Presented in this article are mechanical property and microstructural data for fluoride molten salt infiltrated graphite at high temperature. Four infiltration pressures (0 kPa, 450 kPa, 600 kPa, and ...1000 kPa) and two kinds of graphite (IG-110 and NG-CT-10) were used during molten salt infiltration. After fluoride molten salt infiltration, compression testing and tension testing were performed at 700 °C to determine compressive strength, tensile strength, softening coefficient, stress–strain curve, and absorbed energy. Utilizing scanning electron microscopy (SEM) applied to fracture fragments, SEM micrographs for the fracture surface of molten salt infiltrated graphite and virgin graphite were determined.
Graphite components are constantly subjected to a combined actions of annealing and irradiation due to high temperatures and thermal spike caused by irradiation when reactors are operating, resulting ...in complex microstructures along with matching changes in the material properties and dimensions. This study investigates the evolution process of initial irradiation defects at different annealing temperatures, which is difficult to captured by experiment. The findings indicate that 923K reactor-temperature annealing can also quickly restore isolated self-interstitial atoms and small-sized point defect clusters to intralayer locations on the nanosecond scale. However, multi-interlayer penetration damages and localized point defect aggregation from high-energy irradiation can lead to the disappearance of layered structural information, which allows these damage structures to develop into interlayer dislocations during annealing process. These interlayer dislocations further exacerbate the interlayer expansion of graphite crystal and may elucidate the mechanism behind volume expansion in nuclear graphite within reactors. Fully amorphized regions can also regain a layered structure approximately when guided by residual layered structures at 2000K, while chaotic regions or disordered layered structures form in the absence of guidance. These chaotic regions significantly exacerbate the volume expansion of graphite model, which may be related to the rapid volume increase observed in nuclear graphite components at the end of reactor life. The study provides insights into the transformation of initial irradiation defects into different types of defects under different temperatures and damage states, which serve as a critical foundation for assessing the evolution of irradiation defects in nuclear graphite for reactor applications and annealing studies.
•Using MD to capture annealing evolution on the nanosecond scale.•Insights on formation of nuclear graphite interlayer dislocations during annealing.•Microstructural mechanism of dimensional changes in nuclear graphite during annealing.•Relationship between structural evolution and graphite properties change.
As a phase change material, Wood's alloy is infiltrated into the compressed expanded natural graphite (CENG) in an attempt to improve the thermal conductivity of the alloy. The thermal conductivity ...of the CENG/Wood's alloy composite depends on the bulk density of the CENG. Thermal conductivity of the composites can be 2.8–5.8 times than that of the Wood's alloy. On the other hand, the latent heat of the composites ranges from 29.27 to 34.20J/g. The graphite does not undergo a phase change, so the latent heat would be expected to be linear with the amount of Wood's alloy. The composites have a potential use in the heat sink of the electronic device.
► Compressed expanded natural graphite (CENG) improved the thermal performance of Wood's alloy. ► Thermal conductivity of the CENG/Wood's alloy composites is ∼5 times than that of the Wood's alloy. ► The latent heat would be expected to be linear with the amount of Wood's alloy. ► The composites have a potential use in the heat sink of the electronic device.
Efficient synthesis of primary amines via low-temperature reductive amination of carbonyl compounds using NH3 and H2 as the nitrogen and hydrogen resources is highly desired and challenging in the ...chemistry community. Herein, we employed naturally occurring phytic acid as a renewable precursor to fabricate titanium phosphate (TiP)-supported Ru nanocatalysts with different reduction degrees of RuO2 (Ru/TiP-x, x represents the reduction temperature) by combining ball milling and molten-salt processes. Very interestingly, the obtained Ru/TiP-100 had good catalytic performance for the reductive amination of carbonyl compounds at ambient temperature, resulting from the synergistic cooperation of the support (TiP) and the Ru/RuO2 with a suitable proportion of Ru0 (52%). Various carbonyl compounds could be efficiently converted into the corresponding primary amines with high yields. More importantly, the conversion of other substrates with reducible groups could also be achieved at ambient temperature. Detailed investigations indicated that the partially reduced Ru and the support (TiP) were indispensable. The high activity and selectivity of Ru/TiP-100 catalyst originates from the relatively high acidity and the suitable electron density of metallic Ru0.
In this work, we synthesized tin(IV) phosphonate (SnBPMA) and zirconium phosphonate (ZrBPMA) by the reaction of SnCl
4
·5H
2
O or ZrOCl
2
·8H
2
O with
N
,
N
-bis(phosphonomethyl)aminoacetic acid, ...which was synthesized from a biomaterial glycine through a Mannich-type reaction. The SnBPMA and ZrBPMA were very efficient heterogeneous catalysts for the dehydration of fructose to produce 5-hydroxymethylfurfural (HMF), and the SnBPMA had higher activity than the ZrBPMA. The effects of solvents, temperature, reaction time, and reactant/solvent weight ratio on the reaction catalyzed by SnBPMA were investigated. It was demonstrated that the yield of HMF could reach 86.5% with 1-ethyl-3-methylimidazolium bromide (Emim Br) as solvent, and the SnBPMA and SnBPMA/EmimBr catalytic system could be reused five times without considerable reduction in catalytic efficiency. Further study indicated that the SnBPMA and ZrBPMA in EmimBr were also effective for the dehydration of sucrose and inulin to produce HMF with satisfactory yields.
The mesophase pitch derived graphite foams with low bulk density (L-GF) and high bulk density (H-GF) were spontaneously infiltrated by erythritol to prepare graphite foam/erythritol (GF/erythritol) ...phase change materials (PCMs) with ultrahigh thermal conductivity for medium temperature thermal energy storage applications. Results of thermophysical properties indicated that thermal diffusivity of the GF/erythritol PCMs can be enhanced by 66 and 117 times as compared with that of pristine erythritol in solid (0.36 mm2/s). This enhancement resulting from three-dimensional ordered network of graphite foam can significantly reduce the charging and discharging time of the PCM storage system. Although H-GF as a matrix can obtain a higher thermal conductivity (68.71 W/(m·K)) than L-GF (40.52 W/(m·K)), the smaller porosity cannot allow more erythritol to be absorbed, and its melting enthalpy (178.4 J/g) is lower than L-GF (266.6 J/g). In addition, the enhancement of thermal conductivity and the increase of interfacial surface area caused by graphite foam structure strongly suppresses the supercooling of erythritol, which can be reduced from 86.0 °C to 53.2 °C. The obtained results demonstrated that the GF/erythritol PCM as a stable PCM is a promising material for medium temperature thermal energy storage applications.
•The phase change material with ultrahigh thermal conductivity was obtained.•The supercooling of erythritol can be effectively suppressed.•The graphite foam forms supply a path for heat transferring rapidly.•Increasing grain size of erythritol also contributes to the heat transfer rapidly.
Stable organic nitroxyl radicals are an important class of catalysts for oxidation reactions, but their wide applications are hindered by their steric hinderance, high cost, complex operation, and ...separation procedures. Herein, NO2 in DMSO is shown to effectively catalyze the aerobic oxidative cleavage of C(OH)−C bonds to form a carboxylic group, and NO2 was generated in situ by decomposition of nitrates. A diverse range of secondary alcohols were selectively converted into acids in excellent yields in this transition‐metal‐free system without any additives. Preliminary results also indicate its applicability to depolymerize recalcitrant macromolecular lignin. Detail studies revealed that NO2 from nitrates promoted the reaction, and NO2 served as hydrogen acceptor and radical initiator for the tandem oxidative reaction.
NO2 in DMSO catalyzes the aerobic oxidative cleavage of C(OH)−C bonds to form a carboxylic group, and NO2 was generated in situ by decomposition of nitrates. A diverse range of secondary alcohols were selectively converted into acids in excellent yields in this transition‐metal‐free system without any additives.
Mesocarbon microbeads and the isostatic pressing method were used to prepare binderless nanopore-isotropic graphite (NPIG) as a neutron moderator and reflector, to inhibit liquid fluoride salt and ...Xe135 penetration during use in a molten salt nuclear reactor. The microstructure, thermophysical, and other properties of the NPIG were studied and compared with isostatic graphite (IG-110, TOYO TANSO CO., Ltd., Japan). A high-pressure reactor and a vacuum device were constructed to evaluate the molten salt and Xe135 penetration in the graphite, respectively. The results indicated that NPIG possessed a graphitization degree of 74% and excellent properties such as a high bending strength of 94.1±2.5MPa, a high compressive strength of 230±3MPa, a low porosity of 8.7%, and an average pore diameter of 69nm. The fluoride salt occupation of IG-110 was 13.5wt% under 1.5atm, whereas the salt gain in NPIG remained steady even up to 10atm with an increase of <0.06wt%, demonstrating that the graphite could inhibit the liquid fluoride salt infiltration effectively. The helium diffusion coefficient for NPIG was 8.76×10−5cm2/s, much less than 1.21×10−2cm2/s for IG-110. The NPIG could effectively inhibit liquid fluoride salt and Xe135 penetration.
•Cross-scale elasticity of shales is characterized by big data-based nanoindentation.•Comprehensive big data analytics is developed to process massive indentation data.•An improved criterion for ...selecting optimal bin size is proposed and validated.•A new surround effect model can mathematically depict upscaling and homogenization.•Nanoindentation results agree well with those from micromechanical models.
Shales are a class of multiscale, multiphase, hybrid inorganic-organic composite materials exhibiting both frictional and cohesive behavior, and it is very challenging to characterize and interpret their complex mechanical properties. A statistical nanoindentation approach with pertinent viable data analytics was developed to probe the mechanical properties of shales across different length scales. Grid nanoindentation experiments with continuous stiffness measurement performed on shales to relatively large depths of 6–8 µm obtained massive data, which were processed by the new data analytics: segmentation at selected depths of a great number (e.g., >500) of continuous Young's modulus versus indentation depth curves obtained from unknown constituent phases yielded multiple discretized sub-datasets that were processed to extract individual phases’ elastic moduli at respective segmentation depths via probability density function (PDF)-based deconvolution; these depth-dependent Young's moduli of each phase were then fitted by a newly proposed surround effect model, leading to determination of the properties of both individual phases at the nano/micro-scales (i.e., virtually infinitesimal depths) and the bulk rock at the macroscale (i.e., ~10–100 µm depths). A significant advantage of this massive data-based indentation approach is that the mechanical properties of composite materials such as shales can be probed across different scales by a single measurement technique. In addition, a new criterion, termed Bin Size Index, was formulated for selecting depth-dependent, rational, optimized bin sizes for PDF construction. For the studied shales, results show that five mechanically-distinct phases are discerned, including a virtual interface phase between hard and soft constituents accounting for a majority of indents. Coincidently, the Young's modulus of the bulk rock is nearly the same as that of the interface phase, suggesting that the macroscopic properties of similar composites may be estimated from measurements on the interface of two phases with contrasting mechanical properties. Finally, this approach can guide the selection of appropriate indentation depths to probe the mechanical properties of both highly heterogeneous bulk materials at the macroscale and their individual constituent phases at the nano/micro-scale.
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