水玻璃滤渣/TiO2复合颜料的制备和性能

以生产水玻璃时的滤渣和锐钛型钛白粉（TiO₂）为原料,通过液相机械力化学方法制备滤渣/TiO₂复合粉体,并研究制备工艺条件对复合粉体遮盖力和吸油值的影响。复合颜料制备的最佳实验条件确定为滤渣湿磨时间15 min,pH=8,二者复合时间30 min,复合研磨转速1000 r/min,球料比5:1。当钛白添加量为50%时,复合粉体的遮盖力、吸油值和白度分别为16.06g/m²（该值达到纯钛白的86.92%）、33.74 g/100 g和90.1%。该复合颜料具有类似钛白粉作为颜料的性能,因此可望部分代替纯钛白在涂料和油漆中的应用。     

机械力化学合成CaTiO_3纳米晶的研究

研究了采用高能球磨机混合粉磨CaO ,TiO2 的机械力化学变化过程 .发现在一定操作参数 (行星磨公转转速 30 0r/min ,自转 2 0 0r/min)条件下 ,粉磨初期 ( 2h)为无定形形成期 ,混合物颗粒粒度减小 ,晶格畸变 ,转变为无定形 ,并形成CaTiO3 晶核 ;粉磨中期 ( 2～ 10h)为晶粒生长期 ,CaTiO3 晶粒长大 ;粉磨后期 ( 10h以后 )为动态平衡期 ,晶粒生长与粉磨引起的晶粒减小处于动态平衡 ,锐钛矿型TiO2 能够转变为金红石型TiO2 ,具有较好的反应活性 .XRD ,TEM ,FT -IR研究表明 :混合粉磨CaO ,TiO2 可机械力化学合成CaTiO3 纳米晶体 ,晶粒尺寸为 2 0～ 30nm     

机械力化学合成CaTiO3纳米晶的研究

研究了采用高能球磨机混合粉磨CaO,TiO2的机械力化学变化过程，发现在一定操作参数（行星磨公转转速300r/min，自转200r/min)条件下，粉磨初期（2h)为无定形形成期，混合物颗粒粒度减小，晶格畸变，转变为无定形，并形成CaTiO3晶核；粉磨中期（2－10h)为晶粒生长期，CaTiO3晶粒长大；粉磨后期（10h以后）为动态平衡期，晶粒生长与粉磨引起的晶粒减小处于动态平衡，锐钛矿型TiO2能够转变为金红石型TiO2，具有较好的反应活性，XRD，TEM，FT－IR研究表明：混合粉磨CaO,TiO2可机械力化学合成CaTiO3纳米晶体，晶粒尺寸为20－30nm。     

白炭黑/TiO_2复合颜料的制备及性能研究

亚熔盐法分解钾长石制得的溶液和金红石型钛白粉(TiO_2)为原料,利用硫酸沉淀法制备的白炭黑与钛白粉通过原位复合法制备SiO_2/TiO_2复合颜料,探讨各种工艺条件对制备复合粉体的影响。当TiO_2百分比为60%、搅拌转速300 r/min、反应温度85℃、滴加速度1 m L/min时,所制得的粉体性能最好。复合粉体遮盖力值为22.5 g/m~2,吸油值为67.0 g/100 g,白度为97.0%。     

机械力化学法制备金红石型TiO_2纳米晶体

研究了高能球磨机粉磨锐钛矿型TiO2 的机械力化学变化过程。发现在一定操作参数 (行星磨公转转速30 0r/min、自转 2 0 0r/min)条件下 ,粉磨初期 (5h)为无定形形成期 ,颗粒粒度减小 ,晶格畸变 ,转变为无定形 ,并形成金红石型TiO2 晶核 ;粉磨中期 (5～ 15h)为晶粒长大期 ,金红石型TiO2 晶粒长大 ;粉磨后期 (15h以后 )为动态平衡期 ,晶粒长大与粉磨引起的晶粒减小处于动态平衡 ;XRD、TEM、FT IR研究表明 :行星磨粉磨锐钛矿型TiO2 可使晶型转变为金红石型TiO2 ,晶粒尺寸为 14 .1nm ,颗粒尺寸为 2 0～ 4 0nm。     

PbO和TiO2混合粉磨的机械力化学反应和化学变化

本实验首次发现,在振动磨中混合粉磨PbO和TiO_2化学配比的粉体,能合成PbTiO_2化合物。这种机械力化学反应是以表面能为扩散的主要推动力,使PbO扩散至TiO_2颗粒内并在TiO_2颗粒表面形成PbTiO_2,实验证明在PbTiO_2形成以前,PbO及TiO_2二者受机械力的作用,晶型均已发生了变化,锐钛矿转变为金红石,铅黄转变为密陀僧。由铅黄向密陀僧转变的过程中,当密陀僧的容积成分达到75％时即达平衡状态,然而这种机械化学平衡是亚稳的,继续粉磨超过75h后,平衡即遭破坏,密陀僧又重新转变为铅黄。     

机械合金化制备Ti_3AlC_2导电陶瓷

以Ti、Al、C单质粉体为实验原料,掺杂适量的Si元素,采用高能球磨机制备Ti_3AlC_2导电陶瓷粉体,研究球磨转速和原料配比对合成Ti_3AlC_2导电陶瓷的影响。研究表明:在球磨转速为550 r/min,球料比5∶1和球磨时间3 h的球磨工艺下,可成功制备出Ti_3AlC_2含量为92.4 wt%的混合粉体,通过增加适量Al元素可以促进Ti_3AlC_2的合成;原料粉体按3Ti/1Al/0.1Si/1.8C的化学计量比进行机械合金化,所得粉体中Ti_3AlC_2的含量高达95.1 wt%,并且Si原子替代部分Al原子而形成Ti_3Al(Si)C_2固溶体。     

正交优化纳米碳化硅粉的制备工艺参数

实验选用无水乙醇为液相介质,聚乙烯吡咯烷酮(PVP)作为修饰剂,采用高能球磨法,成功制备出分散良好的纳米碳化硅粉.通过正交实验,分析了球磨时间、碳化硅颗粒的加入量、碳化硅与修饰剂的质量比和转速4个工艺参数对纳米碳化硅粉的产率、产量和粉体的特征粒径D50的影响.结果表明在本实验条件下,制备纳米碳化硅粉的最佳工艺参数为:时间15 h,碳化硅的加入量30 g,碳化硅与修饰剂的质量比2∶1,转速300 r/min.     

凹凸棒石黏土超细粉碎及表面改性一体化研究

以硬脂酸作为改性剂、六偏磷酸钠作为助磨剂,采用搅拌球磨机对凹凸棒石黏土进行超细粉碎与表面改性一体化研究.探讨了搅拌转速、改性时间、球料比、改性剂用量及助磨剂用量对超细粉碎及表面改性效果的影响,得到优化工艺条件:搅拌转速为750 r/min,改性时间为40 min,球料质量比为4∶1,改性剂硬脂酸的加入质量为凹凸棒石黏土质量的4%,助磨剂六偏磷酸钠的加入质量为凹凸棒石黏土质量的0.5%.在优化工艺条件下,改性凹凸棒石黏土粉体的活化指数可达0.97,吸油值为0.34 mL/g,产品粉体中位径d50为0.64 μm.通过对改性前后粉体的红外光谱比较,说明了凹凸棒石黏土机械力化学超细粉碎与表面改性的机理,以及其可行性.     

Mg2Si0.4Sn0.6超微粉体的制备及机理研究

以高纯Mg,Si,Sn粉为原料,采用固相反应合成方法制备得到单相Mg2Si04Sn0.6固溶体粉体,再采用机械球磨的方法对粉体进行细化.利用扫描电子显微镜和X射线衍射仪对不同工艺条件下球磨后的粉体进行形貌及物相分析,研究Mg2Si0.4Sn0.6固溶体球磨过程中颗粒尺寸及组分的变化,认为球磨转速为370 r/min,20:1的球料比,以正己烷为球磨介质,选用WC材质的球磨罐和硬质球,球磨时间30 h,可以得到颗粒尺寸为4～5 μm左右的单相Mg2Si0.4Sn0.6粉体.随着球磨时间的延长,氧化现象加剧,固溶体出现分相,出现MgO和Sn的衍射峰.     

Low-Temperature Densification of Lead Zirconate-Titanate with Vanadium Pentoxide Additive

Additions of 0.1 to 6.0 wt% V₂O, to lead zirconate titanate (PZT) ceramics promoted rapid densification below 975°C, thereby eliminating the need for PbO atmosphere control The base PZT, Pb(Zr_0.53Ti_0.47)O₃, was prepared by coprecipitation from mixed oxides and butoxides. The V₂O₅ was incorporated as a batch addition during the PZT coprecipitation process, as mill additions to the calcined precipitated powder, and to a commercial PZT powder. Densification rates were enhanced by the addition of V₂O₅ (>98% of theoretical density was obtained in ∼15 min at 960°C by the addition of 0.1 to 1.0 wt% V₂O₅, compared to 4 h at 1280°C for the base PZT). Dielectric properties and piezoelectric coefficients varied slightly within the optimum range of 0.25 to 1.0 wt% V₂O₅ addition but were at least comparable to the base PZT. Indications are that V₂O₅ becomes incorporated into the surface layers of the oxide powders during mixing (or in the coprecipitation process) and that the accelerated densification is due to enhanced surface activation and liquid-phase sintering.     

Compositional Change and Compositional Fluctuation in Pb(Zr,Ti)O3 Containing Excess PbO

Compositional changes which take place during sintering of Pb(Zr,Ti)O₃ (PZT) containing excess PbO were studied. The excess PbO forms a liquid phase during the sintering process. The solubility of the TiO₂ component of PZT in liquid PbO is higher than that of ZrO₂ component. Thus, if an excess PbO exists, the composition of PZT phase shifts towards the Ti-lean side. A change in the lattice constants due to this compositional change was actually observed. Coexistence of tetragonal and rhombohedral phases, due to a compositional fluctuation caused by excess PbO, was observed near the morphotropic phase boundary. When PZT containing excess PbO was sintered at 1100°C, a compositional fluctuation occurred early in the process and then decreased with sintering time. These phenomena have agreed with a result of computer simulation of dissolution of TiO₂ component in PZT phase into liquid PbO phase.     

Homogeneity and Properties of Lead Zirconate Titanate Prepared by a Combination of Thermal Spray Decomposition Method with Solid-Phase Reaction

A solution containing titanium and zirconium ions was spray decomposed. The product thus obtained was mixed with PbO powder and fired at high temperatures to obtain Pb(Zr,Ti)O₃ (PZT). A phase of PZT began to form at a very low temperature (450°C). This formation reaction was complete at about 650°C. Reactivity of the spray-decomposed product with lead titanate powder was high. For PZT prepared by this process with a firing condition of 1100°C for 1 h, the compositional fluctuation was estimated from the width of the X-ray diffraction peaks. Fluctuations were about 3 at.%. This value agreed with that estimated from the range of the tetragonal-rhombohedral coexistence region near the morphotropic phase boundary. The peak of the dielectric constant near the Curie temperature was sharp and very high (ε∼12000).     

Preparation of Pb(Zr,Ti)03 Through the Use of Cupferron

An organic chelation reagent, cupferron, was used to coprecipitate Ti⁴⁺ andZr⁴⁺. After the materials were fired, they were mixed with PbO powder and fired again at high temperatures to obtain Pb(Zr,Ti)0₃ (PZT). It was confirmed that this method is useful for the preparation of homogeneous PZT having no compositional fluctuations. No coexistence range of the tetragonal and rhombohedral phases was observed in the PZT compositions near the morphotropic phase boundary.     

Homogenization of Pb(Zr,Ti)O3 by use of molten phase

A method for a homogenization of Pb(Zr,Ti)O₃(PZT) was developed. Powders of PbO and TiO₂ were added into a powder of PZT prepared by the ordinary method. This mixture was heated above the melting point of PbO for several periods of time. PbO and TiO₂ formed a molten phase. After the heat treatment, it was quenched. PbO phase in the sample was removed by dissolving with acetic acid. The chemical homogeneity of the PZT phase was figured out using βcosθ vs. sinθ plots. This analysis showed that the chemical homogeneity in the PZT phase was improved very quickly.     

Sintering of PZT Ceramics: I, Atmosphere Control

Methods of PbO atmosphere control during the sintering of PZT ceramics are briefly reviewed. The problem of atmosphere control of PZT compositions containing a PbO excess (PbO/(Zr,Ti)O₂>1) is discussed. Weight-loss experiments were performed to compare with behavior predicted by reference to the PbO-rich part of the ternary PbO-ZrO₂-TiO₂ phase diagram. The results indicated that the PbO activity of a PZT composition is a function of the excess PbO content, contrary to earlier reports. Experimental procedures were established in order to control the PbO content within satisfactory limits. The effects of various packing powders on the PbO content of sintered PZT compacts were evaluated.     

Reaction Mechanisms in the Formation of PZT Solid Solutions

The solid-state reactions occurring in the system PbO-TiO₂-ZrO₂ were investigated using constant heating rates up to 1000°C. DTA, dilatometric length changes, and XRD analysis were used for characterization. PbO and TiO₂ reacted exothermally to form the product PbTiO₃ with a large volume expansion between 450° and 600°C. Formation of PbZrO₃ from PbO and ZrO₂ occurred endothermally with a large volume expansion between 700° and 800°C. The expansion was due to reaction topology, differential molar volumes of products and reactants, and the pellet microstructure. In the formation of PZT from ternary powder mixtures, PT formed between 450° and 600°C, followed by PZT formation at >700°C with no measurable amounts of PbZrO₃ formed as determined by XRD analysis. The analysis of the mechanisms indicates that the overall kinetics of homogeneous PZT solid-solution formation are determined by either the ionic transport within the perovskite lattice or the phase-boundary reactions leading to perovskite formation and not by the diffusion of Ti across PbO, which is relatively rapid.     

Microwave Effects in Lead Zirconium Titanate Synthesis: Enhanced Kinetics and Changed Mechanisms

A novel, simple, and fast solid-state procedure has been demonstrated for the synthesis of Pb(Zr,Ti)O₃ (PZT), using microwave radiation. The process consists of starting with the respective oxides mixed in the required proportions and exposing the charge to the microwaves. By making one or more of the constituent oxides slightly nonstoichiometric, enormous enhancement in reaction rates has been achieved, and single-phase PZT can be synthesized at temperatures as low as 600°C. Moreover, it has been shown that the combined use of nonstoichiometric precursors and microwave irradiation leads to different reaction pathways for the formation of PZT. Further, the microwave method diminishes PbO loss.