水热改性条件对制备氢氧化镁阻燃剂中试研究的影响

在自行研制的中试设备上用氢氧化钠合成法-水热改性法制备出了高分散氢氧化镁阻燃剂,分析了水热改性条件对制备氢氧化镁的影响.研究发现水热改性温度、水热改性时间、改性剂添加量和水热浆液固含均对水热产物的形貌和一次粒径有一定的影响.在合理的水热改性条件下,能够制备出大晶型、低比表面积、高分散的规则六方片状氢氧化镁阻燃剂.     

用于软质PVC的纳米氢氧化镁阻燃性研究

研究了氢氧化镁阻燃剂对软质聚氯乙烯(PVC)增塑体系的阻燃效果.通过X射线粉末衍射(XRD)、透射电子显微镜(TEM)、热分析等手段对氢氧化镁阻燃剂进行了表征,并考察了氢氧化镁在软质PVC体系中的分散情况.结果表明,氢氧化镁的粒径约为80 nm,改性氢氧化镁在软质PVC中分散较为均匀,每100份软质PVC仅添加40份氢氧化镁就可使体系达到较好的阻燃效果和力学性能.     

纳米氢氧化镁表面改性研究

主要研究了纳米氢氧化镁湿法表面改性的工艺过程,将改性前后的粉体添加到软质PVC体系中测定该体系的氧指数、拉伸强度和断裂伸长率,同时与普通氢氧化镁粉体进行了比较。实验结果表明：在本实验条件下最佳的改性剂为硬脂酸锌,改性时间为0．5h,改性温度为85℃,改性剂用量为5％(质量分数);改性纳米氢氧化镁粉体比普通氢氧化镁和未改性纳米氢氧化镁粉体提高了软质PVC体系的阻燃性能,同时降低了对体系机械力学性能的影响。     

对甲苯磺酸钠诱导直接转化制备氢氧化镁

为了省去酸解步骤,以水镁石为原料制备晶型良好、表面极性较低的氢氧化镁,采用对甲苯磺酸钠作为诱导剂,诱导活化后的水镁石直接转化水热制备氢氧化镁。对水热时间、温度、氢氧化钠溶液浓度做了单因素实验。实验得到最佳反应条件：对甲苯磺酸钠与水镁石粉物质的量比为1∶20、填充度为70%、水热时间为12 h、水热温度为200 ℃、氢氧化钠溶液浓度为5 mol/L。通过谢乐公式计算出所得纳米氢氧化镁的平均晶粒尺寸为14.6 nm。     

超重力技术制备纳米氢氧化镁阻燃剂的应用研究

本文采用超重力技术制备纳米氢氧化镁阻燃剂并对其进行湿法表面改性．应用TEM、XRD、BET、吸油值、沉降速度等方法对改性前后的纳米氢氧化镁粉体进行了分析和表征．将改性前后的纳米氢氧化镁应用到软质PVC体系中。实验结果表明：超重力技术制备的纳米氢氧化镁的粒径为70nm,为六方形片状;经不同改性荆改性的粉体中．以硬脂酸锌改性粉体的应用效果较好;未改性纳米氢氧化镁的比表面为21．5760m^2／g,而改性粉体的比表面为22．0641m^2／g,有一定程度的增大;改性氢氧化镁的沉降速度减慢,吸油值下降．添加量为40份时PVC体系的综合性能较好。     

纳米氢氧化镁阻燃剂在软质PVC中的应用研究

采用不同改性剂对纳米氢氧化镁进行表面改性,通过切片的TEM电镜照片考察了改性前后的粉体在软质PVC体系中的分散情况。研究了纳米氢氧化镁粉体对该体系阻燃性能和机械力学性能的影响,并与微米氢氧化镁粉体进行了比较。实验结果表明：改性后的纳米氢氧化镁粉体在软质PVC体系中有较好分散性;在不同改性剂中,以硬脂酸锌的改性效果较好;改性纳米氢氧化镁的阻燃性能和机械力学性能要优于微米级氢氧化镁;添加量为40克(以100克PVC为基准)时体系的综合性能较好,氧指数可增加8．6％;加入阻燃协效剂,体系的阻燃性能有大幅度的提高,氧指数可增加19.6％。     

硅聚醚原位改性超细氢氧化镁的制备

将氢氧化钠作为沉淀剂,以无水氯化镁为原料,采用双向沉淀法制备超细氢氧化镁(MH),在制备过程中引入硅聚醚使氢氧化镁表面有机化。考察了硅聚醚的添加方式、硅聚醚的添加量、反应温度和搅拌速度等因素对氢氧化镁浆料的过滤性能的影响。利用接触角测定仪、纳米粒度及Zeta电位分析仪、傅里叶红外光谱仪、同步热分析仪等对氢氧化镁粉体的接触角、粒径、表面结构和热稳定性进行了表征。研究结果表明：在硅聚醚的添加方式为在氢氧化钠溶液中添加硅聚醚[Mg(OH)₂-Ⅱ],每100 g MH中硅聚醚的添加量为3 g,反应温度为60℃,搅拌速度为800 r/min的条件下,氢氧化镁浆料的过滤性能最好,过滤速度最快为4.79×10^-4 m/s;在最佳条件下制备的氢氧化镁的接触角比未改性氢氧化镁提高了6倍多;FT-IR分析证明了硅聚醚成功地吸附在氢氧化镁的表面;热分析表明了改性氢氧化镁的热稳定性明显提高。     

镁铝水滑石的水热合成及表征

用一步水热法制得的氢氧化镁作为镁源,采用高过饱和共沉淀水热法制备镁铝水滑石。考察了水热温度、水热时间、氢氧化镁合成条件、晶种等条件对合成水滑石的晶体结构、尺寸、形貌及比表面积的影响。结果表明：采用水热温度为150 ℃、水热时间为3 h合成的氢氧化镁作为原料时,在水热温度为190 ℃、水热时间为12 h条件下制得水滑石的比表面积最小,形貌和结构规整;原料氯化镁中三氧化二硼杂质质量分数为0.020%时,会促进水滑石晶粒径向尺寸和厚度的增加;添加晶种会明显减小水滑石的比表面积,最佳添加量为0.5%（质量分数）。在以上最佳条件下,最终制得水滑石的比表面积达到10.33 m ²/g,水合粒径为878 nm。     

软质PVC阻燃性能研究

研究了氢氧化镁的表面改性及其在软质聚氯乙烯(PVC)中的应用。通过TEM、BET对改性前后的氢氧化镁进行了表征,通过TG对氢氧化镁进行了热失重分析;考察了氢氧化镁用量对软质PVC体系阻燃性能和力学性能的影响。结果表明:改性氢氧化镁比表面积有所增大;在314～430℃范围内,氢氧化镁失重27.5%;改性氢氧化镁在软质PVC体系中有较好的相容性和分散性;添加40g改性氢氧化镁,体系的氧指数由25.5%提高到27.7%,拉伸强度由23.6MPa下降到18.6MPa,既达到了较好的阻燃效果,又对力学性能的影响不大。     

片状氢氧化镁阻燃剂的制备、表面改性及其测试

以六水氯化镁和氢氧化钠为原料,采用两步法即氢氧化钠沉淀-水热处理过程制备出湿氢氧化镁固体,再以硅烷偶联剂KH550对氢氧化镁表面进行改性制得氢氧化镁阻燃剂.适宜的工艺条件为:水热温度160℃,水热时间6 h;表面改性温度80℃,硅烷偶联剂最佳用量为氢氧化镁理论量的5.0％.结果表明:改性氢氧化镁结晶度高、晶粒形貌规整、片状、粒径小(平均粒径300 nm左右)且粒度分布窄;硅烷偶联剂在氢氧化镁粉体表面上发生化学吸附,氢氧化镁表面极性降低,因而具有良好的分散性和疏水性.改性氢氧化镁与EVA树脂组成的复合材料有很好的阻燃性能,氧指数达到29.9.     

Nanocrystalline Seeding Effect on the Crystallization of Two Leucite Precursors

The effect of nanocrystalline leucite seeding with leucite precursors prepared by sol–gel and hydrothermal methods on the leucite crystallization process and the microstructure of its sintered porcelain was studied. The introduced seeds lowered the crystallization temperature of leucite by 100° and 50°C for the precursor prepared by hydrothermal and sol–gel methods, respectively. The crystallization process was changed after the seeds were introduced. As the transition phase during leucite crystallization, kalsilite did not appear after the seeds were added. When the seeded hydrothermally derived precursor was treated at 650° and 700°C, part of the cubic leucite was stabilized to room temperature. This stabilization was due to the crystallization of nanocrystalline leucite on the seeds at a low temperature. The leucite synthesized by the hydrothermal method with seeding at 800°C had an average particle size of 0.4 μm that grew to about 0.6 μm in the sintered porcelain.     

不同酸根离子制备MgO/TiO2对PVC膜性能的影响

采用硫酸镁和氯化镁作为镁源与三氯化钛为钛源,通过水热煅烧法制备氧化镁(MgO)/二氧化钛(TiO2)复合材料,探究不同酸根离子制备的复合材料性能及对聚氯乙烯(PVC)的影响。结果表明,成功制备以硫酸镁为镁源的复合材料(SMT)和以氯化镁为镁源的复合材料(CMT),SMT为球状,CMT为棒状;SMT使得PVC膜的第一阶段热降解温度提高到265℃,热收缩率降低了31%;CMT则使热降解温度提高到270℃,热收缩率降低了37%;加入复合材料后两种PVC膜的力学性能略微下降;经360 h紫外灯照射后,PVC/CMT的拉伸强度上升幅度最大,断裂伸长率下降幅度最小。综合来看,氯化镁作为镁源制备的棒状复合材料对提高PVC性能有较好的效果。     

活性氢氧化镁水热改性制备分散性氢氧化镁

探索了活性氢氧化镁经水热改性制备形貌规则、分散良好的片状氢氧化镁的方法。研究了焙烧-水化对活性氢氧化镁性质的影响及活性氢氧化镁水热改性制备分散性氢氧化镁的工艺规律,并用扫描电子显微镜（SEM）、X射线衍射仪（XRD）、物理吸附仪和激光粒度仪等对水热产物进行了表征。研究结果表明：通过低温焙烧及水化可将团聚态的工业氢氧化镁先转化为活性较高的氢氧化镁,再经温和水热改性即可制得形貌规则、分散性良好的片状氢氧化镁。     

Synthesis and characterization of Linde A zeolite coated with a layered double hydoxide

Linde type A zeolite (zeolite-LTA) coated with layered double hydroxide (LDH) was synthesized by a precipitation of LDH on zeolite-LTA and a hydrothermal treatment. When aqueous solutions containing magnesium chloride, and aluminum chloride were added dropwise to zeolite-LTA suspension at the constant pH of 10 using sodium hydroxide solution and then treated at hydrothermal conditions, LDH-coated zeolite-LTA was obtained. Scanning electron micrograph confirmed that the surface of zeolite-LTA was covered completely by fine LDH particles. The crystal structure of zeolite-LTA was retained even after the hydrothermal treatment and the coating with LDH particles, showing the possible application of the present multifunctional material for simultaneous uptake of harmful cations and anions, such as ammonium and phosphorous ions from wastewater.     

制备条件对氢氧化镁和碱式氯化镁组成和形貌的影响

以六水氯化镁和氨水为原料,水热法合成出了氢氧化镁和碱式氯化镁晶须。利用XRD、SEM、TG、FT-IR对产物的组成和形貌进行表征,同时考察了原料浓度、反应温度、反应时间及表面活性剂对产物形貌的影响。结果表明,在低氯化镁浓度和一定氨水滴加量的条件下产物为厚度20～50 nm,具有规则形状的纳米六方片层及其组合玫瑰花球结构的氢氧化镁,增大氯化镁溶液浓度同时减小氨水滴加量产物为直径0.5 μm、长度200 μm的碱式氯化镁单晶。     

A comparative study of two methods for the synthesis of fly ash-based sodium and potassium type zeolites

Fly ash (FA) from the Rugeley Power Station, West Midlands (England) was used in a study on synthesis at laboratory scale of zeolitic materials under various conditions by two different routes. Zeolitic materials were synthesized from FA by hydrothermal treatment in NaOH (Na-phillipsite, hydroxysodalite, hydroxycancrinite, tobermorite, analcime and herschelite) and KOH (hydroxysodalite, zeolite Barrer-KF, K-chabazite and zeolite Linde Type F) solutions. By fusion with NaOH followed by hydrothermal reaction, FA was converted into faujasite and hydroxysodalite. No zeolitic materials were obtained by this method using KOH as alkali activator. The process of synthesis was optimised by applying a wide range of experimental conditions with a wide range of reaction temperature, time, alkali hydroxide concentration and solid/solution ratio. The efficiency FA-based zeolites (FAZs) for heavy metal and ammonium uptake from synthetic solutions at laboratory scale have been investigated by the authors, revealing that these FAZs may reach appropriate cation exchange capacities for their application in industrial wastewater treatment.     

The use of CTAB to improve the crystallinity and dispersibility of ultrafine magnesium hydroxide by hydrothermal route

The high-dispersed lamellar ultrafine magnesium hydroxide was obtained at relatively low hydrothermal temperature in the presence of cationic surfactant, cetyl trimethyl ammonium bromide (CTAB). The procedure described in this study is attractive since proper amount of CTAB could promote the dissolution and precipitation of magnesium hydroxide in hydrothermal system, resulting in the well-defined morphology, narrow size distribution and good crystallinity of ultrafine particles. The resultant magnesium hydroxide was characterized by X-ray powder diffraction (XRD), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), field-emission scanning electron microscopy (FESEM) and laser diffusion analysis. The method led to the production of particles with mean size of 400 nm and a thickness of 60 nm. The optimal conditions of preparation were hydrothermal treatment at 150 °C for 6 h at pH 11 with Mg²⁺/CTAB molar ratio of 80.     

浓海水制备氢氧化镁颗粒的水热改性

将模拟浓海水和NaOH直接沉淀制备的Mg(OH)2水热处理得到Mg(OH)2阻燃剂粉体,考察了矿化剂和温度对其晶体形貌、结晶性及分散性的影响. 结果表明,在实验温度范围内,碱类矿化剂对晶体形貌的改善优于氯盐矿化剂;矿化剂浓度和水热温度越高,对晶体形貌改善越好,晶体粒径及厚度增加越快,且可减小晶体极性和微观内应变,提高结晶度和分散性. 在水热时间8 h、温度200℃、4.0 mol/L NaOH溶液为矿化剂条件下,可制备出粒度分布均匀、平均粒径约为0.250 mm、厚度约61 nm、团聚指数约为10.95的阻燃型Mg(OH)2.     

Semibatch Production of Pharmaceutical Grade Magnesium Stearate: A Statistical Approach

Fractional factorial design was employed to investigate the effect of feed composition and the major operating variables on the production of pharmaceutical grade magnesium stearate in a double decomposition process. The studied variables were initial stearic acid concentration, initial sodium hydroxide concentration, initial magnesium sulfate concentration, as well as reactor temperature at the time of NaOH addition (the first reaction temperature) and reactor temperature during magnesium sulfate addition (the final reaction temperature), pH of the solution at the end of reaction (final pH). The moisture content of the cake produced after filtration and the yield of magnesium stearate in the dried cake (assay), were the most important responses investigated as a function of feed and operating variables and these were optimized through statistical analysis. The results of the study showed that both magnesium sulfate and NaOH had high positive effects on the final pH, with a nonsignificant effect of the other main factors being observed. Increasing the NaOH concentration and the first reaction temperature led to an increase in the assay production, whereas the binary interaction of stearic acid and NaOH revealed a negative effect. The acid as well as NaOH concentrations exhibited positive influence on the moisture content of the filtered cake. Finally, the simplex optimization method was used to obtain the optimal conditions. The results of the study were successfully adapted to the large scale production of pharmaceutical grade magnesium stearate and pharmaceutical grade product was produced meeting the standards required.