Na_2O对微晶玻璃装饰板烧结和析晶的影响

研究了Na_2O含量对CaO-Al_2O_3-SiO_2系统微晶玻璃装饰板析晶温度、析晶相,烧结收缩及表面气泡的影响。确定了合适的Na_2O含量及烧结温度范围。     

晶核剂对镁铝硅微晶玻璃析晶行为的影响

在MgO-Al_2O_3-SiO_2系统玻璃中分别引入TiO_2、ZrO_2作为晶核剂,采用"两步法"热处理制备微晶玻璃,并研究晶核剂对其析晶行为的影响。实验结果表明,以TiO_2为晶核剂时,MAS玻璃析晶峰温度较低,析晶速率较慢,易于可控析晶,当热处理制度为770℃/4h+950℃/2h,微晶玻璃中析出MgTi_2O_5与MgAl_2O_4两种晶相,且微晶玻璃外观透明。以ZrO_2作为晶核剂时,MAS玻璃析晶峰温度升高,析晶速率增加,在830℃/4h+1 000℃/2h热处理后,析出镁铝硅酸盐及ZrO_2晶体,其中镁铝硅酸盐与β-石英结构类似。     

热分析技术在玻璃结晶动力分析上的应用

本文推导了热分析技术(DTA、DSC)在玻璃结晶动力学分析上应用的理论计算公式;应用差热分析(DTA)测定并计算了 MgO-Al_2O_3-SiO_2-TiO_2系_1统玻璃中镁铝钛酸盐晶核的形成速度随温度的变化曲线,发现在低于该系统玻璃转变点的温度下晶核的形成业已开始,部分样品中晶核形成速度的极大值甚至发现在低于玻璃转变点的温度上;本文还给出了表面晶化占优势的玻璃中结晶成长活化能的计算公式,分析并计算了 MgO-Al_2O_3-SiO_2系统玻璃中β-石英固溶体的结晶成长活化能。     

烧结法制MgO-SiO2-Al2O3-B2O3-KF玻璃陶瓷成分设计优化及显微析晶研究

通过烧结与水淬相结合的方法制备并系统探讨了MgO- SiO2-Al2O3-B2O3-KF玻璃陶瓷的显微析晶.研究表明:MgO-SiO2-Al2O3-B2O3-KF玻璃陶瓷的烧结收缩率与玻璃化及组分的析晶程度相关;析晶程度愈高,烧结坯愈致密;试样中成分配比愈接近云母晶体成分的原子比,玻璃陶瓷的显微析晶程度愈高;在烧结温度为1 000℃时,即开始出现析晶,到1 050℃时,析晶程度达到最高,继续提高烧结温度,显微析晶又发生重熔.     

烧结法制MgO-SiO_2-Al_2O_3-B_2O_3-KF玻璃陶瓷成分设计优化及显微析晶研究

通过烧结与水淬相结合的方法制备并系统探讨了MgO-SiO2-Al2O3-B2O3-KF玻璃陶瓷的显微析晶.研究表明：MgO-SiO2-Al2O3-B2O3-KF玻璃陶瓷的烧结收缩率与玻璃化及组分的析晶程度相关;析晶程度愈高,烧结坯愈致密;试样中成分配比愈接近云母晶体成分的原子比,玻璃陶瓷的显微析晶程度愈高;在烧结温度为1 000℃时,即开始出现析晶,到1 050℃时,析晶程度达到最高,继续提高烧结温度,显微析晶又发生重熔.     

BaO-Ga2O3-GeO2玻璃的析晶机理研究

钡镓锗玻璃是一种性能优异的中红外透过材料,而较差的机械性能严重制约了其应用。研究了钡镓锗玻璃的析晶动力学及其微晶化行为,阐明了析晶机理,为制备透明钡镓锗微晶玻璃提供理论指导。采用非等温方法研究了钡镓锗玻璃的析晶动力学,利用Kissinger模型,计算出析晶活化能Ec,两个析晶峰对应的Ec1=318kJ/mol和Ec2=515kJ/mol。通过Augis-Bennett方程获得了两个析晶峰对应的析晶指数,n-≈3。当低于1 187K(Tc2)进行晶化处理时,钡镓锗微晶玻璃中仅析出ZrO2晶体;随着晶化温度的升高,玻璃的热能持续增大,Ge2Al6O13晶体开始从母体玻璃中孕育并长大。     

SrO-Al2O3-SiO2系统微晶玻璃的晶化行为及性能

通过改变玻璃成分,在不同的热处理制度下制备SrO-Al2O3-SiO2系统微晶玻璃,用DTA、XRD、SEM等手段对该系统微晶玻璃材料的析晶过程进行了研究。在此基础上,讨论了晶化行为对微晶玻璃的热学及力学性能的影响。结果表明:材料的热学性能及力学性能与玻璃成分及热处理制度密切相关。可以找到某一确定组分的基础玻璃,经过较低的核化温度与较高晶化温度热处理后,能够得到力学性能优良、热学性能较好的微晶玻璃材料。     

CaO—Al_2O_3—SiO_2系统玻璃分相对表面析晶成核影响的差热分析研究

本文利用差热分析(DTA)研究了 CaO—Al_2O_3-SiO_2系统不同温度分相热处理以及未分相玻璃中α—方石英和β—硅灰石的析出情况,发现分相预处理使析晶放热峰开始温度有所下降,下降幅度越大对应分相的(富 SiO_2)液滴相数目越多。分析表明,分相对于表面析晶成核也具有促进作用。     

TiO2和Cr2O3作晶核剂制取粉煤灰微晶玻璃晶化行为的研究

研究了以TiO2和Cr2O3为晶核剂制取粉煤灰微晶玻璃的晶化行为,运用DTA、XRD、SEM等测试方法,观察了制品中的晶相种类、含量和微晶体发育形貌,分析了基础玻璃的化学组成、热处理方法和晶核剂对晶化行为的影响.研究表明:利用粉煤灰可以生产透辉石为主晶相的微晶玻璃,粉煤灰掺量可达40%以上.晶核剂种类和基础玻璃的化学组成对析晶行为和晶相种类有重要影响,熔制工艺和热处理方法也会影响析晶行为,本研究的玻璃基础组成有利于透辉石晶体的生成.     

热处理制度对Li2O—Al2O3—SiO2系统玻璃析晶及热膨胀系数的影响

采用传统熔融冷却法获得了以P2O5为成核剂的Li2O-Al2O3-SiO2系统基础玻璃，通过差热分析确定了使该玻璃微晶化的热处理条件，并获得了不同热处理温度下Li2O-Al2O3-SiO2系统低膨胀微晶玻璃；利用X射线衍射分析和扫描电子显微镜对晶化试样的物相和微观结构进行了研究，讨论了热处理制度对玻璃的析晶及热膨胀系数的影响，研究结果表明：以P2O5为成核剂，采用不同热处理制度能获得Li2-Al2O3-SiO2系统低膨胀微晶玻璃；在析晶初始温度下进行热处理，析出β-石英晶体，但晶体生长缓慢，结晶程度低；提高晶化温度，析出β-锂辉石晶体且晶体生长迅速。     

结晶法纯化2′-脱氧腺苷的工艺研究

2′-脱氧腺苷是抗肿瘤类药物的重要中间体,本文采用结晶法分离纯化生物转化液中的2′-脱氧腺苷,探讨了除杂质碱基、生物转化液浓缩倍数、2′-脱氧腺苷的结晶及重结晶工艺条件。结果表明,除杂质碱基的适宜实验条件为pH 7.0,时间24h;原液经浓缩至有效物质量浓度为50.0g/L;2′-脱氧腺苷粗品的结晶pH为10.0,时间6h,以体积分数20%的乙醇为溶剂进行重结晶,纯品总收率达62%,利用高效液相色谱法检测2′-脱氧腺苷,纯度99%。     

丙烯酸等离子体改性纳米TiO2/PET复合体非等温结晶动力学

为提高纳米颗粒在聚合物中的分散性,使用丙烯酸(AA)等离子体聚合技术,在TiO2纳米粉体表面包覆均匀的有机聚合物薄膜.将AA等离子体改性纳米TiO2分散在乙二醇溶液中,与对苯二甲酸聚和获得了包含丙烯酸等离子体改性纳米TiO2的PET复合体.使用DSC法研究了AA等离子体表面改性纳米TiO2粉体对PET复合体结晶性能的影...     

Solidification and crystallization properties of CaO-SiO2-Na2O based mold fluxes

Crystallization properties play an important role in keeping a smooth running of continuous casting process and high sur-face quality of cast strands. To reduce fluorine pollution in slag, a new type of CaO-SiO2-Na2O (CSN) based mold flux was studied. The solidification and crystallization properties, including crystallization temperature, crystallization ratio and solidification minera-graphy, were measured, which were compared with the CaO-SiO2-CaF2 (GF) mold flux. The results show that the crystallization performance is equal to the high fluoride mold powder and CSN can be used for peritectic steel grades sensitive to longitudinal cracking in continuous casting.     

Influence of ZrO_2 on sintering and crystallization of CaO-Al_2O_3-SiO_2 glass-ceramics

1INTRODUCTION Nowadays,glassresearchersandarchitecture designersbecomeinterestedinthesinteringglass ceramics,anewlyappearingmaterialforarchitec turaldecoration[13].Comparedwithnaturalstone materials,sinteringglass ceramicsdecoratedmate rialshavethefollowingadvantages:densestruc tureandhighstrength.Itsbasicglasscomponents belongtoCaO Al2O3SiO2system.Becausenonu cleationagentisrequired,thissystemisattributed tothesuperficialcrystallizationmechanismofglass[4].Theproductionprocessofsinteri…     

二氧化钛包覆对钙镁硅系陶瓷纤维晶化行为的影响

采用液相沉积法在钙镁硅系陶瓷纤维表面制备一层二氧化钛包覆层,通过FESEM、DTA、XRD等测试手段对包覆前后陶瓷纤维的晶化行为进行研究。结果表明,包覆处理使陶瓷纤维的晶化温度从912．5℃提高到936．5℃,析晶峰趋于宽化,陶瓷纤维析晶呈降低趋势;二氧化钛表面包覆不能改变陶瓷纤维中析出的钙（镁）硅酸盐晶相种类,但可在一定程度上抑制晶相的析出。     

亚稳态Bi2SiO5晶体的制备及析晶热力学分析

采用熔体冷却法制备了亚稳态Bi2SiO5硅酸铋晶体,利用XRD、SEM等表征分析了所制备Bi2SiO5多晶的晶型及形貌特征.通过系统在相平衡温度时的可逆相变过程,计算了析晶过程的ΔH、ΔS和ΔG.实验结果表明:组成中当摩尔比Bi2O3/SiO2为1∶1时,所生成的Bi2SiO5晶体在2h保温时间后仍没有发生晶型转变.所制备的单相Bi2SiO5晶粒呈现层状生长,且层与层之间呈现紧密生长.热力学分析表明:当温度T=T0-ΔT=973.15K时,ΔG=-7.478KJ<0,说明从基础熔体中析出Bi2SiO5的过程是自发进行的;同时,熔体中的分相有利于Bi2SiO5晶体的析出.     

Effect of crystallization of CaO—P2O5—SiO2—MgO—F^— glass—ceramics on its mechanical properties

The microstructure of CaO-P2O5-SiO2-MgO-F glass-ceramics during crystallization were investigated and the crystallized phases were identified with DTA(Differential Thermal Analysis),SEM(Scanning Electron Microscope) and XRD(X-ray Diffraction) techniques,The mechanical properties such as bending strength and fracture toughness,as well as their changes with advancing crystallization were determined.The results show that the changes of the mechanical properties are correlated with the microstructures,The sample heated up to 810℃ and soaked for 4h has smaller crystalline size and less volum fraction of fluorophlogopite,so it has higher bending strength (about 190MPa),and higher crack toughness(about 2.63 MPa.m^1/2).     

Experimental Crystallization of Synthetic V-bearing Steelmaking Slag with Al2O3 Doped

The phenomenon of crystallization was implemented in the synthetic V-bearing steelwork slag based on the composition of factory slag from the Masted Co., and the possibility of undercooling as a technique to precipitate V-concentration phase was demonstrated. The effect of 20wt% Al2O3 additive introduced into the slag on intensifing the precipitation was also investigated. X-ray diffraction analysis ( XRD ) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) were used to investigate the slag after heat treatment. It is demonstrated that gehleaite and grossite are the major crystalline phases. Whitlockite with a high content of V2O5 ( called V-concentration phase hereafter) nucleates homogeneously and hetergeneously and grows with decreasing undercooling. At 1548 K, the crystals of V-concentration phase grow up as the duration of time, with a medium grain size of 25μm at 300 rain holding time.     

Effects of heat treatment temperature on crystallization and thermal expansion coefficient of Li_2O-Al_2O_3-SiO_2

The basic glass of Li2 O-Al2 O3-SiO2 system using P2O5 as nucleator was prepared by means of conventional melt quenching technology, and the heat-treatment process was determined by using differential thermal analysis. The crystalline phases and the microstructure of the glass-ceramics were investigated by using X-ray diffraction and scanning electron microscopy. The results show that the glass based on Li2 O-Al2 O3-SiO2 oxides using P2 O5 as nucleator can be prepared at lower melt temperature of 1 450 ℃ and the glass-ceramics with lower thermal expansion coefficient of 21.6 × 10-7 ℃ 1 can also be obtained at 750 ℃. The glass-ceramics contain a few crystal phases in which the main crystal phase is β-quartz solid solution and the second crystal phase is β-spodumene solid solution. When the heat treatment temperature is not higher than 650 ℃, the transparent glass-ceramics containing β-quartzsolid solution can be prepared. β-quartz solid solution changes into β-spodumene solid solution at about 750 ℃. And the appearance of the glass-ceramics changes from translucent, part opaque to complete opaque with increasing temperature.