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Chavez, Luis A.

Publications and source records attributed to Chavez, Luis A..

11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Void-Engineered Metamaterial Delay Line with Built-In Impedance Matching for Ultrasonic Applications

Metamaterials exhibit unique ultrasonic properties that are not always achievable with traditional materials. However, the structures and geometries needed to achieve such properties are often complex and difficult to obtain using common fabrication techniques. In the present research work, we report a novel metamaterial acoustic delay line with built-in impedance matching that is fabricated using a common 3D printer. Delay lines are commonly used in ultrasonic inspection when signals need to be separated in time for improved sensitivity. However, if the impedance of the delay line is not perfectly matched with those of both the sensor and the target medium, a strong standing wave develops in the delay line, leading to a lower energy transmission. The presented metamaterial delay line was designed to match the acoustic impedance at both the sensor and target medium interfaces. This was achieved by introducing graded engineered voids with different densities at both ends of the delay line. The measured impedances of the designed metamaterial samples show a good match with the theoretical predictions. The experimental test results with concrete samples show that the acoustic energy transmission is increased by 120% and the standing wave in the delay line is reduced by over a factor of 2 compared to a commercial delay line.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Low-temperature selective laser sintering 3D printing of PEEK-Nylon blends: Impact of thermal post-processing on mechanical properties and thermal stability

Herein, a high-performance polymer (HPP) (polyether ether ketone, PEEK) blended with a commercial low-temperature polymer (polyamide 12, PA-12) was fabricated using a low-temperature selective laser sintering (SLS) 3D printer. Different post-processing heat treatments were implemented after fabrication to tune the thermal and mechanical properties of printed blends. The specific mechanical modulus of the blend was increased up to 79% in comparison to printed PA-12 samples with heat treatment. Additionally, the thermal resistance of the treated blends greatly exceeded the properties observed using PA-12 alone. This research proposes a methodology to fabricate and engineer HPP using desktop SLS printers through a secondary lower melting temperature material and heat treatments.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The Influence of Printing Parameters, Post-Processing, and Testing Conditions on the Properties of Binder Jetting Additive Manufactured Functional Ceramics

This article outlines the current state-of-the-art binder jetting (BJT) additive manufacturing of functional ceramics. The impact of printing parameters, heat treatment processing, and testing conditions on the observed performance of these ceramics is discussed. Additionally, this article discusses the impact of physical properties such as density and mechanical strength on the overall performance of these functional ceramics. Although printing parameters and initial feedstock are crucial for the printability of the desired parts, other factors play an important role in the performance of the ceramic. Thermal post-processing is crucial to achieve optimized functional properties, while the testing orientation is key to obtaining the maximum output from the part. Finally, future research directions for this field are also discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Fabrication and characterization of 3D printing induced orthotropic functional ceramics

The orthotropic functional properties of additively manufactured ceramics due to the fabrication process was characterized in this study. Spherical, environmentally benign barium titanate (BaTiO 3 ) powders were fabricated using binder jetting 3D printing. Dielectric and piezoelectric properties of these ceramics were characterized as a function of the printing orientation. The dielectric constant of the samples tested normal to the printing layers was observed to be 20% higher than those tested in the parallel fashion. Similarly, the piezoelectric response was found to be over 35% in the normal orientation. With these results, it was shown that the electroding orientation has a direct influence on the functional properties of additively manufactured ceramics. Overall, with less than 37% of the theoretical density, the average piezoelectric coefficient for the perpendicularly tested ceramics was found to be 152.7 pC N -1 , which is 80% of the theoretical value. Finally, the high piezoelectric response obtained with such low densities can lead to the development of more mass efficient, and cost-effective sensing and energy harvesting devices, as well as structures that can be tuned to respond based on the direction of the loads applied.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Particle size influence on material properties of BaTiO 3 ceramics fabricated using freeze-form extrusion 3D printing

Barium titanate (BaTiO 3 ; BTO) is a well-known lead-free piezoelectric material commonly used for sensors and actuators applications. There are several traditional methods to fabricate bulk BTO ceramics; however, most of those methods have restrictions regarding being able to produce a functional and complex shape for specific application needs. Recently, additive manufacturing techniques such as binder jetting have enabled the fabrication of complex designs of piezoelectric ceramics. However, the density achieved is relatively low thus narrowing their applications. This paper presents the fabrication of high-density BaTiO 3 ceramics using Freeze-form Extrusion Fabrication (FEF). The influence on material properties for different ceramic particle size was assessed. It was found that parts printed using finer BaTiO 3 particle sizes achieved better results in terms of density, piezoelectric, and dielectric properties. For this study, the 100 nm BaTiO 3 samples achieved 85.24% density, a high piezoelectric property of 204.61pC/N and dielectric permittivity of 2551. These results demonstrated the feasibility of using FEF additive manufacturing to fabricate high-quality functional ceramics with designed geometry in a mold-free fashion.

36 MATERIALS SCIENCE↗