Introduction to Advanced Functional Ceramics

Advanced functional ceramics mainly include the following types of ceramics:

(1) Piezoelectric ceramics

Piezoelectric ceramic refers to a functional ceramic with piezoelectric effect, which is a type of piezoelectric material. The so-called piezoelectric effect refers to the phenomenon of polarization (or electric field) induced by stress, or stress (or strain) induced by electric field. The former is the positive piezoelectric effect, while the latter is the negative piezoelectric effect. Both are collectively referred to as the piezoelectric effect. Piezoelectric ceramics are a type of polycrystalline material, which can be classified into several types according to crystal structure, such as perovskite type, tungsten bronze type, pyrochlore type, etc. Currently, perovskite type is widely used, such as barium titanate, lead titanate, lead zirconate titanate, etc. There are five main categories of applications: electrical acoustic signals, optical signal processing (frequency devices), transmitting and receiving ultrasonic waves, measurement and control, signal generators (electrical and acoustic signals), and high-voltage power generators. Its application products have reached hundreds, such as piezoelectric ceramic resonators, filters, ultrasonic transducers, piezoelectric buzzers, and piezoelectric transmitters and receivers; Piezoelectric ignition, piezoelectric engine, etc.

(2) Superconducting ceramics

Superconducting ceramics refer to ceramic materials with high-temperature superconducting properties. The so-called superconductor refers to the conductor with zero resistance and diamagnetism, and the temperature reaching this state is called the critical temperature. The earliest discovered superconductors often need to have superconductivity at ultra-low temperatures, making it difficult to be practical. With the continuous deepening of research, it has been found that some oxide ceramics also have superconductivity, and their critical temperature has greatly increased, which brings hope for the realization of superconducting materials, which is now referred to as superconducting ceramics. Superconducting ceramics have zero resistance and diamagnetism and other characteristics. They can be used in the following fields and will produce huge economic and social benefits. Firstly, it is used for power transmission and distribution, with no energy loss (energy saving of 20%), long-term non-destructive energy storage, and can also manufacture high-capacity and high-efficiency superconducting generators; The second is for manufacturing maglev trains; Third, it is used to manufacture ultra-high performance computers and use diamagnetism to treat wastewater and remove poisons. At present, the main composition systems of superconducting ceramics include Y-Ba Cu O system, La Ba C u-0 system, I, a-Sr Cu () system, Ba Pb Bi O system, etc.

(3) Magnetic ceramics

Magnetic ceramics are composite oxides composed of oxygen and one or more metal elements mainly composed of iron, known as ferrite. From the properties and uses of ferrite, magnetic ceramics include soft ferrite, hard ferrite, microwave ferrite, magnetostrictive ferrite, moment ferrite, and magnetic bubble ferrite. Soft ferrite is a type of ferrite that is easy to magnetize and demagnetize, with high magnetic permeability and small residual coercive force. It can be used as a high-frequency magnetic core material to make magnetic cores for inductance coils and transformers in electronic instruments. Produce magnetic head iron core materials for use in video recorders, electronic computers, etc. It also utilizes the nonlinear magnetization curve and magnetic saturation characteristics of soft magnetic ferrite. It is used to make nonlinear reactance devices such as saturation reactors and magnetic amplifiers. Hard magnetic ferrite, on the contrary to high permeability soft magnetic materials, has high coercivity and high residual magnetic induction strength. After magnetization, a stable magnetic field can be generated without the need for external energy, hence it is also known as permanent magnet ferrite. Hard magnetic ferrite can be used in the telecommunications field, such as for making speakers, microphones, magnetic recording pickups, magnetrons, microwave bodies, etc; Used for making electrical instruments such as various electromagnetic instruments, fluxmeters, oscilloscopes, vibration receivers, etc; Used in the field of controller devices such as polarization relays, voltage regulators, temperature and pressure controls, limit switches, permanent magnet "magnetic twisted wire" memories, etc. It is also applied in industrial equipment and other fields. Microwave ferrite is a type of ferrite that, under the action of a high-frequency magnetic field, causes a plane polarized electromagnetic wave to propagate in a certain direction within the ferrite, and the polarization plane will continuously rotate around the propagation direction. It is also known as gyromagnetic ferrite. Microwave ferrite is classified by lattice type, mainly including spinel type, hexagonal type, and garnet type ferrite. Microwave devices using microwave ferrite, representative of which are irreversible devices such as circulators and isolators, utilize their so-called irreversible functions of passing through waves in the positive direction and not passing through waves in the opposite direction; There are also magnetic resonance isolators that utilize resonance effects when the frequency of electron spin magnetic moment motion is consistent with the frequency of external electromagnetic fields. Microwave ferrite is also used in instruments such as attenuators, phase shifters, tuners, switches, filters, oscillators, amplifiers, mixers, and detectors. Magnetostrictive ferrite is a type of ferrite with significant magnetostrictive properties. These materials are mostly used to make ultrasonic transducer and receivers, filters, voltage regulators, harmonic generators, microphones, oscillators, etc. in telecommunications, and ultrasonic delay line memories, twistor memory, etc. in electronic computers and automatic control. The commonly used magnetostrictive ferrite is nickel based ferrite, such as Ni Co, Ni Cu Co, Ni Zn ferrite, etc. Moment ferrite refers to a ferrite with a rectangular hysteresis loop and low coercive force. Mainly used in computer and automation control and component control equipment, as memory elements, logic elements, switching elements, magnetic amplifiers, and magnetoacoustic memory. Compared with rectangular ferrite, magnetic bubble ferrite has the advantages of small memory volume, large capacity, and low power consumption. In view of this, as a memory information component, people

(4) Bioceramics

Bioceramics are ceramic materials with special physiological behaviors that can be used to construct, repair, or replace certain tissues and organs such as human bones and teeth. Bioceramics must meet six conditions, namely biocompatibility, mechanical compatibility, excellent affinity with biological tissues, antithrombotic activity, sterilization, and good physicochemical stability. At present, bioceramics can generally be divided into four categories: ① inert bioceramics, mainly composed of oxide ceramics and non oxide ceramics, including alumina ceramics and various carbon products; ② Surface active ceramics, including hydroxyapatite ceramics, surface active glass, surface active glass ceramics; ③ Absorbent bioceramics, including calcium sulfate, trisodium phosphate, and calcium phosphate ceramics; ④ Biological composites, including ceramic coating, active glass ceramics and organic glass or metal fiber, hydroxyapatite and in-situ bone or polylactic acid, etc.

(5) Nanoceramics

The so-called nanoceramics refer to ceramic materials with nanoscale phases in the microstructure, including grain size, grain boundary width, second phase distribution, gas particle size L, defect size, etc., all at the nanoscale level. Due to the small size effect, surface effect, quantum size effect, and macroscopic quantum tunneling effect of nanoparticles, nanomaterials exhibit a series of characteristics in magnetism, optics, electricity, sensitivity, and other aspects that conventional materials do not possess. Therefore, nanoparticles have broad application prospects in sintering, catalysis, sensing, and other aspects of magnetic materials, electronic materials, optical materials, and high-density materials.

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