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Synthesis of iron boride powder by carbothermic reduction method
No full textThe crystalized Iron boride (FeB) ceramic powder has been successfully obtained through carbothermic reduction method with Fe2O3 and B2O3 powders as a starting materials. It was found that the synthesizing temperature and holding time has fundamental control on the morphology of FeB powder. The microstructure observation showed the irregular FeB crystallites, when increase in annealing temperature and holding time. Further investigations on the reaction mechanism were examined by using TGA/DTA, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that at certain high temperature and considerable amount of holding time were beneficially required to synthesizing the single phase FeB powder. The boron and iron atoms diffused to form Fe2B and the crystallized FeB powder were obtained at 1200 °C after holding 120 min in inert gas atmosphere
Treatment of monazite processed effluent to recover rare earth metals (REMs)
No full textImproper disposal of effluent generated in rare earth mining areas and ore processing industries results in loss of REMs and miserably affects the ecosystem. Thus, their appropriate treatment is required, which can be achieved via environmentally feasible processes. In this connection, systematic scientific adsorption studies were carried out to separate REMs using cationic resin, Amberlite IR120 Na from the effluent generated during monazite processing for REMs recovery. To optimize feasible conditions for REMs recovery, bench scale studies were carried out varying different process parameters viz. pH, contact time, resin dose, etc. It was observed that adsorption of 92.63% La, 92.79% Ce, 91.45% Nd, 90.95% Pr and 95.09% Sm was achieved at aqueous/ resin (A/R) ratio 25 mL/g, pH 1.3 and contact time 10 min. Loading capacity of resin was found to hold 48.57 mg REMs/g resin. The adsorption data followed the second order reaction ((t/q) = (1/h) + (1/qe)(t)) and Langmuir adsorption isotherm (1/q = [(1/k1 qm)(1/Ce)] + (1/qm)). The loaded REMs was effectively eluted using 15% H2SO4 in 10 min. The REMs enriched solution was treated to get pure REM oxides as precipitate. This technical application will be useful for REMs recovery as well as to mitigate environmental pollution
Crystallization and magnetic hardening behaviour of Fe-rich FeSiBNb(Cu) melt-spun alloys
No full textThe sequential, multi-stage crystallization and magnetic hardening behaviour of Fe82B14Si2Nb2, Fe83B13Si2Nb2,
Fe83B12Si2Nb2Cu1 and Fe85B13Nb2 melt-spun alloys have been investigated. The microstructure-crystallizationmagnetic
property relationship was established using X-ray diffractometry (XRD), differential scanning calorimetry
(DSC), magnetometry, transmission electron microscopy (TEM) and magneto-optical Kerr effect microscopy
(MOKE) techniques. The increase of Fe content (> 82 at%) of as-quenched ribbons imparts microstructural
heterogeneity across the ribbon cross–section; i.e., textured α-Fe crystals at the free surface to heteroamorphous
microstructure in the bulk matrix. The isochronal annealing of hetero-amorphous alloys depicts
simultaneous surface and bulk crystallization process occurring before and after the crystallization onset temperature
(Tx1) temperature. The annealing temperature range (Ta < Tx1) coinciding with the paramagnetic
region of the thermo-magnetic plot, induces irreversible magnetic hardening due to simultaneous coarsening of
pre-existing crystal nuclei and exchange de-coupling between nanocrystal and intergranular matrix. The onset of
primary crystallization in the pre-crystallized ribbons results in bimodal nanocrystallite distribution having an
average crystallite size exceeding the ferromagnetic exchange length of Fe-based alloys. The minor Cu addition
alters the growth morphology of pre-existing nuclei from dendrite-like to equiaxed, assisting heterogeneous
nucleation and improving intergranular amorphous stability by delaying boride precipitation. The soft-magnetic
property deterioration of partially crystallized ribbons is discussed within the framework of Extended-Random
Anisotropy models
Toughening of nanocomposite hard coatings
No full textFor engineering applications, hardness must be complimented with high toughness for applications where high contact loads are there. A good combination of hardness, toughness and low coefficient of friction can be achieved, by suitable tailoring of microstructures of coating in hard nanocomposite coatings. Tribologocal applications require hard coatings with tailored functionalities for different applications; hard nanocomposite coatings are potential materials for such applications. Ti and amorphous carbon based systems have shown more promising material. The present review discusses the nanocomposite hard coatings, mechanism of enhancement of toughness, multilayer hard nanocomposite coatings. Here, mainly Ti and Si based nanocomposite has been discussed as carbon based reviews are available in plenty in literature and well documented. Ti-B-N, Ti-Si-B-C, Ti-Si-B-C-N, Si-C-N, Ti-Al-N, Ti-Al-Si-N, Al-Si-N, Ti-Cr-Al-N, Zr-Si-N and some other similar system nanocomposite hard coatings are important where the gradual and intelligent additions of different elements in hard single component phase provides the combination of hardness, toughness and low coefficient of friction. Some of these systems are discussed. In the end, the future directions of research, Technology„ which are required to achieve tough nanocomposite hard coatings for actual applications are also highlighted
Metallic gold thin film micropattern on polydimethylsiloxane film for flexible electronic sensors and circuits
No full textThis work illustrates the importance as well as major challenges related to the development of malleable metallic Au thin film micropattern on soft elastomeric film and then presents a fabrication technique to overcome these challenges for developing reliable, flexible electronic sensors and circuits. A self-assembled
molecular adhesive layer has been introduced between the polydimethylsiloxane (PDMS) and the thin metal film to increase the adhesion and then analyzed the multilayer structure. The contact angle measurement showed
that the introduction (3-mercaptopropyl) trimethoxysilane (MPTMS) molecular adhesive layer increases the hydrophilicity of the PDMS film for a more extended period and Au film on MPTMS coated PDMS shows superior film quality. The random buckles formed on the thin Au film have been successively manipulated using controlled heating after micropatterning. The SEM analysis of the Au thin film confirmed that the deposited film is granular and filled with nanogaps. The electrical characterization of the deposited showed that the sheet resistance of the metal thin is higher compared to the Au thin film on Si surface. This investigation is beneficial for realizing reliable, flexible electronic devices and circuits on soft polymer
Effect of Heating Rate on Decomposition Temperature of Goethite Ore
No full textThe decomposition temperature is available for pure, synthetic, stoichiometric goethite and a particular type of goethite ore. The decomposition temperature depends on the size of grains, temperature, pressure, heating rate and so on. The decomposition temperature of goethite decides the drying and preheating temperature on induration stand during thermal hardening of the pellets. The induration steps are designed based on the thermal behavior of goethite. The goethite ores, because of their chemically combined moisture content, pose special problems. The generation of fines from iron ore due to internal pressure developed from the evaporation of moisture or phase transformation (28% increases in volume) has a harmful effect on induration of pellets and blast furnace performance. Such behavior of iron-bearing materials is evaluated by thermal degradation index. To avoid/control the cracking/breaking of goethite pellet on induration stand, we should be aware of phase transformation temperature and thermal behavior of goethite. Therefore, we can decide the thermal profile for the pelletization of the goethite ore. Therefore, this study is to find out the decomposition temperature of goethite with respect to the mineralogy of ores and heating rate
Strain partitioning between matrix and precipitates during fatigue deformation of 2.25Cr-Mo steel
No full textThe influence of stress rate on load/strain partitioning between different phases of a micro-alloyed 2.25Cr-Mo steel during stress-controlled fatigue deformation at room temperature (RT) was studied by conducting asymmetrical ratcheting fatigue tests employing values of 50-450 MPa/s. Fatigue life (N-f) significantly reduced for tests conducted by employing = 50 MPa/s compared to 450 MPa/s, i.e. N-f = 510 and 24,983 cycles respectively. From TEM studies, it is confirmed that due to load/strain partitioning stacking faults (SFs)/micro-twin formed in M23C6 carbides during high fatigue deformation, whereas dislocation cells are formed in low fatigue deformation. A plausible explanation to account for different cycle life with change in of fatigue deformation is offered
High purity copper recycled from smelter dust by sulfation roasting, water leaching and electrorefining
No full textMetal recycling is drawing high interest in the context declining natural resources and the future circular economy. Smelter dust from copper extraction plants contains copper (Cu), which is both an economic loss and a pollution issue. There is therefore a need for techniques to recover Cu from ultrafine dust. Here we tested sulfation roasting, water leaching and electrorefining to recover Cu. We studied this process by thermochemical simulation and thermogravimetry to optimize sulfation roasting parameters such as time, temperature and quantity of sulfuric acid. Results show that copper can be selectively recovered as 99.9% of pure copper. Moreover, we recycled chemicals by-products of the plant in the process. Our findings suggest that this process is upscalable and should decrease the environmental pollution by Cu
An improved process for the production of low carbon ferromanganese
No full textLow carbon ferromanganese (LC-FeMn) is an essential ingredient for making high strength low alloy steel and stainless steel. The conventional industrial scale silicothermic method for the production of LC-FeMn comprises several energy intensive complex steps consuming about 2000 kWh/ton. We have attempted an improved silicothermic process, which is based on a single step smelting of optimized charge mix in the electric arc furnace (EAF). Thermochemical simulation of the smelting process by FactSage 6.4 showed significant effect of the charge mix basicity (B=CaO/SiO2) on manganese, iron, silicon and phosphorous distribution between the metal and slag. The optimum basicity was found to be 1.5 at the charge mix ratio i.e., Mn ore: Lime: SiMn of 1:1:0.6 in the smelting tests. Under optimum conditions, the energy consumption was about 690 kWh/ton. This approach has potential benefits for the ferromanganese industry in terms of simpler and energy efficient process
Study of thermal and structural characteristics of mechanically milled nanostructured Al-Cu-Fe quasicrystals
No full textSingle phase nanostructured Al-Cu-Fe quascrystalline powders, with various grain sizes, were synthesized by low intensity mechanical milling of spray deposited icosahedral quasicrystals. Structural evolution as a function of temperature was studied in-situ using high energy synchrotron X-ray diffraction. Coefficient of thermal expansion was calculated using the change in d-spacing. The diffraction results revealed a change in the lattice parameter, grain size and quasi-lattice strain with increasing temperature. During heating, onset of appreciable grain growth in different nanostructured quascrystalline powders was observed at a certain critical temperature, which was closely related with the milling time. Quasicrystalline powders milled for 1 and 80 h exhibited appreciable grain coarsening at 923 and 573 K, respectively. For all the samples, the activation energy for grain growth (E-gg) was similar to 30-35 kJ/mol. In addition, the beta Al(Cu,Fe) phase with B2-type structure evolved during heating of powder samples milled for 10 h. Onset temperature for beta phase formation showed an inverse relationship with the milling time