Radiotechnical hot pressed glass fiber plastics for ship aerial fairings and antennas protection in radio connection and radio location systems

The article is devoted to the urgent scientific problem of creation and introduction in shipbuilding of high-strength, water-resistant dielectric glass-reinforced hot pressed plastics on the basis of bi- and polyfunctional epoxy-amine binders and glass fabrics from alkali, quartz and silica glass.

Glass as dielectric for high temperature power capacitors

ABSTRACTModern polypropylene film power capacitors are state of the art for power factor correction and many DC link applications, but their long-term commercial use is limited to temperatures of less than 85°C. The temperature limit is given by the dielectric polypropylene which has a melting point in the range of 140 to 170°C, while glass is much higher. Thus, the temperature limit could potentially be overcome by use of thin, alkali-free glass as dielectric. “Glass capacitors” employing ultra-thin and high purity glass layers are promising devices for high temperature applications in oil, gas, aerospace, hybrid electric vehicles, DC transmission, and pulsed power systems. This includes emerging power electronic systems using silicon carbide switches and diodes.This work analyzes and compares various glasses with a thickness of less than 50 µm by dielectric spectroscopy and elemental analysis. It is demonstrated that glass is attractive as dielectric for a wide frequency range up to 200°C. It argues that the dielectric losses are currently too great for thin glass to be used within a commercial power capacitor.While high temperature prototypes already exist, we demonstrate through our analysis that further developments are required to integrate this promising device into commercial systems. It is seen that even trace amounts of alkali materials can have an impact on losses. These losses must be further reduced through fundamental research into polarization/conduction mechanisms of various glass components.

Use of a Dielectric Glass to Join Dielectric Ceramics for Microwave Filters

Joining of ceramics with glasses has been widely used for artificial teeth, solid oxide fuel cells, electrical devices, high temperature ceramic filters, structural ceramic components for aeronautic engineering, nuclear reactors, and other applications. This study aimed to explore the possibility of using a dielectric glass to connect a dielectric ceramic resonator to a dielectric ceramic support, in order to make miniaturized microwave filters characterized by higher temperature and environmental stability and low dielectric loss. A mixed powder having Bi2O3-SiO2-Al2O3-MgO-ZnO-CaO glass as a matrix and SiO2-Al2O3-MgO as a ceramic filler was used to join the dielectric ceramic resonators made of the CaTiO3-NdAlO3-Al2O3 system to the dielectric ceramic supports made of the ZnO-TiO2-Al2O3-MgO system. In spite of the strong interfacial bonding obtained, microcracks were observed in the joined bodies, suggesting that not only the dielectric loss of the bonding layer but also the match of the thermal expansion coefficients of the components to be joined should be carefully considered and tailored.

Glass Transition in Quantum Dipole Glass Model

We give a description of the phase transition in an ensemble of the electric dipole with internal degrees of freedom in dielectric glass model.The model predicts a freezing of the random projections of the electric dipole moments. The low temperature phase transition from disordered paraelectric phase to the electric dipole orientational like glass phase is considered

Formation of NaNbO3 Crystals in Dielectric Glass and Glass-Ceramics of a Na2O-Nb2O5-Al2O3-SiO2 System

Dielectric glass and glass-ceramics were derived from Na2O-Nb2O5-Al2O3-SiO2 system. Small amount of TiO2 were also introduced into glass compositions to study crystallization behavior of the glass with present of this nucleating agent. Conventional melt-quenching technique was employed for a glass production and the selected bulk glass samples were subjected to the heat-treatment process at appropriate temperature. After six different glass compositions were produced, and by observation with necked eyes, all obtained glass samples are in light brown color and some samples were opaque due to crystallization took place during quenching. Phase identification through XRD patterns show that there were 3 phases, NaNbO3, NaNbO8 and a sodium aluminum silicate compound, found in those opaque glass samples. NaNbO3 is a predominant phase in all samples. Fortunately, clear transparent glass was obtained from the composition with no TiO2 addition. Heat treatment of this glass did not induce phase change, three aforementioned phases still present. Increasing heat treatment time promoted a higher of observed intensity of NaNbO3. But the NaNbO3 crystalline size was not significantly developed with time. The dielectric response of the NaNbO3 crystals in the glass-ceramics samples are influenced by presence of other crystalline phases.