Nanophase ceramic

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Nanophase ceramics are ceramics that are nanophase materials (that is, materials that have grain sizes under 100 nanometers). [1] [2] They have the potential for superplastic deformation. [1] Because of the small grain size and added grain boundaries properties such as ductility, hardness, and reactivity see drastic changes from ceramics with larger grains.

Contents

Structure

The structure of nanophase ceramics is not too different than that of ceramics. The main difference is the amount of surface area per mass. Particles of ceramics have small surface areas, but when those particles are shrunk to within a few nanometers, the surface area of the same amount of a mass of a ceramic greatly increases. [3] So in general, nanophase materials have greater surface areas than that of a similar mass material at a larger scale. [3] This is important because if the surface area is very large the particles can be in contact with more of their surroundings, which in turn increases the reactivity of the material. [3] The reactivity of a material changes the material's mechanical properties and chemical properties, among many other things. [3] This is especially true in nanophase ceramics.

Properties

Nanophase ceramics have unique properties than regular ceramics due to their improved reactivity. [3] Nanophase ceramics exhibit different mechanical properties than their counterpart such as higher hardness, higher fracture toughness, and high ductility. [4] These properties are far from ceramics which behave as brittle, low ductile materials.

Titanium dioxide

Strain rate sensitivity for TiO
2. Strain Rate Sensitivity-page0001.jpg
Strain rate sensitivity for TiO
2
.
Microhardness of TiO
2. Microhardness of titaniumdioxide-page0001.jpg
Microhardness of TiO
2
.

Titanium dioxide (TiO
2
), has been shown to have increased hardness and ductility at the nanoscale. In an experiment, grains of titanium dioxide that had an average size of 12 nanometers were compressed at 1.4 GPa and sintered at 200 °C. [5] The result was a grain hardness of about 2.2 times greater than that of grains of titanium dioxide with an average size of 1.3 micrometers at the same temperature and pressure. [5] In the same experiment, the ductility of titanium dioxide was measured. The strain rate sensitivity of a 250 nanometer grain of titanium dioxide was about 0.0175, while a grain with size of about 20 nanometers had a strain rate sensitivity of approximately .037; a significant increase. [5]

Processing

Nanophase ceramics can be processed from atomic, molecular, or bulk precursors. [6] Gas condensation, chemical precipitation, aerosol reactions, biological templating, chemical vapor deposition, and physical vapor deposition are techniques used to synthesis nanophase ceramics from molecular or atomic precursors. [6] To process nanophase ceramics from bulk precursors, mechanical attrition, crystallization from the amorphous state, and phase separation are used to create nanophase ceramics. [6] Synthesizing nanophase ceramics from atomic or molecular precursors are desired more because a greater control over microscopic aspects of the nanophase ceramic can occur. [6]

Gas condensation

Synthesis of nanophase ceramics using gas condensation. Gas condensation-page0001.jpg
Synthesis of nanophase ceramics using gas condensation.

Gas condensation is one way nanophase ceramics are produced. First, precursor ceramics are evaporated from sources within a gas-condensation chamber. [5] Then the ceramics are condensed in a gas (dependent on the material being synthesized) and transported via convection to a liquid-nitrogen filled cold finger. [5] Next, the ceramic powders are scraped off the cold finger and collect in a funnel below the cold finger. [5] The ceramic powders then become consolidated in a low-pressure compaction device and then in a high-pressure compaction device. [5] This all occurs in a vacuum, so no impurities can enter the chamber and affect the results of the nanophase ceramics. [5]

Applications

Nanophase ceramics have unique properties that make them optimal for a variety of applications.

Drug delivery

Materials used in drug delivery in the past ten years have primarily been polymers. However, nanotechnology has opened the door for the use of ceramics with benefits not previously seen in polymers. The large surface area to volume ratio of nanophase materials makes it possible for large amounts of drugs to be released over long periods of time. Nanoparticles to be filled with drugs can be easily manipulated in size and composition to allow for increased endocytosis of drugs into targeted cells and increased dispersion through fenestrations in capillaries. While these benefits all relate to nanoparticles in general (including polymers), ceramics have other, unique abilities. Unlike polymers, slow degradation of ceramics allows for longer release of the drug. Polymers also tend to swell in liquid which can cause an unwanted burst of drugs. The lack of swelling shown by most ceramics allows for increased control. Ceramics can also be created to match the chemistry of biological cells in the body increasing bioactivity and biocompatibility. Nanophase ceramic drug carriers are also able to target specific cells. This can be done by manufacturing a material to bond to the specific cell or by applying an external magnetic field, attracting the carrier to a specific location.

Bone substitution

Nanophase ceramics have great potential for use in orthopedic medicine. Bone and collagen have structures on the nanoscale. Nanomaterials can be manufactured to simulate these structures which is necessary for grafts and implants to successfully adapt to and handle varying stresses. The surface properties of nanophase ceramics is also very important for bone substitution and regeneration. Nanophase ceramics have much rougher surfaces than larger materials and also have increased surface area. This promotes reactivity and absorption of proteins that assist tissue development. Nano-hydroxyapatite is one nanophase ceramic that is used as a bone substitute. Nano grain size increases the bonding, growth, and differentiation of osteoblasts onto the ceramic. The surfaces of nanophase ceramics can also be modified to be porous allowing osteoblasts to create bone within the structure. The degradation of the ceramic is also important because the rate can be changed by changing the crystallinity. This way as bone grows the substitute can diminish at a similar rate.

Related Research Articles

Ceramic Inorganic, nonmetallic solid prepared by the action of heat

A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick.

Materials science Interdisciplinary field which studies the discovery and design of new materials

The interdisciplinary field of materials science covers the design and discovery of new materials, particularly solids. The field is also commonly termed materials science and engineering emphasizing engineering aspects of building useful items, and materials physics, which emphasizes the use of physics to describe material properties. The intellectual origins of materials science stem from the Age of Enlightenment, when researchers began to use analytical thinking from chemistry, physics, and engineering to understand ancient, phenomenological observations in metallurgy and mineralogy. Materials science still incorporates elements of physics, chemistry, and engineering. As such, the field was long considered by academic institutions as a sub-field of these related fields. Beginning in the 1940s, materials science began to be more widely recognized as a specific and distinct field of science and engineering, and major technical universities around the world created dedicated schools for its study.

Nanomaterials Materials whose granular size lies between 1 to 100 nm

Nanomaterials describe, in principle, materials of which a single unit is sized between 1 and 100 nm.

Nanoparticle Particle with size less than 100 nm

A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At the lowest range, metal particles smaller than 1 nm are usually called atom clusters instead.

In materials science, the sol–gel process is a method for producing solid materials from small molecules. The method is used for the fabrication of metal oxides, especially the oxides of silicon (Si) and titanium (Ti). The process involves conversion of monomers into a colloidal solution (sol) that acts as the precursor for an integrated network of either discrete particles or network polymers. Typical precursors are metal alkoxides.

Microstructure Very small scale structure of material

Microstructure is the very small scale structure of a material, defined as the structure of a prepared surface of material as revealed by an optical microscope above 25× magnification. The microstructure of a material can strongly influence physical properties such as strength, toughness, ductility, hardness, corrosion resistance, high/low temperature behaviour or wear resistance. These properties in turn govern the application of these materials in industrial practice.

Nanophase materials are materials that have grain sizes under 100 nanometres. They have different mechanical and optical properties compared to the large grained materials of the same chemical composition.

Ceramic engineering Science and technology of creating objects from inorganic, non-metallic materials

Ceramic engineering is the science and technology of creating objects from inorganic, non-metallic materials. This is done either by the action of heat, or at lower temperatures using precipitation reactions from high-purity chemical solutions. The term includes the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components and the study of their structure, composition and properties.

Nanochemistry is the combination of chemistry and nano science. Nanochemistry is associated with synthesis of building blocks which are dependent on size, surface, shape and defect properties. Nanochemistry is being used in chemical, materials and physical, science as well as engineering, biological and medical applications. Nanochemistry and other nanoscience fields have the same core concepts but the usages of those concepts are different.

Nanocomposite Solid material with nano-scale structure

Nanocomposite is a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm) or structures having nano-scale repeat distances between the different phases that make up the material.

Polymer nanocomposites (PNC) consist of a polymer or copolymer having nanoparticles or nanofillers dispersed in the polymer matrix. These may be of different shape, but at least one dimension must be in the range of 1–50 nm. These PNC's belong to the category of multi-phase systems that consume nearly 95% of plastics production. These systems require controlled mixing/compounding, stabilization of the achieved dispersion, orientation of the dispersed phase, and the compounding strategies for all MPS, including PNC, are similar. Alternatively, polymer can be infiltrated into 1D, 2D, 3D preform creating high content polymer nanocomposites.

Solid State of matter

Solid is one of the four fundamental states of matter. The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural rigidity and resistance to a force applied to the surface. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire available volume like a gas. The atoms in a solid are bound to each other, either in a regular geometric lattice, or irregularly. Solids cannot be compressed with little pressure whereas gases can be compressed with little pressure because the molecules in a gas are loosely packed.

Anti-Scratch Coating is a type of protective coating or film applied to an object's surface for mitigation against scratches. Scratches are small surface-level cuts left on a surface following interaction with a sharper object. Anti-Scratch coatings provide scratch resistances by containing tiny microscopic materials with scratch-resistant properties. Scratch resistance materials come in the form of additives, filters, and binders. Besides materials, scratch resistances is impacted by coating formation techniques. Scratch resistance is measured using the Scratch-hardness test. Commercially, Anti-Scratch Coatings are used in the automotive, optical, photographic, and Electronics industries, where resale and/or functionality is impaired by scratches. Anti-Scratch Coatings are of growing importance as traditional Scratch resistance materials like metals and glass are replaced with low-scratch resistant plastics.

Nano-scaffolding is a medical process used to regrow tissue and bone, including limbs and organs. The nano-scaffold is a three-dimensional structure composed of polymer fibers very small that are scaled from a Nanometer scale. Developed by the American military, the medical technology uses a microscopic apparatus made of fine polymer fibers called a scaffold. Damaged cells grip to the scaffold and begin to rebuild missing bone and tissue through tiny holes in the scaffold. As tissue grows, the scaffold is absorbed into the body and disappears completely.

Bioceramic

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.

Friction stir processing

Friction stir processing (FSP) is a method of changing the properties of a metal through intense, localized plastic deformation. This deformation is produced by forcibly inserting a non-consumable tool into the workpiece, and revolving the tool in a stirring motion as it is pushed laterally through the workpiece. The precursor of this technique, friction stir welding, is used to join multiple pieces of metal without creating the heat affected zone typical of fusion welding.

Ultra-high-temperature ceramics (UHTCs) are a class of refractory ceramics that offer excellent stability at temperatures exceeding 2000 °C being investigated as possible thermal protection system (TPS) materials, coatings for materials subjected to high temperatures, and bulk materials for heating elements. Broadly speaking, UHTCs are borides, carbides, nitrides, and oxides of early transition metals. Current efforts have focused on heavy, early transition metal borides such as hafnium diboride (HfB2) and zirconium diboride (ZrB2); additional UHTCs under investigation for TPS applications include hafnium nitride (HfN), zirconium nitride (ZrN), titanium carbide (TiC), titanium nitride (TiN), thorium dioxide (ThO2), tantalum carbide (TaC) and their associated composites.

Materials that are used for biomedical or clinical applications are known as biomaterials. The following article deals with fifth generation biomaterials that are used for bone structure replacement. For any material to be classified for biomedical applications, three requirements must be met. The first requirement is that the material must be biocompatible; it means that the organism should not treat it as a foreign object. Secondly, the material should be biodegradable ; the material should harmlessly degrade or dissolve in the body of the organism to allow it to resume natural functioning. Thirdly, the material should be mechanically sound; for the replacement of load-bearing structures, the material should possess equivalent or greater mechanical stability to ensure high reliability of the graft.

Nanolattice

A nanolattice is a synthetic porous material consisting of nanometer-size members patterned into an ordered lattice structure, like a space frame. The nanolattice is a newly emerged material class that has been rapidly developed over the last decade. Nanolattices redefine the limits of the material property space. Despite being composed of 50-99% of air, nanolattices are very mechanically robust because they take advantage of size-dependent properties that we generally see in nanoparticles, nanowires, and thin films. The most typical mechanical properties of nanolattices include ultrahigh strength, damage tolerance, and high stiffness. Thus, nanolattices have a wide range of applications.

This glossary of nanotechnology is a list of definitions of terms and concepts relevant to nanotechnology, its sub-disciplines, and related fields.

References

  1. 1 2 Averback, Robert S. (May 21, 1992). "Nanophase Ceramics: Final Report" (PDF). University of Illinois Urbana-Champaign. Archived (PDF) from the original on November 29, 2014. Retrieved 22 November 2014.
  2. Lei Yang; Brian W. Sheldon & Thomas J. Webster (2010). "Nanophase Ceramics for Improved Drug Delivery: Current Opportunities and Challenges" (PDF). American Ceramic Society Bulletin. p. 24. Retrieved November 22, 2014.
  3. 1 2 3 4 5 "What's So Special about the Nanoscale?". nano.gov. Retrieved December 1, 2014.
  4. Szlufarska, Izabela, Nakano, Aiichiro, Vashista, Priya.(August 5, 2005). "A Crossover in the Mechanical Response of Nanocrystalline Ceramics" sciencemag.com. Volume 309 pgs. 911-913. Accessed December 1, 2014.
  5. 1 2 3 4 5 6 7 8 9 10 11 Siegel, R. W. (1991). "Cluster-Assembled Nanophase Materials". Annual Review of Materials Science . 21: 559–578. Bibcode:1991AnRMS..21..559S. doi:10.1146/annurev.ms.21.080191.003015.
  6. 1 2 3 4 Siegel, Richard W.. "SYNTHESIS, PROPERTIES, AND APPLICATIONS OF NANOPHASE MATERIALS". April 1995. Accessed December 7, 2014.