Preparation of PEO ceramic coating on Ti alloy and its high temperature oxidation resistance

Yongjun Xu,Zhongping Yao,Fangzhou Jia,Yunlong Wang,Zhaohua Jiang,Haitao Bu 한국물리학회 2010 Current Applied Physics Vol.10 No.2

Ceramic coatings were prepared in Na2SiO3–Na2CO3–NaOH system by pulsed bi-polar plasma electrolytic oxidation on Ti–6Al–4V alloy. The phase composition, structure and the elemental distribution of the coatings were studied by XRD, SEM and energy dispersive spectroscopy, respectively. The thermal shock resistance of the coated samples at 850 ℃ was evaluated by the thermal shock tests. The high temperature oxidation resistance of the coating samples at 500 ℃ was investigated. The results showed that the coating was mainly composed of rutile- and anatase TiO2, Increasing the concentration of Na2SiO3, TiO2content decreased gradually while the thickness of the coating increased. There were a large amount of micro pores and sintered particles on the surface of the coatings. Increasing concentration of Na2SiO3, the sintered particles on the surface turned large, and the Si content increased while the Ti content decreased gradually. When the concentration of Na2SiO3 was 15 g/L, the thermal shock resistance of the coatings was better than that of the coatings that prepared under other Na2SiO3 concentrations. The coating samples prepared under the optimized technique process based on the thermal shock tests improved the high temperature oxidation resistance at 500 ℃ greatly, whether considering the isothermal oxidation or the cyclic oxidation.

Preparation and properties of ceramic coating on Q235 carbon steel by plasma electrolytic oxidation

Yunlong Wang,Zhaohua Jiang,Zhongping Yao 한국물리학회 2009 Current Applied Physics Vol.9 No.5

Ceramic coating was achieved on Q235 carbon steel by PEO (plasma electrolytic oxidation, PEO) without any pretreatment in sodium aluminate system. The discharge process as well as the accompanied surface morphology evolution was analyzed. The phase and elemental composition of the coatings were also investigated. The corrosion, mechanical and tribological properties of the ceramic coating were primarily studied. It is found that the coating surface was porous and the thickness of the coating was about 120 lm. The coating mainly consisted of FeAl2O4, Fe3O4 and a little c-A12O3. The corrosion current of the coated sample was 3.082 × 10-7 A/㎠, which was decreased by two orders of magnitude compared with the uncoated one. The micro hardness of the ceramic coating was 1210 Hv, which was about three times as that of the uncoated sample. The friction coefficient of coated sample was also well improved. Investigations revealed that PEO provided a promising technique for preparation of protective ceramic coatings on steels. Ceramic coating was achieved on Q235 carbon steel by PEO (plasma electrolytic oxidation, PEO) without any pretreatment in sodium aluminate system. The discharge process as well as the accompanied surface morphology evolution was analyzed. The phase and elemental composition of the coatings were also investigated. The corrosion, mechanical and tribological properties of the ceramic coating were primarily studied. It is found that the coating surface was porous and the thickness of the coating was about 120 lm. The coating mainly consisted of FeAl2O4, Fe3O4 and a little c-A12O3. The corrosion current of the coated sample was 3.082 × 10-7 A/㎠, which was decreased by two orders of magnitude compared with the uncoated one. The micro hardness of the ceramic coating was 1210 Hv, which was about three times as that of the uncoated sample. The friction coefficient of coated sample was also well improved. Investigations revealed that PEO provided a promising technique for preparation of protective ceramic coatings on steels.

Ni Nanoparticle Anchored on MWCNT as a Novel Electrochemical Sensor for Detection of Phenol

Yajing Wang,Jiankang Wang,Zhongping Yao,Chenyu Liu,Taiping Xie,Qihuang Deng,Zhaohua Jiang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.11

Increasing active sites and enhancing electric conductivity are critical factors to improve sensing performance toward phenol. Herein, Ni nanoparticle was successfully anchored on acidified multiwalled carbon nanotube (a-MWCNT) surface by electroless plating technique to avoid Ni nanoparticle agglomeration and guarantee high conductivity. The crystal structure, phase composition and surface morphology were characterized by XRD, SEM and TEM measurement. The as-prepared Ni/a-MWCNT nanohybrid was immobilized onto glassy carbon electrode (GCE) surface for constructing phenol sensor. The phenol sensing performance indicated that Ni/a-MWCNT/GCE exhibited an amazing detection performance with rapid response time of 4s, a relatively wide detection range from 0.01 mM to 0.48 mM, a detection limit of 7.07 μM and high sensitivity of 566.2 μAmM -1 cm -2. The superior selectivity, reproducibility, stability and applicability in real sample of Ni/a-MWCNT/GCE endowed it with potential application in discharged wastewater.

Effect of additives on structure and corrosion resistance of ceramic coatings on Mg–Li alloy by micro-arc oxidation

Shi Lingling,Xu Yongjun,Li Kang,Yao Zhongping,Wu Songquan 한국물리학회 2010 Current Applied Physics Vol.10 No.3

In order to improve the corrosion resistance of ceramic coatings formed on Mg–5mass%Li substrate by micro-arc oxidation (MAO) method, two kinds of additives (Na2B4O7 and EDTA) were doped in Na2SiO3–Na3PO4 solution system. The surface and cross-section morphology feature, phase composition and elemental composition were examined by SEM, XRD and EDX, respectively. Corrosion resistance of ceramic coating was tested by electrochemical methods. It was revealed that all coatings were composed of MgO and Mg2SiO4, and had porous surface structure. Doping of additives had little effect on the elemental composition, while it influenced the morphological feature of the coating. The results of electrochemical tests showed that the coatings prepared in the solutions with additive had good corrosion resistance. The addition of EDTA to the solution made coatings thinner and more uniform which resulted in better general corrosion resistance. The addition of Na2B4O7 to the solution made coatings much thicker and compacter, which improved the pitting corrosion resistance.

Microstructural Abnormalities of Basal Ganglia and Thalamus in Bipolar and Unipolar Disorders: A Diffusion Kurtosis and Perfusion Imaging Study

Lianping Zhao,Ying Wang,Yanbin Jia,Shuming Zhong,Yao Sun,Zhifeng Zhou,Zhongping Zhang,Li Huang 대한신경정신의학회 2017 PSYCHIATRY INVESTIGATION Vol.14 No.4

Objective: Bipolar disorder (BD) is often misdiagnosed as unipolar depression (UD), leading to mistreatment and poor clinical outcomes. However, little is known about the similarities and differences in subcorticalgray matter regions between BD and UD. Methods: Thirty-five BD patients, 30 UD patients and 40 healthy controls underwent diffusional kurtosis imaging (DKI) and three dimensional arterial spin labeling (3D ASL). The parameters including mean kurtosis (MK), axial kurtosis (Ka), radial kurtosis (Kr), fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (Da), radial diffusivity (Dr) and cerebral blood flow (CBF) were measured by using regions-of-interest analysis in the caudate, putamen and thalamus of the subcortical gray matter regions. Results: UD exhibited differences from controls for DKI measures and CBF in the left putamen and caudate. BD showed differences from controls for DKI measures in the left caudate. Additionally, BD showed lower Ka in right putamen, higher MD in right caudate compared with UD. Receiver operating characteristic analysis revealed the Kr of left caudate had the highest predictive power for distinguishing UD from controls. Conclusion: The two disorders may have overlaps in microstructural abnormality in basal ganglia. The change of caudate may serve as a potential biomarker for UD.