Process modeling, optimization and analysis of esterification reaction of cashew nut shell liquid (CNSL)-derived epoxy resin using response surface methodology

Concept of five-levels-four-factors central composite rotatable design was utilized for the optimization of reaction conditions of cardanol-based vinyl ester resin production, by employing response surfaces methodology, to establish a relationship between the process variables and the extent of conversion under a wide range of operating conditions which resulted in different extent of conversions. The maximum extent of conversion of cardanol-based epoxidised novolac resin (CNE) and methacrylic acid (MA) catalyzed by triphenylphosphine was found to be 95% at optimum set of conditions of molar ratio (1:0.9) between CNE and MA, catalyst concentration (1.49%), reaction temperature (89.96 °C) and reaction time (17,991s). Geometrical representation of the mathematical models in three-dimensional response surface plots and isoresponse contour plots served as a good aid in understanding the behavior of reaction under different operating conditions by only limited sets of experiments. A statistical model predicted that the highest conversion yield of novolac resin would be greater than 95% at the optimized reaction conditions. The predicted values thus obtained were close to the experimental values indicating suitability of the model.     

TEM investigation of MnO2 cathode containing TiS2 and its influence in aqueous lithium secondary battery

The discharge characteristics of manganese dioxide (MnO₂) cathode in the presence of small amounts (1, 3 and 5 wt.%) of TiS₂ additive has been investigated in an alkaline cell using aqueous lithium hydroxide as the electrolyte. The incorporation of small amounts of TiS₂ additives into MnO₂ was found to improve the battery discharge capacity from 150 to 270 mAh/g. However, increasing the additive from 3 to 5 wt.% causes a decrease in the discharge capacity. Hence, the objective is to gain insight into the role of TiS₂ on the discharge characteristics of MnO₂ and its mechanism. For this purpose, we have used transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) techniques.     

Characterization of alkaline-earth oxide additions to the MnO2 cathode in an aqueous secondary battery

The effect of alkaline-earth oxide additions on aqueous rechargeable battery is investigated using microscopic and spectroscopic techniques. The alkaline-earth oxide additions such as magnesium oxide (MgO) and barium oxide (BaO) were physically mixed to the manganese dioxide (MnO₂) cathode of a cell comprising zinc as an anode and aqueous lithium hydroxide as the electrolyte. The results showed that such additions greatly improved the discharge capacity of the battery (from 145 to 195 for MgO and 265 mAh/g for BaO). Capacity fade with subsequent cycling is reduced only for MgO but not for BaO. With an aim to understand the role of these additives and its improvement in cell performance, we have used microscopy, spectroscopy, ion beam analysis and diffraction based techniques to study the process. Transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy analysis (EDS) results showed evidence of crystalline MnO₂ particles for MgO as additive, whereas, MnO₂ particles with diffused structure leading to mixture of phases is observed for BaO additives which is in agreement with X-ray diffraction (XRD) data. This work relates to improvement in the electrochemical behaviour of the Zn-MnO₂ battery while the MgO additive helps to reduce the formation of manganese and zinc such as hetaerolite that hinders the lithium intercalation.     

Socio-economic profile and food safety knowledge and practice of street food vendors in the city of Guwahati,Assam, India

Street food is an integral part of society in all countries – underdeveloped, developing or developed. As such the standard of hygiene maintained is a very vital matter. Every region has its sets of factors affecting the hygiene maintain. In the present study a survey was carried out in Guwahati city to determine the existing socio-economic status and food safety knowledge of street food vendors. Data on socio-economic and business profile of 80 vendors were collected using three standardized proformas.A study was also conducted on the existing knowledge of vendors on food safety and hygiene practices and methods of procurement of raw materials. The knowledge and procurement practices of the vendors were assessed for association with some relevant socio-economic factors. From the study it was observed that majority of street food vendors were mobile food vendors (54%) with the remaining being owners of small restaurants and food handlers. Majority of the food vendors were local to Guwahati city (93%). The average daily income of the mobile food vendors were between Rs. 200 to Rs. 600. It also was noted that only 30%–37% vendors were aware of hygienic practices of food handling and a mere 8%–11% of food vendors had knowledge on biological sources of food contamination.It was concluded that there is a high degree of association between procurement practices with the type of vendors, ownership status and average income. But no outstanding association exists with any socio-economic factor with the knowledge of the vendors on food hygiene. The street food scenario in the city was found to be quite dismal and requires stringent steps to improve matters.     

A study of lithium insertion into MnO2 containing TiS2 additive a battery material in aqueous LiOH solution

The electrochemical behavior and surface characterization of manganese dioxide (MnO₂) containing titanium disulphide (TiS₂) as a cathode in aqueous lithium hydroxide (LiOH) electrolyte battery have been investigated. The electrode reaction of MnO₂ in this electrolyte is shown to be lithium insertion rather than the usual protonation. MnO₂ shows acceptable rechargeability as the battery cathode. The influence of TiS₂ (1, 3 and 5 wt%) additive on the performance of MnO₂ as a cathode has been determined. The products formed on reduction of the cathode material have been characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), fourier transform infrared spectroscopy (IR) and transmission electron microscopy (TEM). It is found that the presence of TiS₂ to ≤3 wt% improves the discharge capacity of MnO₂. However, increasing the additive content above this amount causes a decrease in its discharge capacity.     

Surfactant controlled synthesis of crystalline phosphovanadate nanorods

Phosphovanadate nanorods were obtained in a reaction of vanadium (V) oxide as a precursor and a cationic surfactant, dodecylpyridinium chloride, as structure directing template at pH ∼3 at room temperature. The composition and morphology of the nanorods was established by powder X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), fourier transform infra-red spectroscopy (FTIR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The obtained nanorods have diameters of 40-60 nm with lengths up to 1 μm. The effect of reaction parameters such as concentration of surfactant and pH of the solution on the growth of nanorods has been investigated. A plausible mechanism involving the coalescence of nanoparticle ‘seeds’ leading to one-dimensional nanorods is also discussed. The same reaction when performed under hydrothermal condition, keeping other reaction parameters unchanged, resulted in the formation of phosphovanadate nanospheres of diameter 10-15 nm.     

Analytical investigation to achieve the highest phase difference between two orthogonal components of light in lithium niobate based electro-optic system

Electro-optic Pockels cell are important opto-electronic devices for conduction of optical switching, optical modulation, where an electrical biasing signal acts on a polarized light passing through the system. Since last few decades lots of works are reported in this area. Again, it is observed that a good switching or modulation becomes realized if the depth of modulation is increased by increasing more phase difference between two orthogonal polarized components of light passing through the material against a biasing signal. Here in this paper the authors propose a new scheme, where multi-passing technique is used to create a high degree of phase difference between those two orthogonal polarized components of light against the biasing signal. The multi-passing of light through the material enables more and more optical path length for the light. So, more and more phase difference between the components of light beams, one passing outside the material and other passing through the material multiple times is created. This method ultimately generates a high degree of depth of modulation in optical switching.     

Geotechnical Properties of JSC-1A Lunar Soil Simulant

For the success of planned missions to the moon in the near future, it is essential to have a thorough understanding of the geotechnical behavior of lunar soil. However, only a limited amount of information is available about geotechnical properties of lunar soils. In addition, the amount of lunar soils brought back to Earth is small. To help the development of new regolith moving machines and vehicles that will be used in future missions, a new lunar soil similant JSC-1A has been developed. A group of conventional geotechnical laboratory tests was conducted to characterize the geotechnical properties of the simulant, such as particle size distribution, maximum and minimum bulk densities, compaction characteristics, shear strength parameters, and compressibility.     

The influence of bismuth oxide doping on the rechargeability of aqueous cells using MnO2 cathode and LiOH electrolyte

Bi-doped manganese dioxide (MnO₂) has been prepared from γ-MnO₂ by physical admixture of bismuth oxide (Bi₂O₃). The doping improved the cycling ability of the aqueous cell. These results are discussed and compared with the electrochemical behavior of bismuth-free MnO₂. Batteries using the traditional potassium hydroxide (KOH) electrolyte are non-rechargeable. However, with lithium hydroxide (LiOH) as an electrolyte, the cell becomes rechargeable. Furthermore, the incorporation of bismuth into MnO₂ in the LiOH cell was found to result in significantly longer cycle life, compared with cells using undoped MnO₂. The Bi-doped cell exhibited a greater capacity after 100 discharge cycles, than the undoped cell after just 40 cycles. X-ray diffraction and the microscopic analysis suggest that the presence of Bi³⁺ ions reduces the magnitude of structural changes occurring in MnO₂ during cycling. Comparison with additives assessed in our previous studies (titanium disulfide (TiS₂); titanium boride (TiB₂)) shows that the best rechargeability behavior is obtained for the current Bi-doped MnO₂. As the size of Bi³⁺ ions (0.96 Å) is much larger than Mn³⁺ (0.73 Å) or Mn²⁺ (0.67 Å) they have effectively prevented the formation of non-rechargeable products.     

Lithium insertion into manganese dioxide electrode in MnO2/Zn aqueous battery: Part I. A preliminary study

The discharge characteristics of manganese dioxide (γ-MnO₂ of electrolytic manganese dioxide (EMD) type) as a cathode material in a Zn–MnO₂ battery containing saturated aqueous LiOH electrolyte have been investigated. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) data on the discharged material indicate that lithium is intercalated into the host structure of EMD without the destruction of its core structure. The XPS data show that a layer of insoluble material, possibly Li₂CO₃, is deposited on the cathode, creating a barrier to H₂O, thus preventing the formation of Mn hydroxides, but allowing the migration of Li ions into the MnO₂ structure. The cell could be reversibly charged with 83% of voltaic efficiency at 0.5 mA/cm² current density to a 1.9 V cutoff voltage. The percentage utilization of the cathode material during discharge was 56%.