Solid polymer electrolytes. IV. Preparation and characterization of novel crosslinked epoxy‐siloxane polymer complexes as polymer electrolytes

Two series of novel crosslinked siloxane‐based polymers and their complexes with lithium perchlorate (LiClO₄) were prepared and characterized by Fourier transform infrared spectroscopy, solid‐state NMR (¹³C, ²⁹Si, and ⁷Li nuclei), and differential scanning calorimetry. Their thermal stability and ionic conductivity of these complexes were also investigated by thermogravimetric and AC impedance measurements. In these polymer networks, poly(propylene oxide) chains with different molecular weights were introduced through self‐synthesized epoxy‐siloxane precursors cured with two curing agents. The glass‐transition temperature (T_g) of these copolymers is dependent on the length of the ether units. The dissolution of LiClO₄ considerably increases the T_g of the polyether segments. The dependence of the ionic conductivity was investigated as a function of temperature, LiClO₄ concentration, and the molecular weight of the polyether segments. The ion‐transport behavior was affected by the combination of the ionic mobility and number of carrier ions. The ⁷Li solid‐state NMR line shapes of these polymer complexes suggest a significant interaction between Li⁺ ions and the polymer matrix, and temperature‐ and LiClO₄ concentration‐dependent chemical shifts are correlated with ionic conductivity. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1226–1235, 2002     

Influences of synthesizing temperatures on the properties of Cu<Subscript>2</Subscript>ZnSnS<Subscript>4</Subscript> prepared by sol–gel spin-coated deposition

In this work Cu₂ZnSnS₄ (CZTS) suitable for the absorption layer in solar cells was successfully prepared by sol–gel spin-coated deposition. CZTS precursors were prepared by using solutions of copper (II) chloride, zinc (II) chloride, tin (IV) chloride, and thiourea. Texture structures with kesterite crystallinity reflected from the X-ray diffraction of (112), (200), and (312) planes of the CZTS were obtained as synthesized at a temperature of over 240 °C. The absorption coefficients of the CZTS films are higher than 10⁴ cm⁻¹, and the optical-energy gap is about 1.5 eV. Without sulfurization treatment, a near stoichiometry composition of the CZTS is obtained at a synthesizing temperature of 280 °C.     

Synthesis,characterization, and proton‐conducting properties of organic–inorganic hybrid membranes based on polysiloxane zwitterionomer

The synthesis and characterization of a series of zwitterionic hybrid membranes based on a zwitterionic siloxane precursor (ZS) are described. Flexible, transparent, optically homogeneous films were prepared. With the further incorporation of poly(ethylene glycol) (PEG), the hybrid films became more flexible but translucent. The structure of the inorganic sides was probed with solid‐state ²⁹Si NMR spectroscopy, and the organic sides and the chemical process involved were characterized with solid‐state ¹³C cross‐polarization/magic‐angle spinning NMR. A higher content of ZS led to higher proton conductivity of the hybrid electrolytes. Moreover, the proton conductivity was enhanced by the addition of the plasticizing component of PEG to the hybrid matrix; this was ascribed to the increased water uptake and free volume of the hybrid matrix and the dissociation of sulfonic acid groups. The proton conductivity of these hybrid membranes could be increased up to 3.5 × 10^?2 S/cm by the temperature and relative humidity being increased to 85 °C and 95%, respectively. The proton‐conduction behavior of these hybrid membranes is also briefly discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3444–3453, 2006     

Defect reduction of laterally regrown GaN on GaN/patterned sapphire substrates

Structural properties of GaN epilayers on wet-etched protruding and recess-patterned sapphire substrates (PSSs) have been investigated in detail using high-resolution double-crystal X-ray diffraction (DCXRD) and etch-pit density methods. The DCXRD results reveal various dislocation configurations on both types of PSSs. The etch pits of GaN on the recess PSS exhibit a regular distribution, i.e. less etch pits or threading dislocation density (TDD) onto the recess area than those onto the sapphire mesas. On the contrary, an irregular distribution is observed for the etch pits of GaN on the protruding PSS. A higher crystal quality of the GaN epilayer grown onto the recess PSS can be achieved as compared with that onto the protruding PSS. These data reflect that the GaN epilayer on the recess PSS could be a better template for the second epitaxial lateral overgrowth (ELOG) of GaN. As a result, the GaN epilayers after the ELOG process display the TDDs of around ∼10⁶ cm⁻².     

Low-level radioactive waste measurement comparisons of three gamma-ray counting systems

Three different gamma-ray counting systems constructed by 1–3 HPGe detectors were used in this study to compare their system performance. One measurement scheme involved positioning a single HPGe detector on a movable cart with a 90° collimation angle to the observed item. The other two waste assay systems were configured with two or three HPGe detectors towards the sample drums, while the three-HPGe-detector counting system was in a shielded counter cavity. The measurement consistency of 38 low-level waste drums, system operating costs and acquisition times to achieve the same MDA for these counting systems were compared and discussed in this study.     

Phase separation phenomenon in MOCVD-grown GaInP epitaxial layers

In-rich and Ga-rich GaInP films were intentionally grown on (0 0 1) GaAs substrates by low-pressure MOCVD to investigate the effect of lattice strain on composition. High-resolution X-ray diffraction (HRXRD) measurement showed that a GaInP single layer exhibits a double-diffracted peak phenomenon. Such a double peak represents a composition separation in the grown film, resulting in two absorption cutoff energies in optical absorption analysis. Cross-sectional transmission electron microscopic (TEM) observation confirmed the composition separation in an In-rich GaInP film. Furthermore, the composition separation amount of a Ga-rich GaInP film after substrate removal was found to be ∼0.5%, which reflects the actual effect of lattice strain on composition during growth stage.     

Nitridation of (Ba,Sr)TiO3 films in an inductively coupled plasma

The effects of surface treatment, using ammonia in an inductively coupled plasma, of (Ba,Sr)TiO₃ films on the leakage and dielectric properties of the Pt/(Ba, Sr) TiO₃/Pt capacitors were investigated. To obtain data of the ammonia plasma, a Langmuir probe was used during the experiments. As a result of the exposure of (Ba,Sr)TiO₃ to the plasma, the leakage current density of the (Ba,Sr)TiO₃ capacitor was decreased by two orders of magnitude as compared to that of the non-plasma-treated sample at an applied voltage of 1.5 V. The decrease of leakage currents of (Ba,Sr)TiO₃ films is attributed to the reduction of oxygen vacancies. However, the dielectric constant may be changed by the plasma-induced space charge or ion bombardment. The X-ray photoelectron spectroscopy measurements detected the N 1s peak in the plasma-treated sample. Additional space charges were induced and result in the reduction of the dielectric constant. We assume that the competition of nitrogen incorporation into the oxygen vacancies and plasma-induced damage is the main effect of the nitridation of (Ba,Sr)TiO₃ films in ammonia plasma.     

Solid polymer electrolytes III: Preparation,characterization, and ionic conductivity of new gelled polymer electrolytes based on segmented,perfluoropolyether‐modified polyurethane

New segmented polyurethanes with perfluoropolyether (PFPE) and poly(ethylene oxide) blocks were synthesized from a fluorinated macrodiol mixed with poly(ethylene glycol) (PEG) in different ratios as a soft segment, 2,4‐toluene diisocyanate as a hard segment, and ethylene glycol as a chain extender. Fourier transform infrared, NMR, and thermal analysis [differential scanning calorimetry and thermogravimetric analysis (TGA)] were used to characterize the structures of these copolymers. The copolymer films were immersed in a liquid electrolyte (1 M LiClO₄/propylene carbonate) to form gel‐type electrolytes. The ionic conductivities of these polymer electrolytes were investigated through changes in the copolymer composition and content of the liquid electrolyte. The relative molar ratio of PFPE and PEG in the copolymer played an important role in the conductivity and the capacity to retain the liquid electrolyte solution. The copolymer with a 50/50 PFPE/PEG ratio, having the lowest decomposition temperature shown by TGA, exhibited the highest ionic conductivity and lowest activation energy for ion transportation. The conductivities of these systems were about 10^?3 S cm^?1 at room temperature and 10^?2 S cm^?1 at 70 °C; the films immersed in the liquid electrolyte with an increase of 70 wt % were homogenous with good mechanical properties. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 486–495, 2002; DOI 10.1002/pola.10119     

Hyperbranched polyethyleneimine architecture onto poly(allylamine) by simple synthetic approach and the chelating characters

In resemblance to the ethoxylation of alkylamine or polymeric amines to introduce the nonionic hydrophiles by incorporation of ethylene oxide groups to make surfactants, ethyleneimine (EI) groups were introduced into poly(allylamine) by a simple in situ reaction of this polymer with 2‐chloroethylamine hydrochloride. The resultant polymers were allylic and chain‐pendant with hyperbranched polyethyleneimine. The EI number (n) of the polymers was determined by ¹H NMR. The percentages of primary, secondary, and tertiary amine present were estimated by potentiometric titration. The chelating abilities of the polymers that were applied growth conditions once (G₁, n ≈ 2) and twice (G₂, n ≈ 6) were also examined by potentiometric titration and ultraviolet–visible spectoscopy in the presence of metal ions (Cu⁺²). Continuous‐variation analysis revealed that each repeat unit of G₁ and G₂ behaves as a multident chelate and forms a stable complex with Cu⁺² ions utilizing an average of three EI dents per ion. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3018–3023, 2001