Sessile Drop Test Research Articles

Evaluating the effect of amorphous carbon powder on moisture susceptibility and mechanical resistance of asphalt mixtures

The detrimental effect of water in asphalt mixtures is regarded as one of the major distresses in flexible pavements since it is generally accompanied by mechanical related distresses. This detrimental effect is a complex phenomenon and involves thermodynamic, chemical, physical and mechanical processes. Several methods are used to reduce the moisture sensitivity of mixtures, one of which is to add hydrophobic material in asphalt mixtures as an additive. In this study, amorphous carbon powder, a by-product of paraffin production factory, is used as a replacement of filler (25, 50, 75, and 100%) and as a modifier of bitumen (5, 10, and 15%) to improve the hydrophobicity of mixtures. The sessile drop test was used along with several conventional methods to investigate the hydrophobicity and moisture sensitivity of mixtures. Mechanical stability of mixtures modified by the amorphous carbon powder was also studied using dynamic creep and wheel tracking tests. The results showed that not only did the hydrophobic powder improve the moisture sensitivity, but it also increased the rutting resistance of mixtures. The enhancement of moisture susceptibility was more pronounced when carbon powder was incorporated as filler compared to that of using as binder modifier. However, dynamic creep and wheel tracking test results showed bitumen modified mixtures are more resistant to mechanical deformation. The results of this research provide more insight on the application of waste carbon powder to produce environmental friendly asphalt mixture.

The wettability of coke by pitches with different quinoline-insoluble contents

The properties of pitch as the binder material for carbon anode manufacturing strongly affect the anode properties. Pitches show significant differences in their chemical composition depending on their origin. In this study, five coal tar pitches with different quinoline-insoluble (QI) contents were studied to understand the wettability of one calcined petroleum coke by these pitches using the sessile-drop test. The chemical properties of the coke and pitch were studied using XPS and FT-IR to investigate their wetting mechanism and their interactions. The structures of different pitches and the pitch-coke interface were characterized by optical microscopy and SEM, respectively. The results showed that not only the chemical but also the physical properties of the pitches contribute to the wettability of coke. The wettability increases with increasing heteroatom content in the pitch. The viscosity of pitch is a key parameter controlling the wetting behavior of pitch. The QI content, the solid particle size and their distribution in the pitches play a significant role in the wettability of coke by pitch.

The Effect of Mg on the Wetting Behavior of SiC-Al System

The wetting behavior of SiC by molten Al and Al-Mg alloys using the sessile-drop testing equipment was investigated. The results showed that Mg has a remarkable influence on the wettability and reaction in the Al/SiC system. The contact angle between SiC substrate and molten Al-Mg alloys decreased more quickly with increasing of Mg content. The transition temperature from non-wetting to wetting dropped with increasing of Mg content, suggesting that the addition of Mg does promote the wettability of SiC by molten Al. The role of the Mg addition on the wetting was presumably attributed to its deoxidation as well as the inhibition of the interfacial reaction between Al and SiC.

In vitro study of platelet behaviour on titanium surface modified by plasma

Biomedical devices introduced in the human body interact initially with blood cells, their success being dependent on the result of this interaction. This work aimed to obtain optimum biocompatibility and hemocompatibility of the titanium by plasma treatment. For this, discs of commercially pure titanium (CP) were subjected to plasma nitriding using different mixture of nitrogen and hydrogen; the effect of addition of hydrogen to the nitriding plasma was investigated. Before and after treatment, samples were evaluated in terms of topography and wettability using atomic force microscopy and sessile drop tests, respectively. The titanium biological response was evaluated in vitro through the application of platelet-rich plasma (PRP) on the surfaces modified and analysis of their behaviour from the point of view of surface tension and cell adhesion. Surface properties, such as roughness and wettability, were sensitive to the hydrogen/nitrogen ratio in the nitriding plasma, suggesting a strategy for producing different surfaces of biomedical devices. Results showed to be possible to obtain surfaces with different response to the adhesion of platelets, covering different applications.

Undercooling and Wettability Behavior of Interstitial-Free Steel on TiN, Al2O3 and MgAl2O4 Under Controlled Oxygen Partial Pressure

The heterogeneous undercooling degree of interstitial-free steel (IF steel) on various substrates was measured through observing the recalescence phenomenon by sessile drop method at the oxygen partial pressure of 10−23 atm, where there was no obvious interaction between the steel and the substrate. The wetting behavior of liquid IF steel against different substrates was also studied during the sessile drop test. The results suggested that the undercooling degree increased with the increase of cooling rate, and the effective contact surface area between the liquid steel and the solid substrate could not fully explain the undercooling behavior of the designed cases as there is no interaction layer. Furthermore, a method to calculate the critical contact angle for IF steel against its substrate was developed in this study, which could be adapted to explain the undercooling variance of IF steel with the change of its substrate. The undercooling degree increased with the increase of the critical contact angle, and the critical contact angle was also improved with the increase of lattice disregistry.

Study of the Wettability of Coke by Different Pitches and Their Blends

The properties of coal tar pitch, which is used as the binder material for carbon anode production, strongly affect the anode properties. Pitches have significant differences in their chemical compositions depending on their origin. In this study, four different coal tar pitches and their blends were studied with the aim of understanding the wettability of a calcined petroleum coke by pitch using the sessile-drop test. In this test, contact angle, which is an indication of wettability, is measured. Contact angles decrease with increasing time, and smaller contact angle means better wettability. The chemical properties of pitches and coke were studied using XPS to investigate their interactions and, consequently, the wetting mechanism. The results showed that blending different pitches influences the wettability. The presence of acidic, basic, and heteroatom containing functional groups in pitch might cause acid–base/condensation reactions when they are blended and, thus, influence the wetting behavior of ...

Molten Al and (0001) α-Al2O3 Single Crystal: Interface Stability

The roughness on the “c”-plane (0001) sapphire single crystal reduces wetting of molten aluminum under Ar gas (99.999 pct) and PO2 10−15 Pa from 1073 K to 1473 K (800 °C to 1200 °C). The contact angle effect was partially understood by the roughness factor, R; however, the interfacial phenomenon involving this effect is yet a topic to study as it also depends, between other things, on the shape of droplet and the relationship to its substrate. The theory explains that the surface tension of liquid aluminum obtained by the sessile drop test can be determined just when a substrate is polished or free of any surface imperfection. However, roughness of sapphire (0001) surface promotes an apparent surface tension that exhibits different trends of wetting to that proposed in previous studies. This property adds to the interfacial wetting phenomena obtained from the Al-Al2O3 couple system and provides answers for contact angle trends toward a much more stable interface, which when coupled with thermodynamic conditions may help in the manufacturing, deterioration, and reliability of the system.

Effect of Sb on wetting behavior of near eutectic Sn-Cu solder micro-alloyed with Ni and Ge

Purpose The purpose of this paper is to investigate the effect of Sb (0, 0.2 and 2 wt.%) on wetting performance of lead-free solder of near eutectic Sn-Cu micro-alloyed with Ni and Ge. Design/methodology/approach The melting characteristic of the lead-free alloys was studied using differential scanning calorimetry. Wettability was examined using wetting balance test for two liquid fluxes, water based and alcohol based in two temperatures 265°C and 277°C. Also, contact angle was measured using sessile drop test. Findings It is shown that 0.2 wt.% Sb reduces the melting temperature and pasty range. Moreover, the addition of 0.2 wt.% Sb improves wetting behavior for alcohol-based flux. It is also demonstrated that the effect of Sb on meniscus height in wetting balance test and contact angle in sessile drop test follows the trend of wetting performance. Originality/value It is found that adding 0.2 wt.% Sb improves the wettability of Ni-Ge micro-alloyed Sn-Cu solder; however, higher concentration of Sb does not benefit the alloy.

Effect of Crystallinity on the Wettability of Petroleum Coke by Coal Tar Pitch

Undercalcined coke gained interest as raw material for anodes used in aluminum production since it is reported in the literature that anodes produced with this coke might have lower CO2 reactivity in the electrolytic cell. For any anode-grade coke, it is important to identify a suitable pitch which will bond well with that coke during baking and yield dense anodes. The wettability of petroleum coke by molten pitch indicates the quality of bonding between them and influences the final anode properties. In this study, the effect of coke crystallinity on its wettability by pitch has been studied using the sessile-drop test. Also, the chemical and physical properties of coke and pitch have been studied using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). It was found that the coke physical and chemical properties depend on its calcination temperature and, thereby, greatly affect the wet...

Interaction of bio-coke with different coal tar pitches

The interactions of pyrolyzed and calcined bio-cokes with three coal tar pitches of different properties were studied using a sessile drop test at 170°C. A model was employed to characterize and quantify the spreading and penetration of pitch into bio-coke bed. The pyrolyzed bio-cokes were produced from softwood materials by heat treatment at 426°C. The calcined bio-cokes were produced by calcining the pyrolyzed bio-coke at 1200°C. Optical microscope, SEM/EDS, XRD, and FTIR techniques were used to analyze the coke–pitch interface and study their interaction mechanisms. The results show that the wettability of bio-coke is related to both pitch and coke properties. It is found that the presence of small amount of uniformly distributed small size quinoline insolubles (QI) in pitch seems to help pitch spread and penetrate into the bio-coke bed. Besides, calcination changes the chemical structure of bio-coke, enriches its carbon (C%) content, increases its crystalline length (Lc), and lowers its wettability by pitch.

Wettability of bio-coke by coal tar pitch for its use in carbon anodes

Information on the wettability of a bio-coke substrate is of great value in assessing its possible use as a potential raw material for carbon anode production. In this study, the interaction mechanisms of a coal tar pitch with six bio-coke substrates were studied at a temperature of 170 °C, a typical industrial value for coke-pitch mixing, using a sessile-drop test. Three bio-cokes were produced from different bio-materials by pyrolyzing them to 426 °C, and the other three by further calcining them to 1200 °C. Different techniques were used to analyze the structural and chemical characteristics of the six bio-cokes. The results show that the heat treatment temperature has a significant influence on the chemical properties of bio-cokes and the wettability of pitch/bio-coke systems. The possibility of partial replacement of petroleum coke by bio-coke is discussed from the point view of the suitability of its structure and its wettability.

Chemical interaction between SrAl2Si2O8 and molten aluminum

Wetting and corrosion experiments by molten aluminum alloy were performed on mullite (Al6Si2O13) and/or SrAl2Si2O8 substrates. The SrAl2Si2O8 sustrates were synthesized from a mixture of alumina, silica and strontium carbonate at 1500°C for 4h. The formation of pure monoclinic SrAl2Si2O8 was corroborated by XRD analysis. The mullite sample showed a severe corrosion after the test, while the SrAl2Si2O8 sample showed a discontinue corrosion layer of about 100μm. The wetting angles, obtained from the sessile drop test, were 124° and 128° for mullite in contact with pure Al and Al-Si, respectively, while for SrAl2Si2O8 were 140° and 152°, showing a no wetting behavior.

Investigation into the use of CaZrO3 as a facecoat material in the investment casting of TiAl alloys

Research was carried out to determine the interactions between the filler and stucco materials in CaZrO3 based facecoats during shell firing as well as between the facecoat and a TiAl alloy during the casting process. A ‘flash re-melting’ technique, which gives a similar heating profile to the actual investment casting process, was used to study the phase transformations in the shell moulds. The chemical inertness of the facecoat was then investigated using a sessile drop test using a Ti–45Al–2Nb–2Mn–0.2TiB alloy. In this study, the facecoat compositions and the interaction products between metal and shells were characterized using x-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A severe interaction was found between CaZrO3 filler and Al2O3 stucco, which rapidly damaged the shell surface. As well as oxygen, zirconium and silicon ions from the shell moulds were also observed to penetrate into the TiAl metal to form (Ti, Zr)5(Al, Si)3 phases in the metal/shell interfacial areas.

Effect of the addition of alkaline earth sulfates to mullite ceramics on the corrosion and wetting by Al–Mg alloy

Novel ceramics showing a high corrosion resistance were obtained by adding alkaline earth sulfates to mullite (Al6Si2O13). Powder samples of mullite, mullite–SrSO4 and mullite–BaSO4 were prepared. Disk pellets of 4cm in diameter were conformed by uniaxial pressing at 78MPa and sintered at 1450°C for 6h. Wetting experiments were carried out by the sessile drop test at 900°C using an Al–7Mg alloy. After sintering, substrates of mullite, mullite–SrAl2Si2O8 or mullite–BaAl2Si2O8 were obtained. The contact angles between samples surface of alkaline earth sulfates containing mullite and molten alloy were higher than that corresponding to pure mullite, showing a non-wetting behavior. Cross-section analysis by SEM and EDS of samples after the wetting test showed that the corrosion products were spinel (MgAl2O4) and periclase (MgO). The BaAl2Si2O8-containing samples showed a higher corrosion resistance.

The Influence of ZrO2 Concentration in an Yttria-Based Face Coat for Investment Casting a Ti-45Al-2Mn-2Nb-0.2TiB Alloy Using a Sessile Drop Method

Investment casting is widely used to cast near-net shape components, reducing material waste and process cost. Due to the high reactivity of titanium and its alloys, in order to reduce the interaction between the mold and molten titanium, very costly materials are used in the mold face coat. In order to reduce the material cost while maintaining the chemical inertness of the face coat, ZrO2 was added into an yttria-based face coat in different concentrations in this study. The face coat properties of the different systems were analyzed using dilatometry and XRD. The chemical inertness of the different face coat systems were tested using a sessile drop test using a Ti-45Al-2Mn-2Nb-0.2TiB alloy, and the interactions between the face coat and the alloy were analyzed by the interfacial microstructures, contact angle, and hardness changes. The results showed that small amounts of ZrO2 can be added into yttria without changing the chemical inertness of the face coat. High amounts of ZrO2 in the face coat can interact with TiAl alloy to form different interaction products. Meanwhile, both Y2O3 and ZrO2 filler materials were observed to dissolve in molten TiAl during the sessile drop test.

Novel Fabrication of Un-coated Super-hydrophobic Aluminum via Pulsed Electrochemical Surface Modification

Super-hydrophobic and super-hydrophilic aluminum (Al) surfaces were fabricated via electrochemical surface modification (ECSM) in neutral NaClO3 electrolyte without the addition of secondary chemical coatings. The effects of processing time and applied potential on the surface roughness and wettability were studied. The aluminum surface was characterized using stylus profilometer and scanning electron microscope (SEM). Wettability was evaluated using Sessile Drop Test and a high resolution camera. Results show that surfaces obtained hierarchical rough features and super-hydrophilic behavior after pulse electrochemical machining. Heat treatment at 200°C transitioned the substrates to exhibit super-hydrophobic behavior due to the removal of all moisture from within the micro- and nano-meter scale features on the aluminum surfaces, allowing for the reformation of a natural passivation (oxide) layer with atmospheric interaction. The method proposed in this study for producing super-hydrophobic aluminum surfaces does not require the use of acid or base etching or chemical coatings, such as flouroalkylsilane (FAS). Experimental results reveal increase in contact angle, with increase in applied potential, and decrease in sliding angle.

Synthesis of Al6Si2O13-BaAl2Si2O8-ZrO2-based composites and their wettability by molten Al and an Al-Si alloy

The corrosion of refractory materials by molten aluminum alloys is a common problem during the aluminum recycling. Therefore, special emphasis has been focused in developing corrosion resistant materials by aluminum. In this research, composites based on Al6Si2O13-BaAl2Si2O8-ZrO2 were developed by two different methods. In the first method (S), BaAl2Si2O8, Al6Si2O13 and ZrO2 chemicals were mixed, pressed and sintered (1450°C for 10h). In the second method (R), the composites were obtained in situ by solid state reaction of BaCO3, Al2O3 and ZrSiO4 (1450°C for 10h). In both cases the amount of celsian was varied (8, 16 and 24wt%) and the amount of ZrO2 was kept constant at 20wt%. All the samples were characterized by X-ray diffraction (XRD) to identify the phases formed. A sessile drop test was performed on the samples obtained by the two methods using either pure Al or Al-8Si alloy. Then, the cross-section of the samples was analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The thickness of the corrosion layer, when pure Al was tested, reached only about 266µm after 2h at 1100°C for the samples prepared by the S process. The thickness was greater (around of 488µm) in the case of the Al-8Si alloy for substrates prepared by the S and R processes under the same conditions. However, this is still a minimal penetration. Contact angles between molten metals and substrates were as high as 150° for all the systems, showing a non-wetting behavior. The contact angles obtained in this research were higher than those showed by a mullite substrate under the same conditions. The materials prepared in this work demonstrate to be highly potential composites for refractory applications in the aluminum industry.

Influence of Al2O3 concentration in yttria based face coats for investment casting Ti–45Al–2Mn–2Nb–0·2TiB alloy

An Al2O3–Y2O3 based face coat material was researched by adding Al2O3 into yttria in different concentrations to reduce the mould cost whilst retaining the face coat chemical inertness. The face coat compositions and sintering properties at different temperatures were investigated using X-ray diffraction, friability and dilatometers. Meanwhile, the chemical inertness of the face coats was identified using a sessile drop test method to interact with a Ti–45Al–2Mn–2Nb–0·2TiB alloy. The results show that at different firing temperatures, a series of phase transformations have taken place between Y2O3 and Al2O3, resulting in different face coat compositions and sintering properties. However, the chemical inertness of the face coat against the molten TiAl alloy was not influenced by the phase transformations, and it was dependent on the amount of Al2O3 added to the face coat. In this experiment, no interaction was observed between the Al2O3–Y2O3 face coat material and TiAl alloy when Al2O3 additions were lower than 33·33 mol.-%; however, increasing addition amount of Al2O3 will increase the chance of face coat and metal interaction.

A Comparison of the Chemical Inertness of Two Y2O3-Al2O3-ZrO2 and Y2O3-Al2O3 Face Coat Materials Through Sessile Drop and Investment Casting Methods

Investment casting is uniquely suited to the manufacture of Ti alloys for the production of near net-shape components, reducing material waste, and machining costs. Because of the high reactivity of titanium and its based alloy, the molds which are used in the investment casting process require high chemical inertness, which results in them being very costly and non-recyclable. In order to reduce the cost of these molds, traditionally using yttria as the face coat, two alternative molds are developed in this study with face coat materials of Y2O3-Al2O3 and Y2O3-Al2O3-ZrO2. The slurry properties and chemical inertness of the face coats were evaluated for viscosity, thermal expansion, friability, and phase development. The chemical inertness of these two molds were determined using both the sessile drop test and investment casting to identify the levels of interaction with a Ti-45Al-2Mn-2Nb-0.2B alloy. The results illustrated that the molds using Y2O3-Al2O3 and Y2O3-Al2O3-ZrO2 as the face coats both showed excellent sintering properties and chemical inertness when compared to the yttria face coat. They can consequently be used as two alternative face coats for the investment casting of TiAl alloys.

Engineered CO2 injection: The use of surfactants for enhanced sweep efficiency

Poor CO2 displacement efficiency can exacerbate hydro-chemo-mechanically coupled phenomena in CO2 storage reservoirs, increase the area affected by CO2 in the reservoir, and negatively impact the long-term geological storage of CO2. The injection of CO2 can be engineered using surfactants to improve displacement efficiency. Pendant and sessile drop tests show that a surfonic copolymer decreases the interfacial tension γfl and increases the contact angle θ under reservoir conditions. The combined changes in surface tension and contact angle have a pronounced effect on the capillary factor γfl·cosθ. Injection tests using micro-models and pore network simulations show that a smaller capillary factor transforms the displacement pattern and enhances the pore-scale sweep efficiency of CO2, surpassing 40% in 2-D applications. Surfactant cost may offset the technical advantages identified in this study.