote the outward diffusion of the excess Ni toward the surface as the segregation energy of Ni is lower at the APB/surface intersection. The formation of nanoparticles occurs through the two-step crystallization mechanism, i.e., the nucleation of an amorphous phase followed by crystallization, and via reactive wetting on the oxide support, which facilitates the formation of a stable triple junction and coherent interface, leading to the distinct socketing of nanoparticles to the oxide support. The atomic-scale mechanism unveiled in this study can provide insights into the design of highly stable nanostructures.

Growth behavior and morphology of sidewall intermetallic compounds in Cu/Ni/sn-Ag microbumps during multiple reflows

Sidewall intermetallic compounds (IMCs) grow rapidly by surface diffusion with the bump size shrinking. Cu/Ni/sn-Ag microbumps with thick Ni barrier have been fabricated and the inhibition effect of thick Ni barrier on sidewall IMCs growth during multiple reflows was investigated. Three kinds of sidewall IMCs were found: Ni3Sn4 (main product), Ni3Sn2 and Cu3Sn. The growth kinetics of sidewall Ni3Sn4 showed that the formation of Ni3Sn4 contained two stages: at first, sidewall Ni3Sn4 grew rapidly due to reactive wetting of molten solder; subsequently, the formation slowed down since the solder wetting was blocked by continuous Ni3Sn4 layer, and Ni3Sn2 and Cu3Sn formed by surface diffusion of Sn atoms.

Fabrication of Al-YOF/TiB2 composites by molten-salt-assisted stirring casting

The poor wettability between oxides and Al melt and presence of alumina film on Al melt surface seriously limits the fabrication of Al matrix composites (AMCs) reinforced by oxides via casting method. The wettability of oxides can be improved by modification with fluorine, and the oxyfluoride is more feasible to incorporate into Al melt, but the strength of the oxides may decrease after modification. Therefore, it is necessary to assess the strengthening effect of oxyfluoride by comparison with classical reinforcement. In this work, AMCs reinforced with yttrium oxyfluoride (YOF) and TiB2 were successfully fabricated by molten-salt-assisted stirring casting. YOF particles exhibit a better distribution in Al matrix than TiB2 particles, and the YOF particles show better bonding strength with Al matrix than TiB2 due to reactive wetting. Al-YOF composite shows higher hardness, tensile strength, and ductility than Al-TiB2 composite. The values of microhardness, yield strength (σ0.2) and ultimate tensile strength (σb) of Al-YOF composite are 27.2 HV, 55 MPa and 81 MPa, which are 25.9 %, 62 % and 53 % higher than that of pure Al.

The fabrication of unwettable superhydrophobic surfaces by reactive wetting of AgCuTi into an AAO template

Multi-level hierarchical surface roughness is the key to natural superhydrophobic materials. In this work, rough surfaces of a novel superhydrophobic material are achieved by the reactive wetting technique. The molten AgCuTi alloy is applied to infiltrate into the porous anodic aluminum oxide (AAO) membrane, and wetting of molten AgCuTi is promoted by the reaction layer formed at the interface between AAO and AgCuTi. The AgCuTi infiltrates the AAO nanopores and forms the first-level surface roughness based on reactive wetting. To release the nanostructures embedded in the AAO pores, hydrothermal etching with NaOH aqueous solution was used to remove AAO. Meanwhile, TiO2 nanostructures are synthesized under hydrothermal conditions, resulting in the second-level surface roughness. After modification, the surface is found to exhibit excellent superhydrophobic properties, including a high water contact angle (WCA) and low roll-off angle (RA). The superhydrophobic surface also shows self-cleaning, mechanical durability and long-term stability. The as-prepared surface exhibits excellent repellence for water solutions with different pH values. This method could be applied to fabricate superhydrophobic surfaces on different kinds of materials, showing broad application prospects.

Influence of porous high entropy alloy coating on wetting behavior and interfacial microstructure of Al-Si alloy on steel substrate

A porous FeCoNiCr high entropy alloy (HEA) coating was prepared on steel substrate via vacuum sintering. Wetting behavior of liquid Al-12Si alloy over coated and uncoated steel substrate was comparatively analyzed. The results show that the liquid Al-12Si alloy droplets were quickly spread and infiltrated into the porous structures under the enhanced capillary force by the micro-channels in the porous coating. A complete wetting ~ 0° contact angle (CA) was thus achieved; however, the CA was up to 41.2° in the case of uncoated steel substrate. In the case of uncoated steel substrate, the interfacial microstructure consisted of θ-Al13Fe4, η-Al5Fe2 and τ1-Al2Fe3Si3, while it changed to Cr-enriched FCC, AlFe-enriched BCC and AlNi-enriched B2 +Al-enriched BCC eutectic-like structure embedding in the HEA skeleton. The suppression of the formation of intermetallic compounds (IMCs) at the interface was mainly attributed to the sluggish diffusion and HEA effects of the porous coating. The altered interfacial metallurgical reactions and the enhanced capillary force were contributed to the improvement of wettability. This research provides a new method for improving the wettability and suppressing the interfacial IMCs in reactive metallic wetting systems.

The dissolutive wetting behavior between liquid iron and carbonaceous materials: Experiment and ReaxFF molecular dynamics simulation

• The wettability of molten iron on the graphite prism plane is better than that of the graphite basal plane. • The wetting process of molten iron on the graphite basal plane is different from that on the graphite prism plane. • The iron atoms in contact with the incomplete carbon structure will exhibit a cluster structure. • The exfoliation of carbon atoms in the basal model is more complicated than that in the prism model. Understanding the mechanism of the iron-carbon reactive wetting process is very important to understand the interaction between molten iron and carbonaceous materials in the ironmaking process. In this paper, the method of ReaxFF molecular dynamics simulation was used to study the microscopic mechanisms involved in the iron-carbon reactive wetting process. The study examines spreading area, contact angle, microscopic atomic structure, and the interfacial processes. It was found that the wetting process between molten iron and graphite is different for the different crystal orientations of graphite. The wettability of molten iron on the graphite prism plane is better than that on the basal plane. However, the degree of corrosion of molten iron on the graphite basal plane is greater, which is directly related to the way of exfoliation of atoms at different crystal orientation planes. The exfoliation of carbon atoms in the graphite basal model is more complicated, and there are two steps. The iron atoms are in contact with the graphite layer, leading to the formation of defects, which in turn destroy the graphite structure. Then, the iron atoms come into contact with the unsaturated carbon in the pores of the graphite, thereby exfoliating the carbon atoms from the graphitic structure. And the carbon atom exfoliation method in the graphite prism model is relatively simple.

A chromium carbide coating in-situ formed on C/C composites by the novel reactive wetting strategy to enhance oxidation resistance

A chromium carbide (Cr-C) coating in-situ formed on the C/C substrate is successfully prepared by a novel reactive wetting strategy. The interfacial microstructure and oxidation resistance of coated C/C composites are investigated in detail. The as-prepared coating mainly consists of Cr23C6 and Cr7C3, forming a tight joining with the C/C substrate. Compared to uncoated samples, the oxidation weight loss of coated C/C composites is substantially reduced at high temperatures. Furthermore, the hardness of coated C/C composites is significantly increased, enhancing their ability to resist external damage. This reactive wetting strategy can also be used to prepare uniform coatings on C/C composites with complex grooved structure or large size. Surprisingly, coated C/C composites possess a low weight gain of 3.7% due to thin coating (< 10 µm), which can maintain their advantage of low density.

The Influence of Carbon Sources on the Microstructures of In Situ-Synthesized TiC in Al Melts.

In this work, graphite and diamond are successfully introduced into Al melts and TiC is in situ-synthesized based on reactive wetting. It is found that the microstructures of the prepared TiC-reinforced Al composites are varied with the change in carbon sources and their sizes. TiC particles tend to form agglomerations in the composites prepared by both graphite and diamond, but the size of the TiC particles as well as their agglomerations will decrease with the decrease in the carbon source size. In addition, the Ti-C reaction is also difficult to fully carry out due to the influence of the Al-C reaction. As a result, in addition to TiC particles, Al4C3 will also be present in the composites prepared by graphite, especially when the size of graphite is large. As for the composites prepared by diamond, diamond@Al4C3@TiC core–shell particles will form when the size of the diamond is large, such as 10 μm in this work, and these particles will transform into Al4C3@TiC core–shell particles when the size of the diamond is decreased.

Selective Oxidation of a Medium-Mn Third Generation Advanced High Strength Steel during Austenitizing and Intercritical Annealing

The effect of the simulated continuous galvanizing line N2−5 vol% H2 process atmosphere oxygen partial pressure (pO2) on the external and internal selective oxidation of a prototype medium-Mn third generation (3G) advanced high strength steel was determined during a two-stage heat treatment cycle (i.e., austenitizing and intercritical annealing) which had previously yielded 3G properties. Thick external oxides (∼200 nm) were observed after the austenitizing heat treatment, regardless of the process atmosphere pO2 employed. An intermediate flash pickling step was successful in reducing the external oxide thickness significantly (to ∼30 nm) along with revealing some extruded metallic Fe nodules on the surface. The austenitizing heat treatment also resulted in a solute-depleted surface layer with a minimum thickness of 2 μm. This solute-depleted layer inhibited the formation of external oxides during intercritical annealing, resulting in a surface similar to that observed after flash pickling comprising a near-pure Fe surface with isolated, nodular external oxides. These surfaces are promising in terms of successful reactive wetting of this prototype medium-Mn steel during subsequent continuous hot-dip galvanizing.

Effect of surface orientation on reactive wetting of sapphire by Al–Ti alloys at 1273 K

The effect of surface orientation on the reactive wetting of sapphire by Al–Ti alloys was studied by the modified sessile drop method at 1273 K under a high vacuum atmosphere. The monocrystal α-Al2O3 (sapphire) substrates with different atomic termination surfaces were selected in this study, i.e., C (0,0,0,1), R (1 1(−),0,2), and M (1 1(−),0,0) faces. The order of wettability is R > C ≈ polycrystalline substrate > M, and the final contact angles are 65 ± 0.1° (R), 76 ± 0.2° (C), 76 ± 0.3° (polycrystalline), and 84 ± 0.3° (M), respectively. The addition of Ti does not result in the formation of the continuous reaction layer, but it may contribute to the reaction of 4Al(l)+Al2O3(s)→3Al2O(g)↑. When the interfacial bonding is mainly chemical, the wettability depends on the bonding energy between the terminal atoms of the crystal face and the atoms of the liquid phase. The higher the bonding energy, the better the wettability.

EFFECT OF PULSE DURATION ON THE PROPERTIES OF LASER-WELDED GLASS JOINTS

To explore the effect of pulse duration on the micro-morphology and mechanical properties of laser-welded glass joints, a glass welding experiment was carried out. The microstructure of the molten layer with different pulse durations was shown by field-emission scanning electron microscopy. The pores and distribution characteristics were analyzed, and the porosity variation rule of the welding layer for different pulse durations was obtained. The line-scan analysis of the joint interface was carried out with a D8-Advance type crystal X-ray diffractometer, and the relationship between the thickness of the reactive wetting layer and the pulse duration was obtained. The hardness and welding strength of the laser-welded glass joints were obtained with a Vickers hardness tester and an electronic universal testing machine. This study can provide a theoretical and experimental basis for the laser welding of glass.