Small Crystal Particles Research Articles

Wax crystal dynamics and viscosity abnormal reduction in asphaltene-containing waxy oil at low temperatures

A micro-rheological integration experiment was conducted on model oils without asphaltene and with 0.05 wt% asphaltene. The study examined the viscosity-temperature characteristics of both model oils under different cooling rates and shear rates. Significant changes were observed in the viscosity-temperature curve of the asphaltene-containing model oil. At low shear rates, a distinct wavelet peak was identified in the temperature range of 37-30 °C, where viscosity initially increased, then decreased, and subsequently increased again. This wavelet peak diminished with the increasing shear rate, eventually forming a “buffer platform”. The underlying mechanism was attributed to asphaltene altering the wax crystal behavior from “uniform precipitation network structure formation” to “formation of unstable large aggregates - dissociation into multiple small stable aggregates - growth into larger stable aggregates.” In addition, the wax precipitation rate remained constant in the model oil without asphaltene, while in the asphaltene-containing model oil, the rate significantly accelerated between 34.5 °C and 32.5 °C. And the asphaltenes promoted the formation of small wax crystal particles but inhibited the growth of wax crystal particles.

A bifunctional strategy enabling 4.55 V LiCoO2 with improved electrochemical performance

LiCoO2 (LCO) has been functionally modified with electronic conductor of Al doped ZnO (AZO) and ionic conductor of Li3PO4 (LPO). The physicochemical characterization results demonstrated that the hexagonal structured AZO small crystal particles epitaxial growth formed island-like structures on the surface of LCO particles and LPO filled on the surface of remaining exposed LCO particles. Due to the unique composite coating layer with excellent electronic conductivity and Li ion conductivity, the AZO and LPO coated LCO exhibits outstanding rate capability and cycle stability in the voltage range of 2.75–4.55 V. The modified LCO delivered a specific capacity 206 mA h g−1 at 0.5C rate (100 mA g−1), and the capacity retention was 91.7 % after 50 cycles, which was a remarkable improvement comparing with uncoated LCO (34.8 %). Moreover, it exhibited an outstanding rate property, maintaining a discharge capacity of 161.4 mA h g−1 at 4C. This bifunctional strategy with AZO and Li3PO4 is an efficient approach to improve the electrochemical performance of LCO at high cut-off voltage (>4.5 V).

Studies of material deposition on the graphite divertor tile after the 2019 experimental campaign in EAST

• Detailed analysis of the deposits on the surface of the graphite tile from the divertor dome region has been made after the 2019 experimental campaign. • The porous globular deposits on exposed graphite tile were mainly stacked by columnar grains with size of 2–5 μm and small crystal particles with several hundreds of nanometers in size. • The thickness of the deposits varied from several micrometers to about 120 μm. • As the SiC coating on the graphite tile has a rough surface and exhibited valleys and hills, the deposits on the valleys were typically thicker than that on the hills. • Li was in the form of Li 2 CO 3 . And Mo and W were in MoO3 and WO3 respectively. • The total content of Li 2 CO 3 was found to be higher than 90 wt% with a corresponding Li density in deposits of about 7.22 μg/mm −2 in average. • The intensity of Li was strong and changed only slightly with the depth, which was different from other elements. Elements of W, Mo, Fe, Cu seemed to be more concentrated at the near surface with a depth of about 4 μm. Material erosion and deposition are one of the important topics related to plasma-wall interaction in tokamaks. Detailed analysis of the deposits on the surface of the graphite tile from the divertor dome region has been made after the 2019 experimental campaign. It is indicated that the deposits exhibited porous globular in morphology which were mainly stacked by columnar grains with size of 2–5 μm and small crystal particles with several hundreds of nanometers in size. The thickness of the deposits varied from several micrometers to about 120 μm. As the SiC coating on the graphite tile has a rough surface and exhibited valleys and hills, the deposits on the valleys were typically thicker than that on the hills. The deposits consisted of Li, C, O, W, Mo, Fe, Cu, Ni, et. mainly from the wall conditioning materials and plasma-facing materials. It was noted that Li was in the form of Li 2 CO 3 . And Mo and W were in MoO 3 and WO 3 respectively. The total content of Li 2 CO 3 was found to be higher than 90 wt% with a corresponding Li density in deposits of about 7.22 μg/mm −2 in average due to the routine Li wall conditioning. The depth profile of Li exhibited differently from the other elements. And W has a higher density than Mo, which could be due to the high W erosion from the upper divertor.

Pyrolysis of biomass Tar model compound with various Ni-based catalysts: Influence of promoters characteristics on hydrogen-rich gas formation

This paper studied the conditions and mechanism of hydrogen-rich gas produced from catalytic pyrolysis of toluene by various Ni-based catalysts in a fixed-bed reactor. We specifically focused on the effect of different promoters and promoter characteristics on the physicochemical properties of Ni/HZSM-5 -based catalyst. The results revealed that, a similar initial activity for Ni-catalysts modified different promoters was tested with toluene conversion higher than 85%. The Fe-modified Ni/HZSM-5 catalyst has the most effective catalyst for hydrogen-rich gas production with the gaseous efficiency of 63.4 wt%, mainly gas (H2, CH4) yield of 118.6 mL/g-toluene, H2 yield of 53.4 mL/g-toluene at 800 °C pyrolysis for 40 min. The smaller crystal particles (3.1 nm), high surface area (219.5 m2/g), and sufficient loading quality (4 wt%) for Ni–Fe catalysts provided efficient active sites and promoted the pyrolysis process of toluene. The activity and stability of catalysts were also improved by Ce-modified Ni/ZSM-5 catalyst with the highest gaseous efficiency of 68.0 wt%, but the H2 yield of 40.3 mL/g-toluene was lower. However, Ni–Mg/HZSM-5 catalyst has lowest activity and stability. The catalyst deactivation is associated with nickel sintering and coke formation. After the Ni–Fe/HZ5 catalyst was regenerated twice, it still maintained high catalytic activity.

Fabrication of nano- or micro-powder for hydroxyapatite particles derived from bovine bone

Background: Hydroxyapatite (HA) from bovine bone has been shown to have bone regenerative capability and therefore has potential benefits in bone grafting. However, the extraction procedures are often time-consuming and labor intensive. Therefore, this study aimed to devise a simple process to fabricate HA particles from bovine bone with the potential to be used in bone tissue engineering.
 Methods: In this study, the simple process combined physical and chemical methods to remove numerous organic components, followed by annealing at 600oC to fabricate small crystal HA particles. The organic presence in the HA product was detected by Fourier-transform infrared (FTIR) spectroscopy. The particle size, interconnected porous structure, and the calciumto- phosphorous molar ratio (Ca/P) were examined by X-ray powder diffraction method (XRD), scanning electron microscope (SEM), and energy dispersive X-ray (EDX) analysis.
 Results: The combination method completely removed the organic composition. The results of SEM, XRD, and FTIR demonstrated the formation and preservation of small (nanometer sized) crystal HA particles with the porous structure. The Ca/P ratio was similar to that for natural bone.
 Conclusion: Pure natural HA crystals could be extracted from bovine bone. The combination of chemical and thermal decomposition methods was effective in producing HA particles. The method proposed herein has the advantage of being simple and relatively inexpensive, thereby rendering it beneficial for large-scale application.

Catalytic Pyrolysis of Biomass Tar Using Different Ni-Based HZMS-5: Influence of Promoters Characteristics on Hydrogen-Rich Gas Formation

The study specifically focused on the effect of different promoter characteristics and interactions between Ni-Ce, Ni-Fe, and Ni-Mg on the physicochemical properties of Ni/HZSM-5 catalyst. The results revealed that promoter characteristics are important when determining the form of nickel atomic species, structural properties and catalytic abilities of catalysts. The Fe-modified Ni/ZSM-5 catalyst has the most effective catalyst for hydrogen-rich gas production with the highest gaseous efficiency of 63.4 wt.%, gas yield of 118.6 mL/g toluene, H2 yield of 53.4 mL/g toluene at 800 °C pyrolysis for 1 hour. However, the stability of catalysts improved by incorporating CeO2, the H2 yield was lower (40.3 mL/g). Ni-Mg/HZSM-5 catalyst was slightly less stable. The smaller crystal particles (3.1 nm), high surface area (219.5 m2/g), and sufficient loading (4 wt.%) for Ni-Fe catalysts provide efficient active sites and promote the process for pyrolysis biomass tar. Catalyst’s deactivation is associated with char deposition.

SYNTHESIS AND CHARACTERIZATION OF LiFePO4/PPy/CLAY COMPOSITE AS CATHODE MATERIAL FOR Li-ION BATTERY

SYNTHESIS AND CHARACTERIZATION OF LiFePO4/PPy/CLAY COMPOSITE AS CATHODE MATERIAL FOR Li-ION BATTERY. Conductor polymers have been used previously as a conducting agent or carbon source in various sol-gel and solid state methods to increase the conductivity of LiFePO4. The composite of LiFePO4/PPy/Clay were synthesized by mixing LiFePO4 and clay with a Ppy solution. The characterizations were done by using X-Ray Diffractometer (XRD), Scanning Electron Microscope (SEM) and LCR meter respectively. From XRD analysis it could be deduced that LiFePO4 has an ordered olivine structure with a Pnma space group. The SEM images provide clear evidence that small crystal particles of LiFePO4 either coat the surface of the clay particles or lie among them. These LiFePO4 particles have a small particle size (100–500 nm). With the increasing of LiFePO4 content, these small crystal particles at the surface or among the clay particles are increased. Increasing the PPy content to increase the conductivity of the material obtained. With the addition of clay from 5 to 10 wt. %, the DC conductivity of the blends is clearly observed to increase up to three orders of magnitude.

FeCe nanocomposite with high iron content as efficient catalyst for generation of COx-free hydrogen via ammonia decomposition

FeCe nanocomposite catalysts with different iron contents were synthesized by a facile co-precipitation method. The as-prepared materials were characterized by various techniques including powder X-ray diffraction (XRD), N2 adsorption/desorption and high-resolution transmission electron microscopy (HRTEM). Catalyst with the highest iron content (90FeCe) shows the best activity for the hydrogen generation via ammonia decomposition. 83% NH3 conversion is achieved at 550 °C and nearly full conversion of NH3 is realized at 600 °C with a GHSV of 24000 cm3/(gcat·h). The large content and small size crystal particles of iron species are responsible for the good catalytic performance. Temperature-programmed reduction by hydrogen (H2-TPR) was performed to investigate the interaction between cerium and iron species. It is found that slight cerium can exert strong interaction with iron compound thus effectively prevent the self-aggregation of active iron species, so as to improve the catalytic activity for ammonia decomposition.

Preparation and characterization of Ti/SnO2-Sb2O3/α-PbO2/Ce-Nd-β-PbO2 composite electrode for methyl orange degradation

The present study focused on the preparation, characterization, and application of cerium (Ce) and neodymium (Nd) co-doped lead (PbO2) electrode, i.e., Ti/SnO2-Sb2O3/α-PbO2/Ce-Nd-β-PbO2. The electrochemical activities of the modified electrode were investigated and compared with those of Ce-PbO2, Nd-PbO2, and pure PbO2 electrodes. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface morphology, crystal structure, and elemental states of the modified electrode. The Ce and Nd co-doped PbO2 electrode had smaller crystal particles, more compact structure, and higher activity of electrocatalysis compared with the single-doped and undoped PbO2 electrodes. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were also utilized to study the electrochemical response of the modified electrodes. The results show that the prepared Ce-Nd-PbO2 electrode has the highest O2 evolution potential (OEP) and lowest charge transfer resistance, suggesting that it has the lower energy consumption than the other three kinds of electrodes. Electrochemical oxidation methyl orange (MO) as a model dye wastewater was studied to evaluate the potential applications of this modified electrode in environmental science. It was found that the Ce-Nd-PbO2 electrode exhibited higher MO and chemical oxygen demand (COD) removal efficiency than single-doped and pure PbO2 electrodes.

Enhanced scale inhibition against Ca3(PO4)2and Fe2O3in water using multi-functional fluorescently-tagged antibacterial scale inhibitors

P-Free copolymers display enhanced scale (Ca3(PO4)2and Fe2O3) inhibition, improved antibacterial performance, and reliablein situfluorescence detection of concentration.

Improving THF hydrate formation in the presence of nonanoic acid

Numerous experiments of tetrahydrofuran (THF) hydrate formation are conducted to investigate the potential of nonanoic acid, which is an organic phase change material, as a kind of novel promoters for hydrate formation. The mixture of THF + nonanoic acid + H2O was stirred using an ultra-sonication bath to prepare emulsion. Nonanoic acid forms a series of small crystal particles when the temperature of the emulsion is lowered. These small crystal particles of organic phase change material promote THF hydrate nucleation and growth. The induction time of THF hydrate formation reduces and the rate of hydrate growth increases with the increase of the mass fraction of nonanoic acid when nonanoic acid mass fraction is <3 wt%. However more additives of nonanoic acid do not further promote THF hydrate formation. The average induction time of THF hydrate formation is the smallest with 3 wt% nonanoic acid in this work. The conversion degree of THF hydrates formed with 3 wt% nonanoic acid is about 82.9% at 0.2 °C under static conditions. The experimental results also show that the nucleation of THF hydrate is a stochastic process but nonanoic acid improves the scatter of hydrate induction time. THF hydrate can form within 73 min under 0.2 °C with 3 wt% nonanoic acid in quiescent conditions. The induction time of THF hydrate formation reduces and the rate of hydrate growth increases with the decrease of experimental temperature.

Satellite-based Observational Study of the Tibetan Plateau Vortex: Features of Deep Convective Cloud Tops

In this study, an east-moving Tibetan Plateau vortex (TPV) is analyzed by using the ERA-5 reanalysis and multi-source satellite data, including FengYun-2E, Aqua/MODIS and CALIPSO. The objective is to demonstrate: (i) the usefulness of multi-spectral satellite observations in understanding the evolution of a TPV and the associated rainfall, and (ii) the potential significance of cloud-top quantitative information in improving Southwest China weather forecasts. Results in this study show that the heavy rainfall is caused by the coupling of an east-moving TPV and some low-level weather systems [a Plateau shear line and a Southwest Vortex (SWV)], wherein the TPV is a key component. During the TPV’s life cycle, the rainfall and vortex intensity maintain a significant positive correlation with the convective cloud-top fraction and height within a 2.5◦ radius away from its center. Moreover, its growth is found to be quite sensitive to the cloud phases and particle sizes. In the mature stage when the TPV is coupled with an SWV, an increase of small ice crystal particles and appearance of ring- and U/V-shaped cold cloud-top structures can be seen as the signature of a stronger convection and rainfall enhancement within the TPV. A tropopause folding caused by ageostrophic flows at the upper level may be a key factor in the formation of ring-shaped and U/V-shaped cloud-top structures. Based on these results, we believe that the supplementary quantitative information of an east-moving TPV cloud top collected by multi-spectral satellite observations could help to improve Southwest China short-range/nowcasting weather forecasts.

Character of crystallization particle in bitten transfer pump

In order to understand the flow pattern of salt-out particles in a bittern transfer pump, the population balance model (PBM) coupled with mixture two-phase was applied to calculate the particle flow. User-defined particle growth and nucleation models were used in this study to consider the actual dynamic behavior of the crystallization particle, such as particle growth, nucleation, aggregation and breakage. The result shows that the average particle size is smaller and more evenly distributed among area of the impeller inlet. The size of crystal particles is different at different regions in the impeller passages with the characteristics of small crystal particles near suction side and large crystal particles near pressure side. In addition, the distribution of average particle size near pressure and suction side has an upward trend from inlet to outlet. The distribution of crystal particles on the blade near the tongue is different from other blades whether it is in the pressure surface or suction surface.

Preparation and characterization of Ce and PVP co-doped PbO2 electrode for waste water treatment

In this study, the novel PbO2 electrodes co-doped with rare earth (Ce) and polyvinylpyrrolidone (PVP) were prepared by electrodeposition technique. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used to characterize the surface morphology and crystal structure of the electrodes. In contrast with PbO2, Ce–PbO2, PVP–PbO2 and Ce–PVP–PbO2 electrodes, the Ce–PVP–PbO2 electrode had smaller crystal particles and more compact structure. The electro-catalytic activity of electrodes was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that the prepared Ce–PVP–PbO2 electrode has lower energy consumption and more excellent electrochemical oxidation performance than other three kinds of electrodes. Electrochemical oxidation methyl orange as a model dye wastewater was studied to evaluate the potential applications of this electrode in environmental science. It was found that the Ce–PVP–PbO2 electrode exhibited higher decolorization and COD removal efficiency than other three kinds of electrodes.

Influence of Aluminum Contents on Phase Behavior and Properties of TiN-Sialon-Corundum Composites by Aluminothermic Reduction Nitridation

TiN-Sialon-Corundum composites were synthesized from rutile and quartz by aluminothermic reduction nitridation (ARN) method. The effects of aluminum contents on the phase behavior and properties of products were investigated. At 1500 oC, the main phases of products ARNed for 4 h were large granular corundum, TiN and hexagonal columnar Si3Al3O3N5. In addition, small TiN crystal particles distributed around the Si3Al3O3N5. It suggested that TiN-Sialon-Corundum composites were successfully fabricated by ANR method at 1500 °C for 4h. With increases in the amount of aluminum contents, the compressive strength ,the flexural strength and the bulk density of the composite refractory increased while the apparent porosity decreased. When the the aluminum contents increased to 48.90%, the composites had the highest compressive strength (47.34MPa) ,flexural strength (27.70MPa), bulk density (2.27 g/cm3) and had the lowest apparent porosity (27.57 %).

Effect of magnetic treatment on microstructure and cycle performance of LiFePO4/C cathode material

LiFePO4/C composite was prepared by hydrothermal synthesis along with a magnetic treatment method. The LiFePO4/C composite synthesized without magnetic treatment is an integrated rhombic shape crystal, whereas the LiFePO4/C material synthesized with magnetic treatment presents a rhombus shape which is self-assembled by a number of small crystal particles with an average size of about 100nms. The capacity retention for the LiFePO4/C cathode material synthesized without magnetic treatment is only 77% after 30 charge–discharge cycles at 0.2C, but the LiFePO4/C composite synthesized with magnetic treatment has a capacity retention of 100% after 100 charge–discharge cycles at 1C and 5C. It suggests that magnetic treatment can remove Fe3+ cations effectively during the preparation process and enhance the cycle performance of the LiFePO4/C material.

Preparation and characterization of carbon nanotube and Bi co-doped PbO2 electrode

A novel carbon nanotube and Bi co-doped PbO2 electrode (CNT-Bi-PbO2) was prepared by thermal deposition and electrodeposition technologies. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used to characterize the surface morphology and crystal structure of the electrodes. In contrast with PbO2, Bi-PbO2, and CNT-PbO2 electrodes, the CNT-Bi-PbO2 electrode had smaller crystal particles and more compact structure. The linear voltammetry was utilized to determine the oxygen evolution overpotential of electrodes. The electro-catalytic activity of electrodes was investigated by cyclic voltammetry. The yield of ·OH and electro-catalytic oxidation degradation of p-nitrophenol (p-NP) at four kinds of electrodes were tested. Besides, the stability of electrodes was also determined by accelerated service life tests. The results show that the prepared CNT-Bi-PbO2 electrode had higher oxygen evolution overpotential and more excellent electrochemical oxidation performance than other three kinds of electrodes. The reaction rate constant of p-NP on the CNT-Bi-PbO2 electrode was 1.69 times and the mineralization current efficiency at 180min on CNT-Bi-PbO2 electrode was 1.36 times that on PbO2 electrode. Moreover, the service lifetime of CNT-Bi-PbO2 electrode was 4.16 times as much as that of PbO2 electrode.

Synthesis and Hydrodesulfurization Performance of Bulk Ni-Mo-W Catalyst with High Surface Area

Bulk Ni-Mo-W hydrodesulfurization catalysts with high catalytic activity were synthesized via direct precipitation and controlled pH precipitation method, respectively. Analysis results shows that the preparation method has great influence on the morphology and pore structure, and further influence the hydrodesulfurization activity. The catalyst synthesized by controlled pH precipitation method has much higher surface area and pore volume, 132.9 m2/g and 0.30 mL/g, due to its developed porous structure accumulated by small crystal particles. The activity evaluation indicates that the bulk Ni-Mo-W hydrodesulfurization catalysts has good ultra-deep desulfurization activity of removing complex organic sulfur compounds, such as DBT and Cn-DBT.

Synthesis and Desulfurization Performance of Flower-Like ZnO Materials by Hydrothermal Homogeneous Precipitation Method

To better understand the nature of reactive adsorption of thiophene on Ni/ZnO adsorbent, the effects of ZnO textural structure on the desulfurization activity were investigated. Flower-like ZnO materials were synthesized by hydrothermal homogeneous precipitation method and the corresponding Ni/ZnO adsorbents were prepared by incipient impregnation method. The analysis results showed that both the crystalline sizes and the BET surface areas of flower-like ZnO were better than that of commercial ZnO. The activity evaluations indicated that the Ni/ZnO adsorbents prepared with ZnO possessing a favorable textural structure exhibited good activity of removing thiophene. The evolutions of the main crystalline phases of Ni/ZnO adsorbents before and after reaction confirmed that ZnO played a crucial role in taking up S element and converted it into ZnS in the reactive adsorption process. It was concluded that ZnO with larger surface area and smaller crystal particles resulted in better desulfurization activity, which may be the main reason for the better activities of the Ni/ZnO adsorbents prepared with flower-like ZnO matterials.

Sonocrystallisation of sodium chloride particles for inhalation

Fine sodium chloride particles are of pharmaceutical interest in aerosol delivery for diagnosis of asthma and bronchial related disorders. In this paper, stable NaCl particles with size ranging from approximately 1 μ m to sub-micron range were achieved by sonocrystallisation. The effects of sonocrystallisation temperature, ultrasonic power output and salt concentration were investigated in the ranges of 5 – 35 ∘ C , 22–60 W and 8–34 g/100 g water, respectively, under a fixed ultrasonic frequency of 20 kHz. Size and morphology characterisation of particles were undertaken using laser diffraction and scanning electron microscopy. Optimally prepared particles were spray dried followed by in vitro impaction test for inhalation efficiency determination using an Aeroliser ® . Optimal conditions of temperature ( < 5 ∘ C ), ultrasonic power output ( ∼ 35 W ) and salt concentration ( ∼ 32 g / 100 g water) exist that reduced the size of the crystals to the sub-micron scale. Spray drying increased the size of the prepared particles and altered the cubic shape to more rounded morphology. The fine particle fraction (based on recovery) was improved from approximately 12 to 34% when dispersion air flow rate was increased from 60 to 120 L/min. Sonocrystallisation represents an effective method for the preparation of NaCl particles suitable for pharmaceutical inhalation. The main advantage of this method is that it is rapid, simple and produces small crystal NaCl particles suitable for inhalation.