Why is ceramics brittle

Fiber or whisker is added to the ceramic matrix in a certain way. On the one hand, high-strength fiber whisker can share the additional load; on the other hand, the weak interface between fiber or whisker and the ceramic matrix can be used to create the absorption system of external energy, so as to improve the brittleness of ceramic materials. For example, ceramic matrix composites can be applied to the Leap, CMC components introduced into the engine turbine housing lining.

The improved engine requires much less cooling air than nickel-based superalloys and has a lower specific gravity, saving about 15 percent of the fuel used in previous engines. If two kinds of different materials are put together, the stress must be generated between the two materials due to their different thermal expansion coefficient and elastic modulus, and the stress in the grain interface is the main cause of the weak interface.

Many studies have shown that if nano-sized grains of one substance exists in micron-sized grains of another, known as nano-micron intracrystalline recombination, their strength and toughness are surprisingly improved. As mentioned above, fiber or whiskers are added to the matrix of ceramics for strengthening and toughening.

However, it is difficult to achieve uniform distribution of fiber or whisker with the granular ceramic matrix with a large aspect ratio, which results in the dispersion of composite properties.

Therefore, people assume that if it is possible to form a shape with a certain aspect ratio in the matrix of ceramics, it can achieve the same effect as reinforcing ceramics with fiber or whisker.

Therefore, a part of the ceramic body can generate a certain aspect ratio by itself through special processing. For example, a small amount of liquid phase in the sintering process of alumina ceramics can induce the anisotropic growth of alumina grains, while the strength and toughness of alumina ceramic materials can be greatly improved by forming a large number of rod-shaped crystals with a large aspect ratio in the alumina matrix.

The idea of the laminated composite material is put forward from the conch microstructure in nature, that is, two materials of different components are stacked in a sandwich to form a multilayer laminated composite with parallel interfaces. The material structure of the sample design has many weak interfaces perpendicular to the stress direction.

In metals, their metallic bonds allow the atoms to slide past each other easily. In ceramics, due to their ionic bonds, there is a resistance to the sliding. Since in ceramics the rows cannot slide, the ceramic cannot plastically deform.

Instead, it fractures, which makes it a brittle material. Ceramics, are made by the direct method of heating at very hight temperatures and then rapidly cooling them. Due to this rapid quenching, they do not get enough time to form proper bonds and the bonds which were able to form in that time, become quiet hard due to the rapid processing. In addition to Fine Ceramics, other insulators include paraffin, rubber, plastic, paper and marble.

Because ceramics are fired in a kiln, they can be fashioned into a wide variety of shapes with excellent heat resistance and durability. For these reasons, ceramics have long been used as insulators.

Ceramic based objects are useful because it is cheap to buy, it can be made into many things and although it is fragile and brittle it is a yet a strong product. Some popular ceramic products are kitchenware like plates, mugs, knives and even ceramic cook tops because ceramics is heat resistant and is a thermoset. Due to ceramic materials wide range of properties, they are used for a multitude of applications.

In general, most ceramics are: hard, wear-resistant, brittle, refractory, thermal insulators, electrical insulators, nonmagnetic, oxidation resistant, prone to thermal shock, and chemically stable. Ceramic Processing. Ceramic History. Caltech materials scientist Julia Greer and her colleagues are on the path to developing such a material and many others that possess unheard-of combinations of properties.

For example, they might create a material that is thermally insulating but also extremely lightweight, or one that is simultaneously strong, lightweight, and nonbreakable—properties that are generally thought to be mutually exclusive. Greer's team has developed a method for constructing new structural materials by taking advantage of the unusual properties that solids can have at the nanometer scale, where features are measured in billionths of meters.

In a paper published in the September 12 issue of the journal Science , the Caltech researchers explain how they used the method to produce a ceramic e. This very clearly demonstrates that if you use the concept of the nanoscale to create structures and then use those nanostructures like LEGO to construct larger materials, you can obtain nearly any set of properties you want.

You can create materials by design. The researchers use a direct laser writing method called two-photon lithography to "write" a three-dimensional pattern in a polymer by allowing a laser beam to crosslink and harden the polymer wherever it is focused.

The parts of the polymer that were exposed to the laser remain intact while the rest is dissolved away, revealing a three-dimensional scaffold. That structure can then be coated with a thin layer of just about any kind of material—a metal, an alloy, a glass, a semiconductor, etc.