Papers by Keyword: Metal Composites

Abstract: Melamine formaldehyde composites have been synthesized with chlorides and micro- and nanoparticles of transition metals (Co, Ni, Cu) entered into polymer during the polycondensation of melamine with formaldehyde. The received composites were studied by the X-ray diffraction and scanning electronic microscopy and applied as catalysts to cathode activation in cyclohexanone electrohydrogenation. For composites of MF+MCl₂ it was established higher catalytic activity than for МF+М⁰.

Abstract: This paper presents a new ignition technique to synthesize NiAl based composites using high frequency induction heating to ignite the combustion reaction. A high resolution thermal imaging camera and two infrared thermometers were used to monitor the complete temperature profiles during synthesis. Thermodynamic calculations were performed to predict the combustion temperature and the effect of preheating temperatures. The results show that the combustion reaction for Ni/Al based composites can be ignited using a high frequency induction heater. High density, multi layer TiC-NiAl composites can be produced using this method, but to ignite the combustion reaction by induction heating for the Ni/Al+Ti/C system, there is a limit for the content of Ti/C, above which the ignition will not start. Ultra fine TiC was synthesized using this technique.

Abstract: In this study, metal composite feed stocks were prepared and test samples were produced by powder injection molding and Multiple Live-Feed Molding (MLFM) devices to investigate the effects of fiber content and macro-shear on the fiber fracture. Fiber-length was measured using an image processing system. The results showed that the fiber volume content increased fiber fracture by 9% and viscosity showed 10% increase in fiber fracture. Samples produced by MLFM devices showed a 1% higher fiber fracture compared to the test bars produced by injection molding. Tensile strength of composites was calculated using fiber contents and fiber length. Considerable increase in tensile strength was noted for metal composites with fiber length above a critical length.

Abstract: A model based on the geometry of the phases is introduced in order to investigate the mechanical properties of interpenetrating microstructures. In order to characterize the elastic and elastic-plastic properties of the composite a self consistent unit cell model is applied on a wide range of volume fractions for an Al/TiO₂ composite. Besides the volume fraction a microstructural based parameter is used, the matricity, to describe the mutual circumvention of both phases. Computations are carried out for different temperatures and void volume fractions. In addition a conservative fracture criterion based on critical normal stresses is applied to derive realistic stress strain curves.

Abstract: Nanostructured composites inspired by structural biomaterials such as bone and nacre form intriguing design templates for biomimetic materials. Here we use large scale molecular dynamics to study the shock response of nanocomposites with similar nanoscopic structural features as bone, to determine whether bioinspired nanostructures provide an improved shock mitigating performance. The utilization of these nanostructures is motivated by the toughness of bone under tensile load, which is far greater than its constituent phases and greater than most synthetic materials. To facilitate the computational experiments, we develop a modified version of an Embedded Atom Method (EAM) alloy multi-body interatomic potential to model the mechanical and physical properties of dissimilar phases of the biomimetic bone nanostructure. We find that the geometric arrangement and the specific length scales of design elements at nanoscale does not have a significant effect on shock dissipation, in contrast to the case of tensile loading where the nanostructural length scales strongly influence the mechanical properties. We find that interfacial sliding between the composite’s constituents is a major source of plasticity under shock loading. Based on this finding, we conclude that controlling the interfacial strength can be used to design a material with larger shock absorption. These observations provide valuable insight towards improving the design of nanostructures in shock-absorbing applications, and suggest that by tuning the interfacial properties in the nanocomposite may provide a path to design materials with enhanced shock absorbing capability.

Abstract: In this paper the authors propose a new technology for high volume fraction ceramic/metal composites—pseudo-semi-solid thixoforging, based on metal semi-solid process combing with traditional powder metallurgy technology, and explain the differences with other technologies and characters in detail. At the same time the authors prepare the cup shells with high volume fraction Al2O3/Al composite by this technology. It proves that it is feasible for the high volume fraction ceramic/metal composites forming through metallographic analyses and three-point bending tests. The results show that the tough strength and degree of hardness of the samples with certain plasticity are high. It will play a very big role in accelerating the ceramics composites and high melt point materials being used in more fields and tamp the foundation for further studies of this technology.