Boron carbide-aluminum cermets having microstructures tailored by a
post-densification heat treatment
    74.
    发明授权
    Boron carbide-aluminum cermets having microstructures tailored by a post-densification heat treatment 失效
    具有通过后致密化热处理定制的微结构的碳化硼 - 铝金属陶瓷

    公开(公告)号:US5298468A

    公开(公告)日:1994-03-29

    申请号:US960612

    申请日:1992-10-13

    摘要: Densified boron carbide-aluminum, ceramic-metal composites that are substantially free of AlB.sub.12, AlB.sub.12 C.sub.2 and Al.sub.4 C.sub.3 result from a two stage process. Admixtures of boron carbide are densified under pressure in stage one, In stage two, the densified admixture is heat treated. In both stages, the temperature is less than 800.degree. C. If the temperatures do not exceed 600.degree. C., the resultant densified cermet has only three phases: a) boron carbide; b) Al.sub.4 BC; and c) aluminum.

    摘要翻译: 基本上不含AlB12,AlB12C2和Al4C3的致密碳化硼 - 铝,陶瓷 - 金属复合材料来自两阶段工艺。 在第一阶段,碳化硼的外加剂在压力下致密化。在第二阶段中,将致密化的混合物进行热处理。 在两个阶段中,温度低于800摄氏度。如果温度不超过600摄氏度,则所得到的致密金属陶瓷只有三个阶段:a)碳化硼; b)Al4BC; 和c)铝。

    Cermet or ceramic/glass composites including self-reinforced
.beta.-Silicon nitride, and method of making same
    75.
    发明授权
    Cermet or ceramic/glass composites including self-reinforced .beta.-Silicon nitride, and method of making same 失效
    金属陶瓷或陶瓷/玻璃复合材料,包括自增强β-硅氮化物及其制造方法

    公开(公告)号:US5269989A

    公开(公告)日:1993-12-14

    申请号:US938633

    申请日:1992-09-01

    摘要: Infiltrate a porous, self-reinforced .beta.-Si.sub.3 N.sub.4 preform with a metal or a crystallizable glass to yield a composite material. The preform possesses a low glass phase and has a density of from about 50 to about 70 percent of theoretical density. Prepare the .beta.-Si.sub.3 N.sub.4 preform by subjecting a porous body formed from an .alpha.-Si.sub.3 N.sub.4 powder composition to two sequential heat treatments. The first heat treatment occurs below the .alpha.- to .beta.- conversion temperature and results in a strengthened body that can be machined. The second heat treatment occurs above that temperature and yields the self-reinforced .beta.-Si.sub.3 N.sub.4 preform. Conventional infiltration procedures with an infiltrant that is a metal or a glass results in a Si.sub.3 N.sub.4 /metal or Si.sub.3 N.sub.4 /glass composite material that has 50 to 70 percent of its volume occupied by .beta.-Si.sub.3 N.sub.4 whiskers.

    摘要翻译: 用金属或可结晶玻璃渗透多孔,自增强β-Si3N4预成型体,得到复合材料。 预制棒具有低玻璃相,并且具有理论密度的约50至约70%的密度。 通过将由α-Si 3 N 4粉末组合物形成的多孔体进行两次连续的热处理来制备β-Si 3 N 4预型体。 第一次热处理发生在α至β转化温度以下,并导致可加工的加强体。 第二次热处理发生在该温度以上,并产生自增强的β-Si 3 N 4预制件。 具有金属或玻璃的渗透剂的常规渗透程序导致Si3N4 /金属或Si3N4 /玻璃复合材料,其具有其β-Si 3 N 4晶须占据其体积的50%至70%。

    Dense, self-reinforced silicon nitride ceramic prepared by pressureless
or low pressure gas sintering
    76.
    发明授权
    Dense, self-reinforced silicon nitride ceramic prepared by pressureless or low pressure gas sintering 失效
    通过无压或低压气体烧结制备的密实,自增强氮化硅陶瓷

    公开(公告)号:US5120328A

    公开(公告)日:1992-06-09

    申请号:US657715

    申请日:1991-02-19

    摘要: A dense, self-reinforced silicon nitride ceramic prepared by pressureless sintering or low pressure gas sintering. The composition comprises (a) silicon nitride, at least 20 percent of which is in the form of .beta.-silicon nitride whiskers having a high average aspect ratio, (b) from about 2 to about 10 weight percent of a glassy grain boundary phase containing magnesium oxide, yttrium oxide, silica, zirconia, and optionally, one oxide selected from the group consisting of calcium, gallium, indium and hafnium oxides, and (c) a second crystalline phase in an amount ranging from 0.5 to about 5.0 weight percent comprising zirconium oxide, and (d) optionally, crystalline phases of metal zirconium silicide and/or metal zirconium silicon nitride in a combined amount from 0.1 to 3.0 weight percent, wherein the metal is tantalum, calcium, hafnium, gallium or indium, and wherein when the metal is calcium, hafnium, gallium or indium, the same metal occurs as the metal oxide in the glassy phase. The ceramic exhibits high fracture toughness and high fracture strength and has a density of at least 98 percent of theoretical.

    摘要翻译: 通过无压烧结或低压气体烧结制备的致密的自增强氮化硅陶瓷。 组合物包含(a)氮化硅,其中至少20%是具有高平均纵横比的β-硅氮化物晶须的形式,(b)约2至约10重量%的玻璃态晶界相,其含有 氧化镁,氧化钇,二氧化硅,氧化锆和任选的一种选自钙,镓,铟和铪氧化物的氧化物,和(c)含量为0.5至约5.0重量%的第二结晶相包含 氧化锆和(d)任选的,金属硅化锆和/或金属氮化硅锆的结晶相,其含量为0.1至3.0重量%,其中金属为钽,钙,铪,镓或铟,并且其中当 金属是钙,铪,镓或铟,与玻璃相中的金属氧化物发生相同的金属。 该陶瓷具有高断裂韧性和高断裂强度,其密度至少为理论值的98%。

    Self-reinforced silicon nitride ceramic of high fracture toughness and a
method of preparing the same
    77.
    发明授权
    Self-reinforced silicon nitride ceramic of high fracture toughness and a method of preparing the same 失效
    具有高断裂韧性的自增强氮化硅陶瓷及其制备方法

    公开(公告)号:US5118645A

    公开(公告)日:1992-06-02

    申请号:US572823

    申请日:1990-08-24

    摘要: A process for preparing a self-reinforced silicon nitride ceramic body of high fracture toughness comprising hot-pressing a powdcer mixture containing silicon nitride, a densification aid such as sodium oxide, a conversion aid such as lanthanum oxide and a compound, such as gallium oxide, which enhances growth of .beta.-silicon nitride whiskers-under conditions such that densification and the in situ formation of .beta.-silicon nitride whiskers having a high aspect ratio occur. A novel silicon nitride ceramic of high fracture toughness and high fracture strength is disclosed comprising a .beta.-silicon nitride crystalline phase wherein at least about 20 volume percent of the phase is in the form of whiskers having an average aspect ratio of at least about 2.5; a glassy second phase containing the densification aid, the conversion aid, the compound which enhances growth of .beta.-silicon nitride whiskers, and an amount of silica; and not greater than about 10 weight percent of the total weight as other phases. The glassy phase may also include a minor amount, e.g., up to 5.0 weight percentg, based upon total weight of the ceramic, of aluminum nitride or boron nitride. The glassy phase optionally includes an amount of a secondary reinforcing material such as silicon carbide whiskers.

    摘要翻译: 一种制备高断裂韧性的自增强氮化硅陶瓷体的方法,包括热压含有氮化硅的粉末混合物,致密化助剂如氧化钠,转化助剂如氧化镧和化合物如氧化镓 ,其增强了β-硅氮化物晶须的生长 - 在使得具有高纵横比的β-硅氮化物晶须的致密化和原位形成的条件下。 公开了一种具有高断裂韧性和高断裂强度的新型氮化硅陶瓷,其包括β-氮化硅结晶相,其中该相的至少约20体积百分数为晶须的形式,其平均纵横比为至少约2.5; 含有致密化助剂的玻璃质第二相,转化助剂,增强β-硅氮化物晶须生长的化合物和一定量的二氧化硅; 并且不大于作为其它相的总重量的约10重量%。 玻璃相还可以包括少量,例如,至多5.0重量%,基于陶瓷的总重量,氮化铝或氮化硼。 玻璃相任选地包括一定量的第二增强材料,例如碳化硅晶须。

    Self-reinforced silicon nitride ceramic with crystalline grain boundary
phase, and a method of preparing the same
    78.
    发明授权
    Self-reinforced silicon nitride ceramic with crystalline grain boundary phase, and a method of preparing the same 失效
    具有晶粒边界相的自增强硅氮化硅陶瓷及其制备方法

    公开(公告)号:US5098449A

    公开(公告)日:1992-03-24

    申请号:US657716

    申请日:1991-02-19

    摘要: A fully densified, self-reinforced silicon nitride ceramic body of high fracture toughness and high fracture strength is disclosed comprising (a) .beta.-silicon nitride in the form of whiskers having an average aspect ratio of at least about 2.5, and (b) a crystalline grain boundary phase having an oxynitride apatite structure, as determined by X-ray crystallography.A process for preparing the above identified silicon nitride body comprising hot-pressing a powder mixture containing silicon nitride; silica; a densification aid including strontium oxide; a conversion aid, such as, yttrium oxide; and a compound, such as, calcium oxide which enhances growth of .beta.-silicon nitride whiskers, under conditions such that densification and the in situ formation of .beta.-silicon nitride whiskers having a high aspect ratio occur, and thereafter annealing the densified composition for a time sufficient to produce a crystalline grain boundary phase having an oxynitride apatite structure.