共查询到19条相似文献,搜索用时 875 毫秒
1.
用化学共沉淀法配合高温煅烧合成了几种不同化学组成的NZP族磷酸盐粉体材料,从实验结果和对共沉淀反应过程的理论分析两方面入手,着重研究了反应体系的pH值与形成单相NZP族晶体化合物的关系,以及煅烧温度对NZP族粉体比表面积的影响规律.结果表明:控制液相反应过程的pH值=8.5有利于形成单相的NZP族晶体化合物,结晶形态完整的NZP族化合物的比表面积<30m2/g,在低于晶化温度下煅烧则可以制备大比表面积的NZP族粉体.此外,本研究所合成的NZP族化合物在pH=3~9的水溶液体系中表面带负电荷. 相似文献
2.
一类新型催化剂载体材料的制备研究 总被引:2,自引:0,他引:2
用共沉淀法制备了NZP族磷酸盐类催化剂载体材料,着重研究了煅烧温度度不同的栽体化学组成对其物相、比表面积和孔结构的影响。所制备的载体通过BET氮吸附法(BET)、X射线衍射(XRD)以度透射电镜(TEM)对其进行了表征。结果表明:用共沉淀法制备NZP族栽体的合适的煅烧温度为700℃至900%,此娄栽体的比表面积在10m^2/g至40m^2/g之间,煅烧温度对载体的物相结构和比表面积有很大影响。 相似文献
3.
Ca0.6Mg0.4Zr4P6O24属于NZP结构族化合物,NZP陶瓷材料是一类新发现的低膨胀材料,其典型组成是NaZr2P2O12.本研究采用化学计量的ZrO(OH)2沉淀与Ca2+、Mg2+离子的酸式磷酸盐溶液混合,在80℃烘干.经900℃/16小时煅烧,合成出Ca0.6Mg0.4zr4P相粉体.利用DTA、TG和XRD研究了沉淀一溶液混合法合成Ca0.6Mg0.4Zr4P6O24相的温度和机理. 相似文献
4.
从第13届国际插层化合物大会看插层化合物的最新发展趋势 总被引:3,自引:2,他引:1
2005年6月5日至9日在法国克莱蒙特-弗朗市(Clermont-Ferrand)召开了第13届国际插层化合物大会(13th International Symposium on Intercalation Compounds,ISIC13),来自23个国家的170余名学者参加了此次大会,其中国内的清华大学材料系、北京化工大学可控化学反应重点实验室、武汉理工大学材料学院等10名代表参加了该次大会。大会内容涵盖了插层化合物的合成工艺、胶体化学、材料结构与材料电磁性、电化学性能、纳米材料(包括纳米粒、纳米纤维、纳米复合材料)、插层化合物的自组装技术以及生物分子的插层化合物等七个议题,包括炭材料(富勒烯、石墨、碳纳米管),过渡金属硫族化合物、金属氢氧化物、陶瓷及改性陶瓷、层状金属氧化物及氢氧化物、沸石及磷酸盐和纳米复合材料等七类材料。 相似文献
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《功能材料》2021,52(7)
根据NaZr_2(PO_4)_3(简称NZP)的晶体结构特征和电荷补偿机理,通过掺入Fe~(3+)对NZP固态电解质进行改性,采用微波烧结工艺在950℃保温1.5 h制备了Na_(1+x)Zr_(2-x)Fe_x(PO_4)_3(x=0, 0.1, 0.2, 0.3, 0.4)陶瓷电解质,系统研究了Fe~(3+)掺入量对电解质的物相组成、微观形貌、相对密度以及离子电导率的影响规律。研究结果发现,利用微波烧结工艺,经950℃处理1.5 h后,成功制备出单相、致密的Na_(1+x)Zr_(2-x)Fe_x(PO_4)_3陶瓷电解质,与传统固相烧结相比,极大降低了烧结温度、缩短了制备周期。且随着Fe~(3+)掺入量的增加,样品的相对密度增大,最大为93.8%。阻抗测试结果表明,Fe~(3+)的掺入可提高样品的离子电导率,当Fe~(3+)掺量为0.3~0.4,室温离子电导率约为6.5×10~(-6) S/cm,高温(573 K)下离子电导率达到1.56×10~(-3) S/cm。 相似文献
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笼型倍半硅氧烷(POSS)/聚合物有机无机杂化材料是近年来材料科学领域的一个研究热点。POSS/聚合物杂化材料在很多领域都呈现出了巨大的应用前景,如高温绝缘材料、低介电常数材料、传感器、光学元件材料、催化剂载体等。文中综述了其在航空航天、耐热阻燃、高性能介电材料、多孔功能材料、催化剂、陶瓷前驱体、纳米复合材料和生物齿科材料等方面应用的研究进展。最后,笔者指出目前制约POSS/聚合物杂化材料深入研究和广泛应用的关键原因是POSS化合物的合成。 相似文献
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[NZP]陶瓷零膨胀性能的设计 总被引:1,自引:0,他引:1
研究了「NZP」材料的零膨胀性能,并尝试对零膨胀的「NZP」陶瓷作了设计,从晶体结构、原子复合、各向异性、显微结构和复合材料等方面提出了设计思路。 相似文献
12.
A novel concept of immobilization of light water reactor (LWR) fuel reprocessing waste effluent through interaction with sodium zirconium phosphate (NZP) has been established. Such conversion utilizes waste materials like zirconium and nickel alloys, stainless steel, spent solvent tri-butyl phosphate and concentrated solution of NaNO(3). The resultant multi component NZP material is a physically and chemically stable single phase crystalline product having good mechanical strength. The NZP matrix can also incorporate all types of fission product cations in a stable crystalline lattice structure; therefore, the resultant solid solutions deserve quantification of crystallographic data. In this communication, crystal chemistry of the two types of simulated waste forms (type I-Na(1.49)Zr(1.56)Sn(0.02)Fe(0).(28)Cr(0.07)Ni(0.07)P(3)O(12) and type II-Na(1.35)Ba(0.14)Zr(1.56)Sn(0.02)Fe(0).(28)Cr(0.07)Ni(0.07)P(2.86)Si(0.14)O(12)) has been investigated using General Structure Analysis System (GSAS) programming of the X-ray powder diffraction data. About 4001 data points of each have been subjected to Rietveld analysis to arrive at a satisfactory structural convergence of Rietveld parameters; R-pattern (R(p))=0.0821, R-weighted pattern (R(wp))=0.1266 for type I and R(p)=0.0686, R(wp)=0.0910 for type II. The structure of type I and type II waste forms consist of ZrO(6) octahedra and PO(4) tetrahedra linked by the corners to form a three-dimensional network. Each phosphate group is on a two-fold rotation axis and is linked to four ZrO(6) octahedra while zirconium octahedra lies on a three-fold rotation axis and is connected to six PO(4) tetrahedra. Though the expansion along c-axis and shrinkage along a-axis with slight distortion of bond angles in the synthesized crystal indicate the flexibility of the structure, the waste forms are basically of NZP structure. Morphological examination by SEM reveals that the size of almost rectangular parallelepiped crystallites varies between 0.5 and 1.5 microm. The EDX analysis provides the analytical evidence of immobilization of effluent cations in the matrix. The particle size distributions of the material along selected reflecting planes have been calculated by Scherrer's formula. 相似文献
13.
K. V. Govindan Kutty R. Asuvathraman R. Sridharan 《Journal of Materials Science》1998,33(15):4007-4013
Thermal expansion of the sodium zirconium phosphate (NZP) family of compounds A1/2M2(PO4)3 (A = Ca or Sr; M = Ti, Zr, Hf or Sn) has been measured in the temperature range 298–1273 K by high-temperature X-ray powder diffractometry. Some of the compounds in the series (calcium zirconium phosphate and calcium hafnium phosphate) display the typical thermal expansion behaviour of NZP compounds, namely expansion along the hexagonal c axis and contraction along the a axis. The other compounds, depending on their interstitial and framework composition, behave differently. The observed axial thermal expansion and contraction behaviour is explained on the basis of the crystal chemistry of the compounds. Low-expansion compounds in this series are identified and their expansion anisotropy examined. Infared spectra of the compounds are reported. Differential scanning calorimetry measurements on the tin compounds indicate the occurrence of a diffuse phase transformation at high temperatures. 相似文献
14.
The NaZr2(PO4)3 type structure (abbreviated as NZP or CTP, CaTi4(PO4)6), has emerged as a new family, which has extraordinary technological utility in three fields: fast-ion conductors, radwaste solidification and zero expansion ceramics. NZP or CTP is formed by an extraordinary range of discrete compositions and crystalline solutions. In this paper these compositions are classified according to their crystal chemical substitution scheme, and some uncommon trends in the systematic variation of their lattice parameters are shown. Some of the major trends are explained by correlation with the rotation of polyhedra in the structure. 相似文献
15.
Sébastien Chenu Ronan Lebullenger Patricia Bénard-Rocherullé Guillaume Calvez Olivier Guillou Jean Rocherullé Abdessamad Kidari Mickael J. Pomeroy Stuart Hampshire 《Journal of Materials Science》2012,47(1):486-492
The NZP-type crystal structure allows a large number of ionic substitutions which leads to ceramics with adjustable thermal
expansion properties or interesting ionic conductivity. However, NZP is difficult to fabricate into monoliths because it requires
both high temperatures and long sintering times. An alternative low temperature route to obtain a tungsten (IV) and tin (IV)
containing NZP crystalline phase uses a process of glass reactive sintering of a phosphate glass. Using a microwave oven,
a glass with the appropriate composition in the NaPO3–Sn(II)O–W(VI)O3 ternary diagram is prepared by a conventional melting
and casting technique. After crushing, the glass powder is pressed at room temperature. The green pellet is cured during various
times at temperatures where glass reactive sintering takes place. From XRD and DTA experiments, we have shown that different
parameters influence the achievement of NZP phase. Consequently, specific conditions, such as (i) initial glass composition,
(ii) equimolar quantities of SnO and WO3, (iii) glass particle size lower than 100 μm, and (iv) curing conducted under air,
are required to obtain a glass–ceramic with a single crystalline phase with the NZP-type crystal structure. 相似文献
16.
A. I. Orlova S. G. Samoilov G. N. Kazantsev V. Yu. Volgutov A. Yu. Kazakova 《Radiochemistry》2010,52(6):666-669
Erbium zirconium phosphate Er0.33Zr2(PO4)3, a member of the family of structural analogs of NaZr2(PO4)3 (NZP), was prepared by the sol-gel process and studied by X-ray phase analysis, IR spectroscopy, and differential scanning
calorimetry. The behavior of erbium zirconium phosphate on heating in the temperature interval from 25 to 625°C was studied
by high-temperature X-ray diffraction. Expansion and contraction along different crystallographic directions and contraction
of the structure as a whole were found. The overall contraction is due to higher contribution of the negative axial thermal
expansion coefficients α
a
and α
b
to αav and hence to the volume expansion of the phosphate. On heating to 900°C, the NZP structure is preserved. 相似文献
17.
D. K. Agrawal C. -Y. Huang H. A. McKinstry 《International Journal of Thermophysics》1991,12(4):697-710
A new structural family of low-expansion materials known as NZP has been recently discovered and has generated great interest for wide-ranging applications such as fast ionic conductors, devices requiring good thermal shock resistance, hosts for nuclear wastes, catalyst supports in automobiles, etc. This family is derived from the prototype composition NaZr2P2O12 in which various ionic substitutions can be made leading to numerous new compositions. The bulk thermal expansion of these materials varies from low negative to low positive values and can be controlled and tailored to suit the needs for specific applications. In general, most of the NZP members demonstrate an anisotropy in their lattice thermal expansions, which is the main cause of the low-thermal expansion behavior of these materials. In CaZr4P6O24 and SrZr4P6O24 an opposite anisotropy has been observed which has led to the development of near-zero expansion crystalline solution composition. On the basis of the coupled rotations of the polyhedral network formed by ZrO6 octahedra and PO4 tetrahedra, a crystal structure model to interpret and explain the thermal expansion behavior has been discussed.Paper presented at the Tenth International Thermal Expansion Symposium, June 6–7, 1989, Boulder, Colorado, U.S.A. 相似文献
18.
Reactions between zirconyl nitrate hydrate and condensed phosphates can be used to produce castable low CTE sodium zirconium
phosphate (NZP) monoliths. Reaction between sodium nitrate, zirconyl nitrate hydrate and condensed phosphoric acid at room
temperature (alkali nitrate method) produces monoliths having a heterogeneous microstructure, which are multiphasic in appearance.
Except for the presence of crystalline sodium nitrate, they are X-ray amorphous. Differential thermal analysis revealed two
distinct exothermic crystallization events when these materials are heated. The first event, with an onset temperature of
650°C, is the result of NZP and ZrO2crystallization. The second is the result of ZrP2O7 crystallization. Reaction between zirconyl nitrate hydrate and condensed sodium phosphate (condensed alkali phosphate method)
results in a more homogeneous microstructure in which crystalline zirconium hydrogen phosphate hydrate and sodium nitrate
are present. Two exothermic peaks, with onset temperatures of approximately 570 and 860°C, are observed. The first exotherm
is the result of NZP, ZrO2 and ZrP2O7 crystallization; the second exotherm is the result of a further NZP formation. After heating materials made by these two
methods at 940°C for 24 h, the condensed-alkali-phosphate-method-derived material converted to phase-pure NZP, while the alkali-nitrate-method-derived
material contained ZrP2O7. The differences in phase evolution between the materials prepared by these two methods are attributable to the differences
in chemical and microstructural homogeneity that result from the reactants used.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
19.
Rashmi Chourasia Ashish Bohre Ritu D. Ambastha O. P. Shrivastava P. K. Wattal 《Journal of Materials Science》2010,45(2):533-545
Sodium zirconium phosphate (NZP) is a potential material for immobilization of nuclear effluents. The existence of cesium
containing NZP structure was determined on the basis of crystal data of solid solution. It was found that up to ~9.0 wt% of
cesium could be loaded into NZP formulations without significant changes of the three-dimensional framework structure. The
crystal chemistry of Na1−x
Cs
x
Zr2P3O12 (x = 0.1–0.4) has been investigated using General Structure Analysis System programming. The CsNZP phases crystallize in the
space group R-3c and Z = 6. Powder diffraction data have been subjected to Rietveld refinement to arrive at a satisfactory structural convergence
of R-factors. The unit cell volume and polyhedral (ZrO6 and PO4) distortion increase with rise in the mole% of Cs+ in the NZP matrix. The PO4 stretching and bending vibrations in the infrared region have been assigned. SEM, TEM, and EDAX analysis provide analytical
evidence of cesium in the matrix. 相似文献