Waste fluorescent glass and shell derived glass-ceramics

We prepared glass-ceramics by using fluorescent glass and waste shell as starting materials to recycle waste fluorescent glass containing harmful Hg to human body and waste shell, and to resolve environmental problems. Pressed specimens after quenching and grinding were heat treated at 800°C, 900°C and 1000°C for 1 h, respectively. -wollastonite, gehlenite and sodium calcium silicate were observed by X-ray diffraction studies. Surface morphology and chemical composition were evaluated by field emission-scanning electron microscopy and energy dispersive X-ray spectrometer.     

Removal of phosphate from aqueous solution by biochar derived from anaerobically digested sugar beet tailings

Biochar converted from agricultural residues or other carbon-rich wastes may provide new methods and materials for environmental management, particularly with respect to carbon sequestration and contaminant remediation. In this study, laboratory experiments were conducted to investigate the removal of phosphate from aqueous solution by biochar derived from anaerobically digested sugar beet tailings (DSTC). Batch adsorption kinetic and equilibrium isotherm experiments and post-adsorption characterizations using SEM-EDS, XRD, and FTIR suggested that colloidal and nano-sized MgO (periclase) particles on the biochar surface were the main adsorption sites for aqueous phosphate. Batch adsorption experiments also showed that both initial solution pH and coexisting anions could affect the adsorption of phosphate onto the DSTC biochar. Of the mathematical models used to describe the adsorption kinetics of phosphate removal by the biochar, the Ritchie N_th-order (N=1.14) model showed the best fit. Two heterogeneous isotherm models (Freundlich and Langmuir-Freundlich) fitted the experimental isotherm of phosphate adsorption onto the biochar better than the Langmuir adsorption model. Our results suggest that biochar converted from anaerobically digested sugar beet tailings is a promising alternative adsorbent, which can be used to reclaim phosphate from water or reduce phosphate leaching from fertilized soils. In addition, there is no need to regenerate the exhausted biochar because the phosphate-laden biochar contains abundance of valuable nutrients, which may be used as a slow-release fertilizer to enhance soil fertility and to sequester carbon.     

Rare-earth doped sol-gel derived oxyfluoride glass-ceramics: Structural and optical characterization

Glass-ceramics containing RE³⁺-doped BaF₂ nanocrystals (RE = Eu, Sm, Dy, Ho and Pr) with the size below 10 nm size have been made by using the controlled crystallization at higher temperatures of the RE³⁺-doped SiO₂-BaF₂ xerogels. Photoluminescence measurements have indicated the incorporation of the RE³⁺ ions in both silica network and in the BaF₂ nanocrystals. Thermoluminescence measurements have shown a peak whose position depends on the nature of RE³⁺-dopant as it follows: 140 °C (for Ho³⁺, Dy³⁺), 340 °C (for Sm³⁺) and 370 °C (for Eu³⁺); in Eu³⁺-doped SiO₂ glass the TL peak is shifted to 383 °C. The peaks in glass-ceramics were assigned to the recombination of the electrons thermal released from the RE³⁺-electron traps located in both glass-matrix and BaF₂ nanocrystals. Within the series the trivalent lanthanide ions act as increasingly deeper electron trapping centres.     

Crystallization characteristics of LiNbO3 derived from sol-gel

A sol-gel process for lithium niobate using lithium ethoxide and niobium ethoxide precursors was investigated. Nitric acid and acetic acid were used as catalysts, respectively. The crystallization characteristics of the sol-gel-derived lithium niobate is influenced intensively by catalysts, and the crystallization of LiNbO₃ from the nitric-acid-catalyzed sol-gel can occur at a low temperature near to 300 C.     

Characterization of alpha-cordierite glass-ceramics from fly ash

Batches of alpha-cordierite glass-ceramics, designated as GC-I and GC-II, containing 68 and 64 wt.% fly ash, respectively, were crystallized in the temperature range of 1125-1320 degrees C. The XRD (X-ray powder diffractometer) of the glass-ceramics show that alpha-cordierite became the dominant phase in GC-I and GC-II at 1200 degrees C. GC-I and GC-II, whose solid parts contain 74 and 78 vol.% alpha-cordierite and whose compressive strengths are 35 and 50 MPa, respectively, have the respective linear thermal expansion coefficients of 1.51x10(-6) and 1.43x10(-6)/ degrees C. The fly ash alpha-cordierite glass-ceramics can be employed as kiln furniture, honeycomb substrates for catalysts, and heat exchangers.     

Investigation of aerodynamic characteristics of manganese ore

The results of an investigation of the aerodynamic characteristics of manganese ore, ready for delivery from the pit and sorted out in fractions, are presented for the humidity range 1.3 to 8.5%. The formulas for computing the pressure drop in the bed, the velocity of start of fluidization, and the velocity of entrainment of the particles are also given.     

二氧化锰复合材料吸波特性研究

对二氧化锰的电磁性能和石英/二氧化锰复合材料的吸波性能进行了实验研究.发现二氧化锰具有较好的吸波性能,随着二氧化锰含量的增加,复合材料的吸波性能逐渐增加,并且吸收峰值向低频端漂移.在石英/碳黑复合材料中加入二氧化锰可以大大提高材料的吸波性能.对二氧化锰进行电磁参数测试和TEM电镜分析的结果表明,二氧化锰属于介电损耗介质,其具有的块状和条状结构有利于对电磁波的多次散射和吸收.     

Comparison of the characteristics of hydrothermal carbons derived from holocellulose and crude biomass

The effects of lignin removal on hydrochar were investigated by comparing the structural, chemical, and thermal characteristics of holocellulose and wood powder-derived carbon materials (hydrochar). The hydrochar samples were obtained from hydrothermal carbonization (HTC) of holocellulose and wood powder at 210–230 °C for 9 h. The characteristics of the obtained products were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, elemental analysis, and thermogravimetric analysis. The observations reveal that the onset temperature of the HTC of holocellulose is lower than that of wood powder. The holocellulose-derived hydrochar samples exhibit higher carbon content and thermal stability with higher coalification degree and less complex chemical composition compared with resultant products based on wood powder. These results reveal that the holocellulose is easier to be disintegrated and hydrocarbonized without the shielding effects of lignin and suggest that the lignin removal is beneficial for increasing the rate and efficiency of the polysaccharide in biomass converting into hydrochar.     

玻璃陶瓷的研究与发展

玻璃陶瓷以其优良的性能现已成为一种新型的功能材料和结构材料,备受研究者的瞩目.本文论述了玻璃陶瓷在成分设计、组成体系、显微结构和制备方法上的研究进展,在光、电、生、化等领域的广泛应用,并预测了其未来发展前景.     

New manganese (II) structures derived from 2,6-dichlorobenzoic acid: Syntheses,crystal structures and magnetism

One novel coordination polymer [Mn₂(μ-2,6-DCBA)₃(μ₂-CH₃CO₂)₂(2H₂O)]·2H₂O (2,6-DCBA = 2,6-dichlorobenzoato) (compound 1) has been synthesized by self-assembly of bridging ligand 2,6-dichlorobenzoic acid and manganese acetate tetrahydrate. Single crystal X-ray diffraction analysis reveals that this compound crystallizes in space group P2₁/c with a = 10.1547(7), b = 24.5829(2), c = 12.6606(2) Å, β = 93.707(3), V = 3153.9(3) ų and Z = 4. The Mn(II) ions are connected by 2,6-DCBA and acetate group in μ-bridging mode to form 1D chains. Two water molecules are in the inter-layer space forming strong hydrogen bonds originating 2D layer structure. The preparation of this compound is very sensitive to the synthesis conditions, mainly to the solution pH and solvent yielding other two compounds 2 and 3. In compound 1 Mn(II) atoms in octahedral coordination are arranged in a zig–zag chain, with a trimeric structure repeated periodically along the chain, giving two exchange parameters: J₁ related to a syn–syn bond; and J₂ related to a bond of type anti–anti. A theoretical model was developed and then fitted to the magnetic susceptibility data, revealing an antiferromagnetic arrangement along the chain.     

Microanalysis of the surface in glass-ceramics obtained from muscovite-amblygonite

A new family of glass-ceramics obtained from muscovite-amblygonite mixtures showing a schiller effect or reflecting surface has been obtained. This effect has not been observed in the bulk material. The raw materials contain about 1% iron as Fe²¹. In order to elucidate the correlation between surface structure and/or composition and the schiller surface effect, several surface analysis methods, (ESCA, RBS, EPR and reflection Mössbauer spectroscopy) have been used. It seems that a solid solution of Fe³¹ in the spodumene crystal lattice precipitated from the surface is related to the reflecting effect, which can be controlled by solution of iron oxides in the-spodumene solid solution.     

Production of quasi-sulfoaluminate cementitious materials with electrolytic manganese residue

Electrolytic manganese residue (EMR) is a harmful solid industrial waste that comes from the electrolytic manganese industry and has rarely been recycled in large quantities. To consume as much EMR as possible, quasi-sulfoaluminate cementitious material (Q-SAC) was prepared by firing high amounts of EMR together with limestone and kaolin at approximately 1200 °C (∼50-100 °C lower than that of ordinary sulfoaluminate cement). The major crystalline phases of Q-SAC determined by XRD were calcium sulfoaluminate, dicalcium silicate and calcium sulfate. The final setting times of Q-SAC were less than half an hour. The early and long-term alkalinities of Q-SAC pastes were approximately 2 and 1 lower than those of OPC paste, respectively. The results also showed that Q-SAC prepared by mixing 10-40% of EMR can obtain compressive strength of 35-65 MPa at 56 days. When 5% of gypsum was added, the early and long-term strengths of Q-SAC were approximately 50% and 30% higher, respectively. The results showed that the use of EMR for Q-SAC production is a promising way to recycle EMR because of its low firing temperature and good mechanical performance.     

Microstructure and properties of transparent glass-ceramics

The variation of the microstructure with heat-treatment of transparent glass-ceramics based on the ZnO-Al₂O₃-SiO₂ system has been investigated using X-ray diffraction and transmission electron microscopy. The principal crystalline phase was found to be ZnAl₂O₄, gahnite, when a minimum amount of nucleating agent, ZrO₂, was present. The dependence of mean particle size, volume fraction and mean crystal spacing on the heat-treatment was also studied. It was found that the microstructural parameters were relatively sensitive to the time at the crystallization temperature of 950° C.     

Luminescence concentration quenching and site-occupancy of Eu2+ ions in Na2Ca2Si3O9 phosphors derived from 45S5 glass-ceramics

The phosphors of Na₂Ca_2-2xEu_2xSi₃O₉ (x = 0, 0.03, 0.05, 0.07, 0.09) were first synthesized by sol-gel method. The crystal phase formations of the phosphors were detected by X-ray powder diffraction (XRD) measurements and the structure refinement. The photoluminescence spectra, the concentration quenching, the luminescence decay curves and the luminescence color chromaticity were measured, respectively. The excitation spectra indicate that the phosphors can be effectively excited by near UV-LED chips. Two kinds of Eu²⁺ sites centered at 545 nm and 505 nm were discussed by analyzing the spectra, concentration-dependent luminescence intensity and lifetimes. This is a potential tool for monitoring the bioactivity of 45S5 glass-ceramics in situ.     

Production of composite particles using an innovative continuous dry coating process derived from extrusion

Dry particle coating is used to modify surface properties and monitor the end use properties of powders. These processes are mainly running in batch mode. In certain cases, continuous processes may present interest for specific applications (limitation of investments, stability, versatility…). In this study, the feasibility of dry coating particles by an innovative way derived from the well-known extrusion process was investigated. Adhesion between host and guest particles is induced by mechanical shear stress during processing. A preliminary parametric study on microcrystalline cellulose particles as host particles was carried out in order to determine the operating condition range. Then, coating was successfully performed using talc and a microcrystalline cellulose system, which demonstrates the feasibility of this novel process and led to different morphologies according to the operating conditions.     

Microstructure and properties of transparent glass-ceramics

Crystallization in glasses based on the ZnO-Al₂O₃-SiO₂ system nucleated with ZrO₂ have been studied by electron spin resonance. The glass crystallization has been monitored by observing the change in the coordination of Fe³⁺ ions present in the glasses as an impurity.     

铅锌矿尾料中氧化锌的提取和纯化

利用酸法提取铅锌矿尾料中氧化锌,研究表明,在搅拌转速一定,温度为80℃、硝酸的浓度为3mol/L、液固质量比为5∶1时,铅锌矿尾料中氧化锌的产率能达到62.7%。产品中氧化锌的相对纯度可达99.5%。碱法提取氧化锌,氢氧化钠的浓度为9mol/L时,氧化锌的产率为27.6%。对于浸出液的回收利用则是用浸出液和硝酸配比,再对铅锌矿尾料进行浸出,从而使废液循环利用。     

Preparation and properties of barium titanate glass-ceramics sintered from sol–gel-derived powders

Homogeneous Ba–Ti–B–Si, Ba–Ti–Al–Si and Ba–Ti–B gels have been successfully prepared by the sol–gel process. A novel method is presented for fabricating barium titanate glass-ceramics by sintering the gel powders with small barium titanate crystallites. The structural development, grain size, crystallization process and dielectric properties were systematically studied by differential thermal analysis, thermogravimetric analysis, X-ray diffraction techniques, scanning electron microscopy and dielectric measurements. The glass-ceramic samples were sintered at lower temperatures compared to the barium titanate ceramic sintering, and showed improved dielectric properties. It was found that the small size effect of the barium titanate grains on the dielectric constant in the glass-ceramics was quite evident. Ferroelectric hysteresis loop analyses were also performed to manifest the ferroelectric nature of the barium titanate grains in situ grown from the gels. This revised version was published online in November 2006 with corrections to the Cover Date.     

Preparation of high strength foam glass-ceramics from waste cathode ray tube

The high strength porous foam glass can be widely used as heat insulation, sound absorption, shock wave absorbing constructional materials. The new high strength foam glass-ceramics from waste cathode ray tube were prepared by sintering method, and used SiC as foam agent. In this study, the samples were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and mechanical property. The effect of micro-crystals reinforcement on the bending and compressive strength was investigated by the strength tests. The crystallization behavior of the samples was determined by the applying of XRD and SEM. The experimental results showed that the amazingly high mechanical strength values of 5.61-23.73 MPa can be obtained by changing the dosage of SiC and using the sintering temperature around 840-850 °C, leading to the precipitation of Pb, Pb₃O₄, and Al₆Si₂O₁₃.Good correlations between mechanical strength, precipitation of micro-crystals and SiC dosage were observed.     

Preparation and properties of barium aluminosilicate glass-ceramics

Barium aluminosilicate (BAS) glass-ceramics were prepared by hot-pressing BAS glass powder derived via the sol–gel method, and the microstructure and properties were studied. Through control of composition, BAS glass-ceramics with two different types of microstructure were obtained. One is a sub-micrometre celsian surrounded by a thin layer of glassy phase, and the other is a celsian–mullite composite microstructure. BAS glass-ceramics with the celsian–mullite composite microstructure have a strength of 204 MPa and a creep rate of ≤ 1.03 × 10^-4 h^-1 at 1250 °C. After heat treatment at 1250 °C for 100 h, no significant change of the microstructure was found, and the high-temperature strength did not decrease greatly. The BAS glass-ceramics prove to be a potentially good matrix for fibre- or whisker-reinforced composites for high-temperature applications. This revised version was published online in November 2006 with corrections to the Cover Date.