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Physico-chemical and mechanical properties of Ti_3SiC_2-based materials elaborated from SiC/Ti by reactive spark plasma sintering

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Journal of Advanced Ceramics 2019年第1期8卷 47-61页

作者： Faten TURKI Houyem ABdeRRAZAK Frédéric SCHOENSTEIN Florent TêTARD Mohieddine ABdeLLAOUI Noureddine JOUINI laboratoire des matériaux Utiles Institut National de Recherche et d’Analyse Physico-chimique laboratoire de Sciences des Procédés et matériaux Université Paris 13 Sorbonne Paris Cité CNRS

In this paper, the synthesis of Ti_3 SiC_2 from SiC/Ti powder using reactive spark plasma sintering(R-SPS) in the temperature range of 1300-1400 ℃ is reported. The results show that the purity of Ti_3 SiC_2 is improved up to 75 wt% when the holding time is increased from 10 to 20 min at1400 ℃. The thermodynamic and experimental results indicate that Ti_3 SiC_2 formation takes place via the reaction of a pre-formed TiC phase with the silicides, formed from the eutectic *** analysis of mechanical behaviour indicates that samples with higher percentage of secondary phases exhibit higher microhardness and better resistance compared to the near single phase Ti_3 SiC_2.

关键词： Ti3SiC2 reactive spark plasma sintering(R-SPS) density mechanical properties

Enhanced dielectric performance of Dy-substituted YMn2O5 for high-frequency applications

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Progress in Natural Science:materials International 2021年第5期31卷 762-771页

作者： H.Chouaibi K.Khirouni E.Dhahri laboratoire de Physique Appliquée Faculté des Sciences Université de Sfax laboratoire de Physique des matériaux et des Nanomatériaux Appliquée à l'environnement Faculté des Sciences de Gabès Cité Erriadh Université de Gabès

The dielectric performances as well as the effects of Dy3+ions content at A sites of YMn2O5(YMO) [x=0(YDM0)and x=0.4(YDM0.4)] polycrystalline samples were *** compounds were synthesized via sol-gel method.X-Ray diffraction and Raman measurements proved the high quality of the compounds that crystallized in an orthorhombic structure with the Pbam space ***,impedance spectroscopy and electrical modulus studies revealed that both samples exhibited a non-debye’s type of *** decrease of impedance for YDM0.4compared to the pure YDM0,may be attributed to the decrease in charge transfer *** the fit of impedance spectra,they confirmed that both compounds were simultaneously capacitive and ***,the activation energies obtained from Modulus and complex impedance were proven to be neighboring,suggesting that the relaxation process refers to electron *** each compound,the evolution of ε’and tan & with temperature indicated a clearer relaxor behavior,namely the existence of two *** first one detected at low temperature is related to the charge carriers hopping between Mn3+and Mn4+and the second at high temperature is associated with oxygen *** reduced hopping rate with Dy3+substitution for Y3+ions at A sites is responsible for the decrease in dielectric constant and dielectric *** significant findings demonstrate that these materials can be invested in a fruitful use in UV photo-detector and power applications in high frequency as microwave,millimeter wave signal processing,for civilian,military and space applications.

关键词： Multiferroic Relaxation phenomenon High dielectric constant Relaxor behavior

Structural Morphological and Optical Properties of SnSb_2S_4 Thin Films Grown by Vacuum Evaporation Method

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Journal of materials Science & Technology 2014年第10期30卷 1006-1011页

作者： N.Khedmi M.Ben Rabeh M.Kanzari laboratoire de Photovoltaques et matriaux de Semi-conducteurs-ENIT-Universit de Tunis el Manar BP 37le belvedere1002 TunisTunisie laboratoire de Photovoltaques et matriaux de Semi-conducteurs-ENIT-IPEITunis Montfleury-Universit de Tunis Tunisie

SnSb2S4 thin films were prepared from powder by thermal evaporation under vacuum of 1.33 × 10^-4 Pa （ 10^-6 Torr） on unheated glass substrates. The effect of thickness on the structural, morphological and optical properties of SnSb2S4 thin films was investigated. Films thickness measured by interference fringes method varied from 50 to 700 nm. X-ray diffraction analysis revealed that all the SnSb2S4 films were polycrystalline in spite without heating the substrates and the crystallinity was improved with increasing film thickness. The microstructure parameters： crystallite size, strain and dislocation density were calculated. It was observed that the crystallite size increased and the crystal defects decreased with increasing film thickness. In addition, by increasing the film thickness, an enhancement in the surface roughness root-mean-square （RMS） increased from 2.0 to 6.6 nm. The fundamental optical parameters like band gap, absorption and extinction coefficient were calculated in the strong absorption region of transmittance and reflectance spectrum. The optical absorption measurements indicated that the band （Eg） gap of the thin films decreased from 2.10 to 1.65 eV with increasing film thickness. The refractive indexes were evaluated in transparent region in terms of envelope method, which was suggested by Swanepoul. It was observed that the refractive index increased with increasing film thickness.

关键词： Ternary system Thermal evaporation technique Thin films Thickness Atomic force microscopy (AFM)

Evaluation of stress intensity factors for bi-material interface cracks using displacement jump methods

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Acta Mechanica Sinica 2017年第6期33卷 1051-1064页

作者： K. C. Nehar B. E. Hachi F. Cazes M. Haboussi laboratoire de développement en mécanique et matériaux (LDMM) Université de Djelfa PB 3117 Djelfa Algeria laboratoire des Sciences des Procédés et des matériaux (LSPM) UPR 3407 CNRS Université Paris 13 Paris France

The aim of the present work is to investigate the numerical modeling of interfacial cracks that may appear at the interface between two isotropic elastic materials. The extended finite element method is employed to analyze brittle and bi-material interfacial fatigue crack growth by computing the mixed mode stress intensity factors(SIF). Three different approaches are introduced to compute the SIFs. In the first one, mixed mode SIF is deduced from the computation of the contour integral as per the classical J-integral method,whereas a displacement method is used to evaluate the SIF by using either one or two displacement jumps located along the crack path in the second and third approaches. The displacement jump method is rather classical for mono-materials,but has to our knowledge not been used up to now for a bimaterial. Hence, use of displacement jump for characterizing bi-material cracks constitutes the main contribution of the present study. Several benchmark tests including parametric studies are performed to show the effectiveness of these computational methodologies for SIF considering static and fatigue problems of bi-material structures. It is found that results based on the displacement jump methods are in a very good agreement with those of exact solutions, such as for the J-integral method, but with a larger domain of applicability and a better numerical efficiency(less time consuming and less spurious boundary effect).

关键词： Bi-material interface crack Mixed mode stress intensity factor Displacement jump X-FEM Fatigue crack growth

Prediction model for the diffusion length in silicon-based solar cells

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Journal of Semiconductors 2009年第7期30卷 3-6页

作者： Cheknane A Benouaz T laboratoire d'etude et Dveloppement des matriaux Semiconducteurs et Dilectrques Universit Amar Telidji de Laghouat laboratoire de Modlisation UniversitAbou BakarBelkaid de Tlemcen Algrie

A novel approach to compute diffusion lengths in solar cells is presented. Thus, a simulation is done; it aims to give computational support to the general development of a neural networks （NNs）, which is a very powerful predictive modelling technique used to predict the diffusion length in mono-crystalline silicon solar cells. Furthermore, the computation of the diffusion length and the comparison with measurement data, using the infrared injection method, are presented and discussed.

关键词： diffusion length minority-cartier lifetime infrared injection solar cell prediction modelling

determination and Analysis of Optical Constant of Annealed Sn_2Sb_2S_5 Thin Films

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Acta Metallurgica Sinica(English Letters) 2015年第5期28卷 656-662页

作者： Yousra Fadhli Adel Rabhi Mounir Kanzari laboratoire de Photovoltaque et matriaux Semi-Conducteurs ENIT BP 37 Le belvdère 1002 Tunis Tunisia

The effects of annealing on structural, optical and electrical properties of Sn2Sb2S5 thin films were studied. Sn2Sb2S5 thin films were deposited on no-heated glass substrates by single source vacuum evaporation method. The as- deposited films were annealed in air for 1 h at 100, 200 and 300 ℃. XRD study shows that annealed films are crystallized according to the preferential orientation （602）. Optical measurements show that the thin films have relatively high absorption coefficients in the range of 10s-106 cm-1 in the energy range of 2-3.25 eV. It is also found that Sn2Sb2S5 exhibit two optical direct transitions. The models of Wemple-DiDomenico and Spitzer-Fan were applied for the analysis of the dispersion of the refractive index and the determination of the optical and dielectric constants. The electrical resistivity measurements are recorded, and two activation energy values are determined. The layers annealed at 200 and 300 ℃ exhibit a resistive hysteresis behavior. The properties reported here offer perspective to Sn2SbES5 for its application in many advanced technologies.

关键词： Sn2Sb2S5 thin films Optical constants Electrical properties

Sound scattering in dense granular media

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Chinese Science Bulletin 2009年第23期54卷 4327-4336页

作者： LAURENT J KHIDAS Y LANGLOIS V laboratoire de Physique des matériaux Divisés et des Interfaces Université Paris-Est

The sound propagation in a dense granular medium is basically characterized by the ratio of wavelength to the grain size. Two types of wave transport are distinguished: one corresponds to coherent waves in the long wavelength limit, the other to short-wavelength scattered waves by the inhomogeneous contact force networks. These multiply scattered elastic waves are shown to exhibit a diffusive characteristics of transport over long distances of propagation. determination of the transport mean free path l * and the inelastic absorption (Q-1) allows the inference of the structural properties of the material such as the heterogeneity and internal dissipation. The relevance of our experiments for seismological applications is discussed. Moreover, we apply the correlation technique of the configuration-specific sound scattering to monitoring the dynamic behaviour of the granular medium (irreversible rearrangements) under strong vibration, shearing and thermal cycling, respectively.

关键词：颗粒介质人口密集声散射扩散特征平均自由程晶粒尺寸交通工具结构特性

Existence results for unilateral contact problem with friction of thermo-electro-elasticity

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Applied mathematics and Mechanics(English Edition) 2015年第7期36卷 911-926页

作者： H.BENAISSA EL-H.ESSOUFI R.FAKHAR laboratoire de Recherche en mathématique Informatique et Sciences de l’Ingénieur (MISI) laboratoire de Science des matériaux des Milieux et de la Modélisation (LS3M)Université Hassan 1

This work studies a mathematical model describing the static process of contact between a piezoelectric body and a thermally-electrically conductive foundation. The behavior of the material is modeled with a thermo-electro-elastic constitutive law. The contact is described by Signorini＇s conditions and Tresca＇s friction law including the electrical and thermal conductivity conditions. A variational formulation of the model in the form of a coupled system for displacements, electric potential, and temperature is de- rived. Existence and uniqueness of the solution are proved using the results of variational inequalities and a fixed point theorem.

关键词： static frictional contozt thermo-piezoelectric material Signorini's condi-tion Tresca's friction frictional heat generation variational inequality fixed point process

detection of CO2 and O2 by iron loaded LTL zeolite films

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Frontiers of Chemical Science and Engineering 2018年第1期12卷 94-102页

作者： Veselina Georgieva Richard Retoux Valerie Ruaux Valentin Valtchev Svetlana Mintova laboratoire Catalyse et Spectrochimie (LCS) ENSICAEN CNRS Normandy University 14000 Caen France laboratoire de Cristallographie et Sciences des matériaux (CRISmat) ENSICAEN CNRS Normandy University 14000 Caen France

detection of oxygen and carbon dioxide is important in the field of chemical and biosensors for atmosphere and biosystem monitoring and fermentation processes. The present study reports on the preparation of zeolite films doped with iron nanoparticles for detection of CO2 and O2 in gas phase. Pure nanosized LTL type zeolite with monomodal particle size distribution loaded with iron （Fe-LTL） was prepared under hydrothermal condition from colloidal precursor suspensions. The zeolite was loaded with iron to different levels by ion exchange. The Fe-LTL suspensions were used for preparation of thin films on silicon wafers via spin coating method. The reduction of the iron in the zeolite films was carried out under H2 flow （50% H2 in Ar） at 300 ℃. The presence of iron nanoparticles is proved by in situ ultra-violet-visible spectroscopy. The properties of the films including surface roughness, thickness, porosity, and mechanical stability were studied. In addition, the loading and distribution of iron in the zeolite films were investigated. The Fe-LTL zeolite films were used to detect O2 and CO2 in a concentration dependent mode, followed by IR spectroscopy. The changes in the IR bands at 855 and 642 cm^-1 （Fe O-H and Fe-O bending vibrations） and at 2363 and 2333 cm^-1 （CO2 asymmetric stretching） corresponding to the presence of O2 and CO2, respectively, were evaluated. The response to O2 and CO2 was instant, which was attributed to great accessibility of the iron in the nanosized zeolite crystals. The saturation of the Fe-LTL films with CO2 and O2 at each concentration was reached within less than a minute. The Fe-LTL films detected both oxygen and carbon dioxide in contrast, to the pure LTL zeolite film.

关键词： zeolite films detection of CO2 and O2 adsorption