摘要:
A porous mullite composition is made by Forming a mixture of one or more precursor compounds having the elements present in mullite (e.g., clay, alumina, silica) and a property enhancing compound. The property enhancing compound is a compound having an element selected from the group consisting of Mg, Ca, Fe, Na, K, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu, B, Y, Sc, La and combination thereof. The mixture is shaped and to form a porous green shape which is heated under an atmosphere having a fluorine containing gas to a temperature sufficient to form a mullite composition comprised substantially of acicular mullite grains that are essentially chemically bound.
摘要:
A porous mullite composition is made by forming a mixture of one or more precursor compounds having the elements present in mullite (e.g., clay, alumina, silica) and a property enhancing compound. The property enhancing compound is a compound having an element selected from the group consisting of Mg, Ca, Fe, Na, K, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, B, Y, Sc, La and combination thereof. The mixture is shaped and to form a porous green shape which is heated under an atmosphere having a fluorine containing gas to a temperature sufficient to form a mullite composition comprised substantially of acicular mullite grains that are essentially chemically bound.
摘要:
A process for preparing complex-shaped, ceramic-metal composite articles, comprising: (a) contacting a non-wettable powder that is non-wetting to a metal to be used for infiltration with a shaped ceramic body to form a layer of the non-wettable powder on one or more surfaces of the shaped ceramic body, wherein the shaped ceramic body has a region where there is no layer of the non-wettable powder, and (b) infiltration the shaped ceramic body with the metal through the region or regions where there is no layer of the non-wettable powder, such that a complex-shaped ceramic-metal composite comprising one or more metal phases and one or more ceramic phases is formed, wherein the article has substantially the net shape of the shaped ceramic body and undesirable regions of excess metal on the surface and undesirable phases within the complex-shaped ceramic-metal composite article near the surface are located only in the region or regions where there is no layer of the non-wettable powder. The process of the invention allows the preparation of complex-shaped ceramic-metal composite articles with undesirable regions of excess metal and undesirable phases on the surface(s), of, or within, the article only in the regions where there is, or was, no layer of non-wettable powder. The process of the invention allows the preparation of a complex-shaped ceramic-metal composite article which requires little or no machining of the surface(s) to achieve a finished article. A complex-shaped ceramic-metal composite article is prepared which contains few undesirable regions of excess metal and undesirable phases.
摘要:
A process for preparing complex-shaped, ceramic-metal composite articles, comprising:a) contacting a non-wettable powder that is non-wetting to a metal to be used for infiltration with a shaped ceramic body to form a layer(s) of the non-wettable powder on one or more surface(s) of the shaped ceramic body wherein the shaped ceramic body has a region(s) where there is no layer of the non-wettable powder;b) infiltrating the shaped ceramic body with the metal through the region(s) where there is no layer of the non-wettable powder such that a complex-shaped ceramic-metal composite comprising one or more metal phases and one or more ceramic phases is formed, wherein the article has substantially the net shape of the shaped ceramic body and the undesirable regions of excess metal on the surface and undesirable phases within the complex-shaped ceramic-metal composite article near the surface are located only in the region(s) where there is no layer of the non-wettable powder.A complex-shaped ceramic-metal composite article with undesirable regions of excess metal and undesirable phases on the surface(s) of or within the article only where there is or was no layer of non-wettable powder.The process of the invention allows the preparation of complex-shaped ceramic-metal composite articles with undesirable regions of excess metal and undesirable phases on the surface(s) of or within the article only in the regions where there is or was no layer of non-wettable powder. The process of the invention allows the preparation of a complex-shaped ceramic-metal composite article which requires little or no machining of the surface(s) to achieve a finished article. A complex-shaped ceramic-metal composite article is prepared which contains few undesirable regions of excess metal and undesirable phases.
摘要:
Ceramic metal compositions are described that include a ceramic phase content of at least 60 percent by volume of said composition and a copper metal phase permeating the ceramic phase. The resulting composition is substantially fully densified, having a connected or isolated ceramic grain structure, preferably of fine B.sub.4 C grains of less than 3 micrometers. Flexure strength and fracture toughness for 80 volume percent B.sub.4 C-20 volume percent Cu cermets are 6.62 MPa.multidot.m1/2 and 725 MPa, respectively. The process of the invention includes as a key element, contacting a porous article of ceramic phase with copper metal followed by heating to above melting and subjecting said article to pressure of at least 200 MPa, such that the porous body is filled with metal and the composition is substantially fully densified.
摘要:
Reactive ceramic-metal compositions are described that include a ceramic phase of at least 70 percent by volume, 95 percent of theoretical density and a metal phase that retains its chemical reactivity with the ceramic phase after the composition has been fully densified. The composition may be heat treated after densification to form additional ceramic phases in a controllable manner. Preferred ceramic metal compositions wherein the metal and ceramic components retain reactivity after densification include boron carbide ceramic and Al or Mg metals. The process employed in forming said compositions requires first forming a sintered porous body of the ceramic material followed by contacting with the metal component, which may be in chip or solid bar form. The system is then heated to the melting point of the metal and a pressure of at least 200 MPa is employed such that the porous body is filled with metal and the composition is substantially fully densified. Subsequent heating reacts the metal with the ceramic to form additional B-C-metal phases as desired.
摘要:
An improved soot catalyst is comprised of an alkali compound at least partially coated by a ceramic coating comprised of C bonded to a metal, semimetallic element or combination thereof. The improved soot catalyst may be employed in catalyzed Diesel particulate filters. In one method to make a catalyzed Diesel particulate filter, the improved filter is made by contacting a porous ceramic body having an alkali catalyst thereon, coating the alkali catalyst with an organic ceramic precursor, heating the ceramic body to a temperature in an atmosphere sufficient to decompose the organic ceramic precursor to form the soot catalyst on the porous ceramic body without volatilizing substantial amount of the alkali catalyst away.
摘要:
A ceramic honeycomb filter having improved thermal shock resistance is comprised of a ceramic honeycomb filter that has a heat absorbing material that undergoes a reversible phase change that absorbs at least in part the heat energy, for example, arising from the combustion of Diesel soot entrapped in the filter.
摘要:
A ceramic honeycomb filter having improved thermal shock resistance is comprised of a ceramic honeycomb filter that has a heat absorbing material that undergoes a reversible phase change that absorbs at least in part the heat energy, for example, arising from the combustion of Diesel soot entrapped in the filter.
摘要:
An improved soot catalyst is comprised of an alkali compound at least partially coated by a ceramic coating comprised of C bonded to a metal, semimetallic element or combination thereof. The improved soot catalyst may be employed in catalyzed Diesel particulate filters. In one method to make a catalyzed Diesel particulate filter, the improved filter is made by contacting a porous ceramic body having an alkali catalyst thereon, coating the alkali catalyst with an organic ceramic precursor, heating the ceramic body to a temperature in an atmosphere sufficient to decompose the organic ceramic precursor to form the soot catalyst on the porous ceramic body without volatilizing substantial amount of the alkali catalyst away.