On the use of a powder rheometer to characterize the powder flowability at low consolidation with torque resistances

The Anton Paar Powder Cell was used to measure the torque necessary to rotate an impeller in beds of glass beads, sand and alumina powders aerated between no aeration to the minimum for fluidization. Measured torque values depend on the material tested, on the air flow rate applied, on the impeller depth and on the height of the impeller blade. The effect of the impeller depth is linear for low impeller depth and is less than linear at high depth values. A model was developed for the interpretation of the experimental results based on the idea that the material is shearing on the surface described by the impeller rotation. The model allows to estimate an effectiveness of the impeller in the torque determination and also to predict the torque for the impeller at the at deepest positions at which the wall effects have to be considered. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

<Emphasis Type="SmallCaps">l</Emphasis>-Aspartic acid incorporated optically active poly(amide-imide)s: synthesis and characterization

N-trimelliticimido-l-aspartic acid (1) was prepared from the reaction of trimellitic anhydride with l-aspartic acid in a mixture of glacial acetic acid and pyridine solution (3/2 ratio) under refluxing conditions. The solution polycondensation of the corresponding activated monomer with eight aromatic diamines were carried out in DMAc. The resulting poly(amide-imide)s were obtained in quantitative yields, showed admirable inherent viscosities (0.20–0.36 dl g⁻¹), good optical activity (+7.32o to +15.24o), and were readily soluble in polar aprotic solvents. They start to decompose (T _10%) above 170 °C and display glass-transition temperatures at 120–237 °C. All of the above polymers were fully characterized by UV, FT–IR, and ¹HNMR spectroscopy, elemental analysis, thermogravimetric analyses, DSC, inherent viscosity measurement, and specific rotation.     

Effect of oxide and carbide nanoparticles on tribological properties of phenolic-based nanocomposites

The phenolic-based composites and components are widely used because of their excellent thermal, tribological and mechanical behaviors. In the present study, phenolic resin composed of hexamine, novalac, furfural, and furfuryl alcohol has been used. The effects of two carbide nanoparticles (SiC and TiC) and two oxide nanoparticles (TiO₂ and ZrO₂) on the tribological properties of phenolic resin were experimentally investigated. This paper intends to identify the effects of different fillers, fraction of particles and normal load on wear rate and coefficient of friction in dry sliding wear of phenolic-based nanocomposites against hard metal. The proportions of fillers were 0.5, 1 and 2?vol% and experiments were carried out under 40, 50, 60 and 70?N loads and at 0.2?m/s speed. The fillers were mixed with phenolic resin and molded in the form of a cylinder (8.5?mm diameter?×?25?mm height). The samples were cured at 135?°C with a special heating cycle. The wear tests were performed on pin-on-disk testing apparatus at ambient temperature. The composite pins were tested in dry sliding against carbon steel disk. The worn surfaces of samples have been investigated by SEM and the effects of nanometer particles showed different wear mechanisms. Observations showed that carbide particles have better enhancing effect on tribological properties of phenolic resin as compared to the oxide particles. Nanocomposites with SiC particles showed the best tribological properties among the investigated samples. The optimal content of SiC nanoparticles were 1?vol%.     

Performance evaluation of a novel reactor configuration for oxidative dehydrogenation of ethane to ethylene

A one-dimensional non-isothermal steady state model was developed to simulate the performance of three-reactor configurations for the oxidative dehydrogenation of ethane (ODHE) to ethylene. These configurations consist of side feeding reactor (SFR), conventional fixed bed reactor (CFBR) and membrane reactor (MR). The performance of these reactors was compared in the terms of C₂H₆ conversion, C₂H₄ and CO₂ selectivity and temperature profiles. The use of sectional air injections on the wall of SFR with a limited number of injection points showed that the performance of reactor significantly improves and optimum pattern of oxygen consumption is also obtained. Moreover, our SFR with a liquid coolant medium operates in an effectively controlled temperature profile that is comparable with that of the MR, which is cooled by a coolant stream of air. Hence, an enhancement in the level of selectivity is obtained for the SFR configuration. Consequently, the side feeding procedure can decrease the high operating temperature problem and low ethylene selectivity in the ODHE process. According to obtained results, the SFR would be a proper alternative for both the MR and CFBR.     

Effect of NaOH on the Structure and Corrosion Performance of Alumina and Silica PEO Coatings on Aluminum

The effect of NaOH content of electrolyte on the properties of ceramic coatings, produced in silicate solution, was studied. Morphology, chemical analysis, phase composition, and cross-section of the ceramic coatings were investigated by SEM, EDS, XRD, and OM, respectively. The corrosion resistance and corrosion mechanism were also studied using potentiodynamic polarization and electrochemical impedance spectroscopy in a 3.5% NaCl solution. To study the surface roughness, a brightness SEM image analysis method was used. Results suggested that increasing the NaOH concentration of sediment production size causes thickness and coating roughness to decrease. The lowest corrosion rate belonged to the twofold layer coating produced in 10 g/L of NaOH. Other samples, with higher concentrations of NaOH, had reduced porosity, and thus an increase in the corrosion resistance was observed. These coatings mainly consisted of α/γ-Al₂O₃ and amorphous silica.     

Pack Cementation Coatings for High-Temperature Oxidation Resistance of AISI 304 Stainless Steel

Aluminum and titanium are deposited on the surface of steel by the pack cementation method to improve its hot-corrosion and high-temperature oxidation resistance. In this research, coatings of aluminum and titanium and a two-step coating of aluminum and titanium were applied on an AISI 304 stainless steel substrate. The coating layers were examined by carrying out scanning electron microscopy (SEM) and x-ray diffraction (XRD). The SEM results showed that the aluminized coating consisted of two layers with a thickness of 450???m each, the titanized coating consisted of two layers with a thickness of 100???m each, and the two-step coatings of Al and Ti consisted of three layers with a thickness of 200???m each. The XRD investigation of the coatings showed that the aluminized coating consisted of Al₂O₃, AlCr₂, FeAl, and Fe₃Al phases; the titanized layers contained TiO₂, Ni₃Ti, FeNi, and Fe₂TiO₅ phases; and the two-step coating contained AlNi, Ti₃Al, and FeAl phases. The uncoated and coated specimens were subjected to isothermal oxidation at 1050?°C for 100?h. The oxidation results revealed that the application of a coating layer increased the oxidation resistance of the coated AISI 304 samples as opposed to the uncoated ones.     

Influence of sintering temperature on microstructural changes of ceramic Raschig ring

The thermal behavior of Illitic-kaolinitic clay for manufacturing of low porosity ceramic Raschig rings was characterized during the sintering process. The samples were shaped by extrusion method and fired at different temperatures from 1,100 to 1,300 °C. The main physical-chemical transformations were studied by evaluating changes in shrinkage, water absorption, porosity, mechanical strength, microstructure and mineralogical compositions. The optimum sintering condition was found to obtain maximum mechanical strength. Chemical resistance of ceramic Raschig rings also was determined according standard method. It was shown that the better chemical resistance could be attributed to the different mineralogical compositions, in particular with presence of mullite phase.     

Thermosensitive nanoparticles prepared from poly(N‐isopropylacrylamide‐acrylamide‐vinilpyrrolidone) and its blend with poly(lactide‐co‐glycolide) for efficient drug delivery system

Temperature‐responsive polymers have become increasingly attractive as carrier for the injectable drug delivery systems. In the present work, we have studied the preparation of poly(N‐isopropylacrylamide‐acrylamide‐vinilpyrrolidone) (NIPAAm‐AAm‐VP terpolymer) nanoparticulated terpolymer and its blend with poly(lactide‐co‐glycolide, PLGA; molar ratio of lactide/glycolid 1/3). Thermosensitive terpolymer, poly(NIPAAm‐AAm‐VP) was prepared by free‐radical polymerization in aqueous solution. The nanoparticles of poly(NIPAAm‐AAm‐VP) and its blend with PLGA containing naltrexone were prepared using the evaporation and w/o emulsion‐solvent evaporation methods, respectively. Nanoparticles prepared from terpolymer‐PLGA blend at low polymer concentration (5%) shows larger particle size (>300 nm) and higher drug content%. Various types of nanoparticles showed a burst release of less than 10% after 24 h . The results suggest that by regulating different variables, desired release profiles of naltrexone can be achieved using a blend of PLGA‐poly(NIPAAm‐AAm‐VP) nanoparticulate system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

GTD-111高温合金瞬时液相连接过程中显微组织的变化

研究连接温度和时间对瞬时液相连接GTD-111高温合金显微组织的影响.连接过程采用BNi-3填料,在1080、1120和1160℃下,分别进行195、135和90 min的等温凝固,再进行均匀化热处理.结果表明,在冷却过程中,接头区域连续形成富Ni硼化物、Ni?B?Si三元化合物和共晶γ的金属间化合物和共晶化合物.随着...