Reutilization of waste inert glass from the disposal of polluted dredging spoils by the obtainment of ceramic products for tiles applications

The vitrification treatment has been successfully exploited as a solution for the disposal of polluted dredging spoils from the industrial area close to the Venice Lagoon. The addition of 20% by wt. of glass cullet to the calcined sediments in the vitrification batch provides a suitable chemical composition for the production of an inert glass, despite the compositional variations of the sediments. The obtained waste glass, after being finely ground, has been employed (i) as a raw material for the manufacture of sintered glass-ceramics, by cold pressing and single-step sintering at about 940^∘C, and (ii) as sintering additive (the maximum addition being 10% by wt.) for the manufacture of traditional red single firing ceramic tiles, with a maximum firing temperature of 1186^∘C. Both applications have proved to be promising: in the first case, the sintered glass ceramic product exhibits notable mechanical properties (bending strength > 130 MPa, HV ≈ 6.5 GPa); in the second case, the addition of waste glass does not modify substantially the investigated physical and mechanical properties of the traditional product (water absorption, linear shrinkage, bending strength, planarity).     

Improved mechanical property of foam glass composites toughened by glass fiber

The mechanically improved foam glass composite toughened by glass fiber was prepared by sintering technique, using waste sodium-calcium silicon flat glass powder as main raw materials. In this study, the preparation and properties of the samples were characterized by differential thermal analysis (DTA), field-emission scanning electron microscopy (FESEM) and mechanical property test. The specific strength of the composite was defined for the first time, and applied into the investigation of mechanical property. The results show that the specific improved bending strength of 10.45-22.26 MPa/(g cm^− 3), and the specific compressive strength of 30.45-34.34 MPa/(g cm^− 3) can be displayed when sintered at 790-815 °C with the addition of 5-25 wt.% glass fiber. Good correlations between the microstructure (in particular the fiber distribution), the high specific strength and the high modulus of elasticity of glass fibers.     

Using granite rejects to aid densification and improve mechanical properties of alumina bodies

The industrial use of waste materials in the ceramic industry has been widely investigated. This work describes the research carried out on the manufacturing of alumina bodies with granite reject additions. The reject was used as produced by a local industry that saws granite stones into blocks and slabs. This industrial process produces a significant amount of that reject, which is discarded in sedimentation lagoons, landfill areas or simply thrown in rivers, resulting in environmental pollution. Alumina and the granite reject were ball-mill mixed with 5 wt% manganese oxide and pressed under an uniaxial load of 20 MPa. Samples were subjected to thermal analysis (DTA, TG and dilatometry) and sintered in air at 1300 and 1350^∘C during 1 h in an electric furnace. Sintered specimens were characterized by X-ray diffraction, apparent density, open porosity and flexural strength. The results showed that the addition of granite reject and manganese oxide enables low temperature sintering and remarkably improves (~300%) the cold mechanical properties of the alumina body.     

Inkjet printing of conductive Ag lines and their electrical and mechanical characterization

This paper aims to investigate the effects of the substrate, the printed line thickness and the sintering temperature on the electrical resistivity, Young's modulus and hardness of inkjet-printed Ag thin films. Electrical resistivity was determined from the four-point method and Young's modulus and hardness were evaluated from nanoindentation test. Several models for evaluating Young's modulus and hardness were used and compared to account for the influence of substrates. It is noted that Ag lines on glass have higher resistance and resistivity than those on polyimide (PI) since Ag lines on glass and PI have tensile and compressive residual thermal stresses, respectively, due to the difference of coefficient of thermal expansion between Ag lines and substrates. Young's modulus of Ag films on glass can be predicted by the modified King and Bec models considering the substrate effect, but these models offer unstable results for Ag films on PI. Young's modulus and hardness of Ag films increase with the sintering temperature, and they are little affected by the film thickness when fully sintered.     

Effect of anorthite and diopside on dielectric properties of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/glass composite based on high strength of LTCC substrate

The green sheet of an alumina filler/glass matrix, which is a glass–ceramic based on an anorthite and diopside composite, is a low-fired substrate material for microelectronic packaging. In this study, alumina/glass sheets were prepared using a tape-casting process. The mechanical and dielectric properties of the sintered bodies were examined as a function of the sintering temperature. The volume of the crystalline phases was considered with the peak area of the XRD intensity for evaluating the alumina/glass composite. The flexural strength and dielectric properties of the sintered alumina/glass composites were 167.2 ± 13.1 MPa for the four-point bending test, 5.51 for the dielectric constant and 2,078 MHz for the quality factor, respectively. The dielectric constant was dependent on the volume of crystalline phases present. Jinho Kim and Seongjin Hwang equally contributed to the article.     

纳米SiO2/尼龙66复合材料的力学性能和热性能

采用熔融共混的方法在双螺杆挤出机上制备出纳米SiO₂/尼龙66复合材料,并对其力学性能和热性能进行了研究。结果表明：复合材料的拉伸强度和弹性模量随纳米SiO₂含量的增加而提高。当SiO₂质量分数为3％时,复合材料的拉伸强度达到最大,增幅为11.2％;当SiO₂质量分数为5％时,弹性模量达到最大, 增幅为30.1％。复合材料的储能模量和玻璃化转变温度较纯尼龙66也有明显提高。差示扫描量热法（DSC）分析显示,纳米SiO₂的加入一方面阻碍了尼龙66的结晶过程,降低了材料的结晶温度;另一方面它又能作为形核剂,增加尼龙66的形核位置,提高形核率。     

Sintering and technological properties of alumina/zirconia/nano-TiO2 ceramic composites

The present work focuses on studying the effect of nano TiO₂ (0.0–25 mass%) on the sintering behavior and mechanical properties of alumina/zirconia ceramic composites. Al₂O₃–ZrO₂–TiO₂ oxides mixture was sintered at 1600 °C to obtain the desired composites. The sinterability and the technological properties of these ceramic composites, i.e. the sintering parameters and microhardness as well as thermal shock resistance were investigated. Moreover, phase composition and microstructure of the sintered bodies were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The results revealed that nano TiO₂ is a beneficial component for alumina/zirconia ceramic composites. The batch containing 20 mass% TiO₂ exhibited the highest sintering and mechanical properties as well as resistance to thermal shock. The obtained microstructure exhibited high compacted ceramic matrix composites.     

可切削的氧化锆陶瓷牙科修复体的制备

通过控制CaO_₂-Al_₂O_₃-SiO_₂硅酸盐玻璃粉体,在1300℃低温下液相烧结获得热膨胀系数在7.19×10 ^-6/℃和8.15×10^-6/℃范围内,与修复体饰瓷相近,其强度在340～360MPa,韧性在2.7～3.5 MPa·m^I/2,可切削性与In-Ceram相当的氧化锆陶瓷牙科修复体.     

Fabrication of alumina ceramics from powders made by sol–gel type hydrolysis in microemulsions

The engineering aspects of the preparation of nanostructured alumina ceramic precursors by alcoholate hydrolysis using microemulsions as reaction media are investigated here. The precipitate was subjected to several treatment steps. Although the properties of the primary precipitated powders are independent of the chemical or reaction engineering parameters of the precipitation procedure, the structure of treated powders and sintered, dense ceramics strongly depends on thermal and mechanical handling like crystallization or grinding of the alumina ceramic precursor. Strong differences are manifested in relative densities and sintering kinetics and can be observed by SEM analysis.     

Influence of glass addition and sintering temperature on the structure,mechanical properties and dielectric strength of high-voltage insulators

Soda-lime glass as a substituent for the feldspar was used to prepare high-tension electrical porcelain by standard chemical solid reaction technique. The effect of glass substitution and sintering temperature on the physical properties, microstructure, hardness, modulus of rupture, flexural strength and Dielectric breakdown strength were examined. Zero water absorption (WA %) and apparent porosity (AP %) were achieved for the samples with glass content >15 wt.% sintered at 1100 °C. The apparent density was found to increase with sintering temperature. The Vicker’s micro-hardness increased with both glass addition and sintering temperature. Both of the modulus of rupture (MOR) and flexural strength (σ_f) had maxima values at 15 wt.% glass addition. The structure and morphology were characterized by X-ray diffraction and scanning electron microscope (SEM). It showed the formation of mullite needles at sintering temperature of 1100 °C, which enhanced the mechanical and electrical properties of the porcelain. The dielectric breakdown strength increased with sintering temperature and glass addition. The highest dielectric strength was found at 10 wt.% of glass addition depending on the Na₂O and Fe₂O₃ content.     

低温共烧氧化铝/玻璃复合基板材料的研究

以低软化点的钙硼硅酸盐玻璃和氧化铝粉末为原料,制备了氧化铝/玻璃低温共烧复合基板材料。所需的玻璃粉体采用溶胶-凝胶法制备。研究了烧结温度和氧化铝含量对复合材料的烧结特性、介电性能以及力学性能的影响。结果表明,当氧化铝质量分数为50%,复合材料经950℃、保温2 h烧结后,其εr=5.92,tanδ=5.7×10-4,ρ=1012Ω.cm,抗弯强度σ=167.82 MPa,热膨胀系数α=4.86×10-6/℃,可望作为低温共烧多层陶瓷基板材料应用。     

Sintering and microstructure of materials based on the fluorohydroxyapatite–ZrO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> system

We have studied the influence of the sintering temperature and modifying additives on the phase composition, microstructure, and mechanical strength of a fluorohydroxyapatite-based composite ceramic material containing 20 wt % zirconia. The addition of 5 wt % alumina has been shown to prevent recrystallization processes and contribute to phase composition stabilization. Moreover, the addition of a sintering aid (2 wt %) has made it possible to lower the sintering temperature to 1200°C and raise the bending strength of the material to 143 MPa.     

Synthesis and characterization of borosilicate glass/β-spodumene/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites with low CTE value for LTCC applications

Glass?+?ceramic composites based on low-softening-point borosilicate (BS) glass, β-spodumene and Al₂O₃ were produced in this work. The influence of ceramic filler composition on the microstructure, sintering quality, mechanical properties, thermal properties and dielectric properties of composites were studied. XRD and DSC indicated that both kinds of ceramic filler as well as the BS glass maintained their characteristics after sintering. The addition of β-spodumene would decrease the coefficient of thermal expansion (CTE) value of composites to match with silicon well. The better wetting behavior between β-spodumene and BS glass would lead to better sintering quality, microstructure and dielectric properties for composites containing more β-spodumene. With appropriate Al₂O₃ content, the flexural strength of composites could be enhanced. Composite with 45 wt% BS glass, 30 wt% β-spodumene and 25 wt% Al₂O₃ sintered at 875 °C showed good properties which meet the requirements of low temperature co-fired ceramic applications: dense microstructure with high relative density of 96.27%, proper CTE value of 3.57 ppm/°C, high flexural strength of 156 MPa, low dielectric constant of 6.20 and low dielectric loss of 1.9?×?10^?3.     

脱脂工艺对光固化3D打印堇青石陶瓷性能的影响

光固化3D打印是制造高度复杂结构陶瓷的一种有效方法。打印的样件需要经历脱脂和烧结等热处理才能成为可用的陶瓷件, 脱脂工艺对打印件性能影响巨大。本工作通过研究脱脂工艺对DLP光固化3D打印制备的堇青石陶瓷性能的影响规律, 建立缺陷抑制策略。比较并分析了脱脂气氛和升温速率对陶瓷样件的表面裂纹和元素分布状态的影响, 还对比进一步烧结后样件显微组织、尺寸收缩率、相对密度和弯曲强度等性能。研究发现脱脂气氛对样件各性能影响最大, 使用氩气脱脂可显著降低表面裂纹, 提高相对密度与弯曲强度; 并确定最佳升温速率为1 ℃/min。最终获得表面完整无裂纹且相对密度为(94.6±0.3)%, 弯曲强度为(94.3±3.2) MPa的堇青石陶瓷样件。本研究为光固化3D打印堇青石陶瓷的无缺陷制造与应用提供了科学依据与技术参考。     

Properties of sintered glass-ceramics prepared from plasma vitrified air pollution control residues

Air pollution control (APC) residues, obtained from a major UK energy from waste (EfW) plant, processing municipal solid waste, have been blended with silica and alumina and melted using DC plasma arc technology. The glass produced was crushed, milled, uni-axially pressed and sintered at temperatures between 750 and 1150 °C, and the glass-ceramics formed were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties assessed included Vickers's hardness, flexural strength, Young's modulus and thermal shock resistance. The optimum sintering temperature was found to be 950 °C. This produced a glass-ceramic with high density (～2.58 g/cm³), minimum water absorption (～2%) and relatively high mechanical strength (～81 ± 4 MPa). Thermal shock testing showed that 950 °C sintered samples could withstand a 700 °C quench in water without micro-cracking. The research demonstrates that glass-ceramics can be readily formed from DC plasma treated APC residues and that these have comparable properties to marble and porcelain. This novel approach represents a technically and commercially viable treatment option for APC residues that allow the beneficial reuse of this problematic waste.     

Hollow glass microsphere composites: preparation and properties

Composites consisting of bonded hollow glass microspheres are promising for constructions in which materials are needed that combine a high Young's modulus with a low density. The elastic properties of ideally bonded hollow glass microsphere composites are predicted theoretically. Heat-treated castings of quartz glass microspheres approach the theoretical Young's modulus from below. The best result achieved was a Young's modulus of about 1 GPa with a strength of about 0.8 MPa at a density of about 180 kg m^–3. This was obtained with a casting of quartz glass microspheres, bonded with mono-aluminium phosphate. Composites made by pressing of appropriate microsphere/ binder mixtures, followed by heating, had a density that was lower than for castings but had a Young's modulus far below the theoretical value.     

Ce-Y-ZTA 复相陶瓷的微波烧结

系统研究了Ce-Y-ZTA 复相陶瓷批量试样在2. 45GHz, 功率0. 5～ 5kW 连续可调的矩形多模腔内的微波烧结过程及材料性能。实验表明: 通过合理的保温结构和工艺控制, 可实现高稳定性和重复性的微波快速烧结。相对密度达到99%TD。与常规烧结相比, 微波烧结过程只需约2小时, 致密化温度降低50～ 100℃。烧结后材料具有晶粒尺寸细小、均匀的显微结构, 弯曲强度由600M Pa 提高至670M Pa, 同时获得较高断裂韧性值。      

Effect of powder reactivity on microwave sintering of alumina

Effect of the reactivity of starting alumina powder of varying crystallinity on the sintering behavior in microwave process was studied. From X-ray amorphous to highly crystalline alumina, powders were obtained by conventional heating of compacts made of the precursor amorphous powder by heating it at different temperatures from 800 to 1500 °C. These samples were then sintered in a multimode microwave field of 2.45 GHz for 10 min at 1500 °C. The microwave effect on densification of the various alumina powders was evaluated by comparing the microwave and conventional sintering data. The results show significant microwave enhancement in the densification of the samples without any pretreatment. This enhancement became less significant as the temperature of the pretreatment increased and finally diminished. Since the pretreatment at elevated temperatures made the powder more stable thermodynamically, this study indicates that the sintering enhancement of a ceramic material in microwave is a metastability-related phenomenon.     

3D打印氧化铝陶瓷的气氛脱脂热处理工艺研究

脱脂热处理工艺对于3D打印陶瓷的成形质量具有重要的影响。目前光固化3D打印制备得到的氧化铝生坯经过在空气中的脱脂热处理工艺后烧结最终得到的氧化铝陶瓷存在的微观裂纹等缺陷, 将导致其力学性能较差。本工作研究了基于数字光处理(Digital light processing, DLP)技术的氧化铝陶瓷打印热处理工艺, 将3D打印制备得到的氧化铝陶瓷生坯分别在空气与氩气中脱脂后比较其宏观形貌, 发现在空气下脱脂的氧化铝生坯存在微观裂纹。再将脱脂后的生坯在空气下烧结得到氧化铝陶瓷, 并对其微观形貌和宏观性能进行表征, 发现在氩气下脱脂的氧化铝陶瓷平均晶粒尺寸要比直接在空气中脱脂得到的氧化铝陶瓷平均晶粒尺寸大, 而且晶粒结构致密, 无明显气孔和杂相, 而且具有更高的抗压强度。这说明在氩气中脱脂后烧结得到的氧化铝陶瓷性能更好。在氩气中脱脂的氧化铝致密度最高可达到96.72%, 抗压强度可达到761.7 MPa, 相比于只在空气中脱脂的氧化铝陶瓷性能得到显著提升。     

PTFE/陶瓷/微纤维的成型烧结特性研究

在PTFE／陶瓷／微纤维三元体系复合粉料制备的基础上，用综合热分析方法对复合粉料在热处理过程中发生的物理化学变化进行了探讨，详细比较了预压成型结合自由烧结工艺与热压成型烧结工艺，对介质微观结构，机械力学与电学性能等方面的影响，实验表明：当陶瓷与微纤维含量较高时，采用适当的热压成型烧结工艺可以制备出强度高，损耗低，综合性能优异的微波复合介质材料，用IR光谱，氧指数对复合介质的结构与燃烧性能进行了分析评价。