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In this paper, we investigate the magnetization reversal in single-phase RE 2 Fe 14 B and two-phase ␣-Fe/ RE 2 Fe 14 B with varying nanoscale grain structures and intergranular exchange interactions produced via controlled segregation during crystallization. We show that the loss of coercivity arises because domain-wall processes dominate the magnetic reversal as the exchange interactions increase. Micromagnetic modeling corroborates a transition to strongly cooperative magnetic reversal as the exchange interactions increase. The magnetic reversal is controlled by the growth of interaction domains via discrete domain-wall motion, and the coercivity is intrinsically limited by the presence of interaction domains. To alleviate this problem, we have built an additional length scale into the structure that is below the interaction domain size but above the limit for intergranular exchange interactions to be significant. These "single-interaction domain" structures retain nucleation-type magnetic reversal and high coercivity. We show experimentally that nanocomposite Sm-Co/Co with this additional length scale has excellent coercivity and nucleation-controlled reversal.

Compared to pure zinc plating, zinc alloys provide several advantages. A zinc alloy generally offers superior sacrificial protection to steel since it corrodes more slowly than pure zinc. A search for a non-cyanide zinc plating bath resulted on the development of a zinc nickel sulphamate bath. To obtain better quality zinc-nickel deposits, triethanolamine was added to the bath. In this paper the influence of triethanolamine in zinc-nickel plating from sulphamate bath has been investigated through current efficiency measurements, cyclic voltammetry, scanning electron microscope, and X-ray diffraction techniques. In the presence of triethanolamine in the zinc-nickel sulphamate bath the current efficiency of alloy deposition increased to a maximum of 99% at the current density of 1.5 Adm -2 and thereafter decreased. TEA adsorbed on the electrode surface obeying Henry's isotherm. On mild steel surfaces, uniform smooth slate gray deposit with smaller crystallites was produced, in presence of TEA in solution, and the electrodeposits exhibited additional Zn(OH) 2 and γ-Ni 3 Zn 22 phases. Hydrogen evolution was suppressed by TEA and thereby current efficiency is increased for alloy deposition.Keywords: cyclic voltammetry, electrodeposition, triethanolamine, XRD, Zn-Ni. IntroductionPrecoated electrogalvanised Zn-Ni sheet has offered the automotive and computer industries a superior prefabricated stock resulting in much-improved corrosion resistance. The zinc-nickel alloy deposit has 90 -95% zinc [1] and the deposition is anomalous, i.e., the less noble metal, zinc, deposits preferentially. There are broadly two types of plating baths for Zn-Ni alloy, namely the acid type and the alkaline type [2,3]. The acid bath consists of a mixture of zinc and nickel salts, electrolytes, buffers and optional brighteners. In the alkaline type,

Highly coercive ͑H c up to 37 kOe at 300 K͒, high remanent permanent magnets have been achieved by rapid solidification of binary Sm-Co alloys and Sm-Co alloys modified with Nb and C. Rapidly solidified SmCo x alloys with x ranging from 5 to 11.5 formed predominantly a solid solution TbCu 7 -type SmCo 7 phase, although hcp Co was observed for x Ͼ 7.3. A coercivity value of 10 kOe was observed for x Ͻ 6.1, even though the microstructural scale was on the order of 1 m. The coercivity decreased significantly with the presence of the hcp Co phase, which formed initially as ϳ80 nm grains and, at higher x, as primary dendrites. Additions of 3 at. % Nb or 3 and 5 at. % C profoundly affected the coercivity values. Transmission electron microscopy ͑TEM͒ investigations revealed the origin of the improved coercivity. The addition of Nb resulted in a significant reduction in microstructural scale. The SmCo 7 grain size decreased systematically with Nb content, reaching 150-200 nm at 3 at. % Nb. The addition of C also significantly enhanced the coercivity, which systematically increased with C content and reached 37 kOe at 5 at. % C. The effect of C, however, resulted in morphological changes as TEM revealed the formation of an intergranular phase that effectively isolated the hard magnetic SmCo 7 grains from one another, reducing magnetic interactions. Excellent isotropic energy products of 6 -8 MGOe were also achieved.