Montag, 22. November 2021

Upcoming Seminar Sylvain Dubois

In the frame of IGK within the SFB-TR 87 will be an online seminar on Monday, December 13th, 2021, 14:00 h – 16:00 h, at Materials Chemistry in Aachen.

Pr. Sylvain Dubois, Université de Poitiers:

Part I:             Recent advances in MAX phase solid solutions,

Veronique Brunet-Gauthier, Université de Poitiers:

Part II:             High-temperature oxidation of alumino-forming MAX phases: relationship between powder metallurgy processing routes, microstructural characteristics and oxidation resistance.

Donnerstag, 11. November 2021

Upcoming Seminar Dr. Helmut Riedl on 16/12/2021

Dr. Helmut Riedl from TU Wien is going to talk on December 16, 2021 in the frame of IGK within the SFB-TR 87 on Thursday, December 16th, 2021, 10:00 h – 12:00 h, at Materials Chemistry in Aachen.

Part I: Durability of physical vapor deposited CrN based coatings – Insights on fracture and fatigue mechanisms 

Tailoring the intrinsic fracture characteristics of hard protective coatings towards the fatigue proper-ties of state-of-the-art bulk materials is paramount for extending the fatigue-life of coated compo-nents. Thus, an in-depth knowledge on the failure pathways of ceramic-based thin films – typically lacking in intrinsic ductility – but also coated components under cyclic loading is imperative to extend their lifetime. Within this seminar, I want to discuss novel approaches in the field of fatigue testing of thin films on the example of dc magnetron sputtered as well as cathodic arc evaporated CrN. 

In detail, to reveal the intrinsic fracture toughness (KIC) and critical failure aspects of thin films under various loading conditions quasi-static and cyclic bending of pre-notched, unstrained micro-cantilever beams in conjunction with in-situ synchrotron X-ray diffraction have been performed. Up to the high-cycle fatigue regime (i.e., N = 107 cycles), the failure of CrN coatings is shown to be dominated by the inherent fracture resistance instead of well-described fatigue phenomena, with further correlations drawn to apparent growth irregularities (i.e. macro particles or structural defects). The observed frac-ture behaviour is further associated with large-scale dynamic-mechanical analysis of coated Ti6Al4V platelets to consider stress fields induced by the coating-substrate interface. The results are expected to provide key-insights into the underlying mechanisms promoting crack growth in PVD coated speci-mens combining the world of micro- and macro scale testing methods. 

Part II: Ternary transition metal diborides: A new generation of protective coating materials? 

Future high-performance components used in aviation or energy production require customized protective coating materials to fulfil specific criteria on efficiency as well as durability. Next to well-established nitride-based coatings are boron containing systems an upcoming and highly promising coating class. Here, ternary transition metal diborides are relatively unexplored compared to their bi-nary counterparts such as hard and inelastic TiB2. Typically, these hard ceramic based coatings fail due to their extremely limited capability for plastic deformation as well as a pronounced formation of vol-atile (boron based) oxides. Within this seminar, I want to discuss these specific challenges for different binary and ternary model systems exhibiting outstanding material properties, i.e. long-term oxidation resistance at 1200 °C or a fracture toughness above 4.8 MPa·m1/2, while maintaining super hardness. To systematically describe various aspects in the design and syntheses of non-reactively sputter de-posited boride-based coating materials, a broad set of high-resolution techniques (i.e. HR-TEM, APT, ERDA, or micro-mechanical testing) but also atomistic modelling (DFT using VASP) is applied. 

Mittwoch, 10. November 2021

Dienstag, 9. November 2021

Upcoming Project Workshop – „Future Ideas and Directions“

Ph.D. students, PostDocs, and affiliated members of SFB-TR 87 are invited to contribute ideas and directions towards future joint plasma and materials science research projects. Inspired by the established insights of the past and current funding phases, we ask every subproject to bring up the most exciting and innovative scientific topic in a short pitch. Brainstorming together in the group will enable to generate new ideas and identify promising directions.

The workshop will proceed in two parts:

  1. Participants review challenges presently encountered, as well as possible pathways envisioned to tackle them. (13.01.2022)
  2. Discussion of the proposed topics with a focus on overlap in research questions and a common agenda for potential future proposals. (date to be defined)

We explicitly invite all project areas of SFB-TR 87 and intend to foster a continued exchange towards future collaborations.

Registration: Via email to all organizers listed below, deadline 13.12.2021

Preliminary Agenda

09.45 - 10.00: Welcome

10.00 - 12.00: Pitches (< 10 minutes) + discussion

12.00 - 13.00: Break

13.00 - 1x:00: (depending on the number of participants)

1x.00: End of workshop


Marcus Hans, RWTH Aachen University,

Jan Trieschmann, BTU Cottbus-Senftenberg,

Montag, 8. November 2021

Upcoming Seminar Dr. Michael Tkadletz

Dr. Michael Tkadletz from the Department of Materials Science, Montanuniversität Leoben will held a presentation (via zoom) in the frame of IGK within the SFB-TR 87 on Wednesday, December 1st, 2021, 10:00 h – 12:00 h, at Materials Chemistry in Aachen.

Part I:
Nanolamellar chemical vapor deposited fcc-Ti1-xAlxN – History, peculiarities and future perspectives

With an Al metal ratio x of ~0.8 while still maintaining a single phase face-centered cubic (fcc) structure, chemically vapor deposited (CVD) Ti1-xAlxN represents an intriguing counterpart to physically vapor deposited (PVD) Ti1-xAlxN, which usually exhibits an fcc/wurtzitic dual phase structure already at Al metal ratios of ~0.6-0.7. Considering the metastable nature of fcc-Ti1-xAlxN and the high deposition temperatures of ~800-900 °C necessary in thermally activated CVD processes, which are commonly considered to result in conditions close to thermal equilibrium, this is even more exceptional. The formation of a predominantly fcc structure at such high Al metal ratios is related to the typically observed unique microstructure of CVD fcc-Ti1-xAlxN, consisting of comparatively large grains with alternating Ti-rich and Al-rich fcc-Ti1-xAlxN nanolamellae exhibiting a periodicity of ~10 nm. Within this talk, the historical evolution and the current state of research on CVD Ti1-xAlxN coatings will be outlined, with a special emphasis on the nanolamellar structure. Important aspects such as thermal stability, age hardening be-havior and oxidation resistance will be discussed on the basis of in situ and ex situ character-ization techniques and the results will be compared with PVD Ti1-xAlxN counterparts. Finally, the role of the deposition parameters, contradictions of recent studies and future perspectives will be illuminated.

Part II: 
Synchrotron radiation based X-ray diffraction techniques for the advanced microstruc-
tural characterization of transition metal nitride coatings  

Within this talk, different synchrotron radiation based X-ray diffraction (XRD) techniques which significantly contribute to the establishment of microstructure-property relationships of complex coating systems will be presented. Special emphasis will be laid on requirements, advantages and disadvantages of the different approaches including sample preparation, experimental ex-ecution, calibration as well as data treatment and evaluation. The presentation will cover high resolution 1D powder XRD for the investigation of phase composition and lattice parameters at room and elevated temperature. In situ 2D powder XRD studies performed in inert and am-bient atmosphere will be discussed to highlight the strength of modern evaluation techniques such as sequential and parametric Rietveld refinement. The potential of the unique instrumen-tal combination of in situ powder XRD with simultaneous differential scanning calorimetry to study the thermal and oxidation stability will be demonstrated, allowing to directly correlate phase changes with the recorded heat flow, while in situ experiments performed on compact coating samples reveal the macroscopic strain throughout such events. In addition, the utiliza-tion of laterally resolved diffraction techniques will be discussed on the example of cross-sec-tional X-ray nanodiffraction applied to graded coating samples. Concluding, synchrotron and lab-based XRD techniques and their pros and cons will be compared.