Adsorption mechanism of lead ions at ilmenite/water interface and its influence on ilmenite flotability

Pan Chen,Jihua Zhai,Wei Sun,Yue-hua Hu,Zhigang Yin,Xiangsheng Lai 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.53 No.-

In order to get further understanding of lead ions adsorption onto ilmenite surface, zeta potential analysis, adsorption density calculation, FT-IR and XPS analysis were employed. The results showed that the adsorption of lead ions onto ilmenite surface was a chemically dominating process. Lead species could interact with iron-hydroxyl complex compounds to form a Fe–O–Pb complex. The hydrophobic complex of Pb(OL)2 was also observed. Iron and adsorbed lead ions on ilmenite surface served as the main active-sites via chemisorption with oleate species. Introducing lead ions, as a surface modification means, can efficiently improve ilmenite flotability.

Effects of Ga Content on Dynamic Recrystallization and Mechanical Properties of High Strain Rate Rolled Mg–Ga Alloys

Wensen Huang,Jihua Chen,Hongge Yan,Weijun Xia,Bin Su,Weijun Zhu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.6

The Mg–xGa (x = 1, 2, 3 and 5 in mass%) alloys are subjected to high strain rate rolling (HSRR) at 275 °C with the rollingstrain rate of 9.1 s−1 to develop high performance Mg alloy sheets with high plasticity. Effects of Ga content on microstructureand mechanical properties of the Mg–Ga alloys are investigated by SEM, XRD, tensile testing and etc. The Ga additioncan reduce the critical strain of DRX in Mg alloys, which is associated with the reduced stacking fault energy, the increasedtwinning density during deformation and the more DRX nucleation sites during HSRR. With the Ga content increasing from2 to 3%, the reduced DRX degree is attributable to the hindrance of dynamic precipitates. With the Ga content increasingfrom 3 to 5%, the slightly increased DRX degree can be ascribed to the relatively coarse precipitates. The Mg–2 Ga alloysheet, featured with complete DRX, exhibits an ultra-high plasticity (with the elongation to rupture of 36.6%) and a relativelylow anisotropy of yield strength and plasticity. The Mg–5 Ga alloy sheet has the best comprehensive mechanical properties,with the ultimate tensile strength of 292 MPa, yield strength of 230 MPa and elongation to rupture of 30.3%, which can beascribed to the combination of grain refinement strengthening and precipitation strengthening.

High Strength-Thermal Conductivity Mg–Ga–Ca–Ce Sheet by Hot-Extrusion and Rolling

Mouxin Wu,Xueqi Jiang,Jihua Chen,Hongge Yan,Weijun Xia,Bin Su,Yifu Deng 대한금속·재료학회 2024 METALS AND MATERIALS International Vol.30 No.1

The thermal conductivity of magnesium alloys is increasingly required for fast heat dissipation in the automotive and electronicfields. However, the methods for mechanical property improvement such as grain refinement and alloying tend to deterioratetheir thermal conductivity. In this work, a novel low-alloy Mg–2Ga–0.6Ca–0.6Ce alloy exhibits a surprisingly goodcombination of high strength and high thermal conductivity compared with the other samples. The wrought alloys are of smallgrain sizes (< 2 μm), have high yield strength (> 272 MPa) and exhibit excellent thermal conductivity (> 143 W·m−1·K−1). The as-extruded alloy exhibits excellent yield strength (272 MPa) and high thermal conductivity (144.6 W·m−1·K−1) atroom temperature. After 30% rolling, the yield strength is further increased to 283 MPa, and the thermal conductivity isslightly reduced to 143.2 W·m−1·K−1. The effects of Ca and Ce addition on mechanical properties and thermal conductivityare analyzed from dislocation density, dynamic recrystallization fraction (fDRX), average grain size (dDRX) and texturecharacteristics. The higher yield strength can be attributed to the combination of grain boundary strengthening, dislocationstrengthening and second phase strengthening. Moreover, the addition of Ca and Ce can obviously reduce solute Ga atomsin α-Mg, which is the key to high thermal conductivity. Therefore, adding two alloying elements, Ca and Ce, significantlyimproves both tensile properties and thermal conductivity.

Microstructure, Texture Characteristics, Mechanical and Bio-Corrosion Properties of High Strain Rate Rolled Mg–Zn–Sr Alloys

Hongge Yan,Xiaole Gong,Jihua Chen,Meixin Cheng 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

Microstructure, texture characteristics, mechanical and bio-corrosion properties of the Mg–5Zn–xSr alloys (x=0, 0.2, 0.6,1.0) prepared by high strain rate rolling are carefully studied. A low level of Sr addition enhances dynamic precipitationof nano-scale MgZn2 particles in the as-rolled Mg–5Zn alloy, with 0.6%Sr showing the maximum efciency. These highdensity MgZn2 particles can pin grain boundaries of dynamic recrystallization grains and inhibit their growth. A low levelof Sr addition (≤0.6%) enhances the (0002) basal texture, but 1.0%Sr is just the reverse. The as-rolled Mg–5Zn–0.6Sr alloyexhibits the best combination of ultimate tensile strength (359 MPa) and elongation to rupture (20%). The high strength canbe attributable to a reduced grain size, precipitation and basal texture strengthening. The Mg–5Zn–xSr alloys exhibit excellent bio-corrosion resistance, but a minor Sr addition cannot bring about further bio-corrosion resistance improvement dueto the multiple actions of grain size, DRX degree, dynamic precipitates and texture characteristics. The 0.6%Sr addition cangreatly improve the strength of the as-rolled alloy at no expense of bio-corrosion resistance.

Radon-induced demethylation of Cdk2 CpG island in the rat lung

Cheng Wu,Qiu Chen,Jian Tong,Xin Xie,Fengmei Cui,Yang Jiao,Dandan Qi,Jihua Nie,Tom K. Hei,Qisheng Jiang 한국유전학회 2014 Genes & Genomics Vol.36 No.6

Radon exposure has been linked to lung carcinogenesisin both human and animal studies. The identificationof sequential changes in DNA methylation duringtumour progression and the elucidation of their interplaywith genetic changes will broaden our molecular understandingof this disease. Rats were exposed to 120 or 400working level months (WLM) of radon, lung pathologicalchanges were examined by haematoxylin and eosin staining,lung single cell suspension cell cycles were detected byflow cytometry, lung cell cycle regulated gene (Cdkn2a,P53, Cdk4/2, Mdm4/2 and Rb1 genes) expression wasquantified by real-time PCR and methylation of CpG islandsin the promoters of cell cycle-regulated genes were detectedby bisulfite sequencing PCR. The alveolar walls of rat lungsafter exposured to radon exhibited papillae and the lungbronchial epithelial cells stained positively for proliferatingcell nuclear antigen. The bronchial epithelial cells displayedsome hyperplasia after challenged by 400 WLM of radon. Moreover, G1 arrest decreased; Rb1, Mdm2/4, and Cdk2/4expression decreased and Cdk2 was demethylated at thesecond and sixth CpG loci from base pairs 3092704 to3092953 of chromosome 7. Cdk2 demethylation may beapplicable as a biomarker of early lung damage that wasinduced by radon and other environmental carcinogens.

Bimodal-Structured Al–Mg Alloy with High Strength and Ductility Processed by High Strain Rate Rolling at Medium Temperature

Xinyu Li,Weijun Xia,Jihua Chen,Hongge Yan,Zhenzhen Li,Bin Su,Min Song 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12

A bimodal grain distribution is generated in the Al-6.5Mg alloy deformed by high strain rate rolling (HSRR) at 320 °C, inwhich the fine grains with the average size of 2.1 μm and the coarse grains with the size of hundreds of microns containingultrafine sub-grains are developed. The deformed microstructures are detected by transmission electron microscopy, X-raydiffraction and electron backscattered diffraction. High strength and considerable ductility are achieved in the HSRRed alloyand the high strength is ascribed to solution strengthening, grain (sub-grain) strengthening and dislocation strengthening. The grain (sub-grain) strengthening is the dominant contributor (~ 146 ± 6 MPa) for yield strength. The generation of newfine grains is primarily observed along the deformation bands related to the high Mg solid content and the high strain rate at320 °C. The dynamic recrystallization related to the deformation bands is proposed to build the bimodal grain distributionfor achieving high strength and considerable ductility.

Effect of Strain Rate on the Microstructure and Texture Evolution of the ZK60 Alloy Sheets

Hongge Yan,Qin Wu,Jihua Chen,Weijun Xia,Min Song,Bin Su,Biao Huang 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.3

The dynamic recrystallization (DRX), precipitation and texture evolution of the ZK60 alloy sheets rolled at 300 °C withdifferent strain rates were studied, and the effects of texture on the plasticity were also clarified. The DRX grain sizes at fivestrain rates (5–25 s−1) are 1.4 μm, 1.2 μm, 1.8 μm, 2.4 μm and 2.8 μm, respectively, while the DRX volume fractions are35.8%, 75.0%, 82.0%, 88.0% and 93.0%, respectively. The maximum intensity values of the (0002) texture are 7.91, 8.22,7.64, 5.76 and 5.34 at five strain rates, respectively. The strongest (0002) texture is observed at the strain rate of 10 s−1,which is related to the relatively low DRX volume fraction and the precipitation density. The tensile strength (UTS) and yieldstrength (YS) increases firstly and then decreases, while the elongation (EL) gradually increases with increasing the strainrate, suggesting that the plasticity of the alloy sheet can be improved by decreasing the basal texture intensity and increasingthe dispersion degree of the basal texture. The optimal comprehensive mechanical properties are obtained at the strain rateof 10 s−1, with UTS of 358 MPa, YS of 291 MPa and EL of 21.5%.

Effect of Mg Content on the Damping Behavior of Al–Mg Alloys

Zhenzhen Li,Hongge Yan,Jihua Chen,Weijun Xia,Bin Su,Lu Zhao,Min Song 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

This article investigated the effect of Mg content (4.5, 6.5 and 9.2, in wt%) on the damping capacities of Al–Mg alloys. The results indicate that the damping behavior can be divided into three regions. Region I refers to the low strain amplituderegion (ε < 5 × 10−5), where the damping capacity decreases with increasing the Mg content and has almost no relation withthe strain amplitude. Region II is the middle strain amplitude region (5 × 10−5 < ε < 8 × 10−4), where the damping capacityincreases rapidly with the strain. Region III refers to the high strain amplitude region (8 × 10−4 < ε < 2 × 10−3), where thedamping capacity remains constant and is independent of the strain when the strain is high enough, but increases with the Mgcontent. The damping values Q−1 of Al–4.5Mg, Al–6.5Mg and Al–9.2Mg alloys are 0.01501 ± 0.00032, 0.01633 ± 0.00032and 0.01862 ± 0.00119 at the strain of 1 × 10−3, respectively. The damping capacity in Region I is mainly determined bythe lattice distortion caused by Mg addition and the restoring force caused by pinning points and Suzuki segregation. Theextended dislocations break away from the pinning effect of Mg atoms and become moveable in Region II, and the movementof extended dislocations is the dominant damping mechanism in Region III.

Efficient Metal-Free Synthesis of Dihydro[1,3]oxazines Assisted by Intramolecular Hydrogen Bonding

Jian Wang,Xiangmin Wang,Zhong Zheng,Jihua Ma,Xu Wang,이우경,심영기,윤일,Jinchun Chen,Jiazhu Li 대한화학회 2020 Bulletin of the Korean Chemical Society Vol.41 No.9

A novel and efficient intramolecular hydrogen bonding assisted approach to various dihydro[1,3]oxazines is described. Reaction is carried out under ambient condition without any metal catalysts.

Effect of Polymer Molecular Weight on Morphology and Charge Transport of Small‑Molecular Organic Semiconductors

Zhengran He,Ziyang Zhang,Sheng Bi,Jihua Chen 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.5

The utilization of polymer additives provides an intriguing pathway to tune the electrical performance of solution-grown,small-molecular organic semiconductors. In this study, we report the effect of different polymer molecular weight on thecrystal growth, phase segregation and charge transport of the organic semiconductors. A semicrystalline polymer additivepolyethylene oxide (PEO) with 8000 and 100 K molecular weight was blended with a well-known organic semiconductor6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene). Distinctively different thin film morphology of the resultantTIPS pentacene/PEO blend film was identified and quantitatively characterized. In particular, PEO with a higher molecularweight of 100 K exerted a stronger effect on enhancing film formation, crystal coverage and likely mechanical properties,whereas PEO with an 8000 molecular weight yielded more superior crystal alignment and larger crystal sizes. Bottom-gate,top-contact TIPS pentacene/PEO OTFTs were fabricated to test the charge transport, which indicated loading the PEOpolymer with molecular weight of 8000 demonstrated a five-fold enhancement in the extracted hole mobilities as comparedto the 100 K counterpart. This work of using polymer additives with different molecular weight can be used to tune thecrystallization of other solution-processed high-mobility small-molecular organic semiconductors.