Verification for Particle Size Distribution of Ultrafine Powders by the SAXS Method

The Dividing Distribution Function (DDF) method is one of the methods by which the particle size distribution of ultrafine powder can be evaluated from its small-angle X-ray scattering (SAXS) data. In this paper, the particle size distributions of many different samples were reported, and the reliability of DDF was proved by TEM. For a series of samples, the specific surfaces were measured by the BET method, and also calculated from their particle size distributions obtained by SAXS determination. The two sets of results are systemically compared.     

Determination of size distributions in nanosized powders by TEM,XRD, and SAXS

Crystallite size distributions and particle size distributions were determined by transmissions electron microscopy (TEM), X-ray powder diffraction (XRD), and small-angle X-ray scattering (SAXS) for three commercially available TiO₂ powders (P25, UV100, and TiO2_5?nm) and one SSEC produced powder (SSEC78). The theoretical Guinier model was fitted to the experimental obtained XRD data and compared to analytical expressions. Modeling of the XRD spectra showed a difference between the analytical size dependent expressions and the theoretical Guinier model. Primary particle size distributions were extracted from SAXS measurements by the hard sphere model including an interparticle interference factor. The sizes obtained from SAXS were smaller than the sizes obtained from the XRD experiments; however, a good agreement was obtained between the two techniques. Electron microscopy confirmed the primary particle sizes and the shapes obtained by XRD and SAXS. The SSEC78 powder and the commercially available powders showed different morphologies, but SSEC78, UV100, and TiO2_5?nm all consisted of both primary particles as well as a secondary structure comprised of nanosized primary particles agglomeration into larger clusters. P25 showed the largest primary particle size, but did not show a secondary structure.     

Size and distribution: a comparison of XRD, SAXS and SANS study of II-VI semiconductor nanocrystals

The uniqueness of size dependent functional properties of II-VI semiconductor nanocrystals have led to the development of various techniques for determination of shape, size and distributions, although the accurate measurements of the particle sizes has always been a fundamental task in nanoscience and even become more crucial with the discovery of quantum confinement effect. A comparison of the well established techniques X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and small angle neutron scattering (SANS) with an emphasis on size and distribution of the prepared samples are reported in order to elaborate more precise techniques for the analysis of particles sizes. Modified Scherrer formula for spherical particles has been used to calculate the particle sizes from XRD spectra. Analysis of SAXS data has been reported using Guinier model. Small angle neutron scattering measurements has been performed for ZnO nanocrystals and the scattering data obtained is simulated for polydisperse sphere. The bare ZnO, ZnS and CdS and doped with Mn2+ systems are taken within the framework of our discussion. These materials were synthesized by chemical precipitation route and found to have size distribution from 2 to 6 nm for spherical particles. Sizes determined from various techniques are in good agreement with each other however small angle scattering technique is more reliable than XRD to determine the sizes of the nanoparticles.     

Systematic study of bimodal suspensions of latex nanoparticles using dynamic light scattering

Determining the size of nanoparticles accurately, quickly and easily is becoming more and more important as the use of such particles increases. One of the common techniques for measuring the size of particles in suspension is dynamic light scattering (DLS). In principle, DLS is able to estimate the hydrodynamic particle diameter and its intensity-weighted distribution. However, the measured correlation function or power spectrum must be inverted to obtain this size distribution. The inversion is an ill-posed mathematical problem, and only under certain assumptions can the distribution be determined reliably. Suspensions containing bimodal (or multi-modal) particle size distributions are particularly challenging. This study reports on DLS measurements on a range of bimodal distributions of latex spheres with varying ratios of particle sizes. To determine the efficacy of different inversion techniques, the data has been analyzed both with the algorithms implemented in the DLS instrument’s proprietary analysis software and with other inversion routines based on simple analytical models of the particle size distribution. In addition, the results of the DLS analysis have been compared to scanning and transmission electron microscopy (SEM and TEM) measurements.     

SEM在Pd—Al_2O_3催化剂研究中的应用

用SEM研究了经物理化学方法处理前后的Al_2O_3载体的表面形貌,和在相同载体上用不同方法制备的Pd-Al_2O_3催化剂上钯粒子的大小和分布;用小角X射线散射法测定了催化剂上钯粒子的统计尺寸和大致分布。SAXS的分析结果与SEM结果对照认为二者基本上是吻合的。     

Comparison of Particle Size Distributions Measured Using Different Techniques

In this article, particle size distributions (PSDs) measured by different techniques, including image analysis (IA), laser diffraction (LD), ultrasonic attenuation spectroscopy (UAS), and focused-beam reflectance measurement (FBRM), are compared for spherical glass beads and nonspherical silica flakes. It is shown that particle shape strongly affects the results obtained by different techniques. For spheres, the PSDs obtained by IA, LD, and UAS agree well. There is no consistent result among different particle measurement techniques for nonspherical particles. The conversion between PSDs obtained by IA, LD, and UAS has been based on particle shape factors. Caution must be exercised when a measured chord length distribution (CLD) is used to indicate the PSD during a process because the CLD result obtained by FBRM is complex, depending not only on the PSD, but also on particle optical properties and shape.     

Size distribution of CdS nanocrystal-doped silica xerogels

Pure and porous silica xerogels doped with CdS nanocrystals have been prepared by a sol-gel process. In order to determine parameters convenient for non-linear optical properties, particle size distributions were obtained by two complementary techniques: transmission electron microscopy (conventional, CTEM, and high resolution, HRTEM) and small angle X-ray scattering (SAXS). Monolithic samples having CdO concentrations varying from 5 to 20 wt% have been studied. Details are given of an image analysis technique used to study the CTEM micrographs.     

Characterization of filled rubbers using small-angle X-ray scattering

It is demonstrated how small-angle X-ray scattering (SAXS) can be used to characterize the structure of fillers such as carbon black and silica both before and after their incorporation into natural rubber. It is found that SAXS has significant advantages over conventional techniques such as gas adsorption or electron microscopy in determining both the size and distribution of sizes of the filler particles. The results are shown to be in good agreement with those obtained using conventional techniques. In addition it is demonstrated that SAXS can be used to characterize the filler particlesin situ enabling the volume fraction, particle size and particle surface area to be determined for a filled rubber and factors such as aggregation to be examined.     

Comparison of Particle Size Distributions Measured Using Different Techniques

ABSTRACT

In this article, particle size distributions (PSDs) measured by different techniques, including image analysis (IA), laser diffraction (LD), ultrasonic attenuation spectroscopy (UAS), and focused-beam reflectance measurement (FBRM), are compared for spherical glass beads and nonspherical silica flakes. It is shown that particle shape strongly affects the results obtained by different techniques. For spheres, the PSDs obtained by IA, LD, and UAS agree well. There is no consistent result among different particle measurement techniques for nonspherical particles. The conversion between PSDs obtained by IA, LD, and UAS has been based on particle shape factors. Caution must be exercised when a measured chord length distribution (CLD) is used to indicate the PSD during a process because the CLD result obtained by FBRM is complex, depending not only on the PSD, but also on particle optical properties and shape.     

Structural study on graphene-based particles prepared from old coconut shell by acid–assisted mechanical exfoliation

This work is aimed to identify the structure of the graphene-based particles (GPs) from old coconut shell as the raw material after the mechanical exfoliation processes. The burnt coconut shell was at first heated at 400 °C for 5 h in ambient air. The sample was then stirred in an acid solution (HCl) and then continued by ultrasonication and centrifugation. The exfoliated GPs were characterized by x-ray diffraction (XRD), particle size analyzer (PSA), Fourier-transform infrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM and TEM, respectively), atomic force microscopy (AFM), Raman spectroscopy, and synchrotron wide and small angle x-ray scattering (WAXS and SAXS, respectively). The XRD and WAXS analyses show Bragg peaks corresponding to a pure phase of reduced graphene oxide (rGO). PSA, SEM/TEM, AFM, and Raman analyses show that the use of HCl-assist in the solution during the exfoliation process has successfully reduced particle size of the obtained GPs. SAXS pattern of the exfoliated GPs using the assist of HCl, confirmed by TEM and AFM images, results in the specific particle sizes of between 1.42 and 4.99 nm. The present mechanical exfoliation technique has successfully been applied to obtain several nanometers of GPs and provides an alternative of simple synthesis of biomass – based graphene products.     

Microstructures of microcrystalline silicon thin films prepared by hot wire chemical vapor deposition

Undoped hydrogenated microcrystalline silicon (μc-Si:H) thin films were prepared at low temperature by hot wire chemical vapor deposition (HWCVD). Microstructures of the μc-Si:H films with different H₂/SiH₄ ratios and deposition pressures have been characterized by infrared spectroscopy X-ray diffraction (XRD), Raman scattering, Fourier transform (FTIR), cross-sectional transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The crystallization of silicon thin film was enhanced by hydrogen dilution and deposition pressure. The TEM result shows the columnar growth of μc-Si:H thin films. An initial microcrystalline Si layer on the glass substrate, instead of the amorphous layer commonly observed in plasma enhanced chemical vapor deposition (PECVD), was observed from TEM and backside incident Raman spectra. The SAXS data indicate an enhancement of the mass density of μc-Si:H films by hydrogen dilution. Finally, combining the FTIR data with the SAXS experiment suggests that the Si---H bonds in μc-Si:H and in polycrystalline Si thin films are located at the grain boundaries.     

Revealing Precipitate Development During Hot Rolling and Cooling of a Ti–Nb Micro-Alloyed High Strength Low-Alloy Steel through X-Ray Scattering

High-energy synchrotron X-ray small-angle scattering (SAXS) is used to study the precipitate development during hot rolling and cooling of a commercial Ti–Nb micro-alloyed, high-strength, low-alloy (HSLA) steel. To study precipitation during hot rolling conditions, Gleeble and dilatometer trials are made. Samples are then studied at room temperature using SAXS in conjunction with transmission electron microscopy (TEM). TEM is used to determine the morphology and composition of the precipitates, whilst both TEM and SAXS are used to study the particle sizes. One major advantage with high-energy SAXS is the ability to make measurements after a minimum of sample preparation and in transmission geometry, as opposed to just at prepared surfaces, plus the possibility to determine volume fractions of the precipitates. The measurements show that after deformation at high temperature, particle coarsening occurs and the volume fraction of precipitates increases after holding for 20 s at 900 °C which confirms strain-induced precipitation at finishing rolling conditions. The measurements show that holding at 600 or 650 °C for one hour gives a larger volume fraction of nanosized particles. Coiling simulations with slow cooling from 600 to 470 °C show coarsening of particles and an increase in the volume fraction of the smaller particles compared to holding at a constant temperature.     

制备条件对ZrO_2超细粒子尺寸及分布的影响

本文采用胶体－超临界流体干燥法制备纳米级ＺｒＯ２超细粉料，用透射电镜（ＴＥＭ）、比表面积（ＢＥＴ）和粒度分析法对颗粒尺寸进行观察和测定，并详细考察了制备条件对产品粒子粒度及其分布的影响     

HDI-IPDI型高固含量水性聚氨酯分散体的合成及微观形态

以预聚体分散法合成了固含量达50%的高固含量水性聚氨酯分散体.研究了影响高固含量水性聚氨酯分散体的黏度、粒径、粒径分布及粒子微观形态的因素.结果表明,随着DMPA含量、HDI/IPDI摩尔比及软段分子量(M)n的增加,乳液的黏度增大,粒径减小.粒径分布随着DMPA含量及PBA分子量的增加而变窄,HDI/IPDI对粒径分布的影响较小;在DMPA含量较低或者PBA分子量在2000以下时获得的分散体具有较广的粒径分布.此外,分散液还呈现出二元粒径分布趋势.透射电镜对胶束形态研究表明,随着软段分子量的增加,胶束呈现出聚集趋势,并且随着DMPA含量的增加,聚集更紧密.     

Synthesis of nanocrystalline SnO2 powder by amorphous citrate route

Nanocrystalline SnO₂ has been synthesized by liquid mix technique using citric acid as the complexing agent. The tin oxide powder obtained at different calcination temperatures (773–1223 K) is characterized using powder X-ray diffraction (XRD), SEM, TEM, TG-DTG and UV spectroscopic techniques. The material obtained is nanocrystalline, having particle size in the range of 10–14 nm. The technique is cost-effective and yields the desired product at temperatures as low as 773 K.     

Grain-size analysis of fine and coarse non-plastic grains: comparison of different analysis methods

Grain size is a fundamental property of earth materials. Many techniques for measuring grain size exist, and elucidating the relationships among the different analysis techniques is valuable for understanding what constitutes grain size. In this study, grain-size distributions obtained through dry-mode digital particle imaging using optical microscopy, laser diffraction (LD), and hydrometer sieving (HS) were compared. For most of the investigated samples, the three methods yielded similar size distributions. When performing dry-mode particle optical imaging (DMPOI) measurements of grain size, we recommend using high dispersion pressure. The grain-size distribution curves of finer sands were shifted toward coarser particles in the DMPOI analysis results, compared to the LD and HS results. In contrast, the grain-size distribution curves of glass beads (irrespective of size) were similarly shaped in all three cases. The fractions of sand and silt sizes were relatively consistent among the three methods, but were smaller in the DMPOI results than in the LD and HS results. The median particle size (8–280 µm) was similar among the three methods. DMPOI yielded a lower standard deviation than the other methods. In the HS analysis of the mica sample (consisting of platy layer particles), the curve was clearly shifted toward finer particles, and the granulometric characteristics differed significantly from those obtained using the other methods. Therefore, the three methods appear to differ mainly in terms of their physical interpretations of “grain size” and the effects of the distribution width and high-sensitivity circularity of the particles.     

The Influence of Particle Size on the Mechanical Properties of Dental Glass Ionomer Cements

The toughening potential of a particle‐size reduction is investigated on experimental glass ionomer cements (GICs). A reduction of the particle size results in a reduced fracture toughness. The use of bimodal particle‐size distributions is proposed for the development of tough and workable cements, where small particles provide the reactive surface area and large particles are responsible for crack deflection. Characterization of a GIC‐restored tooth with reference to a composite restoration by nanoindentation demonstrates the clinical relevance of the study. The elastic properties of GICs are well adapted for application in contact with dentine.     

Nanocrystallization as a method of improvement of electrical properties of Fe2O3–PbO2–TeO2 glasses

Selected glasses of Fe₂O₃–PbO₂–TeO₂ system have been transformed into nanomaterials by annealing at a temperature close to the crystallization temperature (T_c). The effects of the annealing of the present samples on the structural and electrical properties were studied by transmission electron micrograph (TEM), X-ray diffraction (XRD), differential scanning calorimeter, density (d) and dc conductivity (σ). TEM and XRD of glass–ceramic naocrystals indicated nanocrystals embedded in the glassy matrix with average particle size of 20–35 nm. The glass–ceramic naocrystals obtained by annealing at T_c exhibit improvement of electrical conductivity up to four orders of magnitude than the starting glasses. This considerable improvement of electrical conductivity after nanocrystallization is attributed to formation of extensive and dense network of electronic conduction paths which are situated between Fe₂O₃ nanocrystals and on their surface. The conduction is attributed to non-adiabatic hopping of small polaron.     

Determination of the size of water-soluble nanoparticles and quantum dots by field-flow fractionation

Field flow fractionation (FFF) technique is used to determine the size of water-soluble Au, ZnS, ZnS-Mn2+ nanoparticles, and CdSe, CdSe-DNA quantum dots (QDs). The results of the FFF measurements are compared with the particle size analysis using conventional techniques like scanning electron microscopy (SEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS) studies. Water-soluble gold nanoparticles (AuNPs) stabilized by mercaptosuccinic acid (MSA) as the ligand when analyzed by the SEM and DLS showed evidence of extensive aggregation, preventing an accurate determination of the average particle size. The TEM analyses without staining offered a facile measurement of the nanoparticle core but average particle size determination required analysis of the TEM image using image analysis software. On the other hand the FFF is seemingly a convenient and easy method for the determination of the average particle size of the AuNPs. In case of the ZnS and ZnS-Mn2+ nanoparticles with mercaptopropionic acid (MPA) as the capping agent severe aggregation prevented accurate estimation of particle sizes even by the high resolution TEM (HRTEM), where as the size determination by the FFF was very facile. Analysis of the CdSe-DNA conjugate by the TEM was difficult as the sample got damaged upon exposure to the electron beam. The FFF cross-flow condition is apparently noninvasive and hence the technique was very effective in characterizing the CdSe-DNA QDs. Furthermore, using this simple technique it was possible to fractionate a sample of the AuNPs. The FFF measurement of water-soluble nanoparticles is an excellent complement to characterization of such particles by the conventional tools.     

Comparative Nanoparticle Size Characterization of EEW Alumina Using Various Measurement Techniques

Modern material science is paying more attention on the development of nanomaterials for superior properties in various fields of applications like mechanical, thermal, electronic, bio-medical etc. For such applications, determination of nanoparticle sizes along with their distribution is important for attaining the desired properties. Particle sizes along with the crystallite sizes of oxides, non-oxides and metallic nanopowders produced by different processes can be determined by different techniques which includes x-ray diffraction/neutron diffraction (XRD/ND), transmission electron microscopy/field emission scanning electron microscopy (TEM/FESEM), Brunauer-Emmett-Teller (BET) surface area method, small angle neutron scattering (SNAS), dynamic light scattering (DLS), static light scattering (SLS), etc. For average nano-metric particle size determination, DLS is the most frequently used technique that gives a distribution that approximates the exact binomial distribution of large numbers of nanoparticulates with varying particle size under investigation (Gaussian distribution). However, the other techniques mainly give either localized distribution of the particles under observation or the distribution derived from type II isotherm. In this investigation, nano-alumina powder produced by the electrical explosion of wire technique (EEW) is used for comparative evaluation of particle size analysis by DLS measurement technique for nanoparticles vis-à-vis to other techniques like XRD (for crystallite size), FESEM, BET, and TEM. The superiority of the DLS technique has been discussed in details with respect to the unique features of its Gaussian distribution nature.