Flocculation of chromite ore fines suspension using polysaccharide based graft copolymers

Graft copolymers are being experimented at the laboratory scale as flocculants. All the four graft copolymers, viz. starch-g-polyacrylamide, amylopectin-g-polyacrylamide, sodium alginate-g-polyacylamide and carboxymethyl cellulose-g-polyacrylamide performed well as flocculants on chromite ore fines suspension. Amylopectin-g-polyacrylamide, in particular, performed superior to the rest of the series from the point of view of settling velocity of flocs which is the most important aspect in solid-liquid separation.     

Nanosilver-Coated Porous SiC–Si3N4 Composite Using Microwave-Assisted Process

Using a novel microwave-assisted process, nano-Ag-coated continuous porous SiC–Si₃N₄ substrate was fabricated from a solution containing AgNO₃ salts and ethylene glycol. The detailed microstructure of the fabricated substrate was investigated depending on the amount of AgNO₃ salts in the starting solution and the microwave irradiation time. From a solution containing 0.4 g of AgNO₃ for 60 s irradiation time, the Ag nanoparticles, ∼25 nm in diameter, were homogeneously coated on the continuous porous SiC–Si₃N₄ matrix as well as on the surface of the Si₃N₄ whiskers. However, the Ag nanoparticles (∼15 nm) deposited from a solution containing 0.6 g of AgNO₃ for 60 s irradiation time showed maximum homogeneity and narrow size distribution. The components of Si, N, and Ag were homogeneously distributed on the deposited layer. The deposited Ag nanoparticles covered with a thin (∼2 nm), amorphous layer had nanocrystallinity and adhered well to the surface of the Si₃N₄ whiskers.     

Optimization of safflower oil transesterification using the Taguchi approach

Biodiesel is an alternative renewable fuel which is produced by using biomass resources. Its physicochemical properties are close to those of the petroleum diesel fuel. This study highlights biodiesel production from safflower seed oil. The main aim of this experimental work is to optimize the process parameters, namely the methanolto-oil molar ratio, catalyst concentration, reaction time and reaction temperature for biodiesel production. The Taguchi robust design approach was used with an L9 orthogonal array to analyze the influence of process factors on performance parameters. The results showed that the optimum yield of biodiesel was 93.8% with viscosity 5.60 c St, with a methanol-to-oil molar ratio of 4:1, catalyst concentration of 1.5 wt%, reaction time of 90 min and reaction temperature of 60 ℃. The catalyst concentration was found to be the most influencing parameter which contributed 51.1% and 50.8% of the total effect on the yield of biodiesel, Y_1, and viscosity of biodiesel, Y_2, respectively.     

Comparison Between Different Processing Schedules for the Development of Ultrafine-Grained Dual-Phase Steel

A comparative study was carried out on the development of ultrafine-grained dual-phase (DP) (ferrite–martensite) structures in a low-carbon microalloyed steel processed using two thermomechanical processing routes, (i) intercritical deformation and (ii) warm-deformation and intercritical annealing. The samples were deformed using Gleeble3500^® simulator, maintaining a constant total strain (ε = 1) and strain rate ( $ \dot \varepsilon $  = 1/s). Evolution of microstructure and micro-texture was investigated by SEM, TEM, and EBSD. Ultrafine-grained DP structures could be formed by careful selection of deformation temperature, T _def (for intercritical deformation) or annealing temperature, T _anneal (for warm-deformation and annealing). Overall, the ferrite grain sizes ranged from 1.5 to 4.0 μm, and the sizes and fractions of the uniformly distributed fine-martensitic islands ranged from 1.5 to 3.0 μm and 15 to 45 pct, respectively. Dynamic strain-induced austenite-to-ferrite transformation followed by continuous (dynamic) recrystallization of the ferrite dictated the grain refinement during intercritical deformation, while, continuous (static) recrystallization by pronounced recovery dictated the grain refinement during the warm-deformation and the annealing. Regarding intercritical deformation, the samples cooled to T _def indicated finer grain size compared with the samples heated to T _def, which are explained in terms of the effects of strain partitioning on the ferrite and the heating during deformation. Alpha-fiber components dominated the texture in all the samples, and the fraction of high-angle boundaries (with >15 deg misorientation) increased with the increasing T _def or T _anneal, depending on the processing schedule. Fine carbide particles, microalloyed precipitates and austenitic islands played important roles in defining the mechanism of grain refinement that involved retarding conventional ferrite recrystallization and ferrite grain growth. With regard to the intercritical deformation, warm-deformation followed by annealing is a simpler process to control in the rolling mill; however, the need for high-power rolling mill and controlled annealing facility imposes industrial challenges.     

Optimization of biodegradation of natural fiber (Chorchorus capsularis): HDPE composite using response surface methodology

Deterioration in mechano-chemical properties due to biodegradation of prepared high-density polyethylene and jute eco-friendly polymer composites in soil and pure microbial culture was investigated through a programmed experimental design. The composite was prepared by compression molding process and then subjected to biodegradation. The biodegradation process was studied using face-centered central composite experimental design protocol and the model equations were formulated to assess the effects of jute fiber loading and treatment time on biodegradation (expressed as percentage loss in composite weight and tensile strength) of the composite. The optimal process conditions corresponding to maximum biodegradation were evaluated for both the media using response surface methodology. The maximum weight losses were 25.8924 % for soil medium and 12.4167 % for pure culture medium at 30 wt% jute fiber loading and 6 months of treatment time. At the derived optimal conditions, the effects of biodegradation were also manifested as 84.2621 and 70.9842 % losses in the tensile strength in soil and pure culture media, respectively. The present study, thus, demonstrates that HDPE/jute composite polymer can be appreciably biodegradable and the extent of biodegradation is more pronounced in soil medium compared to pure microbial culture. The analyses of the evolution of chemical composition and microstructure of the composite before and after biodegradation were performed through Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy. FTIR spectra indicated significant changes in chemical composition due to biodegradation, while the ruptured structure of the treated composite revealed notable changes in the morphology due to biodegradation.     

Solvent Free Microwave Assisted Synthesis of Poly Myristyl Acrylate—Characterization and Evaluation as Additives for Lubricating Oil

Homopolymer of myristyl acrylate was prepared by microwave assisted free radical polymerization method using BZP as initiator with variation of time at a fixed power without any solvent. Characterization of the polymers was done by IR, NMR, and viscometric analysis. Additive performances of each of them (pour point depressant [PPD] and viscosity modifier [VM]) for lubricating oil (lube oil) were also evaluated by standard ASTM methods. A comparison of their performances has also been reported. The molecular weights of the polymers were determined from viscosity measurements in toluene at 313 K and thermal stability was measured by thermogravimetric analysis.     

Convergecast tree management from arbitrary node failure in sensor network

The efficiency and reliability of convergecast in sensor network depends on the correct and efficient accumulation of data to the sink. A tree, rooted at the sink, that utilizes sensor resources properly is an ideal topology for data gathering. Resource constrained sensor nodes are highly prone to sudden crash. So the application demands a quick and efficient repairing of the tree when a node dies. The proposed scheme builds a data gathering tree rooted at the sink. The tree eventually becomes a Breadth First Search (BFS) tree where each node maintains the shortest hop-count to the root to reduce the routing delay. Each node collects some extra neighborhood information during the tree construction. Thus a little pre-processing at each node helps in taking prompt actions to repair the tree through local adjustment if any arbitrary single or multiple nodes fail in future. On failure of a node, each affected node in its vicinity fixes the parent through a pair of control message transmissions. Simulation results show that the repairing delay is significantly less in average and the convergecast messages are delivered with minimum data loss and no redundancy even in presence of node crash.     

Electromechanical controlled phased array dumbbell EBG beam steerer

A steerable phased array antenna driven mechanically is realized by utilizing the variation of dumbbell electromagnetic bandgap (EBG) structures. The variation takes place under the feed line of a 4-element array that gives the change in relative phase shift. The phase shift achieved from different shaping combinations of EBGs shifting under the feed lines. The feed lines are connected with four microstrip patches to yield a 4-element phased array antenna. The mechanical controlled pattern shapes of phase array antenna are simulated in electromagnetic (EM) software Zeland IE3D. Finally the design is fabricated with the help of optical lithography. It can be seen that the beam steering angle can be controlled mechanically without phase shifter and PIN switches.