Typical Particle Size Distribution Research Articles

Numerically quantifying the spectral dependence of the absorption enhancement of partially-coated black carbon with complex microphysical properties

The absorption of black carbon (BC) will be enhanced after it is coated with other components, and the research on the enhancement of BC absorption has become a hot topic in climate research in recent years. Some studies have measured the enhancement of BC absorption in certain specific wavelengths, and these measurement results are often used for the analysis of absorption in other wavelengths as well. This work employs numerical methods to quantitatively study the impact of microphysical characteristics of BC with non-absorbing coating on its spectral characteristics of absorption enhancement. This study defines the absorption enhancement Ångström exponent (EABSAE) to quantitatively describe the spectral characteristics of BC absorption enhancement. There are certain differences in the trends of absorption enhancement in different wavelengths with respect to microphysical characteristics, and EABSAE may deviate significantly from 0. The EABSAE of spherical BC usually varies between -2.5 and 2 in the wavelength range of 440–1064 nm. When considering the influence of complex morphology, the statistically average EABSAE of BC assembles with typical particle size distribution is roughly between -2 and 3. In the atmosphere, brown carbon (BrC) can mix with BC, which makes the EABSAE more complex. The EABSAE of BC coated with BrC can have a higher value. Therefore, an EABSAE value of at least 3 is required to prove the existence of BrC. In addition, the uncertainty in the calculation of absorption at other wavelengths was also evaluated in this work based on the absorption enhancement at a given wavelength.

Experimental and numerical investigation of seepage erosion in sandy cobbles under coupling hydraulic and dynamic load

The internal structure of sandy cobbles strata is sensitive to disturbances in the urban underground environment, but the structural evolution process under coupling hydraulic and dynamic loads remains unexplored. This paper presents a detailed investigation into the migration patterns and mechanisms of fine particles in sandy cobbles induced by coupled hydraulic and dynamic loading. A sandy cobble specimen with a typical particle size distribution (PSD) was designed and tested using an apparatus that included a constant inlet water head control system and an eccentric-vibrator-based dynamic loading system. Based on physical modeling tests, a numerical model was constructed to replicate the internal structural evolution under hydraulic and dynamic loading by calibrating the time history of local permeability. The test results indicate that the application of dynamic load can instantly disrupt the stable internal structure of sandy cobbles under static seepage, imparting kinetic energy to fine particles that detach from the skeleton structure and migrate along the seepage direction. Significant fine particle loss occurs near the seepage outlet, but due to energy loss during migration, fine particles far from the seepage outlet are recaptured by the skeleton pore throats and clogged again in the migration path. As the intensity of the dynamic loading increases, the migration path for fine particles becomes longer, and the amount and size of fine particles lost significantly increase. The changes in the internal structure of the soil are reflected in hydraulic parameters as a transient increase in local flow velocity, an increase in local pore water pressure due to clogging, and a decrease in the overall permeability coefficient with the loss of fine particles. The findings of this study will be useful for future geotechnical engineering design and analysis.

Effect of Particle Size Distributions (PSDs) on ground responses induced by tunnelling in dense coarse-grained soils: A DEM investigation

Tunnelling-induced ground responses in coarse-grained soils often exhibit complex behaviours such as soil arching and progressive ground instability. However, the effect of particle size distributions (PSDs) on ground responses in tunnelling remains largely unexplored. This study provides new insights into PSD’s effect on tunnelling ground response and the underlying mechanism based on granular skeleton quantification. The coarse-grained soils with 9 typical PSDs were modelled by the discrete element method (DEM) with varied granular skeleton structures. A representative volume element (RVE) assembly method, with a novel iteration-based specimen generation method, is developed to build ground models incorporating millions of soil grains, where an eccentric displacement boundary was embedded for reproducing the tunnel volume losses. The results demonstrated that the change in skeleton structures from fine-grains to coarse-grains dominated leads to the acceleration of soil arch emergence and the deceleration of soil arch collapse-rebuilding. With an increase in ded, the strengthened soil arch leads to a more evident deformation localization in ground, and results in more significant hysteresis of ground instability from the tunnel to the surface. The effect of PSDs on ground responses becomes prominent as the overburden thickness decreases and the tunnel volume loss increases, and a decrease in ded would increase the risk of overall failure in tunnelling.

Simulation and sensitivity analysis for cloud and precipitation measurements via spaceborne millimeter-wave radar

Abstract. This study presents a simulation framework for cloud and precipitation measurements via spaceborne millimeter-wave radar composed of eight submodules. To demonstrate the influence of the assumed physical parameters and to improve the microphysical modeling of the hydrometeors, we first conducted a sensitivity analysis. The results indicated that the radar reflectivity was highly sensitive to the particle size distribution (PSD) parameter of the median volume diameter and particle density parameter, which can cause reflectivity variations of several to more than 10 dB. The variation in the prefactor of the mass–power relations that related to the riming degree may result in an uncertainty of approximately 30 %–45 %. The particle shape and orientation also had a significant impact on the radar reflectivity. The spherical assumption may result in an average overestimation of the reflectivity by approximately 4 %–14 %, dependent on the particle type, shape, and orientation. Typical weather cases were simulated using improved physical modeling, accounting for the particle shapes, typical PSD parameters corresponding to the cloud precipitation types, mass–power relations for snow and graupel, and melting modeling. We present and validate the simulation results for a cold-front stratiform cloud and a deep convective process with observations from a W-band cloud profiling radar (CPR) on the CloudSat satellite. The simulated bright band features, echo structure, and intensity showed a good agreement with the CloudSat observations; the average relative error of radar reflectivity in the vertical profile was within 20 %. Our results quantify the uncertainty in the millimeter-wave radar echo simulation that may be caused by the physical model parameters and provide a scientific basis for optimal forward modeling. They also provide suggestions for prior physical parameter constraints for the retrieval of the microphysical properties of clouds and precipitation.

Green fabrication of titanium dioxide nanoparticles and their applications in photocatalytic dye degradation and microbial activities

The green method of metal oxide synthesis is an alternative to the more time consuming and difficult to consume traditional procedures, as the invention achieves a significant yield with minimal effort. Using this method proposed titanium dioxide (TiO2) nanoparticles (NPs) were made and used to make using different plant extracts and the characterization were analysed using X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), and UV−visible spectroscopy. TiO2 NPs were formed in the anatase phase, according to the XRD investigation, and the TEM confirmed their size of 15–28 nm and spherical morphology. According to scanning electron microscopic investigations, the typical particle size distribution of the individual particles was identified as being in the range of 21 nm. UV–visible spectroscopy proved the optical defects of the TiO2 NPs (2.89 eV, 2.98 eV, and 3.17 eV). FTIR was used to confirm the bio-functionality of flavonoids, M-O interactions, and surface interfaces. By using X-ray spectroscopy, it was shown that the TiO2 samples had an improved nanostructure and a 3:1 ratio of O:Ti components. In this particular study, attention was paid to both the photocatalytic and antimicrobial properties of TiO2 NPs. Producing TiO2 NPs requires efforts to reduce their toxicity in an environmentally responsible manner. When the dye methylene blue (MB), which is a significant water pollutant generated by the textile industry, was exposed to the TiO2 NPs, a high photodegradation efficiency was demonstrated, with photodegradation showing a degradation rate of 87%. According to the results, the Diameter Inhibition Zone (DIZ) possesses the highest level of inhibition against disease-causing microbes. As a consequence of these findings, an environmentally friendly and long-term viable option for water purification has been identified.

Study on shear characteristics of calcareous sand with different particle size distribution

For the island and reef project formed by filling calcareous sand, the problems of wide particle size distribution (PSD) and complex mechanical properties have to be faced. Therefore, in order to provide basic mechanical parameters for the construction of the island and reef project, triaxial shear tests were carried out on calcareous sands with five different typical PSDs. The results showed that as particle gradation became narrower, the axial strain corresponding to the strain-softening point all showed a decreasing trend and their differences gradually decreased; the confining pressure has a significant impact on the volumetric deformation modulus of calcareous sand with a wide PSD. The cohesion of calcareous sand showed a positive correlation with non-uniformity and curvature coefficients, while the variation of an internal friction angle showed a parabolic law; the internal friction angle also changes in the parabola with the change of fine particle contents. Furthermore, by establishing the PFC3D discrete element model, it was found that the numerical simulation results were in good agreement with the test results, which verifies the feasibility of the numerical simulation and the rationality of the mesoscopic parameter calibration. It was discovered that the wider the particle gradation range, the greater the axial strain corresponding to the critical coordination number; the sample with a narrow gradation interval was more likely to present a rotating displacement field to form a penetrating shear band. This study can provide design parameters for stability analysis of high and steep slopes in calcareous sand sites.

The Influence of the Fractal Dimension on the Mechanical Behaviors of the Soil–Rock Mixture: A Case Study from Southwest China

As the typical multi-phase geotechnical material, the particle size distribution of the natural soil–rock mixture (S–RM) has a significant impact on the structural and mechanical properties. The coarse grain content used in the laboratory and simulation tests falls short of accurately describing the particle size distribution feature of the entire material. The main subject of this article is the influence of the fractal dimension on mechanical behaviors based on the fractal theory. The double fractal characteristics were principally discussed along with the typical particle size distribution characteristics of the S–RM in the Three Gorges Reservoir and southwest China. The influence of the various fractal dimensions on the mechanical behaviors of S–RM was then investigated using three groups of large–scale triaxial tests, and the responses of the linear and nonlinear strength indexes were analyzed. The results show that the stress–strain curves of S–RM in the hyperbolic shape are visible under various confining pressure, and the nonlinear strength characteristics can be observed. The coarse grain content exhibits a negative correlation to the average fraction dimension. The difference between the coarse and fine grain fraction dimensions becomes considerably more obvious as the coarse grain content increases, which also increases the error when using the average fractal dimension. The voids between the coarse grains cannot be filled with the fine grains as the grain coarseness grows, resulting in a loose structure and a contact frictional effect, which lowers cohesion and raises the peak friction angle.

Enhancing the quartz-clay-feldspar system by nano-Al2O3 addition for electrical insulators: From laboratory to prototype scale

Nanotechnology applications have been increasing in the last years, offering innovative nanomaterials with enhanced characteristics and performance compared to conventional materials. In this work, a nanotechnology concept is proposed to improve the properties of a quartz-clay-feldspar ceramic system. The application target is in the electrical industry as an outdoor insulator. Experimental compositions were obtained by incorporating nano-alumina (nano-Al2O3) in siliceous porcelain to study their influence on the microstructure, physical, mechanical, and electrical properties. Industrial grade raw materials with a typical particle size distribution were used to prepare siliceous porcelain mixtures. Nano-sized alumina powder was added to the raw materials and then mixed to obtain good dispersion and high homogeneity. Specimens were prepared by uniaxial pressed and plastic extrusion processes for laboratory and prototype scale respectively and then were dried and fired, reaching a maximum temperature of 1250 °C. According to the SEM and XRD analysis, it was observed that alumina nanoparticles promote a mechanical strengthening mechanism in the ceramic body, mainly due to the increment of mullite. It was also found that dispersed nano-Al2O3 reinforces the glassy matrix providing a strong barrier that causes the crack deflection when loading. Nanostructured ceramic formulations exhibit higher flexural strength and superior breakdown voltage than conventional porcelain. The results include in this work strengthen the knowledge of nanotechnology concepts to develop advanced electrical porcelain systems.

Fast time response measurements of particle size distributions in the 3–60 nm size range with the nucleation mode aerosol size spectrometer

Abstract. Earth's radiation budget is affected by new particle formation (NPF) and the growth of these nanometre-scale particles to larger sizes where they can directly scatter light or act as cloud condensation nuclei (CCN). Large uncertainties remain in the magnitude and spatiotemporal distribution of nucleation (less than 10 nm diameter) and Aitken (10–60 nm diameter) mode particles. Acquiring size-distribution measurements of these particles over large regions of the free troposphere is most easily accomplished with research aircraft. We report on the design and performance of an airborne instrument, the nucleation mode aerosol size spectrometer (NMASS), which provides size-selected aerosol concentration measurements that can be differenced to identify aerosol properties and processes or inverted to obtain a full size distribution between 3 and 60 nm. By maintaining constant downstream pressure the instrument operates reliably over a large range of ambient pressures and during rapid changes in altitude, making it ideal for aircraft measurements from the boundary layer to the stratosphere. We describe the modifications, operating principles, extensive calibrations, and laboratory and in-flight performance of two NMASS instruments operated in parallel as a 10-channel battery of condensation particle counters (CPCs) in the NASA Atmospheric Tomography Mission (ATom) to investigate NPF and growth to cloud-active sizes in the remote free troposphere. An inversion technique to obtain size distributions from the discrete concentrations of each NMASS channel is described and evaluated. Concentrations measured by the two NMASS instruments flying in parallel are self-consistent and also consistent with measurements made with an optical particle counter. Extensive laboratory calibrations with a range of particle sizes and compositions show repeatability of the response function of the instrument to within 5–8 % and no sensitivity in sizing performance to particle composition. Particle number, surface area, and volume concentrations from the data inversion are determined to better than 20 % for typical particle size distributions. The excellent performance of the NMASS systems provides a strong analytical foundation to explore NPF around the globe in the ATom dataset.

Revisiting the confined comminution of granular materials with the consideration of the initial particle size distributions and repetitive loadings

The initial particle size distributions (PSDs) and cyclic loading effects for the confined comminution tests are studied by using discrete element method (DEM). Three typical PSDs, i.e. the uniform, bimodal and fractal, respectively, are used to explore the general correlations from microscopic quantities to macroscopic quantities during the loading-unloading-reloading procedure. For the initial bimodal packing, it cannot easily generate an ultimate fractal packing. And for the initial uniform and fractal packings, the ultimate fractal dimension of PSD would gradually increase during the reloading procedure. Moreover, the coordination distribution of particles (CNP) is insensitive with the initial PSDs and cyclic loadings. Furthermore, the fractal analysis of the network of force chains is also studied by the box method to evaluate the fractal features of force chains from the general, strong and weak perspectives. Additionally, a new descriptor for interpreting the relationship between the force chains and the composed particles (CFC) is proposed to evaluate the packing geometrical topologies and force chains. It can be used to evaluate the inter-particle structure feature of the granular assemblies. It is interesting to find that CFC is gradually increased with the increasing loading stress, and reaches a peak value in the unloading stage for the same stress state and decreases with the increasing number intensity of force chains.

A novel methodology to study polymodal particle size distributions produced during continuous wet granulation

It is important during powder granulation to obtain particles of a homogeneous size especially in critical situations such as pharmaceutical manufacture. To date, homogeneity of particle size distribution has been defined by the use of the d50 combined with the span of the particle size distribution, which has been found ineffective for polymodal particle size distributions. This work focuses on demonstrating the limitations of the span parameter to quantify homogeneity and proposes a novel improved metric based on the transformation of a typical particle size distribution curve into a homogeneity factor which can vary from 0 to 100%. The potential of this method as a characterisation tool has been demonstrated through its application to the production of granules using two different materials. The workspace of an 11mm twin screw granulator was defined for two common excipients (α-lactose monohydrate and microcrystalline cellulose). Homogeneity of the obtained granules varied dramatically from 0 to 95% in the same workspace, allowing identification of critical process parameters (e.g. feed rate, liquid/solid ratio, torque velocities). In addition it defined the operational conditions required to produce the most homogeneous product within the range 5μm–2.2mm from both materials.

Particle size distributions and organic-inorganic compositions of suspended particulate matters around the Bohai Strait

Laser in situ scattering and transmissometry (LISST) significantly improves our ability to assess particle size distribution (PSD) in seawater, while wide-ranging measurements of the organic-inorganic compositions of suspended particulate matters (SPM) are still difficult by using traditional methods such as microscopy. In this study, PSD properties and SPM compositions around the Bohai Strait (China) were investigated based on the measurements by LISST in combination with hydro-biological parameters collected from a field survey in summer 2014. Four typical PSD shapes were found in the region, namely right-peak, left-peak, double-peak and negative-skew shapes. The double-peak and negative-skew shapes may interconvert into each other along with strong hydrodynamic variation. In the upper layer of the Bohai Sea, organic particles were in the majority, with inorganic particles rarely observed. In the bottom layer, SPM were the mixture of organic and inorganic matters. LISST provided valuable baseline information on size-resolved organic-inorganic compositions of SPM: the size of organic particles mainly ranged from 4 to 20 μm and 40 to 100 μm, while most SPM ranging from 20 to 40 μm were composed of inorganic sediment.

Thermal conductivity of partially saturated microstructures

The growing importance of tight reservoirs exacerbates the necessity of pore-scale studies to characterize porous media from the pore-level point of view. Accurate prediction of pore-scale effective thermal and electrical conductivities leads to proper thermophysical and petrophysical characterization of partially saturated media. In this paper, a numerical framework is offered to predict electrical and thermal conductivities of two-phase saturated microstructures. The immiscible displacement scenarios within the microporosities are conducted utilizing a direct pore morphology-based technique; a set of rules to construct the fluid-fluid interfaces under capillary-driven flows. Subsequently effective thermal and electrical conductivity curves are predicted using steady state diffusion equation. Two sets of microstructures are used as the pore space geometries; real and synthetic. The real media under consideration include binary images of oil/water-wet sandstone and carbonate formations and the fluid systems contain steam-oil and water-oil equilibriums. The swelling spheres algorithm is adapted to generate two-dimensional granular synthetic media based on a typical particle size distribution of Alberta's unconsolidated oil sand. The result packages, including thermal diffusivity and conductivity, electrical conductivity, formation factor, and apparent diffusion coefficient are generated and discussed considering rock types and fluid configurations. The thermal and electrical conductance of well-connected consolidated microstructures appear to be weak functions of water saturation and are mainly controlled by porosity and solid phase configuration.

Role of typical soil particle‐size distributions on the long‐term corrosion behavior of pipeline steel

The electrochemical behavior of X70 pipeline steel in a 1.5 wt% NaCl sandy soil environment with two typical particle size distributions (PSD), continuous gradation (CG), and gap gradation (GG) was investigated using electrochemical measurements, scanning electron microscopy (SEM), and X‐ray diffraction (XRD). The results showed that, as the burial time increased, the corrosion rate of X70 pipeline steel increased in the initial corrosion stage, decreased at an intermediate stage, and then increased in the final stage in these two typical soil PSD environments. However, compared with the soil PSD pertaining to the CG environment, the corrosion rate of steel increased significantly in the GG environment, as evinced by the severe corrosion spots observed on the steel surface, attributed to the fact that, in the soil PSD for the GG environment, both the extent of liquid dispersion, and the number of galvanic cells increased, accelerating the cathodic step, i.e., oxygen‐reduction reaction in the three‐phase boundary (TPB) zone, and anodic step, i.e., the metal dissolution stage, of the X70 pipeline steel corrosion process, respectively. Both the anodic and cathodic processes were activation controlled. Thus, the corrosion of X70 pipeline steel was considerably dependent on the soil PSD in sandy soil environments.

Modified Landweber algorithm for robust particle sizing by using Fraunhofer diffraction.

In this paper, a robust modified Landweber algorithm was proposed to retrieve the particle size distributions from Fraunhofer diffraction. Three typical particle size distributions, i.e., Rosin-Rammler, lognormal, and bimodal normal distributions for particles ranging from 4.8 to 96 μm, were employed to verify the performance of the algorithm. To show its merits, the proposed algorithm was compared with the Tikhonov regularization algorithm and the ℓ1-norm-based algorithm. Simulation results showed that, for noise-free data, both the modified Landweber algorithm and the ℓ1-norm-based algorithm were better than the Tikhonov regularization algorithm in terms of accuracy. When the data was noise-contaminated, the modified Landweber algorithm was superior to the other two algorithms in both accuracy and speed. An experimental setup was also established and the results validated the feasibility and effectiveness of the proposed method.

Fine particle size chestnut flour doughs rheology: Influence of additives

Mixing properties of chestnut flour with typical particle size distribution of wheat flour, incorporated with chia flour (2.5%, 4.0%, 5.0%, 6.0%, 7.5%, flour basis, f.b.), hydroxypropyl methyl cellulose (HPMC) and guar gum (0.5%, 1.0%, 1.5%, 2.0%, f.b.) were determined at 30°C using Mixolab® apparatus. The rheological characterisation at 30°C was achieved by steady shear rate (0.01–10s−1), oscillatory (1–70rads−1 at 0.1% strain) and creep-recovery (loading of 50Pa for 60s) tests. Thermal behaviour of all chestnut flour doughs was also depicted. These rheological properties were significantly modified by the presence of chia flour and hydrocolloids. The values of apparent viscosity at each shear rate as well as the values of storage and loss moduli at each angular frequency decreased with chia flour, HPMC or guar gum addition. Creep-recovery data showed that the addition of chia flour at 6.0% (56.5%), HPMC at 2.0% (63.7%) or guar gum at 2.0% (64.5%) improved significantly the doughs elasticity in comparison to chestnut flour (20.2%). The flow curves and mechanical spectra were successfully fitted using Cross and power models, respectively.

Multifractal analysis of tensile toughness and filler dispersion for polypropylene–CaCO3 composites

Multifractal analyses were performed to elucidate the effect of incorporating maleic anhydride grafted polypropylene (MAPP) into a Polypropylene matrix: (i) on the dispersion of CaCO3 particles and (ii) on the fracture morphology of tensile samples. The box-counting method was applied considering the number of particles and the mean gray value distribution as measured properties of composites. The dispersion analysis exhibited, for the composite with MAPP, a reduction of larger agglomerates sizes without variation of the most frequent size. Similar results were achieved by a typical particle size distribution. Moreover, the morphology of fractured surfaces showed an irregular topography for composites without MAPP suggesting a complex fracture process. Composites with MAPP, on the contrary, displayed a regular surface morphology suggesting a more regular fracture process with an important reduction of ductile mechanisms. This fracture behavior was related to the variation of the singularity width Δα. The results obtained suggest that multifractal theory can be applied to elucidate the relationship between structure and mechanical behavior of PP–CaCO3 composite materials.

The Effect of Rotary Disk Atomizer RPM on Particle Size Distribution in a Semi-Industrial Spray Dryer

Spray drying is the most commonly used method in industry to produce powders on a large scale. One of the major problems in spray drying is control of the product particle size distribution since it is very important for most industries; e.g., catalyst, chemicals, foods, pharmaceuticals, ceramics, etc. The objective of this work is to study the effect of the atomizer rotational speed on the product size distribution. In order to obtain the typical particle size distribution of the required product, a specially designed atomizer disk is used in the study. The particle size distributions under atomizer rotating speeds in the 9,000–10,000 rpm range were measured and discussed.

PM 10, PM 2.5 and PM 1.0—Emissions from industrial plants—Results from measurement programmes in Germany

Emission measurement programmes were carried out at industrial plants in several regions of Germany to determine the fine dust in the waste gases; the PM 10, PM 2.5 and PM 1.0 fractions were sampled using a cascade impactor technique. The installations tested included plants used for: combustion (brown coal, heavy fuel oil, wood), cement production, glass production, asphalt mixing, and processing plants for natural stones and sand, ceramics, metallurgy, chemical production, spray painting, wood processing/chip drying, poultry farming and waste treatment. In addition waste gas samples were taken from small-scale combustion units, like domestic stoves, firing lignite briquettes or wood. In total 303 individual measurement results were obtained during 106 different measurement campaigns. In the study it was found that in more than 70% of the individual emission measurement results from industrial plants and domestic stoves the PM 10 portion amounted to more than 90% and the PM 2.5 portion between 50% and 90% of the total PM (particulate matter) emission. For thermal industrial processes the PM 1.0 portion constituted between 20% and 60% of the total PM emission. Typical particle size distributions for different processes were presented as cumulative frequency distributions and as frequency distributions. The particle size distributions determined for the different plant types show interesting similarities and differences depending on whether the processes are thermal, mechanical, chemical or mixed. Consequently, for the groups of plant investigated, a major finding of this study has been that the particle size distribution is a characteristic of the industrial process. Attempts to correlate particle size distributions of different plants to different gas cleaning technologies did not lead to usable results.

Microwave Assisted Semi-Solvothermal Synthesis of Nanocrystalline Barium Titanate

In an endeavor to synthesize tetragonal nanocrystallites of BaTiO3 at much reduced reaction time, we explored the possibility of performing microwave assisted semi-solvothermal reaction by using Ba(OH)2 . 8H2O and amorphous titanium hydrous gel as precursors and 1,4-butanediol and water as solvent. Typically, such a microwave assisted reaction was accomplished within 2 hrs at 220 degrees C as against 12 hrs required in conventional approach. The crystallized BaTiO3 powders (microwave assisted as well as conventionally processed for reference) were characterized by X-ray diffraction, thermal analysis, infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. We have detected metastable cubic phase by XRD while locally symmetric tetragonal phase by Raman spectroscopy in case of conventional semi-solvothermal processing. On the contrary, we could detect co-existence of tetragonal and cubic phases by XRD and only tetragonal phase by Raman spectroscopy in case of microwave assisted semi-solvothermal processing. The TEM analysis indicates typical particle size distribution in the range of approximately 20 to 80 nm for conventionally processed powder while that in the range of approximately 20 to 50 nm for microwave processed powder. HRTEM images evince the distortion from an ideal cubic structure in case of microwave processed powder which can be correlated with anisotropic lattice contraction during the microwave induced heating. AFM analysis exhibited relatively less aggregation of nanoparticles for microwave assisted process.