Abstract ：

硅酸镁基胶凝材料是由活性氧化镁和硅质原材料及外加剂按照一定比例混合制得,具有低碳排放、轻质高强、隔热保温等优良特点,受到了国内外学者的广泛关注.主要从原料配比、水化机理及其性能的影响因素综述了硅酸镁基胶凝材料的研究进展,硅酸镁基胶凝材料的性能主要受MgO活性、养护温度、Mg/Si比和外加剂、掺合料掺量的影响.其中MgO活性与Mg/Si比对体系反应产物影响显著,养护温度对反应进程起到了控制作用.概述了当前硅酸镁基胶凝材料存在的问题,并提出了可行的改进措施.

Keyword ：

原料配比 硅酸镁基胶凝材料 性能

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Abstract ：

This study aimed to investigate the evolution of compressive strength and microstructure of hydrated magnesium silicate (MgO-SiO2-H2O) cement with Mg(OH)2 (MH) as a modifier under standard and carbonation curing conditions. Isothermal calorimetry, fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetry analysis (TGA) were used to analyze the hydration rate as well as the degree of hydration of the MgO-SiO2-H2O cements, and to determine the types of the physical phases and the mass fractions of the hydration products. The porosity structure and micro-morphology of MgO-SiO2-H2O cement were characterized by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). The results indicated that MH could slightly enhance the fluidity of MgO-SiO2-H2O cement. As the dosage of MH increased, the compressive strength of MgO-SiO2-H2O cement showed an initial increase followed by a decrease, reaching optimal mechanical properties at a 1 % dosage. The addition of 1 % MH accelerated the hydration rate of MgO-SiO2-H2O cement and the formation of M-S-H gel. Carbonation curing could convert a portion of MH into hydrated magnesium carbonates (HMCs), improving the utilization of MgO, reducing the quantity of detrimental pores, and decreasing the porosity. Furthermore, considering the synergistic effects of MH and carbonation curing, the performance of MgO-SiO2-H2O cement could be further enhanced.

Keyword ：

Compressive strength Mg(OH)2 Carbonation curing Mechanism analysis

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Abstract ：

This research investigated the application of municipal solid waste incineration fly ash (MSWIFA), municipal solid waste incineration bottom ash (MSWIBA), and construction waste residue (CWR) as raw materials for the comprehensive conversion into municipal solid waste ceramics employing the SiO2-Al2O3-CaO-MgO (8 wt%) phase diagram. This study aimed to evaluate the influence of the addition of MSWIFA and sintering temperature on important ceramics properties, including linear shrinkage, water absorption, sintering range, and flexural strength. Additionally, relationships were established among these physical parameters using Pearson's correlation coefficient. The thermal behavior of the mixture was analyzed through automatic slag melting point tester and TG-DSC techniques. Furthermore, characterization of the crystalline phase transition and microstructure of sintered samples was performed by XRD, Factsage, and SEM. The results showed that both the addition of MSWIFA and the sintering temperature significantly influenced the crystal phase composition of the sintered ceramics. Moreover, the addition of MSWIFA and the sintering temperature had a significant influence on the pore structure of the ceramics. These ceramics exhibited exceptional properties, such as the extremely low water absorption rate of 0.08 % and the remarkable flexural strength of 124.78 MPa. Ceramics performance indicators were far higher than the requirements of China's national standard GB/T4100-2015. The sintering range had the capability to attain 30 degrees C, guaranteeing the feasibility of practical manufacturing processes. Furthermore, leaching concentration tests conducted on additive-free ceramic samples reveal a low risk of heavy metal contamination, as the heavy metals were effectively solidified within the crystalline and amorphous phases of the ceramics. The comprehensive utilization of MSWIFA, MSWIBA, and CWR for the production of fully solid waste ceramics not only yields cost reduction benefits but also promotes efficient utilization, presenting a feasible and highly promising approach to sustainable waste management.

Keyword ：

Municipal waste incineration bottom ash Municipal waste incineration fly ash Ceramic Factsage Construction waste residue

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Abstract ：

Ni-based catalysts doped with Fe, Co, Cr, and Cu were successfully synthesized via an interesting impregnation method with EDTA for the catalytic decomposition of methane. XRD, N 2 sorption, SEM, H 2 -TPR, and TPO were accomplished for catalyst characterization. Among the Ni-doped catalyst series, the Ni-Cu catalyst carried out better toward the rest of the Ni catalysts, and a rising trend in the CH 4 conversion from 61 to 86 % was perceived with a rise in temperature in the range of 575 - 650 degrees C, which was associated with its high surface area (104.3 m 2 . g -1 ) and good low-temperature reducibility. Furthermore, the maximum CH 4 conversions of 28, 86, 81, and 78 % were acquired over the 50Ni-xCu/SiO 2 .MgO (x = 2.5, 5, 7.5, and 10 wt%) at 650 degrees C with a GHSV = 24000 mL h -1 g cat1 and CH 4 :N 2 = 3:17, respectively. The optimal specimen (5 wt% Cu) with a slow decline in activity depicted better durability in the stability test at 675 degrees C for 300 min compared to the quick deactivation of other Cu loadings within 150 min of reaction initiation. SEM micrograph of spent specimens with diverse Cu loadings indicated that the generated carbon is whisker type.

Keyword ：

SiO 2 .MgO-supported Ni catalyst Hydrogen production Methane decomposition Promoters

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Abstract ：

Although rare earth zirconates (RE2Zr2O7) have garnered attention as viable candidates for thermal barrier coatings (TBCs), they suffer from low fracture toughness and accelerated calcium-magnesium-alumina-silicate (CMAS) melt corrosion at high service temperatures, which impedes their practical application. In this work, we developed a series of REAlO3/RE2Zr2O7 (RE = La, Nd, Sm, Eu, Gd, and Dy) composites with a eutectic composition that not only significantly enhanced the fracture toughness by more than 40% relative to that of RE2Zr2O7 but also exhibited improved resistance to CMAS corrosion. The increase in toughness arises from multiple mechanisms, such as ferroelastic toughening, fine-grain strengthening, and residual stress toughening, all of which trigger more crack defects and energy consumption. Additionally, the CMAS penetration depth of the REAlO3/RE2Zr2O7 composites is approximately 36% lower than that of RE2Zr2O7. Al-O constituents in composites can capture CaO, SiO2, and MgO in CMAS melts and increase their viscosity, resulting in enhanced CMAS corrosion resistance. The thermophysical properties of the REAlO3/RE2Zr2O7 composites were also investigated, and their coefficient of thermal expansion and thermal conductivity are comparable to those of 7-8 wt %Y2O3 partially stabilized ZrO2 (YSZ), indicating their potential as TBC materials.

Keyword ：

calcium-magnesium-alumina-silicate (CMAS) corrosion thermal property eutectic composition REAlO3/RE2Zr2O7 fracture toughness

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Abstract ：

The effects of the type of raw material, mix proportion, and chemical modifier on the mechanical properties and water resistance of magnesium oxysulfate cement (MOS) have been extensively studied. However, the formation mechanism of hydration products remains obscure. This study aims to clarify the hydration mechanism of MOS through a thermodynamic modeling approach and to explore the effects of mix proportion and type and dosage of modifier on the phase assemblage as well as the mechanical properties of hardened paste. The volume fraction of 5Mg(OH)(2)& sdot;MgSO4 & sdot;7H(2)O (5-1-7) is used as a key parameter to establish the relationship between the mix proportion and the compressive strength of the MOS system. The results demonstrate that the thermodynamic modeling method can predict the phase evolution of MOS with various mix proportions. As the molar ratio of reactive-MgO (alpha-MgO) to MgSO4 increases, both the 5-1-7 volume fraction and compressive strength of hardened paste initially increase and then decrease, while decreasing as water dosage increases. The volume fraction of 5-1-7 is proportional to the compressive strength of MOS. Compressive strength is greatest at molar ratio of n(MgO):n(MgSO)(4) = 4-9 and n(H2O):n(MgSO4) = 9-20. The efficiency of modifiers is: citric acid (CA) > tartaric acid > EDTA > phosphoric acid > acetic acid. The modifying mechanism of CA involves the initial formation of 3Mg(OH)(2)& sdot;MgSO4 & sdot;8H(2)O(3-1-8), followed by its transformation into 5-1-7.

Keyword ：

Mechanism of modification Mix proportion Assemblages of hydration products Magnesium oxysulfate cement Thermodynamic modeling

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Abstract ：

Alkyl lactates represent such green added-value chemicals that commonly used as biodegradable green solvents, detergents, pharmaceutical intermediates et al. Catalytic conversion of carbohydrates to methyl lactate (MLA) is a representative way for high-value utilization of biomass and the key lies in the development of highly efficient catalysts. In methanol, strong acid or alkaline catalysts are usually used under high temperature and high pressure, suffering from problems such as low selectivity, high cost or contamination of environment. This study aims to develop an acid-base bifunctional heterogeneous catalyst for the one-pot conversion of sugars to MLA under mild conditions. Sn/Mg composite oxides was synthesized by a coprecipitation method and further modified by poly (vinyl imidazole) ([PVIM]) to tune the hydrophilicity. Effect of polymer and Sn amount, calcination temperature, reaction temperature, catalyst dosage, and substrate concentration were investigated. The acid-base properties were characterized by NH3-TPD, pyridine-FTIR and CO2-TPD analysis. It was found that the presence of medium acid sites and medium base sites played an important role to the cascade reactions of carbohydrates to MLA. An optimum MLA yield of 55.4% was achieved over 10[PVIM]-5Sn/MgO (0.05 g) with complete conversion of glucose (28 mM) at 140 degree celsius, 2 MPa N2 for 10 h. The reaction conditions are mild and no strong acid or strong base catalyst is required. Furthermore, a possible reaction mechanism was proposed that the introduction of [PVIM] effectively regulated the local microenvironment of active sites and the acid base synergism greatly promoted the retro-aldol condensation, dehydration and hydrogen transfer reactions during the conversion of glucose to MLA.

Keyword ：

Sugars Methyl lactate Sn/MgO Bifunctional catalysis

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Abstract ：

采用氢氧化钙(Ca(OH)2)对硅酸镁基胶凝材料中的原材料MgO进行了不同质量比例的替代,对其流动度、凝结时间和抗压强度进行了测试,并结合X射线衍射(XRD)、扫描电子显微镜(SEM-EDS)、热重分析(TG-DTG)和压汞测试(MIP)分析了影响机理.结果表明,Ca(OH)2能够显著增大硅酸镁基胶凝材料的流动度与抗压强度,缩短其凝结时间.XRD、SEM-EDS、TG、MIP测试结果说明了抗压强度提升的原因:Ca(OH)2与硅灰反应生成了 C-S-H凝胶,并且促进了 MgO的水化,提高硅酸镁基胶凝材料的水化程度,使其孔隙率显著降低.

Keyword ：

氢氧化钙 硅酸镁基胶凝材料 流动度 抗压强度 凝结时间

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本发明公开了一种抗摔耐划碱铝硅玻璃及制备方法，按摩尔百分含量计，包括：SiO2 60.00～66.00，Al2O3 13.00～14.50，B2O3 0～3.50，Li2O 6.50～8.80，Na2O 4.50～6.50，K2O 0～0.50，MgO 5.00～7.00，ZnO 0～1.50，ZrO2 0～1.80，Y2O3 0～1.50。本发明的碱铝硅玻璃符合混凝土结构特征，引用氧化锆和/或稀土氧化钇，作为混凝土中的粗石子假想物，氧化铝作为细砂石假想物，以二氧化硅作为水泥胶凝材料，促进玻璃网络结构的实现；基于此，本发明的碱铝硅玻璃通过化学增强工艺处理能够获得极佳的抗摔冲击及耐划伤性能。

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Abstract ：

本发明提供了一种改性赤泥基吸附剂及其制备方法和应用，涉及工业固废资源化利用技术领域。本发明先对赤泥进行酸碱改性(活化和焙烧)，使得赤泥转变为介孔材料，大大提高了赤泥的比表面积和孔容，从而显著提高了二氧化碳气体扩散与吸附性能，使得改性赤泥基吸附剂对二氧化碳的吸附容量明显增加。通过采用浸渍法在所得酸碱改性赤泥上负载MgO，提供了更多的碱性活性位点，对二氧化碳的吸附容量有明显的提高。酸碱改性赤泥对二氧化碳主要进行物理吸附，MgO提供碱性活性位点对二氧化碳进行化学吸附，实现了物理和化学吸附的协同作用，提高了对二氧化碳的吸附容量和吸附速率，在常温常压下即可实现吸附二氧化碳，二氧化碳的脱附温度低。

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