磷酸修饰对纳米Fe2O3热稳定性及光催化性能的影响

通过溶液浸渍蒸干过程实现了磷酸对Fe₂O₃纳米粒子的表面修饰, 研究了磷酸修饰对纳米Fe₂O₃的热稳定性及光催化活性的影响. 结果表明, 磷酸修饰显著提高了Fe₂O₃的热稳定性, 主要归因于磷酸修饰在样品表面抑制了粒子之间的团聚生长. 同时, 在光催化降解气相乙醛和液相苯酚的测试中, 磷酸修饰后热处理温度为600 ℃的样品表现出了最佳的可见光催化性能, 这主要归因于该样品具有高晶化度、 小粒子尺寸及大比表面积, 并且适量的修饰有利于其光催化性能的提高.     

Colorless poly(ether-imide)s deriving from 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride(BPADA) and aromatic bis(ether amine)s bearing pendent trifluoromethyl groups

A series of poly(ether-imide)s (III) characterized by colorless, highly solubility was synthesized from 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride(BPADA) and various fluorinated aromatic diamines (I_a-h) in DMAc via polycondensation to form poly(amic acid) (II), followed by chemical (C) and thermal (H) imidization. These polymers had inherent viscosities ranging from 0.60 to 1.3 dL/g. These polyimides were highly soluble in a variety of organic solvent such as amide-type, ether-type and chlorinated solvents. Moreover, these poly(ether-imide) films were almost colorless, with an ultraviolet-visible absorption cutoff wavelength below 390 nm and low b* value (a yellowness index) of 4.6-18.0. The III series showed strength tensile of 72-101 MPa, elongation at break of 11-25%, initial modulus of 1.5-2.0 GPa. The glass transition temperature (T_g) of III_a-h were in the range of 202-267 °C, and the decomposition temperature above 493 °C and left 40-65% char yield at 800 °C in nitrogen. They had the lower dielectric constants of 3.39-3.72 (1 MHz) and moisture absorptions in the range of 0.11-0.40%.     

Novel organosoluble and colorless poly(ether imide)s based on 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclohexane dianhydride and trifluoromethyl-substituted aromatic bis(ether amine)s

A series of novel fluorinated poly(ether imide)s (IV) having inherent viscosities of 0.70-1.08 dL/g were prepared from 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclohexane dianhydride (I) and various trifluoromethyl (CF₃)-substituted aromatic bis(ether amine)s II_a-g by a standard two-step process with thermal and chemical imidization of poly(amic acid) precursors. These poly(ether imide)s showed excellent solubility in many organic solvents and could be solution-cast into transparent, flexible, and tough films. These films were essentially colorless, with an ultraviolet-visible absorption edge of 375-380 nm and a very low b^∗ value (a yellowness index) of 5.5-7.3. They also showed good thermal stability with glass-transition temperatures of 207-269 °C, 10% weight loss temperatures in excess of 474 °C, and char yields at 800 °C in nitrogen more than 62%. In comparison with analogous V series poly(ether imide)s without the -CF₃ substituents, the IV series polymers showed better solubility, lower color intensity, and lower dielectric constants.     

Rapid laser fabrication of microlens array using colorless liquid photopolymer for AMOLED devices

Microlens array (MLA) is microfabricated using Ultra Violet (UV) laser for display device applications. A colorless liquid photopolymer, Norland Optical Adhesive (NOA) 60, is spin-coated and pre-cured via UV light for completing the laser process. The laser energy controlled by a galvano scanner is radiated on the surface of the NOA 60. A rapid thermal volume expansion inside the material creates microlens array when the Gaussian laser energy is absorbed. The fabrication process conditions for various shapes and densities of MLA using a non-contact surface profiler are investigated. Furthermore, we analyze the optical and display characteristics for the Organic Light Emitting Diode (OLED) devices. Optimized condition furnishes the OLED with the enhancement of light emission by 15%. We show that UV laser technique, which is installed with NOA 60 MLA layer, is eligible for improving the performance of the next generation display devices.     

Performance analysis of symmetrical 10 Gbps colorless WDM-PON using subcarrier modulated downstream and wavelength converted upstream through RSOA

Here we have demonstrated a novel architecture of colorless wavelength division multiplexed-passive optical network (WDM-PON) and analyze its performance which is capable of transmitting 10 Gbps data symmetrically in both downstream and upstream. In this architecture downstream data is subcarrier modulated (SCM) using radio frequency (RF) as subcarrier and laser frequency as carrier with the help of a Mach–Zehnder modulator (MZM). For upstream data modulation an electro-absorption modulator, an optical coupler and reflective semiconductor optical amplifier (RSOA) are used. Upstream data is transmitted through wavelength conversion between pump wavelength and continuous wave light sent from central office (CO) using cross gain modulation (XGM) in RSOA. Pump wavelengths have separate wavelength band than the carrier's wavelength sent from optical network unit (ONU) and can be chosen any one in its band. Since carrier reuse scheme is implemented so all the ONUs are operates in colorless mode. Effect of ER of delay interferometer (DI) on output OCSR of DI for different input OCSR is performed for SCM data. Simulation is performed with all 16 downlink and 16 uplink channels having data rate of 10 Gbps having acceptable performance.     

Enhanced colorless and broadcast capable symmetrical 10-Gbps bidirectional transmission in WDM-PON using RSOA and EAM

Here we proposed a novel architecture of wavelength division multiplexed-passive optical network (WDM-PON) in which the downlink unicast data, broadcast data and uplink unicast data transmission is possible with the symmetric data rate of 10 Gbps. At remote node (RN) cyclic wavelength routing property of array waveguide grating (AWG) and power splitting capacity of power splitter is used in the architecture so that broadcast channel can be overlaid on downlink unicast channels. At ONU carriers sent from central office (CO) is reused for upstream data transmission with the help of integration of a reflective semiconductor amplifier (RSOA) and an electro-absorption modulator (EAM) so there is no need of extra laser sources at ONUs which makes them colorless. EAM can be operated at very high speed; a modulation bandwidth of tens of GHz can be achieved. Broadcast channel causes a limited interference with downlink and uplink unicast channels so it does not affect the system performance. Since each channel has different wavelength so NRZ data is used which eliminates expensive DPSK receivers and detection becomes very easy. Simulation is performed with all channels having data rate of 10 Gbps having acceptable performance.     

Synthesis and characterization of organosoluble aliphatic-aromatic copolyimides based on cycloaliphatic dianhydride

A series of aliphatic-aromatic polyimides have been synthesized. These polyimides were prepared by high-temperature polycondensation of the aliphatic diamines: 1,4-diaminobutane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,9-diaminononane, 1,10-diaminodecane, 1,12-diaminododecane and 4,4^′-methylenebis(2,6-dimethylaniline) with 1,2,3,4-cyclopentanetetracarboxylic dianhydride. Various ratios of diamines (aromatic:aliphatic) have been applied for preparation of copolyimides. Polycondensation proceeded at 190 °C and produced copolyimides with reduced viscosities up to 0.92 dl/g. The polyimides were soluble in a wide range of organic, common solvents and showed high-thermal stability. In most cases these polymers formed flexible films which presented excellent transparency.     

Organosoluble optically transparent poly(amide-imide)s based on 2,2-bis [<Emphasis Type="Italic">N</Emphasis>-(3-carboxyphenyl)phthalimidyl]- hexafluoropropane and 2,2-bis [<Emphasis Type="Italic">N</Emphasis>-(4-carboxyphenyl)phthalimidyl]- hexafluoropropane and various aromatic diamines

 Two diimide-dicarboxylic acids, 2,2-bis[N-(4-carboxyphenyl)phthalimidyl]hexafluoropropane (p-I) and 2,2,-bis[N-(3-carboxyphenyl)phthalimidyl]hexafluoropropane (m-I), were prepared by azeotropic condensation of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride and p-aminobenzoic acid or m-aminobenzoic acid at a 1:2 molar ratio in N,N-dimethylacetamide/toluene. Two series of organosoluble and colorless poly(amide–imide)s were synthesized from diimide–diacid p-I or m-I with ten kinds of aromatic diamines by direct polycondensation using triphenyl phosphite and pyridine as condensing agents. The thin films cast from N,N-dimethylacetamide were measured by UV–vis spectroscopy and Macbeth color-eye colorimetery, the cutoff wavelengths of almost all the films were below 400 nm (361–389 nm) and the values of the parameter b* were between 15.31 and 34.72; these polymers are much lighter in color than other analogous polymers. Almost all the polymer were soluble in N-methyl-2-pyrrolodone, N,N-dimethylacetamide, N,N-dimethylformamide and dimethyl sulfoxide, and some polymers could dissolve in less polar solvents, such as dioxane and tetrahydrofuran, etc. The cast films exhibited yield strengths of 95–131 MPa, tensile strengths ranging from 92 to 130 MPa, elongations at break from 9 to 27%, and initial moduli from 2.1 to 3.3 GPa. The poly(amide–imide)s had glass-transition temperatures between 259 and 328°C and 10%-weight-loss temperatures above 510 °C in nitrogen and air, indicating excellent thermal stability. Received: 25 April 2001 Accepted: 27 June 2001     

Highly Transparent and Colorless Polyimide Film with Low Dielectric Constant by Introducing Meta-substituted Structure and Trifluoromethyl Groups

An effective design strategy for preparing highly transparent polyimide film with low dielectric constant is presented. The key to the strategy is to simultaneously introduce meta-substituted structure and trifluoromethyl in polymer chains. By using this design strategy, a highly transparent polyimide film with low-k was synthesized from 3,5-diaminobenzotrifluoride(m-TFPDA) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride(6 FDA) through a two-step method. The obtained m-TFPDA/6 FDA(CPI) film(～30 μm) possesses high optical transparency(λ_(cutoff)=334 nm, T_(450nm)=85.26%, Haze=0.31) and is close to colorless(L*=96.03, a*=-0.34, b*=2.12, yellow index=3.96). The intrinsic k and dielectric loss value of the film are 2.27 and 0.0013 at 10 kHz, respectively. More importantly, such low dielectric performance could remain stable up to280 °C, and the film shows a low moisture rate(～0.51%), which helps to maintain the low-k property stability in different humid environments.Meanwhile, the film also shows good thermal stability and mechanical properties, with a glass transition temperature(T_g) of 296 °C and the 5 wt%decomposition temperature(T_(d,5%)) of 522 °C under N_2. The tensile strength and tensile modulus of the film are 85.1 MPa and 1.96 GPa,respectively. In addition, the film is soluble in common solvents, which allows simple solution processing and low-cost, continuous roll-to-roll processes. This design strategy is beneficial to improving the transparency, lightening yellow color, lowering the dielectric constant and meanwhile maintaining the comprehensive properties of polyimide films, which is mainly due to the introduced meta-substituted and trifluoromethyl structures effectively inhibiting the transfer of charge transfer complex(CTC) effects and increasing the free volume of film. This design strategy could also be extended to other high-performance polymer systems.     

Preparation of colorless ionic liquids “on water” for spectroscopy

Although colorless ionic liquids (ILs) are most desirable, as synthesized they frequently bear color, despite appearing pure by most analytical techniques. It leads to some uncertainties and limits for the fundamental research and applications of ILs, such as spectroscopy. Using 1-butyl-3-methylimidazolium bromide (BMIMBr), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄) and 1-hexyl-3-methylimidazolium bromide (HMIMBr) as models, we demonstrated that following classic preparing method except that the water was added as solvent, colorless ILs could be facilely prepared. Neither critical pre-treatment of starting materials and pre-cautions during the reaction nor time-consuming and costly post-decolor-purification was needed. The effects of “on water” reaction conditions on preparing colorless IL and the reason why using water as solvent could produce colorless ILs were also preliminary investigated. It was found that the reactant solubility played an important role in the preparation of colorless ILs. Not only as a method to evaluate the quality of as-synthesized ILs, but also as a spectroscopic analytical applications, UV-vis spectra showed that the ILs by this “on water” method was spectral pure and sufficient for future fundamental spectroscopic research and applications.