“卡房”状高纯氢氧化镁粉体的合成及改性

以轻烧镁粉为原料,氨水为沉淀剂,利用直接沉淀法合成"卡房"状高纯氢氧化镁粉体;通过单因素实验研究硫酸镁的浓度、反应温度、反应时间、氨水与镁离子的物质的量比和搅拌转速对氢氧化镁合成的影响,确定最佳反应条件;分别利用添加不同分散剂和水热法对制得样品进行改性;采用扫描电子显微镜、X射线衍射和X射线荧光对样品进行表征。结果表明:不同类型的分散剂均对氢氧化镁的改性效果不明显;水热法改性后氢氧化镁的结晶度等性质均有不同程度的改善,改性时添加浓度为6 mol/L的氢氧化钠效果最佳,可得极性弱、形貌规则、热稳定性良好、结晶度高的氢氧化镁粉体,其中氢氧化镁的质量分数大于99.94%,收率为87.92%。     

Preparation of semi-solid AlSi7Mg alloy slurry through traveling electromagnetic stirring

用低过热度浇注和弱行波电磁搅拌工艺制备半固态AlSi7Mg合金浆料, 研究了浇注温度和搅拌功率对其初生α-Al形貌的影响. 结果表明, 用该工艺可制备初生$\alpha$--Al形貌呈小而圆整的球状晶粒、组织分布均匀、 较大尺寸(直径为127 mm)的半固态AlSi7Mg合金浆料. 浇注温度合适, 短时间弱电磁搅拌(8 s左右)就可获得初生α-Al形貌大部分为球状, 组织分布比较均匀的浆料组织. 浇注温度一定, 适当提高搅拌功率可明显改善初生 α-Al的形貌, 但是过高的搅拌功率并不能使初生α-Al的形貌进一步改善. 用该工艺制备的半固态AlSi7Mg合金浆料, 从其边部到心部的径向组织初生 α-Al形貌经历了一个从枝晶组织向蔷薇状组织再向球状组织转变的过程.     

离子液体添加剂对电沉积氢氧化镁薄膜形貌的影响

以离子液体[MEIM]+[ES]-为晶体生长调控剂,采用简便的电化学方法合成了特定形貌的氢氧化镁纳米结构薄膜.对影响电沉积氢氧化镁薄膜的合成参数(如离子液体的含量、沉积电位和沉积时间)进行了研究,并分别用电镜、X射线衍射和热分析技术对所得氢氧化镁薄膜的形貌和热稳定性进行了表征.此外,该电化学过程可望推广到制备其它形貌独特和性能奇特的纳米/介观结构.     

用行波电磁搅拌制备半固态AlSi7Mg合金浆料

用低过热度浇注和弱行波电磁搅拌工艺制备半固态AlSi7Mg合金浆料,研究了浇注温度和搅拌功率对其初生α-Al形貌的影响.结果表明,用该工艺可制备初生α-Al形貌呈小而圆整的球状晶粒,组织分布均匀,较大尺寸(直径为127 mm)的半固态AlSi7Mg合金浆料.浇注温度合适,短时间弱电磁搅拌(8 S左右)就可获得初生α-Al形貌大部分为球状,组织分布比较均匀的浆料组织.浇注温度一定,适当提高搅拌功率可明显改善初生α-Al的形貌,但是过高的搅拌功率并不能使初生α-Al的形貌进一步改善.用该工艺制备的半固态AlSi7Mg合金浆料,从其边部到心部的径向组织初生α-Al形貌经历了一个从枝晶组织向蔷薇状组织再向球状组织转变的过程.     

离子交换树脂法制备高纯超细氢氧化镁

以强碱性阴离子树脂作为沉淀剂,采用离子交换法制备了高纯超细的氢氧化镁粉体,就离子交换反应过程中的反应温度、反应时间、MgCl2浓度等条件对Mg（OH）2粒径的影响进行了探讨,并利用扫描电镜、微机差热天平、X射线衍射仪对产物进行了表征,实验结果表明,在氯化镁溶液浓度为0．1mol／l,反应温度为60℃,反应时间为16h的条件下可制备出形貌规则、分散性较好的六方片状氢氧化镁,平均粒径可达到100nm左右。     

载Ag白炭黑抗菌剂的制备及性能研究

以AgNO₃为原料，沉淀白炭黑为载体，采用浸渍法制备载Ag白炭黑抗菌剂，以大肠杆菌为例测试了样品的抗菌性能，并对其抗菌过程进行初步分析。利用单因素实验讨论了银离子浓度、反应温度、反应时间和搅拌速度对载Ag白炭黑抗菌率的影响，确定最优制备条件为：银离子浓度0.2mol/L,反应温度80℃,反应时间1.5h,搅拌速度400r/min。在此条件下制备的载Ag白炭黑具有超过99%的抗菌率，银负载量可达3.0%。采用X射线衍射(XRD)、扫描电镜(SEM)、X射线光电子能谱(XPS)和激光粒度仪对载Ag白炭黑的物相结构、形貌特征、化合价和粒度分布进行了表征。结果表明：载银白炭黑为蓬松的、多孔的无定型结构，平均粒径为9.9μm,其中，银以纳米Ag单质的形式存在，均匀负载在二氧化硅表面和孔道上。     

原位沉淀法制备氢氧化镁阻燃棉织物及其性能

以氯化镁为前驱体,棉织物为基体,采用原位沉淀法制备出氢氧化镁阻燃棉织物。研究制备过程中氯化镁浓度、反应时间、反应温度、浸渍时间等参数对原位沉淀处理后棉织物阻燃性能的影响。结果发现影响棉织物阻燃效果的主要因素为氯化镁浓度以及浸渍时间;通过扫描电子显微镜(SEM)和X射线衍射仪(XRD)对阻燃棉织物的结构形貌进行表征,结果表明合成的氢氧化镁颗粒为六边形晶体结构并且均匀附着在棉织物表面;利用热重分析仪(TG)以及微型锥形量热仪(MCC)等对其热稳定性和阻燃性能进行分析,结果表明氢氧化镁主要在凝聚相起阻燃效果,600℃时残渣量比原棉高出30%;热释放速率峰值比纯棉织物下降了55.3%,总热释放减少了21.6%,阻燃效果良好。     

利用轻烧镁粉制备纳米氢氧化镁工艺与机理研究

探讨了以轻烧镁粉和蒸馏水为原料,采用机械力化学法和水化法超细研磨制备六方片纳米氢氧化镁的工艺条件。研究了在氧化镁水化过程中,搅拌磨搅拌速率-研磨时间和料浆固液比对实验产品的粒度、形貌和结构的影响,并对反应机理进行了阐述。实验结果表明最优工艺参数为轻烧镁粉:蒸馏水:研磨介质配比为1∶4∶4、研磨转速为1300 r/min、反应最佳时长为180 min。在此条件下得到的产物为纳米级氢氧化镁,经测试其粒度d_(50)为1.04μm,d_(90)为2.27μm。SEM分析表明样品的表面形貌为六方片状,薄片厚度大约为5～20 nm;XRD分析表明制得的氢氧化镁粉体结晶完全,其平均晶粒尺寸为6.3 nm。     

PMMA纳米微球的制备与表征

以甲基丙烯酸甲酯(MMA)为单体、过硫酸钾为引发剂、十二烷基硫酸钠为乳化剂,采用分散乳液聚合法制备分散聚甲基丙烯酸甲酯(PMMA)微球,并自组装得到有序的空间结构。用粒度仪和扫描电子显微镜(SEM)分析PMMA微球的粒径尺寸和形貌,采用响应面分析法结合单因素趋势变化研究单体、引发剂、乳化剂、搅拌速度以及温度对PMMA微球粒径和分布的影响。结果表明,通过控制实验条件制备出平均粒径为115nm的PMMA微球,其分布集中,粒径随着引发剂量、单体量、温度的增加而增加,但是粒径大小却随着搅拌速度、乳化剂的增加而减小。     

石棉尾矿酸浸液制备氢氧化镁

以石棉尾矿硫酸酸浸液为原料,经过氧化、除铁后得到硫酸镁滤液,采用氨水沉淀法制备氢氧化镁,研究氨水用量、反应温度、反应时间对制备氢氧化镁的影响,并对制备的氢氧化镁样品进行表征。结果表明,利用石棉尾矿酸浸液制备氢氧化镁的适宜工艺条件如下:200 mL酸浸液需要氨水的体积为150 mL,反应温度为70℃,反应时间为40 min;在适宜条件下制备的产物中氢氧化镁的质量分数为93.31%,中位粒径d50为8.42μm,比表面积为35.14 m2/g,白度为98.6%;X射线衍射分析显示氢氧化镁结晶良好。     

镁盐及晶种对氧化镁水化合成氢氧化镁的影响

采用氧化镁水化法制备氢氧化镁,研究硫酸镁、乙酸镁、氯化镁、硝酸镁4种镁盐的添加量对氧化镁水化率的影响,以及镁盐和晶种对氢氧化镁颗粒大小和形貌的影响,利用X射线衍射和扫描电子显微镜对合成的氢氧化镁晶体特性、颗粒大小和形貌进行表征,并对上述因素的影响机理进行探讨。结果表明,随着镁离子浓度的增大,氧化镁的水化率逐渐增大,氧化镁水化率最高可达到98.68%,水化产物氢氧化镁颗粒近似于六方片状,粒径约为200⁵00 nm。     

Solid State Shear Milling to Prepare Magnesium Hydroxide Flame-Retardant Polyamide 6 with High Performance

A novel processing method, that is, solid state shear milling (S3M), was adopted to compound high loading inorganic flame-retardant magnesium hydroxide with polyamide 6 by using our self-designed pan-mill equipment. S3M can effectively pulverize PA6, increase the interfacial interaction of the resin and magnesium hydroxide, and achieve their even blending, thus effectively controlling the state of the dispersion phase in solid state. With the co-milled composite powder as flame retardant master batch filled in original PA6 pellets, it can greatly improve the compatibility of the system, modify the distribution process of magnesium hydroxide, and decrease the dispersion phase size in the following melt processing. As a result, S3M technology can remarkably increase the melt flowability of the composite materials, and obtain obviously enhanced flame retardance and mechanical performance, thus providing an effective solution to the poor processibility and deteriorated performance of magnesium hydroxide flame-retardant PA6 obtained through direct melt processing.     

纳米氢氧化镁粉体的制备及热分解动力学研究

以氯化镁和尿素为原料,采用均匀沉淀法制备出厚度约为20 nm的片状纳米氢氧化镁粉体。利用热重分析法对片状纳米氢氧化镁粉体在不同升温速率下的热分解动力学进行研究,以期深入认识由纳米氢氧化镁粉体热分解得到纳米氧化镁粉体过程的物理化学本质。分别采用Coats-Redfern方程和Dolye方程,对热重分析数据进行了处理和拟合,得到了片状纳米氢氧化镁粉体热分解反应属于Avrami-Erofeev(n=1)的成核和生长为控制步骤的反应机理,其表观活化能E=131 kJ/mol,指前因子A=1.56×1010。     

Mechanochemical synthesis of a hydroxycarbonate form of layered magnesium aluminum hydroxides

Mechanical activation of a mixture of magnesium hydroxide, aluminum hydroxide, and sodium bicarbonate in an AGO-2 planetary mill, followed by water washing leads to the formation of a layered magnesium aluminum hydroxide. The double hydroxide obtained at a magnesium hydroxide to aluminum hydroxide ratio of 3:1 is essentially phase-pure and contains both carbonate and bicarbonate ions in its interlayer spaces. The synthesized double hydroxide was characterized by x-ray diffraction, IR spectroscopy, thermogravimetry, differential thermal analysis, and chemical analysis.     

The role of ammonium citrate washing on the characteristics of mechanochemical–hydrothermal derived magnesium-containing apatites

The role of citrate washing on the physical and chemical characteristics of magnesium-substituted apatites (HAMgs) was performed. HAMgs were synthesized by a mechanochemical–hydrothermal route at room temperature in as little as 1 h, which is five times faster than our previous work. Magnesium-substituted apatites had concentrations as high as 17.6 wt% Mg with a corresponding specific surface area (SSA) of 216 m²/g. A systematic study was performed to examine the influence of increasing magnesium content on the physical and chemical characteristics of the reaction products. As the magnesium content increased from 0 to 17.6 wt%, magnesium-doped apatite crystallite size decreased from 12 to 8.8 nm. The Mg/(Mg + Ca) ratio in the product was enriched relative to that used for the reacting precursor solution. During mechanochemical–hydrothermal reaction, magnesium doped apatites co-crystallize with magnesium hydroxide. Citrate washing serves to remove the magnesium hydroxide phase. The concomitant increase in surface area results because of the removal of this phase. Possible mechanisms for magnesium hydroxide leaching are discussed to explain the measured trends.     

Synthesis of micromesoporous magnesium oxide cubes with nanograin structures in a supercritical carbon dioxide/ethanol solution

Micromesoporous magnesium oxide architectures with cubic morphologies were prepared via the chemical reaction of magnesium hydroxide in a supercritical carbon dioxide (CO2)-ethanol system, and via the sequential thermal combustion of the reaction products. The morphological change to the cube shape from an irregular form was induced by the dehydoxylation-carbonation reaction of magnesium hydroxide with supercritical CO2 at a reaction temperature of 150 degrees C, which leads to the greatly improved carbonation efficiency of magnesium hydroxide to magnesium carbonate. The precursor cubes with 3-5 microm sizes were decarbonized and transformed into the nanocrystalline MgO phase with pore sizes of 1.3-6 nm after calcining at 600 degrees C. The micromesoporous cube with high surface area of 117.5 m2/g was obtained by the thermal decarbonation with phase transition from rhombohedral to cubic phase. As a result, nanograined magnesium oxide cubes with micromesoporous structures and high specific surface areas were formed by the carbonation reaction of the magnesium hydroxide with the supercritical CO2, and the subsequent thermal decomposition of the magnesium carbonate cubes.     

纳米氢氧化镁阻燃剂的研究进展

近年来纳米氢氧化镁阻燃剂越来越受到人们的关注。综述了氢氧化镁的结构及阻燃机理，对氢氧化镁阻燃剂制备过程中的高纯度、超细化、表面极性的改进及团聚问题作了比较详细的阐述，并对今后国内的研究方向提出了建议。     

用水氯镁石制备单分散六角片状氢氧化镁

用水氯镁石为原料,氢氧化钠为沉淀剂,常压下合成氢氧化镁,在不加入任何改性剂的条件下,对反应后的料浆进行水热处理,并用扫描电镜（SEM）、X射线衍射仪（XRD）和激光粒度仪表征所得产品的形貌、结构及粒度分布,主要考察了水热反应时间和水热反应温度对氢氧化镁产品的影响.结果表明：在120℃水热4h条件下的过滤速率是未经水热条...     

Einfluss der chemischen Umgebung auf Morphologie und Struktur von Magnesiumhydroxid auf Magnesiumoberflächen

Influence of the Chemical Environment on the Morphology and Structure of Magnesium Hydroxide formed on Magnesium Surfaces Successful application of magnesium in metal construction is promoted by available methods for surface protection and, if needed, an electrical isolating layer between magnesium and other construction metals of composite materials [1]. Suitable materials for surface protection are polymer coatings, e. g. polymer paints. These coatings require a sufficiently corrosions resistant ground, which up to now normally is a environmentally dangerous, chromium‐containing conversion layer. In case of destruction of a conversion layer, caustic magnesium hydroxide is formed and responsible for a promoted delamination of various commercial polymer paints. Thus, development of a new magnesium – polymer – systems is of great interest. One probably successful possibility is a defined chemical attachment of molecular adhesion promoters to the magnesium conversion layers. These adhesion promoters should include a magnesium hydroxide specific group for a strong chemical attachment to magnesium conversion layer, which is hydrolytically stable in water, and additionally a second adhesive group at the other end of a hydrophobic spacer to ensure the attachment of a polymer. Direct attachment of these molecular adhesion promoters onto magnesium metal is not promising as all known magnesium organic compounds are hydrolytically instable [2]. As the hydroxide conversion coating is a substantial part of a magnesium‐polymer‐composite, the properties of the magnesium hydroxide layer have to be investigated and optimized depending on preparation conditions. In order to characterize the magnesium hydroxide conversion layer we use IR‐spectroscopy, quartz microbalance and Scanning Probe Microscopy. IR‐spectroscopic investigations show the presence of water in hydroxide conversion coatings formed at pH = 7–10. Conversion coatings prepared at pH > 12 are spectroscopically free of water. Taking into account the isoelectric point and the reactions resulting from a pH change, a model for the formation of the hydroxide layer is presented. This model explains the formation of a water free hydroxide layer at pH levels above 12 and the formation of water containing hydroxide layers below pH 12. The topography of the conversion layers is investigated by Scanning Probe Microscopy. If the conversion layer is formed in a solution with low pH a rough structure is built up compared to conversion layers, which are formed in solutions with high pH. These differences can be explained by taking into account the solubility of magnesium hydroxide and the change of OH⁻‐concentration in the solution due to different pH.     

硅丙乳液包覆Mg(OH)2核壳结构纳米粒子的制备与表征

为有效提高Mg(OH)_2纳米粒子在硅丙乳液中的相容性与分散稳定性,在油酸修饰Mg(OH)_2纳米粒子的基础上,以甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸与乙烯基三乙氧基硅烷为共聚单体,通过乳液聚合法制备出具有核壳结构的硅丙乳液包覆Mg(OH)_2复合材料。利用傅里叶变换红外光谱仪(FTIR)、X射线衍射仪(XRD)、透射电子显微镜(TEM)等测试手段对样品结构、形貌进行了表征。通过燃烧实验,研究了硅丙乳液包覆Mg(OH)_2纳米粒子对水性防火涂料阻燃性能的影响。结果表明,油酸通过酯化作用修饰在Mg(OH)_2纳米粒子表面,借助油酸分子中双键结构,丙烯酸类混合单体在纳米Mg(OH)_2表面完成聚合过程,形成以Mg(OH)_2纳米粒子为核、硅丙乳液为壳的复合材料。XRD与热分析表明经硅丙乳液包覆的纳米Mg(OH)_2晶体结构与热稳定性能未受影响。此外,掺杂0.1%(质量分数)的硅丙乳液包覆Mg(OH)_2可使水性防火涂料阻燃时间延长至113 min,较未掺杂水性涂料阻燃时间(91min)提高约23%。