硅酸盐学报

冷烧结α-石英陶瓷中的非晶相-晶相转变

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司明明 ¹^,² , 颜鹏 ¹^,² , 逯紫阳 ¹^,² , 曾鑫强 ¹^,² , 丁奇 ¹^,² , 范宇驰 ¹^,² , 江莞 ¹^,²

硅酸盐学报 | 第15届无机非金属材料专题研讨会专题(一)——研究论文 2026,54(4): 1210-1219

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硅酸盐学报 | 第15届无机非金属材料专题研讨会专题(一)——研究论文 2026, 54(4): 1210-1219

冷烧结α-石英陶瓷中的非晶相-晶相转变

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司明明¹^,², 颜鹏¹^,², 逯紫阳¹^,², 曾鑫强¹^,², 丁奇¹^,², 范宇驰¹^,², 江莞¹^,²

作者信息

^1．东华大学先进纤维材料全国重点实验室，上海 201620

^2．东华大学材料科学与工程学院，上海 201620

司明明（1993—），男，博士，助理研究员。

SI Mingming (1993-), male, Ph.D., Associate Researcher. E-mail: realmms@dhu.edu.cn

通讯作者:

范宇驰（1984—），博士，研究员。

Amorphous-to-Crystalline Phase Transition in Cold-Sintered α-Quartz Ceramics

Mingming SI¹^,², Peng YAN¹^,², Ziyang LU¹^,², Xinqiang ZENG¹^,², Qi DING¹^,², Yuchi FAN¹^,², Wan JIANG¹^,²

Affiliations

^1.State Key Laboratory of Advanced Fiber Materials, Donghua University, Shanghai 201620, China

^2.College of Materials Science and Engineering, Donghua University, Shanghai 201620, China

出版时间: 2026-01-30 doi: 10.14062/j.issn.0454-5648.20250770

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摘要

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冷烧结技术可在远低于传统烧结温度的条件下实现陶瓷致密化，但对低溶解性材料的适用性与相变机制仍缺乏系统研究。本工作以介孔无定形二氧化硅为对象，围绕“非晶-晶体相变的触发机制”这一关键科学问题，系统揭示了辅助液相碱性、烧结温度与压力对α-石英相形成的协同调控规律。结果表明，强碱性溶液（NaOH浓度≥3 mol/L）可通过促进硅氧网络“溶解-再沉积”过程，显著降低相变活化能，实现非晶SiO₂在300 ℃、500 MPa条件下完全转变为α-石英单一相；而中性或弱碱性辅助液相仅能诱导颗粒压实，难以使相变完成。进一步研究表明，相变临界条件为250 ℃与200 MPa，且相变程度随烧结温度与压力提高而加深。在强碱辅助下获得的致密α-石英陶瓷，其相对密度超过95%，硬度、模量及断裂韧性较非晶态分别提升30%、40%和110%。本工作提出一种通过调控辅助液相碱性强弱以精确诱导非晶-晶体转变的策略，为低溶解性陶瓷的低温制备及相工程调控提供了新思路与理论依据。

关键词

冷烧结 / 石英陶瓷 / 力学性能 / α-石英相变

Abstract

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Introduction

Quartz ceramics (SiO₂) possess unique properties such as low thermal expansion, excellent chemical stability, and outstanding dielectric performance, making them widely used in semiconductor manufacturing, optoelectronic devices, and high-frequency electronic components. Traditional sintering of quartz ceramics typically requires temperatures above 1000 ℃, which inevitably induces polymorphic transformations from α-quartz to β-quartz or cristobalite, hindering the preparation of single-phaseα-quartz ceramics. Recently, the cold sintering process (CSP) has emerged as a promising low-temperature densification route for ceramics, utilizing transient liquid phases to induce "dissolution-precipitation" or interfacial reaction mechanisms. However, for low-solubility ceramics such as quartz, CSP often fails to achieve full densification and crystallization due to insufficient dissolution kinetics and weak interfacial reactivity. The critical scientific problem addressed in this work is how to effectively trigger the amorphous-to-crystalline phase transition of low-solubility quartz at low temperature, thereby enabling the preparation of denseα-quartz ceramics.

This study systematically investigates the cooperative effects of transient solvent alkalinity, sintering temperature, and uniaxial pressure on the amorphous-to-α-quartz phase transition during CSP. A transient alkaline liquid phase is introduced to regulate interfacial reactions and crystallization kinetics, aiming to provide a theoretical basis and technical strategy for the low-temperature processing of low-solubility ceramics.

Methods

Amorphous mesoporous silica (SBA-15) powders were used as the starting material. The powders were homogeneously mixed with different transient solvent phases: deionized water (neutral), 5 mol·L^-1 NH₃·H₂O (weak alkaline), and NaOH solutions of varying concentrations (0.5-10.0 mol·L^-1, strong alkaline). Approximately 0.4 g of powder was thoroughly ground with the liquid phase in a mortar and then loaded into a 10 mm diameter steel die. Uniaxial pressures ranging from 200 MPa to 600 MPa were applied, while the sintering temperature was varied between 200 ℃ and 350 ℃. Heating was conducted at a rate of 15 ℃·min^-1 and held for 40 min at the target temperature. After natural cooling, the sintered pellets were mechanically polished for further characterization.

The density of the cold-sintered ceramics was calculated by dimensional and weight measurements using a vernier caliper and electronic balance, and relative density was determined based on the theoretical density of quartz (2.2 g·cm^-3). Phase composition and structural evolution were analyzed using X-ray diffraction (XRD, Cu Kα radiation, λ = 0.154 06 nm, 50 kV, 100 mA, scanning range 10 °-90 °, step size 0.01). Fourier-transform infrared spectroscopy (FTIR-ATR) was used to identify bonding characteristics and confirm phase transitions. Microstructural evolution and fracture features were observed by field-emission scanning electron microscopy (FE-SEM). The mechanical properties of the sintered ceramics were evaluated by Vickers hardness tests (3 kgf load, 10 s dwell), flexural strength using the modified small punch (MSP) method, and fracture toughness (K_IC) calculated by the Anstis equation. Poisson's ratio and Young's modulus were determined by ultrasonic measurements.

This experimental design allows for a systematic investigation of how transient solvent alkalinity, temperature, and pressure cooperatively affect densification and amorphous-to-crystalline transformation during CSP of quartz.

Results and discussion

The phase composition of the sintered bodies was strongly influenced by the type and concentration of transient solvent. Without a liquid phase or with neutral water, the sintered samples remained largely amorphous and exhibited low relative density (~80%). Weak alkaline NH₃·H₂O increased compaction and relative density (~92%) but failed to trigger phase transformation. In contrast, strong alkaline NaOH solutions (≥3 mol·L^-1) effectively promoted the dissolution of Si-OH surface species, forming soluble silicate intermediates. These intermediates subsequently underwent reprecipitation and recrystallization under external pressure and temperature, leading to complete transformation into α-quartz at 300 ℃ and 500 MPa. XRD and FTIR confirmed the disappearance of the amorphous broad peak and the emergence of α-quartz characteristic double peaks at 798 cm^-1and 778 cm^-1, indicating a complete amorphous-to-α-quartz transition.

A clear alkalinity-dependent phase transition sequence was identified: amorphous → keatite (0.5 mol·L^-1NaOH) → keatite +stishovite (1 mol·L^-1) → keatite + α-quartz (3 mol·L^-1) → α-quartz (≥5 mol·L^-1). Simultaneously, relative density increased from 71% (no solvent) to 95.7% (10 mol·L^-1NaOH). SEM revealed that strong alkalinity produced well-defined grain boundaries and uniform microstructures, while weak or neutral conditions resulted in porous, poorly bonded networks.

The phase transition was also sensitive to sintering temperature and pressure. At 200 ℃, no crystallization occurred even at 600 MPa. Crystallization initiated at 250 ℃ and 300 MPa, and complete α-quartz formation occurred at ≥300 ℃ and ≥400 MPa. Increasing pressure facilitated particle rearrangement, pore elimination, and enhanced atomic diffusion at the interface, accelerating phase transition. A comprehensive temperature-pressure-phase diagram was established, clearly delineating the non-crystalline, partially crystalline, and fully crystalline regions.

Mechanical properties were strongly correlated with microstructure and phase composition. The α-quartz ceramics cold-sintered with 5 mol·L^-1 NaOH exhibited a Vickers hardness of 5.1 GPa, Young's modulus of 67.8 GPa, fracture toughness of 0.98 MPa·m^1/2, and flexural strength of (58 ± 7) MPa. These values represent increases of 30%, 40%, and 110% in hardness, modulus, and toughness, respectively, compared to the amorphous samples. The enhanced mechanical properties are attributed to the formation of well-bonded crystalline interfaces that enable efficient stress transfer and crack deflection, unlike the disordered amorphous structure.

Conclusions

This work demonstrates a controllable strategy to induce amorphous-to-α-quartz transformation in low-solubility silica ceramics through the regulation of transient solvent alkalinity during cold sintering. By introducing strong alkaline NaOH solutions (≥3 mol·L^-1), the activation energy for crystallization can be significantly reduced, enabling complete transformation at 300 ℃ under 500 MPa. The critical crystallization threshold was identified at 250 ℃ and 200 MPa, and a detailed temperature-pressure-phase diagram was established to illustrate the transition pathways. The resulting ceramics achieved a relative density above 95% and exhibited excellent mechanical performance, including a Vickers hardness of 5.1 GPa, Young's modulus of 67.8 GPa, fracture toughness of 0.98 MPa·m^1/2, and flexural strength of (58 ± 7) MPa. These results clearly indicate that alkaline regulation during CSP not only enables precise control of phase structure but also produces dense, mechanically robust α-quartz ceramics at dramatically reduced sintering temperatures. This approach provides both fundamental insights and practical guidance for the low-energy fabrication of advanced low-solubility ceramic components.

Key words

cold sintering process / quartz ceramics / mechanical properties / α-quartz phase transformation

引用本文

司明明, 颜鹏, 逯紫阳, 曾鑫强, 丁奇, 范宇驰, 江莞. 冷烧结α-石英陶瓷中的非晶相-晶相转变. 硅酸盐学报, 2026 , 54 (4) : 1210 -1219 . DOI: 10.14062/j.issn.0454-5648.20250770

Mingming SI, Peng YAN, Ziyang LU, Xinqiang ZENG, Qi DING, Yuchi FAN, Wan JIANG. Amorphous-to-Crystalline Phase Transition in Cold-Sintered α-Quartz Ceramics[J]. Journal of the Chinese Ceramic Society, 2026 , 54 (4) : 1210 -1219 . DOI: 10.14062/j.issn.0454-5648.20250770

基金

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国家自然科学基金(52550001; 52502057; 52532002)

参考文献

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2026年第54卷第4期

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文章信息

doi: 10.14062/j.issn.0454-5648.20250770

接收时间：2025-10-27
首发时间：2026-05-20
出版时间：2026-01-30

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出版历史

收稿日期：2025-10-27
修回日期：2025-11-10

基金

国家自然科学基金(52550001; 52502057; 52532002)

作者信息

^1．东华大学先进纤维材料全国重点实验室，上海 201620

^2．东华大学材料科学与工程学院，上海 201620

通讯作者:

范宇驰（1984—），博士，研究员。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20250770

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2种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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