Poly(polyethylene glycol methyl ether methacrylate) as novel solid-solid phase change material for thermal energy storage

Poly(polyethylene glycol methyl ether methacrylate) as novel solid–solid phase change materials (PCMs) for thermal energy storage was prepared via the facile bulk polymerization of polyethylene glycol methyl ether methacrylate and was characterized by Fourier transform infrared, ¹³C-NMR, X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis measurements. Based on the results, it is indicated that the poly (polyethylene glycol methyl ether methacrylate) as novel PCM showed solid–solid properties with suitable transition temperature, high transition enthalpy, and good thermal stability, which was apt to crystallize due to the flexibility of long polyether side chain. This novel PCMs have advantages for the potential application in energy storage. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Sputter-prepared (001) BiFeO

ABSTRACT: Highly textured BiFeO3(001) films were formed on L10-FePt(001) bottom electrodes on glass substrates by sputtering at reduced temperature of 400 oC. Good electric polarization 2Pr = 80 and 95 muC/cm2, comparable to that of the reported epitaxial films, and coercivity Ec = 415 and 435 kV/cm are achieved in the samples with 20-nm- and 30-nm-thick electrode. The BiFeO3(001) films show different degree of compressive strain. The relation between the variations of strain and 2Pr suggests that the enhancement of 2Pr is resulted from the strain-induced rotation of spontaneous polarization. The presented results open possibilities for the applications based on electric-magnetic interactions.     

高分子固-固相变储能材料的研究与应用

综述了各类高分子固-固相变储能材料的性能、储能机理及其优缺点,介绍了此类材料的各种应用, 并对其发展前景做了探讨和展望。高分子固-固相变储能材料具有储能密度大,相变温度恒定,体积变化小,相变过程无液体泄漏等诸多优点,已成为能源开发利用和材料科学研究的新热点。     

Fabrication and characterization of a Ni-YSZ anode support using high-frequency induction heated sintering (HFIHS)

Ni-YSZ cermet anode supports solid oxide fuel cells (SOFCs) were fabricated by high-frequency induction heated sintering (HFIHS) under 60 MPa pressure with powders synthesized by the glycine nitrate process (GNP) as well as mechanically mixed commercial powders. The HFIHS method created a uniformly porous microstructure without abnormal grain growth compared to the conventional sintering method. Samples sintered by HFIHS show higher strength and electrical conductivity than conventionally sintered samples, even though they have similar porosity.     

Energy and Structure of (001) Coincident-Site Twist Boundaries and the Free (001) Surface in MgO: A Theoretical Study

A computer code is described which permits investigation of the energy and structure of coincident-site lattice (CSL) grain boundaries, stacking faults, and free surfaces in ionic crystals. The code uses computational techniques similar to those of Harwell's HADES code for the study of point defects in bulk ionic crystals. Two sets of short-range potentials are used to determine the energy and structure of the free (001) surface and of (001) CSL twist boundaries in MgO with values of Γ, the inverse density of CSL sites, ranging between Γ= 5 and Γ= 65. From comparison of the results obtained by means of the different potentials it is concluded that the Van der Waals attraction between oxygen ions on opposite sides of the interface is mainly responsible for the rather weak cohesion predicted for such bicrystals, whereas Coulombic interactions are found to play only a minor role. It then follows that (i) the (001) plane is not a favored plane for the formation of grain boundaries in pure oxides with NaCl structure and (ii) similarities should exist between (001) twist boundaries in ionic crystals with NaCl structure and in fee metals. These similarities are investigated by comparing calculated boundary structures and energy-vs-misfit angle curves for MgO with recent results for aluminum, copper, silver, and gold, in which a broad spectrum of different interatomic potentials was used. It is suggested that the rather strong cohesion of the pressure-sintered MgO bicrystals of Sun and Balluffi may be due to impurities which have migrated to the boundary during sintering.     

Structure development and interfacial interactions in high‐density polyethylene/hydroxyapatite (HDPE/HA) composites molded with preferred orientation

Composites of high‐density polyethylene (HDPE) filled with sintered and nonsintered hydroxyapatite (HA) powders, designated as HAs and HAns, respectively, were compounded by twin screw extrusion. Compounds with neoalkoxy titanate or zirconate coupling agents were also produced to improve interfacial interaction and filler dispersion in the composites. The composites were molded into tensile test bars using (i) conventional injection molding and (ii) shear‐controlled orientation in injection molding (SCORIM). This latter molding technique was used to deliberately induce a strong anisotropic character to the composites. The mechanical characterization included tensile testing and microhardness measurements. The morphology of the moldings was studied by both polarized light microscopy and scanning electron microscopy, and the structure developed was assessed by wide‐angle X‐ray diffraction. The reinforcing effect of HA particles was found to depend on the molding technique employed. The higher mechanical performance of SCORIM processed composites results from the much higher orientation of the matrix and, to a lesser extent, from the superior degree of filler dispersion compared with conventional moldings. The strong anisotropy of the SCORIM moldings is associated with a clear laminated morphology developed during shear application stage. The titanate and the zirconate coupling agents caused significant variations in the tensile test behavior, but their influence was strongly dependent on the molding technique employed. The application of shear associated with the use of coupling agents promotes the disruption of the HA agglomerates and improves mechanical performance. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2873–2886, 2002     

Long-range chemical interaction in solid-state synthesis: Reaction of Ni with Fe in epitaxial Ni(001)/Ag(001)/Fe(001) trilayers

The effect of Ag interlayers 0, 60, 420, and 900 nm thick on the reaction of Ni with Fe in epitaxial Ni(001)/Ag(001)/Fe(001) trilayers has been studied by XRD, volume magnetocrystalline anisotropy, and magnetization measurements. Minor mixing was observed at the interface between Ag(001)/Ni(001) and Ag(001)/Fe(001) bilayers at temperatures above 900 K. When the epitaxial Ni(001)/Ag(001)/Fe(001) trilayer undergoes thermal annealing, a total atomic exchange between Ni and Ag occurs independently of an Ag interlayer thickness. Solid-state synthesis of alloy phases was found to occur in the sequence Fe/Ni → Ni₃Fe NiFe → γ_par (Fe₃Ni-like phase). Temperatures for the formation of Ni₃Fe and NiFe phases slightly increase with increasing interlayer thickness, while the initiation temperature for the γ_par phase remains intact. We suggest some scenarios for the observed atomic exchange in the system under consideration. The results are rationalized in terms of long-range chemical interaction between Ni and Fe via an Ag interlayer. This means that Ni reacts with Fe despite the fact that a separation between the above atoms is greater than the length of normal chemical bond by a factor of about 10⁴. The article is published in the original.     

Sorption of ethene and ethane on the V2O5(001)/TiO2(001) anatase interface

Simulation techniques have been employed to investigate the differences in the low energy adsorption configurations of ethene and ethane on the TiO₂ supported and unsupported V₂O₅(001) surface. We find that the ethene molecule approaches much closer to thesupported V₂O₅(001) surface which is reflected in the 40 kj mol^–1 higher adsorption energy. The low energy adsorption configuration located for ethane on the supported V₂O₅ shows that the molecule does not approach as close to the supported V₂O₅ surface as does ethene, resulting in the adsorption energy of ethane being 52 kJ mol^–1 lower than that of ethene on the supported V₂O₅ surface.     

Molecular mechanics modelling of interfacial energy and flexibility on cellulose

Molecular mechanics modelling is used to calculate the energies of interaction, hence the molecular level energy of adhesion at the interface with crystalline cellulose I of three different photopolymerizable primers and of a polyester varnish at the interface with the primer/cellulose assembly. The energy of interactions for just one of the primers with the statistically most common conformation of amorphous cellulose has also been obtained for comparison. Experimental results of adhesion by a standard peel test and by thermomechanical analysis, in which the effect of viscoelastic energy dissipation by crack tip propagation has been respectively minimized or is not present, hence in which the energy of interfacial interaction is nothing else but the work of adhesion, correlated well with the energies of interaction calculated by molecular mechanics. An equation correlating the energy of interaction at each finish/cellulose interface with the deflection derived by thermomechanical analysis, and with the number of internal bond rotational degrees of freedom as well as the degree of networking of the finish, has been derived and is presented. A relationship between the intrinsic fracture energy Go and the molecular mechanics-derived energy of interaction at the interface equating this to the square of the work of adhesion is obtained and is presented.     

Correlation between interfacial free energy and albumin adsorption in poly(acrylonitrile–acrylamide–acrylic acid) hydrogels

An investigation on the influence of chemical compositions and surface properties (e.g., surface free energy in air and hydrogel–water interfacial energy) on the adsorption of bovine serum albumin (BSA) at pH 7.4 on to a series of poly(acrylonitrile–acrylamide–acrylic acid) hydrogels was carried out. The interfacial energetics were determined from the contact angle data for air–gel and octane–gel in the water environment and the specific adsorption of BSA was determined with UV–VIS spectroscopy. It is shown that the higher contents of amide and acid groups in hydrogel bulk lead to the greater polar component of surface energy in air and the greater BSA adsorption in aqueous solutions. The BSA adsorption decreases with water amount in gels at lower amide/acid contents and increases at higher contents. The results imply that the interfacial interactions between the protein and the reorganized hydrogel interface in exposure with water, as well as the penetration of protein into pores of swollen gels, influence the BSA adsorption. © 1996 John Wiley & Sons, Inc.     

Effects of the molecular orientation and crystallization on film–substrate interfacial adhesion in poly(ethylene terephthalate) film‐insert moldings

A film and substrate consisting of poly(ethylene terephthalate) were adhered by means of film‐insert molding. Two injection speeds (i.e., 50 and 500 mm/s) were chosen to induce different shear rates (and molecular orientation) between the film and the substrate. Annealing was subsequently performed on these specimens at different times and temperatures to examine the extent of orientation‐induced crystallization of the substrate surfaces embedded under the film. Differential scanning calorimetry thermograms clearly indicated a shift in the position of the secondary (β) crystalline phase toward a higher temperature in specimens molded at a 500 mm/s injection speed, suggesting that a more densely packed and well‐formed crystalline structure was generated because of higher localized orientation of molecules. Polarized Fourier transform infrared spectroscopy analyses provided dichroic ratios of the 1340‐ and 1410‐cm⁻¹ wavelengths, which corresponded to the trans‐glycol conformer and the stable benzene ring, respectively. Drastic increases in the dichroic ratios were observed, especially in specimens molded at a 500 mm/s injection speed after being annealed for 1 min. This could have been caused by the reorientation of molecules fueled by residual stresses, particularly in regions experiencing high shear during molding. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Electrical properties of B-doped homoepitaxial diamond (001) film

Relationship between growth condition and quality of homoepitaxially grown B-doped diamond (001) film has been studied using physical measurements of defect density as a function of doping concentration. In particular, electrical properties of the homoepitaxial diamond film were characterized using measurements of conductivity, carrier concentration and mobility. The highest mobility is found to be about 1000 cm²V⁻¹s⁻¹ at 293 K, indicating that the quality of the CVD diamond film is further improved through optimizing the growth condition. The density of the compensation donor was determined from the temperature-dependent hole concentration. The lowest donor density is found to be 8.4 × 10¹⁵ cm⁻³ in the present work. This is an order of magnitude greater than the lowest value measured in natural IIb diamond. Furthermore, it is also found that the donor density increases with increasing doping concentration during the growth. On the other hand, the mobility decreases rapidly with increasing doping concentration. From these results, we speculate that the compensation donor is an origin of an additional scattering center in diamond, and excessive B-doping makes the quality of the CVD diamond worse.     

Water-induced effects of hydrogen adsorption on Ru(001)

Adsorption and desorption of hydrogen and coadsorption of H₂ with H₂O and CO over Ru(00l) surface have been studied under UHV conditions using the technique of TDS. Surface hydrogen interacts with adsorbed water resulting in an additional desorption state at 510 K which is not easily displaced by CO, but the total number of adsorption sites for hydrogen adsorption is independent of the amount of H₂O predosed at room temperature. Hydrogen adsorption is blocked easily by CO dose (more than 0.5 L) or a small amount of O(a) formed from dissociative adsorption of water, and adsorbed hydrogen formed in the absence of significant water is easily displaced by CO dose at even room temperature.     

Adsorption and Reactivity of CO2 on Potassium-Covered Re(001)

The interaction of CO₂ with potassium-covered Re(001) has been investigated. This system has been studied by means of work function (Δϕ), optical second harmonic generation (SHG), and temperature-programmed desorption (TPD) measurements. Strong electronic interaction between carbon dioxide and potassium is observed upon adsorption at 90 K. This is indicated by a rapid quenching of the SHG signal of K following postadsorption of CO₂, with a quenching cross section of 70 Ų. Work function change measurements are consistent with such interaction, evidenced by an undepolarization effect, namely, further decrease of the work function upon CO₂ adsorption, below the minimum obtained by pure potassium. In the presence of potassium, the dissociation probability of 0.5 ML adsorbed carbon dioxide increases from 0.5 on the clean metal surface to 0.85 on 1 ML potassium-covered Re(001), information obtained from TPD measurements following heating to 1250 K. It is concluded that a K–CO₂ surface compound is formed upon adsorption at 95 K on the potassium-covered surface.     

The interpretation of orientation — strain relationships in rubbers and thermoplastics

The orientation—strain behaviour typical of non-crystalline polymers is examined with reference to new techniques for determining molecular orientation parameters in a variety of crosslinked and thermoplastic materials, as well as the long-established methods based on the optical anisotropy of natural rubber. It is shown that the affinely-deforming ‘random chain’ assumed by conventional theory is not successful in predicting the relationship between chain orientation and strain unless the network is assumed to change significantly with strain. The implications of this observation are discussed in terms of the behaviour of crosslinks and entanglements: the conventional view of anisotropy needs to be supplemented by an approach in which orientation and strain are seen as distinct aspects of a polymer's response to the stress imposed upon it.     

Improvement of piezoelectricity of (Na,K)Nb-based lead-free piezoceramics using [001]-texturing for piezoelectric energy harvesters and actuators

0.96(Na_0.5K_0.5)(Nb_0.93Sb_0.07)O₃?(0.04?x)BaZrO₃?x(Bi_0.5Ag_0.5)ZrO₃[NKNS?(0.04?x)BZ?xBAZ] ceramics are well textured along the [001] direction using 3.0 mol% NaNbO₃ seeds. The textured-NKNS?0.02BZ?0.02BAZ thick film has a rhombohedral-orthorhombic-tetragonal (R-O-T) structure with a large proportion of the O-R structure (> 80%). This specimen exhibits the largest values for d₃₃ (805 pC/N) and d₃₃ ×g₃₃ (29.5 ×10^?12 m²/N), which are the largest d₃₃ and d₃₃ ×g₃₃ values of NKN-based piezoceramics to date. It exhibits a large strain (0.17% at 4.0 kV/mm). Therefore, it is an outstanding piezoceramic material for piezoelectric energy harvesters (PEHs) and actuators. A PEH and actuator are fabricated using this specimen. The PEH shows a large power density (4.3 mW/cm³), which is the largest value among the PEHs produced by lead-free piezoceramics. The actuator exhibits a large acceleration (50.8 G) and displacement (3.9 mm), which are the best actuating properties among the actuators produced by lead-free piezoceramics. Therefore, texturing is an excellent technique for improving the piezoelectricity of NKN-based piezoceramics.     

Gel-combustion, characterization and processing of porous Ni-YSZ cermet for anodes of solid oxide fuel cells (SOFCs)

The NiO-YSZ powder was prepared by the combustion of nitrate-glycine gel, a novel and versatile technique to form the nano-composite. The phase purity of the as-formed powder was confirmed by XRD. Onset sintering temperature was measured and sintering of NiO-YSZ specimens was carried out at 1450 °C for different soaking times. Porosity of the specimens decreases with increasing soaking time. Ni-YSZ cermet with varying open porosities between 23 and 41% was obtained by the in situ reduction of NiO-YSZ. Electrical conductivity, thermal expansion coefficient, and SEM microstructure of the Ni-YSZ specimens possessing varying porosities were evaluated. The electrical conductivity decreased while thermal expansion coefficient remained essentially the same with increasing porosity. SEM results confirmed the presence of interconnected open pores.     

Structural study of β‐SiC(001) films on Si(001) by laser chemical vapor deposition

β‐SiC thin films have been epitaxially grown on Si(001) substrates by laser chemical vapor deposition. The epitaxial relationship was β‐SiC(001){111}//Si(001){111}, and multiple twins {111} planes were identified. The maximum deposition rate was 23.6 μm/h, which is 5‐200 times higher than that of conventional chemical vapor deposition methods. The density of twins increased with increasing β‐SiC thickness. The cross section of the films exhibited a columnar structure, containing twins at {111} planes that were tilted 15.8° to the surface of substrate. The growth mechanism of the films was discussed.     

Morphology Analysis of Si Island Arrays on Si(001)

The formation of nanometer-scale islands is an important issue for bottom-up-based schemes in novel electronic, optoelectronic and magnetoelectronic devices technology. In this work, we present a detailed atomic force microscopy analysis of Si island arrays grown by molecular beam epitaxy. Recent reports have shown that self-assembled distributions of fourfold pyramid-like islands develop in 5-nm thick Si layers grown at substrate temperatures of 650 and 750°C on HF-prepared Si(001) substrates. Looking for wielding control and understanding the phenomena involved in this surface nanostructuring, we develop and apply a formalism that allows for processing large area AFM topographic images in a shot, obtaining surface orientation maps with specific information on facets population. The procedure reveals some noticeable features of these Si island arrays, e.g. a clear anisotropy of the in-plane local slope distributions. Total island volume analysis also indicates mass transport from the substrate surface to the 3D islands, a process presumably related to the presence of trenches around some of the pyramids. Results are discussed within the framework of similar island arrays in homoepitaxial and heteroepitaxial semiconductor systems.