Environmental Recovery by Magnetic Nanocomposites Based on Castor Oil - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 242

apparent variation of mass was recorded and magnetic force calculation (opposite to
gravitational one) was calculated according to

MF =D m g .

(1)

In Equation (1) MF is the magnetic force, Δm is the apparent variation of mass in
the presence of the magnetic field and g is the acceleration of gravity.

Figure 7. Experimental setup to determinate the magnetic force (Lopes et al., 2010; Marcelino, 2010).

The calculated effects of the factors over the magnetic force are shown in Table 1.
This table also showed the standard deviation and confidence degree (p). The results
that present p < 0.05 are statistically significant and they are marked in bold. As one
can see, only time and temperature influence the magnetic force. How bigger this
factors, higher the nanoparticles magnetic force. It can be easier observed in Figure
8, which presents the magnetic force as a temperature and time function. This Figure
makes obvious that the biggest magnetic force is achieved when the time of prepara-
tion and the annealing temperature are equal to 60 min and 250ºC, respectively.

table 1. Calculated effects of the studied factors over the magnetic force of the maghemites.

Factor Effect Standard Deviation p

Average 1.8253E+2 1.5016E+1 1.1990E-3

Curvature -1.3612E+2 5.7509E+1 9.8775E-2

(1)Stirring Speed 8.6621E+1 3.0033E+1 6.3312E-2

(2)Time 1.0003E+2 3.0033E+1 4.4698E-2

(3)Temperature 2.1055E+2 3.0033E+1 5.9610E-3

1 by 2 -8.0325E+1 3.0033E+1 7.5398E-2

2 by 3 8.1612E+1 3.0033E+1 7.2708E-2