Low pressure plasmas

Development of innovative thermal insulating layers and coating processes for injection molding tools

In order to produce high-quality injection molds, the optimization of the molding process parameters plays a crucial role. The application of thermal barrier coatings onto the molding block slightly slows down the cooling of the plastics injected into it. This increases the energy efficiency of the injection process, without compromising the quality of the manufactured parts.

To produce these barrier coatings metal organic chemical vapor deposition (MOCVD) combined with plasma activation is explored (PECVD). Significant improvements are expected regarding the achievable growth rates of the coatings
(>500 nm/h) as well as the required layer thicknesses
(<30 μm). 

Injection molds for plastics processing require coatings for corrosion protection and thermal insulation. For this, a low permeation of the coating material is necessary to avoid the contact of tool surfaces with corrosive media and thus extend their lifetime.

The project investigates the insulating effect of deposited zirconium oxide ceramic coatings. The development and characterisation of deposited ceramic layers will be the main focus of this project. 

Measurements via the 3w method will be used to perform in-situ measurements of the thermal conductivity of the layers.

Videos

A video in German presenting the deposition chamber can be found here:

 

Surface processes in the interaction of high-performance plasmas with HPPMS target surfaces and plastics

In a particle beam experiment, elementary  plasma processes on surfaces are mimicked by sending quantified beams of atoms or ions to metal or plastic surfaces. By this, the production of secondary electrons, the reactive sputtering and layer growth is directly being investigated. Furthermore, the plasma activation of plastic surfaces, barriers and membranes will be analysed. 

In the in-vacuo XPS-HPPMS system, parameters of a HPPMS plasma can be linked to a XPS analysis of the target surface. Using grafted HPPMS targets, the spatial transport of metal atoms in the HPPMS plasmas is investigated. Different Al-Cr-Ti composite and powder metallurgically manufactured targets will be sputtered in reactive Ar/O2 gas mixture and then analysed. Plasma treatments with varying parameters are performed for different substrates and the respective effect of the plasma on the substrate surface is analyzed using XPS.

 

Videos

A video in German presenting the particle beam experiment can be found here:

A video in German presenting XPS chamber can be found here:

 

 

Controlling the permeation of nanocomposite materials

Development of barrier/membrane coatings from silicon oxides with superior mechanical properties (internal stress, porosity, roughness, hardness), specific material composition (studied via FTIR, XPS), and excellent ductility (by embedding silicon nanoparticles in the SiOx matrix).

The aim is to systematically investigate the parameter space for the production of nanocomposite layers as a balance between nanoparticle concentration, matrix layer material (SiOx, SiOCH, a-C:H,
a-Si:H) and layer thickness. It is expected that a low density of nanoparticles will lead to a reduction of the stress in those layers.

 

Videos

A video in German presenting the multi chamber can be found here:

A video in German presenting ICP plasmas can be found here:

 

 

High Power Impulse Magnetron Sputtering (HIPIMS)

 

https://oc-video1.ruhr-uni-bochum.de/paella/ui/watch.html?id=f104a409-5bf6-4feb-b15a-71f6f6165629
figure 1

Magnetron sputtering is a widely used physical vapor deposition (PVD) technique. In magnetron sputtering, permanent magnets are placed behind a piece of metal, a so-called target. The magnetic field confines electrons to the region close to the target, where they can efficiently ionize the working gas (usually argon). A negative voltage is applied to the target, which will attract working gas ions towards the target. These ions hit the target with such high kinetic energy that they remove atoms from the target surface on impact. This process is called sputtering. Sputtered target atoms move through the discharge towards a workpiece, where they form a coating.

High power impulse magnetron sputtering (HiPIMS) is a relatively recent variation where short high voltage pulses are applied to the target instead of a continuous voltage. The result is the formation of very dense transient plasmas with a high fraction of ionized species, improving the quality of the deposited coatings in terms of density, adhesion, and hardness. However, depositing a coating of comparable thickness takes longer with HiPIMS than with traditional magnetron sputtering.

Within the frame of the project DFG TR87, our goal is to understand the physical process inside these HiPIMS plasmas with a particular focus on finding pathways to improve the deposition rate. We employ a wide variety of diagnostic methods, such as time and spatially resolved optical emission spectroscopy, a collection of different electric and magnetic probes, and energy-resolved mass spectrometry. These plasma diagnostics are combined with surface characterization methods such as x-ray photoelectron spectroscopy, which we use to characterize the surface chemistry of the deposited films or the target. 

Videos

Here is a spoke video:

A video in German presenting HiPIMS plasmas can be found here: