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1.
高温热处理对聚酰亚胺薄膜性能的影响   总被引:2,自引:0,他引:2  
研究了高温热处理对聚酰亚胺(PI)薄膜拉伸性能和热性能的影响。在薄膜完全环化后,随着热处理温度的升高,薄膜的拉伸强度、弹性模量先增大后基本保持不变,断裂伸长率先保持不变后明显降低,热膨胀系数也显著降低,而薄膜的玻璃化转变温度略有增大。高温热处理工艺可制备高强度和低热膨胀系数的高性能PI薄膜。  相似文献   

2.
Catalysts for the raction of aromatic isocyanates with aromatic anhydrides to form imides were investigated using a model reaction. Alkali metal acetylacetone chelate compounds exhibited good catalytic efficiency and selectivity in dimethyl sulfoxide (DMSO). These catalysts were used for the preparation of polymide foams. The resulting foams exhibited excellent fire resistance and thermal stability. © 1994 John Wiley & Sons, Inc.  相似文献   

3.
TiO2 nanoceramic films were deposited on glasses by rf magnetron sputtering. This method provides more advantages in controlling the microstructure and composition of the films. TiO preferentially formed and the deposited films tended to become nonstoichiometric by increasing substrate temperature. The morphologies and hydrophilic properties of TiO2 films were significantly affected by the substrate temperature. The nonlinear refractive index of the TiO2 film on the glass substrate measured by Moiré deflectometry was of the order of 10?8 cm2 W?1. Smaller grain size, higher optical energy gap, visible transmission and linear refractive index, and lower stress-optical coefficient were obtained at lower substrate temperature.  相似文献   

4.
Polyamide acid was prepared from pyromellitic dianhydride and p-phenylenediamine and was then reacted with NaH and various kinds of alkyl halides to transform into alkyl esters. The cast films were imidized as fixed on glass substrate to give polyimide films and were then carbonized by heating to 900°C. The electrical conductivity of the carbonized films decreased with the increase of the size of the leaving group at the imidization step. The carbonized films were further heated to 2800°C for graphitization. Their degrees of graphitization and orientation of the graphite crystallite as a function of weight loss at imidization were studied by X-ray diffraction measurement at room temperature and magnetoresistance measurement at liquid nitrogen temperature. Both measurements clearly indicate that the graphitized films prepared from polyamide acid alkyl ester have high degrees of graphitization. It was also made clear that the orientation of the graphitized films increased with the increase of the size of the leaving group at the imidization step. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci John Wiley & Sons, Inc.J Appl Polym Sci 68: 1613–1620, 1998  相似文献   

5.
Aluminum oxide (Al2O3) thin films were deposited on silicon (100) and quartz substrates by pulsed laser deposition (PLD) at an optimized oxygen partial pressure of 3.0×10?3 mbar in the substrate temperatures range 300–973 K. The films were characterized by X-ray diffraction, transmission electron microscopy, atomic force microscopy, spectroscopic ellipsometry, UV–visible spectroscopy and nanoindentation. The X-ray diffraction studies showed that the films deposited at low substrate temperatures (300–673 K) were amorphous Al2O3, whereas those deposited at higher temperatures (≥773 K) were polycrystalline cubic γ-Al2O3. The transmission electron microscopy studies of the film prepared at 673 K, showed diffuse ring pattern indicating the amorphous nature of Al2O3. The surface morphology of the films was examined by atomic force microscopy showing dense and uniform nanostructures with increased surface roughness from 0.3 to 2.3 nm with increasing substrate temperature. The optical studies were carried out by ellipsometry in the energy range 1.5–5.5 eV and revealed that the refractive index increased from 1.69 to 1.75 (λ=632.8 nm) with increasing substrate temperature. The UV–visible spectroscopy analysis indicated higher transmittance (>80%) for all the films. Nanoindentation studies revealed the hardness values of 20.8 and 24.7 GPa for the films prepared at 300 K and 973 K respectively.  相似文献   

6.
A poly(amic acid) derived from pyromellitic dianhydride and oxydianiline was imidized under different conditions. The sample imidized in solution (PI‐1) showed the X‐ray diffraction pattern of a crystalline material, whereas that of the sample imidized in the solid state was essentially amorphous. Both samples were further characterized by 13C‐NMR spectroscopy, IR spectroscopy, electron paramagnetic resonance, and thermogravimetric analysis. The orders of polyimide in both the crystalline and amorphous states are discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1065–1070, 2004  相似文献   

7.
The viscosity, surface tension, and refractive index of 2-day-old film-forming solutions of the CuO-TiO2 system of different composition were compared with the structure and properties of coatings on float glass made from them. Regardless of the composition and firing conditions, the film thickness remained constant. The refractive index and mirror reflection coefficient of the coatings are correlated by a directly proportional dependence. Increasing the firing temperature does not change or increases the values of the refractive index and mirror-reflection coefficient of the films. The chemical resistance of the coatings to water or hydrochloric acid solution is not a function of or improves with an increase in the firing temperature.  相似文献   

8.
In the present work we prepared co-polyimide (PI) fibers with excellent mechanical and dielectric properties by the wet-spinning method. The co-PI fiber exhibited high mechanical property with a tensile strength of 2.61 GPa and modulus of 86.7 Gpa as well as a low dielectric constant and a dielectric loss factor of 2.7463 and 0.00793 at 10 GHz, respectively. The relationship between the properties and the microstructure of co-PI fibers after heat-drawing was investigated. The results revealed that the hydrogen-bond associations and the microvoids structure were highly affected by imidization conditions. Both the formations of the hydrogen-bond associations and the evolution of microvoids were attributed to the change in tensile strength. Furthermore, the fibers prepared at proper conditions possessed fewer surface defects as well as homogeneous inner structure. Our work demonstrates the structure–property relationship in annealed PI fibers, which may provides a new avenue to access high-performance PI fibers.  相似文献   

9.
The imidization of polymerizable reactive mixtures, PMR-15 has been performed in a vacuum oven at isothermal aging temperatures ranging from 65 to 200°C for aging periods of 0.5 to 2.5 h. The weight loss of the resin and chemical changes that occurred as a result of aging were monitored gravimetrically and by FT-IR spectroscopy. Differential scanning calorimetry was used to determine the temperature at which imidization took place. Imidization was observed to commence at 65°C after long aging times, t ≥ 2.5 h and at ∼95°C at a shorter time, t ∼0.5 h. At higher aging temperatures of 135 to 165°C, extensive imidization occurred. This was shown by the dramatic increase in imide absorption bands at 1780 and 1380 cm−1. Beyond 165°C, there were no significant changes in the imide absorption bands, suggesting that imidization was nearly complete. The activation energy for isothermal aging was determined from the slope of the log of the rate of weight loss vs 1/T curve to be ∼4.5 kJ/mol and is lower than the average activation energy for imidization ∼43 kJ/mol obtained from the plot of the log of the rate of increase of the imide carbonyl peak absorption at 1780 cm−1 vs 1/T.  相似文献   

10.
《Ceramics International》2016,42(10):12262-12269
We report the deposition of tin sulfide (Sn2S3) thin films by co-evaporation technique at different substrate temperatures. The influence of substrate temperature on the structural and optical properties of the thin films is investigated. X- ray diffraction (XRD) analysis and Micro-Raman studies confirm the formation of Sn2S3 phase. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used to examine the surface morphology. The transmission spectra of the deposited Sn2S3 thin films have been recorded in the wavelength range of 200–3000 nm using UV–vis-NIR spectrometer. Film thickness (d) and optical constants such as refractive index (n), extinction coefficient (k), real (ε1) and imaginary (ε2) parts of the dielectric constants of thin films are estimated from the optical transmittance. The optical band gaps of the deposited films at different substrate temperatures are in the range of 1.46–1.64 eV. Hall effect measurements confirm the n-type nature of the as-prepared Sn2S3 thin films.  相似文献   

11.
邱玉娟  马晓军  尹兴 《化工进展》2019,38(7):3291-3296
通过溶液浇铸法制备得到纳米氧化石墨烯(GO)/聚羟基丁酸-羟基己酸酯(PHBH)复合膜,利用SEM、XRD、DSC、拉伸测试、阻隔测试及透明度测试等检测手段,研究了不同干燥温度对复合膜结构及性能的影响,优化了制备工艺。结果表明:随着干燥温度的升高,GO在PHBH中的分散性以及复合膜的结晶度、断裂伸长率和阻隔性先增加后减小,而拉伸强度及透光率则随温度的增加而增加。当干燥温度为45℃→55℃梯度升温时,GO在PHBH中均匀分散,且复合膜的断面光滑,有良好的结晶度、热稳定性、力学及阻隔性能,其拉伸强度、断裂伸长率可分别达到20.11MPa、17.47%,且透氧系数及水蒸气透过系数分别为48cm3/(m2·d)、13.33g/(cm2·d),综合性能优于其他干燥温度下的复合膜。  相似文献   

12.
Polyimide Langmuir‐Blodgett (LB) films were prepared with a Pyromellitic dianhydride‐4, 4′ oxydianiline precursor, and the properties of the polyamic acid salt monolayer characterized by different methods. The π‐A relationship revealed that the precursor monolayer exhibits anisotropy on the water surface, the Wilhelmy plate being more sensitive to pressure when it is perpendicular to the compression direction. FTIR results showed that polyamic acid salt LB films have lower imidization energy than the corresponding painting films and can be imidized at lower temperature. The molecular arrangement in the LB films was studied by X‐ray diffraction and polarized FTIR, showing that the polyamic acid salt LB film is of Y‐type, in which the molecules are highly oriented, with the main chain lying parallel to the substrate and the long fatty acid chains stretching out at a certain angle. © 2002 Society of Chemical Industry  相似文献   

13.
14.
In this study, experimental and numerical studies were performed to investigate the relationship among the functionalization method, weight fraction of MWCNTs, thermal imidization cycle, and mechanical properties of various PAI/MWCNT composite films. Poly(amide‐co‐imide)/multiwalled carbon nanotube composite films were prepared by solution mixing and film casting. The effects of chemical functionalization and weight fraction of multiwalled carbon nanotubes on thermal imidization and mechanical properties were investigated through experimental and numerical studies. The time needed to achieve sufficient thermal imidization was reduced with increasing multiwalled carbon nanotube content when compared with that of a pure poly(amide‐co‐imide) film because multiwalled carbon nanotubes have a higher thermal conductivity than pure poly(amide‐co‐imide) resin. Mechanical properties of pure poly(amide‐co‐imide) and poly(amide‐co‐imide)/multiwalled carbon nanotube composite films were increased with increasing imidization time and were improved significantly in the case of the composite film filled with hydrogen peroxide treated multiwalled carbon nanotubes. Both the tensile strength and strain to failure of the multiwalled carbon nanotube filled poly(amide‐co‐imide) film were increased substantially because multiwalled carbon nanotube dispersion was improved and covalent bonding was formed between multiwalled carbon nanotubes and poly(amide‐co‐imide) molecules. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

15.
The crystalline properties of poly(vinylidene fluoride) (PVdF) and its copolymer films, prepared from the solvent (N-methyl-2-pyrrolidone) evaporation at different temperatures and subsequent slow cooling to ambient temperature, were investigated by using polarized optical microscopy, differential scanning calorimetry, wide-angle X-ray diffractometry, and Fourier-transform infrared spectroscopy. The results can provide helpful data for determining the optimal processing conditions of PVdFs as the polymer binder materials in making the electrodes of rechargeable lithium batteries. The morphology analysis gives useful information that the residual solvent remaining after the evaporation shows distinguishable amounts with respect to the temperature regions dividing by the crystallization (Tc) and melting (Tm) points of original PVdF samples. It is also proved that smallest spherulitic state coexisting with dominant α- and minor γ-phase crystals, simultaneously showing the lowest heat of fusion (e.g., the lowest crystallinity), can be obtained when the solvent is evaporated at a temperature between Tc andT m. Letting the minor γ-phase crystals exist by controlling the evaporation temperature like this can be one of the best drying (evaporation) conditions of PVdF-containing slurry in lithium rechargeable battery system.  相似文献   

16.
Highly c-axis oriented ZnO film is often deposited on diamond substrates by RF magnetron sputtering and widely used for high frequency surface acoustic wave (SAW) devices. Deposition temperature is a key factor affecting the quality of the ZnO film. Different quality polished free-standing diamond films prepared by DC Arc Plasma Jet were used as the substrates to deposit ZnO films at different temperatures. Effect of the deposition temperature and the quality of the diamond films on the properties of the ZnO films were investigated by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that highly c-axis oriented ZnO films can be much easier deposited on the optical-grade diamond films with < 111> preferred orientation than the tool-grade diamond films with < 220> preferred orientation. The optimal deposition temperature is 200 °C for highly c-axis oriented and lower roughness ZnO films. Acoustic phase velocity of more than 10,000 m/s for the SAW devices based on the ZnO/optical-grade free-standing diamond films was obtained.  相似文献   

17.
Transparent ZnO and Al-doped ZnO (AZO) thin films have been prepared by radio frequency sputtering deposition at room temperature. The optical, electrical, and structural characteristics of the obtained films have been extensively investigated as a function of sputtering and annealing parameters. Spectrophotometry, X-ray diffraction (XRD), atomic force microscopy (AFM), four-point probe and Hall-effect measurements were employed. The ZnO films generally exhibited excellent crystalline properties, while providing a UV cut-off in the absorption spectrum for optical filtration. AZO thin films exhibited an average transparency (larger than 85%) over the visible region of the spectrum, and resistivity of the order of 10?3 Ω cm was obtained. The carrier concentration and electron mobility values proved to be dependent on the deposition parameters and annealing temperature. The obtained results showed that annealing temperatures higher than 400 °C were not necessary and potentially degraded the electronic properties of the AZO thin films.  相似文献   

18.
通过数理统计技术研究了石膏进厂温度与石膏初凝时间、抗裂性和抗压强度之间的关联性,并进一步讨论了环境温度对进厂石膏温度的影响,结果显示外界环境温度对石膏进厂温度影响甚微,进厂石膏温度与石膏初凝时间之间没有明显关联性,但与抗裂性之间有明显相关性,并随着进厂温度的升高开裂的风险急速升高。进厂石膏温度与石膏抗压强度之间有不明显的相关性,并随着进厂石膏温度的升高而存在强度下降的风险。  相似文献   

19.
《Diamond and Related Materials》2000,9(9-10):1687-1690
Selective diamond films on roughened Si(100) substrates with patternings have been achieved by microwave plasma chemical vapor deposition (MP-CVD). The films have been characterized by scanning electron microscopy (SEM) and Raman spectra. The influence of substrate temperature on the selective deposition of diamond films has been discussed in detail: the diamond nucleation density on the SiO2 mask increased with substrate temperature while the effect of the selective deposition of diamond films deteriorated; the optimized deposition temperature conditions have been concluded.  相似文献   

20.
Casein was grafted with acrylonitrile (AN) and with a binary mixture of acrylonitrile and n-butyl methacrylate (n-BMA). Stress-strain characteristics of these films were analyzed as a function of temperature and rate of extension. The results shows that both the systems are sensitive to temperature. Due to the incorporation of n-BMA, the material becomes flexible since the Tg of the multiphasic polymer was reduced and therefore shows the changes even at lower temperatures when compared to casein grafted with AN. The fracture morphologies of the binary mixture-grafted casein films show that the effect produced by temperature and rate of extension are inversely related. © 1994 John Wiley & Sons, Inc.  相似文献   

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