Anne Leriche

Development of superhydrophilic and superhydrophobic polyester fabric by growing Zinc Oxide nanorods

ZnO nanorods were grown on microfibers of Polyethylene terephthalate (PET) fabric by seeding method to develop hierarchical roughness structure. XRD and XPS analysis show the presence of crystalline ZnO and chemical Zn species at the fiber surface at each stage of the process. Five series of samples with different seed concentrations have been realized, and their surface morphology and topography were characterized by AFM and SEM. Increasing seed concentrations lead to samples with superhydrophilic properties. Not only the water contact angle at fabric surface tends to zero but also the water capillary diffusion inside fabric is faster. Nanostructuration affects the structure inside the fabric, and further experiments with decane liquid have been made to get a better understanding of this effect. To study the superhydrophobicity, nanorods treated samples were modified with octadecyltrimethoxysilane (ODS) by two method; solution deposition and vapor deposition. The superhydrophobicity was characterized by measuring the water contact angle and water sliding angle with 5 μl water droplet. The samples modified with ODS by vapor deposition showed higher water contact angles and low water sliding angle than the ones modified with solution method. The lotus effect has been well correlated with the surface morphology of the nanorods structured fibers. The application of the Cassie-Baxter equation is discussed.

Hydrothermal synthesis of lead zirconium titanate (PZT) powders and their characteristics

Abstract The combined influences of KOH initial concentration and initial lead precursor excess on the characteristics (morphology, powder density, specific surface area, crystalline structure and powder chemical composition) and sintering behaviour of hydrothermally synthesised powders, have been investigated. Optimised conditions (low KOH concentration and presence of lead excess in the feedstock) have been determined that lead to fine deagglomerated and reactive PZT powders densifying at about 850°C. A Pb-rich surface layer has been identified over the grains, that is responsible for this low sintering temperature. Despite the large excess of lead, the core of powders remains lead deficient. But by lowering [KOH] o , it is possible to keep the lead deficiency within a few percent.

Mechanism of PZT crystallisation under hydrothermal conditionsDevelopment of a new synthesis route

Abstract On the basis of a 1-stage hydrothermal process, we first investigated the reaction mechanism responsible for the PZT precipitation. In a first sequence, lead diffuses into the amorphous coprecipitate. By increasing the reaction temperature, these particles dissolve, leading to nucleation and growth of PZT well faceted particles. In a second step, we demonstrated that starting from very fine oxide precursors, a homogeneous PZT solid solution could be formed. Under the same conditions but without any lead precursor, a mixture of KTO (a potassium titanium oxide phase) and tetragonal zirconia is formed. A 2-stage process was developed on these assumptions. The first stage consists in producing the KTO–ZrO2(T) mixture. In the second stage, this mixture is hydrothermally treated in presence of lead precursor. Pure and homogeneous PZT and PLZT powders were obtained throughout this new synthesis route.

Hot isostatic pressing of SiC-platelets/Y-TZP composites

Abstract Composites consisting of Y-TZP matrix with SiC-platelet secondary phase were first densified by a two-step procedure consisting in pressureless sintering, followed by HIPing. Although platelets do not significantly affect matrix packing and microstructure, they modify the transformation of tetragonal into monoclinic zirconia during rupture, mainly according to a load transfer mechanism. In spite of a lower reinforcement by transformation toughening, the composites show higher toughness due to load transfer and crack deflection mechanisms, which are found to be active from room temperature up to 300°C. For higher temperatures, matrix degradation is observed due to cracking or chemical reaction of platelets with oxygen at the matrix-platelet interface.

Creep behaviour of Al2O3–SiC nanocomposites

Abstract Compared with monolithic fine grained Al 2 O 3 , Al 2 O 3 nanocomposites reinforced with SiC nanoparticles display especially high modulus of rupture as well as reduced creep strain. Taking into account the fracture mode change, the morphology of ground surfaces showing plastic grooving, the low sensitivity to wear and the low dependence of erosion rate with grain size, it can be reasonably assumed that the strength improvement is associated with an increase of the interface cohesion (due to bridging by SiC particles) rather than with a grain size refinement involving substructure formation (as initially suggested by Niihara). In the present work, creep tests have been performed and the results agree with such a reinforcement of the mechanical properties by SiC particle bridging Al 2 O 3 –Al 2 O 3 grain boundaries. Indeed, particles pinning the grain boundaries hinder grain boundary sliding resulting in a large improvement in creep resistance. In addition, SiC particles, while counteracting sliding, give rise to a recoverable viscoelastic contribution to creep. Because of the increased interface strength, the samples undergoing creep support stress levels, greater than the threshold value required to activate dislocation motion. The high stress exponent value as well as the presence of a high dislocation density in the strained materials suggests that a lattice mechanism controls the deformation process. Finally, a model is proposed which fits well with the experimental creep results.

Powder process influence on the characteristics of Mn,W,Sb,Ni-doped PZT

Abstract The use of lead zirconate titanate ceramics for applications like actuators implies the development of materials with high mechanical quality factor Q m and high electromechanical coupling coefficient k p . The composition Pb((Zr 0.49 Ti 0.51 ) 0.94 Mn 0.0252 Sb 0.0192 W 0.0156 )O 3 +0.2 wt.% NiO has been studied with this aim in view. Homogeneous, fine and desagglomerated powders are required. A new doped PZT powder elaboration process by hydrothermal route has been developed. The same composition is also prepared by a conventional calcination route. The chemical and physical characteristics of these two kinds of powders are studied and the sintering behaviour has been investigated. Ceramics from the hydrothermal route densify at 850°C while the ceramics from the calcined powders require a sintering temperature of 1150°C. The microstructures were studied and the piezoelectric and ferroelectric properties were determined.

Nonlinearity and scaling behavior in a soft lead zirconate titanate piezoceramic

Lead oxide-based ferroelectrics, represented by lead zirconate titanate [Pb(Zr,Ti)O3] or PZT), are the most widely used materials for piezoelectric actuators, sensors, and transducers due to their excellent piezoelectric properties. Most of these piezoelectric materials are employed under a variety of strains (stress, electrical field, and temperature). It would thus be interesting to predict their behaviors under different excitations without having to perform too much experimental work, i.e., just carry out a single experiment and still be able to provide the other experimental values. The purpose of this paper has thus been to propose several behavioral laws linking the electrical field, temperature and mechanical stress. The first law rendered it possible to express the mechanical stress by an equivalent electric field [ΔE≡αΔT×P(E,T0)]. Subsequently, a law linking the electrical field and temperature {ΔE≡[2β×P(E,θ0)]×Δθ} was proposed. From these two laws, a third law was identified reflecting the mech...

Study the multi self-cleaning characteristics of ZnO nanorods functionalized polyester fabric:

The conditions to make nanorods functionalized fabric superhydrophobic have been optimized to obtain three kinds of self-cleaning characteristics such as physical, chemical, and biological. Physical self-cleaning is the lotus effect which is characterized by measuring both water contact and sliding angles. Chemical self-cleaning is the degradation of color stains and solutions due to photocatalytic effect of ZnO when exposed to ultraviolet. Biological self-cleaning refers to the antibacterial activity of functionalized fabric which is characterized by using a Gram-negative bacterium (Escherichia coli) and a Gram-positive bacterium (Staphyloccocus aureus) by both qualitative and quantitative methods using NF ISO 20743:2009 transfer method. The chemical and biological self-cleanings are studied on nanorods functionalized fabric before and after hydrophobization.

Photocatalytic solution discoloration and self-cleaning by polyester fabric functionalized with ZnO nanorods

Polyester fabric was functionalized with ZnO nanorods grown by hydrothermal method. The ZnO seeds were deposited on fabric which provided the sites for growth of nanorods. The functionalized fabric showed self-cleaning by degrading color stains and solution discoloration under the effect of ultraviolet (UV) light which was studied using two azo and one triphenylemethylene dye. The stained fabric was exposed to UV light and K/S (K = absorption coefficient, S = scattering coefficient) values were measured by spectrophotometer. Most of the stains were degraded in first 300 min and they disappeared completely after 24 h. The solution discoloration was studied by using different concentrations of dyes and was characterized by measuring absorbance. The rubbing and washing durabilities of the functionalized fabric were also investigated.

The effects of sintering temperature and poling condition on the piezoelectric properties of 0.935(Bi0.5Na0.5)TiO3 - 0.065BaTiO3 ceramics

The 0.935(Bi0.5Na0.5) TiO3 -0.065BaTiO3 (abbreviated as BNT6.5BT) lead-free ceramics were prepared by conventional solid state sintering technique. The effects of sintering temperature (1150–1200 °C) and poling condition on its piezoelectric properties were examined. Piezoelectric properties like the piezoelectric constant (d33) and electromechanical factors (kp, kt) depend on the poling field and poling temperature, whereas different poling times, in the 5–30 min range, were not observed to have any significant effect on the piezoelectric properties. With respect to piezoelectric properties, the chosen sintering temperature range is suitable for BNT6.5BT ceramics.