Phosphoric Acid Research Articles

Leaching kinetics of waste pharmaceutical blister package aluminium in phosphoric acid media

This study investigated the process of treating secondary aluminium recovered from waste pharmaceutical blister packages (WPBs) using phosphoric acid solutions as a potential strategy for recycling this currently non-recycled waste material. The findings indicate that, when recycling via the hydrometallurgical process, the aluminium passivated during leaching can be effectively counteracted by employing moderately concentrated phosphoric acid solutions (1.0 M), elevated temperatures (60–80 °C) and specifically the addition of H2O2 (1.25–2.5 vol.%). Under these conditions, complete extraction of aluminium was achieved within four hours. The estimated activation energy (∼82 kJ/mol) indicates that the leaching reaction is primarily limited by the chemical reaction rate rather than film diffusion. An aluminium phosphate solution could be obtained by leaching WPBs in a way that is suitable for subsequent aluminium phosphate crystallisation. This approach could provide a promising pathway for valorising aluminium from the currently under-utilised waste fraction of pharmaceutical blister packages.

A greener RP-HPLC method for quaternary estimation of caffeine, paracetamol, levocetirizine, and phenylephrine acquiring AQbD with stability studies

Abstract The main objective of this article was to develop method and validate quaternary estimation of caffeine (CFE), paracetamol (PCM), levocetirizine (LEV), and phenylephrine (PHE) and to conduct degradation experiments using reverse-phase high-performance liquid chromatography (RP-HPLC). This was the first innovative approach to this drug combination, combining analytical quality by design with green analytical chemistry. This method was developed using HPLC Agilent 1220 Infinity II, a binary solvent delivery pump, an automatic sampling device injector, and a photodiode array detector. Agilent Inertsil ODS 3 (250 mm × 4.6 mm, 5 μm) was used for separation. The mobile phase is composed of ethanol and 10 mM phosphate buffer (pH 3). To adjust the pH, 1% of orthophosphoric acid was used. The flow rate was set to 0.8 ml·min−1, the injection volume was 10 μl, and the detecting wavelength was 220 nm. The analytes were eluted via gradient elution. The retention time for PCM was 3.5 min, CFE was 8.1 min, PHE was 15.9 min, and LEV was 20.5 min. Green evaluation tools used in this research include Green Analytical Procedure Index, analytical eco-scale, analytical greenness, analytical method greenness score, and carbon footprint analysis. The developed method was greener than the previously reported method, as per the results of the greenness evaluation tools.

Use of a natural rock material as a precursor to inhibit corrosion of Ti alloy in an aggressive phosphoric acid medium

The mechanism of interaction between magnesite mineral and phosphoric acid (0.001–0.5 M) in addition to the determination of the protective properties for Ti alloy (working electrode) in phosphoric acid both with and without an inhibitor have been investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. Results of electrochemical tests show that the corrosion resistance of titanium alloy in phosphoric acid solution only increased and hydrogen production decreased by either decreasing acid concentration or increasing immersion time associated with the thickening of the oxide film formed on the alloy surface. On adding magnesite, the corrosion resistance of Ti alloy is enhanced by increasing the phosphoric acid concentration (0.001–0.5 M) due to the formation of sparingly soluble magnesium phosphate film on the alloy surface that inhibits the effect of increasing hydrogen evolution reaction due to the pH value decreases. The increasing adsorption behavior of the magnesite inhibitor and decreasing its diffusion were deduced from EIS measurements. Thus, the addition of 3% magnesite minimizes the corrosion by forming a new protective film (Mg3(PO4)2), which differs from the traditional passive film and prevents the effect of the increase of hydrogen evolution. The surface morphology and chemical composition of the tested alloy were determined using scanning electron microscopy (SEM), Fourier transform Infra-Red spectroscopy (FTIR), X-ray diffraction (XRD), X-ray Fluorescence (XRF) and In situ Raman spectroscopy.

Validation of HPLC-DAD method for analysis of paracetamol and potassium sorbate in liquid oral formulations and its application to forced degradation study

AbstractDue to the frequent use of paracetamol formulations, it is useful to develop an analytical technique for the determination of intact paracetamol in presence of other drugs and excipients or the degradation products. In this study, a simple, isocratic, fast, specific, accurate and precise stability-indicating high performance liquid chromatography (HPLC) method has been developed and validated for simultaneous quantitative determination of paracetamol (PCM) and potassium sorbate (PS) in oral liquid formulations. The chromatographic separation was achieved on Zorbax SB C18 column (150 × 4.6 mm, 5 µm) with Zorbax SB C18 precolumn (12.5 × 4.6 mm, 5 µm) using distilled water pH 2 with ortho-phosphoric acid and acetonitrile (70:30, v/v) as a mobile phase, and UV detection at 235 nm. The temperature of the column was kept constant at 25 °C. The method was validated according to International Conference on harmonization (ICH) guidelines. The method demonstrated excellent linearity, with a correlation coefficient of 0.9996 and 0.9998 for PCM and PS, respectively, over the concentration ranges of 10–600 μg mL−1 (PCM) and 6–500 μg mL−1 (PS). The retention time was found to be 1.98 and 4.86 min for PCM and PS, respectively. Oral liquid formulation samples were subjected to various stress conditions (acidic and alkaline hydrolysis, as well as oxidative, heat and photolytic degradation) for the purpose of forced degradation study. The major degradation of paracetamol was achieved in acidic and basic stress conditions, while thermal and photolytic degradation generally had the least influence. On the other hand, potassium sorbate was highly susceptible to photolytic degradation. It was also shown that the formulation has strong influence on stability of tested compounds. Forced degradation studies demonstrated the stability-indicating power of the method and can be used to assess the stability of paracetamol and potassium sorbate in oral liquid formulations.

Study on the preparation of high-concentration ammonium phosphate suspension fertilizer from wet-process phosphoric acid and its rheological properties

BackgroundNew water-soluble fertilizer can be applied to modern irrigation systems and has significant advantages. This study uses wet-process phosphoric acid as raw material and chelation and suspension technology to prepare water-soluble fertilizer containing high-concentration ammonium phosphate. MethodsFirst, the composition and viscosity of the wet-process phosphoric acid was analyzed, and the ammoniation and chelation processes were explored. Subsequently, four suspension formulations were compared and selected after product analysis. The final process conditions are: 42 wt % (P2O5 %) phosphoric acid, 20 wt % chelating agent, pH = 4.5, 0.03 wt % xanthan gum or 0.02 wt % carboxymethyl cellulose of respectively, and obtain suspension fertilizer by high-speed shearing. Significant FindsThe Bingham model and Casson model were used to fit the rheological data of the two, and R2 values were greater than 0.94. The thixotropic loops of the two were measured using the triangular shear rate variation method mode, and the Huang equation and MBM models were used to fit the thixotropic loop data of the two respectively. In addition, at different pH and temperature, the suspended fertilizer performed well.

Separation of heavy metals from dilute solutions using D2EHPA carrier fixed onto the outer surface of coaxially electrospun core-sheath fibers

In this study, porous membranes based on core-sheath fibers covered with fixed carriers were prepared by coaxial electrospinning for the separation of heavy metal ions from dilute solutions. Cellulose triacetate (CTA) and an extractant di(2-ethylhexyl)phosphoric acid (D2EHPA) were mixed to prepare a sheath-layer solution and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was adopted to prepare a core-layer solution for electrospinning. The morphological and textural properties as well as chemical composition of the fabricated core-sheath fibers were first analyzed to determine the optimal preparation conditions. The ability and selectivity of such fixed D2EHPA carriers were evaluated via the adsorption of Zn2+, Cu2+, and Ni2+ ions from dilute solutions. Dynamic tests revealed that the adsorption of metal ions on the core-sheath fibrous membrane made of 52 wt% PVDF-HFP, 18 wt% D2EHPA, and 30 wt% CTA (on a dry basis) reached equilibrium within 8 h. As expected, all adsorption isotherms at specific equilibrium pH values were well described by the Langmuir equation, ascribed to the chemical reaction nature between metal ions and D2EHPA carrier. The crossflow permeation-adsorption tests of a multi-metal solution in a total recycling mode revealed the adsorption selectivity of Zn2+ over Cu2+ and Ni2+, as observed in conventional liquid–liquid extraction. Four repeated adsorption-regeneration experiments revealed an adsorption efficiency beyond 95 % relative to the first route, demonstrating the satisfactory reusability and stability of the as-prepared core-sheath fibrous membranes for this purpose.

The Impurity Removal and Comprehensive Utilization of Phosphogypsum: A Review.

Phosphogypsum (PG), a byproduct during the phosphoric acid production process, also known as the wet process, contains complex and diverse impurities, resulting in low utilization and considerable accumulation. This leads to a massive waste of land resources and a series of environmental pollution problems. Given the current urgent ecological and environmental situation, developing impurity removal processes with low energy consumption and high efficiency, exploring valuable resource recovery, preparing high value-added PG products, and broadening the comprehensive utilization ways of PG are significant strategies to promote the sustainable consumption of PG and sustainable development of the phosphorus chemical industry. This review comprehensively summarizes the advantages and disadvantages of existing PG impurity removal and utilization technologies and probes into the future development direction, which provides references and ideas for subsequent PG research.

The strategy of micropore confinement via organic macrocyclic cavities for designing novel high-performance proton exchange membranes

The high-temperature hydrogen proton exchange membrane fuel cell is considered a disruptive technology for future energy applications. However, the weak binding strength between the proton carriers (phosphoric acid molecules) with polymer chains reduces the operational stability and proton transfer efficiency at conditions of high temperature and low humidity. In this work, a strategy of micropore confinement via organic macrocyclic cavities (sulfonic calix[4]arenes, sulfonic calix[8]arenes, sulfonated β-cyclodextrin) was developed for designing novel mixed matrix membranes functioning as high-temperature hydrogen proton exchange membranes. Benefitting from the confined micropores constructed by supramolecular cavities, the obtained mixed matrix membranes showed a higher uptake and retention capability of phosphoric acid as well as lower membrane swelling, yielding an enhanced proton conductivity. The proton conductivity of the mixed matrix membranes was 2–3 times higher while the conductivity attenuation was only 58.6% comparing with neat PBI membrane, (140℃, relative humidity = 0). In addition, due to the good compatibility caused by hydrogen bonding between fillers and polymer chains, the volume swelling was only 14% and the mechanical strength of the obtained mixed matrix membranes increased. We believe the strategy of micropore confinement via organic macrocyclic cavities for designing the novel mixed matrix membranes is thought to be of great significance for the research on high-temperature proton exchange membrane.

Sorption Behavior of Azo Dye Congo Red onto Activated Biochar from Haematoxylum campechianum Waste: Gradient Boosting Machine Learning-Assisted Bayesian Optimization for Improved Adsorption Process.

This work aimed to describe the adsorption behavior of Congo red (CR) onto activated biochar material prepared from Haematoxylum campechianum waste (ABHC). The carbon precursor was soaked with phosphoric acid, followed by pyrolysis to convert the precursor into activated biochar. The surface morphology of the adsorbent (before and after dye adsorption) was characterized by scanning electron microscopy (SEM/EDS), BET method, X-ray powder diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) and, lastly, pHpzc was also determined. Batch studies were carried out in the following intervals of pH = 4-10, temperature = 300.15-330.15 K, the dose of adsorbent = 1-10 g/L, and isotherms evaluated the adsorption process to determine the maximum adsorption capacity (Qmax, mg/g). Kinetic studies were performed starting from two different initial concentrations (25 and 50 mg/L) and at a maximum contact time of 48 h. The reusability potential of activated biochar was evaluated by adsorption-desorption cycles. The maximum adsorption capacity obtained with the Langmuir adsorption isotherm model was 114.8 mg/g at 300.15 K, pH = 5.4, and a dose of activated biochar of 1.0 g/L. This study also highlights the application of advanced machine learning techniques to optimize a chemical removal process. Leveraging a comprehensive dataset, a Gradient Boosting regression model was developed and fine-tuned using Bayesian optimization within a Python programming environment. The optimization algorithm efficiently navigated the input space to maximize the removal percentage, resulting in a predicted efficiency of approximately 90.47% under optimal conditions. These findings offer promising insights for enhancing efficiency in similar removal processes, showcasing the potential of machine learning in process optimization and environmental remediation.

Molding the future: Optimization of bioleaching of rare earth elements from electronic waste by Penicillium expansum and insights into its mechanism

The recovery of rare earth elements (REE) from electronic waste is crucial for ensuring future demand security, as there is a high supply risk for this group of elements, and mitigating the environmental impacts of conventional mining. This research focuses on extracting REE from waste printed circuit boards through bioleaching, addressing the limited attention given to this source. A strain of Penicillium expansum demonstrated efficient bioleaching under optimal conditions of 7.5 initial pH, 0.1 mM phosphate concentration, and excluding a buffering agent. The study achieved significant improvements in La and Tb extraction and enhancements in Pr, Nd, and Gd recovery, approaching 70 % within 24 h. Fungal mechanisms involved in REE extraction included fungal pH control, organic acid biosynthesis, phosphate bioavailability, and potential fungal proton pump involvement. This approach offers a promising solution for sustainable REE recovery from e-waste, contributing to resource security and circular economy.

New insights into defluoridation via induced crystallization: Implications of phosphate species regulation for process efficiency and economics

Excess fluoride (F) at low concentrations in groundwater remains a challenge. F removal via fluidized-bed induced crystallization has been receiving increasing attention; however, the precipitant cannot be fully utilized. This results in generation of by-products, inadvertently increases the treatment cost, and impedes the assessment of product purity. In this study, phosphate species regulation was employed to improve the F removal efficiency without decreasing the phosphate utilization efficiency. It shows that F concentration could be reduced from 4.75 to 0.45 mg·L−1, with P concentration in the effluent being only 0.05 mg·L−1 at a P:F molar ratio of 3, involving appropriately mixed phosphate species. Hydroxyapatite (HAP) crystallization, subsequent F adsorption, and directly induced fluorapatite (FAP) crystallization occurred simultaneously in the fluidized bed, which was indirectly confirmed through intermittent operation of the process. The products of the induced crystallization process were FAP and a small amount of HAP, as determined qualitatively using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) tests. Overall, by regulating the phosphate species, the F removal efficiency is maintained, the cost of the precipitant is lowered, and the residual P concentration in the effluent is reduced. The process results in products with FAP as the main component, which can be used as raw material for the phosphoric acid purification process.

Facile phosphorus and oxygen heteroatom functionalization of biochar based on biomass prepared by microwave pyrolysis for adsorption process of cadmium in aqueous solution

AbstractIn this study, in the first stage, biochar is produced from green pistachio hulls (PGHMAC) by microwave heating method, which saves energy, time and cost. In the second step, with the activation of phosphoric acid (H3PO4), the surface properties of the biochar were modified by phosphorus (P) and oxygen (O) doping (O- and P-doped PGHMAC). This adsorbent obtained was applied to remove cadmium (Cd(II)) from wastewater. FTIR, SEM, EDX, and ICP-OES analyses were used for the characterization of the samples. FTIR, EDX, and ICP-OES analysis results showed the presence of oxygen and phosphorus groups on the surface of the relevant adsorbent. The contents of C and O atoms for P- and O-doped PGHMAC were found to be 62.54% and 36.12%, respectively. Also, about 1.29% of P atoms were found with H3PO4 activation. The kinetic, isotherm, and thermodynamic parameters of the adsorption studies were investigated. Maximum Cd(II) adsorption capacities of P- and O-doped PGHMAC at 298 K, 308 K, and 318 K temperatures were calculated as 78.74, 109.89, and 133.33 mg/g by Langmuir model, respectively. The mechanism of Cd(II) adsorption on O- and P-doped PGHMAC has been proposed.

Rapid Development and Validation of Atoltivimab, Maftivimab and Odesivimab in Pharmaceutical Dosage form by using the RP-HPLC Method

Background: The reverse-phase high-performance liquid chromatography (RP-HPLC) method was developed for the quantitative measurement of monoclonal antibodies (Maftivimab, Atoltivimab, and Odesivimab) in the pharmaceutical dosage form. The Food and Drug Administration (FDA) has approved these monoclonal antibodies for the treatment of Zaire ebolavirus infection in adults. Methods: Maftivimab, Atoltivimab, and Odesivimab were separated chromatographically on the Waters Alliance-e2695 platform using the Luna Phenyl Hexyl (250 x 4.6 mm, 5 μm) column and a mobile phase made up of Acetonitrile (ACN) and ortho-phosphoric acid (OPA) buffer in a ratio of 70:30 (v/v). Results: The flow rate was 1.0 ml/min, and a photodiode array (PDA) detector operating at room temperature was used to measure absorption at 282 nm. For Maftivimab, Atoltivimab, and Odesivimab, the theoretical plates were not less than 2000, and the tailing factor shouldn't be greater than 2, accordingly. All measurements have a constant relative standard deviation of peak areas that is less than 2.0. Conclusion: The suggested procedure was approved following the International Conference on Harmonisation (ICH) recommendations. When used for the quantitative analysis of Maftivimab, Atoltivimab, and Odesivimab, the approach was found to be straightforward, affordable, appropriate, exact, accurate, and robust.

Effects of different primers and colouring solutions on orthodontic bonding: shear bond strength and colour change

ObjectivesThis in vitro study evaluated the effect of different colouring solutions and primer systems used in the bonding of brackets on enamel colour change and bond strength.Materials and methods120 premolar teeth were divided into four main groups; brackets were bonded with 37% orthophosphoric acid + Transbond XT Primer in Group 1, 3 M Single Bond Universal in Group 2, Transbond Plus SEP in Group 3, and G-Premio Bond in Group 4. Each group was divided into three subgroups, and the teeth were placed in a cup containing coffee and tea mixture, in a cup containing cola and in distilled water. A bond strength test was applied to all teeth. Colour measurements of all teeth were performed at 2 different times: before bonding and after the bond strength test.ResultsThe average bond strength of the 37% orthophosphoric acid group was higher than that of the other groups. The effect of primer and solution groups on colour change was statistically significant (p = 0.001 and p = 0.023, respectively).ConclusionsIn this study, the bond strength was clinically sufficient in all primer groups. The highest colour change was observed when the tea–coffee solution and Transbond Plus SEP primer were used.Clinical relevanceThis study has identified enamel discoloration and bond strength from different colouring solutions and primer systems used for bonding braces, which can be used to inform clinicians and patients to achieve better treatment results.

Biocompatibility and acid resistance of preformed crowns in children: an in vitro study.

To investigate the in vitro biocompatibility of human gingival fibroblasts with preformed paediatric crowns and resistance to acid exposure at levels that simulate the oral environment. This laboratory study investigated primary HGFs viability, metabolic activity, cytotoxicity, and apoptotic events on preformed metal crown discs, composite resin-coated wells, and monolithic zirconia fragments at 24, 48, and 72h using the ApoTox-Glo Triplex assay. The PPCs were also immersed in 0.1% lactic acid, 0.2% phosphoric acid, or 10% citric acid for 7days at 37°C to reproduce conditions associated with dietary intake or gastric reflux. Samples were then subject to inductively coupled plasma optical emission spectrometry to quantitate the release of ions. The viability of HGFs on stainless steel and CR significantly declined at 48 and 72h, representing potential cytotoxicity (p < 0.05). Cytotoxicity of HGFs was also higher for stainless steel and ZR compared to control (p < 0.05). PMCs and ZR crowns gave minimal ion release. Meanwhile, significant quantities of metallic ions, including copper (Cu), iron (Fe), nickel (Ni), and zinc (Zn), were present in eluates from veneered-preformed metal crowns. As PPCs can be exposed to highly acidic environments for many years, thus the release of metallic ions from V-PMCs should form the further investigation in future studies.

The Measurement Reliability of δ13C of Dissolved Organic Carbon: A Validation for Speleothem Samples

The carbon isotopic composition of dissolved organic carbon (δ13CDOC) in speleothems, based on high-precision U-Th ages, has great potential to reconstruct past ecology, microbial activity, and carbon cycling. Identifying the reliability of the pretreatment and measurement of speleothem δ13CDOC is therefore essential to putting it into practice. Actually, we have previously verified the reliability of the method for speleothem δ13CDOC measurements. However, it was only based on the final δ13CDOC values of homogeneous speleothem powder and is unable to evaluate the effects of different experimental conditions and the impacts of adding acid on δ13CDOC if using speleothem as the study samples. In this study, we used an organic reagent (potassium sorbate) as the study sample and designed a conditional experiment that simulates the protocols for speleothem δ13CDOC analysis and presented the resulting data to inspect the effects of the experimental processes on the analysis of δ13CDOC. The results show that the standard deviation of duplicate samples is 0.1‰, which is close to that of the previous work for organic reagents and water samples, and the results were not affected by different experimental conditions and operation steps (such as adding orthophosphoric acid, digestion time, and storage duration of resulting CO2 in storage vessels), suggesting that this method is robust to detect the speleothem δ13CDOC. Considering the range and standard deviation of results, we proposed that the δ13CDOC record could be used in various studies when the amplitudes of the δ13CDOC record are larger than 0.1‰, especially greater than 0.4‰.

Protection of Si Nanowires against Aβ Toxicity by the Inhibition of Aβ Aggregation.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by the accumulation of amyloid beta (Aβ) plaques in the brain. Aβ1-42 is the main component of Aβ plaque, which is toxic to neuronal cells. Si nanowires (Si NWs) have the advantages of small particle size, high specific surface area, and good biocompatibility, and have potential application prospects in suppressing Aβ aggregation. In this study, we employed the vapor-liquid-solid (VLS) growth mechanism to grow Si NWs using Au nanoparticles as catalysts in a plasma-enhanced chemical vapor deposition (PECVD) system. Subsequently, these Si NWs were transferred to a phosphoric acid buffer solution (PBS). We found that Si NWs significantly reduced cell death in PC12 cells (rat adrenal pheochromocytoma cells) induced by Aβ1-42 oligomers via double staining with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and fluorescein diacetate/propyl iodide (FDA/PI). Most importantly, pre-incubated Si NWs largely prevented Aβ1-42 oligomer-induced PC12 cell death, suggesting that Si NWs exerts an anti-Aβ neuroprotective effect by inhibiting Aβ aggregation. The analysis of Fourier Transform Infrared (FTIR) results demonstrates that Si NWs reduce the toxicity of fibrils and oligomers by intervening in the formation of β-sheet structures, thereby protecting the viability of nerve cells. Our findings suggest that Si NWs may be a potential therapeutic agent for AD by protecting neuronal cells from the toxicity of Aβ1-42.

PTA/CeO2@Pt-based electrochemical sensors to detect xanthine and uric acid, and evaluate fish freshness

In the present study, we constructed an electrochemical sensor using three materials, namely, cerium dioxide (CeO2) composite platinum (Pt) and polymer 3-amino-5-mercapto-1,2,4-triazole (PTA), prepared by hydrothermal method, to detect xanthines and uric acid. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier infrared spectroscopy (FT-IR) were used to characterize the morphology, elemental composition, and structure of materials. The results demonstrated that the PTA/CeO2@Pt composites were prepared. The electrochemical behavior of xanthines and uric acid on PTA/CeO2@Pt composite electrodes was assessed by cyclic voltammetry (CV) and differential pulsed voltammetry (DPV). The results demonstrated that the dropping amount was 20 µL under a phosphoric acid buffer solution (pH 6). The peak current of xanthine (XA) demonstrated two good linear relationships with concentration, the linear regression equation was IXA = 0.3265CXA + 8.1967 R2 = 0.994 in the concentration range of 10–138 µmol/L, whereas it was IXA = 3.9884CXA + 51.661 R2 = 0.992 in the concentration range of 139–330 µmol/L. The detection limit was 10.36 × 10–7 M. The freshness of fish meat was evaluated, and the correlation analysis between evaluation results and results of xanthine detection in fish meat by PTA/CeO2@Pt electrochemical sensor demonstrated that r = 0.945 and P < 0.01 had a good correlation. The sensor could be used to determine the xanthine content in fish to reflect the freshness of fish, thus displaying good application prospects.

Development of a low-temperature novel porous Si3N4–Al2O3 composite with excellent specific mechanical properties

Porous composites of Si3N4 and Al2O3 have potential applications for various engineering applications. Fabrication of porous ceramic composites is generally expensive due to the requirement of high sintering temperatures and expensive raw materials. A relatively simple, cost-effective, versatile, and novel processing technique with phosphoric acid performing the dual roles of binder and pore-former has been proposed in this work. Porous Si3N4–Al2O3 composites with up to 20 vol% Al2O3 content and porosities in the range of 37–54 vol% were fabricated at only 1200 °C. Young's modulus, flexural strength, and compressive strength of the porous composites were found to be in the range of 21–54 GPa, 31–110 MPa, and 39–103 MPa, respectively. The best combination of mechanical properties was achieved at 10 vol% Al2O3 content, which corresponded to 39 % total porosity. The combination of low density and good mechanical properties yielded outstanding specific properties, which are significantly higher than monolithic porous Si3N4. The excellent combination of a low processing cost, tunable porosity and pore morphology, outstanding mechanical properties, as well as the inherent chemical and thermal stability of these porous composites render them potentially very attractive as chemical filters, porous membranes, as well as porous preforms for interpenetrating metal/ceramic composites.

Optimization of the Reaction Temperature During Phosphoric Acid Production Using Fibonacci Numbers and Golden Section Methods

Optimization of the Reaction Temperature During Phosphoric Acid Production Using Fibonacci Numbers and Golden Section Methods