Silicon nitride has been researched intensively, largely in response to the challenge to develop internal combustion engines with hot-zone components made entirely from ceramics. The ceramic engine programs have had only partial success, but this research effort has succeeded in generating a degree of understanding of silicon nitride and of its processing and properties, which in many respects is more advanced than of more widely used technical ceramics. This review examines from the historical standpoint the development of silicon nitride and of its processing into a range of high-grade ceramic materials. The development of understanding of microstructure–property relationships in the silicon nitride materials is also surveyed. Because silicon nitride has close relationships with the SiAlON group of materials, it is impossible to discuss the one without some reference to the other, and a brief mention of the development of the SiAlONs is included for completeness.

Silicon Nitride and Related Materials

An electronic smoking article comprising an aerosol generator and a mechanical aerosol converter insert having the capacity to improve characteristics of aerosol produced by the aerosol generator, including sensory attributes.

Electronic smoking article

An electrically heated smoking system includes a secondary unit capable of receiving a smoking article having an aerosol-forming substrate. The secondary unit includes at least one heating element and an interface for connection to a primary power supply for supplying electrical power to the at least one heating element during a pre-heating mode, to increase the temperature of the aerosol-forming substrate to an operating temperature. The secondary unit further includes a secondary power supply arranged to supply electrical power to the at least one heating element during a smoking mode, to maintain the temperature of the aerosol-forming substrate at substantially the operating temperature. The secondary unit also includes secondary circuitry. The electrically heated smoking system optionally includes a primary unit.

Electrically heated smoking system

This paper critically reviews the existing published experimental evidence for ageing mechanisms in zirconia ceramics. The first part of the paper is concerned with the material and environmental variables affecting the kinetics of the transformation. The current ageing mechanisms are presented and discussed and attention is drawn to the contradictions between the theories. Finally, techniques to retard or prevent the tetragonal-monoclinic phase transformation are presented.

Environmental degradation of zirconia ceramics

An electrically heated smoking system includes a shell and a replaceable mouthpiece. The shell includes an electric power supply and electric circuitry. The mouthpiece includes a liquid storage portion and a capillary wick having a first end and a second end. The first end of the wick extends into the liquid storage portion for contact with liquid therein. The mouthpiece also includes a heating element for heating the second end of the capillary wick, an air outlet, and an aerosol forming chamber between the second end of the capillary wick and the air outlet. When the shell and mouthpiece are engaged or connected, the heating element is in electrical connection with the power supply via the circuitry, and a flowpath for air is defined from at least one air inlet to the air outlet via the aerosol forming chamber. In use, liquid is transferred from the liquid storage portion towards the heating element by capillary action in the wick. Liquid at the second end of the capillary wick is vaporized by the heating element. The supersaturated vapor created, is mixed and carried in the air flow from the at least one air inlet to the aerosol forming chamber. In the aerosol forming chamber, the vapor condenses to form an aerosol, which is carried towards the air outlet.

Electrically heated smoking system having a liquid storage portion

The effects of fabrication variables on the high-temperature strength of hot-pressed Si3N4 containing 5 wt% Y2O3 were studied. Materials containing a crystalline grain-boundary phase, formed as a consequence of a high-temperature presintering heat treatment and identified as Si3N4·Y2O3, had high-temperature strengths significantly superior to those observed for materials containing a glass phase.

Effect of Crystallizing the Grain‐Boundary Glass Phase on the High‐Temperature Strength of Hot‐Pressed Si3N4 Containing Y2O3

This invention provides a silicon nitride circuit board in which a metal circuit plate is bonded to a high thermal conductive silicon nitride substrate having a thermal conductivity of not less than 60 W/m K, wherein a thickness D s of the high thermal conductive silicon nitride substrate and a thickness D M of the metal circuit plate satisfy a relational formula D s ≦2D M . The silicon nitride circuit board is characterized in that, when a load acts on the central portion of the circuit board which is held at a support interval of 50 mm, a maximum deflection is not less than 0.6 mm until the silicon nitride substrate is broken. The silicon nitride circuit board is characterized in that, when an anti-breaking test is performed to the circuit board which is held at a support interval of 50 mm, an anti-breaking strength is not less than 500 MPa. The metal circuit plate or a circuit layer are integrally bonded on the silicon nitride substrate by a direct bonding method, an active metal brazing method, or an metalize method. According to the silicon nitride circuit board with the above arrangement, high thermal conductivity and excellent heat radiation characteristics can be obtained, and heat cycle resistance characteristics can be considerably improved.

Silicon nitride circuit board

There are disclosed a sintered body of ceramics, comprising 0.1 to 10% by weight of yttrium oxide; 0.1 to 10% by weight of aluminum oxide; 0.1 to 10% by weight of aluminum nitride; 0.1 to 5% by weight of at least one silicide selected from the group consisting of magnesium silicide, calcium silicide, titanium silicide, vanadium silicide, chromium silicide, manganese silicide, zirconium silicide, niobium silicide, molybdenum silicide, tantalum silicide and tungsten silicide; and the balance being silicon nitride, and a process for producing a sintered body of ceramics, which comprises molding a powder mixture of the same composition, and sintering the resultant molded compact in a non-oxidative atmosphere. According to the present invention, it is possible to manufacture sintered body having high density and excellent impact resistance.

Sintered body of ceramics and preparation thereof

Disclosed is a silicon nitride-based sintered material having high heat resistance and containing crystal compounds prepared from the silicon nitride and at least one of oxides of the elements belonging to the III A group in the periodic table.

Silicon nitride-based sintered material and method for manufacturing the same

A high thermal conductive silicon nitride sintered body contains: 2.0-7.5% by weight of a rare earth element in terms of the amount of an oxide thereof; at most 0.3% by weight of Li, Na, K, Fe, Ca, Mg, Sr, Ba, Mn and B as impurity cationic elements in terms of total amount thereof; and, if necessary, at most 2.0% by weight of alumina and/or at most 2.0% by weight of aluminum nitride, and comprises a beta-phase type silicon nitride crystal and a grain boundary phase. The silicon nitride sintered body has a thermal conductivity of at least 60 W/m·K. Optionally, the sintered body further contains 0.2-3.0% by weight of at least one compound selected from the group consisting of the oxides, carbides, nitrides, silicides and borides of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W. The sintered body has a porosity of at most 1.5% by volume, a thermal conductivity of at least 60 W/m·K, and a three-point bending strength of at least 80 kg/mm 2 at a room temperature. The sintered body achieves high thermal conductivity and good heat-radiating characteristics, as well as the high-strength characteristics generally inherent in silicon nitride sintered bodies.

Michiyasu Komatsu

Papers

Effect of Crystallizing the Grain‐Boundary Glass Phase on the High‐Temperature Strength of Hot‐Pressed Si3N4 Containing Y2O3

Silicon nitride circuit board

Sintered body of ceramics and preparation thereof

Silicon nitride-based sintered material and method for manufacturing the same

High thermal conductive silicon nitride sintered body and method of producing the same