Preparation of dual mode encoding photochromic electrospun glass nanofibers for anticounterfeiting applications

Photochromism has shown to be a promising tool for improving the authenticity of commercially available products. Additionally, improving the engineering process of authentication patterns has been crucial to offer mechanically reliable anticounterfeiting nanofibers. Herein, the electrospinning technology was applied to develop mechanically reliable and photoluminescent silicon dioxide-based electrospun glass nanofibers (80–110 nm) embedded with lanthanide-activated aluminate (LA) nanoparticles (NPs; 1–2 nm) for anticounterfeiting purposes. The produced nanocomposite films exhibited photochromism from colorless in visible spectrum to green under ultraviolet irradiation. The nanofibrous film transparency was maintained by presenting the strontium aluminate pigment as nano-scaled particles, which improves its distribution and prevents the formation of aggregates in the electrospun glass nanofibrous bulk. After being excited at 365 nm, the nanofibers made of phosphor@glass (LANPs@GLS) displayed an emission band at 519 nm. Increases in the pigment ratio enhanced the hydrophobicity of the LANPs@GLS nanofibers without altering their intrinsic characteristics. The LANPs@GLS films exhibited fast and reversible photochromism without fatigue when activated by UV light. Transparency and flexibility were shown by the nanofibrous mats. The proposed technique is reliable for making a wide range of anticounterfeiting materials.     

Sintering and properties of borosilicate glass/Li-Na-K-feldspar composites for electronic applications

Glass/ceramic composites are considered as one of the most important materials for electronic applications. In the present work, an attempt for using Li-Na-K containing feldspar in addition to borosilicate glass to fabricate glass/ceramic composites having good properties was conducted. Firstly, the glass frit was prepared and grinded by high energy ball mill to get nano powder. Then, five designed batches of glass/feldspar composites containing 10, 20, 30, 40 and 50 wt% feldspar were mixed, pressed and sintered at 850 °C. Bulk density and apparent porosity of sintered specimens were determined by Archimedes method. Identification of the formed phases was examined by X-ray diffraction (XRD) analysis. Microstructure of sintered bodies was examined by scanning electron microscope. Microhardness of sintered samples was determined using Vickers indentation technique whereas the fracture toughness was determined by Indentation Fracture (IF) method. The dielectric constant of sintered composites was measured at 1 MHz. The thermal expansion coefficient (TEC) was also measured in the temperature range from room temperature to 1000 °C. The results revealed that Li-Na-K feldspar and borosilicate glass were successfully used to fabricate composites with good electrical properties and thermal expansion suitable for electronic applications. The inhibition of cristobalite amount and the formation of beta spodumene in addition to the quartz were responsible for the improvement of the electrical and thermal properties. The formed amount of beta spodumene was the ideal amount after which the higher amount can cause crack in the body due to the volume change occurred by the differences in thermal expansion of alpha and beta spodumene.     

Optical and electrical studies of borosilicate glass containing vanadium and cobalt ions for smart windows applications

Borosilicate glass with different concentrations of vanadium and cobalt of the composition (mol%) 40 Na₂B₄O₇- 40 SiO₂- (20–x) V₂O₅- x Co₂O_3, with x=0, 1, 3 and 5 mol% were prepared by melt quenching technique at 1373 K and investigated by X-ray diffraction (XRD) and FTIR spectroscopy. Optical properties of the obtained borosilicate glasses in the UV–vis range were also investigated. Urbach theory has been used to analyze the optical data. The dc electrical conductivity was investigated for all samples in the temperature range from 298 K to 700 K. The ac electrical conductivity was measured in the frequency range from 50 Hz to 2 MHz from 298 to 523 K. Guntini's theory has been used to analyze the electrical data. It was found that Urbach energy decreases with the increase of vanadium content, the sample with x=0 shows the highest absorption in the visible and IR region and an electrical conductivity in the order of 10⁻² Scm⁻¹. The frequency exponent was calculated. A semiconducting behavior has been assessed for the studied glasses. The sample with x=0 has the highest IR absorption, the highest conductivity, at 323 K at different frequencies, and the lowest activation energy; these features are promising for smart windows applications.     

Preparation of VO2/Al-O core-shell structure with enhanced weathering resistance for smart window

VO₂/Al-O core-shell structure (V/AO) was synthesized by a facile method and its application for thermochromic film on smart window was investigated. Comparisons of thermochromic properties and stabilities in different environments between VO₂ and annealed V/AO nanoparticles were made. As a result, VO₂ nanoparticle was easily oxidized and lost thermochromic property. In contrast, with the protection provided by Al-O-based shell, the VO₂ core remained stable at a high temperature (350 °C in air) and in H₂O₂ solution. Especially, thermochromic films made by annealed V/AO nanoparticles almost kept thermochromic performance in damp heating environment (T=60 °C, RH=90%) for 20 days while VO₂ films lost their thermochromic properties after 3 days. Besides, the degradation progress of VO₂ and V/AO nanoparticles in damp heating environment was also explored. Results indicate that Al-O-based shell provides a good protection for the VO₂ core originated from the compact structure of shell, which effectively prevents oxygen and water from eroding VO₂. In summary, the VO₂ nanoparticles coated with Al-O-based shell exhibit a great potential in the application of smart window.     

适用于玻璃幕墙的TA-CNTs/SiO2黑色透明超亲水涂层及性能

将单宁酸改性碳纳米管(TA-CNTs)、树枝状纳米SiO₂溶胶、正硅酸乙酯(TEOS)水解液制成分散液,通过喷涂工艺将其喷涂到载玻片上,经室温固化后得到具有自清洁、防雾效果的TA-CNTs/SiO₂黑色透明涂层载玻片。采用FTIR、TEM、TG对改性前后的碳纳米管进行了表征,通过SEM、AFM、XPS对涂层形貌和元素组成进行了表征和测试,采用接触角测量仪和紫外-可见分光光度计探究了TA-CNTs和TEOS水解液质量对涂层接触角(CA)的影响以及单位面积涂层中TA-CNTs质量对涂层透光率的影响,并对涂层进行了防雾、自清洁和耐磨性评价。结果表明,当TEOS水解液为6.00 g、TA-CNTs为0.16 g时,制备的涂层具有超亲水性(CA=2.5°)、优异的自清洁和防雾效果,其承受120次摩擦实验后仍保持超亲水性,表现出一定的耐磨性。TA-CNTs的加入使涂层表面更为粗糙,有利于减少光反射,从而降低光污染。此外,当单位面积涂层中TA-CNTs质量为2.0×10^–3 g/cm²时,涂层的透光率降至60%,...     

The dissolution behavior in alkaline solutions of a borosilicate glass with and without P2O5

There are a variety of applications for glasses in alkaline environments, including glass fibers and glass‐coated steel to reinforce concrete structures. To understand how a simple glass reacts in such environments, the dissolution behavior of a 25Na₂O–25B₂O₃–50SiO₂ (mol%) glass, doped with and without 3 mol% P₂O₅, in pH 12 KOH and pH 12 KOH saturated with Ca²⁺ ions was studied. Ca²⁺ ions in the solution significantly reduce the glass dissolution rate by forming a passivating calcium silicate hydrate (C–S–H) gel layer on the glass surface. When these corroded glasses were then exposed to Ca‐free KOH, the C–S–H layer redissolves into the undersaturated solution and the glass dissolution rate increases. For phosphate‐doped borosilicate glass, PO₄^3? units released from the dissolving glass react with Ca²⁺ ions in saturated solutions to form crystalline hydroxylapatite on the glass surface, but this layer does not protect the glass from corrosion as well as the C–S–H does. The nature of the C–S–H layer was characterized by Raman spectroscopy, which reveals a gel layer constituted mainly of silicate anions.     

Transparent,thermal insulation and UV-shielding coating for energy efficient glass window

Size-controllable double-shell hollow TiO₂@SiO₂ spheres (DHTSs) were fabricated using a simple sol-gel reaction. The size of DHTSs was controlled by using PS spheres with different size as templates. Moreover, DHTSs was also incorporated into waterborne polyurethane (WPU) matrix to prepare WPU/DHTSs composite film as glass coating. The effect of the diameter of DHTSs on the transparency, thermal insulation and UV-shielding properties of WPU/DHTSs composite film were investigated in detail. And the results revealed that the composite film with 230 nm-sized DHTSs exhibited the optimum performance. In addition, the temperature rise rate in the chamber fitted with the glass coated by WPU/DHTSs composite film (26%) was lower than that fitted with the common glass without coated by anything (48%). Therefore, the transparent coating with excellent thermal insulation and good UV-shielding properties will become a potential energy saving building glass coating.     

Effects of thermal aging on thermo-mechanical behavior of a glass sealant for solid oxide cell applications

Thermo-mechanical properties of a silicate based glass and its potential use for sealing application in intermediate temperature solid oxide cell (SOC) are presented in this paper. Effects of thermal aging are discussed on structural and microstructural evolution, thermal expansion, viscosity, modulus of elasticity, and high-temperature deformation of the glass. The balance between the viscosity and viscous flowing behavior was explored for the non-aged and aged glasses as it is essential to have a successful sealing for a SOC stack. The results reveal a temperature dependence of Young's modulus in which a transition between a slow softening (elastic) regime and a rapid softening one was observed. Crystallization induced by thermal aging led to higher creep resistance, but lower capability of crack healing when inspected by electron microscopy. However, potential of stress relaxation in the aged material was confirmed by the constitutive mechanical models of viscoelasticity.     

Photoluminescence and X-ray excited scintillating properties of Tb3+-doped borosilicate aluminate glass scintillators

lthough single crystal scintillators have excellent performance, they have some drawbacks such as high cost, complicated elaboration method and difficulty of growth on large-scale. Glass scintillators are widely investigated to replace single crystal scintillators because of their simple fabrication method and low cost. In this paper, a series of transparent borosilicate aluminate glass scintillators doped with Tb³⁺ were successfully prepared by traditional melt-quenching method. The structural, luminescent, and X-ray excited scintillating properties were investigated. These glass samples show high stability and high transparency, and present good luminescent and scintillating properties. Sample with Tb³⁺ doping concentration of 10% has the best scintillating performance. The integrated intensity of X-ray excited luminescence is 66.6% of that of commercial Bi₄Ge₃O₁₂ single crystal scintillator, and the quantum efficiency (under 378 nm excitation) is 70.3%. Our findings suggest that Tb³⁺-doped borosilicate aluminate glasses with high light yield might be used as potential scintillators.     

Identification of a smart bond coating for gas turbine engine applications

A smart bond coating was successfully identified for thermal barrier coatings (TBCs) that promotes appropriate protective scales preferentially during service depending on the environmental conditions. It enhances the life of super alloy components life significantly, which is essential for increasing the efficiency of advanced gas turbine engines. It is expected to be a potential bond coating for advanced gas turbine engine blades of different types, i.e., aero, industrial, and marine for their protection against high temperature oxidation, type I, and type II hot corrosion.     

A new potassium-based bioactive glass: Sintering behaviour and possible applications for bioceramic scaffolds

Providing structural support while maintaining bioactivity is one of the most important goals for bioceramic scaffolds, i.e. artificial templates which guide cells to grow in a 3D pattern, facilitating the formation of functional tissues. In the last few years, 45S5 Bioglass^® has been widely investigated as scaffolding material, mainly for its ability to bond to both hard and soft tissues. However, thermal treatments to improve the relatively poor mechanical properties of 45S5 Bioglass^® turn it into a glass-ceramic, decreasing its bioactivity. Therefore, the investigation of new materials as candidates for scaffold applications is necessary. Here a novel glass composition, recently obtained by substituting the sodium oxide with potassium oxide in the 45S5 Bioglass^® formulation, is employed in a feasibility study as scaffolding material. The new glass, named BioK, has the peculiarity to sinter at a relatively low temperature and shows a reduced tendency to crystallize. In this work, BioK has been employed to realize two types of scaffolds. The obtained samples have been fully characterized from a microstructural point of view and compared to each other. Additionally, their excellent bioactivity has been established by means of in vitro tests.     

Effect of aluminum-containing raw materials on the melting of borosilicate glass for fiber

Aluminum-containing raw materials for the synthesis of aluminum-borosilicate glasses for E-glass fiber should be rationally chosen to comprehensively assess their effect on the glass melting processes. The characteristic properties of the chemical, phase, and granulometric composition of the raw materials such as metallurgical alumina, non-metallurgical alumina, disthene, and kaolin were under study. It was revealed that the type of aluminum-containing raw materials significantly influenced the rate of glass formation processes and heat consumption required for these processes. The efficiency of aluminum-containing raw materials is influenced by the following factors: the phase composition, which determines the sequence and rate of phase transformations, as well as the heat-absorbing ability of the furnace batch and glass melt. The most energy-efficient material is non-metallurgical alumina of the White Alumina brand. Using it facilitates saving energy resources for glass formation processes from 2.64% to 16.30% as compared with other types of aluminum-containing raw materials. The use of kaolin proves to be the least efficient due to the additional energy consumption for the process of destruction of the crystal structure of kaolinite, the reduced thermal conductivity of the batch, and the thermal transparency of the borosilicate glass melt.     

Shear strength tests of glass ceramic sealant for solid oxide fuel cells applications

Different approaches are used for the integration of ceramic components in solid oxide fuel cells stacks, where dissimilar materials (ceramics and metals) have to be joined and coupled for a reliable long term operation. This work focuses on the mechanical characterisation of a glass ceramic sealant used for the joining of Crofer22APU metallic interconnect samples as well as the interaction with a preoxidised Crofer22APU. Crofer22APU–glass ceramic sealant joined samples are tested by two different mechanical tests. Hourglass samples with different geometries were tested using an in-house developed torsion test machine at room temperature. In addition, their mechanical strength was also evaluated according to the ISO?13124 standard. The comparison of the two different testing methods, with particular focus on the shear strength of the joined samples, are reviewed and discussed.     

Preparation and characterization of foam glass from waste container glasses and water glass for application in thermal insulations

Glass foams are modern developed building materials which are now favorably competing with conventional materials for applications in thermal insulation. In this study, glass foams are synthesized solely from waste container glasses of mixed colors using sodium silicate (water glass) as foaming agent. Several glass foams of 150 × 150 × 30 mm were prepared from waste glasses of 75 μm, 150 μm and 250 μm size with addition of 15 wt % sodium silicate respectively and pressed uniaxially under a pressure of 10 MPa. The prepared glass foams were then sintered at temperatures of 800 °C and 850 °C respectively. Tests such as bulk density, estimated porosity, flexural strength, compressive strength and microstructure evaluation were used to assess the performance of the developed glass foams. The results showed that with increasing temperature and grain sizes, the percent porosity of the developed foams increased while the bulk density decreased. The microstructure evaluation showed that the finer the grain sizes used, the more homogenized are the pores formed and the higher the temperature, the larger the pores but are mostly closed. Both compressive and flexural strength were found to decrease with grain sizes and higher temperatures. The thermal conductivities of all the developed foam glasses satisfy the standard requirement to be used as an insulating material as their thermal conductivities did not exceed 0.25 W/m.K.     

Eco-friendly tape casting of borosilicate glass/Al2O3 sheets for LTCC applications

This work reports the innovative development of a borosilicate glass/Al₂O₃ tape for LTCC applications using an eco-friendly aqueous tape casting slurry. Polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA) were the respective dispersants, while carboxymethyl cellulose (CMC) and styrene acrylic emulsion (SA) were the respective binders. The results showed that PVP was more suitable than PAA as the dispersant for the aqueous casting slurry, and that 1.5 wt% PVP would achieve well dispersion of CABS glass/Al₂O₃ powder in the aqueous slurry. Moreover, a small amount of 2.0 wt% CMC binder could yield smooth CABS glass/Al₂O₃ tapes crack free. A high-quality CABS glass/Al₂O₃ tape with a smooth surface was made from an aqueous slurry containing 1.5 wt% PVP dispersant, 2.0 wt% CMC binder, and 2.0 wt% PEG-400 plasticizer. The density, tensile strength, and surface roughness of the green tape were 2.05 g/cm³, 0.87 MPa, and 148 nm, respectively. The resulting CABS glass/Al₂O₃ composites sintered at 875 °C exhibited a bulk density of 3.14 g/cm³, a dielectric constant of 8.09, a dielectric loss of 1.0 × 10^?3, a flexural strength of 213 MPa, a thermal expansion coefficient of 5.30 ppm/^°C, and a thermal conductivity of 3.2 W m^?1 K^?1, thus demonstrating its broad prospects in LTCC applications.     

Preparation and characterization of high compressive strength foams from sheet glass

High compressive strength glass foams were produced using sheet glass cullet with the aid of 1 wt.% SiC powder, as gassing agent, and the incorporation of small amounts of an alkali earth aluminosilicate glass powder (AD), which is intrinsically prone to be crystallised to anorthite and diopside. The amount of SiC used as well as the mean particle sizes of the powders of both glasses and SiC were lower than those used in earlier studies. The experimental results showed that homogenous microstructures of large pores could be obtained by adding 1 wt.% SiC. The compressive strength of the glass foams was considerably increased when the incorporated AD-glass was higher than 1 wt.%. It is concluded that the presence of the AD glass is beneficial for the produced glass foams because of the formation of a well packed honeycomb structure which features an optimal distribution of pentagonal- and hexagonal-like shaped pores surrounded by dense struts. The crystallization of wollastonite and diopside inside the struts should also have a positive impact on the mechanical behaviour of the produced porous glass foams.     

N-异丙基丙烯酰胺基智能膨润土制备及其性能

以钠基膨润土为原料，通过硅烷偶联剂KH570的脱水缩合作用将N-异丙基丙烯酰胺（NIPAM）接枝在钠基膨润土表面，制备智能温敏膨润土（NIPAM-B）。采用单因素方法对NIPAM-B的合成指标进行优化，并利用XRD、FTIR技术对NIPAM-B进行表征，同时对NIPAM-B的温敏性、NIPAM-B悬浮液的流变性和悬浮性进行考察，并引入丙烯酸（AA）单体实现温度调控。结果表明，NIPAM-B具有良好的温敏特性，且该智能温敏膨润土悬浮液的流变性在40~60℃范围内表现出稳流特点以及升温增稠的特性。但该智能温敏膨润土相较于膨润土原土而言，悬浮性略有下降。此外，经过引入AA的温度调控作用，发现AA与NIPAM的添加量的物质的量比值每增加10%，智能温敏膨润土的LCST将提高10℃左右。     

Microstructure evolution and cooperative reinforcement mechanisms of Al2O3/Al2O3 joints brazed by low-melting borosilicate glass

The Al₂O₃/SiO₂–B₂O₃–Al₂O₃–Na₂O glass/Al₂O₃ joints reinforced cooperatively by glass matrix and in-situ Al₄B₂O₉ whiskers were obtained via a low-melting borosilicate glass braze. The composition of glass seam transformed from SiO₂–B₂O₃–Na₂O to SiO₂–B₂O₃–Al₂O₃–Na₂O due to continuous diffusion and dissolution of Al₂O₃. An appropriate amount of [AlO₄] units introduced into the glass braze played a vital role in strengthening the glass network structure resulting to considerably improved mechanical strength of the glass seam. Meanwhile, plenty of in-situ Al₄B₂O₉ whiskers growing from the Al₂O₃/glass braze interface to the center of glass seam in various directions generated. Three-dimensional crisscross structures were fabricated at the Al₂O₃/glass braze interface domains, where were enhanced by crack-bridging and pull-out effect of the whiskers. Generally, ascribed to the cooperative reinforcement of the glass matrix in the seam and in-situ Al₄B₂O₉ whiskers at Al₂O₃/glass braze interface domains through reactions of Al₂O₃ and borosilicate glass braze, strength of the as-brazed joints was promoted prominently. The shear strength of the joints reached a maximum of 61 MPa brazed at 1050 °C for 60 min.     

Crystallization and thermal expansion behavior of lithium zinc silicate sealing glass

Effect of heat treatment schedule on the crystallization and thermal expansion behavior of a lithium zinc silicate glass system was investigated by differential scanning calorimeter (DSC), X-ray diffraction, and linear thermal expansion test. Two well-defined crystallization exothermic peaks were observed from the DSC trace. According to the apparent activation energies and avrami parameter values calculated from the two crystallization exothermal peaks, the first crystallization exothermal peak was attributed to a combining surface and internal crystallization behavior, while the second one was found to be internal crystallization. Additionally, the phase evolution and the thermal expansion behavior with increasing heat treatment temperature were found to be closely related. Interestingly, it was found in comparison with previous reports that addition of CaO varies the phase composition of the resulting glass–ceramic in an opposite way to K₂O and the deep rooted reason has been discussed which may cast light on the modulation of properties of glass–ceramic involved crystalline phase of quartz or cristobalite. At last, average thermal expansion coefficient of 7.99–15.38×10⁻⁶ K⁻¹ in the temperature range of 25–400 °C has been obtained with different heat treatment schedules.     

Preparation and characterization of foams from sheet glass and fly ash using carbonates as foaming agents

Glass foams were produced using sheet glass cullet and fly ashes from thermal power plant with added carbonates (commercial dolomite- and calcite-based sludges) as foaming agents. The influence of type and amount of carbonates as well as of the sintering temperature on the apparent density, compressive strength, microstructure and crystalline phases was evaluated. The experimental results showed that homogenous microstructures of large pores could be obtained by adding just 1–2 wt.% carbonates and using low sintering temperature (850 °C), leading to foams presenting apparent density and compressive strength values of about 0.36–0.41 g/cm³ and 2.40–2.80 MPa, respectively. Good correlations between compressive strength, apparent density and microstructure (pore size, struts’ thickness and internal porosity) were observed.