Transformation Route Research Articles

Photocatalytic degradation of phenol over visible light active ZnO/Ag2CO3/Ag2O nanocomposites heterojunction

In this paper, ZnO heterojunction with Ag2CO3/Ag2O mixed phase was synthesized by precipitation and phase transformation routes. The synthesized photocatalysts were characterized by X-ray diffraction (XRD), BET specific surface area, field emission scanning electron microscopy (FESEM), transmission electron microscopy along with energy-dispersive X-ray (TEM-EDX), Fourier transform infrared (FTIR), UV–vis-NIR spectrophotometer to reveal their phase, morphology, purity, and optical properties. The photocatalytic activity of the obtained nanocomposites was measured by the degradation of phenol under visible light irradiation. The results demonstrated that, the heterojunction mixed phase of Ag2CO3/Ag2O over ZnO surfaces has major effect on establishing the performance of the phenol photodegradation process. It can be noted that the Ag2O crystal’s growth over Ag2CO3 heterojunction on ZnO lattice, effectively facilitate charge transfer and suppress recombination of photogenerated electrons and holes, leading to highest impact phenol degradation. The synthesized photocatalyst displayed excellent properties, showing a potential industrial application for the treatment of phenolic wastewater.

ZnCo2O4 ultrathin nanosheets towards the high performance of flexible supercapacitors and bifunctional electrocatalysis

With the growing development of portable electronics, extensive research efforts on power sources with flexible feature have been developed. In that field, all-solid-state thin-film flexible supercapacitor (ASSTFS) has been considered as a favorable and competitive candidate owing to its multiple benefits such as ultrathin configuration, good flexibility and high safety against liquid leakage. Currently, the major drawback of ASSTFSs is their relatively low capacitance due to the intrinsic supercapacitive behavior of the electrode materials as well as the limited surface area. In this study, ultrathin structure was introduced into spinel ZnCo2O4 through a topological transformation route. The obtained ZnCo2O4 ultrathin nanosheet serves large specific surface area, and thus shortens the ion diffusion distance, leading to the exposure of more electrochemically active area to achieve a much higher pseudocapacitance as in ASSTFS. When assembled into a flexible supercapacitor, the device exhibits a high specific capacitance of 5100 μF/cm2 and a high energy density of 31.8 mWh/cm3 at power density of 280 mW/cm3. Furthermore, attributed to the beneficial ultrathin structure, the ZnCo2O4 ultrathin nanosheets also demonstrated the superior oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) performances, all of which demonstrating it a promising candidate for energy conversion and storage applications.

Transformation mechanism of sodium during pyrolysis of Zhundong coal

The modes in which Na occurs play an important role in its release and catalytic effects during thermal utilization of Zhundong coal. The modes of Na transform with increasing temperature during pyrolysis, but the transformation mechanism remains unclear. In this study, an acid-washed coal was used as a substrate to eliminate the influence of Na inherently present in the raw coal. Na2SO4, NaCl, NaHCO3, and sodium carboxylate were loaded onto the acid-washed coal by impregnation or ion exchange. Pyrolysis of the sodium-loaded coals was conducted in a fixed-bed reactor. Transformation of Na in chars was studied over the temperature range 300–900 °C. Interconversion of H2O- and CH3COONH4-soluble sodium occurred below 400 °C. CH3COONH4-soluble sodium mainly transformed to H2O-soluble sodium at 400–600 °C. The transformation of Na from the H2O-soluble to insoluble form occurred above 600 °C. The transformation of Na related to its initial form in the coal. Transformation routes and mechanisms of Na are proposed·H2O-soluble sodium can react with COOH to form CH3COONH4-soluble sodium below 400 °C. The decomposition of CH3COONH4-soluble sodium occurred at temperatures lower than 600 °C. H2O-soluble sodium may combine with minerals or be coated by the carbon matrix to form insoluble sodium above 600 °C. Na that volatilized above 600 °C was mainly in the H2O-soluble form.

Sulfur nanoparticles/disordered mesoporous carbon composite based on nanotemplates in-situ transformation route

Rechargeable lithium/sulfur batteries have been proposed as the most promising high-performance batteries due to their high theoretical capacity and low cost. However, the poor electrical conductivity and structural stability of elemental sulfur and the dissolution of the polysulfides have confined the utilization of elemental sulfur and the cyclic retention of capacity. A novel in-situ route by transforming ZnO nanotemplates into sulfur nanoparticles during the preparation of carbon/sulfur composite is reported for synthesizing sulfur nanoparticles/disordered mesoporous carbon composite, which shows a high specific capacity of 660.8 mAh/g (composite) during the first cycle and an excellent cyclic retention of 87.9% after 100 cycles.

Bridging the Gap between the Direct and Hydrocarbon Pool Mechanisms of the Methanol‐to‐Hydrocarbons Process

AbstractAfter a prolonged effort over many years, the route for the formation of a direct carbon−carbon (C−C) bond during the methanol‐to‐hydrocarbon (MTH) process has very recently been unveiled. However, the relevance of the “direct mechanism”‐derived molecules (that is, methyl acetate) during MTH, and subsequent transformation routes to the conventional hydrocarbon pool (HCP) species, are yet to be established. This important piece of the MTH chemistry puzzle is not only essential from a fundamental perspective, but is also important to maximize catalytic performance. The MTH process was probed over a commercially relevant H‐SAPO‐34 catalyst, using a combination of advanced solid‐state NMR spectroscopy and operando UV/Vis diffuse reflectance spectroscopy coupled to an on‐line mass spectrometer. Spectroscopic evidence is provided for the formation of (olefinic and aromatic) HCP species, which are indeed derived exclusively from the direct C−C bond‐containing acetyl group of methyl acetate. New mechanistic insights have been obtained from the MTH process, including the identification of hydrocarbon‐based co‐catalytic organic reaction centers.

Bridging the Gap between the Direct and Hydrocarbon Pool Mechanisms of the Methanol-to-Hydrocarbons Process.

After a prolonged effort over many years, the route for the formation of a direct carbon−carbon (C−C) bond during the methanol‐to‐hydrocarbon (MTH) process has very recently been unveiled. However, the relevance of the “direct mechanism”‐derived molecules (that is, methyl acetate) during MTH, and subsequent transformation routes to the conventional hydrocarbon pool (HCP) species, are yet to be established. This important piece of the MTH chemistry puzzle is not only essential from a fundamental perspective, but is also important to maximize catalytic performance. The MTH process was probed over a commercially relevant H‐SAPO‐34 catalyst, using a combination of advanced solid‐state NMR spectroscopy and operando UV/Vis diffuse reflectance spectroscopy coupled to an on‐line mass spectrometer. Spectroscopic evidence is provided for the formation of (olefinic and aromatic) HCP species, which are indeed derived exclusively from the direct C−C bond‐containing acetyl group of methyl acetate. New mechanistic insights have been obtained from the MTH process, including the identification of hydrocarbon‐based co‐catalytic organic reaction centers.

Graphite-like carbon nitride (C3N4) modified N-doped LaTiO3 nanocomposite for higher visible light photocatalytic and photo-electrochemical performance

A novel g-C3N4/N doped-LaTiO3 organic-inorganic hybrid (CLT) is synthesized via a sol–gel polymerized complex method followed by a facile solid state transformation route. The as synthesized hybrid is characterized using powder X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV–visible diffuse reflectance spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. The results show that the band gap of LaTiO3 is narrowed and also could absorb visible light after doping of N into the LaTiO3 lattice. It is observed that N-doped LaTiO3 nanoparticles are wrapped with the g-C3N4 nano-sheet layers, forming a heterojunction structure, in the CLT hybrid. The CLT hybrid exhibits not only longer wavelength absorption in the visible region but also an enhancement in the photocatalytic and photocurrent activity under visible light compared to pure N-doped LaTiO3 and g-C3N4. Moreover, the hybrid is photo-stable and reusable. The improved visible light photocatalytic activity of the CLT hybrid is ascribed to its suitable band edge potential, better separation of photoinduced charge carriers owing to the heterojunction, and the synergistic effect of g-C3N4 and N-LaTiO3. Based on the results of photoluminescence, electrochemical impedance, and radical scavenger studies, a possible photocatalytic mechanism for the hybrid is also proposed. The g-C3N4/N-LaTiO3 hetero-structure is expected to provide new insight for the application of rare-earth-metal based perovskite oxides in environmental remediation and could be suitable for water splitting and other energy related applications as well.

Sodiation Behaviors of 1D Van Der Waals Sb2S3 Nanorods By in-Situ TEM and DFT Calculations

Owing to the abundance, low cost and similar electrochemistry of Na to Li, sodium ion batteries (SIBs) are considered an attractive, low-cost alternative to lithium ion batteries (LIBs) for large-scale energy storage [1]. Among various anode materials for SIBs, antimony trisulfide (Sb2S3) has drawn significant attention due its high theoretical capacity of 946 mAh g−1. However, its underlying sodiation behavior is largely unexplored. This work [2] reports the sodiation kinetics and the evolution of phase transformation in carbon-coated 1D van der Waals Sb2S3 nanorods based on the in-situ TEM, density functional theory (DFT) calculations and molecular dynamic (MD) simulations. Unique two-step reaction mechanisms of Sb2S3 nanorods are revealed, including Na+ ion intercalation and conversion/alloying reactions, during the first sodiation process. Na+ ions are inserted into the voids between the (Sb4S6)n moieties at an ultrafast speed of 146 nm s−1 upon the first sodiation, leading to amorphization of the crystalline Sb2S3 and negligible volume expansion of ~54 %. The in-situ SAED analysis verifies that the generated NaxSb2S3 intermediate phases are transformed into Na2S and Na3Sb with a trace of Sb crystals during the consecutive conversion/alloying reactions. Upon subsequent desodiation, the Na+ ions extracted from the crystalline sodiated composites transform to amorphous desodiated products. The DFT calculations attribute such anomalous reaction mechanisms to the unexpectedly low sodium diffusion barrier of Sb2S3 nanorods and the largely improved electronic conductivity arising from the amorphous NaxSb2S3 intermediate phases. These findings on phase transformation routes, dynamics and kinetics occurring during the sodiation/desodiation processes in the Sb2S3 nanostructure will offer insights into better understanding of Na+ ion diffusion mechanisms in van der Waals force stacked materials.

The Transformation of Two-Line Ferrihydrite into Crystalline Products: Effect of pH and Media (Sulfate versus Nitrate)

Two-line ferrihydrite (Fh), ubiquitous in soils, groundwater, and aquatic sediments, may serve as an important sink for sequestering trace metals, metalloids, and organic matter via adsorption/coprecipitation due to its high surface area and reactivity. Although considerable attention has been paid to the transformation process of this thermodynamically metastable solid, little is known about the transformation products, the crystallization rates, or the transformation routes of two-line Fh in sulfate- and calcium-rich environments. This work systematically investigates the transformation of 2-line ferrihydrite produced by using different neutralization reagents (CaO vs NaOH) at different pHs (4 and 8), temperatures (25 °C, 40 °C, and 80 °C), and media (sulfate vs nitrate). X-ray diffraction, Raman, Fourier transform infrared spectroscopy, and chemical extraction were employed to characterize the transformed solids as well as the crystallization rate of 2-line Fh. The results show that the crystallization...

Producing methane, methanol and electricity from organic waste of fermentation reaction using novel microbes

Residual solid and liquid streams from the one-pot CRUDE (Conversion of Raw and Untreated Disposal into Ethanol) process were treated with two separate biochemical routes for renewable energy transformation. The solid residual stream was subjected to thermophilic anaerobic digestion (TAD), which produced 95 ± 7 L methane kg−1 volatile solid with an overall energy efficiency of 12.9 ± 1.7%. A methanotroph, Methyloferula sp., was deployed for oxidation of mixed TAD biogas into methanol. The residual liquid stream from CRUDE process was used in a Microbial Fuel Cell (MFC) to produce electricity. Material balance calculations confirmed the integration of biochemical routes (i.e. CRUDE, TAD, and MFC) for developing a sustainable approach of energy regeneration. The current work demonstrates the utilization of different residual streams originated after food waste processing to release minimal organic load to the environment.

Effect of C and N and their absence on the kinetics of austenite-ferrite phase transformations in Fe-0.5Mn alloy

Investigating the partitioning effect of substitutional and interstitial elements on the migration of transformation interfaces during austenite-ferrite phase transformation in steels with the conventional experimental method is extremely challenging due to interaction between the solute atoms and the transformation interfaces. Additionally, the simultaneous nucleation of new phases during phase transformations limits the accuracy of extracted growth rates from experimental kinetics measurements of phase fractions. In a novel experimental approach, the cyclic partial phase transformation concept is used to avoid the effect of nucleation on total kinetics of phase transformations. In this study, a Fe-0.5Mn alloy in the presence and absence of interstitial C and N additions is subjected to different cyclic transformation routes to examine the possible interaction between solute atoms and migrating interfaces. The experimental results are in semi-quantitative agreement with modelling predictions made by the local equilibrium approach and provide indirect evidence of Mn partitioning at austenite/ferrite interface in absence of any interstitial elements. It is also confirmed that the presence of interstitial elements promotes Mn interaction with the interface, whereas N promotes more Mn partitioning at transformation interface compared to C.

A New Theory of Non-Linear Thermo-Elastic Constitutive Equation of Isotropic Hyperelastic Materials

Considering the influence of temperature and strain variables on materials. According to the relationship of conjugate stress-strain, a complete and irreducible non-linear constitutive equation of isotropic hyperelastic materials is derived and the constitutive equations of 16 types of isotropic hyperelastic materials are given we study the transformation methods and routes of 16 kinds of constitutive equations and the study proves that transformation of two forms of constitutive equation. As an example of application, the non-linear thermo-elastic constitutive equation of isotropic hyperelastic materials is combined with the natural vulcanized rubber experimental data in the existing literature base on MATLAB, The results show that the fitting accuracy is satisfactory.

Biotransformation of macrolide antibiotics using enriched activated sludge culture: Kinetics, transformation routes and ecotoxicological evaluation

The biotransformation of three prominent macrolide antibiotics (azithromycin, clarithromycin and erythromycin) by an activated sludge culture, which was adapted to high concentrations of azithromycin (10 mg/L) was investigated. The study included determination of removal kinetics of the parent compounds, identification of their major biotransformation products (TPs) and assessment of ecotoxicological effects of biotransformation. The chemical analyses were performed by ultra-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry, which enabled a tentative identification of TPs formed during the experiments. The ecotoxicological evaluation included two end-points, residual antibiotic activity and toxicity to freshwater algae. The enriched activated sludge culture was capable of degrading all studied macrolide compounds with high removal efficiencies (>99%) of the parent compounds at elevated concentrations (10 mg/L). The elimination of all three macrolide antibiotics was associated with the formation of different TPs, including several novel compounds previously unreported in the literature. Some of the TPs were rather abundant and contributed significantly to the overall mass balance at the end of the biodegradation experiments. Biodegradation of all investigated macrolides was associated with a pronounced reduction of the residual antibiotic activity and algal toxicity, indicating a rather positive ecotoxicological outcome of the biotransformation processes achieved by the enriched sludge culture.

Composition and Transformation of Sulfur-, Oxygen-, and Nitrogen-Containing Compounds in the Hydrotreating Process of a Low-Temperature Coal Tar

A low-temperature coal tar was subject to a three-stage catalytic hydrotreating reactor. The raw coal tar and its hydrotreating products from each reactor section were characterized by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The removal efficiencies of sulfur, nitrogen, and oxygen were 99.4%, 88.4%, and 78.1%, respectively. The molecular transformation routes of each heteroatomic species are different. Sulfur species were removed from low double bond equivalence (DBE) values to higher values through the whole hydrotreating process. Furanic compounds and basic nitrogen compounds carried out the saturation of aromatic rings before the hydrogenation of low DBE species. Neutral nitrogen compounds were resistant in the processing and cannot be removed completely in the end of the hydroprocessing. The phenolic compounds were the most resistant to hydrotreating during the whole process. The transformation capabilities of heteroatom compounds in the p...

“Feminists make too much noise!”: generational differences and ambivalence in feminist development politics in Ghana

Despite the crucial role feminist movements play in securing progressive development policies, legislation and socio-legal protections for women, labeling women’s rights issues as feminist has contradictory, mostly negative, effects on the women’s movement in Africa. This paper discusses research findings that show that older women (activists) are more likely to self-identify as feminists than younger women in Ghana. I argue that, while resistance to feminism may have roots in anti-imperialism, socio-cultural and economic privileges play a crucial role in such resistance at an individual level. Based on findings discussed in the paper I suggest the following. First, the perceived threat of feminism to African socio-cultural norms dialectically enhances opportunities for advancing women’s rights in development planning through a more transformative civil liberties route as opposed to a “special victims’ unit” approach. Second, further empirical research is needed to assess the impact of various intersecting variables (class, age, ethnicity, sexuality, religion and geographical location) on feminist politics in Africa.

Synthesis, structure, and polymorphic transitions of praseodymium(iii) and neodymium(iii) borohydride, Pr(BH4)3 and Nd(BH4)3.

In this work, praseodymium(iii) borohydride, Pr(BH4)3, and an isotopically enriched analogue, Pr(11BD4)3, are prepared by a new route via a solvate complex, Pr(11BD4)3S(CH3)2. Nd(BH4)3 was synthesized using the same method and the structures, polymorphic transformations, and thermal stabilities of these compounds are investigated in detail. α-Pr(BH4)3 and α-Nd(BH4)3 are isostructural with cubic unit cells (Pa3[combining macron]) stable at room temperature (RT) and a unit cell volume per formula unit (V/Z) of 180.1 and 175.8 Å3, respectively. Heating α-Pr(BH4)3 to T ∼ 190 °C, p(Ar) = 1 bar, introduces a transition to a rhombohedral polymorph, r-Pr(BH4)3 (R3[combining macron]c) with a smaller unit cell volume and a denser structure, V/Z = 156.06 Å3. A similar transition was not observed for Nd(BH4)3. However, heat treatment of α-Pr(BH4)3, at T ∼ 190 °C, p(H2) = 40 bar and α-Nd(BH4)3, at T ∼ 270 °C, p(H2) = 98 bar facilitates reversible formation of another three cubic polymorph, denoted as β, β' and β''-RE(BH4)3 (Fm3[combining macron]c). Moreover, the transition β- to β'- to β''- is considered a rare example of stepwise negative thermal expansion. For Pr(BH4)3, ∼2/3 of the sample takes this route of transformation whereas in argon only ∼5 wt%, and the remaining transforms directly from α- to r-Pr(BH4)3. The β-polymorphs are porous with V/Z = 172.4 and 172.7 Å3 for β''-RE(BH4)3, RE = Pr or Nd, respectively, and are stabilized by the elevated hydrogen pressures. The polymorphic transitions occur due to rotation of RE(BH4)6 octahedra without breaking or forming chemical bonds. Structural DFT optimization reveals the decreasing stability of α-Pr(BH4)3 > β-Pr(BH4)3 > r-Pr(BH4)3.

A convenient and efficient precursor transformation route to well-dispersed, stable, and highly accessible supported Au nanocatalysts with excellent catalytic hydrogenation performances.

A new, convenient, and efficient precursor transformation route for the synthesis of supported Au nanocatalysts was reported. In this strategy, [Au(en)2]3+-riched titanate nanospheres (en: ethylenediamine) with hierarchical flower-like architecture were pre-synthesized via “ammonia etching-ion exchange” processes and then used as the precursors of the objective catalysts. Direct pyrolysis of these precursors, varying in amount of [Au(en)2]3+, led to the formation of Au nanoparticles (AuNPs) with different contents uniformly supported on highly crystalline titania nanoflowers (fTiO2). The fTiO2-supported AuNPs nanocomposites possessed highly open porous structures with large surface areas (142.3–149.3 m2 g−1), which could allow guest molecules to diffuse in and out easily. More interestingly, the formed AuNPs with small size (∼3.8 nm) were well-dispersed and partially embedded into the nanosheets of fTiO2, which was beneficial for achieving high activity while avoiding their detachment from the support during application. Accordingly, the AuNPs/TiO2 catalysts exhibited superior catalytic properties for 4-nitrophenol hydrogenation with significantly higher catalytic efficiencies than many previously reported heterogeneous catalysts. Moreover, the catalytic activity could remain almost unchanged after being recycled several times, demonstrating their high stability. These findings open up a new possibility for rational design and synthesis of supported catalysts for diverse catalytic applications.

A novel topotactic transformation route towards monodispersed YOF:Ln3+ (Ln = Eu, Tb, Yb/Er, Yb/Tm) microcrystals with multicolor emissions

A novel topotactic transformation synthetic strategy from the Y4O(OH)9NO3 precursor towards YOF:Ln3+ with multicolor emissions has been developed based on the topotactic structural matching.

Effect of ferrite-to-austenite phase transformation path on the interface crystallographic character distributions in a duplex stainless steel

The effect of the ferrite to austenite phase transformation route on the microstructure and interface plane character distributions was studied in a duplex stainless steel. Two markedly different austenite morphologies (i.e., equiaxed and Widmanstätten) were produced through diffusional (slow cooling) and semi-shear (air-cooling) transformations, respectively. Both austenite morphologies had textures similar to the as-received condition, which was attributed to a “texture memory” effect. The air-cooled microstructure displayed a significantly higher content of Kurdjumov-Sachs (K-S) and Nishiyama-Wassermann (N-W) interfaces (39%) compared with the slow-cooled one (16%), due to the change in the austenite nucleation and growth mechanism during the phase transformation. A five-parameter analysis of different interfaces revealed that for K-S/N-W orientation relationships, ferrite and austenite terminated on (110) and (111) planes, respectively, regardless of the transformation route. The population of these planes, however, increased as the transformation rate increased. A higher fraction of Σ3 boundaries was observed in the equiaxed austenite morphology compared with its Widmanstätten counterpart, which was mainly attributed to the different kinetics and the growth mode of austenite plates during the phase transformation. Σ9 boundaries were mostly formed where two Σ3 boundaries met and were largely of tilt character because of geometric constraints. The intervariant boundary plane distributions of both austenite microstructures displayed more frequent {111} orientations than other planes for a majority of the boundaries. This trend was markedly stronger for Widmanstätten austenite.

Shape memory TiNi powders produced by plasma rotating electrode process for additive manufacturing

Abstract This study aimed to produce spherical TiNi powders suitable for additive manufacturing by plasma rotating electrode process (PREP). Scanning electron microscopy, X-ray diffractometry and differential scanning calorimetry were used to investigate the surface and inner micro-morphology, phase constituent and martensitic transformation temperature of the surface and inner of the atomized TiNi powders with different particle sizes. The results show that the powder surface becomes smoother and the grain becomes finer gradually with decreasing particle size. All the powders exhibit a main B2-TiNi phase, while large powders with the particle size ≥178 μm contain additional minor Ti2Ni and Ni3Ti secondary phases. These secondary phases are a result of the eutectoid decomposition during cooling. Particles with different particle sizes have experienced different cooling rates during atomization. Various cooling rates cause different martensitic transformation temperatures and routes of the TiNi powders; in particular, the transformation temperature decreases with decreasing particle size.