Polyetherimide-Montmorillonite Nano-Hybrid Composite Membranes: CO2 Permeance Study via Theoretical Models

The incorporation of aminolauric acid modified montmorillonite (f-MMT) in polyetherimide (PEI) has been implemented to develop hollow fibre nano-hybrid composite membranes (NHCMs) with improved gas separation characteristics. The aforementioned characteristics are caused by enhanced f-MMT spatial dispersion and interfacial interactions with PEI matrix. In this study, existing gas permeation models such as, Nielsen, Cussler, Yang–Cussler, Lape–Cussler and Bharadwaj were adopted to estimate the dispersion state of f-MMT and to predict the CO2 permeance in developed NHCMs. It was found out that the average aspect ratio estimated was 53, with 3 numbers of stacks per unit tactoid, which showed that the intercalation f-MMT morphology is the dominating dispersion state of filler in PEI matrix. Moreover, it was observed that Bharadwaj model showed the least average absolute relative error (%AARE) values till 3 wt. % f-MMT loading in the range of ±10 for a pressure range of 2 to 10 bar. Hence, Bharadwaj was the best fit model for the experimental data compared to other models, as it considers the platelets orientation.

The Microstructure Evolution and Mechanical Properties of TiBw/TA15 Composite with Network Structure Prepared by Rapid Current Assisted Sintering

TiBw/TA15 (TA15 alloy reinforced by TiB whiskers) composites with network microstructures were successfully prepared by current-assisted sintering at 1100 °C for 10 min. The influence of the sintering parameters on the microstructures of obtained composites was investigated. The sintering temperature was the main factor affecting the average aspect ratio of TiBw, and the average diameter of TiBw could be controlled for various sintering conditions. Yield strength, ultimate compressive strength, and plastic strain at ambient temperature are 1172.5 MPa, 1818.4 MPa, and 22.4% for the TiBw/TA15 composites, respectively. Moreover, yield strength of the composites at 600 °C is 616.3 MPa, which is 26.1% higher than that of the TA15 titanium alloy. The effect of the TiBw on the microstructure evolution for the alloy matrix was discussed in detail. The strengthening mechanism of the TiBw/TA15 composites with network microstructure was attributed to the microstructure modification induced by TiBw, load bearing effect, and dislocation strengthening effect of the TiBw.

Study on the particle shape of soft clay in Tianjin port

Microscopic analysis of soils has attracted wide attention, but at present, the analysis of particle shape of soft clay is still scarce. In this paper, the fractal dimension of particle aspect ratio, roundness and roughness is studied by selecting typical soil samples in Tianjin Port area. The main conclusions are as follows: (1) The average aspect ratio of clay, silty clay and silt is 1.56, 1.58 and 1.65, respectively, which shows that the smaller the soil particles are, the smaller the aspect ratio of the whole soil sample is; (2) The average roundness of clay, silty clay and silt are 0.91, 0.89 and 0.88, respectively, which indicates that the smaller the soil particles are, the closer the roundness of the whole soil sample is to 1, the closer the soil particles are to the circle. (3) The smaller the soil particles are, the smoother the surface of the particles is, and the smaller the soil particles are, the more obvious the correlation is.

Facile molten salt synthesis of zirconia whiskers

ZrO2 whiskers have been synthesized by a facile molten salt method using ZrOCl2 ? 8H2O and Na3PO4 ? 12H2O as the zirconium source and molten salt, respectively. Differential thermal and thermogravimetric analyses, Xray diffraction analysis, field emission scanning electron microscope and transmission electron microscope were employed to characterize the heating process of the precursor mixture, phase composition of the assynthesized ZrO2 whiskers and the effect of reaction temperature on the synthesis of ZrO2 whiskers. The results show that the ZrO2 whiskers synthesized at 900?C have an average aspect ratio of 30 and preferentially grow along [010] direction. The formation of sodium zirconium phosphate [Na9-4xZrx(PO4)3] (x = 1, 2) and the reaction temperature play an important role in the growth of ZrO2 whiskers. This work also suggests an effective route for mass production of high quality ZrO2 whiskers.

Linking preferred orientations to elastic anisotropy in Muderong Shale, Australia

The significance of shales for unconventional hydrocarbon reservoirs, nuclear waste repositories, and geologic carbon storage has opened new research frontiers in geophysics. Among many of its unique physical properties, elastic anisotropy had long been investigated by experimental and computational approaches. Here, we calculated elastic properties of Cretaceous Muderong Shale from Australia with a self-consistent averaging method based on microstructural information. The volume fraction and crystallographic preferred orientation distributions of constituent minerals were based on synchrotron x-ray diffraction experiments. Aspect ratios of minerals and pores, determined from scanning electron microscopy, were introduced in the self-consistent averaging. Our analysis suggested that phyllosilicates (i.e., illite-mica, illite-smectite, kaolinite, and chlorite) were dominant with [Formula: see text]. The shape of clay platelets displayed an average aspect ratio of 0.05. These platelets were aligned parallel to the bedding plane with a high degree of preferred orientation. The estimated porosity at ambient pressure was [Formula: see text] and was divided into equiaxial pores and flat pores with an average aspect ratio of 0.01. Our model gave results that compared satisfactorily with values derived from ultrasonic velocity measurements, confirming the validity and reliability of our approximations and averaging approach.

Research on Controllable Synthesis of Magnesium Carbonate Tri-Hydrate

In order to promote the comprehensive utilization of salt lake brine resources, magnesium carbonate tri-hydrate (MgCO3·3H2O) was synthetized by low-temperature hydrothermal technique using purified MgCl2-rich brine and ammonium hydrogen carbonate solution as raw materials, the orthogonal experimental as method. The morphology could be tuned by changing the operating parameters. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize the structures and morphologies of the products. The results show that the optimum conditions are as follows : reaction temperature is 40-50°C, n (Mg2+):n (HCO3-)=1:2.2, pH value is 8.8-9.0, stirring speed is 130 r/min, aging time is 3h, reaction time is 70 min. Magnesium carbonate tri-hydrate synthetized is one-dimensional acicular with good settling performance. Average aspect ratio could up to 29.60.

Rod-Shaped Magnetite Nano/Microparticles Synthesis at Ambient Temperature

Here, we reported room temperature synthesis of Fe3O4rod-shaped nano/microparticles by chemical reduction method from FeCl3precursor and NaBH4as the reducing agent in the presence of the pyrrole as a capping agent. The magnetic Fe3O4particles were characterized by several methods, such as SEM, XRD, FTIR, and TGA. The average aspect ratio of Fe3O4rod-shaped particles was ~2.8. These particles were redispersed in deionised water to form a colloidal solution and showed magnetic properties. This economical synthesis route is scalable, and Fe3O4particles can be exploited for various applications such as MRI contrast enhancement, biodiseperations, Ni-Fe batteries, and as a catalyst.

Modeling of Tensile Modulus of Polyolefin-Layered Silicate Nanocomposites: Modified Halpin Tsai Models

The modified forms of Halpin Tsai model for the prediction of tensile modulus of polyolefin-layered silicate nanocomposites are discussed. The assumptions used in the conventional model like perfect alignment of the particulate filler, uniform shape and size of the filler particles as well as interfacial adhesion between the polymer and filler surface do not hold true in the case of polymer nanocomposites especially using polyolefinic matrices. The modulus reduction factors suggested for polar nanocomposites are also dependent on the polymer nature as well as filler morphology in the composite, thus, are not applicable directly to the polyolefin composites. A master curve could be generated for polyolefin nanocomposites which provided more accurate modulus reduction factor value based on the average aspect ratio of the filler. Incorporation of the effects of incomplete exfoliation as well as filler misalignment though improved the prediction capabilities of the model, however, it still did not match the predictions generated from finite element analysis or TEM analysis. The effect of absence of adhesion forces at the interface was incorporated by suggesting simple modification to the modified Halpin Tsai model equation. Master curves could be generated which predicted the relative tensile modulus of the composites accurately if the value of average aspect ratio was known.

Effects of β-Si3N4 Seeds Addition on Microstructure and Mechanical Properties of Porous Si3N4 Ceramics

Porous Si3N4 ceramics were prepared by conventional sintering method with the initial Si3N4 powder added different amounts of β-Si3N4 seeds and 5 wt.% Y2O3. The porosity, density and flexural strength were tested by Archimedes and three-point bending methods, respectively. Microstructure of porous Si3N4 ceramics was studied by scanning electron microscopy. The results showed that the fibrous β-Si3N4 grains developed in the bimodal porous microstructure and the average aspect ratio of 6.42 by adjusting the β-Si3N4 seeds content up to 3 wt.%. Under the porosity of about 42%, the flexural strength of the materials could reached 315.98 MPa.