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Controlled synthesis of SrCO3 dendrites by a simple hydrothermal method
Yonggang Wang,Linlin Yang,Xiaofeng Wang,Yujiang Wang,GAORONG HAN 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.2
In this paper, we report the controlled synthesis of SrCO3 crystals by a simple hydrothermal method without any surfactants and templates. The as-prepared samples were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The effect of pH value, temperature, and reaction time on the formation of SrCO3 crystals was investigated. This novel route is proved to be simple and environment-friendly, which can be extended to the shape-controlled synthesis of other metal oxide nanocrystals.
Controlled synthesis and characterization of BiVO4 dendrites via a hydrothermal method
Yonggang Wang,Linlin Yang,Xiaofeng Wang,Yujiang Wang,GAORONG HAN 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.7
BiVO4 dendrites have been controllably synthesized by a hydrothermal method without any surfactants or templates. Thestructure and morphology of the obtained BiVO4 dendrites were characterized by X-ray powder diffraction, scanning electronmicroscope, transmission electron microscopy, and high-resolution transmission electron microscopy. The effect of the pHvalues, precursors, solution concentrations, reaction temperature, and reaction time on the morphology and structure of theBiVO4 dendrites was systematically studied for the first time. It is found that the morphologies of the obtained BiVO4crystallites can vary from cubic-like to dendritic shape. The BiVO4 dendrites can be successfully fabricated by thehydrothermal method at 150 oC and pH 7 when Bi2(CO3)3 and NH4VO3 were used as precursors The resultant dendriticstructure has four trunks which have ordered branches on the opposite sides of the trunks. A rational mechanism for theoriental growth of the BiVO4 dendrites is discussed. The preparation of BiVO4 dendrites with well-dened shapes may open newopportunities for wide applications of future nanodevices.
Synthesis of PbTiO3 nanowires via a simple hydrothermal method
Yonggang Wang 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.1
PbTiO3 nanowires with diameters of 20-30 nm and lengths of about 2-3 um have been synthesized by a simple surfactant-free hydrothermal method. The resulting products were characterized by X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). It was found that KOH concentration played an important role in the formation of large quantities of PbTiO3 nanowires and a possible mechanism for the formation of nanowires is discussed.
Wang Yonggang,Du Peng,Gan Renbao,Li Zhimin,Ye Qin The Korean Society for Biotechnology and Bioengine 2005 Biotechnology and Bioprocess Engineering Vol.10 No.2
Secretion of the expressed heterologous proteins can reduce the stress to the host cells and is beneficial to their recovery and purification. In this study, fed-batch cultures of Escherichia coli YK537 (pAET-8) were conducted in a 5-L fermentor for the secretory production of human epidermal growth factor (hEGF) whose expression was under the control of alkaline phosphatase promoter. The effects of feeding of glucose and complex nitrogen sources on hEGF production were investigated. When the fed-batch culture was conducted in a chemically de-fined medium, the cell density was 9.68 g/L and the secreted hEGF was 44.7 mg/L in a period of 60 h. When a complex medium was used and glucose was added in pH-stat mode, the secreted hEGF was improved to 345 mg/L. When the culture was fed with glucose at a constant specific rate of $0.25\;gg^{-1}h^{-1}$, hEGF reached 514 mg/L. The effects of adding a solution containing yeast extract and tryptone were further studied. Different rate of the nitrogen source feeding resulted in different levels of phosphate and acetic acid formation, thus affected hEGF expression. At the optimal feeding rate, hEGF production achieved 686 mg/L.
Dirac semimetal-enabled multi-bit coding metasurface for dynamic manipulation of terahertz beams
Zhang Yonggang,Yin Kehao,Liang Lanju,Yao Haiyun,Yan Xin,Hu Xiaofei,Huang Chengcheng,Qiu Fu,Zhang Rui,Li Yuanping,Wang Yaru,Li Zhenhua,Wang Ziqun 한국물리학회 2024 Current Applied Physics Vol.58 No.-
In this study, a switchable multi-bit coding metasurface that is applied under a terahertz (THz) frequency by adjusting the Fermi level (EF) of Dirac semimetals (DSMs) is proposed. At a EF of 0.2 eV, a 1-bit coding metasurface can be applied in the 2.58–2.62 THz. At 0.3 eV, a 3-bit coding metasurface is realized at 1.88 THz, and at 0.05 eV, the phase of the coding units coincides in the 1.5–3 THz. So, different functions of the metasurface can be realized. The proposed coding metasurfaces has promising applications in terahertz communication.
Xinyu Wang,Xin Qian,Yonggang Zhang,Xuefei Wang,Shulin Song,Cheng Zhang 한국탄소학회 2021 Carbon Letters Vol.31 No.3
In this study, nitric acid oxidation with varied treatment temperature and time was conducted on the surfaces of polyacrylonitrile- based ultrahigh modulus carbon fibers. Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and surface tension/dynamic contact angle instruments were used to investigate changes in surface topography and chemical functionality before and after surface treatment. Results showed that the nitric acid oxidation of ultrahigh modulus carbon fibers resulted in decreases in the values of the crystallite thickness Lc and graphitization degree. Meanwhile, increased treating temperature and time made the decreases more obviously. The surfaces of ultrahigh modulus carbon fibers became much more activity and functionality after surface oxidation, e.g., the total surface energy of oxidized samples at 80 °C for 1 h increased by 27.7% compared with untreated fibers. Effects of surface nitric acid oxidation on the mechanical properties of ultrahigh modulus carbon fibers and its reinforced epoxy composites were also researched. Significant decreases happened to the tensile modulus of fibers due to decreased Lc value after the nitric acid oxidation. However, surface treatment had little effect on the tensile strength even as the treating temperature and processing time increased. The highest interfacial shear strength of ultrahigh modulus carbon fibers/epoxy composites increased by 25.7% after the nitric acid oxidation. In the final, surface oxidative mechanism of ultrahigh modulus carbon fibers in the nitric acid oxidation was studied. Different trends of the tensile strength and tensile modulus of fibers in the nitric acid oxidation resulted from the typical skin–core structure.
Spindle Spinel CoFeCoO4 Microparticles/rGO as an Oxygen Reduction and Oxygen Evolution Catalyst
Bowen Wang,Nian Tao,Junchen Liu,Hao Wang,Yinxiao Du,Hujiang Yang,Yonggang Wang,Kai Huang,Ru Zhang,Ming Lei 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.4
The representative spinel-type materials AB2O4 (both A and B are transition metals) electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have been investigated and significant improvements have been achieved in the activity and durability for ORR and OER in the alkaline solution. But CoFeCoO4 was not explored widely like ZnCo2O4 (or NiCo2O4) as the ORR electrocatalyst for its relatively complicated atomic site occupation. CoFeCoO4 has a typical cubic spinel structure with Co2+ in the tetrahedron and Co3+ and Fe3+ in the octahedron. A mixture of Co3+ and Fe3+ in the B site makes the oxide have a wider overlap between transition metal 3d orbit and O 2p orbit, which can lead to an effective charge transfer in the rate-determining steps of ORR process and then enhance the ORR activity. The high electronic conductivity and specific surface area of rGO can accelerate charger transfer and provide more catalytic sites, which would contribute to a faster ORR process. In this work, the porous spindle CoFeCoO4 microparticles which were synthesized by hydrothermal technology, were assembled on the rGO surface to obtain the CoFeCoO4/rGO composite, which exhibited enhanced ORR activity and catalytic stability comparable to that of Pt/C. On the other hand, the OER catalytic activity of the prepared samples was also studied to explore the potential of CoFeCoO4/rGO as a bifunctional oxygen catalyst.
( Junling Wang ),( Ping Li ),( Zhilong Jiang ),( Qiuhui Yang ),( Yuqiang Mi ),( Yonggang Liu ),( Ruifang Shi ),( Yonghe Zhou ),( Jinsheng Wang ),( Wei Lu ),( Si Li ),( Dan Liu ) 대한내과학회 2016 The Korean Journal of Internal Medicine Vol.31 No.3
Background/Aims: This study aimed to verify the reliability of the alcoholic liver disease (ALD)/nonalcoholic fatty liver disease (NAFLD) index (ANI) for distinguishing ALD in patients with hepatic steatosis from NAFLD, and to investigate whether ANI combined with γ-glutamyl transferase (GGT) would enhance the accuracy of diagnosis in China. Methods: A hundred thirty-nine cases of fatty liver disease (FLD) were divided into two groups of ALD and NAFLD. The ANI was calculated with an online calculator. All indicators and ANI values were analyzed using statistical methods. Results: ANI was significantly higher in patients with ALD than in those with NAFLD (7.11 ± 5.77 vs. .3.09 ± 3.89, p < 0.001). With a cut-off value of .0.22, the sensitivity, specificity, and area under the receiver operating characteristic curve (AUROC) of diagnosed ALD cases was 87.1%, 92.5%, and 0.934 (95% confidence interval [CI], 0.879 to 0.969), respectively. The corresponding values for aspartate aminotransferase (AST)/alanine transaminase (ALT), mean corpuscular volume (MCV), and GGT were 75.29%, 72.94%, and 0.826 (95% CI, 0.752 to 0.885); 94.34%, 83.02%, and 0.814 (95% CI, 0.739 to 0.875) and 80.23%, 79.25%, and 0.815 (95% CI, 0.740 to 0.876), respectively. ANI AUROC was significantly higher than the AST/ ALT, MCV, or GGT AUROCs (all p < 0.001), moreover, ANI showed better diagnostic performance. The combination of ANI and GGT showed a better AUROC than ANI alone (0.976 vs. 0.934, p = 0.016). The difference in AUROCs between AST/ALT, MCV, and GGT was not statistically significant (all p > 0.05). Conclusions: ANI can help distinguish ALD from NAFLD with high accuracy; when ANI was combined with GGT, its effectiveness improved further.