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Erosive wear properties of ZA-27 alloy-based nanocomposites: Influence of type, amount, and size of nanoparticle reinforcements

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Friction 2019年第4期7卷 340-350页

作者： Aleksandar VENCL ilija bobic Biljana bobic Kristina JAKIMOVSKA Petr SVOBODA Mara KANDEVA Faculty of Mechanical Engineering University of BelgradeKraljice Marije 16Belgrade 11120Serbia Institute of Nuclear Sciences'Vinca' University of BelgradeMike Petrovica Alasa 12-14Belgrade 11001Serbia Institute of Chemistry Technology and MetallurgyUniversity of BelgradeNjegoseva 12Belgrade 11000Serbia Faculty of Mechanical Engineering in Skopje Ss.Cyril and Methodius UniversityKarposh II bbSkopje 1000Macedonia Faculty of Mechanical Engineering Brno University of TechnologyTechnicka2896/2Brno 61669Czech Republic Faculty of Industrial Technology Technical University of Sofia8 Kliment Ohridski BlvdSofia 1000Bulgaria

Metal matrix nanocomposites(MMnCs)comprise a metal matrix filled with nanosized reinforcements with physical and mechanical properties that are very different from those of the *** ZA-27 alloy-based nanocomposites,the metal matrix provides ductility and toughness,while usually used ceramic reinforcements give high strength and *** ZA-27 alloy-based nanocomposites,reinforced with different types(Si C and Al2O3),amounts(0.2 wt.%,0.3 wt.%,and 0.5 wt.%)and sizes(25 nm,50 nm,and 100 nm)of nanoparticles were produced through the compocasting process with mechanical alloying pre-processing(ball milling).It was previously shown that the presence of nanoparticles in ZA-27 alloy-based nanocomposites led to the formation of a finer structure in the nanocomposites matrix and an improvement in the basic mechanical properties(hardness and compressive yield strength)through the enhanced dislocation density strengthening *** particle erosive wear testing demonstrated that these improvements were followed with an increase in the erosive wear resistance of tested nanocomposites,as ***,by analyzing the influences of type,amount,and size of nanoparticles on the erosive wear resistance of nanocomposites,it was demonstrated that there is an optimal amount of nanoparticles,which in our case is 0.3 wt.%,and that the presence of SiC nanoparticles and smaller nanoparticles in nanocomposites had more beneficial influence on erosive wear resistance.

关键词： ZA-27 alloy nanocomposites nanoparticles compocasting fractography erosive wear

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Corrosion influence on surface appearance and microstructure of compo cast ZA27/SiC_p composites in sodium chloride solution

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Transactions of Nonferrous Metals Society of China 2016年第6期26卷 1512-1521页

作者： Biljana bobic Jelena BAJAT ilija bobic Bore JEGDIC Institute of Chemistry Technology and Metallurgy University of Belgrade Belgrade 11000 Serbia Faculty of Technology and Metallurgy University of Belgrade Belgrade 11000 Serbia "Vinca" Institute of Nuclear Sciences University of Belgrade Belgrade 11000 Serbia

The influence of corrosion on the surface appearance and microstructure of particulate ZA27/SiCp composites was examined after 30 d immersion in a sodium chloride solution with the access of atmospheric oxygen. The composites with different contents of SiC micro-particles were synthesized via compo casting. Microstructural studies by means of optical microscopy （OM） and scanning electron microscopy （SEM） showed that corrosion occurred in the composite matrices, preferentially in regions of the η phase, rich in zinc. The corrosion processes did not affect the silicon carbide particles incorporated in the matrix alloy. According to the results of electrochemical polarization measurements, an increase in the content of SiC particles in the composite matrice has led to the lower corrosion resistance in the composites.

关键词： metal-matrix composites ZA27 alloy corrosion microstructure polarization resistance corrosion rate

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Corrosion behaviour of thixoformed and heat-treated ZA27 alloys in NaCl solution

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Transactions of Nonferrous Metals Society of China 2013年第4期23卷 931-941页

作者： Biljana bobic Jelena BAJAT Zagorka ACIMOVIC-PAVLOVIC ilija bobic Bore JEGDIC Institute"Gosa" University of BelgradeMilana Rakica 3511000 BelgradeSerbia Faculty of Technology and Metallurgy University of BelgradeKarnegijeva 411120 BelgradeSerbia "Vinca"Institute of Nuclear Sciences University of BelgradeMike Petrovica Alasa 12-1411001 BelgradeSerbia

The influence of corrosion on the microstructure of thixoformed and heat-treated ZA27 alloys was investigated. The microstructure of ZA27 alloy was affected by heat treatment. The process of electrochemical corrosion occurs in both ZA27 alloys through the area of r/phase. According to the results of immersion test and electrochemical measurements, the corrosion rate of the thixoformed ZA27 alloy is at least 50% lower than that of the thixoformed and thermally processed alloy. This indicates the unfavourable influence of applied heat treatment （T4 regime） on the corrosion resistance of the thixoformed ZA27 alloy.

关键词： ZA27 alloy thixoforming corrosion heat treatment microstructure

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PZT–NZF/CF ferrite flexible thick films:Structural,dielectric,ferroelectric,and magnetic characterization

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Journal of Advanced Ceramics 2019年第4期8卷 545-554页

作者： J.D.bobic G.Ferreira TEIXEIRA R.GRIGALAITIS S.GYERGYEK M.M.Vijatovic PETROVIC M.Ap.ZAGHETE B.D.STOJANOVIC Belgrade University Universidade Federal de Goiás – UFG Instituto de Química Vilnius University Institute Jozef Stefan Instituto de Quimica-UNESP

The preparation and properties of thick flexible three-phase composite films based on lead zirconium titanate(PZT) and various ferrites(nickel zinc ferrite(NZF) and cobalt ferrite(CF)) were reported in this study. Properties of three-phase composite films were compared with pure polyvinylidene fluoride(PVDF) and PZT–PVDF films. X-ray diffraction data indicated the formation of well crystallized structure of PZT and NZF/CF phases, without the presence of undesirable phases. Scanning electron micrographs showed that the ceramic particles were dispersed homogeneously in the PVDF matrix and atomic force microscopy confirmed that the size of the particles is around 30 nm. Non-saturated hysteresis loops were evident in all samples due to the presence of highly conductive ferrite phases. Under magnetic field of 10 k Oe, composite films exhibited a typical ferromagnetic response. Dielectric properties were investigated in the temperature range from –128 to 250 ℃ and frequency range of 400 Hz–1 MHz. The results showed that the value of dielectric constant of the PVDF/PZT/ferrite composites increased about 25% above the one obtained for pure PVDF.

关键词： flexible thick films three-phase composites ferroelectricity magnetic materials

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Current Status and Possibilities for the Development of the Cattle Breeding in the Primorsko-Goranska County, Croatia

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Journal of Agricultural Science and Technology(A) 2011年第4X期1卷 536-543页

作者： P. Mijic M. Domacinovic I. Klaric T. bobic M. Brajan D. Sostaric Faculty of Agricuhure in Osijek J J. Strossmayer University of Osijek Trg Sv. Trojstva 3 Oso'ek 31000 Croatia Primorako-Goranso County Zrtava fasizma 17/L Roeka 51000 Croatia Center for mountainous agriculture of the Primorsko-Goranska County Stara Susica Ravna Gora 51314 Croatia

At the beginning of 2007 the milk producers from the Primorsko-Goranska County, Croatia were surveyed through the questionnaire in order to determine the current status and to highlight the obstacles and the possibilities of development and improvement of the modern cattle breeding in the observed county. The questionnaire spanned 2001-2006 period and all together 260 families were surveyed. The survey aimed to get as much as possible useful information＇s that would indicate the problems concerning the cattle breeding in this area, and based on these results to give certain guidelines for the improvement of current status. Older age of milk producers, significant number of family farms with small number of cattle and difficult implementation of selective measures due to the small number of cows that were included in milk recording were determined as the main obstacles for cattle breeding development in the surveyed county. It is emphasized that development of cattle breeding in this area should be based upon the increased number of family farms with larger herds. To achieve this it is necessary to retain existing cattle fund, and then gradually increase the number of cattle in the mentioned county through the import of breeding heifers of dairy and combined breeds from neighboring European countries with highly developed cattle breeding. Besides that, it is also necessary to create conditions for the production of organic （ecological） products, which represents the future of agriculture, livestock production, bearing in mind that demanding European market has recognized the value of organic agricultural products that were produced through environment friendly production, which Primorsko-Goranska County, due to its significant natural resources, could easily assure.

关键词： Cattle Primorsko-Goranska County status perspective Croatia.

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Synergistic effect of CeCl3 and benzotriazole on corrosion resistance of naturally aged and artificially aged AA2024 aluminium alloy

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Transactions of Nonferrous Metals Society of China 2020年第6期30卷 1478-1490页

作者： Bore JEGDIĆ Biljana BOBIĆ Bojana RADOJKOVIĆ Jovanka KOVAČINA Dunja MARUNKIĆ University of Belgrade Institute for ChemistryTechnology and MetallurgyBelgradeSerbia

The corrosion behaviours of naturally aged and artificially aged AA2024 aluminium alloys in 0.5 mol/dm3 NaCl solution in the presence of environmentally friendly corrosion inhibitors of 10 mmol/dm3 CeCl3, 10 mmol/dm3 BTA and the inhibitor mixture (5 mmol/dm3 CeCl3 + 5 mmol/dm3 BTA) were analyzed. The goal of this work was to determine the level of the synergistic effect of the inhibitor mixture and to explain the nature of this effect. Corrosion properties of the inhibitor layer were studied using the electrochemical impedance spectroscopy (EIS), while the resistance to pit formation and pit growth was studied by applying potentiodynamic polarisation tests. The results of scanning electron microscopy (SEM/EDS) showed that the size of pits formed in naturally aged aluminium alloy was smaller than that formed in artificially aged alloy. The synergistic effect of the inhibitor mixture on corrosion properties of naturally aged alloy was observed throughout 96 h, and in later phases of testing of artificially aged alloy. The synergistic effect of the inhibitor mixture was not noticed on pit formation and pit growth.

关键词： aluminium alloy pitting corrosion corrosion inhibitor cerium benzotriazole

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对臀先露不成功的针灸转位

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世界核心医学期刊文摘（妇产科学分册） 2006年第10期2卷 36-36页

作者： Vukovic-bobic M. Habek D. 朱晓明 Univer sittsfrauenklinik Sveti Duh Sveti Duh 64 HR-10000 ZagrebCroatia Dr.

A case is presented of fetal oblique position with compound presentation, where acupuncture conversion of breech presentation failed due to the umbilical being wrapped three times around the fetus with a knot in the umbilical cord, so that delivery was terminated by cesarean section. Conversion of the fetal breech presentation was induced by manual acupuncture stimulation of the UB 67 acupoint with simultaneous CTG control in the 35th week of pregnancy. During the first acupuncture stimulation, CTG showed protracted uterine contraction with subsequent regular low amplitude contractions with intensified fetal activity and CTG curve reactivity. In the 39th week of gestation, the patient felt regular contractions verified by CTG records showing reactive curves. Obstetrical examination revealed a cervical dilatation of 4 cm, a compound presentation involving both legs and the umbilical cord, and oblique position. Therefore, a cesarean section according to a modified Misgav-Ladach method was performed and the patient gave birth to a healthy male neonate (3330 g, 49 cm, Apgar 10/10, pH 7.334). The obstetrician should warn the patient of the potential risks and complications associated with any method of breech presentation conversion.

关键词：臀先露复合先露脐带缠绕剖宫产分娩产科医师规律宫缩脐带打结子宫颈扩张斜位终止妊娠

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