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Green and low temperature synthesis of nanocrystalline transition metal ferrites by simple wet chemistry routes

Nano Research 2014年第7期7卷 1027-1042页

作者： stefano Diodati Luciano Pandolfo Andrea Caneschi stefano gialanella Silvia Gross Istituto per I'Energetica e le In terfasi IENI-CNR and INSTM UdR di Padova via Marzolo 11-35131 Padova Italy Dipartimento di Scienze Chimiche Universit& degli Studi di Padova via Marzolo 11-35131 Padova Italy Laboratory of Molecular Magnetism LAMM Dipartimento di Chimica e UdR INSTM di Firenze Polo Scientifico Via della Lastruccia 3 50019 Sesto Fiorentino (FI) Italy Dipartimen to di Ingegneria Industriale Universita degli Studi di Tren to via Mesiano 771-38123 Trento Italy

Crystalline and nanostructured cobalt （CoFe2O4）, nickel （NiFe2O4）, zinc （ZnFe2O4） and manganese （MnFe2O4） spinel ferrites are synthesized with high yields, crystallinity and purity through an easy, quick, reproducible and low-temperature hydrothermal assisted route starting from an aqueous suspension of copredpitated metal oxalates. The use of water as a reaction medium is a further advantage of the chosen protocol. Additionally, the zinc spinel is also prepared through an alternative route combining copredpitation of oxalates from an aqueous solution with thermal decomposition under reflux conditions. The nanocrystalline powders are obtained as a pure crystalline phase already at the extremely low tem- perature of 75 ℃ and no further thermal treatment is needed. The structure and microstructure of the prepared materials is investigated by means of X-ray powder diffraction （XRPD）, while X-ray photoelectron spectroscopy （XPS） and inductively coupled plasma-atomic emission spectroscopy （ICP-AES） analyses are used to gain information about the surface and bulk composition of the samples, respectively, confirming the expected stoichiometry. To investigate the effect of the synthesis protocol on the morphology of the obtained ferrites, transmission electron microscopy （TEM） observations are performed on selected samples. The magnetic properties of the cobalt and manganese spinels are also investigated using a superconducting quantum device magnetometer （SQUID） revealing hard and soft ferrimagnetic behavior, respectively.

关键词： ferrites hydrothermal low temperature wet chemistry green

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Pin-on-disc study of dry sliding behavior of Co-free HVOFcoated disc tested against different friction materials

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Friction 2021年第5期9卷 1242-1258页

作者： Matteo FEDERICI Cinzia MENAPACE Alessandro MANCINI Giovanni STRAFFELINI stefano gialanella Department of Industrial Engineering University of TrentoTrento 32122Italy Brembo S.p.A. StezzanoBergamo 24040Italy

The dry sliding behavior of three commercial friction materials(codenamed FM1,FM2,and FM3)tested against a Co‐free cermet coating produced by high‐velocity oxy‐fuel(HVOF)on gray cast‐iron discs is ***1 is a conventional low‐metallic friction material,FM2 is developed for using against HVOF‐coated discs,and FM3 is a Cu‐free friction material with a low content of abrasives and a relatively high concentration of steel *** the tribological evaluation,they are tested on a pin‐on‐disc(PoD)test rig against Co‐free HVOF‐coated discs,with particular attention to the running‐in stage,which is fundamental for the establishment of a friction layer between the two mating surfaces,i.e.,the pin and *** PoD tests are performed at room temperature(RT)and a high temperature(HT)of 300℃.At RT,all materials exhibit a long running‐in *** HT,no running‐in is observed in FM1 and FM2,whereas a shorter running‐in period,with respect to the RT case,is observed in FM3 followed by the attainment of a comparatively high coefficient of *** RT,the pin wear is mild in all cases but severe at ***3 shows the lowest wear rate at both ***,the coated disc shows no wear when sliding against the FM3 friction *** the results are interpreted considering the microstructural characteristics of the friction layers formed on the sliding *** findings of the present study provide insights into reducing wear in braking system components and hence reducing environmental particulate matter emissions from their wear,through the use of disc coatings.

关键词： friction materials sliding wear high‐velocity oxy‐fuel(HVOF)coatings pin‐on‐disc(PoD)testing

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Characterization of ultrafine particles from hardfacing coated brake rotors

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Friction 2023年第1期11卷 125-140页

作者： Yezhe LYU Ankur SINHA Ulf OLOFSSON stefano gialanella Jens WAHLSTRÖM Department of Mechanical Engineering Sciences Lund UniversityLund SE-22100Sweden Department of Machine Design KTH Royal Institute of TechnologyStockholm SE-10044Sweden Department of Industrial Engineering University of TrentoTrento 38123Italy

Automotive brake rotors are commonly made from gray cast iron(GCI).During usage,brake rotors are gradually worn off and periodically ***,replaced brake rotors are mostly remelted to produce brand-new cast iron products,resulting in a relatively high energy consumption and carbon footprint into the *** addition,automotive brakes emit airborne *** of the emitted particles are categorized as ultrafine,which are sized below 100 nm,leading to a series of health and environmental *** this study,two surface treatment techniques are applied,ie.,high-velocity oxygen fuel(HVOF)and laser cladding(LC),to overlay wear-resistant coatings on conventional GCI brake rotors in order to refurbish the replaced GCI brake rotor and to avoid the remelting *** two coating materials are evaluated in terms of their coefficient of friction(CoF),wear,and ultrafine particle emissions,by comparing them with a typical GCI brake *** results show that the CoF of the HVOF disc is higher than those of the GCI and LC ***,HVOF disc has the lowest wear rate but results in the highest wear rate on the mating brake pad *** LC disc yields a similar wear rate as the GCI *** ultrafine particles from the GCI and LC discs appeared primarily in round,chunky,and flake *** HVOF disc emits unique needle-shaped *** the ultrafine particle range,the GCI and HVOF discs generate particles that are primarily below 100 nm in the running-in period and 200 nm in the steady ***,the LC disc emitted particles that are primarily~200 nm in the entire test run.

关键词： ultrafine particle high-velocity oxygen fuel laser cladding brake particle size distribution particle morphology

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