5. INTERIOR CARS’MATERIALS EMBEDDED WITH MAGNETIC ELEMENTS 41
The test performed on isolatedMnFe2O4nanoparticles revealed a saturation magneti-zation of(62±3)emu/gat a 300Ktemperature and 5Tof an applied field. The presented high values were in the expected range for the NPs, confirming one of the most important reasons for their choice, the notable magnetization that the particles could reach. Liter-ature [67,68] corroborates that in those conditions, the magnetization value obtained is similar to their experiments, certifying the quality of the lab-made MNPs. Yet, the mag-netization does not thoroughly saturate but, instead, has a slow increase with the field.
This phenomenon is not observed in a nanoparticle system since the magnetic moment in-stantly aligns with the applied field. However, as previously referred, among the powder, there are substantial clusters that behave as more complex magnetic materials, possess-ing multiple domains with magnetic moments that can be semi-dependent on each other, contrary to the isolated NPs. In those cases, the magnetic alignment can be difficulted, which retards the complete saturation [69].
Both remanence magnetization and coercive field have associated uncertainties that are greater than the value itself, meaning that, for the used resolution (with only seventy points taken), the quantities can be considered negligible*. The values obtained differ slightly for zero due to NPs’ size distribution since, without the cluster formation, the magnetic moment of each particle would constantly oscillate independent from the rest, preventing multiple equally aligned magnetic moments. This fact would lead to the non-existence of the remanence field, but with the agglomerates’ presence, that independence of moments slightly falls through, allowing few remanence. However, when a minimal external field is applied, the magnetic moments still tend to align with it, reaching close to the saturation magnetization within a small field. Thus, the magnetic properties of the NPs powder indicate encouraging expectations for the following step of NPs embedment into the interior cars’ material to create a magnetic attractive system.
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PROGRAMMABLE MAGNETIC ATTRACTIVE MATERIALS: AN APPROACH FOR SHAPE-CHANGING CARS’INTERIORS
of 300 µm. This procedure allowed the creation of a reference measure of the mass of PVC paste needed for each film. As a precaution, it was always prepared and used in concentration calculus double the reference value, this meaning that for a 300µmfilm, 46 gof PVC paste was used. That way, a 500gbase paste could be divided into four different cups, with 46geach, and then add the desired weight percentage of MNPs. Contrarily, in the lacquers, the same was not possible to be done due to the method used that needs a lacquer bath of 300g, which led to the creation of only one lacquer with a low percentage of MNPs.
TABLE5.1: List of samples fabricated with its identification number, the weight percent-age of NPs in PVC paste, presence of lacquer and weight percentpercent-age of NPs in it, total
thickness (PVC paste + lacquers), and a representative image Sample details
Label NPs in PVC NPs in lacquer Thickness Sample
# (wt%) (wt%) (µm) image
S1 0 0 320
S2 0 1.8 320
S3 2 no lacquer 300
S4 2 0 320
S5 2 1.8 320
S6 4 no lacquer 300
S7 4 0 320
S8 4 1.8 320
S9 13 no lacquer 300
S10 13 no lacquer 550
Table5.1presents all the fabricated samples and their main distinctive characteristics, the weight percentages of NPs in PVC paste and lacquers, complemented by an image of each for a visual demonstration. Samples 1 to 9 were produced with a PVC paste
5. INTERIOR CARS’MATERIALS EMBEDDED WITH MAGNETIC ELEMENTS 43
thickness of 300µm, with some having lacquers applied. Each lacquer, base coat and top coat, added 10µmresulting in some cases in an overall thickness of 320µm. Maintaining the thickness value allowed the study of the influence of the NPs in the film with the increasing weight percentage and the impact of lacquer with NPs.
Tests started using the base PVC paste and producing two samples (samples 1 and 2), one with regular top coat lacquer (Ref sample) and the other with top coat lacquer with a 1.8wt% of NPs both will a full size (A4 size). Creating a reference sample allowed a way to compare the influence of the NPs in PVC paste, while the production of sample 2 permitted the study of the magnetic impact of a reduced concentration lacquer. Moreover, it is possible to denote a visual difference between them since theMnFe2O4nanoparticles have a dark brown/black color and both the paste and lacquer are translucent, an initial confirmation that the embedding was successful.
Afterward, the PVC paste cups with different weight percentages of NPs were pre-pared and used to produce three films, one with each concentration (2, 4, and 13wt%). It was denoted that the presence of NPs in the paste led to the creation of deep scratches in the film, which periodicity would increase with the nanoparticle concentration, compro-mising the integrity of sample 9, the film with 13 wt%. In the other cases, the damage was visible but not critical, something discussed in the following section.
For samples with 2 and 4 wt%, the process after the film production was similar. First, a small strip was cut from the bottom of each film, obtaining samples 3 and 6, respec-tively. After, the rest of the film was coated with the base coat lacquer and posteriorly divided in half. One of the halves had applied the base top coat lacquer, and the other the top coat lacquer with 1.8wt% of NPs. Thus, the film with NPs was maximized to obtain samples with different top lacquers and without any. Visually is understood that increasing the concentration leads to a darker color of the film, resulting in sample 9 being black. Therefore, the overall sample color is modulated by the film, making the different coatings indistinguishable.
As for the 13wt%, due to its integrity problems, it was unfeasible to apply any lacquers to the film, resulting in a singular sample with 300µmthickness. To obtain a film with fewer scratches it was also produced a specimen with 550µm, but even though it had a considerable reduction, the scratches were still too deep to enable the film to go through a coating process.
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PROGRAMMABLE MAGNETIC ATTRACTIVE MATERIALS: AN APPROACH FOR SHAPE-CHANGING CARS’INTERIORS
Nevertheless, all ten samples were analyzed and tested since most experiments only needed a small piece of material to perform the study. Tests ranged from magnetic and structural analysis, using the standard methods of a research environment, to specific analysis usually performed in materials to be applied in cars’ interiors. After the mul-tiple and distinct experiments, it was possible to understand if the NP’s influence turns the material highly magnetic while maintaining the crucial characteristics desired for the common application.