Preparation, Crystallization and Mechanical Properties of Potassium Aluminosilicate Glass-ceramics

In this study,transparent K_(2)O-Al_(2)O_(3)-SiO_(2)(KAS)glass-ceramics with leucite as the main crystalline phase were prepared by melting-quench method and two-step heat treatment.The effects of SiO_(2)/Al_(2)O_(3) ratio and heat treatment on crystallization and mechanical properties were studied.The crystallization kinetics and X-Ray Diffraction(XRD)results showed that SiO_(2)/Al_(2)O_(3) ratio and heat treatment system had a direct impact on the crystallization behavior of potassium aluminosilicate glass-ceramics.When heat-treated at 680℃/2 h and 780℃/1 h,cracks generated on the surface of the sample with the addition of SiO_(2)/Al_(2)O_(3)=4.8(in mol)due to the huge difference in the coefficient of thermal expansion between glass matrix and surface.When the addition of SiO_(2)/Al_(2)O_(3)(in mol)was 4,the sample with leucite as the main crystalline phase showed an excellent fracture toughness(1.46 MPa·m^(0.5))after the heat treatment of 680℃/2 h and 780℃/5 h.And there was a phase transformation from kaliophilite to leucite.The crystalline phases of the sample heat-treated at 680℃/8 h and 780℃/1 h were leucite and kaliophilite,which resulted in the visible light transmittance of 63%and the fracture toughness of 0.91 MPa·m^(0.5).Furthermore,after the heat treatment of 680℃/2 h and 780℃/5 h,the main crystalline phase of the sample with SiO_(2)/Al_(2)O_(3)=3.2(in mol)was still kaliophilite.Because leucite only grows on the surface of the sample and is hard to grow inward,it is hard to achieve the bulk crystallization of leucite in the sample with SiO_(2)/Al_(2)O_(3)=3.2(in mol).

Glass-Ceramics with High Strength and High Transmittance Obtained by Multi-Factor Controlling

The presence of Li_(2)Si_(2)O_(5) and LiAlSi_(4)O_(10) could effectively improve the elastic modulus and transmittance of lithium disilicate(LD)glass-ceramics.Through synergistically modulation of the crystal content and grain size,we obtained high strength and high transmittance of LD glass-ceramics.The optimal sample had a high transmittance of 90.3%,the hardness was 7.72 GPa,the fracture toughness was 1.07 MPa·m^(1/2),and the elastic modulus was 103.1 GPa.

Properties of Ultra-low Thermal Expansion LAS Transparent Glass-ceramics Prepared by Spodumene

The glass-ceramics were prepared with the spodumene mineral as the main raw material,and the effects of ZrO_(2)replacing TiO_(2)on the samples were systematically investigated.The results show that the substitution of ZrO_(2)for TiO_(2)is not conductive to precipitate𝛽β-quartz solid solution phase,but can improve the transparency and flexural strength of glass-ceramics.And the glass-ceramic with the highest visible light transmittance(87%)and flexural strength(231.80 MPa)exhibits an ultra-low thermal expansion of-0.028×10^(-7)K^(-1)in the region of 30-700℃.

Sol-gel Preparation and Infrared Radiation Property of Boron-substituted Cordierite Glass-ceramics

Boron for aluminum substitution in the cordierite structure has been examined by sol-gel preparation of different samples along the compositional junction Mg2Al4-xBxSi5O18 with x=0,0.5,1,1.5.By increasing the x value from 0 to 1.5 the crystallization behavior changed accordingly.Proper amount B2O3 doping can promote the sintering of amorphous cordierite gel,effectively restrain the precipitation of μ-cordierite and enhance the crystallization of α-cordierite.The substitution of B3＋ for Al3＋ in cordierite crystal structure can effectively improve the near-infrared spectral emissivity of this cordierite based glass-ceramics.

Effects of rare earth addition on sintering process and dielectric property of cordierite based glass-ceramics

The effects of rare earth oxide on the sintering and dielectric property of cordierite-based glass-ceramics with non-stoichiometric composition prepared by quenching of molten droplets were investigated. The results show that the addition of rare earth oxide can lower the sintering temperature of cordierite glass-ceramics, improve the densification process and obviously reduce sintering activation energy. It is found that the densification of cordierite-based glass-ceramics is a liquid phase sintering process. The dielectric constant of the sintered compacts enhances with the increase of the density. When the sintering temperature is identical, the rare earth addition is found to have a noticeable effect on the dielectric loss of glass-ceramics. The properties of the glass-ceramics containing rare earth oxide appear to be correct for low firing temperature substrates.

Isotropic sintering shrinkage of 3D glass-ceramic nanolattices:backbone preforming and mechanical enhancement

There is a perpetual pursuit for free-form glasses and ceramics featuring outstanding mechanical properties as well as chemical and thermal resistance.It is a promising idea to shape inorganic materials in three-dimensional(3D)forms to reduce their weight while maintaining high mechanical properties.A popular strategy for the preparation of 3D inorganic materials is to mold the organic–inorganic hybrid photoresists into 3D micro-and nano-structures and remove the organic components by subsequent sintering.However,due to the discrete arrangement of inorganic components in the organic-inorganic hybrid photoresists,it remains a huge challenge to attain isotropic shrinkage during sintering.Herein,we demonstrate the isotropic sintering shrinkage by forming the consecutive–Si–O–Si–O–Zr–O–inorganic backbone in photoresists and fabricating 3D glass–ceramic nanolattices with enhanced mechanical properties.The femtosecond(fs)laser is used in two-photon polymerization(TPP)to fabricate 3D green body structures.After subsequent sintering at 1000℃,high-quality 3D glass–ceramic microstructures can be obtained with perfectly intact and smooth morphology.In-suit compression experiments and finite-element simulations reveal that octahedral-truss(oct-truss)lattices possess remarkable adeptness in bearing stress concentration and maintain the structural integrity to resist rod bending,indicating that this structure is a candidate for preparing lightweight and high stiffness glass–ceramic nanolattices.3D printing of such glasses and ceramics has significant implications in a number of industrial applications,including metamaterials,microelectromechanical systems,photonic crystals,and damage-tolerant lightweight materials.

In situ synthesized Cu-ZSM-5/cordierite for reduction of NO

ZSM-5 zeolites were directly synthesized on the surface of honeycomb cordierite substrates by hydrothermal method and certified by XRD and SEM techniques; the adhesion of ZSM-5 coatings was evaluated by ultrasonic vibration. Cu-ZSM-5/cordierite monolithic catalyst was prepared by ion-exchange and impregnation method and applied for the selective catalytic reduction （SCR） of NO by NH3 using a simulated diesel exhaust. The results show that the cordierite surface is almost completely covered by ZSM-5 crystals and the crystallization time greatly impacts the loadings and adhesion of ZSM-5 coatings on substrate, the NOx removal rate over Cu-ZSM-5/cordierite is above 90% in a temperature range of 240-480℃. Moreover, Cu-ZSM-5/cordierite prepared by different methods shows a wide temperature window （240-540 ℃） with high NO removal activities.

Co-Ni_2P/SBA-15/Cordierite整体式催化剂的制备及其二苯并噻吩加氢脱硫性能(英文)

用共浸渍法制备了Co-Ni2P/SBA-15前躯体,将其调制成活性胶后均匀涂覆到预处理后的堇青石载体上,程序升温还原后制备了一系列Co-Ni2P/SBA-15/堇青石整体式催化剂。采用XRD、N2吸脱附和XPS等对催化剂进行了表征,以1 wt%二苯并噻吩(DBT)/十氢萘溶液为模型化合物,在微型固定床反应器上对催化剂的加氢脱硫(HDS)性能进行了评价。结果表明,不同Co含量的Co-Ni2P/SBA-15/堇青石整体式催化剂中都形成了Ni2P相。Co的加入提高Ni2P/SBA-15/堇青石催化剂的比表面积和孔体积。Co含量为0.55wt%的Co-Ni2P/SBA-15/堇青石整体式催化剂有最好的二苯并噻吩加氢脱硫活性,在380℃,二苯并噻吩转化率能够达到98.8%。Co的加入能够提高二苯并噻吩直接加氢脱硫产物联苯的选择性。

Crystallization kinetics and temperature dependence of energy storage properties of niobate glass-ceramics

Glass-ceramic materials of strontium barium niobate system were prepared through a melt-quenching method. The effects of crystallization temperature on the mierostructure, dielectric property, breakdown strength and energy storage density of barium strontium niobate glass-ceramics were studied. The crystallization mechanism of the glass-ceramics was discussed and should be one-dimensional interfacial growth. The results indicate that the breakdown strength remarkably increases with the increase of crystallization temperature. The glass-ceramic heat treated at 900 ℃ was found to possess optimal properties with breakdown strength of 1300 kV/cm and energy storage density of 2.8 J/cm3, which is promising dielectric materials for high energy storage density dielectrics.

One-step hydrothermal synthesis of Cu-SAPO-34/cordierite and its catalytic performance on NO_x removal from diesel vehicles

Cu-SAPO-34/cordierite catalysts were prepared via one-step hydrothermal synthesis method and their performances to remove NO x from the diesel vehicle exhaust were evaluated. The morphology, structure, Cu content and valence state were characterized by SEM, XRD, ICP and XPS, respectively. The experimental results show the active component Cu of the catalysts via in situ synthesis could significantly improve the selective catalytic reduction （SCR） activities of NOx and the optimal Cu content is in the range of 0.30%-0.40%（mass fraction）. No N 2 O is detected by gas chromatograph （GC） during the evaluation process, which implies that NOx is almost entirely converted to N2 over Cu-SAPO-34/cordierite catalyst. The conversion rate of NOx to N2 by NH3 over catalyst could almost be up to 100%in the temperature range of 300-670 ℃with a space velocity of 12000 h-1 and it is still more than 60% at 300-620 ℃ under 36000 h-1. The catalysts also show the good hydrothermal and chemical stability at the atmosphere with H 2 O.

丙烷在Ce-Fe/Al_2O_3/cordierite上选择性催化还原NO

利用凝胶溶胶法和浸渍法制备了Ce-Fe/Al_2O_3/cordierite催化剂,实验研究了其催化丙烷选择性还原NO的特性。结果表明,当铈的负载量从1%增加至5%时,Ce-Fe/Al_2O_3/cordierite的C_3H_8-SCR性能先增强后减弱,3.5Ce-Fe/Al_2O_3/cordierite具有最佳的脱硝性能,在有氧条件下,600℃时可实现96.5%的脱硝效率。Ce的加入能够提升Fe/Al_2O_3/cordierite催化剂的抗硫性能。烟气中通入0.02%的SO_2后,3.5Ce-Fe/Al_2O_3/cordierite催化丙烷还原NO的转化率始终维持在93%,而没有经过Ce修饰的Fe/Al_2O_3/cordierite的NO转化率从88%下降为80%左右。利用XRD、N_2吸附-脱附、SEM、H_2-TPR、吡啶吸附红外光谱等手段研究了催化剂的物理化学性质。结果表明,加入助剂铈能与Fe形成了固溶体,增加催化剂表面Lew is酸浓度和氧化还原能力,从而提高了催化丙烷还原NO的性能。过多的铈引入会减少Fe_2O_3结晶体的形成,不利于在C_3H_8-SCR反应中形成NO_2/NO_3^-物种,从而导致NO还原效率下降。

Co/Fe/Al_2O_3/cordierite催化C_3H_6选择性还原NO的实验研究

采用溶胶凝胶法和浸渍法制备了负载于蜂窝陶瓷上的Co/Fe/Al_2O_3/cordierite催化剂,在陶瓷管流动反应器上对其催化C_3H_6选择性还原NO的性能进行了测试。结果表明,该催化剂表现出最优脱硝性能,在模拟烟气条件下,当反应温度为550℃时可实现97%的脱硝效率。Co的引入可显著增强Fe/Al_2O_3/cordierite催化剂抗SO_2和H_2O的能力。在模拟烟气中同时引入0.02%SO_2和3%H_2O后,1.5Co/Fe/Al_2O_3/cordierite的脱硝性能受影响甚微,当反应温度高于500℃时1.5Co/Fe/Al_2O_3/cordierite催化C_3H_6还原NO的效率均可达到90%以上;相比之下,未经Co修饰的催化剂Fe/Al_2O_3/cordierite脱硝性能受到了严重的抑制,在整个反应温度区间(200-700℃)内,其催化C_3H_6还原NO的效率最高不足50%。XRD和SEM表征结果表明,经过适量的Co修饰后的1.5Co/Fe/Al_2O_3/cordierite表面变得更疏松,且形成了以钴铁和钴铝双金属氧化物为主要成分的球状晶粒。H_2-TPR结果表明,相比于Fe/Al_2O_3/cordierite,1.5Co/Fe/Al_2O_3/cordierite有更好的低温还原性能。PyFTIR结果表明,Co的引入可使催化剂表面的Lewis酸明显增加,且生成了Brnsted酸。N2吸附-脱附表征结果表明,Co可增大催化剂的比表面积。

整体式Pd/ZSM-5/Cordierite催化剂的制备及其低浓度甲烷燃烧催化性能

以蜂窝状堇青石(Cordierite)为载体,采用聚乙烯醇纤维(PVA)溶液辅助涂覆法制备了整体式Pd/ZSM-5/Cordierite催化剂;利用XRD、N2物理吸附、SEM和XPS等手段对催化剂的结构和性质进行了表征。将该催化剂用于低浓度甲烷催化燃烧,研究了PVA溶液浓度、活性组分负载方式和Pd负载量等因素对Pd/ZSM-5/Cordierite催化剂活性涂层稳定性及低浓度甲烷燃烧催化性能的影响。结果表明,以质量分数为3%的PVA溶液制备的分子筛浆料进行涂层涂覆,所得到的整体式催化剂活性涂层具有良好的牢固度。以Pd/ZSM-5为涂层粉体、Pd整体负载量为1.12‰(质量分数,下同)时,所制备的(Pd/ZSM-5)/Cordierite催化剂具有优异的低浓度甲烷(体积分数为1%)燃烧催化性能,甲烷转化率为10%、50%和90%时的反应温度分别为271、337和385℃。此外,在不同温度下435h长周期测试实验中,该整体式(Pd/ZSM-5)/Cordierite催化剂表现出较高的抗热稳定性,表明其具有良好的低浓度甲烷燃烧处理应用前景。

In-situ Synthesis of ZSM-5 with Different Si/AlRatios on Honeycomb-shaped Cordierite and their Behavior on NO Decomposition

Zeolites ZSM-5 with different Si/Al ratios were in-situ synthesized on the surface ofhoneycomb-shaped cordierite support for the first time. Characterizations of XRD and SEM wereperformed and it has been proved that the zeolite ZSM-5 was grown on the surface of the cordieritehomogeneously. NO decomposition on the Cu exchanged ZSM-5/cordierite monolith catalysts wasalso studied. It was found that the monolith catalysts have a fine initial activity at 673K and GHSVof 10,000h-1. Such method should be a good way to make auto exhaust converter with monolithcatalyst for NOx removal.

Preparation of Cordierite Ceramic Using Mixtures of Ce^(4+)-Modified Amorphous Powder and Oxide Powders

The cordierite ceramic with a high strength and a low thermal expansion coefficient was prepared by using mixtures of Ce4 +-modified cordierite amorphous powder and oxide powders of MgO, Al2O3 and SiO2 as starting materials. The transformation procedure of the powders was analyzed by XRD method and the surface morphology of ceramics was examined by SEM method. The flexural strength was measured in a mechanical property testing machine using the Three-Point-Bending sample. Experimental results show that the ceramic added with 10%(mass fraction) of Ce4+-modified amorphous powder is composed ofα-cordierite and small amount of CeO2 particles, and has a porosity of 15% (volume fraction) and a flexural strength of 32.6 MPa when sintered at 1350℃for 3 h. It is suggested that this low-cost process is suitable for preparing the components such as supports of vehicle exhaust converters and diesel particulate trappers.

Preparation and Characterization of Carbon Nanotubes-Coated Cordierite for Catalyst Supports

The carbon nanotubes-coated cordierite （CNTs-cordierite） was fabricated by pyrolysis of ethine on cordierite with iron catalyst, which was penetrated into the cordierite substrate by vacuum impregnation. The cordierite substrate, carbon naontubes, and CNTs-cordierite were characterized by SEM, TEM/HREM, BET, and TGA. The results show that the carbon nanotubes were distributed uniformly on the surface of cordierite. A significant increase in BET surface area and pore volume was observed, and a suitable pore-size distribution was obtained. On the CNTs-cordierite, carbon nanotubes penetrated into the cordierite substrate, which led to a remarkable stability of the CNTs against ultrasound maltreatment. Growth time is an important factor for thermostability and texture of the sample. The mass increased but the purity decreased with the growth time, which caused the exothermic peak shift to low temperature, and the corresponding full width half maximum （FWHM） of the peak in DTG increased.

Influence of TiO_2 Mineralizer on the Crystalline Structure of Cordierite Synthesized from Aluminum Slag

By adding small amount of TiO2, aluminum slag could be used to synthesize cor- dierite. α-Al2O3, TiO2 and dehydrated talc could generate solid solution to accelerate the solid-state reaction to form cordierite. The experimental results show that the content of cordierite increases with the increase of TiO2 added. 3.0% of TiO2 is determined to be the best amount, because all crystalline substances are converted into cordierite at this content. Philips X’pert plus software analysis shows that when the content of TiO2 is from 0 to 1.0%, cordierite has the same hexagonal structure as the single crystal and the lattice parameters change slightly; when the content of TiO2 is from 1.0 to 2.0%, the cordierite still keeps hexagonal structure but the lattice parameters change greatly; when the content of TiO2 is from 2.0 to 3.5%, the cordierite is converted from hexagonal into rhombic and the lattice parameters change accordingly.

Synthesis of Refractory Cordierite from Calcined Bauxite, Talcum and Quartz

A cordierite was synthesized from calcined bauxite, talcum, and quartz. The properties and microstructure of the cordierite sintered samples were characterized by Archimedes＇ method, thermal dilatometry, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and so on. The experimental results showed that calcined bauxite could broaden the range of synthesizing temperature from 1300 ℃ to 1420 ℃ and get pure cordierite. The bulk density and linear thermal expansion coefficient of the sample synthesized at 1420 ℃ for 2 h were 1.97 g·cm^-3 and 2.1×10^-6 ℃^-1, respectively. The XRD analysis showed that the major crystalline phase was a-cordierite with almost no glassy matters, the SEM images illustrated a small vent hole and the size were 5 -100 μm, the well-grown hexagonal and granular cordierite grains had the sizes distributed among 0.1-8 ;xm, and providing high mechanical strength and lower linear thermal expansion coefficient.

Studies on the Structure and Properties of Cordierite Synthesized by Talc-Magnesite

Homogeneous cordierite has been synthesized at low cost by talc-magnesite and coal gangue as the main raw materials. The mechanism of synthesizing cordierite under such a composing system of raw materials, and the effect of temperature on the crystal cell parameters and microstructure and thermal expansion coefficient of cordierite crystal have been studied via testing methods of XRD, SEM, etc. The result shows that the homogeneous cordierite can be synthesized by the systematic composing materials of ＂talc-magnesite-coal gangue-talc＂ with heat pre-servation at 1350 ℃ for 1 h; as the keeping time is prolonged, Al^3＋ and Mg^2＋ in cordierite crystal are replaced by a few impurity ions such as Fe^3＋, Fe^2＋, etc., and the crystal cell parameters of cordierite present an increase trend; as the high-temperature heat preservation is prolonged, the content of glassy phase in the sample is increased, its density is improved, and its thermal expansion coefficient presents an increase trend.

Influence of Fe_2O_3 Impurity on the Crystalline Structure of Cordierite Synthesized from Waste Aluminum Slag

The influence of Fe2O3 impurity on the crystalline structure of cordierite synthesized from waste aluminum slag is discussed. XRD and SEM techniques were employed to characterize the crystalline structure and microstructure of each specimen. Philips X’pert plus software was used to determine the lattice parameters of each specimen. The results show that the Fe2O3 content of 0.8～1.6wt% is beneficial to the formation of cordierite, with the cordierite amount reaching 90wt%. So 0.8～1.6wt% is considered as the allowable Fe2O3 content in the specimens and 0.8wt% is determined to be the best after overall analysis. Plus software analysis shows that the cordierite in each specimen has the same symmetrical hexagonal structure as the single crystal, and the lattice parameters as well as the lattice dimensions change slightly.