纳米氧化锆的制备和表征

纳米氧化锆被誉为是一种比较理想的多功能催化剂。主要进行纳米氧化锆的合成技术研究,为下一步系统开展纳米氧化锆的性能和应用研究奠定技术基础。基于溶胶-凝胶和水热合成机理,采用氯氧化锆为锆源,非离子表面活性剂脂肪酸甲基乙氧基化物为模板剂合成纳米氧化锆前驱体,重点考察合成温度和干燥煅烧温度对纳米氧化锆孔隙结构的影响,最佳工艺下制备的纳米氧化锆,比表面积可达400m~2/g以上。     

掺杂中孔氧化锆的合成进展

介绍中孔氧化锆的合成机理及国内外研究现状,讨论了影响合成中孔氧化锆的一些因素,特别是对掺杂中孔氧化锆合成的影响。概述了掺杂中孔氧化锆的应用并展望了其发展方向。     

粉煤灰合成沸石的新发展及应用

阐述了利用粉煤灰合成沸石的基本机理，并介绍了传统水热合成法、碱熔融-水热合成法、盐-热（熔-盐）合成法等粉煤灰合成沸石的方法和其最新发展，以及利用传统的水热合成法将粉煤灰合成沸石的工业化应用情况，对粉煤灰合成沸石的应用途径和前景进行了探讨和展望。     

水热法制备氧化锆/碳纳米管复合材料的研究

研究了氧化锆/碳纳米管复合材料制备的工艺条件。通过XRD、BET、TEM和Zeta电位的测试结果分析水热温度、水热时间、表面活性剂、pH等因素对产物的影响,确定了较佳的工艺条件：水热温度为180 ℃、水热时间为11 h、pH=9.5。通过TEM和Zeta电位分析可知,加入表面活性剂十六烷基三甲基溴化铵（CTBA）时,碳纳米管表面与氢氧化锆胶体带异种电荷,相互吸附,氧化锆颗粒能均匀覆盖于碳材料上,效果较好。     

水热合成法在陶瓷工艺中的应用

本文着重介绍水热合成法在陶瓷工艺中的应用,包括水热合成制粉、烧结,制备新的晶体及磁性材料。     

低压条件下纳米氧化锆的水热结晶合成

本文采用水热结晶法研究了在较低压力下纳米氧化锆粉体的制备和性质。制备出了结晶完整、分散性良好、粒度约为十几纳米的超细氧化锆粉体。用XRD、TEM等测试方法对晶相组成、晶粒粒度、晶貌特征等与水热结晶温度及保温时间的关系进行了研究。并对单斜相氧化锆和四方相氧化锆的晶粒形成过程进行了讨论。     

低压条件下纳米氧化锆的水热结晶合成

本文采用水热结晶法研究了在较低压力下纳米氧化锆粉体的制备的性质。制备出了结晶完整、分散性良好、粒度约为十几纳米的超细氧化锆粉体。淫ＸＲＤ、ＴＥＭ等测试方法对晶相组成、晶貌特征等与水热结晶温度及保温时间的关系进行了研究。并对单斜相氧化锆和四方相氧化锆的晶粒形成过程进行了讨论。     

水热改性SO_4~(2-)/ZrO_2催化剂的制备及其对酯化反应的催化性能

通过水热改性氢氧化锆制备了SO42-/ZrO2固体酸催化剂。以冰乙酸和正丁醇的酯化反应为探针反应,确定了固体超强酸的最佳制备条件。分别考察了浸渍硫酸浓度、硫酸浸渍时间和焙烧温度等对催化活性的影响。并以水热改性和未经水热改性氢氧化锆制备SO42-/ZrO2固体超强酸做了对比实验,采用XRD、BET对催化剂进行了表征。实验结果表明:水热改性氢氧化锆制备SO42-/ZrO2固体酸催化剂的最佳条件是:浸渍硫酸浓度为0.5mol/L,浸渍时间是120 m in,焙烧温度500℃。乙酸正丁酯较佳的合成工艺条件是:反应温度105~110℃,反应时间2 h,n(正丁醇)∶n(冰乙酸)=2∶1,催化剂用量占反应投料总质量的0.27%,冰乙酸的酯化率达99.1%。催化剂重复使用4次后催化活性降低5%。     

复合分子筛的合成与应用研究进展

综述了复合分子筛的合成和应用研究进展,介绍了水热合成法等几种方法,分析比较了各种方法的特点。     

沸石分子筛膜的合成与应用

综述了沸石分子筛膜的合成方法和应用。介绍了制备沸石分子筛膜最常州的水热合成法，包括晶种法和原位合成法，以及沸石分子筛膜在气体分离、渗透汽化和膜反应器中的应用。重点阐述了被除数广泛研究的MFI型分子筛膜的制备方法与应用。详细讨沦了多孔支撑体、晶体、水热合成条件以及合成液组成等因素对晶体生长和膜的形态以及对MFI型分子筛膜分离性能的影响，     

水热法制备ZrO2及其复合粉体的研究进展

随着电子和新材料工业的发展,纳米氧化锆及其复合粉体的应用越来越广泛.与纳米ZrO2传统湿化学制备方法相比,显示了水热法制备的优点.水热法包括水热晶化、水热沉淀、水热氧化和微波水热等.论述了水热法制备纳米ZrO2及其复合粉体的各种方法及研究进展,指出了水热法发展方向及所需解决的问题.     

The Tetragonal-Monoclinic Transformation in Zirconia: Lessons Learned and Future Trends

Zirconia ceramics have found broad applications in a variety of energy and biomedical applications because of their unusual combination of strength, fracture toughness, ionic conductivity, and low thermal conductivity. These attractive characteristics are largely associated with the stabilization of the tetragonal and cubic phases through alloying with aliovalent ions. The large concentration of vacancies introduced to charge compensate of the aliovalent alloying is responsible for both the exceptionally high ionic conductivity and the unusually low, and temperature independent, thermal conductivity. The high fracture toughness exhibited by many of zirconia ceramics is attributed to the constraint of the tetragonal-to-monoclinic phase transformation and its release during crack propagation. In other zirconia ceramics containing the tetragonal phase, the high fracture toughness is associated with ferroelastic domain switching. However, many of these attractive features of zirconia, especially fracture toughness and strength, are compromised after prolonged exposure to water vapor at intermediate temperatures (∼30°–300°C) in a process referred to as low-temperature degradation (LTD), and initially identified over two decades ago. This is particularly so for zirconia in biomedical applications, such as hip implants and dental restorations. Less well substantiated is the possibility that the same process can also occur in zirconia used in other applications, for instance, zirconia thermal barrier coatings after long exposure at high temperature. Based on experience with the failure of zirconia femoral heads, as well as studies of LTD, it is shown that many of the problems of LTD can be mitigated by the appropriate choice of alloying and/or process control.     

Hydrothermal Zirconia Powders: A Bibliography

This paper provides references for zirconia powder processing, especially hydrothermal processing and for the properties of hydrothermal zirconia.     

铝掺杂纳米氧化锆的合成与改性研究

氧化锆是一种具有特殊作用的氧化物并受到越来越多的关注。作者利用阳离子表面活性剂(CTAB)的辅助途径,通过前期的制备工艺成功实现了金属铝对纳米氧化锆的掺杂改性。借助XRD,TEM,EDS,Uv-vis以及N2吸附-脱附等方法对样品进行了表征分析;研究表明:金属铝离子能成功地进入氧化锆当中,掺杂改性后的氧化锆相对未掺杂的氧化锆有明显的蓝移,热稳定性显著提高,并且有一定的微孔结构。     

球形四方相氧化锆的水热法合成与表征

以氧氯化锆为原料，尿素为矿化剂，氧化钇为稳定剂，水和乙醇为反应溶剂，结合一步水热的方法，在不添加表面活性剂以及不经过煅烧的前提下，通过改变水热温度、水热时间、醇水比以及氧化钇添加量等条件探究了球形四方相氧化锆的形成机理，制备了结晶性好、粒度分布均匀以及球形度高的四方相氧化锆粉体。     

The Effect of Zirconia Reinforcing Agents on the Microstructure and Mechanical Properties of Hydroxyapatite-Based Nanocomposites

A hydrothermally treated zirconia colloid was introduced during the precipitation of hydroxyapatite (HAP) to achieve an HAP–zirconia nanocomposite. High dispersion of zirconia was achieved at zirconia loadings below 8 wt%. Vickers hardness was optimized with a 1.5 wt% loading of zirconia. A low loading (1.5 wt%) of tetragonal zirconia was able to increase the bending strength of nanocrystalline HAP from 183 to 243 MPa. This HAP–zirconia nanocomposite was sintered to full density by 1000°C under an applied load of 50 MPa. The average grain sizes of HAP and zirconia were maintained at ≤100 nm. With the high strength and low loading of secondary phase, these HAP-based nanocomposites should be attractive for orthopedic and dental implant applications.     

Subeutectoid Degradation of Yttria-Stabilized Tetragonal Zirconia Polycrystal and Ceria-Doped Yttria-Stabilized Tetragonal Zirconia Polycrystal Ceramics

Yttria-doped tetragonal zirconia containing 2 and 3 mol% Y₂O₃ (Y-TZP), and CeO₂-doped Y-TZP containing 0 to 12 mol% CeO₂ were sintered at 1350°C in a tetragonal single-phase field for 2 h in air, and the degradation behavior at low temperature in air and in hot water was observed. X-ray photoelectron spectroscopy studies on the surface of hydrothermally treated samples show evidence for the formation of a YO(OH) species, along with the simultaneous formation of purely tetragonal zirconia nuclei that retain their coherence in the Y-TZP matrix. Above a critical size, the tetragonal nuclei spontaneously transform to a monoclinic structure, giving rise to macro- and microcracking. The strong tetragonal grains degrade to produce a spalling phenomenon that facilitates further degradation. Y-TZP ceramics alloyed with adequate amounts of CeO₂ show no tetragonal-to-monoclinic transformation after hydrothermal treatment.     

Zirconia ceramics in metal-free implant dentistry

Because of their outstanding mechanical properties, chemical stability, and biocompatibility, 3-mol % yttria-stabilised tetragonal zirconia polycrystals (3Y-TZP), known as zirconia ceramics in dentistry, are an important choice for various types of prosthesis. In addition to extensive use for crown and bridge construction, considerable interest has been generated for applications in implant dentistry, including full-contour zirconia crowns as supra-constructions, zirconia abutments, and novel zirconia implants. However, their use among dentist and researchers is controversial, especially compared with the well-established implants made of titanium alloys. As a latecomer, the merits and limitations of 3Y-TZP are awaiting careful investigation. Design, manufacturing, and clinical operation guidelines are urgently needed. The aim of this review was to address the present status of the application of zirconia ceramics related to implant dentistry by analysing the published data from both in vitro and in vivo studies. Suggestions are provided for potential improvements and suitable applications of zirconia ceramics in metal-free implant dentistry.     

Synthesis of 6-nm Ultrafine Monoclinic Zirconia

In the normal paradigm of sintering-densification, grain growth, creep, etc., it is anticipated that, at extremely fine grain size, various phenomena will be exaggerated so as to make direct observation more tractable; this gives impetus to attempts to synthesize such fine-grained materials. In the present case, 6-nm monoclinic zirconia was produced by a hydrothermal technique and is showing very interesting grain growth and rearrangement effects in transmission electron microscopy.     

Influence of Tetragonality on Tetragonal-to-Monoclinic Phase Transformation during Hydrothermal Aging in Plasma-Sprayed Yttria-Stabilized Zirconia Coatings

The influence of tetragonality, which is defined as the lattice parameter ratio c / a , on the tetragonal-to-monoclinic phase transformation during hydrothermal aging was investigated in yttria-stabilized zirconia coatings. The yttria content was adjusted in the range of 4–8 mass% (denoted as x YZ, where x = 4–8 and YZ represents the yttria-stabilized zirconia). The tetragonality of the zirconia in the as-sprayed coatings was less than that in the powders. To change the tetragonality for each yttria content, the coatings were annealed at 1273 K before aging. Without annealing, the phase transformation was prevented only in 8YZ. When annealing was applied, an increase of the tetragonality (i.e., recovery of the tetragonality) was observed, and transformation during hydrothermal aging was also suppressed in 6YZ. It was concluded that the increase in tetragonality that occurred without a change in the yttria content was suggested to be caused by the lattice relaxation of the tetragonal phase, and this relaxation is believed to cause a reduction of the critical yttria concentration, thus preventing the phase transformation.