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<p>[QUOTE="mpcusa, post: 3359922, member: 26550"]<b>Rare-earth magnets</b> are strong <a href="https://en.wikipedia.org/wiki/Permanent_magnet" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Permanent_magnet" rel="nofollow">permanent magnets</a> made from <a href="https://en.wikipedia.org/wiki/Alloy" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Alloy" rel="nofollow">alloys</a> of <a href="https://en.wikipedia.org/wiki/Rare-earth_element" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Rare-earth_element" rel="nofollow">rare-earth elements</a>. Developed in the 1970s and 1980s, rare-earth magnets are the strongest type of permanent magnets made, producing significantly stronger magnetic fields than other types such as <a href="https://en.wikipedia.org/wiki/Ferrite_(magnet)" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Ferrite_(magnet)" rel="nofollow">ferrite</a> or <a href="https://en.wikipedia.org/wiki/Alnico" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Alnico" rel="nofollow">alnico</a> magnets. The <a href="https://en.wikipedia.org/wiki/Magnetic_field" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Magnetic_field" rel="nofollow">magnetic field</a> typically produced by rare-earth magnets can exceed 1.4 <a href="https://en.wikipedia.org/wiki/Tesla_(unit)" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Tesla_(unit)" rel="nofollow">teslas</a>, whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla. There are two types: <a href="https://en.wikipedia.org/wiki/Neodymium_magnet" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Neodymium_magnet" rel="nofollow">neodymium magnets</a> and <a href="https://en.wikipedia.org/wiki/Samarium%E2%80%93cobalt_magnet" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Samarium%E2%80%93cobalt_magnet" rel="nofollow">samarium–cobalt magnets</a>. <a href="https://en.wikipedia.org/wiki/Magnetostriction" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Magnetostriction" rel="nofollow">Magnetostrictive</a> rare-earth magnets such as <a href="https://en.wikipedia.org/wiki/Terfenol-D" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Terfenol-D" rel="nofollow">Terfenol-D</a> also have applications, e.g. in <a href="https://en.wikipedia.org/wiki/Loudspeaker" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Loudspeaker" rel="nofollow">loudspeakers</a>. Rare-earth magnets are extremely <a href="https://en.wikipedia.org/wiki/Brittle" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Brittle" rel="nofollow">brittle</a> and also vulnerable to <a href="https://en.wikipedia.org/wiki/Corrosion" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Corrosion" rel="nofollow">corrosion</a>, so they are usually <a href="https://en.wikipedia.org/wiki/Plating" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Plating" rel="nofollow">plated</a> or <a href="https://en.wikipedia.org/wiki/Coating" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Coating" rel="nofollow">coated</a> to protect them from breaking, chipping, or crumbling into powder.</p><p><br /></p><p>The development of rare-earth magnets began around 1966, when K. J. Strnat and G. Hoffer of the US Air Force Materials Laboratory discovered that an alloy of <a href="https://en.wikipedia.org/wiki/Yttrium" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Yttrium" rel="nofollow">yttrium</a> and <a href="https://en.wikipedia.org/wiki/Cobalt" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Cobalt" rel="nofollow">cobalt</a>, YCo5, had by far the largest <a href="https://en.wikipedia.org/wiki/Magnetic_anisotropy" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Magnetic_anisotropy" rel="nofollow">magnetic anisotropy</a> constant of any material then known.<a href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-Cullity-1" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-Cullity-1" rel="nofollow">[1]</a><a href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-Lovelace-2" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-Lovelace-2" rel="nofollow">[2]</a> The term "rare earth" can be misleading, as these metals are not particularly rare or precious;<a href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-3" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-3" rel="nofollow">[3]</a><a href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-4" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-4" rel="nofollow">[4]</a> they are about as <a href="https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust" rel="nofollow">abundant</a> as tin or lead.<a href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-5" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-5" rel="nofollow">[5]</a> However rare earth ores are unevenly distributed, with the major source being <a href="https://en.wikipedia.org/wiki/China" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/China" rel="nofollow">China</a>,<a href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-Walsh-6" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-Walsh-6" rel="nofollow">[6]</a> which has led countries to classify rare earth metals as strategically important.<a href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-Chu-7" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-Chu-7" rel="nofollow">[7]</a> Recent Chinese export restrictions on these materials have led other countries to initiate research programs to develop strong magnets that do not require them.</p><p><br /></p><p><a href="https://en.wikipedia.org/wiki/File:Neodymium_magnet_lifting_spheres.jpg" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/File:Neodymium_magnet_lifting_spheres.jpg" rel="nofollow"><img src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Neodymium_magnet_lifting_spheres.jpg/120px-Neodymium_magnet_lifting_spheres.jpg" class="bbCodeImage wysiwygImage" alt="" unselectable="on" /></a></p><p>Neodymium magnets (small cylinders) lifting steel balls. As shown here, rare-earth magnets can easily lift thousands of times their own weight.[/QUOTE]</p><p><br /></p>
[QUOTE="mpcusa, post: 3359922, member: 26550"][B]Rare-earth magnets[/B] are strong [URL='https://en.wikipedia.org/wiki/Permanent_magnet']permanent magnets[/URL] made from [URL='https://en.wikipedia.org/wiki/Alloy']alloys[/URL] of [URL='https://en.wikipedia.org/wiki/Rare-earth_element']rare-earth elements[/URL]. Developed in the 1970s and 1980s, rare-earth magnets are the strongest type of permanent magnets made, producing significantly stronger magnetic fields than other types such as [URL='https://en.wikipedia.org/wiki/Ferrite_(magnet)']ferrite[/URL] or [URL='https://en.wikipedia.org/wiki/Alnico']alnico[/URL] magnets. The [URL='https://en.wikipedia.org/wiki/Magnetic_field']magnetic field[/URL] typically produced by rare-earth magnets can exceed 1.4 [URL='https://en.wikipedia.org/wiki/Tesla_(unit)']teslas[/URL], whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla. There are two types: [URL='https://en.wikipedia.org/wiki/Neodymium_magnet']neodymium magnets[/URL] and [URL='https://en.wikipedia.org/wiki/Samarium%E2%80%93cobalt_magnet']samarium–cobalt magnets[/URL]. [URL='https://en.wikipedia.org/wiki/Magnetostriction']Magnetostrictive[/URL] rare-earth magnets such as [URL='https://en.wikipedia.org/wiki/Terfenol-D']Terfenol-D[/URL] also have applications, e.g. in [URL='https://en.wikipedia.org/wiki/Loudspeaker']loudspeakers[/URL]. Rare-earth magnets are extremely [URL='https://en.wikipedia.org/wiki/Brittle']brittle[/URL] and also vulnerable to [URL='https://en.wikipedia.org/wiki/Corrosion']corrosion[/URL], so they are usually [URL='https://en.wikipedia.org/wiki/Plating']plated[/URL] or [URL='https://en.wikipedia.org/wiki/Coating']coated[/URL] to protect them from breaking, chipping, or crumbling into powder. The development of rare-earth magnets began around 1966, when K. J. Strnat and G. Hoffer of the US Air Force Materials Laboratory discovered that an alloy of [URL='https://en.wikipedia.org/wiki/Yttrium']yttrium[/URL] and [URL='https://en.wikipedia.org/wiki/Cobalt']cobalt[/URL], YCo5, had by far the largest [URL='https://en.wikipedia.org/wiki/Magnetic_anisotropy']magnetic anisotropy[/URL] constant of any material then known.[URL='https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-Cullity-1'][1][/URL][URL='https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-Lovelace-2'][2][/URL] The term "rare earth" can be misleading, as these metals are not particularly rare or precious;[URL='https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-3'][3][/URL][URL='https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-4'][4][/URL] they are about as [URL='https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust']abundant[/URL] as tin or lead.[URL='https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-5'][5][/URL] However rare earth ores are unevenly distributed, with the major source being [URL='https://en.wikipedia.org/wiki/China']China[/URL],[URL='https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-Walsh-6'][6][/URL] which has led countries to classify rare earth metals as strategically important.[URL='https://en.wikipedia.org/wiki/Rare-earth_magnet#cite_note-Chu-7'][7][/URL] Recent Chinese export restrictions on these materials have led other countries to initiate research programs to develop strong magnets that do not require them. [URL='https://en.wikipedia.org/wiki/File:Neodymium_magnet_lifting_spheres.jpg'][IMG]https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Neodymium_magnet_lifting_spheres.jpg/120px-Neodymium_magnet_lifting_spheres.jpg[/IMG][/URL] Neodymium magnets (small cylinders) lifting steel balls. As shown here, rare-earth magnets can easily lift thousands of times their own weight.[/QUOTE]
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