Tag Archives: magnetite nanoparticles

Sound-absorbing nanofoam

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In these increasingly noisy days (there’s construction going on around me), news of a cheaper, easier way to dull the noise is very attractive. From a June 25, 2018 Far Eastern Federal University (Russia) press release on EurekAlert,

The breakthrough material reduces a noise level by 100% more efficient comparing to standard analogs, cutting the level of noise transmission by 20-22 dB. The new foam reacts to sound waves not only of high but also of low frequencies, which can damage human health. A young scientist from the Far Eastern Federal University (FEFU) took part in the development.

PARTNERSHIP DEVELOPMENT

Alexey Zavjalov, postdoc, researcher at the Academic Department of Nuclear Technologies School of Natural Science, FEFU, worked as a part of the international team of Russian and South Korean scientists under professor S.P. Bardakhanov. Alexey’s research performance led to the creation of nanofoam – the new noise-absorbing composite material. The results of the work are published in ‘Applied Acoustics’.

‘The problem of noise is the problem of modern technogenic civilization. In South Korea, cities are equipped with round-the-clock working stationary and mobile networks for noise levels monitoring. The urbanization level of such territorially small countries as South Korea is much higher than in Russia. However, in our country this problem is still crucial for big cities,’ – explained Alexey Zavjalov. – ‘The development of new noise-absorbing materials is especially interesting for the automotive industry. Modern people spend a lot of time driving cars and the noise level inside the vehicles’ directly determines the quality of life. For East Asian countries, the issue of noise control is relevant for high-speed rail lines.’ Porous materials are excellent sound absorbers but their noise-absorbing properties can be significantly enhanced by nanoporous grit injected into the foam structure and formed internal channels in it. Alexey Zavjalov has developed approaches for saturation of macroporous foam material with nanoporous grit.

HARMFULNESS OF THE LOW FREQUENCIES NOISES.

Along with the rapid development of nanotechnology, there have been many attempts to mix nano- and microsized materials to create a modified material with enhanced strength, elastic, dynamical and vibrational properties. The acoustic parameters of such materials could not be fundamentally enhanced thus far.

Foam materials are most often used for soundproofing purposes. They provide the proper quality at a reasonable cost, but until today have been effective against high-frequency noise only. At the same time, low frequencies can be much more harmful to human health.

Infra- and low-frequency vibrations and noise (less than 0.4 kHz) are most harmful and dangerous for human health and life. Especially unfavorable is their long-lasting impact, since leads to serious diseases and pathologies. Complaints on such oppressions exceed 35% of the sum total of complaints on harmful environmental conditions.

The foam material, developed by Russian and Korean scientists, demonstrated promising results at medium frequencies and, therefore, more specialized low-frequency noise tests are needed.

CHEAPER AND EASIER FOR APPLICATION THAN AEROGEL.

The improved acoustic characteristics of the newest hybrid nanofoam were obtained by additional impregnation of the standard off-the-shelf sound-absorbing foam with porous granules of silica and magnetite nanoparticles. The porous foam was immersed in nanopowder suspensions in the liquid, subjected to ultrasonic treatment and dried.

The nanoparticles granules formed in the result can be compared structurally to a widely known class of materials – aerogel. It has not only excellent thermal insulation properties but also has a good noise-proof. However, aerogels are quite expensive and complex when used in structures. The new material, created according to the scheme developed by the FEFU researcher, is structurally similar to aerogel but is free of such shortcomings as a high price and engineering problems.

COMPOSITE TECHNOLOGY

The mechanism of sound absorption of a new foam is based on the fact that its sound-absorbing surface is significantly scaled due to the presence of a large number of nanopores in the particles injected, as well as the location of these particles in the foam matrix in the form of distinct channels. Nanoparticles dissipate the energy of a sound wave transforming it into heat. The soundproof properties of the material increase.

Scientists found out that the composite structure is most effective for noise reduction. Thin layers of foam impregnated with nanoparticles are connected to each other in a “sandwich”-construction. This design significantly improves the soundproof properties of the resulting material. The outcome of the study also suggests that the more foamy material is impregnated with nanoparticles, the better it’s sound absorption is.

‘In some approximation, any material can be represented as a network of weights connected by springs. Such a mechanical system always has its own frequency bands, in which the oscillations propagate in the system relatively freely. There are also forbidden frequency bands in which the oscillations rapidly fade out in the system. To effectively extinguish the transmission of oscillations, including sound waves, the materials should be alternated in such a way that the fluctuations that propagate freely in the first material would be in the forbidden band for the second layer,’- commented Alexey Zavjalov. – ‘Of course, for our foam material, this idealization is too crude. However, it allows us to clearly illustrate the fundamentally conditioned necessity of creating a “sandwich” structure.’

RESEARCH OUTCOME

The study showed the effectiveness of the method of foams impregnation with nanosilica or nanomagnetite, which form granules up to several hundred micrometers (in accordance with the pore sizes of the modified foam material) and having pores about 15 nm. This small addition provided a more complex and branched 3D network of nanochannels which led to an additional absorption of noise energy.

Due to the method used, the noise absorption efficiency was achieved in the range of 2.0-6.3 kHz and at lower frequencies 0.5-1.6 kHz. The degree of absorption was increased by 60-100% and the sound transmission was reduced by 20-22 dB, regardless of the type of nanofiller.

‘There is room to further improve the sound absorbing properties of the new material for medium and low frequencies using the” active control” strategy’. – Alexey Zavjalov comments on the plans for further development of such an important scientific topic. – ‘First of all, this refers to the materials obtained by using a magnetite nanopowder. Active noise protection systems have long been used in the world. The main idea is to detect the noise acoustic fields “online” and to generate sound waves in antiphase by means of loudspeakers. That allows achieving a significant reduction of noise in a given area. Concerning the nanofoam, it’s proposed to adapt this approach and to actively exert on a material saturated with granules of magnetite nanoparticles by magnetic fields. This will achieve even better noise reduction.’

Here’s a link to and a citation for the paper,

Hybrid sound-absorbing foam materials with nanostructured grit-impregnated pores by S.P.Bardakhanov, C.M.Lee, V.N.Goverdovskiy, A.P.Zavjalov, K.V.Zobov, M.Chen, Z.H.Xu, I.K.Chakin, D.Yu.Trufanov. Applied Acoustics Volume 139, October 2018, Pages 69-74
https://doi.org/10.1016/j.apacoust.2018.04.024 Available online 23 April 2018.

This paper is behind a paywall.

If you have difficulty seeing the press release on EurekAlert, there is a June 26, 2018 news item on a Russian news site, RSF News and there is an edited version in a June 26, 2018 news item on Azonano.

Breathing nanoparticles into your brain

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Thanks to Dexter Johnson and his Sept. 8, 2016 posting (on the Nanoclast blog on the IEEE [Institute for Electrical and Electronics Engineers]) for bringing this news about nanoparticles in the brain to my attention (Note: Links have been removed),

An international team of researchers, led by Barbara Maher, a professor at Lancaster University, in England, has found evidence that suggests that the nanoparticles that were first detected in the human brain over 20 years ago may have an external rather an internal source.

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These magnetite nanoparticles are an airborne particulate that are abundant in urban environments and formed by combustion or friction-derived heating. In other words, they have been part of the pollution in the air of our cities since the dawn of the Industrial Revolution.

However, according to Andrew Maynard, a professor at Arizona State University, and a noted expert on the risks associated with nanomaterials,  the research indicates that this finding extends beyond magnetite to any airborne nanoscale particles—including those deliberately manufactured.

“The findings further support the possibility of these particles entering the brain via the olfactory nerve if inhaled.  In this respect, they are certainly relevant to our understanding of the possible risks presented by engineered nanomaterials—especially those that are iron-based and have magnetic properties,” said Maynard in an e-mail interview with IEEE Spectrum. “However, ambient exposures to airborne nanoparticles will typically be much higher than those associated with engineered nanoparticles, simply because engineered nanoparticles will usually be manufactured and handled under conditions designed to avoid release and exposure.”

A Sept. 5, 2016 University of Lancaster press release made the research announcement,

Researchers at Lancaster University found abundant magnetite nanoparticles in the brain tissue from 37 individuals aged three to 92-years-old who lived in Mexico City and Manchester. This strongly magnetic mineral is toxic and has been implicated in the production of reactive oxygen species (free radicals) in the human brain, which are associated with neurodegenerative diseases including Alzheimer’s disease.

Professor Barbara Maher, from Lancaster Environment Centre, and colleagues (from Oxford, Glasgow, Manchester and Mexico City) used spectroscopic analysis to identify the particles as magnetite. Unlike angular magnetite particles that are believed to form naturally within the brain, most of the observed particles were spherical, with diameters up to 150 nm, some with fused surfaces, all characteristic of high-temperature formation – such as from vehicle (particularly diesel) engines or open fires.

The spherical particles are often accompanied by nanoparticles containing other metals, such as platinum, nickel, and cobalt.

Professor Maher said: “The particles we found are strikingly similar to the magnetite nanospheres that are abundant in the airborne pollution found in urban settings, especially next to busy roads, and which are formed by combustion or frictional heating from vehicle engines or brakes.”

Other sources of magnetite nanoparticles include open fires and poorly sealed stoves within homes. Particles smaller than 200 nm are small enough to enter the brain directly through the olfactory nerve after breathing air pollution through the nose.

“Our results indicate that magnetite nanoparticles in the atmosphere can enter the human brain, where they might pose a risk to human health, including conditions such as Alzheimer’s disease,” added Professor Maher.

Leading Alzheimer’s researcher Professor David Allsop, of Lancaster University’s Faculty of Health and Medicine, said: “This finding opens up a whole new avenue for research into a possible environmental risk factor for a range of different brain diseases.”

Damian Carrington’s Sept. 5, 2016 article for the Guardian provides a few more details,

“They [the troubling magnetite particles] are abundant,” she [Maher] said. “For every one of [the crystal shaped particles] we saw about 100 of the pollution particles. The thing about magnetite is it is everywhere.” An analysis of roadside air in Lancaster found 200m magnetite particles per cubic metre.

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Other scientists told the Guardian the new work provided strong evidence that most of the magnetite in the brain samples come from air pollution but that the link to Alzheimer’s disease remained speculative.

For anyone who might be concerned about health risks, there’s this from Andrew Maynard’s comments in Dexter Johnson’s Sept. 8, 2016 posting,

“In most workplaces, exposure to intentionally made nanoparticles is likely be small compared to ambient nanoparticles, and so it’s reasonable to assume—at least without further data—that this isn’t a priority concern for engineered nanomaterial production,” said Maynard.

While deliberate nanoscale manufacturing may not carry much risk, Maynard does believe that the research raises serious questions about other manufacturing processes where exposure to high concentrations of airborne nanoscale iron particles is common—such as welding, gouging, or working with molten ore and steel.

It seems everyone is agreed that the findings are concerning but I think it might be good to remember that the percentage of people who develop Alzheimer’s Disease is much smaller than the population of people who have crystals in their brains. In other words, these crystals might (they don’t know) be a factor and likely there would have to be one or more factors to create the condition for developing Alzheimer’s.

Here’s a link to and a citation for the paper,

Magnetite pollution nanoparticles in the human brain by Barbara A. Maher, Imad A. M. Ahmed, Vassil Karloukovski, Donald A. MacLaren, Penelope G. Fouldsd, David Allsop, David M. A. Mann, Ricardo Torres-Jardón, and Lilian Calderon-Garciduenas. PNAS [Proceedings of the National Academy of Sciences] doi: 10.1073/pnas.1605941113

This paper is behind a paywall but Dexter’s posting offers more detail for those who are still curious.