பொருள் அறிவியல் & பொறியியல் இதழ்

Supercapacitors have great electrochemical characteristics such as high energy and power densities, chargedischarge rates, and extremely long cycle life which make them favourable in electronics and other applications. Activated carbon was successfully coated with chitosan, and natural graphite flakes were chemically and thermally modified into expanded graphite; these were structurally and morphologically analysed using FTIR and SEM. FTIR analysis showed the presence of N-H scissoring from amine and amide groups, C-O and C≡C stretching for activated carbon/chitosan (AC/CH) composites and OH group, C=C and C-O stretching for expanded graphite (EG). SEM images show that AC/CH and EG have porous structures; AC/CH has chitosan chunks on activated carbon surface. The fabricated supercapacitors were tested for their specific capacitances, charging rates, and energy and power densities. At potential window of 0.001 V, the lowest specific capacitance, charging rate, energy density, and power density are 0.49 ± 0.0060 F/g, 0.12 ± 0.0018 mC/s, 6.853 × 10^-8 Wh/kg, and 1.556 × 10^-4 W/kg, respectively, which are obtained from 100% EG treatment. The symmetric supercapacitors can reach a specific capacitance of 272 ± 14.47 F/g, charging rate of 65.3 ± 0.81 mC/s, and energy density of 3.786 × 10^-5 Wh/kg and power density of 0.0817 W/kg with 50% AC/CH-50% EG treatment.

The purpose of this article is to develop a unified algorithmic approach for determining the characteristics of cubic lattices. For this, we will establish here the correlations between these characteristics and show that they can be expressed in terms of only two independent parameters, namely, the coordination number and the lattice constant. The main utility of the present approach consists in generating automatically the whole set of the characteristics of cubic lattices.

In this paper, we investigate several types of “natural or bio sourced templates” (sugar, salt, bone, coral, PLA 3D-printed scaffolds) for a simple elaboration of macro porous thermoplastic or thermosetting polymers, especially based on resins commonly used in composites manufacturing. Open-cell, macro porous polymer foams are obtained from resin impregnation of a template. Process consists of 3 simple steps: a) impregnation/infiltration/infusion of the template, b) polymerization of the resin, c) removal of template, mainly by water.
We compared several resins and showed that a low viscosity and a sufficient wettability enable fast impregnation of templates, where impregnation times are <4 min for samples on 10 to 30 mm thicknesses. The resulting polymeric porous structure is the overall replication of the template, exhibiting mainly open pores in the range of 100 to 500 μm, and densities from 0.25 to 0.4 g/cm3. Such open foams behave as sponges and can (re) absorb liquids either polar (water) or alcohols or silicon oil, which are filling the entire void volume. The resin filling step is valuable to introduce additives or functions in the foams (here an impact modifier is tested).

Statistical process control (SPC) is a tool to improve the quality and productivity of processes. The objective of this research was to apply statistical control charts in chemical and food industrial processes and highlight their advantages in the control of processes. For the study, the control data of the processes of 4 industrial plants was used: rectified ethyl alcohol distillation plant, asparagus processing plant, soluble coffee production plant and light liquid fuel production plant. The deductive methodology was applied, based on the type of data: variable or attribute, constant or variable sampling, evaluation of the defective fraction, number of defects, variability of processes. With this, the statistical control chart suitable for the process was selected. The results showed that in the food industry the np and p charts can be used to evaluate the defective fraction and for the number of defects, as was the case in asparagus cans, u and c graphs are used. To control variables, the charts used were XmR, XbarR, Xbar Trend, Fixed limits and XbarS. It was concluded that the control charts in the chemical and food processes is not only applicable, but it allows predicting the behavior of the process and alerts when it tends to go out of control, thus allowing improving the quality.

Composites are prone to delamination damage when impacted by low velocity projectiles because of the poor through-thickness strength. So, some of the problems with composites are their poor impact damage resistance, low post-impact mechanical properties and the difficulties to inspect the impacted area using nondestructive means. Damage characterization of composite materials requires a logical scientific methodology and a wide knowledge of polymeric materials and additionally a direct field experience. Effort is being taken to locate the most solid Non- Destructive Testing “NDT” strategy for characterization of damage in composite materials. In this work, impact response of composite laminates was experimentally studied with drop-tower to determine the energy absorption. Three types of composites were used: carbon fiber, glass fiber and mixed fiber composite laminates. In addition, these composites were characterized visually and using thermography to quantify their post impact damage. It was found with the 3D temperature distribution that there is a strong correlation between the measured temperatures at the impact region with the quantification of the damage using thermal imaging with advanced mid-wave camera.