Micromechanical properties and structural characterization of modern inarticulated brachiopod shells
Identifieur interne : 002433 ( Istex/Corpus ); précédent : 002432; suivant : 002434Micromechanical properties and structural characterization of modern inarticulated brachiopod shells
Auteurs : C. Merkel ; E. Griesshaber ; K. Kelm ; R. Neuser ; G. Jordan ; A. Logan ; W. Mader ; W. W. SchmahlSource :
- Journal of Geophysical Research: Biogeosciences [ 0148-0227 ] ; 2007-06.
Abstract
We investigated micromechanical properties and ultrastructure of the shells of the modern brachiopod species Lingula anatina, Discinisca laevis, and Discradisca stella with scanning electron microscopy (SEM, EDX), transmission electron microscopy (TEM) and Vickers microhardness indentation analyses. The shells are composed of two distinct layers, an outer primary layer and an inner secondary layer. Except for the primary layer in Lingula anatina, which is composed entirely of organic matter, all other shell layers are laminated organic/inorganic composites. The organic matter is built of chitin fibers, which provide the matrix for the incorporation of calcium phosphate. Amorphous calcium phosphate in the outer, primary layer and crystalline apatite is deposited into the inner, secondary layer of the shell. Apatite crystallite sizes in the umbonal region of the shell are about 50 × 50 nm, while within the valves crystallite sizes are significantly smaller, averanging 10 × 25 nm. There is great variation in hardness values between shell layers and between the investigated brachiopod species. The microhardness of the investigated shells is significantly lower than that of inorganic hydroxyapatite. This is caused by the predominantly organic material component that in these shells is either developed as purely organic layers or as an organic fibrous matrix reinforced by crystallites. Our results show that this particular fiber composite material is very efficient for the protection and the support of the soft animal tissue. It lowers the probability of crack formation and effectively impedes crack propagation perpendicular to the shell by crack‐deviation mechanisms. The high degree of mechanical stability and toughness is achieved by two design features. First, there is the fiber composite material which overcomes some detrimental and enhances some advantageous properties of the single constituents, that is the softness and flexibility of chitin and the hardness and brittleness of apatite. Second, there is a hierarchical structuring from the nanometer to a micrometer level. We could identify at least seven levels of hierarchy within the shells.
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DOI: 10.1029/2006JG000253
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Griesshaber</name><affiliation><mods:affiliation>Section of Palaeontology, Department of Earth and Environmental Sciences, Ludwig‐Maximilians University Munich, Munich, Germany</mods:affiliation></affiliation></author><author><name sortKey="Kelm, K" sort="Kelm, K" uniqKey="Kelm K" first="K." last="Kelm">K. Kelm</name><affiliation><mods:affiliation>Institut für Anorganische Chemie, Universität Bonn, Bonn, Germany</mods:affiliation></affiliation></author><author><name sortKey="Neuser, R" sort="Neuser, R" uniqKey="Neuser R" first="R." last="Neuser">R. Neuser</name><affiliation><mods:affiliation>Institut für Geologie, Mineralogie und Geophysik, Ruhr‐Universität Bochum, Bochum, Germany</mods:affiliation></affiliation></author><author><name sortKey="Jordan, G" sort="Jordan, G" uniqKey="Jordan G" first="G." last="Jordan">G. 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Merkel</name><affiliation><mods:affiliation>Section of Applied Crystallography and Materials Science, Department of Earth and Environmental Sciences, Ludwig‐Maximilians University Munich, Munich, Germany</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: casjen.merkel@lrz.uni-muenchen.de</mods:affiliation></affiliation></author><author><name sortKey="Griesshaber, E" sort="Griesshaber, E" uniqKey="Griesshaber E" first="E." last="Griesshaber">E. Griesshaber</name><affiliation><mods:affiliation>Section of Palaeontology, Department of Earth and Environmental Sciences, Ludwig‐Maximilians University Munich, Munich, Germany</mods:affiliation></affiliation></author><author><name sortKey="Kelm, K" sort="Kelm, K" uniqKey="Kelm K" first="K." last="Kelm">K. Kelm</name><affiliation><mods:affiliation>Institut für Anorganische Chemie, Universität Bonn, Bonn, Germany</mods:affiliation></affiliation></author><author><name sortKey="Neuser, R" sort="Neuser, R" uniqKey="Neuser R" first="R." last="Neuser">R. Neuser</name><affiliation><mods:affiliation>Institut für Geologie, Mineralogie und Geophysik, Ruhr‐Universität Bochum, Bochum, Germany</mods:affiliation></affiliation></author><author><name sortKey="Jordan, G" sort="Jordan, G" uniqKey="Jordan G" first="G." last="Jordan">G. Jordan</name><affiliation><mods:affiliation>Section of Applied Crystallography and Materials Science, Department of Earth and Environmental Sciences, Ludwig‐Maximilians University Munich, Munich, Germany</mods:affiliation></affiliation></author><author><name sortKey="Logan, A" sort="Logan, A" uniqKey="Logan A" first="A." last="Logan">A. Logan</name><affiliation><mods:affiliation>Department of Physical Sciences, University of New Brunswick, Saint John, New Brunswick, Canada</mods:affiliation></affiliation></author><author><name sortKey="Mader, W" sort="Mader, W" uniqKey="Mader W" first="W." last="Mader">W. Mader</name><affiliation><mods:affiliation>Institut für Anorganische Chemie, Universität Bonn, Bonn, Germany</mods:affiliation></affiliation></author><author><name sortKey="Schmahl, W W" sort="Schmahl, W W" uniqKey="Schmahl W" first="W. W." last="Schmahl">W. W. Schmahl</name><affiliation><mods:affiliation>Section of Applied Crystallography and Materials Science, Department of Earth and Environmental Sciences, Ludwig‐Maximilians University Munich, Munich, Germany</mods:affiliation></affiliation></author></analytic><monogr></monogr><series><title level="j">Journal of Geophysical Research: Biogeosciences</title><title level="j" type="abbrev">J. Geophys. Res.</title><idno type="ISSN">0148-0227</idno><idno type="eISSN">2156-2202</idno><imprint><publisher>Blackwell Publishing Ltd</publisher><date type="published" when="2007-06">2007-06</date><biblScope unit="volume">112</biblScope><biblScope unit="issue">G2</biblScope><biblScope unit="page" from="/">n/a</biblScope><biblScope unit="page" to="/">n/a</biblScope></imprint><idno type="ISSN">0148-0227</idno></series><idno type="istex">E297CFF8A2080550878E031A88777C331A5489D9</idno><idno type="DOI">10.1029/2006JG000253</idno><idno type="ArticleID">2006JG000253</idno></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0148-0227</idno></seriesStmt></fileDesc><profileDesc><textClass></textClass><langUsage><language ident="en">en</language></langUsage></profileDesc></teiHeader><front><div type="abstract">We investigated micromechanical properties and ultrastructure of the shells of the modern brachiopod species Lingula anatina, Discinisca laevis, and Discradisca stella with scanning electron microscopy (SEM, EDX), transmission electron microscopy (TEM) and Vickers microhardness indentation analyses. The shells are composed of two distinct layers, an outer primary layer and an inner secondary layer. Except for the primary layer in Lingula anatina, which is composed entirely of organic matter, all other shell layers are laminated organic/inorganic composites. The organic matter is built of chitin fibers, which provide the matrix for the incorporation of calcium phosphate. Amorphous calcium phosphate in the outer, primary layer and crystalline apatite is deposited into the inner, secondary layer of the shell. Apatite crystallite sizes in the umbonal region of the shell are about 50 × 50 nm, while within the valves crystallite sizes are significantly smaller, averanging 10 × 25 nm. There is great variation in hardness values between shell layers and between the investigated brachiopod species. The microhardness of the investigated shells is significantly lower than that of inorganic hydroxyapatite. This is caused by the predominantly organic material component that in these shells is either developed as purely organic layers or as an organic fibrous matrix reinforced by crystallites. Our results show that this particular fiber composite material is very efficient for the protection and the support of the soft animal tissue. It lowers the probability of crack formation and effectively impedes crack propagation perpendicular to the shell by crack‐deviation mechanisms. The high degree of mechanical stability and toughness is achieved by two design features. First, there is the fiber composite material which overcomes some detrimental and enhances some advantageous properties of the single constituents, that is the softness and flexibility of chitin and the hardness and brittleness of apatite. Second, there is a hierarchical structuring from the nanometer to a micrometer level. We could identify at least seven levels of hierarchy within the shells.</div></front></TEI><istex><corpusName>wiley</corpusName><author><json:item><name>C. Merkel</name><affiliations><json:string>Section of Applied Crystallography and Materials Science, Department of Earth and Environmental Sciences, Ludwig‐Maximilians University Munich, Munich, Germany</json:string><json:string>E-mail: casjen.merkel@lrz.uni-muenchen.de</json:string></affiliations></json:item><json:item><name>E. Griesshaber</name><affiliations><json:string>Section of Palaeontology, Department of Earth and Environmental Sciences, Ludwig‐Maximilians University Munich, Munich, Germany</json:string></affiliations></json:item><json:item><name>K. Kelm</name><affiliations><json:string>Institut für Anorganische Chemie, Universität Bonn, Bonn, Germany</json:string></affiliations></json:item><json:item><name>R. 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Schmahl</name><affiliations><json:string>Section of Applied Crystallography and Materials Science, Department of Earth and Environmental Sciences, Ludwig‐Maximilians University Munich, Munich, Germany</json:string></affiliations></json:item></author><subject><json:item><lang><json:string>eng</json:string></lang><value>modern inarticulated brachiopod</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>fiber composite structures</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>Vickers microhardness</value></json:item></subject><articleId><json:string>2006JG000253</json:string></articleId><language><json:string>eng</json:string></language><originalGenre><json:string>article</json:string></originalGenre><abstract>We investigated micromechanical properties and ultrastructure of the shells of the modern brachiopod species Lingula anatina, Discinisca laevis, and Discradisca stella with scanning electron microscopy (SEM, EDX), transmission electron microscopy (TEM) and Vickers microhardness indentation analyses. The shells are composed of two distinct layers, an outer primary layer and an inner secondary layer. Except for the primary layer in Lingula anatina, which is composed entirely of organic matter, all other shell layers are laminated organic/inorganic composites. The organic matter is built of chitin fibers, which provide the matrix for the incorporation of calcium phosphate. Amorphous calcium phosphate in the outer, primary layer and crystalline apatite is deposited into the inner, secondary layer of the shell. Apatite crystallite sizes in the umbonal region of the shell are about 50 × 50 nm, while within the valves crystallite sizes are significantly smaller, averanging 10 × 25 nm. There is great variation in hardness values between shell layers and between the investigated brachiopod species. The microhardness of the investigated shells is significantly lower than that of inorganic hydroxyapatite. This is caused by the predominantly organic material component that in these shells is either developed as purely organic layers or as an organic fibrous matrix reinforced by crystallites. Our results show that this particular fiber composite material is very efficient for the protection and the support of the soft animal tissue. It lowers the probability of crack formation and effectively impedes crack propagation perpendicular to the shell by crack‐deviation mechanisms. The high degree of mechanical stability and toughness is achieved by two design features. First, there is the fiber composite material which overcomes some detrimental and enhances some advantageous properties of the single constituents, that is the softness and flexibility of chitin and the hardness and brittleness of apatite. Second, there is a hierarchical structuring from the nanometer to a micrometer level. 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Res.</title><idno type="pISSN">0148-0227</idno><idno type="eISSN">2156-2202</idno><idno type="DOI">10.1002/(ISSN)2156-2202g</idno><imprint><publisher>Blackwell Publishing Ltd</publisher><date type="published" when="2007-06"></date><biblScope unit="volume">112</biblScope><biblScope unit="issue">G2</biblScope><biblScope unit="page" from="/">n/a</biblScope><biblScope unit="page" to="/">n/a</biblScope></imprint></monogr><idno type="istex">E297CFF8A2080550878E031A88777C331A5489D9</idno><idno type="DOI">10.1029/2006JG000253</idno><idno type="ArticleID">2006JG000253</idno></biblStruct></sourceDesc></fileDesc><profileDesc><creation><date>2007</date></creation><langUsage><language ident="en">en</language></langUsage><abstract><p>We investigated micromechanical properties and ultrastructure of the shells of the modern brachiopod species Lingula anatina, Discinisca laevis, and Discradisca stella with scanning electron microscopy (SEM, EDX), transmission electron microscopy (TEM) and Vickers microhardness indentation analyses. The shells are composed of two distinct layers, an outer primary layer and an inner secondary layer. Except for the primary layer in Lingula anatina, which is composed entirely of organic matter, all other shell layers are laminated organic/inorganic composites. The organic matter is built of chitin fibers, which provide the matrix for the incorporation of calcium phosphate. Amorphous calcium phosphate in the outer, primary layer and crystalline apatite is deposited into the inner, secondary layer of the shell. Apatite crystallite sizes in the umbonal region of the shell are about 50 × 50 nm, while within the valves crystallite sizes are significantly smaller, averanging 10 × 25 nm. There is great variation in hardness values between shell layers and between the investigated brachiopod species. The microhardness of the investigated shells is significantly lower than that of inorganic hydroxyapatite. This is caused by the predominantly organic material component that in these shells is either developed as purely organic layers or as an organic fibrous matrix reinforced by crystallites. Our results show that this particular fiber composite material is very efficient for the protection and the support of the soft animal tissue. It lowers the probability of crack formation and effectively impedes crack propagation perpendicular to the shell by crack‐deviation mechanisms. The high degree of mechanical stability and toughness is achieved by two design features. First, there is the fiber composite material which overcomes some detrimental and enhances some advantageous properties of the single constituents, that is the softness and flexibility of chitin and the hardness and brittleness of apatite. Second, there is a hierarchical structuring from the nanometer to a micrometer level. We could identify at least seven levels of hierarchy within the shells.</p></abstract><textClass><keywords scheme="keyword"><list><head>keywords</head><item><term>modern inarticulated brachiopod</term></item><item><term>fiber composite structures</term></item><item><term>Vickers microhardness</term></item></list></keywords></textClass><textClass><keywords scheme="Journal Subject"><list><head>index-terms</head><item><term>BIOGEOSCIENCES</term></item><item><term>Geomicrobiology</term></item><item><term>Macro‐ and micropaleontology</term></item><item><term>Biomineralization</term></item><item><term>MARINE GEOLOGY AND GEOPHYSICS</term></item><item><term>Micropaleontology</term></item><item><term>PALEOCEANOGRAPHY</term></item><item><term>Micropaleontology</term></item></list></keywords></textClass></profileDesc><revisionDesc><change when="2006-06-23">Received</change><change when="2007-01-10">Registration</change><change when="2007-06">Published</change></revisionDesc></teiHeader></istex:fulltextTEI><json:item><extension>txt</extension><original>false</original><mimetype>text/plain</mimetype><uri>https://api-v5.istex.fr/document/E297CFF8A2080550878E031A88777C331A5489D9/fulltext/txt</uri></json:item></fulltext><metadata><istex:metadataXml wicri:clean="Wiley, elements deleted: body"><istex:xmlDeclaration>version="1.0" encoding="UTF-8" standalone="yes"</istex:xmlDeclaration><istex:document><component type="serialArticle" version="2.0" xml:lang="en" xml:id="jgrg138"><header><publicationMeta level="product"><doi>10.1002/(ISSN)2156-2202g</doi><issn type="print">0148-0227</issn><issn type="electronic">2156-2202</issn><idGroup><id type="product" value="JGRG"></id><id type="coden" value="JGREA2"></id></idGroup><titleGroup><title type="main" xml:lang="en" sort="JOURNAL OF GEOPHYSICAL RESEARCH: BIOGEOSCIENCES">Journal of Geophysical Research: Biogeosciences</title><title type="short">J. Geophys. Res.</title></titleGroup></publicationMeta><publicationMeta level="part" position="20"><doi>10.1002/jgrg.v112.G2</doi><idGroup><id type="focusSection" value="7"></id></idGroup><titleGroup><title type="focusSection" xml:lang="en">Journal of Geophysical Research: Biogeosciences</title></titleGroup><numberingGroup><numbering type="journalVolume" number="112">112</numbering><numbering type="journalIssue">G2</numbering></numberingGroup><coverDate startDate="2007-06">June 2007</coverDate></publicationMeta><publicationMeta level="unit" position="260" type="article" status="forIssue"><doi>10.1029/2006JG000253</doi><idGroup><id type="editorialOffice" value="2006JG000253"></id><id type="society" value="G02008"></id><id type="unit" value="JGRG138"></id></idGroup><countGroup><count type="pageTotal" number="12"></count></countGroup><copyright ownership="thirdParty">Copyright 2007 by the American Geophysical Union.</copyright><eventGroup><event type="manuscriptReceived" date="2006-06-23"></event><event type="manuscriptRevised" date="2006-11-21"></event><event type="manuscriptAccepted" date="2007-01-10"></event><event type="firstOnline" date="2007-04-24"></event><event type="publishedOnlineFinalForm" date="2007-04-24"></event><event type="xmlConverted" agent="SPi Global Converter:AGUv3.44_TO_WileyML3Gv1.0.3 version:1.2; WileyML 3G Packaging Tool v1.0" date="2012-12-29"></event><event type="xmlConverted" agent="Converter:WILEY_ML3G_TO_WILEY_ML3GV2 version:3.8.8" date="2014-01-31"></event><event type="xmlConverted" agent="Converter:WML3G_To_WML3G version:4.1.7 mode:FullText,remove_FC" date="2014-10-30"></event></eventGroup><numberingGroup><numbering type="pageFirst">n/a</numbering><numbering type="pageLast">n/a</numbering></numberingGroup><subjectInfo><subject href="http://psi.agu.org/taxonomy5/0400">BIOGEOSCIENCES</subject><subjectInfo><subject href="http://psi.agu.org/taxonomy5/0448">Geomicrobiology</subject><subject href="http://psi.agu.org/taxonomy5/0459">Macro‐ and micropaleontology</subject><subject href="http://psi.agu.org/taxonomy5/0419">Biomineralization</subject></subjectInfo><subject role="crossTerm" href="http://psi.agu.org/taxonomy5/3000">MARINE GEOLOGY AND GEOPHYSICS</subject><subjectInfo><subject role="crossTerm" href="http://psi.agu.org/taxonomy5/3030">Micropaleontology</subject></subjectInfo><subject role="crossTerm" href="http://psi.agu.org/taxonomy5/4900">PALEOCEANOGRAPHY</subject><subjectInfo><subject role="crossTerm" href="http://psi.agu.org/taxonomy5/4944">Micropaleontology</subject></subjectInfo></subjectInfo><selfCitationGroup><citation xml:id="jgrg138-cit-0000" type="self"><author><familyName>Merkel</familyName>, <givenNames>C.</givenNames></author>, <author><givenNames>E.</givenNames> <familyName>Griesshaber</familyName></author>, <author><givenNames>K.</givenNames> <familyName>Kelm</familyName></author>, <author><givenNames>R.</givenNames> <familyName>Neuser</familyName></author>, <author><givenNames>G.</givenNames> <familyName>Jordan</familyName></author>, <author><givenNames>A.</givenNames> <familyName>Logan</familyName></author>, <author><givenNames>W.</givenNames> <familyName>Mader</familyName></author>, and <author><givenNames>W. W.</givenNames> <familyName>Schmahl</familyName></author> (<pubYear year="2007">2007</pubYear>), <articleTitle>Micromechanical properties and structural characterization of modern inarticulated brachiopod shells</articleTitle>, <journalTitle>J. Geophys. Res.</journalTitle>, <vol>112</vol>, G02008, doi:<accessionId ref="info:doi/10.1029/2006JG000253">10.1029/2006JG000253</accessionId>.</citation></selfCitationGroup><linkGroup><link type="toTypesetVersion" href="file:JGRG.JGRG138.pdf"></link></linkGroup></publicationMeta><contentMeta><countGroup><count type="figureTotal" number="10"></count></countGroup><titleGroup><title type="main">Micromechanical properties and structural characterization of modern inarticulated brachiopod shells</title><title type="short">BRACHIOPOD MICROHARDNESS</title><title type="shortAuthors">Merkel <i>et al</i>.</title></titleGroup><creators><creator creatorRole="author" xml:id="jgrg138-cr-0001" affiliationRef="#jgrg138-aff-0001"><personName><givenNames>C.</givenNames> <familyName>Merkel</familyName></personName><contactDetails><email normalForm="casjen.merkel@lrz.uni-muenchen.de">casjen.merkel@lrz.uni-muenchen.de</email></contactDetails></creator><creator creatorRole="author" xml:id="jgrg138-cr-0002" affiliationRef="#jgrg138-aff-0002"><personName><givenNames>E.</givenNames> <familyName>Griesshaber</familyName></personName></creator><creator creatorRole="author" xml:id="jgrg138-cr-0003" affiliationRef="#jgrg138-aff-0003"><personName><givenNames>K.</givenNames> <familyName>Kelm</familyName></personName></creator><creator creatorRole="author" xml:id="jgrg138-cr-0004" affiliationRef="#jgrg138-aff-0004"><personName><givenNames>R.</givenNames> <familyName>Neuser</familyName></personName></creator><creator creatorRole="author" xml:id="jgrg138-cr-0005" affiliationRef="#jgrg138-aff-0001"><personName><givenNames>G.</givenNames> <familyName>Jordan</familyName></personName></creator><creator creatorRole="author" xml:id="jgrg138-cr-0006" affiliationRef="#jgrg138-aff-0005"><personName><givenNames>A.</givenNames> <familyName>Logan</familyName></personName></creator><creator creatorRole="author" xml:id="jgrg138-cr-0007" affiliationRef="#jgrg138-aff-0003"><personName><givenNames>W.</givenNames> <familyName>Mader</familyName></personName></creator><creator creatorRole="author" xml:id="jgrg138-cr-0008" affiliationRef="#jgrg138-aff-0001"><personName><givenNames>W. W.</givenNames> <familyName>Schmahl</familyName></personName></creator></creators><affiliationGroup><affiliation countryCode="DE" type="organization" xml:id="jgrg138-aff-0001"><orgDiv>Section of Applied Crystallography and Materials Science, Department of Earth and Environmental Sciences</orgDiv><orgName>Ludwig‐Maximilians University Munich</orgName><address><city>Munich</city><country>Germany</country></address></affiliation><affiliation countryCode="DE" type="organization" xml:id="jgrg138-aff-0002"><orgDiv>Section of Palaeontology, Department of Earth and Environmental Sciences</orgDiv><orgName>Ludwig‐Maximilians University Munich</orgName><address><city>Munich</city><country>Germany</country></address></affiliation><affiliation countryCode="DE" type="organization" xml:id="jgrg138-aff-0003"><orgDiv>Institut für Anorganische Chemie</orgDiv><orgName>Universität Bonn</orgName><address><city>Bonn</city><country>Germany</country></address></affiliation><affiliation countryCode="DE" type="organization" xml:id="jgrg138-aff-0004"><orgDiv>Institut für Geologie, Mineralogie und Geophysik</orgDiv><orgName>Ruhr‐Universität Bochum</orgName><address><city>Bochum</city><country>Germany</country></address></affiliation><affiliation countryCode="CA" type="organization" xml:id="jgrg138-aff-0005"><orgDiv>Department of Physical Sciences</orgDiv><orgName>University of New Brunswick</orgName><address><city>Saint John, New Brunswick</city><country>Canada</country></address></affiliation></affiliationGroup><keywordGroup type="author"><keyword xml:id="jgrg138-kwd-0001">modern inarticulated brachiopod</keyword><keyword xml:id="jgrg138-kwd-0002">fiber composite structures</keyword><keyword xml:id="jgrg138-kwd-0003">Vickers microhardness</keyword></keywordGroup><abstractGroup><abstract type="main"><p xml:id="jgrg138-para-0001" label="1">We investigated micromechanical properties and ultrastructure of the shells of the modern brachiopod species <i>Lingula anatina</i>, <i>Discinisca laevis</i>, and <i>Discradisca stella</i> with scanning electron microscopy (SEM, EDX), transmission electron microscopy (TEM) and Vickers microhardness indentation analyses. The shells are composed of two distinct layers, an outer primary layer and an inner secondary layer. Except for the primary layer in <i>Lingula anatina</i>, which is composed entirely of organic matter, all other shell layers are laminated organic/inorganic composites. The organic matter is built of chitin fibers, which provide the matrix for the incorporation of calcium phosphate. Amorphous calcium phosphate in the outer, primary layer and crystalline apatite is deposited into the inner, secondary layer of the shell. Apatite crystallite sizes in the umbonal region of the shell are about 50 × 50 nm, while within the valves crystallite sizes are significantly smaller, averanging 10 × 25 nm. There is great variation in hardness values between shell layers and between the investigated brachiopod species. The microhardness of the investigated shells is significantly lower than that of inorganic hydroxyapatite. This is caused by the predominantly organic material component that in these shells is either developed as purely organic layers or as an organic fibrous matrix reinforced by crystallites. Our results show that this particular fiber composite material is very efficient for the protection and the support of the soft animal tissue. It lowers the probability of crack formation and effectively impedes crack propagation perpendicular to the shell by crack‐deviation mechanisms. The high degree of mechanical stability and toughness is achieved by two design features. First, there is the fiber composite material which overcomes some detrimental and enhances some advantageous properties of the single constituents, that is the softness and flexibility of chitin and the hardness and brittleness of apatite. Second, there is a hierarchical structuring from the nanometer to a micrometer level. We could identify at least seven levels of hierarchy within the shells.</p></abstract></abstractGroup></contentMeta></header></component></istex:document></istex:metadataXml><mods version="3.6"><titleInfo lang="en"><title>Micromechanical properties and structural characterization of modern inarticulated brachiopod shells</title></titleInfo><titleInfo type="abbreviated" lang="en"><title>BRACHIOPOD MICROHARDNESS</title></titleInfo><titleInfo type="alternative" contentType="CDATA" lang="en"><title>Micromechanical properties and structural characterization of modern inarticulated brachiopod shells</title></titleInfo><name type="personal"><namePart type="given">C.</namePart><namePart type="family">Merkel</namePart><affiliation>Section of Applied Crystallography and Materials Science, Department of Earth and Environmental Sciences, Ludwig‐Maximilians University Munich, Munich, Germany</affiliation><affiliation>E-mail: casjen.merkel@lrz.uni-muenchen.de</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">E.</namePart><namePart type="family">Griesshaber</namePart><affiliation>Section of Palaeontology, Department of Earth and Environmental Sciences, Ludwig‐Maximilians University Munich, Munich, Germany</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">K.</namePart><namePart type="family">Kelm</namePart><affiliation>Institut für Anorganische Chemie, Universität Bonn, Bonn, Germany</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">R.</namePart><namePart type="family">Neuser</namePart><affiliation>Institut für Geologie, Mineralogie und Geophysik, Ruhr‐Universität Bochum, Bochum, Germany</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">G.</namePart><namePart type="family">Jordan</namePart><affiliation>Section of Applied Crystallography and Materials Science, Department of Earth and Environmental Sciences, Ludwig‐Maximilians University Munich, Munich, Germany</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">A.</namePart><namePart type="family">Logan</namePart><affiliation>Department of Physical Sciences, University of New Brunswick, Saint John, New Brunswick, Canada</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">W.</namePart><namePart type="family">Mader</namePart><affiliation>Institut für Anorganische Chemie, Universität Bonn, Bonn, Germany</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">W. W.</namePart><namePart type="family">Schmahl</namePart><affiliation>Section of Applied Crystallography and Materials Science, Department of Earth and Environmental Sciences, Ludwig‐Maximilians University Munich, Munich, Germany</affiliation><role><roleTerm type="text">author</roleTerm></role></name><typeOfResource>text</typeOfResource><genre type="article" displayLabel="article"></genre><originInfo><publisher>Blackwell Publishing Ltd</publisher><dateIssued encoding="w3cdtf">2007-06</dateIssued><dateCaptured encoding="w3cdtf">2006-06-23</dateCaptured><dateValid encoding="w3cdtf">2007-01-10</dateValid><edition>Merkel, C., E. Griesshaber, K. Kelm, R. Neuser, G. Jordan, A. Logan, W. Mader, and W. W. Schmahl (2007), Micromechanical properties and structural characterization of modern inarticulated brachiopod shells, J. Geophys. Res., 112, G02008, doi:10.1029/2006JG000253.</edition><copyrightDate encoding="w3cdtf">2007</copyrightDate></originInfo><language><languageTerm type="code" authority="rfc3066">en</languageTerm><languageTerm type="code" authority="iso639-2b">eng</languageTerm></language><physicalDescription><internetMediaType>text/html</internetMediaType><extent unit="figures">10</extent></physicalDescription><abstract>We investigated micromechanical properties and ultrastructure of the shells of the modern brachiopod species Lingula anatina, Discinisca laevis, and Discradisca stella with scanning electron microscopy (SEM, EDX), transmission electron microscopy (TEM) and Vickers microhardness indentation analyses. The shells are composed of two distinct layers, an outer primary layer and an inner secondary layer. Except for the primary layer in Lingula anatina, which is composed entirely of organic matter, all other shell layers are laminated organic/inorganic composites. The organic matter is built of chitin fibers, which provide the matrix for the incorporation of calcium phosphate. Amorphous calcium phosphate in the outer, primary layer and crystalline apatite is deposited into the inner, secondary layer of the shell. Apatite crystallite sizes in the umbonal region of the shell are about 50 × 50 nm, while within the valves crystallite sizes are significantly smaller, averanging 10 × 25 nm. There is great variation in hardness values between shell layers and between the investigated brachiopod species. The microhardness of the investigated shells is significantly lower than that of inorganic hydroxyapatite. This is caused by the predominantly organic material component that in these shells is either developed as purely organic layers or as an organic fibrous matrix reinforced by crystallites. Our results show that this particular fiber composite material is very efficient for the protection and the support of the soft animal tissue. It lowers the probability of crack formation and effectively impedes crack propagation perpendicular to the shell by crack‐deviation mechanisms. The high degree of mechanical stability and toughness is achieved by two design features. First, there is the fiber composite material which overcomes some detrimental and enhances some advantageous properties of the single constituents, that is the softness and flexibility of chitin and the hardness and brittleness of apatite. Second, there is a hierarchical structuring from the nanometer to a micrometer level. We could identify at least seven levels of hierarchy within the shells.</abstract><subject><genre>keywords</genre><topic>modern inarticulated brachiopod</topic><topic>fiber composite structures</topic><topic>Vickers microhardness</topic></subject><relatedItem type="host"><titleInfo><title>Journal of Geophysical Research: Biogeosciences</title></titleInfo><titleInfo type="abbreviated"><title>J. Geophys. Res.</title></titleInfo><genre type="journal">journal</genre><subject><genre>index-terms</genre><topic authorityURI="http://psi.agu.org/taxonomy5/0400">BIOGEOSCIENCES</topic><topic authorityURI="http://psi.agu.org/taxonomy5/0448">Geomicrobiology</topic><topic authorityURI="http://psi.agu.org/taxonomy5/0459">Macro‐ and micropaleontology</topic><topic authorityURI="http://psi.agu.org/taxonomy5/0419">Biomineralization</topic><topic authorityURI="http://psi.agu.org/taxonomy5/3000">MARINE GEOLOGY AND GEOPHYSICS</topic><topic authorityURI="http://psi.agu.org/taxonomy5/3030">Micropaleontology</topic><topic authorityURI="http://psi.agu.org/taxonomy5/4900">PALEOCEANOGRAPHY</topic><topic authorityURI="http://psi.agu.org/taxonomy5/4944">Micropaleontology</topic></subject><identifier type="ISSN">0148-0227</identifier><identifier type="eISSN">2156-2202</identifier><identifier type="DOI">10.1002/(ISSN)2156-2202g</identifier><identifier type="CODEN">JGREA2</identifier><identifier type="PublisherID">JGRG</identifier><part><date>2007</date><detail type="volume"><caption>vol.</caption><number>112</number></detail><detail type="issue"><caption>no.</caption><number>G2</number></detail><extent unit="pages"><start>n/a</start><end>n/a</end><total>12</total></extent></part></relatedItem><identifier type="istex">E297CFF8A2080550878E031A88777C331A5489D9</identifier><identifier type="DOI">10.1029/2006JG000253</identifier><identifier type="ArticleID">2006JG000253</identifier><accessCondition type="use and reproduction" contentType="copyright">Copyright 2007 by the American Geophysical Union.</accessCondition><recordInfo><recordContentSource>WILEY</recordContentSource></recordInfo></mods></metadata><serie></serie></istex></record>Pour manipuler ce document sous Unix (Dilib)
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