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1、畢業設計(論文)外文資料翻譯外文出處: A. Safari and D. J. Waller, Fine Scale PZT Fiber/Polymer Composites” 附 件: 1.外文資料翻譯譯文;2.外文原文。 附件1:外文資料翻譯譯文通過注射成型制造壓電陶瓷/聚合物復合材料Leslie J. Bowen 和 Kenneth W. French原料系統(有限)公司摩洛哥康考德希爾克雷斯特大道53號, 郵編01742摘要賓夕法尼亞州立大學材料研究室的研究已經證明通過使用壓電陶瓷/聚合物復合材料可以改進檢漏器(水診器)潛能。作為美國海軍研究局的資助計劃的一部分,旨在開發針對這些合成物
2、且具有成本效益制造技術,材料系統正在尋求一種陶瓷制造方法的注射成型。本文簡要概覽了陶瓷注射成型過程的關鍵細節,并且記敘了制造壓電陶瓷/聚合物復合材料的步驟及方法論。注射成型壓電陶瓷的設備和應用程序都是區別于傳統的材料的加工。緒論壓電陶瓷/聚合物復合材料提供了設計的多功能性和性能優勢,在遙感和驅動應用方面都超越單獨的陶瓷與聚合物的壓電材料。這些合成物已經被開始用于高解析度超聲醫學以及海軍的發展應用。在過去的十三年里,許多復合的配置已經按照一個實驗室的規模被構造且評估。其中最成功的組合之一,被指定復合物的紐納姆號,有一個三維連接陶瓷階段(壓電纖維)內含三維連接有機聚合物的階段。檢漏器的性能系數可使
3、得這個復合物超過那些通過適當選擇階段特征和復合結構的固體材料10000倍。 賓州州立大學復合物的制備是通過在一個跳汰機和封裝環氧樹脂中手調擠壓壓電陶瓷棒,之后限制適當的厚度并極化陶瓷。除了這種材料所展示出的性能優勢,賓州州立大學的工作所凸顯的問題涉及合成物的大規模制造或者甚至以原型為目的。這些是:(1)在通過聚合物封裝時大量的壓電陶瓷光纖的庫存和供給需求。(2)在極化過程中發生率高的介電擊穿是起于在一個典型的大型陣列遇到一個或多個有缺陷的纖維的顯著概率。在過去的五年里,為了提高制造行業的生存能力并降低材料成本已經多次嘗試簡化傳感器的組裝工藝。早期的嘗試包括將壓電陶瓷的固體塊切割至理想的配置和聚
4、合體階段的空缺回填。這項技術已經被超聲醫學工業接受并用于制造高頻傳感器。最近,纖維材料公司已經證明了其用于纖維增強復合材料的編織技術在裝配壓電材料方面的適應性。另外的一項探索技術涉及復制多孔織物已經有適當的連通性。對于極其精密尺度的復合材料,纖維的直徑大約為20至100微米,長寬比大于5以滿足裝置性能需要的目標。因此,這些困難再加上額外的成型與處理龐大數量且無缺陷的極其精細的纖維的挑戰。最近,西門子公司的研究人員表明非常精密尺度的復合材料可以通過一種不定的模具技術來制造。然而,這種方法需要為每一個部分制造一個新的模具。本文介紹一種壓電復合加工的新方法,即:陶瓷注射成型。陶瓷注射成型無論對海軍的
5、壓電陶瓷/聚合物復合材料或是對于極其加工規模的壓電復合材料(如那些所需的高頻超聲醫療及無損評估)都是一種具有成本效益的制造方法。注塑成型過程克服了通過網型預成型陶瓷纖維整列使裝配導向陶瓷纖維進入復合材料傳感器的困難。除了這個優勢,該方法使得比那些以前的設想具有更復雜陶瓷元素幾何的復合傳感器成為可能,以致產生了為提高聲阻抗匹配性的更高的設計柔性以及橫向模式的取消。過程描述注塑成型被廣泛應用于塑料行業作為一種較低成本、形狀復雜的迅速大規模生產。此種方法最適合應用于陶瓷小截面形狀,例如線程導向,以及無需燒結至很高密度的大而復雜的形狀,如渦輪機的葉片鑄造插入。最近,這種方法已被研究用作生產熱發動機渦輪
6、部件的技術。如圖1所示,注塑成型方法已被用于壓電陶瓷的成型。通過將熱塑性塑料與陶瓷粉末的混合物有機結合并注入一個冷卻模具,復雜的形狀就能方便且快速的正常與塑料結合成型。預防例如像金屬接觸硬化的表面,盡量減少金屬從混和與成型器械受到的污染。對于陶瓷,型腔必須無損拆除,迫使高的固體載荷,嚴格控制型腔移除的過程,以及適當的夾具。一旦型腔移除,隨后點火,極化并且環氧樹脂的封裝過程是和那些常規壓電陶瓷/復合材料類似。因此,此方法在替代制造路線上提供了很大優勢:復雜,能夠同時處理許多纖維的近似網狀;快速的生產能力(通常是一部分幾秒);統計過程控制的兼容性;材料的低浪費;有關傳感器設計的柔性(允許PZT中元
7、素空間和形狀的變化);以及在中量至大量之間的低成本。一般來說,由于最初加工的高成本,陶瓷注射成型的方法是最適用于復雜形狀的構成,需要低成本大批量。 圖1 注射成型過程流程 圖2 制作合成物的預成型方法 合成物的制造及評價制造1-3壓電復合材料的方法如圖2a所示,這闡述了使用一個完整的陶瓷胚型到纖維定位作用的壓電陶瓷預先成型的概念。在聚合物封裝后采用磨削去除陶瓷胚。除了簡化許多纖維的處理,這種預先成型的方法允許廣泛地選擇壓電陶瓷元素幾何元素范圍,以使其性能最優化。工具的設計是取得注塑壓電復合材料成功的重要因素。如圖2b所示的方法使用了無需導致額外重組成本的嵌入式的并允許局部變化的設計。圖2c所示
8、如何配置個別的預加工的成品以形成大批生產在實踐中,材料和成型參數必須最優化并成型工具的設計相結合以實現在成型后完整的脫模。關鍵的參數包括:壓電陶瓷/裝夾工具之比,壓電元件的直徑和錐度,壓電陶瓷基本軸向厚度,工具表面的磨光,以及成型零件的脫模機構的設計。為了評估這些工藝參數而不承擔過多的工藝成本,一種工具的設計根據實驗目的采用只有兩排的各自19個壓電陶瓷要素。每一行的要素都包括三個錐角(0,1和2度)以及兩個直徑(0.5mm和1mm)。為了容許成型收縮,預加工的工件尺寸維持在50mmX50mm,以盡量減少在制模周期中的冷卻部分折斷外層纖維的可能性。圖3所示的綠色陶瓷瓶坯的制造使用這種工具配置。請
9、注意,所有壓電陶瓷在成型后的完整的脫模,包括那些沒有縱向尖端不方便的脫模。空氣中的緩慢加熱已經被發現是一個適合去除有機粘合劑的方法。最后,燒壞的粘合劑被燒結在一個理論值在97-98%的富含氧化鉛的氣體中。在燒結這些合成物型坯時沒有遇到任何控制重量減輕的問題,甚至是那些用于高頻超聲的高尺寸精度,高表面質量的型坯。 圖3 注射成型1-3預成型合成物 圖4 電子顯微鏡掃描PZT表面圖4說明了表面為壓模和作為燒結的纖維,顯示出大約10um寬的存在的淺的折線,這是在注射成型過程中特有的。那個沿其長度方向顯現出微小孔型設計的纖維取決于從工具中的脫模過程。圖5所示近似網狀的成型方式用于制造非常精細尺度的型坯
10、的能力;所示壓電元件的尺寸只有30um。由作為這些燒結的表面指出,壓電陶瓷的顯微結構是密集且均勻的,由直徑為2-3um的細碎的等軸晶體構成。 圖5 由近似網狀的成型的精密尺度的合成物為了示范上述合成物制造的方法,注射成型和燒結的纖維行在用于成型合成物型坯的壓電陶瓷被磨光之后,大約總體10%的5H*壓電陶瓷合成物以及環氧樹脂Spurrs在制造時通過環氧成對封裝。圖6所示復合材料樣品使用剛才復合的壓電陶瓷/粘結劑混合物以及再生材料制造。回收復合物和成型的材料似乎是完全可行的,并且結果大大提高材料的利用率。表1比較了使用粉末制造商準備好的那些被報道的用于模壓的5H壓電陶瓷樣品注射成型壓電陶瓷樣品的壓
11、電和介電的性能。當燒結條件最優于壓電陶瓷5H的條件,壓電和介電的性能都較所有材料有可比性。當壓電陶瓷5H的原料物質被考慮到受注射成型設備污染鐵的敏感性,這些有關的測量方法對于這種注射成型的壓電陶瓷材料可以忽略這類污染。*粉末的提供方是俄亥俄州貝德福德的摩根士丹利公司,105A街區。 表1 壓電陶瓷注塑成型的參數 圖6 上述方法精制壓電陶瓷/樹脂合成物的注塑成型總結 陶瓷注射成型已被證明是一種可行的制造壓電陶瓷和壓電陶瓷/聚合物傳感器的方法。注射成型壓電陶瓷的電相關特性區別于那些通過傳統的準備好的粉末壓模,沒有證據證明在混合物以及成型設備中產生的金屬雜質會產生污染影響。通過陶瓷的注射成型來制造合
12、成物型坯,之后使用型坯來形成大批生產,此種方法已經證明用于網狀大量制造壓電復合物傳感器。致謝 這項工作由海軍研究事務所的Stephen E.Newfield先生贊助指導。作者要感謝Hong Pham女士提供的技術援助,以及材料研究實驗所的Tomas Shrout博士,賓州州立大學所做的電器測量工作。參考文獻1 R. E. Newnham等著,復合壓電式傳感器,材料工程,第二卷,93-106頁,1980年12月出版2 C. Nakaya等著,IEEE超音波專業座談會,1985年十月16-18日。P6343 S. D. Darrah等著,大面積壓電復合材料關于活性物質和構造的ADPA會議,亞歷山德
13、里亞,十一月4-8日,1991年,埃德。灣諾爾斯,物理研究所出版,頁139-142 。4 A. Safari and D. J. Waller著,精密尺度的煙點陶瓷纖維/聚合物復合材料,在關于活性物質和構造的ADPA會議上提交,亞里山德里亞,危吉利亞,十一月4-8號,1991年。5 U. Bast, D. Cramer and A. Wolff著,一種用來制造1-3連通形壓電復合材料的新方法,第七屆CIMTEC , 意大利蒙特卡蒂尼, 6月24至30號, 1990年,Ed.P. Vincenzini, Elsevier,2005-2015頁6 G. Bandyopadhyay and K. W
14、. French著,網狀的硅的氮化物應用于發動機的制造,對渦輪增壓器轉自及動力,108,536-539頁,1986年出版7 J. Greim等著,燒結注塑渦輪增壓轉子,第三屆關于熱動力的陶瓷材料及構造國際研討,內華達州拉斯維加斯,1365-1375頁,Amer. Cer. Soc,1989年附件2:外文原文FABRICATION OF PIEZOELECTRIC CERAMlClPOLYMER COMPOSITES BY INJECTION MOLDING.Leslie J. Bowen and Kenneth W. French,Materials Systems Inc.53 Hillcr
15、est Road, Concord, MA 01742AbstractResearch at the Materials Research Laboratory, Pennsylvania State University has demonstrated the potential for improving hydrophone performance using piezoelectric ceramic/polymer composites. As part of an ONR-funded initiative to develop cost-effective manufactur
16、ing technology for these composites, Materials Systems is pursuing an injection molding ceramic fabrication approach. This paper briefly overviews key features of the ceramic injection molding process, then describes the approach and methodology being used to fabricate PZT ceramic/polymer composites
17、. Properties and applications of injection molded PZT ceramics are compared with conventionally processed material.IntroductionPiezoelectric ceramic/polymer composites offer design versatility and performance advantages over both single phase ceramic and polymer piezoelectric materials in both sensi
18、ng and actuating applications. These composites have found use in high resolution medical ultrasound as well as developmental Navy applications. Many composite configurations have been constructed and evaluated on a laboratory scale over the past thirteen years. One of the most successful combinatio
19、ns, designated 1-3 composite in Newnhams notation l 1, has a one-dimensionally connected ceramic phase (PZT fibers) contained within a three-dimensionally connected organic polymer phase. Hydrophone figures of merit for this composite can be made over 10,000 times greater than those of solid PZT cer
20、amic by appropriately selecting the phase characteristics and composite structure.The Penn State composites were fabricated l by hand-aligning extruded PZT ceramic rods in a jig and encapsulating in epoxy resin, followed by slicing to the appropriate thickness and poling the ceramic. Aside from demo
21、nstrating the performance advantages of this material, the Penn State work highlighted the difficulties involved in fabricating 1-3 composites on a large scale, or even for prototype purposes. These are:1) The requirement to align and support large numbers of PZT fibers during encapsulation by the p
22、olymer.2) The high incidence of dielectric breakdown during poling arising from the significant probability of encountering one or more defective fibers in a typical large array. Over the past five years several attempts have been made to simplify the assembly process for 1-3 transducers with the in
23、tention of improving manufacturing viability and lowering the material cost. Early attempts involved dicing solid blocks of PZT ceramic into the desired configuration and back-filling the spaces with a polymer phase. This technique has industry for manufacturing high frequency transducers 2. More re
24、cently, Fiber Materials Corp. has demonstrated the applicability of its weaving technology for fiber-reinforced composites to the assembly of piezoelectric composites 31. Another exploratory technique involves replicating porous fabrics having the appropriate connectivity 4. For extremely fine scale
25、 composites, fibers having diameters in the order of 25 to 100 pn and aspect ratios in excess of five are required to meet device performance objectives. As a result, these difficulties are compounded by the additional challenge of forming and handling extremely fine fibers in large quantities witho
26、ut defects. Recently, researchers at Siemens Corp. have shown that very fine scale composites can be produced by a fugitive mold technique. However, this method requires fabricating a new mold for every part 5. This paper describes a new approach to piezoelectric composite fabrication, viz: Ceramic
27、injection molding. Ceramic injection molding is a costeffective fabrication approach for both Navy piezoelectric ceramic/polymer composites and for the fabrication of ultrafine scale piezoelectric composites, such as those required for high frequency medical ultrasound and nondestructive evaluation.
28、 The injection molding process overcomes the difficulty of assembling oriented ceramic fibers into composite transducers by net-shape preforming ceramic fiber arrays. Aside from this advantage, the process makes possible the construction of composite transducers having more complex ceramic element g
29、eometries than those previously envisioned, leading to greater design flexibility for improved acoustic impedance matching and lateral mode cancellation. Process Description Injection molding is widely used in the plastics industry as a means for rapid mass production of complex shapes at low cost.
30、Its application to ceramics has been most successful for small crosssection shapes, e.g. thread guides, and large, complex shapes which do not require sintering to high density, such as turbine blade casting inserts. More recently, the process has been investigated as a production technology for hea
31、t-engine turbine components 6,7. The injection molding process used for PZT molding is shown schematically in Figure 1.By injecting a hot thermoplastic mixture of ceramic powder and organic binder into a cooled mold, complex shapes can be formed with the ease and rapidity normally associated with pl
32、astics molding. Precautions, such as hard-facing the metal contact surfaces, are important to minimize metallic contamination from the compounding and molding machinery. For ceramics, the binder must be removed nondestructively, necessitating high solids loading, careful control of the binder remova
33、l process, and proper fixturing. Once the binder is removed, the subsequent firing, poling and epoxy encapsulation processes are similar to those used for conventional PZT/polymer composites 1. Thus, the process offers the following advantages over alternative fabrication routes: Complex, near net-s
34、hape capability for handling many fibers simultaneously; rapid throughput (typically seconds per part); compatibility with statistical process control; low material waste; flexibility with respect to transducer design (allows variation in PZT element spacing and shape); and low cost in moderate to h
35、igh volumes. In general, because of the high initial tooling cost, the ceramics injection molding process is best applied to complex-shaped components which require low cost in high volumes. Figure 1 : Injection Molding Process Route. Figure 2: Preform Approach to Composite Fabrication.Composite Fab
36、rication and EvaluationThe approach taken to fabricate 1-3 piezoelectric composites is shown in Figure 2a, which illustrates a PZT ceramic preform concept in which fiber positioning is achieved using a co-molded integral ceramic base. After polymer encapsulation the ceramic base is removed by grindi
37、ng. Aside from easlng the handling of many fibers, this preform approach allows broad latitude in the selection of piezoelectric ceramic element geometry for composite performance optimization. Tool design is important for successful injection molding of piezoelectric composites. The approach shown
38、in Figure 2b uses shaped tool inserts to allow changes in part design without incurring excessive retooling costs. Figure 2c shows how individual preforms are configured to form larger arraysIn practice, material and molding parameters must be optimized and integrated with injection molding tool des
39、ign to realize intact preform ejection after molding. Key parameters include: PZT/binder ratio, PZT element diameter and taper, PZT base thickness, tool surface finish, and the molded part ejection mechanism design. In order to evaluate these process parameters without incurring excessive tool cost,
40、 a tool design having only two rows of 19 PZT elements each has been adopted for experimental purposes. Each row contains elements having three taper angles (0, 1 and 2 degrees) and two diameters (0.5 and l mm). To accommodate molding shrinkage, the size of the preform is maintained at 5Ox50mm to mi
41、nimize the possibility of shearing off the outermost fibers during the cooling portion of the molding cycle.Figure 3 shows green ceramic preforms fabricated using this tool configuration. Note that all of the PZT elements ejected intact after molding, including those having no longitudinal tapering
42、to facilitate ejection. Slow heating in air has been found to be a suitable method for organic binder removal. Finally, the burned-out preforms are sintered in a PbOrich atmosphere to 97-98% of the theoretical density. No problems have been encountered with controlling the weight loss during sinteri
43、ng of these composite preforms, even for those fine-scale, high-surface area preforms which are intended for high frequency ultrasound.Figure 4 illustrates the surfaces of as-molded and as-sintered fibers, showing the presence of shallow fold lines approximately 10pm wide, which are characteristic o
44、f the injection molding process. The fibers exhibit minor grooving along their length due to ejection from the tool. Figure 5 shows the capability of near net-shape molding for fabricating very fine scale preforms; PZT element dimensions only 30pm wide have been demonstrated. The as-sintered surface
45、 of these elements indicates that the PZT ceramic microstructure is dense and uniform,n consisting of equiaxed grains 2-3pm in diameter. Figure 3: Injection Molded 1-3 Composite Preforms. Figure 4: Scanning Electron Micrographs of As-molded(Upper) and As-sintered (Lower) Surfaces of PZT Fibers Figur
46、e 5: Fine-scale 2-2 Composite formed by Near Netshape olding (Upper Micrograph). As-sintered Surface(Lower Micrograph).In order to demonstrate the lay-up approach for composite fabrication, composites of approximately 10 volume percent PZT-5H fibers and Spurrs epoxy resin were fabricated by epoxy en
47、capsulating laid-up pairs of injection molded and sintered fiber rows followed by grinding away the PZT ceramic stock used to mold the composite preform. Figure 6 shows composite samples made from freshly-compounded PZT/binder mixture and from reused material. Recycling of the compounded and molded
48、material appears to be entirely feasible and results in greatly enhanced material utilization. Table 1 compares the piezoelectric and dielectric properties of injection molded PZT ceramic specimens with those reported for pressed PZT-5H samples prepared by the powder manufacturer. When the sintering
49、 conditions are optimized for the PZT-5H formulation, the piezoelectric and dielectric properties are comparable for both materials. Since the donordoped PZT-5H formulation is expected to be particularlysensitive to iron contamination from the injection molding equipment, the implication of these me
50、asurements is that such contamination is negligible in this injection molded PZT material.SummaryCeramic injection molding has been shown to be a viable process for fabricating both PZT ceramics and piezoelectric ceramic/polymer transducers. The electrical properties of injection molded PZT ceramics
51、 are comparable with those prepared by conventional powder pressing, with no evidence of deleterious effects from metallic contamination arising from contact with the compounding and molding equipment. By using ceramic injection molding to fabricate composite preforms, and then laying up the preforms to form larger composite arrays, an approach has been demonstrated for net-shape manufa
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