Engineering topics

Haiquan Guo

Publications and source records attributed to Haiquan Guo.

At least 19 records

NASA NTRS2026

Diamond-Loaded Polyimide Aerogel Scattering Filters and Their Applications in Astrophysical and Planetary Science Observations

Infrared-blocking, aerogel-based scattering filters have a broad range of potential applications in astrophysics and planetary science instruments in the far-infrared, sub-millimeter, and microwave regimes. This paper demonstrates the ability of conductively-loaded, polyimide aerogel filters to meet the mechanical and science instrument requirements for several experiments, including the Cosmology Large Angular Scale Surveyor (CLASS), the Experiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM), and the Sub-millimeter Solar Observation Lunar Volatiles Experiment (SSOLVE). Thermal multi-physics simulations of the filters predict their performance when integrated into a cryogenic receiver. Prototype filters have survived cryogenic cycling to 4 K with no degradation in mechanical properties. Measurement of total hemispherical reflectance and transmittance, as well as cryogenic tests of the aerogel filters in a full receiver context, allow estimates of the integrated infrared emissivity of the filters. Knowledge of the emissivity will help instrument designers incorporate the filters into future experiments in planetary science, astrophysics, and cosmology.

Kyle R Helson↗

NASA NTRS2024

Synthesis of Flexible Polyamide Aerogels Cross-Linked with a Tri-Isocyanate

A new series of flexible polyamide (PA) aerogels was synthesized using terephthaloyl chloride (TPC), 2,2′-dimethylbenzidine (DMBZ) and cross-linked with an inexpensive, commercially available tri-isocyanate (Desmodur N3300A) at polymer concentrations of 6–8 wt.% total solids and repeating units, n, from 30 to 60. The cross-linked DMBZ-based polyamide aerogels obtained, after supercritically drying using liquid CO 2 , had shrinkages of 19–27% with densities ranging from 0.12 g/cm 3 to 0.22 g/cm 3 , porosity and surface areas up to 91% and 309 m 2 /g, respectively, and modulus values ranging from 20.6 to 109 MPa. Evidence suggests that a higher flexibility could be achieved using DMBZ in the polyamide backbone with N3300A as a cross-linker, when compared to previously reported TPC-mPDA-BTC PA aerogels, N3300A-polyimide aerogels, and N3300-reinforced silica aerogels.

aerogels↗

NASA NTRS2024

Post-Synthetic Modification of Yttria-Stabilized Zirconia Aerogels with Silica Coatings for Enhanced Thermal Stability

Maintaining high surface area and porosity at high temperatures is important when considering aerogels for use in thermal management systems. The mesoporous structure of aerogels results in extremely low thermal conductivity, making them lightweight, high performance insulating materials. Maintaining these properties requires innovative routes to suppress sintering and pore collapse as use temperatures rise. The current work aims to improve the pore structure stability of yttria-stabilized zirconia aerogels by the addition of a SiO 2 coating. The functionalization of surface hydroxyl groups by the addition of SiO 2 is hypothesized to mitigate condensation reactions, which are a driving force for shrinkage and pore structure collapse. Zirconia aerogels with 0, 10 and 30 mol% yttria (YO 1.5 ) additions were coated in a tetraethyl orthosilicate (TEOS) solution and exposed to temperatures up to 1200°C. Crystal structure, pore structure, and aerogel morphology were investigated to understand changes in aerogel thermal stability. The SiO 2 coating exhibited a greater influence on pore stability over yttria concentration, with specific surface area of the coated aerogels being twice that of the uncoated aerogels up to 1000°C. However, the presence of the SiO 2 coating promoted rapid sintering and densification at 1200°C, establishing an upper use temperature for SiO 2 and a need to develop other coating chemistries.

aerogel↗

NASA NTRS2023

Thermal Stability of M x O y Doped Zirconia Aerogels (M = Y, Yb, Gd, Ce, Ca) Studied Through 1200°C

The high porosities and low densities of ceramic aerogels offer outstanding insulative performance in applications where weight is a critical factor. The high surface area-to-volume ratios and specific surface areas provide extremely low thermal conductivity, but also contribute to rapid densification of the pore structure at elevated temperatures. This densification diminishes their favorable properties and inhibits use of aerogels in high temperature applications. This work contributes to a design framework for thermally stable aerogels via the study of dopant chemistry (Y, Yb, Gd, Ca, Ce) in zirconia aerogels. The structural evolution was studied to 1200°C using nitrogen physisorption, scanning electron microscopy, and x-ray diffraction. The role of dopant identity and concentration in thermal stability was elucidated. In context of the design framework, dopant chemistry is an aggregate for many closely related material properties, each of which may contribute to aerogel structural evolution. To develop a truly predictive design framework for ceramic-based aerogels, systematic and comprehensive evaluation of thermodynamic and kinetic properties must be performed in conjunction with studies on structural evolution.

aerogel↗

NASA NTRS2023

Optimizing Surfactant Templating of Yttria-Stabilized Zirconia Aerogels for High-Temperature Applications: Effect of Anionic and Nonionic Surfactant

Aerogels, mesoporous materials with extreme material properties including high specific surface area, low density, and low thermal conductivity, can be useful for applications including catalysis, sorption media, and drug delivery. The low thermal conductivity and high surface area of aerogels makes them advantageous as thermal management systems, specifically for aerospace or aeronautics applications. However, the pore collapse and subsequent surface area decrease of aerogels following exposure to high temperatures must be mitigated to allow aerogels to be effectively used in thermal management applications. This work investigates the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant Pluronic® P-123 as surfactant templates in yttria-stabilized zirconia (YSZ) aerogels. By utilizing surfactant templates, known to influence pore structure, it is anticipated that sintering and densification of the aerogels following high-temperature exposure will be mitigated. It was determined that the addition of SDS and P-123 increased the surface area and pore volume of as-dried aerogels and suppressed crystallite growth at high temperatures. However, the impact of surfactant templates on the surface area and pore volume of heat-treated aerogels was negligible, potentially due to low concentrations of surfactant and the removal of the surfactant following high-temperature exposure.

Yttria-stabilized zirconia aerogels↗

NASA NTRS2022

Characterization of Aerogel Scattering Filters for Astronomical Telescopes

We have developed a suite of novel infrared-blocking filters made by embedding scattering particles in a polymer aerogel substrate. Our developments allow us to tune the spectral performance of the filters based on both the composition of the base aerogel material and the properties of the scattering particles. Our filters are targeted for use in a variety of applications, from ground-based CMB experiments to planetary science probes. We summarize the formulations we have fabricated and tested to date, including several polyimide base aerogel formulations incorporating a range of size distributions of diamond scattering particles. We also describe the spectral characterization techniques used to measure the filters’ optical properties, including the development o fa mm-wave Fourier transform spectrometer testbed.

aerogel, filter, blocking, scattering, Fourier Tra↗

NASA NTRS2021

Optimizing Surfactant Templating of Yttria-Stabilized Zirconia Aerogels for High-Temperature Applications: Effect of Cationic Surfactant

Aerogels can be used in spaceflight applications as thermal insulators due to their low density, low thermal conductivity, and tortuous path for solid conduction. However, the aerogel formulation must be optimized to increase the thermal stability of the aerogels, as a drastic densification and decrease in surface area often is exhibited after high-temperature exposure. This work considers yttria-stabilized zirconia (YSZ) aerogels, whichhave low thermal conductivity and are expected to be used for temperatures between 600°C and 1000°C. It is anticipated that new sol-gel chemistries will yield YSZ aerogels that exhibit retained mesoporous structure, increased surface area, and minimized shrinkage upon exposure to higher temperatures in the expected use range. This work investigates the addition of surfactant to 20 mol% YSZ aerogels. The cationic surfactant, cetrimonium bromide (CTAB), was used as the templating agent, preventing the collapse of the mesoporous structure upon gelation and drying. It was determined that adding one-half times the critical micelle concentration of CTAB increased the surface area of the aerogels by 72% and 41% and increased the pore volume following exposure to 600°C and1000°C, respectively. This level of CTAB had the greatest increase in surface area and pore volume as compared to aerogels without CTAB or with twice the critical micelle concentration of CTAB. By optimizing the concentration of CTAB, the thermal stability ofYSZ aerogels can be enhanced to make these materials more efficient when used as thermal management systems.

Yttria-stabilized zirconia aerogel↗

NASA NTRS2021

Fine-tuning Polymers as Flexible Antenna Substrates for Aircraft

The pursuit to design more lightweight aircraft that can travel over greater distances never ceases. One area that has recieved much attention is the development of lighter and more aerodynamic antennas. Researchers at the NASA Glenn Research Center at the forefront of this effort. The research team, which includes Jessica Cashman, Baochau Nguyen, Haiquan Guo, Marcos Pantoja, Kevin Cavicchi, and Mary Ann Meador, is designing flexible polymer materials that can be used to construct lightweight, low-drag antennas that lie along the surface of an aircraft.

Haiquan Guo↗

NASA NTRS2020

Aerogel Scattering Filters for Cosmic Microwave Background Observations

We present the design and performance of broadband and tunable infrared-blocking filters for millimeter and submillimeter astronomy composed of small scattering particles embedded in an aerogel substrate. The ultralow-density (typically<150 mg/cm3) aerogel substrate provides an index of refraction as low as 1.05, removing the need for antireflection coatings and allowing for broadband operation from DC to above 1 THz. The size distribution of the scattering particles can be tuned to provide a variable cutoff frequency. Aerogel filters with embedded high-resistivity silicon powder are being produced at 40 cm diameter to enable large-aperture cryogenic receivers for cosmic microwave background polarimeters, which require large arrays of sub-Kelvin detectors in their search for the signature of an inflationary gravitational-wave background.

Thomas Essinger-Hileman↗

NASA NTRSDate not supplied

The Influence of Yttria Content on the Thermal Stability of Yttria-Stabilized Zirconia Aerogels

Aerogels demonstrate extraordinarily low thermal conductivity and low density, presenting a promising form of lightweight insulation for aerospace applications. The primary challenge is stabilization of the highly porous structure at temperatures to 1200 °C. Upon collapse of the pore structure, the favorable thermal properties and low density are diminished. Yttria-stabilized zirconia (YSZ) aerogels are synthesized to investigate the effect of composition on morphology, phase behavior, and thermal stability (specific surface area, pore size distribution). This work demonstrates the improvement in thermal stability of zirconia aerogels with increased yttria content. To develop insight on the influence of structure on thermal stability, the effects of water content and solids loading are studied and in elucidation of the mechanism by which yttria stabilizes the pore structure. With an improved understanding of aerogel structure and performance, metal oxide aerogels can be developed to withstand the extreme environments of space exploration.

Nathaniel Olson↗

NASA NTRSDate not supplied

Enhanced Thermal Stability of High Yttria Concentration YSZ Aerogels

Aerogels demonstrate extraordinarily low thermal conductivity and low density, presenting a promising form of lightweight insulation for aerospace applications. The primary challenge is stabilization of the highly porous structure at temperatures to 1200 °C. Upon collapse of the pore structure, the favorable thermal properties and low density are diminished. Yttria-stabilized zirconia (YSZ) aerogels are synthesized to investigate the effect of composition on morphology, phase behavior, and thermal stability (specific surface area, pore size distribution). This work demonstrates the improvement in thermal stability of zirconia aerogels with increased yttria content. Furthermore, changes in structure and surface chemistry of YSZ aerogels are studied in both oxidizing and inert atmospheres. With an improved understanding of aerogel structure and performance, metal oxide aerogels can be developed to withstand the extreme environments of space exploration.

Nathaniel Olson↗

NASA NTRSDate not supplied

Optimization of Aerogels for High Temperature Applications

Aerogels can be used in spaceflight applications as thermal insulators due to their low density, low thermal conductivity, and tortuous path for solid conduction. However, the aerogel formulation must be optimized to increase the thermal stability of the aerogels as drastic densification and decrease in surface area is often exhibited after high-temperature exposure. Current research investigates yttria-stabilized zirconia (YSZ) aerogels, which have low thermal conductivity and are expected to be used between 600°C and 1000°C. We anticipate that new sol-gel chemistries and processing will yield YSZ aerogels that display retained mesoporous structure, increased surface area, and minimized shrinkage upon exposure to higher temperatures in the projected use range. This work investigates the cationic surfactant, cetrimonium bromide (CTAB), as a templating agent to prevent the collapse of the aerogel pore structure upon gelation and drying. It was determined that adding one-half times the critical micelle concentration (CMC) of CTAB increased the surface area and pore volume of the aerogels, as compared to aerogels without CTAB or with twice the CMC of CTAB, following high-temperature exposure. By optimizing CTAB, the thermal stability of YSZ aerogels can be enhanced to make these materials more efficient when used as thermal management systems.

Rebecca C Walker↗

NASA NTRSDate not supplied