Wide-Gap Repair of Mar-M247 Superalloy via Powder Metallurgy Route

Xiufang Gong,Yankang Yu,Tianjian Wang,Ye Liu,Lin Zhang,Zhenhuan Gao,Hou Ziyong,Xu Chen,Shuang He,Xuanhui Qu 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.11

Wide-gap defects repair of Mar-M247 superalloy was investigated by utilizing powder metallurgy. New interlayer alloy withrelatively high content of B and Zr was designed based on the isothermal solidification principle. The interlayer alloy ischaracterized by relative low melting temperature (1100 °C), and the contact angle of interlayer on the Mar-M247 substrateis ~ 70º. Based on the thermodynamic calculation results, the mixture powders with 80 wt% substrate powder and 20 wt%interlayer alloy powder was used as a filler to repair the wide gap with width of 2 mm. After repaired at 1230 °C for 2 h, nearfullydense gap was obtained. MC-type carbides, MB2-type boride, M3B2-type boride and Ni5(Zr,Hf)-type intermetallic wereobserved in the liquid zone. After post-weld heat treatment, the block borides, chain carbides and eutectic are successfullyremoved, and the tensile strength of the bonding zone is close to that of the Mar-M247 superalloy.

Microstructure and Thermal Stability of a Ni-Cr-Co-Ti-V-Al High-Entropy Alloy Coating by Laser Surface Alloying

Zhaobing Cai,Xiufang Cui,Guo Jin,Zhe Liu,Wei Zheng,Yang Li,Liquan Wang 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.5

A Ni-Cr-Co-Ti-V-Al high-entropy alloy (HEA) coating with a BCC phase and (Ni, Co)Ti2 compounds was synthesizedsuccessfully by laser surface alloying on a Ti-6Al-4V substrate. The microstructure of as-synthesizedcoatings is typical, namely, the microstructure from the coating to the substrate changes from equiaxed grains tocolumnar grains. After remaining at 900 °C for 8 h, the constituent phases remain unchanged. However, owing tothe unceasing dissolution of the Ti element, the lattice parameter of the BCC HEA phase changes from 3.06 Å to3.16 Å. The thermoanalysis results show that the oxidation film on the Ni-Cr-Co-Ti-V-Al HEA coating is mainlycomposed of TiO2, V2O5, and NiO. The oxidation resistance of this HEA coating may be due to the existence ofNiO and the alloying elements Al, Cr, and Co; the oxidation phenomenon should be responsible for the massincrease in the thermogravimetry process. The differential scanning calorimetry and the dynamic differential scanningcalorimetry curves show that the synthesized HEA coating is stable below 1005 °C.

A Novel Synchronization Technique for High Frequency Rectifier in Wireless Power Transfer

Yongbin Jiang,Min Wu,Zexian Zeng,Yonghui Liu,Xiufang Hu,Laili Wang,Yue Wang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper presents a novel synchronization technique for high frequency rectifier in wireless power transfer (WPT). To overcome the drawbacks of traditional phase-locked method based on DSP controller in high frequency rectifier, a novel phase-locked loop combined with the chained trigger mode (PLL-CTM) is proposed. The reasons why the driver pulses lose have been disclosed in detail. Then, the problem of pulse losing can be solved based on PLL-CTM. Finally, a 500W WPT prototype is built to verify the validity of the proposed synchronization technique.

Microwave-assisted modification of activated carbon with cationic surfactants for enhancement of naphthalene adsorption

Zhonghai Sun,Zhansheng Wu,Dandan Liu,Xiufang He 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.2

Polycyclic aromatic hydrocarbons (PAHs) are toxic pollutants harmful to humans. To improve the adsorption capacity of PAHs on activated carbon (AC) from the aqueous system, AC was modified with cationic surfactants through microwave heating. Naphthalene is a typical PAH used as a model pollutant to test the adsorption properties of sample; the sample with the best adsorption performance was named SAC. The SAC was characterized by SEM, FTIR and BET in detail compared with AC. The specific surface area and the average pore size of SAC increased by nearly 100m2 g−1 and 0.14 nm more than the original AC, respectively. The adsorption experiment was carried out by batch technique with variables such as contact time, adsorbent amount, pH and temperature. Results showed that naphthalene was adsorbed rapidly during the first 20min, and thereafter reached adsorption equilibrium in 40 min. The adsorption kinetics of naphthalene on SAC can be well described by the pseudo-second-order model and the Freundlich isotherm model better fitted the adsorption isotherms of naphthalene on SAC. Naphthalene adsorption process on SAC was spontaneous and temperature was found to negatively affect the adsorption capacity. Furthermore, film diffusion was confirmed the rate limiting step. The π-π stacking electron donor acceptor interaction, hydrophobic interaction and hydrogen bonding may play more key roles in naphthalene adsorption on SAC than AC. Thus, microwave- assisted surfactants modification was proven to be an effective method to enhance the adsorption of naphthalene onto SAC from aqueous solution.

Effects of Physicochemical Properties of Different Base Oils on Friction Coefficient and Surface Roughness in MQL Milling AISI 1045

Qingan Yin,Changhe Li,Lan Dong,Xiufang Bai,Yanbin Zhang,Min Yang,Dongzhou Jia,Runze Li,Zhan-qiang Liu 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.6

Minimum quantity lubrication (MQL) is an emerging green and resource-saving machining technique jetting minute amount lubricants and gas after mixing and atomization. However, MQL development is restricted to mineral oils because of its undegradability and threat to the environment and human health. Vegetable oils can replace mineral oils as base oil for MQL benefitting from its biodegradability and renewable property. Nevertheless, the lubrication mechanism at the tool-workpiece interface of different vegetable oils with various physicochemical properties has not been revealed systematically. In order to verify the interfacial lubrication characteristics of different vegetable oils, MQL milling experiments of AISI 1045 based on fi ve vegetable oils (cottonseed, palm, castor, soybean, and peanut oils) were carried out. The experimental results showed that, palm oil obtained the lowest milling force ( F x = 312 N, F y = 156 N), friction coeffi cient (0.78), and surface roughness values ( Ra = 0.431 μm, RSm = 0.252 mm) and the smoothest surface of workpiece. Furthermore, the physiochemical properties (composition, molecular structure, viscosity, surface tension, and contact angle) of vegetable oil were analyzed. Palm oil with high content of saturated fatty acid, high viscosity and small contact angle can form the lubricating oil fi lm with the highest strength and the largest spreading area at the tool-workpiece interface. Therefore, palm oil can achieve the optimal lubrication effect.

Genome-wide locus-specific DNA methylation repatterning may facilitate rapid evolution of mercury resistance in rice

Cong Weixuan,Li Ning,Wang Jinbin,Kang Ying,Miao Yiling,Xu Chunming,Wang Ziqi,Liu Tongtong,Gong Lei,Liu Bao,Ou Xiufang 한국유전학회 2022 Genes & Genomics Vol.44 No.3

Background: Albeit a relatively stable epigenetic modification, DNA methylation in plants can be repatterned and play important roles in response to biotic and abiotic stresses. However, whether DNA methylation dynamics may contribute to cope with mercury (Hg) stress in plants remains to be fully investigated. Objective: To probe the potential roles of DNA methylation dynamics in coping with Hg stress in rice. Methods: Whole-genome bisulfite sequencing was used to profile the DNA methylation patterns of a rice Hg-resistant line (RHg) selected from a heterozygous mutant of the DNA methyltransferase 1 gene (OsMET1+/-), together with its Hg-sensitive wild-type plants of cv. Nipponbare (Nip) under both normal and Hg stress conditions. Results: Genome-wide locus-specific differential methylation regions (DMRs) were detected between RHg and Nip under normal condition, the predominant DMR patterns were CG hypo-DMRs, CHG hypo-DMRs and CHH hyper-DMRs. In both lines, more hyper- than hypo-DMRs were detected at all three sequence contexts (CG, CHG and CHH) under Hg stress relative to normal condition. Comparison of DNA methylation changes in the two lines under Hg stress indicates that RHg had a more dynamic methylome than the control (Nip). Original DMRs in RHg trended to transform to opposite status (from hyper- to hypo- or vice versa) under Hg stress condition. Gene ontology analysis revealed that Hg-resistance-related DMGs were enriched in diverse biological processes. Conclusions: Our results suggest genome-wide locus-specific DNA methylation repatterning can facilitate rapid acquisition of Hg resistance in rice.

Removal characteristics of Cd(II) ions from aqueous solution on ordered mesoporous carbon

Linhang Lu,Haibo Zhao,Lu Yan,Guowei Wang,Yulin Mao,Xin Wang,Kai Liu,Xiufang Liu,Qian Zhao,Tingshun Jiang 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.10

Ordered mesoporous carbon (CMK-3) was synthesized using SBA-15 mesoporous molecular sieve as a template and sucrose as carbon source. The materials were characterized by XRD, TEM and N2 physical adsorption technique. The resulting CMK-3 was used as adsorbent to remove Cd(II) ions from aqueous solution. The effect of pH, contact time and temperature on adsorption process was investigated in batch experiments. The results showed that the removal percentage could reach ca. 90% at the conditions of initial Cd(II) ions concentration of 20 mg/L, dose of 20mg, pH 6.5, contact time of 3h and 293K. Langmuir and Freundlich models were employed to describe the adsorption equilibrium. The kinetics data were described by the pseudo-first-order and pseudo-second-order models, respectively. The adsorption isotherm was well fitted to the Langmuir model, and the adsorption process was well described by the pseudo-second-order kinetic model.