NOPR Collection:http://nopr.niscpr.res.in/handle/123456789/88192026-10-09T09:05:36Z2026-10-09T09:05:36ZInvestigation on magnetic fluids as lubricantBurcan, JanPiotrowicz, Ewa BurcanSławińska, Annahttp://nopr.niscpr.res.in/handle/123456789/93062010-06-01T16:31:03Z2004-08-01T00:00:00ZTitle: Investigation on magnetic fluids as lubricant
Authors: Burcan, Jan; Piotrowicz, Ewa Burcan; Sławińska, Anna
Abstract: Experimental data
were obtained for the lubricated bearings of precision and fine mechanisms,
operating in the conditions of boundary friction or, at best, of mixed
friction. The use of magnetically active lubricant in the thrust bearing with
the spinning point contact, where the spherical surface rotation in relation to
the axially-symmetrical seat (spherical bowl or plane), makes the fluid film
lubrication possible. It is possible because the addition of new potential
field, that means magnetic field, changes the energetic state of equilibrium
occurring in spinning friction of slides.
Page(s): 338-3422004-08-01T00:00:00ZVerwey type transition in nano-particle spinel ferrite Fe<sub>2.2</sub>Co<sub>0.8</sub>O<sub>4</sub>Chander, SubhashKrishnamurthy, AnjaliSrivastava, Bipin KGupta, AjayNigam, Arun Kumarhttp://nopr.niscpr.res.in/handle/123456789/93052010-06-01T16:30:54Z2004-08-01T00:00:00ZTitle: Verwey type transition in nano-particle spinel ferrite Fe<sub>2.2</sub>Co<sub>0.8</sub>O<sub>4</sub>
Authors: Chander, Subhash; Krishnamurthy, Anjali; Srivastava, Bipin K; Gupta, Ajay; Nigam, Arun Kumar
Abstract: Results are presented on magnetization and Mössbauer
measurements on two multi-disperse nano-particle samples of Co substituted
spinel ferrite Fe<sub>2.2</sub>Co<sub>0.8</sub>O<sub>4</sub> with average
particle sizes of ~ 50 Ǻ and ~ 80 Ǻ. In these nono-particle samples Co occupies
the octahedral site B with ~ 60% preference. The 50 Ǻ average particle sized
sample Co50 is largely in super-paramagnetic state at 300 K and its blocking
temperature <i style="">T</i><sub>B </sub>is<sub> </sub>~ 260 K. 80 Ǻ average
particle sized sample Co80 has its <i style="">T</i><sub>B
</sub>above 300 K. The two samples exhibit magnetic relaxation. Much smaller
moments of the two samples than saturation magnetization for the bulk particle
sample and a loop shift observed in <i style="">M</i>-<i style="">H</i> curves of Co50 recorded in zero field
and field cooling modes are suggestive of spin disordered surfaces. The
nano-particle sample Co80, of the ferrite Fe<sub>2.2</sub>Co<sub>0.8</sub>O<sub>4</sub>
which in its bulk particle state is known to have more than an order of
magnitude higher magneto-crystalline anisotropy than Fe<sub>3</sub>O<sub>4</sub>,
shows signature of a ‘Verwey’ type transition with enhanced magnetic anisotropy
below ~ 90 K. Co50 does not show a ‘Verwey’ type transition. A weak hump in <i style="">M</i>-<i style="">T</i>
curve at a lower temperature of ~ 50 K in Co50 is attributed to disordered spin
freezing.
Page(s): 343-3482004-08-01T00:00:00ZFerroconvection induced by point heat sourceSekar, RVaidyanathan, GVasanthakumari, Rhttp://nopr.niscpr.res.in/handle/123456789/93042010-06-03T16:30:46Z2004-08-01T00:00:00ZTitle: Ferroconvection induced by point heat source
Authors: Sekar, R; Vaidyanathan, G; Vasanthakumari, R
Abstract: A mathematical
model is proposed to study the onset of the free convection in ferrofluid at
low Rayleigh number from an instantaneous point heat source. In this work, the
leading term of series expansion of the dependent variable in terms of Rayleigh
number is considered and is valid in small Rayleigh number regime only. The
rate of heat generation is assumed to be not very high, so that Stoke’s flow
approximation could be used. The flow field is explained by the streamlines at
different times. In the absence of field, the results are compared for the
thermal convection due to the instantaneous point heat source.
Page(s): 331-3372004-08-01T00:00:00ZRheology of transformer oil based ferrofluidsPatel, RajeshUpadhyay, Kinnari Parekh R VMehta, R Vhttp://nopr.niscpr.res.in/handle/123456789/93032010-06-01T16:31:00Z2004-08-01T00:00:00ZTitle: Rheology of transformer oil based ferrofluids
Authors: Patel, Rajesh; Upadhyay, Kinnari Parekh R V; Mehta, R V
Abstract: In the present study
we report results of rheological properties of temperature sensitive
transformer oil based ferrofluids as a function of external magnetic field and
temperature. The field induced viscosity is analyzed using Shliomis model. The
variation of magnetic moment and domain magnetization with temperature has been
deduced from this measurement which agrees with the reported values deduced
from magnetization technique.
Page(s): 301-3042004-08-01T00:00:00Z