Analysis of Ferrous Ferrite (Fe3O4)

Analysis of Ferrous Ferrite (Fe3O4) 1.1 INTRODUCTION: The naturally occurring ferrite is the ferrous ferrite (Fe3O4) as â€Å"Load stone†. In early days it was called as ferromagnetic material. L.Neel, tells us that these materials are â€Å"ferromagnetic† material due to uncompensated anti parallel spin arrangement. Due to interesting intrinsic properties magnetic materials are classified into Ferromagnetic materials, Ferrites. In last decades , in the field of the ferrites expensive development was done by many contributors and found to be technically, commercially useful magnetic material. These materials are at high frequencies, high electrical resistivity of magnetic temperature coefficient of resistance along with low magnetic loss. Basically, Ferrous ferrite (Fe3O4) consist double oxides FeO and Fe2O3 . The properties of these materials are alter by substituting divalent iron ion by divalent cation like Cd2+,Mg2+,Ni2+,Zn2+,Cu2+,Co2+ etc. from transition element. The spinel ferrites are represented as MFe2O4, where M is divalent cations. The magnetic properties are significantly improved by substituting trivalent iron ion by Al3+,Cr3+,Mn4+, Ti4+,Sn4+, Gd3+,Nd3+ etc. for particular applications because of their interesting magnetic and electrical properties with chemical and thermal stabilities[Gadkari A.B et.al. (2010)]. The applications of these materials in fields like electrical components, memory devices, microwave devices telecommunications, electronic industries, dada storage, data processing due to its high resistivity and low power losses. [Ernst Schloeman et al. (2000)] Ferrites are of two type’s,one is hard ferrite and other is soft ferrite. The material which are easily magnetized and demagnetized, it is called soft magnetic material .That means, it can store or transfer magnetic energy in alternating or other changing wave forms. The ferromagnetic materials like iron, nickel, cobalt and some of the rare earths materials shows a unique magnetic behavior. All the magnetic moments of the individual ions or atoms are aligned parallel to some particular direction and the unpaired electron spins line up parallel with each other in the ferromagnetic material. The region in which magnetic dipoles align parallel to each other is called a domain. The structural properties of ferrite are very important. The structural properties of ferrites mainly depends on the manufacturing process of ferrite[Mangalaraja R.V. et al. (2003)]. In fundamental science, magnetic spinel ferrites are of great importance. They are useful especially for find out the fundamental relationship between magnetic properties and their crystalchemistry and structure [ Kalonji G.et.al.(1999)]. They find extensive applications in microwave devices, radar, digital recording, ferrofluids, catalysis and magnetic refrigeration systems [Horvath M.P. et.al. (2007)]. For the spinel ferrite the general formula is AB2O4and it is consisting of an almost perfect cubic closed packed oxygen arrangement, with the cations residing on tetrahedral and octahedralinterstices. Nowadays, magnetic materials are used in various fields. The soft magnetic materials can be attracted to a permanent magnet and the hard magnetic materials become a permanent magnet. In case of soft magnetic materials, the large magnetic fields cannot be generated to the outside but in hard magnetic materials it generates magnetic fields. The magnetic materials like iron, cobalt and nickel ordinarily reveal prominent magnetic property. In industry, the ferromagnetic materials are widely used. In case of metal and alloy magnetic materials, due to their lower electrical resistivity the initial permeability and magnetic flux density is high and loss in eddy current is large at high frequencies. Nowadays, high-frequency characteristics are more useful, so this is occurred in ferrites which is multiplying the thin films. Due to higher electrical resistivity, the soft ferrites has excellent characteristics at high frequency. They are abundantly used for inductors or core materials of trans former. The hard ferrite is also used abundantly as permanent magnets for speakers and motors. The soft ferrite is used into an alternating magnetic field. Ferrites are chemical compounds. They are composed of a ceramic material along with iron oxide as their main component. The magnetic property of the ferrite is due the structure and the arrangement of the ions in the sub lattice. 1.2 SPINEL COMPOUNDS The word spinel which is derived from Italian spinella, diminutive of spine, thorn (from its sharply pointed crystals). In the cubic system, Spinel crystallizes forming octahedral crystals. In spinel super group there are at least 30 oxide minerals included. The majority of spinel compounds belongs to the space group Fd3m. The formula for the principal member of the group has, AB2O4; out of which ‘A’ is a divalent metal ion such as magnesium, iron, nickel, manganese and zinc. The ‘B’ is trivalent metal ions such as aluminium, iron, chromium and/or manganese. Also, titanium Ti4+ and Pb2+ etc. may occupy this site. The solid solutioning which is common process in this group of minerals that means they may contain certain percentages of different ions in any particular specimen [Adams, D. M (1974)]. The oxygen ions are mostly larger than the metallic ions and the spinel structure can be formed by a cubic close packing of O2- ions, in most oxide structures in wh ich the cations (e.g. Co2+, Fe3+) occupy certain interstices. So, the structure of a spinel compound and the highly symmetric structure of diamond is same. The position of the A ions and the positions of carbon atoms occupied in the diamond structure is identical. In this group this could discuss the relatively high hardness and high density. The arrangement in the structure of the other ions shows the symmetry just like diamond structure. This arrangement of the ions verifies the octahedral crystal structure which is the predominant crystal form and also the trademark of the spinels. Now a day, there are well over a hundred compounds are reported of the spinel structure. Most of them are oxides, sulphides, selenides and tellurides and some are halides. There are different cations may be introduced into the spinel structure and several charge combinations are possible, therefore, almost any combination that added and balances eight positive charges of anionic charges [Smyth,D.M.(200 0)],for example Co2+Fe23+O4, Mg22+Ti4+O4, Li1+Al3+Ti4+O4, Li0.51+Al2.53+O4 and Na21+W6+O4, etc. In oxide spinels, there are two types of cations which do not differ in size greatly because the spinel structure is stable only when the cations are rather medium sized and also the radii of the different ionic species in the same compound must be nearly equal. Therefore, similar cation combinations occur in sulphides, e.g. Zn2+Al23+S4 and Cu22+Sn4+S4. Hence, in halide spinels e.g. Li21+Ni3+F4 and Li1+Mn23+/ 4+F4 in which cations are limited to charges of plus 1 and plus 2, give an overall cation: anion ratio of 3 as 4. Most spinels divided into three series determined by a B metal represent aluminate series with Al3+ (Hercynite, Gahnite, Galaxite); a magnetite series with Fe3+ (Magnetite,Magnesioferrite, Franklinite); the chromite series with Cr3+ (Chromite, Magnesiochromite). There is extensive cationic exchange (solid solution) within each series but very little between the series [King, R. J (2004)]. These spinels are classified on the basis of the distribution of cations in the two principal sites which are tetrahedral site (T-) and octahedral site (O-) [West, A. R. (1989)], into three types. 1.2.1 NORMAL SPINEL In normal spinel A (BB) O4, all the divalent (A) cations placed on the tetrahedral (T-) sites and the trivalent (B) cations present on the octahedral (O-) sites. Which can be shown by the formula [A]tet [B2]oct O4. The examples of normal spinel are MgO.Al2O3 = MgAl2O4 (normal, parent mineral) ZnO.Fe2O3 = ZnFe2O4 (normal) FeO.Al2O3 = FeAl2O4 (normal) CoO.Al2O3 = CoAl2O4 (normal) MnO.Al2O3 = MnAl2O4 (normal) NiO.Al2O3 = NiAl2O4 - (normal) 1.2.2 INVERSE SPINEL The inverse spinel, B (AB) O4, the divalent cations occupying on the O-sites and the trivalent cations which are equally divided among the T- and remaining other on O-sites. Which can be represented by formula, [B]tet [A, B]oct O4. The CoFe2O4 is conformably an inverse spinel with a formula; CoxFe1-x (Co1-xFe1+x) O4(with x 0) where x represents the cation distribution factor which discuss the fraction of tetrahedral sites occupied by Co2+ cations [Guire, M. R.D (1989)]. CoO.Fe2O3 = FeCoFeO4 (inverse) NiO.Fe2O3 = FeNiFeO4 - (inverse) MgO.Fe2O3 = FeMgFeO4 (inverse) 1.2.3 RANDOM SPINEL It has an intermediate cation distribution, represented as [B0.67 A0.33]tet [A0.67B1.33]octO4. In this elementary unit cell of spinel structure consists eight tetrahedral and sixteen octahedral sites which are occupied by metal ions and the extreme cases, represent completely normal and inverse spinel, Therefore, the general cation distribution can be represented as [ M(2)iq+M(1)1-ip+]AIV [M(1)p+i/2 M(2)(2-i)/2q+]2BvI O4 where M+(1)p+ and M(2)q+ are the minority and majority cations respectively. Hence, the first quantity in brackets shows the average occupancy of A-sites (coordination number of four (IV)) and the second quantity in brackets shows the average occupancy of B-sites (coordination number of six (VI)). The inversion parameter ÃŽ ³, shows the fraction of A-sites acquired by majority ions.

Bullying: Relational Aggression and Boys

Bullying 1. Why do you think that bullying is an issue to study in Lifespan Development? I believe that bullying should be studies in Lifespan Development because Bullying is a multifaceted form of mistreatment, seen in schools and the workplace. It is characterized by the repeated exposure of one person to physical and emotional aggression like teasing, name calling, mockery, threats, harassment, taunting, hazing, social exclusion or rumours. Lifespan Development is the exploration of the biological, cognitive, and psychosocial changes that occur across different periods of life. So I believe the two go hand in hand. 2. Describe the three components or types of bullying behavior, as observed by researchers. The three important components of bullying : 1. Bullying is aggressive behavior that involves unwanted, negative actions. 2. Bullying involves a pattern of behavior repeated over time. 3. Bullying involves an imbalance of power or strength. 3. Explain how gender influences the styles of bullying. In contrast to girls, boys of any age and ethnic group tend to be physically aggressive (e. g. , hit, kick, slap, push, or punch) . Also, research shows that physical abuse tends to occur more often among boys than girls at all educational levels (e. g. , elementary, high school, college). Also, male college students tend to bully and be bullied through physical and verbal forms of bullying (e. g. , name-calling) more often than college girls. Also, boys may be more accepting of bullying, than are girls. That is, boys may like a girl even if she bullies others. In contrast, girls may still befriend boys that bully, but tend to dislike girls that bully. At the core of these differences is children’s and, indeed, societal beliefs about acceptable behaviors for boys and girls. Many people may see bullying among boys as â€Å"just boys being boys. † So, girls may accept this attitude and tolerate boys’ bullying. However, girls may be less accepting of girls who bully if it is seen as overly aggressive. Girls tend to bully other girls through the peer group. Rather than bully a targeted child directly, girls more often share with other girls (and boys) hurtful information about the targeted child. For example, a girl may tell a group of girls an embarrassing story about another girl. They may create mean names, gossip, and come up with ways of letting the girl know that she is rejected from the peer group (for example, saying mean things about her on Facebook, using her email address to send harassing messages to everyone on her email list, texting her a death threat). These are called â€Å"relational† bullying because they attack relationships and friendships. Another example of bullying experienced more often by girls than boys is sexual (e. g. , touched in private body parts or received sexual messages). Sexual types of bullying may occur at school, in the general community, and on-line. In recent Canadian and U. S. surveys, a significant number of girls report receiving unwanted sexual messages. Fewer boys reported being targeted. This form of bullying combined with messages about rejection from friendships is just as hurtful as being physically attacked, maybe even more hurtful. Rejecting messages can devastate a girl’s sense of enthusiasm for school and learning, self-esteem, and hopes for the future. These forms of bullying can be particularly time-consuming and difficult to resolve given that they involve many people over a period of time. It may even involve adults who react aggressively in defence of their children. In addition, parents and school authorities do not always detect gossiping or other covert bullying behaviors because it’s generally hidden from adults. Thus, they may not be disciplined and â€Å"caught†, which may increase the severity and duration of these behaviours. It may even occur among â€Å"friends†, making it seem that it’s just usual peer conflict. However, when one girl feels powerless in how she is being treated, then bullying is occurring, and adults need to intervene. Reference: http://www. education. com/reference/article/Ref_Bullying_Differences Children at Play 1. What kinds of skills are developed through play? 2. Why do children play? 3. List two kinds of gender preferences in play.

Child Abuse Is The Most Visible Form Of Child Maltreatment

CHAPTER 1 INTRODUCTION Child abuse has been a plague on moral consciousness for more than a century. Child abuse is defined as anything that â€Å"creates or allows to be created a substantial risk of physical injury to such a child by other than accidental means, and which would be likely to cause death or serious or protracted disfigurement, or protracted impairment of physical or emotional health or protracted loss or impairment of the function of any bodily organ (Dickson, 2010). The term â€Å"child abuse† only applies to a child under the age of 18 who meets the criteria above. In the United States, roughly more than five children die each day as a result of child abuse or neglect (Promises2Kids, 2012). The four major forms of child abuse are emotional abuse, sexual abuse, physical abuse, and child neglect. In this research, physical child abuse will be the focus. Physical child abuse is the most visible form of child maltreatment. 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