Search

Carbon nanotube (CNT), particularly single-walled CNT, possesses exceptional properties, and can be utilized in many high-end applications including high-performance electronics. However, the atomic arrangement of a CNT determines its band structure, making the atomic-precision fabrication one of most important topics for the development of this material. In this perspective, the author gives a personal summary on the history, current status of the atomic-precision fabrication of CNT and outlines the remaining challenges as well as the possible paths that may lead the production of atomically precise CNTs from ‘fabrication’ to ‘manufacturing’.

CaCO3particles, due to their unique properties such as biodegradation, pH-sensitivity, and porous surface, have been widely used as carrier materials for delivering drugs, genes, vaccines, and other bioactive molecules. In these applications, CaCO3particles are often administered intravenously. In this sense, the interaction between CaCO3particles and blood components plays a key role in their delivery efficacy and biosafety, though the hemocompatibility of CaCO3particles has not been evaluated until now. Deficiency in the biosafety information has delayed the clinical use of CaCO3particles in delivery systems. In this work, we investigated the biosafety of CaCO3particles, focusing on theirin vitroandin vivoeffects on key blood components (red blood cells, platelets, etc) and coagulation functions. We foundin vitrothat high concentrations of CaCO3particles can cause the aggregation and hemolysis of red blood cells, with platelet activation and coagulation prolongation.In vivo, we found that intravenously injected CaCO3particles at 50 mg kg-1significantly disturbed the red blood cells, and platelet-related blood routine indexes, but did not induce visible abnormalities in the tissue structures of the key organs. Overall, these effects may be due to the enormous adsorption capability of the porous surface of CaCO3particles. 0.1 mg ml-1of the CaCO3particles exhibit excellent compatibility for their practical applications. These results would be expected to greatly promote thein vivoapplications and clinical use of CaCO3particles in biomedicine.

The quality of coffee bean determines the evaluation of coffee cup. The Coffea arabica was selected for initial processing and cup quality analysis by sun and water washing treatment, respectively. The results showed that the caffeic acid was bright in cyclic washing treatment, the balance was the best in washing processing, the mellow in semi-washing was better, but the comprehensive quality of sunning was the best. This study provides a theoretical basis and practical reference for the production and processing of Yunnan coffee.

High-salt organic liquid wastes treating were worldwide problem. It perplexes many chemical industries such as medicine, pesticide, metallurgy, papermaking, printing and dyeing. A new high temperature incineration technology is introduced. This is especially suitable for the treatment of organic waste liquid. At the same time, it is divided into a variety of segmentation technology routes. According to the type and amount of salt or different process routes, incineration technology can effectively transform organic waste liquid into harmless substances. At the same time, the process also recovers salt resources and generates steam, and the gas emission reaches the standard. In this paper, we will compare the different treatment methods for route selection. Through the summary of process optimization, it can provide strong support for innovation decision-making and application planning of liquid waste incineration technology.

A useful and rapid method of measuring the in-plane sheet thermal conductance of single-walled carbon nanotube (SWNT) thin films by steady-state infrared thermography is proposed in this study. The SWNT thin films are suspended between the free ends of two cantilevered silicon thin plates, and the two anchored ends are kept at different but constant temperatures to achieve steady-state heat transport through this silicon–SWNT–silicon bridge in vacuum. The temperature gradient along the bridge is captured with an infrared camera. A silicon plate with known thermal conductivity serves as a reference for calculating the heat flux, so that the sheet thermal conductance of SWNT thin films can be calculated using Fourier's law after deducting the influence of thermal radiation. The thermal conductivity of the 50-nm-thick SWNT thin film is 68.1 W m−1 K−1.

We present the successful synthesis of aligned 13C labeled single-walled carbon nanotube (SWNT) arrays from alcohol by a modified no-flow chemical vapor deposition (CVD) method that makes efficient growth possible using a small amount of carbon source. The synthesis of high-quality SWNTs by this alternative method was confirmed by resonance Raman spectroscopy, which also showed that the quality of the grown SWNTs is uniform in growth direction. The synthesis of 13C labeled SWNTs provides solid evidence for the root growth mechanism in alcohol catalytic CVD, which agrees well with the transmission electron microscopy (TEM) observations.

An optical absorbance technique was used to study the burning temperature and burning mechanism of vertically aligned single-walled carbon nanotube (VA-SWNT) films. The use of this simple optical method is shown to be consistent with the standard thermogravimetric analysis (TGA) method, but it can be applied to a very small amount of SWNTs. Experimental results indicate that burning of the VA-SWNTs is not localized, but occurs throughout the film. Furthermore, thick films have a slightly higher burning temperature than thin films synthesized under the same conditions. This is believed to be due to a higher bundle density and more uniform distribution of SWNTs within thicker films.

Several suspensions containing different types of multi-walled carbon nanotubes (MWCNTs) with different dispersion states were prepared, including homogeneous solutions of MWCNT/polymer composites in an organic solvent. The ultraviolet–visible (UV–vis) absorption spectra from 350 to 750 nm were measured, which showed that the absorbance agreed well with Beer's law and an apparent absorption coefficient was calculated. For mono-dispersed MWCNTs, the apparent absorption coefficient was independent of the diameter and length of the MWCNT. The coefficient can be used to determine the concentration of well-dispersed MWCNTs. For poly-dispersed MWCNTs, large dense agglomerates of MWCNTs caused an obvious decrease in the apparent absorption coefficient. A simple method for characterizing the concentration and dispersion state of MWCNTs in suspension or polymer composites quantitatively by spectrophotometry was developed.

The behaviour of dilaton-gluon coupling (DGC) potential is investigated by studying charmonium spectra, annihilation rates and El transition rates systematically. We find that in the non-relativistic quantum chromodynamics approximation, the charmonium properties can be described by the DGC potential.

Carbon nanotube (CNT) arrays offer the potential to develop nanostructured materials that leverage their outstanding physical properties. Vertically aligned carbon nanotubes (VACNTs), also named CNT forests, CNT arrays, or CNT turfs, can provide high heat conductivity and sufficient mechanical compliance to accommodate thermal expansion mismatch for use as thermal interface materials (TIMs). This paper reports measurements of the in-plane moduli of vertically aligned, single-walled CNT (SWCNT) and multi-walled CNT (MWCNT) films. The mechanical response of these films is related to the nonhomogeneous morphology of the grown nanotubes, such as entangled nanotubes of a top crust layer, aligned CNTs in the middle region, and CNTs in the bottom layer. To investigate how the entanglements govern the overall mechanical moduli of CNT films, we remove the crust layer consisting of CNT entanglements by etching the CNT films from the top. A microfabricated cantilever technique shows that crust removal reduces the resulting moduli of the etched SWCNT films by as much as 40%, whereas the moduli of the etched MWCNT films do not change significantly, suggesting a minimal crust effect on the film modulus for thick MWCNT films (>90 ?m). This improved understanding will allow us to engineer the mechanical moduli of CNT films for TIMs or packaging applications.

PrCo5 nanoflakes with strong texture and high coercivity of 8.15 kOe were prepared by surfactant-assisted ball milling with heat-treated starting powder. The thickness and length of the as-milled nanoflakes are mainly in the ranges of 50–100 nm and 0.5–3 μm, respectively. The x-ray diffraction patterns demonstrate that the heat treatment can increase the single phase and crystallinity of the PrCo5 compound, and combined with the demagnetization curves, indicate that the single phase and crystallinity are important for preparing high-coercivity and strong-textured rare earth permanent magnetic nanoflakes. In addition, the coercivity mechanism of the as-milled PrCo5 nanoflakes is studied by the angle dependence of coercivity for an aligned sample and the field dependence of coercivity, isothermal (IRM) and dc demagnetizing (DCD) remanence curves for an unaligned sample. The results indicate that the coercivity is dominated by co-existing mechanisms of pinning and nucleation. Furthermore, exchange coupling and dipolar coupling also co-exist in the sample.

A nonlinear Schrodinger equation in the presence of chirp and loss terms, which describes the optical solitons in an averaged dispersion-managed (DM) fiber system with fiber losses, is studied via symbolic computation. N-soliton solutions are constructed and verified with the Wronskian technique. Analytic one-, two- and three-soliton solutions are discussed. The soliton has a linear frequency chirp. Soliton width increases exponentially while soliton amplitude, energy and speed decrease exponentially along the DM fiber. As the chirp-loss coefficient increases, soliton width gets wider, while soliton amplitude, energy and speed become smaller. Interactions between the two solitons and among the three solitons are discussed and illustrated. For the larger initial soliton separations, interactions result in some smaller envelopes, which soon disappear due to the chirp-loss effect. When the soliton separations almost reaches zero, solitons interact quasi-periodically along the DM fiber, while each soliton undergoes broadening and decaying.

MgxZn1?xO alloy films were deposited on c-plane sapphire substrates by radio frequency plasma-assisted molecular beam epitaxy (rf-PMBE). The phase segregation occurred when x was larger than 33%. Be doping was found experimentally able to stabilize the high-Mg-content MgZnO alloy. By alloying 1?2% Be into MgZnO, the band gap of as-prepared quaternary alloys can be raised to the solar-blind range (4.5?eV). Calculated formation energy of the alloys based on first principle reveals that a small amount of Be incorporation can reduce the formation energy of high-Mg-content MgZnO alloys and results in a more stable system, which justifies our experimental observations.

We demonstrate the growth of Be x Zn1−x O alloy thin films on c-sapphire substrates by plasma-assisted molecular beam epitaxy. The formation of Be x Zn1−x O is very sensitive to the Be content in the alloy. Be atoms occupy the Zn lattice sites at low Be content, but move partly to the interstitial sites with increasing Be content. We also investigated the thermal stability of N, one of the most frequently used p-type dopants, in the Be x Zn1−x O films. Secondary ion mass spectrometry shows that Be element plays a crucial role in stabilizing N in the Be x Zn1−x O host, which is favourable in improving the solid solubility and the thermal stability of acceptor dopants in ZnO-based wide-gap semiconductors.

In this study, we investigated carbon feedstock decomposition conditions on the synthesis of single-walled carbon nanotubes (SWNTs) by chemical vapor deposition. We simulated gas-phase thermal decomposition of ethanol and dimethyl ether (DME) at typical SWNT growth conditions using the chemical kinetic model, and confirmed the reaction trends and primary products using Fourier transform infrared (FT-IR) spectroscopy. Molar fractions were correlated against residence time in the reactor by adjusting the volumetric gas flow rate, and concentration profiles of reaction species were compared to the predicted decomposition mechanism. Signature peak intensities indicated concentrations of both ethanol and DME.

As the first superconducting RF photo-injector (SRF gun) in practical operation, the SRF gun has been successfully connected to the superconducting linac ELBE at Forschungzentrum Dresden-Rossendorf. The injection with this new gun will improve the beam quality for the users of the radiation source. The SRF gun contains a 3½ cell superconducting accelerating cavity with a frequency of 1.3 GHz. The design is for use of normal conducting photocathodes. At present, caesium telluride photocathodes are applied which are illuminated by an ultraviolet laser beam. The kinetic energy of the produced electron beam is 3 MeV which belongs to a peak electric field of 16 MV/m in the cavity. The maximum bunch charge which is obtained and measured in a Faraday cup is about 400 pC (20 μA average current at a repetition rate of 50 kHz). The SRF gun injector is connected to the ELBE accelerator via a dogleg with two 45° deflection magnets. This connection beam line was commissioned in January 2010. A first beam injection into the ELBE accelerator has been carried out with a bunch charge of 120 pC (6 μA at 50 kHz). Detailed measurements showed that beam loss occurred in the dogleg above 60 pC due to the correlated energy spread. In order to find the optimal operation conditions, energy spread was measured in dependence of bunch charge, laser phase and further gun parameters. The Cs2Te photocathode shows an excellent life time. It is in the gun since May 2010 with about 300 h beam time and about 7 C extracted charge. In the present cavity, the limit for the acceleration gradient is field emission due to some defect on the cavity surface and problems during cleaning. Therefore a modified 3½ niobium cavity has been fabricated, which will increase the RF gradient in the gun and thus improve the beam parameters further.

A carbon nanotube field-effect transistor (CNT-FET) is a promising candidate for future electronic devices; however, its fabrication process is still challenging. We propose a simple fabrication technique for CNT-FET arrays using as-grown single-walled CNTs (SWNTs) as the gate channel. In this study, a hydrophobic self-assembled monolayer (SAM) was used to restrict the catalyst-supporting area after the fabrication of an electrode array. Since it is known that droplets are trapped at rough edges of a hydrophobic surface, the deposition of a liquid-based catalyst, followed by alcohol catalytic chemical vapor deposition (ACCVD) produced SWNTs that grew only at the corners of electrode edges. The current–voltage (I–V) characterization of FETs with a 40 µm channel width showed that 98% of the fabricated devices were electrically connected and more than 50% were functional FETs (I ON/I OFF > 102).

We have investigated ion desorption from single-walled carbon nanotubes (SWNTs) that is induced by soft X-ray illumination in the C 1s core-excitation energy range in order to have insight to the mechanism of defect formation caused by the similar excitation. The mass of desorbed ions was analyzed by a time-of-flight (TOF) spectrometer and the photon energy dependence of the ion yield or the desorption efficiency spectra were measured as a function of the monochromatic photon energy used for illumination. Experimental results exclude the simple detachment of carbon atoms constituting the nanotubes from the cause of the defect formation. Also the photo-induced etching of carbon atoms associated with C–H bond rupture is ruled out from the defect formation mechanism. Auger mechanisms to explain the photo-induced desorption are discussed.

Here, we show that the conventional concept of using SiO2-patterned Si substrates to selectively grow three-dimensional (3D) carbon nanotube structures can also be applied to dip coating. Patterned growth of high-quality vertically aligned single-walled carbon nanotubes (SWNTs) can be easily obtained by this protocol. Apart from the sintering of catalyst into Si at high temperatures, the difference in surface wettability between Si and SiO2 also plays an important role in this selective growth, which we utilize in a novel method of patterning SWNT growth on chemically modified surfaces.

An easy approach to control the carbon nanotube (CNT) array selectivity on Si/SiO2 in the floating chemical vapor deposition (CVD) method by adjusting the operation temperature is demonstrated. Aligned CNTs can be obtained directly on Si using a standard procedure at a relatively low temperature. After analyzing the temperature influence on different substrates, an attempt to grow an ultra-long CNT forest at the optimized temperature and without any feedstock diffusion limitation is discussed.