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To determine the suitable vapour compression refrigeration system for different temperature ranges, this paper established thermodynamic models for a single-stage vapour compression refrigeration system with an economiser (SSRS+E), a two-stage vapour compression refrigeration system (TSRS), and a cascade vapour compression refrigeration system (CRS) and conducted an energetic and economic analysis of it. The results show that compared with TSRS, SSRS+E can save energy by 13.6% and 7.1%, in the evaporating temperatures of -20°C and -25°C, respectively. R744/R717 CRS is superior to TSRS in terms of energy consumption and refrigeration unit investment costs. Compared with TSRS, R744/R717 CRS can save energy by 14.1% and 18.8%, in the evaporating temperatures of -45°C and -50°C, respectively. Based on the energetic and economic analysis, SSRS+E is recommended for use above the evaporating temperature of -25°C. TSRS is recommended for use in the evaporating temperature range of -45°C to -25°C, and R744/R717 CRS is recommended for use below the evaporating temperature of -45°C.

We have reported the high-pressure behavior of energetic material trimethylsilane azide ((CH3)3SiN3, TMSiN3) by in situ Raman scattering and synchrotron angle-dispersive X-ray diffraction (ADXRD) measurements in diamond anvil cells with a pressure up to ∼40 GPa at ambient temperature. The analyses of Raman spectra showed two liquid-liquid phase transitions at 0.13 and 7.9 GPa. The XRD results verified that TMSiN3 remained in a liquid state throughout the phase transitions. In the pressure range of 0.13-2.6 GPa, the distortion of the Si-C3 bond and the shortening of the bond between azide group and silicon atom lead to the first phase transition. The second transition is ascribed to the rotation of methyl group at 7.9 GPa. With further compression, the azide groups become increasingly asymmetric, and completely amorphous at 33.8 GPa. This paper is useful to understand the behavior of azide group and the molecular structural evolution of organic azide under high pressure. The unique high-pressure behavior of the azide group in TMSiN3 may be useful for improving in the formation of the polynitrogen compound with azides.

We proposed and demonstrated a switchable terahertz device composed of patterned graphene and vanadium dioxide (VO 2 ). The device can achieve function switching within the same structure and frequency range. When the graphene Fermi energy level is E F =0.6 eV and the VO 2 is in the metal phase, the proposed terahertz device can act as a broadband absorber with the absorption over 90% from 1.15 to 2.13 THz. When the graphene Fermi energy level is E F =0 eV and the VO 2 is in the insulator phase, the device can be switched into the broadband filter mode, in which the 3 dB bandwidth is 1.22 THz with the center frequency of 1.58 THz.

Here, we report the one-pot synthesis of metal-based zero-dimensional (0D)/two-dimensional (2D) nanocomposites via a modified seed-mediated growth method. In this strategy, two metal precursors (H2...

We report a facile protocol for the one-pot preparation of monodisperse Pd nanoparticles (NPs) supported on ultrathin NiCl2 nanosheets (NSs). The effective protocol can be described as in situ reduction–oxidation–assembly to create Pd/NiCl2 nanocomposites and is applicable for the development of stable yet highly active Pd-based heterogeneous catalysts for organic transformations. The Pd/NiCl2 composite displayed synergistically enhanced catalytic activity, high stability, and good recyclability for the tested model oxidation reaction. The in situ nucleation and growth of NiCl2 NS around Pd NPs guaranteed a clean metal–support interface and greatly facilitated the catalytic reaction. This work provides a novel synthesis method for supported Pd nanocomposites suitable for many important applications.

Hybrid composite materials are particularly useful and offer great opportunities for catalysis due to their multifunctionalities. Taking advantage of the high catalytic properties of bimetallic alloy nanoparticles, the large specific surface area and co-catalytic function of MoS2 nanosheets, we prepare a novel MoS2/PtCu nanocomposite with intrinsic high oxidase- and peroxidase-like activity. The preparation of MoS2/PtCu nanocomposites does not require organic solvents or high temperature. The introduction of single-layer MoS2 nanosheets not only improves porous PtCu nanoparticles with a fine dispersion, but also readily incorporates recognition elements. As a mimic oxidase, the independence of hydrogen peroxide shows the good biocompatibility of MoS2/PtCu for promising bioapplications. On the basis of oxidase-like activity, a novel colorimetric aptasensor (apt-MoS2/PtCu) was developed and its application in the colorimetric detection of cancer cells with different MUC1-protein densities was demonstrated. The as-prepared apt-MoS2/PtCu shows good sensitivity and selectivity to targeting cells. The proposed strategy will facilitate the utilization of MoS2-based nanocomposites with high oxidase/peroxidase activities in biotechnology, biocatalysis etc.

To extend the functionalities of two-dimensional graphene-like layered compounds as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS2 with metal nanoparticles is of great and widespread interest. However, few studies are available on the preparation of bimetallic nanoparticles supported on MoS2. Herein, a facile and efficient method to synthesize MoS2-PtAg nanohybrids by decorating ultrathin MoS2 nanosheets with octahedral Pt74Ag26 alloy nanoparticles has been reported. The as-prepared MoS2-Pt74Ag26 nanohybrids were investigated as novel peroxidase mimics to catalyze the oxidation of classical peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, producing a blue colored reaction and exhibiting typical Michaelis-Menten kinetics. MoS2-Pt74Ag26 has a higher affinity for H2O2 than horseradish peroxidase (HRP) and a higher vmax value with TMB as the substrate than MoS2. The improved catalytic activity of hybrids for colorimetric reactions could be attributed to the synergistic effects of octahedral Pt74Ag26 nanoparticles and ultrathin MoS2 nanosheets as supports. Meanwhile, the generation of active oxygen species (˙OH) by H2O2 decomposition with MoS2-Pt74Ag26 was responsible for the oxidation of TMB. On the basis of these findings, a colorimetric method based on MoS2-Pt74Ag26 nanohybrids that is highly sensitive and selective was developed for glucose detection. Lower values of the limit of detection (LOD) were obtained, which is more sensitive than MoS2 nanosheets.

A novel magnetic-enhanced colorimetric assay was constructed based on aptamer conjugated PtCo bimetallic nanoparticles (NPs) with high oxidase-like catalytic activity, high water solubility, low cell toxicity, and superparamagnetic properties. It was found that the incorporation of magnetic metal Co atoms into NPs could not only be facilitated for magnetic separation, but also resulted in the significantly improved oxidase-like catalytic activity of the nanoparticles for cancer-cell detection without the destructive H2O2. The present work demonstrates a general strategy for the design of multifunctional materials based on bimetallic nanoparticles for different applications, such as biosensors, nanocatalysts and nanomedicine.

The complex pathogenic mechanisms of Alzheimer’s disease (AD) include the aggregation of β-amyloid peptides (Aβ) into oligomers or fibrils as well as Aβ-mediated oxidative stress, which require comprehensive treatment. Therefore, the inhibition of Aβ aggregation and free-radical scavenging are essential for the treatment of AD. Nanoparticles (NPs) have been found to influence Aβ aggregation process in vitro. Herein, we report the inhibition effects of molybdenum disulfide (MoS2) NPs on Aβ aggregation. Polyvinylpyrrolidone-functionalized MoS2 NPs were fabricated by a pulsed laser ablation method. We find that MoS2 NPs exhibit multifunctional effects on Aβ peptides: inhibiting Aβ aggregation, destabilizing Aβ fibrils, alleviating Aβ-induced oxidative stress, as well as Aβ-mediated cell toxicity. Moreover, we show that MoS2 NPs can block the formation of the Ca2+ channel induced by Aβ fibrils in the cell membrane for the first time. Thus, these observations suggest that MoS2 NPs have great potential for a mu...

Due to low cost and high stability, the applications of inorganic nanomaterials as efficient alternatives to natural enzymes are drawing much attention. In this work, novel CuO/Pt nanocomposites with high peroxidase-like activity were designed and applied for the colorimetric detection of ascorbic acid (AA). The nanocomposites were prepared by decorating Pt NPs on the surface of CuO nanosheets, which displayed good uniformity and showed improved distribution and stability. The catalytic activity of the prepared CuO/Pt nanocomposites was tested against various chromogenic substrates in the presence of H2O2, which displayed efficient peroxidase-like activity and high catalytic stability against temperature. The catalytic mechanism of the CuO/Pt nanocomposites was investigated by hydroxyl radical detection. The peroxidase-like activity decreased significantly in the presence of AA. On the basis of the inhibition property, a colorimetric biosensor was constructed by using the CuO/Pt nanocomposites for the detection of AA. It showed a high selectivity against amino acids, carbohydrates and normal ions. Thus, this work provides new insights into the application of inorganic nanocomposite-based nanozymes in the biosensing field.

Only by obtaining a good comprehensive performance of steel/aluminum dissimilar metal joints can the steel/aluminum dissimilar metal joint structure be used more widely in the field of national defense and national production. However, cracks and intermetallic compounds are easy to occur during welding of steel/aluminum, which seriously affects the quality of welded joints. As a kind of low temperature and high efficiency solid phase bonding method, friction welding has been attached great importance in the field of new material connection and high performance equipment manufacturing. Among friction welding methods, the friction stir welding has been paid more and more attention because of various types of welded joints. In this paper, the research progress of friction stir welding of steel/aluminum is introduced from the form and process parameters, which provides the basis for further research.

Nanowires have attracted much attention due to their potential bioapplications, such as delivery of drugs or sensing devices. Here we report the development of a unique cell-capture and release platform based on nanowires. The combination of nanowires, surface-binding peptides, and cell-targeting aptamers leads to specific and efficient capture of cancer cells. Moreover, the binding processes are reversible, which is not only useful for downstream analysis but also for reusability of the substrate. Our work provides a new method in the design of the cell-capture and release platform, which may open up new opportunities of developing cell-separation and diagnosis systems based on cell-capture techniques.

Structural behaviour of cyclo-octane under high pressure is studied by using a synchrotron x-ray source in a diamond anvil cell (DAC) up to 40.2 GPa at room temperature. The cyclo-octane firstly solidifies to the triclinic phase at 0.87GPa. With the increasing pressure, the phase of cyclo-octane changes to the tetragonal phase at about 6.0 GPa and then transforms to amorphous phase above 18.2 GPa, which is kept till to 40.2 GPa. All the phase transitions of cyclo-octane are irreversible.

The compressional behaviour of natural pyrope garnet is investigated by using angle-dispersive synchrotron radiation x-ray diffraction and Raman spectroscopy in a diamond anvil cell at room temperature. The pressure-induced phase transition does not occur under given pressure. The equation of state of pyrope garnet is determined under pressure up to 25.3 GPa. The bulk modulus KT0 is 199 GPa, with its first pressure derivative K'T0 fixed to 4. The Raman spectra of pyrope garnet are studied. A new Raman peak nearly at 743 cm−1 is observed in a bending vibration of the SiO4 tetrahedra frequency range at pressure of about 28 GPa. We suggest that the new Raman peak results from the lattice distortion of the SiO4 tetrahedra. All the Raman frequencies continuously increase with the increasing pressure. The average pressure derivative of the high frequency modes (650–1000 cm−1) is larger than that of the low frequency (smaller than 650 cm−1). Based on these data, the mode Gruneisen parameters for pyrope are obtained.

Nanocrystalline molybdenum nitride (γ-Mo2N) with the cubic structure is prepared by the direct-current arc discharge method in N2 gas, using metal Mo or W rod as a cathode. The x-ray diffraction (XRD) and transmission electron microscopy (TEM) are used to characterize the product. It is found that the conversion of Mo to γ-Mo2N and affinity of Mo to N2 are determined by the nitrogen pressure. Moreover, we compare the effect of Mo and W rod as a cathode for preparing γ-Mo2N. The average size of γ-Mo2N particles is about 5 nm. The rapid quenching mechanism can be used to explain the formation of nanocrystalline γ-Mo2N.

In-situ energy dispersive x-ray diffraction on ZnS nanocrystalline was carried out under high pressure by using a diamond anvil cell. Phase transition of wurtzite of 10 nm ZnS to rocksalt occurred at 16.0 GPa, which was higher than that of the bulk materials. The structures of ZnS nanocrystalline at different pressures were built by using materials studio and the bulk modulus, and the pressure derivative of ZnS nanocrystalline were derived by fitting the equation of Birch-Murnaghan. The resulting modulus was higher than that of the corresponding bulk material, which indicates that the nanomaterial has higher hardness than its bulk materials.

The Raman spectra of PbZr0.3Ti0.7O3 for different grain size as well as at high temperature and high pressure have revealed that its structure is transformed from tetragonal to quasi-cubic phase with decreasing grain size. The phase transition temperature drops down to a lower temperature and the pressure-induced phase transition can be correlated with the diffuse phase transition.

The Raman spectra of nanocrystalline PbTi 0.75 Zr 0.25 O 3 show that its perovskite phase occurred at a higher crystallization temperature during its sol-gel process than the perovskite PbTiO 3 phase. The effects of grain size on the ferroelectric phase transition and the soft mode have been investigated. The phase transition temperature T c is shifted to a lower temperature with decreasing grain size. The possibility that the additional mode occurring in the low frequency Raman spectra might be due to zone boundary transverse acoustical phonons which couple to the q ∼ 0 soft TO phonon mode is confirmed. The Raman spectra, as a function of pressure, reveal that the phase transition may be correlated with Diffuse Phase Transition (DPT).

We study the energy-dispersive x-ray diffraction and Raman scattering of LiTaO3 at high pressure. The result remains stable up to 36 GPa. The average isothermal bulk modulus and its pressure derivative are obtained to be k0 = (225±6) GPa and k0' = 1.3±0.5 at zero pressure by the Birch-Murnaghan equation of state and the ``universal'' equation of state. The linear incompressibility of LiTaO3 between the a- and c-directions differs by a factor of four, which shows that the compression is anisotropic.

Preferred precipitation of the η phase on dispersoids was examined in the 7075, 7050 alloys and 7075 (Zr) alloy containing Zr instead of Cr under the conventional overaged temper. Specimens were solution treated at 470°C, preaged at 120°C for 86.4ks and finally aged at (163-170)°C. The η precipitates nucleate on incoherent dispersoid of the E (Al18 Cr2Mg3) phase inside the grain of the 7075 alloy. This causes serious loss of strength during overaging. Coherent dispersoids of the Al3Zr phase do not act as the nucleation site for η precipitates in the 7050. Therefore, η precipitates appeare only on grain boundaries in the 7050 alloy. The substitution of Cr by Zr in 7075 alloy is found to improve the strength after the conventional overaged temper.

Structural and spectroscopic properties of Sr2ZnTeO6 (SZTO) were investigated by angle-dispersive synchrotron X-ray powder diffraction and Raman spectroscopy in a diamond anvil cell up to 31 GPa at room temperature. Although SZTO remained stable up to the highest pressure, the different pressure coefficients of the normalized axial compressibility were obtained as βab = 8.16 × 10−3 GPa−1 and βc = 7.61 × 10−3 GPa−1. The bulk modulus B0 was determined to be 190(1) GPa by fitting the pressure-volume data using the Birch-Murnaghan equation of state. All the observed Raman modes exhibited a broadening effect under high pressure. The vibrational band v1 around 765 cm−1, which is associated with the Te—O stretching mode in the basal plane of the TeO6 octahedron had the largest pressure coefficient, and the Gruneisen parameters for all the observed phonon modes were also calculated and presented. These parameters could be used to measure the amount of uniaxial or biaxial strain, providing a fundamental tool for monitoring the magnitude of the shift of phonon frequencies with strains.

The effect of external quasi-hydrostatic pressure on the inverse spinel structure of LiCuVO4 was studied in this paper. High-pressure synchrotron X-ray diffraction and Raman spectroscopy measurements were carried out at room temperature up to 35.7 and 40.3 GPa, respectively. At a pressure of about 20 GPa, both Raman spectra and X-ray diffraction results indicate that LiCuVO4 was transformed into a monoclinic phase, which remained stable up to at least 35.7 GPa. Upon release of pressure, the high-pressure phase returned to the initial phase. The pressure dependence of the volume of low pressure orthorhombic phase and high-pressure monoclinic phase were described by a second-order Birch-Murnaghan equation of state, which yielded bulk modulus values of B0 = 197(5) and 232(8) GPa, respectively. The results support the empirical suggestion that the oxide spinels have similar bulk modulus around 200 GPa.

In this study, a novel fluorescent and temperature responsive block copolymer has been designed and synthesized by a reversible addition–fragmentation chain transfer (RAFT) polymerization method in terms of the strategy that N-isopropylacrylamide (NIPAm), maleic anhydride (MAn) and 7-amino-4-methylcoumarin (AMC) act as the temperature responsive unit, the hydrophilic unit and the fluorescent unit, respectively. The successfully synthesized block copolymer was characterized by gel permeation chromatography (GPC) and nuclear magnetic resonance (1H NMR) spectroscopy. Meanwhile, the self-aggregation behaviour in aqueous solution and the thermo-responsive property of the block copolymer were demonstrated by particle size measurement, transmission electron microscopy (TEM) observations and lower critical solution temperature (LCST) determination, respectively. Then the variation of fluorescence intensity with temperature was confirmed. With increasing temperature, shrinking of PNIPAm chains caused the block copolymer to become more hydrophobic above the LCST, assembling larger aggregates with lower interfacial curvature. Thus a part of the fluorescent groups would be embedded inside the enlarged block copolymer micelles, resulting in lower fluorescence intensity. Furthermore, the superior hydrophilicity and biocompatibility of the block copolymer as a thermometer have been demonstrated by application in intracellular temperature sensing of MDCK cells ranging from 24 °C to 38 °C.

High pressure behavior of sodium titanate nanotubes (Na2Ti2O5) is investigated by Raman spectroscopy in a diamond anvil cell (DAC) at room temperature. The two pressure-induced irreversible phase transitions are observed under the given pressure. One occurs at about 4.2 GPa accompanied with a new Raman peak emerging at 834 cm−1 which results from the lattice distortion of the Ti-O network in titanate nanotubes. It can be can be assigned to Ti-O lattice vibrations within lepidocrocite-type (H0.7Ti1.825V0.175O 4H2O)TiO6 octahedral host layers with V being vacancy. The structure of the nanotubes transforms to orthorhombic lepidocrocite structure. Another amorphous phase transition occurs at 16.7 GPa. This phase transition is induced by the collapse of titanate nanotubes. All the Raman bands shift toward higher wavenumbers with a pressure dependence ranging from 1.58–5.6 cm−1/GPa.

In-situ high pressure X-ray diffraction experiments on Heusler-type ferromagnetic shape memory alloy Mn2NiGa under pressure up to 40 GPa have been carried out by using diamond anvil cell device with synchrotron radiation source， and magnetic measurements have also been performed on uninstalled samples by using vibration sample magnetometer. At ambient pressure Mn2NiGa has body centered cubic structure. Two phase transitions in Mn2NiGa were observed during high pressure experiments. The first at about 0.77 GPa is belong to martensitic transformation, and the second at about 20 GPa is isostructural transformation between two different martensites. Meanwhile, a lot of defects and distortion of lattice were generated in martensites due to pressurization. Consequently, coercive force of stress-induced martensites rises up to 204 kA/m and it is almost ten times larger than that of thermo-induced martensites. Pressure processes also make saturation magnetization of martensites decrease rapidly, which reveals the obvious defect effect.

The Raman spectra of Pb1-xBaxTiO3(x=0,0. 2,0. 3) have been measured. Experimental results show that there is an obvious effect of small size of crystal in the system.

Crystal structures and lattice constants have been determined within the pressure range from 1 bar to 47.1 kbar for La 6 NiSi 2 S 14 and from 1 bar to 84.4 kbar for La 6 CoSi 2 S 14 using a Mao-Bell type diamond cell on a four-circle diffractometer. The compression of La 6 NiSi 2 S 14 is slightly anisotropic and La 6 NiSi 2 S 14 is compressed more easily than La 6 CoSi 2 S 14 . Bond distances and bond angles for both substances were calculated based on the refined atomic coordinates data. A phase transition was concluded to take place in the structure of single crystal La 6 CoSi 2 S 14 above 64 kbar.