Effect of different forms of silica on sintering,microstructure and properties of borosilicate glass/Al2O3 composites

The effects of the introduction of silica glass and silica ceramic into Ca-Al-B-Si-O glass/ Al2O3 composites on decreasing the shrinkage and the dielectric constant of samples were investigated by FTIR, DSC, XRD and SEM. The results show that silica ceramic filler can better improve the formation of Si– O–Si network in the composites under high temperature, which leads to increased continuity of glass network at high temperature, and deduces the increase of viscosity of composites and further results in the decrease in the shrinkage of samples. Densification, three-point strength, and dielectric constant of samples decrease with the increase of silica glass or silica ceramic content. By contrast, Ca-Al-B-Si-O glass/Al2O3 composites with 4 wt% silica ceramic exhibit better properties of a bulk density of 2.81 g cm-3, a porosity of 0.3%, a 3dp value of 202 MPa, a ε r value of 7.41, a tan δ value of 8.3×10-4at 10 MHz and a well matching with Ag electrodes. This material is suitable to be used as the LTCC material for the application in wireless communications.     

Low temperature sintering and dielectric properties of Ca-Ba-Al-B-Si-O glass/Al2O3 composites for LTCC applications

The effects of various SiO2 contents on both the microstructures and properties of Ca-Ba- A1-B-Si-O glass/Al2O3 cotrtposites were investigated by FTIR, DSC, XRD and SEM. The experimental results show that increasing SiO2 content in the glass leads to the increase of [SIO4] units, increases the continuity of glass network, and decreases the trend to crystallization of composites. The shrinkage of samples rises rapid around the glass softening temperature and the final shrinkage of samples decreases with increasing SiO2 content in the glass. Borosilicate glass/Al2O3 composites with 60wt% SiO2 sintered at 875 ℃ for 15 min show better properties： a bulk density of 3.10 g,cm-3, a porosity of 0.23 %, a er value of 7.55 and a tan 8 value of 0.00053 （measured at 10 MHz） and a well matching with Ag electrodes.     

Influence of ZrO2 on sintering and crystallization of CaO-Al2O3-SiO2 glass-ceramics

ZrO2 was added into CaO-Al2O3-SiO2 glass-ceramics and the effect of ZrO2 on sintering and crystallization of CaO-Al2O3-SiO2 glass ceramics was investigated. The results show that the sintering shrinkage ratio of glass particles decreases with the increase of the content of ZrO2. ZrO2 has an unfavourable effect on sintering shrinkage ratio of glass particles. The sintering shrinkage ratio of glass particles increases with the increase of sintering temperature. The increase of sintering temperature favors the decrease of the liquid phase viscosity of glass particles. ZrO2 has little effect on crystallization of main crystalline phase （β-wollastonite）. However, it promotes the crystallization at relatively low temperature.     

Effect of nucleating agents and heat treatments on the crystallization of magnesium aluminosilicate transparent glass-ceramics

The crystallization behavior and transparent property of MgO-Al2O3-SiO2 (MAS) glasses with TiO2 and TiO2+ZrO2 as nucleating agents were discussed by differential thermal analysis, X-ray diffraction, field emission-environment scanning electron microscope, energy dispersive spectrum and UV-VIS-NIR scanning spectrophotometer. It was found that the glass crystallized at 950 ℃ with ZrO2 less than 3% could obtain transparent glass ceramic, which presented purple to colorless. With the nucleating agent additives (5% TiO2+3% ZrO2), the colorless transparent glass-ceramics with spinel as the main crystal phase could be prepared, and the transmittance reached about 80% . As the crystallized temperature increase to 1 000 ℃, besides spinel(MgAl2O4), sapphirine (Mg3.5Al9Si1.5O20) and ZrTiO4 precipitated from matrix glass, and the transmitance of glass-ceramic decreased.     

Preparation and properties of crystallizable Glass/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites for LTCC material

The investigated low temperature Co fired ceramics(LTCC) composite of 60wt% CaO-Al2O3-B2O3-SiO2 glass and 40wt% α-Al2O3 as a filler is a non-reactive system, which is a critical part of the low temperature Co fired ceramics process. Through a study on densification process, the phase transformation and microstructure can be revealed. Its composites typically consist of CaO-Al2O3-B2O3-SiO2 glass and α-Al2O3 powders of average particle size (D50=3.49 mm). The sintering behavior, phase evaluation, sintered morphology, and microwave dielectric properties were investigated. In the fire range of 800 to 900 ℃, the composites were crystallized after completion of densification. It is found that the composites start to densify at 825 ℃, simultaneously, the dielectric constant (εr) reaches its maximum. With increasing heat-treatment temperatures, due to the loose microstructure of the material, tanδ increases slightly. The last of the sintered samples were identified as partly Anorthite at 850 ℃. At that temperature it has εr of 7.9 and tanδ less than 1×10-3, and can be used as a promising LTCC material.     

Effect of TiO2 on Crystallization of the Glass Ceramics Prepared from Granite Tailings

The effect of TiO2 on the crystallization behaviors of the glass ceramics prepared from granite tailings was investigated by differential scanning calorimetry(DSC), X-ray diffraction(XRD), and field emission scanning electron microscopy(FESEM). The results showed that the crystallization peak temperature decreased firstly, and then increased with the increase of TiO2 content. The optimum addition amount of TiO2 was 8 wt%. With a single-step heat treatment at 924 ℃ for 1 h, augite precipitated as the only crystalline phase both on the surface and in the interior. The avrami parameter of the sample was 3.25, suggesting a twodimensional crystallization mechanism. The activation energies for phase separation and crystallization of augite were 321.75 and 698.83 k J/mol, respectively.     

Preparation of Al2O3-SiO2-TiO2-ZrO2 Composite Ceramic Membranes by Sol-Gel Method

Al2O3-SiO2- TiO2-ZrO2 supported membranes were prepared by Sol-Gel method. These composite ceramic membranes are level, even and no macro crack. There exist several crystalline phases such as Al2O3, TiO2 ( anatase ), Al2 SiO5 , and ZrO2 in these membranes. Changing the molar ratio of Al:Si: Ti : Zr ,the kinds and content of crystal phases of composite membranes could be different, which may lend to a variety of microstructure of membranes. The surface nanoscale topography and microstructure of membranes were investigated by XRD, SEM, AFM, EPMA. The effects of additives and heat treatments on the surface nanoscale topography and microstracture of composite ceramic membranes were also analyzed.     

Effects of Sr2＋ substitution on the structural,dielectric, and piezoelectric properties of PZT-PMN ceramics

This study described the structural, dielectric, and piezoelectric behavior of Pb1-xSrx[（Zr0.52Ti0.48）0.95（Mn1/3Nb2/3）0.05]O3 ceramics （PSZT-PMN, x=0, 0.025, 0.050, and 0.075）, prepared by a semi-wet route. X-ray diffraction, dielectric, and piezoelectric investigations were carried out to analyze the crystal structure. The relative dielectric constant and dielectric loss were both calculated as the functions of temperature. The room-temperature dielectric constant reaches a maximum for a Sr2＋-modified PZT-PMN ceramic with an x value of 0.050, which corresponds to the morphotropic phase boundary （MPB）. Raman spectroscopy studies also confirm the existence of this MPB for x=0.050. The piezoelectric strain coefficients （d33） value shows a maximum response for this composition. In addition, the phase transition temperature decreases significantly when the Sr2＋concentration increases in the PZT-PMN ceramics.     

Effects of Substrate Temperatures on the Structure and UV-shielding Properties of TiO2-CeO2 Films Deposited on Glass by Radio-frequency Magnetron Sputtering

TiO2-CeO2 films were deposited on soda-lime glass substrates at varied substrate temperatures by rf magnetron sputtering using 40% molar TiO2-60% molar CeO2 ceramic target in Ar：O2=95：5 atmosphere.The structure,surface composition,UV-visible spectra of the films were measured by scanning electron microscopy and X-ray diffraction,and X-ray photoelectron spectroscopy,respectively.The experimental results show that the films are amorphous,there are only Ti^4＋ and Ce^4＋ on the surface of the films,the obtained TiO2-CeO2 films shou a good uniformity and high densification,and the films deposited on the glass can shield ultraviolet light without significant absorpition of visible light,the films deposited on substrates at room temperature and 220℃ absorb UV effectively.     

Effect of ZnO-B_2O_3 Glass Addition on the Microwave Dielectric Properties of BaO-Nd_2O_3-TiO_2-Bi_2O_3 System

The effect of ZnO-B2O3(ZB) glass addition on the sintering behavior, microstructures and microwave dielectric properties of BaO-Nd2O3-TiO2-Bi2O3 (BNTB) system was investigated with the aid of X-ray diffraction, scanning electron microscopy and capacitance meter. It is found that the ZB glass addition, acting as a sintering aid, can effectively lower the sintering temperature of BNTB system to 850 ℃. The dielectric constant of BNTB-ZB ceramics increases with the increase of soaking time and the value of dielectric loss decreased with increasing soak time. The optical dielectric properties at 1 GHz of ε=74, tan δ=4×10-4, and TCC=25 ppm/℃ were obtained for the BNTB system doped with 25 wt% ZB glass sintered at 850 ℃ for 2 h, representing that the BNTB-ZB ceramics could be promising for multilayer low temperature co-fired ceramics applications.     

Preparation and visible-light photocatalytic property of nanostructu- red Fe-doped TiO2 from titanium containing electric furnace molten slag

Nanostructured Fe-doped titanium dioxide was synthesized from titanium containing electric furnace molten slag （TCEFMS） by using an alkali fusion, followed by a hydrolyzation-acidolysis-cMcination route. The effects of Mkali/slag mass ratio, calcinating temperature, calcinating time, and water/slag mass ratio on the extraction efficiency and purity of products were systematically studied in this paper. It is indicated that the best extraction efficiency of nanostructured Fe- doped titanium dioxide is 99.35%, when the molten slag is calcinated at 700℃ for 1 h with the mass ratio of alkali/molten slag of 1.5：1. The influence of alkali/slag mass ratio on the photocatalytic activity of final products was evaluated by the photodegradation of methyl blue under visible light irradiation. A maximum photodegradation efficiency of 88.12% over 30 min was achieved under the optimum conditions.     

Martensitic transformation and magnetic properties of aged Ni-Fe-Ga-Ti shape memory alloy

This article reports the effect of ageing on the microstructure, martensitic transformation, magnetic properties, and mechanical properties of Ni51FelsGa27Ti4 shape memory alloy. There are five specimens of this alloy aged at 573 up to 973 K for 3 h per each. This range of ageing temperature greatly affects the microstructure of the alloy. As the ageing temperature increased from 573 up to 973 K, the microstructure of Ni51FelsGa27Ti4 alloy gradually changed from the entirely martensitic matrix at 573 K to the fully austenitic microstructure at 973 K. The volume fraction of precipi- tated Ni3Ti particles increased with the ageing temperature increasing from 573 to 773 K. Further increasing the ageing temperature to 973 K decreased the content of Ni3Ti in the microstructure. The martensitic transformation tempera- ture was decreased steadily by increasing the ageing temperature. The magnetization saturation, remnant magnetization, and coercivity increased with the ageing temperature increasing up to 773 K. A further increase in ageing temperature decreased these raagnetic properties. Moreover, the hardness values were gradually increased at first by increasing the ageing temperature to 773 K, and then dramatically decreased to the lowest value at 973 K.     

Microstructural and mechanical properties of A1-4.5wt% Cu rein- forced with alumina nanoparticles by stir casting method

The microstructure and mechanical properties of A1-4.5wt% Cu Mloy reinforced with different volume fractions （1.5vo1%, 3vo1%, and 5vo1%） of alumina nanoparticles, fabricated using stir casting method, were investigated. CMculated amounts of alumina nanoparticles （about ~50 nm in size） were ball-milled with aluminum powders in a planetary ball mill for 5 h, and then the packets of milled powders were incorporated into molten Al-4.5wt% Cu alloy. Microstructural studies of the nanocomposites reveal a uniform distribution of alumina nanoparticles in the A1-4.5wt% Cu matrix. The results indicate an outstanding improvement in compression strength and hardness due to the effect of nanoparticle addition. The aging behavior of the composite is also evaluated, indicating that the addition of alumina nanoparticles can accelerate the aging process of the Mloy, resulting in higher peak hardness values.     

Preparation of CaO-Al2O3-SiO2 system glass from molten blast furnace slag

To use the potential heat of molten blast furnace slag completely, a CaO-Al2O3-SiO2 system glass （MSG） was prepared from the molten industrial slag. The corresponding method proposed in this study utilized both slag and its potential heat, improving the production rate and avoiding the environmental pollution. Using appropriate techniques, an MSG with uniform color and superior performances was produced. Based on the experimental results and phase diagram, the chemical composition of MSG by mass is obtained as follows：CaO 27%-33%, SiO2 42%-51%, Al2O3 11%-14%, MgO 6%-8%, and Na2O＋K2O 1%-4%. Thermodynamic processes of MSG preparation were analyzed, and the phases and microstructures of MSG were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that alkali metal oxides serve as the fluxes, calcium oxide serves as the stabilizer, and alumina reinforces the Si-O network. XRD and SEM analyses show that, the prepared MSG displays the glass-feature patterns, the melting process is more complete, and the melt viscosity is lowered with an increase in calcium oxide content;however, a continuous increase in slag content induces the crystalli-zation of glass, leading to the formation of glass subphase. The optimum content of molten slag in MSG is 67.37wt%. With respect to bend-ing strength and acid/alkali resistance, the performance of MSG is better than that of ordinary marble.     

Effect of some operational variables on bubble size in a pilot-scale mechanical flotation machine简

This work aims to provide a relationship of how the key operational variables of frother type and impeller speed affect the size of bubble （D32）. The study was performed using pilot-scale equipment （0.8 m^3） that is up to two orders of magnitude larger than equipment used for studies performed to date by others, and incorporated the key process variables of frother type and impeller speed. The results show that each frother family exhibits a unique CCC95-HLB relationship dependent on n （number of C-atoms in alkyl group） and m （number of propylene oxide group）. Empirical models were developed to predict CCC95 from HLB associated with other two parameters a and ft. The impeller speed-bubble size tests show that D32 is unaffected by increased impeller tip speed across the range of 4.6 to 9.2 m/s （representing the industrial operating range）, although D32 starts to increase below 4.6 m/s. The finding is valid for both coalescing and non-coalescing conditions. The results suggest that the bubble size and bubble size distribution （BSD） being created do not change with increasing impeller speed in the quiescent zone of the flotation.     

Feasibility of developing composite action between concrete and cold-formed steel beam

Cold-formed steel structures are steel structure products constructed from sheets or coils using cold rolling, press brake or bending brake method. These structures are extensively employed in building construction industry due to their light mass, ductility by economic cold forming operations, favorable strength-to-mass ratio and other factors. The utilization of cold formed steel sections with concrete as composite can hugely reduce the construction cost. However, the use of cold formed steel members in composite concrete beams has been very limited. A comprehensive review of developments in composite beam with cold formed steel sections was introduced. It was revealed that employing cold-formed steel channel section to replace reinforcement bars in conventional reinforced concrete beam results in a significant cost reduction without reducing strength capacity. The use of composite beam consisting of cold-formed steel open or close box and filled concrete could also reduce construction cost. Lighter composite girder for bridges with cold-formed steel of U section was introduced. Moreover, types of shear connectors to provide composite action between cold-formed steel beam and concrete slab were presented. However, further studies to investigate the effects of metal decking on the behavior of composite beam with cold-formed steel section and introduction of ductile shear connectors were recommended.     

High permittivity and low dielectric loss analysis of lead free Sr1-xLax（Ti0.5Fe0.5）O3

The structural and electrical properties of lead free Srx-xLax（Tio.sFeo.5）O3 （SLTFO） prepared by standard solid state reaction technique were studied. The X-ray diffraction analysis confirmed the formation of a single-phase cubic perovskite structure. The compositional dependence of lattice constant, density and microstructural studies show that they vary significantly with La3＋ content. When measured at 10 kHz, all the compositions of SLTFO at room temperature exhibit a high permittivity （about 104） and low dielectric loss （about 10-3）. SLTFO also display minimum dielectric loss within the lower and higher limits of frequency, indicating that the samples are of good quality. It is concluded from the calculated ac conductivity that the conduction is due to mixed polarons hopping. The complex impedance plot exhibits a tendency of forming a single semicircular arc for all compositions, which implies a dominance of grain boundary resistance on the impedance. Impedance parameters were determined by fitting the experimental data with Cole-Cole empirical formula. The results of the present experiment indicate that the lead free SLTFO materials with higher permittivity and lower dielectric loss have possible practical applications.     

Pyrolysis characteristics of rubber compositions in medical waste

Thermogravimetric study of rubber compositions （operating glove and catheter） in medical waste was carried out using the thermogravimetric analyser （TGA）,at the heating rate of 20 ℃/min in a stream of N2.The results indicate that the decomposition process of operating glove appears an obvious mass loss stage at 250-485 ℃,while catheter has two obvious stages at 240-510 ℃ and 655-800 ℃,respectively; both samples present endothermic pyrolysis reaction; the decomposition of operating glove and the first mass loss stage of catheter are in agreement with natural rubber pyrolysis; the second mass loss stage of catheter corresponds to CaCO3 decomposition.Based on the experimental results,a novel two-step four-reaction model was established to simulate the whole continuous processes,which could more satisfactorily describe and predict the pyrolysis processes of rubber compositions,being more mechanistic and conveniently serving for the engineering.