Diamond cubic Sn (α-Sn) has many potential optoelectronic applications, but is normally stable only below 13°C. Here we demonstrate the stabilization of α-Sn nanodots at room temperature and above in ...a Ge matrix produced by rapid solidification of a Ge-6.3at%Sn alloy. High resolution transmission electron microscopy (HRTEM) and differential scanning calorimetry (DSC) were employed to study the structure and stability of Sn particles, respectively. We show that the formation pathway of α-Sn is through the decomposition of a Ge-Sn solid solution, which gives a thermodynamic driving force necessary for the formation of α-Sn.
•Demonstrated the stabilization of α-Sn nanodots at room temperature and above in Ge.•Used rapid solidification to produce α-Sn nanodots.•HRTEM and DSC were employed to study the structure and stability of Sn particles.•Showed that the formation pathway of α-Sn is through the decomposition of solid solution.
Barium strontium titanate glass-ceramics were successfully produced with one major crystalline phase when Al^sub 2^O^sub 3^ was added to the melt. A dielectric constant of 1000 and a breakdown ...strength of 800 kV/cm was achieved; however the energy density was only measured to be 0.3-0.9 J/cm^sup 3^. These energy density values were lower than anticipated due to the presence of dendrites and pores in the microstructure. Using BaF^sub 2^ as a refining agent improved the microstructure and doubled the energy density for BST 80/20 samples. However, no refining agent reduced the increasing amount of hysteresis that developed with increasing applied electric field. This phenomenon is believed to be due to interfacial polarization.PUBLICATION ABSTRACT
•This paper presents results on converting rice and wheat husks to zinc silicate.•Raman and XRD confirmed the formation of nanoparticles of zinc silicate.•Zn2SiO4 consisted of pure rhombohedral R3¯ ...phase.
We report a faster, less expensive method of producing zinc silicate nanoparticles. Such particles are used in high volume to make phosphors and anti-corrosion coatings. The approach makes use of phytoliths (plant rocks), which are microscopic, amorphous, and largely silicate particles embedded in plants, that lend themselves to being easily broken down into nanoparticles. Nanoparticles of Zn2SiO4 were produced in a two stage process. In the refinement stage, plant residue, mixed with an appropriate amount of ZnO, was heated in an argon atmosphere to a temperature exceeding 1400°C for four to six hours and then heated in air at 650°C to remove excess carbon. TEM shows 50–100nm nanoparticles. Raman scattering indicates that only the -Zn2SiO4 crystalline phase was present. X-ray analysis indicated pure rhombohedral R3¯ phase results from using rice/wheat husks. Both samples luminesced predominantly at 523nm when illuminated with X-rays or UV laser light.
We have demonstrated that large quantities of β-SiC nanostructures can be obtained from rice husk agricultural waste by using controlled conditions in a thermogravimetric setup. This simple and ...inexpensive method of producing these structures on a large scale is critical for applications in nanoelectronics, nanosensors, and biotechnology. The temperature and atmosphere are two critical elements in forming either α-cristobalite (SiO
2
) or β-SiC. Using different characterization methods (x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy), we have shown that pyrolysis of rice husks in argon atmosphere at 1375°C results in simultaneous formation of carbon nanotubes, β-SiC nanowires/nanorods, and β-SiC powder.
•This paper presents results on converting sorghum leaves to an industrially important material.•Nanosacle particles and nanorods of the silicon carbide were produced by microwave processing.•The ...scanning electron microscopy showed the formation of nanorods and nanotubes of SiC and Carbon.•The transmission electron microscopy confirmed the formation of nanorods along 111 direction.•The presence of 6H/4H stacking faults in 3C phase makes a quantum-well like structure for applications.
Microwave processing and conventional furnace heating of dried sorghum leaves at temperatures in excess of 1400°C in either vacuum or inert atmosphere produced nanoscale particles and nanorods of silicon carbide (SiC). This simple and fast method of producing SiC nanoparticles from sorghum leaves, an agriculture waste, expands on the varied approaches designed toward the mass production of SiC nanoparticles that are potentially pertinent for electronics, optics, biotechnology and structural material applications. Using X-ray diffraction it was found that the processed samples consisted of β (3C)-SiC phase, which was confirmed using transmission electron microscopy. Transmission electron microscopy revealed the formation of nanorods along 111 direction with the presence of stacking faults orthogonal to this direction. The presence of 6H/4H-SiC stacking faults in the 3C phase is explained in terms of their total formation energies. The nanostructures described here can lead to nanoscale optics in the mid-IR such as surface phonon polariton resonators, mid-IR metamaterials, chemical and molecular sensors, nanoscale electronics and high tensile strength filaments for structural composite materials.
Cobalt Oxide (Co
3
O
4
) was reduced to metallic Co using the nut shells of pistachio by heat treatment at temperatures of 1400°C and 1500°C in an argon gas atmosphere. This method for reducing ...Cobalt Oxide may provide a valuable route for reclaiming nanoparticles of metallic Co from waste material. Rietveld analysis of the x-ray diffraction profiles showed the presence of two phases of Co; FCC (γ-Co), and ΒCC phase of Co in addition to the presence of C in the graphite phase. The samples synthesized by processing at 1400°C showed only the FCC phase of Co whereas mixed phases of FCC and BCC Co were formed for samples heat treated at 1500°C. The magnetic properties were determined using VSM and FMR measurements. A magnetic saturation value of 160 emu/g was determined for the FCC phase which is consistent with the literature value. On the other hand, the magnetic saturation value of BCC Co was measured to be 214 emu/g. Magnetic data suggest the average magnetic moment is consistent with FCC cobalt. This simple method of producing BCC-Co has potential industrial and possible medical applications such as magnetic sensors, electromagnetic shielding, magnetic memory, magnetic fluids, magnetic composites and catalysis.
Covetic materials have been claimed to be new types of metal matrix nano-composite materials. These materials are formed from face-centered-cubic metals which are alleged to be super-saturated with ...up to ~ 10 wt pct of activated nano-carbon. The focus of this study was to characterize the chemical composition of copper covetic materials of varying nano-carbon concentrations, and characterize the thermal properties of these materials in order to determine if these materials exhibit enhanced material properties.
Ferric oxide (Fe2O3) was directly reduced to metallic Fe using the carbon source from the coconut shells at temperatures above 1400 °C in argon gas atmospheres. X-ray diffraction analysis showed the ...presence of α-, γ- phases of Fe in addition to the presence of carbon nanotubes (CNTs). By selecting the appropriate ratios of coconut shell powder to Fe2O3, it is demonstrated that pure Fe is produced without any residual ferric oxide. The quantitative analysis of each of the Fe phases and carbon nanotubes was dependent on the temperature and the duration of processing at high temperature. Transmission electron microcopy results showed copious amount of carbon nanotubes in the samples. Magnetic property measurements suggested that, the average magnetic moment is consistent with presence of α-phase and the ferromagnetic γ-phase of Fe. This novel method of producing pure α- and γ-Fe in the presence of carbon nanotubes using coconut shells has potential applications as nanocomposites.
Metallic iron exhibits three distinct crystallographic phases, α-(bcc), γ-(fcc), and δ-(bcc), under variable temperature. In this paper, we show that iron oxide, in the hematite composition, Fe
2
O
3
..., was reduced to its pure metallic form, using carbon obtained from the nut shells of pistachios or walnuts, at temperatures exceeding 1400°C, annealed in argon gas atmosphere. In addition to α-, γ-, and δ-phases of Fe, x-ray diffraction analysis shows the presence of carbon nanotubes (CNTs) and amorphous carbon. There was no residual ferric oxide present as long as the appropriate ratios of nut shell powder to Fe
2
O
3
were selected. The quantity of each of the three Fe phases was a function of the temperature and the time of processing. Transmission electron microcopy revealed the presence of large quantities of CNTs formed during annealing. Magnetic data suggested the average magnetic moment was consistent with α-Fe, but reduced moment for both the γ-Fe and δ-Fe. This is the first observation of producing δ-Fe stable at room temperature along with CNTs. This has potential industrial applications as composites. Although both α- and δ-ferrites are body-centered cubic, δ-ferrite is a more compact structure indicative of higher specific density and hence improved mechanical properties. In addition, the magnetic and structural properties of the metastable Fe provide insights in understanding the novel properties of artificial structures on the nanometer scale made using advanced thin film techniques.
Nanoparticles of Aluminum Nitride (AlN) were synthesized from a thermal treatment of mixtures of aluminum oxide (Al2O3) and either shells of almond, cashew, coconuts, pistachio, or walnuts in a ...nitrogen atmosphere at temperatures in excess of 1450 °C. By selecting the appropriate ratios of each nutshell powder to Al2O3, it is demonstrated that stoichiometric aluminum nitride is produced via carbo-thermal reduction in nitrogen atmosphere. In addition, results show the formation of Al from Al2O3 before transformation to AlN. On the other hand, when Al was mixed with nutshell powder first, mixed phases of AlN and Al4C3 were formed before complete transformation to AlN. X-ray diffraction analysis, Raman scattering and Fourier Transform Infrared spectroscopy confirmed the wurtzite phase of aluminum nitride. Transmission electron microscopy indicated the formation of AlN nanoparticles. The formation of AlN from nutshells offers a simple route and avoids multiple-step processes involving carbon rich agents at elevated temperatures.
•Converting nut shells to an industrially important material of AlN.•Nanoscale particles of AlN were produced by pyrolizing alumina/Al and nut shells.•The TEM confirmed the formation of nanoparticles of aluminum nitride.•XRD and Raman Spectroscopy confirmed pure wurtzite phase of aluminum nitride.
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