Excitation and spectral dependence of the rise and decay time responses of Eu2+- and Dy3+-doped strontium aluminates

Journal of Materials Science: Materials in Electronics - In this paper, we study the phosphorescence rise and decay time responses of Eu2+- and Dy3+-doped strontium aluminates prepared by different...     

Properties of flowable sand concretes reinforced by polypropylene fibers

This paper presents an experimental research on fresh and hardened properties of flowable sand concretes (FSC) reinforced by polypropylene fibers (PF). Tests were conducted on both plain and fiber-reinforced FSC. The fresh properties are tested for viscosity using a programmable DV-II?+?viscometer. For the physical and mechanical properties, drying shrinkage, flexural, and compressive strengths, as well as micro-structural analyses have been studied. Results indicate that all studied mixtures have a pseudo-plastic behavior in fresh state and can be well fitted using power law model. Results also confirmed that PF incorporation increases the viscosity and reduces free shrinkage of FSC. In terms of mechanical strength, results show that incorporating PF would enhance flexural strength. However, a reduction in compressive strength is observed.     

Rheological behavior of Algerian crude oil: effect of temperature and refined product

Abstract

The rheological behavior and its variation with temperature and refined product concentration of a crude oil sample coming from a quagmire of the separation station of Tin Fouye Tabankort oilfield/southern Algeria were investigated experimentally. The experiments were carried out at various temperatures (20, 30 and 50?°C) over the shear rate range of 0 to 700?s^?1 by using a controlled stress rheometer (AR 2000, TA Instrument). The results showed that the crude oil exhibit non-Newtonian of shear thinning behavior at low shear rate and Newtonian behavior at high shear rate and was adequately described by Casson and Herschel–Bulkley models. The rheological measurements through the steady flow test and viscoelastic behavior, including the storage modulus (G′), loss modulus (G″), and complex modulus (G*), has indicated that the rheological properties of the crude oil were greatly influenced by the temperature and the additive concentration.     

Improvement of rheological properties of Algeria crude oil by addition of extra-light crude oil and a surfactant agent

Abstract

Effect of surfactant and extra-light crude oil addition on the rheological behaviors of an Algeria crude oil in order to improving its flowability were studied at low temperature. These rheological properties include steady flow behavior, yield stress and viscoelastic behavior. An AR-2000 rheometer was employed in all of the rheological examination tests. Results show that Toluene and extra-light crude oil addition causes a strong reduction in viscosity, the yield stress and can effectively increase of crude oil transport capacity. The toluene addition gets its best flow capacity and lowest viscosity at 6%. The extra-light crude oil addition obtains its best flow capacity and lowest viscosity at 50%. The viscoelasticity character of the crude oil has indicate a significantly influence by the addition of Toluene and extra-light crude oil.     

Investigating the rheological behavior of Algerian crude oil stemming from station of separation (quagmire)

An experimental study was conducted to investigate the rheological behavior of Algerian crude oil stemming from station of separation (quagmire) of the Tin Fouye Tabankort sector (southern Algeria). The rheological measurements at different temperatures (20°C, 30°C and 50°C) were performed employing AR 2000 rheometer of TA-Instruments. Several parameters such as shear rate, the temperature and the presence of crude oil from another quagmire on the rheological properties have been studied. The experimental results show that the studied crude oil displays non-Newtonian shear thinning behavior at low values of shear rate and a Newtonian behavior at high values of shear rate, which can be best presented by the Casson model. The rheological examination tests (flow and dynamic mode (oscillation)) have shown that the rheological properties of the crude oil were significantly influenced by the temperature and the crude oil addition.     

Comparative studies of the rheological behavior and microstructural properties of emulsions (oil/distilled water phase) and (oil/Lias water phase)

Abstract

The rheological behavior of crude oil and their emulsions were investigated as a function of two water types (distilled water and the LIAS water). The focus of this work is to obtain more knowledge about the effect of LIAS water concentration, which used to maintain pressure and produced from production of crude oil in the oil fields Tin Fouye Tabankort-south Algeria, on the rheological properties of crude oil. The rheological parameters were measured by using AR-2000 rheometer at 15?°C under dynamic and shear testing conditions. The measured data were first classified into two groups for Newtonian and non-Newtonian fluids. Depends on the type and concentration of water, the non-Newtonian behavior was described in better way by the Casson, Power law and the Herschel–Bulkley models. The results indicated that the viscosity, the yield stress, the elastic modulus, (G′), the loss modulus, (G″), and the microstructure of the prepared emulsions not only varied with water concentration but also by water types.     

Influence of the Crystal Growth Temperature on the Formation of Zr Reach Crystalline Phases in a Nuclear Waste Confinement Glass Ceramic

Many glass ceramics are potential candidates for the confinement of radioactive waste. This is the case of glasses embedding radiation-resistant ceramics as zirconolites, pyrochlores or pyroxenes. This study deals with the influence of the crystal growth temperature on the formation of such phases in a nuclear glass ceramic in the system： Al203-SiO2-CaO-MgO-ZrO2-TiO2. The materials with six contents of ZrO2, ranging from 1.00 to 6.40 m.%, are synthesized by a discontinuous method, consisting in a double-melting at 1,350℃, followed by both a nucleation at 564℃, and a crystal growth treatment at： 900, 100 and 1,100 ℃. For the whole of the materials, the morphology reveals a glassy feature, with a opaque aspect. One can also evidence a different crystallization process from the bulk to the surface. The glass ceramics X-ray diffraction analysis （XRD） show that the main identified crystalline skeletons are those of： 2M-zirconolite, CaZrTi207 and ZrO2, depending on the content ofZrO2 in materials and the crystal-growth temperature. The material with the middle content in ZrO2 （4.5 m.%） and crystallized at the middle value ofTc （1,010℃） show the greatest content in zirconolite （87 %）, doped with either lanthanides or alcalin-earth elements, due to the complexity of the mixture of oxides. The temperature of 1,010 ℃ appears to be more selective with regard to the formation of the 2M-zirconolite.     

Experimental investigation of the rheological behavior of algerian crude oils from the quagmires

In this work, the rheological behavior for three types of crude oil coming from different quagmires namely Amassak, Tamendjelt and Tin Fouye of the TFT sector (Tin Fouye Tabankort/South Algeria) has been experimentally investigated. A controlled stress rheometer (AR 2000, TA Instrument) was used throughout this investigation. The experimental measurements in terms of flow and dynamic tests were carried out at different temperatures during the shear rate over the range of 0–700?s^?1 and frequency range of 0.1–10?rad/s. The obtained results show that the viscosity and shear stress of the crude oils decreases about 53.30%, 58.80%, and 59% respectively, when the temperature increased from 10 to 20?°C. The yield stress required to flow of crude oils also decreased to 37.06%, 89.78%, and 77.53% respectively. The dynamic analysis of the crude oils by identifying of the storage modulus (G′) and the loss modulus (G″) has indicated that the rheological properties of crude oils were significantly temperature-dependent.