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Polyethylene glycol has immunoprotective effects on sciatic allografts, but behavioral recovery and graft tolerance require neurorrhaphy and axonal fusion

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Neural Regeneration Research 2025年第4期20卷 1192-1206页

作者： Tyler A.Smith liwen zhou Cameron l.Ghergherehchi Michelle Mikesh Cathy z.Yang Haley O.Tucker JuliAnne Allgood Jared S.bushman George D.bittner Department of Molecular biosciences University of Texas at AustinAustinTXUSA Department of Neuroscience University of Texas at AustinAustinTXUSA Division of Pharmaceutical Sciences University of WyomingLaramieWYUSA

behavioral recovery using(viable)peripheral nerve allografts to repair ablation-type(segmental-loss)peripheral nerve injuries is delayed or poor due to slow and inaccurate axonal ***,such peripheral nerve allografts undergo immunological rejection by the host immune *** contrast,peripheral nerve injuries repaired by polyethylene glycol fusion of peripheral nerve allografts exhibit excellent behavioral recovery within weeks,reduced immune responses,and many axons do not undergo Wallerian *** relative contribution of neurorrhaphy and polyethylene glycol-fusion of axons versus the effects of polyethylene glycol per se was unknown prior to this *** hypothesized that polyethylene glycol might have some immune-protective effects,but polyethylene glycol-fusion was necessary to prevent Wallerian degeneration and functional/behavioral *** examined how polyethylene glycol solutions per se affect functional and behavioral recovery and peripheral nerve allograft morphological and immunological responses in the absence of polyethylene glycol-induced axonal ***-type sciatic nerve injuries in outbred Sprague–Dawley rats were repaired according to a modified protocol using the same solutions as polyethylene glycol-fused peripheral nerve allografts,but peripheral nerve allografts were loose-sutured(loose-sutured polyethylene glycol)with an intentional gap of 1–2 mm to prevent fusion by polyethylene glycol of peripheral nerve allograft axons with host *** to negative control peripheral nerve allografts not treated by polyethylene glycol and in contrast to polyethylene glycol-fused peripheral nerve allografts,animals with loose-sutured polyethylene glycol peripheral nerve allografts exhibited Wallerian degeneration for all axons and myelin degeneration by 7 days postoperatively and did not recover sciatic-mediated behavioral functions by 42 days *** morphological signs of rejection,such as col

关键词： allograft rejection axotomy macrophage myelin nerve repair polyethylene glycol(PEG) sciatic nerve T cell transplantation Wallerian degeneration

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NUMERICAl SIMUlATION OF TEMPERATURE FIElDS IN ElECTROSlAG REMElTING SlAb INGOTS

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Acta Metallurgica Sinica(English letters) 2008年第4期21卷 253-259页

作者： l.z. Chang b.z. li Department of Metallurgical Technology Central Iron ＆ Steel Research Institute Beijing 100081 China

The method based on transient heat transfer model is adopted to simulate electro-slag remelting process. The calculated results of the model show that the process is in the quasi-steady state, and the shape of pool remains unchanged when the height of ingot is approximately 2.5-3 times the thickness of slab ingot. The change in the shape of pool is found to be strongly dependent on the pattern of melting rate, and hence, the power input; the depth of the molten pool increases with the increase in melting speed. It is concluded that a transient heat transfer model has to be used to obtain reliable input information for the entire, operatina time.

关键词： ESR Slab ingot Mathematical model Shape of molten metal pool

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Dispersion and Damage of Carbon Nanotubes in Carbon Nanotube/7055Al Composites During High-Energy ball Milling Process

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Acta Metallurgica Sinica(English letters) 2021年第2期34卷 196-204页

作者： S.bi b.l.Xiao z.H.Ji b.S.liu z.Y.liu z.Y.Ma Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China School of Material Science and Engineering University of Science and Technology of China72 Wenhua RoadShenyang 110016China AVIC Manufacturing Technology Institute Beijing 100024China

High-energy ball milling(HEbM)combined with powder metallurgy route was used to fabricate carbon nanotube(CNT)reinforced 7055 Al *** powder morphology evolution processes(HEbM-1 and HEbM-2)were designed to investigate the dispersion and damage of CNTs during HEbM ***-1 evolution process involved powder fl attening,cold-welding and fracture,while HEbM-2 evolution process consisted of powder fl attening and *** HEbM-1,the repetitive fracture and cold-welding process was effective for dispersing ***,the powder fl attening process in HEbM-2 was unsuccessful in dispersing CNTs due to two reasons:(1)the thickness of fl aky Al powders exceeded the critical value,and(2)the clustered CNTs embedded in fl aky Al powders could not be *** of the broadening of D band and the appearance of a new defect-related D’band,product of I D/I G and full width half maximum of D band,rather than I D/I G,was used to evaluate the actual damage of *** indicates that the damage of CNTs was severe in powder fl attening and fracture stages,while the damage of CNTs was small in powder cold-welding stage.

关键词： Metal matrix composites Carbon nanotubes Powder evolution Dispersion and damage Powder metallurgy

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Evolution of the Microstructure and Strength in the Nugget zone of Friction Stir Welded SiCp/Al-Cu-Mg Composite

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Journal of Materials Science & Technology 2014年第1期30卷 54-60页

作者： D.Wang b.l.Xiao Q.z.Wang z.Y.Ma Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences University of Science and Technology of China

A 6 mm-thick SiCp/2009AI composite plate was successfully joined by friction stir welding （FSW） using an ultrahard material tool to investigate the evolution of the microstructure and the strength in the nugget zone （Nz）. While some SiC particles were broken up during FSW, most of them rotated in the matrix. large compound particles on the interfaces were broken off during FSW, whereas the amorphous layer and small compound particles remained on the interfaces. The dynamically recrystallized AI grains nucleated on the surface of fractured SiC particles during FSW, forming nano-sized grains around the SiC particles. The yield strength of the Nz decreased slightly due to the variation in the size, shape, and distribution of the SiC particles. The clean interfaces were beneficial to the load transfer between SiC particles and AI matrix and then increased the ultimate tensile strength of the Nz.

关键词： Metal-matrix composites Friction stir welding Microstructure Mechanical properties

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High-Speed Friction Stir Welding of T6-Treated b4Cp/6061Al Composite

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Acta Metallurgica Sinica(English letters) 2020年第1期33卷 67-74页

作者： Y.z.li Y.N.zan Q.z.Wang b.l.Xiao z.Y.Ma Key laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China University of Science and Technology of China Shenyang 110016China

T6-treated 20 wt% b4 Cp/6061 Al sheets were joined under welding speeds of 400–1200 mm/min by friction stir welding(FSW) with a threaded cermet pin. The macro-defect-free FSW joints could be achieved at high welding speeds up to 1200 mm/min, but larger plunge depth was required at the welding speeds of 800 and 1200 mm/min to eliminate the tunnel defect. In the nugget zone(Nz) of the joints, the b4 C particles were broken up and uniformly redistributed. The Nz exhibited lower hardness than the base metal(bM), and the hardness value almost did not change with increasing welding speed, attributable to the dissolution of precipitates. Compared with the bM, the joints showed lower tensile strength. As the welding speed increased from 400 to 800 mm/min, the joint efficiencies were nearly the same and up to ~ 73%. When the welding speed increased up to 1200 mm/min, the tensile strength significantly decreased, due to the occurrence of kissing bond defect at the bottom of the Nz. With increasing welding speed, the fracture location of the joints transferred gradually from the heat-affected zone to the Nz due to the kissing bond defects.

关键词： Metal-matrix composites Microstructures Mechanical properties Friction stir welding High-speed welding

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Effect of Carbon Nanotube Orientation on Mechanical Properties and Thermal Expansion Coefficient of Carbon Nanotube-Reinforced Aluminum Matrix Composites

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Acta Metallurgica Sinica(English letters) 2014年第5期27卷 901-908页

作者： z.Y.liu b.l.Xiao W.G.Wang z.Y.Ma School of Materials Science and Engineering Dalian University of Technology Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences School of Mechanical Engineering Liaoning Shihua University

Carbon nanotube-reinforced 2009Al （CNT/2009Al） composites with randomly oriented CNTs and aligned CNTs were fabricated by friction stir processing （FSP） and FSP-rolling, respectively. The CNT/2009A1 composites with aligned CNTs showed much better tensile properties at room temperature and elevated temperature compared with those with the randomly oriented CNTs, which is mainly attributed to larger equivalent aspect ratio of the CNTs and avoidance of preferential fracture problems. However, much finer grain size was not beneficial to obtaining high strength above 473 K. The aligned CNTs resulted in tensile anisotropy, with the best tensile properties being achieved along the direction of CNT aligning. As the off-axis angle increased, the tensile properties were reduced due to the weakening of the load transfer ability. Furthermore, aligned CNTs resulted in much lower coefficient of thermal expansion compared with randomly oriented CNTs.

关键词： Carbon nanotubes Metal matrix composites Mechanical properties Coefficient of thermalexpansion Friction stir processing

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Tensile Strength and Electrical Conductivity of Carbon Nanotube Reinforced Aluminum Matrix Composites Fabricated by Powder Metallurgy Combined with Friction Stir Processing

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Journal of Materials Science & Technology 2014年第7期30卷 649-655页

作者： z.Y.liu b.l.Xiao W.G.Wang z.Y.Ma Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences Dalian University of Technology liaoning Shihua University

A route combining powder metallurgy and subsequent friction stir processing was utilized to fabricate carbon nanotube （CNT） reinforced AI （CNT/AI） and 6061AI （CNT/6061AI） composites. Microstructural observations indicated that CNTs were uniformly dispersed in the matrix in both CNT/AI and CNT/6061AI composites. Mg and Si elements tended to segregate at CNT-AI interfaces in the CNT/6061AI composite during artificial aging treatment. The tensile properties of both the AI and 6061AI were increased by CNT incorporation. The electrical conductivity of CNT/AI was decreased by CNT addition, while CNT/6061AI exhibited an increase in electrical conductivity due to the Mg and Si segregation.

关键词： Carbon nanotubes Metal matrix composites Mechanical properties Electrical properties Friction stir processing

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Achieving large-area bulk Ultrafine Grained Cu via Submerged Multiple-pass Friction Stir Processing

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Journal of Materials Science & Technology 2013年第12期29卷 1111-1115页

作者： P. Xue b.l. Xiao z.Y. Ma Shenyang National laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences 72 Wenhua Road Shenyang 110016 China

large-area bulk ultrafine grained （UFG） pure Cu was successfully prepared by multiple-pass overlapping friction stir processing （FSP） under additional rapid cooling. Overlapping FSP did not exert a significant effect on the microstructure and mechanical properties of the FSP UFG Cu. Similar average grain size was achieved in the transitional zone （Tz） of the multiple-pass FSP sample compared to that in the nugget zone of the single-pass FSP sample, and the Tz exhibited a strong {111}（112） type A fiber shear texture, Very weak softening occurred in the Tz of the multiple-pass FSP UFG Cu, resulting in a relatively uniform hardness distribution throughout the whole processed zone. A high yield strength of - 310 MPa and a uniform elongation of - 13% were achieved in the bulk FSP UFG Cu. This study provides an effective strategy to prepare large-area bulk IUFG materials.

关键词： Friction stir processing Multiple-pass Ultrafine grains Microstructure Mechanical properties

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Constitutive equation and model validation for a 31 vol.% b_4Cp/6061Al composite during hot compression

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Journal of Materials Science & Technology 2018年第10期34卷 1730-1738页

作者： l. zhou C. Cui Q.z. Wang C. li b.l. Xiao z.Y. Ma Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Electromechanical and Vehicle Engineering Yantai University Yantai 264005 China School of Mechanical Engineering Shenyang Ligong University Shenyang 110159 China Nuclear and Radiation Safety Center Ministry of Environmental Protection Beijing 100082 China

An accurate constitutive equation is essential to understanding the flow behavior of b4C/A1 compos-ites during the hot deformation. However, the constitutive equations developed previously in literature are generally for low strain rate deformation. In the present work, we modified the general consti-tutive equation and take the high strain rate correction into account. The constitutive equation for a 31 vol.% b4Cp/6061AI composite was constructed based on the flow stresses measured during isothermal hot compression at temperatures ranging from 375 to 525 ℃ and strain rates from 0.01 to 10 s^-1. The experimental flow stresses were corrected by considering temperature-dependent Arrhenius factor. The modified equation was then verified by using DEFORM-3D finite element analysis to simulate the exper-imental hot compression process. The results show that the modified equation successfully predicts flow stress, load-displacement, and the temperature rise. This helps to optimize the hot deformation process, and to obtain desirable properties, such as reduced porosity and homogenous particle distribution in b4C/AI composites.

关键词： Composites b4C/AI Constitutive equation Hot compression Finite element simulation

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Diffusion behavior of Cr in gradient nanolaminated surface layer on an interstitial-free steel

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Journal of Materials Science & Technology 2019年第3期35卷 460-464页

作者： S.l.Xie z.b.Wang K.lu Shenyang National laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences School of Materials Science and Engineering University of Science and Technology of China

Nanolaminated structures composed of low-angle grain boundaries(lAGbs) possess high thermal stability. In this paper, a gradient nanolaminated(GNl) surface layer with smooth finish was fabricated on an interstitial-free steel by means of surface mechanical rolling treatment. Microstructural observations demonstrated that the average lamellar thickness is about 80 nm in the topmost surface layer and increases with increasing depth. High thermal stability was confirmed in the GNl surface layer after annealing at 500℃. Diffusion measurements showed that effective diffusivity of Cr in GNl layer is 4–6 orders of magnitude higher than lattice diffusivity within the temperature range from 400 to 500℃. This might be attributed to numerous lAGbs or dislocation structures with a higher energy state in the GNl surface layer. This work demonstrates the possibility to advanced chromizing(or other surface alloying)processes of steels with formation of GNl surface layer, so that a thicker alloyed surface layer with a stable nanostructure is achieved.

关键词： Gradient nanolaminated structure Interstitial-free steel Diffusion low-angle grain boundary Surface mechanical rolling treatment

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