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Mechanisms behind the environmental sensitivity of carbon fiber reinforced polytetrafluoroethylene(PTFE)

Friction 2024年第5期12卷 997-1015页

作者： Pontus JOHANSSON P.MARKLUND M.BJORLING Y.SHI Division of Machine Element LuleåUniversity of TechnologyLuleåSE-97187Sweden

Carbon fiber reinforced polytetrafluoroethylene (CF/PTFE) composites are known for their exceptional tribological performance when sliding against steel or cast iron in inert gas environments. Compared to experiments in humid air, about an order of magnitude lower wear rate and several times lower coefficient of friction have been reported for tests conducted in dry nitrogen and hydrogen. Moreover, trace moisture has been shown to affect the friction and wear significantly of this tribosystem, although a possible effect of oxygen cannot be ruled out due to uncertainties regarding the oxygen concentrations. While several studies have pointed out the environmental sensitivity of CF/PTFE, the understanding of the underlying mechanisms are very limited. The objective of this research is to investigate the individual and combined effect of oxygen and moisture on the tribological behavior of CF/PTFE sliding against steel. Additionally, this study aims to elucidate the underlying mechanisms that govern the environmental sensitivity of the system. Climate-controlled three-pin-on-disc experiments were conducted in nitrogen atmospheres at various concentrations of oxygen and moisture. The tribological results clearly demonstrate that both moisture and oxygen contribute to increased friction and wear. However, the adverse effect was much more pronounced for oxygen than moisture. A qualitative method was developed to estimate the tribofilm coverage on the CF/PTFE surface. Results showed strong correlation between high coverage of strongly adhered tribofilm and low wear rate. Moreover, a loosely adhered tribofilm was observed on top of the CF/PTFE surface in presence of moisture. FTIR analysis indicated that the loosely adhered tribofilm found in the moisture-enriched environment contained a significant amount of adsorbed water, which may explain the lower coefficient of friction in presence of moisture compared to oxygen. The adsorbed water in the loosely adhered tribofilm coul

关键词： polymer composite tribofilm tribochemistry atmosphere

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New approach for particle size and shape analysis of iron-based oxygen carriers at multiple oxidation states

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Particuology 2024年第7期90卷 493-503页

作者： Victor Purnomo Marcelo Dal Belo Takehara Robin Faust Lidiya Abdisa Ejjeta Henrik Leion Division of Energy and Materials Department of Chemistry and Chemical EngineeringChalmers University of TechnologyGöteborg 41258Sweden Division of Energy Science Department of Engineering Sciences and MathematicsLuleåUniversity of TechnologyLuleå97187Sweden

One of the crucial issues in the chemical looping technology lies in its bed material:the oxygen *** size analysis of an oxygen carrier is important since in a fluidized bed the material can only work well within a specific size *** the favorable size ranges for oxygen carrier materials have already been reported,none of the published studies has analyzed the particle size and shape of oxygen carriers in ***,the effect of oxygen carriers'oxidation degree on such properties has not been considered *** study aimed to report the particle size and shape analysis of five iron-based oxygen carriers,one natural ore,one synthetic material,and three residue products,at different oxidation degrees using dynamic image analysis(DIA).The oxygen carriers were prepared at different mass conversion degrees in a fluidized bed batch *** size distribution,sphericity,and aspect ratio of the oxygen carrier particles were examined experimentally using a Camsizer *** results show that the DIA method was successfully able to analyze the particle size and shape of our oxygen carriers with satisfying accuracy for *** oxidation state of the investigated materials seems to only affect the particle size and shape of oxygen carriers to a minor ***,exposures to redox cycles in a fluidized bed reactor may alter the particle size and shape of most oxygen carriers.

关键词： Oxygen carrier Size and shape analysis Dynamic image analysis Oxidation state Fluidized bed Chemical looping

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Theoretical analysis and engineering application of controllable shock wave technology for enhancing coalbed methane in soft and low‑permeability coal seams

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International Journal of Coal Science & Technology 2024年第2期11卷 123-142页

作者： Guodong Qiao Zegong Liu Yongmin Zhang Changping Yi Kui Gao Shigui Fu Youzhi Zhao School of Safety Science and Engineering Anhui University of Science and TechnologyHuainan 232001AnhuiChina Institute of Energy Hefei Comprehensive National Science CenterHefei 230031AnhuiChina School of Electrical Engineering Xi’an Jiaotong UniversityXi’an 710049ShanxiChina Division of Mining and Geotechnical Engineering LuleåUniversity of TechnologyLuleåSweden

Coalbed methane(CBM)is a significant factor in triggering coal and gas outburst disaster,while also serving as a clean *** the increasing depth of mining operations,coal seams that exhibit high levels of gas content and low permeability have become increasingly *** controllable shockwave(CSW)technology has proven effective in enhancing CBM in laboratory settings,there is a lack of reports on its field applications in soft and low-permeability coal *** study establishes the governing equations for stress waves induced by *** numerical inversion was employed to analyse the dynamic response of the coal seam during CSW ***,quantitative calculations were performed for the crushed zone,fracture zone,and effective CSW influence range,which guided the selection of field test *** results of the field test unveiled a substantial improvement in the gas permeability coefficient,the average rate of pure methane flowrate,and the mean gas flowrate within a 10 m radius of the antireflection *** enhancements were notable,showing increases of 3 times,13.72 times,and 11.48 times,***,the field test performed on the CSW antireflection gas extraction hole cluster demonstrated a noticeable improvement in CBM *** antireflection,the maximum peak gas concentration and maximum peak pure methane flow reached 71.2%and 2.59 m^(3)/min,*** findings will offer valuable guidance for the application of CSW antireflection technology in soft and low-permeability coal seams.

关键词： CSW antireflection in coal seams CBM extraction enhancement Soft and low-permeability coal seams Field test

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A stable implicit nodal integration-based particle finite element method(N-PFEM)for modelling saturated soil dynamics

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第6期16卷 2172-2183页

作者： Liang Wang Xue Zhang Jingjing Meng Qinghua Lei Department of Earth Sciences ETH ZürichZürich8092Switzerland Department of Civil Engineering and Industrial Design University of LiverpoolLiverpoolL693BXUK Department of Civil Environmental and Natural Resources EngineeringLuleåUniversity of TechnologyLuleå97187Sweden Department of Earth Sciences Uppsala UniversityUppsala75105Sweden

In this study,we present a novel nodal integration-based particle finite element method(N-PFEM)designed for the dynamic analysis of saturated *** approach incorporates the nodal integration technique into a generalised Hellinger-Reissner(HR)variational principle,creating an implicit PFEM *** mitigate the volumetric locking issue in low-order elements,we employ a node-based strain smoothing *** discretising field variables at the centre of smoothing cells,we achieve nodal integration over cells,eliminating the need for sophisticated mapping operations after re-meshing in the *** express the discretised governing equations as a min-max optimisation problem,which is further reformulated as a standard second-order cone programming(SOCP)***,pore water pressure,and displacements are simultaneously determined using the advanced primal-dual interior point ***,our numerical model offers improved accuracy for stresses and pore water pressure compared to the displacement-based PFEM *** experiments demonstrate that the N-PFEM efficiently captures both transient and long-term hydro-mechanical behaviour of saturated soils with high accuracy,obviating the need for stabilisation or regularisation techniques commonly employed in other nodal integration-based PFEM *** work holds significant implications for the development of robust and accurate numerical tools for studying saturated soil dynamics.

关键词： Particle finite element method Nodal integration Dynamic saturated media Second-order cone programming(SOCP)

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Evolution of nonmetallic inclusions in 80-t 9CrMoCoB large-scale ingots during electroslag remelting process

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1525-1539页

作者： Shengchao Duan Min Joo Lee Yao Su Wangzhong Mu Dong Soo Kim Joo Hyun Park School of Mechanical and Materials Engineering North China University of TechnologyBeijing 100144China Department of Materials Science and Chemical Engineering Hanyang UniversityAnsan 15588Rep.of Korea Department of Materials Science and Engineering KTH Royal Institute of TechnologyBrinellvägen 23Stockholm 10044Sweden Department of Engineering Science and Mathematics Division of Materials ScienceLuleåUniversity of Technology97187 LuleåSweden Casting&Forging Business Unit Nuclear Business GroupDoosan EnerbilityChangwon 51711Rep.of Korea

In combination with theoretical calculations,experiments were conducted to investigate the evolution behavior of nonmetallic inclusions(NMIs)during the manufacture of large-scale heat-resistant steel ingots using 9CrMoCoB heat-resistant steel and CaF_(2)–CaO–Al_(2)O_(3)–SiO_(2)–B_(2)O_(3)electroslag remelting(ESR)-type slag in an 80-t industrial ESR *** main types of NMI in the consumable electrode comprised pure alumina,a multiphase oxide consisting of an Al_(2)O_(3)core and liquid CaO–Al_(2)O_(3)–SiO_(2)–MnO shell,and M_(23)C_(6)carbides with an MnS *** Al_(2)O_(3)and MnS inclusions had higher precipitation temperatures than the M_(23)C_(6)-type carbide under equilibrium and nonequilibrium solidification ***,inclusions can act as nucleation sites for carbide layer *** ESR process completely removed the liquid CaO–Al_(2)O_(3)–SiO_(2)–MnO oxide and MnS inclusion with a carbide shell,and only the Al_(2)O_(3)inclusions and Al_(2)O_(3)core with a carbide shell occupied the remelted *** M_(23)C_(6)-type carbides in steel were determined as Cr_(23)C_(6)based on the analysis of transmission electron microscopy *** substitution of Cr with W,Fe,or/and Mo in the Cr_(23)C_(6)lattice caused slight changes in the lattice parameter of the Cr_(23)C_(6)***,Cr_(21.34)Fe_(1.66)C_(6),(Cr_(19)W_(4)C_(6),Cr_(18.4)Mo_(4.6)C_(6),and Cr_(16)Fe_(5)Mo_(2)C_(6)can match the fraction pattern of Cr_(23)C_(6)*** Al_(2)O_(3)inclusions in the remelted ingot formed due to the reduction of CaO,SiO_(2),and MnO components in the liquid *** increased Al content in liquid steel or the higher supersaturation degree of Al_(2)O_(3)precipitation in the remelted ingot than that in the electrode can be attributed to the evaporation of CaF_(2)and the increase in CaO content in the ESR-type slag.

关键词： nonmetallic inclusion heat-resistant steel electroslag remelting M_(23)C_(6) carbide MnS inclusion supersaturation degree

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Effect of hafnium and molybdenum addition on inclusion characteristics in Co-based dual-phase high-entropy alloys

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1639-1650页

作者： Yong Wang Wei Wang Joo Hyun Park Wangzhong Mu Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education&Hubei Provincial Key Laboratory for New Processes of Ironmaking and Steelmaking Wuhan University of Science and TechnologyWuhan 430081China Department of Materials Science and Engineering KTH Royal Institute of TechnologySE-10044StockholmSweden Department of Chemical Engineering Northeast Electric Power UniversityJilin 132012China Department of Materials Science and Chemical Engineering Hanyang UniversityAnsan 15588Korea Engineering Materials Division of Materials ScienceDepartment of Engineering Science and MathematicsLuleå University of Technology97187 LuleåSweden

Specific grades of high-entropy alloys(HEAs)can provide opportunities for optimizing properties toward high-temperature *** this work,the Co-based HEA with a chemical composition of Co_(47.5)Cr_(30)Fe_(7.5)Mn_(7.5)Ni_(7.5)(at%)was *** refractory metallic elements hafnium(Hf)and molybdenum(Mo)were added in small amounts(1.5at%)because of their well-known positive effects on high-temperature *** characteristics were comprehensively explored by using a two-dimensional cross-sectional method and extracted by using a three-dimensional electrolytic extraction *** results revealed that the addition of Hf can reduce Al_(2)O_(3)inclusions and lead to the formation of more stable Hf-rich inclusions as the main *** addition cannot influence the inclusion type but could influence the inclusion characteristics by affecting the physical parameters of the HEA *** calculated coagulation coefficient and collision rate of Al_(2)O_(3)inclusions were higher than those of HfO_(2)inclusions,but the inclusion amount played a larger role in the agglomeration behavior of HfO_(2)and Al_(2)O_(3)*** impurity level and active elements in HEAs were the crucial factors affecting inclusion formation.

关键词： high-entropy alloy non-metallic inclusion agglomeration thermodynamics alloying

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Emerging strategies and developments in oxygen reduction reaction using high-performance platinum-based electrocatalysts

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Nano Research 2024年第5期17卷 3516-3532页

作者： Asad Ali Aatto Laaksonen Guo Huang Shahid Hussain Shuiping Luo Wen Chen Pei Kang Shen Jinliang Zhu Xiaoyan Ji Energy Engineering Division of Energy ScienceLuleåUniversity of Technology97187 LuleåSweden Department of Materials and Environmental Chemistry Arrhenius LaboratoryStockholm UniversitySE-10691 StockholmSweden Center of Advanced Research in Bionanoconjugates and Biopolymers “Petru Poni”Institute of Macromolecular ChemistryIasi 700469Romania State Key Laboratory of Materials-Oriented and Chemical Engineering Nanjing Tech UniversityNanjing 211816China College of Materials Science and Engineering Shenzhen UniversityShenzhen 518060China School of Resources Environment and MaterialsState Key Laboratory of Processing for Non-ferrous Metal and Featured MaterialsGuangxi UniversityNanning 530004China

The global practical implementation of proton exchange membrane fuel cells(PEMFCs)heavily relies on the advancement of highly effective platinum(Pt)-based electrocatalysts for the oxygen reduction reaction(ORR).To achieve high ORR performance,electrocatalysts with highly accessible reactive surfaces are needed to promote the uncovering of active positions for easy mass *** this critical review,we introduce different approaches for the emerging development of effective ORR electrocatalysts,which offer high activity and *** strategies,including morphological engineering,geometric configuration modification via supporting materials,alloys regulation,core-shell,and confinement engineering of single atom electrocatalysts(SAEs),are discussed in line with the goals and requirements of ORR performance *** review the ongoing development of Pt electrocatalysts based on the syntheses,nanoarchitecture,electrochemical performances,and *** eventually explore the obstacles and research directions on further developing more effective electrocatalysts.

关键词： oxygen reduction reaction(ORR) Pt-based electrocatalysts proton exchange membrane fuel cells(PEMFCs) morphology and alloys strategies single atom electrocatalysts(SAEs)

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Color and Gloss Changes of a Lignin-Based Polyurethane Coating under Accelerated Weathering

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Journal of Renewable Materials 2024年第2期12卷 305-323页

作者： Fatemeh Hassani Khorshidi Saeed Kazemi Najafi Farhood Najafi Antonio Pizzi Dick Sandberg Rabi Behrooz Department of Wood Science and Technology Faculty of Natural ResourcesTarbiat Modares UniversityTehranIran Department of Resin and Additives Institute for Color Science and TechnologyP.O.Box 16765-654TehranIran LERMAB University of LorraineBlvd des AiguillettesNancy54000France Wood Science and Engineering LuleåUniversity of TechnologySkellefteåSweden

The purpose of this research study was to investigate the properties of polyurethane coatings based on lignin *** this purpose,the prepared coatings were applied to pine wood surfaces and weathered ***,color and gloss of the coatings were measured before and after the weathering *** emission scanning electron microscopy(FE-SEM)micrographs prepared from the coatings showed that the average size of nano-particles in the polyurethane substrate was approximately 500 *** magnetic resonance(13C-NMR)spectroscopy showed that strong urethane bonds were formed in the nano-lignin-based *** calorimetric analysis(DSC)test revealed that the glass-transition temperature(Tg)of lignin nanoparticles modified with diethylenetriamine(DETA)was 112.8℃ and Tg of lignin nano-particles modified with ethylenediamine(EDA)was 102.5℃,which is lower than the Tg of un-modified lignin(114.6℃)and lignin modified with DETA(126.8℃)and lignin modified with EDA(131.3℃).The coatings modified with lignin nano-particles had a greater change in *** lignin nano-particles in the modified coating are trapping hydroxyl radicals which reduces photoactivity and yellowing of the polyurethane by about 3 times compared to unmodified polyurethane *** weathering test,the nano-lignin-based coating had a rougher surface with a lower contact angle(0.78°)compared to the unmodified polyurethane coating(0.85°).

关键词： Amination propylene carbonate lignin biopolymer polyurethane coating polyol UN SDG 13

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Tigris River Water Quality Quantifying Using the Iraq Water Quality Index (IraqWQI) and Some Statistical Techniques

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Engineering（科研） 2024年第6期16卷 149-166页

作者： Nadhir Al-Ansari Salam Hussein Ewaid Ali Chabuk Salwan Ali Abed Mudhafar A. Salim Jan Laue Riyadh M. Salih Department of Civil Environmental and Natural Resources Engineering Lule University of Technology Lule Sweden Technical College of Shatra Southern Technical University Basra Iraq Department of Environmental Engineering College of Engineering University of Babylon Babylon Iraq Department of Environment College of Science University of Al-Qadisiyah Diwaniyah Iraq Iraqi Organization for Conservation of Nature IOCN Baghdad Iraq National Center for Water Resources Management Ministry of Water Resources Baghdad Iraq

Evaluation of water quality is important for the management of water resources. The current study is focused on the interpretation of the water quality monitoring data of the Tigris River in Iraq by the application of the principal component analysis (PCA), cluster analysis (CA), and water quality index (WQI). Twelve water quality parameters were taken from 14 stations along the river Ca2+, Mg2+, Na+, K+, Cl−, SO42−, HCO3−, NO3−, TH, TDS, BOD5, and EC to apply the PCA and CA. The results show that the mean of all the parameters was under the standards except Ca2+, EC, Mg2+, TH, and SO42−. The amount of EC is the critical factor that affects the river water quality. The PCA obtained one principal component responsible for 97% of the variation caused by different pollution sources. The CA divided the river into three regions of sampling stations with similar water quality, the best in the north, and the worst in the far south. In this paper, the computer-automated tool (IraqWQI) was presented and evaluated, which has been developed by authors to classify and measure the quality of Iraqi surface water. The proposed index is of hundred degrees and includes six variables for drinking water quality Cl−, TH, TDS, COD, DO, and total coliform (TC) according to the Iraqi specifications. The result of the IraqWQI application showed a decrease in the water quality of the river and its suitability for drinking in the south of the country. The best value of the index was (81.48, Good) in Fishkhabour during winter, and the worst value was (46.23, Bad) in Qurnah during summer. The result of this study proved the success and importance of using statistical techniques and WQI as useful tools for the management, control, and conservation of surface water. .

关键词： Component Formatting Style Styling

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Homogenization of Reynolds Equation by Two-Scale Convergence

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Chinese Annals of Mathematics,Series B 2007年第3期28卷 363-374页

作者： Peter WALL Department of Mathematics Lule University of TechnologyS-971 87 Lule Sweden.

To increase the hydrodynamic performance in different machine elements, as e.g. journal bearings and thrust bearings, during lubrication it is important to understand the influence of surface roughness. In this connection one encounters homogenization of the incompressible Reynolds equation, where the roughness of the lubricated surface is assumed to be periodic. This problem has recently been studied in more engineering- oriented papers by using the formal method of multiple scale expansion. In this paper, we rigorously prove both homogenization and corrector results by using two-scale convergence, which may be regarded as a justification of the formal multiple scale expansion method described above. Moreover, some numerical illustrations and results are presented.

关键词： Homogenization Two-scale convergence Reynolds equation Lubrication

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