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Effect of Y_2O_3 stabilized ZrO_2 coating with tri-model structure on bi-layered thermally grown oxide evolution in nano thermal barrier coating systems at elevated temperatures

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Journal of Rare Earths 2014年第1期32卷 57-77页

作者： Mohammadreza Daroonparvar Muhamad Azizi Mat Yajid Noordin Mohd Yusof Hamid Reza Bakhsheshi-Rad Z.Valefi esah hamzah Department of Materials Manufacturing and Industrial Engineering Faculty of Mechanical Engineering Universiti Teknologi Malaysia School of Metallurgy and Materials College of Engineering University of Tehran

Bi-layered thermally grown oxide （TGO） layer plays a major role in the spallation of Y2O3 stabilized ZrO2 （YSZ） layer form the bond coat in the thermal barrier coating （TBC） systems during oxidation. On the other hand, bi-layered TGO formation and growth in the TBC systems with nanostructured YSZ have not been deeply investigated during cyclic oxidation. Hence, Inconel 738/NiCrAlY/normal YSZ and Inconel 738/NiCrAlY/nano YSZ systems were pre-oxidized at 1000 °C and then subjected to cyclic oxidation at 1150 °C. According to microstructural observations, nanostructured YSZ layer over the bond coat should have less mi-cro-cracks and pinholes, due to the compactness of the nanostructure and the presence of nano zones that resulted in lower O infiltration into the nanothermal barrier coating system, formation of thinner and nearly continuous mono-layered thermally grown oxide on the bond coat during pre-oxidation, lower spinels formation at the Al2O3/YSZ interface and finally, reduction of bi-layered thermally grown oxide thickness during cyclic oxidation. It was found that pre-heat treatment and particularly coating microstructure could influence microstructural evolution （bi-layered TGO thickness） and durability of thermal barrier coating systems during cyclic oxidation.

关键词： spinels oxidation three stages TGO growth pre-heat treatment rare earths

Role of Ag addition on microstructure,mechanical properties,corrosion behavior and biocompatibility of porous Ti-30 at%Ta shape memory alloys

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Journal of Central South University 2020年第11期27卷 3175-3187页

作者： Mustafa Khaleel IBRAHIM Safaa Najah SAUD esah hamzah Engku Mohamad NAZIM Faculty of Computer Engineering University of Imam Jafar Sadeq Maysan BranchMaysan 62012Iraq Faculty of Information Sciences and Engineering Management&Science University40100 Shah AlamSelangorMalaysia Faculty of Mechanical Engineering Universiti Teknologi Malaysia81310 UTM Johor BahruJohorMalaysia

In the present study,the thermal,mechanical,and biological properties of xAg/Ti-30Ta(x=0,0.41,0.82 and 2.48 at%)shape memory alloys(SMAs)were *** study was conducted using optical and scanning electron microscopy(SEM),X-ray diffractometry(XRD),compression test,and shape memory *** xAg/Ti-Ta was made using a powder metallurgy technique and microwave-sintering *** results revealed that the addition of Ag has a significant effect on the pore size and shape,whereas the smallest pore size of 11μm was found with the addition of 0.41 at%along with a relative density of 72%.The fracture stress and strain increased with the addition of Ag,reaching the minimum values around 0.41 at%***,this composition showed the maximum stress and strain at fracture ***,0.82 Ag/Ti-Ta shows more excellent corrosion resistance and biocompatibility than other percentages,obtaining almost the same behaviour of the pure Ti and Ti-6Al-4V alloys,which can be recommended for their promising and potential response for biomaterial applications.

关键词： porous xAg/Ti-Ta shape memory alloys(SMAs) microwave sintering process microstructure characteristics mechanical properties and corrosion behavior bioactivity

In vitro microbiologically-induced concrete corrosion behavior of Ag^(+) loaded zeolite-polyurethane coating for concrete sewer applications

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Journal of Central South University 2022年第9期29卷 3171-3185页

作者： Asma KAMARUL ASRI Safaa N.SAUD esah hamzah Zaharah IBRAHIM Faculty of Mechanical Engineering Universiti Teknologi MalaysiaSkudai 81310Malaysia Faculty of Information Sciences and Engineering Management&Science UniversityShah Alam 40100Malaysia Faculty of Bioscience and Bioengineering Universiti Teknologi MalaysiaJohor 81310Malaysia

Microbiologically-induced concrete corrosion(MICC)refers to chemical reactions between biologically produced sulphuric acid and with hydration products in the hardened concrete paste,resulting in an early reduction of strength,deterioration,and very severe circumstances,structural *** paper explores the bactericidal characteristics of cementitious materials with surface coated with modified *** zeolite-polyurethane coating incorporated with silver was studied in environments inoculated with *** bacteria for 8 consecutive *** antibacterial characteristics were evaluated in terms of pH,optical density(OD),sulphate production and bacteria count to determine the effectiveness of the zeolite-polyurethane coatings in environments inoculated with *** bacteria producing the sulphuric *** results revealed that the samples incorporated with silver modified zeolites generally showed antibacterial performance(regardless of the zeolite type)compared with unmodified polyurethane *** was evaluated by the lack of bacteria attachment and the deformed microcolonies on the sample surface,lag in pH reduction,increase in OD,and sulphate *** silver zeolites gained their antibacterial performance from the release of silver ions(Ag^(+))when the sample comes into contact with aqueous *** results in the inhibition of cell functions of the bacteria and subsequently causes cell damage.

关键词： microbiologically-induced corrosion cement zeolite A.thiooxidans silver ions

Microstructure and superelastic properties of free forged Ti-Ni shape-memory alloy

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Transactions of Nonferrous Metals Society of China 2018年第3期28卷 502-514页

作者： Abdollah BAHADOR esah hamzah Katsuyoshi KONDOH Tuty ASMA ABUBAKAR Farazila YUSOF Junko UMEDA Safaa N.SAUD Mustafa K.IBRAHIM Faculty of Mechanical Engineering Universiti Teknologi Malaysia JWRI Osaka University Department of Mechanical Engineering Faculty of EngineeringUniversity of Malaya Faculty of Information Science and Engineering Management and Science University

Elemental titanium(Ti)and nickel(Ni)powders were consolidated by spark plasma sintering(SPS)to fabricate Ti-51%Ni(mole fraction)shape-memory alloys(SMAs).The objective of this study is to enhance the superelasticity of SPS produced Ti-Ni alloy using free forging as a secondary *** from two processes(with and without free forging)were compared in terms of microstructure,transformation temperature and *** results showed that,free forging effectively improved the tensile and shape-memory *** increased from 6.8%to 9.2%after *** maximum strain during superelasticity increased from 5%to 7.5%and the strain recovery rate increased from 72%to 92%.The microstructure of produced Ti-51%Ni SMA consists of the cubic austenite(B2)matrix,monoclinic martensite(B19′),secondary phases(Ti3Ni4,Ti2Ni and TiNi3)and oxides(Ti4Ni2O and Ti3O5).There was a shift towards higher temperatures in the martensitic transformation of free forged specimen(aged at 500°C)due to the decrease in Ni content of B2 *** is related to the presence of Ti3Ni4 precipitates,which were observed using transmission electron microscope(TEM).In conclusion,free forging could improve superelasticity and mechanical properties of Ti-51%Ni SMA.

关键词： shape-memory alloy superelasticity spark-plasma sintering free forging