Exploring the Influence of Milling Parameters on the Wet Mechanochemical Synthesis of Mg-Al Layered Double Hydroxides

The synthesis of Mg-Al layered double hydroxide was explored, through a one-step wet mechanochemical route, using a NETZSCH LME 1 horizontal bead mill. Raw materials selected were MgO and Al(OH)3. The aim of the research was to expand on the understanding of the wet mechanochemical synthesis of Mg-Al LDH. This was done through variation in milling parameters such as rotational speed, retention time, solids loading, bead size and jacket water inlet temperature. LDH synthesis occurred successfully at jacket water temperatures of 50°C and increased retention times. LDH XRD peaks were noted to be broad, but the pattern evident. It was further noted that Al(OH)3 XRD peak reduction occurred readily for increased rotational speeds and residence times, regardless of system temperature. MgO reacted more readily at elevated temperatures.

X-Ray Fluorescence
Samples were dried at 100°C and roasted at 1000°C to determine the mass loss upon ignition. Additionally, 1 g of sample was mixed with 6 g of Lithium tetraborate flux and fused at 1050°C to form a stable glass bead. Analysis was conducted with the use of a Thermo Fischer ARL Perform ‘X Sequential instrument. Samples were characterised using UNIQUANT software.

Particle Size Analysis (PSA)
Collected samples were analysed wet, to ensure full dispersion using a Mastersizer 3000 with Hydro LV liquid unit.

XRD Analysis
Powdered samples were analysed using a PANalytical X’Pert Pro powder diffrac-tometer in θ-θconfiguration, fitted with an X’Celerator detector and variable divergence- and fixed receiving slits. The set-up made use of a Fe filtered Co-Kα (λ= 1.789 Å) source. Sample preparation was conducted using a standardised PANalytical backloading system which provides a random particle dis-tribution. Samples were scanned from 5°to 90°with a step size of 0.008°. Mineralogy was determined using the ICSD database in correlation with X’Pert Highscore plus software

FT-IR spectra for dry samples were obtained with the use of a PerkinElmer 100 Spectrophotometer over a range of 550 – 4000 cm-1. An average of 32 scans at a resolution of 2 cm-1 was used.

Sample morphology was investigated by making use of a Zeiss Gemini 1 cross beam 540 FEG SEM. Powdered samples were coated with graphite 5 times using a Polaron Equipment E5400 SEM auto-coating sputter system.

S1: 1 h, 30 deg C, 1000 rpm, 10 % Solids
S2: 1 h, 30 deg C, 2000 rpm, 10 % Solids
S3: 1 h, 30 deg C, 3000 rpm, 10 % Solids
S4: 1 h, 30 deg C, 2000 rpm, 10 % Solids
S5: 2 h, 30 deg C, 2000 rpm, 10 % Solids
S6: 3 h, 30 deg C, 2000 rpm, 10 % Solids
S7: 1 h, 30 deg C, 2000 rpm, 20 % Solids
S8: 1 h, 30 deg C, 2000 rpm, 30 % Solids
S9: 1 h, 30 deg C, 2000 rpm, 10 % Solids, 0.25 mm
S10: 1 h, 50 deg C, 2000 rpm, 10 % Solids
S11: 2 h, 50 deg C, 2000 rpm, 10 % Solids
S12: 3 h, 50 deg C, 2000 rpm, 10 % Solids
S13: 1 h, 50 deg C, 2000 rpm, 10 % Solids
S14: 1 h, 50 deg C, 1000 rpm, 10 % Solids
S15: 1 h, 50 deg C, 3000 rpm, 10 % Solids

本研究以氧化镁（MgO）和氢氧化铝（Al(OH)₃）为原料，采用NETZSCH LME 1型卧式砂磨机，通过一步湿法机械化学路径探索镁铝层状双氢氧化物（layered double hydroxide, LDH）的合成工艺。本研究旨在深化对镁铝层状双氢氧化物湿法机械化学合成机制的认知，通过调控研磨参数——包括转速、停留时间、固含量、磨珠尺寸及夹套冷却水入口温度——开展实验。实验结果表明，在夹套水温50℃及延长停留时间的条件下可成功合成LDH；所得产物的X射线衍射（X-Ray Diffraction, XRD）峰较为宽化，但特征衍射峰清晰可辨。此外，无论体系温度如何，提高转速与停留时间均可显著促进Al(OH)₃的XRD特征峰强度降低，即其反应程度提升；而MgO在高温环境下更易发生反应。

### X射线荧光光谱分析
将样品置于100℃下干燥，随后在1000℃下焙烧以测定灼烧减量；另取1g样品与6g四硼酸锂熔剂混合，于1050℃下熔融制成稳定的玻璃珠，采用赛默飞世尔（Thermo Fischer）ARL Perform'X 顺序式X射线荧光光谱仪进行分析，并通过UNIQUANT软件完成样品表征。

### 粒度分析（Particle Size Analysis, PSA）
采用配备Hydro LV湿法分散单元的Mastersizer 3000激光粒度仪对采集的样品进行湿法分析，以确保颗粒充分分散。

### X射线衍射分析
采用PANalytical X'Pert Pro型粉末衍射仪（θ-θ构型，配备X'Celerator探测器、可变发散狭缝与固定接收狭缝）对粉末样品进行表征，测试光源为经铁（Fe）滤色的Co-Kα射线（λ=1.789 Å）。样品制备采用标准化的PANalytical背装系统，以实现随机颗粒分布；扫描范围为5°~90°，步长0.008°。物相鉴定采用ICSD数据库结合X'Pert Highscore plus软件完成。

### 傅里叶变换红外光谱分析
采用PerkinElmer 100型分光光度计对干燥样品进行傅里叶变换红外光谱（FT-IR）测试，扫描范围为550~4000 cm⁻¹，分辨率为2 cm⁻¹，取32次扫描的平均值作为测试结果。

### 扫描电子显微镜形貌表征
采用蔡司（Zeiss）Gemini 1交叉束540 FEG扫描电子显微镜（SEM）对样品形貌进行观察；样品制备采用Polaron Equipment E5400型自动溅射镀膜系统进行5次石墨喷镀处理。

本次实验共设置15组样品，具体制备参数如下：
S1：1 h，30℃，1000 rpm，10%固含量
S2：1 h，30℃，2000 rpm，10%固含量
S3：1 h，30℃，3000 rpm，10%固含量
S4：1 h，30℃，2000 rpm，10%固含量
S5：2 h，30℃，2000 rpm，10%固含量
S6：3 h，30℃，2000 rpm，10%固含量
S7：1 h，30℃，2000 rpm，20%固含量
S8：1 h，30℃，2000 rpm，30%固含量
S9：1 h，30℃，2000 rpm，10%固含量，0.25 mm磨珠
S10：1 h，50℃，2000 rpm，10%固含量
S11：2 h，50℃，2000 rpm，10%固含量
S12：3 h，50℃，2000 rpm，10%固含量
S13：1 h，50℃，2000 rpm，10%固含量
S14：1 h，50℃，1000 rpm，10%固含量
S15：1 h，50℃，3000 rpm，10%固含量