Tag Archives: nanosilica

Sound-absorbing nanofoam

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.

Short term exposure to engineered nanoparticles used for semiconductors not too risky?

Short term exposure means anywhere from 30 minutes to 48 hours according to the news release and the concentration is much higher than would be expected in current real life conditions. Still, this research from the University of Arizona and collaborators represents an addition to the data about engineered nanoparticles (ENP) and their possible impact on health and safety. From a Feb. 22, 2016 news item on phys.org,

Short-term exposure to engineered nanoparticles used in semiconductor manufacturing poses little risk to people or the environment, according to a widely read research paper from a University of Arizona-led research team.

Co-authored by 27 researchers from eight U.S. universities, the article, “Physical, chemical and in vitro toxicological characterization of nanoparticles in chemical mechanical planarization suspensions used in the semiconductor industry: towards environmental health and safety assessments,” was published in the Royal Society of Chemistry journal Environmental Science Nano in May 2015. The paper, which calls for further analysis of potential toxicity for longer exposure periods, was one of the journal’s 10 most downloaded papers in 2015.

A Feb. 17, 2016 University of Arizona news release (also on EurekAlert), which originated the news item, provides more detail,

“This study is extremely relevant both for industry and for the public,” said Reyes Sierra, lead researcher of the study and professor of chemical and environmental engineering at the University of Arizona.

Small Wonder

Engineered nanoparticles are used to make semiconductors, solar panels, satellites, food packaging, food additives, batteries, baseball bats, cosmetics, sunscreen and countless other products. They also hold great promise for biomedical applications, such as cancer drug delivery systems.

Designing and studying nano-scale materials is no small feat. Most university researchers produce them in the laboratory to approximate those used in industry. But for this study, Cabot Microelectronics provided slurries of engineered nanoparticles to the researchers.

“Minus a few proprietary ingredients, our slurries were exactly the same as those used by companies like Intel and IBM,” Sierra said. Both companies collaborated on the study.

The engineers analyzed the physical, chemical and biological attributes of four metal oxide nanomaterials — ceria, alumina, and two forms of silica — commonly used in chemical mechanical planarization slurries for making semiconductors.

Clean Manufacturing

Chemical mechanical planarization is the process used to etch and polish silicon wafers to be smooth and flat so the hundreds of silicon chips attached to their surfaces will produce properly functioning circuits. Even the most infinitesimal scratch on a wafer can wreak havoc on the circuitry.

When their work is done, engineered nanoparticles are released to wastewater treatment facilities. Engineered nanoparticles are not regulated, and their prevalence in the environment is poorly understood [emphasis mine].

Researchers at the UA and around the world are studying the potential effects of these tiny and complex materials on human health and the environment.

“One of the few things we know for sure about engineered nanoparticles is that they behave very differently than other materials,” Sierra said. “For example, they have much greater surface area relative to their volume, which can make them more reactive. We don’t know whether this greater reactivity translates to enhanced toxicity.”

The researchers exposed the four nanoparticles, suspended in separate slurries, to adenocarcinoma human alveolar basal epithelial cells at doses up to 2,000 milligrams per liter for 24 to 38 hours, and to marine bacteria cells, Aliivibrio fischeri, up to 1,300 milligrams per liter for approximately 30 minutes.

These concentrations are much higher than would be expected in the environment, Sierra said.

Using a variety of techniques, including toxicity bioassays, electron microscopy, mass spectrometry and laser scattering, to measure such factors as particle size, surface area and particle composition, the researchers determined that all four nanoparticles posed low risk to the human and bacterial cells.

“These nanoparticles showed no adverse effects on the human cells or the bacteria, even at very high concentrations,” Sierra said. “The cells showed the very same behavior as cells that were not exposed to nanoparticles.”

The authors recommended further studies to characterize potential adverse effects at longer exposures and higher concentrations.

“Think of a fish in a stream where wastewater containing nanoparticles is discharged,” Sierra said. “Exposure to the nanoparticles could be for much longer.”

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

Physical, chemical, and in vitro toxicological characterization of nanoparticles in chemical mechanical planarization suspensions used in the semiconductor industry: towards environmental health and safety assessments by David Speed, Paul Westerhoff, Reyes Sierra-Alvarez, Rockford Draper, Paul Pantano, Shyam Aravamudhan, Kai Loon Chen, Kiril Hristovski, Pierre Herckes, Xiangyu Bi, Yu Yang, Chao Zeng, Lila Otero-Gonzalez, Carole Mikoryak, Blake A. Wilson, Karshak Kosaraju, Mubin Tarannum, Steven Crawford, Peng Yi, Xitong Liu, S. V. Babu, Mansour Moinpour, James Ranville, Manuel Montano, Charlie Corredor, Jonathan Posner, and Farhang Shadman. Environ. Sci.: Nano, 2015,2, 227-244 DOI: 10.1039/C5EN00046G First published online 14 May 2015

This is open access but you may need to register before reading the paper.

The bit about nanoparticles’ “… prevalence in the environment is poorly understood …”and the focus of this research reminded me of an April 2014 announcement (my April 8, 2014 posting; scroll down about 40% of the way) regarding a new research network being hosted by Arizona State University, the LCnano network, which is part of the Life Cycle of Nanomaterials project being funded by the US National Science Foundation. The network’s (LCnano) director is Paul Westerhoff who is also one of this report’s authors.