Nanotech Materials for Next-Level Acoustics

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Since the arrival of nanotechnology in the 1980’s, large leaps in composite performance have been made possible by applying  mechanical science on the scale of nanometres and micrometres. In fields such as surface science, chemistry, biology, energy and medicine and in applications of micro fabrication or molecular engineering, a lot of breakthroughs have been reported on what’s possible with organic (carbon) and ceramic based nanocomposites. The more famous ones are certainly Carbon Nano Tubes (CNT), and graphene: the building sheet itself used for CNT’s but now as a single layer in form of a hexagonal bonded lattice of carbon atoms.

Some of these materials and ingredients have become less expensive and have found their way in industrial engineering, and even appeared in some consumer products. Furthermore, scalable and affordable Nanotubes, spheres, and other structures of carbon (and/or of different molecules or materials than carbon) have been discovered, along with many new possibilities for designers and potential manufacturing improvements. Basically, it means that extreme properties previously not possible by classic engineering on a macro scale, are now made possible by rearranging the same basic atoms and molecules on a Nano scale in order to get better practical macro-level results.

Promising properties on paper do not always result in good performance. Many applications of CNT’s are disappointing in performance, especially when considering performance value vs. cost. Most problems are linked to difficult and lacking production processes and dispersion problems. Using commercially available CNT’s in a matrix composite, even if properly made and dispersed, the addition of these carbon nano tubes in the composite trades in gained stiffness against degraded damping properties, regardless of it being made with single walled (SWCNT), double walled (DWCNT) or multi-walled tubes (MWCNT), or the specific length of the tubes implemented.

Unfortunately, some issues also apply to graphene. On paper it may have the single highest stiffness value however, when applied as a coating or an add-on it rarely has real impact on the stiffness performance of structures and membranes: such a thin layer (0,334 nano meter, or 0.00034 micro meter; 200 times less than the thickness of an average human hair) is usually insignificant for the component’s performance. Also, the boosted high paper-value applies for the in-plane direction of the platelet only. This fuels the desire of structuring it as a three-dimensional nanotube (CNT) in order to achieve some actual macro-level improvements when used as an ingredient for a material or component. Thicker, multiplied layers of graphene will fail to help in practice, as these hexagonal layers do not bond and can freely slide over each other. This explains why graphene or Graphene Nano Platelets of fewer layers are more expensive and only fewer than 10 layers are considered actual graphene (transparent): above that it is called exfoliated graphite (grey coloured).

D I L U V I T E™ Nanotech Composites are perhaps today’s best and most versatile example of what can be made possible and put in actual and real delivered performance, when searching specifically for solutions that are usually compromised in anti-vibrational performance by the opposing stiffness and damping properties. These nanocomposites do solve the issues encountered when applying or evaluating purely macro-engineered materials or the actual measured performance of commonly applied Nano materials. Furthermore, the presented product portfolio provides for excellent thermal solutions and is offered against best performance/cost value in the Nanotech industry. Our services comprehend design and material application to meet the specific demands of  any project,  tailored to the most important properties of the developed component or structure, and the production method of the finalized design.

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More on the big battle: Stiffness versus Damping
 

These two properties are desired when fighting off unwanted vibrations that cause side effects, such as distorted (audio) signals and unwanted panel vibrations. Material resonance is perhaps the most overlooked and hard to overcome factor of mechanical dynamics. It causes wear and failure of components, such as seen in the practical tool life in metalworking industries. It will also make the difference between winning a race in motorsports or losing it. Even engines that do not fail during any race could have probably be made faster using materials that keep things non-resonant, as these engines were probably tuned to a more conservative engine configuration to specifically prohibit such failures during the race. Better materials can make things both faster as well as more reliable. That fully counts for industrial production applications as well. In all these applications, structural stiffness must be applied to take on force without bending or deforming (Young’s modulus or storage modulus). And just as important is damping as it helps to expel stored energy by dissipation, turning it into heat (loss factor tangent). Improving stiffness almost always means simultaneously lowering damping, and vice versa; and that is precisely the ‘big battle’. 

A sheet of rubber -which has very high damping- will not ring like a bell when colliding with a force applying motion to it, but at the same time it takes very little force to deform it. At the other end of the spectrum is your family porcelain: it does give a lot of structural stiffness, but it will probably make some harsh resonant noise when stapling them back in the cupboard. Acoustic materials based on plastics and paper pulp composites, provide some kind of middle-compromise.
Some metal alloys such as steel, titanium as well as beryllium-based alloys (beryllium is a very lightweight and stiff metal that is both expensive and toxic) can excel in stiffness, but perform poorly in damping. Aluminium alloys with a density between beryllium and titanium can offer some stiffness but still lack damping. Lightweight magnesium as a pure metal offers fair damping, but it will probably lose those properties when alloyed to make it usable and strong enough for manufacturing: even small amounts of common alloying ingredients, especially those needed for grain refinement of the brittle magnesium, remove all the elevated damping capacity. For the implementation in special damping alloys some very stiff and dense metals like Tungsten have showed real potential but, alloys containing Tungsten in effective amounts in order to provide sufficient increase of stiffness and damping, are very heavy (and quite expensive). This severely limits practical usability. When applied in resin composites, these Tungsten particles are very hard to hold homogeneously dispersed: the heavy particles will sink down during the curing or casting process when mixing is not possible. Often, the result for many aspects is less than poor, and the performance doesn’t justify the costs.

 
Extremely stiff carbon ply epoxy laminates and some engineered ceramics can even provide double or triple the stiffness of steel at much lesser density, but fail in the dissipation of energy when put into resonance for having damping properties comparable to metals, whilst its laminating procedure limits design freedom and increases labour costs. Diamond may lead in stiffness, but again: very poor damping. Combined with high costs, practical application of structures applying diamond films (by Chemical Vapour Deposition) are severely limited and usually only chosen to achieve certain abrasive hardness or elevated conductivity figures. Even in ‘cost-no-object’ applications such as high end speaker membranes, both synthetic diamond and beryllium are starting to disappoint in delivering on the promise of being better or best driver membrane materials. The idea behind increased application of beryllium tweeters, is to enable unflexed ‘pistonic’ movement with main resonant break ups pushed above the audible frequency spectrum. Yet, every resonance has harmonic artefacts beyond  frequency bandwidth making for a costly compromise of stiffness over damping and unrealistic spark over musical realism. Furthermore, super-stiff solutions mostly based on resin with carbon ply or ceramic fillers, offer very poor thermal properties.

D I L U V I T E™ offers custom solutions for virtual any application in need of both stiffness and damping, using assemblies of stiff and high damping Nano compounds and materials. Perhaps even more exceptional: a standalone casted matrix composite were high stiffness goes already hand in hand with high damping and high conductivity, made possible by special metals enhanced with carefully selected Nanotech ingredients into crystalline structures that are ideal for enhancing internal friction at all frequencies, thus cancelling out unwanted resonances.

Those who are seeking the best anti-vibrational and thermal performance versus cost, can choose for the casted NANOCAST-MMC™ or the lightweight NANOCAST-LMMC™. Or cast and form with the even lighter thermoplastic composite NANOCAST-PMC™ that is also applicable for thin-walls. In either way, they will take a leap in engineered performance that allows getting a big step ahead in their playing field. Designers applying D I L U V I T E NANOCAST™ will ultimately not only win the battle between stiffness over damping, but also prevail upon the competition.

For even more advanced anti-vibrational structures, D I L U V I T E™ offers bendable plates with extreme damping: NANOGOLD-SMC™ or the stiffer but less flexible version NANOGOLD-SMC+™. Furthermore, with the two-component powder/liquid NANOCARB-HMC™, virtually any three-dimensional product can be made that should be a leap forward in its anti-vibrational performance.  There is even more possible with the NANOCARB-ULLC™ and NANOCARB-HDLC™ laminates. These are at the pinnacle of the D I L U V I TE portfolio,  pushing far beyond any assumption of maximum anti-vibrational properties, and set a new paradigm in synergy of stiffness and damping.