2024 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2024): Materials: Ceramics, Glasses
Program Organizers: Joseph Beaman, University of Texas at Austin

Monday 1:30 PM
August 12, 2024
Room: Salon F
Location: Hilton Austin

Session Chair: Desiderio Kovar, University of Texas at Austin

1:30 PM
Monolithic Glass Forming using Laser Heated Sculpting: Nishan Khadka¹; Balark Tiwari¹; Todd Sparks²; Robert Landers¹; Edward Kinzel¹; ¹University of Notre Dame; ²Product Innovation and Engineering
    Additive manufacturing of optics is highly desirable across various applications due to its ability to create complex features, accommodate a wide range of materials, and incorporate digital fabrication. This paper presents a novel method of digital glass forming that utilizes localized heating and glass redistribution to create intricate geometries. In this process, glass substrates are positioned relative to a fixed CO2 laser beam using precision 4-axis CNC stages. A stationary graphite forming tool applies stress to the laser-heated region displacing the glass via controlled plowing. This approach is studied for shaping simple optical forms. There are lower compositional changes in the glass than when it is processed at the temperatures associated with melting. The effects of the trajectory of the forming tool relative to the glass and temperature on the final geometry are studied experimentally.

1:50 PM
Innovative Approaches to Fabricate Terahertz Optics with Additive Manufacturing: Manufacture and THz Characterisation of a Silica-Filled Photopolymer: Luke Phillips¹; Alexander Valavanis¹; Andrew Burnett¹; Robert Kay¹; Russell Harris¹; Ehab Saleh²; ¹University of Leeds; ²University of Doha
     Due to the increasing demand for terahertz optics in medical imaging, communication and spectroscopy systems, research into using Additive Manufacturing (AM) to manufacture THz optics is rapidly expanding. However, conventional AM feedstock materials are often absorptive in the THz band, with the absorption coefficient of commercially available photopolymers ranging from 19-27cm^-1 at 1 THz. Unsuitable for low-loss THz applications, such as refractive THz lenses and waveguides. Literature had shown silica to be highly transparent in the THz region, therefore a silica-filled photopolymer sample was manufactured using stereolithography. The sample was then characterised from 1-4 THz using terahertz time-domain spectroscopy.The results were promising, with the composite having a lower absorption coefficient (10.71 cm^-1) and a higher refractive index (1.72) at 1 THz than standard photopolymers. This work demonstrates that AM-produced ceramic-filled photopolymers could offer unique spectral properties in the THz band desirable for THz optics.

2:10 PM
Additive Manufacturing of Oxide and Non-oxide Ceramics for Functional and Structural Applications: Saqlain Zaman¹; Md. Shahjahan Mahmud¹; Joshua Dantzler¹; Alexis Lopez¹; Sabina Arroyo¹; Diana Levya¹; Joseph Munoz¹; Nicholas Ku¹; Lionel Gonzalez¹; Yirong Lin¹; ¹The University of Texas at El Paso
    Ceramics have exceptional thermal, mechanical, electrical, and dielectric properties, and are highly suitable for functional and structural applications in electronics and harsh environments. However, the brittle nature and high hardness of ceramics have historically posed challenges in manufacturing and processing. Recently, the advent of 3D printing has enabled the fabrication of intricate and precise ceramic structures with ease. The article primarily concentrates on showcasing our research of the last decade on the utilization of 3D printing for both oxide and non-oxide ceramics for complex and customized structures to enhance the performance of conventional applications. On the oxide ceramics front, we will showcase our effort in printing piezoelectric ceramics with tunable sensing capabilities, and alumina and zirconia with intricate gradient micro lattices for tunable thermal and mechanical properties. On the non-oxide ceramics front, will showcase our effort in printing UHTC ceramics with fiber reinforcement to engineer mechanical, thermal, and electrical properties.

2:30 PM
Measuring Temperature during AC Selective Laser Flash Sintering: Joey Zamora¹; David Khanan¹; Joseph Beaman¹; Desiderio Kovar¹; ¹University of Texas at Austin
     Selective laser flash sintering (SLFS) is proposed as a method for directly additively manufacturing ceramics without the need for a polymeric binder. Understanding the onset of the flash event is essential in SLFS because it is necessary to interrupt the flash before thermal runaway and cracking occur. The onset of flash is characterized by a sharp increase in both the current flowing through the sample and resulting temperature rise associated with Joule heating. Thus, a high-speed temperature measurement of the highly dynamic hot region is needed to allow for a repeatable additive manufacturing process. A coaxial photodiode is studied in this research for its sensitivity at the near-infrared wavelengths and its very short response times. Experiments are conducted using alternating electric fields in the SLFS system to determine the sensitivity of this technique to measure temperaturesduring SLFS.

2:50 PM
Sol-Gel Synthesis Integrated 3D Printing of Lithium Nickel Cobalt Manganese Oxide: Luyang Liu¹; Xiangfan Chen¹; ¹Arizona State University
    Polycrystalline lithium nickel cobalt manganese oxide (LiNixCoyMn1-x-yO2, NCM) ceramics have emerged as promising lithium intercalation materials due to their high capacity, good cycling stability, and excellent thermal resilience. These properties make NCM ceramics popular for lithium battery cathodes. However, conventional fabrication methods such as powder metallurgy suffer from expenses, time consumption, and limitations in customizing structures. This study introduces a novel approach to fabricating NCM ceramics with 3D free-form structures. Sol-gel synthesis produces photocurable colloidal solutions, while a home-built micro-continuous liquid interface production system prints resins with varying ion concentrations (x and y) into 3D hydrogels. After thermal dehydration, debinding, and sintering, polycrystalline NCM ceramics with different atomic ratios of Ni, Mn and Co (NCM 111, NCM 811, and NCM 901) featuring distinguishable grains are successfully produced, demonstrating potential applications such as high-surface-area electrodes.

3:10 PM Break

3:40 PM
Using Laser Ultrasonics to Measure Localized Changes in Young’s Modulus caused by Select Laser Flash Sintering: Christina Nissen¹; Joseph Beaman¹; Desiderio Kovar¹; ¹University of Texas at Austin
    Select laser flash sintering (SLFS) is a process that requires the onset of initial stage sintering without proceeding to intermediate stage sintering. Because there is minimal change in density at this stage, traditional non-destructive techniques for determining the onset of sintering cannot be employed. In this study we use model experiments that show that changes in the Young’s modulus are strongly correlated to different levels of early-stage sintering. We then study time of flight measurements made with a laser ultrasonic system on samples that have been scanned with an SLFS laser. We show that this technique can differentiate between unsintered and partially sintered regions, even in the earliest stages of sintering. The use of laser ultrasonics to detect the onset of sintering has applications for SLFS and other powder-bed additive manufacturing processes.

4:00 PM
Design Guidelines for Material Extrusion Based Additive Manufacturing: Generation of Rules for Ceramics and Comparison to Polymer Standards: Hollis Waites¹; Tieshu Huang¹; Jeremy Watts¹; Greg Hilmas¹; Ming Leu¹; ¹Missouri University of Science and Technology
    Design guidelines for material extrusion (MEX) of polymers in additive manufacturing (AM) are much more common and developed than those for ceramic AM. The similarities and differences between the properties of these two materials and their extrusion processes are discussed, specifically in viscosity and extrusion and solidification methods. Experimental measurements of some geometric limits for the Ceramic On-Demand Extrusion (CODE) process are described and compared to the limits found in the ASTM F3529-21 standard for MEX-Polymers. A number of guidelines for CODE and similar ceramic AM processes are generated and demonstrated, such as the removal of supports, increase in particle migration for fully enclosed cavities, and gap-spanning differences. Altogether, this provides groundwork and identifies future opportunities for development for design rules for MEX-Ceramics.

4:20 PM
Influence of Light Intensity and Exposure Time on Cure Depth and Overpolymerization in Ceramic Vat Photopolymerization: Nellie Pestian¹; Alex Gonzalez¹; Geoff Brennecka¹; Craig Brice¹; Joy Gockel¹; ¹Colorado School of Mines
    Ceramic part production via vat photopolymerization is a complex process, with many potential sources of variability for the final product. It is crucial to understand the source and magnitude of any variability in order to produce reliable parts with this process. One potential source of variability lies in the interaction of light with slurry, which is investigated in this work by curing single-layer samples with different light intensities and exposure times, then measuring the cure depth (along the z-axis) and the overpolymerization (in the x-y plane). The experiments are repeated for two popular technical ceramics, high-purity alumina and yttria-stabilized zirconia, to determine whether the methods and conclusions are transferrable to different materials. This presentation reports statistical modeling and analysis of both cure depth and overpolymerization as a function of process parameters, while highlighting potential sources of process variability. Finally, connections are made between observations in single-layer samples and bulk parts.

4:40 PM
Minimizing Drying Defects for Large-Scale Parts Fabricated by Ceramic On-Demand Extrusion: Abid Hasan Rafi¹; David Lipke¹; Jeremy Watts¹; Greg Hilmas¹; Ming Leu¹; ¹Missouri University of Science and Technology
    Fabricating large-scale solid ceramic parts via material extrusion remains challenging due to uneven drying, warping, and cracking of printed layers over extended printing times. This study addresses these challenges by investigating and mitigating issues arising from the continuous drying of deposited ceramic paste. Using a ceramic aqueous paste made of ZrB₂/SiC (70/30 by vol.%), the Ceramic On-Demand Extrusion (CODE) process was employed. Large-scale parts with larger surface areas and reduced paste flow rates contribute to drying defects caused by uneven water evaporation. This study explored water evaporation behavior across various flow rates, surface areas, and printing patterns of deposited layers. The optimal flow rate was determined to prevent these defects on printed layers. Additionally, the role of build plate material in drying behavior was examined, with changes to build plate conditions significantly enhancing the prevention of warping and shape deformations in large-scale solid ceramic parts.

5:00 PM
Hybrid Manufacturing of Glass using Femtosecond Machining and Digital Glass Forming: Nishan Khadka¹; Balark Tiwari¹; Todd Sparks²; Robert Landers¹; Edward Kinzel¹; ¹University of Notre Dame; ²Product Innovation and Engineering
    Digital fabrication enables precise, flexible, and scalable manufacturing of intricate optical elements from traditional optics to complex microstructures and freeform optics. This paper presents a hybrid approach that combines filament-fed laser additive manufacturing with femtosecond laser micromachining for shaping optical elements with precision. Using a 4-axis CNC stage, substrates are controlled relative to a CO2 laser, locally heated to form optical elements, followed by surface mapping and registration for femtosecond laser micromachining. Machining accuracy and quality through surface roughness and controlled glass reflow to improve quality are also discussed.