Mechanical alloying of a mixture of copper and nickel powders has been applied for the preparation of copper–nickel alloy particles in the nanometer range. The particles were designed to be used for ...controlled magnetic hyperthermia applications. The milling conditions were optimized using the desired alloy composition. Utilizing a ball-to-powder mass ratio of 20, we could obtain a nanocrystalline Cu
27.5Ni
72.5 (at%) alloy with a crystallite size of around 10
nm and a Curie temperature of 45
°C.
Thermal demagnetization in the vicinity of the Curie temperature of the nanoparticles was determined by thermomagnetic measurements using an adapted TGA–SDTA apparatus. The size and morphology of the particles were determined by XRD measurements and TEM analyses. The magnetic properties were also examined with a VSM. The magnetic heating effects were measured for the powdered material.
► Cu
x
Ni
1−
x
nanoparticles were synthesized for magnetic hyperthermia applications. ► Generated heat can be controlled using nanoparticles with adaptable Curie temperature. ► Methodology for the synthesis and characterization of CuNi nanoparticles is reported. ► Structural properties, magnetic properties and temperature rises were investigated.
Overall energy of interaction between two oleic- and ricinoleic-acid-coated nanoparticles in different organic solvents. The additional repulsion between the ricinoleic-acid-coated nanoparticles ...exist, because of the polar interactions, in contrast to the oleic-acid-coated nanoparticles.
Display omitted
► Colloidal stability of suspensions is correlated to dielectric constant of solvent. ► OA-nanoparticles cannot be dispersed in solvents that have
ε > 5. ► RA-nanoparticles can be dispersed in solvents that have
ε > 5. ► RA-nanoparticles are electron-acceptors; OA- nanoparticles are electron-donors. ► Solvation forces improved colloidal stability of RA-nanoparticles.
The colloidal stability of oleic- and ricinoleic-acid-coated nanoparticles in organic solvents with dielectric constants
ε
r ranging from 2.0 to 9.8 was studied. Although the acids are structurally similar, there is an
OH group in the ricinoleic acid’s tail, a marked improvement in the colloidal stability of the ricinoleic-acid-coated magnetic nanoparticles in moderately polar organic solvents and monomer methyl methacrylate was observed as a result. The bonding of both acids provokes a significant change in the surface properties of the iron-oxide nanoparticles. A clear shift from a strong electron-donor to a weak electron-donor was confirmed with the bonding of the oleic acid. The effect of ricinoleic acid bonding is even more dramatic: a clear shift toward a weak electron-acceptor is evident. A detailed analysis of the total energy of interaction, including the vOCG theory, between two particles was used to describe the different behaviors of the coated nanoparticles. In the case of the oleic acid nanoparticles in an apolar medium, such as decane, a small net attraction of ∼0.84
k
B
T, which is insufficient to cause nanoparticles agglomeration, exists. In polar media the net attraction is larger than 1.5
k
B
T, resulting in precipitation of the oleic-acid-coated nanoparticles. The same findings apply to the ricinoleic-acid-coated nanoparticles, but only when dispersed in the apolar medium. In the polar medium an additional repulsion due to polar solvation forces exists, resulting in a decrease of the net attraction to as low as ∼0.14
k
B
T.
Ceramic composites in the BaTiO
3
–(Bi
1/2
Na
1/2
)TiO
3
system exhibiting a positive temperature coefficient of electrical resistivity effect were prepared using a conventional solid-state reaction ...method. The composite samples were sintered in nitrogen to achieve their final-phase properties, a high resistivity jump of ∼ 10
3
at about 170 °C. The resistivity anomaly of the composite composed of a conducting network based on a conducting BaTiO
3
and a highly resistive ferroelectric phase with a Curie temperature (T
C
) of 170 °C was explained in the light of ferroelectric phase-transition-assisted anomaly in the resistivity (FPTAA).
Polyacrylic acid (PAA)-coated magnetic nanoparticles (MNP@PAA) were synthesized and evaluated as draw solutes in the forward osmosis (FO) process. MNP@PAA were synthesized by microwave irradiation ...and chemical co-precipitation from aqueous solutions of Fe
and Fe
salts. The results showed that the synthesized MNPs have spherical shapes of maghemite Fe
O
and superparamagnetic properties, which allow draw solution (DS) recovery using an external magnetic field. Synthesized MNP, coated with PAA, yielded an osmotic pressure of ~12.8 bar at a 0.7% concentration, resulting in an initial water flux of 8.1 LMH. The MNP@PAA particles were captured by an external magnetic field, rinsed in ethanol, and re-concentrated as DS in repetitive FO experiments with deionized water as a feed solution (FS). The osmotic pressure of the re-concentrated DS was 4.1 bar at a 0.35% concentration, resulting in an initial water flux of 2.1 LMH. Taken together, the results show the feasibility of using MNP@PAA particles as draw solutes.
This concise review delves into the realm of superparamagnetic nanoparticles, specifically focusing on Fe2O3, Mg1+xFe2−2xTixO4, Ni1−xCux, and CrxNi1−x, along with their synthesis methods and ...applications in magnetic hyperthermia. Remarkable advancements have been made in controlling the size and shape of these nanoparticles, achieved through various synthesis techniques such as coprecipitation, mechanical milling, microemulsion, and sol–gel synthesis. Through this review, our objective is to present the outcomes of diverse synthesis methods, the surface treatment of superparamagnetic nanoparticles, their magnetic properties, and Curie temperature, and elucidate their impact on heating efficiency when subjected to high-frequency magnetic fields.
In this study, citric acid (CA)-coated magnetite Fe3O4 magnetic nanoparticles (Fe3O4@CA MNPs) for use as draw solution (DS) agents in forward osmosis (FO) were synthesized by co-precipitation and ...characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS), transmission electron microscopy (TEM) and magnetic measurements. Prepared 3.7% w/w colloidal solutions of Fe3O4@CA MNPs exhibited an osmotic pressure of 18.7 bar after purification without aggregation and a sufficient magnetization of 44 emu/g to allow DS regeneration by an external magnetic field. Fe3O4@CA suspensions were used as DS in FO cross-flow filtration with deionized (DI) water as FS and with the active layer of the FO membrane facing the FS and NaCl as a reference DS. The same transmembrane bulk osmotic pressure resulted in different water fluxes for NaCl and MNPs, respectively. Thus the initial water flux with Fe3O4@CA was 9.2 LMH whereas for 0.45 M NaCl as DS it was 14.1 LMH. The reverse solute flux was 0.08 GMH for Fe3O4@CA and 2.5 GMH for NaCl. These differences are ascribed to a more pronounced internal dilutive concentration polarization with Fe3O4@CA as DS compared to NaCl as DS. This research demonstrated that the proposed Fe3O4@CA can be used as a potential low reverse solute flux DS for FO processes.
The solid solubility of R ions (R = Ho3+, Dy3+, and Y3+) in the BaTiO3 perovskite structure was studied by quantitative electron‐probe microanalysis (EPMA) using wavelength‐dispersive spectroscopy ...(WDS), scanning electron microscopy (SEM), and X‐ray diffractometry (XRD). Highly doped BaTiO3 samples were prepared using mixed‐oxide technology including equilibration at 1400° and 1500°C in ambient air. The solubility was found to depend mainly on the starting composition. In the TiO2‐rich samples a relatively low concentration of R incorporated preferentially at the Ba2+ lattice sites (solubility limit ∼Ba0.986R0.014Ti0.9965(V″Ti″)0.0035O3at 1400°C). In BaO‐rich samples a high concentration of R entered the BaTiO3 structure at the Ti4+ lattice sites (solubility limit ∼BaTi0.85R0.15O2.925(VO••)0.075at 1500°C). Ho3+, Dy3+, and Y3+incorporated preferentially at the Ti4+ lattice sites stabilize the hexagonal polymorph of BaTiO3. The phase equilibria of the Ho3+–BaTiO3 solid solutions were presented in a BaO–Ho2O3–TiO2phase diagram.
The synthesis of magnetic nanoparticles (MNPs) coated with hydrophilic poly-sodium-acrylate (PSA) ligands was studied to assess PSA-MNP complexes as draw solution (DS) solutes in forward osmosis ...(FO). For MNP-based DS, the surface modification and the size of the MNPs are two crucial factors to achieve a high osmolality. Superparamagnetic nanoparticles (NP) with functional groups attached may represent the ideal DS where chemical modifications of the NPs can be used in optimizing the DS osmolality and the magnetic properties allows for efficient recovery (DS re-concentration) using an external magnetic field. In this study MNPs with diameters of 4 nm have been prepared by controlled chemical co-precipitation of magnetite phase from aqueous solutions containing suitable salts of Fe
and Fe
under inert atmosphere and a pure magnetite phase could be verified by X-ray diffraction. Magnetic colloid suspensions containing PSA-coated MNPs with three different molar ratios of PSA:MNP = 1:1, 1:2 and 1:3 were prepared and assessed in terms of osmotic pressure, aggregation propensity and magnetization. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of PSA on coated MNPs and pristine PSA-MNPs with a molar ratio PSA:MNP = 1:1 exhibited an osmotic pressure of 30 bar. Molar ratios of PSA:MNP = 1:2 and 1:3 lead to the formation of less stabile magnetic colloid solutions, which led to the formation of aggregates with larger average hydrodynamic sizes and modest osmotic pressures (5.5 bar and 0.2 bar, respectively). After purification with ultrafiltration, the 1:1 nanoparticles exhibited an osmotic pressure of 9 bar with no aggregation and a sufficient magnetization of 25 emu/g to allow for DS regeneration using an external magnetic field. However, it was observed that the amount of PSA molecules attached to the MNPs decreased during DS recycling steps, leaving only strong chelate-bonded core-shell PSA as coating on the MNPs. This demonstrates the crucial role of MNP coating robustness in designing an efficient MNP-based DS for FO.
Nanosized Fe
0.2Ni
0.8 particles were prepared by reducing their salts with sodium borohydride (NaBH
4) in cationic water-in-oil (w/o) microemulsions of water/cetyl-trimethyl-amonium bromide (CTAB) ...and
n-butanol/isooctane at 25
°C. According to the TEM and X-ray diffraction analyses, the synthesized particles were around 4–12
nm in size. Due to their nanodimensions, the particles had a primitive cubic (pc) structure rather than the body-centered cubic (BCC) structure of the bulk material. An examination of the synthesis from the reverse micelle reveals that the morphology of the iron–nickel alloy nanoparticles depends mainly on the microemulsion's composition. The magnetization of the nanoparticles was much lower than that of the bulk material, reflecting the influence of the nanodimensions on the particles’ magnetizations.
Barium hexaferrite BaFe12O19 nanoparticles with a single‐domain size were synthesized using a controlled hydrothermal process involving the LaMer–Dinger principle and the Ostwald ripening mechanism. ...Nanocrystalline particles of BaFe12O19 were obtained when the molar ratio of the precursor composition Ba(OH)2·8H2O/γ‐Fe2O3 was 0.3 and the concentration of the suspension was about 1 wt%. The as‐synthesized crystalline BaFe12O19 platelets approximately 50 nm in length and 5 nm in thickness exhibited a saturation magnetization of 40 Am2/kg.
PDF
