Crystallization kinetics and magnetic properties of spinel transition metal ferrite nanoparticles

Yukun Sun,Dongyun Li,Pengzhao Gao,Zhouli Lu,Hongliang Ge 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.5

Spinel transition metal ferrite TMFe2O4 (TM = Co2+, Ni2+, Cu2+, and Zn2+) nanoparticles were prepared via a template-assistedsol-gel method followed by a calcining process, using metal nitrate precursors as raw materials. The prepared specimens werecharacterized using X-ray diffraction (XRD) and a vibrating sample magnetometer (VSM). Their structures, magneticproperties, crystallization kinetics, and the influence of crystal size (D) on the magnetic properties were investigated. It wasfound that the crystal sizes of TMFe2O4 were positively proportional to the calcined temperature and time, and thecrystallization growth activation energy (Ea) increased with the increase of metal ionic radius. The optimum calcinationparameters were obtained to form a crystal closest to the standard crystal. Additionally, the saturation magnetization ofinverse spinel structure specimens was enhanced monotonously and their coercivity showed a potential decrease trend, whilethere was an opposite change trend for normal spinel structure specimens.

Protection Provided by a Gabexate Mesylate Thermo-Sensitive In Situ Gel for Rats with Grade III Pancreatic Trauma

Hanjing Gao,Qing Song,Faqin Lv,Shan Wang,Yiru Wang,Xiaoyan Li,Yukun Luo,Xingguo Mei,Jie Tang 거트앤리버 소화기연관학회협의회 2017 Gut and Liver Vol.11 No.1

Background/Aims: This study investigated the protection provided by gabexate mesylate thermo-sensitive in-situ gel (GMTI) against grade III pancreatic trauma in rats. Methods: A grade III pancreatic trauma model with main pancreatic duct dividing was established, and the pancreas anatomical diagram, ascites, and serum biochemical indices, including amylase, lipase, C-reactive protein (CRP), interleukin 6 (IL- 6), and tumor necrosis factor-α (TNF-α), were examined. The pancreas was sliced and stained with hematoxylin eosin and subjected to terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Results: Ascites, serum amylase, lipase, CRP, IL-6, and TNF-α levels were significantly increased in the pancreas trauma (PT) groups with prolonged trauma time and were significantly decreased after GMTI treatment. The morphological structure of the pancreas was loose, the acinus was significantly damaged, the nuclei were irregular and hyperchromatic, and there was inflammatory cell invasion in the PT group compared to the control. After GMTI treatment, the morphological structure of the pancreas was restored, and the damaged acinus and inflammatory cell invasion were decreased compared to the PT group. Moreover, the cell apoptosis index was significantly increased in the PT group and restored to the same levels as the control group after GMTI treatment. Conclusions: GMTI, a novel formulation and drug delivery method, exhibited specific effective protection against PT with acute pancreatitis therapy and has potential value as a minimally invasive adjuvant therapy for PT with acute pancreatitis.

Enhancement mechanism of SO2 removal with calcium hydroxide in the presence of NO2

Jihui Gao,Guoqing Chen,Xiaolin Fu,Yijun Yin,Shaohua Wu,Yukun Qin 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.2

The enhancement mechanism of SO2 removal by the presence of NO2 under low temperature and humid conditions was studied in a fixed bed reactor system. The presence of NO2 in the flue gas can enhance SO2 removal. The interaction between SO2 and NO2 in gas phase could not explain the effect of NO2 on SO2 removal under lowtemperature and humid conditions. When Ca(NO3)2 and Ca(NO2)2 as additive were added on the surface of sorbent,the desulfurization activity of sorbent decreased. However, the sorbent pretreated by NO2 for a moment has higher SO2removal. The oxidization of SO32− to SO42− and the evolution of sorbent surface structure in the presence of NO2 can explain the enhancement of SO2 removal by the presence of NO2. HSO3− and SO3− reacted with NO2 to form sulfate,which can accelerate the hydrolysis of SO2. The reaction between NO2 and Ca(OH)2 can make the unreacted sorbet under the SO2 removal product exposed to the reactant gas.

Mechanism of SO_2 adsorption and desorption on commercial activated coke

Fei Sun,,Jihui Gao,Yuwen Zhu,,Yukun Qin 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.11

We used commercial activated coke (AC) as adsorbent and fixed-bed, FTIR, N_2 adsorption, ion chromatograph as research methods to study the SO2 removal mechanism in the presence of O_2 and H_2O and adsorbate (H_2SO_4)desorption mechanism by combined regeneration. The results showed that AC saturation sulfur retention (52.6 mg/g)in SO_2+O_2+H_2O atmosphere was 4.6 times as much as that (11.4mg/g) in SO_2+O_2 atmosphere and 5.0 times as much as that (10.6 mg/g) in SO_2+O_2 atmosphere at 90 ℃. O-2 and H_2O were necessary in AC desulfurization process. Reaction of SO_3 and H-2O (g) and condensation of sulfuric acid vapor were the dynamic of AC desulfurization process. Water vapor blowing in combined regeneration inhibited the reaction between H_2SO_4 and carbon, and consequently reduced the chemical lost of carbon. AC cumulative quality loss (53.6%) of five-times in C-R was still less than that (62.4%)of three-times in H-R. Water vapor blowing inhibited reactivation effect, as a result reducing the changes of AC pore structure and surface functional groups. Adsorbate H_2SO_4 generated in desulfurization evaporated to sulfuric acid vapor due to the high temperature in regeneration and was carried out by water vapor.

Preparation and characterization of activated carbons for SO_2 adsorption from Taixi anthracite by physical activation with steam

Yuwen Zhu,Jihui Gao,Fei Sun,Yukun Qin 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.12

Taixi anthracite was used as a precursor to prepare activated carbons (AC) for SO_2 adsorption from flue gas. In this work the activated carbons were prepared by physical activation with steam. Specifically, the effects of activation temperature and burn-off degree on the physico-chemical properties of the resulting AC samples were comparatively studied. The different types of pore volumes, pore size distributions and surface chemistries of the activated carbons on the SO_2 adsorption were also analyzed. The results show that the increasing burn-off leads to samples with continuous evolution of all types of pores except ultramicropore. The ultramicropore volume increases to a maximum of 0.169 cm^3/g at around 50% burn-off and then decreases for 850℃ activation. At higher activation temperature, the micropore volume decreases and the mesopore structure develops to a certain extent. For all the resulting AC samples,the quantities of the basic surface sites always appear much higher than the amount of the acidic sites. The activated carbon prepared with higher micropore volume, smaller median pore diameter and higher quantities of the basic surface sites represents better SO_2 sorption property.

A Three-Dimensional ZnO/CdS/NiFe Layered Double Hydroxide Photoanode Coupled with a Cu2O Photocathode in a Tandem Cell for Overall Solar Water Splitting

Jia Liu,Yinghua Zhang,Zhiming Bai,Zhian Huang,Yukun Gao,Yuan Yao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.11

An integrated tandem photoelectrochemical (PEC) cell, composed of a three-dimensional (3D) ZnO/CdS/NiFe layered double hydroxide (LDH) core/shell/hierarchical nanowire arrays (NWAs) photoanode and a p-Cu2O photocathode, was designed for unassisted overall solar water splitting in this study. The optical and photoelectrochemical characteristics of ZnO-based photoanodes and Cu2O photocathode were investigated. The results show that ZnO/CdS/NiFe LDH nanostructures offer significantly enhanced performances with a photocurrent density reaching 5.8 mA · cm -2 at 0.9 V and an onset potential as early as 0.1 V (versus RHE). The enhancement can be attributed to the existence of CdS nanoparticles (NPs) which boosts the light absorption in visible region and enhances charge separation. Moreover, the introduction of NiFe LDH nanoplates, with unique hierarchical mesoporous architecture, promotes electrochemical reactions by providing more active sites as co-catalyst. On the above basis, the ZnO/CdS/NiFe LDH–Cu2O two-electrode tandem cell system was established. At zero bias, the device shows a photocurrent density of 0.4 mA · cm -2 along with the corresponding solar-to-hydrogen (STH) conversion efficiency reaching 0.50%. Our results indicate that the tandem PEC cells consisting of metal–oxide–semiconductor photoelectrodes based on Earth-abundant and low-cost materials hold promising application potential for overall solar water splitting.

Photoelectrocatalytic Oxidation of Methane into Methanol Over ZnO Nanowire Arrays Decorated with Plasmonic Au Nanoparticles

Jia Liu,Yinghua Zhang,Zhian Huang,Zhiming Bai,Yukun Gao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.2

The pursuit for efficient conversion of methane under ambient conditions remains a challenge. Here, we reported photoelectrocatalytic oxidation of methane into methanol over ZnO nanowire arrays (NWAs) decorated with Au nanoparticles (NPs) under simulated sunlight illumination with ambient conditions. The photoelectrochemical (PEC) performances of the ZnO and ZnO/Au photoanodes were investigated to analyze the behavior and intensity of the reaction process of methane oxidation. The Faradaic efficiency of ZnO/Au was calculated to be 32.11%, nearly three times of 11.69% for ZnO. The above results show that ZnO NWAs exhibited exceptional activity as photoanode for photoelelctrocatalytic methane oxidation, and the decoration of Au NPs further enhanced the photo-activity via the surface plasmon resonance expanding its absorption spectra to visible region. On the other hand, as a co-catalyst, Au can promote the oxidation of methane by providing the trapping sites and active sites to facilitate the separation and also suppress the recombination of photogenerated charges and the existence of Au can boost the reaction by lowering the activation energy. This research demonstrates that ZnO NWAs decorated with Au NPs hold great promise for photoelectrocatalytic methane oxidation.