Electromagnetic Interference Shielding and Joule Heating Properties of Flexible, Lightweight, and Hydrophobic MXene/Nickel-Coated Polyester Fabrics Manufactured by Dip-Dry Coating and Electroless Plating.

High-performance electromagnetic interference (EMI) shielding materials with high flexibility, low density, and hydrophobic surface are crucial for modern integrated electronics and telecommunication systems in advanced industries like aerospace, military, artificial intelligence, and wearable electronics. In this study, we present flexible and hydrophobic MXene/Ni-coated polyester (PET) fabrics featuring a double-layered structure, fabricated via a facile and scalable dip-dry coating process followed by electroless nickel plating. Increasing the dip-dry coating iterations up to 10 cycles boosts the MXene loading content (∼31 wt %) and electrical conductivity (∼86 S/cm) of MXene-coated PET fabrics, while maintaining constant porosity (∼95%). The addition of a Ni layer enhances hydrophobicity, achieving a high water contact angle of ∼114° compared to only MXene-coated PET fabrics (∼49°). Furthermore, the 30 µm thick MXene/Ni-coated PET fabric demonstrates superior electrical conductivity (∼113.8 S/cm) and EMI shielding effectiveness (∼35.7 dB at 8-12 GHz) compared to only MXene- or Ni-coated PET fabrics. The EMI shielding performance of the MXene/Ni-coated PET fabric remains more stable in an air environment than only MXene-coated fabrics due to the outer Ni layer with excellent hydrophobicity and oxidation stability. Additionally, the MXene/Ni-coated PET fabric exhibits impressive Joule heating performance, swiftly converting electrical energy into heat and reaching high steady-state temperatures (32-92 °C) at low applied voltages (0.5-1.5 V).

Preparation of Uniform Nano Liposomes Using Focused Ultrasonic Technology.

Liposomes are microspheres produced by placing phospholipids in aqueous solutions. Liposomes have the advantage of being able to encapsulate both hydrophilic and hydrophobic functional substances and are thus important mediators used in cosmetics and pharmaceuticals. It is important for liposomes to have small sizes, uniform particle size distribution, and long-term stability. Previously, liposomes have been prepared using a homo mixer, microfluidizer, and horn and bath types of sonicators. However, it is difficult to produce liposomes with small sizes and uniform particle size distribution using these methods. Therefore, we have developed a focused ultrasound method to produce nano-sized liposomes with better size control. In this study, the liposome solutions were prepared using the focused ultrasound method and conventional methods. The liposome solutions were characterized for their size distribution, stability, and morphology. Results showed that the liposome solution prepared using focused ultrasonic equipment had a uniform particle size distribution with an average size of 113.6 nm and a polydispersity index value of 0.124. Furthermore, the solution showed good stability in dynamic light scattering measurements for 4 d and Turbiscan measurements for 1 week.

Chitin Nanofiber-Reinforced Waterborne Polyurethane Nanocomposite Films with Enhanced Thermal and Mechanical Performance.

To attain eco-friendly polyurethane composites with enhanced thermal and mechanical properties, in this study, a series of cationic waterborne polyurethane (cWPU) nanocomposite films reinforced with 1-50 wt% chitin nanofiber (ChNF) loadings was fabricated by a facile aqueous dispersion casting. The microstructure, thermal and mechanical properties of the nanocomposite films were investigated by considering the loading content and the interfacial interaction of ChNF in the cWPU matrix. For the purpose, a hard/soft segmented cWPU with an average particle size of ∼151 nm in aqueous dispersion was synthesized by using poly(tetramethylene glycol), isophorone diisocyanate, N-methyldiethanolamine, and 1,4-butanediol. The FT-IR spectra confirmed the existence of specific hydrogen-bonding interactions between hydroxyl/acetyl amine/ammonium groups of ChNFs and urethane/protonated amine groups of cWPU hard segments. Accordingly, the thermal decomposition temperatures of cWPU/ChNF nanocomposite films increased with increasing the ChNF content. In addition, the storage moduli of cWPU/ChNF nanocomposite films increased significantly with the increment of ChNF content up to ∼7 wt%, which stems from the restricted chain mobility of cWPU backbones composed of semicrystalline soft segments and hard segments interacting with ChNFs via multiple hydrogen-bonding interactions.

Effects of Poly(ethylene-co-glycidyl methacrylate) on the Microstructure, Thermal, Rheological, and Mechanical Properties of Thermotropic Liquid Crystalline Polyester Blends.

In this study, a series of thermotropic liquid crystalline polyester (TLCP)-based blends containing 1-30 wt% poly(ethylene-co-glycidyl methacrylate) (PEGMA) were fabricated by masterbatch-assisted melt-compounding. The scanning electron microscopy (SEM) images showed a uniformly dispersed microfibrillar structure for the TLCP component in cryogenically-fractured blends, without any phase-separated domains. The FT-IR spectra showed that the carbonyl stretching bands of TLCP/PEGMA blends shifted to higher wavenumbers, suggesting the presence of specific interactions and/or grafting reactions between carboxyl/hydroxyl groups of TLCP and glycidyl methacrylate groups of PEGMA. Accordingly, the melting and crystallization temperatures of the PEGMA component in the blends were greatly lowered compared to the TLCP component. The thermal decomposition peak temperatures of the PEGMA and TLCP components in the blends were characterized as higher than those of neat PEGMA and neat TLCP, respectively. From the rheological data collected at 300 °C, the shear moduli and complex viscosities for the blend with 30 wt% PEGMA were found to be much higher than those of neat PEGMA, which supports the existence of PEGMA-g-TLCP formed during the melt-compounding. The dynamic mechanical thermal analysis (DMA) analyses demonstrated that the storage moduli of the blends decreased slightly with the PEGMA content up to 3 wt%, increased at the PEGMA content of 5 wt%, and decreased again at PEGMA contents above 7 wt%. The maximum storage moduli for the blend with 5 wt% PEGMA are interpreted to be due to the reinforcing effect of PEGMA-g-TLCP copolymers.

Microstructure and Thermoelectric Characterization of Composite Nanofiber Webs Derived from Polyacrylonitrile and Sodium Cobalt Oxide Precursors.

We report the microstructure and thermoelectric properties of composite nanofiber webs, which were fabricated by dual-electrospinning of polyacrylonitrile (PAN) and sodium cobalt oxide (NaCo2O4) precursor solutions with different input compositions and following heat-treatment at 600-900 °C for simultaneous carbonation and calcination. The SEM and EDS mapping images revealed that PAN-derived carbon nanofibers (CNFs) and NaCo2O4-based ceramic nanofibers coexisted in the composite nanofiber webs and that their relative contents could be controlled by the input compositions. The Seebeck coefficient increased from ~26.77 to ~73.28 µV/K and from ~14.83 to ~40.56 µV/K with increasing the relative content of NaCo2O4 nanofibers in the composite nanofiber webs fabricated at 700 and 800 °C, respectively. On the other hand, the electrical conductivity of the composite nanofiber webs increased with the decrement of the relative content of NaCo2O4 nanofibers as well as the increment of the heat-treatment temperature. Owing to the opposite contributions of NaCo2O4 nanofibers and CNFs to the Seebeck coefficient, electrical conductivity and thermal conductivity, a maximum power factor of ~5.79 µW/mK2 and a figure of merit of ~0.01 were attained for CNF/NaCo2O4-based composite nanofiber webs fabricated at 45 wt% input composition of NaCo2O4 and at heat-treatment of 700 °C.

Effect of Polycondensation Catalyst on Fiber Structure Development in High-Speed Melt Spinning of Poly (Ethylene Terephthalate).

We conducted a preliminary study on fiber structural development in the high-speed melt spinning of environmentally friendly polyethylene terephthalate (Ti-PET) synthesized with 25 ppm of titanium-based catalyst, which was compared with conventional PET (Sb-PET) synthesized with 260 ppm of antimony-based catalyst. Gel permeation chromatography of Ti- and Sb-PET resins of intrinsic viscosity 0.63 confirmed that both resins have similar molecular weights and distributions. However, differential scanning calorimetry revealed that the Ti-PET resin exhibited a lower melt-crystallization peak and isothermal melt-crystallization rate than the Sb-PET resin. High-speed melt spinning of the Ti- and Sb-PET was possible up to a spinning velocity of 6 km/min. Two-dimensional wide-angle X-ray diffraction analyses showed that the molecular orientation of the obtained as-spun Ti- and Sb-PET fibers increased with spinning velocity, and a highly oriented, crystalline structure by orientation-induced crystallization started to appear from 5 km/min. Notably, Ti-PET fibers showed a lower degree of crystalline structural development and lower tensile strength compared with Sb-PET fibers under the high-speed spinning conditions. Our results suggest that the catalyst in PET resins can act as nucleating agents in thermal- and orientation-induced crystallization, and that differences in catalyst content can influence PET fiber structure development under extreme conditions in high-speed melt spinning.

Influences of cellulose nanofibril on microstructures and physical properties of waterborne polyurethane-based nanocomposite films.

We herein report the effects of carboxymethylated cellulose nanofibril (c-CNF) on the microstructure, thermal and mechanical properties of waterborne polyurethane (WPU)-based nanocomposite films. For the purpose, an aqueous dispersion of hard/soft segmented WPU with a mean particle size of ∼169 nm was manufactured by using poly(propylene glycol), isophorone diisocyanate, 2,2-dimethylolpropionic acid and 1,4-butanediol. WPU nanocomposite films with 1-50 wt% c-CNF loadings were then manufactured via an efficient casting method. The FT-IR spectra revealed the presence of hydrogen-bonding interactions between the urethane/urea groups of WPU hard segments and the carboxymethyl/hydroxyl groups of c-CNF. Accordingly, the thermal and thermo-oxidative stability of the nanocomposite films was noticeably enhanced by the introduction of c-CNF. In addition, the storage moduli of the nanocomposite films as well as the glass transition temperatures of WPU hard segments increased significantly with increasing the c-CNF content by ∼7 wt% owing to the specific interactions between c-CNF and WPU hard segments.

Microstructure, thermal and mechanical properties of composite films based on carboxymethylated nanocellulose and polyacrylamide.

For attaining eco-friendly nanocellulose-based films with enhanced thermal and mechanical properties, a series of composite films was fabricated by using a facile casting method of aqueous carboxymethylated cellulose nanofibril (c-CNF) dispersions with different contents (0-20 wt%) of polyacrylamide (PAM). The microstructure, thermal and mechanical properties of c-CNF/PAM composite films were investigated as a function of the PAM content. The FT-IR spectra revealed the presence of specific interactions between c-CNF and PAM in the composite films. Accordingly, the mechanical moduli of the films were highly improved with the addition of PAM. The storage modulus of the composite film with 20 wt% PAM were measured to be ˜935 MPa at 30 °C, which was far higher than the modulus ˜17 MPa for the neat c-CNF film. In addition, the thermal decomposition temperatures were found to increase from ˜303 °C for the neat c-CNF film to ˜312 °C for the composite film with 20 wt% PAM.

Electric Heating Performance of Pyrolyzed Photoresist Films Prepared by Proton Irradiation and Pyrolysis.

In this study, pyrolyzed photoresist films (PPFs) were prepared using commercial SU8 photoresist by proton irradiation and pyrolysis. SU8 thin films were irradiated with high-energy proton ions and then pyrolyzed in a tube furnace at 1000 °C under inert atmosphere. The carbonization yield of the PPFs increased with an increasing fluence due to the formation of more crosslinked network structures at a higher fluence. The electrical resistance decreased with an increasing fluence due to the higher remaining thickness and carbonization yield at a higher fluence. Therefore, the PPFs prepared at 1 × 1016 ions/cm2 showed the maximum temperature of 150 °C at 20 V and a high electric power efficiency of 1.57 mW/°C.

Highly Effective Electromagnetic Interference Shielding Materials based on Silver Nanowire/Cellulose Papers.

We fabricated silver nanowire (AgNW)-coated cellulose papers with a hierarchical structure by an efficient and facile dip-coating process, and investigated their microstructures, electrical conductivity and electromagnetic interference (EMI) shielding effectiveness. SEM images confirm that AgNWs are coated dominantly on the paper surfaces, although they exist partially in the inner parts of the cellulose papers, which demonstrates that the AgNW density gradually decreases in thickness direction of the AgNW/cellulose papers. This result is supported by the anisotropic apparent electrical conductivity of the AgNW/cellulose papers depending on in-plane or thickness direction. Even for a AgNW/cellulose paper obtained by a single dip-coating cycle, the apparent electrical conductivity in the in-plane direction of 0.34 S/cm is achieved, which is far higher than the neat cellulose paper with ∼10(-11) S/cm. In addition, the apparent electrical conductivity of the papers in the in-plane direction increases significantly from 0.34 to 67.51 S/cm with increasing the number of dip-coating cycle. Moreover, although the AgNW/cellulose paper with 67.51 S/cm possesses 0.53 vol % AgNW only, it exhibits high EMI shielding performance of ∼48.6 dB at 1 GHz. This indicates that the cellulose paper structure is highly effective to form a conductive AgNW network. Overall, it can be concluded that the AgNW/cellulose papers with high flexibility and low density can be used as electrically conductive components and EMI shielding elements in advanced application areas.

High Performance Flexible Piezoelectric Nanogenerators based on BaTiO3 Nanofibers in Different Alignment Modes.

Piezoelectric nanogenerators, harvesting energy from mechanical stimuli in our living environments, hold great promise to power sustainable self-sufficient micro/nanosystems and mobile/portable electronics. BaTiO3 as a lead-free material with high piezoelectric coefficient and dielectric constant has been widely examined to realize nanogenerators, capacitors, sensors, etc. In this study, polydimethylsiloxane (PDMS)-based flexible composites including BaTiO3 nanofibers with different alignment modes were manufactured and their piezoelectric performance was examined. For the study, BaTiO3 nanofibers were prepared by an electrospinning technique utilizing a sol-gel precursor and following calcination process, and they were then aligned vertically or horizontally or randomly in PDMS matrix-based nanogenerators. The morphological structures of BaTiO3 nanofibers and their nanogenerators were analyzed by using SEM images. The crystal structures of the nanogenerators before and after poling were characterized by X-ray diffraction. The dielectric and piezoelectric properties of the nanogenerators were investigated as a function of the nanofiber alignment mode. The nanogenerator with BaTiO3 nanofibers aligned vertically in the PDMS matrix sheet achieved high piezoelectric performance of an output power of 0.1841 µW with maximum voltage of 2.67 V and current of 261.40 nA under a low mechanical stress of 0.002 MPa, in addition to a high dielectric constant of 40.23 at 100 Hz. The harvested energy could thus power a commercial LED directly or be stored into capacitors after rectification.

Regenerated cellulose/multiwalled carbon nanotube composite films with efficient electric heating performance.

We have manufactured regenerated cellulose-based composite films reinforced with pristine multiwalled carbon nanotube (MWCNT) by a facile casting of cellulose/DMAc/LiCl solutions containing 0.2-10.0wt% MWCNT and have investigated their application as electric heating materials by examining microstructure, thermal stability, and electrical properties. TEM images showed that the pristine MWCNT was dispersed well in the regenerated cellulose matrix. The composite films were found to be stable thermally up to ∼275°C. The electrical resistivity of the regenerated cellulose/MWCNT composite films decreased significantly from ∼10(9)Ωcm to ∼10(1)Ωcm with increasing the MWCNT loading, particularly at a certain MWCNT content between 2.0 and 3.0wt%. Accordingly, the composite films with 5.0-10.0wt% MWCNT contents, which possessed low electrical resistivity of ∼10(2)-10(1)Ωcm, exhibited excellent electric heating performance in aspects of temperature responsiveness, steady-state maximum temperature, and electrical energy efficiency at constant applied voltages. For instance, the composite film with 10.0wt% MWCNT had well-controlled steady-state maximum temperatures of 40-189°C at 20-80V, characteristic temperature growth constant of ∼1s, and electric power efficiency of ∼5.4mW/°C, which performance remained unchanged under repeated experiments for several hours.

Microstructure and performance of multiwalled carbon nanotube/m-aramid composite films as electric heating elements.

We report microstructure of thermomechanically stable multiwalled carbon nanotube (MWCNT)/poly(m-phenylene isophthalamide) (m-aramid) composite films containing 0.0-10.0 wt % MWCNTs and their performance as electric heating elements. FE-SEM images show that the MWCNTs are well dispersed in the composite films and are wrapped with m-aramid chains and that the interfacial thickness of m-aramid wrapped MWCNTs decreases with the MWCNT content. The electrical resistivity of films varies from ∼10(13) Ω cm for the neat m-aramid to ∼10(0) Ω cm of the film with 10.0 wt % MWCNT owing to the formation of a conductive three-dimensional network of MWCNTs. Accordingly, the performance of MWCNT/m-aramid films as electric heating elements is strongly dependent on MWCNT content as well as applied voltage. For the composite film with 10.0 wt % MWCNT, a maximum temperature of ∼176 °C is attained even at a low applied voltage of 10 V. The excellent performance such as rapid temperature response and high electric power efficiency at given applied voltages is found to be related with the microstructural features of the MWCNT/m-aramid films.

Influence of surface property on the crystallization of hentetracontane under nanoscopic cylindrical confinement.

The crystallization behavior and the orientation of linear alkane hentetracontane (C41) confined in cylindrical nanoporous alumina templates with different surface energies were investigated by nonisothermal crystallization and X-ray diffraction. The surface of pristine nanoporous alumina was modified to have low surface energy by grafting with polydimethylsiloxane. In the pristine nanoporous alumina, C41 crystallized at two crystallization temperature ranges, lower than bulk, and exhibited the decreased Avrami exponents. C41 in the surface-modified nanoporous alumina showed the inhibition of crystallization at higher temperature range among the two crystallization temperature ranges but the enhancement of crystallization at much lower temperature ranges than in the pristine nanoporous alumina. It was clearly shown that those variations of crystallization behavior imply the surface effect on crystallization. The crystal orientation was also affected by surface-modification of the alumina template. The a-axis of orthorhombic C41 crystals in the pristine nanoporous alumina was preferentially oriented parallel to the pore axis, while b- and c-axes were perpendicular to the pore axis. C41 crystals in the surface-modified nanoporous alumina showed two types of orientation. One was identical to that in the pristine nanoporous alumina, and the other was the orientation that the crystals were tilted with respect to the c-axis as the (110) plane parallel to the pore axis.

Superhydrophobic PLA fabrics prepared by UV photo-grafting of hydrophobic silica particles possessing vinyl groups.

Superhydrophobic poly(lactic acid) (PLA) fabrics are prepared by UV photo-grafting of hydrophobic silica particles possessing vinyl functional groups on the surfaces, which is a novel one-step process to provide surface with roughness as well as hydrophobicity simultaneously. For this purpose, hydrophobic silica particles with vinyl groups and average diameter of 1.51+/-0.05 microm are synthesized via a sol-gel process. The silica particles possessing vinyl groups are found to be effectively immobilized on PLA fabrics via UV photo-grafting reaction. The water contact angle of the treated PLA fabric is measured to be approximately 150 degrees, which is high enough to exhibit the Lotus effect as a result of the superhydrophobicity.

New type of dual solid-state thermochromism: modulation of intramolecular charge transfer by intermolecular pi-pi interactions, kinetic trapping of the aci-nitro group, and reversible molecular locking.

When heated above room temperature, some crystalline polymorphs of the 1,3-bis(hydroxyalkylamino)-4,6-dinitrobenzenes (BDBn, n = 2-5), bis(hydroxyalkyl) analogues of the intramolecular charge-transfer molecule 1,3-diamino-4,6-dinitrobenzene, exhibit "dual" thermochromism: gradual color change from yellow to orange at lower temperatures, and sharp color change from orange to red at higher temperatures. These two thermochromic changes are related to different solid-state processes. When allowed to cool to room temperature, the yellow color of the thermochromic molecules with different alkyl length (n) is recovered with unexpectedly different kinetics, the order of the respective rate constants ranging from 10(-7)-10(-6) s(-1) for BDB2 to about 0.1 s(-1) in the case of BDB3. The thermochromic mechanism and the reasons behind the different kinetics were clarified on the basis of detailed crystallographic characterization, kinetic thermoanalysis, and spectroscopic study of eight crystalline forms (seven polymorphs and one solvate). It was found that the polymorphism is due to the possibility of "locking" and "unlocking" of the alkyl arms by formation of a strong intramolecular hydrogen bond between the hydroxyl groups at their hydroxyl termini. The locking of BDB2, with shortest alkyl arms, is reversible and it can be controlled thermally; either of the two conformations can be obtained in the solid state by proper thermal treatment. By use of high temperature in situ single crystal X-ray diffraction analysis of BDB3, direct evidence was obtained that the gradual thermochromic change is related to increased distance and weakened pi-pi interactions between the stacked benzene rings: the lattice expands preferably in the stacking direction, causing enhanced oscillator strength and red shift of the absorption edge of the intramolecular charge transfer transition. The second, sharp thermochromic change had been assigned previously to solid-solid phase transition triggered by intramolecular proton transfer of one amino proton to the nitro group, whereupon an aci-nitro form is thermally populated. Contrary to the numerous examples of solid thermochromic molecules based on either pericyclic reactions or keto-enol tautomerism, this system appears to be the first organic thermochromic family where the thermochromic change appears as an effect of intermolecular pi-pi interactions and thermal intramolecular proton transfer to aromatic nitro group.

Superhydrophobicity of cotton fabrics treated with silica nanoparticles and water-repellent agent.

To obtain the superhydrophobic water-repellent cotton fabrics, cotton fabrics were treated with silica nanoparticles and/or a cost-effective water-repellent agent (WR agent). Two different silica nanoparticles were synthesized via a sol-gel process and their shapes, sizes, and compositions were characterized. It was found that silica particles are spherical and have diameters of 143 and 378 nm. For the cotton fabrics treated with the WR agent alone, the water contact angles on the fabric surface remained lower than 20 degrees at the WR agent concentration of 0.3 wt% or less. Silica nanoparticle treatment itself did not change the hydrophilic surface of cotton fabric, indicating that water drops were adsorbed into fabrics due to the hydroxyl groups on both cotton and silica nanoparticle surfaces. However, for the cotton fabrics treated with both silica nanoparticles and the WR agent, a contact angle above 130 degrees can be obtained even at the very low WR agent concentration of 0.1 wt%. Therefore, superhydrophobic cotton fabrics could be obtained via the combined treatment of silica nanoparticle and WR agent, which is cost effective compared with fluorinate silane treatment.

Preparation and lead ion removal property of hydroxyapatite/polyacrylamide composite hydrogels.

We report the synthesis of hydroxyapatite/polyacrylamide (HAp/PAAm) composite hydrogels with various HAp contents by free radical polymerization and their removal capability of Pb(2+) ions in aqueous solutions with controlled initial Pb(2+) ion concentrations and pH values of 2-5. The swelling ratio of the composite gels in aqueous solutions decreases with increasing the HAp content in the gels. The composite gel with higher HAp content exhibits the higher removal capacity of Pb(2+) ions owing to the higher adsorption sites for Pb(2+) ions, but shows the slower removal rate of Pb(2+) ions due to the lower degree of swelling. The removal mechanism of Pb(2+) ion is very sensitive to the pH value in aqueous solution, although the removed amount of Pb(2+) ion is nearly same, regardless of pH values of 2-5. The removal mechanism, the dissolution of HAp in the composite gel and subsequent precipitation of hydroxypyromorphite (HPy), is dominant at lower pH 2-3, whereas the mechanism, the adsorption of Pb(2+) ions on the composite gel and following cation exchange reaction between Pb(2+) ions adsorbed and Ca(2+) of HAp, is dominant at higher pH 4-5. The equilibrium removal process of Pb(2+) ions by the composite gels at pH 5 is described well with the Langmuir isotherm model. The equilibrium removal capacities of the composite gels with 30, 50, and 70 wt.% HAp contents are evaluated to be 123, 178, and 209 mg/g, respectively.

Removal of lead ions in aqueous solution by hydroxyapatite/polyurethane composite foams.

We have prepared hydroxyapatite/polyurehthane (HAp/PU) composite foams with two different HAp contents of 20 and 50 wt.% and investigated their removal capability of Pb2+ ions from aqueous solutions with various initial Pb2+ ion concentrations and pH values of 2-6. HAp/PU composite foams synthesized exhibited well-developed open pore structures which provide paths for the aqueous solution and adsorption sites for Pb2+ ions. With increasing the HAp content in the composites, the removal capability of Pb2+ ions by the composite foams increases owing to the higher adsorption capacity, whereas the removal rate is slower due to the less uniform dispersity of HAp in composite foams. The removal rate of Pb2+ ions is also slower with increasing the initial Pb2+ ion concentration in aqueous solutions. The removal mechanism of Pb2+ ion by the composites is varied, depending on the pH value of aqueous solution: the dissolution of HAp and precipitation of hydroypyromorphite is dominant at lower pH 2-3, the adsorption of Pb2+ ions on the HAp/PU composite surface and ion exchange reaction between Ca2+ of HAp and Pb2+ in aqueous solution is dominant at higher pH 5-6, and two removal mechanisms compete at pH 4. The equilibrium removal process of Pb2+ ions by the HAp/PU composite foam at pH 5 was described well with the Langmuir isotherm model, resulting in the maximum adsorption capacity of 150 mg/g for the composite foam with 50 wt.% HAp content.

From homogeneous to heterogeneous nucleation of chain molecules under nanoscopic cylindrical confinement.

The crystallization of monodisperse linear polyethylene confined in nanoporous alumina is investigated with the calorimetric measurements. We observe a drastic change in crystallization behavior, specifically nucleation, with a decrease in the pore diameter. Crystallization in relatively larger pores with the diameters of 62 and 110 nm occurs at lower temperatures within a very narrow range, whereas crystallization in smaller pores with diameters of 15-48 nm occurs at a higher and broad range of temperatures. Nucleation and crystallization kinetics in nanopores is discussed based on classical nucleation theory as well as the Avrami theory.