微波干燥技术及其在陶瓷坯体干燥中的应用研究

阐述了微波干燥的基本原理、理论及其特点，同时分析了微波应用于陶瓷坯体干燥的几个技术问题；也对其在国内外陶瓷材料干燥中的应用进行了研究分析。     

微波干燥技术在纳米材料制备中的研究进展

湿化学法是制备纳米材料的一种重要方法，但采用湿化学法制备的纳米粉体均存在干燥的过程，干燥方法的选择将对材料最终性能将产生明显的影响。微波干燥技术是最近发展而来的一种新型干燥技术，作者对几种微波干燥的模型以及微波干燥制备纳米粉体的进展作了说明。     

红外干燥不能提高蚕茧的干燥速率

通过大量实验,测定了蚕蛹、茧层的红外吸收图谱,选择相应波长范围的红外涂料和红外灯泡,在不同温度和不同堆放厚度条件下测定了蚕茧的干燥曲线,并与不采用红外线的干燥曲线进行了比较,结果表明红外线未能够提高蚕茧的干燥速率。实验还测定了0.25～25μm范围内单片茧层的红外线透过曲线,结果表明,在所测范围内,红外线的透过率为零,这说明红外线无法穿透茧层。茧层的水分含量很低(约10%),蚕蛹的水分含量很高(约80%),蚕茧干燥的主要目的是除掉蚕蛹中的水分,但茧层包含着蚕蛹,红外线无法穿透茧层对蛹体进行快速干燥。而且,茧层的红外吸收率很低,也不能通过茧层快速吸收红外线热能,然后传给蚕蛹来提高干燥速率,这便是红外线不能提高蚕茧干燥速率的原因。这一结论对国内外蚕业界探讨蚕茧干燥的理论与实践有重要的参考意义。     

微波技术在陶瓷工业中的应用

本文综述了近年来微波技术在陶瓷工业中的一些最新研究状况，包括微波加热。烧结，微波加热干燥，并对应用中的经济效益和应注意的问题做了分析。     

微波干燥技术的应用进展

阐述了微波干燥的原理、特点以及微波技术在国内外的研究和应用现状，同时对该技术在复混肥料干燥中的应用进行了预测分析。     

微波干燥技术在纳米材料制备中的研究进展

湿化学法是制备纳米材料的一种重要方法,但采用湿化学法制备的纳米粉体均存在干燥的过程,干燥方法的选择将对材料最终性能将产生明显的影响。微波干燥技术是最近发展而来的一种新型干燥技术,作者对几种微波干燥的模型以及微波干燥制备纳米粉体的进展作了说明。     

微波技术在种子干燥方面的研究进展

干燥是种子加工的重要环节，微波干燥技术具有独特的优点和特点。近十几年来，国内外在种子微波干燥方面的研究取得了不少成果，而有关这方面的综述却未见报道。本文在阐述微波干燥机理和特点基础上，就近年来国内外微波技术在种子干燥方面的研究进展作一综述，并探讨微波技术在种子干燥方面的应用前景。     

我国微波干燥技术应用研究进展

阐述了微波干燥技术的特点,对我国微波干燥技术在食品工业、材料化工、医药工业、矿产开采业、陶瓷工业、实验室分析、湿天然橡胶加工等方面的应用研究现状进行了综述：特别是对我国微波干燥技术在取代传统的燃烧柴油、燃烧煤、燃烧木材等方式为手段产生的热空气为介质,干燥湿天然橡胶的研究进展进行了详细阐述;同时对我国微波干燥技术的应用前景尤其在湿天然橡胶干燥加工中的应用前景进行了展望,并对我国微波干燥技术目前存在的问题及究方向作了预测分析。     

微波技术在分子筛研究中的应用

综述了微波辐射技术在各种分子筛的合成、活性组分的负载，分子筛催化剂的再生活化等方面的应用。     

微波干燥技术在蜂窝陶瓷中的应用

蜂窝陶瓷挤压成形后的强度低、难干燥等问题．严重制约了蜂窝陶瓷的广泛应用。近年来,微波干燥技术已应用于蜂窝陶瓷上,可以解决其强度低、难干燥等问题。结果表明,微波干燥技术能降低成形后蜂窝陶瓷坯体约10％的水分。通过分析蜂窝陶瓷干燥的过程,提出了热风干燥与微波干燥相组合的方法,结合两者的优势,以达到优化节能的目的。     

Mechanical properties of silkworm cocoons

Silkworm caterpillars, Bombyx mori, construct cocoons in order to protect their moth pupas against possible attacks from the outside. We experimentally measured the mechanical properties (Young's modulus, tensile strength, and thermo-mechanical parameters) of normal compact cocoons and the variations of these properties in the thickness direction of a cocoon. Tension tests were carried out by using rectangular specimens of two types, either cut from a normal compact cocoon or peeled from its different layers, respectively. We found that, on one hand, the overall or thickness-averaged mechanical properties of B. mori cocoons are excellent. More interestingly, on the other hand, the elastic modulus, strength and thermo-mechanical parameters all vary along the thickness direction of a cocoon in an apt manner, further enhancing its ability to resist possible attacks from the outside. In addition, the properties of a cocoon show distinct differences in the longitudinal and transverse directions. The relation between the mechanical properties and microstructures is discussed. Finally, the main features of the fracture process of cocoons and silks were also analyzed based on SEM observations. This study was attempted to gain an understanding of the mechanical behaviors and their dependence on the microstructures of cocoons, and it might be also helpful in guiding the design of novel safe-guarding devices and biomimetic materials.     

微波技术在石油工业中的应用研究进展

微波作为一种新的技术手段,已广泛应用于各个领域。作者综述了微波技术在石油工业领域的应用和研究状况,展望了微波技术在石油工业领域的应用前景。     

微波加热在毛条烘干中的应用研究

介绍了应用微波加热烘干毛条的基本原理,研究了微波干燥设备的烘干效率、节能效果及烘干效果,结果表明,微波加热可以应用于纺织印染行业,为微波加热在纺织印染行业的推广应用提供了研究基础。通过生产应用,在计算微波加热毛条烘干工艺参数时,微波烘干机的干燥效率可取1.1kg/kW﹒h,微波干燥后,毛条含水率均匀,颜色前后色差无变化,纤维的强度和手感得到改善,微波干燥节能效果,比射频烘干节能约20%。     

Extraction of isoflavonoids from Pueraria by combining ultrasound with microwave vacuum

This study proposes a new method to quickly extract and dry isoflavonoids from Pueraria Lobata Ohwi (Pueraria) by combining ultrasound and microwave technologies. The time required to extract isoflavonoids at comparable levels of production by ultrasound disruption was 20 times shorter than by conventional reflux extraction. Moreover, test results for drying the extracted substance from Pueraria show that the microwave-vacuum method is 10 times faster than the conventional two-step vacuum approach. Finally, different instrumental analyses of isoflavonoids obtained from Pueraria using the proposed new method show that extraction by ultrasound disruption and microwave-vacuum drying affects neither the structure nor the composition of the extracted substance.     

Drying kinetics and microstructure evolution of nano-zirconia under microwave pretreatment

The effects of microwave power and sample quality on microwave drying kinetics and characteristics of zirconia were studied. It is found that by increasing the microwave power and decreasing the sample mass, the surface diffusion coefficient (D_eff) appears to an upward tendency. The corresponding value D_eff at a sample mass of 10, 20, 30, and 40g are 1.849E-14, 2.443E-14, 3.210E-14, and 3.278E-14 m²/s, respectively. The corresponding value D_eff at a microwave power of 300, 400, 500, 600, and 700W are 1.270E-14, 1.784E-14, 2.619E-14, 3.392E-14, and 4.497E-14 m²/s, respectively. Besides, the materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR) to evaluate the changes of materials before and after drying. The results show that microwave accelerates the drying of zirconia and increases its dispersibility. The heat conduction direction of microwave drying is the same as that of moisture diffusion, which avoids being affected by heat inertia and heat transfer loss. The drying process is fast and efficient, and the microwave directly penetrates the product, avoiding the disadvantage of slow evaporation caused by the temperature gradient.     

Optimization of microwave freeze drying strategy of mushrooms (Agaricus bisporus) based on porosity change behavior

ABSTRACT

For dehydrated foods, porosity is a crucial parameter which affects mass and heat transfers, and is related to the product quality. It is important to monitor porosity change behavior to optimize the drying process. To achieve faster drying along with high product quality, microwave freeze drying (MFD) was applied to mushrooms dehydration processing. The relationship between porosity (include total, open-, and closed-pore porosity) and dried mushroom qualities was studied, and a suitable microwave loading strategy was obtained. It was found that lots of open pores could transform to closed pores while the moisture content (MC) was below 0.25?±?0.05?g/g (db), and the closed-pore porosity was arrived at a relatively stable level at moisture content below 0.17?±?0.03?g/g (db). Both total porosity and closed-pore porosity had a significant influence (P?<?0.01) on texture of MFD mushroom, and open-pore porosity had a significant effect (P?<?0.01) on rehydration ratio of MFD mushroom. According to the porosity change behavior of mushrooms, a dynamic microwave loading strategy can be used to reduce drying time and keep product quality during MFD process.     

微波加热技术在材料工程中的应用与进展

综合介绍了微波加热的原理、特点与应用研究的进展，讨论了微波加热用于材料工程中的重要意义。     

The energy consumption and color analysis of freeze/microwave freeze banana chips

This study investigated the energy consumption of preparing banana chips by freeze drying (FD) and microwave freeze drying (MFD) methods. The results in this study showed that the energy consumption for 400 g fresh banana (about 95 g dried samples) by FD process and MFD process are about 35.73 × 10⁶ J (9.92 kW h) and 21.76 × 10⁶ J (6.57 kW h), respectively. Compared to the traditional FD process, MFD can save up to 35.7% energy and 40% drying time. Increasing the heating power in the secondary drying stage of MFD process had been confirmed to result in decrease in both the energy consumption and drying time. After increasing the microwave power in the secondary drying stage from 1.0 W/g to 1.5 W/g in MFD process, total energy consumption is about 18.12 × 10⁶ J (5.56 kW h) and drying time can be reduced from 360 min to 270 min. The sensory evaluation of produced banana chips at different drying conditions (1.0 W/g, 1.5 W/g and 2.0 W/g) revealed that the sensory properties are acceptable by the customers except the 2 W/g microwave power dried product. Thus, the method that increased the heating powder in the secondary drying stage of the MFD process could potentially be an effective method to reduce the energy consumption without seriously sacrificing the color of the end product.     

A kinetic study of microwave and fluidized-bed drying of a Chinese lignite

The drying kinetics of Chinese lignite in nitrogen fluidized-bed, superheated steam fluidized-bed and microwave were investigated. The changes in the mass as a function of drying time were measured under various drying conditions. The variations of moisture ratio with time were used to test ten different thin-layer empirical drying models given in the literature. In studying the consistency of all the models, some statistical tests, such as χ², residual sum of squares (RSS) and F-value were also used as well as coefficient of determination R². In nitrogen fluidized-bed and superheated steam fluidized-bed, the Midilli–Kucuk model best described the lignite drying process. Drying data in microwave were best described by the Page model, indicative of a difference in kinetics between the two drying methods. This difference was attributed to different heat transfer mechanisms under conventional and microwave drying conditions. The effects of drying parameters in nitrogen fluidized-bed, superheated steam fluidized-bed and microwave drying on the constants and coefficients of the selected models were studied by multiple regression analysis. The apparent diffusion coefficient of moisture in samples was obtained from the kinetics data and the apparent activation energies under nitrogen fluidized-bed, superheated steam fluidized-bed and microwave drying were found to be rather similar.     

Moisture flow characteristics and variation patterns of dielectric constants in bitter gourd slices during microwave hot-airflow vibrating drying

Abstract

The uniformity of microwave-dried bitter gourd slices was poor, and a microwave hot-airflow vibrating drying (MHAVD) apparatus was used to carry out an in-depth elucidation of moisture flow characteristics underlying the variation in dielectric characteristics. Low-field nuclear magnetic resonance and imaging (LF-NMR/MRI) was used to measure the moisture state and distribution during different drying stages, and the relationship model between moisture semaphore and moisture ratio were analyzed. A vector network analyzer was used to measure the patterns in the variation of dielectric characteristics in bitter gourd slices at different drying stages. As a result, the temperature and moisture distribution of bitter gourd slices during MHAVD was uniform caused by hot air and vibration, and the water semaphore in NMR gradually decreased, but the bound water semaphore increased during certain drying stages. There is a significant linear relationship between the total semaphore A₂ and the moisture ratio M_R in bitter gourd slices per unit dry basis mass in the NMR spectrum (R² = 0.99). As moisture decreases, the ability of the material to store microwaves and convert electromagnetic energy to heat energy decreases, the ability of the material to absorb microwaves decreases, and the microwave penetration significantly increases. The moisture flow characteristics in bitter gourd slices is related to the variation of dielectric characteristics during MHAVD, and drying uniformity was improved.