Magneto-mechanical deformation of \ch{Ni50Mn28Ga22} shape memory alloy

This study deals with pseudoplastic deformation of Ni50Mn28Ga22 alloy exhibiting mechanically and magnetically induced crystal reorientation. The new approach was introduced, taking into account crystals with single initial variant as well as nucleation of different orientation. Initially, observations from optical microscope and AFM (atomic force microscope) were correlated with the mechanical measurements from stress-strain machine to characterize boundaries between crystal variants. These observations were subsequently used to clarify the results of the mechanical deformation tests. By magnetizing samples in VSM (vibrating-sample magnetometer), analogous magnetic measurements to mechanical tests were conducted. The two types of measurements were then compared with respect to energy. The discrepancy found between the model and measurements is in agreement with previous studies. Some experimental factors and possible errors that may affect measurement have been discussed. Nevertheless, the observed differences remain an unresolved issue suggesting a need for a modification of the model.

Highly Improved Photocatalytic Activity of Magnetically Separable Ferroferric Oxide@Zinc Oxide/Carbon Nitride Nanocomposites and Interface Mechanism

To develop an efficient and recyclable photocatalyst, ternary magnetic Fe3O4@ZnO/g-C3N4 nanocomposites were synthesized for the photodegradation of methylene blue (MB). The microstructures, magnetic response and photocatalytic activity of the as-prepared nanocomposites were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), N2 adsorption–desorption isotherms and spectrophotometer. All results indicate that ZnO nanoparticles anchor on the surface of Fe3O4 nanoparticles and Fe3O4@ZnO exists on the surface of g-C3N4 to form Fe3O4@ZnO/g-C3N4 nanocomposites. The photocatalytic activity to MB of Fe3O4@ZnO/g-C3N4 nanocomposites is significantly higher than those of pristine g-C3N4 and Fe3O4@ZnO. Owing to the heterojunctions between the interface of g-C3N4 and ZnO, the high separation efficiency of the photogenerated electrons and holes increases the radicals [Formula: see text]OH and [Formula: see text]O[Formula: see text] to photodegrade MB. Fe3O4@ZnO/g-C3N4 (20%) presents the highest MB removal of 93.74% and could be easily separated from solution with magnetic separation method.

Preparation and Characterization of Green Fe3 O4 Nanoparticle Using the Aqueous Plant Extract of Gundelia tournefortii L.

In this work, the magnetite nanoparticles (Fe3O4-NPs) synthesized using a simple, fast, and environmentally acceptable green approach. Gundelia Tournefortii Extract, an aqueous plant extract, was used for the first time in green synthesis to prepare nanoparticles as reducing, capping, and stabilizing agents. Such biomolecules as flavonoids, alkaloids, and antioxidants are found in the aqueous leaf extract, and their presence has been determined to have an important role in the synthesis of Fe3O4-NPs. The techniques used in this analysis include Fourier Transform Infrared, Scanning Electron Microscopy, Energy-Dispersive X-ray spectroscopy, X-ray Diffraction, Transmission Electron Microscopy, and Vibrating Sample Magnetometer. The Vibrating Sample Magnetometer demonstrated that the samples were superparamagnetic, with a magnetization value of 48.6 emu/g. The prepared nanoparticle was applied to remove Chrystal Violet (CV), Malachite Green(MG), and Safranin (S) dyes from prepared aqueous solutions with the adsorption capacity of 13.9, 15.6, and 14.4 mg/g respectively.

Sintesis Nanokomposit Fe3O4/TiO2 Sebagai Fotokatalis yang Dapat Diambil Kembali Dalam Fotoreduksi Limbah Ion Perak(I)

Sintesis nanokomposit Fe3O4/TiO2 sebagai fotokatalis yang dapat diambil kembali dalam fotoreduksi limbah ion Ag(I) telah dilakukan. Sintesis diawali dengan sintesis magnetit (Fe3O4) melalui kopresipitasi dan sonikasi. Pelapisan TiO2 dilakukan dengan proses sol-gel dengan penambahan benih atau seed TiO2 degusa, dan diikuti perlakuan termal pada suhu 500 °C. Hasil sintesis dikarakterisasi dengan fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope-energy dispersive X-ray (SEM-EDX), vibrating sample magnetometer (VSM) dan diffuse reflectance-UV (DR-UV). Uji aktivitas fotokatalis nanokomposit Fe3O4/TiO2 dilakukan terhadap fotoreduksi ion Ag(I) dengan sistem batch dalam reaktor tertutup yang dilengkapi dengan lampu UV. Hasil penelitian menunjukkan bahwa nanokomposit Fe3O4/TiO2 memiliki kemampuan fotokatalitik yang baik. Nanokomposit Fe3O4/TiO2 memiliki kemampuan fotoreduksi lebih baik dibanding TiO2 tanpa modifikasi. Fotoreduksi ion Ag(I) 12,5 ppm berlangsung optimum pada pH 6 dan waktu reaksi 90 menit dengan hasil sebesar 98,6 %.

Fabrication of attapulgite/magnetic aminated chitosan composite as efficient and reusable adsorbent for Cr (VI) ions

An efficient composite was constructed based on aminated chitosan (NH2Cs), attapulgite (ATP) clay and magnetic Fe3O4 for adsorptive removal of Cr(VI) ions. The as-fabricated ATP@Fe3O4-NH2Cs composite was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analyzer (TGA), Scanning Electron Microscope (SEM), Zeta potential (ZP), Vibrating Sample Magnetometer (VSM), Brunauer–Emmett–Teller method (BET) and X-ray photoelectron spectroscope (XPS). A significant improve in the adsorption profile was established at pH 2 in the order of ATP@Fe3O4-NH2Cs(1:3) > ATP@Fe3O4-NH2Cs(1:1) > ATP@Fe3O4-NH2Cs(3:1) > Fe3O4-NH2Cs > ATP. The maximum removal (%) of Cr(VI) exceeded 94% within a short equilibrium time of 60 min. The adsorption process obeyed the pseudo 2nd order and followed the Langmuir isotherm model with a maximum monolayer adsorption capacity of 294.12 mg/g. In addition, thermodynamics studies elucidated that the adsorption process was spontaneous, randomness and endothermic process. Interestingly, the developed adsorbent retained respectable adsorption properties with acceptable removal efficiency exceeded 58% after ten sequential cycles of reuse. Besides, the results hypothesize that the adsorption process occurs via electrostatic interactions, reduction of Cr(VI) to Cr(III) and ion-exchanging. These findings substantiate that the ATP@Fe3O4-NH2Cs composite could be effectively applied as a reusable adsorbent for removing of Cr(VI) ions from aqueous solutions.

INVESTIGASI SIFAT MAGNET DAN LUAS PERMUKAAN BENTONIT TERMAGNETISASI SEBAGAI ADSORBEN CEPAT PISAH

Bentonit merupakan material alam yang memiliki kecenderungan yang tinggi membentuk koloid, ukuran partikelnya yang dapat membesar sampai beberapa kali lipat jika terkontak dengan air dan membentuk suspensi, akan menimbulkan kesulitan dalam proses pemisahannya dari fasa cair setelah proses adsorpsi. Salah satu upaya untuk mengatasi kelemahan tersebut ialah dengan melakukan modifikasi bentonit menggunakan magnetit (Fe3O4), yang akan mengakibatkan adanya sifat kemagnetan pada material tersebut. Sifat kemagnetan ini diharapkan memudahkan pemisahan partikel–partikel bentonit termodifikasi setelah proses adsorpsi dapat dilakukan dengan mudah dan cepat menggunakan medan magnet eksternal. Dalam studi ini dikaji sifat kemagnetan bentonit termagnetisasi menggunakan instrumen VSM (Vibrating Sample Magnetometer) dan dikaji luas permukaan bentonit teraktivasi dan bentonit termagnetisasi menggunakan SSA (Surface Sorption Analyzer) berdasarkan persamaan BET.Hasil penelitian menunjukkan bahwa analisis VSM memberikan nilai Ms pada Fe3O4 murni lebih besar (64 emu/g) dibandingkan bentonit termagnetisasi (11 emu/g). Berdasarkan data analisis SSA diperoleh bahwa sampel bentonit termagnetisasi memiliki luas permukaan spesifik yang lebih kecil bila dibandingkan dengan bentonit teraktivasi, yaitu masing-masing sebesar 222 dan 138 m2/g.

Effect of Reaction Time on the Coercivity of Barium Ferrite Synthesized by Hydrothermal Process

The barium ferrite BaFe12O19 with c-plane anisotropy, which possessed relative high saturation magnetization and low coercivity, had been synthesized by hydrothermal method with different reaction time of 5 h, 8 h,11 h,14 h, and 17 h. The X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM) were used to study the phase composition, microstructure and magnetic properties of barium ferrite, respectively. The results showed the intensities of the peak were enhanced and there was no impurity phase. With the prolonging of the reaction time to 11 h, 14 h and 17 h, the grain size increased, and the equivalent diameter was about 1 μm, and the thickness was about 100 nm. When the reaction time was 17 h，the coercivity of barium ferrite was 1104 Oe. The reduction of coercivity was ascribed to the increase of particle size and the reduction in magnetic anisotropy.

Phase transformation, Mechanical Properties and Corrosion Behavior of 304L Austenitic Stainless Steel Rolled at Room and Cryo Temperatures

The present work investigates the effect of rolling (90% thickness reduction) on phase transformation, mechanical properties, and corrosion behaviour of 304L-austenitic stainless steel through cryorolling and room temperature rolling. The processed steel sheets were characterised through X-ray diffraction (XRD), electron backscattered diffraction (EBSD), and vibrating sample magnetometer (VSM). The analysis of XRD patterns, EBSD scan, and vibrating sample magnetometer results confirmed the transformation of the austenitic phase to the martensitic phase during rolling. Cryorolling resulted in improved tensile strength and microhardness of 1808 MPa and 538 VHN, respectively, as compared to 1566 MPa and 504 VHN for room temperature rolling. The enhancement in properties of cryorolled steel is attributed to its higher dislocation density compared to room temperature rolled steel. The corrosion behaviour was assessed via linear polarisation corrosion tests. Corrosion resistance was found to decrease with increasing rolling reduction in both room temperature rolled and cryorolled specimens.

Spheroid Nickel Nanoparticles Synthesized in CTAB Solution Using Gamma Radiation

Pure nickel nanoparticles with some paired grain shaped has been successfully synthesized using gamma radiation technique in aqueous system at ambient temperature without using reducing agent. Cetyl trimethylammonium bromide was used to prevent oxidation during radiolysis process and help to shape the nickel nanoparticles into spheroid. Synthesized nanoparticles were characterized using X-ray diffraction, tunnelling electron microscopy and vibrating sample magnetometer. The particles formed are crystallized with fcc phase without any oxidation state. The particle size ranging from 20 – 50 nm which consists of unique morphology of paired spheroid. Vibrating sample magnetometer analysis shows that sample has ferromagnetic properties with value of magnetic remanence smaller that bulk due to its size.

Facile Organometallic Synthesis of Fe-Based Nanomaterials by Hot Injection Reaction

Fe-based colloids with a core/shell structure consisting of metallic iron and iron oxide were synthesized by a facile hot injection reaction of iron pentacarbonyl in a multi-surfactant mixture. The size of the colloidal particles was affected by the reaction temperature and the results demonstrated that their stability against complete oxidation related to their size. The crystal structure and the morphology were identified by powder X-ray diffraction and transmission electron microscopy, while the magnetic properties were studied at room temperature with a vibrating sample magnetometer. The injection temperature plays a very crucial role and higher temperatures enhance the stability and the resistance against oxidation. For the case of injection at 315 °C, the nanoparticles had around a 10 nm mean diameter and revealed 132 emu/g. Remarkably, a stable dispersion was created due to the colloids’ surface functionalization in a nonpolar solvent.