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Lamellar crystals laterally bounded by {110} faces only (nontruncated lozenges) are obtained from 1% octacosane solutions of alkanes n-dohexacontahectane (C162H326) and n-octanonacontahectane (C198H398) at the highest crystallization temperatures, i.e., 103 °C < T c < 108 °C and 108 °C < T c < 110 °C, respectively. This is in contrast with polydisperse polyethylene where {110}-bounded lozenges form only at low T c. Crystals grown from 1-phenyldecane at the highest T c are also nontruncated. However, while the crystals obtained from octacosane are faceted and rhombic, those grown from phenyldecane have their {110} faces asymmetrically curved at the obtuse apexes. This gives the crystals a leaf-shaped appearance, normally associated with {100}-bounded lamellae. To distinguish it from the established {100} bounded lenticular crystal morphology, the new habit is designated “a-axis lenticular”. The particular type of curvature found for {110} faces is explained qualitatively by assuming a different rate of propagation in the two opposite directions of a new layer of stems. The “sharp” step travels faster, at a rate v s, toward the acute apex, while the “blunt” step travels more slowly, at a rate v b, toward the obtuse apex. The asymmetry is due to the absence of a mirror plane bisecting the {110} growth face.

An in situ study of solution crystallization kinetics and morphology of the long alkane n-C246H494 has been performed by interference optical microscopy using a T-jump hot stage. The crystallization temperatures (T c) covered the full range of extended-chain and part of the once-folded chain range. A drastic change in crystal habit, from broad curved-faced “truncated lozenge” to needle-shape, occurs as T c is lowered toward the extended- to folded-chain transition. Crystal shapes were fitted to the Mansfield ellipse and T c dependencies of the following parameters were determined:  growth rates of {100} and {110} faces (G 100 and G 110), as well as the rates of secondary nucleation i 100 and layer propagation v 100 on {100} faces. With decreasing T c, all four rates first pass through a maximum and then a minimum at the transition. G 100 is more retarded by self-poisoning than G 110. Furthermore, at the minimum i 100 is impeded significantly more compared to v 100, resulting in straight {100} facets. The fact that v 100 passes through a minimum is the first evidence that the barrier to layer propagation (“substrate completion”) is entropic rather than surface energy based. Significantly, the changes in crystal habit with decreasing T c correspond to similar albeit less drastic changes which occur in polyethylene with increasing T c. It is thus suggested that self-poisoning also operates in polyethylene, and increasingly so at higher temperatures. Finally, the binary phase diagram C246H494−n-octacosane solvent exhibits classical behavior, reasonably well described by the Flory−Huggins theory.

A series of Mn x Fe 3−x O 4 (0 ≤ x ≤ 1) nanoparticles was successfully synthesized via a simple coprecipitation method. The starting material was a natural magnetite purified from local iron sand. Crystallite nanoparticles were produced by drying without using a high calcination temperature. Rietveld analysis of the X-ray diffractometry (XRD) data for all samples demonstrated that the Mn ions partially substituted the Fe ions in the spinel cubic structure of the Fe 3 O 4 to form Mn x Fe 3−x O 4 phases. We applied two lognormal spherical and single mass fractal models to the analysis of the small-angle neutron scattering (SANS) data and revealed that the primary Mn x Fe 3−x O 4 particles ranged in size from 1.5 to 3.8 nm and formed three-dimensional Darminto

Manganese (Mn)-doped black iron oxide (Fe3O4) magnetic fluids in the system of MnxFe[Formula: see text]O4 were successfully synthesized from natural magnetite (iron sand) by using co-precipitation method at room temperature. The analyses of the small angle neutron scattering (SANS) data by applying a log-normal sphere with a mass fractal models for [Formula: see text] and [Formula: see text] and two log-normal spheres with a single mass fractal models for [Formula: see text], 0.75 and 1 revealed that the primary particles of the MnxFe[Formula: see text]O4 fluids tended to decrease from 3.8[Formula: see text]nm to 1.5[Formula: see text]nm along with the increasing fraction of Mn contents. The fractal dimension ([Formula: see text]) increased from about 1.2 to 2.7 as the Mn contents were increasing; which physically represents an aggregation of the MnxFe[Formula: see text]O4 particles in the fluids growing up from 1 to 3 dimensions to consolidate a more compact structure. The magnetization curves of the fluids exhibited an increasing saturation magnetization from [Formula: see text] to [Formula: see text], and a decreasing on [Formula: see text] and 0.75, with the maximum achievement of [Formula: see text]. These phenomena may probably be due to the combined effects, arising from cationic and dopant distributions, aggregation and its size, and also fractal dimension. Furthermore, the decrease of blocking temperature of the MnxFe[Formula: see text]O4 magnetic fluids could be associated with the reduced particle sizes, while the freezing temperature had its highest peak intensity when it collectively occurred with the blocking temperature at a similar point of about 270[Formula: see text]K.