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1.
Geopolymer was prepared with various SiO2/Na2O mole ratios and mechanical tests and microstructural analyses are performed to investigate how the constituents affect its mechanical behavior in distinct stress states. Laboratory results reveal that the SiO2/Na2O ratio affects the polymerization by influencing the formation of silicon Q4(mAl) structures. The proportion of Q4(4Al) correlates positively with the mechanical characteristics of geopolymer, and the proportion of Q4(2Al) correlates negatively with the mechanical characteristics of geopolymer. The proportions of Q4(mAl) affect the stress–strain curve and the failure modes of geopolymer under various confining pressures. Three types of stress–strain curves with different peak strengths and plastic deformations are obtained. Incomplete polymerization generates a geopolymer with an imperfect microstructure, which determines the plastic deformation while unloading. Polymerization of a geopolymer affects its apparent cohesion and friction angle. However, the friction-induced strength declines drastically when the failure mode changes from the split mode to the shear mode. 相似文献
2.
Jianfeng Wu Cheng Hu Chen Ping Xiaohong Xu Weiheng Xiang 《Ceramics International》2018,44(16):19590-19596
To prolong the service life of cordierite–spodumene composite ceramics applied to the solar heat transmission pipeline, the zircon modifier was introduced to improve the corrosion resistance of the ceramics. The effects of zircon on the density, bending strength, crystalline phase, microstructure and chemical stability were studied. The results showed that the sintering temperature range of the composite ceramics was broadened to 40–60?°C with the introduction of 5–15?wt% zircon. Moreover, the mechanical strength and corrosion resistance of the ceramic materials were improved with the zircon introduction. In particular, sample C3 containing 15?wt% of zircon and sintered at 1360?°C exhibited the best performance, which had the 0.03% Wa, 0.07% Pa, 2.34?g?cm?3 Db and 100.17?MPa bending strength. After acid and alkali corrosion, the water absorption was still less than 0.5% and the strength loss rate decreased to less than 5.3%. The XRD and SEM analyses demonstrated that the ZrSiO4 grains dispersed at the grain boundaries could enhance the mechanical properties. Furthermore, the existence of the Zr4+ ions not only reduced the cationic solubility of the glassy phases but also led to a reaction with OH? to form Zr(OH)4 on the surfaces. This improved the corrosion resistance of the composite ceramics and endowed it with a high residual strength after the acid and alkali corrosion. 相似文献
3.
Shu Yan Xue Feng Kai Huang Xiaoqi Ren Yang Zhao Pengfei Xing 《International Journal of Applied Ceramic Technology》2023,20(3):1591-1605
In order to realize the value-added resource utilization of solid waste, geopolymer particle adsorbents were prepared at low temperatures using silica-aluminum-rich fly ash and steel slag powders as raw materials. In order to investigate the mechanism of their adsorption of dyes and heavy metal ions from wastewater, the effects of steel slag/fly ash ratio, adsorbent dosage, initial concentration of methylene blue (MB) and Cu2+ solution, adsorption time and temperature on the adsorption performance of the fly ash/steel slag-based geopolymer adsorbents were investigated, systematically. Results presented that the adsorption capacities of MB and Cu2+ were 33.30 and 24.15 mg/g, and the removal efficiencies were 99.90% and 96.59% with the dosages of 3 and 4 g/L geopolymer adsorbents (steel slag/fly ash ratio of 20 wt.%), respectively. The adsorption processes of MB and Cu2+ on the adsorbents were in accordance with the proposed pseudo-second-order and Langmuir isotherm models, which mainly included physical and chemical adsorption mechanisms. The adsorption was a spontaneous endothermic process. The fly ash/steel slag-based geopolymer had good removal ability for dyes and heavy metal ions, and it could maintain good adsorption performance after three cycles of regeneration. It had potential application in wastewater treatment. 相似文献
4.
Xiao Chen Zidong Niu Jie Wang Guo Rui Zhu Mingkai Zhou 《Ceramics International》2018,44(15):18173-18180
The mechanical properties and microstructure of geopolymer are affected by the molar ratio of SiO2/Al2O3. Meanwhile, organic polymer has the effect of improving the toughness of geopolymer, which depends on the SiO2/Al2O3 ratio of geopolymer inevitably. Therefore, it is important to investigate the effect of the organic polymer on the mechanical properties and microstructure of geopolymer with varying SiO2/Al2O3 ratio for using organic polymer to modify geopolymer. In this work, the SiO2/Al2O3 ratios of metakaolin-based geopolymers are adjusted to 2.0, 2.5, 3.0, 3.5 and 4.0 by adding silica fume and β-Al2O3, with Na2O/SiO2, H2O/SiO2 being maintained at 0.2, 4.0, respectively. The geopolymers with each SiO2/Al2O3 ratios are modified by addition of 0, 0.4, 0.8, 1.2 and 1.6?wt% of sodium polyacrylate (PAAS).The mechanical properties of these samples are measured and the rate of change is used to characterize the effect of PAAS on the metakalin-based geopolymers. The mechanism is also shown by 29Si NMR, XPS and FTIR. The results show that the effects of polymer on the mechanical properties of metakaolin-based geopolymer are affected by SiO2/Al2O3 ratio and the effect becomes less obvious with SiO2/Al2O3 ratio increasing from 2.0 to 4.0. Incorporation of PAAS can reduce the degree of polymerization of [SiO]4 or [AlO]4 in geopolymer and form the Si?O?C bond, which are two main reasons for polymer improving the toughness of geopolymer. But these effects decrease when the SiO2/Al2O3 ratio of geopolymer increases from 2.0 to 4.0, which is corresponding to the effect on the mechanical properties. The toughening effect of organic polymer on geopolymer depends on the SiO2/Al2O3 ratio of geopolymer, and only the geopolymer with lower SiO2/Al2O3 ratio (no more than 2.5 in this work) can be significantly toughening modified by organic polymer. Therefore, it is necessary to consider the SiO2/Al2O3 ratio of the geopolymer when geopolymer modified by organic polymer is designed. 相似文献
5.
This study aimed to investigate the mechanical behavior of an environmentally friendly granulated blast furnace slag-based geopolymer matrix reinforced with modified multi-walled carbon nanotubes (MWCNTs). The modified MWCNTs were obtained using a modification method combining nitric acid and sulfuric acid and were then dispersed using sodium dodecylsulfate (SDS) as a dispersant. Two types and three concentrations of MWCNTs were mixed directly into the aqueous solution, sonicated, and then mechanically mixed with waste granulated blast furnace slag to form the geopolymer matrix. Raman and Fourier transform infrared (FT-IR) spectroscopy were used to evaluate the ordered structure and crystallization degree of the modified MWCNTs. Then, the dispersity of the modified MWCNTs was characterized using transmission electron microscopy (TEM). The compressive and bending strengths were measured to evaluate the mechanical behavior of specimens. Moreover, the polycondensation products, polycondensation degree, pore structure, and microscopic morphology of the geopolymer matrix were analyzed using X-ray diffraction (XRD), FT-IR spectroscopy, nuclear magnetic resonance (NMR), mercury intrusion porosimetry (MIP), and field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDS). The experimental results showed that the incorporation of 0.1% functionalized MWCNTs had an optimal influence on the fluidity and mechanical behavior. The slump diameters of geopolymers with 0.1% functionalized MWCNTs with and without SDS were increased by 16.3% and 23.5%, respectively, compared with the reference geopolymer matrix. For geopolymer matrix samples at a curing age of 28 d, the compressive strength of geopolymers with 0.1% functionalized MWCNTs with and without SDS were increased by 16.3% and 17.6%, respectively. For the bending strength, the corresponding increases were 17.6% and 18.7%, respectively. It was found that functionalized MWCNTs could increase the degree of polycondensation, leading to a more traditional amorphous N-A-S-H phase, a finer C–S–H phase, more Q4 (2Al) and Q4 (3Al), and lower porosity. In addition, the propagation of micro-cracks in the geopolymers was inhibited by the incorporation of functionalized MWCNTs. 相似文献
6.
Christophe Chlique David Lambertin Pascal Antonucci Fabien Frizon Philippe Deniard 《Journal of the American Ceramic Society》2015,98(4):1308-1313
The purpose of this work was to study the role of cesium in sodium‐based geopolymer and its thermal stability for nuclear waste management. A series of mixed sodium and cesium geopolymer samples (Na1?x Cs x )2O·Al2O3·SiO2·12H2O (referred to as (Na1? x Cs x )‐GP, where x = 0, 0.08, 0.15, 0.42, 1) have been prepared. All geopolymer samples were heated at 1100°C for 24 h. Pollucite (CsAlSi2O6) and feldspathoid (CsAlSiO4) were crystallized from Cs‐GP. Nepheline (NaAlSiO4) and a small amount of crystallized silica were obtained from Na‐GP. The other geopolymers (Na1? x Cs x )‐GP (x = 0.08, 0.15, 0.42) led to pollucite and nepheline main phases. Amorphous silica phase was observed in all the geopolymer samples with various amounts. Phase quantification and scanning electron microscope revealed that higher Cs concentrations in Na‐GP tend to decrease the amorphous phase while improving pollucite and nepheline phase quantification. The amorphous geopolymers have also been studied by pair distribution function analysis. Tetrahedral chains formed by T–O bonding (with T = Si, Al) were shown to be more tighten around Cs+ than around Na+. It led to shorter Cs–T bond than Na–T bond matching the higher solvation property of Na+. Furthermore, thermal study analysis pointed out the fact that geopolymer samples (Na1? x Cs x )‐GP, can be considered as solid solutions. 相似文献
7.
To explore the synergistic effect of glass fibre and Al powder on the mechanical properties of glass-ceramics, blast furnace slag was chosen as the main material, and glass fibre and Al powder as reinforcement materials. The phase compositions, microstructures, compressive properties, and apparent density of the glass-ceramics with varying quantities of glass fibre and Al powder were investigated. The experimental results indicated that Al powder could exist as a simple substance in glass-ceramics and form a dense net coating on the surface of blast furnace slag to improve the plasticity of the glass-ceramic. The glass fibre had better reinforcement effect than Al powder because of its extremely high mechanical strength. The plasticity of glass-ceramics, however, severely decreased; the glass-ceramics exhibited brittle failure during compression. A slight increase in the content of CaSi2 and SiO2 in the glass-ceramics was closely related to the addition of glass fibre. Considering safety and economy, glass-ceramics with 6% Al and 14% glass fibre (S4) have the best mechanical properties. The compressive strength, strain at maximum force, and apparent density were 40?MPa, 19% and 1.974?g/cm3, respectively. 相似文献
8.
Recently, the sustainable utilization of REE-bearing slag for the recovery and application of rare-earth elements (REEs) has attracted considerable attention. However, a limited amount of thermodynamic data and crystal information for REE systems has been reported, which greatly limits the utilization of REE-bearing slag. In this study, the isothermal phase diagram of the CaO–SiO2–CaF2(30 wt%)-P2O5(10 wt%)-Ce2O3 system was constructed to provide phase equilibria data for the REEs in REE-bearing slag. The formation mechanism of britholite (Ca5-xCex[(Si,P)O4]3F) in the quinary system was found: it evolved from Ca5(PO4)3F, when a Ce3+ replaced a Ca2+, there would be a SiO44? instead of a PO43?. The phase equilibria and formation mechanism of REEs in the CaO–SiO2–CaF2–P2O5–Ce2O3 system are supplied to provide the data required for sustainable utilization of REE-bearing slag. 相似文献
9.
A comparative study on CaO–MgO–Al2O3–SiO2 slag and CaO–MgO–Al2O3–SiO2–Cr2O3 slag was conducted to investigate the distribution of the elements at the gas-slag interface. The effect of redox states of chromium on the distribution of sulfur and oxygen at the interface was revealed by gas-slag equilibrium method using X-ray photoelectron spectroscopy at 1873K. From the analysis of the S2p core-level spectra, the negative divalent sulfur(S2?) was detected at the interface in the Cr-bearing slag, which directly proved that sulfur exists in the form of S2? in the slag for the first time. However, the S2? peak is very weak at the interface of Cr-free slag. The reason for the difference between the two slags may be due to chromium changing the interface structure. According to the O1s and Cr2p core-level spectra, non-bridged oxygen(O?) increased, while bridged oxygen(O0) decreased with the etching depth deepened. The increase of NBO/BO and Cr2+/Cr3+ elucidates that Cr3+ can modify the structure of the slag as basicity substance, but its effect is weaker than that of Cr2+. Meanwhile, due to the affinity of sulfur and chromium, the addition of chromium may also lead to the enhancement of the S2? peak at the gas-slag interface. Gradient change of elements at the interface proved the existence of the boundary layer. 相似文献
10.
《Ceramics International》2021,47(21):29949-29959
High carbon footprint of cement production is the major drawback of plain cement concrete resulting in environmental pollution. Geopolymer composites paste can be effectively used as an alternative to Portland cement in the construction industry for a sustainable environment. The demand for high-performance composites and sustainable construction is increasing day by day. Therefore, the present experimental program has endeavored to investigate the mechanical performance of basalt fiber-reinforced fly ash-based geopolymer pastes with various contents of nano CaCO3. The content of basalt fibers was fixed at 2% by weight for all specimens while the studied contents of nano CaCO3 were 0%, 1%, 2%, and 3%, respectively. The compressive strength, compressive stress-strain response, flexural strength, bending stress-strain response, elastic modulus, toughness modulus, toughness indices, fracture toughness, impact strength, hardness, and microstructural analysis of all four geopolymer composite pastes with varying contents of nano CaCO3 using scanning electron microscopy (SEM) were evaluated. The results revealed that the use of 3% nano CaCO3 in basalt fiber-reinforced geopolymer paste presented the highest values of compressive strength and hardness while the use of 2% nano CaCO3 showed the highest values of flexural strength, impact strength, and fracture toughness of composite paste. The SEM results indicated that the addition of nano CaCO3 improved the microstructure and provided a denser geopolymer paste by refining the interfacial zones and accelerating the geopolymerization reaction. 相似文献
11.
Junrui Yang Lei Wang Xinrong Tan Qian Zhi Ruibin Yang Guopeng Zhang Zhongxia Liu Xianghong Ge Erjun Liang 《Ceramics International》2018,44(9):10744-10752
A 2024Al metal matrix composite with 10?vol% negative expansion ceramic ZrMgMo3O12 was fabricated by vacuum hot pressing, and the influence of sintering temperature on the microstructure and thermal expansion coefficient (CTE) of alloys was investigated. Experimental results showed that all ZrMgMo3O12p/2024Al composites sintered at 500–530?°C had a similar reticular structure and exhibited different linear expansion coefficients at 40–150?°C and 150–300?°C. The addition of 10?vol% ZrMgMo3O12 decreased the CTEs of 2024Al by ~ 16% at 40–150?°C and by ~ 7% at 150–300?°C. This addition also increased the hardness of 2024Al by ~ 23%. The density of the composites and the content of Al2Cu in ZrMgMo3O12p/2024Al increased as the sintering temperature increased. The CTEs of the composites decreased, whereas hardness increased. Thermal cycling from 40?°C to 300?°C caused the CTEs of the composites to decrease gradually and reach a stable value after seven cycles. The lowest CTEs of 15.4?×?10?6 °C?1 at 40–150?°C and 20.1?×?10?6 °C?1 at 150–300?°C were obtained after 10 thermal cycles and were reduced by ~ 32% and ~ 17%, respectively, compared with the CTE of the 2024Al. Among the current reinforcements, ZrMgMo3O12 negative expansion ceramics showed the highest efficiency to decrease the CTE of Al matrix composites. 相似文献
12.
ABSTRACTGlass ceramic foams were fabricated with powder sintering technology at a low temperature (900°C), using water-quenched titanium-bearing blast furnace slag (WTS) and waste glass as the primary raw materials. Additionally, calcium carbonate, sodium borate and sodium phosphate were chosen as sintering aids to form excellent performance products. The effects of calcium carbonate additions on foaming process, crystal content, morphology and properties of the prepared samples were systematically researched. The research indicates that increasing the calcium carbonate content made the foaming process harder and the pore size got more uniform. Consequently, the compressive strength and bulk density increased, while the porosity and water absorption decreased. The homogenous porous structures and optimal comprehensive properties were achieved with 5–7?wt-% CaCO3 addition, including a bulk density of 0.79–0.82?g?cm–3, porosity of 73.13–75.28%, water absorption of 3.29–3.75% and compressive strength of 13.13–13.85?MPa. 相似文献
13.
Abdul W. Bhuiya Michael Hu Kaushik Sankar Patrick F. Keane Daniel Ribero Waltraud M. Kriven 《Journal of the American Ceramic Society》2021,104(6):2767-2779
Potassium-based, geopolymer composites were made with BASF® metakaolin and Mymensingh clay-derived metakaolin from Bangladesh. Since the natural Mymensingh clay contained 40 wt.% quartz, this same amount of quartz particulates was added to the BASF® metakaolin to make a synthetic analog of the natural calcined clay. By analogy with bone china, bone ash or calcined hydroxyapatite (5CaO•3P2O5 or “HA”) particles, having a Ca: P ratio of 3.3:1, were added to make the three types of geopolymer-based composites described above. For less refractory particulate additions, dicalcium phosphate (DCP) (2CaO•P2O5 or “DCP”) particles, having a Ca: P ratio of 2:1, were also added to another set of geopolymers. The ambient temperature compressive and flexural strengths were measured for all of the geopolymer composites. The HA or DCP reinforced geopolymer composites were fabricated and heat-treated to 1150°C/1 h, after which they were converted to their mineralogical analogs. Their mechanical properties of compressive and 3-point flexural strengths were again measured. Flexural strengths of 22.42 ± 11.0 MPa and 31.97 ± 8.3 MPa were measured in 1 × 1 × 10 cm3 heat-treated geopolymer bars reinforced with 10 wt.% of DCP and in geopolymer reinforced with 10 wt.% DCP +40 wt.% quartz additions, respectively. Significant improvements to ambient temperature properties were observed due to the self-healing effect of the flowing amorphous DCP, whose presence was verified by SEM. The geopolymer samples exhibited reduced water absorption (WA) (on a percentage dry weight basis) of within 0.03-0.5% after being heated at 1100℃/1 h and 1125℃/1 h, as compared with those at room temperature, which varied between 2.56% and 7.89%. 相似文献
14.
Phase equilibria of the ZnO–SiO2, Al2O3–SiO2 and ZnO–Al2O3–SiO2 systems at liquidus were characterized at 1340–1740 °C in air. The ZnO–Al2O3 subsolidus phase equilibria were derived from the experiments with the SiO2- and CaO + SiO2-containing slags. High-temperature equilibration on silica or platinum substrates, followed by quenching and direct measurement of Zn, Al, Si and Ca concentrations in the phases with the electron probe X-ray microanalysis (EPMA) was used to accurately characterize the system. Special attention was given to zincite phase that was shown to consist of two separate ranges of compositions: round-shaped low-Al zincite (<2 mol.% AlO1.5) and platy high-Al zincite (4–11 mol.% AlO1.5). A technique was developed for more accurate measurement of the ZnO solubility in the low-ZnO phases (corundum, mullite, tridymite and cristobalite) surrounded by the ZnO-containing slag, using l-line for Zn instead of K-line, avoiding the interference of secondary X-ray fluorescence. Solubility of ZnO was found to be below 0.03 mol.% in corundum and cristobalite, and below 0.3 mol.% in mullite. Present experimental data were used to obtain a self-consistent set of parameters of the thermodynamic models for all phases in this system using FactSage computer package. The modified quasichemical model with two sublattices (Zn2+, Al3+, Si4+) (O2?) was used for the liquid slag phase; the compound energy formalism was used for the spinel (Zn2+,Al3+)[Zn2+,Al3+,Va]2O2-4 and mullite Al3+2(Al3+,Si4+) (O2?,Va)5 phases; the Bragg-Williams formalism was used for the zincite (ZnO, Al2O3); other solid phases (tridymite and cristobalite SiO2, corundum Al2O3, and willemite Zn2SiO4) were described as stoichiometric. Present study is a part of the research program on the characterization of the multicomponent Pb–Zn–Cu–Fe–Ca–Si–O–S–Al–Mg–Cr–As–Sn–Sb–Bi–Ag–Au–Ni system. 相似文献
15.
Ana Fernández‐Jiménez Fatima Zibouche Nassima Boudissa Ines García‐Lodeiro Mohamed Tahar Abadlia Angel Palomo 《Journal of the American Ceramic Society》2013,96(6):1991-1998
This article reports on research into the use of solid alkalis (Na2CO3 and K2CO3) as activators to obtain hybrid cement (cement whose hydration generates a mix of C–A–S–H and (N,C)–A–S–H gels) from a blend of 20% clínker + 40% blast furnace slag + 40% metakaolin. More specifically, the study aimed to determine the effect of activator dosage (5 and 8 wt%) and type of alkaline cation (Na+ or K+) on the 2‐ and 28‐d mechanical strength of the end materials. The findings showed that the highest mechanical strength values were obtained with 5% Na2CO3. According to the XRD, NMR, and SEM/EDX analyses conducted on the reaction products, the alkalinity and solubilized chemical species generated by adding 5% Na2CO3 to the system yielded a mix of (N,C)–A–S–H and C–A–S–H cementitious gels as the main reaction products. The secondary reaction products included metastable (3CaO·Al2O3·CaCO3·11H2O‐type) carboaluminates that evolved into the calcite or vaterite forms of calcium carbonate. When K2CO3 was used (instead of Na2CO3), a (3CaO·Al2O3·0.5Ca(OH)2·0.5CaCO3·11H2O‐type) hemicarboaluminate also formed. The study also revealed that Na+ favors coagulation/precipitation more effectively than K+, generating gels with a wider range of Qn species. 相似文献
16.
《Ceramics International》2020,46(12):20027-20037
Properties of fly ash (FA) and metakaolin (MK) based geopolymer/alkali-activated mortar modified with polyvinyl alcohol (PVA) fiber and nano-SiO2, including workability, compressive strength, flexural performance, elastic modulus and fracture property were tested in this study. PVA fiber content varies from 0 to 1.2%. Nano-SiO2 content is 0 and 1%. Adaptive neuro-fuzzy interfacial systems (ANFIS) method was used to establish the artificial intelligence (AI) model to predict the fracture parameters of geopolymer/alkali-activated mortars. The inputs of ANFIS models include PVA fiber content, nano-SiO2 content, compressive strength, flexural strength, elastic modulus, critical crack mouth opening displacement, crack load and peak load. The outputs of ANFIS model include critical effective crack length, initiation fracture toughness, unstable fracture toughness, and fracture energy. Experiment results showed that PVA fiber addition enhanced the mechanical properties especially the compressive strength and fracture performance, but decreased the workability. 0.8%–1.0% was considered as the optimal content of PVA fiber. Addition of 1% nano-SiO2 shows a slight improvement on both workability and mechanical properties of the mortar no matter how much fiber is added. Based on the ANFIS algorithm and 42 sets of experimental data, the trained models were proved to have high accuracy with root mean square error (RMSE) under 0.15, mean absolute error (MAE) under 0.01, and coefficient of determination (R2) over 0.85. The ANFIS model established in this study combined the fracture properties with the basic mechanical properties of geopolymer/alkali-activated composites, which can provide a new method to assess the fracture performance of geopolymer/alkali-activated mortars modified with PVA fiber and nano-SiO2 in the future. 相似文献
17.
Zhenglong Liu Chengji Deng Chao Yu Xing Wang Jun Ding Hongxi Zhu 《Ceramics International》2018,44(12):13944-13950
C-SiC composite powders were prepared by salt-assisted synthesis from Si powders, graphite, and a molten salt medium (NaCl and NaF) with the molar ratio of Si/C =?1/2 at 1300?°C for 3?h. After the C-SiC composite powders part and complete replacement of the graphite, the mechanical properties, oxidation resistance and slag-corrosion resistance of the Al2O3-C materials were studied by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), as well as with dedicated equipment. The results indicated that SiC whiskers, with lengths of 10–50?nm, formed on the surface of the flake graphite, and the activation energy of oxidation of the C-SiC composite powder increased by 45.72?kJ?mol?1 as compared to that of flake graphite. Furthermore, the decarburization area and slag erosion area of the Al2O3-C material decreased after 3?wt% of C-SiC composite powder was substituted for the flake graphite. Meanwhile, the cold modulus of rupture was maintained when 3?wt% of C-SiC composite powder was added. This improved both the oxidation and slag resistance of the Al2O3-C materials. 相似文献
18.
Dong-Bin Dang Hui Gao Yan Bai Xue-Fu Hu Fang Yang Yang Chen Jing-Yang Niu 《Inorganic chemistry communications》2010,13(1):37-41
A novel two-dimensional helical coordination polymer [Ag(CH3CN)4][Ag3(CH3CN)8(SiMo12O40)] (1) has been gained by the conventional self-assembly reaction, and characterized by IR, elemental analysis, UV, TG technique and X-ray single crystal diffraction. Each [SiMo12O40]4? cluster interconnects with three bimetallic cation subunits through three Mo–O–Ag bridges, meanwhile, each bimetallic cation subunit is surrounded by three [SiMo12O40]4? to form an unprecedented two-dimensional network structure. The metal–metal bonds between Ag(1) and Ag(2) atoms from the adjacent helical chains connects the chains together into a chiral 2D helical network. The 2D network structures are further interconnected with each other to form a 3D supramolecular network through multiform intermolecular hydrogen bonds. The luminescent properties of the coordination polymer in the solid state were investigated. 相似文献
19.
《Ceramics International》2020,46(5):6205-6211
This study utilized the single hot thermocouple technique to examine the dissolution behavior of lumped magnesium oxide (MgO) in CaO–Al2O3–SiO2 ternary slags. The aluminum oxide (Al2O3) content in the slag (C/S = 1) varied from 10% to 30%; the MgO sphere with a diameter of 1 mm was placed in molten slags at 1,550 °C. Results showed that the dissolution rate decreased as the Al2O3 content increased up to 20%. Over 20% Al2O3, MgAl2O4 was formed at the interface of MgO and it did not fully melt at 30% Al2O3. The dissolution behavior and the formation of MgAl2O4 were analyzed by a phase diagram provided by Factsage 7.0 software. In the case of less than 20% Al2O3 content, apparent sphere radii were measured; the shrinking core model was then applied to understand the dissolution mechanism. The dissolution rate of both slags was controlled by boundary layer diffusion. The dissolution rate at 20% Al2O3 slag appeared to fit the behavior to the boundary layer diffusion, although it deviated during the middle stage of the dissolution because of MgAl2O4 formation. The 10% Al2O3 slag fitted well to the boundary layer diffusion curve; the obtained diffusion coefficient was 0.94 × 10−9 m2/s. 相似文献
20.
Shuang Yin Limei Pan Xia Fang Yufeng Li Yanpu Li Yongbao Feng Tai Qiu Jian Yang 《Ceramics International》2019,45(8):9994-10003
In this study, the low–toxicity monomer N, N–dimethylacrylamide (DMAA), serving as both gelling agent and pore–forming agent, was adopted to fabricate porous Si3N4 ceramics with a regulatable microstructure and property by aqueous gelcasting. Results indicate that monomer content played an important role in regulating and optimizing the properties of sintered bodies. With increasing monomer content (5.94–30.69?wt%), both slurry viscosity (maximum 0.14?Pa?s at 95.40 s?1) and green body strength (11.35–49.23?MPa) exhibited monotonic increasing trends, demonstrating superior mechanical properties to those obtained using the neurovirulent acrylamide (AM) gelling system. The increased monomer content not only improved porosity, but also promoted α→β–Si3N4 transformation as well as β–Si3N4 grain growth through enhancing the connectivity of interlocking pores and accelerating the vapor phase transport during liquid–phase sintering. These variations in phase composition and microstructure derived from the varied monomer content further resulted in monotonic changes in porosity (40.32–51.50%), mean pore size (0.27–0.38?μm), flexural strength (202.77–132.15?MPa), fracture toughness (2.93–2.32?MPa?m1/2), dielectric constant (3.48–2.78) and loss (3.52–3.09?×?10?3) at 10?GHz for sintered bodies, displaying an excellent comprehensive properties. This study suggests a promising prospect for DMAA in preparation of high–performance porous Si3N4 ceramics by aqueous gelcasting. 相似文献