HEAT SHRINKING BEHAVIOUR OF γ-RADIATION CROSSLINKED POLYETHYLENE

Heat shrinking material of γ-radiation erosslinked polyethylene is widely used for various application in industry. In this study, DSC, TMA, WAXD and density measurement techniques were used to investigate the influence of MI and thermal history of LDPE on the effectiveness of network formation. Based on the results of heat stretching and heat shrinkage tests, it is found that the formation of a network as perfect as possible is indispensable to the irradiated material if good heat shrinkage property is desired. To this end, quenching technique and polyethylene with appropriate MI must be used so that an effective radiation effect will be obtained with a minimum amount of radiation dose. In spite of that the mechanical property of the irradiated polyethylene in the rubbery state is basically in agreement with the classical expression of the theory of high elasticity, only about 90% shrinkage can be reached. Besides, the heat shrinkage temperature T_s and the % shrinkage Sare both related to the radiation dose.     

A Fast and Room-temperature Self-healing Thermal Conductive Polymer Composite

Thermal conducting materials may be damaged during long-term use, resulting in the increase of thermal resistance and therefore inefficient heat dissipation. The introduction of self-healing ability may solve this problem, but the realization of fast and room-temperature selfhealing in thermal conducting composites is quite challenging. Herein, we choose a flexible poly(dimethylsiloxane) polymer material(PDMSCOOH) as the matrix and graphene nanosheets as the thermal conductive filler to prepare ...     

Precise in-situ and ex-situ study on thermal behavior of LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2/graphite coin cell:From part to the whole cell

Multiple mode calorimetry and C80 micro-calorimeter are used to investigate the impact of cathode and anode on heat generation of lithium ion battery.The thermal behaviors of LiNi_xCo_yMn_zO₂/graphite full cell are discussed under normal operating and elevating temperature.Affected by negative entropy change,lithium intercalation presents more exotherms than deintercalation for both electrode materials.The contributions of irreversible and reversible heat to the total heat generation of graphite are evaluated.The phase transitions correlated with voltages and lithium contents are determined.Based on the analysis of half-cell,the effect of two electrodes(with the same capacity)on overall heat generation is nearly the same and anode of full cell plays a key role in charging while cathode dominates in discharging.Thermal behaviors of lithiated graphite and delithiated LiNi_xCo_yMn_zO₂ electrolyte and their coexisting system are identified to further explore their influence on battery safety.The breakdown of solid electrolyte interface(SEI)at around 82℃ is considered as a crucial factor affecting the thermal stability of full cell.The oxidation of electrolyte induced by oxygen released from cathode material turns out to be one of the main heat sources.These accurate results are of great significance to improve the existing thermal management system and provide basic data for the prediction of battery performance.     

Synthesis and thermal properties of poly(styrene-co-acrylonitrile)-graft-polyethylene glycol copolymers as novel solid–solid phase change materials for thermal energy storage

A novel poly(styrene-co-acrylonitrile)-graft-polyethylene glycol(SAN-g-PEG) copolymer was synthesized as new solid–solid phase change materials(SSPCMs) by grafting PEG to the main chain of poly(styrene-co-acrylonitrile). The chemical structure of the SAN-g-PEG was confirmed by the Fourier transform infrared(FT-IR) and proton nuclear magnetic resonance(1H NMR) spectroscopy techniques. The thermal energy storage properties and the storage durability of the SAN-g-PEG were investigated by differential scanning calorimetry(DSC). The SAN-g-PEG was endowed with the solid–solid phase transition temperatures within the range of 23–36 8C and the latent heat enthalpy ranged from 66.8 k J/kg to 68.3 k J/kg. Thermal cycling tests revealed that the SAN-g-PEG kept great heat storage durability after 1000 thermal cycles. The thermal stability was evaluated by a thermal gravity analysis(TGA), and the initial decomposition temperature(Td) of SAN-g-PEG is 350 8C, which proves that the SAN-g-PEG possessed good thermal stability.     

Preparation and Characterization of Microencapsulated Hexadecane Used for Thermal Energy Storage

Polyurea microcapsules about 2.5μm in diameter containing phase change material for thermal energy storage application were synthesized and characterized by interfacial polycondensation method with toluene-2,4-diisocyanate and ethylenediamine as monomers in an emulsion system. Hexadecane was used as a phase change material and OP, which is nonionic surfactant, and used as an emulsifier. The chemical structure and thermal behavior of the microcapsules were investigated by FTIR and thermal analysis respectively. The results show encapsulated hexadecane has a good potential as a solar energy storage material.     

Advanced X-Ray Laboratory Microbeam Techniques Applied to Metallurgy

X-ray experiments with a spatial resolution of lower then 1 μm have been achieved with microfocus sources by means of high brilliance 3^rd generation synchrotrons. Recently the availability of high-sensitivity, high-resolution and large area detectors, as for example image plate, has allowed the analysis of samples with a spatial resolution of few tens of micrometers also with conventional laboratory sources. X-ray microdiffraction (μXRD) experiments have also been considered with increasing interest for phase identification and to evaluate the crystallite size distribution and preferred orientation. Coupled with X-ray microfluorescence (μXRF), this technique allows a complete characterisation of very small samples and/or with complex geometry. In this paper interesting applications of these laboratory techniques for the characterisation of deposits from superheater tubes of solid waste incinerator are shown. The high resolution of the probe allows the precise determination of the mixture of salts and oxides forming the deposits. This information is mandatory for the understanding of corrosion mechanisms which take place in the tubes. The results obtained by μXRD and μXRF are integrated by others techniques, such as Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDXS).     

Temperature Controlled Lateral Pattern Formation in Confined Polymer Thin Films

The thermal induced topography change in a model system consisting of a polymer film on a Si substrate capped by a thin metal layer has been studied by using AFM. Regular lateral patterns over large areas were observed on the surface when the system was heated to a sufficiently high temperature. 2D-FFT analysis to the AFM images indicates that the patterns are isotropic and have well defined periodicities. The periodicities of the characteristic patterns are found to depend strongly on the annealing temperature. The study of the ki-netics of the formation reveals that such a topography forms almost instantaneously once the critical tempera-ture is reached. It is suggested that this wave-like surface morphology is driven by the thermal expansion co-efficient mismatch of the different layers. This method for generating regular wave-like patterns could be used as a general method for patterning various organic materials into micro/nanostructures.     

Synthesis and Characterization of Yttrium Doped Nano-zirconia by a Cationic Surfactant-assisted Route

1INTRODUCTION Zirconia is a kind of metal oxide material with high melting point(2700℃),high boiling point,small thermal conductivity,large coefficient of ther-mal expansion,high temperature resistance,good abrasive resistance and favorable resistance to corrosion.Due to its both acid and alkaline surface centers,zirconia is an ideal catalytic material with acid group bi-functions[1].In addition,owing to the excellent ionic exchange property as well as the chemical and mechanical stabilit…     

Catalytic Combustion of Methane over Ti-Pillared Clay Supported Copper Catalysts

A natural montmorillonite, produced from Laiyang of Shandong Province, was pillared by Tipolycations to form Ti-pillared clay (Ti-PILC), and characterized by BET surface area, infrared spectra and thermal analysis. The characterization results show that Ti-PILC has a larger surface area and more hydroxyl groups than that of the natural clay, thus was used as the catalytic carriers to prepare supported Cu catalysts (Cu/TiopILC). The 20%Cu/Ti-PILC with 10mmol/g of Ti/clay shows a high catalytic performance of methane combustion in the temperature range of 400-500℃.     

Microencapsulation of n-Eicosane as Energy Storage Material

For heat energy storage application, polynrea microcapsules containing phase change material, n-eicosane, were synthesized by using interfacial polymerization method with toluene-2,4-diisocyanate (TDI) and diethylenetriamine(DETA) as monomers in an emulsion system. Poly(ethylene glycol)octyl-phenyl ether (OP), a nonionic surfactant,was the emulsifier for the system. The experimental result indicates that TDI was reacted with DETA in a mass ratio of 3 to 1. FF-IR spectra confirm the formation of wall material, polyurea, from the two monomers, TDI and DETA.Encapsulation efficiency of n-eicosane is about 75%. Microcapsule of n-eicosane melts at a temperature close to that of n-eicosane, while its stored heat energy varies with core material n-eicosane when wall material fixed.Thermo-gravimetric analysis shows that core material n-eicosane, micro-n-eicosane and wall material polyurea can withstand temperatures up to 130, 170 and 250℃, respectively.     

Sulfur-decorated nanomesh graphene for high-performance supercapacitors

Sulfur-decorated nanomesh graphene(S@G) has been synthesized by a 155℃ heat treatment of a mixture of nanomesh graphene and S. The as-obtained S@G materials keep a high specific surface area,and exhibit obviously enhanced conductivity and hydrophilicity as compared to the pristine graphene.X-ray photoelectron spectroscopy and thermogravimetric analysis indicate that most S atoms in the S@G samples are stably combined with nanomesh graphene via covalent bonds rather than exist as free elemental S. As an electrode material for aqueous supercapacitors, the S@G with a S content of 5 wt% delivers a specific capacitance up to 257 F/g at the current density of 0.25 A/g, which is 23.6% higher than that of the undoped graphene. Our results provide a simple approach to scalable synthesis of S-doped porous carbon materials, which have potential applications in the high-performance capacitive energy storage devices.     

Comparative study of electrochemical and thermal oxidation of pyrite

The oxidation of pyrite was studied as a function of grain size, employing voltammetric and thermal analysis. The data obtained with the electrochemical experiments are consistent with the results shown in the thermogravimetry-differential thermogravimetry (TG-DTG) records. The use of both techniques revealed that oxidation of the mineral is affected by the grain size employed. The maximum yield of SO₄ ^2– was obtained from electrodes constructed with <210 μm-sized particles. The same behavior was observed during thermal decomposition. When the temperature surpasses 490 °C, the small particles (<210 μm) oxidize in a single step which is not affected by changes in the rate of air flow, indicative of their higher reactivity among the ground mineral electrodes. The comparison between the results obtained by the two methods suggests that, below 490 °C or 0.6 V, pyrite oxidation, either in air or in aqueous media, is similar and depends on the semiconducting properties of the mineral. Electronic Publication     

Photoelectrochemical study of MoO_3 assorted morphology films formed by thermal evaporation

Molybdenum oxide nanostructured thin films were grown on fluorine doped tin oxide(FTO), indium doped tin oxide(ITO) and ordinary glass substrates by thermal evaporation process without vacuum and catalysts using molybdenum trioxide(MoO_3) powder as a source material and oxygen as a carrier gas.Various morphologies including nanobelts, disks and hexagonal rod-like nanostructures were obtained by changing the source and substrate temperatures during the growth of MoO_3 thin films. Structural parameters, morphology, composition and surface features of the films were characterized by XRD, SEM, EDAX,XPS, AFM and Raman spectroscopy. The films were orthorhombic in structure with preferred orientation along(0 1 0) plane. Morphology analysis reveals randomly aligned nanobelts with 40 nm in thickness and a width of 800 nm and 3–12 mm in length. The disks have 1.5 μm diameters, 1 μm thickness and hexagonal rod-like nanostructures with a length, breath and width of 2 μm, 1 μm and 100 nm are formed. The samples were investigated under dark and photocurrent conditions in H_2SO_4 aqueous solution as a function of applied potential. The photocurrent density of samples prepared on ITO and FTO substrate samples were compared and the results are discussed.     

Study on the Vortex of the Qinghai-Xizang (Tibet) Plateau in Summer

In this paper an ideal model for the formation and development of the Qinghai-Xizang Plateau vortex is presented by a large number of statistical data and typical case studies. It points out that the Plateau vortex is shallow and thermal originated from a strong heat source near the surface of the west of the Plateau. Then moving eastward , it develops and becomes stronger and thicker with larger upward vertical velocity, and causes great precipitation in the middle Plateau. But at this time the heat source in the vortex becomes weaker, and even the heat sink occurs near the surface. Consequently, it disappears in a cold trough with a strong heat sink in the east of the Plateau. The heat source (sink) is mainly determined by the vertical eddy flux convergence (divergence) of the sensible heat caused by the cumulus convection and turbu-lance. Both the nonuniform heating (cooling) at the surface and the convergence (divergence) of the eddy kinetic energy coact and play an important role in the genesis (di     

Interface Reconstruction Study by Functional Scanning Probe Microscope in Li-ion Battery Research

Interfacial reaction is a critical factor of lithium ion battery, but is also complicated and difficult to characterize. Scanning probe microscope(SPM) is one of the most effective tools to reveal the interface reconstruction and interfacial properties(including the morphologies, mechanical properties and electricity properties) of energy material at nanoscale and at real time. In this paper, we briefly summarized the principles of AFM, conductive AFM(C-AFM) and Kelvin probe force microscope(KPFM), as well as their application to investigate the interface reconstruction of lithium-ion battery electrode material.     

DETERMINATION OF DEGREE OF BONDED PHASE AT SILICA,GEL SURFACE USED FOR CHROMOTOGRAPHIC PACKING MATERIALS

Most of the packing materials used for liquid chtomototyraphy takes silica,gel as base The surface cf silica gel is modified by grafting of various functional bond phase to meet the purpose of separation and analysis.In some literatures,only the grafting method and the elemental analysis of bonded phase were reported.No detail quantitative determination has yet been published.This article describes the quantitative determination of material grafted on silica gel prepared by coupling reaction of silica gel with different concentrations of v-glycidoxyproplsiyl(P-GOPS) in water by differential thermal analysis(DTA) thermogravimetry(TG),element analysis(EA) and solution adsorption method.The results obtained are in agreement with those obtained by X-ray photon scat tering(XPS) method     

STUDY ON LOW Ni CATALYST FOR METHANATION OF TOWN GAS

On the basis of the characterization of typical catalysts by activityevaluation,TPR,XRD and TEM,the effects of nickel content and promoterssuch as MgO,La_2O_3,and MnO_2 were discussed.Formation of MgNiO_2 by thecombination of promoter MgO with NiO increases the catalyst stability.Promot-er La_2O_3 is found well-distributed on the catalyst surface in the form of La_2O_3without any interaction with uther components.With physically scattering ef-fect,La_2O_3 can prohibit active component Ni from sintreing at high temperatureand then improve its thermal stability.It also affects the catalyst activity andreducibility.Introduction of La_2O_3 decreases the content of small Ni crystallite,and is helpful to the prohibition of carbon deposition.A new Ni-based town gasmethanation catalyst of low Ni content with high activity and high carbon depo-sition resistance is successfully developed in the laboratory.     

Preparation of nanocrystalline γ-Al_2O_3 catalyst using different procedures for methanol dehydration to dimethyl ether

A series of nanocrystalline γ-alumina are synthesized by different procedures, namely, thermal decomposition method (sample A), precipita-tion method (sample B) and sol-gel method using sucrose and hexadecyltrimethyl ammonium bromide (CTAB) as templates (samples C and D, respectively). Textural and acidic properties of γ-alumina samples are characterized by XRD, N2 adsorption-desorption and NH3-TPD techniques. Vapor-phase dehydration of methanol into dimethyl ether is carried out over these samples. Among them, sample C shows the highest catalytic activity. NH3-TPD analysis reveals that the sample with smaller crystallite size possesses higher concentration of medium acidic sites and consequently higher catalytic activity. Thermal decomposition method leads to decrease in both surface area and moderate acidity, therefore it is the cause of lower catalytic activity.     

Determination of Ultratrace Silver Using Surfactant as Sensitizer by Catalytic Near Field Laser Thermal Lens Spectrometry

Introduction Thermal lens spectrometry (TLS) is an excellent method for trace analysis.1-3 Methods classified as TLS are based upon a thermal change in the optical proper-ties of a sample on the absorption of laser energy which leads to a temperature rise in the sample and conse-quently to the formation of an inhomogeneous spatial profile of the refractive index. The change in the diver-gence of a laser beam on the resulting optical element (thermal lens) is proportional to the amount of abs…     

程序升温汽化大体积进样气相色谱法同时测定空气中的甲醛及其他10种羰基污染物（英文）

Long-term indoor-air limit for formaldehyde stipulated by the European Commission is 1 μg/m3,while the World Health Organization has set a threshold of 100 μg/m3 that should not be exceeded for more than 30 min. To date,however,only a few analytical techniques have been developed that can be used to detect formaldehyde at these very restrictive limits. Thus,there is a need to develop for comprehensive methods for analyzing airborne formaldehyde and other carbonyl pollutants in the ambient environment. The aim of this study is to develop a highly sensitive online automated preconcentration gas chromatographic method using large-volume injection with a programmed temperature vaporization injector for the analysis of airborne formaldehyde and ten other carbonyl compounds. The influence of several parameters,such as the maximum volume injected,programmed temperature vaporization transfer time and temperature,carrier gas flow rate,and type of packing material was investigated. After optimization,highly satisfactory results in terms of the absolute and methodological detection limits were achieved,i. e. as low as the μg/m3 level for all the carbonyl pollutants studied. A commercially available sampler,originally designed for active sampling,was evaluated as a passive sampling device;this optimized technique was applied to monitor the concentrations of carbonyl pollutants in the indoor air of ten public buildings in Florence. The strength of this methodology lies both in the low detection limits reached in the simultaneous analysis of a wide group of 2,4-dinitrophenylhydrazine derivatives,and the potential adaptability of this method to other gas chromatographic applications to achieve lower sensitivity.