We report on the realization of particle size, morphology, and chemical composition controlled cobalt ferrite nanoparticles (CFO NPs) with tunable magnetic properties for application in electronic and electromagnetic devices. The effect of oleic acid concentration (0.0–0.1 M) on the structural, physical, chemical, electronic, and magnetic properties of solvothermally synthesized CFO NPs is investigated in detail by using the oleic acid (OA) based chemical method for synthesis. Crystalline, cubic, and chemically homogeneous CFO NPs (5–15 nm) can be obtained by controlling the OA concentration. Spectroscopic analyses revealed that the OA molecules form covalent bonds with CFO NPs. The particle-size control was achieved by bridging bidentate interactions between the OA molecules and CFO NPs. Detailed magnetic measurements revealed that the OA concentration helps to effectively control the magnetic behavior of particle-size-controlled CFO NPs. The interfacing between OA molecules and CFO surface atoms leads to modified magnetism which is the key to understand the underlying mechanisms and utilize magnetic nanoparticles in practical applications. The anisotropy constant variation directly with nanoparticle size indicates that the magnetocrystalline component governs the magnetic anisotropy in OA coated CFO. Removal of OA (after thermal treatment) induces enhanced magnetic anisotropy and exchange bias as consequence of surface component. The results and analyses suggest that the molecular coating of nanoparticles offers the most important and critical step to design novel nanostructured magnetic materials for current and emerging electronic device technologies.

Iron-rich and highly ordered 2D-hexagonal mesoporous ferrisilicates containing predominantly tetrahedrally coordinated Fe 3+ in the silica network have been prepared using cetyltrimethylammonium bromide (CTAB) as the structure-directing agent (SDA) under mild alkaline hydrothermal conditions (initial pH ) 8-8.5 in the synthesis gel). The optimum limit of iron loading for the ordered mesophase in the present study was 8.2 wt %; beyond this limit, disordered iron oxide/silica phase was observed in the same pH range. These mesoporous ferrisilicate samples were characterized using XRD, N 2 sorption, EPR, SEM-EDX, TEM, FT-IR and UV-visible spectroscopies, and Mo ¨ssbauer measurements. The average pore diameters were 2.2-2.8 nm, and the mesopore volumes were 0.39-0.5 cm 3 g -1 . Moderately high Brønsted acidity was observed in the temperature-programmed desorption (TPD) pattern of ammonia over these mesoporous ferrisilicate materials. Wet chemical analysis, EPR, and Mo ¨ssbauer spectroscopic data suggested that most of the iron species are tetrahedrally coordinated Fe 3+ attached to the silica framework.

Reversible bidirectional shape memory is developed in thermoplastic polyurethane by designing different components to enable molecular switching from actuator domain to self-assembled rigid hard domain and vice versa under a temperature cycle. Polycaprolactone based special polyurethanes have been synthesized which exhibit appropriate self-assembly behavior suitable for the shape memory effect. Reversible bidirectional shape memory has been reported through induced strain and giving shape at particular temperature, and the results are compared with conventional polyurethanes which do not show any shape memory effect. The correlation between chemical structures, self-assembly, structural evolution, and shape memory effect has been made. Self-gripping is demonstrated revealing the novel mechanism of molecular flipping and temperature-induced structural change along with molecular aggregation.

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The authors report on the effect of manganese (Mn) substitution on the crystal chemistry, morphology, particle size distribution characteristics, chemical bonding, structure, and magnetic properties of cobalt ferrite (CoFe 2 O 4 ) nanoparticles (NPs) synthesized by a simple, cost-effective, and eco-friendly one-pot aqueous hydrothermal method. Crystal structure analyses indicate that the Mn(II)-substituted cobalt ferrites, Co 1– x Mn x Fe 2 O 4 (CMFO, x = 0.0–0.5), were crystalline with a cubic inverse spinel structure (space group Fd 3 m ). The average crystallite size increases from 8 to 14 nm with increasing Mn(II) content; the crystal growth follows an exponential growth function while the lattice parameters follow Vegard’s law. Chemical bonding analyses made using Raman spectroscopic studies further confirm the cubic inverse spinel phase. The relative changes in specific vibrational modes related to octahedral sites as a function of Mn content suggest a gradual change of measure of inversion of the ferrite lattice at nanoscale dimensions. Small-angle X-ray scattering and electron microscopy revealed a narrow particle size distribution with the spherical shape morphology of the CMFO NPs. The zero-field-cooled and field-cooled magnetic measurements revealed the superparamagnetic behavior of CMFO NPs at room temperature. The sample with x = 0.3 indicates a lower value of blocking temperature (9.16 K) with the improved (maximum) value of saturation magnetization. The results and the structure-composition–property correlation suggest that the economic, eco-friendly hydrothermal approach can be adopted to process superparamagnetic nanostructured magnetic materials at a relatively lower temperature for practical electronic and electromagnetic device applications.

The supramolecular synthon namely primary ammonium dicarboxylate (PAD) synthon has been exploited to generate a new series of salt based low molecular weight gelators (LMWGs) derived from ferrocenedicarboxylic acid (FDCA) and primary amines Me-(CH 2 ) n -NH 2 (n ¼ 3-15). While most of the salts are capable of forming gels with DMSO and DMF, nearly all of them show a tendency to form gels with at least one of the solvents studied. Structure property correlation based on single crystal and powder X-ray diffraction data in combination with optical-, scanning-, and transmission-electron microscopy reveals that the supramolecular synthon approach adopted herein for designing LMWGs is indeed useful and allows one to get an easy access to a new series of organometallic gelators.

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This research work investigates the tensile strength and elastic modulus of the alumina nanoparticles, glass fiber, and carbon fiber reinforced epoxy composites. The first type composites were made by adding 1-5 wt % (in the interval of 1%) of alumina to the epoxy matrix, whereas the second and third categories of composites were made by adding 1-5 wt % short glass, carbon fibers to the matrix. A fourth type of composite has also been synthesized by incorporating both alumina particles (2 wt %) and fibers to the epoxy. Results showed that the longitudinal modulus has significantly improved because of the filler additions. Both tensile strength and modulus are further better for hybrid composites consisting both alumina particles and glass fibers or carbon fibers.