Strain in crystals detected by X-ray

Publisher’s version / Version de l'éditeur:

Nature, 209, 5018, pp. 34-36, 1966-05-01

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.

https://nrc-publications.canada.ca/eng/copyright

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.

Questions? Contact the NRC Publications Archive team at

PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.

NRC Publications Archive

Archives des publications du CNRC

This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur.

For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.

https://doi.org/10.1038/209034a0

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

Strain in crystals detected by X-ray

Gillott, J. E.; Sereda, P. J.

https://publications-cnrc.canada.ca/fra/droits

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.

NRC Publications Record / Notice d'Archives des publications de CNRC:

https://nrc-publications.canada.ca/eng/view/object/?id=aa39d33e-3d9c-4967-95ce-79f208fc318d

https://publications-cnrc.canada.ca/fra/voir/objet/?id=aa39d33e-3d9c-4967-95ce-79f208fc318d

STRAIN I N CRYSTALS DETECTED

BY X-WAY

By J.

E.

GILLOTT

and

P.

J.

SEREDA

Division of ~ u i l d i n ~ Research, National Research Council, Ottawa, Canada

I

T is usof111 to lcilo~v xvhetllor the crystals fonn~ing a, rigicl polycrystalli~io body two strained, especially mhon such boclios LLro forrnocl b y compaction of tho pon~clcrocl n~icro- crystalline ~llaterial i ~ t m o d c r ~ ~ t o pross~u-s. Rt:sicl(.~al intenla1 stross in tho crystals intry havo a n ii~fluci~co 011 its inochanical properties, piwtic~llc~riy its stability, mllcil subjccted to cyclicnl coiiclitions.

X-ray diffraction tr:~rismissioil Lauo photographs of deformed polycrystalline matorials ofton ~ 1 1 0 ~ ~ astorism, the radial distortion of tho spots1:" This articlo cliscusscs the use of this tccl~nicluo to detect strains in samples of hydri~tcd comont, &(OH),, ancl mialytical roagciit graclc NaCl in tho for111 of cbnlpi~cts, pomclcrs, a,nd xv;~f'ors.

I n this technicluc, unfiltcrecl copper X-raclia,tion was einployocl ancl the cliffri~ction pi~ttel.iis x~~orc rccorclecl 011 film hold either by a flat-plnto holdor ~no~ultocl ut a clista~icc of 4 en1 frorn t11c st~lllplo 01% by :L cylinc1ric:~l cassctto of

6.73 cm diameter. Tho sa~nplcs nrcro a.lso os:rmined on tho petrographic microscope.

A norini~l port,lancl (:oillc~lt xvr~s 11sed xvhich nrns hydrated by two prococlurcs. I11 tlic k s t the cemont mns ll;yclrat,od essontinlly to ~ ~ l ~ l p l ~ t i ~ l l in a11 oxccss of xvate~. b y con- tinnous rotation in n bottle on a whccl. Tho hyclmtocl ccrnont w ~ s rocoverccl as ,z pon-der. 111 i,he scconcl t;ho cenlent was hydrated in tho nor~llnl fashion as a p;~stc with a wnhor/cemont ratio of 0.5 by weight.

Two varioiics of Ca(OH), wcro investigated. One variety formod ns a hycli~~~tion p~ociuct of ceincnt. W%on hydration was ci~rriccl ollt, in a11 excess of water the crysti~ls i~oachod a size of about 1 111111. Thcy xx'oro sepnratecl by sieving from tho l~yclr~tccl ceineilt powder. T l ~ ~ ~ s e c o n c l variety of Cn(Ol-I)I cl*yst~~ls was grown by tho cliff~~sion technicluo of JohnstonQ~sing CaCl, ancl NaOH.

Thc compacts n-ore illacle in a mould 1.25 in. in dinrnctcr and the c l ~ ~ n n t i t y of pox~der nras ndjustod so t h a t a'ter conll~action tho samplo liacl a, thicl~ncss of 0.25-0.5 lllm who11 prcssurcs in tlic riu11gc of 51000-l.00,000 1b.jii1.~ a-ere employecl. Somc comptrc.ts of XaC1 were anncaled in a n l ~ m e li~rnacc a t tr tomper;~I;ure of 500" C. SSiafers of dilne~lsio~ls similar to thc compacts were c ~ i t fi.on1 a cylincler of normally l~yclr~~tecl cc~ncnt by mcans of :L diamond saw. Pomcler serrq~lcs wer? gcntly prcssccl 1)y

hand into a flat-plate holder and held in place by admixture with a small quantity of gum.

Laue photographs obtainod from wafers of the cement hydrated as a paste showed marked asterism (Fig. l a ) . This was also present on Laue photographs of the com- pacted and umcompacted sainplos of cement powder hydrated in an excess of wator.

A

Laue photograph of the uncompacted Ca(OH), separated by sieving from the cement hydrated in an oxcoss of water also showed asterisnl (Fig. l b ) . The film was remarlrably similar in appearance to that obtained from the cemont powder hydrated in an oxcess of water, suggesting that in this case the observed diffraction effocts resulted largely from the Ca(OfI), crystals. The radial clistortion of spots mas even inore marlred on a uhotopreah obtained from this material after it had been c6mpaciodLat 20,000 lb./in.?. The powdqr sample of Ca(OH), crystals grown by tlle slow diffusion process gave Laue photographs which showed very little asterism. Laue photographs of this material after com- paction at 20,000 lb./in.? showed a similar amount of asterism to that observed on films of the uncompacted Ca(OH), separated from tho cement powder by sieving. A single crystal of the Ca(OH), separated from the hydrated cement powder showed distorted spots on discontinuous Debyo-Schorrcr pomdor rings; Laue spots shelved asterism.

The NaCl (roagent grade) uncompacted powder sample gave a Laue photog~apph mhich sholvcd sonlo asterisnl. Conlpaction at 800, 6,000 and 20,000 lb./in.? was accom- panied by a prof;rossivc i~~crcase in the aino~ult of asterism shoum O I L tho Lauo photographs. Lhlnoaling the compact

for 1 11 a t 500" C removed a largo amount of the asterism from the corrospoi~dirrg Loue p h o t ~ g ~ a p h . Annealing for 42 h was rocpired before tho Lano photograph of tho coinp~wt sl~owcd no asterism. Thoro wi~s only o very slow decrease wit11 time in tho amount of asterisin present on Lauo photographs of an NaCl coillpact conditioned in a

desiccator hold a t 50 por cent r.elati\o humidity. This result is in accord with that of Lowis and Pearson4, who studied X-ray diffraction-line broadening in the alkali halides.

X-ray photographs of the polyclystallino samples exam- ined showod discontinuous Debyo-Schoner rings, but these were sometimos only visiblo in the boclr refloxioil region. Their absonce in tho front rofloxion region on somo photog~aphs was attribu~ted to absorption in sonlevhat thicker or denser sainplos. Spots were commonly dis- tortecl aro~md the circumforonco of the circlo. After annealing the circumferential streal<s on tlm photographs from tho NaCl compacts were replaced by small sharp spots, tho extent of the replacement depending on the length of annoaling tilllo. Photographs of the Co(OH), separated by sieving from the cement powder showod this effect though no attempt was made to anneal the

sample. The DebyeScherror rings n7ere gonornlly more continuous on photographs of compacted samples than on photographs of ~mcompacted samplos and tho sizo of tho spots was ofton roducccl.

Most of tho sainplos .cvoro osanlincd unclor low power magnification undor tho binocular and a t higher inagni- fication under the petrographic microscope. Tho Ca(OH), crystals which grow as a product wllon tho comont was hydrated in an excoss of wetor wero plate-lilco. Those grown by tho diffusion techiliclue of Johnston3 were of different morphology. They wore elongated normal to tho base (0001) in tho forin of hexagonal prisms which were sometiines hollow. Difforoilces in shape of &(OH),

Fig. 1. X-ray dilftaction photogrnphs showing asterism. a, Cement

wafer llydr~ted as u paste; 6 , Cs(OIl), sieved from cemcnt hydrated In

excess water

crysti~ls llavo Leo~l rlisc~~sscd by I-IcdillVill t o r ~ r ~ s of diff<::ronccs in p o n - t h rate or1 cliffcrcnt faccs. R o sug- gcstcd that tho prcsclLcc o:F a \wry loxv conccntr~~tiorl of imp~nitics which absorb on gron%ll steps such as screw tlislocations may :~Eect the gro~vth mcclmllism~. Ilo f o ~ ~ n c l that gronrth of prisnl faccs began a t n lowcr concentrn,tio~l of s o l ~ ~ t i o n tlla11 clicl gro\r!,11 011 tho prism bn,scs. Oilco growth llizcl started, hen-c-\-cr, a n i~lcrc:!,sc in solutior~ co~lcolltl~nt~ion cnusccl 3 more ra.pid ir~crcnso ill growth rate on tho basal s~lrL':~cc thnn on tho cclges of tho c1:ystals. Predonli~~nllt growth oil basnl s~lrfaocs favonrs long rocl- likc cryst.o.ls \vhcrca.s, if the growth is ~naillly on tile oclgcs, pl;~tes are produced. Diffc~~cllces in cor~ccntrabion bctxvccn tho C~CI,-KLLOH i~ncl Iiyclrt~ting comcnt systonl and n~ucll llighcr eoncol~trn,tioi~ in thc latter of' impurities wii;l~ possiblo groxt-th-i11tcrfcri11g proporiics may l~nvo influellcecl tlie difhrrnco ill inorp21010gg of tho txro types of Ca(OEI),. The C~L(OH), sicvcd out; from tho cellla~lt poxvclcr contni~~ccl srnnll i~lclnsions symmctricnlly arra,llgccl in hosagonnl form. Some of tllc inolusions within the llesagolls :~l~poarccl to si~ow a spiral arrangcn~cnt (Fig. 2). This is s~lggestivo of rotiztion cltuilq grox~411 a,nd may rc?sult from a scrcw clislocntion typc of growth n~echanism. Al tor~lnt,ivcl y, tho llletl~od of proparntion llloy be rcspon-

siblo as this involves c o n t i n ~ ~ o u s rotation on n TT-hcel. 6

~ C T V of tho C~I,(OI-I:)~ crystalls contained ru~~clomly oriontecl loth-sl~apccl illclusions of' largcr size tlla11 tho symmctricd inclusions. The Ca(OH), sho~vod unclnlatory cst~iilction on rotation of tho lnicroscopc stage ullcler crossccl polars.

'rho classical interprr:ta;lion of asterism is that it is duo to ~liffroct~ion from crystals in which tho lattice is bcnt. i\lmcnliug romovos tho rlistortion ancl tho clifEraction

strealrs are replaced b y sharp spots charactonstic of diffraction from a n uilclefoimcd crystal. Tho soparation of tho streaks into a number of sharp spots is attributed

to polygonizatioil or tho fragmentation of tho largor distortocl crystal into a nulnbcr of ~vcll-definod sub-grains which differ slightly in oriontation.

011tho basis of this vio~v it appoars t h a t tllero is dis- t,ortion in tho crystal lattice of the Ca(OH), f o r i n d d u i n g llydrntion of ceincnt in a n oscoss of U ~ L L ~ C Y . This con- ciusion is supported b y tho ulld~datory estinctioil observed undor crossed polars on the petrographic microscope. Tlle similar effocts observed on the X-ray photog~aphs of tho cement llydratod as a paste suggest t h a t distortccl Ca(0H ) ?

mas also forinccl during tho pasto liyclrntion process. The polygonization ill tho separatocl ~mamloalcd crysta.1~ implios t h a t partial rccrystnllization also tool< placo n-hell a n osccss of water mas prcscnt. V(bry little lattico dis- tortion was prcsoilt ill tho cl.yslals of' Ca(OI1), g r o ~ \ ~ i by slow diflEusion. Compaction rcsu~ltcd in clefornx~tion and

a reduction in tho size of tho crystals. Sin1ila.r conclusions

apply to tho results obtained with tho NaCl pov9dors and compacts.

Tho evidoncc of distortion in the crystal lattice leads to tho coilclusioil t h a t t h e crystal was 'subjected to some form of stress a t some stage in its formation. This T V ~ S certainly tho case during compaction, bnt such stress is difficult to acco~ult for whcn crystals grow from solution ill a frcc nlcdiunl, as was the case for tlic Ca(OH), formod b y h3ftkation of ccnloilt in a rotati~lg bottlc. Tllc fact that inclusions Tvoro obscrvod i n tho c ~ y s t ~ a l s of Ca(OH), (Fig. 2) ma<y ncco~~ill; for tho prcscnco of strain. IVl~cil cemoiit hydrntcs as a paste it is accepta.blo to consider t h a t stross is applied on tho growing crystal, b o c a ~ ~ s o tho prodncts lilust accoimodnto t o tho spaces formed b y tlic struct~are of tho unhyrlmtecl p ~ ~ r t ~ i c l o s as well as to tho prinmry l ~ y d r n t i o i ~ proclucts.

Tho importallt rl~~estioii is nl~c5tller clistortion in crystals is ovicleilco for tho prcsoi~co of rcsiclual intcrllal stross. If so, ono ~voulcl anticipnte that such crystals would bo lnorc roactivo, might rccryst,allizc (agc) morc I-ondily, and woulcl bo loss stnblo dinloilsio~l:~lly cspocially ulldor cyclical COIL- ditioils of t01~1porat;~~m or m o i s t ~ ~ r c chango, t h a n crystals of tho sa.mo sizo llaring no rcsiclual internal stress.

Ccrtninly in t l ~ c case of NuCl, tho lattice clistortioi~ toiiclod to disappear aftcr almo;~ling, inclicati~~g t h a t tho distortioil I-csultccl fro111 rcsicluul iiltorllal st~.css. Residual intcrilnl strcss irl crystals mny have a sigl~ificnllt influonce or1 tho mcchailical proportics of a tigicl polycrystallino body.

U:~rrett, C. S., S'lr~~clnre of Jlclals, . I 1 (3lcGrarv-LIill, 1862).

'

Taylor, A , , S-,'(LU illcl~tllograph.~/, 767 (J. \\'ilcy, 1861).

Jollnston, J., J. ~ l ? u e i . . Clrertt. Soc., 3 6 , 16 (1814).

'

I;emis, D., : ~ n d Pc:rrson, IT., Xallrre, 196, 162 (1962).

W e d i n , It., Swedish Cement :md Co~lcrctc Res., I m t . I'roc., No. 33

(1962).