Broad Particle Size Research Articles

INVESTIGATION OF QUALITY TARGET PROCESS PARAMETERS (QTPP) AND CRITICAL MATERIAL ATTRIBUTES (CMA) OF NANOCELLULOSE AS A POTENTIAL EXCIPIENT

Objective: The current work highlights the use of the Quality by Design (QbD) for optimization of Nanocellulose (NC) production from corn husk by two techniques, namely, Acid hydrolysis (AH) and High pressure homogenization (HPH).
 Methods: Characterization of NC involved Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM). For the risk assessment, QbD Software was used. According to this results 32 factorial design was applied in which two independent variables (acid concentration and time for AH whereas pressure and no of passes for HPH) and two dependent variables (particle size and yield) were selected.
 Results: FTIR showed similarity in the peaks which indicates there is no change in parent molecular structure of cellulose. TGA confirmed that the NC extracted by both the methods showed improved thermal property at onset temperature of 290 °C as compared to Avicel PH101, 270 °C. XRD results showed that the crystallinity index of the extracted nano cellulose from both the method was 83.15% which indicates transition and reorientation of corn husk into compact crystalline cellulosic structure after removal of non-cellulosic materials. TEM images indicated that the fibers were well dispersed and the treatment had reduced the size of fibers with average dimensions of 100 to 1000 nm in length. Product assay revealed that as the acid concentration and time is increased, narrow particle size is observed whereas lower number of passes and pressure resulted in a broader particle size. Studies on the variables and the experiment of NC preparation contributed a maximum yield of 77% in case of AH and 83 % in case of HPH.
 Conclusion: Evident from the results, NC prepared by QbD approach had better flow property and compatibility. Hence it is suitable for usage as an excipient in product design for variety of tailor made customized oral dosage forms in pharmaceutical industry.

Filtration properties of kraft lignin: The influence of xylan and precipitation conditions. - OPEN ACCESS

LignoBoost lignin powder was dissolved together with xylan and re-precipitated. The influence of the (i) precipitation temperature, (ii) rate of acidification and (iii) final pH of the slurries on the resulting material and its filtration properties was investigated. In the case of slow acidification, larger agglomerates were obtained for slurries with higher precipitation temperatures as well as with higher ionic strengths. Fast acidification led to a more heterogeneous formation of particles, having a broader particle size distribution, compared to slow acidification. Chemical analysis of different layers of the filter cakes formed revealed that xylan was distributed evenly on the solid lignin, reinforcing the hypothesis that xylan is sorbed onto the lignin agglomerates when precipitated together with lignin. Furthermore, the resulting lignin-xylan mixtures were found to be more difficult to filter in the case of a higher final pH of the slurry (pH 4), close to the pKa values of the carboxylic acid groups of xylan, compared to lower pH values (pH 1-3). This is likely the result of an increase in electrostatic repulsive interactions between the particles/agglomerates at higher pH: a locally more porous solid structure is formed, leading to a larger solid/liquid surface area during filtration.

Polydisperse spherical colloidal silica particles: Preparation and application**Project supported by the National Major Scientific and Technological Special Project during the Twelfth Five-year Plan Period of China (Grant No. 2009ZX02030-1), the National Natural Science Foundation of China (Grant No. 51205387), the Science and Technology Commission of Shanghai, China (Grant No. 11nm0500300), and the Science and Technology Commission of Shanghai, China (Grant

A new industrial method has been developed to produce polydisperse spherical colloidal silica particles with a very broad particle size, ranging from 20–95 nm. The process uses a reactor in which the original seed solution is heated to 100°C, and then active silicic acid and the seed solution are titrated to the reactor continuously with a constant rate. The original seeds and the titrated seeds in the reactor will go through different particle growth cycles to form different particle sizes. Both the particles’ size distribution and morphology have been characterized by dynamic light scattering (DLS) and the focus ion beam (FIB) system. In addition, the as-prepared polydisperse colloidal silica particle in the application of sapphire wafer’s chemical mechanical polishing (CMP) process has been tested. The material removal rate (MRR) of this kind of abrasive has been tested and verified to be much faster than traditional monodisperse silica particles. Finally, the mechanism of sapphire CMP process by this kind of polydisperse silica particles has been investigated to explore the reasons for the high polishing rate.

Inverse opal photoelectrode of Nb-doped TiO2 nanoparticles for dye-sensitized solar cell

In this study, Nb-doped TiO2 nanoparticles were prepared by solution synthesis, and utilized as photoelectrode for dye-sensitized solar cell aiming to obtain better photon-to-current conversion efficiency. Nb doping was carried out using two different Nb precursors, and subsequent hydrothermal treatment resulted in the size-controlled (~10 nm) Nb-doped TiO2 nanoparticles with typical ellipsoidal shapes and anatase morphologies. It was observed that NbCl2 precursor resulted in more uniform particle size, while Nb oxalate resulted in relatively broader particle size distributions and higher aspect ratio ellipsoid. Using these nanoparticles, 10 μm-thick porous inverse opal (IO) photoelectrodes were fabricated by coating the mixed aqueous dispersions of Nb-TiO2 nanoparticles and polystyrene particles of 270 nm diameter on conductive glass followed by thermal sintering. DSSC single cell performance tests revealed that a photoelectrode from 2 mol% Nb- TiO2 obtained from NbCl2 exhibited 20 % enhancement for solar cell efficiency compared to bare TiO2 IO.

The Effect of Milling Time and Sintering Temperature on Synthesis of PbTiO<sub>3</sub> by Mechanical Alloying

PbTiO3 is one of electroceramic materials which can be applied for electronics and microelectronics due to their dielectric, pyroelectric, and piezoelectric properties. The members of PbTiO3-based ferroelectrics are widely used in multilayer, actuator and sensor capacitor. At room temperature, PbTiO3 has a tetragonal perovskite structure. In this research, PbTiO3 particles are synthesized by mechanical alloying method with variation of milling time and sintering temperature. The milling time variation is taken for 10, 20 and 30 hours. Sintering temperature variation is performed at 850, 900 and 1000°C. The powders used in the milling process are PbO and TiO2 powders. X-Ray Diffraction (XRD) and Scanning Electron Microscopy–Electron Difraction X-ray (SEM-EDX) are performed to analyze the formation of PbTiO3 phase. It is found that the synthesized powders contain 100% PbTiO3 phase for all sintering temperatures. The PbTiO3 particles have agglomeration shape with a broad particle size. The electrical properties of PbTiO3 are measured using electrical test device. Electricity test analysis shows that the synthesized PbTiO3 behaves as semiconductor-like.

Enhancing fluidization stability and improving separation performance of fine lignite with vibrated gas‐solid fluidized bed

A vibrated gas‐solid fluidized bed was proposed and tested to improve and upgrade fine lignite. A broad particle size (0.074–0.3 mm) of magnetite powder was prepared and used as main separating medium solids for coal improvement. The fluidization stability of the bed, including the fluidization index, fluctuations of bed pressure drop, and uniformity of bed density, was greatly enhanced by introducing the vibration energy to the static bed. The vibrated separation shows positive effects to improve the surface morphology of lignite and upgrade its quality to a certain degree. Ash‐content segregation of fine lignite samples obviously occurs by the joint effects of fluidized gas and vibration. The optimal segregation degree Sash values of 0.73 and 0.70 were achieved with suitable operating factors. The density‐dependent separation performance indicates that the ash and sulfur contents of lignite were sharply reduced with the probable error E values of 0.060 and 0.065 g/cm3. However, the overall E value for 6–1 mm sized fine lignite increases to 0.12 g/cm3 due to the shift in the D50 with particle size. The products of low‐ash clean coal, middlings, and high‐ash gangue were effectively obtained by successive separations. The dry coal improvement technology provides an alternative approach for the clean utilization of fine coal.

Joining of Ceramic Components in the Green State via LPIM

It has been successfully demonstrated that ceramic materials can be joined in the green state without a second phase by using low pressure injection molded parts. The investigation of the joining interface revealed that a high quality interface can be achieved by carefully adjusting the different manufacturing steps. The use of monomodal particle size distribution in the used powder CT3000SG is inferior to a broader particle size distribution obtained by replacing 33% of the finer alumina powder by coarser CT1200SG. In this way the dewaxing process is significantly improved when the wall thickness of the part exceeds 3 mm. The investigation of the mechanical properties of the joined and sintered parts revealed, that the bending strength of the joined specimens achieved about 80 % of the unjoined, monolithic specimens.

Random particle packing with large particle size variations using reduced-dimension algorithms

We present a reduced-dimension, ballistic deposition, Monte Carlo particle packing algorithm and discuss its application to the analysis of the microstructure of hard-sphere systems with broad particle size distributions.We extend our earlier approach (the “central string”algorithm) to a reduced-dimension, quasi-3D approach. Our results for monomodal hard-sphere packs exhibit a calculated packing fraction that is slightly less than the generally accepted value for a maximally random jammed state. The pair distribution functions obtained from simulations of composite structures with large particle size differences demonstrate that the algorithm provides information heretofore not attainable with existing simulation methods, and yields detailed understanding of the microstructure of these composite systems.

Synthesis of Al-doped LiMn2O4spinels by mechanical alloying and rotary heating

LiMn2O4 has been widely studied as the cathode material for Li-ion batteries because of its low cost, environmental merit and relatively high voltage [1–3]. However, it shows significant capacity fading and poor cycleability. A very effective way for improving the cycling performance of LiMn2O4 is to synthesize manganese-substituted LiMx Mn2−x O4 spinel phase by doping with divalent or trivalent ions (M = Al, Mg, Co, Ni, Fe, Ti, Zn and Cr, etc.) [4–8]. The conventional synthesis method of LiMn2O4 is direct solid-solid reaction of oxides and carbonate of manganese and either LiOH, or Li2CO3 and LiNO3 at high temperatures to enhance the diffusion process and obtain a well-ordered structure. Due to this high temperature, there are some disadvantages such as broader particle size distribution, longer reaction time or other unwanted phases. However, solid-state reaction technology is easy and simple, and is one of the most suitable techniques for industrialization. The obstacles to the solid-state reaction are mainly the higher synthesis temperature and longer high temperature reaction time, together with the difficulties in the effective controls of chemical composition and microstructures. In recent years great progress has been mode in developing new synthesis methods of LiMn2O4 [9–13]. One of the main approaches is mechanical alloying. The works of Kosova et al. [11–13] on LiMn2O4 showed that mechanical alloying significantly decreased the synthesis temperature and the resulting products exhibited tolerable electrochemical performances. Mechanical alloying can produce particle and grain sizes down to the nanoscale, together with structure defects. Energetic lattice defects, combined with short diffusion distances, are the driving forces for faster solid-state alloying and chemical reactions at low temperatures. The high temperature furnaces for solid-state synthesis, at present, are mainly periodical kilns or furnaces. The powders in these equipments are static. Therefore the temperature field within the powders is often nonuniform during heating or cooling, especially for mass production, which will result in non-uniform chemical composition and non-uniform particle size distribution in a batch of synthesized powders. On the other hand, these mechanically alloyed initial powders easily grow during the following high temperature treatment,

Technical note: use of laser diffraction for particle size distribution measurements in duodenal digesta.

Duodenal samples from three lactating cows were used to measure the particle size distribution by wet sieving and by laser diffraction (LD). The median particle size was calculated in the size range where the methods overlapped, and the median particle size was not different between the methods (P = 0.98). The particle size data were also fitted to a log normal distribution function. The logarithmic mean particle size (log10mean) tended to be larger for wet sieving (P = 0.06), and the logarithmic standard deviation (log10SD) was similar for the two methods (P = 0.32). In addition, duodenal samples from the same three animals were fractionated into five different size classes by wet sieving. Particle size distributions were measured by LD and by microscopic image analysis (MIA) for each of the size classes. The log10mean particle size calculated by LD was inside the sieve size range of the four smallest size classes. Log10mean particle size calculated by LD was smaller than log10mean calculated by MIA for two size classes (106 to 300 microm and 300 to 600 microm), and LD gave generally broader particle size distributions than MIA. This study showed that duodenal particle size distributions measured by LD and wet sieving were similar and LD is therefore an alternative method for particle size distribution measurements in postruminal digesta.

Processing Effects on The Morphology of Hydrothermally Derived Nanocrystalline Lead Titanate

ABSTRACTNanocrystalline lead titanate was synthesized by reacting nanocrystalline titanium oxide in aqueous solutions of potassium hydroxide and lead acetate at 200 degrees C. X-ray diffraction (XRD) and TEM studies suggest that the initial KOH concentration influenced the nucleation and growth behavior of the lead titanate nanoparticles. Powders were processed in aqueous solutions containing 0.10 M lead acetate and a Pb:Ti ratio of 1, with varying concentrations of KOH. Powders processed in 0.01 M KOH were composed of irregularly shaped particles with 50-100 nm in size, processing in 0.10 M KOH produced particles with finger-like morphology and broader particle size distribution, and processing in 1.0 M KOH resulted in anisometric plates with (001) facets, and 100-200 nm in size. XRD studies have shown systematic variations in the position and symmetry of reflections with a l component as a function of particle size. This indicates that the c/a ratio of lead titanate increases with decreasing nanoparticle size

Polymer dispersion preparation by flow induced phase inversion emulsification. Part 1 The effect of silica on emulsification and dispersion characteristics

Low density polyethylene (LDPE) melt was emulsified in the presence of a hydrophobically modified water soluble polymer (HMWSP) and colloidal hydrophilic silica using the Flow Induced Phase Inversion (FIPI) emulsification technique. HMWSP was used as the surface active material. After the emulsification, LDPE melt was solidified to obtain a polymeric dispersion. Silica was used to aid the emulsification and improve the emulsion/dispersion characteristics. It was shown that the presence of silica increases the amount of aqueous phase necessary for phase inversion from water-in-LDPE melt to LDPE melt-in-water emulsion. The mean particle size and particle size span increased in the presence of silica. However, due to broader particle size distribution, the viscosity was lowered. The dispersions with silica appeared to form a more uniform film compared with the dispersion without silica. When the silica concentration is less than 1% in aqueous phase, an emulsion is obtained. At 2% silica level, a wet powdery material is obtained. This material can be diluted to obtain a dispersion or it could be used in powder coating.

Preparation of nanometric titanium hydrous oxide particles by vapour phase hydrolysis of titanium tetrabutoxide

Spherical titanium nanoparticles in the range of 60 to 500 nm have been obtained by a vapour-phase hydrolysis procedure using titanium tetrabutoxide as raw material. In this work, different parameters such as alkoxide temperature, water temperature, carrier gas flow rate, inlet pressure, vacuum and dilution of the raw material were tested. The most important parameters in order to obtain nanoparticles of low mean size were the flow rate, the alkoxide temperature and the inlet pressure. When the temperature decreases the mean size decreases obtaining nanoparticles below 100 nm when the temperature is set up to 125°C. On the other hand, as the flow rate that pass through the alkoxide increases the particle size decreases. Same behaviour is observed when the pressure inlet is increased. In all cases, these results are attributed to a minor concentration of the alkoxide (low amount of alkoxide molecules) in the gas stream. The other parameters, vacuum, water temperature and dilution of the alkoxide did not show any important influence in the particle size as the other ones. Polydispersity (broad or narrow particle size distribution) has the same trend. The alkoxide temperature and carrier flow rate generate narrow distributions while the other parameters produces broad distributions. FT-IR analysis of these nanoparticles showed that for sizes below 100 nm the alkoxide is fully hydrolysed and as the particle size increases the nanoparticle has more alkoxide or alcohol retained inside. The heat treatment of these nanoparticles produces a decreasing in the particle size and in all cases, the spherical shape is retained and no blackening in the nanoparticles of higher size is observed.

On standardizing the ‘Water Drop Penetration Time’ and the ‘Molarity of an Ethanol Droplet’ techniques to classify soil hydrophobicity: A case study using medium textured soils

Two common methods to assess soil hydrophobicity are the ‘Water Drop Penetration Time’ and ‘Molarity of an Ethanol Droplet’ techniques. For these, uncertainty exists regarding the representativeness of laboratory tests reflecting field conditions, their replicability, and the comparability of results between the two techniques. Using air-dried soils with a broad particle size and hydrophobicity range, this study shows that a high representativeness and replicability of results can be achieved. A close relationship between the two tests was found for highly, but not for moderately hydrophobic soils. Guidelines are suggested to increase representativeness, replicability and comparability of results in future studies. © 1998 John Wiley & Sons, Ltd.