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Influence of plasma peening on oxidation of H13 hot work steel in water vapor

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中国有色金属学会会刊：英文版 2004年第Z1期14卷 305-309页

作者： MIN Yong-an xu Xiao WU Xiao-chun li lin xu Luo-ping School of Materials Science and Engineering Shanghai University Shanghai 200072 China School of Materials Science and Engineering Shanghai University Shanghai 200072 China School of Materials Science and Engineering Shanghai University Shanghai 200072 China School of Materials Science and Engineering Shanghai University Shanghai 200072 China School of Materials Science and Engineering Shanghai University Shanghai 200072 China

The surface oxidation films on H13 steel samples, obtained by different oxidation processes were observed by optical microscope. It is shown that the oxidation speed of H13 steel is increased remarkably due to the surface modification of plasma peening. Further researches were made by XRD, SEM and EDS. The activation of H13 surface caused by plasma peening and the subsequent higher oxygen diffusion rate into the steel seem to be the main reasons of higher oxidation speed. The nitride layer, generally formed on the steel surface under plasma nitriding process, can be substituted by oxide in subsequent oxidation process, which can reduce the risk of heat cracking in some hot work applications. Therefore, the plasma nitriding plus oxidation process is a proper choice for some hot work dies, which demands high hardness to avoid indentation as well as high toughness to avoid cracks.

关键词： oxidation hot work tool steel plasma nitriding surface treatment

High-speed penetration of ogive-nose projectiles into thick concrete targets:Tests and a projectile nose evolution model

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Defence Technology（防务技术） 2024年第2期32卷 553-571页

作者： xu li Yan liu Junbo Yan Zhenqing Shi Hongfu Wang Yingliang xu Fenglei Huang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing401120China China Research and Development Academy of Machinery Equipment Beijing100089China

The majority of the projectiles used in the hypersonic penetration study are solid flat-nosed cylindrical projectiles with a diameter of less than 20 *** study aims to fill the gap in the experimental and analytical study of the evolution of the nose shape of larger hollow projectiles under hypersonic *** the hypersonic penetration test,eight ogive-nose AerMet100 steel projectiles with a diameter of 40 mm were launched to hit concrete targets with impact velocities that ranged from 1351 to 1877 m/*** erosion of the projectiles was observed during high-speed penetration of heterogeneous targets,and apparent localized mushrooming occurred in the front nose of recovered *** examining the damage to projectiles,a linear relationship was found between the relative length reduction rate and the initial kinetic energy of projectiles in different penetration ***,microscopic analysis revealed the forming mechanism of the localized mushrooming phenomenon for eroding penetration,i.e.,material spall erosion abrasion mechanism,material flow and redistribution abrasion mechanism and localized radial upsetting deformation ***,a model of highspeed penetration that included erosion was established on the basis of a model of the evolution of the projectile nose that considers radial upsetting;the model was validated by test data from the literature and the present *** upon the impact velocity,v0,the projectile nose may behave as undistorted,radially distorted or *** to the effects of abrasion of the projectile and enhancement of radial upsetting on the duration and amplitude of the secondary rising segment in the pulse shape of projectile deceleration,the predicted DOP had an upper limit.

关键词： High-speed penetration Concrete target Erosion Projectile nose evolution model

Enhanced room temperature magnetoresistance in maganites La_(0.60)Sr_(0.25-y)Na_(0.15)Δ_yMnO_(31)

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Rare Metals 2006年第Z1期25卷 515-520页

作者： TANG Guide ZHAO Fuwei li Zhuangzhi HOU Denglu ZHAO xu li Zhiqing Department of Physics Hebei Normal University Shijiazhuang 050016 China Department of Physics Hebei Normal University Shijiazhuang 050016 China Department of Physics Hebei Normal University Shijiazhuang 050016 China Department of Physics Hebei Normal University Shijiazhuang 050016 China Department of Physics Hebei Normal University Shijiazhuang 050016 China Department of Applied PhysicsSchool of ScienceTianjin UniversityTianjin 300072China

Bulk polycrystalline samples of La0.60Sr0.4MnO3 and La0.60Sr0.25-yNa0.15ΔyMnO3 with 0.00≤y≤0.15 (“Δ” representing cation vacancy) were successfully synthesized using the sol-gel method. The structural, magnetic, and electrical properties of the polycrystalline of the samples were investigated. The results of X-ray powder diffraction patterns show that these compounds crystallize in a distorted rhombohedral structure with the space group R3C. The measurement shows that, with vacancy content y increasing, the unit cell volume V of samples increases, furthermore, the Curie temperature TC decreases. The temperature dependence of resistivity shows that all samples undergo a metal-semiconductor transition accompanying a ferromagnetic to paramagnetic transition with the increase of temperature. Under an applied filed of 1.8 T, a maximum room temperature magnetoresistance (MR) of 20% is obtained at 293 K for the compound La0.60Sr0.1Na0.15Δ0.15MnO3. The MR peak value of La0.60Sr0.1Na0.15Δ0.15MnO3 increases 2 times more than that of La0.60Sr0.40MnO3 (MRP=6.4%, TMR=373 K), and the MR peak is shifted from 373 K to room temperature.

关键词： perovskite manganite sol-gel method magnetoresistance crystal structure magnetic property

Mechanism of low thermal conductivity of xonotlite-silica aerogel nanoporous super insulation material

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Journal of University of Science and Technology Beijing 2008年第5期15卷 649-653页

作者： Hailong Yang Wen Ni Deping Chen Guoqiang xu Tao liang li xu Civil and Environmental Engineering School University of Science and Technology Beijing Beijing 100083 China

In an effort to incorporate the low thermal conductivity of the silica aerogel and the superior structure strength of the xonotlite,a composite material of these two was produced. It was synthesized under vacuum condition and dried by supercritical drying technique. The thermal conductivity of the new material,which is at 298K with the gas pressure ranging from 1.01×10^5 to 1×10^-2 Pa,was measured using the transient hot-strip method. The mechanism of the low thermal conductivity was studied. The results indicate that the low thermal conductivity mainly results from the significant decrease of gaseous thermal conductivity of the new material due to the restriction of the motion of gas molecules in its fine structures. The formation of the fine structures is because the new material takes the pore structure of the silica aerogel which consists of mainly nanometer-sized pores.

关键词： silica aerogel xonotlite nanometer-sized pore super insulation thermal conductivity

Preparation of natural brucite nanofibers by the dispersion method

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Journal of University of Science and Technology Beijing 2008年第4期15卷 489-494页

作者： li xu Wen Ni Wenping li Xingde liu Hailong Yang Xiaoguang Yang State Key Laboratory of the Ministry of Education of China for High-Efficient Mining ＆ Safety of Metal Mines University of Science and Technology Beijing Beijing 100083 China China Electric Power Research Institute Beijing 102401 China Kemeos Aluminate Technologies Ltd. Beijing 100027 China

The preparation of natural brucite nanofibers through dispersion by the wet process is described. The test results indicate that brucite fibers can be well dispersed by using sodium dioctyl sulfosuccinate （OT） as the dispersant at a dispersant/fiber mass ratio of 0.15：1, dispersing for 30 min at a water/solid mass ratio of 20：1. The prepared nanofibers were characterized with X-ray diffraction （XRD）, scanning electron microscope （SEM）, and transmission electron microscope （TEM）. It is shown that the prepared single brucite nanofiber is around 30 nm in diameter and the talus of the nonsingle brucite nanofibers is about 50-150 nm in diameter. Natural brucite mineral fibers were treated by the dispersion method to obtain nanomaterials. These fibers have significant advantages over artificial nanofibers both in yield and in cost.

关键词： brucite nanofiber sodium dioctyl sulfosuccinate (OT) ultrasonic dispersion method

Single-molecule force spectroscopy study of the effect of cigarette carcinogens on thrombomodulin–thrombin interaction

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Science Bulletin 2016年第15期61卷 1187-1194页

作者： Jianli liu xuejie Zhang Xiaofeng Wang li xu Jingyuan li Xiaohong Fang Key Laboratory of Molecular Nanostructure and Nanotechnology Institute of Chemistry Chinese Academy ofSciences Beijing 100190 China Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety Institute of High Energy Physics Chinese Academyof Sciences Beijing 100049 China

Exposure to cigarette smoke is a major risk factor for cancer and cardiovascular disease. Thrombosis is regarded as the main reason for smoking-related car- diovascular disease. However, the detail mechanism of how smoking promotes thrombosis is not fully under- stood. In this work, we investigated the impacts of one major cigarette carcinogens 4-（methylnitrosamino）-l-（3- pyridyl）-l-butanone （NNK） as well as its metabolite 4-（methylnitrosamino）- 1-（3-pyridyl）- 1-butanol （NNAL） on a key process in thrombosis regulation： thrombin- thrombomodulin （TM） binding. Atomic force microscopy based single-molecule force spectroscopy was applied to measure both in vitro and in vivo binding force of thrombin to TM in the absence and presence of NNK and NNAL respectively. The results revealed that NNK and NNAL can reduce the binding probability of TM and thrombin. The inhibition effect and underlying mechanism was further studied by molecular simulation. As indicated by our results, the cigarette carcinogens could cause a higher risk of thrombosis through the disruption of TM- thrombin interaction.

关键词： Cigarette carcinogens Thrombin Thrombomodulin AFM Single-molecule forcespectroscopy Molecular simulation

Recovery of scandium from bauxite residue——red mud:a review

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Rare Metals 2016年第12期35卷 887-900页

作者： Na Zhang Hong-xu li Xiao-Ming liu School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing Key Laboratory of Rare and Precious Metals Green Recycling and Extraction University of Science and Technology Beijing

Red mud is a slimy caustic residue generated from alumina production. Taking into account the rela- tively considerable content and availability of scandium, red mud can be viewed as an important and promising scandium resource rather than a solid waste. This paper is primarily to review the investigations of scandium recov- ery from red mud based on the most widely used hydrometallurgical processes including acid leaching, sol- vent extraction and ion exchange adsorption. It is thought that recovery of scandium from red mud should be con- sidered as a direct objective rather than a by-product in the development of overall flowsheet. In order to achieve environmentally-friendly processes with high scandium recovery and low cost, more attention is required to be paid to optimizing the selective leaching of scandium to decrease mineral acid consumption and alleviate pollution, and developing new solvent extraction systems and novel ion exchange adsorption materials with high selectivity and recognition for scandium.

关键词： Red mud Scandium Acid leaching Solvent extraction Ion exchange Selectivity

A clinicopathological analysis in unsuspected gallbladder carcinoma: A report of 23 cases

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World Journal of Gastroenterology 2007年第12期13卷 1857-1861页

作者： li-Ning xu Sheng-Quan Zou Department of Hepatobiliary Surgery of PLA General Hospital Beijing 100853 China Department of General Surgery of Tongji Hospital Tongji Medical College of Huazhong University of Science and Technology Wuhan 430030 Hubei Province China

AIM： To study the clinicopathological characteristics of unsuspected gallbladder carcinoma （UGC）. METHODS： We retrospectively studied 23 cases of UGC in Tongji Hospital, and compared their clinicopathological characteristics with 33 cases of preoperatively diagnosed gallbladder carcinoma （PDGC）. RESULTS： The proportion of UGC coexisting with cholecystolithiasis was significantly higher than that of PDGC （x^2 = 13.53, P 〈 0.01）. The infection rate of hepatitis B virus was 21.74% （5/23） in UGC and 30.30% （10/33） in PDGC. Nine （39.13%） of 23 patients with UGC and 8/33 （24.24） PDGC had contact with schistosome pestilent water. The rate of multiple pregnancies was 56.52% （13/23） in the patients with UGC and 42.42% （14/33） in PDGC. The primary location of the UGC was mostly in the neck and body of the gallbladder, and that of the PDGC was often in the body and bottom. The incidence of Nevin stage I and 11 UGC was significantly higher than that of PDGC （x^2 = 4.44, P 〈 0.05 and 2 = 4.96, P 〈 0.05） while that of Nevin stage V UGC was significantly lower than that of PDGC （x^2 = 7.59, P 〈 0.01）. According to the grading of carcinoma, the incidence of well-differentiated UGC was significantly higher than that of PDGC （2 = 4.16, P 〈 0.05）, and that of poorlydifferentiated UGC was significantly lower than that of PDGC （x^2 = 4.48, P 〈 0.05）.CONCLUSION： There are different characteristics between UGC and PDGC, such as in primary location, malignant degree and incidence of coexistence with cholecystolithiasis. Cholecystolithiasis, hepatitis B, schistosome and multiple pregnancies were high risk factors for gallbladder carcinoma.

关键词： Gallbladder neoplasms Clinical pathology Diagnostic techniques and procedures Diagnostic errors Surgery

Thickness measurement approach for plasma sprayed coatings using ultrasonic testing technique

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中国有色金属学会会刊：英文版 2004年第Z1期14卷 88-91页

作者： liN li li Xi-meng xu Zhi-hui LEI Ming-kai NDT&E Laboratory NDT&E Laboratory NDT&E Laboratory Surface Engineering Laboratory Dalian University of Technology Dalian 116024 China

The special ultrasonic testing system has been developed for thickness measurement of plasma sprayed coatings. The ultrasonic immersion method was used to obtain stable coupling condition and avoid other disadvantages of contact method. Spherical acoustic lens were designed to focus ultrasonic beam so as to improve beam directivity and concentrate ultrasonic energy. To increase testing precision and avoid mussy wave signals, moderate pulse width and frequency of the transducer has been selected. The displacement of transducer in X-Y-Z directions was precisely manipulated by step-controlled system to insure the accuracy of focus length and repetition of measurement. Optimized testing conditions (with the transducer of center frequency of 10 MHz and crystal diameter of 8 mm, focus length of 9.5 mm, diameter of focal column of 0. 1 mm and length of focal column of 0.27 mm) were selected to determine the thickness between 285 -414 μm of ZrO2 coatings plasma sprayed on the nickel based superalloy. The frequency interval of the periodic extremums in ultrasonic power spectra decreases with increasing coating thickness. The ultrasonic results accord with those of metallographical method.

关键词： plasma sprayed coatings thickness measurement ultrasonic testing interference