Formation of calcium aluminoferrites in the ternary CaO–Al2O3–Fe2O3 system during solid-phase reactions

IF 7.4 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Construction and Building Materials Pub Date : 2024-11-16 DOI:10.1016/j.conbuildmat.2024.139117

Svetlana V. Samchenko, Andrey V. Korshunov

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引用次数: 0

Abstract

The ferrite phase in the cement composition has a reduced heat release during hydration, improves mechanical properties and increases the corrosion resistance of cement materials. In this article, the formation of C₂A_xF_1–x-type aluminoferrites in the CaO–Al₂O₃–Fe₂O₃ system during solid-phase reactions was studied. A system of empirical equations has been proposed that allows calculating the thermodynamic functions (Δ_fH°₂₉₈, Δ_fG°₂₉₈) of the formation of calcium aluminoferrites of any composition within a continuous series C₂A₀_.₆₆₇F₀_.₃₃₃ (C₆A₂F) – C₂F. Analysis of the various pathways of aluminoferrites formation has been conducted, taking into consideration the formation of intermediate phases in the ternary system. Based on a comparison of experimental data for mixtures of C+F, C+A, and C+A+F, a temperature sequence for phase formation (C₂F, CF, amorphous [CA]_am, C₂(A)F, CA, C₁₂A₇, C₂A_xF_1–x, eutectic liquid) in ternary oxide systems has been established. It has been shown that the amorphous aluminate phase present in the reaction system within the temperature range of 850–1100°C plays a crucial role in the formation of aluminoferrites. Among the investigated ternary oxide mixtures, whose initial composition corresponds to the stoichiometries of C₆A₂F, C₄AF, C₆AF₂, and C₈AF₃, only a certain aluminoferrite (brownmillerite), with a sufficiently high yield (∼53 wt% at 1200 °C), is formed in a 4 C+A+F mixture. An explanation has been proposed for the similarity in morphology between the sintered α-Fe₂O₃ and the calcined products of the C+F and C+A+F oxide mixtures when T>1000°C. The results of this work can be used to improve existing technologies and develop new methods for the production of iron-rich binders and additives based on calcium ferrites and aluminoferrites. The results of this work allow us to clarify the patterns of phase formation of calcium aluminoferrites under conditions of solid-phase reactions.

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三元 CaO-Al2O3-Fe2O3 体系中钙铝铁氧体在固相反应过程中的形成

水泥成分中的铁素体相可减少水化过程中的热量释放，改善水泥材料的机械性能并提高其耐腐蚀性。本文研究了 CaO-Al2O3-Fe2O3 体系在固相反应过程中形成 C2AxF1-x 型铝铁氧体的过程。该研究提出了一套经验方程，可以计算在连续系列 C2A0.667F0.333 (C6A2F) - C2F 中形成任何成分的钙铝铁氧体的热力学函数（ΔfH°298、ΔfG°298）。考虑到三元体系中中间相的形成，对形成铝铁氧体的各种途径进行了分析。根据对 C+F、C+A 和 C+A+F 混合物实验数据的比较，确定了三元氧化物体系中相形成的温度顺序（C2F、CF、无定形 [CA]am、C2(A)F、CA、C12A7、C2AxF1-x、共晶液）。研究表明，在 850-1100°C 的温度范围内，反应体系中存在的无定形铝酸盐相对铁铝酸盐的形成起着至关重要的作用。在所研究的三元氧化物混合物（其初始成分与 C6A2F、C4AF、C6AF2 和 C8AF3 的化学计量相符）中，只有某种铝铁氧体（褐铁矿）能在 4 C+A+F 混合物中形成，且产量足够高（1200 °C时为 53 wt%）。对于烧结的 α-Fe2O3 与 C+F 和 C+A+F 氧化物混合物的煅烧产物在 T>1000°C 时的形态相似性，已经提出了解释。这项工作的结果可用于改进现有技术和开发新方法，以生产基于钙铁氧体和铝铁氧体的富铁粘合剂和添加剂。这项工作的结果使我们能够明确钙铝铁氧体在固相反应条件下的相形成模式。

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来源期刊

Construction and Building Materials 工程技术-材料科学：综合

CiteScore

13.80

自引率

21.60%

发文量

3632

审稿时长

82 days

期刊介绍： Construction and Building Materials offers an international platform for sharing innovative and original research and development in the realm of construction and building materials, along with their practical applications in new projects and repair practices. The journal publishes a diverse array of pioneering research and application papers, detailing laboratory investigations and, to a limited extent, numerical analyses or reports on full-scale projects. Multi-part papers are discouraged. Additionally, Construction and Building Materials features comprehensive case studies and insightful review articles that contribute to new insights in the field. Our focus is on papers related to construction materials, excluding those on structural engineering, geotechnics, and unbound highway layers. Covered materials and technologies encompass cement, concrete reinforcement, bricks and mortars, additives, corrosion technology, ceramics, timber, steel, polymers, glass fibers, recycled materials, bamboo, rammed earth, non-conventional building materials, bituminous materials, and applications in railway materials.