纳米氢氧化铝包覆超细红磷粉末研究

介绍了一种纳米氢氧化铝包覆超细红磷粉末的简易制备方法,其关键步骤是:高能球磨得到的红磷颗粒必须经过水力浮选,浮选得到的红磷颗粒尺寸在100~200 nm,呈类球形;浮选得到的红磷颗粒再进行纳米氢氧化铝包覆。包覆后的产物用扫描电镜(SEM)、紫外-可见分光光度计(UV-Vis)以及差热分析仪(DSC-TG)进行表征。结果表明,红磷的颜色成功地被纳米氢氧化铝所掩盖。产物在阻燃领域具有应用前景。     

用氯化钠制备纳米超细非晶二氧化硅微粒的研究

本文报导了用氯化钠制备纳米超细非晶二氧化硅微粒的方法。探讨了纳米超细非晶二氧化硅微粒的结构特征及其影响因素。     

高浓度水热法制备改性纳米氢氧化铝及流变性能

从流变学角度对高浓度水热法制备改性纳米氢氧化铝(MATH)进行了研究。流变研究结果表明:纳米氢氧化铝(ATH)悬浮液是黏度极高的时变性非牛顿流体,其黏度随质量分数增加而显著增加。在酸性条件下,采用流变的方法筛选出对纳米ATH悬浮液有明显降黏作用的改性聚合物分散剂。将改性聚合物分散剂添加在高浓度ATH水热改性反应中,纳米ATH悬浮液的最大固含量从78g/L提高到293g/L,成功制备出了超薄菱形、热失重温度超过350℃、热失重率约为50%的改性纳米氢氧化铝。     

FeSiBPCu系非晶纳米晶合金的制备及软磁性能的研究

主要采用元素替代的方法对合金进行成分设计,应用单辊旋淬法和非晶晶化法制备了六种Fe_(83)Si_4B_(12-x)P_xCu_1(x=0,2,4,6,8,10)非晶纳米晶合金。利用X射线衍射(XRD)并结合差示扫描量热法(DSC)表征了非晶态软磁合金的非晶形成能力、热稳定性、晶化过程。采用振动样品磁强计(VSM)测量非晶合金和纳米晶合金的磁性能,系统研究了合金元素和退火工艺对非晶纳米晶软磁合金结构和性能的影响,获得了具有高饱和磁化强度和低矫顽力的软磁合金材料。     

超重力法制备超细改性氢氧化铝的中试实验研究

采用超重力碳分联合水热改性的方法制得到超细改性氢氧化铝(ATH).讨论了超重力及水热和成法制备超细改性ATH从小试到中试的实验,分析了放大准则并对各个过程的产品作TEM表征及TG测试.结果显示放大过程中未产生对产品性能有不利影响.100t/a的中试得到了粒径相对较小的氢氧化铝阻燃剂,其失重曲线的特征是产品的失重(脱水)在330℃之后,300℃到500℃的整体失重率达到48%～51%.     

氢氧化铝表面改性及在高抗冲聚苯乙烯中的应用

选用钛酸酯偶联剂对高性能纳米氢氧化铝(ATH)进行表面改性,以改善其在高抗冲聚苯乙烯(HIPS)中的分散性。利用透射电镜(TEM)和傅立叶红外光谱仪(FTIR)表征了高性能纳米氢氧化铝的改性效果,研究了改性条件对高性能纳米氢氧化铝/高抗冲聚苯乙烯复合材料性能的影响。结果表明,在偶联剂质量分数1.5%,改性时间20 min,改性温度85℃的条件下,高性能纳米氢氧化铝/高抗冲聚苯乙烯复合材料的综合性能较好。改性后高性能纳米氢氧化铝的分散性得以有效的改善,其表面确实包覆了偶联剂分子。     

非晶Sm-Co溅射膜的垂直各向异性

非晶稀土(RE)-过渡金属(TM)膜的一个共同特征是具有单轴各向异性,这个单轴各向异性的强度和取向,主要取决于非晶膜的成分、基片温度和膜的制造方法。非晶Sm_(25)Co_(75)溅射膜在控制溅射条件下可获得大的垂直各向异性。非晶膜的磁各向异性的起源可以有若干个机构,主要有磁各向异性微结构和原子对有序(短程有序)机构等。本文具体讨论了非晶Sm-Co溅射膜的垂直各向异性的来源可能有三个方面:(1)柱状微结构的形状各向异性;(2)负偏压的作用导致原子对有序和柱状微结构的细化;(3)垂直静磁场感生的垂直单轴各向异性。     

类海胆形二氧化钛纳米晶的制备及生长过程研究

用水热法制备了由纳米棒自组装生长的类海胆形状的TiO_2纳米晶,所得产物经X射线粉末衍射(XRD)和扫描电子显微镜(SEM)表征,证实了类海胆形状微结构是由纳米棒组成的。根据不同反应时间得到的产物形貌推测了类海胆形状微结构的形成过程。     

超细氢氧化铝对天然橡胶性能影响的研究

研究了超细氢氧化铝表面处理前后对天然橡胶力学性能及阻燃性能的影响.结果表明,天然橡胶中单用超细氢氧化铝作为阻燃剂时,需要大量填充才能达到较好的阻燃效果,当超细氢氧化铝添加量超过150份时,垂直燃烧能达到阻燃FV-0级别,氧指数超过29％,但此时硫化胶的力学性能较差.通过对超细氢氧化铝进行表面处理的方式,可在保证阻燃性能...     

阻燃剂配比和添加量对PE基木塑地板性能的影响

以聚乙烯(PE)、橡胶木木粉、氢氧化铝制备阻燃型木塑地板。通过测试物理力学性能和燃烧性能,研究了纳米氢氧化铝添加量、纳米氢氧化铝与非纳米氢氧化铝配比对木塑地板24 h吸水率、弯曲破坏载荷、氧指数、烟密度等级的影响。结果表明,当纳米氢氧化铝的质量分数从5%增加到15%时,木塑地板24 h吸水率降低23.2%、弯曲破坏载荷呈先增加后减小的趋势、氧指数上升16.69%、烟密度等级呈先减小后增加的趋势;随着纳米氢氧化铝与非纳米氢氧化铝配比的增加,木塑地板24 h吸水率降低28.6%、弯曲破坏载荷增加4.5%、氧指数上升8.5%、烟密度等级下降19.5%。     

用弗雷德盐沉降去除水体中镉的絮凝形态

用微/纳结构的弗雷德盐乳液作吸附-絮凝剂以絮凝法去除水体中重金属镉。结果表明,弗雷德盐絮凝沉降镉的去除率达97.8%。背散射与点能谱的研究表明,弗雷德盐在水处理过程中经历了溶解-再结晶,形成稳定性更高的六方柱形方解石和无定型氢氧化铝。水体中部分镉离子吸附或共沉淀在六方柱形方解石表面;另有部分镉离子吸附或共沉淀在水解生成的无定形氢氧化铝胶体中。XRD谱图比较证实,还有部分镉以类质同象取代方解石中的钙进入晶格。     

立方形氧化铝的合成与表征

1.0 g碱式碳酸镁为碱源,在110℃加入15 mL氨水,通过20 g过量硫酸铝的均匀共沉淀反应,制备出了粒径约为500 nm的立方形Al(OH)3。对获得的Al(OH)3在不同温度进行焙烧,结果发现,450~600℃焙烧出的样品为无定形氧化铝;850℃焙烧的样品为κ-、θ-和η-Al2O3的混合物;当温度高于1 200℃时,得到纯相的α-Al2O3。通过SEM和TEM对焙烧前后的样品进行观察显示,样品的形貌不受温度的影响,均为立方形。     

白云石制备的纳米氢氧化镁的性能及其影响因素

探讨了白云石碳化法制备纳米级氢氧化镁的工艺条件,研究了沉淀剂、反应温度对纳米级氢氧化镁形貌的影响,以及表面活性剂对纳米级氢氧化镁分散性的改善,并对反应机理进行了阐述.结果表明:以氨水为沉淀剂所得的纳米氢氧化镁近似六边形的薄片状,平均粒径为16nm,其结构稳定性优于以氢氧化钠为沉淀剂的产品.当反应温度为30℃时,Mg(OH)_2形成细小晶核,薄片的厚度为5～7nm,晶粒粒径为10～15nm;反应温度为50℃时,晶核开始生长为大晶粒,但排列无规则;反应温度为70℃时,Mg(OH)_2薄片的厚度增至10nm左右,晶粒粒径为10～20nm,具有规则排列的完整晶粒:反应温度为80℃时,Mg(OH)_2晶粒具有不规则排列.加入表面活性剂聚乙二醇或十二烷基硫酸钠可以提高纳米粒子的分散性.当表面活性剂聚乙二醇用量为氢氧化镁的3.0%(以质量计,下同)时,纳米氢氧化镁的分散性最好,片层的厚度约为10 nm,平均粒径为20 nm.当表面活性剂十二烷基硫酸钠用量为氢氧化镁的4.0%时,纳米氢氧化镁具有较好的分散效果,平均粒径为20nm.     

Nanostructural characterization of Al(OH)3 formed during the hydration of calcium sulfoaluminate cement

Ye'elimite (Ca₄Al₆SO₁₆) is a main mineral in calcium sulfoaluminate cements. Aluminum hydroxide is one of the products formed by hydration of ye'elimite. To characterize this phase, various aluminum hydroxides were synthesized from their chemical constituents using sol‐gel processing and compared with the aluminum hydroxide formed during the hydration of ye'elimite. The nanostructure of aluminum hydroxide formed during the hydration of ye'elimite was investigated in detail using X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, inductively coupled plasma optical emission spectroscopy, and ²⁷Al magic angle spinning nuclear magnetic resonance spectroscopy. No evidence was observed that indicated the existence of amorphous aluminum hydroxide in the hydration of ye'elimite. The pH values, thermogravimetric analysis, particle morphology, and Al‐O coordination indicated that the aluminum hydroxide from the hydration of ye'elimite had a crystal‐like structure. The X‐ray diffraction analysis, particle sizes, and ion activity product showed that the aluminum hydroxide from the hydration of ye'elimite had a microcrystalline structure.     

Microstructure of amorphous aluminum hydroxide in belite-calcium sulfoaluminate cement

Belite-calcium sulfoaluminate (BCSA) cement is a promising low-CO₂ alternative to ordinary Portland cement. Herein, aluminum hydroxide (AH₃), the main amorphous hydration product of BCSA cement, was investigated in detail. The microstructure of AH₃ with various quantities of gypsum was investigated via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The AH₃ with various morphologies were observed and confirmed in the resulting pastes. Particular attention was paid to the fact that AH₃ always contained a small amount of Ca according to the results of EDS analysis. The AH₃ was then characterized via high resolution transmission electron microscopy (HRTEM). The results of HRTEM indicated that Ca arose from nanosized tricalcium aluminate hexahydrate which existed in the AH₃.     

Production of Nanosized YAG Powders with Spherical Morphology and Nonaggregation via a Solvothermal Method

Monodispersed nanosized yttrium aluminum garnet (YAG) powder was synthesized via a mixed-solvent thermal method using stoichiometric amounts of inorganic aluminum and yttrium salts. Pure-phase YAG crystalline powder was obtained at low temperature (290°C) and low pressure (10 MPa). The resulting products were characterized by X-ray powder diffraction (XRD), infrared, and transmission electron microscopy (TEM). XRD results showed that single-phase YAG could be formed directly from an amorphous precursor at 280°C and become fully developed at 290°C. TEM images showed that the YAG powder particles in the study were basically spherical in shape and well-dispersed with a mean grain size of about 60 nm.     

Effects of Acidification on Dewaterability and Aluminum Concentration of Alum Sludge

This study utilizes the Terzaghi-Voigt model to characterize the effects of acidification on the dewaterability of alum sludge. Alum sludge, which was obtained from the sedimentation basins of a water treatment plant using poly aluminum chloride as coagulant, was acidified to different pH levels with sulfuric acid. The dewaterability of the acidified sludge was characterized by expression tests. The results show dewaterability enhancement was insignificant until pH was below 4. Further improvement in dewaterability can be achieved by polymer conditioning. The Terzaghi-Voigt model can be applied to explain the difference in dewaterability between acidified and original sludges. Results also show dissolved aluminum concentrations were controlled by minerals in the influent rather than amorphous aluminum hydroxide.     

Processing and kinetics studies on the alumina enrichment of coal fly ash by fractionating silicon dioxide as nano particles

Coal fly ash produced in the northern China is a potential bauxite substitute for aluminum production because of its high alumina content. However, this industrial application has been limited for its high silicon content. Alumina enrichment by removing silicon becomes a key technology for its utilization. A novel process was developed to fractionate the coal fly ash into high purity nano silicon particles and aluminum enriched residual ash. The procedure has major steps as sodium silicate dissolution with sodium hydroxide, first carbonation to remove impurities, second carbonation to precipitate silicon, and silicon precipitate recovery as a mesospheric nano particles product. Morphological and X-ray diffraction evidences indicated the glassy amorphous silicon content of the ash was dissolved in the sodium hydroxide solution whereas mullite remained in the residue. Kinetics study indicated that the second carbonation was a kinetically second order medium fast multi-phase reaction in which sodium silicate was precipitated as silicic acid. It was found that the reaction was controlled by the mass transferring resistance in the liquid membrane. These nano silicon dioxide particles were in size of 50 nm with a purity of 96%. Alumina content in process residue was slightly increased from 42.00 to 49.20%. Silicon dioxide content was reduced from 48.89 to 30.26%. Ratio of alumina/silica was increased from 0.86 to 1.63.     

供水管道中含铝管垢的形成机理及其结构组成

该文探讨了供水管道中铝的来源及其在管道内壁蓄积沉淀形成含铝管垢的机理。重点介绍了无定形氢氧化铝、硅铝酸盐、镁铝酸盐和磷酸盐等典型含铝管垢在给水管网中的形成条件和结构特征;为了减少输配水过程中铝的蓄积释放,保障管网稳定运行和居民饮水健康,建议通过水质调节措施来控制管网中含铝管垢的生成量;最后指出了今后的研究方向。     

Abstracts from Naihuo Cailiao (Refractories)——A Chinese-Language Bimonthly

Synthesis of MeAl2O4 spinel from mechanically ac-tivated mixtures of magnesium hydroxide-boehm-ite or-aluminum tri-hydroxide.Ye Guotian,GeorgeOprea,Tom Troczynski.(321-325).Magnesium alu-minate spinel.Mechanical activation,Synthesis-Magne-sium hydroxide,boehmite and amorphous aluminum tri-hydroxide were used as the starting materials.