Consolidation and Densification Methods For Fibrous Monolith Processing

Abstract

Methods for consolidation and densification of fibrous monolith composite structures are provided. Consolidation and densification of two- and three-dimensional fibrous monolith components having complex geometries can be achieved by pressureless sintering. The fibrous monolith composites are formed from filaments having at least a first material composition generally surrounded by a second material composition. The composites are sintered at a pressure of no more than about 30 psi to provide consolidated and densified fibrous monolith composites.

1 . A process for consolidation and densification of fibrous monolith composite materials comprising: 
 a. providing a fibrous monolith composite material including a first uniformly suspended mixture forming a central portion and a second uniformly suspended mixture forming a boundary portion, the first uniformly suspended mixture generally surrounded by the second uniformly suspended mixture,    b. heating the fibrous monolith composite material at a first temperature below at least one of the melting temperatures of the first and second uniformly suspended mixtures, and    c. holding for a period of time before heating to a second temperature greater than the first temperature, at a pressure of between about 1 to about 30 psi, to consolidate and densify the first and second uniformly suspended mixtures.    
   
   
       2 . The process of  claim 1  wherein the first temperature is below the lowest melting temperature of the first and second uniformly suspended mixtures.  
   
   
       3 . The process of  claim 1  wherein at least one of the first or second uniformly suspended mixtures contains a sintering aid.  
   
   
       4 . The process of  claim 3  wherein said sintering aid is selected from the group consisting of aluminum oxide and yttrium oxide with silicon nitride, silicon carbide with zirconium carbide, zirconium metal with zirconium diboride, or hafnium hydride and carbon with hafnium carbide.  
   
   
       5 . The process of  claim 1  wherein said central portion comprises a structural material selected from the group consisting of a metal, metal alloy, carbide, nitride, boride, oxide, phosphate or silicide, or a combination thereof.  
   
   
       6 . The process of  claim 5  wherein the composition of the second uniformly suspended mixture comprises a material selected from the group consisting of fluoromica, lanthanum phosphate, graphite, boron nitride, nickel oxide, iron oxide, metal powder, or metal alloy.  
   
   
       7 . The process of  claim 1  wherein the first and second uniformly suspended mixtures include powders selected from the group consisting of diamond, graphite, ceramic oxides, ceramic carbides, ceramic nitrides, ceramic borides, ceramic silicides, metals, or intermetallics.  
   
   
       8 . The process of  claim 7  wherein the first and second uniformly suspended mixtures include powders selected from the group consisting of aluminum oxides, barium oxides, beryllium oxides, calcium oxides, cobalt oxides, chromium oxides, dysprosium oxides, hafnium oxides, lanthanum oxides, magnesium oxides, manganese oxides, niobium oxides, nickel oxides, tin oxides, aluminum phosphate, yttrium phosphate, lead oxides, lead titanate, lead zirconate, silicon oxides, silicates, thorium oxides, titanium oxides, uranium oxides, yttrium oxides, yttrium aluminate, zirconium oxides, zirconium oxide alloys, boron carbides, iron carbides, hafnium carbides, molybdenum carbides, silicon carbides, tantalum carbides, titanium carbides, uranium carbides, tungsten carbides, zirconium carbides, aluminum nitrides, cubic boron nitrides, hexagonal boron nitrides, hafnium nitride, silicon nitrides, titanium nitrides, uranium nitrides, yttrium nitrides, zirconium nitrides, aluminum boride, hafnium boride, molybdenum boride, titanium boride, zirconium boride, molybdenum disilicide, alkali metals, alkali metal alloys, alkali earth metals, alkali earth metal alloys, titanium, iron, nickel, chromium, cobalt, molybdenum, tungsten, hafnium, rhenium, rhodium, niobium, tantalum, iridium, platinum, zirconium, palladium, transition metals, transition metal alloys, cerium, ytterbium, rare earth metals, rare earth metal alloys, aluminum, carbon, lead, tin, silicon, or a combination thereof.