Liquid Infiltrates Research Articles

Microstructure and properties of different carbon fiber reinforced ceramic composites brazed joint by Si–Ti alloy filler

The brazing of C/C and Cf/SiC composites was achieved using Si–14Ti eutectic filler. The wetting behavior of the Si–Ti filler on the composites, as well as the microstructure and performance of the joints at different brazing temperatures, were characterized. The results showed that the contact angle of Si–Ti eutectic filler on precursor infiltration and pyrolysis (PIP)-Cf/SiC composite surface is only 60°, while it exhibits good spreading effect on liquid silicon infiltration (LSI)-Cf/SiC and C/C composite surfaces. Although Si–Ti filler and carbon fiber reinforced composites (C/C, PIP-Cf/SiC and LSI-Cf/SiC) react to form SiC, the joint shows different mechanical performance. The liquid filler infiltrates into the gaps between fiber bundles and reacts with C/C to form a SiC reaction layer at the interface. However, the presence of numerous defects at the brazed joint between Si–Ti filler and PIP-Cf/SiC results in the shear strength of only 28 MPa for the C/C-PIP-Cf/SiC joint. While for the C/C-LSI-Cf/SiC joint, due to the residual Si in the LSI-Cf/SiC composites, the liquid filler infiltrates intensely into LSI-Cf/SiC to form a unique Cf/SiC–Si–TiSi2 compound infiltration layer. The shear strength of C/C-LSI-Cf/SiC joints reaches 47 MPa, with fracture occurring in both substrates and brazed seam. The present study offers theoretical support for the investigation of Si-based fillers in brazing carbon fiber reinforced ceramic matrix composites.

Symplectite formation in ultramafic achondrites by impact percolation of a sulfide melt

The ungrouped dunitic achondrite Northwest Africa (NWA) 12217 contains symplectic spinel-pyroxene veins that are mineralogically identical to symplectites in other ultramafic planetary materials. The morphology and amount of chromite present in these features relative to the Cr in their olivine hosts suggest an exogenous origin. Petrological experiments show that a Cr laden sulfide liquid reacts with olivine to produce pyroxene by scavenging Mg and Fe from olivine to crystallize chromite. The liquid infiltrates cracks and grain boundaries within the olivine and produces a vein-like symplectic chromite-pyroxene mineralogy similar to that observed in NWA 12217. This process is likely responsible for forming the symplectites in the related ultramafic achondrites NWA 12319, 12562, and 13954, along with many other achondrites. The nucleosynthetic Cr isotopic composition of chromites appears to be in disequilibrium with that of silicates in NWA 12217, suggesting that the liquids responsible for the symplectite forming reaction are at least partially sourced from a different parent body and result from an impact.

Interfacial structure and properties of anodized 6061 Al alloy joints by ultrasonic-assisted hot dipping and soldering using a Sn–9Zn–2Al filler metal

Al alloy joints soldered with Sn-based filler metal are susceptible to corrosion and early failure when exposed to moisture, resulting in severe accidents and substantial economic losses. This study proposes a method to prevent galvanic corrosion by separating Al alloys and Sn-based filler metals with an insulating barrier layer of anodized aluminum oxide (AAO) composed of Al2O3. The successful joining of anodized aluminum alloy (AAA) with Sn–9Zn–2Al was achieved through ultrasonic-assisted hot dipping and soldering in air at 240 °C. Microstructural examination revealed strong bonding between the solder alloy and AAO, with the solder infiltrating the AAO nanotubes and a transition layer consisting of two sublayers at the interface: amorphous ZnO mixed with nanocrystals (ZnO and Al2O3) and amorphous Al2O3. The shear strength of the joints ranged from 31.8 to 32.8 MPa when subjected to ultrasonic hot dipping for 0.5–2.0 s, with no significant difference observed. Fracture initiation and propagation occur within the transition layer at the interface. The shear strength of joints subjected to dipping for more than 3.0 s decreased slightly to 27.9 MPa due to localized peeling off of AAO from the Al substrate. The formation of the interface involves the segregation of Al and Zn on the liquid filler metal surface, driven by differences in atomic activity. Due to the jet force from cavitation, an Al-rich liquid infiltrates the nanotube, resulting in the formation of Zn–O at the interface and Al–O both at the interface and within the nanotube. Throughout this process, the wetting model shifts from a Cassie state to a near-Wenzel state. Immersion tests of two types of joints, Al/SnZnAl/Al and AAA/SnZnAl/AAA, confirmed that galvanic corrosion of Sn/Al was completely inhibited by the latter. Consequently, AAA joints demonstrate excellent corrosion resistance, validating this approach as a promising solution to the Al/Sn galvanic corrosion issue.

Sintering window and sintering mechanism for diamond

High performance sintered diamond tools, such as those applied to wire drawing and rock drilling, represent a considerable advance in hard materials technology. A dense diamond-metal composite is produced using liquid phase sintering. With a cemented carbide substrate, a cobalt-rich liquid infiltrates between the diamond grains at temperatures near 1400 °C. For small diamond particles (nominally below 20 μm), a combination of high pressure (5 GPa or more) and high temperature (1400 °C or more) gives full density in minutes. A sintering window is defined by the pressure and temperature combination that avoids graphitization while ensuring cobalt melt infiltration. The sintering mechanism is carbon transport by dissolution of graphite from low pressure regions away from grain contacts with precipitation of diamond at grain contacts under high pressure. Sinter bonds preferentially nucleate at surface defects, such as screw dislocation spirals. Bonding rates depend on particle size, carbon solubility, temperature, pressure, and hold time. Calculations are shown for interface reaction site limited growth kinetics.

Effect of Ion Size on Pressure-Induced Infiltration of a Zeolite-Based Nanofluidic System.

A nanofluidic system consists of a nano-porous medium and functional liquid, which demonstrates a higher energy absorption density compared to conventional systems for energy absorption. Alterations in the composition of the functional liquid can significantly impact the properties of a nanofluidic system. In this paper, the widely used zeolite ZSM-5 was chosen as the porous medium to establish a nanofluidic system. Three distinct electrolyte solutions, namely KCl aqueous solutions, NaCl aqueous solutions and MgCl2 aqueous solutions were employed as functional liquids while pure water served as the reference condition for configuring four kinds of nanofluidic systems. Pressure-induced percolation experiments were performed on the four zeolite-based systems. The difference in the infiltration process between the electrolyte solution systems and the deionized water system has been ascertained. The effect of the ion size on the infiltration and defiltration process has been determined. The results show that the introduction of ions induces a hydration effect, resulting in a higher critical infiltration pressure of the electrolyte solution system compared to an aqueous solution system. The magnitude of cation charge directly correlates with the strength of the hydration effect and the corresponding increase in critical infiltration pressure. Upon entering the nanochannel, the liquid infiltrates primarily in the form of ions rather than a cation hydration form. The larger the ion size, the shallower the penetration depth after entering the nanopore channel and the larger the corresponding relative outflow rate. The present work will provide valuable theoretical complementary and experimental data support for nanofluidic system applications.

A Novel Menthol-Cementing Sampling Technique for Cohesionless Coarse-Grained Fillers

It is difficult to test the engineering properties of undisturbed cohesionless coarse-grained fillers in the laboratory, especially those with low water contents because most sampling methods disturb the natural structure of the filler. This study proposes a novel sampling method that uses menthol as a temporary cement to obtain samples that are more resistant to disturbance. Liquid menthol infiltrates the interparticle spaces and cements the particles together as it cools, forming a high-strength structure. The samples can then be cut with a cutting ring (for grain sizes ≤ 0.5 mm) or a cutting machine (for grain sizes > 0.5 mm) to prepare the final samples, from which the menthol is removed by heating. To demonstrate the feasibility of the method, a number of laboratory experiments were performed, including sampling tests, confined compressive strength tests, vibration tests, drop tests, and CT scans. The optimal particle temperature for introducing the liquid menthol is 70°C, while 90°C is optimal for removing the cemented menthol. For both cost and anti-disturbance reasons, 20°C is suggested as a suitable storage temperature for menthol-cemented samples. The interspace structure undergoes less change with increases in sample depth and with larger grain sizes. We recommend that the lower two-third of the depth of a menthol-cemented block is used as the final sample for laboratory testing.

Micro-Scale Permeability Characterization of Carbon Fiber Composites Using Micrograph Volume Elements

To manufacture a high-performance structure made of continuous fiber reinforced plastics, Liquid Composite Molding processes are used, where a liquid resin infiltrates the dry fibers. For a good infiltration quality without dry spots, it is important to predict the resin flow correctly. Knowledge of the local permeability is an essential precondition for mold-filling simulations. In our approach, the intra-bundle permeability parallel and transverse to the fibers is characterized via periodic fluid dynamic simulations of micro-scale volume elements (VE). We evaluate and compare two approaches: First, an approach to generate VEs based on a statistical distribution of the fibers and fiber diameters. Second, an approach based on micrograph images of samples manufactured with Tailored Fiber Placement (TFP) using the measured fiber distribution. The micrograph images show a higher heterogeneity of the distribution than the statistically generated VEs, which is characterized by large resin areas. This heterogeneity leads to a significantly different permeability compared to the stochastic approach. In conclusion, a pure stochastic approach needs to contain the large heterogeneity of the fiber distribution to predict correct permeability values.

In-operando dynamic visualization of flow through porous preforms based on X-ray phase contrast imaging

Direct visualization is often sought to elucidate flow patterns and validate models to predict the filling kinetics during processes whereby a liquid resin infiltrates a textile porous preform. Here, X-ray phase contrast interferometry is evaluated to image in-operando constant flow rate impregnation experiments of a model fluid into glass, carbon and flax fabrics and a 3D printed structure. A methodology is presented to build the dynamic saturation curve based on image analysis of the dark field images, in which the pixel intensity values are transformed into saturation level versus position and time. The results prove the suitability of this technique to observe the progressive saturation averaged through the thickness of translucent and non-translucent preforms. The porosity network formed by the layers of fabric, the refractive properties of the material, the fabric geometry and its position relative to the X-ray setup are reported to be the main parameters affecting image contrast.

Solid-liquid Diffusion Interconnection Method Based on Cu-In Secondary Micro Nano Layer

A solid-liquid diffusion interconnection method based on Cu-In secondary micro nano layer is proposed. The substrate surfaces of two copper indium secondary micro nano layers with special morphology are contacted with each other, and the contact area is heated to carry out solid-liquid interconnection. The special morphology of copper indium micro nano layer includes copper needle layer and indium micro layer coated on it. During interconnection, liquid indium infiltrates copper needle layer and forms intermetallic compound with good plasticity. The microstructure, intermetallic compounds and shear strength of the interface were analyzed by scanning electron microscope (SEM), transmission electron microscope (TEM) and welding strength tester. The results show that this solid-liquid interconnection method can obtain good interconnection quality and it is of great significance to green packaging.

(Invited) Nanocrevasse-Rich Carbon Fibers for Scalable Production and Stable Performance of Lithium and Sodium Metal Anodes

The metallic lithium (Li) and sodium (Na) anodes have long been considered as ideal anodes for high energy density batteries due to its high theoretical capacity and lowest reduction potential. However, the challenges induced by dendritic growth on metallic Li and Na anodes hinder the practical applications. Finding a stable host structure with polar functional groups is an essential strategy to prevent the Li and Na dendrite growth with improved electrochemical performance. Recently, many researchers have concentrated on development of host structure for storing the Li/Na metal. Nevertheless, complexity and inconvenience of the synthetic process still require further improvement of Li/Na metal anodes. In this talk, we will introduce a facile synthetic method to fabricate alkali metal/carbon composites which contain nanocrevasses in carbon fibers to facilitate the penetration of molten alkali metal via capillary forces. When the molten alkali metal is contacted to the carbon fibers with rGO-like crevasses, the metallic liquid infiltrates into the fine gaps within a few seconds. As well, the nanocrevasses provide a pretty large surface area which is enough to lower the specific current, ultimately leading to suppression of dendritic formation. The resulting alkali metal/carbon composites exhibit stable long-term cycling over hundreds of cycles. In addition, Unlike previous studies that focused on improving the performance of metal batteries, we carried out the test after applying the composite to actual equipment with scalable production process using recycled metal waste. Thus, the addition of nanocrevasses to carbon fiber as a scaffold for alkali metals can generate environmentally friendly and cost-effective composites for practical electrode applications References Go, W.; Kim, M.-H.; Park, J.; Lim, C.H.; Joo, S.H.; Kim, Y.; Lee, H.-W. Nano Lett. 2019, 19, 1504-1511.Lin, D.; Liu, Y.; Liang, Z.; Lee, H.-W.; Sun, J.; Wang, H.; Yan, K.; Xie, J.; Cui, Y. Nat. Nanotechnol. 2016, 11, 626-632.Zhang, R.; Chen, X.; Chen, X.; Cheng, X.; Zhang, X.; Yan, C.; Zhang, Q. Chem. int. Ed. 2017, 56, 7764-7768.Yun, J.H.; Kim, J.H.; Kim, D.K.; Lee, H.-W. Nano Lett. 2018, 18, 475–481. Figure 1

When Lotus Leaves Prevent Metal from Melting — Biomimetic Surfaces for High Temperature Applications

Functional properties of biological surfaces have gained increasing interest in the last two decades, especially with regard to wetting and self-cleaning. Here, biological surfaces of arthropods (Collembola) and plants (sacred Lotus) served as models for the principle design of high temperature resistant surfaces used in blast furnaces to prevent tuyeres from melting. Tuyeres are double-walled, watercooled pipes supplying the blast furnace with hot air to keep the reduction and melting process running. Tuyere failure is mainly caused by melting of the wall after direct contact with liquid iron, resulting in the partial shut down of the blast furnace and huge energy losses. As a new approach to avoid tuyere failure we developed a new type of tuyere surface with (i) defined cone shaped indentations and (ii) a heat resistant zirconium/corundum coating with “ferrophobic” properties i.e. it forms with liquid iron of 1500 °C a contact angle exceeding 130°. Theoretical considerations indicate that liquid iron infiltrates these indentations only partially if this contact angle and the aperture angle of the cone satisfy an inequality condition. Since heat conductivity of the remaining gas trapped inside the cones is by five orders of magnitude lower than in copper, the overall heat flow into the tuyere is substantially reduced and the outer walls are much less prone to melting.

Cryogenic quenching enhancement of a nanoporous surface

Quenching heat transfer is of fundamental interest in cryogenic chilldown applications. Surface configuration can improve quenching heat transfer and clear understanding of the effect of different surface characteristics is necessary. In the present study, the effect of anodic aluminum oxide (AAO) surface on pool quenching is investigated. The AAO surface and other four types of surfaces are quenched in liquid nitrogen and a theoretical model is applied to further investigate the effect of surface thermal resistance. It is shown that the total chilldown time is decreased from 63.8 s on electropolishing surface to 33.4 s on the AAO surface. By comparisons with other surfaces, it is found that the effect of the AAO surface results from two aspects: surface thermal resistance and nanopore structure. For surface thermal resistance, it is indicated by the consistence of numerical and experimental results that the end of film boiling is resulted from the decrease of local surface temperature that is not high enough to sustain the local vapor film, even though the bulk temperature is still high. For the nanopore structure, it is theoretically estimated that the nanopores will be kept filled with vapor at the surface temperature higher than the critical pinning state temperature (94.4 K). This phenomenon of vapor-filled nanopores reduces the liquid–solid contact area and local vapor generation rate, resulting in a higher temperature of the Leidenfrost point (LFP) and lower heat flux in partial nucleate boiling regime. When the surface temperature drops below the critical pinning state temperature, liquid nitrogen infiltrates into the nanopores and a heat flux jump appears.

Direct observation of hot tearing of Al-7%Si-0.35%Mg alloy

Hot tearing of an Al-7%Si-0.35%Mg alloy T-shaped specimen was analyzed by direct observation of cracking and a finite element method (FEM) stress simulation. The semi-solid state during cooling enables direct observation of corner surface cracks. Crack opening appears to begin before the solid fraction reaches 0.3. However, a liquid phase infiltrates and disturbs the crack opening process. After the onset of the eutectic reaction, crack opening resumes and is detected as hot tearing. The FEM stress analysis revealed that tensile stress concentrates at the corners of the T-shaped specimen. The tensile stress increases with time at the initial stage of solidification, peaks at around 170 s, and then decreases. Microstructural observation of cooled and quenched specimens reveals that if the inter-dendritic liquid phase is adequate and has high fluidity, then healing of the crack occurs.

Anisotropy in the hydrophobic and oleophilic characteristics of patterned surfaces

A significant difference in the wetting angles of water and oil was observed on patterned substrates, combining interstitial spaces along with hydrophobic solid surfaces, as a function of the orientation. The difference was ascribed to a modification of the liquid–interstice interfacial surface energy due to different degrees of penetration of the liquid. A roughness metric related to the extent to which the liquid infiltrates the interstice normalized by the geometrically determined area is proposed. This study has implications in modulating surface slip behavior and would be of importance in guiding liquid droplets.

Fluid Imbibition-Coulped Laser Interferometry As a Tool for Optical Biosensing with Anodic Aluminum Oxide

Optofluidics is a technology based on the fusion between microfluidics and optics. It is related to a variety of phenomena in which an interaction between light and fluids is found. It can be applied to the control of fluid properties by light, to the design of variable geometry optical elements by means of the adaptability of the fluid or by using optics to interrogate fluid properties. On the other hand, anodic aluminum oxide (AAO) is a porous material obtained by the electrochemical anodization of aluminum with a growing interest in nanotechnology because of its cost-effective production process and its promising variety of applications[1]. Recently, we have introduced an optofluidic technique called fluid imbibition-coupled laser interferometry (FICLI), based on the study by optical means of the liquid infiltration dynamics into AAO. We demonstrated its high accuracy for the characterization of the material[2,3]. In this work, we explore the possibilities of using such a sensitive technique as a sensor of biological species. Fluid imbibition-coupled laser interferometry consists of the measurement of the capillary filling dynamics of a fluid into the AAO nanopores. Such measurement is performed by monitoring light intensity interferometric fluctuations of a laser beam in real-time as the liquid infiltrates the pores. An illustration of the measurement system can be seen in the figure. AAO membranes with 50 µm-long pores are used (see SEM pictures in the figure) and the laser beam is reflected at its top and bottom interfaces creating a time-resolved intereference. Light intensity fluctuations are measured by a photodetector and a high-speed data acquisition system, and are analyzed on the basis of mathematical models of the filling kinetics. This technique has shown enough accuracy to demonstrate that AAO nanopores are actually conical with an angle as small as 0.007º. The processing of the time-resolved interferograms, as the one shown in the figure, can be done in several ways. The simplest method consists of measuring the filling time of the pores from each side of the membrane and combine these measurements with the information about the fluid and the surface properties (viscosity, surface tension, contact angle) to obtain the values of the radius at each pore end. A more elaborate method permits the determination of the pore profile by the inversion of the filling dynamics integral equations provided accurate measurement of the time-resolved interferograms for the filling from each end of the pores are obtained. In this work we introduce an alternative method based on the discretization of the filling dynamics equations, what permits to obtain a direct and accurate determination of the average radius of the nanopores. In order to evaluate the accuracy of this alternative method we applied different modifications to the pore geometry and we measured the pore radius modification by the different methods. Pore radius increase was achieved by applying controlled wet etching to the as-produced AOO membranes with increasing time. On the other hand, pore radius decrease was achieved by depositing successive bilayers of polyelectrolytes. Results show that the proposed technique is accurate enough to sense pore radius variations as small as 4 nm, in the range of the size of many biological macromoleclues such as proteins, antibodies or aptamers. With this ability in mind, we have studied the application of the technique to sense such biological species. In this communication we will report our results on the measurement of the changes in the filling dynamics of AAO membranes after the functionalization of their surface and the attachment of the different molecules: i) proteins like bovine serum albumin (BSA), ii) the successive attachment of the IgG-aIgG antibody-antigen pair with a view to the application of the technique as an immunosensor and iii) the attachment of an aptamer and the detection of changes in their conformation.

Wettability and work of adhesion of liquid sulfur on carbon materials for electrical energy storage applications

The wettability of glassy, microcrystalline and nanocrystalline carbon materials by liquid sulfur is studied by the sessile-drop technique applying the contact heating and drop-dispension procedures. Liquid sulfur shows a good wetting on all examined substrates just after melting, although the contact angle depends on the type and structure of the carbon material. Sulfur drops remain on the surfaces of glassy carbon and electrographite, whereas the liquid infiltrates into the substrates pressed from carbon micro- or nanoparticles. In the latter case, the infiltration rate increases along with decreasing size of particles used for preparation of the substrates, indicating a role of capillarity. The wetting and adhesion in the sulfur-carbon material systems are determined by the van der Waals interactions.

Laminate squeeze casting of carbon fiber reinforced aluminum matrix composites

Abstract Carbon fiber reinforced aluminum matrix composites show an excellent combination of lightweight, mechanical properties, ease of processing and low costs. However, standard liquid infiltration squeeze casting often requires complex preforms in order to control fiber configuration and distribution. It also requires relatively high pressures to overcome the pressure drop across the preform, which can lead to preform compaction and damage and can limit the maximum component thickness that can be thoroughly infiltrated. Therefore, a laminate squeeze casting process is investigated as alternative whereby alternate layers of fiber fabrics and aluminum sheets are hot consolidated. Liquid infiltrates the fiber fabrics from their two respective neighboring aluminum layers, thereby reducing the infiltration distance from the entire component height to only half the thickness of individual fiber layers. This results in a rapid and thorough infiltration. Composites with fiber contents between 7 and 14 vol% are successfully fabricated. Despite complete melting of the aluminum layers at 850 °C, optical and scanning electron microscopy investigations show that hydrostatic pressure practically preserves the laminate configuration during fabrication and no fiber agglomeration occurs. The composites show good fiber–matrix bonding. No noticeable fiber damage is observed despite some carbide formation primarily at interfaces. A composite hardness over 50% higher compared to the reference 6061 matrix alloy is achieved at a carbon fiber content of 7.4 vol%.

Saturation front evolution for liquid infiltration into a gas filled porous medium with counter-current flow

The infiltration of liquid into a gas saturated porous network is investigated. Particular attention is paid to the situation in which a pressure gradient in the porous medium drives a gas flow upwards, while a more dense liquid infiltrates down into the reservoir due to gravity. There are two flows in opposite directions. A model is proposed, based upon a compressible gas phase and an incompressible liquid phase. The volume fluxes in each phase are assumed to be governed by Darcy type flow laws, modified to include the permeability caused by both the solid matrix and the impeding of the gas flow by the liquid phase. Isothermal flows are examined in the absence of phase changes. The proposed model is an extension of the traditional Buckley–Leverett model and is used to consider a variety of flows, including carbon sequestration in a porous medium below the seabed and rainfall infiltration into a lava dome.

Experimental Study on Mold Flux Lubrication for Continuous Casting

A new experimental apparatus for simulating mold oscillation of continuous casting was developed to clarify the flux lubrication mechanism in mold channel. Mixed oil which was simulated mold flux was poured and infiltrated down into the channel, and the consumption, liquid level and pressure of mixed oil were detected in the process of oscillation as well as the mechanism of flux process. The results show that the channel of flux with a profile becomes wider along the casting direction, and the lag time of periodical shifting pressure to the oscillating motion is strongly dependent on the flux viscosity and oscillation frequency. The liquid film thickness of flux has a significant influence on the infiltration behavior compared with the oscillating motion of the mold. The liquid flux infiltrates down from the end of positive strip time to the beginning of next positive strip time, and the infiltration is largely dependent on the negative strip time in between. The increase of viscosity of flux, casting speed and oscillation frequency enhances the liquid friction due to the reduction of the mold flux consumption. On the contrary, the higher non‐sinusoidal oscillation factor improves the infiltration and decreases the frictional force. The oscillation amplitude increases the consumption and liquid friction slightly.

Development and Evaluation of Appropriate Concepts for Sewage Disposal and Treatment in a Rural Area, Central Java, Indonesia on the Example of the Village Pucanganom

In the province of Yogyakarta in Java, the district of Gunung Kidul is considered to be one of the poorest areas in Indonesia. Here, water shortages greatly affect the population, especially during the dry season, which lasts from April to October. Sanitation Systems in Gunung Kidul consist, either pit latrines or pour flush toilets. Without any treatment the liquid phase infiltrates in to the ground and the septic tanks are hardly ever emptied, thus posing an evident contamination potential to groundwater. So, the current situation about waste water and its treatment is inadequate. Due to this reason within the Integrated Water Resources Management Indonesia Project (IWRM) a so called pilot village Pucanganom was selected to develop an appropriate waste water treatment system considering basis conditions and resultant indicators which were weighted by the Analytical Hierarchy Process Method (AHP). The following paper will describe the application of the method to find an adaptable sanitary system for a village in Gunung Kidul, Indonesia.