Low Surface Free Energy Research Articles

Predictive materials and structures design of perpendicular magnetic anisotropy in magnetic tunnel junctions

The regular mechanism guiding for the selection of heavy metals (HMs) that adapt to different structures is thoroughly investigated. A predictive materials design framework is established based on the element distribution states analysis from high-resolution transmission electron microscopy (HRTEM) experiments to guide the complex design explorations for spin-orbit torque (SOT) devices. Based on surface free energy and formation enthalpy analyses, it is found that not only a critical HM material type but also an appropriate structure selection will contribute to the excellent magnetic properties required for SOT device control and design. Furthermore, the HM layers with high formation enthalpy value are critical for device performance enhancement, and HM layers with a high (low) surface free energy are better choices for the bottom (top) structure. The researches help to establish a predictive materials design framework, and is effective in designing memory cells with critical SOT effect.

Novel graphene-based ternary nanocomposite coatings as ecofriendly antifouling brush surfaces

Since the ban on TBT compounds in antifouling paints in 2003, silicone foul-release (FR) coatings have elicited increasing attention and market share as environmentally benign and cost-effective alternatives. Herein, the catalytic hydrosilation approach was used to develop a series of elastomeric nanocomposites of polydimethylsiloxane top coat packed with graphene oxide (GO) sheets ornamented with anatase TiO2 nanorods (GO/TiO2 NRs). A simple two-phase process was used to create a unique, simple, cost-effective, and environment-friendly GO/TiO2 nanocomposite. The GO surface containing epoxy, OH, CO, and COOH results in the adhesion of TiO2 NRs to the surfaces via charge-transfer interaction and physisorption including π–π interactions and hydrogen bondings. To investigate the structure–property relationship, different concentrations of GO/TiO2 nanofillers were injected into the composite top coat nanosurfaces through an in situ approach. A controlled hydrothermal technique was used to successfully prepare single crystals of organic-capped anatase TiO2 NRs with 10 nm mean width, 20 nm length, and growth in the [101] direction. Surface nonwettability with rough topological structure and low surface free energy (SFE) has sparked considerable attention. The obtained virgin and GO/TiO2 filled composites' physical, mechanical, and anticorrosive properties were also examined. Various microfouling species were selected to test the biological inertness of the coated specimens for up to four weeks in the laboratory. The findings shed light on the impact of GO/TiO2 filler distribution and topological roughness to enhance the modeled nanopaints' fouling repellency and superhydrophobicity. The water-contact angle (152°) considerably increased, the SFE (12.3 mN/m) decreased, and the rough topology improved with the addition of nanofillers until 1 wt% without any changes in the bulk mechanical characteristics. A 45-day field trial in natural seawater was carried out in a tropical area to confirm the coatings' durability and FR performance based on the screening process and image analysis. Thus, we obtained a promising FR nanocomposite top coat for marine coating applications and healthcare facilities with great thermal stability, superhydrophobicity, surface inertness against fouling adherence, cost-effectiveness, and increased lifetime.

The Synergistic Effect of the Laser Beam on the Thermionic Vacuum Arc Method for Titanium-Doped Chromium Thin Film Deposition

Laser-Induced Thermionic Vacuum Arc (LTVA) provides a better way to produce uniform metallic thin films than the classical Thermionic Vacuum Arc (TVA) method. In Ti-doped chromium thin films produced using LTVA, the amorphous chromium is superimposed with small bcc chromium nanoparticles. These amorphous/crystalline structures with small crystallites induce lower roughness and electrical resistivity, reducing electron–phonon scattering and increasing charge transport across LTVA thin films. A significant shift in resistivity for the LTVA samples is observed due to electron scattering on the phonon–crystalline structures in the TVA samples which exhibit larger crystallites. Meanwhile, the wettability measurements reveal a higher contact angle, resulting in a lower surface free energy and consecutively lower dissociation energy for the LTVA-produced thin films than the TVA samples.

Preparation of a superhydrophobic coating based on polysiloxane modified SiO2 and study on its anti-icing performance

An anti-icing surface with superhydrophobic properties was designed by combining poly(methyl-3,3,3-trifluoropropyl siloxane) (PMTFPS) modified silica with a low surface free energy fluorine‑silicone resin. The hydrophobic silica particles were characterized using SEM, FTIR, and XPS. The hydrophobicity, wettability and wear resistance of the resulting coating were analyzed. The anti-icing and de-icing properties of the coatings were also characterized in terms of complete icing time and ice adhesion strength. The obtained SiO2-PMTFPS coating achieved a contact angle of 158.5° and a roll-off angle of 1°. Compared with tinplate sheets, icing time is delayed by 200% at −10 °C and 800% at −15 °C. Ice adhesion strength decreases by 91.8% compared with tinplate, making ice relatively easy to remove. After sandpaper abrasion and immersion in solutions with different pH and temperature, the coating is proven to exhibit good abrasion resistance and chemical durability in water solutions.

Adhesive less Silica Nanoparticle Coating on Nylon Woven Fabric and Its Characterization

Environment-friendly functional woven fabric with light weight has higher market demand in this era. This paper is aimed to prepare and characterize super-hydrophobic nylon-6 woven fabric by using silica nanoparticles, coupling agent 3-aminopropyltriethoxysilane (APTES), and a long chain hydrophobic agent hexadecyltrimethoxysilan (HDTMS). Synthesize of silica nanoparticles is processed with a modified Stöber method resulting in a mono-dispersed particle whose diameter is 51-60 nm. In this experiment chemical bonds presenting over the surface silica nanoparticle are Si–CH3 and Si–OH and Due to the reaction between the hydrolyzed APTES and the first layered surface, Si–OH group is specter onto the surface. The hydrolyzed HDTMS molecules created a bond to the surface by the formation of Si–O–Si bonds. As result, a long chain of organo-silane with low surface free energy is introduced onto the fabric surface. The hydrophobic coated surface appeared after spray coating with additional treatment without any adhesive. The super-hydrophobic nylon-6 woven fabric has been coated by spray method with static water contact angle 151.8. Characterization manifests a good self-cleaning tendency and low permeability difference.

Electrospun Azo-Cellulose Fabric: A Smart Polysaccharidic Photo-Actuator.

A natural polysaccharide-based smart photo-actuator is fabricated via electrospinning of cellulose 4-phenyl azobenzoate (Azo-Cel) from its organic solution in a mixture of high-volatile acetone, a poor solvent of Azo-Cel, and low-volatile N,N-dimethylacetamide (DMAc), a good solvent of Azo-Cel. At an optimal polymer concentration (17wt%) and solvent mixing ratio (acetone/DMAc=3/2 (v/v)), stable electrified polymer jets are formed and continuous nanofibers and their nonwoven fabric can be drawn on a cylinder-shaped rotating drum electrode under a high electric field (25kV). Scanning electron microscopic observation of the Azo-Cel fabric confirms that the fabric consists of uniaxially aligned nanofibers with a mean diameter of 207nm. The water contact angle of the Azo-Cel fabric reversibly decreases and increases in response to alternate irradiation with UV and visible light to induce geometric deformation of the azobenzene moiety between the trans and cis isomers, which lead to lower and higher surface free energies, respectively. In addition, self-standing Azo-Cel fabric exhibits a UV-driven photo-mechanical asymmetric bending deformation toward the light source.

Evaluation of Cr-based thin film metallic glass as a potential replacement of PVD chromium coating on plastic mold surface

In this article, a CrCoNbB thin film metallic glass (TFMG) is fabricated by DC power magnetron sputtering. Its microstructure, surface properties, mechanical properties and thermal stability are characterized. Results are compared with sputter-deposited chromium (Cr) coating which is an industrial popular choice of hard coating by physical vapor deposition (PVD). We obtained a fully amorphous Cr48Co31Nb7B14 TFMG with glass transition (Tg) and crystallization (Tx) temperatures at 530 °C and 615 °C, respectively. Nanoindentation revealed that Cr48Co31Nb7B14 TFMG has significantly lower surface roughness and higher hardness than Cr. Also, in nano-scratch test with normal load applied between 0.5 mN ~ 9 mN, Cr48Co31Nb7B14 TFMG has a lower coefficient of friction (CoF) than Cr. Annealing the TFMG above Tg at 550 °C for 60 min showed no sign of crystallization, implying excellent thermal stability. Contact angle analysis also revealed that the TFMG has very low surface free energy (SFE), specifically a low polar component. We also discovered that spreading of molten low-density polyethylene (LDPE) on Cr48Co31Nb7B14 TFMG is weaker than on Cr film as a consequence of its low SFE. In summary, Cr48Co31Nb7B14 TFMG has advantages such as high hardness and thermal stability, low roughness, friction and surface energy compared to PVD Cr coating. Low adhesion to molten LDPE also suggests its potential in applications such as injection mold coating where lower friction and higher wear resistance is preferred.

Mechanistic understanding of the aspect ratio-dependent adjuvanticity of engineered aluminum oxyhydroxide nanorods in prophylactic vaccines

Aluminum oxyhydroxide (AlOOH) adjuvants are widely used in human vaccines. However, the interaction mechanisms at the material-bio interface, and further understandings on physicochemical property-dependent modulation of the immune responses still remain uncertain. Herein, a library of AlOOH nanorods with well-defined aspect ratios is designed to explore the mechanisms of adjuvanticity. The aspect ratios of AlOOH nanorods were demonstrated to be intrinsically modulated by the hydroxide supersaturation level during crystal growth, leading to the differences in surface free energy (SFE). As a result, higher aspect ratio AlOOH nanoadjuvants with lower SFE exhibited more hydrophobic surface, resulting in more membrane depolarization, cellular uptake and dendritic cell (DC) activation. By using hepatitis B surface antigen (HBsAg) virus-like particles (VLPs) or SARS-CoV-2 spike protein receptor-binding domain (RBD) as model antigens, AlOOH nanorods with higher aspect ratio were determined to elicit more potent humoral immune responses, which could be attributed to the enhanced DC activation and the efficient antigen trafficking to the draining lymph nodes. Our findings highlight the critical role of aspect ratio of AlOOH nanorods in modulating adjuvanticity, and further provide a design strategy for engineered nanoadjuvants for prophylactic vaccines.

Periodontal Pathogen Adhesion, Cytotoxicity, and Surface Free Energy of Different Materials for an Implant Prosthesis Screw Access Hole.

Background and Objectives: Oral implant restorations are an excellent treatment option for edentulous patients; however, periodontopathogenic bacteria have been found in the microgaps between implant−abutment junctions. Implant designs to limit the microgaps have been extensively studied. However, studies have shown microgaps continue to exist, allowing for the leakage of bacteria into the implant system. Screw access hole materials are used to fill the access hole void. The use of materials with beneficial properties could provide bacterial leakage prevention. The aim of this study was to examine the surface free energy, cytotoxicity, and bacterial adhesion of selected screw access hole materials such as cotton, polytetrafluoroethylene (PTFE) tape, paraffin wax−polyolefin thermoplastic (PF), paraffin wax (Wax), gutta-percha (GP), and caviton EX (CE). Materials and Methods: A sessile drop test was performed to observe the contact angle and calculate the surface free energy of each material in order to determine the level of hydrophobicity. Cytotoxicity was examined in a mouse gingival epithelial cell line for day 1 and day 3. Bacterial adhesion was tested with Porphyromonas gingivalis, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans. Results: PTFE, PF, and wax presented low surface free energies of 19.34, 23.041, and 24.883 mN.m-1, respectively. No cytotoxicity was observed, except for GP and CE. Concurrently, the bacterial adhesion was also the lowest in PTFE and PF. Conclusions: Within the limits of this study, PTFE and PF showed an excellent biocompatibility with few bacterial adhesions. These materials could be potential screw access hole materials in clinical settings.

A novel strategy for rapid development of a self-sustaining symbiotic algal-bacterial granular sludge: Applying algal-mycelial pellets as nuclei

Algal-bacterial granular sludge (ABGS) is a promising technology for wastewater treatment, benefiting from the synergetic interactions between algae and bacteria. However, the rapid start-up of the ABGS system is not trivial. Herein, a novel strategy was proposed by applying the algal-mycelial pellets (AMPs) as the primary nuclei for accelerating the development of a self-sustaining symbiotic ABGS system. The results indicated that by using this strategy complete granulation was shortened to 12 days, much shorter than the control system without AMPs dosage (28 days). The ABGS had a large particle diameter (3.3 mm), compact granular structure (1.0253 g/mL), and excellent settleability (SVI30 of 53.2 mL/g). Moreover, 98.6% of COD, 80.8% of TN and 80.0% of PO43−-P were removed by the ABGS. The nuclei of targeted algae (Chlorella) and filamentous fungi (Aspergillus niger), the enhanced production of extracellular polymeric substances (especially proteins) and the enrichment of functional bacteria (such as Neomegalonema and Flavobacterium) facilitated the granules development. The low surface free energy (-69.56 mJ/m2) and energy barrier (89.93 KT) were the inherent mechanisms for the strong surface hydrophobicity, the easy bacterial adhesion, and the short granulation period. This study provides an economically feasible approach to accelerate ABGS granulation and sustain system stability.

Preparation of fluorine- and nanoparticle-free superwetting polybenzoxazine/cellulose composites for efficient oil/water separations

Considering the dangers of spilled oil, it is important to develop economical materials for the rapid removal of oil contaminants. Herein, we report the successful synthesis of a furan-based polybenzoxazine (Fu-PBZ) and present an easy method for preparing robust superhydrophobic surfaces on a cotton fabric and filter paper, using a non-solvent-induced phase inversion method. The cured Fu-PBZ possessed unusual flexibility, low surface free energy (as low as 13.5 mJ m−2), and an extremely high glass transition temperature. The Fu-PBZ-modified cotton fabric (Fu-PBZ@CF) and Fu-PBZ-modified filter paper (Fu-PBZ@FP) both possessed superhydrophobicity and superoleophilicity. Fu-PBZ@CF exhibited excellent separation performance for versatile oil/water mixtures with permeation fluxes of up to 116,000 L m−2 h−1 and efficiency greater than 98%. Fu-PBZ@FP exhibited a permeation flux of up to 5010 L m−2 h−1 and oil purity greater than 99.96% in separating the surfactant-stabilized water-in-oil emulsions. The low surface free energy and hydrophobicity of the binder polymer provided by the self-roughness of the Fu-PBZ coating assisted the substrates in recovering their superhydrophobic property even after repeated applications, rendering our modified materials a viable candidate for practical applications.

Superhydrophobic micro-nano structured PTFE/WO3 coating on low-temperature steel with outstanding anti-pollution, anti-icing, and anti-fouling performance

The fabrication of superhydrophobic coatings on the low-temperature steels has rarely been explored to this day. Herein, we designed and fabricated a superhydrophobic micro-nano structured composite coating on the E40 low-temperature steel, which was composed of an underlying WO3 coating derived from the pulsed electrodeposition process and a top polytetrafluoroethylene (PTFE) layer obtained from the magnetron sputtering. The synergistic effect of the hierarchical micro-/nanostructures of the WO3 coating and the low surface free energy of the fluorine-containing PTFE layer makes the PTFE/WO3 coating superhydrophobic, which demonstrated a water contact angle of 159° and a water roll-off angle of ≤1°. The PTFE/WO3 coating exhibited outstanding anti-pollution properties towards both the solid pollutant such as carbon black particles and the liquid pollutant such as black ink. Importantly, the PTFE/WO3 coating demonstrated excellent anti-icing properties with low icing temperature and small ice-adhesion strength, while simultaneously possessing outstanding anti-fouling performance. The present work provides a new strategy for fabricating coatings with multifunctionality on metallic materials which can work under low-temperature and biofouling conditions.

Determination and optimisation of Resonant Acoustic Mixing (RAM) efficiency in Polymer Bonded eXplosive (PBX) processing

An investigation into how the efficiency (time and energy required for homogeneity) of Resonant Acoustic Mixing (RAM) can be determined and optimised was undertaken. An idealised Polymer Bonded eXplosive (PBX) simulant based on glass microbeads (28.3 μm D50, 62% v/v in binder and plasticiser) was used for mixing. Mixing evolution was monitored using machine output data, whereby the mixer ‘intensity’ (related to power draw) was plotted against time. Experiments were undertaken with three acceleration settings, three mixer units, and three vessel materials of low, medium, and high surface free energy. Different stages of the mixer ‘intensity’ profiles were found to correspond to discrete stages of mixing, as well as further rheological changes due to continued frictional heating, thus viscosity reduction, beyond homogeneity being achieved. Time to mixing completion was found to be repeatable within a standard deviation of ±10%, strongly dependent on acceleration setting, and additionally dependent on vessel material, though additional data is required to confirm this. A significant difference in mixing time was observed between different LabRAM units. Partial vacuum application without degassing was beneficial for mixing. Finally, a paradigm linking the ‘movement modes’ of mixing was constructed, based on literature observations and the experimental results.

Wettability and corrosion performance of arc-sprayed Fe-based amorphous coatings

Amorphous coatings (ACs) with the composition of Fe49.7Cr18Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 were deposited by the arc-spraying technique. The wettability and corrosion performance of Fe-based ACs in 3.5% NaCl solution were investigated using contact angle measurements and electrochemical tests, respectively. Results showed that by controlling the spraying potential, the phase constituent, microstructure, hardness, wettability, and corrosion performance of the coatings were manipulated. With a spraying potential of 26 V, the highly glassy AC exhibited a denser microstructure, higher microhardness, lower surface free energy, and better corrosion resistance than the others. The superior corrosion resistance of the coatings was closely related to the surface hydrophobicity, which was dominantly governed by the microstructure of the coatings. This finding demonstrates the importance of a homogeneous and compact structure for anti-corrosion and provides a quick prediction of corrosion performance among ACs.

Combination of Universal Chemical Deposition and Unique Liquid Etching for the Design of Superhydrophobic Aramid Paper with Bioinspired Multiscale Hierarchical Dendritic Structure.

It is urgent and significant for the further development of superhydrophobic materials to exploit a facile, low-cost, scalable, and eco-friendly method for the manufacture of superhydrophobic materials with self-cleaning, antifouling, directional transportation, and other characteristics. Herein, an outstanding superhydrophobic material composed of a flexible microconvex aramid paper substrate, micron-scale cone-shaped copper, micro-nanoscale dendritic copper oxide, and hydrophobic copper stearate film has been successfully constructed through delicate architectural design and a convenient preparation approach. Based on the microstructure evolution and composition analysis results, it is revealed that the cone-shaped copper was etched into a dendritic copper oxide structure step by step from the top to bottom and from the outside to inside in an alkaline liquid environment. Moreover, by virtue of the compositional features and structural characteristics, the constructed superhydrophobic material showcased a high contact angle (CA), low sliding angle (SA), high porosity, low surface free energy, and adhesion work. Meanwhile, the dendritic microstructure analysis, the calculation of solid-liquid interfacial tension, and the force analysis of water droplets jointly revealed the mechanism of the bounce and merged bounce of water droplets. Finally, this superhydrophobic material has the functions of self-cleaning, antifouling, and directional transportation, especially by controlling the deformation of the material to realize the transportation of water droplets in a specified direction.

Preventing algae adhesion using lubricant-modified polydimethylsiloxane/polythiourethane nanocomposite

To meet the need for an environmentally friendly fouling-release coating with high mechanical strength and good adhesion to substrates, a four-component nanocomposite was developed by a simple and industrially applicable blending approach. The nanocomposite consists of mechanically stable matrix polythiourethane (PTU), 1 wt% low surface free energy and rubber-like polydimethylsiloxane (PDMS), 1 wt% lubricant silicone oil, and 1 wt% tetrapodal shaped micro-nano ZnO (t-ZnO) filler particles, hereafter named PPZO. The rubber-like PDMS formed microdomains at the PTU/air interface, while silicone oil was distributed between the PDMS microdomains. The tensile strength of PPZO nanocomposite was approximately 63 MPa, two to four hundred times higher than the tensile strength of previously reported oil-modified coatings. The adhesion strength of PPZO to the substrate was 30 times higher than that of pure PDMS. After a five-month dynamic field test, the PPZO surface revealed much less biofouling than the references (AlMg3 and PTU), confirming its long-term biofouling control property. The attached algae on PPZO could easily and completely be removed by gentle brush cleaning. The good biofouling control property of PPZO can be attributed to the increased water repellency (signified by the increased water contact angle) and the surface slippage by silicone oil incorporation.

Stable superhydrophobic wood surface constracting by KH580 and nano-Al2O3 on polydopamine coating with two process methods

Superhydrophobic treatment of wood is of great significance for improving the service life of wood and expanding its application fields. In this study, two process methods were designed to meet above requirements. Using polydopamine (PDA), 3-mercaptopropyltriethoxysilane (KH580) and nano-Al2O3 as the micro-nano structure maker and octadecyltrichlorosilane (OTS) as a low surface free energy agent to modify rough surface in order to prepare superhydrophobic wood samples (Wood@One-step and Wood@Two-step). The contact angle (CA) and sliding angle (SA) of the Wood@One-step were 155.3° and 4.76°, respectively; the CA and SA of the Wood@Two-step were 152.9° and 7.65°, respectively. Surface electron microscopy (SEM) images showed that the surface of Wood@One-step and Wood@Two-step were honeycomb structure and layered stacking structure respectively. The superhydrophobic properties of Wood@One-step were superior because of its more reasonable micro-nano roughness. Atomic force microscope (AFM) images presented that the nano-Al2O3 particles could effectively provide nano-level roughness. X-ray photoelectron spectroscopy (XPS) analysis showed that KH580 had covalent interaction with PDA. Thermogravimetric (TG) analysis, the immersion of acid-base solution and organic solution revealed that obtained superhydrophobic wood samples had excellent stability in the face of environmental challenges.

Benefits of Residual Aluminum Oxide for Sand Blasting Titanium Dental Implants: Osseointegration and Bactericidal Effects.

Objectives. The purpose of this work was to determine the influence of residual alumina after sand blasting treatment in titanium dental implants. This paper studied the effect of alumina on physico-chemical surface properties, such as: surface wettability, surface energy. Osseointegration and bacteria adhesion were determined in order to determine the effect of the abrasive particles. Materials and Methods. Three surfaces were studied: (1) as-received, (2) rough surface with residual alumina from sand blasting on the surface and (3) with the same roughness but without residual alumina. Roughness was determined by white light interferometer microscopy. Surface wettability was evaluated with a contact angle video-based system and the surface free energy by means of Owens and Wendt equation. Scanning electron microscopy equipped with microanalysis was used to study the morphology and determine the chemical composition of the surfaces. Bacteria (Lactobacillus salivarius and Streptococcus sanguinis) were cultured in each surface. In total, 110 dental implants were placed into the bone of eight minipigs in order to compare the osseointegration. The percentage of bone-to-implant contact was determined after 4 and 6 weeks of implantation with histometric analysis. Results. The surfaces with residual alumina presented a lower surface free energy than clean surfaces. The in vivo studies demonstrated that the residual alumina accelerated bone tissue growth at different implantation times, in relation to clean dental implants. In addition, residual alumina showed a bactericidal effect by decreasing the quantity of bacteria adhering to the titanium. Conclusions. It is possible to verify the benefits that the alumina (percentages around 8% in weight) produces on the surface of titanium dental implants. Clinical relevance. Clinicians should be aware of the benefits of sand-blasted alumina due to the physico-chemical surface changes demonstrated in in vivo tests.

Inhibition of adhesion of CaCO3 scale by polydopamine/polytetrafluoroethylene coating with stability and anticorrosion properties

AbstractReduction of calcium carbonate (CaCO3) scale formation on the equipment surface is essential in a wide variety of industrial fields. In this work, polydopamine/polytetrafluoroethylene (PDA/PTFE) coating prepared by the simple immersion on stainless steel (SS) surfaces was developed to suppress the CaCO3 scale adhesion. The PDA/PTFE‐coated surface showed the higher hydrophobicity (water contact angle = 133.50°) and lower surface free energy (11.92 mN/m) than the stainless‐steel surface. The scale inhibiting rate of the coated surface was up to 76.8% after 12‐hour immersion in the CaCO3 solution in comparison with the untreated SS. More bubbles were observed on the PDA/PTFE‐coated surfaces, and the number of bubbles increased with increasing solution temperature leading to less area for the scale adhesion. As a result, the PDA/PTFE coated surfaces have the higher antiscale ability at the higher solution temperature. Furthermore, the stripping and electrochemical corrosion tests demonstrated that the PDA/PTFE coating has the better stability and anticorrosion ability. The PDA/PTFE coating with the superior properties has potential application for the long‐lasting reduction of the scale formation.

First-principles characterisation and comparison of clean, hydrated, and defect α-Al2O3 and α-Fe2O3 (110) surfaces

ABSTRACT Structural models of the (110) termination of α-Al2O3 and α-Fe2O3 are studied using Density Functional Theory (DFT) calculations and thermodynamics to determine the details of the mineral-water interface structure and stability. Prior experiments have characterised these interfaces, but the X-ray reflectivity techniques used cannot identify the distribution of protons on surface sites. In addition, the alumina (110) surface displays two different surface structures stable in water, with their occurrence dependent on sample preparation conditions. We use theory and modelling to determine the thermodynamically preferred surface structures, including protonation states of surface oxygen functional groups, as a function of temperature and pressure. Consistent with studies of other facets of alumina and hematite, we find that thermodynamically unfavourable defect structures, upon hydration and hydroxylation, show comparable stability to the hydrated forms of ideal terminations. The model results are compared to experimental characterisation of hydrated (110) alumina and hematite surfaces with good agreement between the best-fit structures from experiments and the lowest surface free energy structures from theory and modelling. Electronic structure analysis of the exposed surface functional groups is presented, and we highlight instances in which the electronic density of states differs between oxygen functional groups that have similar coordination environments.