Heterogeneous Dispersion Research Articles

Multi-functional Strategy: Ammonium Citrate-Modified SnO2 ETL for Efficient and Stable Perovskite Solar Cells.

The tin oxide (SnO2) electron transport layer (ETL) plays a crucial role in perovskite solar cells (PSCs). However, the heterogeneous dispersion of commercial SnO2 colloidal precursors is far from optimized, resulting in dissatisfied device performance with SnO2 ETL. Herein, a multifunctional modification material, ammonium citrate (TAC), is used to modify the SnO2 ETL, bringing four benefits: (1) due to the electrostatic interaction between TAC molecules and SnO2 colloidal particles, more uniformly dispersed colloidal particles are obtained; (2) the TAC molecules distributed on the surface of SnO2 provide nucleation sites for the perovskite film growth, promoting the vertical growth of the perovskite crystal; (3) TAC-doped SnO2 shows higher electron conductivity and better film quality than pristine SnO2 while offering better energy-level alignment with the perovskite layer; and (4) TAC has functional groups of C═O and N-H containing lone pair electrons, which can passivate the defects on the surface of SnO2 and perovskite films through chemical bonding and inhibit the device hysteresis. In the end, the device based on TAC-doped ETL achieved an increased power conversion efficiency (PCE) of 21.58 from 19.75% of the reference without such treatment. Meanwhile, the PSCs using the TAC-doped SnO2 as the ETL maintained 88% of their initial PCE after being stored for about 1000 h under dark conditions and controlled RH of 10-25%.

Heterogeneous velocity and dispersions coefficient influence on ionic transport model in creeks

This paper shows the rate of ionic concentration in the creek, different station point were used to monitor their variation rates of concentration in the creek, the transport system were developed based on the investigation carried out to observed the source of contamination in the study environment, the process were applied in other to determine the significant parameters that influence the transport process of the contaminant, these generates variations of the creek velocity and dispersion coefficient, the flow rates experienced heterogeneity in its depositions through its velocity rates at different station points, such parameters were integrated in the system to generated derived simulation values, the graphical representation experience decrease with respect to increase in distance, these condition observed were due to variations of the creek flow rates through velocity of flows in different figures, such conditions were observed to pressured the system that determine the concentration rates at different figures, these figures reflects different station points that validated the predictive values through experimental data for model validation, the generated results were above the permissible limited as an acceptable standard of 0.3Mg/L, the study is imperative because the rate of ionic content in different locations has been determined, their influential parameters has be observed in the study environment, there rates of concentrations which reflects the significant parameters that pressured it transport process in the creek has been observed, these were all determined in the study environment, proofing the validation of the model for ionic concentration in the study area.

Novel preparation of lithium‐ion battery wet‐processed separator based on the synergistic effect of porous skeleton nano‐Al2O3in situ blending and synchro‐draw

AbstractRoutine lithium‐ion battery separators with uneven micropores and poor electrolyte affinity raise ion transport barriers and become the battery‐performance‐limiting factors. A wet‐processed separator with homogeneous porous structure and porous skeleton nano‐Al2O3 in situ blending is readily prepared by thermally induced phase separation of paraffin, nano‐Al2O3 and ultra‐high molecular weight polyethylene (UHMWPE) in this work. SEM, ImageJ statistical analysis, porosity and Gurley calculation show that a separator that has undergone asynchronous drawing exhibits ample sturdy fibrils, heterogeneous pore size dispersion, poor permeability and strong anisotropy. However, UHMWPE deforms much more uniformly under a synchro‐draw, which distinctly lessens coarse fibrils, centralizes porous construction after stretching and brings better isotropy for the separator. Additionally, nano‐Al2O3 scattered in the cast film further weakens the heterogeneity of micropores stemming from the uneven thermally induced phase separation. Wettability tests and thermal diagnoses also show that nano‐Al2O3 on the porous skeleton strengthens the thermal stability and electrolyte affinity of the separator. Consequently, batteries containing nano‐Al2O3 composite separators show much higher electrochemical stability, ionic conductivity and Li+ transport number because of the synergistic effect of the even microvoids and nano‐Al2O3 on the porous skeleton, which expedites Li+ transport and endows superior lithium‐ion battery performance. © 2022 Society of Industrial Chemistry.

Unsaturated Transport Modeling: Random‐Walk Particle‐Tracking as a Numerical‐Dispersion Free and Efficient Alternative to Eulerian Methods

AbstractLagrangian methods, such as the random‐walk particle‐tracking (RWPT), are often qualified as a potentially valuable alternative to error‐prone Eulerian methods for simulating solute transport in unsaturated porous media. Yet, the RWPT method has not yet been validated against ‐ and compared to ‐ currently used Eulerian solutions for simulating solute transport under a range of typical unsaturated conditions. This paper presents a new implementation of the RWPT approach for advective ‐ dispersive transport problems under variably saturated conditions. We first show that, as previously demonstrated for a heterogeneous dispersion tensor, using an interpolation scheme in the RWPT algorithm performs well for problems with abrupt changes in the water content. The new model is then compared against a simple 1D uniform transport problem, for which an analytical solution exist, and against a variety of 1D and 3D numerical solutions using the different Eulerian schemes implemented in Hydrus software suite. Results show that, while the Eulerian solutions significantly suffer from numerical dispersion in case of a coarse spatial discretization of the simulation domain, the new Lagrangian model provides accurate solutions for all problems. Furthermore, RWPT reproduces accurately solute transport for typical unsaturated flow conditions (infiltration, evaporation). Moreover, the Lagrangian model appears to be orders of magnitude faster than its Eulerian alternative to solve a 3D heterogeneous problem. Thus, RWPT should be seen as an attractive, stable and efficient alternative for simulating solute transport in the vadose zone, especially in case of complex and large problems.

Organizational-Performance Pay and Compensation Dispersion

We document the performance implications of compensation dispersion under organizational-performance pay, a scheme where individual compensation consists of a pre-designated share of rewards contingent on organizational performance. We examine the field setting of professional eSports athletes facing an exogenous change in the distribution of shares of team-based rewards. We find that unequal, heterogeneous share dispersion—relative to equal, homogeneous compression—results in lower organizational performance. While share dispersion aligns the incentives of high-share individuals with the organization’s—motivating them to contribute more—it also engenders unfavorable social comparison among low-share individuals—demoralizing them into contributing much less. A complementary controlled experiment validates the findings and demonstrates that organizational-performance pay, relative to other payment schemes, exacerbates the consequences of dispersion, especially when reward-sharing is cognitively salient.

Fractal water structures affected by softener agent in cotton cloths

Broadband dielectric spectroscopy (BDS) measurements were performed on cotton cloth samples with softener agents in natural environments, and a recent analytical technique of fractal analysis refined in dielectric spectroscopy was used for water structures. Three relaxation processes observed in the GHz, MHz, and kHz regions were attributed to the dynamic behaviors of hydrogen-bonding networks (HBNs) of water and interacting molecules, hydrated polymer chains, and ions restricted in the interfaces of large structures. Fractal analysis of the GHz region suggested that the GHz frequency process was retained, even in the dry state, revealing a broad spatial distribution of HBN fragments of various sizes. This typical tendency for heterogeneous hydration in cotton cloth was emphasized by the addition of a softener agent, as the value of Cole–Cole’s relaxation time distribution parameter changed from 0.55 to 0.41. The addition of the softener agent still retained the GHz frequency process, even in the dry state. This result means that the softener inhibited the formation of hydration sites on the cellulose surface and induced the dispersion of hydration sites. Thus, HBNs are fragmented by the softener agent. On the other hand, water molecules still aggregate to retain HBNs in a restricted area. The heterogeneous dispersion of HBN fragments broadens the GHz relaxation process, and the lower-frequency tail overlaps with the lower relaxation process because of chain dynamics with interacting water molecules. The structure formed by these water molecules, which is restricted by polymer chains and related to the stiffening effect of cotton fabric, is also heterogeneously hindered by the appropriate concentration of the softening agent. These indications were also consistent with the T2 relaxation time obtained using the Carr–Purcell–Meiboom–Gill method of nuclear magnetic resonance measurements and are consequently reflected in the hydration model for macroscopic properties of cotton fabric.Graphical abstract

Reactive precipitation of vaterite calcium carbonate microspheres in supercritical carbon dioxide-water dispersion by microfluidics

Vaterite, a polymorphic form of precipitated calcium carbonate, is an interesting material for various applications such as formulation of drug delivery systems due to its nanoporous structure. One of the carbonation processes to obtain nanostructured microspheres of vaterite consists in mixing an aqueous calcium phase with a supercritical CO2 phase, resulting in a heterogeneous dispersion. In this study, a continuous microfluidic method has been evaluated to produce monodisperse porous vaterite microparticles. A high-pressure microfluidic set-up has been developed, revealing that the dimensions and the dispersity of the CaCO3 particles are not affected by pressure but can be decreased by increasing the flow rate of the scCO2 and aqueous phases or addition of polymers in the aqueous phase. These observations were shown not to be related to the degree of dispersion of each phase within the microfluidic channel but to the interaction of the polymer with the CaCO3 particles and to the depressurization step at the end of the channel.

In Situ Synthesis of Silver Nanoparticles on Flame-Retardant Cotton Textiles Treated with Biological Phytic Acid and Antibacterial Activity.

Fabrics were flame-retardant finished using phytic acid, a cost-effective, ecologically acceptable, and easily available flame-retardant finishing chemical. Then, on the surface of the completed fabric, silver nanoparticles (Ag NPs) were grown in situ to minimize Ag NPs aggregation and heterogeneous post-finishing and to increase washing durability. Thus, flame-retardant and antibacterial qualities were added to textiles. The as-prepared textiles were evaluated for their combustion performance, thermal performance, and antibacterial capabilities. At the same time, their microstructures were studied using X-ray diffractometry (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The findings indicated that flame-retardant textiles had an excellent launderability (limiting oxygen index = 31% after 20 washing cycles). Meanwhile, Ag NPs-loaded flame-retardant textiles demonstrated self-extinguishing properties, with a limiting oxygen index (LOI) of 27%. Bacteriostatic widths of flame-retardant antibacterial textiles against Escherichia coli and Staphylococcus aureus were 5.28 and 4.32 mm, respectively, indicating that Ag NPs-loaded flame-retardant fabrics have certain flame-retardant and antibacterial capabilities. SEM and TEM analysis indicated that nanoparticles were uniformly dispersed over Ag NPs-loaded flame-retardant textiles and were around 20 nm in size. When compared to flame-retardant textiles, Ag NPs-loaded flame-retardant fabrics showed varied binding energy of P and N on the surface and Ag ion emergence. Thermogravimetric analysis at various heating rates revealed that the main pyrolysis temperature range of flame-retardant fabrics decreased, while the main pyrolysis temperature range of Ag NPs-loaded flame-retardant fabrics increased; the heating rate influenced the pyrolysis range but not the fabric mass loss. In situ reduction synthesis of Ag NPs-loaded flame-retardant textiles may successfully reduce agglomeration and heterogeneous dispersion of nano-materials during post-finishing.

Synthesis of eugenol-functionalized polyhedral oligomer silsesquioxane for low-k bismaleimide resin combined with excellent mechanical and thermal properties as well as its composite reinforced by silicon fiber

Introducing porous materials into resin matrix is effective to achieve low dielectric constant (low-k) value but challenge for simultaneously improving mechanical and thermal properties due to the heterogeneous dispersion of these fillers. Herein, a novel eugenol-functionalized cage-like (pore size, 1–2 nm) polyhedral oligomeric silsesquioxane (EG-POSS) was designed and synthesized, which exhibits excellent solubility and reactivity with BD-type bismaleimide resin. Thus, 4 wt% incorporated EG-POSS is uniformly dispersed in resin matrix and the resultant hybrid (BDEP-0.04) shows outstanding comprehensive performance, especially on dielectric, mechanical and thermal properties. Specifically, the dielectric constant (k) and loss (tan δ) at 1 MHz are reduced to 2.88 and 0.010 from 3.33 and 0.013. Meanwhile, the corresponding impact strength and flexural strength are improved to 18.75 KJ/m2 and 159.01 MPa, increased by 63.63 % and 27.29 %. In addition, BDEP-0.04 also exhibits the excellent thermal stability with glass transition temperature (Tg) of 290 °C, which is 8 °C higher than BD resin. Based on the lower k and tanδ value of BDEP-0.04 hybrid resin, as well as its better adhesion with silica fiber, the wave-transparent and mechanical properties of silica fiber reinforced composites (SF/BDEP-0.04) are further improved, showing that the wave transmission efficiency (94.2%), flexural strength (309.99 MPa), flexural modulus (15.70 GPa) and interlaminar shear strength (35.41 MPa) are all greatly higher than those of SF/BD. It’s concluded that EG-POSS is effective to optimize and balance the dielectric, mechanical and thermal properties of BD-type bismaleimide resin and SFs/BD composites, which is valuable for practical application in wave-transparent field.

A Secure Multi-party Data Federation System

In the era of big data, data is of great value as an essential factor in production. It is of great significance to implement its analysis, mining, and utilization of large-scale data via data sharing. However, due to the heterogeneous dispersion of data and increasingly rigorous privacy protection regulations, data owners cannot arbitrarily share data, and thus data owners are turned into data silos. Since data federation can achieve collaborative queries while preserving the privacy of data silos, we present in this paper a secure multi-party relational data federation system based on the idea of federated computation that ``data stays, computation moves.'' The system is compatible with a variety of relational databases and can shield users from the heterogeneity of the underlying data from multiple data owners. On the basis of secret sharing, the system implements the secure multi-party operator library supporting the secure multi-party basic operations, and the resulting reconstruction process of operators is optimized with higher execution efficiency. On this basis, the system supports query operations such as Summation (SUM), Averaging (AVG), Minimization/Maximization (MIN/MAX), equi-join, and $\theta $-join and makes full use of multi-party features to reduce data interactions among data owners and security overhead, thus effectively supporting efficient data sharing. Finally, experiments are conducted on the benchmark dataset TPC-H. The experimental results show that the system can support more data owners than the current data federation systems SMCQL and Conclave and has higher execution efficiency in a variety of query operations, exceeding the existing systems by as much as 3.75 times.

과산화물 상용화제 첨가가 생분해 바이오 플라스틱 필름의 물성에 미치는 영향

The need for biodegradable plastic continues to increase, improvement of physical properties is necessary for actual use in the market. In this study, composite film was produced by adding peroxide additives to bioplastic according to concentration to investigate changes in the melt index, elongation, morphology, and TGA of the composite film. The addition of peroxide compatibilizer showed superior elongation of film and TGA compared to those of control. The added amount of compatibilizer affected the extrusion process, and it was revealed that adding an appropriate amount of peroxidizer is important. Analysis of the composite film‘s morphology revealed a heterogeneous dispersion sequence due to different rates of crystallization depending on the resin, and surface physical properties were best in the group added with 4% peroxide. The results above showed that the test group added with 4% peroxide compatibilizer was superior in the production of composite biodegradable film.

Bi-level decentralized control of electric heating loads considering wind power accommodation in real-time electricity market

Flexible resources on demand-side, such as electric heating loads (EHLs), are perceived as an effective way of supporting the power balance of power grids with large scale renewable energy integration. However, it is difficult to quickly, effectively and evenly aggregate and schedule a large population of these loads because of their heterogeneity and geographic dispersion. The efficiency and effectiveness of optimal control are important for achieving the power balance between power source and load, especially in real-time scheduling. Moreover, the even load allocation between these heterogeneous loads also needs to motivate users participation in real-time power balance. To follow wind power in the real-time electricity market, this study presents a bi-level control method for EHLs based on distributed optimization computing, which considers the bi-level queuing method, different load control modes and multi-time scales between different control levels. First, each load group, which includes a large population of EHLs is controlled by a distributed server (DS); all the load groups are scheduled by the central management server (CMS), which deals with the wind farm or electricity retailer. Next, a distributed optimization model is built based on the bi-level control structure, in which the different power balance statuses and multi-time scales between the electricity market and EHLs are considered. Furthermore, considering the power balance on the multi-time scales, layer-by-layer load allocation optimization through the bi-level time-varying temperature queuing method, and the load-leveling optimization, serve as the sequential optimization problems. Finally, a simulation including 12,500 EHLs based on measured data in northern China is carried out. The results show that the proposed approach can effectively realize real-time power balance between wind power and EHLs, while maintaining uniform load allocation between the EHLs.

Efficacy and Safety of Rivaroxaban Compared with Other Therapies Used in Patients with Peripheral Artery Disease Undergoing Peripheral Revascularization: A Systematic Literature Review and Network Meta-Analysis.

Background The guidelines on antithrombotic treatment in patients with symptomatic peripheral artery disease (PAD) undergoing peripheral revascularization of the lower extremities were developed based on heterogeneous trials, assessing various dose regimens and recruiting patients who were subjected to different revascularization procedures. Objective To compare efficacy and safety of treatments used in patients with PAD undergoing peripheral revascularization accounting for between-trial heterogeneity and large dispersion of the quality of evidence. Methods A systematic literature review of randomised controlled trials (RCTs) recruiting adult patients with PAD receiving antithrombotics was conducted until January 2020. Hazard ratios (HR) were pooled using Bayesian network meta-analysis. The estimated between-treatment effects were presented as HR together with 95% credible intervals. The base case analysis included studies recruiting patients following recent peripheral revascularization, who received treatment regimens administered within the recommended therapeutic window, while a sensitivity scenario included all identified trials. Results Thirteen RCTs were identified (8 RCTs enrolled patients following peripheral revascularization and 5 RCTs regardless of the previous revascularization). Five trials, recruiting an overall of 8349 patients, were considered for the base case analysis. Of those, 6564 patients were recruited in the VOYAGER PAD trial comparing rivaroxaban plus aspirin (RIV plus ASA) versus ASA. RIV plus ASA was associated with a lower risk of repeated peripheral revascularization versus ASA monotherapy (HR = 0.88 [0.79, 0.99]), however having a trend towards an increased rate of major bleeding (HR = 1.43 [0.98, 2.11]). There was no evidence for differences between RIV plus ASA and dual antiplatelet therapy and vitamin K antagonists plus ASA. Similar results were observed in sensitivity analyses. Conclusions RIV plus ASA is associated with reduced risk of revascularization compared with ASA monotherapy, but the evidence for other comparators, in particular antiplatelet regimens, was insufficient to guide treatment decisions and highlights the challenge in establishing the magnitude of comparative efficacy using existing RCTs.

Hydrodynamic simulations of non-spherical particle dispersions in downer reactor with second-order moment turbulence model

A second-order moment kinetic frictional stress model coupled with a non-spherical drag coefficient between particle and gas phases is proposed to model the hydrodynamics of non-spherical particle flow in downer reactor. The heterogeneous dispersions of particle and the Reynolds stresses between gas and particle are numerically simulated. Results show that predictions are in good agreement with the experimental data. An increase in irregular shape degree leads to the enlargement for the dense ring of particle volume fraction, the particle velocity and its fluctuation, the normal and shear stress, and the granular temperature, as well as the encouragement of granular temperature peaks towards wall region. Strongly heterogeneous characteristics are found at the second acceleration region, which the amplitudes of normal and shear stresses are approximately twice larger than those of fully development flow. Higher heterogeneous indexes correspond to the homogeneous flow, and its larger gradient indicates that hydrodynamics is transiting from homogenous to heterogenous flow. Frequency of article collisions is on the order of 102.

Waste office paper filled polylactic acid composite filaments for 3D printing

Developing 3D printable waste paper based biocomposites is a potentially greener alternative to traditional waste paper recycling methods. In this paper, waste office paper (WOP) filled polylactide acid (PLA) biocomposites were prepared as filaments for Fused Filament Fabrication (FFF). The morphology, rheology, thermal properties, and physical properties of PLA-WOP composites were investigated. Results revealed that the addition of WOP improved the composites’ melt flow abilities. The Tg and Tm of composites remained similar to the neat PLA. However, tensile strengths of the prints decreased with the increase of WOP content, which could be attributed to the heterogeneous dispersion and aggregation caused by the abundance of WOP in the system. When 5% WOP was used, the elongation at break increased in comparison with pure PLA specimens. Nonetheless, when the WOP content was increased to 15%, the elongation at break decreased. To improve the mechanical properties of the prints, a silane coupling agent (γ-methacryloxypropyltrimethoxylsilane, KH570) was used to modify WOP granules. The mechanical properties were clearly enhanced post KH570 treatment. Furthermore, FTIR analyses demonstrated that the hydrogen bonding improved interfacial adhesion between WOP fillers and the PLA matrix. Thermal decomposition showed that the PLA-WOP composites had virtually no degradation below 260 °C, indicating that the composite filaments are safe for indoor 3D printing.

NANOEMULSION FOR TOPICAL THERAPY OF ACNE: OPTIMIZATION AND EVALUATION

The present investigation was aimed / carried out to develop a nano-sized emulsion-based vehicle containing 13-cis-retinoic acid as a means of increasing its permeability and be a suitable topical therapy for acne. Various heterogeneous dispersions were formulated by spontaneous nano emulsification method using 9% w/w propylene glycol dicaprylate/dicaprate, 27% w/w caprylocaproyl macrogol glycerides, 9% w/w polyglyceryl–6–dioleate and 55% w/w distilled water as an external phase. All plain and 13- cis-retinoic acid loaded nanoemulsions were clear and showed suitable physicochemical parameters for desired topical delivery and stability. The permeation profiles of 13-cis-retinoic acid through rat skin from selected optimized nanoemulsion formulation followed zero order kinetics. The microscopic observations indicate that the optimized nanoemulsion has no significant effect on the microscopic structure of the skin and epithelial cells appeared mostly unchanged. The surface epithelium lining and the granular cellular structure of the skin were totally intact. Hence, developed nanoemulsion containing 13-cis-retinoic acid would be a potential drug delivery vehicle for effective management of acne.

Spatial population genetics in heavily managed species: Separating patterns of historical translocation from contemporary gene flow in white-tailed deer.

Approximately 100 years ago, unregulated harvest nearly eliminated white‐tailed deer (Odocoileus virginianus) from eastern North America, which subsequently served to catalyze wildlife management as a national priority. An extensive stock‐replenishment effort soon followed, with deer broadly translocated among states as a means of re‐establishment. However, an unintended consequence was that natural patterns of gene flow became obscured and pretranslocation signatures of population structure were replaced. We applied cutting‐edge molecular and biogeographic tools to disentangle genetic signatures of historical management from those reflecting spatially heterogeneous dispersal by evaluating 35,099 single nucleotide polymorphisms (SNPs) derived via reduced‐representation genomic sequencing from 1143 deer sampled statewide in Arkansas. We then employed Simpson's diversity index to summarize ancestry assignments and visualize spatial genetic transitions. Using sub‐sampled transects across these transitions, we tested clinal patterns across loci against theoretical expectations of their response under scenarios of re‐colonization and restricted dispersal. Two salient results emerged: (A) Genetic signatures from historic translocations are demonstrably apparent; and (B) Geographic filters (major rivers; urban centers; highways) now act as inflection points for the distribution of this contemporary ancestry. These results yielded a statewide assessment of contemporary population structure in deer as driven by historic translocations as well as ongoing processes. In addition, the analytical framework employed herein to effectively decipher extant/historic drivers of deer distribution in Arkansas is also applicable for other biodiversity elements with similarly complex demographic histories.

Preparation of black-titanium dioxide nanotubes by thermal decomposition of sodium borohydride

Titanium dioxide is a very attractive material in catalysis. Although the titanium dioxide exhibits superior proper-ties in ultra violet radiation, activity of the catalyst can be improved by some modifications specially for daylight radiation. Titanium dioxide was colored by thermal decomposition of sodium borohydride at 400 0C. The gray colored nanotube-titanium dioxide obtained where the molar ratio of titanium dioxide to sodium borohydride, 1.2 and 0.6. The black nanotube-titanium dioxide was prepared by making the ratio 0.3. While heterogeneous dispersion observed after coloring of commercial titanium dioxide, all photocatalysts prepared from nanotube-titanium dioxide were perfectly homogeneous after coloring. Structural properties of photocatalysts analysed by using XRD, BET and SEM. The nanotube form of titanium dioxide prepared by hydrothermal method. The nanotube photocatalysts are anatase and have high surface area. The activities of colored nanotubes investigated according to these structural properties. Photocatalysts could not be colored homogeneously with the hydrogen reduction process but efficient reduction and coloration obtained with sodium borohydride. The visible region activities of photocatalysts increased by coloring with sodium borohydride compared to coloring by hydrogen. While the surface structure is important, all prepared nanotube-titanium photocatalysts exhibited more efficient color removal yield with regard to commercial one. More active catalysts prepared for absorption of daylight energy and 98.4 % color removal yield from 30 ppm methylene blue solution obtained with black nanotube-titanium dioxide photocatalyst.

Microstructure and dynamic mechanical properties epoxy/asphaltene composites

Asphaltenes tend to aggregate to nanoparticles or clusters in crude oil and solvents over a wide concentration and temperature range. In the present paper, asphaltenes extracted from the base asphalt was used as a filler to introduce into epoxy resin. The microstructure and evolution of asphaltenes aggregation in the epoxy resin were observed using laser scanning confocal microscopy. Furthermore, the effect of asphaltenes on the viscosity, dynamic mechanical behavior, thermostability, mechanical properties of epoxy resin was evaluated by Brookfield rotational viscometer, dynamic mechanical analysis, thermogravimetric analysis and universal testing machine. The presence of asphaltenes increased the viscosity of the neat epoxy during all stages of cure reaction. The viscosity of epoxy/asphaltenes composites increased with the filler concentration. Fractal asphaltenes aggregation formed in the composites with 1 mass% asphaltenes. Network microstructures of asphaltenes aggregation appeared in the epoxy phase with a further increase of asphaltenes content. Moreover, the increase of asphaltenes loading resulted in denser network microstructures in the epoxy matrix. Aggregation evolution revealed that asphaltenes particles redispersed evenly in the epoxy resin in the form of some aggregates at the beginning of curing. During the cure reaction of epoxy, asphaltenes aggregates started to agglomerate and grow to network microstructures. The presence of asphaltenes led to the enhancement of the storage modulus of the neat epoxy at the rubbery stage. The glass transition temperature (Tg) of the epoxy composites slightly increased with the increase of asphaltenes loading. The epoxy composite with 5 mass% asphaltenes had higher Tg than the neat epoxy. The inclusion of asphaltenes had a negligible effect on the damping properties and thermal stability of the neat epoxy. The aggregation and heterogeneous dispersion of asphaltenes resulted in the decrease of the tensile strength and elongation at break of the neat epoxy. However, the inclusion of asphaltenes significantly enhanced Young’s modulus of the neat epoxy. Young’s modulus of the neat epoxy was increased by more than fourfold with the addition of 5 mass% asphaltenes.

Analyzing ophthalmic suspension particle size distributions using laser diffraction: Placebo background subtraction method

The current study demonstrated that the presence of excipients can interfere with the measurement of particle size distribution (PSD), a critical quality attribute of ophthalmic suspensions, by laser diffraction (LD) and that a placebo background subtraction approach can eliminate the impact of excipients on the PSD measurement. Commercially available loteprednol etabonate and brinzolamide ophthalmic suspensions were used as model suspensions. The impact of excipients in these formulations on the LD measurements was determined using a one-factor-at-a-time experimental design approach, using National Institute of Standards and Technology (NIST) traceable polystyrene particle size standards as references. Among the evaluated excipients, polymers containing polyacrylic acid were found to interfere with the PSD analysis by creating the LD signals correspond to particles ranging from a few micrometers to a hundred micrometers in size. As a result, the measured PSD of active pharmaceutical ingredient (API) particles in the formulation overlapped with or superimposed on the excipient PSD signal, leading to erroneous interpretation of the API particle size. Additionally, dispersion of brinzolamide particles in unsaturated solutions led to rapid dissolution of brinzolamide particles during the measurement, resulting in underestimation of the particle size range. Here, a placebo background subtraction approach was developed to eliminate the interference of the excipients. This newly developed LD method was also evaluated using orthogonal methods, including polarized light microscopy and scanning electron microscopy (SEM). The strategy used in this study to eliminate the interference of excipients may also be useful for other heterogeneous dispersions where excipient interference may be of concern.