Name: multi-material ceramic-based components – additive manufacturing of black-and-white zirconia components by thermoplastic 3d-printing (ceram - t3dp)
Uploaded: 2019-01-07T14:00:00.000+00:00
Duration: 8 min 29 s
Description: Watch this Scientific Journal Video about Multi-material Ceramic-Based Components â€“ Additive Manufacturing of Black-and-white Zirconia Components by Thermoplastic 3D-Printing CerAM - T3DP at Jo

This project has received funding from the European Union&#39;s Horizon 2020 Research and Innovation Program under Grant Agreement No 678503.

1. Thermoplastic Suspension for CerAM -&#160;T3DP
<ol>
	<li>Selection of powders
	<ol>
		<li>For the preparation of the black thermoplastic suspensions use black zirconia powders zirconia black - 1 and zirconia black - 2.</li>
		<li>For the preparation of the white thermoplastic suspensions use zirconia white - 1 and zirconia white - 2. 
		NOTE: The manufacturer of zirconia black - 2 uses pigments (4.2 wt.-%) for the coloring of the zirconia and also states that both powders have the same sintering behavior. Additionally, the high percentage of alumina (20.43 wt.-%) contributes to the white color of zirconia white - 2. The powders zirconia black - 1 and zirconia white - 1 have a different composition and thus require a different sintering temperature for complete densification. In contrast to zirconia white - 1, zirconia black - 1 consists at most 5 wt.-% pigments. The recommended sintering temperatures are 1400 &#176;C for zirconia black - 1 and 1350 &#176;C for zirconia white - 1.</li>
	</ol>
	</li>
	<li>Characterize the powders regarding&#160;shape, surface area and particle size distribution. 
	NOTE: Electron scanning microscopy images have been used to characterize the shape of the particles. The particle size distribution of the utilized powders was measured by a laser diffraction method (laser diffractometer). The measurements for the specific surface properties of the used powders have been provided by the manufacture.</li>
	<li>For the preparation of the different zirconia suspensions&#160;melt a mixture of paraffin and beeswax at a temperature of 100 &#176;C in a heatable dissolver and homogenize the polymer mixture.
	<ol>
		<li>Then add the powder in several steps to reach a powder content of 40&#160;vol.%.</li>
		<li>Homogenize the powder-polymer-mixture by stirring for 2 h at 100 &#176;C. Ensure that all suspensions have the same powder content (40&#160;vol.%).</li>
	</ol>
	</li>
	<li>Characterization of suspensions
	<ol>
		<li>Characterize the rheological behavior of the molten suspension using a rheometer for shear rates in a range between 0-5,000/s for different temperatures in a range between 85 &#176;C and 110 &#176;C. 
		NOTE: We used a rheometer&#160;adjustable between -25 &#176;C to 200 &#176;C with a plate/plate measuring system (25 mm diameter). The torque was measured, and the dynamic viscosity was calculated.</li>
		<li>Plot the dynamic viscosity as&#160;function of the shear rate and make sure that the dynamic viscosity is below 100 Pa&#183;s for a shear rate of 10/s, below 20 Pa&#183;s for a shear rate of 100/s and below 1 Pa&#183;s for a shear rate of 5,000/s or increase the temperature within the permissible range.</li>
		<li>Change the suspension composition by adding polymer mixture if the dynamic viscosity is too high even for a temperature of 110 &#176;C.</li>
	</ol>
	</li>
</ol>
2. Manufacturing of Single and Multi-Material Components by CerAM -&#160;T3DP
<ol>
	<li>Used device 
	Figure 1 shows a CAD-drawing of the used CerAM -&#160;T3DP-device with one profile scanner and three different micro dispensing systems, which can work simultaneously or alternately. Use two of them to produce black-and-white components.
	<ol>
		<li>Set the deposition of the droplets to a frequency up to 100/s and the axes to move with a maximum velocity of 20 mm/s.</li>
	</ol>
	</li>
	<li>Investigation of deposition parameters 
	Investigate the influence of deposition parameters (working velocities of the micro dispensing system; temperatures of suspension reservoir and nozzle; velocity of the axis) on the properties of the resulting droplets (shape; volume; homogeneity) or droplet chains (shape; volume; homogeneity).
	<ol>
		<li>Vary the deposition parameters and deposit single droplets as well as droplet chains by using different frequencies and axes velocities for deposition. 
		NOTE: The influence of the dispenser parameters on the properties of the materials has been discussed before25. Parameter value boundaries have only been determined&#160;empirically.</li>
		<li>Make sure that that the variance in droplet chain height and width should not exceed 3 %. Vary the parameters pulse width, droplet fusion factor (DFF) and extrusion width (slicing parameter) to compensate diameter differences up to 100 microns and height differences up to 50 microns. 
		NOTE: It is not necessary and probably not possible to realize perfectly shaped hemispheres as single droplets, but you have to make sure that the homogeneity of the droplet formation is very high to guarantee a homogenous building of the components.</li>
		<li>Repeat this step with different initial parameters to find a parameter set which provides the most homogenous droplet shape with respect to droplet diameter, width&#160;and height.</li>
	</ol>
	</li>
	<li>Manufacturing of single-material test components
	<ol>
		<li>Use a generated 3D model of the desired part and save the file as STL or AMF file format.</li>
		<li>Use a slicing program (e.g. Slicer 1 or Slicer 2) to generate the corresponding G-code. Set the properties for the droplet shape acquired in step 2.2.</li>
		<li>Upload the G-code and fill the process parameters to the CerAM -&#160;T3DP-device. Set the CerAM -&#160;T3DP-device for the parameters obtained in step 2.2 that did correspond to the droplet shape provided to the slicer. Start the device software to start the building job. 
		NOTE: It is beneficial to manufacture certain test samples before building the desired part or using new suspensions.</li>
	</ol>
	</li>
	<li>CerAM -&#160;T3DP of multi-material components
	<ol>
		<li>For each material involved execute step 2.2.</li>
		<li>Select dispensing parameters for both materials which have approximately the same droplet characteristics.</li>
		<li>Adjust the layer heights by changing the distance between the single droplets and the resulting overlap to avoid differences in heights for the different materials, which can result in large defects and faulty components. 
		NOTE: By reducing the distance between two droplets and the associated greater overlap, the width and height of the droplet chain increases due to the nearly constant volume of the single droplets. It can be observed that the droplet chain width increases faster than the droplet chain height.</li>
		<li>Use a generated 3D model of the desired part and save the file as AMF files. If supported by the slicer multiple component areas can also be saved in STL file format.</li>
		<li>In order to print multi-material components, assign corresponding component areas to the associated material in the slicing software by allocating a corresponding micro dispensing system for each material.</li>
		<li>Generate the G-codes for each material by using the slicer software.</li>
		<li>Upload the G-code and fill the process parameters to the CerAM -&#160;T3DP-device. Set the CerAM -&#160;T3DP-device for the parameters obtained in step 2.2 that did correspond to the droplet shape provided to the slicer. Start the device software to start the building job.</li>
	</ol>
	</li>
</ol>
3. Co-Debinding and Co-Sintering of Single- and Multi-Material Components
<ol>
	<li>Debind the green samples in the following separate steps.
	<ol>
		<li>First, put the samples in a loose bulk of coarse-grained alumina powder (powder bed) to structurally support the samples as well as to ensure a homogeneous temperature distribution and to promote the removal of the binder materials by capillary forces.</li>
		<li>Perform a debinding with a very low heating rate in a furnace (debinding furnace) under air-atmosphere up to 270 &#176;C. Set the heating rate to 4 K/h to ensure a defect-free debinding.</li>
	</ol>
	</li>
	<li>After this first debinding step carefully remove the bedding powder for example with a fine brush. Place the samples on alumina kiln furniture.</li>
	<li>Apply a second debinding step under air-atmosphere up to 900 &#176;C (12 K/h) in the same furnace. 
	NOTE: All remaining organic binder materials were thermally removed, while within in the same step a pre-sintering of the zirconia particles was initiated to enable the subsequent transfer of the samples to a sintering kiln.</li>
	<li>Finally&#160;sinter the samples under air-atmosphere at 1,350 &#176;C (180 K/h) for 2 h in a suitable furnace (sintering furnace). Characterize the shrinkage of the components by length measurement in three dimensions and make sure that it is about 20% for each direction.</li>
</ol>
4. Characterization of Single- and Multi-Material Components
<ol>
	<li>Cut the samples properly and polish the surface using ceramographic methods.</li>
	<li>Apply investigations on the microstructure by using Field Emission Scanning Electron Microscope (FESEM).</li>
	<li>Visually inspect the porosity of the two phases and at the boundary interface of the used materials. To obtain a more detailed result perform an interface analysis, e.g. by FESEM and subsequent picture analysis to investigate the porosity within the sintered microstructure. 
	The targeted porosity is below 1%. If the porosity is too high, vary the deposition parameter rising (2.2) and/or the regime of the thermal treatment (3).</li>
</ol>

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The authors have nothing to disclose.

The characterization of the rheological behavior of the molten suspension at high shear rates up to 5000/s is necessary since the assessment of the conditions within the used micro dispensing systems (geometry of piston and nozzle chamber, velocity of piston) revealed that shear rates of 5000/s and higher are generated in the micro dispensing system during the deposition process25.
The investigation of the printing parameters should be done to aid with the calibration of the dispenser for the manufacturing of multi-material components. The influence of the dispenser parameters on the properties of the materials has been discussed in25. Parameter value boundaries have only been determent empirically. Experience so far shows that the variance in droplet chain height and width should not exceed 3 %. Diameter differences up to 100 microns and height differences up to 50 microns can be compensated by the parameters pulse width, droplet fusion factor (DFF) and extrusion width (slicing parameter).
It is critical for the printing process that the layer heights of the different materials are adjusted to each other by changing the distance between the single droplets, since it would result in an unevenness within a layer if the heights of the different materials do not match. An unevenness leads to large defects and faulty components. By reducing the distance between two droplets and the associated greater overlap, the width and height of the droplet chain increases due to the nearly constant volume of the single droplets. It can be observed that the droplet chain width increases faster than the droplet chain height.It is not necessary and probably not possible to realize perfectly shaped hemispheres as single droplets, but you have to make sure by determining the fitting dispensing parameters that the homogeneity of the droplet formation is very high to guarantee a homogenous building of the components.
The measurement at 85 &#176;C simulates the rheological behavior of the suspensions in the feeding cartridge of the micro dispensing system. Above 90 &#176;C, the decomposition of the binder components begins (Figure 7). All suspensions show nearly similar behavior. The used nozzle temperature of the micro dispensing system was 100 &#176;C. This temperature promotes the droplet formation due to the low viscosity caused by increasing the suspensions temperature while passing the nozzle. Because of the short dwell time of the suspensions within the nozzle at this temperature the decomposition is not influencing the material behavior significantly.
The multi-color components could be sintered nearly defect-free, but for the zirconia black - 2 and zirconia white - 2 powders the color of the white phase turned into pink. The cause for the color change are&#160;diffusion processes between the different materials during sintering. This is only an effect at the surface and can be removed by a grinding step. But this is very challenging for complex structures made by AM technologies.
Within the multi-color components&#160;planar and interwoven boundary interfaces developed between the two different compositions. Thus, regardless of the drop-bound deposition of the material, the arrangement of the different microstructures can be realized very precisely. Furthermore, the droplet shape can be exploited to increase the boundary interface between two materials. So far only discrete material transitions have been produced. Future research may also involve the production of gradual changes between materials.

Functionally Graded Materials (FGM) are materials with a variety of properties concerning transitions in the microstructure or in the material1. These transitions can be discrete or continuous. Different kinds of FGM are known, such as components with material gradients, graded porosity as well as multi-colored components.
FGM-components can be manufactured by single conventional shaping technologies2,3,4,5,6,7 or by a combination of these technologies, for example, by in-mold labeling as a combination of tape casting and injection molding8,9.
Additive manufacturing (AM) allows for the production of components with a so far unprecedented freedom of design. This is considered the state of the art shaping technology for polymers and metals. First commercial processes for the processing of&#160;ceramics are available10, and nearly all known AM technologies are used for AM of ceramics in laboratories all over the world11,12,13.
To combine the benefits of AM with the benefits of FGM to ceramic-based 4D components (three dimensions for the geometry and one degree of freedom concerning the material properties at each position) the Thermoplastic 3D-Printing (CerAM -&#160;T3DP) has been developed at Fraunhofer IKTS in Dresden, Germany, as a direct AM technology. This allows the AM of multi-material components14,15,16,17. CerAM -&#160;T3DP is based on the selective deposition of single droplets of particle filled thermoplastic suspensions. By utilizing multiple dosing systems, different thermoplastic suspensions can be deposited beside each other layer by layer to produce bulk material as well as property gradients within the additively manufactured green components18. Unlike indirect AM processes, in which previously deposited materials solidify selectively over the entire layer, the CerAM -&#160;T3DP process does not require the additional effort of removing any non-solidified material prior to the deposition of the next material, making it more suitable for the AM of multi-material components.
Although utilizing the CerAM -&#160;T3DP process allows the AM of FGM and the realization of ceramic-based components with unprecedented properties, there are challenges to overcome regarding the necessary thermal treatment after the AM process, in order to obtain a multi-material composite. In particular, the paired powders in the composite material need to be successfully co-sintered, for which the sintering of the components has to be performed at the same temperature and atmosphere. Therefore, it is a prerequisite for all materials to have a comparable sintering temperature and behavior (starting temperature of sintering, shrinkage behavior). In order to avoid critical mechanical stress during cooling, the coefficient of thermal expansion of all materials has to be approximately equal11.
The combination of materials with different properties in one component opens the door to components with unprecedented properties for manifold applications. E.g. stainless steel-zirconia composites can be used as cutting tools, wear resistant components, energy, and fuel cell components or as bipolar surgical tools19,20,21,22,23,24. Such components could be realized by CerAM -&#160;T3DP14,15,16,17, too, after the adjustment of the sintering behavior by a special milling process16.
Ceramic-based FGM with a graded porosity like dense and porous zirconia combine very good mechanical properties in the dense areas with a high active surface of the porous areas. Such like components can be additively manufactured by CerAM -&#160;T3DP18.
In this paper, we investigate the AM of zirconia components with two different colors in one component by CerAM -&#160;T3DP. We chose white and black zirconia because this combination in one ceramic component is interesting for jewelry applications. The demand of&#160;individualized luxury goods is very high and still growing. Technologies which allow the AM of ceramic-based multi-material components with a high resolution and very good surface properties will allow to satisfy this demand. Ceramics like zirconia are used for example to produce watch components like watch cases and bezels or for rings because of the special haptics, glance, hardness and lower weight compared to metals.

<table><tbody><tr><td>&lt;strong&gt;Material&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Zirconia black - 1</td><td>TZ-3Y-Black</td><td>Tosoh</td><td></td></tr><tr><td>Zirconia black - 2</td><td>ZirPro ColorYZ Black</td><td>Saint Gobain</td><td></td></tr><tr><td>Zirconia white - 1</td><td>TZ-3Y-Black</td><td>Tosoh</td><td></td></tr><tr><td>Zirconia white - 2</td><td>ZirPro ColorYZ Arctic White</td><td>Saint Gobain</td><td></td></tr><tr><td>&lt;strong&gt;Equipment&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>laser diffractometer</td><td>Mastersizer 2000</td><td>Malvern Instruments Ltd., United Kingdom</td><td></td></tr><tr><td>dissolver</td><td>DISPERMAT CA 20-C</td><td>VMA-Getzmann GmbH, Germany</td><td></td></tr><tr><td>rheometer</td><td>Modular Compact Rheometer MCR 302&amp;nbsp;</td><td>Anton Paar, Graz, Austria</td><td></td></tr><tr><td>micro dispensing system</td><td>MDS 3250</td><td>Vermes, Germany&amp;nbsp;&amp;nbsp;</td><td></td></tr><tr><td>T3DP-device&amp;nbsp;</td><td>IKTS-T3DP-device &quot;TRUDE&quot;, in-house development</td><td>Fraunhofer IKTS, not commerzialized</td><td></td></tr><tr><td>profile scanner</td><td>LJ-V7020</td><td>Keyence&amp;nbsp;&amp;nbsp;</td><td></td></tr><tr><td>Slicer 1</td><td>Slic3r</td><td>open source software</td><td></td></tr><tr><td>Slicer 2</td><td>Simplify3D</td><td>Simplofy3D</td><td></td></tr><tr><td>debinding furnace</td><td>NA120/45</td><td>Nabertherm, Germany</td><td></td></tr><tr><td>sintering furnace</td><td>LH 15/12</td><td>Nabertherm, Germany&amp;nbsp;</td><td></td></tr><tr><td>FESEM</td><td>Gemini 982&amp;nbsp;</td><td>Zeiss, Germany&amp;nbsp;</td><td></td></tr></tbody></table>

multi-material ceramic-based components &#8211; additive manufacturing of black-and-white zirconia components by thermoplastic 3d-printing (ceram - t3dp)

To combine the benefits of Additive Manufacturing (AM) with the benefits of Functionally Graded Materials (FGM) to ceramic-based 4D components (three dimensions for the geometry and one degree of freedom concerning the material properties at each position) the Thermoplastic 3D-Printing (CerAM -&#160;T3DP) was developed. It is a direct AM technology which allows the AM of multi-material components. To demonstrate the advantages of this technology black-and-white zirconia components were additively manufactured and co-sintered defect-free.
Two different pairs of black and white zirconia powders were used to prepare different thermoplastic suspensions. Appropriate dispensing parameters were investigated to manufacture single-material test components and adjusted for the additive manufacturing of multi-color zirconia components.

For the production of measured components, only powders of the same manufacturer have been combined for each multi-material component. Experiments with powders of different manufactures in one component are still ongoing. For this purpose, the different shrink rates have to be considered.
The measurement result of the average particle diameter (d50) of the zirconia white - 1 after dispersion was 0.37 &#181;m. The manufacturer states an actual particle size of 0.04 &#181;m (one order of magnitude less). The average particle size (d50) of the zirconia black - 1 is 0.5 &#181;m. Figure 2 (A) shows the FESEM analysis of the zirconia white - 1 and Figure 2 (B) a FESEM-image of the surface of a granulate in detail. Figure 2 (C) and Figure 2 (D) show the same for zirconia black - 1. Both untreated powders consist of big spherical granules (diameter up to 100 &#181;m) which is typical for dry pressing raw materials. The FESEM-images of the granulate surfaces show the primary particles of the zirconia white - 1 (Figure 2 (B)) and zirconia black - 1 (Figure 2 (D)) with an actual particle size of almost 0.04 &#181;m.
The Figure 2 (E) &#8211; 2 (H) show the FESEM-images of the zirconia white - 2 and zirconia black - 2. The measured average particle sizes (d50) of the zirconia powders zirconia white - 2 and zirconia black - 2 are 0.27 &#181;m and 0.25 &#181;m, respectively, wherein the particles are present as spherical granules with diameters up to 100 &#181;m (Figure 2 (E) and Figure 2 (G)). The size of the white powders primary particles is below 0.1 &#181;m (Figure 2 (F)). The black powders primary particles are up to 0.5 &#181;m in diameter (Figure 2 (H)).
Figure 3 (A) shows the dynamic viscosity of the suspensions based on zirconia white - 1 and zirconia black - 1 as a function of the shear rate and in dependence of the temperature (85 &#176;C and 100 &#176;C). Both suspensions show a shear thinning behavior regardless of the temperature.
Table 1 summarizes the measured viscosities of the suspensions at different shear rates and for different temperatures.
Figure 3 (B) shows the rheological behavior of the suspensions based on zirconia white - 2 and zirconia black - 2 (85 &#176;C and 100 &#176;C). All graphs show a shear thinning behavior. Table 2 summarizes the measured viscosities of the suspensions at different shear rates and for different temperatures.
In addition to shear rate-controlled measurements, long-term measurements were carried out. Figure 3 (C) shows the course of the dynamic viscosity during the long-term measurements for all four suspensions at a constant shear rate of 10/s over 2 h. While the dynamic viscosity of the white zirconia suspensions (zirconia white - 1 and zirconia white - 2) is nearly constant (Table 3), the dynamic viscosity tends to decrease slightly of the black zirconia (zirconia black - 1 and zirconia black - 2).
After the empirical determination of the dosing parameters the manufacturing of single component, three dimensional structures became manageable for each suspension. Figure 4 (A) shows a complex sintered test structure based on the suspension made of zirconia white - 1 and additively manufactured by CerAM -&#160;T3DP. The same test structure additively manufactured by CerAM -&#160;T3DP and the zirconia black - 1-suspension is shown in Figure 4 (B).
Figure 4 (C) shows a sintered test structure based on the zirconia suspensions of the zirconia white - 2, Figure 4 (D) a sintered test structure based on zirconia black - 2. Subsequent to the manufacturing of the single-color components the manufacturing of multi-color components took place. The Figure 4 (D) to 4 (F) show some sintered multi-color zirconia components additive manufacturing using the CerAM -&#160;T3DP.
Figure 5 (A) and Figure 5 (B) show FESEM-images of the microstructure of multi-color components with a clearly distinguishable interface between the two suspensions based on the zirconia powders zirconia white - 1 (top) and zirconia black - 1 (bottom).
An energy-dispersive X-ray spectroscopic analysis (EDX) showed that in the microstructure of the sintered&#160;zirconia black - 1 more alumina crust occurs (Figures 6 (A-C)). To evaluate the composition of the and zirconia black - 1-microstructure especially in the dark areas in more detail further EDX investigations took place (Figures 6 (D-G)) which showed the precipitation of alumina (Figure 6 (E)).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57538/57538fig1.jpg" /> 
Figure 1: CAD-drawing of used CerAM -&#160;T3DP-device with three micro dispensing units and one surface scanner. <a href="/files/ftp_upload/57538/57538fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57538/57538fig2.jpg" /> 
Figure 2: FESEM-image of used zirconia granulates. (A) zirconia white - 1 granulates - overview and (B) surface; (C)zirconia black - 1 granulates - overview and (D) surface; (E) zirconia white - 2 granulates - overview and (F) surface; (G) zirconia black - 2 granulates - overview and (H) surface.
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/57538/57538fig3.jpg" /> 
Figure 3: Rheological behavior of thermoplastic suspensions. (A) based on the zirconia powders zirconia white - 1 and zirconia black - 1; (B) based on the zirconia powders zirconia white - 2 and zirconia black - 2; (C) comparison of all four suspensions during a long-term measurement at a constant shear rate of 10/s.
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/57538/57538fig4.jpg" /> 
Figure 4: Sintered single- and multi-material test structures additively manufactured by T3DP. (A) based on zirconia white - 1 -suspension; (B) based on zirconia black - 1 -suspension; (C) based on zirconia white - 2 -suspension; (D) based on zirconia black - 2 -suspension; (E) based on zirconia white - 1 - and zirconia black - 1 -suspension; (F) based on zirconia white - 2- and zirconia black - 2 -suspension - frame-like structure and (G) ring-like structure.
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/57538/57538fig5.jpg" /> 
Figure 5: FESEM-images. FESEM-images of cross section at interface between sintered zirconia white - 1 (top) and zirconia black - 1 (bottom); (A) planar interface and (B) interwoven interface
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/57538/57538fig6.jpg" /> 
Figure 6: Results of EDX measurements at sintered zirconia white - 1 / zirconia black - 1 -interface. (A) Overview about measurement fields 1 + 2 and (D) 3 - 5; results of measurement (B) field 1, (C) field 2, (E) field 3, (F) field 4 and (G) field 5.
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/57538/57538fig7.jpg" /> 
Figure 7: Mass change of the zirconia white - 1- and zirconia black - 1 -suspensions during thermal decomposition <a href="/files/ftp_upload/57538/57538fig7large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Table 1" src="/files/ftp_upload/57538/57538table1.jpg" /> 
Table 1: Dynamic viscosity of thermoplastic suspensions based on the zirconia powders zirconia white - 1 and zirconia black - 1. <a href="/files/ftp_upload/57538/Table_01.pdf">Please click here to download this file.</a>
<img alt="Table 2" src="/files/ftp_upload/57538/57538table2.jpg" /> 
Table 2: Dynamic viscosity of thermoplastic suspensions based on the zirconia powders zirconia white - 2 and zirconia black - 2. <a href="/files/ftp_upload/57538/Table_02.pdf">Please click here to download this file.</a>
<img alt="Table 3" src="/files/ftp_upload/57538/57538table3.jpg" /> 
Table 3: Dynamic viscosity of all four suspensions during the long-term measurement at a constant shear rate of 10/s. <a href="/files/ftp_upload/57538/Table_03.pdf">Please click here to download this file.</a>

Watch this Scientific Journal Video about Multi-material Ceramic-Based Components â€“ Additive Manufacturing of Black-and-white Zirconia Components by Thermoplastic 3D-Printing CerAM - T3DP at Jo

Multi-material Ceramic-Based Components &#8211; Additive Manufacturing of Black-and-white Zirconia Components by Thermoplastic 3D-Printing (CerAM - T3DP)

Here we describe a protocol for additively manufacturing black-and-white zirconia components by Thermoplastic 3D-Printing (CerAM -&#160;T3DP) and co-sintering defect-free.

To combine the benefits of Additive Manufacturing (AM) with the benefits of Functionally Graded Materials (FGM) to ceramic-based 4D components (three ...

multi-material-ceramic-based-components-additive-manufacturing-black

Universidad San Sebastian

Research

JoVE Journal

Engineering

11.1K Views.  Fraunhofer Institute for Ceramic Technologies and Systems IKTS. Here we describe a protocol for additively manufacturing black-and-white zirconia components by Thermoplastic 3D-Printing (CerAM - T3DP) and co-sintering defect-free.

Video: Multi-material Ceramic-Based Components – Additive Manufacturing of Black-and-white Zirconia Components by Thermoplastic 3D-Printing (CerAM - T3DP)

Micro 3D Printing Using a Digital Projector and its Application in the Study of Soft Materials Mechanics

Buckling is a classical topic in mechanics. While buckling has long been studied as one of the major structural failure modes1, it has recently drawn new attention as a unique mechanism for pattern transformation. Nature is full of such examples where a wealth of exotic patterns are formed through mechanical instability2-5. Inspired by this elegant mechanism, many studies have demonstrated creation and transformation of patterns using soft materials such as elastomers and hydrogels6-11. Swelling gels are of particular interest because they can spontaneously trigger mechanical instability to create various patterns without the need of external force6-10. Recently, we have reported demonstration of full control over buckling pattern of micro-scaled tubular gels using projection micro-stereolithography (P&mu;SL), a three-dimensional (3D) manufacturing technology capable of rapidly converting computer generated 3D models into physical objects at high resolution12,13. Here we present a simple method to build up a simplified P&mu;SL system using a commercially available digital data projector to study swelling-induced buckling instability for controlled pattern transformation.
A simple desktop 3D printer is built using an off-the-shelf digital data projector and simple optical components such as a convex lens and a mirror14. Cross-sectional images extracted from a 3D solid model is projected on the photosensitive resin surface in sequence, polymerizing liquid resin into a desired 3D solid structure in a layer-by-layer fashion. Even with this simple configuration and easy process, arbitrary 3D objects can be readily fabricated with sub-100 &mu;m resolution.
This desktop 3D printer holds potential in the study of soft material mechanics by offering a great opportunity to explore various 3D geometries. We use this system to fabricate tubular shaped hydrogel structure with different dimensions. Fixed on the bottom to the substrate, the tubular gel develops inhomogeneous stress during swelling, which gives rise to buckling instability. Various wavy patterns appear along the circumference of the tube when the gel structures undergo buckling. Experiment shows that circumferential buckling of desired mode can be created in a controlled manner. Pattern transformation of three-dimensionally structured tubular gels has significant implication not only in mechanics and material science, but also in many other emerging fields such as tunable matamaterials.

We demonstrate controlled pattern transformation of swelling gel tubes by elastic instability. A simple projection micro stereo-lithography setup is built using an off-the-shelf digital data projector to fabricate three-dimensional polymeric structures in a layer-by-layer fashion. Swelling hydrogel tubes under mechanical constraint display various circumferential buckling modes depending on dimension.

Buckling is a classical topic in mechanics. While buckling has long been studied as one of the major structural failure modes1, it has recently drawn new ...

Micro-masonry for 3D Additive Micromanufacturing

Transfer printing is a method to transfer solid micro/nanoscale materials (herein called &#8216;inks&#8217;) from a substrate where they are generated to a different substrate by utilizing elastomeric stamps. Transfer printing enables the integration of heterogeneous materials to fabricate unexampled structures or functional systems that are found in recent advanced devices such as flexible and stretchable solar cells and LED arrays. While transfer printing exhibits unique features in material assembly capability, the use of adhesive layers or the surface modification such as deposition of self-assembled monolayer (SAM) on substrates for enhancing printing processes hinders its wide adaptation in microassembly of microelectromechanical system (MEMS) structures and devices. To overcome this shortcoming, we developed an advanced mode of transfer printing which deterministically assembles individual microscale objects solely through controlling surface contact area without any surface alteration. The absence of an adhesive layer or other modification and the subsequent material bonding processes ensure not only mechanical bonding, but also thermal and electrical connection between assembled materials, which further opens various applications in adaptation in building unusual MEMS devices.

This paper introduces a 3D additive micromanufacturing strategy (termed &#8216;micro-masonry&#8217;) for the flexible fabrication of microelectromechanical system (MEMS) structures and devices. This approach involves transfer printing-based assembly of micro/nanoscale materials in conjunction with rapid thermal annealing-enabled material bonding techniques.

Transfer printing is a method to transfer solid micro/nanoscale materials (herein called &#8216;inks&#8217;) from a substrate where they are generated to ...

Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application

In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto silicon (Si) substrates via different synthesized temperatures by using plasma enhanced chemical vapor deposition (PECVD) system. The effects of different synthesized temperatures on the crystal structure, surface morphologies and optical properties have been investigated. The X-ray diffraction (XRD) patterns indicated that the intensity of (0002) diffraction peak became stronger with increasing synthesized temperature until 400 oC. The diffraction intensity of (0002) peak gradually became weaker accompanying with appearance of (10-10) diffraction peak as the synthesized temperature up to excess of 400 oC. The RT photoluminescence (PL) spectra exhibited a strong near-band-edge (NBE) emission observed at around 375 nm and a negligible deep-level (DL) emission located at around 575 nm under high c-axis ZnO thin films. Field emission scanning electron microscopy (FE-SEM) images revealed the homogeneous surface and with small grain size distribution. The ZnO thin films have also been synthesized onto glass substrates under the same parameters for measuring the transmittance.
For the purpose of ultraviolet (UV) photodetector application, the interdigitated platinum (Pt) thin film (thickness ~100 nm) fabricated via conventional optical lithography process and radio frequency (RF) magnetron sputtering. In order to reach Ohmic contact, the device was annealed in argon circumstances at 450 oC by rapid thermal annealing (RTA) system for 10 min. After the systematic measurements, the current-voltage (I-V) curve of photo and dark current and time-dependent photocurrent response results exhibited a good responsivity and reliability, indicating that the high c-axis ZnO thin film is a suitable sensing layer for UV photodetector application.

We offered a method to directly synthesize high c-axis (0002) ZnO thin film by plasma enhanced chemical vapor deposition. The as-synthesized ZnO thin film combined with Pt interdigitated electrode was used as sensing layer for ultraviolet photodetector, showing a high performance through a combination of its good responsivity and reliability.

In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto ...

Digital Printing of Titanium Dioxide for Dye Sensitized Solar Cells

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less environmentally damaging with lower processing temperatures presenting a viable and low cost alternative to conventional production. This paper further enhances these environmental credentials by evaluating the digital printing and therefore additive production route for these cells. This is achieved here by investigating the formation and performance of a metal oxide photoelectrode using nanoparticle sized titanium dioxide. An ink-jettable material was formulated, characterized and printed with a piezoelectric inkjet head to produce a 2.6 &#181;m thick layer. The resultant printed layer was fabricated into a functioning cell with an active area of 0.25 cm2 and a power conversion efficiency of 3.5%. The binder-free formulation resulted in a reduced processing temperature of 250 &#176;C, compatible with flexible polyamide substrates which are stable up to temperatures of 350 &#730;C. The authors are continuing to develop this process route by investigating inkjet printing of other layers within dye sensitized solar cells.

This paper investigates the suitability of inkjet printing for the manufacturing of dye-sensitized solar cells. A binder-free TiO2 nanoparticle ink was formulated and printed onto a FTO glass substrate. The printed layer was fabricated into a cell with an active area of 0.25 cm2 and an efficiency of 3.5%.

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less ...

Experimental Procedure for Warm Spinning of Cast Aluminum Components

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to improve material properties. With a wide array of processing parameters which can affect both the shape attained and resulting material properties, this type of processing is notoriously difficult to commission. A simplified, light-duty version of the process has been designed and implemented for full-size automotive wheels. The apparatus is intended to assist in understanding the deformation mechanisms and the material response to this type of processing. An experimental protocol has been developed to prepare for, and subsequently perform forming trials and is described for as-cast A356 wheel blanks. The thermal profile attained, along with instrumentation details are provided. Similitude with full-scale forming operations which impart significantly more deformation at faster rates is discussed.

An experimental protocol for instrumented warm rotary forming of cast aluminum alloys employing a bespoke industrially scaled apparatus is presented. Experimental considerations including thermal and mechanical effects are discussed, as well as similitude with full-scale processing of automotive wheels.

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

Fused Filament Fabrication (FFF) of Metal-Ceramic Components

Technical ceramics are widely used for industrial and research applications, as well as for consumer goods. Today, the demand for complex geometries with diverse customization options and favorable production methods is increasing continuously. With fused filament fabrication (FFF), it is possible to produce large and complex components quickly with high material efficiency. In FFF, a continuous thermoplastic filament is melted in a heated nozzle and deposited below. The computer-controlled print head is moved in order to build up the desired shape layer by layer. Investigations regarding printing of metals or ceramics are increasing more and more in research and industry. This study focuses on additive manufacturing (AM) with a multi-material approach to combine a metal (stainless steel) with a technical ceramic (zirconia: ZrO2). Combining these materials offers a broad variety of applications due to their different electrical and mechanical properties. The paper shows the main issues in preparation of the material and feedstock, device development, and printing of these composites.

Fused Filament Fabrication FFF of Metal-Ceramic Components

This study shows multi-material additive manufacturing (AM) using fused filament fabrication (FFF) of stainless steel and zirconia.

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Additive Manufacturing of Functionally Graded Ceramic Materials by Stereolithography

An additive manufacturing technology is applied to obtain functionally graded ceramic parts. This technology, based on digital light processing/stereolithography, is developed within the scope of the CerAMfacturing European research project. A three-dimensional (3-D) hemi-maxillary bone-like structure is 3-D printed using custom aluminum oxide polymeric mixtures. The powders and mixtures are fully analyzed in terms of rheological behavior in order to ensure proper material handling during the printing process. The possibility to print functionally graded materials using the Admaflex technology is explained in this document. Field-emission scanning electron microscopy (FESEM) show that the sintered aluminum oxide ceramic part has a porosity lower than 1% and no remainder of the original layered structure is found after analysis.

This manuscript describes the processing of single multifunctional ceramic components (e.g., combinations of dense-porous structures) additively manufactured by stereolithography.

An additive manufacturing technology is applied to obtain functionally graded ceramic parts. This technology, based on digital light ...

Negative Additive Manufacturing of Complex Shaped Boron Carbides

Boron carbide (B4C) is one of the hardest materials in existence. However, this attractive property also limits its machineability into complex shapes for high wear, high hardness, and lightweight material applications such as armors. To overcome this challenge, negative additive manufacturing (AM) is employed to produce complex geometries of boron carbides at various length scales. Negative AM first involves gelcasting a suspension into a 3D-printed plastic mold. The mold is then dissolved away, leaving behind a green body as a negative copy. Resorcinol-formaldehyde (RF) is used as a novel gelling agent because unlike traditional hydrogels, there is little to no shrinkage, which allows for extremely complex molds to be used. Furthermore, this gelling agent can be pyrolyzed to leave behind ~50 wt% carbon, which is a highly effective sintering aid for B4C. Due to this highly homogenous distribution of in situ carbon within the B4C matrix, less than 2% porosity can be achieved after sintering. This protocol highlights in detail the methodology for creating near fully dense boron carbide parts with highly complex geometries.

A method called negative additive manufacturing is used to produce near fully dense complex shaped boron carbide parts of various length scales. This technique is possible via the formulation of a novel suspension involving resorcinol-formaldehyde as a unique gelling agent that leaves behind a homogenous carbon sintering aid after pyrolysis.

Boron carbide (B4C) is one of the hardest materials in existence. However, this attractive property also limits its machineability into complex shapes for ...

Chemistry

Ceramic Omnidirectional Bioprinting in Cell-Laden Suspensions for the Generation of Bone Analogs

Structurally, bone tissue is an inorganic-organic composite containing metabolically active cells embedded within a hierarchical, highly mineralized matrix. This organization is challenging to replicate due to the heterogeneous environment of bone. Ceramic omnidirectional bioprinting in cell-suspensions (COBICS) is a microgel-based bioprinting technique that uniquely replicates the mineral and cellular structure of bone. COBICS prints complex, biologically relevant constructs without the need for sacrificial support materials or harsh postprocessing steps (e.g., radiation and high-temperature sintering), which are two of the biggest challenges in the additive manufacturing of bone mimetic constructs. This technique is enabled via the freeform extrusion of a novel calcium phosphate-based ink within a gelatin-based microgel suspension. The yield-stress properties of the suspension allow deposition and support the printed bone structure. UV crosslinking and nanoprecipitation then "lock" it in place. The ability to print nanostructured bone-mimetic ceramics within cell-laden biomaterials provides spatiotemporal control over macro- and micro-architecture and facilitates the real-time fabrication of complex bone constructs in clinical settings.

This protocol describes a 3D printing technique to fabricate bone-like structures by depositing a calcium phosphate ink in a gelatin-based granular support. Printed bone analogs are deposited in freeform, with flexibility for direct harvesting of the print or crosslinking within a living cell matrix for multiphasic constructs.

Structurally, bone tissue is an inorganic-organic composite containing metabolically active cells embedded within a hierarchical, highly mineralized ...

Multi-material Ceramic-Based Components – Additive Manufacturing of Black-and-white Zirconia Components by Thermoplastic 3D-Printing (CerAM - T3DP)

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