Impact of a Multi-step Heat Treatment on Different Manufacturing Routes of 18CrNiMo7-6 Steel

Metallurgical and Materials Transactions A - Effect of an optimized multi-step heat treatment routine on conventional (machining from wrought bar stock) and alternate manufacturing routes (hot...     

Reduction and Swelling of Fired Hematite Iron Ore Pellets by Non-coking Coal Fines for Application in Sponge Ironmaking

In the present investigation, the reduction and swelling behaviors (in low grade coal) of fired iron ore pellets, prepared by blending hematite iron ore fines of ?100, ?18 + 25, and ?10 + 16 mesh sizes in different proportions, have been studied in the temperature range of 850–1000°C with an objective to promote massive utilization of fines in sponge ironmaking. An increase in temperature up to the range studied (850–1000°C) substantially enhanced the reduction rate and the rate was found to be highest in the first 15–30 min at all these temperatures. All the fired pellets, made by mixing iron ore particles of ± 100 mesh size, have shown approximately the same reduction rates and slightly higher swelling indices than those made from fines of ?100 mesh size only. In all the fired pellets reduced at temperatures of 850°C and 900°C, the results indicated an increase in the extent of swelling with reduction time. Reduction of fired pellets at temperatures of 950°C and 1000°C exhibited shrinkage in their reduced products, and the extent of this shrinkage increased with increase in exposure time.     

Fixed bed column adsorption of ACID Yellow 17 dye onto Tamarind Seed Powder

The intention of this study was to explore the efficacy and feasibility for Acid Yellow 17 adsorption onto fixed bed column of Tamarind Seed Powder. The effect of various parameters like flow rate, initial concentration of dye, bed height, and pH were exploited in this study. The Thomas, Yoon–Nelson, Bed Depth Service Time (BDST), and Adams and Bohart model were analysed to evaluate the column adsorption performance. The adsorption capacity, rate constant and correlation coefficient associated to each model for column adsorption was calculated and mentioned. The adsorption capacity increases with increasing initial dye concentration and bed height and decreasing flow rate. The maximum adsorption capacity related to Adams and Bohart model was found to be 978.5 mg/g at initial concentration of 50 ppm at constant flow rate of 15 mL/min, bed height of 15 cm, and pH 7. Le but de cette étude était d'explorer l'efficacité et la faisabilité de l'Acid Yellow 17 adsorption sur colonne à lit fixe de Tamarind Seed Powder. L'effet de différents paramètres comme le débit, la concentration initiale de colorant, la hauteur du lit et le pH ont été exploitées dans cette étude. Le Thomas, Yoon‐Nelson, BDST et Adams et le modèle Bohart ont été analysées pour évaluer les performances d'adsorption colonne. La capacité d'adsorption, constante de vitesse et coefficient de corrélation associé à chaque modèle de la colonne d'adsorption a été calculé et mentionné. Les augmentations de capacité d'adsorption avec une concentration croissante de colorant initial et un lit en hauteur et le débit diminue. La capacité maximale d'adsorption liées au modèle Adams et Bohart a été trouvé à 978,5 mg/g à la concentration initiale de 50 ppm à débit constant de 15 ml/min, la hauteur du lit de 15 cm et un pH de 7.     

Microwave absorption study of carbon nano tubes dispersed hard/soft ferrite nanocomposite

Nickel substituted strontium hexaferrite, SrNi₂Fe₁₀O₁₉·(SrFe₁₂O₁₉/NiFe₂O₄) nanoparticles have been synthesized by low combustion method by citrate precursors using sol to gel (S–G) followed by gel to nano crystalline (G–N) conversion. The resulting ‘as-synthesized’ powder is heat treated (HT) at 800 and 1000 °C for 4 h in nitrogen atmosphere. The hysteresis loops show an increase in saturation magnetization from 27.443 to 63.706 emu/g with increasing HT temperatures. The multiwalled carbon nano tubes (CNTs) were synthesized by thermal decomposition of acetylene gas over iron-catalyst deposited on silicon wafer in the temperature range of 750–800 °C. A microwave absorbing medium is prepared by adding CNTs in the nickel substituted strontium hexaferrite nanoparticles. Addition of certain mass of CNTs improves the microwave absorption properties and wave band of SrFe₁₂O₁₉/NiFe₂O₄ absorbent. When 10 wt% CNTs is mixed with SrFe₁₂O₁₉/NiFe₂O₄ nanoparticles to fabricate a composite with 2 mm thickness, the maximum reflection loss reaches to ?36.817 dB at 9.292 GHz and ?10 dB bandwidth reaches 3.27 GHz.     

Study on a System with a Neutral Barrier for High Explosives and a Zirconium‐Based Solid Incendiary

In the aim of defeating targets protected by fortification, it is necessary to develop systems that are able to create a leak in the fortification and destroy targets inside the fortification. A boat‐tailed hemispherical high explosive charge was designed to create the leak and an incendiary charge was prepared to burn the targets inside the fortification. A metallic neutral barrier was used to attenuate the back pressure generated by the front end hemispherical high explosive charge. In order to reduce the back blast, a boat‐tailed hemispherical charge with the composition cyclotrimethylene trinitramine and trinitrotoluene (RDX/TNT 60/40) was prepared. The blast pressure obtained from unconfined boat‐tailed high explosive charges using a linear pressure gauge brought to light that the pressure at the front end had a value of 2.3 MPa at 100 cm; and a value of 0.4 MPa at 75 cm distance at the rear end. A hemispherical boat tailed shaped charge with a mild steel liner of 1 mm thickness and 40 mm curvature radius was prepared. The incendiary composition comprised of finely divided metal powder dispersed in a polymer matrix consisting of 77 % zirconium and 20 % ester gum resin with 3 % polymeric binder (SBR, PIB). The incendiary composition was prepared and pelletized. Experiments for the design of the neutral barrier were conducted with the boat‐tailed hemispherical charge. A mild steel plate of 7.5 mm thickness was selected as neutral barrier. Static evaluation of the system against a hard target was carried out. It created a hole of 190 mm diameter in a reinforced concrete cement (RCC) target of 100 mm thickness. A neutral barrier of 7.5 mm thickness attenuates the back blast of the hemispherical boat‐tailed charge. Burning incendiary cinders were passed through this hole and dispersed at approx. 5 m distance. These cinders burnt for > 3 min with a temperature output of 1873 K.     

Branched polymeric media: boron-chelating resins from hyperbranched polyethylenimine

Extraction of boron from aqueous solutions using selective resins is important in a variety of applications including desalination, ultrapure water production, and nuclear power generation. Today's commercial boron-selective resins are exclusively prepared by functionalization of styrene-divinylbenzene (STY-DVB) beads with N-methylglucamine to produce resins with boron-chelating groups. However, such boron-selective resins have a limited binding capacity with a maximum free base content of 0.7 eq/L, which corresponds to a sorption capacity of 1.16 ± 0.03 mMol/g in aqueous solutions with equilibrium boron concentration of ～70 mM. In this article, we describe the synthesis and characterization of a new resin that can selectively extract boron from aqueous solutions. We show that branched polyethylenimine (PEI) beads obtained from an inverse suspension process can be reacted with glucono-1,5-d-lactone to afford a resin consisting of spherical beads with high density of boron-chelating groups. This resin has a sorption capacity of 1.93 ± 0.04 mMol/g in aqueous solution with equilibrium boron concentration of ～70 mM, which is 66% percent larger than that of standard commercial STY-DVB resins. Our new boron-selective resin also shows excellent regeneration efficiency using a standard acid wash with a 1.0 M HCl solution followed by neutralization with a 0.1 M NaOH solution.     

Performance of MRC combining multi-antenna cooperative relay network

Performance of cooperative relaying employing infrastructure based fixed relays having multiple antennas has been investigated. Employing MGF based approach, closed form expression for outage probability and bit error rate performance of BPSK signal have been derived, when relay and destination are assumed to perform MRC combining of the signals. The effect of relay placement on the system performance has also been studied under different path loss conditions.     

Studies on the de/re-hydrogenation characteristic of Mg(NH2)2/LiH mixture admixed with carbon nanofibres

The effect of carbon nanofibres (CNFs) on the de/re-hydrogenation characteristics of 1:2 magnesium amide (Mg(NH₂)₂) and lithium hydride (LiH) mixture is investigated. It is found that the desorption as well as absorption characteristic of the 1:2 Mg(NH₂)₂/LiH mixture is improved with admixing of different shaped (planar and helical) CNFs separately. The different shaped CNFs were synthesized through catalytic decomposition of acetylene gas over LaNi₅ alloy. The synthesized CNFs contain Ni-metal nano particles. Among two different types of nanofibres namely planar carbon nanofibres (PCNFs) and helical carbon nanofibres (HCNFs), the later was found to act as a better catalyst. The decomposition temperature of the pristine Mg(NH₂)₂/LiH mixture is ∼250 °C, reduced to 150 and 140 °C for the PCNF and HCNF admixed Mg(NH₂)₂/LiH mixture respectively. The activation energy for dehydrogenation reaction was found to ∼97.2 kJ/mol, which is further reduced to ∼67 and ∼65 kJ/mol for the PCNF and HCNF admixed Mg(NH₂)₂/LiH mixture respectively. The lowering of decomposition temperature and enhancement in desorption kinetics, with admixing of different shaped CNFs are described and discussed.     

Accurate CAD-Model Analysis of Multilayer Microstrip Line on Anisotropic Substrate

Computationally efficient equivalent isotropic relative permittivity of the multilayer microstrip line on the uniaxial anisotropic substrate for 0 < w/h ≤ 10, anisotropic ratio0.5 ≤ n ≤ 3.0. Model has accuracy 0.5% against the full-wave method. It computes effective relative permittivity and characteristic impedance of microstrip on composite anisotropic substrates with deviation 4.5% respectively against the EM- software HFSS. Dispersion in multilayer anisotropic substrate microstrip up to mm wave range with high accuracy against the results of HFSS. The proposed models could be incorporated in the computer aided design for development of the components on the uniaxial anisotropic substrates.