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In this study, a novel nitrated bacterial cellulose/2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/ammonium perchlorate nanoenergetic composite was successfully prepared by the sol–gel ...

In this work, an experimental study of melting heat transfer of nano-enhanced phase change materials (NePCM) in a differentially-heated rectangular cavity was performed. Two height-to-width aspect ratios of the cavity, i.e., 0.9 and 1.5, were investigated. The model NePCM samples were prepared by dispersing graphene nanoplatelets (GNP) into 1-tetradecanol, having a nominal melting point of 37°C, at loadings up to 3 wt.%. The viscosity was found to have a more than 10-fold increase at the highest loading of GNP. During the melting experiments, the wall superheat at the heating boundary was set to be 10°C or 30°C. It was shown that with increasing the loading of GNP, both the heat storage and heat transfer rates during melting decelerate to some extent, at all geometrical and thermal configurations. This suggested that the use of NePCM in such cavity may not be able to enhance the heat storage rate due to the dramatic growth in viscosity, which deteriorates significantly natural convective heat transfer during melting to overweigh the enhanced heat conduction by only a decent increase in thermal conductivity. This also suggested that the numerically predicted melting accelerations and heat transfer enhancements, as a result of the increased thermal conductivity, in the literature are likely overestimated because the negative effects due to viscosity growth are underestimated.

A typical polyol that experiences solid-solid phase transitions, pentaerythritol (PE) has been proposed as a promising phase change material candidate for latent heat storage pertinent to the temperature range for industrial waste heat recovery. Upon increasing the temperature to over the solid-solid phase transition point (∼459 K), body-centered tetragonal crystalline structure of PE (α phase) is transformed into orientationally disordered face-centered cubic crystalline structure (γ phase). The thermal conductivity of PE at both α and γ phases is of great practical interest. In this work, the in situ X-ray diffraction and Fourier transformer infrared spectroscopy were used to characterize the crystalline structure transition of PE, in combination with the differential scanning calorimetry results. Molecular dynamics simulations were performed to elucidate the relationship between the thermal conductivity variation of PE and its crystalline structures at the atomic level. It was found that after the α-to-γ phase transition, the rearrangement and rotation of the O H···O bonds lead to indeterminate positions of the O and H atoms in the γ phase. The destruction and weakening of the hydrogen bonds can be the major change in the crystalline structures, leading to the reduction of the thermal conductivity of PE by a half after the α-to-γ phase transition.

The classical problem of close-contact melting heat transfer on a heated horizontal plate was revisited experimentally in the presence of nano-enhanced phase change materials (NePCM), which were prepared by dispersing graphene nanoplatelets into 1-tetradecanol at loadings up to 3 wt%. The melting experiments were performed by measuring the instantaneous height, which represents the melt fraction, of a cylindrically-shaped solid NePCM sample placed vertically on a horizontal plate that was maintained at constant wall superheats. The measured variations of melt fraction were found to agree well with the predictions of a theoretical model, where the measured loading- and temperature-dependent effective thermophysical properties of the various NePCM samples were adopted for calculation. It was shown that melting can be accelerated by the 1 wt% sample. With further increasing the loading to 3 wt%, however, melting slows down due to the dramatic growth in viscosity. The thermal resistance across the melt film becomes higher as a result of the thickened film at the higher viscosity, which offsets the contribution of enhanced thermal conductivity. Due to the loss of heat storage capacity upon introduction of the nanoparticles, the higher melting rate was revealed to not necessarily lead to an improved heat storage rate.

Polypropylene (PP) material has been widely used in the biomedical field for decades due to its high reliability in biochemical reactions. However, a pure PP material microfluidic chip has rarely been reported. Herein, a simple and rapid method has been developed to fabricate a pure PP microfluidic chip by a thermal bonding process using a PP film and PP substrate. An experiment for two-temperature PCR in the pure PP microfluidic system without a pre-treatment process has been successfully carried out. It is shown that the PP microfluidic chip has a high structural strength, tightness for water sealing, and low nonspecific adsorption, which promotes the practical application of microfluidics in the biomedical field. Compared to other existing microfluidic chip technologies, our pure PP material microfluidic chip and its fabrication method have many advantages such as high-speed production rate and extremely low cost. It can be achieved in industrial assembly lines for standardized manufacturing.

Developing an autonomous self-healing polyurethane (PU) elastomer with excellent mechanical properties and high ductility has attracted increasing attention. Nowadays, the synthesis of elastomers with excellent mechanical properties and rapid self-healing at room temperature faces a huge challenge. Herein, This work reports a new supramolecular PU with excellent mechanical properties and rapid self-healing at room temperature through the introduction of T-type chain extender into the supramolecular polymer chain. The introduction of T-chain extender can be used to enhance the mechanical strength of PU, and the multiple hydrogen bonds on the side-chain provide theoretical support for the rapid self-healing ability of PU. Maximum stress of the synthesized PU can reach 3.4 ± 0.15 Mpa, and maximum elongation at break can reach 3200% ± 160%. Due to flexibility and re-constructability of side-chain hydrogen bonds, PU stress repair efficiency can reach 96.7%, and can be self-healing scratches rapidly and effectively at room temperature. The mechanical properties and self-healing properties of PU can be adjusted by the content of T-type chain extender. The PU is applied to the metal surface coating, which has excellent acid-base resistance, bond strength up to 2.9 ± 0.1 Mpa, and the ability to eliminate local damage on the coating surface quickly at room temperature.

The thermal contact resistance (TCR) between the interfaces of phase change materials (PCMs) and their encapsulation materials, usually thin-walled metals, have a great impact on the heat storage/retrieval rates of PCM-based latent heat storage (LHS) systems. However, the TCR data beteween metal/PCM interfaces are rarely reported in the literature. In this work, an improved self-designed steady-state apparatus was adopted to measure the TCR between the interfaces of erythritol, a cost-effective sugar alcohol with great potential for medium-temperature LHS, and multiple metals including SS304, nickel silver (a copper-nickel-zinc ternary alloy), and 1060 Al. The metal/erythritol composites were prepared by naturally solidifying molten erythritol on the surface of thin metal plates. The variation of the TCR between metal/erythritol interfaces was measured as a function of the surface roughness (of the metal plates) and the contact pressure applied (between the interfaces). With the decrease of surface roughness, the TCR also decreases due to the better contact between the interfaces as observed by a microscope. Comparing to SS304 and nickel silver, the 1060 Al/erythritol composites exhibit a significant reduction of TCR by ~40% when rising the contact pressure from 0 MPa to 7 MPa, for all surface roughness levels tested. The in situ measured sample thickness variations confirmed that upon pressurization, the softer metal, i.e., 1060 Al, experiences more micro-deformation at the interface. In addition, correlations of the TCR data between metal/erthyritol interfaces were proposed with the surface roughness and contact pressure. The results and correlations attained in this work could serve as a reference for the thermal design of LHS units using erythritol.

Designed printed circuit boards (PCBs) are alternative substrates for master mold construction of microfluidic devices. However, the rough supportive material molds rough replicas and causes difficulty in device sealing. To overcome this difficulty, a copper layer is used to generate a smooth surface. Some other researchers have used thermoplastic elastomers, which are typically much easier to bond, instead of the general polymer polydimethysiloxane (PDMS). This study presents an extremely simple approach for fabricating PDMS-based microfluidic devices using PCBs as masters. Unlike those reported in the previous studies, commoditized PCBs fabricated at a common PCB manufactory were directly used as the master molds. Two layers of semi-cured silicone of a distinct base to curing agent ratios were bonded together by additional curing. Efficient bonding was accomplished and avoided insufficient adhesion due to the rough surfaces of the PDMS replicas. Highly monodisperse droplets with polydispersity values smaller than 1% were stably formed using the easy fabricated devices. Essential operations in droplet microfluidics were reliably conducted in the PDMS-based devices. Moreover, the droplets were orderly sorted by the microstructures in the fabricated multi-height devices. The fabrication process provided a simple, convenient and reliable approach to prepare the general polymer PDMS-based microfluidic devices with a minimal requirement for equipment.

The bulk thermal conductivity of thin films having a sub-millimeter thickness, made of composite phase change materials (PCM) and utilized as an emerging thermal interfacial material (TIM) for thermal management of electronics, was determined using the transient plane source (TPS) technique. The actual bulk thermal conductivity of the thin film samples was obtained by deconvoluting the thermal contact resistance (TCR) during the measurement process, according to the linear relationship between the nominal bulk thermal resistance and the thickness. The slope of the correlation curve is the reciprocal of film sample thermal conductivity and the intercept is the overall TCR. For the PCM35 thin film samples (which melt at around 35 °C) having three nominal thicknesses of 271±1 μm, 460±2 μm and 511±2 μm, the corrected results in the solid and liquid state were found to be approximately 0.487 W/m·K and 0.186 W/m·K, respectively. It was shown that the corrected values are greater than the direct readings from the TPS instrument as the latter involves the effect of TCR across multiple interfaces. The results obtained in this work could serve as reference property data for design of thermal management systems involving such phase change TIM.

Toward accelerated latent heat storage, the unconstrained melting heat transfer in spherical capsules was revisited experimentally in the presence of nano-enhanced phase-change materials (NePCMs), with an emphasis on the influence of capsule size on the rates of melting, heat transfer, and latent heat storage. It was shown that increasing the size of the spherical capsule leads to two competing effects, i.e., thicker molten layer in the close-contact melting (CCM) region and stronger natural convection. However, the NePCM with a high loading (3 wt % graphite nanoplatelets (GNPs)) is not preferred for all capsule sizes as a result of the significantly deteriorated heat transfer in both CCM and natural convection, because the dramatic viscosity growth at such a high loading leads to increased thermal resistance across the molten layer and loss of natural convection that overweigh the increased thermal conductivity. The 1 wt % NePCM sample was exhibited to be able to facilitate latent heat storage for two cases, i.e., in the smallest capsule having a radius of 14.92 mm at a higher wall superheat of 30 °C and in the intermedium 24.85 mm capsule at a lower wall superheat of only 10 °C. It was suggested that a relatively low loading of a specific NePCM can cause a faster rate of latent heat storage over the baseline case of the matrix phase-change material (PCM), if the capsule size (and the wall superheat) can be adjusted properly to regulate the molten layer thickness and the intensity of natural convection.

Freestanding graphene films are desired to be widely applied in biosensor fabrication due to their distinctive physical properties and improved performance. Chemical vapor deposition has been developed to efficiently fabricate large-area graphene. However, some of the fabricated graphene films might break or be contaminated in the current transferring step using polymers. A stable and high-quality transfer method is needed. Herein, we report on an advanced transfer method of large-area graphene film which uses fullerene as a supporting substrate. Unlike polymers, which are commonly eliminated by being dissolved in an organic solution, fullerene can be easily removed by evaporation in a vacuum because it has a different heat stability to graphene. By using the improved transferring method, the percentage of integrated freestanding films after transferring was increased from 60.7% to 93.4%. The vacuum is beneficial in terms of keeping the brittle freestanding films intact. Graphene films transferred using fullerene showed an advanced flatness and a simplicial elementary composition in comparison to those transferred using polymers. Even through there is trace residue, this stable allotrope of graphene is considered to have almost no impact on biomolecule sensing. These advantages make the fullerene transferring method an attractive candidate for fabricating large-area freestanding graphene films, especially for using in the field of biochemistry analysis and biosensors.

In recent years, as a novel photocatalyst with the excellent ability to absorb visible light, BiVO4 has drawn increasing attention. In this paper, the photocatalytic mechanism and the electronic band structure of BiVO4 were introduced in detail. On the basis of main modifications of BiVO4, progress in BiVO4 photocatalyst for degradation was further reviewed. The aim of this work is to provide guideline for the intensive studies of BiVO4 in future.

In this paper, the synthesis methods of silver nanowires including template, self-assembled, hydrothermal synthesis and polyol methods are reviewed. In addition, the application and development of the silver nanowires are introduced.

Compared with microfluidic devices, the fabrication of structure-controllable and designable nanochannel devices has been considered to have high costs and complex procedures, which require expensive equipment and high-quality raw materials. Exploring fast, simple and inexpensive approaches in nanochannel fabrication will be greatly helpful to speed up laboratory studies of nanofluidics. Here we developed a simple and inexpensive approach to fabricate a nanochannel device with a glass/epoxy resin/glass structure. The grooves were engraved using a UV laser on an aluminum sacrificial layer on the substrate glass, and epoxy resin was coated on the substrate and stuffed fully into the grooves. Another glass plate with holes for fluidic inlets and outlets was bonded on the top of the resin layer. The nanochannels were formed by etching thin sacrificial layers electrochemically. Meanwhile, the microstructures of the fluidic outlets and inlets could be fabricated simultaneously to the nanochannel formation. The total processing time for the simple nanochannel device took less than 10 hours. Optically transparent nanochannels with a depth of up to 20 nm were achieved. Nanofluidic behaviors in the nanochannels were observed under both optical and fluorescence microscopes.

Thin-walled materials, such as alloys, polymers, and glasses, with a thickness between 0.1 and 1 mm have been widely utilized in the encapsulation structures of electronic devices (e.g., the shells of laptops, cellphones, and cameras). The thermal contact resistance (TCR) and bulk thermal conductivity of these thin-walled materials are the key parameters for thermal design of electronic devices. In order to measure the TCR of thin-walled materials having a sub-millimeter thickness, an improved steady-state method was proposed in this work, which is based on the ASTM D5470 standard with the improvement being relied on in situ detection on the sample thickness variations. Such an improved apparatus was designed and constructed, which is equipped with a high-precision laser displacement sensor for measuring the sample thickness. Numerical simulations were performed to verify the heat dissipation from the insulated rods and the experimental uncertainties were analyzed. The measured bulk thermal conductivity was compared with those obtained by traditional steady-state, laser flash and transient plane source methods. The overall TCR of thin-walled stainless steel (SS304) was determined to be of the order of 10-4 m2·K/W, which was in good agreement with that of bulk SS304 samples having similar surface roughness (TCR = 3.13 × 10−4 m2·K/W).

Nanofluidic devices have many potential applications in biomedical field. One of the technical barriers of nanofluidics is to drive nanofluids in nanochannels with super-high hydraulic resistance (MPa scale) and super-small volume (fL scale). Electric field driving method (eg. electroosmotic flow) is commonly used in nanofluidics, since the conventional pumps applied in microfluidics are limited by their low pressure and low control precision. However, the electric field driving method is not suitable for all kinds of the nanofluids, which could affect the biochemical reactions, and lead to electrolytic reactions. We have developed a new type of high pressure nanofluidic micro-pump based on electrolysis. The pump system consists of electrolytic chamber, pressure sensor, control circuit, electrolytic electrodes and sample chamber that connects to nanofluidic chip. In our nanofluidic micro-pump system, high pressure gas generated from the electrolytic chamber pushes the liquid sample into the nanochannel, and the driving pressure to the fluidic sample can stably reach to 20MPa. Our high pressure micro-pump is suitable for both microfluidic and nanofluidic applications due to its very high output pressure, high control precision, fast response and wide output range.

Based on the EFTTRA-T2 experiment results, we study the transmutation characteristics of pressurized water reactors (PWR) after coating a thin layer of Tc-99 on the fuel rods. Our calculation shows that for the same Tc-99 loading amount, the effect on the PWR k eff after coating Tc-99 on the PWR fuel rods is much less than that of the homogeneous addition of Tc-99 to uranium dioxide nuclear fuel. If we just coat 0.2λ c (0.0065 mm) thickness Tc-99 on PWR fuel rods, the total Tc-99 coating amount is about 291.37 kg, this is approximately equivalent to the 4 PWR Tc-99 annual outputs, and the system k eff merely decreases to 0.98530. Loading Tc-99 to the PWR is equivalent to introducing extra poisons to PWR system to control excess reactivity, some control poisons like boric acid concentration in primary coolant or burnable poison rods in fuel assemblies are needed to be removed to keep the reactor in criticality. As Tc-99 coating thickness increases from 0.05λ c to 0.2λ c , no matter which substitution pattern is used, B16→12 or C16→12, the system k eff variations are almost the same and can return to criticality again after removing corresponding burnable poison rods from fuel assemblies. For coating 0.15λ c or 0.2λ c thickness on the fuel rods of PWR, the system k eff is slightly below the criticality either in B16→12 or C16→12 substitution pattern, we may reduce the concentration of the boric acid slightly to let the system in criticality again. Our calculation results indicate that the optimal coating thickness of Tc-99 on PWR fuel rods is probably between 0.15λ c to 0.2λ c , i.e. 0.00488–0.0065 mm.

DNA encodes the genetic information; recently, it has also become a key player in material science. Given the specific Watson-Crick base-pairing interactions between only four types of nucleotides, well-designed DNA self-assembly can be programmable and predictable. Stem-loops, sticky ends, Holliday junctions, DNA tiles, and lattices are typical motifs for forming DNA-based structures. The oligonucleotides experience thermal annealing in a near-neutral buffer containing a divalent cation (usually Mg2+ ) to produce a variety of DNA nanostructures. These structures not only show beautiful landscape, but can also be endowed with multifaceted functionalities. This Review begins with the fundamental characterization and evolutionary trajectory of DNA-based artificial structures, but concentrates on their biomedical applications. The coverage spans from controlled drug delivery to high therapeutic profile and accurate diagnosis. A variety of DNA-based materials, including aptamers, hydrogels, origamis, and tetrahedrons, are widely utilized in different biomedical fields. In addition, to achieve better performance and functionality, material hybridization is widely witnessed, and DNA nanostructure modification is also discussed. Although there are impressive advances and high expectations, the development of DNA-based structures/technologies is still hindered by several commonly recognized challenges, such as nuclease instability, lack of pharmacokinetics data, and relatively high synthesis cost.

Assumption of check values usually requires complex process. We present a simple approach to fabricate micro ball check valves by using agarose droplets as spools, which provides high assembly efficiency and robust performance.

To combine the technical functions and advantages of solid-core fiber Bragg gratings (FBGs) and hollow-core optical fibers (HCFs), the hollow and filled FBGs in nano-bore optical fibers (NBFs) with nano-bore in the GeO2-doped core are proposed. The fundamental mode field, effective mode index, and confinement loss of NBF with 50 nm– 7 μ m -diameter hollow and filled nano-bore are numerically investigated by the finite element method. The reflected spectra of FBGs in NBFs are obtained by the transmission matrix method. The hollow FBGs in NBFs can be acheived with (∼5% power fraction in the bore and the (∼0.9 reflectivity when bore diameter is less than 3 μ m . The filled FBGs can be realized with (∼1% power fraction and 0.98 reflectivity with different fillings including o-xylene, trichloroethylene, and chloroform for 800-nm bore diameter. The feasibility of the index sensing by our proposed NBF FBG is also analyzed and discussed. The experimental fabrication of hollow and filled FBGs are discussed and can be achieved by current techniques. The aim of this work is to establish a principle prototype for investigating the HCFs and solid-core FBGs-based fiber-optic platforms, which are useful for applications such as the simultaneous chemical and physical sensing at the same position.

Erosion wear is an important failure mode existing in hydropowder, petroleum, chemical industry and other fields. Nanostructured WC-Co materials possess excellent erosion wear resistance due to their outstanding combination of high hardness and excellent fracture toughness. Nanostructured WC-12Co coating was prepared by means of High Velocity Oxygen Fuel (HVOF) spraying technology in this research. The simulating experiment system was developed to study the erosion wear properties. The corundum sand with main composition of Al2O3 was used to investigate the dynamic erosion properties of nanostructured WC-12Co coating. The dynamic failure mechanism of the coatings was also analyzed by Scanning Electron Microscope (SEM). The results show that the coating is worn layer by layer in the erosion test. The bonding between the layers and the thickness of the coating should be increased to elongate the coating life.

In this paper, WC-12Co coating are prepared by two HVOF systems. The biggest difference between these two systems is the fuel gas use. Morphology and mechanical properties of the coatings are analyzed. The results show that the coating sprayed with Airplane Kerosene fuel gas is denser and the WC particles distribute more even than that sprayed with propane fuel gas. And the WC particles melt more fully. The hardness, Young’s Modules and fracture toughness of the coating sprayed with Airplane Kerosene fuel gas is higher than that sprayed with propane fuel gas.

Mesoporous silica nanoparticles (MSNs) have been explored extensively as solid supports for proteins in biological and medical applications. Small (200 nm) MSNs with ordered large pores (5 nm), capable of encapsulating therapeutic small molecules suitable for delivery applications in vivo, are rare however. Here we present small, elongated, cuboidal, MSNs with average dimensions of 90 × 43 nm that possess disk-shaped cavities, stacked on top of each other, which run parallel to the short axis of the particle. Amine functionalization was achieved by modifying the MSN surface with 3-aminopropyltriethoxysilane or 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane (AP-MSNs and AEP-MSNs) and were shown to have similar dimensions to the nonfunctionalized MSNs. The dimensions of these particles, and their large surface areas as measured by nitrogen adsorption-desorption isotherms, make them ideal scaffolds for protein encapsulation and delivery. We therefore investigated the encapsulation and release behavior for seven model proteins (α-lactalbumin, ovalbumin, bovine serum albumin, catalase, hemoglobin, lysozyme, and cytochrome c). It was discovered that all types of MSNs used in this study allow rapid encapsulation, with a high loading capacity, for all proteins studied. Furthermore, the release profiles of the proteins were tunable. The variation in both rate and amount of protein uptake and release was found to be determined by the surface chemistry of the MSNs, together with the isoelectric point (pI), and molecular weight of the proteins, as well as by the ionic strength of the buffer. These MSNs with their large surface area and optimal dimensions provide a scaffold with a high encapsulation efficiency and controllable release profiles for a variety of proteins, enabling potential applications in fields such as drug delivery and protein therapy.

YAG:Ce phosphors were synthesized by co-precipitation method. The photoluminescence intensity of samples sintered by the two-step route increases by about 10%, and with 0.5 wt.% NH4Cl added as flux, surface morphologies and size distribution are improved. The white LEDs were fabricated using as-obtained phosphors. It shows natural white light with chromaticity coordinates of (0.3083, 0.3163), color temperature (Tc) of 6886 K, the average CRI of 75, and the luminous efficacy of 85 ml/W. Therefore, The as-obtained YAG:Ce phosphors could be regard to have potential application in white LED devices.

The cellular uptake and localization of photosensitizer-loaded nanoparticles have significant impact on photodynamic therapy (PDT) efficacy due to short lifetime and limited action radius of singlet oxygen. Herein, we develop poly(ethylene glycol) (PEG)- and polyethylenimine (PEI)-functionalized zinc(II) phthalocyanine (ZnPc)-loaded mesoporous silica nanoparticles (MSNs), which are able to distribute in the cytosol by endolysosomal escape. In this photosensitizer-carrier system (PEG-PEI-MSNs/ZnPc), ZnPc is a PDT agent; MSNs are the nanocarrier for encapsulating ZnPc; PEI facilitates endosomal escape; and PEG enhances biocompatibility. The as-synthesized PEG-PEI-MSNs/ZnPc have a high escape efficiency from the lysosome to the cytosol due to the "proton sponge" effect of PEI. Compared with the ZnPc-loaded MSNs, the phototoxicity of the PEG-PEI-MSNs/ZnPc is greatly enhanced in vitro. By measuring the mitochondrial membrane potential, a significant loss of >80% Δψm after treatment with PEG-PEI-MSNs/ZnPc-PDT is observed. It is further demonstrated that the ultra-efficient passive tumor targeting and excellent PDT efficacy are achieved in tumor-bearing mice upon intravenous injection of PEG-PEI-MSNs/ZnPc and the followed light exposure. We present here a strategy for enhancement of PDT efficacy by endolysosomal escape and highlight the promise of using multifunctional MSNs for cancer therapy.

In this paper, LaNi4.7Al0.3 alloy samples were obtained via melting in middle frequency influence fire .In addition, The alloy pellets were milled for absorbing and desorbing Hydrogen ability study, The P-V-T measurement provided us with poisonous effect on the oxidation of LaNi4.7Al0.3.To understand the poisoning mechanism of O2 on LaNi4.7Al0.3, the X-ray photoelectron spectroscopy (XPS) was introduced to analyzed the process of poisoning of LaNi4.7Al0.3 alloy, Which revealed the changes of the valence of the elements of the alloy LaNi4.7Al0.3 poisoned by O2.

In this paper, the boiling heat transfer test rig was designed and built, while the characteristics of boiling Heat Transfer of refrigerants in micro-channel was researched. The wall temperature of micro-channel was measured by TH5104 Infrared thermography. The results showed that there were obvious variations for wall temperature of micro-channel along the axial direction when boiling heat transfer occurred in the micro-channel. The temperature distribution affected obviously by the heat flux, mass flow rate; vapor quality and heat transfer model.

The transmutation target of nuclear waste material has been fabrication by a powder metallurgy method by using Alumina as the matrix and CNTs as reinforcement. The effect of different nanotube contents on the fracture toughness and the bending strength was investigation. The results showed the fracture toughness and the bending strength of composites increased with increasing CNTs mass fraction when the content of CNTs was less than 1.5%. However, when the contents of CNTs greater than 1.5%, the fracture toughness and the bending strength of composites decreased as the content of CNTs increased. Possible mechanisms are discussed in detail in the paper.

National Nature Science Foundation of China[30870648, 30870617, 30500127, 31070845]; Natural Science Found of Fujian Province[C0510005]

Different grain size of starting powder was choosed and different sintering additives were used to fabricate Si3N4 ceramics by pressureless sintering. Samples’ relative density and mechanical properties including Vickers hardness, bending strength and fracture toughness were tested. Then XRD, SEM and EDS were carried out to identify phase and observe microstructure and fracture morphology. The result shows that high purity α phase Si3N4 powder of 5 μm is suitable for sintering and combination of 5 wt.% MgO +5 wt.% Y2O3 is most effective within six kinds of sintering aids.

Al-NaI radioactive transmutation target was prepared by powder metallurgy. The existing way of the phase of target was analyzed by the application of XRD and its microstructure and morphology was observed by SEM. Then EDS was used for micro-area energy spectrum analysis and the property of target with different NaI was measured and compared. The results show that NaI is uniformly distributed within the aluminum matrix. The relative density and bending strength of transmutation targets decrease with the increasing content of NaI. The hardness and electrical resistivity of transmutation targets increase with the increasing content of NaI.

A self-powered drug delivery system based on cellulose–polypyrrole (PPy) composite film was developed. The cellulose–PPy composite film was prepared by deposition of drug-contained PPy film on the inner and outer surfaces of a porous cellulose film. After coating a thin layer of active metal such as magnesium on the one side of the composite film, the drug stored in the PPy film can be released autonomously upon exposure to the electrolyte solution. It was confirmed that the drug release from the system followed the galvanic cell mechanism. The amount of the drug released and the release rate of drug can be controlled by adjusting the thicknesses and types of the active metals, respectively. Since the cellulose film is biodegradable and the system obtained is flexible and lightweight, it is therefore expected that this drug delivery system can find in vivo applications. Keywords: Polypyrrole, Drug delivery, Conducting polymers, Cellulose

CeO2@SiO2 (core@shell) nanoparticles were prepared by means of chemical precipitation technique. Results from X-ray diffraction, transmission electron microscopy (TEM), and Zeta-potential analyses provide strong microscopic and spectroscopic evidences to prove that CeO2 particles have been encapsulated inside amorphous SiO2 shell. As revealed from TEM investigations, the average grain size of CeO2@SiO2 is significantly smaller than that of uncoated CeO2 nanoparticles prepared under the same conditions, indicating it is an effective method to restrict the grain enlargement of nanocrystalline CeO2 by coating a thin layer of SiO2 at elevated temperatures. The CeO2@SiO2 nanoparticles display a similar surface electric character behavior to that of SiO2, and its dispersibility in water is improved.

The present study provides a novel approach to produce pure and stable atomic fluorine anions (F−) in the gas phase by using the F− storage emission material of [Ca24Al28O64]4+·(O2−)0.35(F−)3.30 (abbreviated as C12A7-F−), synthesized by the solid-state reaction of CaF2, CaCO3, and γ-Al2O3. The anionic species stored in the C12A7-F− material were dominated by the F− anions, about (1.9 ± 0.3) × 1021 cm−3, accompanied by a small amount of O2−, O−, and O2−, via ion chromatography and electron paramagnetic resonance measurements, which corroborates that the anionic species emitted from the C12A7-F− surface were dominated by the F− anions (about 90%) together with a small amount of the O− anions and electrons, identified by a time-of-flight mass spectroscopy. The absolute emission current density of F− was sensitive to the surface temperature and extraction field, reaching about 16.7 ± 0.8 µA/cm2 at 800 °C and 1200 V/cm. A pure and stable atomic fluorine anion beam was developed by using an electrochemistry imp...

In this work, a new kind of biodegradable pH-sensitive hydrogel was successfully synthesized by UV-initiated free radical polymerization. The obtained hydrogel was characterized by (1)H NMR and FTIR. Swelling behavior in different aqueous media and pH responsivity of the hydrogels were studied in detail as well. With increase in pH from 1.2 to 7.2, swelling ratio of the hydrogel increased. The morphology was observed by scanning electron microscopy, and the hydrolytic degradation behavior was also investigated in this work.

A series of low molecular weight poly(ethylene glycol)–polycaprolactone–poly(ethylene glycol) (PEG–PCL–PEG) biodegradable block copolymers were successfully synthesized using isophorone diisocyanate (IPDI) as the coupling agent, and were characterized using 1H NMR and Fourier transform infrared spectroscopy. The aqueous solutions of the PEG–PCL–PEG copolymers displayed a special thermosensitive gel–sol transition when the concentration was above the corresponding critical gel concentration. Gel–sol phase diagrams were recorded using the test-tube-inversion method; they depended on the hydrophilic/hydrophobic balance in the macromolecular structure, as well as some other factors, including the heating history, volume, and the ageing time of the copolymer aqueous solutions and dissolution temperature of the copolymers. As a result, the gel–sol transition temperature range could be altered, which might be very useful for application in injectable drug delivery systems.

A series of biodegradable PCL-PEG-PCL block copolymers were successfully synthesized by ring-opening polymerization of epsilon-caprolactone initiated by poly(ethylene glycol) (PEG), which were characterized by (1)H NMR, (13)C NMR, and FTIR. Their aqueous solution displayed special gel-sol transition behavior with temperature increasing from 4 to 100 degrees C, when the polymer concentration was above corresponding critical gel concentration (CGC). The gel-sol phase diagram was recorded using test tube inverting method and DSC method, which depended not only on chemical composition of copolymers, but also on heating history of copolymer's aqueous solution. As a result, the gel-sol transition temperature could be adjusted, which might be very useful for its application in biomedical fields such as injectable drug delivery system. And the typical shell-core structure of PCL-PEG-PCL micelles was introduced. The micelle-packing and partial crystallization might be the key gelation machanism for this gel-sol transition behavior of PCL-PEG-PCL aqueous solution.

The effects of annealing process on the electrical conductivity and mechanical properties of Cu-Te alloys were studied via AG-10TA electronic universal machine, SB2230 digital electric bridge, SEM and EDS. The results show that recrystallization and precipitation occur simultaneously during the annealing process of Cu-Te alloys. Tellurium precipitates as Cu2Te second phase. The grain size increases with the increasing of annealing temperature and time. The electrical conductivity increases monotonously. The tensile strength of Cu-Te alloy is higher than that of pure copper.

Solid phase minisequencing is an effective single nucleotide determination technique. However, two main methods currently used are both time and money consuming. Here, we introduced a more economical and time efficient approach, called 2-color encoding minisequencing, in which four varieties of nucleotides were labeled by the combination of two fluorescence dyes. Such code was sensitive for different nucleotides, and the sequencing results were highly uniform and repeatable.

Tuning the surface properties of mesoporous silica is desirable for many applications, such as catalysis. We present a new modification method of calcined mesoporous silica, based on the thermal grafting of 1,7-octadiene. This easy method generates a high loading of terminal alkenes. We show that the modified surface is directly available for thiol-ene click chemistry, which enables a wide variety of molecules to be attached to this alkene-functionalized mesoporous silica.

The growing interest in cell sorting and trapping is driving the demand for high performance technologies. Using labeling techniques or external forces, cells can be identified by a series of methods. However, all of these methods require complicated systems with expensive devices. Based on inherent differences in cellular morphology, cells can be sorted by specific structures in microfluidic devices. The weir filter is a basic and efficient cell sorting and trapping structure. However, in some existing weir devices, because of cell deformability and high flow velocity in gaps, trapped cells may become stuck or even pass through the gaps. Here, we designed and fabricated a microfluidic device with interdigital channels for cell sorting and trapping. The chip consisted of a sheet of silicone elastomer polydimethylsiloxane and a sheet of glass. A square-wave-like weir was designed in the middle of the channel, comprising the interdigital channels. The square-wave pattern extended the weir length by three times with the channel width remaining constant. Compared with a straight weir, this structure exhibited a notably higher trapping capacity. Interdigital channels provided more space to slow down the rate of the pressure decrease, which prevented the cells from becoming stuck in the gaps. Sorting a mixture K562 and blood cells to trap cells demonstrated the efficiency of the chip with the interdigital channel to sort and trap large and less deformable cells. With stable and efficient cell sorting and trapping abilities, the chip with an interdigital channel may be widely applied in scientific research fields.

We conducted a systematic study on neutronic characteristics of Tc-99 transmutation in pressurized water reactor (PWR) in this paper. We divided the core into three zones. The U-235 enrichment is 1.8%, 2.4% and 3.1% respectively. The loading patterns of Tc-99 include homogeneous loading and heterogeneous loading. In the homogeneous pattern, the mass fraction of Tc-99 raises from 0 to 2% stepped by 0.25%. The calculation result shows that the keff of the core decreases significantly when the Tc-99 mass fraction reaches 2%. In the practical situation, the Tc-99 mass should not exceed 2% in a homogeneous pattern. We choose the Tc-99 coating of fuel pellet as the transmutation rod form in the heterogeneous pattern, which can reduce the self-shielding effects. There are 44 transmutation rods per assembly, replacing part of fuel rods directly. We evaluate the effect of the arrangement of transmutation rods on the characteristic values such as keff and neutron spectrum of the core. In both homogeneous and heterogeneous patterns, the assembly flux near the outer edge of the core has an increasing trend. Our further study shows that much more epithermal neutrons and fast neutrons enter the reflecting layer and bounce back to the core again after moderation and reflection.Copyright © 2013 by ASME

In this article, nano-magnetite particles (ferrofluid, Fe3O4) were prepared by chemical co-deposition method. A series of biodegradable triblock poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) (PCL-PEG-PCL, PCEC) copolymers were synthesized by ring-opening polymerization method from epsilon-caprolactone (epsilon-CL) initiated by poly(ethylene glycol) diol (PEG) using stannous octoate as catalyst. And the magnetic PCEC composite microspheres were prepared by solvent diffusion method. The properties of the ferrofluid, PCEC copolymer, and magnetic PCEC microspheres were studied in detail by SEM, VSM, XRD, Malvern Laser Particle Sizer, 1H-NMR, GPC, and TG/DTG. Effects of macromolecular weight and concentration of polymer, and the time for ultrasound dispersion on properties of magnetic microspheres were also investigated. The obtained magnetic PCEC microspheres might have great potential application in targeted drug delivery system or cell separation.

This paper develops a theory to reveal the effect of small amounts of non-condensable gas on laminar filmwise condensation of a vapour-gas mixture flowing turbulently in a vertical tube. The reductions in heat transfer due to the non-condensable gas are found to be more significant at low pressures and at low Reynolds numbers of the mixture. Comparisons of the theory with some experimental data reported in the literature are in good agreement.

The fatigue crack growth rate in 18–8 austenitic stainless steel can be effectively reduced due to the strain-induced transformation at the fatigue crack tip. X-ray diffraction analyses of fracture surfaces indicate that the type of transformation products corresponds to different fracture mechanisms of materials. The transformation products are mainly α - Martensite for the fatigue striation mechanism, but e-Martensite for the dimple mechanism. Experimental evidence shows that an extreme plastic region exists at the fatigue crack tip.