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Interface reaction during titanium alloys investment casting by residue gas in ceramic mold

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Rare Metals 2019年第4期38卷 327-335页

作者： Ya-Meng Wei zhi-gang lu Xin-Yi Li Xin Guo Department of Mechanical Engineering Tsinghua University Beijing 100084 China State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084 China Academy of Opto-Eletronics Chinese Academy of Sciences Beijing 100094 China

The chemical reaction between mold material and titanium melt during investment casting was studied intensively. However, the in fluence of residue gas in ceramic mold on interface reaction remains unclear. In this investigation, the effect of residue gas in Y2O3-silica sol shell mold on interface reaction during Ti-6A1-4V alloy investment casting was investigated. Two groups of shell molds were prepared by adding different kinds of pore formers, i.e., spherical starch particles or nylon fibers, respectively. Ti-6Al-4V alloy was cast under vacuum by gravity casting through cold crucible induction melting (CCIM) method. Porosity of different shell molds was measured based on Archimedean method. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were employed to characterize the micromorphology and composition of the reaction area, respectively. White light interferometer (WLI) was used to obtain the surface topography of the shell mold. The results show that the direct chemical reaction is very weak for all specimens. The release of residue gas in closed pores is the key factor influencing surface defects. However, open pores make nearly no difference on the interface reaction.

关键词： Titanium alloy Investment casting Residue gas Y2O3: Silica sol

Reaction between Ti–6Al–4V and Y_2O_3–SiO_2 based face shell for investment casting

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Rare Metals 2016年第12期35卷 901-908页

作者： Ya-Meng Wei zhi-gang lu Guang-Peng Wu Xing-Quan Long Department of Mechanical Engineering Tsinghua University State Key Laboratory of Tribology Tsinghua University Guizhou Anji Aviation Investment Casting Co. Ltd.

The pH value and viscosity of Y2O3-SiO2 （Y-Si） slurry made by Y2O3 powders and silica sol for the face coat of Ti-6Al-4V investment casting were measured. The thermal behavior of the shell made by the Y-Si face coat system was investigated by differential scanning calorimeter （DSC）, thermal gravimetric （TG） analysis combined with mass spectrometry （MS）, and the phase transformations were determined by X-ray diffraction （XRD）. Hot strength, residual strength, linear expansion coefficient, and wearing resistance performance of the shell were also tested. The microstructure and elements distri- bution of the interaction layer were studied by scanning electron microscope （SEM） and energy-dispersive spectrometer （EDS）, respectively. The microhardness tester was applied for the microhardness. The results showed that the slurry was stable for at least 60 h. A very small amount of YZrO3 was formed below 1050℃ and Y2SiO5 was formed around 1450℃. The shell made by Y-Si system had good mechanical property which could reduce cracks during the procedure of dewaxing and inclusions during pouring. Some Al volatilized from the melt, permeated the surface of the face coat shell, and formed the black reaction layer, which blocked the permeation of O so that O penetration was limited to 5μm. The depth of Si penetration was about 60 μm. The hard layer was also around 60 μm.

关键词： Investment casting Titanium alloy Silica sol Yttrium oxide Interface reaction

Effect of SiO_2 concentration in silica sol on interface reaction during titanium alloy investment casting

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China Foundry 2018年第1期15卷 23-30页

作者： Ya-meng Wei Ke-hui Hu zhi-gang lu Department of Mechanical Engineering Tsinghua Universit Beijing 100084 China State Key Laboratory of Tribology Tsinghua University Beijing 100084 China

Using silica sol as a binder for titanium investment casting is very attractive due to its good stability and reasonable cost as compared with yttrium sol and zirconium sol. However, the mechanism of interface reaction in the related system remains unclear. In this investigation, the interface reaction between Y_2O_3-SiO_2(YSi) shell mold and titanium alloys was studied. A group of shell molds were prepared by using Y_2O_3 sand and silica sol with different contents of SiO_2. Ti-6Al-4V alloy was cast under vacuum by gravity casting through cold crucible induction melting(CCIM) method. Scanning electron microscopy(SEM) and energy dispersive x-ray spectroscopy(EDS) were employed to characterize the micromorphology and composition of the reaction area, respectively X-ray photoelectron spectroscopy(XPS) was used to confirm the valence state of relevant elements. White ligh interferometer(WLI) was used to obtain the surface topography of Y-Si shells. The results show that the thickness of reaction layers is below 3 μm when the SiO_2 content of silica sol is below 20 wt.%. Whereas, when the SiO_2 content increases to 25 wt.%, the thickness of the reaction layer increases sharply to about 15 μm. There is a good balance between chemical inertness and mechanical performance when the SiO_2 content is between 15 and 20 wt.%. Moreover, it was found that the distribution of SiO_2 and the roughness at the surface of the shell are the key factors that determine the level of reaction.

关键词： titanium alloy investment casting Y2O3 silica sol surface roughness

A New Ecdysteroid from Rhaponticum uniflorum

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Chinese Chemical Letters 2001年第9期12卷 797-798页

作者： Yong Hong ZHANG Xin Pu LI zhi gang lu Han Qing WANG Lanzhou Institute of Chemical Physics Chinese Academy of SciencesLanzhou 730000 Lanzhou Institute of Animal Science and Animal Medicine Lanzhou 730050

A new phytoecdysteroid was isolated from the root of Rhaponticum uniflorum. Its structure has been shown to be 2, 3, 20, 22-diacetonide ajugasterone.

关键词： Rhaponticum uniflorum compositae 2, 3, 20, 22-diacetonide ajugasterone

Microstructure and properties of 3D-printed alumina ceramics with different heating rates in vacuum debinding

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Rare Metals 2020年第5期39卷 577-588页

作者： He Li Yong-Sheng Liu Yan-Song Liu Qing-Feng Zeng Ke-Hui Hu Jing-Jing Liang zhi-gang lu Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical UniversityXi'an 710072China NPU-SAS Joint Research Center of Advanced Ceramics Northwestern Polytechnical UniversityXi'an 710072China Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China State Key Laboratory of Tribology Tsinghua University Beijing 100084China Institute of Metal Research Chinese Academy of Sciences Shenyang 110016China

The effect of heating rates during vacuum debinding on the microstructure and mechanical properties of alumina ceramics are discussed in this *** threedimensional(3D)-printed alumina ceramics examined in this study were found to have a layered structure,and interlayer spacing increased as the heating rate increased The pore diameter,shrinkage,flexural strength and hardness were found to decrease as the heating rate increased due to weak interfacial bonding between alumina particles Shrinkage was found to be much larger along the Z direction than along the X or Y directions due to the layer-bylayer forming mode during 3D printing.0.5°C·min-1is considered the optimum heating rate,yielding ceramics with interlayer spacing of 0.65 lm,shrinkage of 2.6%2.3%and 4.0%along the X,Y and Z directions,respectively,flexural strength of 27.5 MPa,hardness of29.8 GPa,Vickers hardness of HV 266.5,pore diameter of356.8 nm,bulk density of 2.5 g·cm-3,and open porosity of38.4%.The debinding procedure used in this study could be used to produce a high-quality ceramic which can be used for fabricating alumina ceramic cores.

关键词： Heating rate Vacuum debinding Alumina ceramics Three-dimensional(3D)printing Stereolithography

Simulation results of the online tritiated water measurement system

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Nuclear Science and Techniques 2021年第11期32卷 96-104页

作者： Rui-Yang Xu Chun-Hui Dong Xiao-Qing Mao Qing-Xian Zhang Hui Gong Kai-yong Liao zhi-gang lu Liang-quan Ge zhi-Yu Gao Ting-Fang luo Qi-Chang Huang Chengdu University of Technology Chengdu 610059China Nuclear Power Institute of China Chengdu 610005China

Currently,the liquid scintillation method is widely used to measure the activity of tritiated water in the primary circuit of nuclear power plants,which leads to the continuous production of radioactive waste during *** addition,the real-time activity information of tritiated water cannot be *** solve this problem,herein we present an online tritiated water measurement method based on plastic scintillators that used the optical transport process in the Geant 4 software toolkit to build a model of plastic scintillation detection for tritiated *** simulation,the basic geometric dimensions of the detector were *** this dimension,using one detector to measure for 3 h,when the tritiated water activity was 100 Bq/L,its resolution was 16%(16 Bq/L).In addition,calculations were performed for the presence of other background signals to obtain the minimum detectable concentration.

关键词： Tritiated water Geant 4 Plastic scintillators Measurement system

LDFF,the large molecular weight DNA fragmentation factor,is responsible for the large molecular weight DNA degradation during apoptosis in Xenopus egg extracts

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Cell Research 2004年第2期14卷 134-140页

作者： zhi gang lu, Chuan Mao ZHANG~*, Zhong He ZHAI~* Department of Cell Biology and Genetics, College of Life Sciences, Peking University, Beijing 100871, China. Department of Cell Biology and Genetics College of Life Sciences Peking University Beijing China

DNA degradation is a biochemical hallmark in apoptosis. It has been demonstrated in many cell types that there are two stages of DNA fragmentation during the apoptotic execution. In the early stage, chromatin DNA is cut into large molecular weight DNA fragments, although the responsible nuclease(s) has not been recognized. In the late stage, the chromatin DNA is cleaved further into short oligonucleosomal fragments by a well-characterized nuclease in apoptosis, the caspase-activated DNase (CAD/DFF40). In this study, we demonstrate that large molecular weight DNA fragmentation also occurs in Xenopus egg extracts in apoptosis. We show that the large molecular weight DNA fragmentation factor (LDFF) is not the Xenopus CAD homolog XCAD. LDFF is activated by caspase-3. The large molecular weight DNA fragmentation activity of LDFF is Mg2+-dependent and Ca2+-independent, can occur in both acidic and neutral pH conditions and can tolerate 45℃ treatment. These results indicate that LDFF in Xenopus egg extr

关键词： apoptosis caspase-activated DNase (CAD) large molecular weight DNA fragmentation factor (LDFF).

Research on the influences of motion characteristics of jetting projectile charge under water

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Defence Technology（防务技术） 2024年第3期33卷 411-425页

作者： Xing Chen Yong-gang lu Institute of Systems Engineering China Academy of Engineering PhysicsMianyang 621900SichuanChina

Shaped charge warhead is important for enhancing the damage performance of underwater *** paper used finite element analysis software and based on JPC water penetration experiments to examine the influence of liner parameters(wall thickness,material),charge aspect ratio,and stand-off distance on the movement characteristics of JPC in *** findings reveal that the head diameter of the JPC increases and experiences significant erosion after entering the water,the effective length of the JPC in water undergoes two distinct phases:a growth phase and a decrease phase,with the velocity of the JPC decaying *** the liner thickness,stand-off distance and the charge aspect ratio can improve the erosion resistance and the velocity retention capacity of the *** optimal ranges for liner thickness and stand-off distance are 0.0363D_(k) to 0.0545D_(k)(D_(k) is the charge diameter),the stand-off distance should be within 1.0D_(k).After the charge aspect ratio higher than 1.25,the charge structure exerts minimal influence the movement characteristics of the JPC in *** density plays a crucial role in the velocity decay pattern of the JPC during *** with higher densities exhibit superior velocity retention capabilities in water,with the velocity decay pattern converging if the densities are ***,copper,tantalum and tungsten liners are deemed appropriate for underwater shaped charge ***,the results will provide an important reference for the design of underwater shaped charge warhead.

关键词： JPC Movement characteristics Underwater penetration Numerical simulation

Inhibition of viability of human retinal microvascular endothelial cells by vialinin A under high glucose condition

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International Journal of Ophthalmology(English edition) 2024年第10期17卷 1809-1815页

作者： zhi-gang Chen Gao-Qin Liu Wei-Ming Liu Pei-Rong lu Department of Ophthalmology the First Affiliated Hospital of Soochow UniversitySuzhou 215006Jiangsu ProvinceChina Jiangsu Clinical Immunology Institute the First Affiliated Hospital of Soochow UniversitySuzhou 215006Jiangsu ProvinceChina

AIM:To investigate the effects of vialinin A on viability of human retinal endothelial cells(HRECs)under high glucose condition and its potential ***:The HRECs were divided into four groups:normal glucose control group(NG,5 mmol/L D-glucose),high glucose group(HG,30 mmol/L D-glucose),HG+1μmol/L vialinin A group,and HG+5μmol/L vialinin A *** cell viabilities were measured with cell counting kit-8(CCK-8)assay for proliferation,with scratch assay for migration,and tube formation,for evaluation of the impact of vialinin A on cellular ***-time PCR and Western blotting were used to determine the expression level of vascular endothelial growth factor(VEGF).RESULTS:The proliferative capacity and migration of HRECs was reduced by 5μmol/L vialinin A in high glucose environment(both Plucose-induced tube formation of *** expression level of VEGF and PI3K in HRECs was also significantly decreased by vialinin A(PluSION:Vialinin A inhibits the cell viability of *** may serve as a potential target for anti-angiogenic therapy.

关键词： vialinin A vascular endothelial growth factor human retinal endothelial cells cell viability