以炭黑为还原剂制备硅酸锆晶须的研究

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王三海, 江伟辉, 冯果, 刘健敏, 苗立锋, 王洪达. 以炭黑为还原剂制备硅酸锆晶须的研究. 无机材料学报, 2014, 29(8): 835-838
WANG San-Hai, JIANG Wei-Hui, FENG Guo, LIU Jian-Min, MIAO Li-Feng, WANG Hong-Da. Preparation of Zircon Whisker Using Carbon Black as Reducing Agent. 无机材料学报, 2014, 29(8): 835-838 复制到剪切板

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以炭黑为还原剂制备硅酸锆晶须的研究

王三海¹, 江伟辉^1,², 冯果¹, 刘健敏¹, 苗立锋¹, 王洪达¹

1. 景德镇陶瓷学院材料科学与工程学院, 景德镇 333000

2. 江西省先进陶瓷材料重点实验室, 景德镇 333001

通讯作者: 江伟辉, 教授. E-mail:jwhjiang@163.com

作者简介: 王三海(1986-), 男, 硕士研究生. E-mail:wangsanhai0@sina.com

基金:国家自然科学基金(51162013, 51362014); 江西省主要学科学术和技术带头人培养计划(20113BCB22009);

摘要

以无水四氯化锆为锆源, 正硅酸乙酯(TEOS)为硅源, 氟化锂为矿化剂, 乙醇为溶剂, 炭黑为还原剂, 采用非水解溶胶-凝胶法在700 ℃制备得到硅酸锆晶须, 借助TG-DTA、XRD和TEM等测试手段研究了炭黑加入方式及用量对硅酸锆合成与形貌的影响。结果表明: 炭黑以悬浮液形式加入有助于硅酸锆的一维择优生长; 炭黑用量为6wt%时能获得直径为30~90 nm, 长径比为6~15, 沿[001]方向择优生长的硅酸锆晶须。炭黑与氧反应形成二氧化碳和一氧化碳, 炭黑加入方式及用量能够调控反应体系的氧分压。降低氧分压有利于形成更多的气相SiF₄, 这是促进ZrSiO₄一维定向生长的基础, 但氧分压过低又妨碍ZrSiO₄晶体的合成。因此, 适当氧分压有利于ZrSiO₄晶须的生长。

关键词: 非水解溶胶-凝胶法; 炭黑; 硅酸锆; 晶须

中图分类号:TQ174 文献标志码:A 文章编号:1000-324X(2014)08-0835-04

Preparation of Zircon Whisker Using Carbon Black as Reducing Agent

WANG San-Hai¹, JIANG Wei-Hui^1,², FENG Guo¹, LIU Jian-Min¹, MIAO Li-Feng¹, WANG Hong-Da¹

1. School of Material Science and Engineering, Jingdezhen Ceramic Institute, Jingdezhen 333000, China

2. Jiangxi Key Laboratory of Advanced Ceramic Materials, Jingdezhen 333001, China

Fund:National Natural Science Foundation of China(51162013, 51362014); Major Discipline Academic and Technical Leader Training Plan Project of Jiangxi Province(20113BCB22009);

Abstract

Zircon whisker was synthesized at 700 ℃via non-hydrolytic Sol-Gel method using anhydrous zirconium tetrachloride (ZrCl₄) as zirconium source, tetraethylorthosilicate (TEOS) as silicon source, lithium fluoride (LiF) as mineralizer, ethanol as solvent and carbon black as reducing agent. Thermogravimetric analysis and differential thermal analysis (TG-DTA), X-ray diffraction analysis (XRD) and transmission electron microscope (TEM) were employed to characterize the influences of adding ways and amount of carbon black on the synthesis and morphology of zircon whisker. The results show that the carbon black added in form of suspension is favorable to the one-dimension growth of zircon. When 6wt% carbon black is added, optimized zircon whiskers are achieved along the growth direction of [001], which diameter and aspect ratio are in the range of 30-90 nm and 6-15, respectively. Because of carbon black reacting with oxygen to form carbon dioxide and monoxide, the adding way and amount of carbon black efficiently regulate the oxygen partial pressure in the reaction system. Reducing oxygen partial pressure can form more SiF₄gas, which is the basis of one-dimensional direction growth of zircon. However, excessively low oxygen partial pressure is against the ZrSiO₄ formation. Therefore, appropriate oxygen partial pressure can promote the growth of zircon whisker.

Keyword: zircon; whisker; non-hydrolytic Sol-Gel method; carbon black

Show Figures

晶须是一种纤维状的单晶体, 直径非常小, 原子排列高度有序, 不存在大晶体中常见的缺陷(空位、孪晶或晶界等), 其强度接近完整晶体的理论值^{[ 1]}, 因此晶须的制备与应用受到世界各国的高度重视。但是, 目前已实现工业化应用的晶须只有碳化硅^{[ 2, 3]}、氮化硅^{[ 4]}、氧化铝^{[ 5]}、钛酸钾^{[ 6]}、氮化钛^{[ 7]}、硼酸铝^{[ 8]}和莫来石^{[ 9, 10, 11]}等少数几个品种, 而应用最广泛的碳化硅、氮化硅等非氧化物晶须价格昂贵且高温抗氧化性能差, 因此开发各种具有优异性能的晶须新材料及其制备新技术是材料学研究的一个重要方向。

硅酸锆不但具有熔点高(2500℃) 、热导率低(室温下为5.1 W/(m·℃), 1000 ℃为3.5 W/(m·℃))和热膨胀系数( α)小( α在25~1400 ℃为4.1×10^-6 /℃)等优点^{[ 12, 13]}, 而且化学及相稳定性好、抗氧化能力强。硅酸锆的机械强度在1400 ℃高温下也不衰减, 具有比莫来石和氧化铝更好的抗热震性, 其临界热震温差Δ T_c达280℃, 远高于莫来石(200℃)和氧化铝(150 ℃), 特别适合于在高温以及温度急剧变化的恶劣环境下使用^{[ 14]}。因此, 将硅酸锆制备成晶须, 能够充分发挥硅酸锆的优势, 使其成为一种新型耐高温、抗热震、高温强度大、化学稳定性好、抗氧化能力强的复合材料增强体。

虽然硅酸锆晶须具有非常好的应用前景, 但国内外至今还未见硅酸锆晶须的制备报道。在前期采用非水解溶胶-凝胶法低温合成硅酸锆粉体的基础上^{[ 15]}, 本工作通过添加炭黑来调控硅酸锆晶体的生长形貌, 制得硅酸锆晶须, 研究了炭黑加入方式及用量对硅酸锆合成与一维择优生长的影响, 并对其显微结构进行了表征。

1 实验方法

1.1 样品制备

在手套箱中将8 mL TEOS加入到100 mL锥形瓶中, 然后依次加入无水LiF和无水ZrCl₄(用量分别按摩尔比计算: Li:Si = 0.3, Si:Zr = 1.2:1)。待混合均匀后, 按照前驱体浓度1 mol/L添加溶剂乙醇, 并继续搅拌, 再经110 ℃油浴回流24 h, 得到硅酸锆前驱体溶胶。

将30 mL乙醇倒入烧杯中, 加入聚乙烯醇缩丁醛(PVB), 不断搅拌, 待PVB溶解之后, 加入炭黑, 均匀搅拌, 得到炭黑悬浮液。将炭黑悬浮液缓慢加入硅酸锆前驱体溶胶中, 得到冻状凝胶, 再在100 ℃干燥后, 得到硅酸锆干凝胶, 然后经700 ℃热处理30 min获得最终产物。

1.2 样品表征

采用NETZSC HSTA449C综合热分析仪对凝胶粉体进行热分析(DTA - TG); 使用D8-Advance型X射线衍射仪(X-ray diffraction meter, XRD)对样品进行物相分析(Cu靶, K_α辐射, 管压为40 kV, 管电流为30 mA, λ = 0.154 nm, 扫描范围10°~70°, 扫描速率0.02 °/min); 用JEM-2010型透射电子显微镜(transmis-sion electron microscope, TEM)观察样品形貌, 并通过选区电子衍射与高分辨像分析晶须的取向生长。

2 结果与讨论

2.1 硅酸锆干凝胶热处理过程中的物相变化

为了分析添加炭黑后所得ZrSiO₄干凝胶在热处理过程中的物相转变过程, 首先对干凝胶进行DTA-TG测试, 见图1, 其中测试气氛为空气, PVB用量为5wt%(占乙醇质量百分比, 下同), 炭黑用量为3wt%。在此基础上, 对干凝胶经不同温度热处理所得样品进行XRD测试, 见图2。

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	图1 添加炭黑所制干凝胶的DTA-TG曲线Fig. 1 DTA-TG curves of xerogel prepared by adding carbon black

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	图2 不同热处理温度所制样品的XRD图谱Fig. 2 XRD patterns of the samples annealed at different temperatures

图1显示DTA曲线在168.1 ℃附近出现明显的吸热峰, 对应的TG曲线在室温’300 ℃范围内有14.77%的失重, 这是由部分残余有机物的分解、前驱体缩聚反应产生的卤代烷气体以及有机溶剂的挥发所致。图2显示热处理温度为500 ℃时, 样品的XRD图谱中出现较弱的四方氧化锆(t-ZrO₂)与单斜氧化锆(m-ZrO₂)衍射峰; 热处理温度提高到550 ℃时, 样品的XRD图谱中t-ZrO₂与m-ZrO₂衍射峰均有所增强, 但没有新的物相形成。由此可以推断, 图1 中DTA曲线在300~550 ℃之间较宽的放热峰是由无定型ZrO₂析晶形成t-ZrO₂与m-ZrO₂晶相以及部分炭黑氧化所引起的。当热处理温度升高到600 ℃时, 样品的XRD图谱中出现微弱的ZrSiO₄衍射峰; 而将热处理温度进一步提高到650 ℃, ZrSiO₄衍射峰强度明显提高, t-ZrO₂与m-ZrO₂衍射峰极其微弱。由此说明图1中DTA曲线中582.7 ℃处的吸热峰是由ZrSiO₄晶相的形成所致。另外, 800 ℃热处理样品的硅酸锆衍射峰虽然比700 ℃和650 ℃热处理样品的有所加强, 但没有新相产生, 由此可以推断DTA曲线中800.2 ℃附近较宽的放热峰与炭黑的进一步氧化有关。

2.2 炭黑添加方式对硅酸锆生长形貌的影响

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	图3 不同炭黑添加方式所得样品的TEM照片Fig. 3 TEM images of samples prepared by adding carbon black with different ways (a) In form of suspension; (b) Mixed with xerogel directly

图3为炭黑以悬浮液的形式加入硅酸锆溶胶内(a)或者炭黑与硅酸锆干凝胶直接混合(b)所得样品的TEM照片, 其中PVB用量为5wt%, 炭黑用量为3 wt%。从图3可以看出, 炭黑以悬浮液的形式加入所得的样品中出现少量直径为40~100 nm, 长径比为3~5的短棒状晶体, 同时在短棒状晶体附近有较多的硅酸锆颗粒(见图3(a))。而将炭黑与干凝胶直接混合所得的样品(见图3 (b))基本由硅酸锆颗粒组成, 很难观察到短棒状晶体。由此可见: 以悬浮液形式向硅酸锆溶胶中加入炭黑有助于硅酸锆晶体的一维择优生长。硅酸锆凝胶在加热过程中发生了以下化学反应:

C+O₂→CO₂(1)

2C+O₂→2CO(2)

4LiF +SiO₂→SiF₄+2Li₂O (3)

SiF₄↑→Si⁴⁺+4e^-+2F₂ (4)

SiO₂+2F₂→SiF₄+O₂ (5)

SiF₄+ZrO₂+O₂→ZrSiO₄ +2F₂(6)

炭黑与氧反应形成二氧化碳和一氧化碳(见反应(1)与反应(2)), 由此调控体系的氧分压。减小氧分压有利于反应向右进行产生更多的气相SiF₄(见反应(5)), 这是促进ZrSiO₄一维定向生长的基础, 但降低氧分压又妨碍ZrSiO₄晶体的合成(见反应(6))。因此, 适当氧分压有利于ZrSiO₄晶须的生长。炭黑以悬浮液的形式加入到硅酸锆溶胶内, 炭黑表面会形成硅酸锆凝胶保护层, 使得炭黑在高温下不会迅速氧化, 确保反应体系能维持适中的氧分压, 从而有助于硅酸锆的一维择优生长。而将炭黑与硅酸锆干凝胶直接混合, 炭黑表面没有保护层, 它在高温下与氧气剧烈反应而消耗大量的氧气, 导致体系氧分压过低, 不利于反应(6)的进行, 致使硅酸锆晶体难以一维生长。

2.3 炭黑添加量对硅酸锆生长形貌的影响

图4给出炭黑添加量分别为0 (a)、3wt%(b)、 6 wt%(c)和9wt%(d)时所制备样品的TEM照片, 其中PVB用量为5wt%, 炭黑以悬浮液的形式加入硅酸锆溶胶中。从图4可以看出, 没有添加炭黑时, 样品由无规则形状的硅酸锆颗粒组成; 当加入3wt%炭黑时, 出现少量直径为40~100 nm, 长径比为3~5的短棒状晶体, 并在短棒状晶体附近存在较多的硅酸锆颗粒; 当炭黑添加量增加到6wt%时, 样品中主要由大量直径为30~90 nm, 长径比为6~15的硅酸锆晶须组成, 并含有少量的硅酸锆颗粒; 炭黑添加量进一步增加到9wt%时, 硅酸锆晶须的数量却明显减少, 样品中还夹杂着大量的硅酸锆颗粒。由此可见, 适量的炭黑有助于硅酸锆晶须的一维生长, 而过多或过少的炭黑都不利于制备硅酸锆晶须。究其原因, 炭黑过少时, 体系氧分压过大, 不利于SiF₄生成(见反应(5)), 这就抑制了硅酸锆的一维生长; 而炭黑过多则会使氧分压过小, 这又会影响硅酸锆的合成(见反应(6)), 同样不利于硅酸锆晶须的生长。只有当炭黑适量(6wt%)时, 氧分压大小适中, 有助于硅酸锆晶须的一维择优生长。不过, 由于通常使用的炭黑具有一定的颗粒分布, 加之炭黑与硅酸锆干凝胶粉混合难以达到理想的均匀性, 造成反应体系内局部的氧分压不一致, 导致在形成硅酸锆晶须的同时也产生了少量的硅酸锆颗粒。

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	图4 不同炭黑含量制备样品的TEM照片Fig. 4 TEM photographs of samples prepared at different carbon black contents(a) 0; (b) 3wt%; (c) 6wt%; (d) 9wt%

2.4 硅酸锆晶须的结构表征

图5给出硅酸锆晶须的TEM照片、选区电子衍射花样(SAED)及高分辨透射电镜(HRTEM)照片。从图5(a)可以明显看出, 硅酸锆晶须表面光洁、轮廓清晰、发育良好、直晶率较高。通过对图5 (a)中电子衍射花样的标定可以证明硅酸锆晶须为单晶结构, 经计算得出其晶胞参数为: a= b = 0.6612 nm, c = 0.5993 nm, 与硅酸锆(PDF#06-0266)的晶胞参数一致。此外, 从图5(a)还可以得知硅酸锆晶须的晶带轴为[010], 再结合图5(b)的高分辨HRTEM照片对(101)及(10)晶面的标定, 可以确定硅酸锆晶须的生长方向平行于[001], 即沿 c轴择优生长。

	Figure Option View Download New Window
	图5 硅酸锆晶须的(a)TEM和(b) HRTEM照片Fig. 5 TEM (a) and HRTEM (b) images of zircon whiskerInset in Fig. 5 (a) is the corresponding SAED pattern

3 结论

实验以炭黑为还原剂, 采用非水解溶胶-凝胶法在700℃制备出硅酸锆晶须。研究表明: 炭黑以悬浮液的形式加入有助于硅酸锆的一维择优生长。当炭黑添加量为6 wt%时可获得直径为30~90 nm, 长径比为6~15, 沿[001]方向择优生长的硅酸锆晶须, 添加过多或过少的炭黑均会影响硅酸锆晶须的生长。炭黑作为还原剂调控反应过程中的氧分压大小, 是能否制备硅酸锆晶须的关键。

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2005

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... 晶须是一种纤维状的单晶体, 直径非常小, 原子排列高度有序, 不存在大晶体中常见的缺陷(空位、孪晶或晶界等), 其强度接近完整晶体的理论值^[1], 因此晶须的制备与应用受到世界各国的高度重视 ...

2013

1.789

0.0

Ceramics International. 2013, 39(1):null-null

Fabrication and characterization of SiC whisker reinforced reaction bonded SiC composite

... 但是, 目前已实现工业化应用的晶须只有碳化硅^[2,3]、氮化硅^[4]、氧化铝^[5]、钛酸钾^[6]、氮化钛^[7]、硼酸铝^[8]和莫来石^[9,10,11]等少数几个品种, 而应用最广泛的碳化硅、氮化硅等非氧化物晶须价格昂贵且高温抗氧化性能差, 因此开发各种具有优异性能的晶须新材料及其制备新技术是材料学研究的一个重要方向 ...

2005

2.224

0.0

Materials Letters. 2005, 59(19):null-null

Microstructure and growth mechanism of SiC whiskers on carbon/carbon composites prepared by CVD

2010

3.941

0.0

Acta Mater.. 2010, 58(1):146-161 DOI:10.1016/j.actamat.2009.08.064

The c-axis texturing of seeded Si₃N₄ with b-Si₃N₄ whiskers by slip casting in a rotating magnetic field

Abstract The c -axis texture development in seeded Si 3 N 4 with β-Si 3 N 4 whiskers by slip casting in a rotating magnetic field was investigated by powder X-ray diffraction, scanning electron microscopy and thermal anisotropy evaluation, including the effects of magnetic flux density, suspension rheological properties and rotational speed. By increasing the magnetic flux density from 1 to 12 T, the c -axis orientation of β-Si 3 N 4 whiskers is achieved in the well-dispersed 30 vol.% suspension but hindered in the flocculated 40 vol.% suspension. The degree of orientation tends to decrease with increasing rotational speed from 5 to 30 rpm. The green body shows no density gradient but nonuniform orientation of β-Si 3 N 4 whiskers regardless of the rotational speed, resulting in the similar nonuniform texture in the sintered body. The nonuniform texture is featured in three major layers: lower surface, inner region and upper surface, corresponding to the lower, higher and lower c -axis orientation, respectively. The resultant c -axis textured Si 3 N 4 exhibits thermal anisotropy as high as 55%, slightly lower than the intrinsic thermal anisotropy (62%) of β-Si 3 N 4 . A theoretical analysis is performed to help understand the key factors affecting the orientation of β-Si 3 N 4 whiskers by slip casting in the rotating magnetic field. The formation mechanisms of the nonuniform texture were discussed.

2010

2.163

0.0

J. Mater. Sci.. 2010, 45(1):177-181 DOI:10.1007/s10853-009-3913-x

Synthesis and formation of alumina whiskers from hydrothermal solution

1.Chinese Academy of Sciences CAS Key Laboratory of Salt Lake Resources and Chemistry, Qinghai Institute of Salt Lakes Xining 810008 China 2.Graduate University of Chinese Academy of Sciences Beijing 100049 China

Al 2 O 3 whiskers with an average length of 5 μm have been synthesized from hydrothermal solution. Al(NO 3 ) 3 and urea were mixed and put into a Teflon-lined stainless steel autoclave and then treated at 120 °C to fabricate precursor whiskers NH 4 Al(OH) 2 CO 3 (AACH). AACH whiskers were heated at 1200 °C in a furnace to obtain Al 2 O 3 whiskers. The time-dependent examinations revealed that the formation process of AACH whiskers involves two sequential processes: a short liquid–solid deposition process in the initial stage and a long Ostwald ripening process. During calcinations, AACH transforms to amorphism then to α-Al 2 O 3 . The escape of NH 3 and CO 2 induced the distortion and toothlike morphology on the surface of the Al 2 O 3 whiskers.

2004

2.107

0.0

Journal of the American Ceramic Society. 2004, 87(3):326-330

High Quality and Yield in Potassium Titanate Whiskers Synthesized by Calcination from Hydrous Titania

Ningzhong Bao 1 ,Liming Shen 2 ,Xin Feng 1 andXiaohua Lu 1,†

1 College of Chemical Engineering, Nanjing University of Technology, Nanjing 210009, People's Republic of China 2 College of Material Science and Engineering, Nanjing University of Technology, Nanjing 210009, People's Republic of China

> Hydrous titanium dioxide (TiO 2 · n H 2 O) was used to prepare K 2 Ti 2 O 5 single crystals, K 2 Ti 4 O 9 whiskers and K 2 Ti 6 O 13 whiskers at 820°, 940°, and 1110°C, respectively, by calcination. At T 2 Ti 2 O 5 single crystals at 820°C. Subsequently, K 2 Ti 2 O 5 single crystals convert into K 2 Ti 4 O 9 whiskers at 940°C, and K 2 Ti 4 O 9 whiskers further convert into K 2 Ti 6 O 13 whiskers at 1110°C. The reaction temperatures for the generations of these types of potassium titanates were all 10°–40°C lower than the corresponding temperatures when anatase was used as the reactant. The whiskers synthesized in the present study exhibited uniform size, good morphology, and a high yield.

2002

2.163

0.0

J. Mater. Sci.. 2002, 37(8):1693-1699 DOI:10.1023/A:1014981722160

Formation of TiN whiskers through carbothermal reduction of TiO₂

1.Defence Metallurgical Research Laboratory Kanchanbagh, Hyderabad 500058 India

Formation of TiN whiskers through carbothermal reduction of TiO 2 in nitrogen was studied. Effect of (i) addition of potassium (K 2 CO 3 ) and nickel (NiCl 2 ), (ii) reaction temperature on the formation of whiskers was studied. Addition of K 2 CO 3 has strong influence on the formation whiskers. The yield of whisker was maximum at 920–1000°C. At higher temperatures, formation of particulates of TiN was the dominant process. Increase in K 2 CO 3 concentration increased the formation of (i) whiskers at low temperatures 815°–920°C, (ii) particulates at high temperatures 1000°–1100°C. A vapor-liquid-solid growth mechanism of whisker formation was identified. K 2 CO 3 has been identified as an essential constituent for the formation of a low melting liquid by reaction with TiO 2 and NiCl 2 . Continuous supply of TiO, nitrogen and CO to this complex K-Ni-Ti liquid droplet lead to the precipitation of TiN whisker.

2004

2.163

0.0

Journal of Materials Science. 2004, 39(4):1445-1447 DOI:10.1023/B:JMSC.0000013914.91971.8b

Synthesis of aluminum borate whiskers via flux method with and without microwaves

S. W. Kim (1) , S. G. Lee (1) , J. K. Kim (1) , J. Y. Kwon (1) , H. C. Park (1) , S. S. Park (2)

1. Department of Inorganic Materials Engineering, Pusan National University, Pusan, 609-735, Korea 2. Division of Chemical Engineering, Pukyong National University, Pusan, 608-739, Korea

1.Pusan National University 2.Pukyong National University

2013

0.0

Journal of Wuhan University of Technology-Mater. Sci. Ed.. 2013, 28(3):471-475

Preparation of mullite whiskers and their enhancement effect on ceramic matrix composites

Jinhua Zhang 张锦化 (1) (2) , Hongdan Wu (1) , Suxin Zhang (2) , Jishun Yu (2) , Shu’en Hou 侯书恩 (1)

1. Engineering Research Center of Nano-Materials of Mineral of Education, Faculty of Material Science and Chemical Engineering, China University of Geosciences, Wuhan, 430074, China 2. State Key Laboratory of Geological Processes and Mineral Resources, Wuhan, 430074, China

Mullite whiskers were facilely prepared by sintering kyanite at high temperature, with the addition of AlF 3 ·3H 2 O. The as-prepared whiskers have been characterized systematically in terms of phase composition, morphology, and structure. Results showed that the morphology and size of mullite whiskers were strongly depended on the content of AlF 3 ·3H 2 O and sintering temperature. At temperatures in the range of 1 100 to 1 500°C with 4 wt% addition of AlF 3 ·3H 2 O, the well-shaped mullite whiskers were obtained. For an instance, the mullite whiskers with 5–10 μm in length and 0.1–0.2 μm in cross-section could be formed at 1 400°C, with 4 wt% addition of AlF 3 ·3H 2 O. Moreover, results showed that the addition of mullite whiskers into ceramic matrix enhanced its fracture toughness significantly.

2010

0.0

J. Inorg. Mater.. 2010, 25(5):532-536 DOI:10.3724/SP.J.1077.2010.00532

Preparation of mullite whisker via non-hydrolytic Sol-Gel route

1. School of Material Science and Engineering, Jingdezhen Ceramic Institute, Jingdezhen 333001, China; 2. Key Laboratory of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China

Mullite whisker was prepared via nonhydrolytic Sol-Gel route using tetraethoxysilane and anhydrous aluminium chloride as precursors and ether as oxygen donor.The prepared mullite whisker is 0.2-2.0μm in diameter, with aspect ratio of 60-70. Effects of processing parameters on the mullite whisker were also studied by means of XRD, SEM and TEM, including activity of mullite xerogel, addition way and amount of mineralizer AlF 3 , forming pressure and calcining temperature. The results indicate that the mullite xerogel prepared by the constant pressure reflux, transforms into the whisker with high yield and good quality after being shaped into disc at the pressure of 12MPa and calcined at 1200℃ for 1h with outside addition of 3wt% AlF 3 .

以正硅酸乙酯和无水氯化铝为前驱体, 乙醚为氧供体, 采用非水解溶胶凝胶法制备了直径为0.2~20μm, 长径比高达60~70的莫来石晶须. 借助XRD、SEM和TEM等测试手段研究了莫来石干凝胶粉的活性、矿化剂氟化铝引入方式及其用量、成型压力以及煅烧温度等工艺参数对合成莫来石晶须的影响. 结果表明：采用恒压回流工艺制备的莫来石干凝胶粉, 在12MPa压力下压制成片状, 以外置方式引入3wt%的氟化铝, 在1200℃保温1h可制备质量较好的莫来石晶须.

2009

0.0

1998

2.163

0.0

Journal of Materials Science. 1998, 33(19):4821-4828

Sol–gel synthesis of zircon–effect of addition of lithium ions

M. Shoyama (1) , N. Matsumoto (2) , T. Hashimoto (2) , H. Nasu (2) , K. Kamiya (2)

1. Mie Prefectural Ceramic Research Institute, Iga Branch, Marubashira,, Ayama-cho, Ayama-gun, Mie, 518-13,, Japan 2. Department of Chemistry for Materials, Faculty of Engineering,, Mie University,, Kamihama-cho, Tsu-shi, Mie, 514,, Japan

The sol–gel method was applied to the preparation of zircon, ZrSiO4 powders. The addition of lithium ions to the ZrO2·SiO2 gels was found to be very effective to produce zircon at temperatures as low as 800–900°C. The zircon formation process in the gels was followed by using X-ray diffraction and i.r. analysis methods. A possible mineralizing mechanism of lithium ions, which is essentially different from the previous ones for the solid-state reaction, was proposed. Namely, the formation of orthosilicate such as Li4SiO4 as an intermediate compound was considered to trigger the zircon formation at low heat-treatment temperatures.

... 10^-6 /℃)等优点^[12,13], 而且化学及相稳定性好、抗氧化能力强 ...

2005

2.107

0.0

... 10^-6 /℃)等优点^[12,13], 而且化学及相稳定性好、抗氧化能力强 ...

1992

2.107

0.0

Journal of the American Ceramic Society. 1992, 75(9):2420-2426

Preparation of High-Purity ZrSiO₄ Powder Using Sol–Gel Processing and Mechanical Properties of the Sintered Body

Toshiyuki Mori 1,† ,Hiroshi Yamamura 1 ,Hidehiko Kobayashi 2 andTakashi Mitamura 2,†

1 Tsukuba Research Laboratory, TOSOH Company, Ltd., Tsukuba, Japan 305 2 Department of Applied Chemistry, Faculty of Engineering, Saitama University, Urawa, Japan 338

> Effects of the concentration of ZrOCl 2 , calcination temperature, heating rate, and the size of secondary particles after hydrolysis on the preparation of high-purity ZrSiO 4 fine powders from ZrOCl 2 .8H 2 O (0.2 M to 1.7 M ) and equimolar colloidal SiO 2 using sol–gel processing have been studied. Mechanical properties of the sintered ZrSiO 4 from the high-purity ZrSiO 4 powders have been also investigated. Single-phase ZrSiO 4 fine powders were synthesized at 1300°C by forming ZrSiO 4 precursors having a Zr–O–Si bond, which was found in all the hydrolysis solutions, and by controlling a secondary particle size after hydrolysis. The conversion rate of ZrSiO 4 precursor gels to ZrSiO 4 powders from concentrations other than 0.4 M ZrOCl 2 .8H 2 O increased when the heating rate was high, whereupon the crystallization of unreacted ZrO 2 and SiO 2 was depressed and the propagation and increase of ZrSiO 4 nuclei in the gels were accelerated. The density of the ZrSiO 4 sintered bodies, manufactured by firing the ZrSiO 4 compacts at 1600° to 1700°C, was more than 95% of the theoretical density, and the grain size ranged around 2 to 4 μm. The mechanical strength was 320 MPa (room temperature to 1400°C), and the thermal shock resistance was superior to that of mullite and alumina, with fairly high stability at higher temperatures.

... T_c达280℃, 远高于莫来石(200℃)和氧化铝(150 ℃), 特别适合于在高温以及温度急剧变化的恶劣环境下使用^[14] ...

2011

0.0

0.969

Journal of The Chinese Ceramic Society. 2011, 39(3):383-386

Effect of non-hydrolytic gelation process on synthesis of zircon at low temperature

以工业纯无水ZrCl4、正硅酸乙酯(Si(OC2H5)4)为前驱体,LiF为矿化剂,通过非水解溶胶-凝胶法低温合成出硅酸锆粉体.应用热重-差热分析、X射线衍射和透射电子显微镜等研究了不同非水解凝胶化工艺对低温合成硅酸锆的影响.结果表明:通过容弹工艺无法低温合成硅酸锆;采用回流工艺虽然能低温合成出硅酸锆粉体,但所制得的硅酸锆晶体轮廓不清、发育较差.只有将回流和容弹工艺相结合才能在700℃合成出充分发育的四方柱状硅酸锆晶体.

... 在前期采用非水解溶胶-凝胶法低温合成硅酸锆粉体的基础上^[15], 本工作通过添加炭黑来调控硅酸锆晶体的生长形貌, 制得硅酸锆晶须, 研究了炭黑加入方式及用量对硅酸锆合成与一维择优生长的影响, 并对其显微结构进行了表征 ...