Formation Of ZnAl2O4 Research Articles

Modeling phase separation mechanisms in oxy‐fluoride glass‐ceramics containing SrF2:Ln3+ and ZnAl2O4:Cr3+ nanocrystals

AbstractIt is imperative to develop a comprehensive understanding of phase separation mechanisms in multi‐phase oxy‐fluoride glass ceramics (GCs) to customize their structural and optical characteristics for particular applications in photonics. The manuscript utilizes molecular dynamics (MD) simulations to examine the phase separation mechanisms in SiO2–Al2O3–SrF2–ZnF2–LnF3‐CrF3 (where Ln represents the lanthanide elements) GCs during the simultaneous precipitation of SrF2: Ln3+ and ZnAl2O4: Cr3+ nanocrystals. Insights into the atomic‐level interactions that regulate the separation and formation of distinct phases rich in fluoride and oxide are obtained through MD simulations. The results reveal that Sr2+ and Ln3+ ions partition preferentially into the fluoride phase, whereas Zn2+ and Cr3+ associate with the oxide aluminosilicate network. Remarkably, the separated fluoride and oxide phases bear structural similarities with the existing experimental outcomes. The introduction of SrF2 facilitates phase separation in oxy‐fluoride glass system by causing the formation of SrF2: Ln3+ nanocrystals in regions abundant in fluoride, while the substitution of ZnF2 for SrF2 results in the formation of ZnAl2O4: Cr3+ nanocrystals originating from the separated oxide phase. Therefore, the reported simulations offer molecular‐level insights into the mechanisms underlying phase separation and the functions of various glass components, thereby facilitating the development of customized oxy‐fluoride GCs with tailored properties.

Structural and compositional gradients in alternating current sintered aluminum-doped zinc oxide

Flash sintering revitalizes the exploration of electric field and current effects on the microstructure with novel phenomena including rapid densification, low-temperature sintering, and unique microstructures. The aim of this study is to investigate the influence of electric current on the microstructural development of Al-doped ZnO (nAl=4at.%). We apply two sintering techniques, namely spark plasma sintering (SPS) and flash spark plasma sintering (FSPS), both conducted under identical conditions (AC, f=50Hz, |E→0|=25V/cm, p=180MPa) for three different temperatures 600∘C, 800∘C and 1000∘C. The distinguishing factor between the two techniques lies in the passage of electric current flow through the specimens in the case of FSPS. The resulting microstructures of the sintered pellets are examined by XRD, SEM, EDX, TEM and SAED to identify the process-related differences. While SPS specimens reveal a homogeneous microstructure, FSPS specimens exhibit a complex microstructure which consists of two distinct regions. The major volume of the FSPS pellets exhibits a structural gradient with coarse ZnO grains and ZnAl2O4 spinel precipitates in the center to fine ZnO grains at the periphery. This microstructure results from Joule heating and geometry-dependent heat dissipation, creating a symmetric temperature profile with a hot center. A minor volume of the FSPS specimens shows a gradient in microstructure and composition. Here, ZnAl2O4 spinel precipitates accumulate in the center and the periphery reveals Al-depleted, dense and very coarse grains. Electromigration of Al-cations and the thermodynamically favored formation of ZnAl2O4 in the hot center are proposed as underlying causes for the observed microstructure. The electric current in FSPS significantly alters the microstructure and composition of sintered specimen where dopant electromigration is most significant under high current densities above |J→|=29(5)A/cm2.

Controllable engineering of new ZnAl2O4-decorated LiNi0·8Mn0·1Co0·1O2 cathode materials for high performance lithium-ion batteries

Fast and continuous growth in the market of energy storage systems has increased the demand for powerful cathode materials with excellent electrochemical characteristics. In this scene, the micron-sized particles of commercial NMC811 electrode were decorated with ZnAl2O4 nanoparticles via facile coprecipitation method. The slight shifts in XRD peaks to higher angles and in FTIR bands to lower frequencies confirm the formation of ZnAl2O4 coating film surrounding NMC811 particles. The morphological features of ZAO@NMC811 core-shell particles were deeply investigated by FESEM/EDS and HRTEM/SAED techniques. XPS results of the coated sample revealed the co-existence of Zn2+ and Al3+ ions on the surface of NMC811 structure. The charge and discharge capacities of modified NMC811 were significantly increased by 5.7 and 9% achieving about 221 and 188.5 mAhg−1, respectively after first cycle. The reduction in the separation potentials of both anodic and cathodic CV scans gives a strong indication for enhancing the structure stability and lowering the polarization between NMC811 particles after coating. The modified NMC811 exhibited higher capacity retention ∼82% than that ∼ 60.2% of pristine NMC811 after 100 cycles upon 1 C. EIS results of both types of cells elucidated the enhancement of electronic and ionic conductivity as well as Li+ ions diffusion for ZAO@NMC811 cell after cycling. The suggested ZAO coating material is cheaper, easily fabricated and considerably improved the electrochemical performance of pure NMC811 cathode compared to the reported coating materials.

Plasma electrolytic oxidation of zinc alloy in a phosphate-aluminate electrolyte

In the frame of this work, plasma electrolytic oxidation of a zinc alloy was performed in a phosphate-aluminate electrolyte as a first approach. Phase composition and microstructure of the formed PEO coating was analysed as a function of treatment time and applied current density. The coatings are mainly composed out of ZnAl2O4 and ZnO with some smaller amounts of AlPO4 and Zn2P2O7. The coating formation starts with ZnO at lower discharge energies and changes to the reactive formation of ZnAl2O4 when the discharge energy is increasing. The phase composition is only influenced by the final voltage and not by the current density. Latter is only determining the growth rate of the coating. However, stresses in the coatings are high and the layers are cracked and seems to flake-off already during PEO processing, thus at longer treatment times the coating thickness is not increasing anymore. To prevent extensive flaking-off of the coating a constant voltage PEO “repair” mode was introduced partly successfully at the end of the treatment.

Effects of SiO2, Al2O3 and Fe2O3 on leachability of Zn, Cu and Cr in ceramics incorporated with electroplating sludge

Large amounts of electroplating sludge generated in electroplating industry require recycling or alternative recovery solutions to minimize environmental impact caused by the waste. The use of electroplating sludge as raw materials in the production of building materials is a feasible alternative to valorize this waste. In this study, the effects of SiO2, Al2O3 and Fe2O3 on the leachability of heavy metals (i.e. Zn, Cu and Cr(III)) during firing ceramics with the addition of electroplating sludge were examined. The results showed that Zn preferably combined with Cr(III) to form ZnCr2O4 in comparison to the formation of ZnAl2O4 and ZnFe2O4, and Zn could also be incorporated into Zn2SiO4 structure. However, Zn spinel structure have better resistance against acid attack comparing with Zn2SiO4. Cu can only be transformed into spinel phases of CuAl2O4 and CuFe2O4. SiO2, Al2O3 and Fe2O3 make less contributions to the immobilization of Cr(III). The presence of CaO severely impacted the formation of spinel phases, especially for Cr spinel. Moreover, Cr(III) would be oxidized into Cr(VI) due to the presence of CaO. It appears that the presence of SiO2 may inhibit the oxidation of Cr(III) comparing with Al2O3 and Fe2O3, which can be attributed to the interaction of CaO with SiO2 decreasing the amount of CaO. This study can provide a basic understanding for the leachability of Zn, Cu and Cr during the use of solid waste containing heavy metals in the production of clay bricks or ceramics.

Modificação da superfície do ZnAl1,9Eu0,05O4 visando a obtenção do híbrido ZnAl1,9Eu0,05O4/SiO2 para aplicação como biossensor

Resumo Este trabalho teve como objetivo investigar a modificação de superfície do ZnAl1,9Eu0,05O4 visando a obtenção do híbrido ZnAl1,9Eu0,05O4/SiO2 para aplicação como biossensor. Inicialmente as nanopartículas de ZnAl1,9Eu0,05O4 foram sintetizadas por reação de combustão e, subsequentemente, as suas superfícies foram modificadas com o agente silano. As amostras foram caracterizadas por difração de raios X, microscopia eletrônica de varredura (MEV), espectroscopia de infravermelho com transformada de Fourier (FTIR) e espectroscopia de excitação e de emissão. Os resultados evidenciaram a formação da fase majoritária do ZnAl2O4. Através de MEV observou-se a presença de aglomerados de aspecto duro, com formato irregular na forma de placas, com presença de poucos poros irregulares e variáveis. A modificação da superfície foi confirmada por FTIR através dos grupos silanóis e siloxanos. Os espectros de excitação e de emissão revelaram a presença de uma banda larga da matriz ZnAl2O4 e transições finas e intensas do íon európio provenientes da dopagem do óxido não estequiométrico ZnAl2O4 com o európio. Pelos resultados de emissão e excitação constatou-se que a luminescência do híbrido ZnAl1,9Eu0,05O4/SiO2 apresentou uma pequena diminuição em relação às nanopartículas de ZnAl1,9Eu0,05O4, sendo esta diminuição praticamente insignificante diante dos benefícios da silanização ocasionada pela introdução de grupos funcionais que promovem a conjugação do híbrido ZnAl1,9Eu0,05O4/SiO2 com biomoléculas, sendo este promissor para aplicação como biossensor aplicado na área biomédica para o diagnóstico e tratamento de doenças.

Microstructure evolution and mechanical properties of ZnAl2O4-reinforced Al2O3/Al2O3 joints brazed with a bismuth borate zinc glass

Amorphous bismuth borate zinc glass with a composition of 40Bi2O3–40B2O3–20ZnO (in mol.%) was used as a braze to join 95wt.% purity alumina ceramics (95Al2O3) in air. The interfacial phases in the brazed joints were characterized using scanning electron microscopy, transmission electron microscopy. Zinc aluminate (ZnAl2O4) was identified as the main reaction product in the joints due to the chemical reaction between the Al2O3 substrate and ZnO from the glass. Typical microstructure of the Al2O3/Al2O3 brazed joints was Al2O3 substrate/glassy matrix phase+ZnAl2O4 particles/Al2O3 substrate. The dependence of the microstructure and mechanical properties on brazing temperature was investigated. The size of ZnAl2O4 increased with an increase in brazing temperature. It was found the room lap shear strength of Al2O3/Al2O3 joints firstly increased and then declined with increasing brazing temperature. The maximum lap shear strength of 95MPa was obtained for the samples brazed at 675°C for 30min, which was mainly attributed to the formation of ZnAl2O4.

Investigation on phase evolution of the ZnO-B2O3-SiO2 glass ceramics

ZnO-B2O3-SiO2-Al2O3-Na2O glass doped with nucleating agent TiO2 was prepared with melting-quenching method and the effect of nucleating agent on the crystallization behavior and phase evolution of this glass was investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The experimental results show that the glass transition temperature and the first crystallization temperature decrease from 630 °C and 765 °C to 595 °C and 740 °C, respectively, with introduction of TiO2 into glass. There is no diffraction peaks in the XRD pattern but it is no longer transparent for the base glass without nucleating agent after heat treatment, which suggests the serious phase separation occurred, and the observation by SEM indicates that the phase separation is developed by nucleation and growth mechanism. However, there are two different crystals ZnAl2O4 and NaAlSiO4 present in the glass containing TiO2 after heat treating at 575 °C for 2 h and 740 °C for 6 h, respectively. What is interesting is that NaAlSiO4 disappears as the crystallization time at 740 °C increases from 6 h to 12 h, and more ZnAl2O4 crystal is formed, namely, the further formation of ZnAl2O4 is at cost of NaAlSiO4 with increasing crystallization time. And observation of the morphology of glass ceramics shows great difference with increasing crystallization time. Moreover, the ability of ZnO-B2O3-SiO2-Al2O3-Na2O glass ceramics against attacking of 1M HCl solution is increased by the crystals precipitated in heat treatment process.

Influence of dopant metal ions on the formation of cordierite using combined SAXS/WAXS and EXAFS/WAXS techniques

Time-resolved combined scattering and spectroscopic techniques were used to understand in detail the formation of cordierite ceramic from two sources, (a) zeolite B and (b) cordierite glass systems. Time-resolved in situ combined EXAFS/XRD (at the Zn K-edge) investigation of the zinc oxide mixed zeolite B reveal that a series of transformations occur before the formation of cordierite ceramic. In particular the study revealed that addition of small amounts of zinc oxide promote the transformation of cordierite, through the formation of ZnAl2O4, at lower temperatures compared to the system without zinc oxide. Using in situ time-resolved SAXS/WAXS technique chromium doped in the cordierite glass system was investigated which revealed that, in addition to the formation of phase pure cordierite phase some amount of MgCr2O4 spinel phase are also produced.

Study of Nanocrystalline ZnAl<sub>2</sub>O<sub>4</sub> and ZnFe<sub>2</sub>O<sub>4</sub> with SiO<sub>2</sub> on Structural and Optical Properties Synthesized by Sol-Gel Method

Zinc aluminate (ZnAl2O4) and zinc ferrite (ZnFe2O4) nanocrystalline structures dispersed into SiO2 matrix were prepared by sol-gel method. Phase formation of ZnAl2O4 and ZnFe2O4 was confirmed by X-ray diffraction (XRD) analysis. The crystallite sizes was determine using Scherer’s equation from the broadening of dominant peak at (311) plane. It was found the crystallite size of both compound decreased due to the decrement compositions of Zn2+ ion and Al3+ / Fe3+ ions. The crystallite sizes for ZnAl2O4 and ZnFe2O4 was calculated to be around ~ 14.16 – 11.27 nm and ~ 11.27 – 4.72 nm, respectively. FTIR analysis was done to determine the formation of spinel structures. FTIR results analysis confirmed that the formation of spinel structure where it has been observed that the bands around 800 cm-1 was associated to the vibrations of aluminum-oxygen and metal-oxygen-aluminum bonds. This characteristic was identified to the formation of zinc aluminate spinel structure. The optical properties have been done to determine the energy bandgap of ZnAl2O4 and ZnFe2O4 samples. The Uv-Visible absorption spectra have been done within wavelength 300 – 800 nm and the graph was plotted into the Tauc plot. This new dielectric material was purposed to improve the value of dielectric permittivity with addition of SiO2 where it can be applied as microwave dielectric material without changing the original spinel structures.

Incorporation of zinc for fabrication of low-cost spinel-based composite ceramic membrane support to achieve its stabilization

In order to reduce environment risk of zinc, a spinel-based porous membrane support was prepared by the high-temperature reaction of zinc and bauxite mineral. The phase evolution process, shrinkage, porosity, mechanical property, pore size distribution, gas permeation flux and microstructure were systematically studied. The XRD results, based on a Zn/Al stoichiometric composition of 1/2, show a formation of ZnAl2O4 structure starting from 1000°C and then accomplished at 1300°C. For spinel-based composite membrane, shrinkage and porosity are mainly influenced by a combination of an expansion induced by ZnAl2O4 formation and a general densification due to amorphous liquid SiO2. The highest porosity, as high as 44%, is observed in ZnAl4 membrane support among all the investigated compositions. Compared with pure bauxite (Al), ZnAl4 composite membrane support is reinforced by ZnAl2O4 phase and inter-locked mullite crystals, which is proved by the empirical strength–porosity relationships. Also, an increase in average pore diameter and gas flux can be observed in ZnAl4. A prolonged leaching experiment reveals the zinc can be successfully incorporated into ceramic membrane support via formation of ZnAl2O4, which has substantially better resistance toward acidic attack.

Mechanisms of zinc incorporation in aluminosilicate crystalline structures and the leaching behaviour of product phases

This study quantitatively evaluates a waste-to-resource strategy of blending zinc-laden sludge and clay material for low-cost ceramic products. Using ZnO as the simulated zinc-laden sludge to sinter with kaolinite, both zinc aluminate spinel (ZnAl2O4) and willemite (Zn2SiO4) phases were formed during the sintering process. To analyse the details of zinc incorporation reactions, γ-Al2O3 and quartz were further used as precursors to observe ZnAl2O4 and Zn2SiO4 formations. By firing the ZnO mixtures and their corresponding precursors at 750–1350°C for 3 h, the efficiency of zinc transformation was determined through Rietveld refinement analyses of X-ray diffraction data. The results also show different incorporation behaviour for kaolinite and mullite precursors during the formation of ZnAl2O4 and Zn2SiO4 in the system. In addition, with a competitive formation between ZnAl2O4 and Zn2SiO4, the ZnAl2O4 spinel phase is predominant at temperatures higher than 1050°C. This study used a prolonged leaching test modified from the US Environmental Protection Agency's toxicity characteristic leaching procedure to evaluate ZnO, ZnAl2O4, and Zn2SiO4 product phases. The zinc concentrations in ZnO and Zn2SiO4 leachates were about two orders of magnitude higher than that of ZnAl2O4 leachate at the end of the experiment, indicating that ZnAl2O4 formation is the preferred stabilization mechanism for incorporating zinc in ceramic products.

Novel Lead‐free Glass/Ceramics System with Low Permittivity, Low Loss for LTCC Application

The lead‐free, low‐softening point ZnO‐Bi2O3‐B2O3 glass with low permittivity, low loss and small coefficient of thermal expansion was prepared by melt‐quenching method. ZnO‐Bi2O3‐B2O3 glass + Al2O3 system were prepared below 850°C by the conventional ceramic route. Sintering behavior and microstructure of this system were investigated using X‐ray diffraction, differential scanning calorimetry, and scanning electron microscopic techniques. Results revealed that ZnO‐Bi2O3‐B2O3 glass and Al2O3 reacted during the firing process, which led to the formation of ZnAl2O4. Glass concentration needed to be 65 wt% for better densification. The dense system sintered at 825°C for 30 min exhibited good dielectric properties: small permittivity of 5.73 and low loss tangent of 8.94 × 10−4 at 1 MHz. Its coefficient of thermal expansion (5.57 × 10−6/K) well matched to that of GaAs chip (5.6 × 10−6/K). The bending strength was also characterized (129.9 MPa). The prepared system was suitable for LTCC application.

Enhanced mechanical, dielectric, and microwave absorption properties of ZnO/ZrSiO4 composite ceramics by adding Al2 O3 powders

The ZnO/ZrSiO4 composite ceramics with different Al2O3 additions are fabricated by pressureless sintering method. The addition of Al2O3 contributes to the formation of ZnAl2O4, which results in the enhancement of bulk densities as well as flexural strengths of the ceramics by promoting the mass transportation movement. Both the complex permittivity and dielectric loss increase firstly then decrease as the Al2O3 content enhances from 0 to 7 wt%. The bulk density and ZnO content are the main factors to affect the dielectric performance of the ceramics. Owing to the higher dielectric loss, the ceramic with 3 wt% Al2O3 addition presents the better microwave absorption property. The effective absorption bandwidth of the ceramic in 2.4 mm thickness is 8.8–11.9 GHz, with a minimum reflection loss of −25.36 dB at 10.4 GHz. As the thickness of the ceramic increases, the absorption peak shifts toward the lower frequency region, which indicates the absorption bandwidth can be tailored by changing the thickness.

Synthesis and characterization of nanocrystalline zinc aluminate spinel powder by sol–gel method

Single-phase nanocrystalline zinc aluminate (ZnAl2O4) spinel powder has been synthesized by the sol–gel method. Zinc aluminate nanoparticles were formed at 600°C, which is at much lower temperature than by solid state reactions. Formation of ZnAl2O4 and their particle size depend on the calcination temperature. Calcination temperature also affects the specific surface area and pore volume. The nanocrystalline zinc aluminate was characterized by powder X-ray diffraction, FT-IR spectroscopy, thermal gravimetric analysis, diffuse reflectance spectroscopy, surface area measurements, field emission scanning electron microscopy coupled with energy dispersive X-ray analysis and transmission electron microscopy. Catalytic reactivity of nanocrystalline zinc aluminate was tested for the reduction of 4-nitrophenol to 4-aminophenol using NaBH4.

Investigation on the sulfur state and phase transformation of spent and regenerated S zorb sorbents using XPS and XRD

A series of industrial S zorb sorbents extracted from production line were characterized by XPS and XRD. The formation of ZnAl2O4 and Zn2SiO4 is the major reason for the deactivation of spent sorbent. The stability of the Zn-containing spinel species leads to the decrease of the desulfurization efficiency of regenerated sorbent. The chemical states of sulfur atom were examined by XPS. The depth distribution of sulfur species and the reductive behavior of sulfate in H2 atmosphere were explored using Ar+ etching XPS and in situ XPS. The formation of sulfate species in the regeneration process decreases the content of ZnO in the surface significantly and should be avoided. XPS and XRD are excellent tools to follow the sulfur chemical states and phase evolution of S zorb sorbent, respectively, which provide important information for the investigation of deactivation pathways and regenerated mechanisms for S zorb sorbent.

Synthesis and characterization of nanosized zinc aluminate spinel from a novel Zn–Al layered double hydroxide precursor

In this paper, a novel Zn–Al layered double hydroxide (LDH) with composition [ZnAl2(OH)6]CO3·nH2O was prepared using the urea method. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed its layered crystalline structure. Nanosized zinc aluminate spinel was successfully synthesized by calcining [ZnAl2(OH)6]CO3·nH2O at the temperatures 700°C or above. The formation of ZnAl2O4 was monitored via XRD, Fourier transform infrared spectroscopy (FTIR), thermogravimetric and differential thermal analysis (TG-DTA). The optical and textural properties of the Zn–Al LDH and its calcined products were studied via UV–vis diffuse reflection spectroscopy and nitrogen sorption analysis. The band gap value of the sample calcined at 900°C is in the range of 3.8–4.0eV and the specific surface area decreases with increasing calcination temperatures.

Incorporating Simulated Zinc Ash by Kaolinite- and Sludge-based Ceramics: Phase Transformation and Product Leachability

Zinc is one of the hazardous metals commonly found in municipal solid waste incineration (MSWI) ash, and this study reveals the stabilization mechanisms when sintering zinc-laden ash and ceramic precursors as a waste-to-resource strategy. Using ZnO to simulate the zinc-laden ash and sintering with kaolinite and mullite ceramic precursors, both zinc aluminate spinel (ZnAl2O4) and willemite (Zn2SiO4) phases were found in the products under the tested thermal conditions. The results also indicate that kaolinite and mullite precursors exhibit different incorporation behavior, and ZnAl2O4 and Zn2SiO4 were found to be competitive as the Zn-hosting phases in the system. A prolonged leaching test was used to evaluate the leachability of potential product phases in the system. The concentrations of zinc in ZnO and Zn2SiO4 leachates were about two orders of magnitude higher than that in ZnAl2O4 leachate, indicating the preference of forming ZnAl2O4 for zinc stabilization. Furthermore, the aluminum-rich sludge generated from waterworks could be beneficially used as a material resource to stabilize zinc in this study. The X-ray diffraction (XRD) pattern collected from the 1150 °C and 3-h sintered sample shows the success of incorporating zinc into the ZnAl2O4 spinel structure with waterworks sludge precursor. The formation of ZnAl2O4 indicates a strong potential for employing aluminum- and silicon-based materials to thermally immobilize zinc and achieve the beneficial use of metal-laden MSWI ash.

Effect of ball milling on formation of ZnAl2O4 by reduction reaction of ZnO and Al powder mixture

It is well known that thermal energy generated during high energy milling / alloying can facilitate the reduction reaction, leading to formation of compounds and oxide reinforced composites. Solid state reduction reaction by the mixture of high purity fine zinc oxide and metallic Al powders is investigated. The ZnO powders are added to aluminum powder in ball milled and milled conditions, and then attrition milled for different times. The former is called double ball milled, and the latter is called single ball milled since it is only attrition milled. The results are further studied and verified by XRD, SEM, DTA and particle size analyzer. The complete reduction of ZnO to Zn is almost obtained in powders double ball milled for 10 h, which is converted to ZnAl2O4 when vacuum annealed. In the case of single ball milled powder, reduction of ZnO is partially done and no ZnAl2O4 phase forms after annealing.

From Layered Double Hydroxides to ZnO-based Mixed Metal Oxides by Thermal Decomposition: Transformation Mechanism and UV-Blocking Properties of the Product

Thermal decomposition of layered double hydroxides (LDHs) is a way of fabricating mixed metal oxide (MMO) nanocomposite materials composed of metal oxide and spinel phases. A detailed understanding of the mechanism of the transformation of the LDH precursor to the MMO should allow the properties of the resulting MMO nanocomposites to be tailored to specific applications. Here we report a systematic investigation of the structure, composition, and morphology evolution from ZnAl-LDHs to ZnO-based MMO nanocomposites composed of ZnO and ZnAl2O4 on calcination at different temperatures. The nucleation and oriented growth of ZnO crystallites and the formation of ZnAl2O4 were monitored by high resolution transmission electron microscopy (HRTEM) combined with selected-area electron diffraction (SAED), in situ X-ray diffraction (XRD), solid-state 27Al magic-angle spinning nuclear magnetic resonance (27Al MAS NMR), and thermogravimetric and differential thermal analyses (TG−DTA). The layered structure of the LDH pr...