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PBO fibers/fluorine-containing liquid crystal compound modified cyanate ester wave-transparent laminated composites with excellent mechanical and flame retardance properties

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Journal of Materials Science & Technology 2023年第21期152卷 16-29页

作者： Zheng Liu Xiaoli Fan Junliang Zhang Lixin Chen Yusheng Tang Jie Kong Junwei Gu Shaanxi Key Laboratory of Macromolecular Science and Technology School of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China

Bisphenol A dicyanate ester resins modified by fluorine-containing liquid crystal compound(LCFE)are applied as polymer matrix(LCFE-BADCy),poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as rein-forcements,and fluorine/adamantane PBO precursor(pre FABPBO)as interfacial compatibilizer to prepare the corresponding PBO fibers/FABPBO/LCFE-BADCy wave-transparent laminated *** could improve the order degree of BADCy cured network,in favor of enhancing the wave-transparent perfor-mance,mechanical properties,and intrinsic thermal *** dielectric constant and dielectric loss of PBO fibers/FABPBO/LCFE-BADCy composites are highly temperature(25–200℃)and frequency(10^(4)–10^(7) Hz and 8.2–12.4 GHz)stable with the value of 2.49 and 0.003 under 10^(6) Hz at 25℃,and the corresponding wave transmission efficiency is 95.0%,higher than that of 92.5%for PBO fibers/BADCy *** interlamellar shear strength and flexural strength are respectively 50.7 MPa and 682.5 MPa,38.1%and 16.2%higher than those of PBO fibers/BADCy ***,the volume resistivity,breakdown voltage,heat resistance index,glass transition temperature,flame retardant grade,and ul-timate oxygen index of PBO fibers/FABPBO/LCFE-BADCy composites are respectively 5.3×10^(15)Ωcm,29.75 kV/mm,217.2℃,245.7℃,V-1 grade,and 33.6%,expected to be performed as a new generation of“lightweight/loading/wave-transparent”electromagnetic window materials in advanced military weapons and civil communication base station.

关键词： Bisphenol A dicyanate ester(BADCy)resins Fluorine-containing liquid crystal compound Poly(p-phenylene-2,6-benzobisoxazole) (PBO)fibers Fluorine/adamantane PBO precursor Wave-transparent laminated composites

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Effect of mechanical anisotropy on material removal rate and surface quality during polishing CdZnTe wafers

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Rare Metals 2011年第4期30卷 381-386页

作者： LI Yan JIE Wanqi KANG Renke GAO Hang State Key laboratory of Solidification Processing Northwestern Polytechnical University Xi＇an 710072 China Key Laboratory for Precision and Non-Traditional Machining Technology （Ministry of Education of China） Dalian University of Technology Dalian 116024 China

The mechanical characters of CdZnTe crystal were investigated by nanoscratch tests, and the effects of mechanical anisotropy on the material removal rate and surface quality were studied by polishing tests. There is a peak of frictional coefficient at the early stage of scratch, and increasing the vertical force will result in the increase of peak value correspondingly. The fluctuation phenomenon of frictional coefficient is generated at high vertical force. The lateral forces show the apparent twofold and threefold symmetries on （110） and （111） planes, respectively. To obtain high surface quality, low polishing pressure and hard direction （〈 T10 〉 directions on （110） plane and 〈 112 〉 directions on （111） plane） should be selected, and to achieve high material removal rate, high polishing pressure and soft direction （〈001〉 directions on （110） plane and 〈 121 〉 directions on （111） plane） should be selected.

关键词： cadmium compounds single crystals nanoscratch tests frictional coefficient material removal rate surface quality anisotropy

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Branched Fluorine/Adamantane Interfacial Compatibilizer for PBO Fibers/Cyanate Ester Wave-Transparent Laminated Composites

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Chinese Journal of Chemistry 2023年第8期41卷 939-950页

作者： Zheng Liu Xiaoli Fan Muyi Han Hao Li Junliang Zhang Lixin Chen Qiju Zhu Junwei Gu Shaanxi Key Laboratory of Macromolecular Science and Technology School of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi'anShaanxi710072 China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'anShaanxi710072 China Queen Mary University of London Engineering School Northwestern Polytechnical UniversityXi'anShaanxi710072 China Xi'an Modern Control Technology Research Institute Xi'anShaanxi710068 China

Comprehensive Summary Branched fluorine/adamantane PBO precursor(preFABPBO),synthesized via random co-condensation between 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoro propane,1,3-adamantanedicarbonyl dichloride,and trimesoyl chloride,is performed as interfacial compatibilizer,bisphenol A dicyanate ester(BADCy)resin as polymer matrix,and poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as reinforcements to prepare PBO fibers/FABPBO-BADCy wave-transparent laminated composites by high temperature *** mechanical properties,wave-transparent performances,and heat resistances of PBO fibers/BADCy composites are simultaneously improved by the addition of *** interlaminar shear strength(ILSS)and flexural strength of PBO fibers/FABPBO-BADCy composites are 48.9 and 665.3 MPa,respectively,increased by 33.2%and 13.3%compared to those of PBO fibers/BADCy composites(36.7 and 587.4 MPa).The dielectric constant and dielectric loss values at 106 Hz are 2.53 and 0.003,respectively,lower than those of PBO fibers/BADCy composites(3.06 and 0.006),and the corresponding wave transmission efficiency is 94.8%,which also presents excellent stability over the wide temperature(25-200℃)and frequency range(103-107 Hz and 8.2-12.4 GHz).Meanwhile,the heat resistance index and glass transition temperature are 229.9℃and 247.5℃,also better than those of PBO fibers/BADCy composites(229.6℃and 247.1℃).

关键词： Polymers Interface Materials science Mechanical properties Wave-transparent laminated composites

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Large electric field-induced strain in the novel BNKTAN-BNBLTZ lead-free ceramics

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Journal of Materials Science & Technology 2020年第10期42卷 15-22页

作者： Chao Wang Qiang Li Weiming Zhang Huiqing Fan State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China

(1-x)Bi0.5(Na0.82K0.18)0.5Ti0.96(Al0.5Nb0.5)0.04O3-xBi0.46Na0.46Ba0.5La0.02Ti0.97Zr0.03O3 lead-free ceramics(abbreviated as BNKTAN-100x BNBLTZ)was prepared by the conventional solid *** patterns and EDS spectrums revealed that a stable solid solution had been formed between BNBLTZ and *** the introduction of BNBLTZ anti-ferroelectric content,BNKTAN relaxor ferroelectrics exhibited the excellent field-induced-strain for x=0.04 corresponding to electric field-induced strain S^0.505%and normal strain d33*~777 pm/V at 65 kV/*** large strain response was attributed to the emergence of PNRs in the relaxation ***,an excellent fatigue resistance performance was obtained within 105cycles(S=0.505%–0.495%and d33*=777–758 pm/V,65 kV/cm).It suggested that prepared ceramics had the great potential to strain sensor and actuators.

关键词： BNT-based ceramics Ferroelectric properties Strain Fatigue resistance

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Continuous droplet rebound on heated surfaces and its effects on heat transfer property: A lattice Boltzmann study

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Chinese Physics B 2021年第4期30卷 351-360页

作者： Qing-Yu Zhang Qi-Peng Dong Shan-Lin Wang Zhi-Jun Wang Jian Zhou Shagang School of Iron and Steel Soochow UniversitySuzhou 215137China State Key Laboratory of Environmental-Friendly Energy Materials School of Materials Science and EngineeringSouthwest University of Science and TechnologyMianyang 621010China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an 710072China

A thermal multiphase lattice Boltzmann(LB) model is used to study the behavior of droplet impact on hot surface and the relevant heat transfer *** validating the correctness of the codes through the D^(2) law,the simulations of intrinsic contact angle and the temperature-dependent surface tension are *** LB model is then used to simulate the droplet impact on smooth and micro-hole heated *** the smooth surface,the impinging droplet is reluctant to rebound,unless the intrinsic wettability of the solid surface is fairly *** the micro-hole surface,however,the micro-holes provide favorable sites for generating a high-pressure vapor cushion underneath the impinging droplet,which thereby facilitates the continuous droplet *** the continuously rebounding *** time evolution of volume and temperature display obvious *** achievable height of the rebounding droplet increases as the intrinsic wettability of the solid surface becomes better,and the maximum transient heat flux is found to be directly proportional to the droplet rebounding *** a certain time interval,the continuous rebounding behavior of the droplet is favorable for enhancing the total heat quantity/heat transfer efficiency,and the influence of intrinsic wettability on the total heat during droplet impingement is greater than that of the *** LB simulations not only present different states of droplets on hot surfaces,but also guide the design of the micro-hole surface with desirable heat transfer properties.

关键词： droplet rebound heat transfer droplet impact lattice Boltzmann model

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Study on lattice vibrational properties and Raman spectra of Bi_2Te_3 based on density-functional perturbation theory

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Chinese Physics B 2014年第8期23卷 420-425页

作者：冯松科李双明傅恒志 State Key Laboratory of Solidification Processing Northwestern Polytechnical University (NPU)

We present a variational density-functional perturbation theory （DFPT） to investigate the lattice dynamics and vibra- tional properties of single crystal bismuth telluride material. The phonon dispersion curves and phonon density of states （DOS） of the material were obtained. The phonon dispersions are divided into two fields by a phonon gap. In the lower field, atomic vibrations of both Bi and Te contribute to the DOS. In the higher field, most contributions come from Te atoms. The calculated Born effective charges and dielectric constants reveal a great anisotropy in the crystal. The largest Born effective charge generates a significant dynamic charge transferring along the c axis. By DFPT calculation, the greatest LO-TO splitting takes place in the infrared phonon modes and reaches 1.7 THz in the Brillouin zone center. The Raman spectra and peaks corresponding to respective atomic vibration modes were found to be in good agreement with the experimental data.

关键词： density-functional perturbation theory Bi2Te3 material lattice vibrational properties Raman spectra

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Effects of Y_2O_3/Y on Si-B co-deposition coating prepared through HAPC method on pure molybdenum

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Journal of Rare Earths 2016年第9期34卷 952-957页

作者：田晓东郭喜平孙志平李梅王利捷 State Key Laboratory of Solidification Processing Northwestern Polytechnical University School of Materials Science and Engineering Chang'an University

In order to clarify the effects of reactive element Y on the properties of Si-B co-deposition coating on Mo substrate, the Si-B-Y2O3 and Si-B-Y co-deposition coatings were prepared at 1300 ℃ for 5 h by using the pack mixtures 16Si-4B-xY2O3/Y- 4NaF-（76–x）Al2O3 （wt.%,x=0, 0.5, 1, 2, 4, 8）. X-ray diffraction （XRD）, energy dispersive spectroscopy （EDS） and wavelength dis-persive spectroscopy （WDS） techniques were used to analyze the structure and oxidation behavior of these coatings. The results re-vealed that the Si-B-Y2O3 and Si-B-Y co-deposition coatings had the same structure with that of the Si-B co-deposition coating. However, Y was incorporated into these coatings and the thicknesses of these coatings were thicker than that of the Si-B co-deposition coating. In addition, the Si-B-Y co-deposition coating demonstrated better cyclic oxidation resistance than the Si-B co-deposition coating at 1100 ℃. The modifying mechanism of Y on the Si-B co-deposition coating was discussed.

关键词： molybdenum reactive element Si-B co-deposition coating oxidation rare earths

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Effects of SiC amount on phase compositions and properties of Ti_3SiC_2-based composites

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Journal of Central South University 2015年第1期22卷 14-22页

作者：蔡艳芝殷小玮尹洪峰 College of Materials & Mineral Resources Xi'an University of Architecture and Technology State Key Laboratory of Solidification Processing (Northwestern Polytechnical University)

The phase compositions and properties of Ti3SiC2-based composites with SiC addition of 5%-30% in mass fraction fabricated by in-situ reaction and hot pressing sintering were studied. SiC addition effectively prevented TiC synthesis but facilitated SiC synthesis. The Ti3SiC2/Ti C-SiC composite had better oxidation resistance when SiC added quantity reached 20% but poorer oxidation resistance with SiC addition under 15% than Ti3SiC2/TiC composite at higher temperatures. There were more than half of the original SiC and a few Ti3SiC2 remaining in Ti3SiC2/Ti C-SiC with 20% SiC addition, but all constituents in Ti3Si2/TiC composite were oxidized after 12 h in air at 1500 °C. The oxidation scale thickness of TS30, 1505.78 μm, was near a half of that of T,2715 μm, at 1500 °C for 20 h. Ti3SiC2/Ti C composite had a flexural strength of 474 MPa, which was surpassed by Ti3SiC2/TiC-SiC composites when SiC added amount reached 15%. The strength reached the peak of 518 MPa at 20% SiC added amount.

关键词： in-situ reaction composites oxidation mechanical properties

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Misorientation dependent thermal condition-solute field cooperative effect on competitive grain growth in the converging case during directional solidification of a nickel-base superalloy

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Journal of Materials Science & Technology 2022年第1期96卷 151-159页

作者： X.B.Meng J.G.Li C.N.Jing J.D.Liu S.Y.Ma J.J.Liang C.W.Zhang M.Wang B.T.Tang T.Lin J.L.Chen X.L.Zhang Q.Li School of Mechanical and Automotive Engineering Qilu University of Technology(Shandong Academy of Sciences)Jinan 250353China Institute of Metal Research Chinese Academy of SciencesShenyang110016China School of Materials Science and Engineering Shandong Jianzhu UniversityJinan 250014China AECC Shenyang Liming Aero-Engine Co. LTD.Shenyang110043China College of Material Science and Engineering North Minzu UniversityYinchuan 750021China Faculty of electro-mechanical information Weifang University of Science and TechnologyShouguang262700China

Nowadays,thermal condition and solute field are considered as the potential dominant factors controlling competitive grain growth during directional solidification ***,the controlling modes and critical conditions of competitive grain growth have been drastically debated over the past two *** this work,thermal condition and solute field are combined to study the competitive grain growth in the converging case by experimental observation and numerical simulation of bicrystal *** find the competitive grain growth is controlled by the cooperative effect of thermal condition and solute field,and the controlling modes are related to the bicrystal misorientation between favorably and unfavorably oriented *** the unfavorably oriented grain is low misoriented,unfavorably oriented grain dominates grain selection,and the competitive grain growth performs as solute field ***,with the increase of unfavorably oriented grain’s misorientation,the grain selection converts into favorably oriented grain domination,and the competitive grain growth changes to thermal condition *** explain these abnormal transformation phenomena,we propose a misorientation dependent thermal condition-solute field cooperative domination model and identify the critical conditions by a critical misorientation(θ_(cm)).According to dynamic equation of dendrite growth,we calculate the critical misorientationθ;to prove this *** theoretical calculation results agree well with the experimental results.

关键词： Competitive grain growth Cooperative effect Thermal condition Solute field Critical misorientation Unusual overgrowth Abnormal transformation

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Influence of mechanical reduction amount on internal quality of continuous casting billets by thermal and numerical simulation

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Journal of Iron and Steel Research International 2023年第6期30卷 1234-1243页

作者： Dan-qing Jiang Shu-jian Sun Han Wu Yang-jian Xu Fu-hai Zhu Zhen-qiang Zhang Jiang Wang Zhong-ming Ren School of Materials Science and Engineering Shanghai UniversityShanghai 200444China State Key Laboratory of Advanced Special Steel Shanghai UniversityShanghai 200444China

With establishment of thermal and numerical simulation models,the influence of reduction amount on solidification structure,segregation and shrinkage porosity of continuous casting(CC)billets was *** thermal–mechanical coupled simulation results indicated that with an increase in reduction amount,the temperature in the central area decreases,and the reduction efficiency firstly increases and then decreases,reaching the maximum value at reduction amount of 6 *** analysis showed that increasing the reduction amount is beneficial for the refinement of central solidification ***,the internal cracks are more likely to appear at higher reduction *** X-ray computerized tomography results revealed that a higher reduction amount can significantly reduce the volume fraction and equivalent diameter of the central shrinkage porosities of CC billets and increase the sphericity of ***,the macrosegregation of carbon along the central line is improved as the reduction amount increases;while the reduction amount exceeds 8 mm,the segregation degree will not change any more.

关键词： Mechanical reduction Solidification structure Porosity Thermal simulation Continuous casting billet

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