The effect of sulfur, temperature, holding time and reductant on the selective reduction of limonite ore

2020 ◽  
Author(s):  
Fathan Bahfie ◽  
Achmad Shofi ◽  
Fajar Nurjaman ◽  
Ulin Herlina ◽  
Nanda Ayu Septiana ◽  
...  
Keyword(s):  
Grain Size ◽  
Metal Oxide ◽  
Magnetic Separation ◽  
Selective Reduction ◽  
Holding Time ◽  
Average Grain Size ◽  
Laterite Ore

Abstract Laterite ore is used as the manufacture of ferronickel. One method that can increase the levels of nickel in limonite ore is selective reduction. Selective reduction is a process to reduce the metal oxide to the metal with additives. The selective reduction of limonite ore by using the reductant 5%, 10%, and 15% and the sulfur 10 % as additive. The process of selective reduction is performed at the temperature of 950, 1050, and 1150°C with a holding time of 60, 90, and 120 minutes and followed by magnetic separation to separate between the concentrate and tailings. AAS characterization indicates the optimum value at the temperature of 1150°C with 5% reductant and the reduction of the holding time for 60 minutes which give the effect on the grade and recovery of nickel those are 3.72wt% and 95.67%, respectively. The decreasing of grain size of ferronickel in the sample form an average grain size of 38.07μm and the forming of FeS phase which is caused the addition of sulfur.

scholarly journals Characterization and Alumina Leachability of 12CaO·7Al2O3with Different Holding Times

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Hui-lan Sun ◽  
Bo Wang ◽  
Jian-xin Zhang ◽  
Shu-feng Zong
Keyword(s):  
Grain Size ◽  
Surface Morphology ◽  
Lattice Constant ◽  
Preferred Orientation ◽  
Holding Time ◽  
Synthesis Time ◽  
Rate Of Increase ◽  
Average Grain Size ◽  
Long Time ◽  
Scherrer Formula

The effect of synthesis time on phase compositions, lattice constant, average grain size, preferred orientation, and surface morphology of 12CaO·7Al2O3synthesized at 1500°C was analyzed by XRD and SEM. The results indicate that the main phase of samples synthesized is 12CaO·7Al2O3when holding time is over 30 min. The lattice constant increases and the preferred orientation decreases as synthesis time prolongs. The average grain size of samples is about 59 nm calculated by Scherrer formula, and it does not change with synthesis time. The synthesis time affects the micromorphology of samples greatly. There are more and bigger holes in samples synthesized for long time. The aspects mentioned above cause the alumina leaching ratio of 12CaO·7Al2O3to increase with the prolonging of synthesis time, but the rate of increase drops.

Microstructural Evolution of AZ31 Mg Wrought Alloy during Partial Remelting for Thixoextrusion

2006 ◽  
Vol 116-117 ◽  
pp. 251-254
Author(s):  
Young Ok Yoon ◽  
Shae K. Kim
Keyword(s):  
Grain Size ◽  
Microstructural Evolution ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Holding Time ◽  
Interesting Point ◽  
Grain Sizes ◽  
Partial Remelting ◽  
Average Grain Size ◽  
Holding Temperature

An attempt has been made to investigate feasibility of thixoextrusion for AZ31 Mg wrought alloy through simple partial remelting. Microstructural evolution of AZ31 Mg wrought alloy for thixoextrusion was investigated as functions of isothermal holding temperature and time in the partially remelted semisolid state. The interesting point of this study was that the thixotropic structures of AZ31 Mg wrought alloy without additional pretreatment could be obtained through simple partial remelting. The uniform average grain size and liquid fraction according to the isothermal holding time were very important for the thixoextrusion. Because, it is must be considered on actual extrusion time. The liquid fraction was increased with increasing isothermal holding temperature and time. But, the liquid fraction was almost uniform after 10 min. The average grain size was decreased with increasing isothermal holding temperature. On the other hand, as the holding time increased, the average grain sizes were uniform at 615 and 622. This phenomenon is very useful for thixoextrusion in terms of process control such as actual extrusion time.

Effects of Melt Holding Time on as Cast Microstructure and Tensile Properties of Sr-Modified AS31Alloy

2014 ◽  
Vol 697 ◽  
pp. 67-71 ◽  
Author(s):  
Jin Wei Wang ◽  
Ji Xue Zhou ◽  
Bai Chang Ma ◽  
Shou Qiu Tang ◽  
Fu Min Chu ◽  
...  
Keyword(s):  
Grain Size ◽  
Elevated Temperature ◽  
Ambient Temperature ◽  
Tensile Properties ◽  
Holding Time ◽  
Chinese Script ◽  
Modification Effect ◽  
Average Grain Size ◽  
Polyhedral Shape ◽  
Cast Microstructure

Melt holding time has important influences on the modification effect of Sr modified AS31 alloy. Effects of different melt holding time (30min, 60min, 90min and 120min) at 700°C on as cast microstructure and tensile properties both at ambient temperature and elevated temperature of Sr-modified AS31 alloy were studied. There exist polyhedral shape, fine fibers shape and a few Chinese script Mg2Si particles in Sr-modified AS31 alloys. And the average grain size is smallest in Sr-modified AS31 alloys with holding time at 700°C for 30min. The ultimate strength, yield strength and elongation at both ambient temperature and 150°C decrease gradually when the melt holding time increases from 30min to 120min. In the process of smelting of Sr-modified AS31. The burning loss of Sr element becomes more serious with the prolongation of melt holding time, which contributes to the modification effect reducing.

Effect of Nanosized Particles on the Mechanical Properties of Y2O3

2013 ◽  
Vol 750 ◽  
pp. 44-47
Author(s):  
Hadi Razavi Khosroshahi ◽  
Xin Liu ◽  
Noritaka Saito ◽  
Kunihiko Nakashima ◽  
Kenji Kaneko
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Relative Density ◽  
Holding Time ◽  
Second Step ◽  
Nanosized Particles ◽  
Firing Schedule ◽  
Average Grain Size ◽  
Optimum Firing ◽  
Series Of Experiments

A systematic series of experiments was performed to determine the optimum firing schedule of Y2O3. A two-step sintering with subsequent profile succeeded to fabricate Y2O3 ceramic with the relative density of 97.6% and the average grain size of 0.46 μm: first step and second step temperature of T1 = 1490 °C and T2 = 1350 °C, respectively and second step holding time of t2 = 20 h. After the firing schedule of pure Y2O3 was determined, two types of TiO2/Y2O3 and ZrO2/Y2O3 composites were fabricated for the further improvement of mechanical properties. According to results, ZrO2/Y2O3 composite showed a dramatic increase in strength and toughness as 417 MPa and 4.4 MPa.m1/2, respectively.

Effect of Partial Remelting Procedure on the Microstructural Evolution of 7075 Al Wrought Alloy for Thixoextrusion

2006 ◽  
Vol 116-117 ◽  
pp. 336-339 ◽  
Author(s):  
Hyung Ho Jo ◽  
Young Ok Yoon ◽  
Jin Kyu Lee ◽  
Shae K. Kim
Keyword(s):  
Grain Size ◽  
Feasibility Study ◽  
Microstructural Evolution ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Holding Time ◽  
Interesting Point ◽  
Partial Remelting ◽  
Average Grain Size ◽  
Holding Temperature

The feasibility study for thixoextrusion of 7075 Al wrought alloys was carried out with respect to reheating profile, isothermal holding temperature and time during the partial remelting through simple partial remelting. The reheating rates were 40/min and 60/min. The isothermal holding temperatures were controlled at 609, 622, 628 and 632 for 0, 2, 5, 10 and 30 min. The interesting point of this study was that the thixotropic structures of 7075 Al wrought alloy without additional pretreatment could be obtained through simple partial remelting. The average grain size was significantly smaller in the quickly heated specimen. The liquid fraction was increased with increasing isothermal holding temperature and time while the average grain size was inversely proportional to isothermal holding temperature and time. However, there was no big change of liquid fraction and average grain size with respect to isothermal holding time. The important fact that the liquid fraction and average grain size were almost uniform after 5 min is considered very useful for thixoextrusion in terms of actual extrusion time.

Recrystallisation Behaviour of Cu-20Ni-5Sn Alloy

2011 ◽  
Vol 194-196 ◽  
pp. 1352-1356
Author(s):  
Rui Qing Liu ◽  
Li Jun Peng ◽  
Jian Sheng Yang
Keyword(s):  
Grain Size ◽  
Annealing Temperature ◽  
Research Result ◽  
Cold Deformation ◽  
Kinetic Mechanism ◽  
Holding Time ◽  
Recrystallization Temperature ◽  
Total Deformation ◽  
Hardness Tester ◽  
Average Grain Size

Investigate effects of annealing temperature and holding time on the recrystallization temperature, hardness, microstructure and average grain size of Cu-20Ni-5Sn alloy by hardness tester, microscope and XRD. Research the kinetic mechanism of grain growth of recrystallization of Cu-20Ni-5Sn alloy. The research result shows that the recrystallization temperature declines with the increase of cold-deformation. The recrystallization temperature is at about 500°C ~650°C respectively for 50% and 60% total cold deformation, and is about 470°C ~620°C respectively for 70% and 85% total deformation. The grains grow up with the increase of annealing temperature and holding time.

Surface Modification and its Influence on the Microstructure and Creep Resistance of Nickel Based Superalloy René 77 / Modyfikacja Powierzchniowa Oraz Jej Wpływ Na Mikrostrukture I Wytrzymałosc Na Pełzanie Odlewów Z Nadstopu Niklu Ren´E 77

2013 ◽  
Vol 58 (1) ◽  
pp. 95-98 ◽  
Author(s):  
M. Zielinska ◽  
J. Sieniawski
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Surface Modification ◽  
Turbine Blades ◽  
Processing Parameters ◽  
Grain Structure ◽  
Creep Tests ◽  
Cobalt Aluminate ◽  
Nickel Based Superalloy ◽  
Average Grain Size

Superalloy René 77 is very wide used for turbine blades, turbine disks of aircraft engines which work up to 1050°C. These elements are generally produced by the investment casting method. Turbine blades produced by conventional precision casting methods have coarse and inhomogeneous grain structure. Such a material often does not fulfil basic requirements, which concern mechanical properties for the stuff used in aeronautical engineering. The incorporation of controlled grain size improved mechanical properties. This control of grain size in the casting operation was accomplished by the control of processing parameters such as casting temperature, mould preheating temperature, and the use of grain nucleates in the face of the mould. For nickel and cobalt based superalloys, it was found that cobalt aluminate (CoAl2O4) has the best nucleating effect. The objective of this work was to determine the influence of the inoculant’s content (cobalt aluminate) in the surface layer of the ceramic mould on the microstructure and mechanical properties at high temperature of nickel based superalloy René 77. For this purpose, the ceramic moulds were made with different concentration of cobalt aluminate in the primary slurry was from 0 to 10% mass. in zirconium flour. Stepped and cylindrical samples were casted for microstructure and mechanical examinations. The average grain size of the matrix ( phase), was determined on the stepped samples. The influence of surface modification on the grain size of up to section thickness was considered. The microstructure investigations with the use of light microscopy and scanning electron microscopy (SEM) enable to examine the influence of the surface modification on the morphology of ’ phase and carbides precipitations. Verification of the influence of CoAl2O4 on the mechanical properties of castings were investigated on the basis of results obtained form creep tests.

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