Incorporation of palladium into pyrite: Insights from X-ray absorption spectroscopy analysis and modelling

Pyrite (FeS2) often accommodates elevated concentrations of platinum-group elements in ores of magmatic and hydrothermal origin. In order to elucidate the role of pyrite in concentrating Pd, Pd-doped synthetic crystals were studied via X-ray absorption spectroscopy (XAS). Crystals were obtained by salt-flux method in the system saturated with respect to Pd at the temperature of 580 °C and sulphur fugacity of log f (S2) = -0.4. Scanning electron microscopy, electron probe microanalysis, and laser ablation inductively coupled plasma mass spectrometry studies demonstrated a uniform distribution of Pd within the pyrite crystals. The median and average values of Pd content of ∼0.7 ± 0.1 wt% were measured. Comparison of the Pd K-edge X-ray absorption near edge structure (XANES) spectra with the spectra of standards revealed that the formal oxidation state of Pd was close to +2. Fitting of the extended X-ray absorption fine structure (EXAFS) and Finite Difference Method for Near-Edge Structure (FDMNES) theoretical simulations of XANES spectra showed that Pd substituted for Fe in the crystal structure of pyrite. The isomorphous Pd in pyrite was octahedrally coordinated by S atoms at ∼2.385 Å. The PdS interatomic distance was 5.6 % larger than that of FeS due to the difference in their covalent radii of ∼5.3 %. The expansion caused by the incorporation of Pd into the pyrite structure disappeared at the distance of R > 3 Å. The information on the state of Pd in pyrite, including the local atomic environment and formal oxidation state, is essential for scientific and industrial purposes, e.g. physical-chemical modelling and improvement of leaching and extraction processing respectively.

Construction of Co1-xZnxFe2xGa2-2xO4 (0<x≤0.6) Solid Solutions for Improving Solar Fuels Production in Photocatalytic CO2 Reduction by H2O Vapour

Solid solutions are garnering substantial attention in the realm of solar energy utilization due to their tunable electronic properties, encompassing band edge positions and charge-carrier mobilities. In this study, we designed and synthesized Co1-xZnxFe2xGa2-2xO4 (0 Collapse

Key Words

• CO2 conversion
• Co1-xZnxFe2xGa2–2xO4
• Solid solution
• molten salts
• photosynthesis

Collapse

MESH Headings Collapse

Grants

• 2023AAC02002 Natural Science Foundation of Ningxia Province
• 21862015, 21865022 Innovative Research Group Project of the National Natural Science Foundation of China

Collapse

Affiliation(s)

Qiang Wang State Key Laboratory of High-efficiency, Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China
Li Li State Key Laboratory of High-efficiency, Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China
Jiaxue Lu State Key Laboratory of High-efficiency, Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China
Yao Chai State Key Laboratory of High-efficiency, Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China
Jinni Shen State Key Lab of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou, 350116, P. R. China
Jun Liang State Key Laboratory of High-efficiency, Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China

Collapse

Boosted elimination of florfenicol by BiOClxBr1-x solid solutions via photocatalytic ozonation under visible light

In this work, a series of BiOClxBr1-x (BCB) solid solutions are facilely designed for visible-light-driven photocatalytic ozonation (PCO) degradation of florfenicol (FF) in water environments, which could add to the library of efficient, cost-effective and robust nanocatalysts for water purification. BCB solid solutions in the structure of 2D nanosheets are achieved involving the etching of BiOBr "micro-flowers" with HCl at different concentrations, allowing a removal ratio of FF up to 97.3 % within 1 h, superior to bare BiOBr and bare BiOCl. A strengthened synergistic effect between photocatalysis and ozonation is substantiated, where the separation of photo-induced charge transfer is accelerated, the band gap is tuned and the utilization efficiency of ozone is enhanced. This facilitates the production of reactive oxygen species identified as •OH, •O2-, and 1O2 that will attack the FF molecule for degradation based on three pathways.

Synergistic photocatalytic degradation mechanism of BiOClxI1-x-OVs based on oxygen vacancies and internal electric field-mediated solid solution

The easy recombination of photoexcited electron-hole pairs is a serious constraint for the application of photocatalysts. In this work, a range of BiOClxI1-x solid solutions with abundant oxygen vacancies (BiOClxI1-x-OVs) were synthesized. In particular, the optimal BiOCl0.5I0.5-OVs sample exhibited almost 100% removal of bisphenol A (BPA) within 45 min visible light exposure, which was 22.4, 3.1 and 4.5 times greater than BiOCl, BiOCl-OVs and BiOCl0.5I0.5, respectively. Besides, the apparent quantum yield of BPA degradation reaches 0.24%, better than some other photocatalysts. Benefiting from the synergism of oxygen vacancies and solid solution, BiOCl0.5I0.5-OVs gained an enhanced photocatalytic capacity. Oxygen vacancies induced an intermediate defective energy level in BiOClxI1-x-OVs materials, promoting the generation of photogenerated electrons and the molecular oxygen adsorption to produce more active oxygen radicals. Meanwhile, the fabricated solid solution structure enhanced the internal electric field between BiOCl layers, achieving rapid migration of photoexcited electrons and effective segregation of photoinduced charge carriers. Thus, this study provides a viable idea to solve the problems of poor visible light absorption of BiOCl-based photocatalysts and easy reorganization of electrons and holes in the photocatalysts.

Bismuth-rich oxyhalide (Bi7O9I3-Bi4O5Br2) solid-solution photocatalysts for the degradation of phenolic compounds under visible light

HYPOTHESIS

The development of solid-solution photocatalysts with tunable bandgaps and band structures, which are significant factors that influence their photocatalytic properties, is crucial.

EXPERIMENTS

We fabricated a series of novel bismuth-rich Bi₇O₉I₃-Bi₄O₅Br₂ solid-solution photocatalysts with controlled I:Br molar ratios (denoted as B-I_xBr_1-x, x  = 0.2, 0.3, 0.4, or 0.6) via a rapid, facile, and energy-efficient microwave-heating route. The photodegradations under visible-light irradiation of the phenolic compounds (4-nitrophenol (4NP), 3-nitrophenol (3NP), and bisphenol A (BPA)), and the simultaneous photodegradation of BPA and rhodamine B (RhB) in a coexisting BPA - RhB system were investigated.

FINDINGS

The B-I_0.3Br_0.7 solid solution provided the highest photocatalytic activity toward 4NP degradation, with degradation rates 32 and 4 times higher than those of Bi₇O₉I₃ and Bi₄O₅Br₂, respectively. The photodegradation efficiency of the studied phenolic compounds followed the order BPA (97.5%) > 4NP (72.8%) > 3NP (27.5%). The RhB-sensitization mechanism significantly enhanced the photodegradation efficiency of BPA. Electrochemical measurements demonstrated the efficient separation and migration of charge carriers in the B-I_0.3Br_0.7 solid solution, which enhanced the photocatalytic activity. The B-I_0.3Br_0.7 solid solution effectively activated molecular oxygen to produce •O₂^-, which subsequently produced other reactive species, including H₂O₂ and •OH, as revealed by reactive-species trapping, nitroblue tetrazolium transformation, and o-tolidine oxidation experiments.

Dispersible CdS1-xSex solid-solution nanocrystal photocatalysts: Photoinduced self-transformation synthesis and enhanced hydrogen-evolution activity

Modulating the electronic structure of Cadmium sulfide (CdS) by non-metallic elements to produce solid-solution photocatalysts serves as a potential route to improve its performance of photocatalytic hydrogen (H₂) evolution. However, exploring an effective synthetic route of CdS-based solid solution is still a great challenge. Herein, the CdS_1-xSe_x solid-solution nanocrystals were successfully synthesized by an accessible photoinduced self-transformation route, including the direct formation of dispersible CdS_1-x(SeS)_x and the in situ self-transformation of selenosulfide ((SeS)^2-) to Se^2- by photoexcited electrons. The prepared CdS_1-xSe_x solid-solution photocatalysts possess a small crystallite size of ca. 5 nm and their bandgaps can be easily tuned in a wide range of 1.84-2.28 eV by tailoring the mole ratio of Se/S. The resultant CdS_0.90Se_0.10 solid-solution photocatalyst realizes the highest H₂-production tempo of 94.6 μmol·h^-1, which is 1.6 folds higher than that of CdS. The experimental and theoretical studies supported that the incorporation of Se atoms could not only narrow the bandgap value to reinforce visible-light absorption, but also tune its electronic structure to optimize interfacial H₂-evolution dynamics, thus achieving an efficient photocatalytic H₂-production rate of the dispersible CdS_1-xSe_x solid solution. This study may deliver advanced inspirations for optimizing the electronic structure of photocatalysts towards sustainable H₂ production.

Micro-Raman spectroscopic analysis on natural carbonates: linear relations found via biaxial plotting of peak frequencies for cation substituted species

Carbonates are ubiquitous minerals carrying important information on aqueous environments where they precipitated on the Earth and space. While their ideal chemical formulae are denoted as simple as MCO₃ or M₁M₂(CO₃)₂ (M: metal cations), natural carbonates generally form solid-solution series and their compositions deviate from the ideal formulae. Since their cation composition due to the substitution provides a sensitive indicator for chemical and thermodynamic environments of aqueous solutions where they precipitated, their composition analysis has been widely carried out from the environmental/geochemical/astrochemical aspects. However, in widely used back-scattered electron and energy dispersion X-Ray analyses, samples should be generally sliced and/or their surface be polished prior to the measurements. For analyzing rare samples with small sizes, such as ones sampled from deep-sea and/or meteorites and asteroids, a non-destructive method without any pretreatments has been strongly desired. Here, a novel analytical method for discriminating various carbonates with Raman micro-spectroscopy is demonstrated, showing that the biaxial plot of the peak frequencies of their lattice modes linearly moves upon partial substitution of the cations. The cation substitution leads to linear movement in the biaxial map, and the slopes of the movement were different for Mg²⁺-Fe²⁺ and Mn²⁺-Fe²⁺ substitutions. This finding suggests that the micro-Raman analysis would be a non-destructive analytical method for evaluating the relative amount of Mg²⁺, Fe²⁺, and Mn²⁺ in dolomite-ankerite-kutnohorite solid-solution series, as well as Mg²⁺/Fe²⁺ ratio for magnesite-breunnerite-siderite. It would be helpful for analyzing the present and past terrestrial and cosmochemical environments.

Ultrafine multi-metal (Zn, Cd, Pb) sulfide aggregates formation in periodically water-logged organic soil

This study investigates authigenic metal (Zn, Cd, and Pb) sulfides formed in the upper (4-20 cm) layer of severely degraded soil close to ZnPb smelter in CE Europe (southern Poland). The soil layer is circumneutral (pH 6.0-6.8), organic, occasionally water-logged, and contains on average 26,400 mg kg^-1 Zn, 18,800 mg kg^-1 Pb, 1300 mg kg^-1 Cd, and 2500 mg kg^-1 of sulfur. The distribution of the authigenic sulfide mineralization is uneven, showing close association with the remains of vascular plants (Equisetaceae, Carex, and herbs). A combination of focused ion beam (FIB) technology with scanning (SEM) and transmission electron microscopy (TEM) is used to reveal the structure and organization of the metal sulfides at micro- and nanoscale resolution. The sulfides form spheroidal and botryoidal porous aggregates composed of nanocrystalline (<5 nm) ZnCd sulfide solid solution and minor discrete PbS (galena) crystals up to 15 nm. The solid solution exists in a cubic (sphalerite) polytype over a whole Zn/Cd range. An intricate core-shell structure is found to be a characteristic feature of the aggregates in which high-Zn outer layers encapsulate Cd-rich sulfide core. PbS resides between the Cd-rich and Cd poor sulfide within nano sites of increased porosity. The study highlights the importance of nanoscale analyses for the prediction of metal behavior in soils. The sulfide self-organization into complex structures and Cd encapsulation inside high-Zn sulfide indicate the occurrence of a self-sustainable mechanism specific to polluted periodically water-logged soil that limits Cd mobility. However, as the reduced Cd mobility is obtained at the Zn expense, the soil gets Cd enriched relative to Zn over extended periods. Although the study proves PbS crystallization in the soil, the process seems environmentally irrelevant even at high Pb contents, being suppressed by other soil processes (e.g., Pb sorption on organic matter). Our findings are valuable in remediation strategies and the management of contaminated soils rich in organic matter that address the mobility of toxic metals and their transfer into living organisms.

Mechanisms and thermodynamic modelling of iodide sorption on AFm phases

Both, experimental and modelling evidence is presented in this study showing that interlayer anion exchange is the dominant sorption mechanism for iodide (I^-) on AFm phases. AFm phases are Ca-Al(Fe) based layered double hydroxides (LDH) known for their large potential for the immobilization of anionic radionuclides, such as dose-relevant iodine-129, emanating from low- and intermediate-level radioactive waste (L/ILW) repositories. Monosulfate, sulfide-AFm, hemicarbonate and monocarbonate are safety-relevant AFm phases, expected to be present in the cementitious near-field of such repositories. Their ability to bind I^- was investigated in a series of sorption and co-precipitation experiments. The sorption of I^- on different AFm phases was found to depend on the type of the interlayer anion. Sorption R_d values are very similar for monosulfate, sulfide-AFm and hemicarbonate. A slightly higher uptake occurs by AFm phases with a singly charged anion in the interlayer (HS-AFm) as compared to AFm with divalent ions (monosulfate), whereas uptake by hemicarbonate is intermediate. No significant sorption occurs onto monocarbonate. Our derived thermodynamic solid solution models reproduce the experimentally obtained sorption isotherms on HS-AFm, hemicarbonate and monosulfate, indicating that anion exchange in the interlayer is the dominant mechanism and that the contribution of I^- electrostatic surface sorption to the overall uptake is negligible.

Anchoring bismuth oxybromo-iodide solid solutions on flexible electrospun polyacrylonitrile nanofiber mats for floating photocatalysis

Constructing floating photocatalysts with highly efficient visible-light utilization is a promising approach for practical photocatalytic wastewater treatment. In this study, we anchored bismuth oxybromo-iodide (BiOBr_xI_1-x (0 ≤ x ≤ 1)) on flexible electrospun polyacrylonitrile (PAN) nanofiber mats to create BiOBr_xI_1-x@PAN nanofibers with tunable light absorption properties as floating photocatalysts at room temperature. As x increased, the photocatalytic activity of the BiOBr_xI_1-x@PAN nanofibers with similar loading content initially increased, and then decreased, for the degradation of bisphenol A (BPA) and methyl orange (MO) under visible-light irradiation (λ > 420 nm) conditions. The BiOBr_xI_1-x@PAN (0 < x < 1) nanofibers exhibited better photocatalytic performance compared to the BiOBr@PAN and BiOI@PAN nanofibers. Under visible-light irradiation, the BPA degradation rate of the BiOBr_0.5I_0.5@PAN nanofibers was 1.9 times higher than that of the BiOI@PAN nanofibers, while the BiOBr@PAN nanofibers had no noticeable degradation performance. The MO degradation rate of the BiOBr_0.5I_0.5@PAN nanofibers was 2.5 and 3.2 times higher than that of the BiOBr@PAN and BiOI@PAN nanofibers, respectively. The enhanced performance possibly originated from a balance between the light absorption and redox capabilities, along with efficient separation of electron-hole pairs in the BiOBr_0.5I_0.5@PAN nanofibers, as determined by ultraviolet-visible diffuse reflectance spectroscopy, X-ray photoelectron spectra analysis of the valence bands, and photocurrent response characterization. Compared to the powder structures, the BiOBr_xI_1-x@PAN nanofibers showed enhanced performance due to the excellent dispersion and immobilization of the BiOBr_xI_1-x solid solution, which provided more active sites during photocatalytic degradation. In addition, their flexible self-supporting structures allowed for floating photocatalysis near the water surface. They could be reused directly without separation and maximized the absorption of visible light during the photocatalytic reaction. Therefore, these solid-solution-based floatable nanofiber photocatalysts are good potential candidates for wastewater treatment applications.

Scalemic mixtures preparation for optimized composition of ibuprofen solid dosage forms

The stable and metastable phase diagrams between the sinister and the rectus ibuprofen enantiomers were established by means of thermal analysis and X-ray powder diffraction experiments as a function of temperature. The results obtained allow proving for the first time the existence, for the stable system, of a solid solution by mixing the racemic ibuprofen with one of its enantiomers for low concentration of the enantiomer. Since the rectus ibuprofen is a non-active pharmaceutical agent which can be partially bio-converted into the sinister enantiomer, the present work offers a new approach for scalemic mixtures preparation in order to improve the benefit/risk ratio related to ibuprofen solid dosage form administration.

Dissolution and solubility of calcite-rhodochrosite solid solutions [(Ca1-xMnx)CO3] at 25 °C

A complete series of calcite-rhodochrosite solid solutions [(Ca_1-xMn_x)CO₃] are prepared, and their dissolution processes in various water samples are experimentally investigated. The crystal morphologies of the solid solutions vary from blocky spherical crystal aggregates to smaller spheres with an increasing incorporation of Mn in the solids. Regarding dissolution in N₂-degassed water, air-saturated water and CO₂-saturated water at 25 °C, the aqueous Ca and Mn concentrations reach their highest values after 1240-2400 h, 6-12 h and < 1 h, respectively, and then decrease gradually to a steady state; additionally, the ion activity products (log_IAP) at the final steady state (≈ solubility products in log_K_sp) are estimated to be - 8.46 ± 0.06, - 8.44 ± 0.10 and - 8.59 ± 0.10 for calcite [CaCO₃], respectively, and - 10.25 ± 0.08, - 10.26 ± 0.10 and - 10.28 ± 0.03, for rhodochrosite [MnCO₃], respectively. As X_Mn increases, the log_IAP values decrease from - 8.44 ~ - 8.59 for calcite to - 10.25 ~ - 10.28 for rhodochrosite. The aqueous Mn concentrations increase with an increasing Mn/(Ca + Mn) molar ratio (X_Mn) of the (Ca_1-xMn_x)CO₃ solid solutions, while the aqueous Ca concentrations show the highest values at X_Mn = 0.53-0.63. In the constructed Lippmann diagram of subregular (Ca_1-xMn_x)CO₃ solid solutions, the solids dissolve incongruently, and the data points of the aqueous solutions move progressively up to the Lippmann solutus curve and then along the solutus curve or saturation curve of pure MnCO₃ to the Mn-poor side. The microcrystalline cores of the spherical crystal aggregates are preferentially dissolved to form core hollows while simultaneously precipitating Mn-rich hexagonal prisms.

Highly efficient In-Mo(O,S)2 oxy-sulfide for degradation of organic pollutants under visible light irradiation: An example of photocatalyst on its dye selectivity

Environmentally toxic organic pollutants, namely methylene blue (MB), neutral red (NR), Rhodamine B (RhB), and methyl orange (MO) dyes contain highly toxic, carcinogenic, non-biodegradable, and colored pigments which cause harm for humans and aquatic organisms even at low concentrations. To detoxify these toxic organic pollutants from the wastewater, the bimetallic solid solution-typed In-Mo(O,S)₂ catalyst with various indium (In) contents were synthesized at low temperature through a simple precipitation method. The morphological, structural, chemical compositions, electrochemical and optical properties of the catalysts were thoroughly characterized. The photodegradation performance of the In-Mo(O,S)₂ catalysts over the cationic, anionic and neutral dyes were studied under visible light irradiation. It has been observed that the photocatalytic activity was enhanced as In was added to the Mo(O,S)₂ catalyst, and In-Mo(O,S)₂-20 was found to be the best composition to completely degrade four organic dyes. The dye degradation had rate constant values of 9.5 × 10^-2 min^-1, 6.3 × 10^-2 min^-1, 4.4 × 10^-2 min^-1, and 15.7 × 10^-1 min^-1 for MB (20 ppm), NR (20 ppm), RhB (10 ppm), and MO (10 ppm) dyes, respectively. The active species for degradation of MB is different from those for RhB and MO. Single phase In-Mo(O,S)₂-20 capable to degrade four kinds of dyes at a fast rate is a good photocatalyst.

A Novel One-Step Hydrothermal Preparation of Ru/SnxTi1-xO2 Diesel Oxidation Catalysts and its Low-Temperature Performance

The rutile Sn_xTi_1-xO₂ (x = 0, 0.33, 0.5, 0.67, 1) solid solution was synthesized by a one-step hydrothermal method, in which tetrabutyl titanate and Tin (IV) chloride pentahydrate were used as raw materials. A series of Ru/Sn_xTi_1-xO₂ were then prepared by the impregnation process in RuCl₃ to investigate the performance and stability of CO and C₃H₈ oxidation. These catalysts were characterized through XRD, N₂ adsorption-desorption, FT-IR, TEM, XPS, H₂-TPR, and O₂-TPD techniques. The effect of Sn/Ti molar ratio and hydrothermal condition on the low-temperature catalytic oxidized performance and stability of Ru/Sn_xTi_1-xO₂ were investigated. The results indicated that Ru/Sn_0.67Ti_0.33O₂ catalyst showed an excellent activity and stability at low temperatures. The CO conversion reached 50% at 180 °C and 90% at 240 °C. Besides, the C₃H₈ conversion reached 50% at 320 °C, the complete conversion of C₃H₈ realized at 500 °C, and no deactivation occurs after 12 h of catalytic reaction. The excellent low-temperature activity and stability of the Ru/Sn_0.67Ti_0.33O₂ were attributed to the following factors. Firstly, XRD results showed that Sn⁴⁺ was successfully introduced into the lattice of TiO₂ to replace Ti⁴⁺ forming a homogeneous solid solution (containing -Sn⁴⁺-O-Ti⁴⁺- species), which was consistent with TEM and N₂ adsorption-desorption results. The introduction of Sn could suppress the growth of anatase crystal and promote the formation of rutile phase, and this phase transition was helpful to improve the low-temperature activity of the catalysts. Secondly, TEM images showed that ultrafine Ru nanoparticles (~ 5 nm) were dispersed on Sn_0.67Ti_0.33O₂ support, suggesting that the formation of Sn_xTi_1-xO₂ solid solution was beneficial to the dispersion of Ru particles.

Evaluation of the catalytic oxidation of soot by CeOX-LaMnO3 at different O2 pressures synthesized by ultrasonic-assisted hydrothermal method

In this work, the synthesis of catalyst with perovskite structure and chemical formula La_1-XCe_XMnO₃ at x = 0 - 0.5 were successfully obtained by an ultrasonic-assisted hydrothermal method. Results show that the addition of Ce in La_1-XCe_XMnO₃ have not substantial effect in textural and morphological properties; however, the formation of a new crystalline phase with final composition CeO_X-La_1-XCe_XMnO₃ was detected at values x > 0.3. All synthesized catalysts were tested in the soot oxidation under both, loose and tight contact in 20% O₂/N₂ or 5% O₂/N₂ atmospheres. CeO_X-La_1-XCe_XMnO₃ at x = 0.3 resulted in the best catalytic activity with activation energy values of 57.9 kJ^.mol^-1. The interaction between Ce³⁺ and Mn⁴⁺ species in this catalyst can transfer electrons generating Mn³⁺ and Ce⁴⁺. This reduction from Mn⁴⁺ to Mn³⁺ is accompanied by migration of vacancies to the surface promoting the adsorbed oxygen from the gas phase, need for balancing the chemical states. By increasing the temperature above 300 °C, the bulk oxygen migration to the surface is enhanced being the responsible for the oxygen availability. The formation of CeO_X-La_1-XCe_XMnO₃ promotes a stable redox cycle allowing the reusability of this catalyst even at low oxygen pressures after three different reaction cycles.

Highly efficient and irreversible removal of cadmium through the formation of a solid solution

Sulfur-containing materials are very attractive for the efficient decontamination of some heavy metals. However, the effective and irreversible removal of Cd²⁺, coupled with a high uptake efficiency, remains a great challenge due to the relatively low bond dissociation energy of CdS. Herein, we propose a new strategy to overcome this challenge, by the incorporation of Cd²⁺ into a stable Zn_xCd_1-xS solid solution, rather than into CdS. This can be realised through the adsorption of Cd²⁺ by ZnS nanoparticles, which have exhibited a Cd²⁺ uptake capacity of approximate 400 mg g^-1. Through this adsorption mechanism, the Cd²⁺ concentration in a contaminated solution could effectively be reduced from 50 ppb to <3 ppb, a WHO limit acceptable for drinking water. In addition, ZnS continued to exhibit this noteworthy uptake capacity even in the presence of Cu²⁺, Pb²⁺, and Hg²⁺. ZnS displayed high chemical stability. Particles aged in air for 3 months still retained a> 80% uptake capacity for Cd²⁺, compared with only 9% uptake capacity for similarly-aged FeS particles. This work reveals a new mechanism for Cd²⁺ removal with ZnS and establishes a valuable starting point for further studies into the formation of solid solutions for hazardous heavy metal removal applications.

CeCu composite oxide for chlorophenol effective removal by heterogeneous catalytic wet peroxide oxidation

CeCu solid solution oxide catalysts were prepared by the complex method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS). And its activity in the catalytic wet peroxide oxidation (CWPO) of 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) in water was investigated. The results showed that the Cu²⁺ ions dissolved into the CeO₂ lattice to form CeCu solid solution oxide with a coarse, interconnected, porous, and cotton-like morphology. The metal-oxygen bonds were weakened by the formation of solid solution in the CeCu oxide catalyst. This weakening facilitated the activation and decomposition of the H₂O₂ to form highly oxidative HO· species that can lead to significant chlorophenol mineralization. The formation of CeCu solid solution oxide can effectively inhibit the Cu ions to be leached from the used CeCu oxide catalysts, which can ensure the CeCu oxide catalysts to adapt to a wide pH range of 2.1-7.9 and exhibit good reusability. CWPO reaction of 4-CP and 2,4-DCP molecules on CeCu oxide catalysts conforms to the first-order kinetic equation: y = 6959.3x - 17.2 and y = 9725x - 25.4, respectively. And the reaction activation energies are 57.8 and 80.8 kJ/mol, respectively. The TOC removals of 4-CP and 2,4-DCP can exceed 88 and 82%, and the dechlorination rates of 4-CP and 2,4-DCP are higher than 95 and 99.5%, respectively.

Ultrafast removal of arsenic using solid solution of aero-gel based Ce1-XTixO2-Y oxide nanoparticles

An aero-gel based solid solution of titanium and cerium oxide nanoparticles have been used for the first time for ultra fast and trace level removal of arsenic from water. The interconnected long range ordered mesoporous structure was observed from TEM analysis which has been verified as an essential facet for the fast removal of arsenic in this study. The HR-XRD spectra indicated the face centred cubic structure with Fm3¯m space group. Le-Bail refinement and Raman spectroscopy confirmed the formation of single phase solid solution of Ce_1-XTi_xO_2-Y oxide nanoparticles. The HR-XPS and FT-IR study indicated the surface complexation and partial oxidation of As(III) to As(V) via electron transfer mechanism by reduction of Ce(IV) to Ce(III) and Ti(IV) to Ti(III) simultaneously during adsorption process. The kinetics study demonstrated 99% removal of As(III) within 10 min of initiating the adsorption process. The effect of pH and interfering ions confirmed the wide range of applicability for solid solution of titania and cerium oxide nanoparticles over the different environmental conditions for the removal of arsenic. The adsorption capacity for our best adsorbent (Ce_0.8Ti_0.2O_2-y) was found to be 2 × 10⁵ mg kg^-1 while the lowest concentration of water body system was 7 μg L^-1 which is the minimum concentration of arsenic achieved by any metal oxide based adsorbent.

Raman spectroscopy and structural study of baryte-hashemite solid solution from pyrometamorphic rocks of the Hatrurim Complex, Israel

A number of the baryte, BaSO₄, - hashemite, BaCrO₄, solid solution compounds were synthesized previously. In this study, Raman spectra of naturally occurring phases belonging to the baryte-hashemite series from the pyrometamorphic rocks of the Hatrurim Complex were investigated. The Raman spectrum of natural hashemite, obtained for the first time, shows the position of the fundamental bands for the chromate anion vibrations. The bands related to the stretching vibrations (ν₁, ν₃) occur at 864 cm^-1 and in 871-909 cm^-1 regions, whereas the bending vibrations (ν₂, ν₄) are visible in the 346-360 cm^-1 and 400-422 cm^-1 range, respectively. Received results allowed to observe a gradual shift of bands in baryte-hashemite solid solution as a consequence of the substitution by different cations. The position of bands depends on the Cr/S ratio in analysed samples, and it is determined by differences in atomic mass, and ionic radii between Cr⁶⁺ and S⁶⁺, which affect changes in the strength and length of bonds. The occupancy of the same atomic position by two different cations enables to notice variations of polyhedra geometry, and unit cell parameters despite that baryte and hashemite are isostructural and crystallize in the same Pnma space group. We also confirm that the immobilization of the toxic (CrO₄)^2- ion in the baryte structure may occur directly without oxygen state reduction, we propose to using a baryte-hashemite solid solution as a reservoir for the incorporation of Cr as an environmental pollutant.

Crystallization and solid solution attainment of samarium doped ZnO nanorods via a combined ultrasonic-microwave irradiation approach

An advanced sol-gel method is developed via combined ultrasound-microwave irradiation and utilized for the crystallization of pristine and samarium doped zinc oxide nanorods. Organic structure directing agents directed one dimensional growth and air-annealing was applied as post-thermal treatment. Microstructural, optical, and solid state survey was pursued by PXRD, FESEM, TEM, EDS, FTIR, DRS, PL, micro-Raman, H₂-TPR, and ESR techniques. Phase analysis by diffraction patterns confirmed the efficacy of irradiation strategy as it improves the crystallinity degree, expedites the hexagonal close pack morphology, and conducts lattice imperfection. Accordingly, aspect ratio and electronic evolution parallel to dopant content is favored. Electron microscopy demonstrated the flake-like rearrangement of nanorods as well as a structure-related growth where a direct proportion exists between atomic packing factor in lattice and aspect ratio. Textural investigation by EDS and FTIR rejected the presence of any impurity verifying an integrated composition. Reflectance and luminescence spectra exhibited characteristic optical behavior with shifts corresponding to dopant concentration. Also, band gap energies increased with samarium addition depicting an opposite trend with respect to unit cell variation. Finally, Raman, TPR, and ESR spectra provided detailed dopant-dependent trends on the internal solid state and defect chemistry of the nanorods. In this regard, maximum shifts in E₂^high and E₁^LO phonon modes duly correlated with the vibrations of zinc and oxygen atoms, surface oxygen and bulk ZnO reduction bands, emergence and alteration of samarium centers, along with the dominance of zinc and oxygen vacancies were all resulted due to the utmost lattice imperfection in SZO1.

Enhanced activity and stability of La-doped CeO2 monolithic catalysts for lean-oxygen methane combustion

Effective utilization of coal bed methane is very significant for energy utilization and environment protection. Catalytic combustion of methane is a promising way to eliminate trace amounts of oxygen in the coal bed methane and the key to this technology is the development of high-efficiency catalysts. Herein, we report a series of Ce_1-xLa_xO_2-δ (x = 0-0.8) monolithic catalysts for the catalytic combustion of methane, which are prepared by citric acid method. The structural characterization shows that the substitution of La enhance the oxygen vacancy concentration and reducibility of the supports and promote the migration of the surface oxygen, as a result improve the catalytic activity of CeO₂. M-Ce_0.8La_0.2O_2-δ (monolithic catalyst, Ce_0.8La_0.2O_2-δ coated on cordierite honeycomb) exhibits outstanding activity for methane combustion, and the temperature for 10 and 90% methane conversion are 495 and 580 °C, respectively. Additionally, Ce_0.8La_0.2O_2-δ monolithic catalyst presents excellent stability at high temperature. These Ce_1-xLa_xO_2-δ monolithic materials with a small amount of La incorporation therefore show promises as highly efficient solid solution catalysts for lean-oxygen methane combustion. Graphical abstract ᅟ.

Structure Peculiarities of Micro- and Nanocrystalline Perovskite Ferrites La1-x Sm x FeO3

Micro- and nanocrystalline lanthanum-samarium ferrites La_1-x Sm _x FeO₃ with orthorhombic perovskite structure were obtained by using both solid state reactions (x = 0.2, 0.4, 0.6 and 0.8) and sol-gel synthesis (x = 0.5) techniques. Obtained structural parameters of both series of La_1-x Sm _x FeO₃ are in excellent agreement with the "pure" LaFeO₃ and SmFeO₃ compounds, thus proving formation of continuous solid solution in the LaFeO₃-SmFeO₃ system. Peculiarity of La_1-x Sm _x FeO₃ solid solution is divergence behaviour of unit cell dimensions with increasing x: systematic decrease of the a and c lattice parameters is accompanied with increasing b parameter. Such behaviour of the unit cell dimensions in La_1-x Sm _x FeO₃ series led to crossover of the a and c perovskite lattice parameters and formation of dimensionally tetragonal structure near x = 0.04. Linear decrease of the unit cell volume of La_1-x Sm _x FeO₃ with decreasing x according with the Vegard's rule indicate absence of short-range ordering of R-cations in the LaFeO₃-SmFeO₃ system.

Spectroscopy of the Surface Polaritons in the CdXZn(1-X)P2 Solid Solutions

Here we report on the analysis of the effect of the doping of CdP₂ single crystals by ZnP₂ nanoclusters on the dispersion of the surface polaritons (SP). The ATR spectroscopic technique has been applied to excite the SP in the Cd_XZn_(1-X)P₂ system. Analysis of the obtained spectra has shown that the doping of CdP₂ single crystals by ZnP₂ nanoclusters result in the position and the width of the dispersion branches of the SP. This effect is more pronounced in the low frequency dispersion branches. These SP branches are originated from phonons which correspond to the motion of the cation sublattice.

Structural Behaviour of Solid Solutions in the NdAlO3-SrTiO3 System

Single-phase mixed aluminates-titanates Nd_1-x Sr _x Al_1-x Ti _x O₃ (x = 0.3 ÷ 0.9) were prepared from stoichiometric amounts of constituent oxides Nd₂O₃, Al₂O₃, TiO₂ and strontium carbonate SrCO₃ by solid-state reaction technique in air at 1773 K. Crystal structure parameters of Nd_1-x Sr _x Al_1-x Ti _x O₃ were refined by full-profile Rietveld refinement in space groups R [Formula: see text] c (x = 0.3, 0.5, 0.7 and 0.8) and Pm [Formula: see text] m (x = 0.9). Comparison of the obtained structural parameters with the literature data for the end members of the system NdAlO₃ and SrTiO₃ revealed formation of two kinds of solid solutions Nd_1-xSr_xAl_1-xTi_xO₃ with the cubic and rhombohedral perovskite structure. Morphotropic rhombohedral-to-cubic phase transition in Nd_1-xSr_xAl_1-xTi_xO₃ series occurs at x = 0.84. Based on the results obtained as well as the literature data for the parent compounds, the tentative phase diagram of the NdAlO₃-SrTiO₃ pseudo-binary system have been constructed.

Uptake of nickel by synthetic mackinawite

The uptake of aqueous Ni(II) by synthetic mackinawite (FeS) was examined in anaerobic batch experiments at near-neutral pH (5.2 to 8.4). Initial molar ratios of Ni(II) to FeS ranged from 0.008 to 0.83 and maximum Ni concentrations in mackinawite, expressed as the cation mol fraction, were as high as X_Ni = 0.56 (Fe_{1 - x} Ni _x S; 0 ≤ x ≤ 1). Greater than 99% Ni removal from solution occurred when Ni loading remained below 0.13 ± 0.03 (1σ) mol Ni per mol FeS due to sorption of Ni at the mackinawite surface. Characterization of experimental solids using X-ray diffraction and Raman spectroscopy showed patterns characteristic of nanocrystalline mackinawite; no evidence of nickel monosulfide (α-NiS or millerite), polydymite (Ni₃S₄), or godlevskite [(Ni,Fe)₉S₈] formation was indicated regardless of the amount of Ni loading. Slight expansion of the c-axis correlated with increasing Ni content in synthetic mackinawite, from c = 5.07 ± 0.01 Å at X_Ni = 0.02 to c = 5.10 ± 0.01 Å at X_Ni = 0.38. Ni K-edge extended X-ray absorption fine structure (EXAFS) spectra of synthetic Ni-bearing mackinawite are similar in phase and amplitude to the Fe K-edge EXAFS spectrum of Ni-free mackinawite, indicating that the molecular environment of Ni²⁺ in Ni-bearing mackinawite is similar to that of Fe²⁺ in Ni-free mackinawite. EXAFS data fitting of Ni-bearing mackinawite with X_Ni = 0.42 indicated a coordination number of 4.04 ± 0.30 and an average Ni_S bond distance of 2.28 Å, in good agreement with the Fe_S bond distance of 2.26 Å in mackinawite, tetrahedral Fe coordination, and slight lattice expansion along the c-axis. At lower Ni loadings (X_Ni = 0.05-0.11), EXAFS analysis showed a decrease in Ni_S coordination towards CN = 3, which reflects the influence of sorbed Ni. Continued Ni uptake, past the maximum amount of sorption, was accompanied by proportional molar release of Fe to solution. Interstitial occupancy of Ni within the mackinawite interlayer may be transitional to structural substitution of Fe. The Ni-mackinawite solid-solution is described by a one-site binary mixing model: LnKd=lnKe-(W/RT)(1-2XNi) where K_d is the distribution coefficient, K_e is the ratio of equilibrium constants for Ni-mackinawite and mackinawite (14.4 ± 1.3), W is an ion interaction parameter, and X_Ni is the mole fraction of end-member NiS in the solid solution. The experimentally determined value of W is 17.74 ± 1.15 kJ/mol and indicates significant non-ideality of the solid solution. Transformation processes were evaluated by aging Ni-mackinawite with polysulfides and solutions saturated with air. Reaction of Ni-mackinawite with polysulfides led to the formation of pyrite (FeS₂) and Ni retention in the solid phase. When Ni-mackinawite was aged in the presence of dissolved oxygen, transformation to goethite (FeOOH) and violarite (FeNi₂S₄) was observed.

TiZrNbTaMo high-entropy alloy designed for orthopedic implants: As-cast microstructure and mechanical properties

Combining the high-entropy alloy (HEA) concept with property requirement for orthopedic implants, we designed a Ti₂₀Zr₂₀Nb₂₀Ta₂₀Mo₂₀ equiatomic HEA. The arc-melted microstructures, compressive properties and potentiodynamic polarization behavior in phosphate buffer solution (PBS) were studied in detail. It was revealed that the as-cast TiZrNbTaMo HEA consisted of dual phases with bcc structure, major bcc1 and minor bcc2 phases with the lattice parameters of 0.3310nm and 0.3379nm, respectively. As confirmed by nanoindentation tests, the bcc1 phase is somewhat harder and stiffer than the bcc2 phase. The TiZrNbTaMo HEA exhibited Young's modulus of 153GPa, Vickers microhardness of 4.9GPa, compressive yield strength of σ_y=1390MPa and apparent plastic strain of ε_p≈6% prior to failure. Moreover, the TiZrNbTaMo HEA manifested excellent corrosion resistance in PBS, comparable to the Ti6Al4V alloy, and pitting resistance remarkably superior to the 316L SS and CoCrMo alloys. These preliminary advantages of the TiZrNbTaMo HEA over the current orthopedic implant metals in mechanical properties and corrosion resistance offer an opportunity to explore new orthopedic-implant alloys based on the TiZrNbTaMo concentrated composition.

Concentration- and Temperature-Induced Phase Transitions in PrAlO3-SrTiO3 System

Single-phase mixed aluminates-titanates Pr1-x Sr x Al1-x Ti x O3 (x = 0.1, 0.2, 0.3, 0.5, 0.7) with rhombohedral perovskite structure were prepared by solid-state reaction technique at 1823-1873 K. Morphotropic rhombohedral-to-cubic phase transition in Pr1-x Sr x Al1-x Ti x O3 series is predicted to occur at x = 0.88. The temperature-induced structural phase transition R  [Formula: see text]  с - Pm [Formula: see text]  m in Pr0.5Sr0.5Al0.5Ti0.5O3, detected at 930 K by in situ high-temperature X-ray synchrotron powder diffraction, occurs at considerably lower temperature as the corresponding transformation in the parent compound PrAlO3 (1770 K). Such remarkable drop of the transition temperature is explained by gradual decrease of the perovskite structure deformation in the Pr1-x Sr x Al1-x Ti x O3 series with increasing Sr and Ti contents as a consequence of the increasing Goldschmidt tolerance factor. For Pr0.3Sr0.7Al0.3Ti0.7O3 phase, a sequence of the low-temperature phase transformation R  [Formula: see text]  с - Immb(C2/m) - I4/mcm was detected.

The Role of ZnP2 Nanoclusters in the Vibrational Properties of Cd x Zn(1 - x)P2 Solid Solutions

This study reports an analysis of the IR reflectance and Raman spectra of Cd x Zn(1 - x)P2 solid solutions. We have analyzed the effect of the doping of the CdP2 single crystal by the ZnP2 nanoclusters on the vibrational properties of studied samples: ε 0, ε inf, phonon frequencies, and strengths. These dependencies might be used as an alternative non-destructive way for the control of the Cd x Zn(1 - x)P2 composition. The obtained results show that variation of the concentration of ZnP2 nanoclusters opens a space to design the tailored material properties for the industrial applications.

Characterization, dissolution and solubility of the hydroxypyromorphite-hydroxyapatite solid solution [(PbxCa1-x)5(PO4)3OH] at 25 °C and pH 2-9

BACKGROUND

The interaction between Ca-HAP and Pb(2+) solution can result in the formation of a hydroxyapatite-hydroxypyromorphite solid solution [(PbxCa1-x)5(PO4)3(OH)], which can greatly affect the transport and distribution of toxic Pb in water, rock and soil. Therefore, it's necessary to know the physicochemical properties of (PbxCa1-x)5(PO4)3(OH), predominantly its thermodynamic solubility and stability in aqueous solution. Nevertheless, no experiment on the dissolution and related thermodynamic data has been reported.

RESULTS

Dissolution of the hydroxypyromorphite-hydroxyapatite solid solution [(PbxCa1-x)5(PO4)3(OH)] in aqueous solution at 25 °C was experimentally studied. The aqueous concentrations were greatly affected by the Pb/(Pb + Ca) molar ratios (XPb) of the solids. For the solids with high XPb [(Pb0.89Ca0.11)5(PO4)3OH], the aqueous Pb(2+) concentrations increased rapidly with time and reached a peak value after 240-720 h dissolution, and then decreased gradually and reached a stable state after 5040 h dissolution. For the solids with low XPb (0.00-0.80), the aqueous Pb(2+) concentrations increased quickly with time and reached a peak value after 1-12 h dissolution, and then decreased gradually and attained a stable state after 720-2160 h dissolution.

CONCLUSIONS

The dissolution process of the solids with high XPb (0.89-1.00) was different from that of the solids with low XPb (0.00-0.80). The average K sp values were estimated to be 10(-80.77±0.20) (10(-80.57)-10(-80.96)) for hydroxypyromorphite [Pb5(PO4)3OH] and 10(-58.38±0.07) (10(-58.31)-10(-58.46)) for calcium hydroxyapatite [Ca5(PO4)3OH]. The Gibbs free energies of formation (ΔG f (o) ) were determined to be -3796.71 and -6314.63 kJ/mol, respectively. The solubility decreased with the increasing Pb/(Pb + Ca) molar ratios (XPb) of (PbxCa1‒x)5(PO4)3(OH). For the dissolution at 25 °C with an initial pH of 2.00, the experimental data plotted on the Lippmann diagram showed that the solid solution (PbxCa1-x)5(PO4)3(OH) dissolved stoichiometrically at the early stage of dissolution and moved gradually up to the Lippmann solutus curve and the saturation curve for Pb5(PO4)3OH, and then the data points moved along the Lippmann solutus curve from right to left. The Pb-rich (PbxCa1-x)5(PO4)3(OH) was in equilibrium with the Ca-rich aqueous solution. Graphical abstractLippmann diagrams for dissolution of the hydroxypyromorphite-hydroxyapatite solid solution [(PbxCa1-x)5(PO4)3OH] at 25 ˚C and an initial pH of 2.00.

Activity and hydrothermal stability of CeO₂-ZrO₂-WO₃ for the selective catalytic reduction of NOx with NH₃

A series of CeO2-ZrO2-WO3 (CZW) catalysts prepared by a hydrothermal synthesis method showed excellent catalytic activity for selective catalytic reduction (SCR) of NO with NH3 over a wide temperature of 150-550°C. The effect of hydrothermal treatment of CZW catalysts on SCR activity was investigated in the presence of 10% H2O. The fresh catalyst showed above 90% NOx conversion at 201-459°C, which is applicable to diesel exhaust NOx purification (200-440°C). The SCR activity results indicated that hydrothermal aging decreased the SCR activity of CZW at low temperatures (below 300°C), while the activity was notably enhanced at high temperature (above 450°C). The aged CZW catalyst (hydrothermal aging at 700°C for 8 hr) showed almost 80% NOx conversion at 229-550°C, while the V2O5-WO3/TiO2 catalyst presented above 80% NOx conversion at 308-370°C. The effect of structural changes, acidity, and redox properties of CZW on the SCR activity was investigated. The results indicated that the excellent hydrothermal stability of CZW was mainly due to the CeO2-ZrO2 solid solution, amorphous WO3 phase and optimal acidity. In addition, the formation of WO3 clusters increased in size as the hydrothermal aging temperature increased, resulting in the collapse of structure, which could further affect the acidity and redox properties.

Arsenate substitution in lead hydroxyl apatites: A Raman spectroscopic study

A total of seven compounds of the hydroxylpyromorphite Pb10(PO4)6(OH)2 - hydroxylmimetite Pb10(AsO4)6(OH)2 (HPY-HMI) solid solution series were synthesized at 80°C from aqueous solutions and characterized using Raman spectroscopy. The positions of the bands in all spectra of the series depend on the content of arsenates and phosphates shifting to lower wavenumbers with substitution of (AsO4)(3-) for (PO4)(3-). This shift results from the decreasing bond strength of X-O (where X=P, As) and higher atomic mass of As than P. The position and intensity of major (PO4)(3-) and (AsO4)(3-) bands in Raman spectra exhibit linear correlation with As content, while the ratio of the intensities of these peaks shows exponential correlation. This results due to different polarizability of (PO4)(3-) and (AsO4)(3-) molecules. A small carbonate band develops with increasing As content indicating that hydroxyl lead apatites adopt the (CO3)(2-) ions, particularly at the arsenate end of the series.

Thermally-activated constitutive model including dislocation interactions, aging and recovery for strain path dependence of solid solution strengthened alloys: Application to AA5754-O

A thermally-activated constitutive model is developed based on dislocation interactions, crystallographic orientations and microstructural evolution to describe the elasto-plastic stress-strain behavior during multi-axial loading. The aim is to contribute to the quantification of complex strain path response in solid solution strengthened alloys. In detail, dislocation/dislocation interactions are incorporated in the model to quantify latent and kinematic hardening phenomena during loading path changes. Dislocation density-based constitutive relations are included to account for dislocation features such as dislocation forests, walls and channels. Moreover specifically, dislocation/solute atom interactions are also considered in order to account for both dynamic and static strain aging as well as static recovery. The model is validated against multiple multi-axial data sets for AA5754-O with changes of loading path and various degrees of pre-strain and time intervals between tests.

Graphene sheets grafted three-dimensional BiOBr0.2I0.8 microspheres with excellent photocatalytic activity under visible light

A series of graphene sheets grafted three-dimensional BiOBr0.2I0.8 microspheres with different graphene contents have been synthesized by a simple one-step solvothermal method. The BiOBr0.2I0.8 microspheres were composed of numerous nanoplates with a thickness of about 10nm and dispersed uniformly on the surface of graphene. The assembled BiOBr0.2I0.8/graphene composites exhibited excellent photocatalytic activity in the degradation of rhodamine B (RhB) and phenol under visible light irradiation (λ>420 nm). The optimal graphene content was found to be 10.0 wt.%, and the corresponding photocatalytic activity in degradation of RhB and phenol was 3.19 and 3.27 times that of pure BiOBr0.2I0.8, respectively. The enhanced photocatalytic activity could be attributed to more effective charge transportations and separations, larger specific surface areas and the increased light absorption. A possible photocatalytic mechanism of the BiOBr0.2I0.8/graphene composites was also proposed.

A novel approach to accelerate the reaction between Ti and Al

Pure Ti foils and SiCp/Al composite foils were employed to investigate the parabolic growth kinetics of TiAl3 at 660°C. Compared with pure Al foils, the introduction of SiC particles significantly refined TiAl3 grain size by the solid solution of silicon. Corresponding refinement mechanisms were concluded from the perspective of the nucleation of TiAl3. Micromechanics analysis shows that the fine TiAl3 grains own a small viscous resistance, and subsequently an improvement in the reaction rate could be achieved. This meaningful law also applies extensively to Ni/Al and Fe/Al systems.

Melt extrusion with poorly soluble drugs

Melt extrusion (ME) over recent years has found widespread application as a viable drug delivery option in the drug development process. ME applications include taste masking, solid-state stability enhancement, sustained drug release and solubility enhancement. While ME can result in amorphous or crystalline solid dispersions depending upon several factors, solubility enhancement applications are centered around generating amorphous dispersions, primarily because of the free energy benefits they offer. In line with the purview of the current issue, this review assesses the utility of ME as a means of enhancing solubility of poorly soluble drugs/chemicals. The review describes major processing aspects of ME technology, definition and understanding of the amorphous state, manufacturability, analytical characterization and biopharmaceutical performance testing to better understand the strength and weakness of this formulation strategy for poorly soluble drugs. In addition, this paper highlights the potential advantages of employing a fusion of techniques, including pharmaceutical co-crystals and spray drying/solvent evaporation, facilitating the design of formulations of API exhibiting specific physico-chemical characteristics. Finally, the review presents some successful case studies of commercialized ME based products.