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ANTIOXIDANT DEPLETION AND OIT VALUES OF HIGH IMPACT PP STRANDS

Chinese Journal of Polymer Science 2009年第3期27卷 435-445页

作者： Werner W.Müller Ines Jakob Chunshan Li Renate Tatzky-Gerth federal Institute for materials research and testing(BAM) D-12200 BerlinGermany

The service life of a polyolefin product depends to large extent on the type and amount of the antioxidants added. During the manufacturing,storage and use of the product the antioxidants are depleted by physical processes and chemical degradation,and this impairs its long-term *** initial and in-use oxidation stability is often characterized and monitored by the measurement of the oxidative induction time(OIT),and service life predictions are based on the rate of decrease of the OIT *** study the correlation between the OIT value and the actual antioxidant concentration,eight random arrays of high-impact polypropylene(PP)strands stabilized using six different antioxidant packages(composed of Irgafos 168,Irganox 1010 and 1330,Chimassorb 944)were immersed in hot water(80℃and 90℃)and oven aged in air (80℃)for more than two years,and the change of OIT values and antioxidant concentrations was *** phosphitic and phenolic stabilizers water immersion is generally a more critical aging condition than oven aging in air,while for the hindered amine stabilizers(HAS)the opposite was *** expected,a linear correlation between OIT values and concentrations was found for the'classical'package of phosphitic and phenolic *** the case of Irganox 1330,the change of the OIT values during aging was considerably slower than the change of *** when zero concentration was reached according to the vanishing peak height in the chromatogram,a considerable OIT value was still *** may be due to unidentified degradation products of Irganox 1330 which still act as antioxidants in the long *** of HAS(Chimassorb 944)seems to enhance the initial OIT of stabilized phenolic samples and the long-term effectiveness of the phenolic stabilization under air oven aging ***,the marked long-term effectiveness of the HAS itself and the slow change with time of the concentration were not detectable by OIT measurements

关键词： Polypropylene Stabilizers Oxidative resistance Antioxidant depletion Oxidative induction time

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Printable Aligned Single-Walled Carbon Nanotube Film with Outstanding Thermal Conductivity and Electromagnetic Interference Shielding Performance

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Nano-Micro Letters 2022年第11期14卷 143-156页

作者： Zhihui Zeng Gang Wang Brendan F.Wolan Na Wu Changxian Wang Shanyu Zhao Shengying Yue Bin Li Weidong He Jiurong Liu Joseph W.Lyding Key Laboratory for Liquid-Solid Structural Evolution and Processing of materials Ministry of EducationSchool of Materials Science and EngineeringShandong UniversityShandongJinan 250061People’s Republic of China Department of Electrical and Computer Engineering Beckman Institute for Advanced Science and TechnologyUniversity of Illinois at Urbana-ChampaignUrbanaIL 61801USA Department of Chemistry Swiss Federal Institute of Technology in Zurich(ETH Zürich)8092 ZurichSwitzerland School of materials Science and Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore Empa Swiss Federal Laboratories for Materials Science and TechnologyÜberland Strasse 1298600 DübendorfSwitzerland Institute for Advanced Technology Shandong UniversityJinan 250061People’s Republic of China

Ultrathin,lightweight,and flexible aligned single-walled carbon nanotube(SWCNT)films are fabricated by a facile,environmentally friendly,and scalable printing *** aligned pattern and outstanding intrinsic properties render“metal-like”thermal conductivity of the SWCNT films,as well as excellent mechanical strength,flexibility,and ***,the aligned cellular microstructure promotes the electromagnetic interference(EMI)shielding ability of the SWCNTs,leading to excellent shielding effectiveness(SE)of~39 to 90 dB despite a density of only~0.6 g cm^(−3) at thicknesses of merely 1.5-24μm,*** ultrahigh thickness-specific SE of 25693 dB mm^(−1) and an unprecedented normalized specific SE of 428222 dB cm^(2)g^(−1) are accomplished by the freestanding SWCNT films,significantly surpassing previously reported shielding *** addition to an EMI SE greater than 54 dB in an ultra-broadband frequency range of around 400 GHz,the films demonstrate excellent EMI shielding stability and reliability when subjected to mechanical deformation,chemical(acid/alkali/organic solvent)corrosion,and high-/low-temperature *** novel printed SWCNT films offer significant potential for practical applications in the aerospace,defense,precision components,and smart wearable electronics industries.

关键词： Aligned film Single-walled carbon nanotube Lightweight Flexible Thermal conductivity Electromagnetic interference shielding

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Attenuation of ground vibrations due to different technical sources

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Earthquake Engineering and Engineering Vibration 2010年第3期9卷 337-344页

作者： L.Auersch S.Said federal Institute of Material research and testing

The attenuation of technically induced surface waves is studied theoretically and experimentally. In this paper, nineteen measurements of ground vibrations induced by eight different technical sources including road and rail traffic, vibratory and impulsive construction work or pile driving, explosions, hammer impulses and mass drops are described, and it is shown that the technically induced ground vibrations exhibit a power-law attenuation v - r ~ where the exponents q are in the range of 0.5 to 2.0 and depend on the source types. Comparisons performed demonstrate that the measured exponents are considerably higher than theoretically expected. Some potential effects on ground vibration attenuation are theoretically analyzed. The most important effect is due to the material or scattering damping. Each frequency component is attenuated exponentially as exp（-kr）, but for a broad-band excitation, the sum of the exponential laws also yields a power law but with a high exponent. Additional effects are discussed, for example the dispersion of the Rayleigh wave due to soil layering, which yields an additional exponent of 0.5 in cases of impulsive loading.

关键词： wave attenuation environmental vibrations field tests material damping scattering damping Rayleigh wave

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Simple and fast prediction of train-induced track forces,ground and building vibrations

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Railway Engineering Science 2020年第3期28卷 232-250页

作者： Lutz Auersch federal Institute of materials research and testing D-12200 BerlinGermany

A simple and fast prediction scheme is presented for train-induced ground and building *** models such as(one-dimensional)transfer matrices are used for the vehicle–track–soil interaction and for the building–soil *** wave propagation through layered soils is approximated by a frequency-dependent homogeneous *** prediction is divided into the parts“emission”(excitation by railway traffic),“transmission”(wave propagation through the soil)and“immission”(transfer into a building).The link between the modules is made by the excitation force between emission and transmission,and by the free-field vibration between transmission and *** formula for the simple vehicle–track,soil and building models are given in this *** behaviour of the models is demonstrated by typical examples,including the mitigation of train vibrations by elastic track elements,the low-and high-frequency cut-offs characteristic for layered soils,and the interacting soil,wall and floor resonances of multi-storey *** is shown that the results of the simple prediction models can well represent the behaviour of the more time-consuming detailed models,the finite-element boundary-element models of the track,the wavenumber integrals for the soil and the three-dimensional finite-element models of the *** addition,measurement examples are given for each part of the prediction,confirming that the methods provide reasonable *** the prediction models are fast in calculation,many predictions can be done,for example to assess the environmental effect along a new railway *** simple models have the additional advantage that the user needs to know only a minimum of ***,the prediction is fast and user-friendly,but also theoretically and experimentally well-founded.

关键词： Railway-induced vibration Ground vibration Layered soil Building response Excitation forces Track and vehicle irregularities

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Estimating emissions of HCFC-22 and CFC-11 in China by atmospheric observations and inverse modeling

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Science China Chemistry 2012年第10期55卷 2233-2241页

作者： AN XingQin HENNE Stephan YAO Bo VOLLMER Martin K. ZHOU LingXi LI Yan Chinese Academy of Meteorological Sciences China Meteorological AdministrationBeijing 100081China Empa Swiss Federal Laboratories for Materials Testing and ResearchAir Pollution and Environmental TechnologyDubendorf Switzerland

This paper presents the estimation of Chinese emissions of HCFC-22 and CFC-11 in 2009 by an inverse modeling method based on in-situ measurement data from the Shangdianzi Global Atmosphere Watch (GAW) Regional Station (SDZ) and atmospheric transport simulations. After inversion (a-posteriori) estimates of the Chinese emissions in 2009 increased by 6.6% for HCFC-22 from 91.7 (± 83.6) to 98.3 (± 47.4) kt/yr and by 22.5% for CFC-11 from 13 (±12.6) to 15.8 (±7.2) kt/yr compared to an a-priori emission. While the model simulation with a-priori emissions already captured the main features of the observed variability at the measurement site, the model performance (in terms of correlation and mean-square-error) improved using a-posteriori emissions. The inversion reduced the root-mean-square (RMS) error by 4% and 10% for HCFC-22 and CFC-11, respectively.

关键词： HCFC-22 CFC-11 排放量逆向建模大气观测中国估算模型模拟

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Yb-and Er concentration dependence of the upconversion luminescence of highly doped NaYF_(4):Yb,Er/NaYF_(4):Lu core/shell nanocrystals prepared by a water-free synthesis

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Nano research 2022年第10期15卷 9639-9646页

作者： Christian Würth Bettina Grauel Monika Pons Florian Frenzel Philipp Rissiek Kerstin Rücker Markus Haase Ute Resch-Genger federal Institute for materials research and testing(BAM) Division BiophotonicsRichard-Willstaetter-Str.1112489 BerlinGermany Institut für Chemie Neuer Materialien Fachbereich Biologie/ChemieUniversität OsnabrückBarbarastraße 749076 OsnabrückGermany

High sensitizer and activator concentrations have been increasingly examined to improve the performance of multi-color emissive upconversion(UC)nanocrystals(UCNC)like NaYF_(4):Yb,Er and first strategies were reported to reduce concentration quenching in highly doped *** luminescence(UCL)is,however,controlled not only by dopant concentration,yet by an interplay of different parameters including size,crystal and shell quality,and excitation power density(P).Thus,identifying optimum dopant concentrations requires systematic studies of UCNC designed to minimize additional quenching pathways and quantitative ***,we quantify the dopant concentration dependence of the UCL quantum yield(ΦUC)of solid NaYF_(4):Yb,Er/NaYF_(4):Lu upconversion core/shell nanocrystals of varying Yb3+and Er3+concentrations(Yb3+series:20%‒98%Yb3+;2%Er3+;Er3+series:60%Yb3+;2%‒40%Er3+).To circumvent other luminescence quenching processes,an elaborate synthesis yielding OH-free UCNC with recordΦUC of~9%and~25 nm core particles with a thick surface shell were *** Yb3+concentrations barely reduceΦUC from~9%(20%Yb3+)to~7%(98%Yb3+)for an Er3+concentration of 2%,thereby allowing to strongly increase the particle absorption cross section and UCNC *** an increased Er3+concentration reducesΦUC from~7%(2%Er3+)to 1%(40%)for 60%Yb3+.Nevertheless,at very high P(>1 MW/cm^(2))used for microscopic studies,highly Er3+-doped UCNC display a high brightness because of reduced *** findings underline the importance of synthesis control and will pave the road to many fundamental studies of UC materials.

关键词： highly doped upconversion nanocrystals core/shell nanoparticles upconversion luminescence efficiency NaYF_(4):Yb Er concentration quenching

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Interfacial assembly of two-dimensional MXenes

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Journal of Energy Chemistry 2021年第9期30卷 417-434页

作者： Chuanfang(John)Zhang Laboratory for Functional Polymers Swiss Federal Laboratories for Materials Science and Technology(Empa)ETH DomainUberlandstrasse 129CH-8600 DubendorfSwitzerland

Two-dimensional(2D) transition metal carbides, carbonitrides and nitrides, known as MXenes, are emerging quickly at the frontiers of 2D materials world. Their exotic properties such as the highest electrical conductivity among all solution-processed 2 D materials, the best electromagnetic interference shielding performance outperforming that of copper or aluminum at a nanoscale thickness, as well as the highest volumetric capacitance for pseudocapacitors, have been attracting extensive fundamental research and applications. Their unique surface chemistries, that is, hydrophilic groups terminated on the surface of MXenes after etching and delamination, enable plenty of opportunities for assembling into MXene building blocks. Particularly, assembling at liquid–liquid, liquid–solid, liquid–air, and solid–solid interfaces allows the efficient fabrication of various structures, including MXene surfactants, MXene heterostructures, MXene transparent films. Interfacial assembly of MXenes is of significance in unveiling more versatilities of MXenes as well as impacts on novel MXene-based architectures, based on which enhanced performance of devices is achieved. As such, this review focuses on the interfacial assembly of MXenes, explaining mechanisms behind various assembling and providing classical examples for corresponding interfacial assembling techniques. Applications of these as-assembled architectures are also discussed in brief. We believe this review may shed light on the interfacial chemistry of MXenes, thus guiding more efficient fabrication of MXene-based functional films/coatings/electrodes/devices.

关键词： Interfacial assembly MXene Interfacial tension Crosslinking Heterostructures

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testing and modelling of transient adhesion phenomena in rolling-sliding contacts

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Friction 2024年第5期12卷 1016-1027页

作者： Daniel KVARDA Alexander MEIERHOFER Klaus SIX Faculty of Mechanical Engineering Brno University of TechnologyBrno61669Czech Republic Virtual Vehicle research GmbH Graz8010Austria

Transient adhesion effects in rolling–sliding contacts influence all aspects of train–track *** is of high importance specifically when these effects result in critically low adhesion,which poses a risk to traction and braking of railway *** study presents a model that can replicate the transient changes of the coefficient of adhesion with tested water and solid particle *** experimental data for the model are measured using a commercial ball-on-disc *** experimental results showed a liquid reservoir in front of the contact area that slowly reduces in *** observation was used in the modelling approach to divide the calculation into two stages where the reservoir is present and when it *** model was able to reproduce the occurrence of low adhesion region seen in experimental results with different particle concentrations.

关键词： coefficient of adhesion tribology transient effects wheel-rail contact

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Thermochemical Treatment——Technologies for Recovery and Utilisation of materials

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过程工程学报 2006年第2期6卷 231-236页

作者： Gerd Kley Rudolf Brenneis Burkart Adamczyk Franz-Georg Simon Division Waste Treatment and Remedial Eng. Federal Inst. Materials Research and Testing BAM Berlin 12200 Germany

The arc furnace technology is an ideally suited process for the treatment of hazardous and problematic waste. The operation conditions of the furnace can be adapted for optimal transformation of the waste material input into raw materials and usable products. The process can significantly reduce the impact of contaminated wastes and industrial residues, and enable material conversion and separation. Thus, the products of the process have various applications. The capability of the process is illustrated with three examples, the treatment of bottom ash and filter ash from waste incineration plants, of stainless steel slags and of chromium-containing residues from the refractory industry.

关键词：热化学处理原料分离耐火材料不锈钢

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Dynamic track-soil interaction——calculations and measurements of slab and ballast tracks

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2021年第1期22卷 21-36页

作者： Lutz AUERSCH Samir SAID federal Institute of Material research and testing Berlin 12200Germany

The dynamic behaviour of slab and ballast tracks was investigated using measurements and *** impacts and train passages were analysed and measurements were made using geophones(velocity transducers)which had been time-integrated to *** calculations were carried out in the frequency-wavenumber domain for multi-beamon-continuous soil *** characteristics of the different tracks and track elements were established in theory and by *** frequency-dependent compliances(displacement transfer functions)showed clear rail-on-railpad resonances or highly damped track-soil *** to the rail and sleeper,the track slab had much lower *** slab track usually had the highest rail amplitudes due to soft *** passage yielded track displacements which were a superposition of the axle loads from the two neighbouring axles of a bogie and from the two bogies of two neighbouring *** global behaviour was characteristic of the track slab of the slab track,whereas the rails of the slab and the ballast tracks behaved more locally with only one bogie of *** measurements agreed very well with the theory of continuous soil in the case of the six measured slab tracks and acceptably well for the six measured ballast *** measurements allowed us to find appropriate model parameters and to check the *** example,the Winkler model of the soil was found to be less appropriate because it reacted more locally.

关键词： Slab track Ballast track Train passage Hammer impact Track-soil interaction

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