Search

Liquid-phase sintering anorthite (LSA) glass-ceramics with degradation in citric-acid solution have been prepared from CaO–Al 2 O 3 –SiO 2 –B 2 O 3 low-melting compositions. By means of the chemical corrosion of the glass phases, LSA glass-ceramics are effectively degraded in the citric acid solution. Then, the influence of B 2 O 3 and rare-earth (RE) on the structures of glass phases, the degradation of LSA glass-ceramics in the citric-acid solutions, and the dielectric properties are investigated systematically. The results suggest that when the B 2 O 3 molar ratio in the composition CaO–Al 2 O 3 –SiO 2 –B 2 O 3 is 0.5, doping LSA glass-ceramics with RE can reduce the quantity of bridging oxygen and [BO 4 ] units in the glass phase, as well as the degree of network connection of [AlO 4 ] units in the glass network. Conversely, when the B 2 O 3 molar ratio is decreased down to 0.3, doping RE into LSA glass-ceramics increases the quantity of bridging oxygen and [BO 4 ] units for glass phase. This improvement in chemical stability effectively impedes the degradation of LSA glass-ceramics in citric-acid solutions. Concurrently, the degradation mechanism of LSA glass-ceramics in citric acid solution is analyzed and explained in terms of classical glass corrosion theory, while the microstructural characteristics of LSA glass-ceramics are utilized to investigate their dielectric properties. It indicates that the dielectric loss and dielectric constant of LSA glass-ceramics are significantly lowered as a result of the existence of the glass phase. Especially when the B 2 O 3 molar ratio in the composition CaO–Al 2 O 3 –SiO 2 –B 2 O 3 is 0.3, and the La 2 O 3 doping percentage into LSA glass-ceramics is 0.5 wt%, the LSA glass-ceramics exhibit the lowest dielectric loss value of 3.13 × 10−3 and ε r = 4.17. Developing the LSA glass-ceramic with degradation in organic acids can provide a new idea for the recycling and disposal of e-waste. [ABSTRACT FROM AUTHOR]

The degradation of environmentally friendly CaO–Al 2 O 3 –SiO 2 –B 2 O 3 (CASB) glass-ceramics, which consist of anorthite and glass phase, was investigated in three natural organic acid solutions. The results indicated that citric acid had the most significant effect on the degradation of CASB glass-ceramics. While the chemical stability of anorthite is relatively poor, the glass phase also contributed significantly to the effective degradation of CASB glass-ceramics. Subsequently, Ba2+ or Sr2+ was used for full or partial substitution of Ca2+ in CASB glass-ceramics, and the degradation-controlling mechanism of the substituted CASB glass-ceramics was further researched. The full substitution of Ca2+ in CASB glass-ceramics by the two cations resulted in the occurrence of borate [BO 4 ] units in the glass phases, and the interlinkage of [BO 4 ] with broken silicate [SiO 4 ] network structures caused a complementary network effect. Consequently, the degradation of CASB glass-ceramics by organic acids was reduced due to the improvements in the chemical stability of the modified glass-ceramics. Additionally, degradation control can also be achieved based on a mixed-alkali effect, originating from the partial substitution of Ca2+ in CASB glass-ceramics by Ba2+ or Sr2+. The degradable glass-ceramics have the potential to be applied in low-temperature co-fired ceramic technology because of their good physical properties, which include a dielectric constant of 3–5, a dielectric loss as low as 10−3, a coefficient of thermal expansion of 3–9 × 10−6/°C, and an average bending strength of about 47 MPa. Noticeably, the development of the degradable glass-ceramics is helpful to the low-cost and pollution-free recycling of valuable metal electrodes, which is significant for the sustainable development of electronic packaging technologies. [ABSTRACT FROM AUTHOR]

The rapid urbanization of modern societies has heightened the need to understand how urban environments can enhance residents' well-being. This study addresses this by exploring the roles of leisure environments and activities in the process of restoration and their contributions to leisure satisfaction. The findings indicate that both the perceived restorativeness of the leisure environment and the perceived restorativeness of leisure activities have a positive influence on the outcome of restoration, with the former exhibiting a slightly stronger effect. The restoration outcome significantly predicts leisure satisfaction—specifically, the restoration outcome fully mediates the relationship between the perceived restorativeness of leisure environment and leisure satisfaction, while it partially mediates the association between the perceived restorativeness of leisure activities and leisure satisfaction. Furthermore, the overall impact of leisure activities on leisure satisfaction is considerably greater than that of the leisure environment. This study advances the existing literature on restorative environments research by uncovering the relative effectiveness of settings and activities in the restoration process, thereby providing significant implications for managers of urban public spaces and leisure business establishments. • Leisure environment and activities are pivotal in facilitating restorative experiences. • The restoration outcome strongly predicts leisure satisfaction • Restoration outcome fully mediates the leisure environment-satisfaction link. • Restoration outcome partially mediates the leisure activities-satisfaction relationship. • Leisure activities have a stronger impact on satisfaction than leisure environment. [ABSTRACT FROM AUTHOR]

In this work, by focusing on widespread problem of thermal mismatch caused by different coefficients of thermal expansion (CTE) in electronic packaging materials, low-temperature co-fired ceramic (LTCC) materials with tunable CTE values were designed. By substituting Ba2+ with Sr2+ and replacing quartz with alumina and zirconia, respectively, BaO–Al 2 O 3 –SiO 2 –B 2 O 3 /quartz LTCC composites with CTE of 7.05–9.52 × 10−6/°C were developed. Results show that major crystalline phases of LTCC composite materials are quartz and hexacelsian. By replacing quartz with alumina or zirconia, sintering behavior and subsequently thermal expansion and dielectric properties were modulated. On the other hand, substituting Ba2+ with Sr2+ can be beneficial to the densification of composite materials. The introduction of Sr2+ triggered mixed alkali effect and hindered the crystallization of hexacelsian phase, which can further improve mechanical properties. Finally, sandwich structure module of BaO–Al 2 O 3 –SiO 2 –B 2 O 3 /quartz with gradient CTE values was obtained, which showed potential for electronic packaging with sustained thermal compatibility under cyclic temperatures. [ABSTRACT FROM AUTHOR]

Glass/ceramic composites applied in the field of low-temperature co-fired ceramics (LTCC) were successfully prepared at 670–710 °C by using waste soda-lime glass (WG) as a binder and natural volcanic ash as a ceramic raw material. Based on the theories of suppression and supplementary network effects, alkaline-earth metal ions (R2+, R = Mg, Ca, Sr, and Ba) and B 2 O 3 were applied to improve the dielectric properties of WG and composites, respectively. The influence of R2+ on the crystal phase evolution, microstructure, mechanical, dielectric, and thermal properties of WG-volcanic ash-based composites were systematically investigated. By doping 2.5 wt% Ba2+ to the environment-friendly LTCC composites, physical properties i.e., ε r of 4.86 at 1 MHz, tan δ of 6.32 × 10−3, coefficient of thermal expansion of 8.72 × 10−6/°C, and thermal conductivity of 1.04 W/(m·K) are obtained. It is worth mentioning that the environment-friendly LTCC composite uses WG with a low glass transition temperature to reduce the sintering temperature and a tiny amount of a modifier to adjust the dielectric performance instead of synthesizing specific crystals by adding lots of chemical reagents. These, in turn, do not only have the potential to be used in the LTCC packaging technology but also have significance for sustainable development. Additionally, because of good chemical compatibility between aluminum and the composites, the environment-friendly LTCC composites with ultra-low sintering temperature have the potential ability to lower the cost of LTCC packaging materials. [ABSTRACT FROM AUTHOR]

• The asbestos waste-derived glass-ceramics LTCC were successfully prepared below 950 °C. • The relation between sample structural evolution and its performance was investigated. • The asbestos waste-derived glass-ceramics possess good dielectric properties. • This work promotes the reuse of asbestos waste and waste soda-lime-silicate glass. In this work, the harmless-treated asbestos wool is employed to develop waste-derived glass-ceramic LTCC materials with reliable properties. The waste asbestos wool was first fired at 700 °C for 2 h in order to destroy its hazardous fiber structures. Subsequently, glass-ceramic LTCCs with Ca 2 MgSi 2 O 7 and Na 4 Ca 4 Si 6 O 18 phases were successfully synthesized at temperature below 950 °C using waste soda-lime-silicate (SLS) glass and innocuous asbestos wool. In addition, alkaline earth metal oxides MO (M = Mg, Sr, Ba) were doped into the glass-ceramics as a structural modification to improve their dielectric properties. The findings indicate that the formation of CaMgSiO 4 crystals in MgO-doped glass-ceramics resulted in an increase in porosity, which consequently deteriorated their dielectric and mechanical qualities. In contrast, doping glass ceramics with 2.5 wt.% SrO or BaO may reduce their sintering temperature and enhance their properties by eliminating coarse grains. In particular, the glass-ceramics doped with 2.5 wt.% BaO possess excellent dielectric properties [ ε r : 5.71, tan δ : 8.7 × 10−3 at 1 MHz and ε r : 7.21, tan δ : 2.77 × 10−3 at 10 GHz], a thermal expansion coefficient of 9.77 × 10−6 /°C (50-300 °C), and a thermal conductivity of 1.16 W/(m·K). The current research can serve as a guide for the development of sustainable and eco-friendly electronic materials and the safe recycling of asbestos waste. [ABSTRACT FROM AUTHOR]