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Writer: Srajan Ebaen
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Grey matter. We all have it. It's what we do with it where we differ.
There's even really dark matter, still hypothetical likely composed of as yet unknown sub-atomic particles. Its presence is implied by a variety of astrophysical observations. Those include gravitational effects that can't be explained by accepted theories unless there was more matter present than can be seen. This dark matter doesn't appear to interact with observable electromagnetic radiation like light. It's invisible to the entire electromagnetic spectrum. That makes it extremely difficult to detect, hence dark matter.
If your grey matter were lodged in the busy skull of one Ivo Sparidæns of Dutch speaker house Æquo Audio, you'd not worry about hypothetical dark matter. You'd engineer your own very much concrete but strange matter to design better speaker enclosures and drivers. Hello Diluvite™, an umbrella term for a new portfolio of nano-enhanced composite materials spun off by Æquo Audio.
It all starts with that age-old battle between stiffness and damping. The more of one you pursue, the less of the other you get in a slow dance of mutual exclusivity.
"Stiffness and damping are the two desired properties when fighting off unwanted vibrations that cause side effects like distorted audio signal and panel vibrations. Stiffness helps to take on force without bending or deforming (Young's modulus, storage modulus) whilst damping sheds energy via dissipation (loss factor tan). Metals like certain aluminium alloys, steels, titanium and beryllium (lightweight and stiff but expensive and toxic) excel at stiffness but self-damp poorly. Certain pure metals like magnesium have good damping but lose those properties when alloyed to become strong enough for manufacturing.
"Extremely stiff carbon-ply epoxy laminates and ceramics can offer double or triple the stiffness of metals but fail the loss of energy when made to resonate. The actual procedure of laminating carbon ply also limits design freedom and increases labour costs.
"Diamond may lead in hardness but suffers poor damping combined with high cost. Both synthetic diamond and beryllium are starting to disappoint as the promised solution in high-end loudspeaker driver membranes because they do raise odd-order harmonics whilst lowering even-order harmonic distortion at the lower end of the usable bandwidth. Furthermore, most of the resin-based and ceramic super-stiff solutions offer poor thermal properties.
"Since the arrival of nanotech in the '80s, large leaps in composites performance have become possible by applying technologies on the scale of nanometres and micrometres in surface science, chemistry, biology, energy and medicine. In micro fabrication and molecular engineering, many breakthroughs report on what’s possible with organic (carbon) and ceramic-based composites. The more famous ones are carbon nano-tubes (CNT) and graphene where the building sheet used for CNT is a single layer of hexagonally bonded carbon molecules.
"But promising specs on paper don't always make for good performance. Many carbon nano-tube applications disappoint on cost vs performance. Most issues are linked to lacking production processes and dispersion problems. Also, commercially available CNT in a matrix composite—regardless of single walled, double walled or multi walled even when properly dispersed—will always trade gained stiffness against poorer damping."
If you're Ivo, you're deep into these hi-tech materials sciences. You'd start there and eventually end up with different nanotech composites which feature very unusual property combinations.
The first is a metal matrix composite or MMC of extreme stiffness and high damping. "It provides better damping than any commercially available alloy, surpassing even lead while being far stiffer than alloys of aluminium. Its unique crystal structure makes for excellent damping loss of virtually the same high value at any frequency from 0.01Hz to >100khz, something normally never seen in alloys or polymers that suffer resonance problems at certain frequencies.
"The composite is stable up to temperatures beyond 300° C and comparable to aluminium alloys for its excellent thermal conductivity where it can be used as heat sink in advanced audio cabinets and chassis as well as specific aerospace applications. Energy dissipation is maximized while density remains significantly lower than steel. It is free of toxins like lead, mercury or beryllium. Although the material as cast is naturally corrosion resistant already, all properties can be further enhanced with our specific Vantacoat™ surface treatments."
Developed for lightweight uses and smaller parts including speaker driver membranes, Ivo's new polymer matrix composite (PMC) "sets a new standard for its combination of low mass, high stiffness and high damping. This composite can be pressure-cast or forged by hot-compacting and is seven times lighter than our Nanocast MMC and up to two times lighter than carbon-fibre applications. The resulting damping properties are far better than any recent CNT polymer/resin solutions whilst providing stiffness higher than that of high-modulus epoxy resins. Additionally and as with Nanocast MMC, this polymer version is a standalone solution without laminating, making possible complex forged or moulded designs even at much thinner wall requirements than those applicable for metal casting or thin-ply laminations."
Not content to leave good enough alone, Ivo's Diluvite Nano-Gold™ material aims at "ultimate high damping in structures/designs made with our Diluvite nanotech composite portfolio. This advanced compound is specially structured to be applied as an ultra-high energy dissipating sheet solution added to Nanocast MMC or any flat surface of materials chosen for their extreme stiffness but lacking in damping loss. The most effective version of the compound sheet is a 4mm thick matrix holding titanium nitrite-coated tungsten carbide solids. Chosen for their ultimate stiffness which is over three times higher than advanced steels combined with a density that's more than five times heavier than granite rock, these carefully designed particles have a special 3D-sloped prism shape to dissipate any vibrational force vector regardless of its direction. This results in utmost efficiency at preventing and eliminating any resonance in designs like anti-vibration platforms and high-end speaker cabinets. The clear viscoelastic polymer matrix gives an interesting view into a micro-level tri-directional and macro-level non-directional matrix as formed by the chaos of triangles/prisms. The clear resin is specifically capable to allow a straight passage of infrared radiation to be reflected by the triangles. Gold is the colour proven to be most effective for heat shielding." There's even a new coating material to further enhance the properties of the above substances.
For the ultimate deadlock between stiffness and damping, one would use Nanocast MMC™ finished in Vantacoat™ sandwiched with the Nano-Gold™ ultra-damping compound. "Glued together with a special viscoelastic high-strength epoxy adhesive, the two sandwiched materials plus coating deliver a very design-flexible solution of great stiffness and ultra-high damping plus great thermal properties. Those applications in need of ultimate anti-vibrational performance can be created by sandwiching the Gold compound sheet between two layers of Nanocast MMC whose outer surfaces are enhanced with ultra-high stiffness versions of Vantacoat sprayed in extra thick coatings of up to several millimetres." As of April 2020, the Diluvite portfolio of nanotech composites in fact counted nine different materials already.
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