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Role of Tin Additions on Properties and Phases of Smco 5 Alloys

Thesis Info

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Author

Zaigham, Hamid

Program

PhD

Institute

Ghulam Ishaq Khan Institute of Engineering Sciences and Technology

City

Swabi

Province

KPK

Country

Pakistan

Thesis Completing Year

2011

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1276

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727125460

Similar


The samarium cobalt (SmCo 5 ) magnets provide higher magnetic force density, unlike the Alnico and other previously used magnets. The small sized magnets embedded in the properly designed appliance provide the forces necessary in dental, biomechanical treatments, removable partial dentures and implant prosthodontics. Cast SmCo 5-x Sn x (x=0.01, 0.06, and 0.12) alloys were prepared by arc melting with subsequent thermal homogenization. Microstructural and x-ray diffraction studies revealed that the alloys contain three phases i.e. SmCo 5 , Sm 2 Co 7 and Sm 2 Co 17 . The addition of Sn also caused grain refinement of the alloys. It was found that Sn addition had promoted nucleation of Sm 2 Co 17 , segregation of solute atoms and increase in unit cell volume, consequently, significant augmentation in remanence to maximum magnetization ratios were achieved. The nano-phase structures and magnetic properties of as milled powders were investigated. The Sn additions resulted in development of nanocrystalline structures producing exchange-coupled magnets with better remanence magnetization to maximum magnetization ratios (M r /M max ), typically 0.92 at 9.9 kOe coercivity. In addition, it was observed that the Sn concentrations lead to higher M r /M max ratios and maximum magnetization accompanying lower coercivity. X-ray diffraction revealed formation of 2:17 and 2:7 phases in 1:5 matrix, which were found to be dependent on Sn percentage. It appeared that higher Sn concentrations promoted 2:17 phase and helped in the formation of nano-sized phases. The investigation of sintered bulk SmCo 5-x Sn x alloys elucidated the presence of exchange coupling phenomena. Addition of Sn in the alloys developed nanocrystalline structure that in turn appeared to be responsible for producing exchange coupled magnets. The exchange coupling mechanism was evaluated by switching field distribution (SFD), dc—demagnetization M r (H) and magnetization M(H) curves as function reverse applied field (H r ). Sn additions resulted in increase in maximum magnetization and enhanced exchange coupling phenomena. The energy product (BH max ) of 7.4 MGOe iv(59.2 kJ/m 3 ), remanence magnetization to maximum magnetization ratios (M r /M max ) of 0.97 and remanence coercivity to intrinsic coercivity ratios (H r /H ci ) of 1.75 were achieved for sintered alloy containing 0.01 % Sn. Exchanged coupling and magnetic properties of SmCo 5 alloys containing Sn were investigated in sintered magnets with and without magnetic field annealing. It was found that applying magnetic field along the alignment direction of the samples was favorable for enhancing the reversibility in comparison to annealing without magnetic field. The remanence coercivity to intrinsic coercivity ratio increased from 1.75 to 2.0 with magnetic field annealing. The effect of Sn additions on electrochemical corrosion properties of sintered nanocrystalline SmCo 5-x Sn x alloys in comparison to conventional SmCo 5 binary alloy was investigated with the dc cyclic polarization technique in simulated marine environment. It was observed that Sn additions significantly reduced the corrosion rate up to 84% with only 0.01% Sn and it was further decreased to 90% with 0.12% Sn compared to the binary SmCo 5 alloy. The results showed that the corrosion rate was reduced with decrease in grain size. Scanning electron microscopy revealed pitting mechanism for both the binary and ternary alloys. Improved corrosion resistance of the alloys with Sn alloying is attributed to the interaction of Sn with grain boundary phases altering potential of the electrochemically more active samarium rich phases around the grain boundaries. This work has shown that Sn additions can be beneficial to the magnetic properties and enhanced the corrosion resistance of the alloys.
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میں جو سوئے عیش رواں ہوا، یہ زیاں ہوا

میں جو سوئے عیش رواں ہوا، یہ زیاں ہوا
مجھے کیوں نہ اس کا گماں ہوا، یہ زیاں ہوا

میرے دل میں کوئی مقیم تھا یہی سود تھا
یہ جو خالی دل کا مکاں ہوا، یہ زیاں ہوا

تری بے رُخی کا جو بار تھا کوئی کم نہ تھا
یہی بار بارِ گراں ہوا، یہ زیاں ہوا

مجھے شوقِ دیدِ حرم نہیں یہ ستم نہیں؟
مجھے شوقِ کوئے بتاں ہوا، یہ زیاں ہوا

میری کلفتیں جو نہاں رہیں یہ تو ٹھیک تھا
مرا درد ہے جو عیاں ہوا، یہ زیاں ہوا

وہ تو مہربانی سے کہہ رہے تھے بیاں کرو
جو نہ حال مجھ سے بیاں ہوا، یہ زیاں ہوا

محدثين كے ہاں قراء ثلاثہ كا مقام و مرتبہ اور علم حديث ميں ان كى خدمات

Allah Himself has taken the responsibility to protect the Holy Quran and the Hadith of the Holy Prophet. He Himself has provided the sources of their protection. One of the means of the protection that was the creation of such a group of the Qura who not only served the Holy Quran but also provided worth mentioning services in Ahadith of the Holy Prophet. But their services are hidden from us. By Qura the researcher means those Qura whose recitation styles and narrations are studied and taught in the different quarters of the world who are known as Qura Saba & Ashra (سبعہ وعشرہ). They are ten imams each with two Ravi’s. They are thirty Qura in total. I have selected only last three Imam & their two narrators in this Article. These Qurra are known as Qurra Thlathah (قراء ثلاثہ).  The services of these imams have been highlighted in the light of the following eleven Ahadith books. Sihah:   Sahih Bukhari, Sahih Muslim, Sahih Ibn-e-Habban, Sahih Ibn-e-Khuzeema. Sunan: Sunan Abu Dawud, Sunan al-Tirmidhi, Sunan al-Nasai, Sunan Ibn Majah, and Sunan al-Kubra. Masaneed: Musnad Ahmad ibn Hanbal, Musnad Abu Ya`la al-Mawsili. How many people have reported them and what is the standard of the weakness and soundness of those narrators have also been discussed in this article. Besides these books of Ahadith, these Ahadith have been searched in other books of Ahadith also. The status of these Qura has been explained in the light of the commentary of Muhadithin. Whether Ahadith critics have declared them thiqa or weak or have declared them as average sadooq. The most important thing is that there is no one weak reporter in these imam qura. Two out of three imam qura are ranked as thiqa and one sadooq. And among the narrators of these qura one is thiqa, one sadooq, and nobody are weak reporters. There is silence about the remaining four reporters of these qura. The reason is that there is no hadith reported from them. Because of all this their religious and scholarly authenticity could be determined. The narrations of these thalathah (ثلاثہ) Qura are confined to reporting the Holy Quran but they have also reported about every part of fiqh and they have been utilized and refered to  

Exploring the Teachers Assessment Strategies of Social Skills of Lower Primary Students

Assessment is a process of collecting data for the purposes of making decisions about students' (Salvia &Ysseldyke, 2001) academic progress as well as social and physical development. Teachers adopt a variety of assessment strategies in order to make decisions about students' academic performance with social skill demonstration in the classroom. Social skills are the skills employed when interacting with other people at an interpersonal level (Hargie, Saunders & Dickson, 1994). Good social skills include things such as cooperating, compromising and respecting the personal space of others (Masty& Schwab 2006). Teachers' assessment strategies of social skills can help in facilitating a smooth learning environment and facilitate students' achievement in the class, and the same habit may continue throughout the life of the individual. The study explores the strategies that teachers use to assess students' social skills and why they use them in a lower primary section of a private English medium O'levels Islamic school in Karachi, Pakistan. The study employed a case study method to explore the phenomenon. My sampling criteria were purposive. I conducted my study in the school where I am presently employed as a teacher. I positioned myself as a researcher in the school in order to collect authentic and trustworthy data. The research participants were four teachers (two from grade one and two from grade two). The data were collected through semi-structured interviews, observations of teachers' assessment strategies, and document analysis of assessment policy document and report cards. The data suggests that teachers use a variety of formal and informal assessment strategies to assess students' social skills. However, they are either not aware or confused about the assessment strategies they use and the reasons behind their usage. It is here that the teachers need to get acquainted with the assessment knowledge which will help them to reflect on their present assessment practices and develop informed understanding for the reasons of assessment. This study can prove beneficial to the school and the teachers in developing this informed understanding about the assessment of social skills. Furthermore, it can help them in learning more about the formal and informal assessment strategies that the lower primary teachers of the school adopt for the assessment of social skills. The findings of this study may provide useful insights for the particular school and other schools that adopt the same as essment procedures in developing a framework based on the principles for the assessment