Y.A.C. Jande

Manufacturing of Functionally Graded Porous Products by Selective Laser Sintering

Selective laser sintering (SLS) is a rapid prototyping technique which is used to manufacture plastic and metal models. The porosity of the final product obtained by SLS can be controlled by changing the energy density level used during the manufacturing process. The energy density level is itself dependent upon manufacturing parameters such as laser power, hatching distance and scanning speed. Through mechanical characterization techniques, it is possible to quantitatively relate the energy density levels to particular strength values. The present study is directed towards manufacturing functionally graded polyamide products by changing the energy density level in a predetermined manner. The mechanical properties of the functionally graded components are characterized by means of tensile testing. Both homogeneous and functionally graded specimens are produced and tested in order to examine the influence of the energy density level on the mechanical response and on the ultimate tensile and rupture strengths. Selective laser sintering is shown to possess the potential to produce functionally graded porous specimens with controlled variations in physical and mechanical properties.

Integrating reverse electrodialysis with constant current operating capacitive deionization

The presence of a salinity gradient between saline water streams may result in the production of electricity via either reverse electrodialysis (RED) or forward osmosis. While the former system generates electricity because of the ionic current, the latter process produces electricity due to the osmotic pressure. In this study, RED is coupled with capacitive deionization (CDI) so that highly pure water, fresh water and electricity could be generated simultaneously. A CDI cell is operated at constant current, and it generated ultrapure water and two streams (a lower salinity stream of approximately 17.4 mol NaCl per m(3) and a high salinity stream of approximately 512.8 mol NaCl per m(3)) to be fed to the RED stack from a 15,000 ppm CDI feed concentration. The performed simulation reveals that, the total power generated from the RED using infinitely divided electrodes is 0.57 W/m(2) electrode area. The use of RED in a CDI plant introduces a new approach to minimize CDI brine concentration, which would otherwise have a negative impact on the environment if it were disposed directly without prior treatment.

Hybrid CV-CC operation of capacitive deionization in comparison with constant current and constant voltage

ABSTRACT Capacitive deionization (CDI) is a technique used to desalinate saline water by means of electrical potential applied to the electrode along both sides of a spacer channel through which water flows. CDI operates either at constant voltage (CV) or at constant current (CC) operation to desalinate saline water. The purity of the water is the main requirement at the outlet of the cell. The lowest effluent concentration is achieved within a very short time by operating the CDI cell at CV, but after that the effluent concentration continues to increase. On the other hand, in CC, the lowest concentration is achieved later as compared with CV, but once it is achieved it continues to remain constant until the target voltage is reached. In this paper, we combine both CV and CC operation to get the lowest concentration for maximum time during the adsorption process so that more desalinated water is produced. We compare hybrid CV-CC and constant voltage and constant current in terms of effluent concentration, energy consumption per ion removal, water recovery, and water quality by varying operational parameters like cell potential. It was observed that ultrapure water can be produced with hybrid CV-CC operation by systematically varying different process parameters like flow rate and cell potential to get better results.

Ultrapure water from seawater using integrated reverse osmosis-capacitive deionization system

AbstractThe use of water for particular application depends on its purity level. In accordance with the world health organization, water with total dissolved salts (TDS) less than 500 ppm can be considered good for human consumption. Ultrapure water is used in areas such as semiconductor industry, pharmaceuticals, and laboratories. Purification processes like electrodeionization process, thermal processes, and membrane processes are used to produce ultrapure water from very low salinity (10–200 ppm) water source. In this study, seawater is desalinated to produce ultrapure water using the integrated reverse osmosis (RO)-capacitive deionization (CDI). The RO permeate is fed to the CDI cell to generate the high purity water. It has been found that, with the use of RO-CDI integrated system, seawater can be used to produce ultrapure water with TDS less than 2 ppm and potable water with TDS less than 400 ppm by consuming 3.171 kWh/m3 of energy. The proposed integrated RO-CDI system is of significant interest in...

Production of graded porous polyamide structures and polyamide-epoxy composites via selective laser sintering

Selective laser sintering was used for producing uniformly porous and graded porous polyamide structures. The porous structures were infiltrated with epoxy to produce composites. The porous and composite specimens were physically and mechanically characterized. Within the capabilities of the selective laser sintering machine and the materials used, porosities in the range 5–29% could be obtained in a controlled, repeatable manner. The ultimate tensile strength of the produced uniformly porous polyamide structures ranged from 20 MPa (for 29% porosity) to 44 MPa (for 5% porosity). The graded porous structures exhibited continuously changing porosity grades. As the number of grade increments rose, the grade profile fit closely with the design grade profile. The grades need to be constructed at porosities 9% or more for clear grade variation. Five percent porosity remained in all epoxy-polyamide composites after infiltration of the polyamide preforms with epoxy resin. Improvement in strength with epoxy infiltration was observed for preform porosities above 9%. The composite strength varied from 37 MPa to 44 MPa with respect to epoxy resin volume fraction. The maximum strength of the composites was found to be the same as the strength of the sintered polyamide powder (44 MPa).