Hot wall bell-type furnaces and methods of treating metal and/or ceramic articles. A method of treating a metal/ceramic article includes placing the article with a tray/fixture on a furnace hearth. A retort bell can be placed over the fixture with the article. A furnace bell is then placed over the retort bell. A retort pressure in the retort bell can be reduced to a first vacuum pressure, and a support pressure in a plenum space between the retort bell and the furnace bell can be reduced to a second vacuum pressure. The article can be heated to a treatment temperature which can be maintained along with the first vacuum pressure and second vacuum pressure to treat the article to form a treated article. The article can be one or more of a green body to be sintered, a sintered article, and a cast article to be treated by any suitable heat treatment.

Hot wall bell-type furnaces and methods of treating metal and/or ceramic articles. A method of treating a metal/ceramic article includes placing the article with a tray/fixture on a furnace hearth. A retort bell can be placed over the fixture with the article. A furnace bell is then placed over the retort bell. A retort pressure in the retort bell can be reduced to a first vacuum pressure, and a support pressure in a plenum space between the retort bell and the furnace bell can be reduced to a second vacuum pressure. The article can be heated to a treatment temperature which can be maintained along with the first vacuum pressure and second vacuum pressure to treat the article to form a treated article. The article can be one or more of a green body to be sintered, a sintered article, and a cast article to be treated by any suitable heat treatment.

A stove includes a stage, a stove, a housing, and an exhaust pipe is disclosed. Wherein, the stove is disposed on the stage and includes a chamber made of metal and a thermal insulation structure. The chamber includes a cavity, an entry, and an air outlet. The thermal insulation structure covers an exterior of the chamber. The housing is disposed outside of the stove and joined to the stage. An isolation space is formed between the housing and the stove. The exhaust pipe passes through the housing and communicates with the air outlet and the exterior of the housing. The heat source is adapted to heat the cavity. Whereby, a compact size kiln is realized.

A stove includes a stage, a stove, a housing, and an exhaust pipe is disclosed. Wherein, the stove is disposed on the stage and includes a chamber made of metal and a thermal insulation structure. The chamber includes a cavity, an entry, and an air outlet. The thermal insulation structure covers an exterior of the chamber. The housing is disposed outside of the stove and joined to the stage. An isolation space is formed between the housing and the stove. The exhaust pipe passes through the housing and communicates with the air outlet and the exterior of the housing. The heat source is adapted to heat the cavity. Whereby, a compact size kiln is realized.

A kiln including a stove and a heat source wherein the stove includes a chamber, an air guide structure, an exhaust pipe and a heat storage member. The chamber includes a cavity, an entry, and an air outlet. The air outlet is located between a top of the front section of the cavity and the entry. The air guide structure communicates with the air outlet and includes a guide plate. The exhaust pipe is disposed above the guide plate, and an exhaust channel is formed by the guide plate of the air guide structure and the exhaust pipe. The heat storage member covers an exterior of the cavity which is corresponding to the top of the front section of the cavity, and contacts the air guide structure. The heat source is disposed in the stove and adapted to heat the cavity.

A kiln including a stove and a heat source wherein the stove includes a chamber, an air guide structure, an exhaust pipe and a heat storage member. The chamber includes a cavity, an entry, and an air outlet. The air outlet is located between a top of the front section of the cavity and the entry. The air guide structure communicates with the air outlet and includes a guide plate. The exhaust pipe is disposed above the guide plate, and an exhaust channel is formed by the guide plate of the air guide structure and the exhaust pipe. The heat storage member covers an exterior of the cavity which is corresponding to the top of the front section of the cavity, and contacts the air guide structure. The heat source is disposed in the stove and adapted to heat the cavity.

A carbon fiber bundle, wherein an average single-fiber fineness is from 1.0 to 2.4 dtex and a roundness is from 0.7 to 0.9 in a shape of a cross-section perpendicular to a fiber axis of a single fiber; the roundness being determined with equation (1): roundness=4S/L.sup.2, where S is a cross-sectional area of the single fiber and L is a circumferential length of the single fiber, and S and L are obtained by observing, under an SEM, the cross-section of the single fiber perpendicular to the fiber axis of the single fiber and analyzing the obtained image.

A carbon fiber bundle, wherein an average single-fiber fineness is from 1.0 to 2.4 dtex and a roundness is from 0.7 to 0.9 in a shape of a cross-section perpendicular to a fiber axis of a single fiber; the roundness being determined with equation (1): roundness=4S/L.sup.2, where S is a cross-sectional area of the single fiber and L is a circumferential length of the single fiber, and S and L are obtained by observing, under an SEM, the cross-section of the single fiber perpendicular to the fiber axis of the single fiber and analyzing the obtained image.

A carbon fiber bundle, wherein an average single-fiber fineness is from 1.0 to 2.4 dtex and a roundness is from 0.7 to 0.9 in a shape of a cross-section perpendicular to a fiber axis of a single fiber; the roundness being determined with equation (1): roundness=4S/L.sup.2, where S is a cross-sectional area of the single fiber and L is a circumferential length of the single fiber, and S and L are obtained by observing, under an SEM, the cross-section of the single fiber perpendicular to the fiber axis of the single fiber and analyzing the obtained image.

A carbon fiber bundle, wherein an average single-fiber fineness is from 1.0 to 2.4 dtex and a roundness is from 0.7 to 0.9 in a shape of a cross-section perpendicular to a fiber axis of a single fiber; the roundness being determined with equation (1): roundness=4S/L.sup.2, where S is a cross-sectional area of the single fiber and L is a circumferential length of the single fiber, and S and L are obtained by observing, under an SEM, the cross-section of the single fiber perpendicular to the fiber axis of the single fiber and analyzing the obtained image.