Search

Recent observations of crystallization by thermal chemical vapor deposition systems indicate that the classical mechanism of nucleation and growth is followed. Information on aragonite nanocrystal growth and formation on substrate have been lacking due to the lack of reports on diffusional growth that can observe calcium carbonate nucleation processes in thin film formation. This report is important due to the additive‐free method able to grow stable single‐phase nanocrystals without the presence of other phases, amorphous or impurities. This work demonstrates homogeneous nucleation occurred in gas phase reaction in a constant flow of carbon dioxide gas (100 sccm) with optimally 0.5 M calcium chloride precursor in atmospheric pressure at 400 °C resulting in a calculated crystallite size of 27.8 nm. X‐ray diffraction and energy dispersive spectrometer confirm the presence of calcium carbonate nanocrystal, whereas its structural changes are observed by its micrograph from field emission scanning electron microscope. The aim is to convey its importance in gaining control of aragonite nanocrystal morphology and structural properties, and thus generate nanocrystals with controlled phase. This work may contribute to development of more sensitive and crucial applications of calcium carbonate nanocrystal thin film such as in biosensors and biomedical. [ABSTRACT FROM AUTHOR]

Two dimensional (2D) materials have found various applications because of their unique physical properties. For example, graphene has been used as the electron transparent membrane for liquid cell transmission electron microscopy (TEM) due to its high mechanical strength and flexibility, single-atom thickness, chemical inertness, etc. Here, we report using 2D MoS2 as a functional substrate as well as the membrane window for liquid cell TEM, which is enabled by our facile and polymer-free MoS2 transfer process. This provides the opportunity to investigate the growth of Pt nanocrystals on MoS2 substrates, which elucidates the formation mechanisms of such heterostructured 2D materials. We find that Pt nanocrystals formed in MoS2 liquid cells have a strong tendency to align their crystal lattice with that of MoS2, suggesting a van der Waals epitaxial relationship. Importantly, we can study its impact on the kinetics of the nanocrystal formation. The development of MoS2 liquid cells will allow further study of various liquid phenomena on MoS2, and the polymer-free MoS2 transfer process will be implemented in a wide range of applications.

In this work, we prepared equiatomic AlCoCrFeNi high-entropy alloy (HEA)-particle-toughened, Zr-based metallic glass composites by spark plasma sintering. By adding HEA particles as the second phase, the strength and plasticity of the Zr-based metallic glass composites improved concomitantly. After fracture, high-density dislocations and nanocrystals were formed in the HEA particles due to local severe plastic deformation, which consumed massive strain energy to enable the resistance to crack formation. Substantial lattice distortion imparted a remarkable work-hardening capacity to the HEAs and enhanced crack-tip dislocation trapping, and thus led to an extreme refinement of the grain size. Finite-element analyses indicated that the strain hardening behavior of HEA particles reduced the magnitude of strain localization, promoted generation of multiple shear bands, and stabilized shear band propagation. We attribute the enhanced strength-ductility synergy in the current composites to high-density dislocations and nanocrystal formation in the HEA particles, and stable propagation of multiple shear bands.

Abstract: Bioremediation is an innovative and alternative technology to remove heavy metal pollutants from aqueous solution using biomass from various microorganisms like algae, fungi and bacteria. In this study biosorption of zinc onto live, dead and dried biomass of Fusarium spp. was investigated as a function of initial zinc(II) concentration, pH, temperature, agitation and inoculum volume. It was observed that dried, dead and live biomass efficiently removed zinc at 60min at an initial pH of 6.0±0.3. Temperature of 40°C was optimum at agitation speed of 150 or 200rpm. The initial metal concentration (10–320mgL−1) significantly influenced the biosorption of the fungi. Overall, biosorption was high with 30–60% by dried, live and dead biomass. In addition to this, the potential of Fusarium spp. to produce zinc nanocrystals was determined by transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction and fourier transform infrared spectroscopy, which showed that dead biomass was not significantly involved in production of zinc nanocrystals. [ABSTRACT FROM AUTHOR]

Abstract: 3C-SiC nanocrystallites were epitaxially formed on a single crystalline Si surface covered by a 150nm thick SiO2 capping layer after low dose carbon implantation and subsequent high temperature annealing in CO atmosphere. Carbon implantation is used to introduce nucleation sites by forming silicon–carbon clusters at the SiO2/Si interface facilitating the growth of 3C-SiC nanocrystallites. [Copyright &y& Elsevier]

Abstract: The kinetics of crystallization of a soft magnetic amorphous Fe40Ni38B18Mo4 alloy was studied by TEM, EDX and resistivity methods. The kinetic parameters were measured from TEM studies and resistivity measurements. Nanocrystals of the fcc FeNi phase were found to crystallize by a primary crystallization mechanism followed by slow growth kinetics. The volume fraction measured by TEM matches well with that calculated from resistivity results and a TTT diagram was constructed. Quantitative measurements of the nucleation and growth rates as a function of temperature and time were performed. The nucleation rate was found to decrease with an increase in heat treatment time due to an increase in boron content in the amorphous matrix as the crystallization took place. The crystal growth was found to slow down considerably due to the presence of Mo. The crystal size was calculated according to the Michels model and compared to our experimental results. Molybdenum was found to dramatically alter the energetics of crystallization, the morphology of the crystals and particularly the kinetics of crystallization. These results offer a method of creating new families of nanostructured magnetic materials by suitable molybdenum addition. [Copyright &y& Elsevier]

High-resolution and analytical electron microscopy techniques are used to characterize Ge-implanted hexagonal SiC. After annealing the implanted samples at 1200°C, Ge is found to be located preferentially on interstitial sites. After annealing at 1600°C, small nanocrystals of strained cubic and hexagonal (or faulted cubic) Ge and Ge Si form. Occasionally, hexagonal (or faulted cubic) Si nanocrystals are observed also. [ABSTRACT FROM PUBLISHER]

The current state-of-the-art of colloidal II-VI nanocrystal formation using the aqueous/thiol synthesis route is described. Work on single component and heterostructures and mixed compound quantum dots is discussed. The purpose of the work is to provide a range of infrared (IR)-emitting materials with high quantum efficiency (QE) as potential gain media for future ultrawideband optical amplifiers for high-capacity wavelength-division multiplexing (WDM) telecommunications systems. Physical and chemical factors influencing particle sizes are described [ABSTRACT FROM PUBLISHER]

Thermally poled fused silica glass was characterized with second-harmonic optical and scanning electron microscopy. It was found that, along with the creation of a second-order nonlinearity (SON) layer under the anode surface, a layer of nanometer-sized crystalline particles exists near the anode surface. Its spatial distribution, as well as the average crystal size, was measured and compared with that of the induced SON. [ABSTRACT FROM PUBLISHER]

Two dimensional (2D) materials have found various applications because of their unique physical properties. For example, graphene has been used as the electron transparent membrane for liquid cell transmission electron microscopy (TEM) due to its high mechanical strength and flexibility, single-atom thickness, chemical inertness, etc. Here, we report using 2D MoS 2 as a functional substrate as well as the membrane window for liquid cell TEM, which is enabled by our facile and polymer-free MoS 2 transfer process. This provides the opportunity to investigate the growth of Pt nanocrystals on MoS 2 substrates, which elucidates the formation mechanisms of such heterostructured 2D materials. We find that Pt nanocrystals formed in MoS 2 liquid cells have a strong tendency to align their crystal lattice with that of MoS 2 , suggesting a van der Waals epitaxial relationship. Importantly, we can study its impact on the kinetics of the nanocrystal formation. The development of MoS 2 liquid cells will allow further study of various liquid phenomena on MoS 2 , and the polymer-free MoS 2 transfer process will be implemented in a wide range of applications.