Introduction to Advanced Functional Ceramics

Classification of advanced functional ceramics: (l) Piezoelectric ceramics
Piezoelectric ceramics refers to a functional ceramics with piezoelectric effect, which is one of piezoelectric materials. The so-called piezoelectric effect refers to the phenomenon that the polarization (or electric field) is induced by stress, or the stress (or strain) is induced by the electric field. The former is a positive piezoelectric effect, and the latter is a negative piezoelectric effect. Electric effect. Piezoelectric ceramics is a kind of polycrystal. According to the crystal structure, there are perovskite type, tungsten bronze type, pyrochlore type, etc. Currently, perovskite type is widely used, such as barium titanate, lead titanate, zirconium titanium Lead acid, etc.Mainly used in the field of radio technology, such as ultrasonic transducers, resonators, filters, piezoelectric ignition, piezoelectric motors, etc.; (2) Superconducting ceramics
Superconducting ceramics refer to ceramic materials with high temperature superconducting properties. The so-called superconductor refers to a conductor with only zero resistance and diamagnetism, and the temperature at which this state is reached is called the critical temperature. The earliest discovered superconductors often require ultra-low temperature to have superconductivity, which is difficult to be practical. With the deepening of research, it has been found that some oxide ceramics also have superconductivity, and their critical temperature is greatly increased, which brings hope for the realization of conductive materials, which is the superconducting ceramics that people now refer to. Since superconducting ceramics have the characteristics of zero resistance and diamagnetism, they can be used in the following major fields, and will produce huge economic and social benefits. First, it is used for power transmission and distribution, with no energy loss (20% energy saving), long-term energy storage without loss, and can also manufacture large-capacity, high-efficiency superconducting generators; the second is for the manufacture of maglev trains; the third is It is used in the manufacture of ultra-high-performance computers and the use of diamagnetism for wastewater treatment and detoxification. At present, the main composition systems of superconducting ceramics are Y-Ba-Cu-0 series, La-Ba-Cu-() series, IJa-Sr-Cu-() series, Ba-Pb-Bi-() series and so on.

(3) Magnetic ceramics
Magnetic ceramics include soft ferrite, hard ferrite, microwave ferrite, magnetostrictive ferrite, moment ferrite and magnetic bubble ferrite. Soft ferrites are a class of ferrites that are easy to magnetize and demagnetize, with high permeability and small remanence and coercivity. It can be used as a high-frequency magnetic core material to make coils of electronic instruments and magnetic cores of transformers, etc., which are used in video recorders, electronic computers, etc. People also use the nonlinear and magnetic saturation characteristics of the magnetization curve of soft ferrite to make nonlinear reactive devices such as saturable reactors and magnetic amplifiers. Advanced ceramic preparation process Hard ferrite is opposite to high permeability soft magnetic material, which has high coercivity and high residual magnetic induction. After magnetization, a stable magnetic field can be generated without external lifting capacity, so it is also called permanent magnet ferrite. Hard ferrite can be used in the field of telecommunications, such as making speakers, microphones, magnetic recording pickups, magnetrons, microwave devices, etc.; used to make various electromagnetic instruments, flux meters, oscilloscopes, vibration receivers for electrical instruments etc.; used in the field of control devices such as polarizing relays, voltage regulators, temperature and pressure controls, limit switches, permanent magnet “magnetic twisted wire” memory, etc.: also used in industrial equipment and other fields. Microwave ferrite is a kind of ferrite whose polarization plane will continuously rotate around the direction of propagation when plane-polarized electromagnetic waves propagate in a certain direction in the ferrite under the action of a high-frequency magnetic field, also known as gyromagnetic ferrite. Microwave ferrites are classified by lattice types, mainly including spinel, hexagonal and garnet ferrites. Microwave devices using microwave ferrites are representative of irreversible devices such as circulators and isolators, that is, the so-called irreversible function that uses the electric wave in the forward direction and the electric wave in the reverse direction; there are also those that use the electron spin magnetic moment to move at the same frequency. When the frequency of the external electromagnetic field is the same, the magnetic resonance isolator of the resonance effect occurs. Microwave ferrites are also used in attenuators, phase shifters, tuners, switches, filters, oscillators, amplifiers, mixers, detectors and other instruments. Magnetostrictive ferrites are ferrites with remarkable magnetostrictive properties. Such materials are mostly used to make acoustic wave transducers and receivers, and to make filters, voltage stabilizers, harmonic generators, microphones, oscillators, etc. in telecommunications. In the aspect of electronic computer and automatic control, ultrasonic delay line memory, magnetic twisted line memory, etc. are produced. Changjin’s magnetostrictive ferrites are nickel-based ferrites such as Ni-Co-based, Ni-Cu-Co-based, and Ni-Zn ferrites. The moment-avoiding ferrite refers to a ferrite with a rectangular hysteresis loop and a small coercivity. Mainly used in computer and automation control and component control equipment, as memory element, logic element, switching element, magnetic amplifier memory and magneto-acoustic memory. Compared with the rectangular ferrite, the magnetic bubble ferrite has the advantages of small memory volume, large capacity and low power consumption. In view of this, as a memory information element, people place their hopes on a magnetic bubble material. (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, sterilization, and good physical and chemical stability. At present, bioceramics can be generally divided into four categories: ①Inert bioceramics, mainly composed of oxide ceramics and non-oxide ceramics, including alumina ceramics and various carbon products; ②Surface 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 biocomposites, including ceramic coatings, living glass ceramics and plexiglass or metal fibers, Hydroxyapatite and autogenous bone or polylactic acid, etc. (5) Nano ceramics
The so-called nano-ceramics refer to ceramic materials whose microstructures have nanoscale dimensions, including grain size, grain boundary width, second phase distribution, pore size, 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 properties that conventional materials do not have in terms of magnetism, light, electricity, sensitivity, etc. It has broad application prospects in materials, electronic materials, optical materials, sintering, frogization, and sensing of high-density materials.Processing/powder preparation, ingredient mixing, grinding, mixing