NTU MSE shadowing programme - Day 5 & 6

Classified.

Day 5

Differential Scanning Calorimetry (DSC) - your one-stop solution to solve all thermal needs (citation needed). Want to obtain glass transition temperature range? How about crystallization, melting, cross-linking, and oxidation temperatures? Then DSC is the technique for you!  

That is, after weighing <5mg of sample in a microbalance and carefully loading it onto a hydraulic press to encapsulate it in an aluminium hermetic pan which is then placed into the carefully programmed DSC machine pre-cooled to 193K. Now, you might question: what if you're careless (lazy) during preparation? Well, you get equally deserving results:

 Lehman Brothers anyone?

When you are supposed to get this:

Check out those curves~

As seen from the (professionally done) PolyUtherene graph, glass transition temperature is at 217K followed by the 256K peak (crystallization tempertature) and the 300K melting range. For our sample, we should have increased the sampling frequency to get a more defined graph. Time wasted, lesson learnt, time well-spent.

After Lunch, it was yet again the return of the Jason-saga. We went from door-to-door (passed-by many doors, more like) to find the best coffee in NTU and finally found it! Wanna make a guess where is it? Well, I'll let you keep on guessing while I enjoy my coffee till Day 5 is over.

(*Hint: It is somewhere at 23.4 degrees northeast down under up above the sky so high in the Bermuda Triangle.) 

Day 6
Classified.

No really, classified.

Well, some lab visits here and there....

Fine - We got the opportunity to enter several advanced defence laboratories (for Singaporeans only. Jealous?). There, we got treated to an awesome showcase of several projects: Ever thought that plasma-imbued nano-composite armour technology was so Tony Stark? Well, so did we. Keyword: did. The rest are..... Classified... so just let these pictures speak for themselves: 

 Tainted glass? Nope. Neodymium-doped Yttrium Aluminium Garnet.

Same material 10 years down the road....

 All we can say: What a waste of Diamonds....

Latest innovation for SK-II facial treatment

Then again, some parts are just so Classified that picture-taking was forbidden (even before entering). Lets just say that at some secret location X, there's this special machine Y that does magic for next-gen prototype ceramics. At secret location Z, things are encased in steel tanks and flying about in mach 3 that will even make sheets of tungsten carbide cry (So much for toughness). This giant will make Spilt-Hopkinson pressure bars look like infants.

But here's something we can share: Focused Ion Beam Microscopy and Micro-machining (probably where nano-tubes are manufactured). Scaled-down material testing on the nano-scale removes the need of the aforementioned beast apparatus for testing during R&D phase.

Like as before, let these pictures do the talking:

Nano-sized ceramic grains with contours

Focused Ion Beam Microscopy. Tony Stark be proud.

What your hair's hair will look like

We will be continuing our tour tomorrow. Stay tuned....


But then again, it's classified.

NTU MSE shadowing programme - Day 3 & 4

Toughening of Materials

Day 3

Today, we are introduced to the various methods of toughening materials. As metioned previously, our results from day 2 is out today.

 Epoxy with 40% K1

Pure Epoxy

Scoring points for presentation skills

By visual inspection, it seems that our synthetic foam (Epoxy with 40% K1) experienced some shrinkage during curing unlike our pure Epoxy sample which turned out fine. We found out that we can rectify this problem through kneading the hardening sample in the mould every hour instead of leaving it to cure overnight. How serious is the shrinkage? Calculations show that compared to the 7.44% by mass of uncontrolled air pockets in the pure Epoxy sample, the shrinkage caused the percentage to shoot up till a 29.3% high for the 40% K1 sample. This is undesirable as such air pockets would render mechanical stress tests inaccurate due to the differing dimensions of the two Epoxy samples. Nonetheless, it is a vaulable lesson learnt and the samples are still valid for thermogravimetric analysis to compare their thermal resistivity - which will be done in Day 4.

After withdrawing our samples from their moulds, we proceed with the post-curing treatment to maximise the material's mechanical potential. Enter material toughening. For polymers such as our samples, we could apply some heat treatment to our samples to strengthen them (also known as promoting cross-linkaging). 

Thermoset polymers, like the ones we made, have a glass transition temperature and a melting temperature - which is the temperature in which the polymer enters a fluid-like phase and the temperature in which the thermoset polymer decomposes. When such thermoset polymers are heated within the range of their glass transition temperature and their melting temperature, polymer strands (which are more mobile during the fluid-like phase) are able to entangle more which makes them harder to seperate. This bounds to improve the sample's mechanical properties as more energy is required to undo this process.

Cross-Linkage Entanglement of polymer fiber/strands
Or your first time in NTU, perhaps?
 

Hence this concludes our time spent in Day 3.

Day 4

As mentioned earlier, our samples are ready for some testing after the post-curing treatment. We were introduced to Thermogravimetric analysis - which is essentially a measure of a material's rate of change in weight of the material as a function of temperature or time in a controlled atmosphere. In our case, we used high purity (inert) Nitrogen gas as our atmosphere as we want to prevent undesirable oxidation of our samples. We also cross-referred our sample's performance with other materials such as low performing plastic(PE) from file covers and high performing prototype polymer used in jet turbines(D4). Results are as shown:

As seen above, 40% K1 Epoxy fared better than oridnary plastic (PE) and pure Epoxy. This can be seen from the graph as our sample started loosing weight (dip in y-axis) at a slightly higher temperature. This is because the Epoxy structure contains glass microspheres of air which improves its thermal resistivity as air is an insulator of heat. Not only does it improve the thermal resistivity, the microspheres we added will reinforce its mechanical strength. This is as the microspheres will cause the cracks in the structure to dissipate (linear to branched) when a shear force is applied. As more energy is required to push the integrity of our sample past the threshold (longer distance travelled by cracks), it is harder to fail under stress. This is yet another toughening method which also reduces material density and ultimately lowers weight.

To make our tests more conclusive, we will be embarking on differential scanning calorimetry. Using this technique, it is possible to observe crystallisation and fusion events as well as the glass transition temperature of the different samples. Differential Scanning Calorimetry can also be used to study oxidation as well as other chemical reactions
 .

TGA Q500 machine we used today for the test 

TGA 2950 with typical graphs of the results of other thermal analysis methods

As such, we look forward to yet another day in Pulau NTU.

NTU MSE shadowing programme - Day 1 & 2

Learning Experiences

Day 1

Being our first time here at MSE, it is really a wonder that we did not get lost and managed to arrive to the briefing on time. We first met each other in the E learning studio - like minded people intertested in the field of defence materials. There, we are introduced to the intriguing field of material science and engineering. In school, we're taught basic sciences like Chemistry, Biology, and Physics. However, this is superceeded by applied sciences (such as Materials Sciences) which is an integration of the basic sciences used in practical situations. Thus, this is really an eye-opener for us as we are able to appreciate the materials that we have always taken for granted. 

The safety induction briefing taught us varied ways to prevent common laboratory haphazards - through a safety video by the chief safety and health officer of NTU. After which, we had a safety quiz. Contrary to popular belief, the safety quiz was not that easy whatsoever. For example, we have to dilute concentrated acid by pouring acid into water but not the other way around - which we were considered lucky to not figure it out the hard way. We passed the test and was issued with our very own access card. 

We met Jason, our supervisor, who is a fellow food-lover. We wasted no time into exchanging views and he shared insights of the various eateries around NTU that was worth a try. He is very approchable and it made our conversations light and enjoyable. We spent the rest of the day discussing in the student recreation room which conveniently housed coffee stations to our delight. Day 2 awaits...

Day 2
Early in the morning we went on a culinary adventure to seek out the best breakfast in NTU. Based on insider knowledge, Quap cafe proved itself to be one of the best places to dine (actually, it was just the nearest to the Research Techoplaza). We kick started the day with a lovely presentation by Dr Liu regarding syntactic foams as a solution to lighten defence materials whilst retaining mechanical properties.

This has abstract but real implications - no more complaints about heavy backpacks for instance. Suspending microspheres into hardening Epoxy resins aims to reduce the material density of conventional polymers. Though, admittedly, there are several trade-offs in doing so. Where tensile strength is compromised, weight and electrical conductivity is reduced which suits the need of, say, combat engineers.

We then have a hands-on sesson in making such ploymers and the weight difference from conventional Epoxy is astounding. We have yet to obtain mechanical test results from our materials. Lunch was yet another opportunity for us to explore the culinary landscape of NTU - and indeed, Jason proves to be the best tour guide for our tastebuds. And now, we find ourselves left in general wonderment of what is to become the breakfast venue for Day 3....