Vljudno vas vabimo na cikel predavanj prof. dr. Bikramjit-a Basu-ja (Materials Research Center, Indian Institute of Science, Bangalore, INDIA), ki se bodo zvrstila v času od 9. do 12. aprila 2018. Predavanja bodo v predavalnici DS-P1 na Aškerčevi cesti 6, Ljubljana.  

                                                                                    Ponedeljek,  9. 4. 2018 ob 9.00 v predavalnici DS-P1

Lecture a title “Engineering ceramics and their composites - An Overview”

Engineering ceramic materials are widely being investigated as an alternative to traditional metallic materials for various demanding tribological applications. Such widespread research interests are driven by the fact that ceramics have a clear advantage over metallic materials, in terms of high elastic modulus, high hardness, high compressive strength as well as ability to retain properties at high temperature. However, the reliability of ceramics in view of their brittleness or poor facture toughness remain a major challenge. Another issue is the sensitivity of ceramics towards environmental degradation in properties. This presentation will cover the conventional manufacturing of ceramics with a particular emphasize on understanding the process science.

Torek,  10. 4. 2018 ob 9.00 v predavalnici DS-P1

Lecture a title “Engineering ceramics: Tailoring material variables for tribological application of Ceramics”

This presentation will provide an overview of the experimental results from our groups, where we will demonstrate the microsturucture-toughness-wear correlation in some of the model ceramic systems. Specific examples of the case studies from our own research will be provided to demonstrate how humid atmosphere or high temperature environment influence the wear properties of structural ceramics of cutting tool cermets, respectively. We will also discuss the specific advantages and disadvantages of the surface coatings under various tribological scenario, including abrasion, erosion etc.Finally, we will presenthow the material characteristics define their properties and tribologicalresponse as well as how to design ceramic-based materials for specific tribological application.

Sreda,  11. 4. 2018 ob 9.00 v predavalnici DS-P1

Lecture a title “Thermo-erosive stability assessment of ZrB₂-SiC composites for supersonic applications: Experimental and computational analysis”

Among ultrahigh temperature ceramics (UHTC), ZrB₂-based ceramics have received the most attention for applications in the leading edge of hypersonic space vehicles. Despite significant research efforts, the development of ZrB₂-SiC based ceramics in reference to performance-qualifying property assessment (shock resistance, ablation, etc.) together with the design of thermal protection system(TPS) has not been extensively reported in literature. While briefly presenting our recent research in this direction, I shall discuss myriad of opportunities and challenges ahead in TPSdesign for hypersonic space vehicles.

This presentation will mostly focus on the thermo-erosive stability of spark plasma sintered ZrB₂-SiC based multiphase ceramic composites using a combination of experimental work and computational analysis. High temperature erosion tests were conducted at 1073K in thermo-erosive environment for 1200 seconds. The careful selection of test parameters allows us to conduct the experiment with the net energy deposition per unit area of 50.5 MJ/m². Based on the extensive XRD and SEM-EDS analysis, the thermo-erosive mechanisms are qualitatively discussed. Extensive finite element (FE) analysis with high quality structural elements was conducted to determine the spatial temperature and stress distribution in the eroded region. Besides, the thermodynamic feasibility of competing oxidation reactions at the analytically computed temperatures was thereafter realistically assessed to support the oxidation mechanisms. Summarising, the presentation will provide a thorough understanding on the thermo-erosive-structural stability in applications, where erosion can limit the performance of ceramic composites.

Četrtek,  12. 4. 2018 ob 8.00 v predavalnici DS-P1

Lecture a title “Exploring Sliding wear of Materials at Cryogenic Environment”

In last few decades, the researchers have developed significant understanding on the tribological behavior of ceramics in ambient and high temperatures under unlubricated conditions, with less understanding at subzero temperatures. It is recognized that the source of experimental results in such demanding triboenvironment is rather limited and only leading space laboratories such as NAL, Japan and NASA, USA have reported their findings in a small number of technical reports, not available in the scientific community readily. This presentation will provide an overview of the experimental results from our groups to demonstrate the results of some critical experiments to unravel the influence of the cryogenic environment on the sliding wear behavior of engineering ceramics. In particular, our recent research results on brittle ceramics (Al₂O₃, ZrO₂) as well as on some high purity metals (Ti, Cu etc.) will be presented. Based on the results discussed in the presentation, SiC ceramics emerge as better ball bearing materials for cryogenic wear applications in space shuttle.

Due to the inherent dependence of thermal and mechanical properties of materials on the temperature, it will be emphasized that one should consider the microstructural changes that take place underneath the tribocontact as well as and the effect of changes in materials properties on the friction and wear behavior at cryogenic temperatures. The presented work is highly relevant to space scientists, who are involved in the selection and design of materials for ball bearings applications in high-speed cryogenic turbopumps.