High-pressure glass-ceramics for iodine nuclear waste immobilization: Preliminary experimental results

Several matrix types have been considered for the immobilization of iodine radioisotopes from which glass-ceramics represent a serious candidate; however, I-bearing glass-ceramics are challenging owing to the iodine volatility. We have synthesised glass-ceramics from the partial crystallization of a parental glass enriched with different iodine sources (I₂ and I₂O₅) under high-pressure conditions (up to 1.5 GPa). The samples were characterized using Scanning and Transmission Electron Microscopy and X-ray Diffraction. Using standard synthesis protocol: melting, nucleation and crystal growth, we have obtained glass-ceramics showing the coexistence between I-bearing glass (<0.8 mol.% I), nepheline (NaAlSiO₄) and iodosodalite (Na₈Al₆Si₆O₂₄I₂ with up to 14 mol.% I). For several samples, we observed also the presence NaPt₃O₄ witnessing a chemical reaction between the container walls and the inside experimental charge. The structure of iodosodalite is entirely resolved by Rietveld refinement of the XRD pattern for I₂ experiments whereas it cannot be solved for I₂O₅ experiments suggesting a change in the iodosodalite structure probably due to the β cage filling by IO₃⁻ clusters instead of I⁻. Our present work could represent a potential solution to tackle the problem of iodine radioisotopes immobilization.     

Iodine Pentoxide Nano‐rods for High Density Energetic Materials

The iodine pentoxide is one of the most advanced oxidizers for nanostructured energetic formulations among the thermites due to the highest energy release per volume 25.7 kJ cm⁻³. The size and shape of iodine pentoxide particles have a strong impact on the pressurization rates during the reaction. Although micro‐sized iodine pentoxide particles are commercially available, nano‐sized particles, which are desired for various nano‐energetic applications, are not available on the market. Conventional wet chemical methods are unable to produce iodine pentoxide nanoparticles due to high solubility in water. In this study, we demonstrate fabrication of iodine pentoxide nano‐rods by high energy mechanical treatment of micro‐sized I₂O₅ particles. Tuning the energy dose in high‐energy ball milling is allowing to produce I₂O₅ nano‐rods with diameter of 50–100 nm and length of 300–600 nm. The produced nano‐rods exhibited 10 % smaller decomposition energy compared to the precursor of micro particles. The experiments showed that the nano‐energetic materials prepared with nano‐sized I₂O₅ rods have pressure discharge value of 43.4 MPa g⁻¹ which is two times higher than using commercial iodine pentoxide particles.     

Colored rubber vulcanizates with some magnetic properties

A new composite based on natural rubber vulcanizates loaded with the newly prepared iron oxide–aluminum oxide (Fe₂O₃·Al₂O₃) fillers were prepared and their physical and magnetic studies were investigated. The prepared fillers were evaluated as reinforcing fillers with some magnetic properties; these properties were dependent on the ratio of iron oxide to aluminum oxide in each prepared ratio of these fillers. Rheological properties of rubber mixes containing (1Fe₂O₃:3Al₂O₃) and (1Fe₂O₃:1Al₂O₃) fillers exhibited better properties than mixes containing (3Fe₂O₃:1Al₂O₃) and (α‐Fe₂O₃), which showed almost the same behavior. Physical properties such as tensile strength, stress at 100 and 200% strain, Young's modulus, and hardness were increased by increasing the volume fraction of the investigated fillers concentration in the mixed vulcanizates. Measured rheological and physical results were inversely related to the magnetic properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:494–505, 2006     

A novel Nd3+-doped MgO-Al2O3-SiO2-based transparent glass-ceramics: Toward excellent fluorescence properties

Generally, glass-ceramics have superior properties compared to their parent glasses. Here, we prepared a novel Nd³⁺-doped MgO-Al₂O₃-SiO₂-based transparent glass-ceramics with excellent fluorescence properties. The effects of Nd₂O₃ content on the structure and properties of glass-ceramics were studied, aiming to provide a key guidance for preparing this transparent glass-ceramics. The results revealed that the glass stability increased originally and then decreased with increasing Nd₂O₃ content, so did the variation of wavenumbers in infrared spectra. And these glass-ceramics are mainly composed of cordierite with residual glassy phase. The three phenomenological intensity parameters (Ω_2,4,6) and radiative properties were estimated by Judd-Ofelt theory, and the values of Ω₂ first decreased and then increased with increasing Nd₂O₃ content. Three main emission peaks ascribed to the transitions from ⁴F_3/2 to ⁴I_9/2, ⁴I_11/2, ⁴I_13/2 at 898, 1057, 1330  nm were observed, respectively. The branching ratios for ⁴F_3/2→⁴I_11/2 transition increased as the Nd₂O₃ content raised, and the fluorescence lifetimes of the ⁴F_3/2 level were found to increase first and then decrease with Nd₂O₃ content (from 181 to 726 μs). The excellent fluorescence properties indicate that this novel glass-ceramics can be used as a potential solid-state optical functional material for 1.06 μm laser emission.     

Self‐nucleation behaviors of olefinic blocky copolymer/montmorillonite nanocomposites with collapsed and intercalated clay layers

The self‐nucleation behavior of olefinic blocky copolymer (OBC) / organically modified montmorillonite (OMMT) nanocomposites with a novel collapsed clay structure (c‐OMMT) was studied and compared with that of the nanocomposites with an intercalated clay structure (OBC/i‐OMMT). Their behaviors appear different in three temperature domains, Domain I (D_I) in which the polymer is completely melted and only the heterogeneous nuclei are present, Domain II (D_II) in which only self‐nucleation occurs and Domain III (D_III) where both self‐nucleation and annealing take place. As the OMMT loading increases, the boundary temperature of D_I and D_II (T_I→II) shifts to lower temperature and D_II becomes narrower. For the OBC/c‐OMMT nanocomposites, the T_I→II or T_I→III (the boundary temperature of D_I and D_III) can be lower than the end melting temperature ( ) and leads to appearance of a subdomain of D_I, D_I′, in which the self‐nuclei of un‐melted fragmental crystals exist but the following crystallization is still initiated by c‐OMMT. D_II may even disappear at high c‐OMMT loadings. By contrast, the T_I→II of the OBC/i‐OMMT nanocomposites is always approximate to or higher than the . D_II does not disappear and no D_I′ is observed for the OBC/i‐OMMT nanocomposites. The nucleation efficiency of c‐OMMT is also evidently higher than that of i‐OMMT. These results verify that the c‐OMMT has stronger nucleation ability than i‐OMMT at the same OMMT loading. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41771.     

Quartz crystal microbalance study of the growth of indium(III) sulphide films from a chemical solution

The growth of indium(III) sulphide thin films from aqueous thioacetamide (TA)-In(III) solution has been studied with a quartz crystal microbalance (QCM). It is found that the growth of the film consists in the parallel deposition of In₂S₃ and In₂O₃. Both processes are induced by sulphide anions (S²⁻) produced after decomposition of thioacetamide. In₂S₃ is deposited by precipitation of crystallites formed in the bulk solution. On stirred solutions this reaction is hindered due to the disruption of the nucleation centres. On the other hand, In₂O₃ is deposited by electrochemical reduction of naturally dissolved oxygen (O₂) by the S²⁻ anions, followed by chemical reaction with In³⁺. This process is of electroless-chemical nature and has important consequences on the properties of the films. Both reaction mechanisms, chemical and electroless-chemical, compete under different experimental conditions: temperature, solution composition, stirring. For instances, the deposit of In₂O₃ is favoured at low bath temperature, in aerated solutions, giving rise to films with higher oxide proportion. Additives like hydrochloric acid and acetic acid also favour In₂O₃ deposition. The system has easy possibility to tune chemical and physical properties of the films, like composition, transparency and absorption edge, of interest for photovoltaic applications.     

Potential Biocides: Iodine‐Producing Pyrotechnics

Currently there is a need for specialized pyrotechnic materials to combat the threat of biological weapons. Materials have been characterized based on their potential to produce heat and molecular iodine gas (I₂) to kill spore‐forming bacteria (e. g. anthrax). One formulation, already proven to kill anthrax simulants, is diiodine pentoxide with aluminum; however, it suffers from poor stability and storage problems. The heat and iodine gas output from this mixture and candidate replacement mixtures were measured with bomb calorimetry and extraction and analysis of I₂ by UV‐Vis. Of the mixtures analyzed, calcium iodate and aluminum was found to be the highest producer of I₂. The heat output of this mixture and others can be tuned by adding more fuel, with the cost of some iodine. Products of combustion were analyzed by thermal analysis (SDT), XPS, XRD, and LC/MS. Evidence for various metal iodides and metal oxides was collected with these methods.     

Effects of Gd3+ substitution on the structure,photoluminescence, scintillation,and thermometric features of Pr3+:Lu2Zr2O7 phosphors

In this study, it is shown how the photoluminescence, scintillation, and optical thermometric properties are managed via the introduction of Gd³⁺ ions into Pr³⁺:Lu₂Zr₂O₇. Raman spectra validate that partial replacement of Lu³⁺ with Gd³⁺ can promote the phase transition of Lu₂Zr₂O₇ host from the defective fluorite structure to the ordered pyrochlore one. Upon 289 nm excitation, all the samples emit the 483 (³P₀ → ³H₄), 581 (¹D₂ → ³H₄), 611 (³P₀ → ³H₆), 636 (³P₀ → ³F₂), and 714 nm (³P₀ → ³F₄) emissions from Pr³⁺ ions, which are enhanced with the addition of Gd³⁺ ions due to the modification of crystal structure. Dissimilarly, the X-ray excited luminescence spectra consist of a strong emission located at 314 nm from Gd³⁺ ions (⁶P_7/2 → ⁸S_7/2), together with the typical emissions from Pr³⁺ ions, which exhibit different dependences on the Gd³⁺ concentration. When the luminescence intensity ratio between the ³P₀ → ³H₆ (611 nm) and ¹D₂ → ³H₄ (581 nm) transitions is selected for temperature sensing, Pr³⁺:(Lu_0.75Gd_0.25)₂Zr₂O₇ shows the optimal relative sensing sensitivity of 0.78% K⁻¹ at 303 K, which is higher than that of the Gd³⁺-free sample. Therefore, the developed Pr³⁺:(Lu, Gd)₂Zr₂O₇ phosphors have the applicative potential for optical thermometry, X-ray detection, and photodynamic therapy.     

Multipath optical thermometry realized in CaSc2O4: Yb3+/Er3+ with high sensitivity and superior resolution

Design and fabrication of contactless optical thermometer with rapid and accurate performance has become a research hotspot in recent years. Herein, CaSc₂O₄: Yb³⁺/Er³⁺ is employed as the intermediary for temperature sensing under the excitation of 980 nm, which is proven to afford an ultra-sensitive and high-resolution optical thermometry in multiple ways based on the fluorescence intensity ratio (FIR) technology. The optimal thermal sensing behaviors are realized by the FIR of Er³⁺:²H_11/2 → ⁴I_15/2 to ⁴S_3/2 → ⁴I_15/2 transition, which has a relative sensitivity of 1184/T² and a minimal resolution of 0.03 K along with a maximal absolute error of 0.96 K. Besides that, the FIR between the thermally coupled Stark sublevels of Er³⁺:⁴F_9/2 manifold (FIR_R) as well as that of Er³⁺: ⁴I_13/2 manifold (FIR_N) can also provide excellent optical thermometry. The relative sensitivity of FIR_R-based and FIR_N-based optical thermometers are calculated to be 402/T² and 366/T², respectively, with a same minimal resolution of 0.09 K, which possess the potential to be used for biomedicine due to the inherent advantage of their operating wavelengths located in the biological window. The results demonstrate that CaSc₂O₄: Yb³⁺/Er³⁺ is a promising candidate for temperature sensing with multipath, high sensitivity, and superior resolution.     

Adjacent relations of primary phase fields and invariant reactions of the system CaO-SiO2-Nb2O5-La2O3

The adjacent relation of primary phase fields and corresponding invariant reactions of the system CaO-SiO₂-Nb₂O₅-La₂O₃ are of great importance for the study on its phase diagram. In the present work, the phase equilibrium in the high w(La₂O₃) region of CaO-SiO₂-Nb₂O₅-La₂O₃ system was studied by thermodynamic equilibrium experiment. The adjacent relation of primary phase fields was determined and represented in the form of adjacent tetrahedrons. The Alkemade Rule applicable to quaternary phase diagram was deduced, which can be used to infer the liquidus temperature trend on univariant curves. The rule was then used to determine the possible temperature range of invariant reactions corresponding to the adjacent tetrahedron in CaO-SiO₂-Nb₂O₅-La₂O₃ system, and the result was shown in the form of Schairer diagram. Finally, the reaction types of five invariant points were determined according to the Lever Rule for quaternary phase diagram, including: ① L₁+CaO·3SiO₂·2La₂O₃→CaO·SiO₂+SiO₂+La₂O₃·Nb₂O₅, ② L₂→CaO·SiO₂+La₂O₃·Nb₂O₅+SiO₂+CaO·Nb₂O₅, ③ L₃+CaO·3SiO₂·2La₂O₃+2CaO·Nb₂O₅→10CaO·6SiO₂·Nb₂O₅+La₂O₃·Nb₂O₅, ④ L₄+10CaO·6SiO₂·Nb₂O₅→CaO·SiO₂+2CaO·Nb₂O₅+La₂O₃·Nb₂O₅, ⑤ L₅+2CaO·Nb₂O₅→CaO·Nb₂O₅+La₂O₃·Nb₂O₅+CaO·SiO₂.     

Controlled synthesis of Bi2O3–YSZ composite powders and their sintering behavior for high-performance electrolytes

Bismuth oxide (Bi₂O₃) is a promising additive to decrease the sintering temperature of yttria-stabilized zirconia (YSZ)-based electrolyte for solid oxide fuel cell application. However, Bi₂O₃ tends to grow into large column bars (>50 µm) in a chemical coprecipitation method, which dramatically limits the mixing uniformity of Bi₂O₃ and YSZ, even much worse than that of mechanical mixing. In this study, the reaction temperature was increased from room temperature to 90°C to increase the number of nucleation during the violate reaction between Bi³⁺ solution and YSZ suspension in NaOH. On this basis, the violence of the reaction was further moderated by adding half of NaOH first, then YSZ powders and the other half of an NaOH solution. The size of Bi₂O₃ was further decreased to sub-micrometer and Bi₂O₃ was homogeneously mixed with YSZ particles, even when its addition amount was as large as 20 mol%. These composite powders effectively promoted the sintering behavior of YSZ. The sintering temperature of YSZ was decreased to 900 and 1000°C with 10 and 5 mol% Bi₂O₃ doping, respectively. Increasing the doping ratio induced severe volatilization of Bi₂O₃ and pore formation. Raising the sintering temperature (no more than 1200°C) enhanced the doping effect of Bi₂O₃ into the YSZ lattice but induced instability in the YSZ crystal structure.     

Laser Ignition of Nano‐Composite Energetic Loose Powders

Laser ignition experiments were conducted to better understand parameters that influence ignition of energetic materials. A Nd:YAG laser (10 ms, 1.5 J, 3 mm spot diameter) was used to heat the top surface of an energetic powder composed of nanometric aluminum (Al) combined stoichiometrically with an oxidizer (copper oxide (CuO), iodine pentoxide (I₂O₅), polytetrafluoroethylene (C₂F₄), molybdenum trioxide (MoO₃) or iron oxide (Fe₂O₃)). Ignition delay time was calculated as the difference between first light of the laser’s flash lamp and the energetic material. Results show that laser energy required for ignition is dependent on pre‐ignition reactions, phase change/decomposition temperatures, confinement, and laser absorbance.     

Green Up‐Conversion Photoluminescence and Dielectric Relaxation of Ho3+/Yb3+‐Codoped Bi2Ti2O7 Pyrochlore Thin Films

Ho³⁺/Yb³⁺‐codoped Bi₂Ti₂O₇ pyrochlore thin films were prepared by a chemical solution deposition method, and their visible up‐conversion (UC) photoluminescence and dielectric relaxation were studied. Ho and Yb can be doped into Bi₂Ti₂O₇ lattice and single pyrochlore phase is maintained. Intense visible UC photoluminescence can be observed under the excitation of a 980‐nm diode laser. Two UC emission bands centered at 551 nm and 665 nm in the spectra can be assigned to ⁵F₄, ⁵S₂→⁵I₈ and ⁵F₅→⁵I₈ transitions of Ho³⁺ ions, respectively. The dependence of their UC emission intensity on pumping power indicates that both the green and red emissions of the thin films are two‐photon process. In addition, a Stokes near‐infrared emission centered at 1200 nm can be detected, which is due to ⁵I₆→⁵I₈ transition of Ho³⁺ ions. The thin films prepared on indium tin oxide–coated glass substrates exhibit a relatively high dielectric constant and a low dielectric loss as well as a good bias voltage stability. The dielectric relaxation of the thin films was also analyzed based on the temperature‐ and frequency‐dependent dielectric properties. This study suggests that Ho³⁺/Yb³⁺‐codoped Bi₂Ti₂O₇ thin films are promising materials for developing multifunctional optoelectronic thin film devices.     

Intense upconversion luminescence and energy‐transfer mechanism of Ho3+/Yb3+ co‐doped SrLu2O4 phosphor

A series of novel SrLu₂O₄: x Ho³⁺, y Yb³⁺ phosphors (x=0.005‐0.05, y=0.1‐0.6) were synthesized by a simple solid‐state reaction method. The phase purity, morphology, and upconversion luminescence were measured by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. The doping concentrations and sintering temperature were optimized to be x=0.01, y=0.5 and T=1400°C to obtain the strongest emission intensity. Under 980 nm laser diode excitation, the SrLu₂O₄:Ho³⁺, Yb³⁺ phosphors exhibit intense green upconversion (UC) emission band centered at 541 nm (⁵F₄,⁵S₂→⁵I₈) and weak red emission peaked at 673 nm (⁵F₅→⁵I₈). Under different pump‐power excitation, the UC luminescence can be finely tuned from yellow‐green to green light region to some extent. Based on energy level diagram, the energy‐transfer mechanisms are investigated in detail according to the analysis of pump‐power dependence and luminescence decay curves. The energy‐transfer mechanisms for green and red UC emissions can be determined to be two‐photon absorption processes. Compared with commercial NaYF₄:Er³⁺, Yb³⁺ and common Y₂O₃:Ho³⁺, Yb³⁺ phosphors, the SrLu_1.49Ho_0.01Yb_0.5O₄ sample shows good color monochromaticity and relatively high UC luminescence intensity. The results imply that SrLu₂O₄:Ho³⁺, Yb³⁺ can be a good candidate for green UC material in display fields.     

Improved evidence for the existence of an intermediate phase during hydration of tricalcium silicate

Tricalcium silicate (Ca₃SiO₅) with a very small particle size of approximately 50 nm has been prepared and hydrated for a very short time (5 min) by two different modes in a paste experiment, using a water/solid-ratio of 1.20, and by hydration as a suspension employing a water/solid-ratio of 4000. A phase containing uncondensed silicate monomers close to hydrogen atoms (either hydroxyl groups or water molecules) was formed in both experiments. This phase is distinct from anhydrous tricalcium silicate and from the calcium-silicate-hydrate (C-S-H) phase, commonly identified as the hydration product of tricalcium silicate. In the paste experiment, approximately 79% of silicon atoms were present in the hydrated phase containing silicate monomers as determined from ²⁹Si{¹H} CP/MAS NMR. This result is used to show that the hydrated silicate monomers are part of a separate phase and that they cannot be attributed to a hydroxylated surface of tricalcium silicate after contact with water. The phase containing hydrated silicate monomers is metastable with respect to the C-S-H phase since it transforms into the latter in a half saturated calcium hydroxide solution. These data is used to emphasize that the hydration of tricalcium silicate proceeds in two consecutive steps. In the first reaction, an intermediate phase containing hydrated silicate monomers is formed which is subsequently transformed into C-S-H as the final hydration product in the second step. The introduction of an intermediate phase in calculations of the early hydration of tricalcium silicate can explain the presence of the induction period. It is shown that heterogeneous nucleation on appropriate crystal surfaces is able to reduce the length of the induction period and thus to accelerate the reaction of tricalcium silicate with water.     

The effect of lanthanum oxide (La2O3) on the structure and crystallization of poly(vinylidene fluoride)

Rare earth polymers, due to their excellent luminescence, fluorescence, laser protective, optical and magnetic properties, have attracted much research attention in recent years. However, little attention has been paid to the effect of rare earths on the structure and crystallization of polymers, which is of important significance in the development of functional polymers. X‐ray diffraction and differential scanning calorimetry were used to investigate the structure and crystallization behavior of a poly(vinylidene fluoride) (PVDF)/lanthanum oxide (La₂O₃) composite. The results showed that the degree of perfection, crystal size, crystallization rate and isothermal crystallization activation energy of PVDF in the composite decreased, compared with pure PVDF. The spherulite nucleation and growth for PVDF and PVDF composite were analyzed in detail using the Lauritzen‐Hoffman equation. The modified Avrami equation and the Mo equation were used to study the non‐isothermal crystallization kinetics. The addition of La₂O₃ did not change the crystal structure and nucleation process for PVDF, but it decreased markedly the crystal growth rate and led to the formation of unstable crystals. This was attributed to the fact that too much La₂O₃ prevented PVDF molecular chains from moving and arranging in an orderly manner into crystals. Copyright © 2010 Society of Chemical Industry     

Working mechanism of calcium nitrate as an accelerator for Portland cement hydration

Precast concrete, cold weather concreting, and the emerging technique of concrete additive manufacturing are applications in which the acceleration of cement hydration plays a critical role. To allow precise control of early cement hydration in these applications, a thorough understanding of the working mechanisms of cement hydration accelerators is required. This study contributes to the understanding of the mechanism by which calcium nitrate (Ca(NO₃)₂) influences early cement hydration. The influence of Ca(NO₃)₂ on the hydration of an ordinary Portland cement has been followed by isothermal calorimetry, in situ X-ray diffraction (XRD), quantitative XRD, compressive strength testing, and the analysis of the pore solution composition. Further, the initial pore solution, the initial phase composition, and the phase composition in the fully hydrated cement have been estimated by thermodynamic calculations to corroborate the experimentally obtained results. The results indicate that Ca(NO₃)₂, especially at the highest analyzed dosage of 5 wt.%, enhances the formation of ettringite and a nitrate-containing AFm phase. Furthermore, Ca(NO₃)₂ accelerates alite hydration. Besides the increased Ca concentration in solution, it has been found that a reduction of the Al concentration in the initial pore solution by Ca(NO₃)₂ possibly contributes to the accelerating effect of Ca(NO₃)₂ on alite hydration.     

Catalytic Effect of Two Shapes of Nano‐Fe2O3 on Hexanitrohexaazaisowurtzitane Using a Non‐Isothermal Decomposition Kinetic Method

Nanosized Fe₂O₃ particles (nano‐Fe₂O₃) with two shapes (tetrakaidecahedral and grainy) were synthesized by hydrothermal methods. The morphologies and structures were characterized using a combination of experimental techniques including X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Two composites containing CL‐20 (hexanitrohexaazaisowurtzitane, HNIW) and tetrakaidecahedral nano‐Fe₂O₃ [nmT‐Fe₂O₃/CL‐20] or grainy nano‐Fe₂O₃/CL‐20 (nmG‐Fe₂O₃/CL‐20) were prepared. The thermal behaviors of the two composites and pure CL‐20 were investigated using differential scanning calorimetry (DSC). Non‐isothermal decomposition kinetic parameters and the thermal decomposition mechanism of the two composites and CL‐20 were obtained. The apparent activation energy (E_a) of the main thermal decomposition reaction of CL‐20, nmT‐Fe₂O₃/CL‐20 and nmG‐Fe₂O₃/CL‐20 are 181.94, 179.17, and 176.18 kJ mol⁻¹, respectively. The thermal decomposition mechanism of CL‐20 as well as nmT‐Fe₂O₃/CL‐20 was controlled by the Avrami‐Erofeev equation (n=2/5) assumed as random nucleation and subsequent growth, while, the reaction mechanism of the composite nmG‐Fe₂O₃/CL‐20 was controlled by the Mample Power law (n=1/2). The reason for this difference may be due to the different morphology and particle size of the two nano‐Fe₂O₃ particles.     

Preparation and evaluation of α-Al2O3 supported lithium ion sieve membranes for Li+ extraction

Spinel lithium manganese oxide ion-sieves have been considered the most promising adsorbents to extract Li⁺ from brines and sea water. Here, we report a lithium ion-sieve which was successfully loaded onto tubular α-Al₂O₃ ceramic substrates by dipping crystallization and post-calcination method. The lithium manganese oxide Li₄Mn₅O₁₂ was first synthesized onto tubular α-Al₂O₃ ceramic substrates as the ion-sieve precursor (i.e. L-AA), and the corresponding lithium ion-sieve (i.e. H-AA) was obtained after acid pickling. The chemical and morphological properties of the ion-sieve were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Both L-AA and H-AA showed characteristic peaks of α-Al₂O₃ and cubic phase Li₄Mn₅O₁₂, and the peaks representing cubic phase could still exist after pickling. The lithium manganese oxide Li₄Mn₅O₁₂ could be uniformly loaded not only on the surface of α-Al₂O₃ substrates but also inside the pores. Moreover, we found that the equilibrium adsorption capacity of H-AA was 22.9 mg·g⁻¹. After 12 h adsorption, the adsorption balance was reached. After 5 cycles of adsorption, the adsorption capacity of H-AA was 60.88% of the initial adsorption capacity. The process of H-AA adsorption for Li⁺ correlated with pseudo-second order kinetic model and Langmuir model. Adsorption thermodynamic parameters regarding enthalpy (∆ H), Gibbs free energy (∆ G) and entropy (∆ S) were calculated. For the dynamic adsorption–desorption process of H-AA, the H-AA exhibited excellent adsorption performance to Li⁺ with the Li⁺ dynamic adsorption capacity of 9.74 mg·g⁻¹ and the Mn²⁺ dissolution loss rate of 0.99%. After 3 dynamic adsorption–desorption cycles, 80% of the initial dynamic adsorption capacity was still kept.     

The influence of an ion-exchange resin on the kinetics of hydration of tricalcium silicate

The addition of a finely-ground ion-exchange resin makes it possible to modify the hydration kinetics of C₃S pastes. Analyses of the liquid phase in pastes and more dilute suspensions show that the resin exchanges calcium ions for sodium ions very rapidly during the early stage of hydration and therefore the concentration of silica in solution increases. The resin impacts the hydration of C₃S by other mechanisms which depends on the resin quantity added. For a high resin quantity, the induction period is very short, but the longer-term hydration is enhanced compared to a reference sample without resin. We hypothesize that the surface of the resin can provide sites for the nucleation and growth of C-S-H hydrates and/or portlandite far away from the surface of the C₃S grains. This consequently increases the quantity of hydrates that can precipitate before a continuous hydrate layer forms over the surfaces of C₃S particles.