Wet-etched asymmetric spherical nanoparticles with controllable pit structure and application in non-aqueous foam

Soft Matter ◽  
2021 ◽  
Author(s):  
Gen Li ◽  
Keliang Wang ◽  
Chunjing Lu
Keyword(s):  
Colloidal Particles ◽  
Spherical Particles ◽  
Spherical Nanoparticles ◽  
Aqueous Foam ◽  
Wet Chemical

The structure of colloidal particles is one of the factors that significantly affect their properties. Asymmetrical spherical particles with pit structures were prepared by using NH4F to perform wet chemical...

Preparation and characterization of uniform submicrometer metal niobate particles: Part II. Magnesium niobate and potassium niobate

1992 ◽  
Vol 7 (4) ◽  
pp. 912-918 ◽  
Author(s):  
Myung Jin Kim ◽  
Egon Matijević
Keyword(s):  
Colloidal Particles ◽  
Spherical Particles ◽  
Potassium Niobate ◽  
Homogeneous Precipitation ◽  
Potassium Salts ◽  
Chemical Mechanisms ◽  
Magnesium Niobate

Amorphous spherical particles of magnesium and potassium niobates were produced by homogeneous precipitation in solutions of magnesium and potassium salts, respectively, in the presence of polymeric niobium oxo-hydroxide ions. At pH 9 solids of definitive compositions were achieved and converted to crystalline powders of MgNb2O6 and KNbO3 on calcination. Chemical mechanisms for the formation and transformation of such colloidal particles are offered.

Estimation and fingerprinting of the size distribution of non-interacting spherical particles from small-angle scattering data

2021 ◽  
Vol 54 (5) ◽  
Author(s):  
Debasis Sen ◽  
Ashwani Kumar ◽  
Avik Das ◽  
Jitendra Bahadur
Keyword(s):  
Size Distribution ◽  
Small Angle ◽  
Colloidal Particles ◽  
Nonlinear Least Squares ◽  
Small Angle Scattering ◽  
Spherical Particles ◽  
Scattering Data ◽  
Fitting Procedure ◽  
Angle Scattering ◽  
Log Normal

A new method to estimate the size distribution of non-interacting colloidal particles from small-angle scattering data is presented. The method demonstrates that the distribution can be efficiently retrieved through features of the scattering data when plotted in the Porod representation, thus avoiding the standard fitting procedure of nonlinear least squares. The present approach is elaborated using log-normal and Weibull distributions. The method can differentiate whether the distribution actually follows the functionality of either of these two distributions, unlike the standard fitting procedure which requires a prior assumption of the functionality of the distribution. After validation with various simulated scattering profiles, the formalism is used to estimate the size distribution from experimental small-angle X-ray scattering data from two different dilute dispersions of silica. At present the method is limited to monomodal distributions of dilute spherical particles only.

scholarly journals FORMATION OF NANO-AND ULTRAFINE PALLADIUM POWDERS IN THE PRESENCE OF «RED-OX»SYSTEM«TITANIUM (III) - TITANIUM (IV)»

2020 ◽  
Vol 5 (443) ◽  
pp. 21-27
Author(s):  
Bayeshov A.B., ◽  
◽  
Gaipov T.E., ◽  
Bayeshova A.K., ◽  
◽  
...  
Keyword(s):  
Electrochemical Method ◽  
Colloidal Particles ◽  
New Technology ◽  
Atomic State ◽  
Spherical Particles ◽  
Nanodispersed Powder ◽  
Palladium Powder ◽  
The Stability ◽  
Trivalent Titanium ◽  
Over Time

The results of studies on the processes of obtaining ultra - and nanodispersed palladium powders from sulphate solutions by a combined chemical and electrochemical method in the presence of a "red-ox" system of titanium (III) - titanium (IV) are presented. It has been shown that when a titanium trivalent sulphate solution is added to a solution containing palladium (II) ions, palladium ions are immediately reduced to elemental state to form a nanodispersed powder. The completeness of the above-mentioned oxidizing-reducing reactions is established on the basis of calculating the equilibrium constant (K), which is 1034 and indicates that trivalent titanium ions completely reduce palladium ions to elemental state. Effect of initial concentration of palladium ions on amount of formed palladium powder with addition of equivalent amount of trivalent titanium ions is investigated. According to the authors, upon reduction of palladium ions, elemental palladium is formed in the atomic state, and over time, the atoms begin to combine with each other. Subsequently, atomic particles are combined into colloidal particles. It has been found that in the absence of coagulants, the colloidal palladium solution is stable for 2-3 hours, and in the presence of gelatin, the stability increases and remains for 36 hours. It was shown that in all experiments powders with spherical particles are formed, the average sizes of which range from 0.116-0.240 microns. Based on the results of the presented studies, a new technology for producing ultra - and nano-sized palladium powders is proposed.

Colloidal Particles: Spherical Yttrium Iron Garnet

1998 ◽  
Vol 517 ◽  
Author(s):  
R.H.M. Godoi ◽  
M. Jafelicci ◽  
R.F.C. Marques ◽  
L.C. Varanda
Keyword(s):  
Homogeneous Nucleation ◽  
Colloidal Particles ◽  
Spherical Particles ◽  
Phase Identification ◽  
Yttrium Iron ◽  
X Ray ◽  
Electron Microscopies ◽  
Dispersion Media ◽  
Iron Garnet ◽  
Different Characteristics

AbstractThe purpose of this work is to obtain spherical particles YIG from micrometric to nanometric scales. The spherical particles were obtained from cation hydrolysis in acid medium by adding urea or ammonia in order to carry out a homogeneous nucleation process up to 90°C. Different composition and morphology were achieved by changing reactant concentrations, precipitation agent and stabilizing agent. X-ray diffractometry, electrophoretic mobility, transmission and scanning electron microscopies were carried out on these particles to investigate the phase identification, mobility, morphology and particle size. Crystalline YIG, with spherical characteristics, was obtained. The surface potential presented different characteristics for different dispersion media.

Dissolved Urate Promotes Calcium Oxalate Crystallization: Epitaxy is Not the Cause

1993 ◽  
Vol 85 (3) ◽  
pp. 303-307 ◽  
Author(s):  
Phulwinder K. Grover ◽  
Rosemary L. Ryall ◽  
Villis R. Marshall
Keyword(s):  
Calcium Oxalate ◽  
Heterogeneous Nucleation ◽  
Colloidal Particles ◽  
Renal Stones ◽  
Urine Samples ◽  
Ultrafiltration Membranes ◽  
Calcium Oxalate Crystallization ◽  
Crystallization Experiments ◽  
Before And After ◽  
Wet Chemical

1. Increasing the concentration of dissolved urate promotes the crystallization of calcium oxalate from urine. The possibility was investigated that this effect may be caused by heterogeneous nucleation of calcium oxalate by particles of crystalline urate. 2. Urine samples were collected from 10 healthy men, centrifuged and filtered, and a solution of sodium urate was added to increase the medium urate concentration from 2.2 to 5.6 mmol/l. Calcium oxalate crystallization was induced by the addition of oxalate, followed by incubation for 90 min in a shaking waterbath at 37°C. The crystalline material was filtered out and the urate concentration was determined in the filtrate. 3. No difference in the urate concentration before and after induction of calcium oxalate crystallization was observed. These findings were confirmed by infra-red spectroscopy, X-ray powder diffraction and ultraviolet wet chemical analysis with detection limits of 5-10, 1.0 and 0.055%, respectively; urate was not detected in the calcium oxalate crystals. 4. In addition, three urine samples were collected and passed through 10 kDa ultrafiltration membranes to remove any colloidal particles which might have been present. The urate concentration was increased and an oxalate load was added as before, prior to incubation at 37°C in a shaking water bath for 5 min, followed by passage through 10 kDa ultrafiltration membranes. Scanning electron microscopy revealed no particles on the membranes thereby indicating that colloidal or crystalline urate was not formed early in the crystallization experiments. 5. It was concluded that the promotion of calcium oxalate crystallization by urate, and thereby the formation of calcium oxalate renal stones, is not caused by heterogeneous nucleation and subsequent epitaxial growth of calcium oxalate upon particles of urate.

scholarly journals Self-assembly mechanism in colloids: perspectives from statistical physics

Open Physics ◽  
2012 ◽  
Vol 10 (3) ◽  
Author(s):  
Achille Giacometti
Keyword(s):  
Integral Equation ◽  
Self Assembly ◽  
Hard Sphere ◽  
Statistical Physics ◽  
Colloidal Particles ◽  
Building Blocks ◽  
Computational Effort ◽  
Spherical Particles ◽  
Square Well ◽  
Patchy Colloids

AbstractMotivated by recent experimental findings in chemical synthesis of colloidal particles, we draw an analogy between self-assembly processes occurring in biological systems (e.g. protein folding) and a new exciting possibility in the field of material science. We consider a self-assembly process whose elementary building blocks are decorated patchy colloids of various types, that spontaneously drive the system toward a unique and predetermined targeted macroscopic structure. To this aim, we discuss a simple theoretical model — the Kern-Frenkel model — describing a fluid of colloidal spherical particles with a pre-defined number and distribution of solvophobic and solvophilic regions on their surface. The solvophobic and solvophilic regions are described via a short-range square-well and a hard-sphere potentials, respectively. Integral equation and perturbation theories are presented to discuss structural and thermodynamical properties, with particular emphasis on the computation of the fluid-fluid (or gas-liquid) transition in the temperaturedensity plane. The model allows the description of both one and two attractive caps, as a function of the fraction of covered attractive surface, thus interpolating between a square-well and a hard-sphere fluid, upon changing the coverage. By comparison with Monte Carlo simulations, we assess the pros and the cons of both integral equation and perturbation theories in the present context of patchy colloids, where the computational effort for numerical simulations is rather demanding.

scholarly journals Efficient design, accurate fabrication and effective characterization of plasmonic quasicrystalline arrays of nano-spherical particles

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Farhad A. Namin ◽  
Yu A. Yuwen ◽  
Liu Liu ◽  
Anastasios H. Panaretos ◽  
Douglas H. Werner ◽  
...  
Keyword(s):  
Periodic Structures ◽  
Mie Theory ◽  
Quantitative Model ◽  
Spherical Particles ◽  
Two Dimensional ◽  
Efficient Design ◽  
Spherical Nanoparticles ◽  
Quantitative Results ◽  
Spherical Arrays

Abstract In this paper, the scattering properties of two-dimensional quasicrystalline plasmonic lattices are investigated. We combine a newly developed synthesis technique, which allows for accurate fabrication of spherical nanoparticles, with a recently published variation of generalized multiparticle Mie theory to develop the first quantitative model for plasmonic nano-spherical arrays based on quasicrystalline morphologies. In particular, we study the scattering properties of Penrose and Ammann- Beenker gold spherical nanoparticle array lattices. We demonstrate that by using quasicrystalline lattices, one can obtain multi-band or broadband plasmonic resonances which are not possible in periodic structures. Unlike previously published works, our technique provides quantitative results which show excellent agreement with experimental measurements.

Laminar Convective Heat Transfer of Alumina-Polyalphaolefin Nanofluids Containing Spherical and Non-Spherical Nanoparticles

2011 ◽  
Author(s):  
Leyuan Yu ◽  
Dong Liu ◽  
Frank Botz
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Thermophysical Properties ◽  
Stokes Equations ◽  
Effective Medium Theory ◽  
Spherical Particles ◽  
Spherical Nanoparticles ◽  
Fluid Medium ◽  
The Past

As a promising candidate for advanced heat transfer fluids, nanofluids have been studied extensively during the past decade. In contrast to the early reports of dramatic heat transfer enhancement even at extremely low particle concentrations, the most recent studies suggest the laminar convective heat transfer of nanofluids is only mildly augmented and can be predicted by the conventional Navier-Stokes equations. The majority of the past studies were limited to water-based nanofluids synthesized from spherical nanoparticles. No systematic information is yet available for the convective heat transfer of nanofluids containing non-spherical particles, especially those formulated with the base fluid other than water. An experimental study was conducted in this work to investigate the thermophysical properties and convective heat transfer characteristics of Al2O3-Polyalphaolefin (PAO) nanofluids containing both spherical and rod-like nanoparticles. The effective viscosity and thermal conductivity were measured and compared to predictions from the effective medium theory. The friction factor and local Nusselt number were also measured for the laminar flow regime. It was found that established theoretical correlations can satisfactorily predict the experimental data for nanofluids containing spherical nanoparticles; however, they are less successful for nanofluids with nanorods. The possible reasons may be attributed to the shear-induced alignment of non-spherical nanoparticles and its subsequent influence on the development of the thermal boundary layer. The results suggest that the hydrodynamic interactions between the non-spherical nanoparticles and the surrounding fluid medium have a significant impact on the thermophysical properties as well as on the thermal transport characteristics of nanofluids.

Optically Induced Rapid Electrokinetic Patterning of Non-Spherical Particles: Study of Colloidal Phase Transition

2010 ◽  
Author(s):  
Raviraj Vijay Thakur ◽  
Steven Wereley
Keyword(s):  
Phase Transition ◽  
Fluid Mechanics ◽  
Electrode Surface ◽  
Colloidal Particles ◽  
Spherical Particles ◽  
Lab On Chip ◽  
Chip Technology ◽  
Sorting Technique ◽  
On Chip ◽  
Rapid Electrokinetic Patterning

Patterning of colloidal particles on surfaces is an application that has evinced wide interest from the fluid mechanics community, due to its possible applicability in a number of engineering situations such as manufacture of photonic crystals[1], bioengineering tissues[2] and lab on chip technology[3], etc. Recently Kumar et al. had proposed the technique of rapid electrokinetic patterning (REP) [4], a hybrid opto-electric manipulation technique that can manipulate and pattern colloidal particles on an electrode surface. REP utilizes optical landscapes to create local gradients in temperature on an electrode substrate. This allows local changes in permittivity and conductivity of the fluid. Colloidal particles can then be dynamically patterned at the illuminated locations of the electrode surface. REP can be used for capturing selective group of particles and thus it serves as a sorting technique too [5].

SMOOTHED PROFILE METHOD TO SIMULATE COLLOIDAL PARTICLES IN COMPLEX FLUIDS

2009 ◽  
Vol 20 (09) ◽  
pp. 1457-1465 ◽  
Author(s):  
RYOICHI YAMAMOTO ◽  
YASUYA NAKAYAMA ◽  
KANG KIM
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Colloidal Particles ◽  
Stokes Equations ◽  
Electrolyte Solutions ◽  
Rigid Body Dynamics ◽  
Spherical Particles ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Charged Colloids

A new direct numerical simulation scheme, called "Smoothed Profile (SP) method," is presented. The SP method, as a direct numerical simulation of particulate flow, provides a way to couple continuum fluid dynamics with rigid-body dynamics through smoothed profile of colloidal particle. Our formulation includes extensions to colloids in multicomponent solvents such as charged colloids in electrolyte solutions. This method enables us to compute the time evolutions of colloidal particles, ions, and host fluids simultaneously by solving Newton, advection-diffusion, and Navier–Stokes equations so that the electro-hydrodynamic couplings can be fully taken into account. The electrophoretic mobilities of charged spherical particles are calculated in several situations. The comparisons with approximation theories show quantitative agreements for dilute dispersions without any empirical parameters.

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