Film degradation - sometimes when needed
There are many processes around us, both spontaneous and artificial, with degradation or flaking of the film or coating. A typical example is etching or etching, for example in pipeline infrastructure, which is an undesirable process, but is highly desirable when manufacturing electronic components. Another area where film peeling is required is the use of detergents to remove oil. In both cases, it is important to understand the degradation and flaking of the material so that it can be optimized and controlled. It can prevent unnecessary degradation and increase the rate of falling off the film to be degraded. In order to be able to control this process, degradation or spalling must be simulated and understood. QCM-D, in principle, is a balance that measures tiny masses that can measure and quantify the degradation of the membrane, both quantitatively and in terms of kinetics.
Qualitative and quantitative measurement of film degradation
When the film degrades, the surface loses its mass. The thickness of the initial surface bonding layer is also reduced. This is two parameters that QCM-D can measure in real time at the nanoscale.
Example 1: Evaluating cleaning efficiency
For example, let's look at the degradation of the film when cleaning the surface. We have a greased surface that we want to clean with a detergent. As shown in Figure 1, we follow the steps below.
1. We began to deposit a thin layer of oil on the surface. This layer is the pollutant we are going to remove. The background solution is water. We can see that no mass is removed in this step, ie the oil is insoluble in water.
2. Next, we introduce the detergent and then let it flow on the oil.
3. The detergent will flow over the surface and begin to interact with the oil. Here we can see that the thickness of the oil layer is increasing. This is expected because the detergent will seep into the oil and cause it to swell.
4. Next, the oil begins to break and is peeled off from the surface. We see a decrease in thickness.
5. After the washing step, we add the rinsing step, that is, rinse with water. Once again, we see that as the rinse washes away the oil from the surface, the thickness decreases.
6. Finally, 60% of the oil is removed from the surface.
Figure 1 uses the QCM-D technology to monitor the cleaning process.
Evaluation of film degradation under different conditions
Monitoring mass and thickness as a function of time makes it easy to characterize and evaluate the degradation behavior of the material and the quality of the exfoliation. It is also possible to compare degradation behavior under different conditions, for example by varying concentrations, temperatures and pH values.
Example 2: Comparing the performance of two different detergents
In the first example, we evaluated the desorption behavior and the decontamination efficiency of the detergent, where we extend it. Now, we use the same experimental procedure to compare the cleaning performance of Cleaners A and B. The results of the change in oil thickness over time are shown in Figure 2, indicating that detergent B acts faster than detergent A, but the overall cleaning efficiency is lower. We also noticed that detergent A caused a more pronounced expansion (increased thickness) of the initial oil film than detergent B.
Figure 2 A function of oil thickness as a function of time for evaluating the cleaning effect of two different detergents, water being used as a control.
Other applications for film degradation
In addition to these two examples, other types of degradation can be characterized by measuring mass loss, such as enzymatic reactions, dissolution, photodegradation, and temperature-induced degradation.
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