THE METHODS TO AVOID THE FORMATION OF METALLIC SILICIDE AT THE INTERFACE OF METAL/SILICON NITRIDE, AND THEIR APPLICATION FOR JOININGS

研究了金属与氮化硅高温反应的动力学和机理。本研究的目的是描述金属/氮化硅界面不形成脆性产物的条件。由于一些金属硅化物的力学性能以及金属和硅体系的固溶体的报道较少，促使我们对它们进行研究。测定了硅化物和固溶体的机械强度、杨氏模量和线性热膨胀系数。由于固溶体具有延展性，因此它们似乎适合于连接。利用片状金属和氮化硅样品，对反应层进行了观察。镍在1273 k和1373 k时只形成固溶层，没有硅化物。金属硅化层在铁和钴的情况下，甚至在1173 k形成。镍固溶体中硅含量很低，且分布均匀。反应动力学服从线性速率定律。因此，速率决定步骤是氮化硅的分解反应。反应速率常数可表示为：k(ms^<-1>) = 2.0 × 10^<-4> exp（-165kJmol^<-1>/RT）。采用粉末金属-氮化硅混合物，通过测量反应过程中释放的氮来观察反应行为。实验结果与块状试样的结果基本一致。镍合金中的铝、钛、铬等合金元素促进了氮化硅的分解。但是，它们的大量存在对合金元素形成氮化物和硅化物的固溶形成有不利的影响。

THE KINETICS AND MECHANISM OF HIGH TEMPERATURE REACTIONS OF METALS WITH SILICON NITRIDE WERE INVESTIGATED. IT WAS THE PURPOSE OF THE PRESENT INVESTIGATION TO DESCRIBE THE CONDITIONS TO FORM NO BRITTLE PRODUCTS AT THE INTERFACE OF METAL/SILICON NITRIDE. THE PAUCITY OF REPORTS ON MECHANICAL PROPERTIES OF SOME METAL SILICIDES AND THE SOLID SOLUTIONS OF METAL AND SILICON SYSTEMS PROMPTED US TO INVESTIGATE THEM. MECHANICAL STRENGTH, YOUNG'S MODULUS AND LINEAR THERMAL EXPANSION COEFFICIENTS OF THE SILICIDES AND SOLID SOLUTIONS WERE MEASURED. BECAUSE THE SOLID SOLUTIONS WERE DUCTILE THEY APPEARED TO BE SUITABLE FOR JOINING. USING PLATE LIKE SAMPLES OF METALS AND SILICON NITRIDE, THE REACTION LAYERS WERE OBSERVED. IN THE CASE OF NICKEL, ONLY A SOLID SOLUTION LAYER WAS FORMED WITHOUT ANY SILICIDES AT 1273 K AND 1373 K. METALS SILICIDE LAYERS WERE FORMED IN THE CASES OF IRON AND COBALT EVEN AT 1173 K. THE SILICON CONTENT OF NICKEL SOLID SOLUTION WERE VERY LOW AND ITS DISTRIBUTION WAS UNIFORM. AND THE REACTION KINETICS OBEYED THE LINEAR RATE LAW. THUS, THE RATE DETERMINING STEP WAS THE DECOMPOSITION REACTION OF SILICON NITRIDE. THE REACTION RATE CONSTANT CAN BE EXPRESSED AS FOLLOWS: k(ms^<-1>) = 2.0 x 10^<-4> exp(-165kJmol^<-1>/RT). USING POWDERED METAL-SILICON NITRIDE MIXTURES, THE REACTION BEHAVIORS WERE OBSERVED BY MEANS OF MEASUREMENTS OF THE LIBERATED NITROGEN DURING THE REACTIONS. THE RESULTS OF THE EXPERIMENTS AGREED APPROXIMATELY WITH THOSE OF BLOCK SAMPLES. FURTHERMORE, THE ALLOYING ELEMENTS SUCH AS ALUMINUM, TITANIUN AND CHROMIUM IN NICKEL ALLOY PROMOTED THE DECOMPOSITION OF SILICON NITRIDE. BUT, THE LARGE AMOUNTS OF THEM HAD A BAD EFFECT ON THE SOLID-SOLUTION FORMATIONS TO FORM NITRIDE AND SILICIDE OF THE ALLOYING ELEMENTS.