不同球磨粉碎工艺对固相合成?-磷酸三钙纯度和粒度的影响

采用纳米球磨-超声搅拌工艺制备了β-磷酸三钙粉体,并与传统固相合成工艺进行了对比研究。采用差示扫描量热(DSC)、X射线衍射(XRD)、红外(FTIR)、纳米粒度测试、扫描电镜(SEM)、透射电镜(TEM)及X射线荧光光谱(XRF)等手段对两种工艺所制备粉体进行了纯度和粒度表征。结果表明:相比传统工艺,经过纳米球磨-超声搅拌工艺制备出的β-TCP粉体纯度可达97%以上,平均粒径为666 nm。粉体的纯度高、粒径分布更均匀。同时,纳米球磨加工后的原料平均粒度更小,分散性更好。该工艺有望用于粉体材料的固相合成。     

低温超强碱法制备引入有机添加剂的纳米四方多晶氧化锆粉体及其性能

采用引入有机添加剂的低温超强碱法,控制适当的工艺条件,得到了室温稳定的纳米四方／立方多晶氧化锆粉体。采用X射线荧光光谱、X射线衍射、透射电镜、粒度分析仪等手段对粉体性能进行了表征。实验结果表明：该粉体在室温和小于873K热处理时,均以稳定的立方或四方相存在,粉体粒径为9nm左右。在1123K处理的粉体分散性好、粒度小、粒度分布较窄,粉体颗粒的平均粒径为0．46μm。所制备的粉体具有纯度高、氯离子等杂质少等特点。与其它湿化学法相比,加入有机添加剂的低温超强碱法具有工艺操作简单、节约资源和环境污染小的优点。     

超细镁铝尖晶石粉体制备及表征

在实验室条件下分别进行了溶胶-凝胶法、凝胶-沉淀法和固相合成法实验,制备了不同粒度的镁铝尖晶石超细粉体,并对其进行了XRD分析,发现其相组成单一,纯度较高.经过激光粒度分析仪测得凝胶-沉淀法和固相合成法制得的粉体平均粒径分别为505和1780 nm,且分布比较均匀.通过SEM发现溶胶-凝胶法一次粒子为纳米级,团聚比较严重,在1000℃的最佳焙烧温度下可以获得比较完全的尖晶石相和团聚现象不很明显的镁铝尖晶石粉体.     

微波水热法用于制备纳米氧化锌粉体的研究

以氯化锌和氢氧化钠为原料,采用微波水热法制备了纳米氧化锌粉体,并采用X射线衍射（XRD）和透射电镜（TEM）对粉体的粒度、形貌、纯度进行了表征。通过单因素实验考察了反应温度、微波反应时间、微波功率、锌离子与氢氧根的浓度比等因素对氧化锌粉体的产率和粒径的影响,再通过正交试验得到最优制备条件。最佳制备工艺条件：锌离子与氢氧根的浓度比为1∶1.2、反应温度为 120 ℃、反应时间为 10 min、微波功率为500 W。在此条件下所得氧化锌粉体的晶型为六方晶相,产率达到93.5%,平均粒度约70 nm,粒径分布较窄,结晶完整。     

球形纳米氧化钇的制备与表征

以尿素为沉淀剂,硝酸钇为钇源,十六烷基三甲基溴化铵为分散剂,采用均相沉淀法制备球形纳米氧化钇粉体,研究了反应物浓度比、表面活性剂用量、反应时间、搅拌转速、反应温度对氧化钇形貌及粒径的影响。通过激光粒度分析、X射线衍射（XRD）分析、扫描电镜（SEM）分析、傅里叶红外光谱（FTIR）分析等手段对样品进行表征。结果表明,反应物浓度比、反应时间、搅拌转速、反应温度会影响粉体的尺寸,适量CTAB的加入可显著降低氧化钇的粒径;在最佳工艺条件下,可制得粒径大小为110~130 nm的球形氧化钇粉体。     

管式气体分散式反应器制备纳米碳酸钙

以石灰石为原料，利用管式气体分散式反应器新工艺制备出了粒径30～70nm的碳酸钙粉体。采用X射线衍射（XRD）、扫描电镜（SEM）、粒度分布仪及红外光谱仪（Fr-IR）等测试手段，对产品的物相、形貌和粒度分布进行了表征。X射线衍射表明产物为六方晶系方解石型碳酸钙并且产品结晶性能良好；扫描电镜及粒度分析表明粒度大小均匀、分散性良好；红外光谱表明改性后硬脂酸钠已吸附在碳酸钙表面，碳酸钙颗粒基本呈单分散状态。管式气体分散式反应器制备纳米碳酸钙粉体的优点是工艺简单，操作容易，原料易得，生产的产品粒径小，粒度分布窄，易于工业化生产。     

沉淀-超声法制备纳米二氧化硅

在化学沉淀超声分散条件下,研究了体系pH值、表面活性剂种类、分散剂用量、干燥方式、超声分散等因素对产物纳米二氧化硅粒径的影响。通过实验确定了沉淀-超声法制备纳米二氧化硅的最佳工艺条件。采用XRD、TG-DTA及激光粒度仪等测试手段对产物进行了表征。结果表明:在最佳工艺条件下制得了粒径为40 nm的二氧化硅粉体。研究表明,沉淀-超声法是一种制备纳米二氧化硅的简单的新方法,所得粉体粒径小,粒径分布窄,实验条件要求低,操作简便、易行,便于工业化生产。     

溶胶-胶水热合成法制备纳米CoAl2O4粉体

以仲丁醇铝和硝酸钴为原料,用溶胶-凝胶水热合成法制备了纳米CoAl2O4粉体,探讨了水热合成中前驱体的制备工艺条件,并用X射线衍射和扫描电镜等手段分析了水热系统中反应温度、反应时间对纳米CoAl2O4粉体的形成以及形貌的影响.结果表明:前驱体在250℃的水热系统中反应24 h,能制备出较纯净、结晶完整、粒度均匀、粒径小、尖晶石结构的纳米CoAl2O4粉体,其平均粒度约为50～60nm.     

超重力反应沉淀法制备白炭黑的研究

利用超重力反应沉淀法，以水玻璃和二氧化碳为原料，制备了平均一次粒径为15－20nm的白炭黑粉体，研究了反应条件对产品粒径的影响，通过透射电镜（TEM），红外（IR），X射线衍射（XRD）和差热一热重分析（DTA－TG）等手段检测了产品的性能，通过超重力反应沉淀法制备的白炭黑粉体，具有颗粒较细，粒度分布窄的特点，而超重力的制备方法也具有易于工业化的明显优点。     

常压水热合成纳米氧化锆工艺研究

以ZrOCl2.8H2O和氨水为主要原料,利用常压水热工艺制备出纳米氧化锆粉体,系统研究了氧氯化锆浓度、pH、反应温度及时间对产物晶型、粒度的影响,得出制备氧化锆纳米粉体的最佳工艺条件。并结合X射线衍射分析、透射电镜等方法对样品进行表征。结果表明,所制得的氧化锆样品为纳米氧化锆粉体,且粒度较均匀、分散性好,平均粒径约为7 nm。     

Synthesis of LaB6 powders from La2O3, B2O3 and Mg blends via a mechanochemical route

This study reports a room temperature mechanochemical route for the synthesis of LaB₆ powders from La₂O₃–B₂O₃–Mg blends. The synthesis reaction was driven by high-energy ball milling and was gradually examined in terms of milling duration and process control agent. Following the mechanochemical synthesis, unwanted MgO phase and Fe contamination worn off from the milling vial/balls were removed with HCl acid leaching under the effect of ultrasonic stirring. Pure LaB₆ powders were obtained after repeated centrifuging, repeated washing and drying. Subsequent annealing was performed in a tube furnace at 800 °C for 5 h under Ar atmosphere in order to reveal residual elements. Phase and microstructural characterizations of the milled, leached and annealed powders were performed using X-ray diffractometry (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. A novel route for producing fine-grained LaB₆ powders was accomplished with shorter reaction times resulting in higher purity.     

羰基镍粉焙烧制备高纯度微米氧化亚镍粉体的研究

以羰基镍粉为原料,采用焙烧法制备了氧化亚镍,并将其球磨后得到微米粉体。采用热重-差示扫描量热仪（TG-DSC）研究了羰基镍粉在空气气氛中加热时的氧化行为,利用激光粒度分析仪、等离子体光谱仪、X射线衍射仪（XRD）和扫描电镜（SEM）等分析了样品结构、成分和形貌。结果表明：空气和氧气两种气氛对产物纯度影响不明显。在两种载气条件下,通过优化焙烧温度和焙烧时间（焙烧温度为700 ℃、焙烧时间为2 h、载气流量为1.5 L/min）,羰基镍粉可直接焙烧制备得到纯度为100%、结晶度高的面心立方体氧化亚镍,球磨后得到粒度为4~19 μm的类球形微米氧化亚镍粉末。制备过程具有工艺简单、环境友好的特点。     

Microstructure of (Hf-Ta-Zr-Nb)C high-entropy carbide at micro and nano/atomic level

A High Entropy (Hf-Ta-Zr-Nb)C Ultra-High Temperature Ceramic (UHTC) was fabricated by ball milling and Spark Plasma Sintering (SPS) with a density of 99%. The microstructure characteristics were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) in combination with electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM). Atomic structure and local chemical disorder was determined by means of scanning transmission electron microscopy (STEM) in conjunction with energy dispersive X-ray spectroscopy (EDS). According to the results, high purity, dense and homogeneous high entropy carbide with Fm-3?m crystal structure was successfully produced. The grain size ranged from approximately 5?μm to 25?μm with average grain size of 12?μm. Chemical analyses proved that all grains had the same chemical composition at the micro as well as on the nano/atomic level without any detectable segregation. The approximately 1.5?nm thin amorphous grain boundary phase contained impurities that came from the starting powders and the ball milling process.     

MgAl2O4 nanopowder synthesis by microwave assisted high energy ball-milling

This paper reports the development of a new process for the synthesis of spinel nano powder via microwave assisted high energy ball milling of a powder mixture containing Al(OH)₃ and Mg(OH)₂. X-ray diffraction (XRD), Simultaneous thermal analysis (STA), FTIR spectrometer, BET and scanning electron microscopy (SEM) techniques were utilized to characterize the as-milled and annealed samples. X-ray diffraction results provide evidence for the formation of a completely amorphous phase after milling for 8 h. It is found that highly ordered MgAl₂O₄ spinel can be obtained by calcination the as-milled powder over 800 °C. Also, SEM observations of synthesized powders showed that the particle size of powders lies in the nano meter range compared with the BET results (about 28–149 nm). The DTA–TG analyses were carried out to investigate the effect of microwave heating on the synthesis temperature compared to the conventional heat treatment by conventional furnace. Synthesis of powders with different heating methods showed that microwave heating reduces the synthesis temperature by about 200 °C.     

The effect of the wet-milling process on sintering temperature and the amount of additive of SiAlON ceramics

In this study, nano-sized SiAlON powders were produced by wet milling at elevated speeds as a top-to-bottom process. Before the milling process, different milling times and mediums were performed for the determination of the most efficient milling system. The milled powders were characterized by BET and X-ray diffraction (XRD) measurements and the results were compared to standard samples. The standard powders were produced using a conventional process (the ball to powder ratio was 1:1.5, at 300 rpm, for 1.5 h) having a few hundred nanometer particle size. The nano powders were milled using a wet-milling process in an optimum medium so that the particle size was decreased down to ≈70 nm. The samples, produced from the nano powders, were densified at 150 °C lower degrees than the sintering temperature of samples which were produced by a conventional method (185 nm). However, the phase transformation of α → β-SiAlON was also observed related to the amount of additives. This transformation affected the mechanical properties of the SiAlON ceramic. The results were discussed using the relationship between density, phase composition, microstructure and mechanical properties.     

Preparation and characterization of nano‐Sb2O3/poly(butylene terephthalate) composite powders based on high‐energy ball milling

In this work, a kind of composite powders with good dispersion and distribution of nano‐Sb₂O₃ particles in poly(butylene terephthalate) (PBT) was prepared by the high‐energy ball milling (HEBM). The effects of the milling time on the structure, morphology, particle size distribution, and thermal behavior of the nano‐Sb₂O₃/PBT composite powders were characterized by Fourier transform infrared spectroscopy, scanning electron microscope, laser diffraction particle size analyzer, and thermal analysis (TGA, DTG and DSC) techniques. The results showed that the regular shape of PBT powders was converted into flakes and the nano‐Sb₂O₃ particles were well deagglomerated and better dispersed in the PBT matrix during the HEBM process. The mechanochemical activation that was provided by the HEBM process caused a reduction in the molecular weight of PBT, which result in favoring the first step of thermal degradation. Furthermore, two T_g’s were obtained in the case of the nanocomposite powders when the milling time was over 3 h, one of them being slightly higher than that of the pure PBT, which indicated that there was a special interaction between PBT and nano‐Sb₂O₃ particles. However, the HEBM process leaded to a decreasing of the PBT crystallinity. J. VINYL ADDIT. TECHNOL., 25:91–97, 2019. © 2018 Society of Plastics Engineers     

Synthesis and characterization of high-energy ball milled nanostructured Fe50Ni50

Mechanical alloying is a non-equilibrium process for materials synthesis. It has been used to obtain nanocrystalline binary system FeNi.

Fe and Ni elemental powders have been ball milled in a planetary mill (Pulverisette 7, Fritsch) for various times up to several hours. The morphology of the powders was examined using scanning electron microscopy (SEM). X-ray diffraction (XRD) has been employed to follow the structural evolution during the ball milling process. The X-ray patterns were analysed by the MAUD procedure, which is based on the Rietveld method combined with a Fourier analysis, well adapted for broadened diffraction peaks. The grain size was found to be about 5 nm and the residual strain was about 0.021% after 322 h of milling. The as-milled samples, characterized by Mössbauer spectroscopy (MS) contain a mixture of (bcc) and γ (fcc) phases after 48 h of ball milling.     

Microwave synthesis and sintering of forsterite nanopowder produced by high energy ball milling

This paper reports the development of a new process for the synthesis and sintering of forsterite nanopowder via microwave-assisted high energy ball milling of a powder mixture containing silica gel and Mg(OH)₂. X-ray diffraction (XRD), FTIR spectrometer, BET, scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) techniques were utilized to characterize the as-milled and annealed samples. X-ray diffraction results showed that highly ordered forsterite can be obtained through the calcination of the as-milled powder over 900 °C. In addition, SEM and TEM observations of the synthesized powders showed that the particle size of the powder lies in the nanometer range, also being compared with the BET results (about 45 to 64.5 nm). Microwave sintering (MS) of the forsterite nanopowder produced with high energy ball milling and subsequent microwave heating resulted in remarkable enhancement in densification in comparison with conventional sintering (CS) at lower temperatures.     

Characterization of blue CoAl2O4 nano-pigment synthesized by ultrasonic hydrothermal method

Nano-sized CoAl₂O₄ pigments, which have received significant attention as a coloring agent in glaze and bulk tile compositions, were successfully synthesized by substituting mechanical stirring during hydrothermal process with ultrasonic irradiation. Difference in physicochemical and optical properties of the CoAl₂O₄ pigments prepared by an ultrasonic-assisted-hydrothermal method was characterized using simultaneous thermo-gravimetric and differential thermal analysis (TG–DTA), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy, CIELAB colorimetric analysis, and testing in ceramic glazes and bodies. The ultrasonic-assisted CoAl₂O₄ pigments present a narrow particle size distribution with vivid blue color, and better thermal stability, allowing their use for ceramic inks processed at high temperature. Application of ultrasonic irradiation during the hydrothermal process produces nano-sized powders with better physicochemical and optical properties.     

Evaluation of Ultrasonic Treatment for the Size Reduction of HNS and HMX in Comparison to Solvent‐Antisolvent Crystallization

The paper presents and compares two methods for the synthesis of fine particles of the high explosives HNS and HMX by ultrasonic treatment and solvent/antisolvent crystallization. The effect of ultrasonic treatment on the particle size of explosives was studied by varying the amplitude and frequency of ultrasonication for different time periods using an ultrasonic probe and an ultrasonic bath. Solvent/antisolvent recrystallization was performed by varying the process parameters including stirring rate, antisolvent temperature etc. In addition to FT‐IR spectroscopy and thermal analysis by TGA/DSC; the particle size and shape of fine powders of the explosives HMX and HNS were determined using particle size analysis and scanning electron microscopy (SEM). Ultrasonic treatment of the probes resulted in the finer grains of HMX compared to solvent‐antisolvent crystallization. However in the case of HNS, solvent‐antisolvent crystallization produced finer particles compared to ultrasonication.