Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula Al2O3. It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium oxide. It is commonly called alumina and may also be called aloxide, aloxite, or alundum in various forms and applications. It occurs naturally in its crystalline polymorphic phase α-Al2O3 as the mineral corundum, varieties of which form the precious gemstones ruby and sapphire. Al2O3 is used to produce aluminium metal, as an abrasive owing to its hardness, and as a refractory material owing to its high melting point.
A monolayer is a single, closely packed layer of entities, commonly atoms or molecules. Monolayers can also be made out of cells. Self-assembled monolayers form spontaneously on surfaces. Monolayers of layered crystals like graphene and molybdenum disulfide are generally called 2D materials.
Polyelectrolytes are polymers whose repeating units bear an electrolyte group. Polycations and polyanions are polyelectrolytes. These groups dissociate in aqueous solutions (water), making the polymers charged. Polyelectrolyte properties are thus similar to both electrolytes (salts) and polymers and are sometimes called polysalts. Like salts, their solutions are electrically conductive. Like polymers, their solutions are often viscous. Charged molecular chains, commonly present in soft matter systems, play a fundamental role in determining structure, stability and the interactions of various molecular assemblies. Theoretical approaches to describe their statistical properties differ profoundly from those of their electrically neutral counterparts, while technological and industrial fields exploit their unique properties. Many biological molecules are polyelectrolytes. For instance, polypeptides, glycosaminoglycans, and DNA are polyelectrolytes. Both natural and synthetic polyelectrolytes are used in a variety of industries.
An artificial membrane, or synthetic membrane, is a synthetically created membrane which is usually intended for separation purposes in laboratory or in industry. Synthetic membranes have been successfully used for small and large-scale industrial processes since the middle of the twentieth century. A wide variety of synthetic membranes is known. They can be produced from organic materials such as polymers and liquids, as well as inorganic materials. Most commercially utilized synthetic membranes in industry are made of polymeric structures. They can be classified based on their surface chemistry, bulk structure, morphology, and production method. The chemical and physical properties of synthetic membranes and separated particles as well as separation driving force define a particular membrane separation process. The most commonly used driving forces of a membrane process in industry are pressure and concentration gradient. The respective membrane process is therefore known as filtration. Synthetic membranes utilized in a separation process can be of different geometry and flow configurations. They can also be categorized based on their application and separation regime. The best known synthetic membrane separation processes include water purification, reverse osmosis, dehydrogenation of natural gas, removal of cell particles by microfiltration and ultrafiltration, removal of microorganisms from dairy products, and dialysis.
A coating is a covering that is applied to the surface of an object, or substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. powder coatings.
Physical vapor deposition (PVD), sometimes called physical vapor transport (PVT), describes a variety of vacuum deposition methods which can be used to produce thin films and coatings on substrates including metals, ceramics, glass, and polymers. PVD is characterized by a process in which the material transitions from a condensed phase to a vapor phase and then back to a thin film condensed phase. The most common PVD processes are sputtering and evaporation. PVD is used in the manufacturing of items which require thin films for optical, mechanical, electrical, acoustic or chemical functions. Examples include semiconductor devices such as thin-film solar cells, microelectromechanical devices such as thin film bulk acoustic resonator, aluminized PET film for food packaging and balloons, and titanium nitride coated cutting tools for metalworking. Besides PVD tools for fabrication, special smaller tools used mainly for scientific purposes have been developed.
Thermal spraying techniques are coating processes in which melted materials are sprayed onto a surface. The "feedstock" is heated by electrical or chemical means.
Surface engineering is the sub-discipline of materials science which deals with the surface of solid matter. It has applications to chemistry, mechanical engineering, and electrical engineering.
In materials science Functionally Graded Materials (FGMs) may be characterized by the variation in composition and structure gradually over volume, resulting in corresponding changes in the properties of the material. The materials can be designed for specific function and applications. Various approaches based on the bulk, preform processing, layer processing and melt processing are used to fabricate the functionally graded materials.
Janus particles are special types of nanoparticles or microparticles whose surfaces have two or more distinct physical properties. This unique surface of Janus particles allows two different types of chemistry to occur on the same particle. The simplest case of a Janus particle is achieved by dividing the particle into two distinct parts, each of them either made of a different material, or bearing different functional groups. For example, a Janus particle may have one half of its surface composed of hydrophilic groups and the other half hydrophobic groups, the particles might have two surfaces of different color, fluorescence, or magnetic properties. This gives these particles unique properties related to their asymmetric structure and/or functionalization.
Bioceramics and bioglasses are ceramic materials that are biocompatible. Bioceramics are an important subset of biomaterials. Bioceramics range in biocompatibility from the ceramic oxides, which are inert in the body, to the other extreme of resorbable materials, which are eventually replaced by the body after they have assisted repair. Bioceramics are used in many types of medical procedures. Bioceramics are typically used as rigid materials in surgical implants, though some bioceramics are flexible. The ceramic materials used are not the same as porcelain type ceramic materials. Rather, bioceramics are closely related to either the body's own materials or are extremely durable metal oxides.
Nanocellulose is a term referring to nano-structured cellulose. This may be either cellulose nanocrystal, cellulose nanofibers (CNF) also called nanofibrillated cellulose (NFC), or bacterial nanocellulose, which refers to nano-structured cellulose produced by bacteria.
Adsorption is the adhesion of ions or molecules onto the surface of another phase. Adsorption may occur via physisorption and chemisorption. Ions and molecules can adsorb to many types of surfaces including polymer surfaces. A polymer is a large molecule composed of repeating subunits bound together by covalent bonds. In dilute solution, polymers form globule structures. When a polymer adsorbs to a surface that it interacts favorably with, the globule is essentially squashed, and the polymer has a pancake structure.
Biomaterials are materials that are used in contact with biological systems. Biocompatibility and applicability of surface modification with current uses of metallic, polymeric and ceramic biomaterials allow alteration of properties to enhance performance in a biological environment while retaining bulk properties of the desired device.
Polymeric materials have widespread application due to their versatile characteristics, cost-effectiveness, and highly tailored production. The science of polymer synthesis allows for excellent control over the properties of a bulk polymer sample. However, surface interactions of polymer substrates are an essential area of study in biotechnology, nanotechnology, and in all forms of coating applications. In these cases, the surface characteristics of the polymer and material, and the resulting forces between them largely determine its utility and reliability. In biomedical applications for example, the bodily response to foreign material, and thus biocompatibility, is governed by surface interactions. In addition, surface science is integral part of the formulation, manufacturing, and application of coatings.
Biomaterials exhibit various degrees of compatibility with the harsh environment within a living organism. They need to be nonreactive chemically and physically with the body, as well as integrate when deposited into tissue. The extent of compatibility varies based on the application and material required. Often modifications to the surface of a biomaterial system are required to maximize performance. The surface can be modified in many ways, including plasma modification and applying coatings to the substrate. Surface modifications can be used to affect surface energy, adhesion, biocompatibility, chemical inertness, lubricity, sterility, asepsis, thrombogenicity, susceptibility to corrosion, degradation, and hydrophilicity.
As with any material implanted in the body, it is important to minimize or eliminate foreign body response and maximize effectual integration. Neural implants have the potential to increase the quality of life for patients with such disabilities as Alzheimer's, Parkinson's, epilepsy, depression, and migraines. With the complexity of interfaces between a neural implant and brain tissue, adverse reactions such as fibrous tissue encapsulation that hinder the functionality, occur. Surface modifications to these implants can help improve the tissue-implant interface, increasing the lifetime and effectiveness of the implant.
Molecular layer deposition (MLD) is a vapour phase thin film deposition technique based on self-limiting surface reactions carried out in a sequential manner. Essentially, MLD resembles the well established technique of atomic layer deposition (ALD) but, whereas ALD is limited to exclusively inorganic coatings, the precursor chemistry in MLD can use small, bifunctional organic molecules as well. This enables, as well as the growth of organic layers in a process similar to polymerization, the linking of both types of building blocks together in a controlled way to build up organic-inorganic hybrid materials.
Polymer derived ceramics (PDCs) are ceramic materials formed by the pyrolysis of preceramic polymers, usually under inert atmosphere.
Derived from atomic layer deposition (ALD), sequential infiltration synthesis (SIS) is a technique in which a polymer is infused with inorganic material using sequential, self-limiting exposures to gaseous precursors, allowing for the precise control over the composition, structure and properties of materials. This synthesis involves metal-organic vapor-phase precursors and co-reactants dissolving and diffusing into polymers, interacting with the polymer functional groups via reversible complex formation and/or irreversible chemical reactions yielding desired composite materials, which may be nanostructured. The metal-organic precursor (A) and co-react vapor (B) are supplied in an alternating ABAB sequence. Following SIS, the organic phase can be removed thermally or chemically to leave only the inorganic components behind. The precise control over the infiltration and synthesis via SIS allows the creation of materials with tailored properties like composition, mechanics, stoichiometry, porosity, conductivity, refractive index, and chemical functionality on the nanoscale. This empowers SIS to have a wide range of applications from electronics to energy storage to catalysis. SIS is sometimes referred to as "multiple pulsed vapor-phase infiltration" (MPI), "vapor phase infiltration" (VPI)” or "sequential vapor infiltration" (SVI)".
