DESIGN, ASSEMBLY AND CHARACTERIZATION OF COMPOSITE ...

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70.0 g of ENP 800 nickel powder is added. A rigorous mixing, using the non-contact planetary mixer (AR-250, THINKY, Tokyo, Japan), is applied for 2 minutes to homogenize the aqueous nickel suspension at φsolids = 0.57. Subsequently, 1.40 g of HPMC stock solution and 0.35 g of Darvan 821A are added to the suspension, followed by thorough mixing. Finally, 1.10 g of DI water is mixed with the nickel gel to lower the solid volume fraction to φsolids = 0.472. Following this preparation, the Ni colloidal gel may be consistently extruded though a 200 diameter µm printing tip (5127-0.25-B, EFD, East Providence, RI). 4.2.4. Rheological Characterization of Nickel Gels The viscoelastic behavior of the Ni ink is characterized by oscillatory shear measurement for Darvan 821A:PEI-25K ratios of 5:2, 3:2 and 2:2. The Bohlin C-VOR 200 rheometer with the C14 serrated cup and bob geometry is used to measure rheological properties. Temperature is fixed at 23 °C and a solvent trap is used to minimize water evaporation. For oscillatory measurement of shear modulus, the nickel ink is subject to a 60 minute oscillatory pre-shear at 1Hz with a controlled shear stress at 0.02 Pa, then undisturbed for 30 minutes. Afterwards, an increasing shear stress (τ) from 10 Pa to 1000 Pa is applied. Complex shear modulus (G*) is measured as a function of stress amplitude, but elastic shear modulus (G') is the only data reported. The yield stress (τy) of the gel is taken as the stress magnitude where G' dropped to 90% of the maximum value during a stress sweep experiment starting from low stress. 116
4.2.5. Thermal Degradation of Binders Binder removal for green Ni structures is carried out in air in a tube furnace (Thermolyne F21100, Barnstead International, Dubuque, Iowa) for 8 hours with a temperature set point at 260 °C and a heating ramp rate of 5 °C/min. A thermogravimetric analyzer (TG/DTA 6200, SII Nano Technology, Tokyo, Japan) is used to characterize thermal degradation of polymer additives under the same conditions. 4.2.6. Sintering and Metallography Densification of Ni powder compacts is carried out at 900 °C for 2 hours in a reducing atmosphere. A tube furnace (GSL 1600X, MTI Corporation, Richmond, CA) is used for this sintering process. A high purity gas mixture of 2% H2 and 98% N2 is used in the furnace at a flow rate of 50 standard cubic centimeters per minute at 23°C (controlled by a mass flow controller: Tylan FC-260, Entegris, Chaska, Minnesota). Two cycles of vacuuming and flushing are first used to purge air out of the alumina tube prior to the thermal cycle. The temperature profile for sintering is shown in Figure 4.1. A ramp to 700 °C at 5 °C/min is followed by an isothermal hold of 2 hours. This is followed by a ramp to 900 o C at 2 °C/min and an isothermal hold of 2 hours. Finally the sintered nickel is cooled to room temperature at 5 °C/min and the flowing gas is terminated. Following sintering, the density of Ni structures is measured using the Archimedes immersion method. 117
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DESIGN, ASSEMBLY AND CHARACTERIZATI
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ACKNOWLEDGEMENTS First and foremost
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CHAPTER 5 BARIUM TITANATE NICKEL CO
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Table 6.1 Formulations of aqueous c
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Figure 2.12 Schematic illustrations
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Figure 2.35 Schematic of the SHS pr
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Figure 4.9 Sintered nickel lattices
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Figure 6.12 Optical image of the cr
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1.1. Motivation CHAPTER 1 INTRODUCT
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and characterizing rheological prop
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2.1. Materials System CHAPTER 2 BAC
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2.2. Reentrant Structures and Ceram
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devices would provide self-sustaini
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a) b) Figure 2.4 Schematic illustra
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production of concept models, injec
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Fused Deposition Modeling (FDM) was
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Laser Engineered Net Shaping (LENS)
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Inkjet printing (IP) 27 is based on
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Table 2.1 Comparisons of various SF
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Figure 2.11 Processing steps involv
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2.4.1 Colloidal Inks The printing i
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Robocasting has lacked a well-desig
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Table 2.2 Example polymers that dep
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2.6. Sintering In robocasting, sint
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Figure 2.15 Sphere and plate model
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where
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2.5.3 Solid State Sintering In this
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Figure 2.18 Illustration of neck gr
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2.5.3.4 Final Stage During this sta
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Figure 2.23 Schematic diagram of th
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2.5.4.2 Rearrangement With the form
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2.5.4.6 Spreading of Sintering Aid
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Driven by reduction of free energy,
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2.5.5 Sintering Atmosphere Sinterin
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2.7. Composite Materials In this re
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Figure 2.29 Types of composite mate
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Table 2.6 Examples of composite mat
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Table 2.7 Examples of FGM applicati
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2.7.3 Processing For the fabricatio
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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
Page 93 and 94: leading to a characteristic time τ
Page 95 and 96: 3.1 Introduction CHAPTER 3 AQUEOUS
Page 97 and 98: occurs in a multi-step process: fir
Page 99 and 100: a) b) Figure 3.1 a) SEM image of as
Page 101 and 102: 3.2.3 Preparation of Carbon Black C
Page 103 and 104: 3.2.5 Drying Shrinkage Characteriza
Page 105 and 106: the optimized surfactant concentrat
Page 107 and 108: The storage modulus of a colloidal
Page 109 and 110: For HA ink, yield stress
Page 111 and 112: In the case of the aqueous carbon b
Page 113 and 114: PPO units of Pluronic F-127 may ads
Page 115 and 116: a) b) Figure 3.6 A carbon black lat
Page 117 and 118: a) b) Figure 3.7 SEM images of a) c
Page 119 and 120: TGA plot is in agreement with previ
Page 121 and 122: a) b) Figure 3.9 Thermogravimetric
Page 123 and 124: 3.3.8 Fabrication of Complex Cerami
Page 125 and 126: c) d) 109
Page 127 and 128: 3.4 Conclusion A fugitive support m
Page 129 and 130: metal inks have been reported for R
Page 131: Midland, MI) 5% by weight stock sol
Page 135 and 136: 4.3. Results and Discussion 4.3.1.
Page 137 and 138: 4.3.2. Preparation of Nickel Ink Su
Page 139 and 140: 260 °C for 8 hours, the residual c
Page 141 and 142: Table 4.1 Calculated residual carbo
Page 143 and 144: a) b) Figure 4.6 Sintered Ni struct
Page 145 and 146: temperature 138, 139 lead to 92-95%
Page 147 and 148: Figure 4.8 Scanning electron microg
Page 149 and 150: c) Figure 4.9 Sintered nickel latti
Page 151 and 152: 5.1. Introduction CHAPTER 5 BARIUM
Page 153 and 154: materials within the overall struct
Page 155 and 156: 40:60, 60:40, 80:20 are separately
Page 157 and 158: 5.2.3. Rheological Characterization
Page 159 and 160: 5.2.5. Co-sintering and Re-oxidatio
Page 161 and 162: mixing, BT and Ni phases appear uni
Page 163 and 164: The combined use of PAA and PAA-90K
Page 165 and 166: To quantify this difference in sint
Page 167 and 168: As the BT and Ni particles used in
Page 169 and 170: The reducing atmosphere used in the
Page 171 and 172: Figure 5.7 Vickers hardness number
Page 173 and 174: 5.3.6. Fabrication of BT-Ni composi
Page 175 and 176: modify the sintering kinetics of th
Page 177 and 178: a) b) Figure 5.10 Co-sintered compo
Page 179 and 180: 5.4. Conclusions Freeform fabricati
Page 181 and 182: 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
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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
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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
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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
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References A.1. Du, Z., Sarofim, A.
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Name: Jian Xu Date of Degree: May,
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