Abstract: A method of densifying an annular porous structure comprises stacking a plurality of annular porous structures to form a porous structure stack in a graphite susceptor, wherein the graphite susceptor is disposed within a vessel. The method includes disposing a graphite panel within the graphite susceptor and located radially inward from the porous structure stack. The method includes flowing a reactant gas into the vessel.

Abstract: A method of densifying an annular porous structure comprises stacking a plurality of annular porous structures to form a porous structure stack in a graphite susceptor, wherein the graphite susceptor is disposed within a vessel. The method includes disposing a graphite panel within the graphite susceptor and located radially inward from the porous structure stack. The method includes flowing a reactant gas into the vessel.

Abstract: A method and apparatus for decreasing the radial temperature gradient in CVI/CVD furnaces is provided. The apparatus may comprise a graphite susceptor disposed within a vessel. Porous structures may be stacked within the graphite susceptor. The stack of porous structures may form a circular shape proximate a radially inward surface of the graphite susceptor. Graphite panels may be disposed within the graphite susceptor. The graphite panels may be located proximate a radially inward surface of the porous structures. The graphite panels may radiate heat radially outward and towards the graphite susceptor. Reactant gas may be flowed into the graphite susceptor.

Abstract: A method and apparatus for decreasing the radial temperature gradient in CVI/CVD furnaces is provided. The apparatus may comprise a graphite susceptor disposed within a vessel. Porous structures may be stacked within the graphite susceptor. The stack of porous structures may form a circular shape proximate a radially inward surface of the graphite susceptor. Graphite panels may be disposed within the graphite susceptor. The graphite panels may be located proximate a radially inward surface of the porous structures. The graphite panels may radiate heat radially outward and towards the graphite susceptor. Reactant gas may be flowed into the graphite susceptor.

Abstract: A process for densifying porous structures inside a furnace using non-pressure gradient CVI/CVD includes disposing a number of porous structures in a stack within a furnace. The stack has a center opening region extending through the porous structures and an outer region extending along the outside of the porous structures. Channels provide fluid communication between the center opening region and the outer region. A first portion of a gas composition is introduced to the center opening region. A second portion of the gas composition is introduced to the outer region. The porous structures are densified from an average density of less than 0.60 g/cm3 to an average density of greater than 1.70 g/cm3 in a single cycle of non-pressure gradient CVI/CVD.

Abstract: A pressure gradient CVI/CVD process includes providing a furnace defining an outer volume. Porous structures and ring-like spacers are assembled in a stack with a ring-like spacer between each adjacent pair of porous structures. The stack of porous structures is disposed between a bottom plate and a top plate in the furnace, wherein the bottom plate, the stack of porous structures, and the ring-like spacers define an enclosed cavity. A channel provides fluid communication between the enclosed cavity and the outer volume. A gas composition is introduced into the enclosed cavity. A portion of the gas composition flows through the channel. A pressure gradient is maintained between the enclosed cavity and the outer volume. The gas composition in the outer volume is provided at a pressure of at least about 15 torr. The porous structures are densified.

Abstract: A method for densifying porous structures inside a furnace using non-pressure gradient CVI/CVD in a single cycle is described. A hardware assembly for use in the single cycle non-pressure gradient CVI/CVD process is provided as well are process and process conditions are described.

Abstract: A method of chemical vapor infiltration and deposition includes stacking a number of porous structures in a stack in a furnace. The stack has a center opening region extending through the porous structures and an outer region extending along the porous structures. A first portion of a reactant gas is introduced to the center opening region. A second portion of the reactant gas is introduced to the outer region. The first portion and the second portion are controlled proportions thereby introducing predetermined portions of the reactant gas to both the center opening region and the outer region. The change in weight of the entire furnace, including contents, is measured during the chemical vapor infiltration and deposition process. The rate of weight change is monitored.

Abstract: An apparatus and method for densifying porous structures inside a furnace using pressure gradient CVI/CVD. The apparatus includes a stack of porous structures where each porous structure has an aperture therethrough. The apparatus also includes at least one ring-like spacer disposed within the stack of porous structures between neighboring porous structures. The ring-like spacer encircles the apertures of the neighboring porous structures. The stack of porous structures and the at least one ring-like spacer define an enclosed cavity including each porous structure aperture. A channel provides fluid communication between the enclosed cavity and an outer volume defined by the interior surface of the furnace.

Abstract: The invention relates to pressure gradient processes for forcing infiltration of a reactant gas into a porous structure. The process comprises the steps of partially densifying a porous structure with a pressure gradient CVI/CVD process in which a first potion of the porous structure is subjected to greater pressure than a second portion of the porous structure. The process is suited for the simultaneous CVI/CVD processing of large quantities of aircraft brake.

Abstract: A method and apparatus for cooling a furnace configured for processing refractory composites comprising a cooling gas flowed in a closed circuit through the furnace and over a cooling element disposed within the furnace. The cooling gas can flow either by natural convection or a convective force.

Abstract: A hardware assembly is provided for controlling a first portion of gas and a second portion of gas in a furnace. The first portion of the gas is introduced to a center opening region of a stack of porous structures. The second portion of the gas is introduced to an outer region of the stack of porous structures. Most of the gas flows out of the hardware assembly from either the center opening region or the outer region while some of the gas flows out through small holes from the other region. A densification method is also provided with two densification processes in which the gas flows in opposite directions in the two densification processes.

Abstract: A hardware assembly is provided for controlling a first portion of gas and a second portion of gas in a furnace. The first portion of the gas is introduced to a center opening region of a stack of porous structures. The second portion of the gas is introduced to an outer region of the stack of porous structures. Most of the gas flows out of the hardware assembly from either the center opening region or the outer region while some of the gas flows out through small holes from the other region. A densification method is also provided with two densification processes in which the gas flows in opposite directions in the two densification processes.

Abstract: A method and apparatus for cooling a furnace configured for processing refractory composites comprising a cooling gas flowed in a closed circuit through the furnace and over a cooling element disposed within the furnace. The cooling gas can flow either by natural convection or a convective force.

Abstract: A hardware assembly is provided for controlling a first portion of gas and a second portion of gas in a furnace. The first portion of the gas is introduced to a center opening region of a stack of porous structures. The second portion of the gas is introduced to an outer region of the stack of porous structures. Most of the gas flows out of the hardware assembly from either the center opening region or the outer region while some of the gas flows out through small holes from the other region. A densification method is also provided with two densification processes in which the gas flows in opposite directions in the two densification processes.

Abstract: The invention relates to method and apparatus for cooling a furnace configured for processing refractory composites. More specifically, the invention is directed to method and apparatus for cooling a furnace more rapidly than prior art methods. According to the invention, a cooling gas is flowed in a closed circuit through the furnace, over the refractory composites disposed within the furnace, and over a cooling element disposed within the furnace. The cooling gas may be flowed by natural convection or by force.

Abstract: The invention relates to method and apparatus for cooling a furnace configured for processing refractory composites. More specifically, the invention is directed to method and apparatus for cooling a furnace more rapidly than prior art methods. According to the invention, a cooling gas is flowed in a closed circuit through the furnace, over the refractory composites disposed within the furnace, and over a cooling element disposed within the furnace. The cooling gas may be flowed by natural convection or by force.

Abstract: The invention relates to the field of high temperature composites made by the chemical vapor infiltration and deposition of a binding matrix within a porous structure. More particularly, the invention relates to pressure gradient processes for forcing infiltration of a reactant gas into a porous structure, apparatus for carrying out those processes, and the resulting products. The invention is particularly suited for the simultaneous CVI/CVD processing of large quantities (hundreds) of aircraft brake disks.

Abstract: The invention relates to a susceptor lid for use in a CVI/CVD furnace. More specifically, the invention is directed to a lid configured to consecutively run CVI/CVD and heat treatment processes without opening the furnace. The susceptor lid according to the invention comprises: a susceptor lid body having a gas exhaust hole, the susceptor lid body having a top surface and a bottom surface; and an exhaust lid disposed over the gas exhaust hole, with a clearance between the exhaust lid and the gas exhaust hole such that exhaust gas pressure within the clearance is approximately equal to, or less than the exhaust gas pressure within the gas exhaust hole, the exhaust lid being positioned to block the majority of the radiation from below the bottom surface of the susceptor lid body.

Abstract: A gas preheater for use in a CVI/CVD furnace that receives a reactant gas from a gas inlet, comprising a sealed baffle structure disposed within the furnace. The sealed baffle structure has a baffle structure inlet and baffle structure outlet. A sealed duct structure is disposed within the furnace, said sealed duct structure being sealed around the gas inlet and said baffle structure such that substantially all of the reaction gas received from the gas inlet is directed to and forced to flow through said sealed baffle structure to said baffle structure outlet.