Advances in ferrofluid technology

Raj, K.; Moskowitz, Barry; Casciari, R.

doi:10.1016/0304-8853(95)00365-7

Cited by 598 publications

(331 citation statements)

References 6 publications

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“…Fig. 3 shows that E m [2] is smaller than E m [1]. Indeed, the increase in the piston diameter generates the crushing of the ferrofluid seal and consequently a diminution in the magnetic energy.…”

Section: Determination Of the Piston Optimal Shapementioning

confidence: 92%

“…Consequently, we use the expressions determined by Babic and Akyel for studying the magnetic energy density e m (r, z). Let us consider a ring permanent magnet whose polarization is radial and directed towards the centre of the ring (0), the radial and axial components h (1) r (r, z) and h (1) z (r, z) are expressed as follows:…”

Section: Energy Calculation Of the Ferrofluid Sealmentioning

confidence: 99%

“…To do so, the magnetic energy in the ferrofluid seal is first calculated when the inner piston does not crush the ferrofluid. The value obtained is denoted E m [1]. Second, the same geometry is considered but the piston has a larger diameter and it crushes the ferrofluid seal (Fig.…”

Section: Determination Of the Piston Optimal Shapementioning

confidence: 99%

“…However, such analytical approaches can also be used for the study of ferrofluid seals submitted to magnetic fields higher than 1 T. Strictly speaking, most studies dealing with ferrofluids are carried out by using several terms in the equation of equilibrium describing the ferrofluid [1]. However, not all these terms have the same weight and in some conditions, some of them can be omitted.…”

Section: Introductionmentioning

confidence: 99%

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Design of Ironless Loudspeakers With Ferrofluid Seals: Analytical Study Based on the Coulombian Model

Ravaud¹,

Lemarquand²

2009

PIER B

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Abstract-This paper presents an analytical method based on the coulombian model of a magnet for studying a ferrofluid seal in ironless electrodynamic loudspeakers. Such an approach differs from the ones generally used for studying such geometries because the ferrofluid used is submitted to a magnetic field greater than 1 T which saturates the ferrofluid. Consequently, its shape and its mechanical properties depend mainly on the magnetic field produced by the permanent magnets that constitute the ironless structure. The motor is constituted of outer stacked ring permanent magnets and the inner moving part is a piston. In addition, one ferrofluid seal is used for centering the moving part and ensuring the airtightness between the loudspeaker faces. The ferrofluid seal also exerts a pull back force on the moving piston. It is noted that this force depends on the lateral shape of the moving piston. Therefore, the piston profile is analytically studied in this paper. A peculiar attention is given to profiles that ensure the axial pull back force to be proportional to the piston displacement. Furthermore, a geometrical method is presented to design the shape of the ferrofluid seal according to the chosen piston profile. It can be noted that such a profile is elliptical in this study. Then, the magnetic energy of the ferrofluid seal is determined with the analytical expression of the magnetic energy density. Such an expression allows us to calculate the axial force created by the ferrofluid seal for a given profile.

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Section: Determination Of the Piston Optimal Shapementioning

confidence: 92%

Section: Energy Calculation Of the Ferrofluid Sealmentioning

confidence: 99%

Section: Determination Of the Piston Optimal Shapementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Design of Ironless Loudspeakers With Ferrofluid Seals: Analytical Study Based on the Coulombian Model

Ravaud¹,

Lemarquand²

2009

PIER B

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“…Soon after, Leo and Rudolph [10] filed an application for a patent on a viscous damper using ferrofluid. From 1970's to 1990's, Raj et al [11][12][13][14] discussed commercial applications of ferrofluid damping, and other researchers [15][16][17][18][19][20] introduced ferrofluid damping applications as an important part in their papers. It is worth noting that Raj and Moskowitz [21] have made an excellent review on damping applications of ferrofluids in 1980, including rotary viscous inertia damper, linear damper, damper/seal assembly, and dashpot.…”

Section: Introductionmentioning

confidence: 99%

Damping Applications of Ferrofluids: A Review

Huang¹,

Yao²,

Zhang³

et al. 2017

Journal of Magnetics

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Ferrofluids are a special category of smart nanomaterials which shows normal liquid behavior coupled with superparamagnetic properties. One of the earliest and most prospective applications of ferrofluids is in damping, which has prominent advantages compared with conventional damping devices: simplicity, flexibility and reliability. This paper presents the basic principles that play a major role in the design of ferrofluid damping devices. The characteristics of typical ferrofluid damping devices including dampers, vibration isolators, and dynamic vibration absorbers are compared and summarized, and then recent progress of vibration energy harvesters based on ferrofluid is briefly described. Additionally, we proposed a novel ferrofluid dynamic vibration absorber in this paper, and its damping efficiency was verified with experiments. In the end, the critical problems and research directions of the ferrofluid damping technology in the future are raised.

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Role of Microwave Sintering in the Preparation of Ferrites for High Frequency Applications

Bharadwaj¹,

Murthy²

2014

Advanced Sensor and Detection Materials

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It is proven that the microwave sintering method is the truly low temperature method for the preparation of nanocrystalline magnetic oxide materials of diff erent sizes and shapes. Th is method saves time, energy, and cost. Th e materials can be produced in either a batch or continuous process using the said method. Th e key novelty of our work is the use of microwave sintering to dramatically enhance the kinetics of crystallization by one to two orders of magnitude. Th is paper will summarize the results obtained on various systems of soft ferrites, and Garnets (Ni-Cu-Zn ferrites, Mg-Cu-Zn ferrites, Ni-Zn ferrites, Co-Zn ferrites, Mn-Zn ferrites, YIG and GdIG, etc.), which were prepared by using microwave sintering method for various applications such as multilayer chip inductors, high frequency, microwave devices, and multilayered transformer cores, etc. All of these systems were sintered at a low temperature of 900 o C/ 30 minutes. Th e phase identifi cation, crystallinity, and morphology of the prepared powder were characterized by X-ray diff raction and transmission electron microscopy (TEM). Th e ferrites obtained with grain sizes varying from 80 nm to120 nm with high surface area ~ 26.8 m 2 g -1 to 156 m 2 g -1 . Th e performance of the sintered ferrites has been estimated from the studies of dependence of complex permittivity and permeability spectra on the frequency and temperature and it was found that the microwave sintered ferrites show improved dielectric and magnetic properties over conventionally sintered ferrites.

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Advances in ferrofluid technology

Cited by 598 publications

References 6 publications

Design of Ironless Loudspeakers With Ferrofluid Seals: Analytical Study Based on the Coulombian Model

Design of Ironless Loudspeakers With Ferrofluid Seals: Analytical Study Based on the Coulombian Model

Damping Applications of Ferrofluids: A Review

Role of Microwave Sintering in the Preparation of Ferrites for High Frequency Applications

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