APPLICATIONS OF X-RAY MICRODIFFRACTION IN THE IMAGING INDUSTRY

Transcription

1 352 APPLICATIONS OF X-RAY MICRODIFFRACTION IN THE IMAGING INDUSTRY Thoms N. Blnton Estmn Kodk Compny, Reserch Lortories Foundtion Science Center, Rochester, New York , USA ABSTRACT Chrcteriztion of mterils used in the digitl imging industry hs een performed using micro X-ry diffrction (microxrd) techniques. Cse studies re descried tht demonstrte the use of microxrd for identifiction of phses, texture, nd microstructure morphology of components used in imging pplictions. INTRODUCTION Digitl imging is comprised of cpture, storge nd disply of n imge. Whether it is digitl cmer, secure disk (SD) crd, ink jet printer, or liquid crystl disply, the growth of this industry hs required the development of new mterils. Criticl to this development re nlyticl techniques cple of chrcterizing composition nd microstructure. X-ry diffrction is one of the most importnt tools ville for nlyzing solids, with microdiffrction eing criticl component for the success of emerging technologies nd in some instnces the only technique cple of providing the nswer to mterils nlysis question. The originl microdiffrctometers were X-ry diffrction (XRD) cmers. Lue, Deye-Scherrer, precession, nd Sttton cmers, shown in Figure 1, re exmples of erly instrumenttion tht were used for micro diffrction nlysis. c d Figure 1. MicroXRD cmers ) Lue, ) Deye-Scherrer, c) precession, d) Sttton. Though their populrity hs diminished with the vilility of modern X-ry diffrctometers, these cmers still function s useful instruments for X-ry diffrction nlysis. Improvements in

2 This document ws presented t the Denver X-ry Conference (DXC) on Applictions of X-ry Anlysis. Sponsored y the Interntionl Centre for Diffrction Dt (ICDD). This document is provided y ICDD in coopertion with the uthors nd presenters of the DXC for the express purpose of educting the scientific community. All copyrights for the document re retined y ICDD. Usge is restricted for the purposes of eduction nd scientific reserch. DXC Wesite ICDD Wesite -

3 353 X-ry sources, optics, nd detectors hve resulted in microdiffrction systems tht re cple of nlyzing very smll smples or regions on smple qulittively nd quntittively nd in timely mnner. With microdiffrctometer, the smple size is typiclly few millimeters down to 50 microns in dimeter. It is possile to nlyze smples down to 10 microns in dimeter when comprised of high Z elements. Anlysis techniques include confirmtion of crystllinity, phse identifiction, texture, nd residul stress. The microdiffrctometer used in this study is shown in Figure 2. Figure 2. Estmn Kodk microdiffrctometer. Typiclly, the detector used for microxrd nlysis is two-dimensionl. X-ry photogrphic film [1], imge pltes [2], nd multiwire detectors [3] re the principle detectors of choice depending on the ppliction nd results required for nlysis. Exmples of diffrction dt otined using these detectors re demonstrted in Figure 3. c Figure 3. Two-dimensionl XRD ptterns () Film ck reflection Lue pttern of eryl single crystl, () imge plte trnsmission Lue pttern of polyethylene-2,6-nphthlte film, (c) multiwire grzing incidence pttern of silver ehente in polyvinyl lcohol. Film will provide the est resolution of ll detectors ut dt collection nd chemicl processing times re long. Imge plte detectors sed on photostimulle BBrF:Eu 2+ re n order of mgnitude fster thn film nd on flexile support llowing for use nywhere film is used, ut require the use of lser scnning system for dt redout. Multiwire detectors offer rel time viewing of dt collection llowing for immedite ssessment of smple lignment nd diffrction pttern qulity, ut will hve lower resolution nd intensity dynmic rnge thn imge plte detectors. For pplictions descried in this study, the multiwire detector ws utilized.

4 354 In ddition to microxrd, other nlyticl techniques tht re complimentry in the chrcteriztion of smll smples include microftir, micrormn, scnning electron microscopy nd trnsmission electron microscopy. EXPERIMENTAL All microxrd dt were collected using microdiffrctometer comprised of Rigku copper rotting node X-ry source, nd Bruker goniometer consisting of Goeel mirrors ligned for CuKα rdition, XYZ smple stge, video lignment cmer, nd GADDS two-dimensionl (2D) multiwire detector. The operting power for the X-ry source ws 30kV, 60mA. The finl X-ry em size ws controlled with collimtors nd rnged from microns in dimeter depending on the smple size. Dt collection times rnged from 60 seconds to 10 minutes depending on the mteril composition, smple size, nd smple crystllinity. Smples were evluted s received nd mounted on n pproprite smple holder for dt collection. Dt nlysis ws performed using softwre from Bruker (GADDS nd EVA) or MDI (Jde). Some 2D diffrction ptterns re converted to one-dimensionl (1D) intensity versus 2-thet diffrction ptterns for phse identifiction nlysis. RESULTS AND DISCUSSION Motion Picture Imger Movies shown in theters hve egun the trnsformtion from film to digitl projection. The imger chip used for projecting the movie onto movie screen will ecome very hot during use. The sustrte (Figure 4) used to hold the imger must e thermlly stle nd hve n expnsion coefficient mtched to the imger to insure the projected imge on the screen remins in focus. * Figure 4. Motion picture imger ssemly, ckside. Loction of microxrd nlysis mrked y *. Loction of imger on the front side of the sustrte mrked y the rectngulr ox. A group of imger ssemlies ws found to produce uncceptle imge qulity. The cuse ws ttriuted to either the imger chips or the sustrtes provided y n externl supplier. A request ws mde to determine the phse composition of these sustrtes without exposing the imger to n X-ry em. Micro X-ry fluorescence determined tht silicon ws present in the sustrte. The microxrd pttern collected from the sustrte (Figure 5) shows diffrction rings tht re spotty indicting very lrge crystlline grins in the sustrte.

5 355 2 Figure 5. MicroXRD dt from the ckside of the imger sustrte. Inset is the originl 2D pttern; X-Y plot is result of integrtion of the 2D pttern nd conversion to trditionl 1D XRD pttern. Comining XRF nd the 1D XRD pttern results, serch of the Powder Diffrction File (PDF) [4] llowed for confirmtion of silicon nd silicon cride s phses present in the sustrte. With this informtion it ws determined tht the composition of the imger sustrte ws not correct resulting in therml expnsion coefficient tht ws not mtched with the imger. This mismtch explined the defocusing of the projected imge. Becuse of the smll size of the X- ry em during the collection of microxrd dt, the imger devices hd not een exposed to direct X-ry em. The imgers were preserved nd could e removed from the defective sustrtes to e used on other imger ssemlies. CRT Cthode Digitl print services utilize high intensity light sources for printing photogrphic pictures. These light sources use cthode ry tues (CRT) contining cthode ssemlies (Figure 6) tht re expected to e in service for greter thn 20,000 (20K) hours. Erly filure (<2K hours) of some CRTs prompted n investigtion s to the cuse. The supplier of these cthodes indicted tht the electron-generting portion ws comprised of tungsten (W) nd the surrounding cup ws comprised of tntlum (T), nd tht nothing hd chnged in the mnufcture process of CRTs. Figure 6. CRT cthode. Imge on the left is the W region,, imge on the right is the T cup.

6 356 MicroXRD ptterns (Figure 7) were collected in the W region for new cthode, cthode operted for 26K hours nd still working, nd cthode tht filed fter 1K hours of opertion. c Figure 7. MicroXRD two-dimensionl (inset) nd corresponding 1D diffrction ptterns for () new cthode, () working cthode 26K hours of opertion, (c) filed cthode 1K hours of opertion, collected in the respective W regions. Phse identifiction determined tht two phses were present in the W region of the new cthode, tungsten nd osmium (Os) (W nd Os confirmed y micro XRF). The supplier did not indicte the presence of osmium. The sence of complete knowledge of the composition of components is often prolem when deling with externl suppliers. Note tht in the 2D microxrd pttern of Figure 7 the diffrction rings due to W re spotty (lrge grin) wheres the rings due to Os re continuous (smll grin). This microstructure oservtion would not e possile using conventionl point detector for XRD dt collection. For the used cthodes, oth showed the presence of two phses. Tungsten is present t reduced intensity, nd Os is sent. In oth of these smples the dditionl phse could e indexed sed on hexgonl unit cell with lttice constnts of = Å nd c = Å. A mtch for ny W or Os phses or lloys with this unit cell ws mde for Os (1-x) W x phse with Mg structure type, using Person s Hndook

7 357 [5]. At this point, there ws no ovious nswer to explin why one cthode ws working fter 26K hours nd the other filed fter 1K hours. The next step ws to nlyze the T cup region. Anlysis of the new nd 26K hour cthodes reveled the presence of T metl. No other phses were detected. When the filed cthode ws nlyzed, severl dditionl diffrction rings in ddition to T metl were oserved (Figure 8). Figure 8. MicroXRD two-dimensionl nd corresponding 1D diffrction ptterns for () working cthode 26K hours of opertion, () filed cthode 1K hours of opertion, oth collected in the respective T cup regions. Phse identifiction for the filed cthode smpled reveled tht T 2 O 5 ws present. Tntlum is n excellent gettering element for oxygen nd the presence of T 2 O 5 explins why the cthode filed premturely. With these findings, the mnufcturer of the CRTs concluded tht new type of sel (originl discussion indicted no mnufcturing chnges!) eing used ws not working properly nd oxygen ws eing llowed to enter the CRT. Replcement of the defective sels solved the prolem nd service lifetimes returned to the expected 20K+ hours. Plstic Cmer Ger Gers in digitl nd film cmers cn e mde of plstic to help reduce weight nd cost. Typiclly, these gers re mde using n injection molding process, followed y cooling period

8 358 efore the finished ger is removed from the mold. In one site mnufcturing plstic gers, the ger teeth were found to e distorted rendering the ger unusle. A visul comprison of good versus d ger cn e found in Figure 9. Figure 9. Section of cmer plstic ger () good, undistorted teeth nd () d, distorted teeth. MicroFTIR confirmed tht the polymer in oth smples ws polymethylene oxide (PMO). XRD nlysis ws requested to determine if there were crystllinity differences etween the two smples. The use of conventionl diffrctometer would not llow chrcteriztion in only the region of the ger teeth, s the X-ry em would e s lrge s the entire ger. MicroXRD is well suited for this nlysis since the X-ry em cn e collimted to irrdite single tooth. Two-dimensionl diffrction ptterns for oth smples re shown in Figure 10. Figure 10. MicroXRD two-dimensionl XRD ptterns for () good ger tooth nd () d ger tooth. Both diffrction ptterns in Figure 10 show the (100) nd (200) PMO diffrction rings. In Figure 10, the rings re uniform in intensity indicting rndom orienttion of crystllites. In Figure 10, the rings re not uniform in intensity, indicting tht texture (preferred orienttion) of the crystllites is present. The preferred orienttion is n indiction tht the d ger tooth ws pulled during processing t temperture elow the melting point of PMO. A review of the

9 359 mnufcturing procedure reveled tht chnge in the process hd een instituted recently. The hold time etween injection molding nd relese from the mold ws shortened, with the intention of incresing the numer of gers produced in production cycle. With the reduced hold time, the PMO ws t higher temperture during the relese step nd the ger teeth were sticking to the mold nd eing stretched when eing removed. A return to the originl hold time for cooling fter injection molding eliminted the distortion of the ger teeth. Cly-PEO Nnocomposite Cly-polymer nnocomposite mterils hve received significnt ttention from the industril community ecuse of their wide rnge of novel physicl properties [6]. Cly hs een identified s n inexpensive, trnsprent, environmentlly enign nnoprticulte mteril with unique, electricl, mechnicl, opticl, nd rheologicl properties, which re of interest in the imging industry, including pplictions in ink jet receiver medi [7]. X-ry diffrction ptterns of cly films show sl plne (00L) diffrction peks. The interplnr distnce etween (001) plnes is defined s the sl plne spcing. This spcing cn e used s mesure to determine the extent (or sence) of polymer insertion into the cly lyers s function of composition. Free stnding films of NCloisite cly nd polyethylene oxide (PEO)/NCloisite cly (80/20 wt/wt) were provided for XRD nlysis. These films were initilly nlyzed on Rigku D2000 Brgg-Brentno diffrctometer equipped with copper rotting node, diffrcted em grphite monochromtor tuned to CuKα rdition, nd scintilltion point detector. Dt were collected using reflection mode geometry. The resulting diffrction ptterns re shown in Figure 11. Figure 11. Brgg-Brentno diffrctometer ptterns for () NCloisite nd () PEO/NCloisite 80/20 wt/wt. Both scns collected in reflection mode geometry. The diffrction pttern of the NCloisite film hs sl plne (001) diffrction pek t ~ thet corresponding to d 001 = 12.5 Å. The PEO/NCloisite film in Figure 11 shows the (001) pek hs shifted to lower ngle giving d 001 = 26.0 Å. It is lso noteworthy tht multiple orders of (00L) diffrction peks re oserved in Figure 11 indicting tht the lttice of the PEO/NCloisite nnocomposite is more ordered thn net NCloisite. The results in Figure 11 confirm tht NCloisite hs een interclted y PEO. However, with the PEO/NCloisite rtio t 80/20, there is excess PEO tht would e expected to e crystlline. A differentil scnning clorimetry (DSC) scn of the 80/20 PEO/NCloisite smple showed melt pek t 61 ºC, indicting crystlline PEO ws present in the smple. A diffrctometer scn of net PEO film

10 360 shows two prominent diffrction peks t ~19 nd 23 2-thet (Figure 12). These diffrction peks were not oserved in Figure 11. Figure 12. Brgg Brentno diffrctometer pttern for PEO, reflection mode geometry. To investigte the sence of PEO diffrction pttern in Figure 11, the PEO/NCloisite film ws nlyzed on the microdiffrctometer. A smple ws mounted with the smple edge perpendiculr to the X-ry em to pproximte the reflection mode geometry of the Brgg- Brentno diffrctometer, nd mounted with the film plne perpendiculr to the X-ry em for trnsmission mode geometry. The 2D diffrction ptterns re shown in Figure 13. Figure 13. MicroXRD two-dimensionl XRD ptterns for 80/20 PEO/NCloisite film () reflection mode geometry () trnsmission mode geometry. The white rectngles pproximte the equivlent region tht would e scnned with point detector on Brgg-Brentno diffrctometer In Figure 13 there re diffrction rcs in the equtoril nd meridinl positions. In Figure 13 there re two prominent diffrction rings. The equtoril rcs in Figure 13 re due to the

11 361 NCloisite cly interclted with PEO. The meridinl rcs in Figure 13 nd diffrction rings in Figure 13 re due to PEO. The white rectngulr ox on Figure 13 shows the region of the diffrction pttern tht scintilltion detector would detect. The point detector will never e in the correct position to see the PEO meridin rcs, which explins why PEO ws not oserved in the diffrction pttern of Figure 12. Hd trnsmission diffrction pttern een collected using the Brgg-Brentno diffrctometer, the PEO diffrction peks would hve een oserved s indicted y the white rectngle on FIGURE 13. In ddition to ddressing the presence of PEO, the 2D diffrction ptterns llow one to define the microstructure of the PEO/NCloisite nnocomposite. The equtoril rcs indicte tht NCloisite pltelets lie prllel to the film plne. The PEO meridinl rcs in Figure 13 nd PEO rings in Figure 13 re n indiction tht crystlline PEO plnes re perpendiculr to the film plne ut re cylindriclly symmetricl within the film plne. This microstructure is illustrted in Figure 14. PEO Cly Figure 14. Microstructure model of NCloisite interclted with PEO. Though the originl request ws to determine if PEO intercted with NCloisite cly, the use of microdiffrctometer with 2D detector llowed for more complete understnding of the nnocomposite. With this enhnced knowledge the composition cn e modified to otin desired physicl properties. SUMMARY MicroXRD hs een descried s n importnt nlyticl tool for chrcterizing mterils used in digitl imging. Comining smll dimeter X-ry em with two-dimensionl detector, mterils nlysis including phse identifiction, preferred orienttion, production concerns, nd new mterils development hs een successfully demonstrted.

12 362 ACKNOWLEDGEMENTS The uthor would like to thnk Kodk collegues Crig Brnes for ssistnce with XRD dt collection, Mrk Morse for XRF dt, nd YunQio Ro, Frnk Ehrne, nd Shron Mrkel for providing the nlyzed smples. REFERENCES [1] Blnton, T.N., Powd. Diff., 2003, 2, [2] Etough, M.O., Rodriguez, M.A., Blnton, T.N., Tissot, R.G., Adv. X-ry Anl., 1999, 41, [3] He, B.B., Powd. Diff., 2003, 2, [4] Powder Diffrction File Relese 2004, Interntionl Centre for Diffrction Dt, 12 Cmpus Boulevrd, Newtown Squre, PA 19073, USA. [5] Villrs, P., Clvert, L.D., Person s Hndook of Crystllogrphic Dt for Intermetllic Phses Vol. 2, Amer. Soc. Metls: Metls Prk, Ohio, 1985, [6] Pinnvi, T.J., Bell, G.W., Polymer-Cly Nnocomposites, John Wiley & Sons: Chichester, 2000, [7] Mjumdr, D., Blnton, T.N., Schwrk, D.W., Appl. Cly Sci., 2003, 23,