Crystalline Phase Change Research Articles

Self-assembly and energy storage potentials of biphasic phase change azobenzene liquid crystalline block copolymers

Flexible polymeric materials with potentials in energy storage have attracted extensive attention in today's sustainable society. Here, we reported a series of crystalline-liquid crystalline biphasic phase change block copolymers, poly(ethylene oxide)-b-poly(11-(4-(4-cyanophenylazo)phenoxy)undecane methacrylate) (PEO-b-PMAAzo), and studied the UV and Li+ ions coordination-mediated self-assembly for the potentials in phase change energy storage and solid electrolytes. The PEO-b-PMAAzo BCPs possess both the solid-liquid phase transition of PEO and the photo-chemical-thermal energy transition of PMAAzo block. Meanwhile, PEO has the capability to coordinate with the Li+ for the ionic conductivity. We explored the binary phase change behaviors and thermal energy density of the BCPs with different lithium ion concentrations before and after UV irradiation. The addition of LiTFSI salts increases the interaction parameters (χ) of the BCPs leading to phase transition of the self-assembled nanostructures. The phase diagram covering LAM, HEX, GYR, Fddd and HPL nanostructures facilitating ion transport was demonstrated. The PMAAzo block enabled the solid feature of the BCPs and ensured the high energy density and high conductivity. This work demonstrates that the combination of the functional polymers in one BCP not only provides multiple morphology tunabilities but also enables multiple functionalities from energy conversation and storage to ionic conductive electrolytes.

Adsorption and nucleation mechanism of molten carbonate on nano-SiC surface

Molten carbonate is an important thermal storage media for high temperature thermal energy storage system. However, the specific heat capacity (SHC) of carbonate is less than 2 J/g K, which limits its application prospects. Nano-SiC was used to improve the SHC of carbonate at high temperature in our previous work. The SHC of binary carbonate increased by 83 % with the addition of nano-SiC. However, the improvement mechanism is not clear. In this study, the adsorption and nucleation mechanism of molten carbonate on nano-SiC surface were clarified. The DFT calculation results show that the adsorption energy of Li+, Na+ and CO32− is −310, −259 and −654 kJ/mol, respectively, which means the addition of nano-SiC causes a non-uniform distribution of molten carbonate ions around its surface. This affects the subsequent nucleation and results in carbonate segregation. Na2CO3 is the most thermodynamically favorable to adsorb and nucleate, followed by LiNaCO3, and Li2CO3 is the most difficult. The crystalline phase changes of carbonate on nano-SiC surface from solid to liquid phase during melting process were obtained in-situ and the results are consistent with the DFT calculations. Therefore, the adsorption and nucleation mechanism of molten carbonate on nano-SiC surface is well elucidated by the calculations and experiments of this study.

Investigating the effects of calcination temperature on porous clay heterostructure characteristics

This study focuses on finding the optimal calcination temperature for synthesizing porous clay heterostructures (PCH). PCH was prepared using montmorillonite at different temperatures (200–800 °C) in a closed N2 environment. Samples were characterized via N2-physisorption, scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) to investigate the influence of calcination temperature. Characterizations show that the PCH composite exhibits an increasing surface profile observed by increasing specific surface area, changes in crystalline phases, porous surface, and varied particle size distribution. The position (degree and wavelength) and intensities of minerals and functional groups in PCH shift with temperature, as observed in both FTIR and XRD. This shows that variables such as heating rate, calcination temperature, and environment affect the structural changes in the clay material. In terms of active phase development, structural behavior, and material strength, the correct calcination temperature proved to be crucial.

Radiation shielding, optical, structural, morphological, and thermal features for tellurite glass ceramics

A new series of tellurite glass-ceramic was prepared for potential utilization in the radiation shielding field. The thermal features of parent glasses were assessed to choose the best heat treatment technique. The morphological and structural properties of glass ceramics were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR). The UV absorption was utilized to calculate the optical features of glass ceramics. The shielding properties were computed based on the Phy-X software. The transformation of glasses to glass ceramics enhanced the density of all glass ceramics. XRD results exhibited an orthorhombic BaTeO3 crystalline phase for the TMSB0 and TMSB5 samples. It is proved that the monoclinic molybdenum tellurium oxide (Mo5TeO16) crystalline phase for TMSB10, TMSB15, and TMSB20 samples. Also, the change in crystalline phase resulted from adding MoO3 instead of TeO2. SEM results affirmed the role of MoO3 in improving the structure of glass ceramics. The thermal stability and weight loss of TMSB20 samples are higher than other glasses. Also, the adding MoO3 led to a slight enhancement in the radiation shielding properties of the prepared samples. Data indicate that adding MoO3 to the glasses enhanced the glass-ceramic samples' thermal, structural, and radiation protection properties.

Antimicrobial polysaccharide hydrogels embedded with methyl-β-cyclodextrin/thyme oil inclusion complexes for exceptional mechanical performance and chilled chicken breast preservation

While hydrogels have potential for food packaging, limited research on hydrogels with excellent mechanical performance and antibacterial activity for preserving chicken breasts. Herein, we created antibacterial hydrogels by embedding methyl-β-cyclodextrin/thyme oil inclusion complexes (MCD/TO-ICs) into a polyvinyl alcohol matrix containing dendrobium polysaccharides and guar gum in varying ratios using freeze-thaw cycling method. The resulting hydrogels exhibited a more compact structure than those without MCD/TO-ICs, enhancing thermal stability and increasing glass transition temperature due to additional intermolecular interactions between polymer chains that inhibited chain movement. XRD analysis showed no significant changes in crystalline phase, enabling formation of a 3D network through abundant hydrogen bonding. Moreover, the hydrogel demonstrated exceptional durability, with a toughness of 350 ± 25 kJ/m3 and adequate tearing resistance of 340 ± 30 J/m2, capable of lifting 3 kg weight, 1200 times greater than the hydrogel itself. Additionally, the hydrogels displayed excellent antimicrobial activity and antioxidant properties. Importantly, the hydrogels effectively maintained TVB-N levels and microbial counts within acceptable ranges, preserving sensory properties and extending the shelf life of chilled chicken breasts by four days. This study highlights the potential of MCD/TO-IC-incorporated polysaccharide hydrogels as safe and effective active packaging solutions for preserving chilled chicken in food industry.

Enhancing piezoelectric effect of PVDF electrospun fiber through NiO nanoparticles for wearable applications

Flexible electrospun fiber-based piezoelectric nanogenerator (PENG) has attracted a lot of interest due to its ability of generating electrical energy from mechanical energy sources. The present work aims to improve the piezoelectric output of PENG devices based on electrospun polyvinylidene fluoride (PVDF) doped with nickel oxide nanoparticles (NiO NPs) in different concentrations (2, 4, 6, 8 and 10 wt.-%). Crystalline phase changes and β-crystalline content in electrospun fibers were evaluated using XRD and FTIR-ATR, respectively. Surface morphology and surface roughness of the electrospun fibers were observed using FE-SEM and AFM, respectively. The hydrophobic nature of the fibers was analyzed using a wettability test. PENG output voltage and short-circuit current performance of neat PVDF and PVDF doped with NiO (PN) composite electrospun fibers were calculated using a customized variable-pressure setup with an optimized force of 1.0 kgf and 1.0 Hz frequency. Neat PVDF-based PENG exhibited only 1.7 V and 0.7 μA, whereas, PVDF doped with 6 wt.-% NiO NP (PN-6) based PENG generated a high output voltage of 5.5 V and 1.83 μA current. The optimized PN-6 PENG device is demonstrated for use in wearable devices towards identifying certain body movements like tapping, wrist movement, walking and running.

Cold crystallization of polytrimethylene terephthalate and copolymers

The melt of crystalline polymers normally crystalize on cooling and the polymer melts with low critical cooling rate would easily solidify as glass during cooling to their glass transition temperature (Tg). The glassy process exhibits variety within each kind of polymer melts in the slope of the viscosity-temperature visibility, and the rate of the excess conformational entropy in the polymer melt over the crystalline phase changes in the Tg approaching. Polytrimethylene terephthalate (PTT) and a series of polytrimethylene terephthalate copolyesters (PTTG) with different molar ratios of 1,3-propylene glycol (1,3-PDO) to 1,4-cyclohexanedimethanol (1,4-CHDM) were synthesized to modify the chain flexibility and the critical cooling rate. The glassy samples were obtained via quenching the melts of PTT and copolymers below the Tg to characterize the cold crystallization behaviors. The evolutions of the crystalline structure of the amorphous samples were in situ investigated via DSC and simultaneous WAXS/SAXS approaches during heating. The polymer chain dynamics and the critical cooling rates of the PTT and copolymers were estimated by rheological testing and DSC characterization. The results indicate that the chain conformation adjustment of PTT and copolymers is relate to the comonomers in the copolymers, and the cold crystallization behaviors can be divided into three temperature ranges during heating. The first involves rapid transition from a pre-ordered phase to a crystalline phase, the second is the adjustment of defects in an imperfect crystalline phase, and the third may refer crystal reorganization before melting. The crystallization ability of the samples could be due to the ability of chain conformation adjustment with comonomer content till the crystallization is no longer obvious during heating. The cold crystallization behaviors of the samples were discussed based on the polymer chain dynamics and it is convinced that would be helpful to understand the crystallization and processing of polymers.

Influence of 3D printed surface micro-structures on molding performance and dental bonding properties of zirconia

ObjectivesTo investigate the influence of the 3D printed micro-structured surfaces on the bond strength of zirconia to resin cement. MethodsZirconia specimens were divided into five groups based on manufacturing technique and surface preparation: (1) milled zirconia (M group); (2) milled zirconia airborne abraded (MA group); (3) printed zirconia (M group); (4) printed zirconia airborne abraded (PA group); and (5) printed zirconia with micro-structured surface (PM group). The surface morphology, cross-sectional morphology, and elemental composition were observed using a scanning electron microscope (SEM). Surface roughness was measured using a laser scanning confocal microscope (SLCM). Shear bond strength (SBS) was measured using a universal testing machine after bonding resin cement (n = 10). The failure modes of the bonded fracture interfaces were observed and counted using a stereomicroscope and a SEM. In addition, boundary dimensional accuracy (n = 10) and micro-structural dimensional accuracy (n = 20) of printed zirconia specimens with micro-structured surfaces were measured using digital calipers and Fiji software. The crystalline phase changes before and after surface treatment were investigated using X-ray diffractometry. Data was analysed using one-way ANOVA and Tukey HSD post-hoc tests (α = 0.05). ResultThe surface micro-structures of the PM group had regular morphology and no obvious defects. The surface roughness results showed that the PM group had higher Sa (42.21±1.38 um) and Ra (21.25±1.80 um) values than the other four groups (p < 0.001). The SBS test showed that the bond strength of the PM group reached 11.23 ± 0.66 MPa, which was 55.97% (p < 0.001) higher than that of the P group (7.20 ± 1.14 MPa). The boundary dimensional accuracy of the PM group was proficient (diameter: 99.63 ± 0.31%, thickness: 98.05 ± 1.12%), and the actual fabrication dimensions of the hexagonal micro-structures reached 77.45%-80.01% of the original design. The micro-structured surface did not affect the crystalline phase of zirconia. ConclusionsThe current study illustrates that 3D-printed microstructured surfaces effectively improve the bond strength of zirconia to resin cements. Clinical significanceWith the advantage of 3D printing, this study provides a new idea for improving the bonding properties of zirconia.

Accelerated aging resistance, abrasion resistance and other properties of alkali-activated slag mortars containing limestone powder

The Earth's crust is widely recognized for its abundance of limestone (LS). Limestone powder (LSP) has a wide range of potential properties that make it suitable for various applications and fields. It has found extensive usage in Portland cement-based materials. Recently, the incorporation of LSP into geopolymers is becoming more of a concern than before and has become a hot topic. In this article, high range of LSP (2.5–50 wt%) was introduced into alkali-activated slag (AAS) mortars activated with NaOH and sodium silicate solution as a substitution of slag. For the first time, the effect of LSP on the accelerated aging resistance and abrasion resistance of AAS mortars was examined. In addition, the typical traditional routine properties such as flowability, setting time, mechanical strength, water absorption, and total porosity were studied. Sophisticated equipment was utilized to observe the changes in crystalline phases, hydration products, and microstructures of selected samples. The results showed higher flowability and longer setting time with including LSP. As the amount of LSP increased as the flowability and setting time increased. The introduction of 2.5–25% LSP positively affected the mechanical strength, aging resistance, abrasion resistance and transport properties. In contrast, the introduction of 35% did not show an essential change, whilst the introduction of 50% LSP negatively affected the mentioned properties.

Metavalent or Hypervalent Bonding: Is There a Chance for Reconciliation?

A family of solids including crystalline phase change materials such as GeTe and Sb2 Te3 , topological insulators like Bi2 Se3, and halide perovskites such as CsPbI3 possesses an unconventional property portfolio that seems incompatible with ionic, metallic, or covalent bonding. Instead, evidence is found for a bonding mechanism characterized by half-filled p-bands and a competition between electron localization and delocalization. Different bonding concepts have recently been suggested based on quantum chemical bonding descriptors which either define the bonds in these solids as electron-deficient (metavalent) or electron-rich (hypervalent). This disagreement raises concerns about the accuracy of quantum-chemical bonding descriptors is showed. Here independent of the approach chosen, electron-deficient bonds govern the materials mentioned above is showed. A detailed analysis of bonding in electron-rich XeF2 and electron-deficient GeTe shows that in both cases p-electrons govern bonding, while s-electrons only play a minor role. Yet, the properties of the electron-deficient crystals are very different from molecular crystals of electron-rich XeF2 or electron-deficient B2 H6 . The unique properties of phase change materials and related solids can be attributed to an extended system of half-filled bonds, providing further arguments as to why a distinct nomenclature such as metavalent bonding is adequate and appropriate for these solids.

Piezoelectric, mechanical, and crystallographic properties of polyvinylidene fluoride‐hexafluoropropylene based composites reinforced by different dimensional carbon nanomaterials

AbstractPolymer based piezoelectric materials are increasingly used because of their lightweight and flexibility. To understand the effects of different dimensional carbon nanomaterials on the properties of polyvinylidene fluoride‐hexafluoropropylene (PVDF‐HFP) based composites, carbon black (CB), carbon nanotube (CNT), and few‐layer graphene (FLG) were used to reinforce PVDF‐HFP for preparing different composites, respectively. Their piezoelectric, mechanical, and crystallographic properties were tested. The results show that CB/PVDF‐HFP composite film has the best piezoelectric property, successively followed by FLG/PVDF‐HFP and CNT/PVDF‐HFP at 0.5%, 0.05%, and 0.1% contents of CB, FLG, and CNT, respectively. In the initial crystallization stage, CB better plays the best role of crystallization core, increasing the electroactive crystalline phase content and crystallization rate. The appropriate contents of CNT and FLG promote the formation of β crystalline phase. In the polarization stage, CB forms a uniform nonconductive network in the composite film and shows the best polarization effect. CNT tends to form connections and has the worst polarization effect. FLG forms a “microcapacitor” structure to enhance the local polarization effect. The effects of CB, CNT, and FLG on crystalline phase changes and piezoelectric property enhancements of PVDF‐HFP based composites are mainly due to their differences in size, morphology, and quantity.Highlights Effects of CB, CNT, and FLG on the piezoelectricity of PVDF‐HFP are investigated; CB more obviously increases the piezoelectricity of PVDF‐HFP than CNT and FLG; α, β, and γ crystalline phase changes in PVDF‐HFP based composites are understood; CB forms smaller and more uniform crystal cores in PVDF‐HFP than CNT and FLG; CB markedly increases the contents of electroactive crystalline phases in PVDF‐HFP.

Obtaining of a rich-cellulose material from black wattle (Acacia mearnsii De Wild.) bark residues.

Black wattle (Acacia mearnsii De Wild.) barksare residues produced by tannin industries in huge quantities, which are normally discharged on environmental or used for energy production. Therefore, this study aimed to evaluate the use of black wattle bark residues as a raw material on obtaining of a rich-cellulose material by alkaline (MET1), acetosolv (MET2), and organosolv (MET3) procedures. The results obtained indicated that the alkaline methodology, followed by a bleaching step (MET1), promoted klason lignin and hemicellulose removals more efficiently. It was possible to observe that better results were achieved using NaOH concentration of 6% (wt%), at 65 °C for 2.5 h, presenting a yield of 63.24 ± 1.25%, and a reduction on klason lignin content of almost 90.45%. Regarding the bleaching step, it was possible to obtain a material free of non-cellulosic compounds with a yield of 78.28 ± 1.48%. Thermogravimetric analysis indicated the removal of lignin and hemicellulose as well as an increase in cellulose degradation temperature, due to changes in crystalline phases. According toX-ray diffraction (XRD), the procedures employed have led to an increase in crystallinity from 66.27 to 91.78% due to the removal of non-cellulosic compounds. Scanning electron microscopy (SEM) showed morphological alterations in accordance with the removal of non-cellulosic compounds.

Multifunctional hydrogels simultaneously featuring ultrahigh stretchability, remarkable tearing resistance, and reusable fluorescence for information encoding–decoding and smart anticounterfeiting

Fluorescent hydrogels with fluorescent dyes are widely used for anti-counterfeiting encryption. However, developing highly stretchable and remarkable tear-resistant hydrogels with reusable fluorescence for anti-counterfeiting purposes remains challenging. In this study, we fabricated and characterized double network (DN) hydrogels comprising polyvinyl alcohol-borax (PVA-borax) as the first network and poly(methacrylamide-co-polyethylene glycol-co-pyrenylmethyl acrylate) (P(MAM-co-PEGMA-co-PyMA)) as the second network with varying MAM to PEGMA ratios. SEM images showed the hydrogels had 3D porous structures. FT-IR and thermal properties analysis (DSC and TGA) indicated the presence of hydrogen bonds between PVA-borax and P(MAM-co-PEGMA-co-PyMA) without any chemical bonds. The red shift in characteristic absorption bands at 841 and 710 cm−1 further confirmed the presence of π-π* interactions between pyrene moieties. XRD analysis revealed no significant changes in crystalline phase of the hydrogels, which facilitated the formation of a 3D network due to abundant hydrogen bond presence. When the MAM to PEGMA ratio was adjusted to 9:2, the resulting hydrogels exhibited remarkable properties such as ultra-high stretchability (strain over 3300 %), excellent notch-insensitivity, and exceptional tear resistance (tearing energy over 3.25 × 105 J/m2). Importantly, the hydrogel's fluorescence intensity could be reversibly changed by alternatively adding Fe3+ and EDTA-2Na. It could be reused more than 10 times while maintaining a fluorescence intensity of around 80 %, demonstrating its reliability as a versatile hydrogel probe for Fe3+ detection with “ON-OFF-ON” fluorescence behavior. Furthermore, the hydrogels demonstrated exceptional 2D encryption and decryption capabilities, highlighting their potential applications in information storage and data security. To improve the level of anti-counterfeiting, multiple encryption approaches such as QR codes and ASCII binary codes were rationally designed. Overall, this study successfully developed a universal DN hydrogel platform with ultra-high stretchability and remarkable tear resistance, capable of rapid encoding and decoding of complex information for smart anti-counterfeiting.

Organic phase change composite separators to enhance the safety performance of lithium-ion batteries

Lithium-ion batteries have received a great deal of attention on the world stage due to their high-power density and superior electronic properties. Herein, a novel phase change composite separator was successfully fabricated into lithium-ion battery cells by microfluidic technology. The phase change material composite separator was manufactured with polyethylene (PE) as the base film and employing the crystalline phase change property of polyethylene oxide (PEO). The phase change solution was atomized and delivered to the surface of the separator using high-pressure inert gases, and then crystallized on the separator substrate by controlling the temperature difference. The capacity retention and capacity recovery of the manufactured phase change material composite separator cells were 96.9% and 97.8%, respectively. In addition, the cells demonstrated superior multiplier performance (∼98% capacity retention at 1C). Additionally, the phase change material was introduced into the separator coating layer to increase the heat resistance of the separator, while the electrochemical performance was exceptional and the safety performance was favorable, thus alleviating the heat accumulation inside the battery at the source and effectively enhancing the safety of lithium-ion batteries.

Thermally Reentrant Crystalline Phase Change in Perovskite-Derivative Nickelate Enabling Reversible Switching of Room-Temperature Electrical Resistivity.

Reversible switching of room-temperature electrical resistivity due to crystal-amorphous transition is demonstrated in various chalcogenides for development of non-volatile phase change memory. However, such reversible thermal switching of room-temperature electrical resistivity has not reported in transition metal oxides so far, despite their enormous studies on the electrical conduction like metal-insulator transition and colossal magnetoresistance effect. In this study, a thermally reversible switching of room-temperature electrical resistivity is reported with gigantic variation in a layered nickelate Sr2.5 Bi0.5 NiO5 (1201-SBNO) composed of (Sr1.5 Bi0.5 )O2 rock-salt and SrNiO3 perovskite layers via unique crystalline phase changes between the conducting 1201-SBNO with ordered (O-1201), disordered Sr/Bi arrangements in the (Sr1.5 Bi0.5 )O2 layer (D-1201), and insulating oxygen-deficient double perovskite Sr2 BiNiO4.5 (d-perovskite). The O-1201 is reentrant by high-temperature annealing of ≈1000°C through crystalline phase change into the D-1201 and d-perovskite, resulting in the thermally reversible switching of room-temperature electrical resistivity with 102 - and 109 -fold variation, respectively. The 1201-SBNO is the first oxide to show the thermally reversible switching of room-temperature electrical resistivity via the crystalline phase changes, providing a new perspective on the electrical conduction for transition metal oxides.

Green synthesis and catalytic activity assessment of bespoke nano-catalyst for eco-friendly green propellant systems based on hydrogen peroxide

AbstractMuch effort has been devoted to replace pollutant, toxic, cancerogenic hydrazine-based propellants. Hydrogen peroxide could secure promising characteristics as well as high density specific impulse. Effective catalysts with high durability are required to commence H2O2 decompositions, and to inherit hypergolic nature with different hydrocarbon fuels. Silver nanoparticles (18 nm) were synthesized via hydrogen gas evolved by water electrolysis. MnO2 (20 nm) was developed in a sustainable manner via green hydrothermal processing. High crystalline, mono-dispersed particles were developed. Catalytic activity was assessed via precise measurements of liquid temperature profile (LTP) up to the boiling point of hydrogen peroxide. Whereas silver demonstrated LTP peak within 20 s; MnO2 experienced LTP within 40 s. Catalyst survivability was recorded via precise measurement of life time mass loss rate upon catalyst addition to hydrogen peroxide. While silver nano-catalyst demonstrated high performance at the reaction start; silver was found to be poisoned with crystalline phase change to silver oxide within 20 s. On the contrary, manganese oxide experienced high durable catalytic action. Consequently, MnO2 could be candidate for H2O2 monopropellant thrusters as catalyst bed. On the other hand, silver nanoparticles could be candidate for a single use in bipropellant system to inherit hypergolicity. This study presents a pioneering report on facile synthesis of catalyst nanoparticles; comprehensive catalytic activity assessment of silver to manganese oxide for H2O2 decomposition was represented. Proper catalyst assortment for practical applications was represented.

Superlattice-like Sb70Se30/HfO2 thin films for high thermal stability and low power consumption phase change memory

We have fabricated Sb70Se30/HfO2 superlattice-like structure thin films for phase change memory by magnetron sputtering method, and investigated the effect of the HfO2 layer on the crystalline characteristics and phase change behavior of Sb70Se30/HfO2 thin films. The experimental results show that as the HfO2 thickness increases, the crystallization temperature rises, the data retention capacity increases as well as the band gap widens, which is beneficial for improving the thermal stability and reliability of Sb70Se30/HfO2 thin films. It was also found that the HfO2 composite layer inhibited the grain growth of the Sb70Se30 thin film, reducing the grain size and resulting in a smoother surface. In addition, the volume fluctuation of the Sb70Se30/HfO2 thin films changes by only 5.58% between amorphous and crystalline. The threshold and reset voltages of the cell based on Sb70Se30/HfO2 thin films are 1.52 V and 2.4 V respectively. We found that the HfO2 composite layer plays a significant role in improving thermal stability, refining grain size of Sb70Se30 phase change films and reducing device power consumption.

Effects of loaded-mineral elements on CO enhancement of wheat straw pyrolysis in low-concentration CO2 atmosphere

Pyrolysis of biomass in the CO2 atmosphere can enhance CO yield (CO enhancement), which can improve flammable gas yield and promote CO2 conversion. In this work, to investigate the effects of mineral elements on CO enhancement in the pyrolysis of biomass under the low-concentration CO2 atmosphere, acid-washing wheat straw (AWS) was individually loaded with relative amounts of 3.43 wt% K, 1.75 wt% Ca, 0.75 wt% Fe, 0.72 wt% Al, 0.32 wt% Mg, and 5.70 wt% Si which were derived from elemental determinations of X-ray fluorescence analysis. Pyrolysis experiments were conducted in 5% CO2 (95% N2, Vol) and pure N2 as a reference at an optimal temperature of 715 °C. Results revealed that CO enhancement of mineral elements loaded biomass pyrolysis in a low-concentration CO2 atmosphere can be affected by mineral elements. The loaded Al, Mg, and Si have no obvious influences on CO enhancement. Significantly, the loaded K, Ca, and Fe can reinforce the CO enhancement. The CO yields increase from 61.54 mL/g (AWS) to 76.57 mL/g (K), 71.10 mL/g (Ca) and 68.89 mL/g (Fe) in N2, respectively. However, under the 5% CO2 atmosphere, the CO yields increase from 67.11 mL/g (AWS) to 133.36 mL/g (K), 112.92 mL/g (Ca), and 78.40 mL/g (Fe), respectively. Interestingly, the loaded K, Ca, and Fe shows incredible reinforcements of CO enhancement at a holding stage of 715 °C in the 5% CO2 atmosphere, increasing from 30.42 mL/g (AWS) to 71.32 mL/g (K), 74.62 mL/g (Ca), and 44.41 mL/g (Fe), respectively. The interactions between the loaded-mineral elements and CO2 were justified by the CO enhancement, crystalline phase changes, and the changed organic groups of chars from the 5% CO2 atmosphere. And we proposed the possible mechanistic effects. (1) K can promote the interactions between the biomass pyrolysis intermediates and CO2 to form more CO. (2) The synergy between CO2 and the loaded Ca promotes the thermal dissociations of Ca combing to biochar and further reactions for CO enhancement. (3) Fe catalyzed the cracking of C-O groups and provided fragments of O-containing groups (especially OH) for CO2 to improve CO yield. This study provides some references for CO2 utilization in biomass pyrolysis to increase the yield of CO.

Pseudocapacitive enhancement of brucite-like β-Co(OH)2 nanoflakes after the removal of intercalated water

Ultrathin brucite-like β-Co(OH)2 nanoflakes are prepared by a modified solvothermal method, and further thermal treatment is conducted at different temperatures to remove their intercalated and physically adsorbed water molecules and then enhance their pseudocapacitive performance. With the increase of the thermal treatment temperature from 60 to 140 °C, the morphology, size and crystalline phase of the pristine β-Co(OH)2 gradually change. The Sample-100 shows the best pseudocapacitive performance, without obvious changes in morphology, size and crystalline phase after being thermally treated at 100 °C, and it presents high pseudocapacitance of 659.1 Fg-1 at 1 A g−1, increasing by 44.2% comparing with that of the pristine β-Co(OH)2 nanoflakes. And it also exhibits superior cycling stability with capacitance retention of 95.7% after 8000 cycles at 10 A g−1. This study also demonstrates a facile strategy to improve the pseudocapacitive performance of materials with intercalated water.

Influence of chloride solutions on the leaching of heavy metals from cement hydrates

This study investigates how chloride-based salts affect the immobilization and leaching of Cu, Zn, and Pb from cement hydrates and analyzes the associated internal changes in crystalline phase. Results showed that the amount of Pb leached is highest in mortar when it contacts with CaCl2solution.A key reason for this outcome is thatcalcium silicate hydrate (CSH)has the lowest Pb adsorption in CaCl2 solution.Exposure to MgCl2 solution resulted in the decomposition of most portlandite to form brucite in mortars, lowering the pH to ∼9. This caused the lowest leaching rate of Cu, Zn, and Pb inMgCl2solution.