This CAREER program describes an integrated research and educational project to develop hard and tough boron carbide and aluminium magnesium boride based laminates with controlled compressive and tensile stresses in separate layers. The research produces fundamental knowledge and understanding of the interrelationships between processing, residual stresses, and mechanical behavior of boron rich multilayered ceramic composites. This project will lead to the development of wear resistant, damage-tolerant ceramics with enhanced mechanical properties far exceeding those of currently available non-oxide ceramics. The proposed project provides an ideal basis for mechanical, Materials and aerospace engineering students to actively participate in project-based learning. Integrated research and educational activities include outreach to a diverse group of middle and high school students and research opportunities and course enhancements for undergraduate students. Graduate students are involved in research, presentations at technical meetings, and mentor undergraduate and high school student researchers. Special efforts are made to attract underrepresented students to careers in materials science and engineering through the high school outreach and undergraduate research components. In addition, students will benefit from global research opportunities through the project's collaboration with a new network of international researchers. Ultimately, societal benefits will come with the development of novel reliable and robust systems and devices. TECHNICAL DETAILS: Laminates with strong interfaces provide high fracture toughness, increased wear resistance and damage tolerance. As a result, these composites exhibit improved reliability and durability. The enhancement of the mechanical performance of laminates is obtained through design of controlled residual stresses in separate layers. The proposed modeling-experimental program is designed to demonstrate unequivocally that the concept of controlled residual stresses can be employed to produce high performance ceramic laminates. Samples of boron rich multilayered ceramics with controlled residual stresses are designed and further manufactured by rolling and hot pressing/hot isostatic pressing. Additionally, tape casting and spark plasma sintering are to be used for the laminate manufacturing. The research results in a clear identification of the microstructural parameters that control residual stresses in laminates. Mechanical properties such as strength, hardness, wear resistance, and fracture toughness are to be measured to confirm the increase in the mechanical performance of the laminates. The PI takes part in a Bridges summer program at her university to attract bright and talented students to engineering. Graduate and undergraduate students have a unique opportunity to be a part of a cutting-edge, international materials development research team and to publish their results.
The project deals with the design and development of boron rich ceramics design as laminate or particulate ceramic composites prepared by different processing techniques. B4C ceramic laminates with strong or weak interfaces could be manufactured using hot pressing technique to produce bulk dense ceramic composites. The ReB2, OsB2, and Ir-B ceramic nanopowders are to be produced by mechanochemical synthesis, as no other technique allows the processing of these hard to synthesize boron rich solids. OsB2 ceramic was densified by Spark Plasma Sintering. . It was also shown that AlMgB14 ceramics could be produced by direct sintering of Al, Mg, and B powder during hot pressing or Spark Plasma Sintering techniques. Al-B4C and Al-Al2O3 metal matrix composites are to be produced by the metal infiltration technique. All the composites exhibited unique mechanical behavior. The fracture toughness of layered ceramic composites was significantly increased as a result of the presence of thermal compressive residual stresses preventing the catastrophic crack propagation, while OsB2 ceramic exhibited very high hardness and Young’s modulus as measured by nanoindentation. One ReB2-type hexagonal OsB2 phase and three Ir-B phases: ReB2-type and AlB2 type IrB2 and orthorhombic IrB monoboride phases - were synthesized for the first time using mechanochemical synthesis approach. A high hardness of 32GPa and high Young’s modulus of 572 GPa of ReB2 tyoe hexagonal OsB2 phase was measured using nanoindentation. The project allowed training of undergraduate and graduate students, including participation of one MS student at Ecole Polytechnique de Lausanne, where the PI performed research during her sabbatical year with the support of NSF-ERC research initiative.
