Long-term Stability Studies Research Articles

Thermal Stability of the Eutectic Composition in NaCl-CaCl2-MgCl2 Ternary System Used for Thermal Energy Storage Applications

The ternary eutectic chloride salt (NaCl-CaCl2-MgCl2) was designed and prepared for thermal energy storage over 550°C in a concentration solar power system. The melting temperature and fusion enthalpy of the eutectic salt were measured experimentally using the Differential Scanning Calorimeter (DSC) technique which were determined to be 420.83°C and 201.50 J/g, respectively. The thermal stability including the short-term and the long-term thermal stability of the ternary system was investigated by the Thermo-gravimetric Analyzer (TGA) technique and the DSC technique. The thermal properties of the eutectic mixture kept stable during the short-term thermal cycling test. The weight loss of the eutectic salt was less than 5%, and the melting temperature and fusion enthalpy changed slightly as the temperature increased below 650°C in the long-term isothermal stability study. The thermal stability test revealed that the ternary eutectic system demonstrated excellent thermal stability below 650°C which was taken as the upper limit temperature of the ternary system. The eutectic composition was characterized by the X-Ray Diffraction (XRD) technique before and after thermal treatment to provide preliminary analysis on the mechanism of thermal instability. The results suggested that the ternary eutectic chloride salt was a potential candidate for applying in high-temperature thermal energy storage.

Physical Characterization of Tobramycin Inhalation Powder: II. State Diagram of an Amorphous Engineered Particle Formulation.

Tobramycin Inhalation Powder (TIP) is a spray-dried engineered particle formulation used in TOBI Podhaler, a drug-device combination for treatment of cystic fibrosis (CF). A TIP particle consists of two phases: amorphous, glassy tobramycin sulfate and a gel-phase phospholipid (DSPC). The objective of this work was to characterize both the amorphous and gel phases following exposure of TIP to a broad range of RH and temperature. Because, in principle, changes in either particle morphology or the solid-state form of the drug could affect drug delivery or biopharmaceutical properties, understanding physical stability was critical to development and registration of this product. Studies included morphological assessments of particles, thermal analysis to measure the gel-to-liquid crystalline phase transition (Tm) of the phospholipid and the glass transition temperature (Tg) of tobramycin sulfate, enthalpy relaxation measurements to estimate structural relaxation times, and gravimetric vapor sorption to measure moisture sorption isotherms of TIP and its components. Collectively, these data enabled development of a state diagram for TIP-a map of the environmental conditions under which physical stability can be expected. This diagram shows that, at long-term storage conditions, TIP is at least 50 °C below the Tg of the amorphous phase and at least 40 °C below the Tm of the gel phase. Enthalpy relaxation measurements demonstrate that the characteristic structural relaxation times under these storage conditions are many orders of magnitude greater than that at Tg. These data, along with long-term physicochemical stability studies conducted during product development, demonstrate that TIP is physically stable, remaining as a mechanical solid over time scales and conditions relevant to a pharmaceutical product. This met a key design goal in the development of TIP: a room-temperature-stable formulation (3-year shelf life) that obviates the need for refrigeration for long-term storage. This has enabled development of TOBI Podhaler-an approved inhaled drug product that meaningfully reduces the treatment burden of CF patients worldwide.

A study of long-term stability and antimicrobial activity of chlorhexidine, polyhexamethylene biguanide, and silver nanoparticle incorporated in sericin-based wound dressing

In this study, three kinds of antiseptics which were 0.05% chlorhexidine, 0.2% polyhexamethylene biguanide (PHMB), or 200 ppm silver nanoparticle was introduced to incorporate in the sericin-based scaffold to produce the antimicrobial dressing for the treatment of infected chronic wound. The effects of antiseptic incorporation on the stability, release of sericin, and short-term and long-term (6 months) antimicrobial activity of the sericin dressing against gram-negative and gram-positive bacteria were investigated. We showed that the incorporation of each antiseptic did not have significant effect on the internal morphology (pore size ~ 73–105 μm), elasticity (Young’s modulus ~ 200–500 kPa), and the sericin release behavior of the sericin-based dressing. The release of sericin from the dressing was prolonged over 120 h and thereafter. Comparing among three antiseptics, 0.05% chlorhexidine incorporated in the sericin dressing showed the highest immediate and long-term (6 months) antimicrobial effect (largest inhibition zone) against most bacteria either gram-positive or gram-negative bacteria. The in vivo safety test following ISO10993 standard (Biological evaluation of medical devices – Part 6: Tests for local effects after implantation) confirmed that the sericin dressing incorporating 0.05% chlorhexidine did not irritate to tissue, comparing with the commercial material used generally in clinic (Allevyn®, Smith & Nephew). We suggested the sericin dressing incorporating 0.05% chlorhexidine for the treatment of infected chronic wound. Chlorhexidine would reduce the risk of infection while the sericin may promote wound healing.

Thermal properties and thermal stability of the ternary eutectic salt NaCl-CaCl2-MgCl2 used in high-temperature thermal energy storage process

The ternary eutectic chloride salt (NaCl-CaCl2-MgCl2) was designed and prepared for thermal energy storage over 500°C in a concentrated solar power system. The thermal properties of the eutectic salt were measured experimentally using the Differential Scanning Calorimeter (DSC) technique, and the thermal stability including the long-term and short-term thermal stability of the ternary system was investigated by the Thermo-gravimetric Analyzer (TGA) technique and the DSC technique. The results indicated that the melting temperature and fusion enthalpy were 420.83°C and 201.50J/g, respectively, and the specific heat capacity was 1.49J/(g·°C). In the long-term isothermal stability study, the total weight loss of the eutectic salt was less than 5% below 650°C, and the melting temperature and fusion enthalpy changed slightly as the temperature increased. The ternary eutectic system demonstrated excellent thermal stability below 650°C, which was defined as the upper temperature limit of the ternary system. During the short-term thermal cycling test, the stability and recyclability of the ternary salt were verified in future during the working temperature, generally 50°C lower than the upper temperature limit. The eutectic composition before and after thermal treatment was characterized by the X-ray Diffraction (XRD) technique to analyze the mechanism of thermal instability. The mechanism of thermal instability turned out to be the thermal decomposition of the generated magnesium chloride hexahydrate at high temperature. It was proved that the ternary eutectic chloride salt was a potential candidate for high-temperature thermal energy storage applications up to 650°C.

Physical Compatibility of Propofol-Sufentanil Mixtures.

Combined infusions of propofol and sufentanil preparations are frequently used in clinical practice to induce anesthesia and analgesia. However, the stability of propofol emulsions can be affected by dilution with another preparation, sometimes leading to particle coalescence and enlargement. Such unwanted effects can lead to fat embolism syndrome after intravenous application. This study describes the physical stability of 5 commercially available propofol preparations mixed with sufentanil citrate solutions. Two common markers of emulsion stability were used in this study; namely, the zeta potential and size distribution of the emulsion droplets. Both were measured using dynamic light scattering. The data for the pure propofol preparations and their mixtures with sufentanil citrate solution were compared. The absolute value of zeta potential decreased in 4 of the 5 propofol preparations after they had been mixed with sufentanil citrate. This effect indicates a lowering of repulsive interactions between the emulsion droplets. Although this phenomenon tends to cause agglomeration, none of the studied mixtures displayed a substantial increase in droplet size within 24 hours of blending. However, our long-term stability study revealed the instability of some of the propofol-sufentanil samples. Two of the 5 studied mixtures displayed a continual increase in particle size. The same 2 preparations showed the greatest reductions in the absolute value of zeta potential, thereby confirming the correlation of both measurement methods. The increase in particle size was more distinct in the samples stored at higher temperatures and with higher sufentanil concentrations. To ensure the microbial stability of an emulsion infusion preparation, clinical regulations require that such preparations should be applied to patients within 12 hours of opening. In this respect, we can confirm that during this period, none of the studied propofol-sufentanil mixtures displayed any physical instability that could lead to particle enlargement; thus, fat embolism should not be a risk after their intravenous application. However, our long-term stability study revealed differences between commercially available preparations containing the same active ingredient; some of the mixtures showed an increase in particle size and polydispersity over a longer period. Although our results should not be generalized beyond the particular propofol-sufentanil preparations and concentrations studied here, they do suggest that, as a general principle, a compatibility study should be performed for any preparation before the first intravenous application to exclude the risk of droplet aggregation.

Novel low melting point binary nitrates for thermal energy storage applications

19 kinds of different ratio of binary mixed molten salt have been formulated, and the formulation of a low melting point binary molten salt has been exploited and its primary thermophysical properties were presented here. The eutectic temperature of the selected binary salt mixture was determined to be 116.9℃. Further the decomposition point, specific heat, density, viscosity, thermal conductivity and corrosion were determined respectively. Sensible thermal storage cost of the novel eutectic mixture was found to be lower than that of conventional solar salt and HITEC salt. The performance of the binary salt mixture taken at different stages during the test of 1200-h exposure to constant high temperature was discussed based on the results obtained from long-term thermal stability studies. The results show that thermodynamic properties of the molten salt show perfect repeatability before and after the experiments, and most variations rate of the thermal physical properties is within±10%, which can be considered as an implication that the candidate has good thermal stability. Therefore, this new kind of binary molten salt thermal storage materials is more competitive and promising to be used in solar power generation systems while providing a comprehensive data for its engineering application and theoretical research.

ДОСЛІДЖЕННЯ СТАБІЛЬНОСТІ ПРЕПАРАТУ «КОРВАЛОЛ» У ФОРМІ СУБЛІНГВАЛЬНИХ ТАБЛЕТОК

Introduction. In today's world, oral tablets is the most convenient and widely used in medical practice dosage form. The patients prefers solid dosage forms due to their ease of transportation, capability of self-dosage drug dose and painless application. However, some categories of patients, especially elderly patients, have difficulties in swallowing dosage forms in the solid form. For these categories of patients developed sublingual tablet form - a drug that combines practicality and convenience of the pill and dissolves quickly in the mouth and easily enters the gastrointestinal tract. In addition, numerous clinical studies have shown that the therapeutic effect for sublingual tablets comes earlier than for traditional tablets that dissolve in the stomach of the patient because drug absorption through the mucous begins immediately after oral administration. [1-4]."Korvalol" drops used for treatment of temporary nervous system disorders, disorders of the autonomic nervous system, cardiovascular system, spastic pain [5]. The product is aimed for the elderly patients, for whom need immediate help, so the most appropriate is development sublingual tablets, similar to "Korvalol" drops.For drugs used in medical practice in addition to the requirements of efficiency and safety are increased pharmacopoeial requirements for quality. Drugs should remain effective throughout the all period of storage, so stability is one of the main requirements for the quality of drugs [6].The purpose of these studies was stability studies and determining the shelf life of the drug "Korvalol" in the form of sublingual tablets during the long-term storage.Materials and Methods:Stability studies conducted for three pilot batches: 10910, 20910, 30910 for sublingual tablets "Korvalol" manufactured on JSC "Farmak". Tests were conducted for tablets in the package for sale (polyvinyl chloride light-shielded film and aluminum foil with printing). To determine the shelf life long-term stability researches were conducted at a temperature of 15 to 250C and relative humidity of 60 ± 5%, control points were 0, 3, 6, 9, 12, 18, 24 months. The study of accelerated stability was conducted at 40 ±20C and relative humidity of 75 ± 5%, control points were 0, 3, 6 months.Results and discussionAs a result, the study found that during two years of storage in the original packaging at a temperature of 15 to 250C and relative humidity of 60 ± 5% three researched batches of sublingual tablets "Korvalol" showed formulation stability throughout all of the period. Quantitative and qualitative indicators of the quality of the drug are within acceptable norms throughout all of the studied period.Packaging provides protection from external influence of the drug, microbiological parameters did not change and fully meet the requirements of the specification.Results of the study of long-term stability demonstrate the rationality of the drug composition, and optimal manufacturing technology. Excipients were chosen according to technological, physico-chemical and functional characteristics.ConclusionsResearched long-term and accelerated stability of sublingual tablets "Korvalol"Physicochemical and pharmacological studies of sublingual tablets "Korvalol" completed. The research results are included to the specification of the drug.Proved stability of the drug in the proposed package for two years storage at a temperature of 15 to 250C and relative humidity of 60 ± 5%.

Long-Term Physical Stability of PVP- and PVPVA-Amorphous Solid Dispersions.

The preparation of amorphous solid dispersion (ASD) formulations is a promising strategy to improve the bioavailability of an active pharmaceutical ingredient (API). By dissolving the API in a polymer it is stabilized in its amorphous form, which usually shows higher water solubility than its crystalline counterpart. To prevent recrystallization, the long-term physical stability of ASD formulations is of big interest. In this work, the solubility of the APIs acetaminophen and naproxen in the excipient polymers poly(vinylpyrrolidone) (PVP K25) and poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA64) was calculated with three models: the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT), the Flory-Huggins model (FH), and an empirical model (Kyeremateng et al., J. Pharm. Sci, 2014, 103, 2847-2858). PC-SAFT and FH were further used to predict the influence of relative humidity (RH) on the API solubility in the polymers. The Gordon-Taylor equation was applied to model the glass-transition temperature of dry ASD and at humid conditions. The calculations were validated by 18 months-long stability studies at standardized storage conditions, 25 °C/0% RH, 25 °C/60% RH, and 40 °C/75% RH. The results of the three modeling approaches for the API solubility in polymers agreed with the experimental solubility data, which are only accessible at high temperatures in dry polymers. However, at room temperature FH resulted in a lower solubility of the APIs in the dry polymers than PC-SAFT and the empirical model. The impact of RH on the solubility of acetaminophen was predicted to be small, but naproxen solubility in the polymers was predicted to decrease with increasing RH with both, PC-SAFT and FH. At 25 °C/60% RH and 40 °C/75% RH, PC-SAFT is in agreement with all results of the long-term stability studies, while FH underestimates the acetaminophen solubility in PVP K25 and PVPVA64.

Preserving rapid prototypes: a review

Rapid Prototyping (RP) has revolutionized the world of manufacturing. It has gained popularity among designers and artists, having developed from a visualization tool to a manufacturing tool for end-use products. Rapid-prototyped objects are being accessed by museums and the technology is being adopted for conservation applications. The review identifies the current most commonly used polymer based RP technologies and materials that are likely to enter museum collections, and formulates informed research topics related to their conservation. A knowledge exchange project was conducted with artists and designers using the technology via an online survey and interviews. The main technologies and materials used by artists and designers were identified and investigated including research that has been done into the stability of RP manufactured objects. Since these may be uniquely post-processed by artists and designers, RP objects are often irreplaceable, i.e. cannot simply be reprinted. The evolution from rapid prototyping (RP) to additive manufacturing (AM) has resulted in extensive research into the mechanical properties and short-term stability of prototypes. However, very little research has been conducted into RP from the conservation perspective particularly long-term stability studies. Since RP technology is rapidly developing, it is crucial that conservators and scientists follow and inform these developments.

Development of an apple juice certified reference material for cadmium, lead, total arsenic and arsenic species

In the development of the apple juice certified reference material, isotope dilution mass spectrometry method was used for the assignment of certified values and long-term stability study for cadmium and lead. For total arsenic, inorganic arsenic, as well as dimethylarsenic acid, standard addition method was used. The analytes were found to be homogenous and stable over a period of at least 4.5 months at storage temperature of −20°C (long-term stability). The certified mass fraction values were (0.220±0.011) mg/kg for cadmium, (0.245±0.014) mg/kg for lead, (0.185±0.015) mg/kg for total arsenic, (0.124±0.012) mg/kg for inorganic arsenic [As(III)+As(V)] and (0.0601±0.0052) mg/kg for DMAA. The recovery of the arsenic species was over 99%. This apple juice certified reference material can be used for method validation or as a quality control material by routine testing laboratories.

Effects of operational limits of DFIG wind turbines on long-term voltage stability studies

This paper investigates the effects of doubly fed induction generators (DFIGs) operational limits on long-term voltage stability. DFIG operational limits are defined based on wind generator's capability curve in terms of the actual terminal voltage and wind speed. Also, the limitations of the converter, machine and wind turbine are considered in DFIG control schemes. The evolution of different variables is examined using two models for DFIG operational limits: fixed limits and variable limits. Time domain simulations have been performed in three different cases: constant wind speed, ramp up event, and ramp down event. This study also considers the dynamic models of over excitation limiter (OEL) and on-load tap changers (OLTC) combined with static and dynamic loads. Some important conclusions can be extracted from the simulation results, which can help in choosing the appropriate model to represent the DFIG operational limits in long-term voltage stability studies.

Selective RP-HPLC method for determination of quetiapine in presence of coadministered drugs: Application for long-term stability study of quetiapine in whole blood

Incidence of suicidal attempts presents an explanation for the high prevalence of quetiapine (QTI) in forensic cases. Thus, the interpretation of its concentrations in biological specimens is needed, but in forensic toxicology, potential postmortem changes such as instability of the target drugs should be taken in consideration. High-performance liquid chromatography (HPLC) method has been developed for determination of QTI. This method was based on reversed phase (RP)-HPLC separation of QTI on a C-18 column (150 mm × 4.6 mm, 5 μm) with elution system of acetonitrile—methanol—0.025 M phosphate buffer (pH 2.5), containing 1 mL TEA in each 250 mL, in a ratio of 40:30:30%, v/v, at the flow rate of 1.2 mL min−1 using mirtazapine as internal standard (IS). The proposed method was applied to the determination of QTI in plasma in presence of coadministered drugs. The application of the proposed method was extended for long-term stability study of two different concentration levels of QTI in the whole blood.

Activity and Long-Term Stability Study of Pt-Y/C Electrocatalysts for Oxygen Reduction Reaction

Pt-Y/C catalysts were prepared by a modified formic acid method and their activities for oxygen reduction reaction (ORR) were evaluated. X-ray diffraction analysis showed that no alloy was formed between the metals, while x-ray photoelectron spectroscopy revealed that yttrium is present as Y2O3, Y(OH)3, and Y-O-Pt. The Pt-Y/C 7:3 material had the highest specific activity (94 µA cmPt -2) for ORR, and was superior to other Pt-Y/C materials. Following repetitive potential cycling, ORR activity of the Pt-Y/C 7:3 catalyst decreased in a similar proportion to that of Pt/C. X-ray photoelectron spectroscopy results of the aged ultrathin catalyst layer were in agreement with energy-dispersive x-ray spectroscopy data. These studies revealed that the intensities of the Y 3d peaks were suppressed due to voltammetric cycling and that while Y2O3 and Y(OH)3 dissolved, Y-O-Pt remained in the catalyst.

Maximum-power-point tracking during outdoor ageing of solar cells

This paper describes how to select a passive load which would the most accurately follow the maximum-power-point (MPP) of small laboratory size solar cells installed outdoors in Central Europe. Either resistor or diode type of passive load have been used as a low-cost alternative to active MPP trackers (designed especially for a long-term outdoor stability study of different types of small size laboratory solar cells). The dye-sensitized solar cells have been chosen as a representative case since they exhibit similar current–voltage (I–V) characteristics dependence at different light intensities (G) and cell temperatures (TC) as other solar cell’s technologies. The results showed that the most efficient tracking was achieved when the I–V characteristic of the optimal resistor or diode cross the MPP of the solar cell measured at G=73mW/cm2 and TC=25°C. A significantly better tracking could be obtained when instead of a resistor an optimal diode is used; the optimal diode consumes 96.5% of the annual energy that would be potentially produced by the solar cell connected to ideal MPP tracker while the optimal resistor consumes only 83.5% of that energy.

Development and use of specific ELISA methods for quantifying the biological activity of bevacizumab, cetuximab and trastuzumab in stability studies.

Bevacizumab (BVZ), cetuximab (CTX) and trastuzumab (TTZ) are monoclonal antibodies (mAbs) used worldwide for the treatment of several widespread kinds of cancer. They are marketed as medicines under their respective tradenames: Avastin(®), Erbitux(®) and Herceptin(®). The aim of this research was to develop in-house specific enzyme-linked immunosorbent assays (ELISA) to assess the long-term stability of these three mabs. These assays assess the biological functionality of the mAbs by quantifying their biological activity. For this purpose, we developed an indirect ELISA procedure whereby the specific antigens against which the mAbs are directed are used as specific "capturing" antibodies on the ELISA plates. We therefore used vascular endothelial growth factor (VEGF) in the ELISA for BVZ; human epidermal growth factor receptor (hEGFR) in the ELISA for CTX and human receptor HER2 (hHER2) in the ELISA for TTZ. After the mAbs had attached to their antigen, we used an anti-human IgG (whole molecule) peroxidase-conjugate and o-phenylenediaminedihydrochloride substrate. The reaction was stopped using sulphuric acid and absorbance was recorded at a wavelength of 450nm. The three ELISA methods were validated in terms of calibration models, range of the assay, limits of detection and quantitation, intra and interday precision and accuracy, and specificity by cross reactions. Forced degradation studies were also conducted on the medicines, providing useful information. Finally, the proposed ELISA were successfully used in a long-term stability study to quantify the remaining biological activity in medicines that had been opened and then stored under two different storage conditions, i.e. refrigerated at 4°C and frozen at -20°C. Results indicated that BVZ (Avastin(®)) is the most stable of the three in terms of its biological functionality.

Activity and Long-Term Stability Study of Pt-Y/C Electrocatalysts for Oxygen Reduction Reaction

The recent improvements of the proton exchange membrane fuel cell (PEMFC) make this device a promising energy conversion technology. Nonetheless, the high overpotential of the oxygen reduction reaction (ORR) remains an obstacle, motivating the search for new electrocatalyst materials which are not only active, but also stable for the ORR in the PEMFC operating conditions. Recently, computational results showed that platinum alloyed with early transition metals, such as yttrium, are more active and stable compared to pure Pt. Furthermore, electrochemical measurements of sputtering PtY electrodes revealed that those materials exhibit better ORR activity and stability compared to Pt electrodes. Despite the better performance of the sputtering materials, the use of Pt-Y electrocatalysts in PEMFC demands the development of carbon-supported nanoparticles catalysts. However, to the date, few papers reported the activity of Pt-Y/C materials. Besides, the effects of accelerated aging tests on the carbon supported material activity and compositions still unexplored. In this contribution, carbon supported Pt-Y electrocatalysts (20% wt. metal loading) were prepared, with varying Pt:Y compositions of 9:1, 7:3 and 1:1, were synthesized using a modified formic acid method. The catalysts were characterized using several X-ray techniques. The catalysts metallic loading and Pt:Y ratio were analyzed using Energy Dispersion Spectroscopy (EDS). Structural parameters such the mean crystallite size, the interatomic distance between Pt atoms and the lattice parameter were obtained using the X-ray diffraction (XRD). Finally, X-ray Photoelectron Spectroscopy (XPS) revealed that yttrium is present as three different species, all in the Y3+ oxidation state. The electrochemical tests were performed in a three electrodes cell configuration. The catalysts ORR activities were studied employing the rotating disk electrode (RDE) technique. Potential sweeps between 0.1 and 1.1 V at a scan rate of 5 mV s-1 and RDE rotation rates of 100, 400, 900, 1600, and 2500 rpm were performed after oxygen saturation of the electrolyte. Table 1 summarizes the current density values calculated from 1600 rpm data at 0.9 V. Current values normalized by electrode geometric area (j and jk ) and the mass activity (jk-mass ) exhibited by the Pt-Y/C 9:1 catalyst are similar to those of Pt/C material. With regard to the specific activity (jk-esp ), the current normalized by electrochemical surface area, Pt-Y/C 7:3 exhibited an enhancement of almost 20% compared to Pt/C. This result is also superior to others PtY/C catalysts previously reported. The Pt-Y/C 7:3 catalyst was submitted to an accelerated aging test that consisted of 3,000 potential cycling test. After the stability test the material ORR activity was revaluated. Changes in catalyst composition were analyzed performing the EDS and XPS experiments directly on the working electrode, while the transmission electron microcopy (TEM) was used in order to demonstrate modifications on the catalyst mean particle size and distribution on the carbon support. Table 1. Summary of current density values obtained at 0.9 V and rotation velocity of 1600 rpm. Aecsa (cmPt 2) j (mA cm-2) jk (mA cm-2) jk-mass (mA mgpt -1) jk-esp (µA cmPt -2) Pt-Y/C 1:1 0.45 0.05 0.05 3 23 Pt-Y/C 7:3 0.92 0.44 0.48 21 103 Pt-Y/C 9:1 2.13 0.72 0.85 32 78 Pt/C 1.87 0.71 0.83 30 88

PVDF/CaCO3 composite hollow fiber membrane for CO2 absorption in gas–liquid membrane contactor

Porous hydrophobic polyvinylidene fluoride (PVDF) composite hollow fiber membranes were fabricated via phase inversion method by embedding different amounts of hydrophobic calcium carbonate (CaCO3) nano-particles in the polymer matrix. The effects of nano-particle loadings on the morphology, structure and performance of the spun membranes in gas–liquid contactors were investigated. The incorporation of hydrophobic nano-particles into the polymer network enabled the formation of more abundant and narrower finger-like pores in the composite membranes compared to plain PVDF membrane. Moreover, the addition of nano-particles enhanced the surface roughness, permeation rate, porosity and wettability resistance of the composite membranes. CO2 absorption performance of the fabricated membranes was evaluated via a gas–liquid membrane contactor system. The CO2 flux was improved to some extent by increasing the mixing ratio of CaCO3. Peak absorption performance of 1.52 × 10−3 mol m−2 s−1 at 300 ml/min absorbent flow rate was achieved when 20/100 weight ratio of CaCO3/PVDF was employed. However, further increase of the ratio resulted in a composite membrane with lower absorption performance than the other composite membranes. Moreover, a long-term stability study of the composite membrane with the best CO2 absorption flux showed no decline in performance in the initial 210 h of operation, indicating that the membrane possesses high potential for gas–liquid contactor applications.

Spray pyrolytically grown NiAlOx cermets for solar thermal selective absorbers: spectral properties and thermal stability

After deposition of NiAlOx thin films on stainless-steel substrates by the spray pyrolysis technique, various properties of the films were investigated using Fourier transform infrared spectroscopy, UV–visible reflectance spectrophotometry, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Optical quantities were determined using reflectance spectra in the relevant spectrum region. At first the optimal substrate temperature was selected and then different nickel to aluminium ratios were examined to find the efficient solar absorber. The SEM revealed changes in morphology due to different molar ratios. The XRD of the selected sample showed a mixture of nickel and nickel oxide phases with the strong presence of substrate peaks and without the presence of alumina phase while in the EDX test the peaks corresponding to O, Al and Ni appeared. Long-term thermal stability study was performed by means of performance criterion concept.

Preparation and Long-Term Stability Study of Steel Fiber/Graphite Conductive Concrete

The steel fiber/graphite conductive concrete is applied in power system grounding. In high soil resistivity regions, the common methods for reducing the grounding resistance are not practical. It is difficult for grounding resistance of substations to meet the requirements of working earthing and safety earthing. In order to solve this problem, a steel fiber/graphite conductive concrete is developed in this paper. Steel fiber and graphite are added as conductive fillers. The long-term stability of the steel fiber/graphite conductive concrete is studied. The experiment results show that steel fiber/graphite conductive concrete not only maintains excellent conductivity, but also has good mechanical strength and corrosion resistance in 300 days.

Structure and Long-Term Stability of Alkylphosphonic Acid Monolayers on SS316L Stainless Steel.

Surface modification of stainless steel (SS316L) to improve surface properties or durability is an important avenue of research, as SS316L is widely used in industry and science. We studied, therefore, the formation and stability of a series of organic monolayers on SS316L under industrially relevant conditions. These included acidic (pH 3), basic (pH 11), neutral (Milli-Q water), and physiological conditions [10 mM phosphate-buffered saline (PBS)], as well as dry heating (120 °C). SS316L was modified with alkylphosphonic acids of chain length (CH2)n with n varying between 3 and 18. While alkylphosphonic acids of all chain lengths formed self-assembled monolayers with hydrophobic properties, only monolayers of chain lengths 12-18 formed ordered monolayers, as evidenced by static water contact angle (SCA), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and infrared reflection absorption spectroscopy (IRRAS). A long-term stability study revealed the excellent stability of monolayers with chain lengths 12-18 for up to 30 days in acid, neutral, and physiological solutions, and for up to 7 days under dry heating. Under strong basic conditions a partial breakdown of the monolayer was observed, especially for the shorter chain lengths. Finally, the effect of multivalent surface attachment on monolayer stability was explored by means of a series of divalent bisphosphonic acids.