均匀沉淀水热法三维花球微/纳米Sm2O3的合成与表征

本文以六次甲基四胺(Hexamethylenetetramine, C6H12N4)和六水合硝酸钐[Sm(NO3)3·6H2O]为原料,采用均匀沉淀水热法合成Sm2O3前驱体Sm(OH)3,利用热重(TG)和X射线衍射(XRD)分析方法确定了得到微/纳米Sm2O3的适宜焙烧温度为800 °C。前驱体Sm(OH)3经800 °C焙烧后得到微/纳米Sm2O3,利用XRD和扫描电子显微镜(SEM)对产物的晶型、形貌及尺寸进行了表征。考察了反应时间、反应温度对产物形貌和尺寸的影响。结果表明：制得的微/纳米Sm2O3及其前驱体Sm(OH)3分别为立方和六方晶相结构;随着反应时间的增长,微/纳米Sm2O3的形貌由片状逐渐自组装为三维花球;随着反应温度的升高,微/纳米Sm2O3三维花球的粒径逐渐增大,组成三维花球结构的纳米片逐渐变厚且组装更加紧密。     

利用铅锌废渣制备纳米ZnO的试验研究

以铅锌废渣为锌源,通过浸取、除杂、蒸发、干燥和焙烧等步骤制备纳米ZnO.ZnO前驱体的X射线衍射(XRD)、红外光谱分析(IR)、热重(TGA)和差热分析(DSC)分析表明:ZnO 前驱体是无定型碱式碳酸锌(Zn5 (CO3)2(OH)6),加热过程中它先分解成ZnO和Zn(OH)2,然后Zn(OH)2进一步分解成ZnO.焙烧产物的XRD、扫描电镜(SEM)和粒度分析显示:在400 ℃的温度下下焙烧时,ZnO前驱体分解产物是红锌矿(ZnO)和Ashoverite (Zn(OH)2);在500 ℃和600 ℃焙烧时,前驱体完全转化为红锌矿,其形貌不规则,但是前驱体在500 ℃焙烧时,产物ZnO的粒径较小,主要分布在80~150 nm,在600 ℃焙烧时,产物的颗粒团聚严重.     

Glycothermal法制备钛酸铋镧纳米晶

以分析纯Bi2O3、La2O3、TiCl4为原料,NaOH为矿化剂,通过Glycothermal法制备了具有板状形貌的钛酸铋镧(BLT)纳米晶。采用X线衍射(XRD)和场发射扫描电镜(FESEM)等测试手段对纳米晶的微结构进行了表征,并研究了醇水体积比、反应时间和矿化剂加入量等因素对晶粒尺寸、形貌及结晶性的影响关系。结果表明:BLT纳米晶尺寸随醇水体积比增加而减小;随着反应时间的延长,晶粒尺寸与结晶度逐渐增大;随着矿化剂量的增加,晶粒宽厚比逐渐增大。当醇水体积比为1∶5、反应时间为24 h、矿化剂引入量为0.266 mol/L时,BLT纳米晶宽厚比可达2.67。     

不同水热条件下氧化镧的制备和表征

以硝酸镧溶液为原料,以聚乙二醇800为分散剂,用六次甲基四胺作沉淀剂,经水热反应制取前驱体,再经焙烧制得纳米氧化镧。考察了不同水热条件,如水热温度,反应时间,前驱物浓度和冷却方式对制备产品形貌的影响,采用XRD和TEM对粉体进行了表征。结果表明,氧化镧颗粒随着水热温度的提高,反应时间的增长以及前驱物浓度的提高而逐渐长大,团聚现象逐渐加剧;自然冷却方式较之骤冷的方式更加有利于形成小颗粒的氧化镧产品。     

NiO纳米晶的机械化学合成及其电化学性能

以NaCl为稀释剂,NaOH,NiCl2.6H2O为原料,采用固相机械化学反应制备Ni(OH)2前驱体。前驱体经焙烧可制得呈面心立方晶型的黑色NiO纳米晶粉末。用差热/热重分析前驱体的热处理过程,X射线衍射表征样品的结构,透射电镜(transmission electron microscope,TEM)观察粉末的形貌特征。TEM观察表明:产物为立方形颗粒,颗粒平均尺寸在80 nm左右,呈现良好的单分散性。用循环伏安法测试NiO的电化学性能,并计算其比电容值,考察前驱体焙烧温度对所得NiO电极的电化学性能的影响。研究发现:400℃处理所得NiO纳米材料在同一扫描速率下的充放电电流最大,比电容值最大,当扫描速度为1 mV/s时其比电容值可达209.32 F/g。     

微乳-沉淀法制备纳米尖晶石型MgFe_2O_4及表征

首先对油包水 (W/O)型微乳液进行了制备研究 ,探明了一定条件下W/O型微乳液中的最大增溶水量。进而利用W /O型微乳液作为“微反应器”并用沉淀法制备Mg(OH) 2 Fe(OH) 3 复合氢氧化物 ,最后将此复合氢氧化物进行高温固相反应、晶化制得了纳米尖晶石型MgFe2 O4 。通过XRD、TEM及颜色测量 ,对纳米MgFe2 O4 进行了表征 ,探讨了纳米粒子的量子尺寸效应     

超声喷雾热解法制备超细ZnO粉体的研究

以六水合硝酸锌为原料,采用超声喷雾热解法制备了Zn O超细粉体。采用X射线衍射仪(XRD),扫描电子显微镜(SEM)等表征手段对所制备产物进行表征,并探讨了反应温度、前驱体浓度对Zn O尺寸和形貌的影响。结果表明:在反应温度为800℃、前驱体浓度为0.4 mol/L的条件下,所得到的产物粒径分布较窄且颗粒的球形度较好。     

纳米铁磁性合金包裹氧化铝复合微球的制备

用非均相沉淀法制备了CoFe,CoNi,CoFeNi包裹氧化铝3种微球前驱体,在还原气氛中于720 ℃焙烧2 h获得了包裹层颗粒分布均匀的纳米多元铁磁性合金/氧化铝复合微球.利用红外光谱、扫描电镜、能量散射光谱仪、X射线衍射仪对前驱体及热还原产物的成分、结构及形貌进行了表征,还分析研究了前驱体热分解过程.结果表明:包裹层CoFe,CoFeNi合金粒子的平均粒径为70～80 nm,CoNi合金粒子小于50 nm.前驱体的包裹层分别为无定型Fe2O3·nH2O,NiCO3·2Ni(OH)2·2H2O,Co2(OH)2CO3的混合物,热处理后这些无定型结构分别转变成了CoFe,CoNi和CoFeNi固溶体合金.     

甘露醇-硝酸铝溶液燃烧法制备γ-Al_2O_3纳米粉体

以九水硝酸铝,甘露醇和氨水的混合溶液作为前驱体溶液,采用溶液-燃烧法直接焙烧一步合成纳米γ-Al2O3。利用XRD、TEM和N2吸附-脱附等方法对最终形成的氧化铝进行了表征。结果表明,九水硝酸铝与甘露醇物质的量之比为26:15,前驱体溶液的p H值为4,焙烧温度为800℃,焙烧时间为4 h,在此条件下,可制备出蓬松且晶粒尺寸在4~6 nm之间的γ-Al2O3纳米粉体。     

EDTA-柠檬酸络合法制备葡萄状硅酸钇纳米晶

分别以硝酸钇(Y(NO3)3·6H2O)和正硅酸乙酯(TEOS)为起始原料,首次尝试采用乙二胺四乙酸(EDTA)-柠檬酸(CA)络合法制备合成硅酸钇(Y2Si2O7)纳米晶陶瓷粉体,研究并讨论了样品前驱体pH值和烧结温度等工艺参数对硅酸钇粉体微观形貌及其合成机理的影响.利用XRD、FE-SEM、T-IR和TGA-DTA等分析方法对制备的样品进行了表征.结果表明,在前驱体溶胶pH值为9.38、煅烧温度为1050℃时的工艺条件下,可以得到晶粒尺寸为50 nm左右、主要组成为α-Y2Si2 O7相硅酸钇粉体;粉体晶粒尺寸随烧结温度升高而增大,且粉体晶粒形貌为葡萄状的组织结构;而在前驱体溶胶pH值为4.00时,采用该方法合成的产物则是物相组成为单硅酸钇(Y2 SiO5)陶瓷粉体.     

Effect of sintering temperature on the morphology,crystallinity and mechanical properties of carbonated hydroxyapatite (CHA)

Effect of sintering temperature on the physical and mechanical properties of synthesized B-type carbonated hydroxyapatite (CHA) over a range of temperature in CO₂ atmosphere has been investigated. The B-type CHA in nano size was synthesized at room temperature by using a direct pouring wet chemical precipitation method. The synthesized CHA powders were subsequently consolidated by sintering treatment from 800 to 1100 °C. The sintered CHA samples were evaluated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, X-ray fluorescence (XRF), carbon-hydrogen-nitrogen-sulfur-oxygen (CHNS/O) elemental analyzer, Field emission scanning electron microscopy (FESEM), and Vicker's indentation technique. The results obtained from XRD and FESEM indicated that the synthesized B-type CHA powders were nanometer in size. The crystallinity and crystallite size of the sintered CHA samples were increased due to increasing sintering temperature. The heat treatment between 800 °C and 1000 °C has resulted in coarsening and increased hardness of the sintered CHA samples. However, these properties began to deteriorate when sintering beyond 1100 °C due the formation of calcium oxide.     

Preparation and Characterization of Nano‐TATB Explosive

Nano‐TATB was prepared by solvent/nonsolvent recrystallization with concentrated sulfuric acid as solvent and water as nonsolvent. Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) were used to characterize the appearance and the size of the particles. The results revealed that nano‐TATB particles have the shape of spheres or ellipsoids with a size of about 60 nm. Due to their small diameter and high surface energy, the particles tended to agglomerate. By using X‐ray powder diffraction (XRD), broadening of diffraction peaks and decreasing intensity were observed, when the particle sizes decreases to the nanometer size range. The corrected average particle size of nano‐TATB was estimated using the Scherrer equation and the size ranged from 27 nm to 41 nm. Furthermore, the specific surface area and pore diameter of nano‐TATB were determined by BET method. The values were 22 m²/g and 1.7 nm respectively. Thermogravimetric (TG) and Differential Scanning Calorimetric (DSC) curves revealed that thermal decomposition of nano‐TATB occurs in the range of 356.5 °C–376.5 °C and its weight loss takes place at about 230 °C. Furthermore, a slight increase in the weight loss was observed for nano‐TATB in comparison with micro‐TATB.     

Nano‐sized silica supported Me2Si(Ind)2ZrCl2/MAO catalyst for ethylene polymerization

Nano‐sized and micro‐sized silica particles were used to support a zirconocene catalyst [racemic‐dimethylsilbis(1‐indenyl)zirconium dichloride], with methylaluminoxane as a cocatalyst. The resulting catalyst was used to catalyze the polymerization of ethylene in the temperature range of 40–70°C. Polyethylene samples produced were characterized with scanning electron microscopy (SEM), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). Nano‐sized catalyst exhibited better ethylene polymerization activity than micro‐sized catalyst. At the optimum temperature of 60°C, nano‐sized catalyst's activity was two times the micro‐sized catalyst's activity. Polymers obtained with nano‐sized catalyst had higher molecular weight (based on GPC measurements) and higher crystallinity (based on XRD and DSC measurements) than those obtained with micro‐sized catalyst. The better performances of nano‐sized catalyst were attributed to its large external surface area and its absence of internal diffusion resistance. SEM indicated that polymer morphology contained discrete tiny particles with thin long fiberous interlamellar links. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Evolution of phase composition and microstructure of commercial Al2O3 gel in different heat treatment condition

Evolutions of phase composition and microstructure of commercial Al₂O₃ gel in different heat treatment conditions (temperature, atmosphere and additives) were investigated. There was almost no effect of atmosphere and carbon additive on phase evolution of Al₂O₃ gel during heating, γ-Al₂O₃ formed at 800?°C, γ-Al₂O₃ and minor θ-Al₂O₃ co-existed at 1000 °C, and single phase of ɑ-Al₂O₃ occurred at heating temperature ≥1200?°C. Atmosphere and carbon had great effects on morphology and crystal size of Al₂O₃ particles. Crystal size of spherical-shape Al₂O₃ particles was 10–20?nm after heating at 800–1000?°C in air, afterwards, they rapidly grew into micro or macro scale when temperature was above 1200?°C, and sintering phenomena of worm-like Al₂O₃ particles were observed. In the presence of carbon, spherical-shape Al₂O₃ particles grew slightly from 10 to 20?nm to 50–60?nm with the temperature increasing from 800?°C to 1500?°C in reducing atmosphere, carbon inclusions in Al₂O₃ grain boundaries triggered a steric hindrance of Al₂O₃ particles growth. Al₂O₃ gel had a high reactive ability and could react with microsilica to form nano mullite crystals at relatively lower temperature.     

Sol-Gel synthesis and characterization of SiC–B4C nano powder

In the present research, SiC–B₄C nano powders were synthesized through sol–gel process in water–solvent–catalyst–dispersant system. In order to evaluate the formation mechanism of the product during sol-gel process, TEM, SEM, DTA/TG, BET, XRD, FTIR and DLS analysis methods were employed. The nanometric size of precursor was controlled by dispersing agents and controlling pH inside the sol. DLS analysis revealed that the particles of the precursor inside the sol were below 10 nm. FTIR results indicated that the (Si–O–B) bonds were formed in the dried gel powder, due to hydrolysis and condensation reactions. DTA analysis confirmed that the synthesis temperature was lower than 1400 °C. XRD results implied the presence of cubic β-SiC and the rhombohedral B₄C phases, which were formed simultaneously in the SiC–B₄C nanopowder. BET analysis indicated a high surface area for the particles of about 171.42 m²/g, and that the surfaces of these particles were meso porous. SEM analysis exhibited that SiC– B₄C particle size was in the range of 20–40 nm with homogenous morphology. Ultimately, the TEM/EDS microstructural analysis showed that B₄C and SiC particles were formed simultaneously and uniformly in the final product.     

Catalytic Oxidation of CO Over Synthesized Nickel Ferrite Nanoparticles from Fly Ash

Catalytic oxidation of carbon monoxide (CO) gas over nanosized nickel ferrites prepared from fly ash has been investigated. X-ray diffraction analyses showed that pure crystalline nickel ferrite, NiFe₂O₄, phase can be obtained by thermal treatment of the precursors at temperature >800 °C for 120 min in the studied pH range, from 7 (neutral) to 12 (highly alkaline). In the temperature range 500 ≤ T ≤ 800 °C, impure low crystalline NiFe₂O₄ phase formed. The main impurities are FeO (OH) and Fe₂O₃ · H₂O phases. Higher magnetization (32 emu/g) is obtained for a precursor precipitated at pH 10 and thermally treated at 1,200 °C for 120 min. The catalytic oxidation of CO over nanocrystalline NiFe₂O₄ powders was studied using quadrupole mass gas analyzer system. The main parameters as crystal size, surface area and firing temperature are used to clarify the efficiency of using NiFe₂O₄ powders in catalytic oxidation of CO. It was found that the efficiency of catalytic oxidation decreased by increasing firing temperature and crystallite size of the samples. The lower crystal size (2–8.5 nm), the higher surface area (25–55 m²/g) and the presence of impurities FeO(OH) phase enhanced CO adsorption and consequently its oxidation.     

Comparison of cure characteristics and mechanical properties of nano and micro silica‐filled CSM elastomers

In this study, the effect of micro and nano silica and their combination on mechanical and thermal properties of Chlorosulfonated Polyethylene compounds were investigated. Cure characteristics were studied using a Monsanto Moving Die Rheometer at 155°C. Incorporation of nano silica accelerated the vulcanization whereas the micro silica particles decelerated the curing process. Both micro and nano silica increased the crosslink density as evidenced by swelling test. However, this value has been more improved in CSM/nano silica composites. The physico‐mechanical properties of CSM/nano silica are superior compared to CSM/micro silica. Nano silica provided reinforcing efficiency which is not only because of higher specific surface area but also because of various interactions and especially physical interactions which are discussed in the text. Nano silica particles also improved the thermal properties more efficiently. Incorporation of 15 phr (part per hundred) nano and 5 phr micro silica to polymer improved the initial decomposition temperature for about 51°C and 16°C, respectively, using a TGA. The combination of micro and nano silica, showed that by coupling nano and micro fillers, the loading of fillers can be minimized. In other words, the hybrid samples with a lower filler loading behave as efficient as their separate counterpart with higher loading. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42668.