Effect of process parameters on size,shape, and distribution of Sb<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles

Antimony trioxide (Sb₂O₃) nanoparticles with particle sizes ranging from 2 to 12 nm, spherical in shape, and well-distributed were successfully synthesized by chemical reduction method. The nanoparticles were synthesized in the presence of hydrazine as a reduction agent in ethylene glycol through the reaction between antimony trichloride and sodium hydroxide. Effects of reaction temperature, reaction time, precursor concentration and boiling temperature on the particle size, shape, and distribution of the Sb₂O₃ nanoparticles were investigated. Morphology of the nanoparticles was examined by transmission electron microscope (TEM). It was revealed that the particle size increased when reaction temperature, reaction time and concentration of precursor were increased. Moreover, the mixture needed to be boiled prior to the addition of hydrazine as a reduction agent, in order to obtain an optimum reduction. X-ray diffraction (XRD) was employed to study the crystallinity and phase of the nanoparticles. The nanoparticles were determined as cubic phase of Sb₂O₃ (ICDD file no. 00-043-1071) by XRD. Interrelation between UV–vis absorption spectra of the nanoparticles and their particle size were obtained.     

Synthesis and sintering of biomimetic hydroxyapatite nanoparticles for biomedical applications

Synthesis of monodisperse nanoparticles with uniform morphology and narrow size distribution as achieved by nature is a challenge to materials scientists. Mimicking the process of biomineralization has led to the development of biomolecules mediated synthesis of nanoparticles that overcomes many of the problems associated with nanoparticle synthesis. Termed as biomimetics this paradigm shift in the philosophy of synthesis of materials is very advantageous for the design-based synthesis of nanoparticles. The effect of concentration of a protein named bovine serum albumin on particle size, morphology and degree of crystallinity of biomimetically synthesized hydroxyapatite particles, has been studied. Results establish 0.5% protein as the required concentration to produce 30–40 nm sized hydroxyapatite particles with an optimum degree of crystallinity as required for biomedical applications. These particles synthesized under certain stringent conditions are found to have stoichiometric calcium:phosphorus ratio of 1.67 and exhibit restricted grain growth during sintering.     

Effective mechanochemical synthesis of sulfide solid electrolyte Li3PS4 in a high energy ball mill by process investigation

Mechanochemical syntheses have a high potential as environmentally friendly and scalable processes. However, especially in case of solid electrolytes, these syntheses are reported as very time consuming with process times up to several days. In this study, the sulfide solid electrolyte Li₃PS₄ was successfully synthesized in less than 5 h after a systematic variation and subsequently optimization of the process parameters in a high energy ball mill. The synthesized electrolyte samples were characterized according to their composition, morphology, particle size distribution and ionic conductivity. Therefore, a better understanding of the process-structure–property relations and process efficiency was achieved. Thus, the results allow a correlation between the stressing conditions and kinetic rates. The stressing conditions are mainly affected by process parameters such as rotational speed, grinding media size and grinding media filling ratio. The kinetic of the mechanochemical process is highly dependent on the normal power input by head-on collisions, leading to a reduction of conversion time with increasing specific power input. The different sets of investigated process parameters also exhibit systematic effects on the crystallinity and particle size distribution of the solid electrolytes. As a result, a highly enhanced process with lowest specific energy demand was achieved by using the largest grinding media with highest rotational speeds at medium grinding media filling ratio.     

Effects of process conditions on the properties of silicon nanoparticles synthesized by gas phase reactions using inductive coupled plasma

Silicon nanoparticles were synthesized by passing monosilane through a quartz tube wrapped with Inductive Coupled Plasma (ICP) coil. Microstructures of synthesized silicon nanoparticles were investigated with various process conditions. To research the effects of process parameters on the properties of nanoparticles, we verified the partial pressure of monosilane, the plasma power and the working pressure. The highly crystalline silicon nanoparticles were only achieved at the proper partial pressure of the reactive gas and plasma power. Partial pressure determined not only the particle size but also the crystallinity of the nanoparticles. The plasma power was controlled from 50 to 100 W which determined not the particle size but the crystallinity of nanoparticles. Especially, too low a power resulted in amorphous particles with an average sizes of 5.25 nm. As the working pressure increased, the amount of produced nanoparticles linearly increased and the maximum production yield was at 76 mg/hr. Controlling those parameters, we achieved monodispersed single crystalline silicon nanoparticles with an average diameter of 7.52 nm. Silicon nanoparticles in this study can be applied to light absorbing material for solar cells and the wavelength down-converter material of Light Emitting Diode (LED).     

Synthesis of crystalline MgO nanoparticle with mesoporous-assembled structure via a surfactant-modified sol-gel process

Highly crystalline MgO nanoparticles with the mesoporous-assembled structure were synthesized via a modified sol-gel process with the aid of a structure-directing surfactant under mild conditions. X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected-area electron diffraction (SAED) analyses revealed that the synthesized MgO possessed high crystallinity with the particle size in nanosized range. N₂ adsorption-desorption and pore size distribution analyses indicated that its pore size distribution was in a narrow mesoporous range, which originated from an assembly of the MgO nanoparticles.     

The influence of diluent gas composition and temperature on SiC nanopowder formation by CVD

Crystalline cubic silicon carbide (3C-SiC) nanopowders were synthesized using hexamethyldisilane (HMDS) in a resistance heated chemical vapour deposition (CVD) reactor. The effects of different diluent gases on the synthesis of the SiC powder were also studied. The deposited powder was characterized using high-resolution X-ray diffraction (HRXRD) analysis, transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and BET surface area measurements. The crystallite size was estimated to be in the range of nanometer (10–20 nm) from XRD data and the particle size (∼10–30 nm) was obtained by TEM, HRTEM and BET. The growth condition was optimized in terms of crystallinity, chemical composition and deposition rate by varying different parameters such as the diluent gas (H₂/Ar ratio) and temperature.     

Properties of Iron Oxide Nanoparticles Synthesized at?Different?Temperatures

Iron oxide nanoparticles were synthesized by co-precipitation in air atmosphere at different temperatures and their structural and magnetic properties were investigated. The mean particle sizes of iron oxide nanoparticles were calculated from the X-ray diffraction (XRD) patterns using the Scherrer equation. Fourier transform infrared spectroscopy analysis exhibited the vibration bands at 563 cm^?1 and 620 cm^?1 confirming the formation of Fe₃O₄ and ??-Fe₂O₃, respectively. Morphological observation was made by a transmission electron microscope and the particle size of iron oxide nanoparticles was found to be around 9 nm which is consistent with the particle size calculated according to the XRD patterns. It was observed that the intensity of the peaks in the patterns and crystallinity increased as the temperature increased. Magnetization curves showed zero coercivities indicating that the samples are superparamagnetic.     

聚乙二醇体系中含铜化合物液相热解法制备纳米铜粉

以聚乙二醇(PEG200)为分散介质,氢氧化铜为铜源,采用液相热解法制备纳米铜粉。用X射线衍射仪(XRD)和透射电子显微镜(TEM)对产物进行表征,考察了不同种类的络合剂和表面活性剂对纳米铜粒径和形貌的影响。研究结果表明:在PEG200分散介质中于220℃恒温3h可以得到单质铜粉,其结晶性较好,粒径为30~40nm;添加乙二胺络合剂可得到纤维状的纳米铜粉,用乙二胺络合再添加不同的表面活性剂能减小纳米铜粉的粒径并改变其形貌;在纳米铜的制备中PEG同时起着还原剂和结构导向剂的作用。     

An investigation on the properties of SnO2 nanoparticles synthesized using two different methods

Tin oxide SnO₂ nanoparticles have been synthesized using chemical co-precipitation and solvothermal methods. The structures and morphologies of SnO₂ prepared using both routes were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier infrared absorption spectroscopy (FT-IR), UV–Vis Spectroscopy and BET specific surface area. The XRD patterns showed the presence of the tetragonal structure in the nanometric range and both crystallinity as well as crystal size increased with the increasing in temperature. The size of the produced tin dioxide nanoparticles was from 6.2 to 10.6 nm by solvothermal route while it was from 9.3 to 16.2 nm for nanoparticles by co-precipitation pathway. Furthermore, TEM results showed that the sizes of SnO₂ particles in all powders were tetragonal like structure and the grain size was increased with temperature. FT-IR spectra revealed that intensity of the transverse optical mode of Sn–O stretching vibration was increased with the sintering temperature while the bending vibration of O–Sn–O showed a blue shift. The optical band gap was shifted to a lower energy with increasing temperature due to the improvement of the crystallinity and the value was varied from 2.9 to 4.25 eV. The specific surface area of the as-made SnO₂ in comparison with such calcined samples decreased with increasing the calcination temperature due to the changes in the sample particle size and in the sample crystal phases.     

Investigation on microstructural and optical properties of CuSbS<Subscript>2</Subscript> nanoparticles synthesized by hydrothermal technique

CuSbS₂ nanopowder was synthesized using simple hydrothermal technique at relatively low temperature of 150?°C for duration of 8 h. The obtained nanoparticles were characterized by means of X-Ray Diffraction, Specific Surface Area analyzer (BET), Diffraction Ray Spectroscopy and Transmission Electron Microscopy. The structural properties showed that the CuSbS₂ nanoparticles exhibited a pure orthorhombic phase with high crystallinity and particle size in the average of 18 nm. The material exhibited a broad absorption in a wide wavelength range from UV to visible light corresponding to a direct band gap of 1.42 eV. The synthesized material seems to be promising candidates for photovoltaic and/or photocatalytic applications.     

Preparation of cobalt nanoparticles by hydrogen reduction of cobalt chloride in the gas phase

Cobalt nanoparticles were produced by the hydrogen reduction of cobalt chloride vapor in a multistage tubular aerosol flow reactor. Reaction zone temperature, preheating temperature, mole fractions of CoCl₂ and H₂, and residence time were considered as key process variables for the control of particle size and size distribution. Ranging from 50 to 78 nm in average diameter, cobalt nanoparticles with narrow size distributions were synthesized throughout our experiments. All of the considered process variables affected the particle size and size distribution in the synthesis of cobalt nanoparticles. As the reaction zone temperature and the CoCl₂ mole fraction increased, the average particle diameter increased. But the average particle diameter decreased as the residence time of reactants increased.     

The synthesis of titanoniobate compound characteristic of various particle morphologies through a novel solvothermal route

Potassium titanoniobate (KTiNbO₅) polycrystalline powders were synthesized by the sol-gel method and a novel preparation route which was described as a combination technique of the sol-gel process and solvothermal treatment. The synthesis processes, the structure and morphology characterizations for the as-prepared KTiNbO₅ particles were investigated by using thermal analysis, X-ray powder diffraction, electron microscopy and other techniques. The KTiNbO₅ particles synthesized in this work showed various morphologies depending on the different reaction processes. The KTiNbO₅ compound obtained through 2-propanol solvothermal treatment exhibited unique particle morphology characteristic of sphere shape with the average size of 300 nm in diameter. In addition, the result that the formation of the spherical particle shape occurred during the solvothermal process was demonstrated.     

Preparation of SrTiO3 nanoparticles by the combination of solid phase grinding and low temperature calcining

Spherical SrTiO₃ nanoparticles with diameters of 15-35 nm were successfully synthesized by a solid phase grinding followed by low-temperature (400-600 °C) calcination method, using strontium hydroxide and tetrabutyl titanate as reactants. The as-synthesized samples were characterized by XRD, FT-IR, SEM and TEM, and the formation process of the products was investigated by means of TG-DTA. The results show that the as-synthesized SrTiO₃ nanoparticles with uniform sizes belong to cubic perovskite structure. The crystallite size and crystallinity increase with the increasing of calcination temperature. In the meantime, the crystal water contained in the reactant of strontium hydroxide also affects the crystallinity of products.     

Preparation and characterization of nano-sized Sr0.7Ca0.3TiO3 crystallines by low temperature aqueous synthesis method

Nano-sized calcium strontium titanate (Sr_0.7Ca_0.3TiO₃) particles were prepared by low temperature aqueous synthesis method at temperature as low as 90 °C and under ambient pressure. To improve the morphology and crystallinity of the particles, the hydrothermal treatment was used. The lattice structure, particle size, particle morphology, and hydroxyl defects of Sr_0.7Ca_0.3TiO₃ particles were investigated by using XRD, TEM, FE-SEM, TG and FT-IR measurements. The as-prepared particles with size about 100 nm were single cubic phase crystallines which consist of aggregates of small rounded nanocrystals about 10 nm in diameter. However, in as-prepared crystallines, a hydroxyl group was detected as a lattice defect. After the hydrothermal treatment, the hydroxyl groups in Sr_0.7Ca_0.3TiO₃ nanoparticles were partially released from the perovskite lattice. The morphology and crystallinity of the hydrothermally treated particles were observably improved.     

Microwave-assisted hydrothermal synthesis and characterizations of PrF3 hollow nanoparticles

PrF₃ hollow nanoparticles were synthesized by the microwave-assisted heating hydrothermal treatment of the corresponding colloidal rare earth fluorides precipitates. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The TEM imaging showed that the PrF₃ nanoparticles prepared in this way had hollow sphere-like morphology with the mean particle size of about 31 nm. XRD showed that the PrF₃ hollow nanoparticles had high purity and high crystallinity.     

Novel synthesis of nanocrystalline CeO2 by mechanochemical and water-in-oil microemulsion methods

Nanocrystalline cerium dioxide (CeO₂) had been synthesized by two different methods which were mechanochemical and water-in-oil microemulsion. Effects of synthesis conditions on properties of nanocrystalline cerium dioxide were investigated. X-ray diffraction (XRD) was used to characterize the phase and crystallite size of synthesized cerium dioxide nanoparticles. XRD results showed that face centered cubic CeO₂ nanoparticles with crystallite size in nanometer scale were formed. The crystallinity increased with increasing annealing temperature. The average specific surface area of the particles was probed using gas adsorption-desorption measurements. The average particles size was calculated from the specific surface area and was determined to be 5.2 nm for microemulsion samples and 6.9 nm for mechanochemical samples. These results showed that properties of synthesized cerium dioxide could be tailored by adjusting the synthesis conditions.     

Synthesis of cerium hydroxycarbonate powders via a hydrothermal technique

CeOHCO₃ powders have been directly synthesized using a hydrothermal process at temperatures as low as 160°C. The well-dispersed powders are obtained in a short period of reaction time during hydrothermal reaction via the hydrolysis of urea. For synthesizing CeOHCO₃, the concentration of urea is found to be a crucial determinant, which has significant effects on the morphology of the derived powders. When low urea concentrations are provided, the formed particles are rhomboidal platelets. On the other hand, the high urea concentrations cause the shape of the powders to become prismatic. Increasing the concentration of urea tends to increase the particle size as well as the aspect ratio of CeOHCO₃ powders. After further heating at 500°C, a phase transformation from orthorhombic CeOHCO₃ to cubic CeO₂ takes place. The crystallinity and size of CeO₂ strongly depend on the particle size of CeOHCO₃.     

Role of particle size in visible light photocatalysis of Congo Red using TiO<Subscript>2</Subscript>·[ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript>]<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> nanocomposites

TiO₂·[ZnFe₂O₄] _x (x = 0·0-0·5) nanocomposites (NCs) with an average particle size of 72·4 nm were synthesized by the method of co-precipitation/hydrolysis (CPH). For the comparison of particle-size dependent effects, a set of polycrystalline samples with similar compositions was also prepared by solid state reaction (SSR) route. Average particle size for SSR prepared samples was about 3·0 μm. All the samples were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size analyzer, Raman spectroscopy and Fourier transform infra-red (FTIR) spectroscopy. Their visible light photocatalytic activity was tested for the degradation of Congo Red dye. Maximum photodegradation was observed for the NC with x = 0·1 synthesized by CPH (particle size, 71 nm). Similar composition prepared by SSR method (particle size, 6·19 μm) showed lower photoactivity in comparison even with that observed for pure TiO₂ (particle size, 4·03 μm). It was, therefore, concluded that enhanced photodegradation is directly related to the reduced particle size of the composites, which implies that photosensitization is the process primarily involved. Although, doping of TiO₂ with ZnFe₂O₄ does extend the cut-off wavelength towards visible parts of the spectrum, its contribution in the enhancement is not as significant as that due to the photosensitization.     

Crystallinity enhancement of flame-made LiCo0.25Ni0.75O2 nanoparticles by heat-treatment

LiCo_0.25Ni_0.75O₂ nanoparticles of 22.8 nm in geometric mean diameter were synthesized by flame spray pyrolysis from aqueous droplets of nitrate compounds of lithium, cobalt and nickel. The crystallinity of the as-prepared LiCo_0.25Ni_0.75O₂ particles was enhanced by post-heat-treatment at various conditions, such as temperature, duration, and atmospheric gas with different flow rates. The effect of heat-treatment on the particle morphology and crystallinity was investigated systematically. Higher heat-treating temperature under normal air atmosphere improved hexagonal ordering and sufficient O₂ flow during the heat-treatment reduced the cation mixing problem.     

Synthesis and tuning of ordering and crystallinity of mesoporous titanium dioxide film

Synthesis of well-organized and highly crystalline mesoporous titania (TiO₂) film is demonstrated using triblock copolymer (Pluronic P123) as a structure directing template, through the evaporation induced self-assembly (EISA) process. The issue of thermal and structural stability of a mesoporous TiO₂ film was addressed via optimization of annealing temperature and time. An anatase phase, high crystallinity TiO₂ film with ordered pores was obtained at 430 °C after annealing for 15 min. The synthesized film was crack free with TiO₂ nanoparticle size of 10–15 nm, quasi-hexagonal pore diameter in the range of 8–10 nm and film thickness of ~ 150 nm.