An-Najah Blogs :: Ghassan Saffarini, Physics Department, Faculty of Science http://blogs.najah.edu/author/ghassan-saffarini An-Najah Blogs :: Ghassan Saffarini, Physics Department, Faculty of Science en-us Wed, 28 Oct 2020 16:00:56 IST Wed, 28 Oct 2020 16:00:56 IST webmaster@najah.edu webmaster@najah.edu Mean-coordination number dependence of the fragility in Ge-Se-In glass forming liquidshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Mean-coordination-number-dependence-of-the-fragility-1Published ArticlesDifferential scanning calorimetry measurements have been performed on elemental Se as well as on GexSe94xIn6 x frac14; 4 8 and 11 at and on GeySe88yIn12 y frac14; 5 7 and 9 at chalcogenide glasses From the cooling rate dependence of the fictive temperaturethe apparent activation energies Dh and the fragility indices m as defined in the strongfragile glass-forming liquid concept are determined It is found that in GeSeIn system there is an evolution from strong m frac14; 67 to fragile m frac14; 116 glass-forming liquids The dependence of m on the mean-coordination number Z is also obtained This dependence is rationalized by assuming that in this glassy alloy system there is a tendency for the formation of In2Se3 clusters r 2006 Elsevier BV All rights reserved The composition dependence of the optical band gap in Ge–Se–In thin films http://blogs.najah.edu/staff/ghassan-saffarini/article/The-composition-dependence-of-the-optical-band-gap-in-GendashSendashIn-thin-films-Published ArticlesBulk glasses with the chemical composition Gey Se94yIn6 8y30 at have been prepared from high purity constituent elements Fragments of the bulk glasses are used to deposit thin films by vacuum thermal evaporation The optical band gaps Eg s of the as-deposited films have been measured The allowed optical transition is found to be indirect The relation of Eg to the covalent coordination number Z is demonstrated by varying the composition parameter y of the thin films A maximum in the compositional dependence of Eg is attained at Z=263 The cohesive energies CE of the investigated samples have also been calculated using the method suggested by the chemical bond approach It is found that the composition dependence of the CE also possesses a peak at Z=263 A plausible explanation based on the bonding considerations between the constituents has been provided for the understanding of the Eg-Z and CE-Z dependences for these GeSeIn thin films Optical Materials Volume 29 Issue 9 May 2007 Pages 1143-1147 CR-39 detector compared with Kodalpha film type (LR115) in terms of radon concentrationhttp://blogs.najah.edu/staff/ghassan-saffarini/article/CR-39-detector-compared-with-Kodalpha-film-type-LR115-in-terms-of-radon-concentrationPublished ArticlesCR-39 detectors and Kodalpha film type LR115 were compared in terms of radon radiation concentration Thirteen CR-39 detectors with the same number of Kodalpha film type LR115 were used in this study The correlation factor between the radon concentrations obtained by the two groups of detectors was found to be 099 Detector time efficiency DTE was calculated for both types of detectors DTE of Kodalpha film is larger than that of CR-39 detector and this indicates that LR115 is more efficient and sensitive for radon radiation than CR-39 detector Nuclear Instruments and Methods in Physics Research Section A: Accelerators Spectrometers Detectors and Associated Equipment Volume 574 Issue 2 1 May 2007 Pages 289-291 http:dxdoiorg101016jnima200701168Compactness in Relation to the Mean Coordination Number in Glassy Gexbi6s94-Xhttp://blogs.najah.edu/staff/ghassan-saffarini/article/Compactness-in-Relation-to-the-Mean-Coordination-Number-in-Glassy-Gexbi6s94-XPublished Articles The compactness of the structure of glassy GexBi6S94-x 14 x 26 at is determined from the measured densities The peculiarities observed in the compactness-composition dependence are understood using Phillips-Thorpe and Tanakas topological models proposed for the structure of these covalently bonded solids Thermal stability and percolation threshold of Ge–Se–Fe glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Thermal-stability-and-percolation-threshold-of-GendashSendashFe-glasses-2Published ArticlesThe characteristic temperatures such as the glass transition temperature Tg the onset temperature of crystallization Tc and the melting temperatures Tm have been determined for glasses belonging to the GexSe100 x yFey y=2 4 and 6 at Differential scanning calorimetry and differential thermal analysis measurements have been used for their determination These temperatures have been used to evaluate the thermal stability of the investigated glassy alloys using Dietzel T and Hruby Hr criteria The variations of T and Hr with the average coordination number n have been specified It is found that both T and Hr exhibit a maximum at n=24 This observation is a realization of Phillips\Thorpe threshold where the maximum stability of the network is just obtained if the percolation threshold limit is reached The overall mean bond energies of the studied compositions have also been calculated and their correlation with the glass transition temperature is discussed 2006 Elsevier BV All rights reservedEstimation of the Lifetime Risk of Lung Cancer Due to Radon in Inhabitants of the Old City of Nablus in Palestine http://blogs.najah.edu/staff/ghassan-saffarini/article/Estimation-of-the-Lifetime-Risk-of-Lung-Cancer-Due-to-Radon-in-Inhabitants-of-the-Old--City-of-Nablus-in-Palestine--Published ArticlesThe lifetime lung cancer risk in inhabitants of the old city of Nablus has been estimated using the measured indoor radon concentrations in their homes It is found that the lung cancer risk factor is higher in females as compared to males living in the same home The lung cancer risk factor ranged between 33x10-4 to 54x10-4 and 47x10-4 to 77x10-4 for males and females respectivelyComposition dependence of the heat capacity jump in Ge-Se-In chalcogenide glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Composition-dependence-of-the-heat-capacity-jump-in-Ge-Se-In-chalcogenide-glassesPublished ArticlesIndoor Radon Concentration Measurement In Homes in Old City of Nablus.http://blogs.najah.edu/staff/ghassan-saffarini/article/Estimate-of-lung-cancer-in-inhibitants-of-the-old-city-of-Nablus-due-to-radon-gas-Published Articles Fourth Symposium on Use of Nuclear Techniques in Environmental Studies Center for Theoretical and Applied Physical Sciences Yarmouk University Irbid Jordan 13-15 September 2004 Optical band gap in relation to the average coordination number in Ge - S - Bi thin filmshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Optical-band-gap-in-relation-to-the-average-coordination-number-in-Ge---S---Bi-thin-filmsPublished ArticlesChalcogenide glasses belonging to the GexS94 - xBi6 system 14 x 2833 at have been prepared from high purity constituent elements Thin films of the same materials have been deposited by vacuum thermal evaporation Optical absorbance measurements have been performed on the as-deposited films The allowed optical transition is found to be indirect and the corresponding optical gaps Eg are determined The variation of Eg with the average coordination number r is also investigated The observed Eg - r dependence is discussed on the basis of the chemical bonding between the constituents and the rigidity percolation threshold behavior of the network PHYSICA STATUS SOLIDI B-BASIC RESEARCH Volume 239 Issue 1 Pages 251 - 256Mechanical percolation and structural transition in Ge–S–Bi bulk glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Mechanical-percolation-and-structural-transition-in-GendashSndashBi-bulk-glassesPublished ArticlesThe compositional dependence of the mean atomic volume Va and the packing density p of the GexS94xBi6 glassy system in the range 14x26 x in at have been investigated Particular features in the compositional dependence of these physicochemical properties on the bond density n have been found Specifically at n=246 Va and p exhibit a minimum and a maximum respectively whereas at n=256 Va displays a maximum and p passes through a minimum These features are explained using the topological arguments proposed in PhillipsThorpe and Tanakas models Materials Letters Volume 57 Issue 1 November 2002 Pages 219-222Modified Gibbs-DiMarzio equation applied to the Ge-Se-Fe and Ge-Se-In chalcogenide glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Modified-Gibbs-DiMarzio-equation-applied-to-the-Ge-Se-Fe-and-Ge-Se-In-chalcogenide-glassesPublished ArticlesJOURNAL OF MATERIALS SCIENCE LETTERSVolume: 21Issue: 19Pages: 1481-1483Published: OCT 1 2002The effect of compositional variations on the glass-transition and crystallisation temperatures in Ge-Se-In glasses http://blogs.najah.edu/staff/ghassan-saffarini/article/The-effect-of-compositional-variations-on-the-glass-transition-and-crystallisation-temperatures-in-Ge-Se-In-glasses-Published ArticlesThe glass-transition Tg and crystallisation Tx temperatures of glassy GexSeyIn12 7x28 have been determined from differential scanning calorimetry measurements The variations of Tg and Tx with composition have been specified It has been found that Tg reaches a maximum at 614K for the composition Ge2333 Se6467 In12 while Tx passes through a minimum at 740K for the same composition The values of the cohesive energies of the studied compositions have also been estimated using the chemical bond approach method It is found that the composition Ge2333Se6467In12 possesses the maximum cohesive energy These results are explained in terms of the structure of Ge-Se-In glasses Applied Physics A: Materials Science Processing Volume 74 Number 2 February 2002Molar volume and compactness versus mean coordination number in GeSeFe glasses: observation of a threshold behaviorhttp://blogs.najah.edu/staff/ghassan-saffarini/article/Molar-volume-and-compactness-versus-mean-coordination-number-in-GeSeFe-glasses-observation-of-a-threshold-behaviorPublished ArticlesMolar volumes V and compactness values of 34 glassy compositions of the GeSeFe system have been obtained using their measured densities The propertycomposition dependences are examined in light of the models proposed for the structure of these network glasses Applied Physics A: Materials Science Processing Volume 73 Number 5 November 2001The influence of mechanical and chemical thresholds on the free volume percentage in Ge–Se–(Fe,In) chalcogenide glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/The-influence-of-mechanical-and-chemical-thresholds-on-the-free-volume-percentage-in-GendashSendashFeIn-chalcogenide-glassesPublished ArticlesAssuming that the increase in the volume during melting of a solid is inherent in the amorphous state supercooled liquid then the structure of amorphous solids should contain free volume In the present paper we determine the free volume percentage FVP in GeSeFeIn chalcogenide glasses and examine its relationship with the mean coordination number Physica B: Condensed Matter Volume 305 Issues 3-4 November 2001 Pages 293-297Strong-fragile glass forming liquid concept applied to GeTe chalcogenide glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Strong-fragile-glass-forming-liquid-concept-applied-to-GeTe-chalcogenide-glassesPublished ArticlesThe values of the thermal heat-capacity changes at the glass transition temperature Tg Cp=CplCpg and the values of the apparent activation energy h of the sub Tg relaxation process are determined for GexTe1x 015x020 vitreous alloys by means of differential scanning calorimetry investigations The values of h are then used to determine the values of the fragility index m The comparison of these new data to those already obtained on the GexSe1x vitreous system leads to conclude that both systems exhibit strong thermodynamic character The stronger thermodynamic character is reached at the PhillipsThorpes floppy-to-rigid transition On the other hand we find that GexTe1x exhibits a kinetically fragile character which decreases as the amount of Ge increases in the alloy Physica B: Condensed Matter Volume 304 Issues 1-4 September 2001 Pages 228-236Extended X-ray absorption fine structure study on Bi modified GeS bulk glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Extended-X-ray-absorption-fine-structure-study-on-Bi-modified-GeS-bulk-glassesPublished ArticlesEXAFS measurements have been performed from the Ge K edge and Bi L-III edge on GeSBi glasses with 6 8 and 16 Bi at and on crystalline Bi2S3 As expected Ge is found to be fourfold coordinated with S atoms It is also found that Bi is only coordinated with S with a coordination number CN = 4 This result for the CN of Bi contradicts the conclusion of Elliot and Steel On the basis of the obtained CN of Bi it is possible to exclude the presence of Bi2S3 microcrystalline inclusions and to assert that these glasses are homogeneous at the microscopic level JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALSVolume: 3Issue: 2Pages: 485-490Published: JUN 2001X-ray photoelectron spectroscopic measurements on glassy Ge20S80−xBix (x=0,16)http://blogs.najah.edu/staff/ghassan-saffarini/article/X-ray-photoelectron-spectroscopic-measurements-on-glassy-Ge20S80minusxBix-x016Published ArticlesX-ray photoelectron spectroscopy measurements have been performed on n-type Bi-modified Ge20S64Bi16 glass The observed chemical shifts show that Bi is incorporated as a positive charged center into the matrix of Ge20S80 parent glass Materials Letters Volume 46 Issue 6 December 2000 Pages 327-331Differential Scanning Calorimetry and X-Ray Photoelectron Spectroscopy Studies on Se100-xInx Systemhttp://blogs.najah.edu/staff/ghassan-saffarini/article/Differential-Scanning-Calorimetry-and-X-Ray-Photoelectron-Spectroscopy-Studies-on-Se100-xInx-SystemPublished ArticlesChalocogenide glasses in the Se100-xInxsystem in the composition range 0 x 29 x in at were prepared from high purity Se and In Differential scanning calorimetry results clearly indicate that the thermal stability of the glasses decreases upon increasing x The values of the glass transition temperatures Tg were found to be composition independent which is interpreted by envisaging the formation of In2Se3 microclusters that do not contribute to the Tg values of the glasses and that these values remain to be essentially determined by that of the Sen chains of the Se glassy matrix The X-ray photoelectron spectroscopy results lend further support to the formation of In2Se3 microclusters physica status solidi a Volume 179 Issue 1 Pages 109 - 115Topological phase transitions in Ge-In-Se glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Topological-phase-transitions-in-Ge-In-Se-glassesPublished ArticlesSource: JOURNAL OF MATERIALS SCIENCE LETTERSVolume: 19Issue: 9Pages: 797-798Published: MAY 2000UNESCO meeting for a SR-source in the Middle East, Paris, France, 15-16 June 1999.http://blogs.najah.edu/staff/ghassan-saffarini/article/UNESCO-meeting-for-a-SR-source-in-the-Middle-East-Paris-France-15-16-June-1999Published Articles UNESCO meeting for a SR-source in the Middle East Paris France 15-16 June 1999 Atomic Density versus Average Coordination Number in Ge-In-Se Glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Atomic-Density-versus-Average-Coordination-Number-in-Ge-In-Se-GlassesPublished ArticlesThe variation of the atomic density with the average coordination number Z for glasses belonging to the GexIn6Se94-x and GexIn12Se88-x families of the Ge-In-Se system is investigated The - Z dependence displays broad maxima at Z values of 242 and 258 for families with 6 and 12 at In respectively These maxima are ascribed to changes from a floppy to a rigid type network and from a two-dimensional layered structure to a three-dimensional network respectively The minima exhibited in the - Z dependence at Z = 263 for the In6 family and at Z = 271 for the In12 family corresponding to the tie-line compositions are attributed to chemical ordering effects physica status solidi b Volume 213 Issue 2 Pages 261 - 265Extended X-ray Absorption Fine Structure Study on Ge28.33 In6 Se65.67 Glasshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Extended-X-ray-Absorption-Fine-Structure-Study-on-Ge2833-In6-Se6567-GlassPublished ArticlesThe local environment of indium atoms in the chalcogenide glass with the stoichiometric composition Ge28 33 In6 Se65 67 has been investigated using extended X-ray absorption fine structure EXAFS technique It is found that indium is only coordinated with selenium atoms with a value of three for its coordination numberExperimental Studies on Ge-S-Ag Glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Experimental-Studies-on-Ge-S-Ag-GlassesPublished ArticlesGlasses belonging to the Ge-S-Ag system were investigated by differential scanning calorimetry DSC and X-ray diffraction XRD The DSC results show that the glass transition temperature Tg the onset crystallization temperature Tc as well as the temperature interval Tc -- Tg decrease with increasing amount of Ag content in the glass The decrease of Tc - Tg indicates that the thermal stability of the glass decreases The X-ray structure factors obtained on glasses with 5 10 and 15 at Ag have a first sharp diffraction peak FSDP characteristic of intermediate range order whose intensity decreases gradually with increasing Ag content in the glass up to 15 at For the glasses with Ag content 20 at this FSDP is totally absent These results may be taken as prima facie evidence that the decrease or the absence of intermediate range order in the glass decrease its thermal stability physica status solidi a Volume 170 Issue 1 Pages 23 - 28Compositional trends of the compactness in ternary chalcogenide glasses of the Ge–In–Se system http://blogs.najah.edu/staff/ghassan-saffarini/article/Compositional-trends-of-the-compactness-in-ternary-chalcogenide-glasses-of-the-GendashInndashSe-system-Published ArticlesChalcogenide glasses from the GexInySe100xy system with y=6 and 12at have been prepared from high purity Ge In and Se The compactness of the structure of the glasses is determined from the measured densities of the glasses The peculiarities observed in the -composition dependence are interpreted by using the ordered bond network model and the topological models proposed to describe the atomic arrangements in these solids Physica B: Condensed Matter Volume 253 Issues 1-2 1 October 1998 Pages 52-55An EXAFS investigation of the local order around indium in Ge–Se–In glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/An-EXAFS-investigation-of-the-local-order-around-indium-in-GendashSendashIn-glassesPublished ArticlesEXAFS measurements were performed at the In K edge on devitrified Ge5Se80In15 and on a series of vitreous GeSeIn alloys The results indicate that the In atoms have essentially the same local surroundings in all of the samples investigated We found that an In atom is surrounded by three Se atoms at a distance of about 0259 nm and forms In2Se3 microclusters Journal of Non-Crystalline Solids Volumes 232-234 11 July 1998 Pages 634-637Intermediate range order in Se1−xSx bulk glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Intermediate-range-order-in-Se1minusxSx-bulk-glassesPublished ArticlesSe1xSx bulk glasses within the composition range 01x05 were prepared from high purity constituent elements The X-ray structure factors obtained from these glasses show the presence of the first sharp diffraction peak FSDP which is the most universal signature of intermediate range order IRO The position and the full-width at half-maximum FWHM of the observed FSDP which relate respectively to the intercluster distance and the cluster size remain essentially the same The intensity of this peak increases with the amount of S content in the glasses We interpret these results by proposing that the IRO in this system is related to the formation of ring-like clusters Materials Letters Volume 35 Issues 5-6 June 1998 Pages 314-316Local environment of indium in Ge23.33Se64.67In12 chalcogenide glasshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Local-environment-of-indium-in-Ge2333Se6467In12-chalcogenide-glassPublished ArticlesEXAFS measurements from the In K edge on Ge2333Se6467In12 glass have been performed For this glass it is found that In is only coordinated with Se atoms By complementing the EXAFS results obtained from the fitting procedure followed in this work with the earlier reported DSC results obtained on this system it is concluded that in this glass the coordination number of In is equal to three Moreover this approach of coupling EXAFS with DSC results allows one to calibrate the factor for systems which lack a reference material or systems for which an ab initio calculation cannot be performed as in our case Materials Letters Volume 35 Issues 5-6 June 1998 Pages 309-313Chemical ordering in Ge-S-Ag glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/Chemical-ordering-in-Ge-S-Ag-glassesPublished ArticlesSource: JOURNAL OF MATERIALS SCIENCE LETTERSVolume: 17Issue: 7Pages: 531-532Published: APR 1 1998Crystallization of AsxSe1−x from the glassy state (0.005<x<0.03)http://blogs.najah.edu/staff/ghassan-saffarini/article/Crystallization-of-AsxSe1minusx-from-the-glassy-state-0005ltxlt003Published ArticlesThe crystallization of AsxSe1x from the glassy state 0005x003 is analyzed from calorimetric investigations For each composition the apparent activation energy for the crystallization reaction is determined with the Kissinger method Upon increasing x the apparent activation energy decreases It is also found that the dependence of the inverse of the apparent activation energy for crystallization falls linearly with the reciprocal of the mean temperature used in the experiment The latter result unambiguously indicates that the crystallization process for AsxSe1x in the composition range investigated is mainly controlled by the viscosity of the medium Therefore the crystallization reaction totally disappears when the amount of As atoms in the alloys reaches such a value capable of connecting enough Se chains to block their movement Physica B: Condensed Matter Volume 245 Issue 3 4 March 1998 Pages 256-262About the coordination number of indium in GexSe1 − x − y Iny glasseshttp://blogs.najah.edu/staff/ghassan-saffarini/article/About-the-coordination-number-of-indium-in-GexSe1-minus-x-minus-y-Iny-glassesPublished ArticlesThe results obtained by many authors on the GeSeIn vitreous system in particular those concerning the variations of the glass transition temperature Tg with the average coordination number Z are investigated from a new perspective From the assumption that In atoms participate in the formation of In2Se3 microclusters we show that the variations of Tg with Z of the alloy are consistent with Sreerams relationship and with Tanakas structural transition model We conclude that In is threefold coordinated with Se atoms to form In2Se3 microclusters and that these microclusters do not contribute to the variations of Tg with the alloy composition Materials Letters Volume 28 Issues 4-6 October 1996 Pages 451-45534- Eighth SESAME users' meeting, Petra, Jordan, 19-21 November, 2009.http://blogs.najah.edu/staff/ghassan-saffarini/article/34-Eighth-SESAME-users-meeting-Petra-Jordan-19-21-November-2009General Posts Eighth SESAME users meeting Petra Jordan 19-21 November 2009 Sixth SESAME users' meeting, Amman, Jordan, 17-19 November, 2007http://blogs.najah.edu/staff/ghassan-saffarini/article/Sixth-SESAME-users-meeting-Amman-Jordan-17-19-November-2007General Posts Sixth SESAME users meeting Amman Jordan 17-19 November 2007 The XI International Conference on the Physics of Non-http://blogs.najah.edu/staff/ghassan-saffarini/article/The-XI-International-Conference-on-the-Physics-of-Non-General Posts The XI International Conference on the Physics of Non- Crystalline Solids Rhodes-Greece 29 Oct- 2 Nov 2006 Fifth International Conference on Inorganic Materials, Ljubljana, Slovinia,23-26 September, 2006.http://blogs.najah.edu/staff/ghassan-saffarini/article/Fifth-International-Conference-on-Inorganic-Materials-Ljubljana-Slovinia23-26-September-2006General PostsFifth International Conference on Inorganic Materials Ljubljana Slovinia 23-26 September 2006ICTP school on synchrotron radiation and applications, Trieste, Italy, 8-26 May, 2006.http://blogs.najah.edu/staff/ghassan-saffarini/article/ICTP-school-on-synchrotron-radiation-and-applications-8-26-May-2006General Posts ICTP school on synchrotron radiation and applicationsTrieste Italy8-26 May 2006 Summer University, EMC-PLC and IT, Tishreen University,http://blogs.najah.edu/staff/ghassan-saffarini/article/Summer-University-EMC-PLC-and-IT-Tishreen-UniversityGeneral Posts Summer University EMC-PLC and IT Tishreen University Latakia- Syria 23-31 August 2004 The First Workshop in Medical Physics, United Arab Emirates University, 31-03-2004http://blogs.najah.edu/staff/ghassan-saffarini/article/The-First-Workshop-in-Medical-Physics-United-Arab-Emirates-University-31-03-2004General PostsThe First Workshop in Medical Physics United Arab Emirates University 31-03-2004JSPS Asian Science Seminar : Synchrotron Radiation Science,Al-Balqa’ Applied University, Al Salt, Jordan, 19-28 October,2002http://blogs.najah.edu/staff/ghassan-saffarini/article/JSPS-Asian-Science-Seminar--Synchrotron-Radiation-ScienceAl-Balqarsquo-Applied-University-Al-Salt-Jordan-19-28-October2002General Posts JSPS Asian Science Seminar : Synchrotron Radiation Science Al-Balqa Applied University Al Salt Jordan 19-28 October 2002 First International workshop on Amorphous and Nanostructuredhttp://blogs.najah.edu/staff/ghassan-saffarini/article/First-International-workshop-on-Amorphous-and-NanostructuredGeneral Posts First International workshop on Amorphous and Nanostructured Chalcogenides Fundamentals and applications Bucharest Romania 24-28 June 2001 UNESCO meeting on SESAME, Amman, Jordan, 21-22 June 2000http://blogs.najah.edu/staff/ghassan-saffarini/article/UNESCO-meeting-on-SESAME-Amman-Jordan-21-22-June-2000General Posts UNESCO meeting on SESAME Synchrotron-light for Experimental science and Applications in the Middle East Amman Jordan 21-22 June 2000 The first conference on medical physics and its applications,http://blogs.najah.edu/staff/ghassan-saffarini/article/The-first-conference-on-medical-physics-and-its-applicationsGeneral Posts The first conference on medical physics and its applications Zarka Private University Jordan 24-26 April 2000 Physics community,German Synchrotron Light Source ..,Physics Today, Augest Issue Part 1, page 56http://blogs.najah.edu/staff/ghassan-saffarini/article/Physics-communityGerman-Synchrotron-Light-SourcePhysics-TodayGeneral PostsOr as Palestinian physicist Ghassan Saffarini puts itwe dont want to end up with a cathedral in the desert Toni FederUNESCO committee meeting for a SR-source in the Middle East, Berlin, Germany, 19-21 Aug. 1999.http://blogs.najah.edu/staff/ghassan-saffarini/article/UNESCO-committee-meeting-for-a-SR-source-in-the-Middle-East-Berlin-Germany-19-21-Aug-1999-1General Posts UNESCO committee meeting for a SR-source in the Middle East Berlin Germany 19-21 Aug 1999 Third workshop on physics and technology of thin films, Trieste,http://blogs.najah.edu/staff/ghassan-saffarini/article/Third-workshop-on-physics-and-technology-of-thin-films-TriesteGeneral Posts Third workshop on physics and technology of thin films Trieste Italy 8-2631999 Seminar on experimental techniques in high-energy and synchrotron radiation (SR) physics, Torino, Italy 3-8/11/1997http://blogs.najah.edu/staff/ghassan-saffarini/article/Seminar-on-experimental-techniques-in-high-energy-and-synchrotron-radiation-SR-physics-Torino-Italy-3-8111997General Posts Seminar on experimental techniques in high-energy and synchrotron radiation SR physics Torino Italy 3-8111997 Seventh International conference on the structure of noncrystallinehttp://blogs.najah.edu/staff/ghassan-saffarini/article/Seventh-International-conference-on-the-structure-of-noncrystallineGeneral Posts Seventh International conference on the structure of noncrystalline materials Cagliari Sardegna Italy 15-19 Sep 1997 On Going Researchhttp://blogs.najah.edu/staff/ghassan-saffarini/article/On-Going-Research-1On Going ResearchesFragility index determination of Ge40S60 chalcogenide glass To determine the value of the fragility index m it is necessary to choose an expression for the relaxation time For a glass the relaxation time depends on the temperature and on some order parameters defining the structure of the glass Among the different expressions describing these variations that we may find in the literature for we use here the Tool-Narayanaswamy-Moynihan TNM expression which is given by: 1 where x 0 x 1 is the non-linearity or Narayanaswamy parameter ∆h is the apparent activation energy for enthalpy relaxation Tf is the fictive temperature defined as the temperature at which the structure of the glass would be in equilibrium if instantaneously brought to it and the other symbols carry their usual meanings For a given glass we must have a given value of ∆h In the liquid state the value of the non-linearity parameter is unity By assuming that the heating or cooling a glass is equivalent to a succession of identical isothermal steps it follows that q= constant q is the cooling or heating rate Under these assumptions it is easy to demonstrate that the apparent activation energy ∆h the cooling rate q- and the fictive temperature Tf are related via the relation: 2 Thus the variations of ln q- with reciprocal Tf allows us to determine the value of ∆h if Tf is known This fictive temperature can be calculated graphically on a calorimetric curve using the so-called equal areas construction method using the following integral form: 3 where T is any temperature above the transition region at which Cp is equal to the equilibrium liquid value CpL and T1 is a temperature well below the transition region Finally for a given value of the cooling rate q- and for a non-aged glass reheated up to its liquid state with a heating rate q such that q= q- the values of Tg and Tf are identified Thus knowing ∆h and Tg the value of the fragility index m can be obtained from 4 The Ge40S60 sample is prepared from a mixture of high purity 99999 Ge and S according to the melt-quench technique Variations of the heat capacity changes at Tg are measured by differential scanning calorimetry using DSC 2920 modulated TA instrument calorimeter run in the conventional mode To obtain good reproducibility the same sample sealed in an aluminium pan is used during all measurements To determine ∆h cooling experiments are performed From the rejuvenation temperature Tr about 10 K above Tg the sample is cooled down at the cooling rates of 100 50 20 10 5 1 Kmin Then they are immediately reheated at q =10 Kmin up to Tr To erase any aging effects in experiments the sample is kept for 3 min at Tr before any cooling run The calorimeter is calibrated in temperature and enthalpy of melting of pure indium A small lump of glass 1825 mg is sealed in aluminium pan and referenced to an empty one The results of this measurement will be the subject of a coming article