IntroductionThe force of interaction between colloidal particles plays an important role on the stability and rheology of the ceramic slurries and forming of the green bodies. The well-known DLVO theory, which states that the net energy of interaction is a sum of van der Waals and electrical forces, provides a theoretical tool for predicting these forces quantitatively[1，2]。范德华的力主要取决于相互作用的物体的块状特性，而不是溶液化学。然而，静电力受到溶液特性的显着影响，并被操纵以控制流变学和稳定性。它是由于离子在溶液中和固体表面上不同化学活性而产生的电气双层。在氧化物 - 水系统中，质子浓度是确定表面电荷的主要参数，因此通过诸如Al-OH等反应的静电力，因此静电力0+H+→al-哦2+或al-哦0→al —o-+H+。 DLVO理论已被证明可以很好地代表胶体系统的互动行为。最好的证据之一是舒尔兹·马迪（Shulze-Hardy）规则，它可以直接源自DLVO理论[3]。However, its testing with direct measurements of the interparticle forces has been possible after the introduction of the Surface Force Apparatus (SFA)[[4-6]。SFA can only be used with transparent substrates such as mica, glass or quartz since it relies on interference fringes. Also, this procedure practically has no lateral resolution[[7]。 The Atomic Force Microscopy-Colloid Probe Method (AFM-CPM), which does not suffer from such shortcomings, has been finding wide use in recent years for interparticle force measurements[8，9]。In this method, the bending of a tiny cantilever which carries an attached colloid particle at its free end is measured optically by a laser-photo detector system as it is brought closer to a substrate. The amount of deflection can be directly related to the interactive force between the colloid and the substrate if the spring constant of the cantilever is known. Using Derjaguin's approximation, the force of interaction can be translated to the energy of interaction if the colloid’s diameter is much larger than the gap between the surfaces. The forces in the order of few picoNewtons can be detected by AFM which theoretically has a quantum level resolution (better than 10-24j）[10]。Ducker等人将读者指向开创性的作品。[[10, 11]and reviews by Parker[11]，Claesson等。[12]，senden[13]and Hodges[14]For details. The direct force measurements in recent years have shown that the oxide-water interface displays an unusual behavior which cannot be accounted for by the DLVO theory, especially at distances shorter than 10 nm[15-21]。其他几项工作ssuggest the presence of a long-range attractive interaction (>100 nm) in the case of hydrophobic surfaces[[22-24]。对于氧化物 - 水系统，一种解释是在5 nm以下的分离处存在排斥的“水合力”。Karaman等。[[18]使用AFM-CPM观察到，血浆氧化的氧化氧化铝表面总是在3-6.5范围内表现出排斥力。尽管它们的力距离曲线与大于3-5 nm的分离理论很好地吻合，但看不到独特的能量屏障和主要最小值。表面在蓝宝石和的中间pH中排斥的事实α- 铝表面应相反。[27]也令人惊讶。这种行为归因于由于氧化铝的肿胀，在基本pH的表面上存在厚的排斥水合层（15 nm）。但是，没有为基本pH范围提供力曲线。他们还建议在较低的pH值下使用“薄”凝胶，与在pH 3.5处观察到的始终抑制相互作用能量冲突。 In this study, systematic normal and lateral force microscopy measurements were carried out betweenα- 铝胶体探针和0001蓝宝石表面在强酸性，中性和强碱性溶液中使用AFM-CPM。目的是更肯定地确定pH对氧化物 - 水系统中的互动力的影响，以获得这些力与水合行为之间的相关性，并确定测量值与DLVO理论的相关性。 Materials and Method使用0001个苏巴尔底物（来自日本的一家公司）和Á-ALUMINA粉末（来自日本的Admatechs Co.）进行了力量测量以及FTIR和TG-DTGA研究。Á-ALUMINA粉末和蓝宝石的等电点为8.9和5。1[25]。The sapphire was atomically smooth with a Ra value of 0.11 nm with a maximum peak-to-valley distance of 0.92 nm. Micro-contact紫外线处理的角度测量蓝宝石表面
没有接触表明表面在治疗后表面是完全干净和亲水性的。The rectangular tipless cantilevers (TL-FM-50 from Nanosensors, Switzerland) were used to prepare the colloid probes. The cantilevers were individually tested for their dimensions, resonant frequencies and Q factors in air at room temperature to determine the normal spring constant for each cantilever[26-28]。Though there are methods to determine the lateral spring constant of a rectangular cantilever28, presence of a glue layer fixing the colloid on the cantilever and of the particle itself introduce unknowns which would make such constant unreliable. Therefore, the lateral force data in this paper is reported in terms of deflection, which is equivalent to the force normalized for the spring constant since deflection=lateral force/lateral spring constant. Such normalization requires that the same colloid probe is used throughout a given set of lateral force measurements for meaningful comparison of data. 在pH 3.5处使用重复的倾d-脉络膜化过程，以分离单个α-铝胶体探针并清洁其表面。具有0.1μm分辨率的微型操纵器（日本Suruga Seiki Co. Ltd.的M501-1202-M型号）用于选择，定位并使用快速的环氧胶（Araldite araldite AR-R30-Nichiban Co。图1给出了一些代表性图片。 扫描探针显微镜（SPA 400，日本精工，日本）用于正常和横向力测量。将液体细胞，蓝宝石和胶体探针均用紫外线 - 血浆处理10分钟（来自日本Sen Light Corp.的PL16-110D），用乙醇，蒸馏水洗涤，最后用实验溶液丰富。每次测量前10分钟将整个组件浸入实验溶液中。在1μm的中心和1μm的中心和拐角处获得了五次正常力测量square area on the sapphire surface. Thisprocedure was repeated 4 times on the corners of a larger, 20 μm by 20 μm area, resulting in 20 force measurements for each test. The lateral force measurement was obtained immediately after each normal force measurement over the same locations. However, a given lateral force measurement was repeated 10 times on a single location at different distances from the surface to differentiate the effect of probe-surface separation on the frictional force. The approach speed of the probe was 30 nm/sec in the normal mode; the drag length and speed were 100 nm and 50 nm/sec in the lateral mode. 力测量以压电翻译 - 局限器偏转信号的形式产生原始数据。These数据需要转换为实际的力距离曲线。图2显示了原始数据以及所得的力距离曲线和转换过程中使用的算法。在横向力测量的情况下，直接使用挠度信号，特别注意使用相同的胶体探针为整个组OF测量。 Poisson-Boltzmann方程的完整数值溶液满足每个分离间隙的两个表面上的表面电势会导致潜在曲线，这是距每个表面距离的函数。然后，可以从每个分离间隙的这些潜在剖面直接计算表面之间的静电压力，即每单位面积的相互作用力。这些计算中使用的表面电势在pH 3.5处的两个表面为+90 mV，pH 7.7时 +40/-40 mV和-90 mV均为pH 12的两个表面，基于ZETA的ZETA电位测量，0001-Sapphire表面的文献数据[25]。
在解决方案中处理的Á-ALUMINA粉末pH 3.5 and 12 (in 10-4M KCl) were analyzed by FTIR (Spectrum GX FTIR-DRIFT from Perkin Elmer, USA) and TG-DTGA (2000S from Mac Sciences Co. Ltd., Japan) to assess the water at the α-alumina surface. Results andDiscussion通过AFM-Colloid探针法确定的分离与正常力曲线在图3中给出了3.5、7.7和12.0的pH值。该图还包括使用Derjaguin方法根据力计算出的相互作用能量。结果显示了研究的三个pH值的相互作用能量的主要差异。在pH 3.5处，这两个表面都被带积极充电，分离约10 nm处存在一个非常明确的排斥屏障。在更紧密的接近时，力很快就会吸引人。对于pH 7.7，对于两个相对带电的表面的所有分离，这种相互作用都是有吸引力的。在pH 12时，交互式力不显示排斥屏障也没有有吸引力的区域，并且始终对所有分离都具有排斥性。文献中也报道了类似的行为[15-19]并归因于由表面的一层水合氧化物引起的排斥力。Preliminary results of the lateral forces measurements at pH 3.5 and 12 show that the frictional forces differ markedly at acidic and basic pH values (Figure 2) such that the frictional force is much smaller in thepH 12的情况下，表面上的水合层被猜测。 
图1。Normal interaction forces between the á-alumina colloid probe and the sapphire substrate at different pH (C0= 10-4M KCL;t = 25oC; kn=2.8 N/m; R=5.4μm）。 
图2。Á-ALUMINA胶体探针和蓝宝石底物之间的横向相互作用力是在不同pH下探针表面分离的函数（C0= 10-4M KCL;t = 25oC; R=5.4μm）。 Presence of such a hydrated layer was indicated by FTIR-DRIFT spectra of theα- 在pH 3.5和pH 12溶液中处理的铝粉24小时（图3）。2800-3800厘米之间的OH伸展区域-1was deeper for pH 12, suggesting that theα-alumina surface contained more H-bonded water at basic pH. A broad hydroxyl stretching region forseveral alumina powders was also observed using FTIR-DRIFT in the literature[[29]。对同一样品的TG和DTGA分析表明，样品中几乎所有水都丢失了100。oc为pH 3.5，而pH 12样品在100°C以上的温度下保留了一些水，支持存在一些更强粘结的水（图4）。化学吸附的水α- 文献中也报道了铝[[30, 31]。 
数字3。FTIR-DRIFT spectra (normalized with respect to the pH 12 spectra) of the H-bonded water region for theα- 在pH 3.5和pH 12溶液中处理的铝酸样品24小时。 
图4。TG and DTGA data for theα- 用pH 3.5和pH 12溶液处理24小时的铝酸样品。 结论正常和横向AFM-Colloid探针力测量α-alumina colloids and 0001-sapphire substrate were carried out in solutions of pH 3.5, 7.7 and 12. For normal force, the interaction of protonated, positively chargedα- 铝表面在10 nm处显示出明确的排斥性屏障，然后最小吸引人。对于预期，对相对带电的表面的部队在pH 7.7上总是很有吸引力。在基本的pH中，两个表面都被带负电，交互式力量短，并且总是排斥力，因此不存在有吸引力的最低限度。对于横向力，在基本的pH值下，摩擦似乎小得多，这很可能是由于观察到的短距离排斥力的存在。似乎在基本pH值的氧化铝表面上可能存在水合层的存在。这样的层可能会阻碍表面的近距离接近，并导致正常和横向相互作用中观察到的行为。这些发现对陶瓷泥浆的稳定性和流变行为以及绿色体的形成具有重要意义。 参考1。L. E. Shoemaker, “Joining Techniques for Ferritic Oxide Dispersion Strengthened Alloys”, proceedings of the International Conference on Trends in Welding Research, Gatlinburg, TN, USA, ASM International, 371-377, May 1986. 2。E. Lugscheider, H. Schmoor and U. Eritt, “Optimization of Repair-brazing Processes for Gas Turbine Blades”, Brazing, High Temperature Brazing and Diffusion Welding, Deutscher Verlag fur Schweisstechnik GmbH, Dusseldorf (Germany), 259-261, 1995. 3。W. F. Gale和E. R. Wallach，“瞬态液体相结合中的微结构发育”，Metall。Trans A，22A，2451-2457，1991。 4。M. C. Chaturvedi, O. A. Ojo and N. L. Richards, “Diffusion Brazing of Cast Inconel 738 Superalloy”, AZo Journal of Materials online, DOI: 10.2240/azojomo0123, 2005. (This paper was also published in print form in Advances in Technology of Materials and Materials Processing, 6 [2] (2004) 206-213). 5。H. Nakagawa，C。H。Lee和T. H. North，“在瞬态液相悬浮料期间基金金属溶解行为的建模”，Metall。反式。A，22A，543-555，1991。 6。L. J. Park, H. J. Ryu, S. H. Hong and Y. G. Kim, “Microstructure and Mechanical Behavior of Mechanically Alloyed ODS Ni-Base Superalloy for Aerospace Gas Turbine Application”, Advanced Performance Materials, 5(4), 279-290, 1998. 7。ASM手册，“合金相图”，俄亥俄州金属公园，第1卷。3，第313页，1992年。 8。T. I. Khan和E. R. Wallach，“连接ODS铁质合金时的瞬态液相扩散键和相关的重结晶现象”，J。Mater。Sci。，第31卷，第2973-2943页，1996年。 接触Details |