Fabrication and Microwave Properties of Three-Dimensional Photonic Crystals With a Diamond Structure Composed of Ceramic Spheres in Resin

Three-dimensional photonic crystals with a diamond structure composed of YSZ (3 mol% Y₂O₃-stabilized ZrO₂) spheres in a resin matrix were fabricated by using stereolithography. The lattice constant was 12 mm and the diameter of the spheres was 5 mm. These photonic crystals made of ceramic spheres showed complete photonic band gaps at around 12 GHz between the eighth and ninth bands. The propagation characteristics of microwaves agreed well with the calculated results using the plane wave expansion method.     

Microwave Absorption in Photonic Crystals Composed of SiC/Resin with a Diamond Structure

Three-dimensional photonic crystals were fabricated by infiltrating an epoxy mold with a SiC/polyester mixture. The epoxy molds with normal or inverse diamond structures were formed by stereolithography. The size of the mold was 45 mm × 18 mm × 18mm, and the lattice constant of the photonic crystals was 18 mm. The effects of the epoxy mold type, aspect ratio (the ratio of height and diameter of a diamond lattice rod), and number of sample units on the formation of photonic band gap (PBG) and microwave absorption ability along the 〈100〉 direction were studied. The attenuations of microwave transmission and reflection were measured through the photonic crystal samples at a frequency range of 3–12 GHz with a network analyzer. The results obtained suggest that the combination of the absorbing material SiC and diamond structure has a dual effect to form a PBG with a high absorption ability.     

Fabrication of Ceramic–Polymer Photonic Crystals by Stereolithography and Their Microwave Properties

Three-dimensional photonic crystals with periodic variations in the dielectric constant were fabricated using a stereolithographic rapid prototyping method. The structures were composed of millimeter-scale ordered epoxy lattices in which ceramic particles with high dielectric constants (such as silica and titania) were dispersed. These crystals were designed to reflect microwaves via the formation of photonic band gaps in a gigahertz range. The attenuation of transmission amplitude through the photonic crystals, which was measured as a function of frequency using a network analyzer, clearly showed the formation of band gaps in the microwave range.     

Fabrication of Metallodielectric Photonic Crystals with a Diamond Structure and their Microwave Properties

Three-dimensional (3D) metallodielectric photonic crystals with a diamond structure were fabricated in order to investigate the formation of stop bands and the absorption ability for microwaves with the dielectric absorbing media embedded into the 3D metal lattice. First, the metallic photonic crystals were prepared by filling the epoxy molds formed by stereolithography with a metal alloy having a low melting point of 70°C, followed by removal of the molds. The metallodielectric photonic crystals were then fabricated by infiltrating the porous metal crystal with a SiC/polyester mixture. The lattice constant of photonic crystals was 15 mm. The effects of different aspect ratios of diamond lattice rods, number of metallic lattice units along Γ-L 〈1 1 1〉, Γ-X 〈1 0 0〉, and Γ-K 〈1 1 0〉 directions, and metallodielectric samples along the Γ-X 〈1 0 0〉 direction on the formation of stop band and microwave absorption ability were investigated in the frequency range from 3 to 30 GHz. Metallodielectric photonic crystals formed showed good absorption ability. The measured transmission spectra of the metallic and metallodielectric crystals agreed well with the simulation of the transmission line modeling method.     

Fabrication of Ceramic Photonic Crystals with Diamond Structure for Microwave Applications

A process for fabricating three-dimensional photonic crystals composed of SiO₂–TiO₂-based ceramics with a diamond structure was investigated. An epoxy structure having an inverse diamond configuration was fabricated by stereolithography, a rapid prototyping method. The epoxy structure was infiltrated with a ceramic slurry and then cold isostatically pressed. After sintering at 670°C for 5 h in air, the epoxy was burned off, leaving behind the desired structure of a ceramic photonic crystal. The calculated band diagram indicated that an absolute photonic band gap for all wave vectors existed. The measurement of transmission in the 〈100〉 direction from 10 to 20 GHz showed that a complete band gap formed at about 14.7–18.5 GHz. The magnitude of the maximum attenuation was as large as 30 dB at 17 GHz, which indicated that the fabricated structure worked well as a photonic crystal.     

SiO2光子晶体的垂直沉积制备与光学性能研究

采用改进的St(o)ber法合成了不同粒径的单分散SiO2微球颗粒,用种子液法制备了平均粒径约为550 nm的单分散SiO2微球颗粒,在可见光波段垂直沉积制备了SiO2光子晶体薄膜.采用紫外-可见分光光度计测试了不同反应物浓度配比所得微球制备的光子晶体薄膜的光学性能,并分析了退火对光反射性能的影响.     

可调制光子晶体材料的研究进展和展望

可调制光子晶体材料是一类通过调节自身光子带隙结构对外场刺激做出响应的先进光子材料,它比传统的非调制光子晶体表现出更加优异的性能,近年来已成为光子晶体研究中的一个重要领域。本文简单介绍了近年来可调制光子晶体材料的发展状况,阐述了其调制机理及存在的问题,同时对未来光子晶体材料的发展提出了展望。     

Fabrication of Photonic Crystal with a Diamond Structure Having an Air Cavity Defect and its Microwave Properties

Three-dimensional photonic crystals with a diamond lattice structure consisting of 5 × 5 × 5 unit cells with the unit cell dimension of 15 mm were fabricated using TiO₂-based ceramic particles dispersed epoxy by stereolithography. The diamond lattice showed a perfect band gap between 14.3 and 15.8 GHz. An air cavity defect with a rectangular shape (15 mm × 45 mm × 15 mm) was introduced at the center of the crystal by extracting 3 unit cells in order to investigate the shape effect of the defect on the formation of localized defect modes of electromagnetic wave. When microwaves were radiated normal to the wide sides (45 mm × 15 mm) of the rectangular shape defect, a sharp localized mode appeared at the middle of the band gap. However, no localized mode was observed for incident waves normal to the smaller side (15 mm × 15 mm) because of the symmetry mismatching between internal eigenmodes in the defect cavity and incident plane waves. The mode analysis using a simple cavity model showed the penetration of the electric field of resonant modes about 2.4 mm into the host lattice.     

二维光折变光子晶体的制作及应用

对4个点光源进行光学傅里叶变换,在自散焦光折变掺铁铌酸锂晶体中成功制作了具有300余条波导的光子晶体,并实验证明了该光子晶体具有导向较长波长光的性质。随后利用理论模型制作了具有不同周期的2种四方形光子晶体。     

Fabrication of Three-Dimensional Micro Photonic Crystals of Resin-Incorporating TiO2 Particles and their Terahertz Wave Properties

Three-dimensional (3D) photonic crystals with a diamond structure made from 40 vol% TiO₂–acrylate dielectric composites were formed by means of a CAD/CAM micro-stereolithography system. The lattice constant of the diamond unit cell was 500 μm and the forming accuracy was 10 μm. The photonic band gap in the Γ–X 〈100〉 direction measured by terahertz-time-domain spectroscopy appeared at 280–360 GHz, which agreed fairly well with the band gap calculated by the plane wave expansion method.     

Effects of Epoxy Resin on Gelcasting Process and Mechanical Properties of Alumina Ceramics

A gelling system based on the polymerization of epoxy resin ethylene glycol diglycidyl ether (EGDGE) and 3,3′‐Diaminodipropylamine (DPTA) was developed for gelcasting alumina ceramics. The gelation process of 50 vol% alumina‐epoxy resin suspensions were investigated in accordance with the change in temperature and epoxy resin concentration. The activation energy E_a of polymerization reaction was 63.76 kJ/mol and no significant gelation was observed at 25°C during the test for 50 vol% Al₂O₃ suspensions with 10 wt% EGDGE. With the increase in EGDGE concentration, Al₂O₃ green bodies exhibited higher relative density, flexural strength, and Weibull modulus, reaching 64.4%, 41.03 MPa, and 12.51, respectively, when EGDGE concentration was 20 wt%. However, for sintered Al₂O₃ bodies, the highest characteristic strength and Weibull modulus were obtained for 15 wt% EGDGE concentration, reaching 367.57 MPa and 14.52, respectively.     

Effect of Porosity and Grain Size on the Microwave Dielectric Properties of Sintered Alumina

The real part of the permittivity (epsilon') and the tan of sintered alumina (Al₂O₃) at about 9 GHz have been measured. The dielectric properties have been examined as a function of purity, pore volume, and sintered grain size. The tan is found to depend very strongly on the pore volume, purity, and grain size. ɛ' is far less sensitive to impurities and grain size. The dependence of ɛ' on porosity can be described by simple mixture models as expected. A model of losses in single crystals cannot be extended easily to these materials where extrinsic factors such as porosity, random crystal orientation, grain boundaries, microcracks, and impurities dominate. These factors have been studied in an attempt to describe the tan δ and ɛ' of sintered polycrystalline alumina. In this work, the tan δ for alumina has been studied in near-theoretical density ranges between 9.1 × 10₋₅ and 2.4 × 10₋₅ depending on grain size.     

微波辐射APT–g-PAMPS高吸水性树脂的制备及性能

以凹凸棒黏土(APT)和2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为原料,过硫酸钾(KPS)为引发剂,N,N'-亚甲基双丙烯酰胺(NMBA)为交联剂,采用微波辐射法接枝共聚合成了APT-g-PAMPS耐盐性复合高吸水性树脂,用FTIR和XRD对复合吸水性树脂的结构进行了表征。考察了微波功率和时间及APT用量对树脂吸水倍率的影响,测定了不同APT用量高吸水性树脂的吸水速率、保水性能及反复吸水性能。FTIR和XRD结果显示,APT和有机单体之间发生了接枝共聚反应,其反应仅在APT的表面进行,单体并没有插入到APT的层间。结果表明,微波功率为195 W,辐射时间为2.5 min,w(APT)=5%时,树脂在去离子水和生理盐水中的吸水倍率分别为987g/g和102 g/g。该复合高吸水性树脂具有较快的吸水速率、较强的保水性能和较好的反复吸水性能。在体系中引入适量APT能够显著提高复合吸水树脂的吸水能力和耐盐性能,同时能明显加快树脂的吸水速率和提高树脂的保水性能。     

以水性环氧树脂为凝胶体系的氧化铝空心球浆料的流变性能

以水性环氧树脂为凝胶体系,研究了氧化铝空心球陶瓷浆料的流变性能,考察了水性环氧树脂溶液含量、固化温度对水性环氧树脂溶液和不同固相含量氧化铝空心球陶瓷浆料凝胶过程的影响。结果表明:在同一温度下,随水性环氧树脂溶液质量分数的增加,凝胶时间缩短,当水性环氧树脂含量从15.4%(质量分数)增加到28.8%时,溶液凝胶时间从99.3min缩短至38.2min;固化温度升高后,溶液凝胶时间明显缩短,从20℃时的125.3min下降到50℃时的5.8min。以水性环氧树脂为凝胶体系的氧化铝空心球浆料也存在上述规律,随浆料固相含量增加,凝胶时间缩短。以水性环氧树脂为凝胶体系成功制备出氧化铝空心球多孔陶瓷。     

微波辐射阿拉伯胶接枝2-丙烯酰胺基-2-甲基丙磺酸制备高吸水树脂及溶胀性能

以阿拉伯胶(GA)、2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为原料,N,N-亚甲基双丙烯酰胺(NMBA)为交联剂,过硫酸钾(APS)为引发剂,采用微波辐射方法制备了GA-g-PAMPS高吸水性树脂。探讨了单体配比、交联剂用量、引发剂用量、中和度、微波功率和辐射时间对吸水倍率的影响,研究了树脂的溶胀性能,并用FTIR对吸水性树脂的结构进行了表征。结果表明:最佳合成条件下得到的树脂吸去离子水倍率为683 g/g,吸生理盐水倍率为137 g/g。树脂的吸水倍率随着无机盐溶液浓度的增加而减小,在不同价态金属离子盐溶液中,树脂的吸水倍率从大到小的顺序为Na ClBa Cl2Fe Cl3,树脂具有较高的吸水速率和较好的重复吸水性能。     

微波辐射制备阿拉伯胶接枝2-丙烯酰胺基-2-甲基丙磺酸高吸水树脂及溶胀性能

以阿拉伯胶(GA),2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为原料,N,N-亚甲基双丙烯酰胺(NMBA)为交联剂,过硫酸钾(APS）为引发剂,采用微波辐射方法制备了GA-g-PAMPS 高吸水性树脂。探讨了单体配比、交联剂用量、引发剂用量、中和度、微波功率和辐射时间对吸水倍率的影响,研究了树脂的溶胀性能,并用FTIR对吸水性树脂的结构进行了表征。结果表明：最佳合成条件下树脂吸去离子水倍率为683g/g,吸生理盐水倍率为137g/g。树脂的吸水倍率随着无机盐溶液浓度的增加而减小,在不同价态金属离子盐溶液中,树脂的吸水倍率顺序为NaCl>BaCl2> FeCl3,树脂具有较高的吸水速率和较好的重复吸水性能。     

微波辐射制备阿拉伯胶接枝2-丙烯酰胺基-2-甲基丙磺酸高吸水树脂及溶胀性能

以阿拉伯胶(GA),2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为原料,N,N-亚甲基双丙烯酰胺(NMBA)为交联剂,过硫酸钾(APS）为引发剂,采用微波辐射方法制备了GA-g-PAMPS 高吸水性树脂。探讨了单体配比、交联剂用量、引发剂用量、中和度、微波功率和辐射时间对吸水倍率的影响,研究了树脂的溶胀性能,并用FTIR对吸水性树脂的结构进行了表征。结果表明：最佳合成条件下树脂吸去离子水倍率为683g/g,吸生理盐水倍率为137g/g。树脂的吸水倍率随着无机盐溶液浓度的增加而减小,在不同价态金属离子盐溶液中,树脂的吸水倍率顺序为NaCl>BaCl2> FeCl3,树脂具有较高的吸水速率和较好的重复吸水性能。     

Fabrication and Measurement of Micro Three-Dimensional Photonic Crystals of SiO2 Ceramic for Terahertz Wave Applications

Three-dimensional (3D) photonic crystals with a diamond structure made of a dense SiO₂ ceramic were successfully fabricated using a CAD/CAM micro-stereolithography and sintering process. The designed lattice constant of the diamond unit cell was 500 μm and the forming tolerance from 50 vol% SiO₂ paste (before sintering) was around 15 μm. After the SiO₂-resin photonic crystals were formed via micro-stereolithography, they were converted to pure SiO₂ ceramic photonic crystals of 99% theoretical density by sintering at 1400°C. The electromagnetic wave propagation in these dense SiO₂ photonic crystals was measured by terahertz-time-domain spectroscopy. The results showed that the band gap appeared between 470 and 580 GHz in the Γ– X 〈100〉 direction, between 490 and 630 GHz in the Γ– K 〈110〉 direction, and between 400 and 510 GHz in the Γ– L 〈111〉 direction, resulting in the formation of a common band gap in all directions between 490 and 510 GHz. These results agreed well with the band gaps calculated by the plane wave expansion method.     

一种3D打印光敏树脂的研制及性能

以改性环氧丙烯酸酯为预聚物,采用自由基-阳离子杂化聚合法制备了可在405 nm光照下固化的3D打印光敏树脂。研究了预聚物、稀释剂、光引发剂的含量对光敏树脂力学性能、黏度和体积收缩率的影响。结果表明,当光引发剂添加量为4%时,力学性能最优化;当改性环氧丙烯酸酯含量在48%~58%时,该体系能满足3D打印光固化材料的使用要求;采用本方法制备的光敏树脂具有卓越的热稳定性。