DESIGN, ASSEMBLY AND CHARACTERIZATION OF COMPOSITE ...

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Robocasting of composite materials requires printing multiple ink compositions. Such printing may be achieved in several ways: 1) serial extrusion through a nozzle array, Figure 2.12b, 2) parallel extrusion through a mixing nozzle, Figure 2.12c, and 3) one that combines these two extrusion features. Preliminary success in parallel extrusion has been demonstrated in recent study; 31 but serial extrusion is used for fabrication of the composite structures in this work. Figure 2.12 Schematic illustrations of multi-ink printing: a) the robotic gantry system used by robocasting, b) the arrayed nozzle assembly for serial extrusion, and c) the mixing nozzle assembly for parallel extrusion. 32 24
2.4.1 Colloidal Inks The printing ink for Robocasting consists of high solids fraction, low binder concentration aqueous colloidal gels. To formulate these inks, a two step process of dispersion followed by controlled flocculation is typical. The resulting ink exhibits Herschel-Bulkley (shear-thinning with yield stress) flow behavior. The controlled flocculation step is achieved by pH change, bridging flocculation through addition of oppositely charged polyelectrolyte, and salt addition or a combination of these. A schematic illustration of the concept of ink formulation is provided in Figure 2.13. All these methods induce a systematic change to the colloidal dispersion by diminishing the repulsive energy between stabilized particles, such that flocculation of the particles yields an interconnecting particle network. Various particulate materials, including ceramics, 5, 6, 30, 32-34 metals, 35 and polymer, 36 have been employed for the ink preparation. With these inks, complex structures have been assembled, such as space-filling solids, high aspect-ratio walls, and periodic lattices. 6, 30, 34 Applications for these novel materials include sensors, 6 photonic materials, 30 tissue engineering scaffolds, 33 composites, 35 and catalyst supports. To allow extrusion through small diameter nozzles (~Ø0.1-1 mm), these inks have weak mechanical strength and low yield stress: shear elastic modulus on the order of 0.1 MPa, and yield stress around 100 Pa (measured by oscillatory rheometry at 1Hz). 31 Fabrication of structural features such as long spanning beams or extensive internal voids requires a support structure of fugitive material. 25
Page 1 and 2: DESIGN, ASSEMBLY AND CHARACTERIZATI
Page 3 and 4: ACKNOWLEDGEMENTS First and foremost
Page 5 and 6: CHAPTER 5 BARIUM TITANATE NICKEL CO
Page 7 and 8: Table 6.1 Formulations of aqueous c
Page 9 and 10: Figure 2.12 Schematic illustrations
Page 11 and 12: Figure 2.35 Schematic of the SHS pr
Page 13 and 14: Figure 4.9 Sintered nickel lattices
Page 15 and 16: Figure 6.12 Optical image of the cr
Page 17 and 18: 1.1. Motivation CHAPTER 1 INTRODUCT
Page 19 and 20: and characterizing rheological prop
Page 21 and 22: 2.1. Materials System CHAPTER 2 BAC
Page 23 and 24: 2.2. Reentrant Structures and Ceram
Page 25 and 26: devices would provide self-sustaini
Page 27 and 28: a) b) Figure 2.4 Schematic illustra
Page 29 and 30: production of concept models, injec
Page 31 and 32: Fused Deposition Modeling (FDM) was
Page 33 and 34: Laser Engineered Net Shaping (LENS)
Page 35 and 36: Inkjet printing (IP) 27 is based on
Page 37 and 38: Table 2.1 Comparisons of various SF
Page 39: Figure 2.11 Processing steps involv
Page 43 and 44: Robocasting has lacked a well-desig
Page 45 and 46: Table 2.2 Example polymers that dep
Page 47 and 48: 2.6. Sintering In robocasting, sint
Page 49 and 50: Figure 2.15 Sphere and plate model
Page 51 and 52: where
Page 53 and 54: 2.5.3 Solid State Sintering In this
Page 55 and 56: Figure 2.18 Illustration of neck gr
Page 57 and 58: 2.5.3.4 Final Stage During this sta
Page 59 and 60: Figure 2.23 Schematic diagram of th
Page 61 and 62: 2.5.4.2 Rearrangement With the form
Page 63 and 64: 2.5.4.6 Spreading of Sintering Aid
Page 65 and 66: Driven by reduction of free energy,
Page 67 and 68: 2.5.5 Sintering Atmosphere Sinterin
Page 69 and 70: 2.7. Composite Materials In this re
Page 71 and 72: Figure 2.29 Types of composite mate
Page 73 and 74: Table 2.6 Examples of composite mat
Page 75 and 76: Table 2.7 Examples of FGM applicati
Page 77 and 78: 2.7.3 Processing For the fabricatio
Page 79 and 80: prepared discrete layers of uniform
Page 81 and 82: Powder densification processes gene
Page 83 and 84: The specific volume fraction beyond
Page 85 and 86: a) b) Figure 2.34 a) Volume fractio
Page 87 and 88: When the powders are densified in s
Page 89 and 90: Various FGM coating processes are a
Page 91 and 92:
of FGMs, such as partially reactive
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leading to a characteristic time τ
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3.1 Introduction CHAPTER 3 AQUEOUS
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occurs in a multi-step process: fir
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a) b) Figure 3.1 a) SEM image of as
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3.2.3 Preparation of Carbon Black C
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3.2.5 Drying Shrinkage Characteriza
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the optimized surfactant concentrat
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The storage modulus of a colloidal
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For HA ink, yield stress
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In the case of the aqueous carbon b
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PPO units of Pluronic F-127 may ads
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a) b) Figure 3.6 A carbon black lat
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a) b) Figure 3.7 SEM images of a) c
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TGA plot is in agreement with previ
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a) b) Figure 3.9 Thermogravimetric
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3.3.8 Fabrication of Complex Cerami
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c) d) 109
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3.4 Conclusion A fugitive support m
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metal inks have been reported for R
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Midland, MI) 5% by weight stock sol
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4.2.5. Thermal Degradation of Binde
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4.3. Results and Discussion 4.3.1.
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4.3.2. Preparation of Nickel Ink Su
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260 °C for 8 hours, the residual c
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Table 4.1 Calculated residual carbo
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a) b) Figure 4.6 Sintered Ni struct
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temperature 138, 139 lead to 92-95%
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Figure 4.8 Scanning electron microg
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c) Figure 4.9 Sintered nickel latti
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5.1. Introduction CHAPTER 5 BARIUM
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materials within the overall struct
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40:60, 60:40, 80:20 are separately
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5.2.3. Rheological Characterization
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5.2.5. Co-sintering and Re-oxidatio
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mixing, BT and Ni phases appear uni
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The combined use of PAA and PAA-90K
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To quantify this difference in sint
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As the BT and Ni particles used in
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The reducing atmosphere used in the
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Figure 5.7 Vickers hardness number
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5.3.6. Fabrication of BT-Ni composi
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modify the sintering kinetics of th
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a) b) Figure 5.10 Co-sintered compo
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5.4. Conclusions Freeform fabricati
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Liquid phase sintering involves usi
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(pH=4.4, 31.5% by weight) (Adva Flo
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concentration of 7 mg/mL in the aqu
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Table 6.1 Formulations of aqueous c
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thickness. Each layer of the struct
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6.2.6. Hardness Test Microindentati
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micrographs for these two powders.
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Second, the added LiAC∙2H2O is am
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Figure 6.3 Oscillatory behavior for
Page 199 and 200:
a) b) Figure 6.4 Sintering strain c
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mass transport in LFBT network. 167
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The above discussion is mainly focu
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Figure 6.8 shows the bowtie-shaped
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Figure 6.10 A NPR composite of para
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etween BT and Ni phases. But Zn ele
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Figure 6.13 Scanning electron micro
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Figure 6.15 shows the mapping of Ti
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Figure 6.17 and Figure 6.18 show el
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Figure 6.19 shows element mapping f
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6.3.7. Piezoelectricity and Dielect
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6.4. Conclusions Aqueous colloidal
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geometric features, including non-s
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3. Development of aqueous colloidal
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7.2. Recommendations In the context
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gelation behavior. κ-carrageenan i
Page 231 and 232:
REFERENCES 1. Larsson 9301647, 1993
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29. Simchi, A.; Petzoldt, F.; Pohl,
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61. Bouvard, D., Acta Metallurgica
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92. Morissette, S. L.; Lewis, J. A.
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120. Boehm, H. P., Some Aspects of
Page 241 and 242:
150. Atkinson, A., Growth of Nio an
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APPENDICES A. Mathematical Modeling
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and
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conditions: Equation A.12 is solved
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and with
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a) b) Figure B.1 a) Freeze-dried st
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a) Figure C.1 Cr-Ni lattices of 5Cr
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E. Binary Phase Diagram of ZnO-B2O3
Page 257 and 258:
References A.1. Du, Z., Sarofim, A.
Page 259:
Name: Jian Xu Date of Degree: May,
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