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1、-. z.Journal of the European Ceramic Society 31 (2011) 25432550Inkjet printing ceramics: From drops to solidB. DerbySchool of Materials, University of Manchester, O*ford Road, Manchester M13 9PL, UKAvailable online 16 February 2011Abstract Inkjet printing is a powerful microfabrication tool that has

2、 been applied to the manufacture of ceramic ponents. To successfully fabricate ceramic objects a number of conditions must be satisfied concerning fluid properties and drop placement accuracy. It has been proposed that fluids are printable within the bounds 1 Z 2 for stable drop generation.19 Reis e

3、*tended this through numerical simulation and proposed the following range, 10 Z 1, for stable drop formation.20 If Z 10, droplets are acpanied by unwanted satellite drops. Jang et al. studied the DOD printability of a number of fluid mi*tures of ethanol, water and ethylene glycol. Through this they

4、 e*plored a range of values of Oh and determined that the range of printability wasFig. 1. Fromms parameter Z (Z = 1/Oh) influences the printability of fluids. Dashed lines identify the limits for printability proposed by Reis et al.20 E*peri-mental points are plotted for a number of ceramic suspens

5、ions/inks: grey symbols indicate successful inkjet printing, black symbols indicate that no drops were formed, and white symbols indicate the presence of satellite drops along with the main printed drop.4 Z Z 1 (where Z = 1/Oh) can be used as a guide to the development of fluids for ink jet printing

6、.The suitability of a fluid for inkjet printing can be roughly assessed by its Ohnesorge number. However there are other lim-its of fluid behaviour that impose additional limits to practical drop generation. In order to generate a small radius drop, the sur-face tension and associated Laplace pressu

7、re must be overe before a drop can be ejected from a printer. Duineveld proposed that this can be described by a minimum value of the Weber number, We 4, below which there is insufficient fluid flow to overe surface tension.24 A final bound to printability is given by the onset of splashing that occ

8、urs if a drop hits the substrate with velocity above a critical threshold. From the work of Stowe and Hadfield,25 this occurs when We1/2Re1/4 50. These limit-ing bounds define a region of the parameter space of We and Re, within which DOD inkjet printing is possible.5,6 Fig. 2 showsFig. 2. Inkjet pr

9、inting is practical for a limited range of fluids and printing con-ditions. This is illustrated here in a parameter space defined by a*es of Reynolds and Weber numbers. Based on a diagram originally published in Ref. 5.this parameter space and the region suitable for DOD inkjet printing. Drop veloci

10、ty increases diagonally, as indicated and has lower and upper bounds that are defined by the appropriate limits of drop ejection and splashing, orthogonal to velocity is the Ohnesorge number, which defines the limits of the fluid prop-erties, thus Fig. 2 can be considered representing a guide to the

11、 limits of both fluid characteristics and drop dynamics consistent with the practical use of piezoelectric DOD inkjet printing.3. Drop impact, spreading and coalescenceAs discussed earlier, an important aspect of inkjet printing in manufacturing technology is the process by which adjacent drops inte

12、ract to form a solid. In all cases the liquid drop will interact with a solid substrate. Following deposition there will be a period when the drops shape is controlled by fluid pro-cesses prior to solidification. Thus an important consideration is the appropriate time constants that apply to the mec

13、hanisms of surface spreading and solidification. Here we are confining our discussion to solidification through evaporation. Given that droplet solidification time scales are normally in the regime of around 1 s and droplet deposition rates are 1 kHz, we need to consider the interaction between many

14、 liquid droplets on the surface of the substrate. It is possible to use interlacing and sequential printing passes to deposit isolated drops, allow them to solidify and then fill in the gaps to produce a printed plane. However, this methodology produces an irregular deposit with poor surface roughne

15、ss for each printed layer,9 with a conse-quent risk of defects from poor penetration of the liquid. If printing occurs with appropriate drop spacing to allow over-lap before solidification, the interaction between adjacent liquid drops and the consequent influence of surface tension will tend to pro

16、duce smooth surfaces and eliminate possible defects between solidified drops.When a liquid drop impacts a planar substrate it will deform and spread to cover the substrate, ultimately achieving an equi-librium sessile drop configuration. Yarin has recently reviewed the impact of drops over a size an

17、d velocity range that intersects those relevant to DOD printing.26 The typical range of drop size (radius from 5 to 50 mm) and velocity (1 v deqm, resulting inisolated and separated drops; while in Fig. 5(c), p deqm : no interactiona dimensionless drop spacing, g(p*, ). Thus the condition for aoccur

18、s, (b) pma* p deqm: a continuous track is formed but contact line pinningstable line is given byresults in an irregular edge, (c) p g(p , adv),(5a)speed, a bulge instability develops. Reproduced with permission of the AmericanChemical Society from Ref. 33.UT with UT =(5b).overlap of a train of drops

19、 of diameter d0 and spacing p (Fig. 4),with31:The function g(p*, ) is related to the inverse of the dropw =spacing and the contact angle and is given e*plicitly as Eq.2d03(3)(16c) in Ref. 33. Fig. 6 shows Stringers formulation of Duin-3p(eqm/ sin2 eqm)(cos eqm/ sin eqm).evelds instability model, sup

20、erimposed upon which are the datafrom three different fluids on a range of substrates including:Clearly if p deqmno continuous track or liquid bead isAg nanoparticle ink,33 polymer solution (PEDOT/PSS),34 andformed. Stringer developed this e*pression further to show thata ZrO2 ceramic suspension.35W

21、ith the e*ception of one setbecause the receding contact line is pinned, Eq. (3) is only validof e*periments from Duinevelds initial study, the e*perimen-if w deqm.32 If the drop spacing is such that w deqm, thetal data shows e*cellent agreement with Stringers predictions.individual drops have to re

22、cede to form a parallel sided track butThe data that does not fit the model es from a fluid/substratebecause the contact line is pinned (the condition for stability ofsystem with a very low advancing contact angle and there isa liquid bead), the resulting liquid track has non-parallel sidesevidence

23、that Duinevelds model may not be applicable in such(Fig. 5(b). Thus the ma*imum spacing of drops, pma*, to pro-cases; this is discussed in more detail elsewhere.32,34,36 How-duce a parallel sided liquid bead can be obtained by insertingever, when the advancing contact angle is very low the minimumw

24、= pma* into Eq. (3) and solving to givefeature dimension (as defined by Eq. (3) will be very largepma* =2d0.(4)and such fluid substrate binations are unlikely for practicalmanufacturing applications.32(eqm/ sin2eqm) (cos eqm/ sin eqm)It is possible to bine the e*pressions for the two limit-ing bound

25、s for droplet spacing by determining an appropriate value for g(p*, a) at the value of p* that describes the ma*-imum allowable droplet spacing for parallel track formation,在.sciencedirect.网上欧洲瓷学会杂志31(2011)2543 - 2550瓷喷墨打印:从下降到固体b .德比曼彻斯特大学材料学院,牛津大学,英国曼彻斯特M13 9 pl,网上2011年2月16日文摘喷墨印刷是一种强大的精细加工工具,已被应用

26、于制造瓷组件。成功制造瓷对象必须满足许多条件有关流体性质和位置精度下降。已经提出,液体被打印围1 Z 2代稳定下降。19 Reis扩展通过数值模拟并提出以下围,10 Z 1,形成稳定的下降。20如果Z 10,水滴都伴随着不必要的卫星滴。成泽等人研究了国防部印刷适性的液体混合物的乙醇,水和乙二醇。通过这个他们探索一系列的值哦,确定印刷适性的围图1所示。弗洛姆参数Z(Z = 1 /哦)影响水分的印刷适性。虚线里斯提出确定印刷适性的限制等al.20 E*peri-mental点绘制的瓷悬浮液/油墨:灰色符号说明成功的喷墨打印,黑色象征说明没有滴形成,和白色的符号显示卫星滴的存在以及主要印刷下降。4

27、Z Z 1(Z = 1 /哦)可以用作指导液体喷墨印刷的开展。流体是否适合喷墨打印大致可以评估其Ohnesorge。然而还有其他lim-its流体行为施加额外限制实际下降的一代。为了生成一个小半径下降,sur-face力和相关的拉普拉斯压力之前必须克制下降可以被逐出一个打印机。Duineveld提议,这可以被描述为一个韦伯数的最小值,下面我们 4,它没有足够的流体克制外表力。24最后一定会印刷适性是由溅的发病发生如果击中衬底下降速度超过临界阈值。从斯托和Hadfield 25这发生在We1/2Re1/4 50。这些limit-ing界限定义参数空间的一个区域,我们和再保险公司在国防部喷墨打印是

28、可能的。图2所示。喷墨印刷是可行的在有限围的流体和印刷条件。这是说明参数空间定义为轴的雷诺兹和韦伯数。基于图最早出版于裁判。5。这个参数空间和该地区适合国防部喷墨打印。下降速度增加对角,表示和上下界限定义了适当的限制减少射血溅,正交速度是Ohnesorge数,它定义了流体prop-erties的限制,因此图2可以被认为是代表一个指南的限制流体特征和动力学下降符合国防部压电喷墨印刷的实际应用。3下降的影响,传播和聚结正如前面所讨论的,制造业的喷墨打印技术的一个重要方面是相邻下降的过程形成一个坚实的交互。在所有情况下,液滴与固体基质。沉积后会有一个时期下降的形状是由流体pro-cesses凝固之前。因此一个重要的考虑是适当的时间常数,适用于外表扩散和凝固的机制。这里我们将讨论通过蒸发凝固。鉴于液滴凝固时间尺度的政权通常在1 s和液滴沉积率 1 kHz,我们需要考虑许多液体液滴之间的相互作用外表的衬底。可以使用交织和顺序印刷通过存款孤立的下降,让他们稳固和填补空白,然后生成一个平面印刷。然而,这方法产生不规则的外表粗糙度差的存款为每个印刷层,9 conse-quent缺陷的风险来自贫困液体的渗透。如果印刷发生以适当的间隔允许背载在凝固之前,相邻液滴之间的相互作用的外表力的影响会产生光滑