Ni(OH)2纳米粉体的制备及影响因素的控制

采用控制结晶法制备了Ni(OH)2纳米粉体.讨论了阴离子种类、pH值、加氨量等制备条件对Ni(OH)2纳米粉体性质的影响.应用XRD、TEM等微观分析手段对Ni(OH)2粉体的形态和结构进行了表征.结果表明在选择Ni(NO3)2为原料,溶液pH=11.0,加氨量控制在n(NH3)/n(Ni2+)=1.5,于50℃～60℃合成温度下反应30 min～40min,可获得晶型结构为β-Ni(OH)2,粉体颗粒的平均粒径为50nm～70 nm,形状为球形或类球形的纳米Ni(OH)2粉体.     

湿化学法合成纳米SnO_2:pH值和温度对颗粒尺寸和形貌的影响（英文）

用SnCl_2.2H_2O的水溶液为前躯体合成了纳米级SnO_2粉体,研究了pH和水解温度对纳米颗粒尺寸的影响。pH变化范围为2~10,温度从25℃到85℃变化,所得的样品分别用XRD、SEM和TEM进行了表征,分析结果表明,纳米粉体的颗粒尺寸受pH及温度的影响而颗粒形貌基本保持不变。猜测两种条件下颗粒长大的主要原因不同:改变pH值条件主要影响颗粒的团聚而水解温度的变化则影响晶粒长大过程。     

纳米晶(Gd,Lu)_2O_3:Eu粉体的合成及发光性能(英文)

通过燃烧法制备得到(Gd,Lu)203:Eu纳米粉体。利用傅里叶红外光谱仪,x射线衍射仪,高分辨透射电镜,激发和发射光谱来表征样品的结构和发光性质。结果表明,将燃烧法制备得到的粉体在800℃煅烧1h后,(Gd,Lu)203:Eu纳米粉体结晶为立方结构。通过增加硝酸盐(N)和甘氨酸(G)的摩尔比,经过煅烧的粉体颗粒的尺寸从15 nm增加到50nm,后又减小到40nm。而且发射光谱和激发光谱的性质比较依赖样品的颗粒尺寸。同时也发现,在此条件下制备得到的粉体非常适合制备(Gd,Lu)203:Eu的透明陶瓷。     

表面活性修饰沉淀法制备纳米铌钪酸铅

采用一种表面活性修饰沉淀法,成功地在700℃的低温下合成钙钛矿相Pb(Sc1/2Nb1/2)O3(PSN)纳米粉体。通过X射线衍射、扫描电镜、透射电镜等现代测试手段对纳米粉体进行表征。结果表明,PSN纳米粉体的晶粒尺寸在80nm左右。分析认为,纳米粉体的获得是由其前驱体的高分散性决定的,其原因在于四甲基氢氧化铵(TMAH)和十六烷基三甲基溴化铵(CTAB)的复合作用。对纳米PSN粉体的形成机制进行了详细讨论。本实验提出的表面修饰沉淀法为合成含铌钙钛矿多元化合物提供了一种新的低成本路径。     

水热法合成不同形貌纳米氧化钇粉体

以Y(NO)3为原料,在不同pH值条件下,采用水热法合成了氧化钇(Y2O3)前驱体,在不同温度下烧结得到了Y2O3纳米粉体。采用XRD、FT-IR分析前驱体的结构、成分,TG-DTG分析前驱体的热分解过程,FE-SEM分析前驱体及产物的形貌。结果表明:起始溶液pH值对前驱体的化学组成及Y2O3的形貌有显著的影响,随pH值的增大,前驱体及Y2O3的形貌由片状结构逐渐转变为棒状结构,煅烧温度对形貌影响不大。     

明胶网络凝胶法制备纳米镍锌铁氧体粉体

pH值对明胶网络凝胶法制备镍锌铁氧体纳米粉体具有决定性的作用,最佳pH值范围为9至11.加入添加剂可在较低的煅烧温度下使杂相消失并得到单相镍锌铁氧体产物.当明胶的用量由5%上升至20%(质量分数,下同)时,经700 ℃煅烧2 h后,产物晶粒由46 nm减少至10 nm,可通过改变明胶浓度的方法调控镍锌铁氧体的晶粒.镍锌铁氧体的比饱和磁化强度和矫顽力分别随粉体晶粒尺寸的增加呈先下降后上升的趋势.     

新型纳米磷酸铝致密陶瓷薄膜的制备与表征

在有机调整剂CTAB的作用下,将磷酸二氢铝溶液用氨水调节pH值在一定温度下合成纳米磷酸铝粉体,然后经高温烧结制得致密陶瓷薄膜.利用场发射扫描电镜(FESEM)表征了纳米磷酸铝的形貌特征和烧结后的陶瓷薄膜结构,热重(TG/DTA)分析了磷酸铝粉体烧结过程的失重和相转变吸放热过程,X射线衍射(XRD)分析跟踪了不同温度段烧结体系的组成变化趋势.结果表明,温度和pH值对磷酸铝纳米粉体的颗粒形貌和尺寸有较大的影响,纳米磷酸铝粉体在800℃左右即开始发生烧结,与普通磷酸铝陶瓷相比,烧结难度大大降低,同时烧结软化温度段相对较宽,利于针对不同应用体系进行烧结选择.FESEM表明,经1200℃烧结后形成的陶瓷薄膜与普通磷酸铝陶瓷膜相比具有很好的致密性,有利于发挥其在高温防护方面的作用.     

pH值和煅烧温度对Cu-Ni纳米合金的合成和特性的影响（英文）

用柠檬酸-凝胶法合成的前驱体制备Cu-Ni纳米合金。研究溶液初始pH值和煅烧温度对Cu-Ni纳米颗粒的成分、晶粒结构、纯度、形貌、均匀性和晶粒尺寸的影响。这两种参数对合成的纳米颗粒的晶粒结构、成分和晶粒尺寸都有很大的影响。溶液初始pH值为1时制备的Cu-Ni纳米合金不含杂质,在300、400和500℃煅烧分别得到Cu_(0.42)Ni_(0.58)、Cu_(0.45)Ni_(0.55)和Cu_(0.52)Ni_(0.48)。溶液初始pH值为1.6和3时,所得Cu-Ni纳米合金的晶粒尺寸随着煅烧温度的升高而增大。pH值为3时所得Cu-Ni纳米合金的Ni含量随着煅烧温度的升高而逐渐增加。     

溶胶-凝胶法低温制备氧化钒晶体（英文）

采用溶胶-凝胶法在大水体系下制备了V_2O5纳米晶体。利用X射线衍射仪(XRD)和透射电镜(TEM)时样品的结构与形貌进行了分析。结果表明:当pH3时,随着pH值减小,产物的结晶度越高,晶粒尺寸越大;当人(水:丙酮酸钒摩尔比)大于200时,W越大,产物结晶度越高,晶粒尺寸越大。当pH≤1和W≥200时,在低温50℃下,通过溶胶-凝胶法制备了V_2O_5·1.6H_2O晶体,在400℃热处理后得到了较纯的V2O5晶体,该晶粒平均尺寸约为8 nm。     

镧/镱共掺杂二氧化锡纳米粉体的制备与表征

以LaCl3.7H2O、Yb(NO3)3.6H2O、SnCl4.5H2O为原料,氨水为沉淀剂,PEG-600作分散剂,采用化学共沉淀法制备出了镧/镱共掺杂二氧化锡纳米粉体。考察了反应pH值、煅烧温度、镧掺杂量对镧/镱共掺杂二氧化锡粉体的物相和形貌的影响,对粉末的前驱体进行综合热分析(TG-DTA),利用X射线衍射(XRD)仪、扫描电镜(SEM)对最终产物的结构和形貌进行表征,优化得到共沉淀法制备的最佳条件:反应温度60℃,pH值为9,煅烧温度800℃,镧/镱/锡的摩尔掺杂比为0.5:1:8.5。     

Preparation and characterization of yttrium iron garnet (YIG) nanocrystalline powders by auto-combustion of nitrate-citrate gel

The nitrate–citrate gel exhibits auto-catalytic behavior, which can be used to synthesize nanocrystalline YIG powders. In this study, yttrium iron garnet (Y₃Fe₅O₁₂) nanocrystalline powders were prepared by a sol–gel auto-combustion process. The influence of metal nitrates to citric acid molar ratio (MN/CA) of the precursor solution on the combustion behavior and crystallite size of synthesized powders was investigated by scanning electron microscopy (SEM), thermal analyses (DTA/TGA) and X-ray diffraction (XRD). The results show that with increasing MN/CA value, the combustion rate increases and the single-phase YIG forms at a higher temperature. The crystallite size of the single phase YIG prepared with different MN/CA values and calcined at 800 °C for 3 h are in the range of 38–70 nm. In addition, the crystallite size of the powders increased with increasing the calcination temperature.     

Spark plasma sintering of high-toughness ZrO2 materials doped with yttrium

Zirconia powders doped with yttrium prepared by special liquid-phase precipitation method were sintered by spark plasma sintering (SPS) to obtain high performance samples.The microstructure,phase composition,and mechanical properties of the samples were studied.The results of X-ray diffraction (XRD),Raman spectrum,and transmission electron microscope (TEM) show that the phase is tetragonal.The powders with large surface area and high sintering activity,due to small crystallite size,could be densified at 1100℃.The highest relative density of the sample obtained at 1300℃ is higher than 99% (the tetragonal phase is 6.08 g/cm3).The Hv and Kic are 13.76 GPa and 15.4 MPa.m1/2,respectively.     

液料等离子热喷法制备Fe3+/TiO2纳米粉末

通过对液料等离子热喷前驱物添加掺杂成分实现了液料等离子热喷TiO2纳米粉末的掺杂改性,并利用TEM,XRD及XPS对其进行表征.结果表明,采用液料等离子热喷法可以制备Fe3 掺杂TiO2纳米粉末,所制备粉末形貌基本呈球形或近球形,粒径分布为10～35 nm,掺杂量小于2.0%时粉末为锐钛矿及金红石相混晶,Fd3 掺杂促进锐钛矿向金红石相的转变,掺杂量为10.0%时析出了Fe2Ti3O9相.Fe3 掺杂不会引起TiO2粒径的大范围波动.粉末中含有O,Ti,Fe和C等元素,Fe元素在TiO2中仍为 3价.     

纳米NiO-YSZ复合粉体原位合成及电极微结构修饰

采用氨水沉淀原位合成法制备了NiO-YSZ(Y_2O_3稳定的ZrO_2)复合粉体,通过XRD、FESEM研究了溶液pH值对粉体性能的影响,并用干压法和丝网印刷法将氢电极分为支撑层(500 μm)、过渡层(20 μm)和功能层(10 μm)三层进行梯度化制备,采用YSZ/SDC双层电解质,通过共烧结技术将SDC(Sc掺杂CeO_2)(6 μm)作为YSZ(4 μm)电解质和Ba_0.5Sr_0.5Co_0.8Fe_0.2O_(3-δ)(BSCF,20 ìm)氧电极的隔离层.结果表明,合成NiO-YSZ复合粉体的最佳pH值为8.5,粉体呈泡沫状团聚,NiO的平均晶粒粒径为13 nm,产率为94.5%.850 ℃时制备的单体SOEC在70%、80%和90% 3种水蒸气含量的氢电极气氛下,电解池在1.5 V的产氢速率分别为266、381和558 N·mL/cm~2·h.在850 ℃、90%水蒸气含量的氢电极气氛下,以0.33 A/cm~2恒流电解1 h前、后的电解电压分别为1.09和1.16 V,电解池具备较好的稳定性.     

Synthesis of hexagonal barium ferrite nanoparticle by sol-gel method

M-type Ba hexaferrites were successfully synthesized by sol-gel method. Several synthesizing factors, such as pH value, citric acid/metal ion ratio, and dispersion agent were mainly discussed. Fine and pure powders of BaFe12O19 were optimally synthesized under the conditions of the pH value is 7 and citricacid/metal ion ratio is 3. The X-ray diffraction analysis demonstrates that no impurity is observed in the synthesized powders after presintered at 450 ℃ and calcinated at 1100 ℃. SEM observations indicate that the size of the synthesized BaFe12O19 powders is small and uniform distribution. It can also be learned from SEM that the co-synthesizing sol-gel method can be in favor ofthe formation of finer particles.     

Solid-state synthesis and spark plasma sintering of SrZrO3 ceramics

SrZrO₃ powders are obtained by solid state reaction from SrCO₃ and ZrO₂ precursors, without involving intermediate calcination and grinding steps. The resulted powders are essentially within a single phase, with sub-micron average crystallite size. Pellets of these powders show a relatively poor sintering behavior, when fired up to 1600 °C. Alternatively, spark plasma sintering technique is used in order to obtain nearly 100% dense samples at the expense of excessive grain coarsening (i.e., up to 5 μm in diameter). Crystalline structure, composition and morphology of the specimens obtained in this work are investigated by X-ray diffraction, scanning and transmission electron microscopy together with energy dispersive X-ray spectroscopy.     

纳米级ITO粉体对烧结法制备靶材的影响

采用化学共沉淀法制备ITO前驱物,分别于600及1000℃下热处理前驱物,得到两种ITO粉体.粉体模压成型得到素坯,在400～1550℃内采用烧结法、氧气氛下烧结素坯制备出ITO靶材.对粉体及靶材进行表征和分析,研究了烧结过程中晶粒生长情况、靶材微结构与温度之间关系及靶材的失氧现象.得出600℃粉体为单相ITO固溶体、粒径为15 nm,1000℃粉体有少量SnO2析出、粒径为28 nm且其分散性和晶化程度优于600℃的粉体.两种粉体烧结制备靶材过程符合Coble固相烧结理论,1550℃时晶体出现类似二维成核生长方式的生长台阶.靶材密度随温度升高而增加,1550℃时随保温时间延长而增加.靶材致密化过程由团聚程度及团聚体大小决定,1000℃粉体制备的靶材密度高于600℃粉体所制靶材.两类靶材含氧量均低于理论值,1000℃粉体所制靶材含氧量高于600℃的含氧量.     

Synthesis and characterization of W-Cu nanopowders by a wet-chemical method

A wet-chemical process was employed to prepare W-Cu nanopowders. Precursors containing some tungstates were obtained by adding precipitants into a complex solution containing ammonium metatungstate and copper nitrate, afterwards spray-drying the complex solutions. The precursor powders were then calcined and hydrogen-reduced to convert into W-Cu powders. Phase constitution and morphology of the precursors, the calcined powders, as well as the reduced powders were characterized. Relations between the ratio of W to Cu in the complex solutions and the phase constitution of the calcined precursors were investigated. The effects of the reduction temperature and H₂ flow rate on the hydrogen reduction kinetics and the crystallite size of the W-Cu powder were also studied. It was shown that the wet-chemical process produces W-Cu powders with nanosized particles of about 100 nm. The composition of the calcined precursors varies with the ratio of W to Cu in the complex solution, and only CuWO₄ was found in the calcined precursors when the ratio of W to Cu is 74:26(wt.%). The reduction temperature and H₂ flow rate have a great influence on the hydrogen-reduction process and the crystallite size of the resulting W-Cu powders.     

Low temperature synthesis of nanocrystalline lanthanum monoaluminate powders by chemical coprecipitation

Nanocrystalline lanthanum monoaluminate (LaAlO₃) powders were prepared by chemical coprecipitation using 25 vol.% of NH₄OH, 0.05 M La(NO₃)₃·6H₂O and 0.05 M Al(NO₃)₃·9H₂O aqueous solutions as the starting materials. Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analyses (TGA/DTA), X-ray diffraction (XRD), Raman spectrometry, specific surface area (BET) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction (ED) were utilized to characterize the LaAlO₃ powders prepared by chemical coprecipitation. The crystallization temperature of the LaAlO₃ precursor gels precipitated at pH 9 is estimated as 810 °C by TG/DTA. The XRD pattern of the LaAlO₃ precursor gels precipitated at pH 8–12 and calcined at 700 °C for 6 h shows a broad arciform continuum exist between 24° and 32° and sharp peaks of LaAlO₃ except the precursor gels precipitated at pH 9. For the LaAlO₃ precursor gels precipitated at pH 9 and calcined at 700 °C for 6 h, the formation of the perovskite LaAlO₃ phase occurs and the presence of crystalline impurities is not found. The crystallite size of LaAlO₃ slightly increases from 37.8 to 41.5 nm with calcination temperature increasing from 700 to 900 °C for 6 h. The LaAlO₃ powders prepared by chemical coprecipitation have a considerably large specific surface of 30 m²/g. The relative density greater than 97% is obtained when these nanocrystalline LaAlO₃ powders are sintered at 1550 °C for 2 h.     

Synthesis of nano-crystalline RuAl by mechanical alloying

Nano-crystalline RuAl was synthesised by mechanical alloying. The evolution of the nano-crystalline RuAl phase during the mechanical alloying process using ruthenium and aluminium powders was studied. During the milling process, the peaks corresponding to reflections from the aluminium planes disappeared. The variation of crystallite size and microstrain with milling time was evaluated using X-ray diffraction (XRD) patterns. though the XRD results showed the formation of a RuAl phase after 7h of milling, scanning electron microscopy studies revealed that the RuAl phase was formed after 2h of milling. The analysis revealed that average crystallite sizes of 17 and 120 nm were obtained for RuAl and Ru phases, respectively, during the milling process. Density value of 97 % of the theoretical value was obtained for the milled powder mixture after cold compaction and sintering.