# Aging Characteristics of ZSM-5 Zeolite on Low-Frequency Acoustic Applications

## TL;DR

This paper studies how aging affects ZSM-5 zeolite's acoustic performance, showing that water helps protect its structure from damage by acetic acid.

## Contribution

The study reveals the protective role of water in preventing acetic acid-induced degradation of ZSM-5's acoustic properties.

## Key findings

- Water vapor enhances ZSM-5 structure and lowers water content, increasing resonance offset.
- Acetic acid adsorption damages ZSM-5 pores through physical and chemical mechanisms.
- A water-acetic acid vapor mixture preserves ZSM-5 acoustic performance by preferential water adsorption.

## Abstract

Zeolite is increasingly recognized for its enhancement of low-frequency acoustic performance in microspeakers. The aging characteristics of zeolite have been regarded as the critical factor for the commercial viability of mobile phones products, but the mechanism remains ambiguous. Here, the low-frequency acoustic performance of hierarchically structured ZSM-5 was investigated through aging with water and acetic acid (AA). It was discovered that water vapor augmented the resonance offset as it enhanced the structure of the zeolite, resulting in a lower water content. The resonance offset of ZSM-5 significantly decreased after the adsorption of AA vapor, as excessive AA was adsorbed through both physical and chemical adsorption, causing partial destruction of supermicropore and mesopores. The performance of ZMS-5 stored with vapor of AA and water mixture did not significantly deteriorate, indicating that water effectively protected the pores of zeolite to prevent excessive adsorption of AA. This was attributed to the fact that water was adsorbed by Brønsted acid sites of ZSM-5 more preferentially than AA, thereby avoiding excessive adsorption of AA.