[meteorite-list] Is there room for a meteorite question ?
From: MexicoDoug_at_aol.com <MexicoDoug_at_meteoritecentral.com>
Date: Thu Apr 22 10:17:45 2004 Message-ID: <11a.2c2d3e0c.2d0aa15a_at_aol.com> --part1_11a.2c2d3e0c.2d0aa15a_boundary Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en And for a more complete stab at answering your question from a proud=20 "newbee". Note you really asked two questions. =20 1. If upon cooling there is expansion and 2. If the density is the same as=20 non-crystalline materials formed on earth in the same ally proportions.=20 To question 1: If I understand your question properly at first reading you=20 think that Fe-Ni mixtures upon cooling in the proper proportions forming tae= nite=20 / kamacite might expand? No way. Those structures do not form until after=20 the alloy is already solid, though in an amorphous (non-crystalline) state w= ith=20 selective atom mobility. Those migrations of atoms occur to release heat=20 energy flowing out of the system because of decreasing boundary temperatures= and=20 the law of heat flowing from higher to colder temperatures. The migrations=20 are happening as these new crystal structures settle down from vibrations an= d=20 fall into their little unit cells, allowing for a more dense material. For=20= an=20 expansion they would have to rip apart the already developed solid=20 structure...causing perhaps a very brittle substance even. Now your other question, whether the "terrestrial" amorphous material has th= e=20 same density as a "crystalline" meteorite material. That's something I'm=20 sure you know if you think a minute. Of course it does not have the same=20 density. So save your iron meteorites for better experiments, and don't mel= t them to=20 see. The amorphous material probably won't even have as an extremely=20 precisely definable density. It ought to vary because it is amorphous. Whe= ther=20 statistics averages the density out or not is a separate question and of cou= rse=20 will depend on exactly what alloy %'s you have and how well they are mixed o= n a=20 macro scale...the history of how the sample was cooled, etc. Does graphite=20 have the same density as diamond? No. You cite water, when freezing, as expanding as your model, since water (0.92= =20 g/mL) in equilibrium at 0=C2=B0C is denser than ice (1.00 g/mL). Water is w= eird,=20 and one of the anomalous things that explains life. The short answer on why= it=20 expands upon decreasing temperature at atmospheric pressure from 4=C2=B0C to= 0=C2=B0C=20 is a softening of proton (hydrogen) bonding and disruption of that nicely=20 organized structure as it is an ionic (solution) type attraction that is des= troyed=20 as the molecules begin to fall down from their bounciness caused by higher=20 temperatures. So the destruction of the hydrogen bonds happens upon cooling= . =20 Another way to say that is the melting of the hydrogen bonds upon cooling= =E2=80=A6 In=20 its amorphous, hydrogen-bondless state oxygen atoms find themselves not=20 tolerating such close density as before when all were moderated by the hydro= gen=20 atoms. So they repel each other an average of about 8% volume increase. Wa= ter=20 would be less than 0.92 g/mL at room temperature if not for the hydrogen bon= ding.=20 Probably about 0.90, and then it would behave like most of the other=20 molecules upon freezing. There are no comparably scaled ionic like attractions going on in the metal=20 alloys as they cool. So there is no comparison to the special case of water= . =20 Additionally, you should know that water ice has about 20 described=20 crystalline structures, and they are, not coincidentally, not all the same d= ensity! You=20 need to know the history of it. Do you think super cooled hail is the same=20 as the cubes floating in your ice tea? No. And the rockhounds can probably= =20 come up with a good list of structures with different densities but the same= =20 molecular proportions. Every sample is individual: so back to the meteorite experiment. Each=20 meteorite has a different history as in temperatures and pressures. Each ha= s=20 different impurities, so you will need to do more that just reproduce the al= loy=20 proportions...actually by now it seems pretty clear that the proposed experi= ment=20 is not a good idea. All those impurities disrupt perfect conditions. So=20 oceans don't freeze at 0=C2=B0C, they are a few degrees colder, because of t= he=20 impurities. All that affects densities, not to mention any molecular flatul= ence=20 causing micro pores, uniformly or not. Ooops. Just checking to see if anyo= ne read=20 this far... PS Ice floats. Can you imagine solid pieces of metal alloy floating as it i= s=20 melted...that was the easier explanation... Saludos Doug Dawn Mexico En un mensaje con fecha 12/11/2003 2:58:13 PM Mexico Standard Time,=20 khill_at_cpsmedical.com escribe: >=20 >=20 >=20 > Question: When water turns to ice the change to a crystal structure > expands the volume (decreases density). Does this density/expansion chang= e > also occur with the development of taenite/kamacite > lattices? ie. at the same temperature is the density of an iron meteorit= e > match the density of a "terrestrial" matching mixture that is > "noncrystalline"? Guess you could melt down one of your irons and compare= ? >=20 > Fly Hill >=20 > >----- Original Message -----=20 > >From: "mark ford" <markf_at_ssl.gb.com> > >To: <meteorite-list_at_meteoritecentral.com> > >Sent: Tuesday, December 09, 2003 8:41 AM > >Subject: RE: [meteorite-list] Is there room for a meteorite question ? > > > > > >> > >> > >> > >> > >> > >>On the same note, thermal expansion... > >> > >>Presumably as the core solidifies (cools down) it would contract, would > >>it not?, what effect would that have on the crystalline structure > >>(widmanstatten) would there be a gradual stress/distortion in the > >>taenite/kamacite boundries ? > >> > >> > >>I guess as the core is such a big mass, any significant thermal > >>contraction distortion would hardly be noticeable in a small hand > >>specimen but I would imagine the thermal contraction in something the > >>size of a large planetary body would be massive. > >> > >> > >> > >>Mark Ford > >> > >> > >> > >> > > > >-------------------------------------------------------------------------= - > >-- > >>The information contained in this email may be commercially sensitive > >and/or > >>legally privileged. It is intended solely for the person(s) to whom it > is > >>addressed. If you are not a named recipient, you are on notice of its > >status. > >>Please notify the sender immediately by reply e-mail and then delete > this > >>message from your system. You must not disclose it to any other person, > >>copy or distribute it or use it for any purpose. >=20 --part1_11a.2c2d3e0c.2d0aa15a_boundary Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en <HTML><FONT FACE=3Darial,helvetica><FONT SIZE=3D2 FAMILY=3D"SANSSERIF" FACE= =3D"Arial" LANG=3D"0">And for a more complete stab at answering your questio= n from a proud "newbee". Note you really asked two questions. <B= R> <BR> 1. If upon cooling there is expansion and 2. If the density is the same as n= on-crystalline materials formed on earth in the same ally proportions. <BR> <BR> To question 1: If I understand your question properly at first reading you t= hink that Fe-Ni mixtures upon cooling in the proper proportions forming taen= ite / kamacite might expand? No way. Those structures do not for= m until after the alloy is already solid, though in an amorphous (non-crysta= lline) state with selective atom mobility. Those migrations of atoms o= ccur to release heat energy flowing out of the system because of decreasing=20= boundary temperatures and the law of heat flowing from higher to colder temp= eratures. The migrations are happening as these new crystal structures= settle down from vibrations and fall into their little unit cells, allowing= for a more dense material. For an expansion they would have to rip ap= art the already developed solid structure...causing perhaps a very brittle s= ubstance even.<BR> <BR> Now your other question, whether the "terrestrial" amorphous material has th= e same density as a "crystalline" meteorite material. That's something= I'm sure you know if you think a minute. Of course it does not have t= he same density. So save your iron meteorites for better experiments,=20= and don't melt them to see. The amorphous material probably won't even= have as an extremely precisely definable density. It ought to vary be= cause it is amorphous. Whether statistics averages the density out or=20= not is a separate question and of course will depend on exactly what alloy %= 's you have and how well they are mixed on a macro scale...the history of ho= w the sample was cooled, etc. Does graphite have the same density as d= iamond? No.<BR> <BR> You cite water, when freezing, as expanding as your model, since water (0.92= g/mL) in equilibrium at 0=C2=B0C is denser than ice (1.00 g/mL). Wate= r is weird, and one of the anomalous things that explains life. The sh= ort answer on why it expands upon decreasing temperature at atmospheric pres= sure from 4=C2=B0C to 0=C2=B0C is a softening of proton (hydrogen) bonding a= nd disruption of that nicely organized structure as it is an ionic (solution= ) type attraction that is destroyed as the molecules begin to fall down from= their bounciness caused by higher temperatures. So the destruction of= the hydrogen bonds happens upon cooling. Another way to say that is t= he melting of the hydrogen bonds upon cooling=E2=80=A6 In its amorphou= s, hydrogen-bondless state oxygen atoms find themselves not tolerating such=20= close density as before when all were moderated by the hydrogen atoms. = So they repel each other an average of about 8% volume increase. Wate= r would be less than 0.92 g/mL at room temperature if not for the hydrogen b= onding. Probably about 0.90, and then it would behave like most of the= other molecules upon freezing.<BR> <BR> There are no comparably scaled ionic like attractions going on in the metal=20= alloys as they cool. So there is no comparison to the special case of=20= water. Additionally, you should know that water ice has about 20 descr= ibed crystalline structures, and they are, not coincidentally, not all the s= ame density! You need to know the history of it. Do you think su= per cooled hail is the same as the cubes floating in your ice tea? No.= And the rockhounds can probably come up with a good list of structure= s with different densities but the same molecular proportions.<BR> <BR> Every sample is individual: so back to the meteorite experiment. Each=20= meteorite has a different history as in temperatures and pressures. Ea= ch has different impurities, so you will need to do more that just reproduce= the alloy proportions...actually by now it seems pretty clear that the prop= osed experiment is not a good idea. All those impurities disrupt perfe= ct conditions. So oceans don't freeze at 0=C2=B0C, they are a few degr= ees colder, because of the impurities. All that affects densities, not= to mention any molecular flatulence causing micro pores, uniformly or not.&= nbsp; Ooops. Just checking to see if anyone read this far...<BR> <BR> PS Ice floats. Can you imagine solid pieces of metal alloy floating as= it is melted...that was the easier explanation...<BR> <BR> Saludos<BR> Doug Dawn<BR> Mexico<BR> <BR> En un mensaje con fecha 12/11/2003 2:58:13 PM Mexico Standard Time, khill_at_cp= smedical.com escribe:<BR> <BR> <BLOCKQUOTE TYPE=3DCITE style=3D"BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT= : 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px"><BR> <BR> <BR> Question: When water turns to ice the change to a crystal struct= ure<BR> expands the volume (decreases density). Does this density/expansion ch= ange<BR> also occur with the development of taenite/kamacite<BR> lattices? ie. at the same temperature is the density of an iron=20= meteorite<BR> match the density of a "terrestrial" matching mixture that is<BR> "noncrystalline"? Guess you could melt down one of your irons and comp= are?<BR> <BR> Fly Hill<BR> <BR> >----- Original Message ----- <BR> >From: "mark ford" <markf_at_ssl.gb.com><BR> >To: <meteorite-list_at_meteoritecentral.com><BR> >Sent: Tuesday, December 09, 2003 8:41 AM<BR> >Subject: RE: [meteorite-list] Is there room for a meteorite question ?<B= R> ><BR> ><BR> >><BR> >><BR> >><BR> >><BR> >><BR> >>On the same note, thermal expansion...<BR> >><BR> >>Presumably as the core solidifies (cools down) it would contract, wo= uld<BR> >>it not?, what effect would that have on the crystalline structure<BR= > >>(widmanstatten) would there be a gradual stress/distortion in the<BR= > >>taenite/kamacite boundries ?<BR> >><BR> >><BR> >>I guess as the core is such a big mass, any significant thermal<BR> >>contraction distortion would hardly be noticeable in a small hand<BR= > >>specimen but I would imagine the thermal contraction in something th= e<BR> >>size of a large planetary body would be massive.<BR> >><BR> >><BR> >><BR> >>Mark Ford<BR> >><BR> >><BR> >><BR> >><BR> ><BR> >------------------------------------------------------------------------= --<BR> >--<BR> >>The information contained in this email may be commercially sensitiv= e<BR> >and/or<BR> >>legally privileged. It is intended solely for the person(s) to whom=20= it<BR> is<BR> >>addressed. If you are not a named recipient, you are on notice of it= s<BR> >status.<BR> >>Please notify the sender immediately by reply e-mail and then delete= <BR> this<BR> >>message from your system. You must not disclose it to any other pers= on,<BR> >>copy or distribute it or use it for any purpose.<BR> </BLOCKQUOTE><BR> <BR> </FONT></HTML> --part1_11a.2c2d3e0c.2d0aa15a_boundary-- Received on Thu 11 Dec 2003 11:43:06 PM PST |
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