Weight Percentage Ratios Research Articles

Synergistic effect of a hybrid additive for hydrogen peroxide-based low toxicity hypergolic propellants

Hypergolic bipropellants based on high-test peroxide (HTP, >85% H2O2) have traditionally emerged as low-toxicity propellants for space applications. However, the late-ignition performance of HTP-based fuel restricts its potential use in particular applications, such as high-precision auxiliary response thrusters. In this study, the synergistic effects of new hybrid additives (reactive additive: catalytic additive), NaBH4:NaI, and NaBH4:NH4I were, for the first time, demonstrated to improve the ignition performance of low-toxicity fuels with 95 wt.% H2O2. The effect of changes in the weight percentage ratios of the reactive and catalytic additives on the ignition performance was investigated. The fuels without additives were non-hypergolic with 95 wt.% H2O2. However, at specific concentrations, the hybrid additives in fuels markedly lowered the ignition delay time (IDT) to less than 3 ms. Notably, ethylenediamine containing 10 wt.% hybrid additives of NaBH4:NaI and NaBH4:NH4I at a specific additive weight ratio (6.5:3.5) yielded an average IDT of 2.75 and 2.69 ms, respectively. Thermal analysis revealed that the hybrid additive improved the thermal stability of the fuels. The theoretical vacuum-specific impulse of these fuels was calculated using the NASA-CEA code. The results of this study confirm the validity of our approach for developing relatively low-toxicity hypergolic fuels for space propulsion.

Molten salt electrodeposition of aluminum on mild steel: effect of process parameters on surface morphology and corrosion properties

The electrodeposition of aluminum on mild steel in a molten salt electrolyte consisting of a mixture of AlCl3/NaCl/KCl (weight percent ratio of 80:10:10) was studied. Parametric studies were carried out to evaluate the effect of different parameters such as current density, electrolysis time, and intermediate coating layer on the coating morphology and coating-to-substrate adhesion. The quality and morphology of the coating were investigated using scanning electron microscope (SEM) and x-ray map analyses. The effect of heat treatment of the coated samples on the interface stability and formation of intermetallic compounds at the Al-Fe interface was also investigated. Cross-sectional examination by SEM as well as energy dispersive spectroscopy (EDS) line scan showed that upon annealing at temperatures in the range of 350 °C–550 °C, brittle Fe-Al intermetallic layers were formed at the interface. This shows that high-temperature service conditions can adversely affect the coating properties. The apparent activation energy of the formation of such intermetallic layers was calculated based on thickness measurements on these layers. The optimum conditions for electroplating were determined as current density of 0.022 A.cm−2 and electroplating time of 60 min. Potentiodynamic polarization tests were used to evaluate the corrosion resistance of the samples in 3.5 wt% NaCl solution. Considering the corrosion rate of coated samples which is much lower than the bare substrate, it was concluded that the electrodeposited coatings could efficiently protect the steel substrate against corrosion in corrosive media.

English

BACKGROUND Dimensional change and porosity in the polymethylmethacrylate based prosthesis affects its clinical performance. Hence, the present study aimed to evaluate the porosity and water sorption present in the modified polymethyl methacrylate polymer composite. METHODS Control group without fibre reinforcement and test groups with fibre reinforcement were prepared for the study. Three different fibres such as boron free-E glass fibre, untreated and plasma-treated polypropylene fibres in varying weight percentage and aspect ratio were considered for reinforcement. The porosity of the fractured surface was observed through a scanning electron microscope (scanning electron microscope) and sorption measured based on international standards organization (ISO) 1567:1999. RESULTS Control group exhibited porous structures, whereas all fibre-reinforced groups did not exhibit porous structure at the fracture surface. There was a significant difference in the sorption rate between control and test group (p < 0.001). Among fibrereinforced test groups, boron free E glass fibre reinforced polymethylmethacrylate exhibited maximum sorption followed by polypropylene fibre reinforced polymer test groups (p < 0.001). However, all samples showed sorption rate within the ISO specification. CONCLUSIONS Fiber reinforcement is an effective method to reduce porosity and water sorption in polymethylmethacrylate based polymer composite regardless of the fibre type. KEY WORDS Polymer Composite, Porosity, Water Sorption, Fiber Reinforcement, Polymethylmethacrylate

Un-doped and Er-adsorbed layered Nb2C MXene for efficient hydrazine sensing application

In this work, 2D Nb2C MXene, synthesized from the wet-chemical etching route, is used as direct electrode material for electrochemical hydrazine sensing. Also, the Erbium (Er)adsorbed Nb2C MXene was prepared using the hydrothermal process in a weight-percentage ratio of 2.5%, 5%, 7.5% and 10%. The X-ray diffraction of Nb2C and Er-doped Nb2C samples confirmed the existence of 2D MXene structure with c-lattice parameter increase from 13.83 Å to 22.7 Å and successful adsorption of Er into MXene, respectively. The scanning electron microscopy (SEM) shows the layered structure morphology of all the samples with clear sheet separation. The sample with the highest surface area, determined by Brunauer–Emmett–Teller (BET) technique, was used for hydrazine sensing using cyclic voltammetry and linear sweep voltammetry techniques. The sensitivity for MXene and Er-doped sample was observed to be 169µA m−1 M−1 cm−2 and 276µA m−1 M−1 cm−2, respectively which shows that the Er-doped MXene is much more sensitive than the unmodified one. Our results provide hydrazine sensing ability for 2D Nb2C MXene as well as Er-doped Nb2C which will help explore their potential for future sensor applications.

Application of sodium chloride as space holder for powder injection molding of alloy Titanium–Hydroxyapatite composites

The development of porous metal structures, especially for the use of titanium alloys in bone implant applications, has attracted the attention of researchers. However, forming porous structures in titanium composites via powder injection molding (PIM) remains in the early stages of analysis, allowing the determination of processing parameters to be studied in greater detail. In this study, the critical PIM parameters for processing porous alloy titanium–hydroxyapatite composites were identified via the space holder method. Titanium alloy (Ti6Al4V) was mixed with hydroxyapatite (HA) at a weight percentage ratio of 9:1 with 20 wt.% sodium chloride (NaCl) as the space holder. Feedstock was prepared by combining the powder with a binder system. Pseudoplastic flow activity, which was the desired rheological property needed for PIM, in the feedstock was determined. A tensile bar specimen was successfully injected with a green strength of 2.92 MPa. The space holder was then removed via water leaching, whereas the binders were removed by a debinding step before being sintered in a high-vacuum condition for 3 h at 1350 °C. The sintered parts were interconnected and had a porosity level of 37.03%. Energy dispersive X-ray mapping revealed that the porous titanium–hydroxyapatite composite contained titanium (Ti), calcium (Ca), phosphorus (P), and oxygen (O) components. This study indicated that the combination of PIM and the space holder method is a promising technique for manufacturing near net-shaped porous titanium–hydroxyapatite composites.

Mechanical modeling of metal thin films on elastomers for femtosecond laser patterned interconnects

In this work, we present the mechanical analysis of thin Au/Ti film deposited on elastomer substrate, e.g. Polydimethylsiloxane (PDMS) comparing to samples on Kapton®. After deposition, the metal was patterned by ultrashort (270 femtosecond) pulse laser ablation. Minimizing the thermal damage to the substrate, reducing Heat Affected Zone (HAZ) compared to previously demonstrated laser patterning with longer pulses. One of the major issues in the metallization of thick elastomers is the formation of wrinkles followed by brittle cracks in the metallic thin film during the process, deteriorating the metal lines performance and reliability. Such cracking has not been observed on polyimide. The crack formation was investigated using stress analysis of the metallic-elastomeric system, assuming that cracking appears when the stress in the metal film is exceeding a critical value. A general mechanical model and analysis of a multilayer and multi-material laminated system is presented and applied to the specific case of Au/Ti on PDMS. Using this model, the root cause for the stress development in the metallic film has been investigated.A series of samples had been prepared using various elastomer substrates made of Sylgard 184, Dow Corning PDMS. A series of samples was prepared using different monomer/cross-linker ratios in the range of 1:2 to 1:19 monomer to cross-linker weight percentage ratio. Using the thin film stress analysis, the inner stress between and inside the different layers was calculated. Based on the calculations, we could estimate the specific stress in the metallic film. Using this value, we could choose the right specific materials that would not surpass their critical failure stress. This hypothesis was tested and verified by the failure analysis conducted by optical microscope and scanning electrons microscopy (SEM) secondary electrons (SE) images. We report here on a good correlation between the mechanical analysis predictions and the various samples integrity. Therefore, using that model, we could define a “safe zone”, i.e. for what elastic modulus and Coefficient of Thermal Expansion (CTE) there are no “mud-crack” defects.

Concentration dependent thermo-optical properties and nonlinear optical switching behavior of bimetallic Au-Ag nanoparticles synthesized by femtosecond laser ablation

Concentration, morphology and composition-dependent thermal diffusivity changes occurring in bimetallic Au-Ag nanoparticles synthesized by femtosecond laser ablation were investigated using a dual- beam mode matched thermal lens technique. The synthesis utilized the variation in ablation time of silver plate kept immersed in already synthesized gold nanoparticle seeds. Thermal diffusivity values were found to increase both with an increase in concentration of the samples as well as an increase in Ag/Au weight percentage ratio. Au-Ag core–shell and nanoalloy structure show much greater variation in the thermal diffusivity compared to the other samples. A possible explanation could be the modified surface state density of the bimetallic nanoparticles. A single beam z scan technique using an Nd:YAG laser operating at a wavelength of 532 nm was employed for the nonlinear optical characterization of the samples. At a fixed laser input fluence, a switching behavior from saturable absorption (SA) to reverse saturable absorption (RSA) was observed as the ablation time of the silver plate in gold nanoparticle solution increased. The effect of laser input fluence on nonlinear optical properties of core–shell and nanoalloy structures was also studied and the optical limiting threshold of nanoalloy was calculated. The results revealed an increase in the nonlinear absorption coefficient with an increase in input fluence. A linear variation of the limiting threshold was also observed with an increase in input fluence. Thermal diffusivity studies find applications in photo thermal therapies and optical limiting properties find application in optoelectronic switches.

Growth performance, carcass traits and meat quality of lambs fed increasing level of Macadamia nut cake.

A total of 40 lambs were divided into four different treatments according to the inclusion level of the macadamia nut cake: C-control (0%), M1 (6.5%), M2 (12%) and M3 (20%). Feed was provided twice a day; animal weighing along with body condition scoring occurred within a 14-day interval. The lambs were slaughtered at the end of the performance test. Analysis of variance was performed through the Mixed procedure of the SAS, as well as linear and quadratic regression analysis. The groups presented differences between the treatments (P <0.05) for dry matter intake (DMI), ethereal extract intake (EEI), consumption in relation to live weight percentage and feed conversion ratio (FCR). The lowest mean DMI was obtained by the animals that received the M2 and differed from the C treatment, whose average was the highest. The EEI was highest for the M3 group and the FCR was also better for this group. There was a linear effect for EEI and FCR, and quadratic for crude protein intake. There was no effect for carcass characteristics, and only initial pH had a decreasing linear effect. The macadamia nut cake was effective in promoting the performance of the animals, since there was an improvement in feed conversion.

Tribological and Mechanical Properties of Epoxy Reinforced by Hybrid Nanoparticles

Abstract In the present work, the nano-Aluminum oxide (Al2O3), nano-Silicon Carbide (SiC), or a hybrid of them were infused into epoxy resin with an ultrasonic system with various weight percentage ratios of the nanoparticles. Small punch testing (SPT) and indirect tension testing were adopted to measure the tensile properties of the present nanocomposites. Pin-on-ring wear testing was also performed to examine wear performance of epoxy Al2O3 and SiC nanocomposites. The Finite Element Analysis method is introduced to simulate the indirect tension test and SPT to give a complete vision of the stress distribution in the nanocomposite specimen during the loading, and to examine its mode of failure. Good agreement between the numerical and experimental results was observed. The addition of nanoparticles from Al2O3 or SiC improves the wear resistance of epoxy. Furthermore, epoxy with nano-Al2O3 has a higher wear resistance than that with nano-SiC. The tensile strength and modulus of elasticity of epoxy are reduced by adding the Al2O3 nanoparticle. The synergistic effect is not observed in the present study.

Oxidation and hot corrosion behavior of a directionally solidified W richen cobalt-based superalloy

In this study, isothermal and hot corrosion in molten 75 mass% Na2SO4+25 mass% NaCl at 900 °C was carried out on an W richen Co-based directionally solidified Co-27.53Cr-9.85W-10.29Ni-0.75Al superalloy. For comparison, K38G with composition of 16.34Cr-4Al-1.77Mo-3.81Ti-2.66W-8.38Co were also conducted under same condition. Isothermal oxidation indicates that Co-based superalloy forms a Co-oxide dispersion chromia scale. However, K38G forms a purer chromia scale due to higher weight percentage ratio of Cr to Al. Under molten Na2SO4-NaCl salts, the defects in Ni/Co oxide dispersion chromia layer make it feasible that the molten salt can penetrates along grain boundaries into the internal interface to form internal sulfides, which causes the spallation of scales and significantly decreases its hot corrosion resistance.

Graphene/PSMA composite for gas sensing application

This paper presents the fabrication of conducting polymer sensor which comprise of graphene-poly styrene-co-maleic acid (PSMA) composite that responds to volatile organic compound (VOC) via a change in the electrical resistance of the sensors. Five sensors composed of different material ratio were fabricated to find out the most prominent weight percentage ratio (wt %) for optimum sensor response. Those materials were deposited onto silver electrode using drop-casting method. NI Card PCIE-6323 measures the voltage obtained from the sensor circuit and the resistance of the gas sensor monitored using LabVIEW instrument. It was observed from the experiments that combination of 60% graphene and 40% PSMA gives the highest sensor response.

Experimental Investigation for Some Properties of PMMA Denture Base Strengthened by Different Nanoadditives

In dental and medical applications, poly-methyl methacrylate (PMMA) has been widely accepted due to the excellent biocompatibility and easy fabrication. Yet, some of the physical and mechanical characteristics of this compound are considered inferior. Seven groups of PMMA nano-composite samples were reported to be fabricated at laboratory temperature . These samples could be used in manufacturing the complete or partial maxillary denture base. The aim of this research is to prepare nano-composite materials which consist of PMMA as a matrix material and two different types of powder (prepared nanoparticles of SnO2 and natural egg shell powder (ESP)) as strengthening materials. The selected additives were used in many cases as pure or hybrid composites, specifically with weight percentage ratios of 1 and 2 wt%. Several analytical tests, namely AFM, FTIR, XRD and SEM, were used on the prepared nanoparticles. In addition, several tests were applied to assess the mechanical behavior before and after the reinforcement, including thermal conductivity, Vickers micro-Hardness, and water absorption. The results showed that the maximum amount of energy absorption in the composites was 1% at different types of additives, while a significant increase in thermal conductivity was recorded as the SnO2NPs percentage was increased. For surface micro-hardness, an obvious trend of increase was observed with the increase in additive percentage. The highest measured values of micro-hardness (19.59VHS and 13.30VHS) were recorded for the pure composites of 2% ESP and 2% SnO2, respectively. The results of water absorption test showed that higher percentages of ESP and SnO2, separately, within the pure composite resulted in higher water absorption capacity and an increased value of diffusion coefficient (D).

Moving towards resource efficiency and circular economy in the brick manufacturing sector in Zimbabwe

The life cycle assessment of the ABC (Pvt) Ltd brick manufacturing plant has considered land use, fossil resource scarcity, water consumption, global warming and fine particulate matter formation as the impact categories for assessment, with clay mining and coal as the input flows with the highest significant contributions to environmental load. The phase of clay mining (65.8%) is significantly impacting on all the investigated impact categories followed by brick moulding (24.8%) and brick roasting (9.4%) phases, respectively. Hotspots were assessed to identify potential for resource efficiency and circular economy at ABC bricks, Zimbabwe. It can be concluded that ABC is severely polluting the air with emissions above the Environmental Management Agency (EMA) standards for SO2, CO, PM and NOx thus putting kiln workers at risk of respiratory diseases. The calculated Air Quality Index (AQI) ranks CO as the most affecting pollutant with an average score of ∼600. Clay production efficiency was also determined, and an analysis revealed that extrusion and clamping stage contributed highly to the clay losses during brick moulding. Therefore, focus must be placed on these process steps to reduce raw material losses. Furthermore, an environmental waste (fly ash) was used in different weight percentage ratios of 10%, 20% and 100% to substitute clay. The increase of the fly ash content in the brick making process proved to significantly reduce the environmental load among the selected impact categories. ABC uses clay as its main raw material hence the high demand for clay. Strategies should include accounting of used clay daily and raw materials substitution. If ABC uses fly ash from its brick kilns and from other thermal power plant boilers to mix with clay in brick production, then the quantity of clay demanded will be reduced. Using fly ash will reduce rate of clay extraction while at the same time solving the problem of fly ash disposal in Zimbabwe. This circular option will ultimately result in reduced pit expansion, hence reducing top-soil loss and environmental degradation. It should not be disregarded that top-soil loss in turn affects food security. By adopting appropriate technologies, implementing resource efficiency, and designing circular economy patterns, the brick manufacturing sector in Zimbabwe may not only reduce production waste but also comply with enforced environmental protection legislation.

A Regenerable, Electrodeposited, Iron-Group Electrocatalyst for the Oxygen Evolution Reaction

Fe-Ni-based oxides and oxyhydroxides have been recognized as interesting oxygen evolution reaction (OER) electrocatalysts, and thus could be alternatives to replace rare and expensive metal oxides (e.g., IrO2 and RuO2) for water electrolysis in the generation of hydrogen to store energy from intermittent sources, such as solar and wind. However, these materials may suffer from deactivation during the OER due to changes in the active phases. In this study, a methodology to regenerate the OER activity of aged, electrodeposited Fe-Ni-Co electrocatalysts in an alkaline electrolyte is presented.The Fe-Ni-Co thin films were electrodeposited over a range of current density from a boric acid electrolyte onto rotating cylinder electrodes (RCE). The resulting deposits had different Fe and Ni compositions, containing a small amount of Co, and were used to characterize the OER in 1 M KOH. Linear sweep voltammetry was used to generate a surface oxide and measure the OER kinetics. The electroactive surface areas were accessed using an electrochemical ferricyanide/ferrocyanide redox reaction. The OER kinetics were found to be a function of deposit composition, with the lowest Tafel slope and overpotential (at 10 mA/cm2) observed at a metal weight percentage ratio, Fe/(Ni+Co), of 1.2. The electrocatalyst became less active upon chronopotentiometric aging at 10 mA/cm2 for 30 hours. Notably, when the aged catalyst was reduced by applying a cathodic current density, the electrocatalytic activity recovered. The spectra of Fe, Ni, Co L-edge and O K-edge from X-ray absorption near edge spectroscopy (XANES) suggested that the aging and recovery are due to the redistribution of the electron density between O, and Fe and Ni. Co was found to be predominately in the metallic state.

Phase formation and microstructure analyses of La0.6Sr0.4CoO3-δ-BaCe0.54Zr0.36Y0.1O2.95 composite material prepared by solid state mixing method

A composite material of La0.6Sr0.4CoO3-δ-BaCe0.54Zr0.36Y0.1O2.95 (LSC-BCZY) was prepared by mixing sol-gel derived LSC and BCZY powders in different weight percentage (wt%) ratio of LSC to BCZY (LSC:BCZY). The prepared composite powders were denoted as S1 (30:70), S2 (50:50) and S3 (70:30). The powders were characterized by an X-ray diffractometer (XRD), a Brunauer-Emmett-Teller (BET) surface area and porosity analyzer and a scanning electron microscope (SEM) equipped with an energy dispersive X-ray (EDX) spectrometer. XRD analysis confirmed that all of the powders were not pure enough due to the presence of impurity phases such as barium carbonate (BaCO3) and strontium carbonate (SrCO3) and unknown phases. S1 powder has the highest amount of impurity phases (81.19 %) and the largest BET surface area (4.82 m2 g−1). All of the powders formed typical clump-like network structure as proven by SEM analysis. EDX analysis revealed that the elemental compositions of La, Sr and Zr were deviated from their nominal mole fractions in all powders due to the Zr-rich clusters formation. The results indicate that the formation of pure and homogenous LSC-BCZY composite powder prepared by solid state mixing method requires further modification and improvement of the preparation method.

Performance Improvement of Tetraethylorthosilicate Consolidated Andesite Rock by Adding Titanium Tetraisopropoxyde and Silica Particles

A study to improve the performance of andesite mortar and rock consolidated with tetraethylorthosilicate (TEOS) sol and a solvent of ethanol in the presence of titanium tetraisopropoxyde (TTIP) and silica particles has been conducted. The improvements include minimizing the shrinkage using silica particles from rice husk ash, rheological property suitability of the consolidant, and mechanical properties of the consolidated mortar and rock. The effect of TTIP concentration, ethanol volume, and addition of the silica particles on rheological properties of TEOS-based consolidant, and also mechanical properties of the consolidated mortar and rock were evaluated. The results showed that the increase of TTIP content in the consolidant shortens the gelling time, and the weight percentage ratio of TTIP:TEOS:ethanol of 5%:55%:40% was the optimum composition for the consolidation. Consolidation of andesite block using that composition significantly increased the compressive strength up to 57.61% (0.58 kgf/mm2). The addition of 2% of silica particles into the consolidant decreased the gel shrinkage and increased the Young modulus of the mortar. The presence of water in the andesite matrix reduced the consolidation performance, and 0.5% was the maximum percentage of water content acceptable for the consolidation.

Electrochemical properties of Rubpy-reduced graphene oxide synergized by ultrasonication for label-free quercetin sensing

Tuning the interfacial properties of oxygenated graphene and reduced graphene oxide (rGO) with optical/electrochemically active molecules are highly useful for sensor studies. Herein, we demonstrate the ultrasonochemical mediated simultaneous reduction of oxygenated graphene and adsorption of ruthenium bipyridine complex (Rubpy) on the planes of rGO nanosheets. Different weight percentage ratio of Rubpy was decorated on the planes of rGO by simple alteration in the sonication parameters. Intercalation of Rubpy complex influences the electron cloud of inherent graphitic carbon network and intermolecular oxygenated functional moieties on the rGO matrix. Activation of CN network derived from bipyridine ligands of organometallic coordination compound, Rubpy, on the rGO planes enable an amplified electron mobility at the interface of electrode beneficial for electrocatalytic analysis. rGO-Rubpy modified electrode enabled direct electrochemical redox reaction of quercetin, exhibiting a linear detection range of 0.05–50 µM, with a lowest detection limit of 0.002 µM. Demonstrated label-free sensor platform display selectivity toward quercetin even in the presence of interferents and sensitivity in the real sample, promising for complementary analytical application.

Ignition of nickel coated aluminum agglomerates using shock tube

Al is used as additives for solid propellants due to its high energy density. However, Al is difficult to ignite since it is covered with a protective oxide film having a high melting point. One method suggested to solve this problem is surface coating with other metal particles. Thus, in this study, Al particles were coated with Ni nanoparticles by a simple spray drying technique. The coating process was carried out by varying the weight percent of Ni to Al particles. The crystalline structure of Ni-coated Al particles was retained without any intermetallic or additional phase formation, as identified by XRD. SEM and EDS results show uniform and continuous coating of Ni-nanoparticles on the surface of 10 µm Al particles was formed when the sample was prepared using an equal weight percentage ratio of Ni and Al. When the ratio of Ni to Al was decreased, the Ni-nanoparticles only partly covered the surface of the Al particles. The presence of elements was confirmed from the XPS analysis with strong surface interaction between Ni nanoparticles and Al particles. Ni-coated Al particles in an air atmosphere showed higher exothermic energy than pure Al particles. Ignition performance of Ni-coated Al particles obtained from a shock tube experiment at high temperature demonstrated the significant decrease in ignition delay time as the Ni content in the sample increased.

Fast photodegradation of rhodamine B and caffeine using ZnO-hydroxyapatite composites under UV-light illumination

Zinc oxide-hydroxyapatite composites were prepared using wet impregnation method. Firstly, a natural phosphate ore rich in silica and calcium phosphate was sieved to separate silica phase from phosphate phase. Then, through a chemical precipitation method, a pure hydroxyapatite (HAP) was obtained, which was used as a support for ZnO immobilization and applied for the photodegradation of two toxic contaminants: a transparent molecule (caffeine) and dye molecule (rhodamine B). During the present work two weight ratio percentages of zinc oxide were used: 25 wt.% and 50 wt.% of ZnO relative to HAP. The samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), X-ray Fluorescence (XRF), BET surface area (SBET), Scanning Electron Microscopy (SEM-EDS) and by Transmission Electron Microscopy (TEM-STEM). The immobilization of ZnO on HAP surface followed by thermal treatment at 400 °C for 2 h to get a homogenous dispersion of ZnO on the hydroxyapatite support. At high ZnO impregnation percentage, photodegradation performances of ZnO-HAP under UV illumination were fast and superior than the ZnO photocatalyst alone. The results showed that due to the presence of HAP, the conversion of both molecules became faster and greater, since it promotes the synergic phenomena of adsorption and photocatalysis. The toxicity of the treated substrate solutions obtained in the corn kernels germination test indicated a low toxicity after the photodegradation processes, probably due to a high mineralization degree.

Efficient photocatalytic degradation of environmental pollutant with enhanced photocarrier separation in novel Z-scheme a-MnO2 nanorod/a-MoO3 nanocomposites

Novel a-MnO2 nanorod/a-MoO3 nanocomposites were fabricated by simple template free methods. Hydrothermal and thermal treatment of ammonium heptamolybdate tetrahydrate in static air were applied for fabrication of MnO2 and MoO3 respectively. FT-IR, XRD, XPS, SEM, Raman, EDX, Point of zero charge, BET, DRS, PL, Photocurrent-time and TEM analyses were used to verify the a-MnO2/a-MoO3 structure and properties. A detailed study on photodegradation of acid blue 92 has been investigated under visible light irradiation. The MoO3 elevated the a-MnO2 nanorod photocatalytic activity and optical band gap investigation demonstrated that a-MnO2 /a-MoO3 heterojunction, is an active photocatalyst in visible light. Different parameters like catalyst dosage, organic dye concentration, calcination temperature, pH, weight percent ratio of MoO3 to MnO2 were optimized and kinetics study showed that degradation processes of acid blue 92 were first-order. Reaction mechanism was proposed based on the scavenger usage and radical trapping experiments. The as-prepared photocatalysts demonstrated excellent reusability capability and there were no obvious loss of activities after four cycles. High photocatalytic activities in a-MnO2/a-MoO3 nanostructure are attributed to the strong oxidative ability, efficient charge separation and transfer the electron-hole through the a-MnO2 and a-MoO3.