Figure 1 Expansion of gallium inside a carbon nanotube with increasing temperature. a-c, Changing level of the gallium meniscus at 58℃ (a), 490℃ (b) and 45℃ (c); scale bar, 75nm. d, Height of the gallium meniscus plotted against temperature, measured in steps of 30–50℃; results are averaged (green curve) from closely similar measurements obtained during heating (red) and cooling (blue). The nanothermometer was synthesized in a vertical radiofrequency furnace (which differs from a one-step arc-discharge method). A homogeneous mixture of Ga2O3 and pure, amorphous, active carbon (weight ratio, 7.8:1) was reacted in an open carbon crucible under a flow of pure N2 gas: at 1,360℃, the reaction Ga2O3(solid)&2C(solid)ÕGa2O(vapour)&2CO(vapour) occurs. However, on the inner surface of a pure graphite outlet pipe at the top of the furnace, the temperature is lower (around 800℃), causing the reaction Ga2O(vapour)&3CO(vapour)Õ 2Ga(liquid)&C(solid)&2CO2(vapour) to occur, during which the nanothermometers' are created.

A variety of silicon based multilevel branched submicrometer/ nanostructures, such as branched nanowheatheads, big branched nanowheat-heads, and branched nanowires, have been rationally synthesized via a simple one-step, inexpensive, and catalyst-free fabrication technique. High-resolution transmission electron microscopy studies suggested that the main stem of wheat head and the nanotips of silicon branched nanowheat-heads are single crystals with the preferential growth direction along the [112] and [112] and orientation, respectively. Compared with big branched nanowheat-heads and branched nanowires, the room-temperature Raman frequency of branched nanowheat-heads is blue-shifted and its full width at half-maximum broadens. A moderately strong photoluminescence emission at 550 nm was suggested to be induced by defects, such as stacking faults or the SiOx surface in the branched nanowheat-heads, suggesting potential applications in light-emitting nanodevices. These studies shed light on new opportunities for fabricating different 3-dimensional nanostructures based on their property investigation.

We report here temperature measurement by means of a Ga-filled C nanotube thermometer with diameter,150 nm and length; 12mm. The method relies on the initial identification and calibration of a nanothermometer in a transmission electron microscope TEM, followed by placing it into an air-filled furnace whose temperature is to be measured, and final TEM reading of a postmeasurement gradation mark visible inside the tubular channel. The mark originates from the fact that, at high temperature, the Ga column tip exposed to the air through the open C nanotube end oxidizes, and a thin Ga oxide layer sticks to the nanotube walls upon cooling. The temperature according to this gradation mark coincides closely with nominal furnace temperature controlled by standard means. The method paves the way for practical temperature measurements using a C nanothermometer in air and within spatially localized regions e.g., dimensions of tens of micrometers.

Indium-filled carbon nanotubes were synthesized via a simple chemical vapor deposition. The carbon nanotubes had diameters of 100-200 nm and length of; 10mm. The melting and expansion behavior of the indium in carbon nanotubes were investigated in an analytical transmission electron microscope. It was found that the melting and expansion behavior of indium were different from that in a macroscopic state. The melting behavior was explained using a particular equation developed for a nanoscale indium column. The analysis of the expansion behavior allows us to clarify the problems of indium filling usage in carbon nanotube-based nanothermometer.

Thermodynamic analysis was performed with respect to the effect of surface tension on the expansion characteristics of a one-dimensional nanoscale liquid Ga column inside a carbon nanotube. The analysis showed that the surface tension affects the column inner pressure, and that the smaller the column diameter, the greater the surface effect. Based on the analysis, it is quantitatively explained why a liquid Ga column with 75 nm diameter has virtually the same expansion coefficient as that of Ga in a macroscopic state in the range of 50 to 500℃, and suggested that the volumetric expansion coefficient can be directly used for the calibration of a given nanothermometer with a diameter larger than 10nm.

Large yield of β-Ga2O3 nanorods with metal Ga tip were efficiently synthesized. They were deposited on surface of amorphous C fibers by decomposition of Ga2O vapor at around 1000℃, where Ga2O vapor was produced at 1360℃ by a reaction between pure Ga2O3 and active carbon powders. The nanorods had diameters ranging from 10 to 100 nm and lengths of up to several tens micrometers. Twins and edge dislocations having a Burgers vector of 0.0859 Å @2.66, 3.66, 1] existed in the nanorods. A redshift of 4-23 cm-1 was found in the Raman scattering spectrum of nanorods compared with that of a pure Ga2O3 powder. This phenomenon was explained qualitatively in terms of the defects in the nanorods.

SiC nanorods with 20-100 nm diameter and 10–100μm length were synthesized by reaction between SiO and amorphous activated carbon (AAC) at 1380℃. Microstructural characterization of the SiC nanorods was carried out by high resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS). The SiC nanorods grow on either a chain or from facets of SiC nanoparticles. They are usually straight and preferentially orientated along the [111] direction. Branching phenomenon exists for these nanorods. Typical SiC nanorod tip was analyzed by HRTEM image and EDS analysis. Based on an experimental analysis, a formation mechanism is proposed to explain the microstructural characterization of the SiC nanorods.

Si3N4/SiC interface structure in SiC-nanocrystal-embedded a-Si3N4 nanorods was studied by high-resolution transmission electron microscopy. The SiC-nanocrystal-embedded a-Si3N4 nanorods were synthesized by the method of carbothermal reduction of SiO in pure N2 atmosphere, while the SiC nanocrystals were produced from a substitution of SiC for Si3N4. Between SiC and Si3N4, there are three kinds of plane configurations and a set of orientation relationships, i.e., Si3N4, and nearly (111)SiC//(1010)Si3N4 with low-angle discrepancy of either 3

α-Si3N4 K15nanorods with 20-80 nm width were synthesized by carbothermal reduction of SiO with amorphous activated carbon (AAC) as a reductant. Microstructural characterization of the synthesized nanorods was carried out by high resolution transmission electron microscopy (HRTEM)and energy dispersive X-ray analysis. Many Si3N4 nanorods were found to be twisted. Each twisted nanorod contained several straight Si3N4 parts. The straight parts had the rod axes orientated along the〈1010〉direction, which is the closest packing direction of a-Si3N4. There were two kinds of joints between the two adjacent straight Si3N4 parts. Formation mechanism of the Si3N4 nanorods is discussed.

Ge3N4 nanobelts 30-300 nm in width were synthesized by thermal reduction of a mixed Ge+SiO2 powder in NH3 atmosphere. These nanobelts were studied by high-resolution transmission electron microscope equipped with an x-ray energy dispersive spectrometer. In these synthesized nanobelts, the existence of α and β phases of Ge3N4 was identified. The a phase exhibiting slight difference from an ideal α-Ge3N4 phase was also found in the present Ge3N4 material. The mechanism of formation of the Ge3N4 nanobelts is discussed.