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Preparation Techniques
Published in Mihir Kumar Purkait, Randeep Singh, Membrane Technology in Separation Science, 2018
Mihir Kumar Purkait, Randeep Singh
The first step in the phase inversion process is the successful dispersion of the required materials in a solvent. The dispersion has three primary goals: deagglomeration of the particles, complete coating of the particles with the dispersant, and avoiding agglomeration of the particles by using charge and steric effects. The suspension is degassed after the addition and mixing of binders and plasticizers into the suspension. The binders should be such that they should increase the spinnability and invertability of the suspension for the successful production of the ceramic hollow fiber membranes. Degassing is important to avoid membrane defects due to the presence of air bubbles. Degassing is done by keeping the suspension in air or in vacuum for a specific period of time. The next step in the process is the spinning of the suspension for the production of ceramic hollow fiber membranes. A spinning apparatus is used for the spinning of the suspension. The suspension passes through a tube in the orifice spinneret and the rate of flow is controlled by the nitrogen gas pressure or a gear pump. The suspension is directly extruded into a coagulation bath, where phase inversion takes place and then the formed tube is passed through the washing bath and then dried. The last step in the process is sintering, where the dried ceramic hollow fibers go through three steps of the sintering process, namely, presintering, thermolysis, and final sintering. These steps are explained in the preceding sections. The ceramic hollow fiber membranes are ready for use after the successful completion of the sintering process. Nowadays, ceramic hollow fiber membranes are successfully used for gas separation and production applications.
Processing and performance assessment of particulate TiB2 reinforced aluminum MMC developed via a novel hybrid ultrasonic casting system
Published in Materials and Manufacturing Processes, 2022
Amar Sheelwant, Sunil Dutta, Kartheek. S. M. Sonti, Suresh Kumar Reddy Narala
The stir casting (SC) setup employed to synthesize Al-TiB2 MMC includes an Inconel crucible (Ø180 mm x 200 mm), an electrical furnace (max. temperature 1100°C) with a thermocouple accuracy of 1°C. A 0.25 hp AC motor was used to rotate the stirrer (max. up to 1400 RPM). In this technique, pure aluminum ingots were cut into the desired size and melted in the crucible. The furnace temperature was maintained at 850°C throughout the process (heating rate: 5°C/ min) of melting until pouring. After melting, slag was removed from the liquid aluminum’s surface, and later argon gas was used for degassing the liquid metal, as shown in Fig. 1(a). At this stage, preheated (up to 350°C) TiB2 particles 10 wt% were fed into the furnace using the particle feeder attachment provided on top of the furnace. After adding the particles, a stainless-steel stirrer (blade angle 45º) was introduced into the liquid metal and stirred for nearly 10–15 minutes at an average speed of 550 RPM. Finally, the liquid metal mixture was bottom poured using a connecting pipe into a preheated (350°C) cylindrical/square shaped SS310 stainless steel mold.
Evaluating the cytotoxicity of tin dioxide nanofibers
Published in Journal of Environmental Science and Health, Part A, 2018
Ashley S. Reynolds, Tanya H. Pierre, Rebecca McCall, Ji Wu, Worlanyo E. Gato
The synthesized SnDNFs were characterized using various techniques. The sample was prepared for scanning electron microscopy (SEM) by cutting a small piece of the fiber and placing it on double-sided tape on the sample holder. Next, the sample needed to be coated with gold particles to improve electron signals. After the sample was coated, the sample was placed in the SEM and be analyzed. SEM was used to determine the size and structure of the fiber. To prepare the sample for Raman spectroscopy, a small piece of fiber was cut and placed on a glass slide, and firmly pressed flat with another glass slide. Raman spectroscopy was used to identify the molecules in the sample and their chemical bonding. Results from using this method can be compared to the literature to establish if the crystalline structure is rutile or anatase. In order to more accurately verify the crystalline structure powder x-ray diffraction was performed. To complete PXRD, the sample was crushed and placed on a sample holder and acetone was deposited on the fibers to create a slurry. The sample was laid on a sample rack and run in the instrument. Brunauer-Emmett-Teller (BET) theory was used to determine the surface area of fibers. This test was done by degassing the sample then running the examination under liquid nitrogen.
Effect of T6, RRA and nano chromium carbide content on microstructure and mechanical properties of AA7075-Cr3C2 nanocomposite
Published in Particulate Science and Technology, 2022
Abhishek Sharma, Pushyamitra Mishra
The AA-7075 based nanocomposite was synthesized by adding milled powder (master powder) of pure aluminum powder and Cr3C2 nano particles into the melt via stir casting technique. Initially, the required amount of AA7075 was kept for heating in the graphite crucible at the temperature of 800°C for melting. Simultaneously the mold was kept at the temperature of 450°C in the furnace for preheating. As the alloy achieved liquid state, cleansing and drossing were performed to remove the slag formed by using coverall-11 flux. Then the degassing of molten alloy was performed by purging high purity nitrogen gas. The melt was then stirred mechanically at the speed of 300rpm up to vortex formation. Thereafter the preheated milled powder of matrix and reinforcement distributed into multiple small packets of aluminum foil was added into the vortex of the melt. The reinforcement with varying weight percent (0,0.5,1.0,1.5 and 2.0%) was added to obtain samples with five different compositions. Also, the magnesium (1wt.%) in the form of small cubes were added into the melt in order to improve the wettability of the added reinforcement. The melt was then left for 10min for thorough stirring to ensure uniform distribution of the reinforcement in the matrix. The stirring temperature was kept at 800°C. Finally, the melt was poured into the preheated mold and left for cooling. The solidified as cast samples were machined to achieve standard dimension for microstructural characterization and mechanical testing. The schematic diagram for the synthesis of nanocomposite is shown in Figure 3.