Reduction Of Surface Free Energy Research Articles

Toward an Enhanced Hydrophilic TiO2 Nanoparticles Adsorption at Air-Liquid Interface Through Ion Regulation.

This study investigates the dynamic properties of air-liquid interfacial tension for hydrophilic TiO2 P25 utilizing the pendant drop method. Additionally, it examines the interfacial adsorption mechanism of hydrophilic TiO2 particles, considering the characteristics of particle surface charge distribution in relation to ion regulation to enhance particle interface adsorption. Experimental results reveal that in the absence of ion addition, the TiO2 P25 suspension system exhibits limited interfacial adsorption due to its superhydrophilicity, regardless of particle concentration. The addition of NaCl increases the surface charge density of the particles, strengthens the electrostatic attraction between particles and the interface, and enhances particle adsorption. Specifically, at a low NaCl concentration (0.01 wt %), the increased surface charge density and contact angle of the particles elevate particle activity and high interfacial packing density. At a higher NaCl concentration (0.1 wt %), while NaCl further increases the particle contact angle, the increased effective cross-sectional area of the air-liquid interface occupied by individual particles leads to a reduction in surface free energy. Despite the enhanced electrostatic attraction, this results in a lower packing density.

Microstructure of ternary Sn-Bi-xCu alloy on mechanical properties, current endurance and corrosion morphology via cycling corrosion test

Low melting temperature of Sn-58 wt.% Bi (SB) solders adding 0.5wt.% Cu (SB05C) and 1.7wt.% Cu (SB17C) concentrations were evaluated for the signal transmission in the 3D IC package. Microstructure combined with phase analysis and Pandat simulation were together with to explain the relationship among the mechanical property, electrical endurance and corrosion resistance. By Cu decoration, the presence Cu6Sn5 intermetallic compound (IMC) acts as heterogeneous nucleation sites to reduce surface free energy and generate fine Bi grain that resulted in higher hardness value. The power-law was used to explain the mechanism of interfacial IMC growth, both Cu6Sn5 and Cu3Sn formation were speculated to be volume diffusion control and surface reaction domination, respectively. The fracture morphology by shear testing indicates that earliest plastic deformation accompanied with brittle rupture were major factors due to the intergranular fracture and Cu6Sn5 compound induced bulk fracture. By cycling corrosion test (CCT), the lump shape of SnO2 by-product was found among solders at three cycling. After seven cycling, Sn phase has been completely corroded and Cu6Sn5 IMC began to be corroded forming circle shape of Cu2O but Bi phase still not be corroded among solders. In the electrical endurance, dense Cu6Sn5 dispersed in solder bulk and fine grain size were feasible to induce current crowding and joule heating, thus Cu deteriorated SB solders is easily failed.

Development of hydrophilic carbon fiber textiles using seed-assisted hydrothermal deposition of ZnO nanostructures for enhanced interfacial interaction in CFRP composites

Two-step hydrothermal deposition of zinc-oxide (ZnO) nanorods was used to functionalize carbon fiber textiles in order to produce increased hydrophilicity on fiber surface. On carbon fiber textiles, tightly packed ZnO nanorods developed after five seed cycles and 5 h of growth treatment in a 30 mM precursor salt based on the hydrothermal synthesis. Extensive characterizations have been performed on field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Energy-dispersive X-ray spectroscopy, High resolution transmission electron microscopy, Photoluminescence spectroscopy, and Raman spectroscopy to assess the different aspects such as structural, morphological, elemental, and wettability of the plain and ZnO-modified carbon fiber textiles. ZnO nanomaterial having hexagonal nanorods shape and wurtzite crystalline structure were uniformly deposited on the fabrics. Owing to the wettability study, ZnO prisms improved the hydrophilicity of virgin carbon fiber textiles to enable strong bonds with polymer matrix. The findings highlight the significant improvement in the static water contact angle as a result of the samples' ZnO coating's ability to reduce surface free energy. The improved hydrophilicity in carbon fiber may enhance the bonding between carbon fibers and matrix materials in composite materials. Hydrophilic carbon fibers are more easily wetted by the matrix materials, allowing for better penetration of the matrix into the fiber structure.

Enhanced anti-bacterial adhesion effect of FDMA/SR833s based dental resin composites by using 1H,1H-heptafluorobutyl methacrylate as partial diluent

With the purpose of further reducing surface free energy to achieve better anti-bacterial adhesion effect of fluorinated dimethacrylate (FDMA)/tricyclo (5.2.1.0) decanedimethanol diacrylate (SR833s) based dental resin composites (DS), 1H,1H-heptafluorobutyl methacrylate (FBMA) was used to partially replace SR933s as reactive diluent. According to the degree of substitution, the obtained resin composites were marked as DSF-1 (20 wt.% of SR833s was replaced by FBMA), DSF-2 (40 wt.% of SR833s was replaced by FBMA), and DSF-3 (60 wt.% of SR833s was replaced by FBMA). Bisphenol A glycidyl dimethacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) based resin composite (BT) was used as control. The influence of FBMA concentration on double bond conversion (DC), contact angle, surface free energy, anti-bacterial adhesion effect against Streptococcus mutans (S. mutans), volumetric shrinkage (VS) and shrinkage stress (SS), flexural strength (FS) and modulus (FM), water sorption (WS) and solubility (SL) were investigated. The results showed that FBMA addition could reduce surface free energy from 44.6 mN/m for DS to 32.9 mN/m for DSF-3, and lead to better anti-bacterial adhesion effect (the amounts of adherent bacteria decreased from 2.03 × 105 CFU/mm2 for DS to 6.44 × 104 CFU/mm2 for DSF-3). The FBMA had no negative effects on DC, VS, SS, WS, and SL. Too high a concentration of FBMA reduced FS and FM before water immersion, but the values were still higher than those of BT.

Enhanced scale inhibition and anti-wax capacities of passive materials via ultrasonic rolling processing

Scale damage and wax formation on pipelines surface have become prevalent issues in the development and production of the oil and gas industry throughout the world. The utilization of the ultrasonic surface rolling process (USRP) on pipeline surfaces is a promising protective approach and its universal verification for the enhancement of the scale inhibition and anti-wax capacities of passive materials is presented in this work. The effect of USRP on surface integrity (including roughness, cross-sectional microstructure, residual stress and water contact angle), scaling and wax deposition behavior, passive film structure and characteristics are experimentally analyzed by comparing three passive materials (13Cr stainless steel, 825 nickel-base alloy and Ti6Al4V alloy) with 3Cr carbon steel. The results indicate that USRP can effectively reduce the surface roughness and contribute to the growth of passive film due to the enriched passive elements on the metal surface, which consequently endow the passive materials with reduced surface free energy and enhanced anti-scaling/anti-wax capacities. Furthermore, benefitting from the surface passivation, the enhancement in the corrosion resistance of the film helps to provide good chemical stability. The main reason for why USRP has a protective effect on the scale inhibition and anti-wax capacities of the passive materials is also elucidated. The input energy of USRP not only achieves chip-free polishing and triggers structural response changes in the surface and subsurface plastic deformation but also produces a unique passivation response that can alter the chemical composition, thickness, compactness and defect density of the passive film. This in turn leads to significant changes in its corrosion resistance, which is related to the semiconductor characteristics of the materials, surface energy, and hydrophilic–hydrophobic physical and chemical properties. This results in a significant inhibitory effect on the deposition of scaling ions or wax crystals at the passive film/solution interface.

Improving the performance of a polyamine shale inhibitor by introducing a hydrophobic group in oil and gas development

Wellbore instability in complex shale formations is a major technical problem that threatens drilling safety and efficiency. In this paper, a hydrophobic cationic polyamine shale inhibitor (HCPA) was prepared by introducing a hydrophobic group in the molecular structure of an amine-based shale inhibitor having a branched structure. The shale inhibition performance of HCPA and the amine-based shale inhibitor without the hydrophobic group (CPA) was investigated. The hydration inhibition mechanism of HCPA was studied by experiments of zeta potential, particle size, contact angle, thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), etc. The evaluation results show that HCPA had a better performance than CPA in terms of inhibition of hydration swelling, hydration dispersion and mud making, which indicates that the hydrophobic group is beneficial to improve the inhibition ability of the amine-based shale inhibitor. The mechanism study shows that there is no hydrogen bond between HCPA and clay. The adsorption on the clay surface is mainly driven by electrostatic interaction, which reduces the repulsion of the electric double layer and thus inhibits the osmotic swelling of clay. HCPA could increase the water contact angle of the rock from 36.6° to 133° at a concentration 0.5%, beneficial to reduce surface free energy. The bentonite modified by HCPA had a lower weight loss of at 200 °C than bentonite modified by CPA according to TGA test, and the interlayer spacing of HCPA-modified bentonite was reduced compared with that of the unmodified bentonite, indicating that the ability of bentonite to adsorb water molecules is reduced after the introduction of hydrophobic groups, beneficial to inhibit the crystalline swelling of clays. In addition, HCPA can reduce the imbibition capacity of rocks by reducing the surface tension of water. Therefore, the concept of introducing hydrophobic groups in the molecular structure proposed herein could provide an avenue to develop high-performance shale inhibitors.

Micro-strain governed photoluminescence emission intensity of sol-gel spin coated Eu doped ZnO thin films

The objective of the present study is to analyze the role of surface free energy and microstrain on optical properties of Eu- (1, 2, 3, 5 and 6 at.%) doped sol-gel spin coated ZnO film on glass substrates. X-ray diffraction results revealed the presence of (100) plane indicating highly oriented monocrystalline film. The crystallite size was in the range of 43 to 86 nm, and the microstrain in ZnO thin films decreased from 0.00079 to 0.00040 with Eu doping. UV–vis transmission indicated transparency of 80 to 95 percent with a dip at 377 nm for undoped ZnO, which was slightly displaced to 380 nm on doping with Eu. The reduction in band gap values calculated using Tauc's plot was in the range of 3.33 to 3.17 eV. The photoluminescence (PL) emission spectra demonstrated unaltered UV emission peak on doping with Eu, however, the reduction in PL intensity was governed by microstrain induced in ZnO thin film by Eu doping. PL intensity and microstrain both decreased with Eu doping up to 3 at.%, then increased for Eu 5 at.% and eventually decreased again for Eu 6 at.%. Field emission scanning electron microscopy results exhibited a variety of irregular multi-dimensional morphological characteristics. Rectangular, square, and spherical structures were observed in 1, 2, 5, and 6 at.% Eu doped ZnO thin film. In contrast, 3 at.% Eu doping revealed long chain linkage structures that stuck together. The water contact angle measurements established the hydrophilic nature of all the doped-films. The reduced surface free energy was implied by decreased contact angle for Eu doped ZnO thin films (1, 2, and 3 at.%). This result suggested that surface free energy can be tuned with the Eu-content in ZnO. Such synergistic optical and mechanical features in ZnO based materials can give opening to diverse applications ranging from brain inspired neural network to reduction of power consumption.

Optimal loading of iron nanoparticles on reverse osmosis membrane surface to reduce biofouling

Biofouling is one of the major challenges for reverse osmosis (RO) membranes. Commercial RO membranes coated with different loadings (0.1, 0.3, 0.5, 0.7 and 0.9 wt% in solution) of iron nanoparticles (nZVI or FeNPs) were submitted to accelerated biofouling under high-pressure crossflow, using pretreated, sterilized seawater from the Sea of Cortez (Mexico) inoculated with Bacillus halotolerans MCC1 (109 CFU mL−1) as feed. FeNPs were synthesized and characterized (zeta potential, XRD, and SEM) via a reduction method. Coated and uncoated membranes were characterized for roughness, contact angle, surface free energy, XPS, FESEM, water and salt permeance, membrane resistance, fouled flux and fouling resistance. The coated membranes showed a slight increase in roughness and contact angle and a reduction in surface free energy. After accelerated biofouling, the coated membranes showed lower hydraulic resistance and higher permeate flux than the uncoated membrane, albeit with slightly lower salt rejection. Moreover, membrane autopsies revealed a highly significant reduction in biofilm thickness, total cells, TOC, and live and dead cells for the coated membranes relative to the uncoated membrane. The FeNP loading using a 0.3 wt% solution was found to be the most suitable tradeoff between biofilm prevention and flux decline for desalination processes.

Characteristics of methane adsorption/desorption heat and energy with respect to coal rank

Changes of heat and energy during methane adsorption and desorption are essential factors affecting the production of coalbed methane. To characterize adsorption and desorption behaviors, low-temperature nitrogen adsorption experiments and methane isothermal adsorption/desorption experiments were carried out on coals with different rank. The Brunauer–Emmett–Teller (BET) specific surface area (SSA) of the coal samples studied range from 0.29 m2 g−1 to 2.31 m2 g−1, and Barrett–Joyner–Halenda (BJH) pore volume ranges from 0.95 × 10−3 cm3 g−1 to 6.14 × 10−3 cm3 g−1. It is observed that the BET SSA and BJH pore volume decrease first and then increase with the increase of coal rank. The isometric heat in the adsorption process is less than that in the desorption process. There is an energy difference between adsorption and desorption, which makes the sorption process irreversible. The larger the Langmuir volume, the higher the adsorption capacity, making the external energy required for the adsorption process smaller and the limit isosteric heat more minor. At different temperatures, the Gibbs free energy of samples BD-1, LL-1 and HC-1 changes between 2.26–2.98 kJ mol−1, 2.05–3.24 kJ mol−1 and 1.91–3.08 kJ mol−1, respectively, indicating that the process of methane desorption on coal is a spontaneous reaction. The cumulative reduction of surface free energy (Δγ) and the reduction of surface free energy at each pressure point (Δγp) show that the adsorption capacity of the low- and medium-rank coal are more easily affected by temperature, while that of the high-rank coal is less affected by temperature. Moreover, the smaller the BET SSA, the greater Δγ and Δγp.

Methane Adsorption Behavior and Energy Variations of Brittle Tectonically Deformed Coal under High Temperature and High Pressure.

This paper aims to reveal the methane adsorption characteristics of brittle tectonically deformed coal (TDC) under high temperature and high equilibrium pressure and the surface free energy changes during methane adsorption. Taking the anthracite of the Yangquan mining area of China as the research object, methane adsorption tests of high temperature and high pressure were conducted to discuss the influences of coal deformation, temperature, and pressure on the gas adsorption behaviors of coal under the in situ conditions of deep coal seams. Results indicated that coal deformation and pressure had positive effects on the methane adsorption capacity of coal, whereas temperature showed negative effects. Meanwhile, the negative influences of temperature rise on gas adsorption gradually increased with the equilibrium pressure and the enhancement of coal deformation. In a given adsorption system, the adsorption potential decreased with increasing pressure while increased with temperature. In contrast, the adsorption space increased with increasing pressure and decreased with temperature rise. Meanwhile, adsorption potential decreased with the increase in adsorption space. In the process of methane adsorption, with increasing adsorption pressure, the cumulative reduction of surface free energy gradually increased, whereas the surface free energy reduction at each pressure point decreased. The cumulative and incremental reduction of surface free energy at each pressure point gradually decreased with the increase in temperature. The reduction of adsorption space and cumulative surface free energy and the changes in surface free energy at each pressure point of brittle TDCs were higher than those of primary structure coal, and the changes in the strongly deformed coal (granulitic and mortar coal) were more significant than those of the weakly deformed coal (cataclastic coal). Based on the adsorption potential theory, we drew the adsorption characteristic curves and established adsorption capacity prediction models of primary structure coal and brittle TDCs.

Impact of surface free energy on electrostatic extraction of particles from a bed

HypothesisElectrostatic extraction of particles from a bed to a pendent droplet to form liquid marbles has previously been investigated with respect to particle conductivity, size and shape, however, interparticle forces have not been specifically interrogated. If cohesion is the dominant force within the particle bed, then particles will be more readily extracted with reduced surface free energy. ExperimentsGlass particles were surface-modified using various alkyltrichlorosilanes. The surface free energy was measured for each sample using colloid probe atomic force microscopy (AFM) and sessile drop measurements on similarly modified glass slides. The ease of electrostatic particle extraction of each particle sample to a pendent droplet was compared by quantifying the electric field force required for successful extraction as a function of the measured surface free energy. FindingsSurface free energy calculated from sessile droplet measurements and AFM were not in agreement, as work of adhesion of a liquid droplet on a planar substrate is not representative of the contact between particles. Ease of electrostatic extraction of particles was observed to generally decrease as a function of AFM-derived surface free energy, confirming this is a critical factor in electrostatic delivery of particles to a pendent droplet. Roughness was also shown to inhibit particle extraction.

Fabrication of superhydrophobic & catalytic bifunctional MnO2 @ Al2O3 composite ceramic membrane for oxidation of desulfurization waste solution

A novel superhydrophobic & catalytic bifunctional MnO2@Al2O3 composite ceramic membrane was prepared, and characterized for catalytic oxidation of sulfite through membrane aeration. Manganese dioxide on the ceramic membrane was fabricated via the hydrothermal synthesis method with ammonium persulfate and manganese sulfate. The three-dimensional structure and rough surface were formed by the staggered spines of sea urchins-like MnO2 particles. Stearic acid was used as the hydrophobic modifying reagent to reduce surface free energy. The synthesized composites exhibit excellent superhydrophobicity with a maximum static water contact angle of 164.9° ± 5.3°. The reaction parameters could affect the hydrophobicity by changing the morphology of MnO2. The bifunctional membrane could also promote the oxidation rate of sulfite, which was increased by 44.0% in Na2SO3 solution and 64.2% in (NH4)2SO3 solution.

Preparation of biomimetic hair-like composite coatings with water-collecting and superamphiphobic properties

Superamphiphobic coatings have been widely used in self-cleaning and antifouling materials because of their unique liquid repellency. In this study, magnetic Fe3O4 particles and resin were sprayed to construct hierarchical scales of texture, and 1H,1H,2H,2H-perfluorodecyltriethoxysilane was used to reduce surface free energy, and a biomimetic hair-like composite coating was prepared. The microstructure and chemical composition of the coating was characterized by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Both aqueous and oily liquid droplets can retain a perfectly quasispherical shape on the coating surface. The biomimetic hair-like composite coating exhibited superior water-collecting and superamphiphobic properties as well stable resistance against severe temperature, concentrated acidic, alkaline solutions and mechanical damages. This design strategy may provide useful guidelines for the fabrication of large-scale regular superamphiphobic surfaces.

Strongly antireflective nano-textured Ge surface by ion-beam induced self-organization

Designing materials surfaces for reducing the reflection of light is imperative towards enhancing the performance of optical and optoelectronic devices. We show that ion implantation under specific experimental conditions is a single step and controllable process to minimize reflection over a large wavelength range by growth of surface nanostructure in a self-organized fashion. For instance, we show a strong reduction in optical reflectance in the ultraviolet–visible-infrared wavelength range (300–3000 nm) for Ge with the evolution of nanoscale self-organized patterns under energetic ion bombardment at oblique angles. As pattern coarsening takes place with increasing ion fluence (for subtle incident angles), the optical reflectance reduces to a significant extent. The evolution of saw-tooth-like structures on Ge surface, at an oblique incidence of 60° to the fluence of 3 × 1018 ions cm−2, leads to a huge reduction in optical reflectance (below 4% over a wide spectral range) and makes it behave effectively like a black-Ge specimen. The huge reduction in the optical reflectance is found to be related to the dimension of the surface features evolved under ion implantation at room temperature. The observed surface morphology gives rise to an effective gradient in refractive index from the top toward the bottom of the patterned surface. Thus, the reduction in refractive index is calculated and correlated with the respective surface morphology. We have also studied change in the wetting property of ion-induced patterned surfaces and correlated it with the reduction in surface free energy due to the presence of oxygen.

Influence of pore structure and surface free energy on the contents of adsorbed and free methane in tectonically deformed coal

Differences in pore and surface free energy affect the occurrence of adsorbed and free methane in tectonically deformed coal (TDC), which influences coalbed methane extraction and coal mine safety. Therefore, eight middle-rank TDC samples from the Yueliangtian coal mine (Guizhou Province, Southwest China) were screened. Pore volume and specific surface area were explored via mercury intrusion, nitrogen adsorption/desorption, and carbon dioxide adsorption approaches. Based on the low-field nuclear magnetic resonance analysis for powdered TDC, the relaxation time (T2) amplitudes and the contents of adsorbed and free methane, the surface free energy reduction (SFER), and adsorption potential were measured. 1) The pore specific surface area, pore volume, T2 amplitudes and contents of adsorbed and free methane, SFER, and adsorption potential of the strongly deformed coal are obviously larger than those of the weakly deformed coal. Adsorbed methane content is dominantly affected by micropore specific surface area, and free methane content is primarily influenced by macropore volume. 2) The methane T2 spectra of the TDC contain three distinctive peaks; the first, P1 (T2 < 2 ms), represents adsorbed methane, and the second, P2 (2–40 ms), corresponds to free methane. As the pressure increases, both the T2 amplitude rate and content rate of adsorbed methane decrease, while those of free methane rise. 3) With the enhancement of tectonic deformation, the specific surface area and volume of pores increase (especially those of micropores and macropores), more adsorption positions and storage space for adsorbed and free methane become available, and the SFER and adsorption potential of the TDC are enhanced, leading to increases in the T2 amplitudes and contents of adsorbed and free methane. The present research will help improve the accuracy of coalbed methane evaluation and the prevention of coal and gas outbursts.

Improved permeation, separation and antifouling performance of customized polyacrylonitrile ultrafiltration membranes

Tailored polyacrylonitrile (PAN) ultrafiltration (UF) membranes are fabricated with Pluronic-F127 and polyethylene glycol phosphate decorated calcium carbonate (PGP-CaCO3) additives with the aim of high water permeation, macromolecular rejection and antifouling properties. The nanoscale CaCO3 synthesis is carried out via a single step carbonization route using PGP as a hydrophilic modifier to introduce hydroxyl groups onto its surface. The topographies of the nanoparticles are investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). PAN/PGP-CaCO3 mixed matrix membranes (MMMs) are fabricated via phase inversion method and examined by attenuated total reflectance-Fourier infra-red spectroscopy (ATR-FTIR), mechanical stability, thermo-gravimetric analysis (TGA) and scanning electron microscopy (SEM) to explore the changes in membrane properties due to the well-dispersed PGP-CaCO3 in the PAN membrane matrix. The UF performance of the membranes is investigated in terms of pure water flux, macromolecular rejection and antifouling property. The fouling resistance of membranes is assessed using bovine serum albumin (BSA) and humic acid (HA) as model foulants. The membrane loaded with 0.75wt.% (M3) of PGP-CaCO3 manifested increased wettability with reduced surface free energy leading to a higher pure water flux of 366L/m2h. M3 also displayed a rejection of 93.9% for BSA and 93.2% for HA. The success of the modification can be confirmed as the membrane M3 exhibited lower flux decline and displayed a flux recovery ratio of 90.98% during HA filtration. The results demonstrated the potential use of PAN/PGP-CaCO3 membranes in water treatment.

Super-amphiphobic, strong self-cleaning and high-efficiency water-based drilling fluids

Abstract Based on the amphiphobic theory on underground rock surface, a super-amphiphobic agent is developed and evaluated which can form nano-micro papilla structure on rock, filter cake and metal surface, reduce surface free energy, prevent collapse, protect reservoir, lubricate and increase drilling speed. With this super-amphiphobic agent as the core agent, a super-amphiphobic, strong self-cleaning and high-performance water-based drilling fluid system has been developed by combining with other agents based on drilled formation, and compared with high-performance water-based drilling fluid and typical oil based drilling fluid commonly used in oilfields. The results show that the super-amphiphobic, strong self-cleaning and high-performance water-based drilling fluid has better rheology, and high temperature and high pressure filtration similar with that of oil-based drilling fluid, inhibiting and lubricating properties close to oil based drilling fluid. Besides, the super-amphiphobic system is non-toxic, safe and environmentally friendly. Field tests show this newly developed drilling fluid system can prevent wellbore collapse, reservoir damage and pipe-sticking, increase drilling speed and lower drilling cost, meeting the requirement of safe, high efficient, economic and environmentally friendly drilling. Compared with other drilling fluids, this new drilling fluid system can reduce downhole complexities by 82.9%, enhance the drilling speed by about 18.5%, lower drilling fluid cost by 39.3%, and increase the daily oil output by more than 1.5 times in the same block.

Energy variation in coal samples with different particle sizes in the process of adsorption and desorption

The study of energy variation rules in the process of gas adsorption and desorption in coal is important to predict mine outburst disasters. In this study, an adsorption-desorption experimental device was developed and used to evaluate six coal samples of various particle sizes under different pressure conditions. Temperature was measured in real-time throughout the process. The rate of temperature change, maximum temperature variation, and adsorption quantity increased with particle size and an increase in equilibrium pressure. There is a positive linear relationship between adsorption quantity and temperature variation. This study focused on energy variation during adsorption and desorption. The results showed that the smaller the coal particle size, the larger the reduction in surface free energy and the change in heat. With an increase in equilibrium pressure, the rate of reduction in the surface free energy slows gradually, indicating that there is a non-uniform adsorption potential field on the surface of coal. By comparing the difference of temperature and heat data between a columnar coal sample and a granular coal sample in the process of adsorption and desorption, it can be concluded that the surface free energy is converted into heat and deformation energy in the adsorption process, and the deformation energy is converted into heat energy in the desorption process.

Changes of water related properties in radiata pine wood due to heat treatment

Wood is a green and renewable building material, however, the hygroscopicity restrict its use in the field of construction and building. To study the effect of heat treatment (HT) on wood hygroscopicity and other water related properties, radiata pine wood was subjected to HT at four temperature levels of 185, 200, 215 and 230 °C, for the duration of 4 h. Overall, the equilibrium moisture content, moisture adsorption, water absorption and volume swelling ratio were all decreased, while hygroscopic hysteresis was enhanced with increasing HT temperature. The surface wettability was clearly weakened after HT, reflected as the increased contact angle and reduced surface free energy.

Condensate blockage remediation in a gas reservoir through wettability alteration using natural CaCO3 nanoparticles

Wettability alteration of near-wellbore region from liquid-wetting to gas-wetting has been known as a feasible method for eliminating condensate blockage in gas condensate reservoirs. In this research, the natural CaCO3 (Bio-Ca) nanoparticles containing chitin were used as environmentally friendly and cost-effective agents which can act as nanocomposite for wettability alteration. For this purpose, their performance was evaluated on wettability alteration of the gas/oil systems by conducting contact angle measurements and sand pack flooding tests. In addition, for evaluating the stability of nanofluids, zeta potential measurement was conducted. The Bio-Ca nanoparticles were produced using cuttlebone (Sepia Pharaonis) taken from the Persian Gulf. Also, silica nanoparticle was used as a scale for comparison of its performance with the newly synthesized nanoparticle. Four influencing factors including nanofluid concentration, gas flow rate, oil type, and nanoparticle type were investigated and the optimum conditions for improving oil recovery and gas/oil relative permeabilities were also obtained using Taguchi method. The values of zeta potential implied that both nanofluids are stable at the given pH. The results of the contact angle measurement indicated that the contact angles of condensate droplet raised from 0° to 105° after treating the rock surface by Bio-Ca nanofluid with a concentration of 0.05 wt. %. This is happened because of the increase in roughness with reduction of surface free energy of rock surface along with disjointing pressure mechanism. Analysis of variance showed the importance of considering the simultaneous effect of these parameters on oil recovery and relative permeabilities for wettability alteration purposes. Results show that the optimum conditions for increasing oil recovery using Bio-Ca nanoparticles include the nanofluid concentration of 0.05 wt. %, using normal heptane as a liquid phase, and a gas flow rate of 100 cc/min. Besides, for gas and oil relative permeability endpoints as a second response parameter, the most effective parameter is gas flow rate of 55 cc/min. Results of this work are confirmed that the Bio-Ca nanoparticles play a vital role in wettability alteration, which can alter the wettability of the medium from strongly oleophilic to oleophobic due to their biostructure.