International Journal of Minerals, Metallurgy and Materials

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Prognosis of residual coal gas capacity made by the ‘Express’ method

Pavel Prokop, Pavel Zapletal, Ivo Pěgřímek

2011, 18(2): 127-131. doi: 10.1007/s12613-011-0411-3

中文摘要(135) PDF(8) SpringerLink

摘要:
An easy, reliable, and inexpensive method, called ‘Express’ method, was described to determine the residual gas capacity of deep mines using results from an air and gas balance. Air and gas balances are common elements of mine management and must be performed periodically. Using the process described here to obtain balance results, it is straightforward to obtain the residual gas capacity, which is an important parameter for decision-making in current mine operations. After a mine is closed, the residual gas capacity becomes a dominant factor used to select methods to protect against gas emissions from the closed underground area or perhaps to provide information for the use of gas reserves. The proposed ‘Express’ method is a much simpler method to obtain the residual gas capacity than other procedures used for this purpose to date.

Sintering behaviour of feldspar and influence of electric charge effects

W. Gallala, M. E. Gaied

2011, 18(2): 132-137. doi: 10.1007/s12613-011-0412-2

中文摘要(259) PDF(14) SpringerLink

摘要:
The characterization of feldspar for electric porcelain and the behaviour of these materials after heating at 1230℃ were studied. X-ray diffraction (XRD) and scanning electronic microscopy (SEM) were used to identify the present phases and the densification level. Feldspar sand was treated by flotation. The floated feldspar is constituted by microcline, quartz, and minor amounts of albite. The microstructure of sintered feldspar at 1230℃ is essentially vitreous with open microporosities. The dielectrical properties of composites were characterized by using the induced courant method (ICM), which indicates that the charge trapping capacity depends on the mineralogical and chemical composition of feldspar.

Use of mesophilic and thermophilic bacteria for the improvement of copper extraction from a low-grade ore

E. Darezereshki, M. Schaffie, M. Lotfalian, S. A. Seiedbaghery, M. Ranjbar

2011, 18(2): 138-143. doi: 10.1007/s12613-011-0413-1

中文摘要(183) PDF(10) SpringerLink

摘要:
Bioleaching was examined for copper extraction from a low grade ore using mesophilic and moderate thermophilic bacteria. Five equal size columns were used for the leaching of the ore. Sulfuric acid solution with a flow rate of 3.12 L·m^-2·h^-1 and pH 1.5 passed through each column continuously for 90 d. In the first and the second column, bioleaching was performed without agglomeration of the ore and on the agglomerated ore, respectively. 28wt% of the copper was extracted in the first column after 40 d, while this figure was 38wt% in the second column. After 90 d, however, the overall extractions were almost the same for both of them. Bioleaching with mesophilic bacteria was performed in the third column without agglomeration of the ore and in the fourth column on the agglomerated ore. After 40 d, copper extractions in the third and the fourth columns were 62wt% and 70wt%, respectively. Copper extractions were 75wt% for both the columns after 90 d. For the last column, bioleaching was performed with moderate thermophilic bacteria and agglomerated ore. Copper extractions were 80wt% and 85wt% after 40 and 90 d, respectively. It was concluded that crushing and agglomeration of the ore using bacteria could enhance the copper extraction considerably.

Cleaning IF molten steel with dispersed in-situ heterophases induced by the composite sphere explosive reaction in RH ladles

Fu-ping Tang, Zhen Li, Xiao-feng Wang, Ben-wen Chen, Peng Fei

2011, 18(2): 144-149. doi: 10.1007/s12613-011-0414-0

中文摘要(196) PDF(13) SpringerLink

摘要:
A novel fine inclusion removal technology was put forward with dispersed in-situ heterophases induced by the composite sphere explosive reaction. A composite sphere with this function was designed and prepared using a laboratory scale batch-type balling disc (at 12 r/min), and the composite sphere was fed at the end of the RH refining process. The results indicate that inclusions in the IF molten steel can be removed effectively by feeding composite spheres in RH ladle. Compared with conventional inclusion removal technology, using this novel technology, the amount of oxide inclusions can be decreased to a lower level and the inclusion size becomes finer, the total oxygen content in the as-cast slab can approach 5×10^-6, and the cost per ton of steel produced can be reduced by 5–12 Yuan RMB.

Crystallization behavior of F-free mold fluxes

Zuo-tai Zhang, Guang-hua Wen, Ying-yi Zhang

2011, 18(2): 150-158. doi: 10.1007/s12613-011-0415-z

中文摘要(162) PDF(9) SpringerLink

摘要:
The time-temperature-transformation (TTT) diagrams of F-free mold fluxes was constructed using single hot thermocouple technique (SHTT) and confocal scanning laser microscopy (CSLM) to study the crystallization behavior of F-free mold fluxes. The tendency of crystallization is found to increase whereas the incubation time decreases with increasing basicity. Zirconia addition enhances the crystallization tendency due to its limited solubility in the slag melt and the solid particles acting as nucleation sites. Pseudo-wollastonite is found to precipitate in the slag with low basicity (CS-1 and CS-2), kilchoanite and larnite are formed with further increasing basicity (CS-3), and larnite is finally formed as the basicity beyond unit (CS-4). The crystal morphology changes with varying compositions and isothermal temperatures. The measured growth rate is found to be linear with time under isothermal conditions and decreases with increasing isothermal temperature.

Effect of M-EMS on the solidification structure of a steel billet

Hua-jie Wu, Ning Wei, Yan-ping Bao, Guo-xin Wang, Chao-ping Xiao, Jin-jin Liu

2011, 18(2): 159-164. doi: 10.1007/s12613-011-0416-y

中文摘要(201) PDF(23) SpringerLink

摘要:
Effects of mold electromagnetic stirring (M-EMS) on the solidification structure of 45# steel billet were investigated by examination of interdendritic corrosion. The results show that the primary and secondary dendrite arm spacings increase from the edge of the billet to the center and decrease obviously with increasing electromagnetic torque, which will be beneficial to refine the solidification structure and enlarge the equiaxed crystal zone. The ratio of equiaxed crystal increases by 15.9% with the electromagnetic torque increasing from 230 to 400 cN·cm. The increase of stirring intensity can improve the cooling rate and the impact of M-EMS on it reduces from the edge of the billet to the central area, where the cooling rates are similar at different torques. The closer to the central area, the less the influence of M-EMS on the cooling rate is. The ratio of the primary to secondary dendrite arm spacing is approximately 2.0, namely, λ₁≈2λ₂, and is constant irrespective of the stirring intensity and position of the billet. Original position analysis (OPA) results indicate that the center segregation of the billet is greatly improved, and the more uniform and compact solidification structure will be obtained with the increase of stirring intensity.

Effects of low-frequency electromagnetic field on the surface quality of 7050 aluminum alloy ingots during the hot-top casting process

Xiang-jie Wang, Jian-zhong Cui, Yu-bo Zuo, Zhi-hao Zhao, Hai-tao Zhang

2011, 18(2): 165-168. doi: 10.1007/s12613-011-0417-x

中文摘要(179) PDF(8) SpringerLink

摘要:
To improve the quality of 7050 aluminum alloy ingots, low-frequency electromagnetic (LFE) field was applied during the conventional hot-top casting process. Macrostructures and microstructures of the ingots by the conventional and LFE hot-top casting processes were studied. The experimental results show that when the LFE field is turn off during the hot-top casting process, cold folding appears, and the as-cast structure becomes very coarse. Additionally, the thickness of the shell zone is much thinner during the low-frequency electromagnetic hot-top casting process than that during the conventional hot-top casting process. Some reasons for low-frequency electromagnetic field improving the surface quality, refining the structure of the ingot, and minimizing the thickness of the shell zone have been studied.

Effects of deoxidizing degree on the pitting corrosion behavior of carbon and manganese steels

Guo-liang Cao, Guo-min Li, Shan Chen, Wan-shun Chang, Xue-qun Chen

2011, 18(2): 169-177. doi: 10.1007/s12613-011-0418-9

中文摘要(215) PDF(8) SpringerLink

摘要:
Nine steels with different deoxidizing degrees and two comparative steels were selected. Their pitting initiation susceptibility was compared by means of potentiodynamic polarization tests in 3wt% NaCl solution. The pit propagation rate was evaluated in artificial sea water and 3wt% sea salt solution by simulating occluded corrosion cell (SOCC) test and hanging plate test, respectively. The composition of inclusions and corrosive feature were studied by scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and optical microscopy (OM). The results indicate that sulfide inclusions in steel are the sites for pit nucleation. The sulphide inclusions vary in shape from short spindle-like to long strip-like with increasing deoxidizing degree. Under the same conditions, the lower the deoxidizing degree gets, the lower the pitting initiation susceptibility becomes, and the stronger the resistance to pit propagation exhibits. For steels with different deoxidizing degrees, their pitting initiation susceptibility is mainly influenced by thermodynamic stability, while the pit propagation rate is primarily subject to the characteristics of inclusions in steel.

Passivation process of X80 pipeline steel in bicarbonate solutions

Jian-long Zhou, Xiao-gang Li, Cui-wei Du, Ying Pan, Tao Li, Qian Liu

2011, 18(2): 178-184. doi: 10.1007/s12613-011-0419-8

中文摘要(212) PDF(14) SpringerLink

摘要:
The passivation process of X80 pipeline steel in bicarbonate solutions was investigated using potentiodynamic, dynamic electrochemical impedance spectroscopy (DEIS), and Mott-Schottky measurements. The results show that the shape of polarization curves changes with HCO₃^- concentration. The critical ‘passive’ concentration is 0.009 mol/L HCO₃^- for X80 pipeline steel in bicarbonate solutions. No anodic current peak exists in HCO₃^- solutions when the concentration is lower than 0.009 mol/L, whereas there are one and two anodic current peaks when the HCO₃^- concentration ranges from 0.009 to 0.05 mol/L and is higher than 0.1 mol/L, respectively. DEIS measurements show that there exist active dissolution range, transition range, pre-passive range, passive layer formation range, passive range, and trans-passive range for X80 pipeline steel in the 0.1 mol/L HCO₃^- solutions. The results of DEIS measurements are in complete agreement with the potentiodynamic diagram. An equivalent circuit containing three sub-layers is used to explain the Nyquist plots in the passive range. Analyses are well made for explaining the corresponding fitted capacitance and impedance. The Mott-Schottky plots show that the passive film of X80 pipeline steel is an n-type semiconductor, and capacitance measurements are in good accordance with the results of DEIS experiment.

Flow stress model considering the transformation-induced plasticity effect and the inelastic strain recovery behavior

Hai-yan Yu, Li Bao

2011, 18(2): 185-191. doi: 10.1007/s12613-011-0420-2

中文摘要(214) PDF(7) SpringerLink

摘要:
On the basis of continuum mechanics and the Mori-Tanaka mean field theory, a micro-mechanical flow stress model that considered both the transformation-induced plasticity (TRIP) effect and the inelastic strain recovery behavior of TRIP multiphase steels was presented. The relation between the volume fraction of constituent phases and plastic strain was introduced to characterize the transformation-induced plasticity effect of TRIP steels. Loading-unloading-reloading uniaxial tension tests of TRIP600 steel were carried out and the strain recovery behavior after unloading was analyzed. From the experimental data, an empirical elastic modulus expression is extracted to characterize the inelastic strain recovery. A comparison of the predicted flow stress with the experimental data shows a good agreement. The mechanism of the transformation-induced plasticity effect and the inelastic recovery effect acting on the flow stress is also discussed in detail.

Effect of Si on austenite stabilization, martensite morphology, and magnetic properties in Fe-26%Ni-x%Si alloys

H. Gungunes, E. Yasar, M. Dikici

2011, 18(2): 192-196. doi: 10.1007/s12613-011-0421-1

中文摘要(264) PDF(13) SpringerLink

摘要:
The effect of Si on the austenite stabilization, martensite morphology, and magnetic properties in Fe-26%Ni-x%Si (x=3.5, 5, and 6) alloys have been studied by means of transmission electron microscopy (TEM) and Mössbauer spectroscopy techniques. TEM observations reveal that the martensite morphology is closely dependent on the Si content. The volume fraction changes of martensite and austenite phases, the hyperfine magnetic field, and isomer shift values have been determined by Mössbauer spectroscopy. The Mössbauer study reveals that the hyperfine magnetic field, the isomer shift values and the volume fraction of martensite decrease with increasing Si content.

Surface recrystallization of a single crystal nickel-base superalloy

Jie Meng, Tao Jin, Xiao-feng Sun, Zhuang-qi Hu

2011, 18(2): 197-202. doi: 10.1007/s12613-011-0422-0

中文摘要(227) PDF(21) SpringerLink

摘要:
The recrystallization behavior of a single crystal nickel-base superalloy was investigated by shot peening and subsequent annealing. Two kinds of recrystallization microstructures, which are intensively dependent on the annealing temperature, are shown in the nickel-base superalloy after shot peening and subsequent annealing. Surface recrystallized grains are obtained when the superalloy is annealed at solution treatment temperature. The nucleation of recrystallization originates from the dendritic core, where rapid dissolution of γ' particles occurs. Cellular recrystallization is observed after annealing at lower temperatures. Cellular structures induced by high diffusivity of the moving boundary and more γ' particles dissolution led by residual stress are developed from the surface region. Recrystallized kinetics of the shot-peened alloy annealed at 1050℃ accords with the Johnson-Mehl-Avrami-Kolmogorov equation. The low Avrami exponent is caused by the inhomogeneous distribution of stored energy, the decreasing of stored energy during recovery, and the strong resistance of boundary migration by γ' particles.

Influence of Nd and Y additions on the corrosion behaviour of extruded Mg-Zn-Zr alloys

Jian-wei Chang, Jun Duo, Ya-zhen Xiang, Hai-yan Yang, Wen-jiang Ding, Ying-hong Peng

2011, 18(2): 203-209. doi: 10.1007/s12613-011-0423-z

中文摘要(150) PDF(13) SpringerLink

摘要:
To improve the corrosion resistance of wrought magnesium alloys through rare earth (RE) additions, the corrosion behaviour of Mg-5Zn-0.3Zr-xNd (x=0, 1, and 2; wt%) and Mg-5Zn-0.3Zr-2Nd-yY (y=0.5 and 1; wt%) alloys in a 5wt% NaCl solution was investigated using immersion test and electrochemical measurements. The results of immersion test show that Mg-5Zn-0.3Zr-2Nd alloy exhibits the best corrosion resistance among the tested alloys. Electrochemical measurements show that secondary phases in RE-containing Mg-5Zn-0.3Zr alloys behave as less noble cathodes in micro-galvanic corrosion and suppress the cathodic process. The additions of Nd and Y into Mg-5Zn-0.3Zr alloy also improve the compactness of the corrosion product film and are beneficial to the corrosion resistance.

Hydrogen absorption behavior of TA15 alloy

Xue-ping Ren, Fang-fang Zhang, Qing-miao Guo, Hong-liang Hou, Yao-qi Wang

2011, 18(2): 210-215. doi: 10.1007/s12613-011-0424-y

中文摘要(158) PDF(13) SpringerLink

摘要:
The hydrogen absorption kinetics of TA15 titanium alloy at 973–1123 K was studied using a tube-type hydrogen treatment furnace. The hydrogen absorption kinetic curves obtained were analyzed according to a series of mechanism equations to reveal the kinetic parameters and mechanism of the hydrogen absorption process. The results show that both the hydrogen absorption rate and the equilibrium hydrogen pressure increase and the time to reach equilibrium is shortened with increasing temperature. It is found that only the second hydrogen absorption period exists in the hydrogen absorption process of TA15 alloy between 973 and 1123 K, and the activation energy is 54.889 kJ/mol for hydrogen absorption. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results demonstrate that δ hydride forms between 973 and 1123 K, and β phase decreases with the increase of temperature. Orthorhombic α″ martensite is generated at 1073-1123 K, and their amount increases with increasing temperature.

Lithium intercalation mechanism for β-SnSb in Sn-Sb thin films

Qiang Ru, Qin Tian, She-jun Hu, Ling-zhi Zhao

2011, 18(2): 216-222. doi: 10.1007/s12613-011-0425-x

中文摘要(160) PDF(7) SpringerLink

摘要:
Based on the first-principles plane wave pseudo-potential method, the electronic structure and electrochemical performance of Li_xSn₄Sb₄ (x=2, 4, 6, and 8) and Li_xSn_1-xSb₄ (x=9, 10, 11, and 12) phases were calculated. A Sn-Sb thin film on a Cu foil was also prepared by radio frequency magnetron sputtering. The surface morphology, composition, and lithium intercalation/extraction behavior of the fabricated film were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV). Lithium atoms can easily insert into and extract out of the β-SnSb cell due to the low lithium intercalation formation energy. It is found that lithium atoms first occupy the interstitial sites, and then Sn atoms at the lattice positions are replaced by excessive lithium. The dissociative Sn atoms continue to produce different Li-Sn phases, which will affect the electrode stability and lead to the undesirable effect due to their large volume expansion ratio. The calculated lithium intercalation potential is stable at about 0.7 V, which is consistent with the experimental result.

Microstructure characterization of a pressureless infiltrating oxidized SiCp preform by Al-8Mg

Shu-bin Ren, Xiao-yu Shen, Xin-bo He, Xuan-hui Qu

2011, 18(2): 223-228. doi: 10.1007/s12613-011-0426-9

中文摘要(214) PDF(6) SpringerLink

摘要:
The microstructure of a pressureless infiltrating 55vol% oxidized SiC preform by Al-8Mg alloy was characterized by transmission electron microscopy (TEM), high resolution TEM (HRTEM), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction. The TEM image of the interface between Al and SiC shows that the surface of SiC is covered by a rough nanocrystal layer of MgAl₂O₄, Al₂O₃, and Si, produced by the interfacial reaction of Al, Mg, and SiO₂ on the surface of SiC. The Al-SiC interface is also examined by HRTEM to be better understood how MgAl₂O₄ and Al₂O₃ are produced. Dendritic Al₂O₃ crystals are embedded in the pores of the composite generated from the mutual bonding of SiO₂ on the surface of SiC. Columnar AlN crystals of about 250 nm in length are bunched vertically on the SiC particle surface.

Mechanism of brittle-ductile transition of a glass-ceramic rigid substrate

Yu-li Sun, Dun-wen Zuo, Hong-yu Wang, Yong-wei Zhu, Jun Li

2011, 18(2): 229-233. doi: 10.1007/s12613-011-0427-8

中文摘要(224) PDF(11) SpringerLink

摘要:
The hardness, elastic modulus, and scratch resistance of a glass-ceramic rigid substrate were measured by nanoindentation and nanoscratch, and the fracture toughness was measured by indentation using a Vickers indenter. The results show that the hardness and elastic modulus at a peak indentation depth of 200 nm are 9.04 and 94.70 GPa, respectively. These values reflect the properties of the glass-ceramic rigid substrate. The fracture toughness value of the glass-ceramic rigid substrate is 2.63 MPa·m^1/2. The material removal mechanisms are seen to be directly related to normal force on the tip. The critical load and scratch depth estimated from the scratch depth profile after scratching and the friction profile are 268.60 mN and 335.10 nm, respectively. If the load and scratch depth are under the critical values, the glass-ceramic rigid substrate will undergo plastic flow rather than fracture. The formula of critical depth of cut described by Bifnao et al. is modified based on the difference of critical scratch depth

Hydration mechanism of a cementitious material prepared with Si-Mn slag

Xu-fang Zhang, Wen Ni, Jun-yu Wu, Li-ping Zhu

2011, 18(2): 234-239. doi: 10.1007/s12613-011-0428-7

中文摘要(196) PDF(7) SpringerLink

摘要:
A cementitious material was prepared by mixing 80wt% Si-Mn slag powder, 10wt% lime, and 10wt% anhydrite. The compressive strength of mortar samples reaches 51.48 MPa after 28 d curing. The analyses of X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that much ettringite is formed in the sample cured for 3 d, and C-S-H gel increases rapidly during subsequent curing. Nuclear magnetic resonance (NMR) analysis of ²⁹Si and ²⁷Al and infrared spectroscopy (IR) analysis show that aluminum decomposition from tetrahedral network of the slag glass and its subsequent migration and re-combination play an important role in the process of hydration and strength development of the samples.

Filler effect of fine particle sand on the compressive strength of mortar

Chai Jaturapitakkul, Jatuphon Tangpagasit, Sawang Songmue, Kraiwood Kiattikomol

2011, 18(2): 240-246. doi: 10.1007/s12613-011-0429-6

中文摘要(205) PDF(8) SpringerLink

摘要:
The river sand, which is a non-pozzolanic material, was ground into 3 different particle sizes. Portland cement type I was replaced by the ground river sands at 10wt%–40wt% of binder to cast mortar. Compressive strengths of mortar were investigated and the filler effect of different fine particles of sand on the compressive strength of mortar was evaluated. The results show that the compressive strength of mortar contributed from the filler effect of smaller particles is higher than that of the coarser ones. The difference in compressive strength of mortar tends to be greater as the difference in ground river sand fineness increases. The results also suggest that ASTM C618 specification is not practically suitable for specifying pozzolan in concrete since the strength activity index of mortar containing ground river sand (high crystalline phase) with 33.8wt% of particles retained on a 45-μm sieve can pass the strength requirement.

Physicochemical characterization of Baizhi particles by ultrafine pulverization

Lian-wei Yang, Peng Sun, Guo-sheng Gai, Yu-fen Yang, Yu-rong Wang

2011, 18(2): 247-251. doi: 10.1007/s12613-011-0430-0

中文摘要(283) PDF(6) SpringerLink

摘要:
Baizhi, as a medicinal plant, has been demonstrated to be useful for the treatment of aches and pains in China. The physicochemical characterization of Baizhi particles is greatly influenced by ultrafine pulverization. To study the physicochemical characterization of Baizhi, the raw plant material of Baizhi was ground to 6 μm particles by a high speed centrifugal sheering (HSCS) pulverizer. The micron particles were characterized by optical microscopy and scanning electron microscopy (SEM). Imperatorin is one of the active ingredients of Baizhi, and its extraction yield is determined to evaluate the chemical characterization of Baizhi powder. Imperatorin was analyzed by high performance liquid chromatography (HPLC). The results show that after ultrafine pulverization, the plant cell walls are broken into pieces and the extraction yield of imperatorin is increased by 11.93% compared with the normal particles.

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