Amount Of ZnO Research Articles

Effect of different IFS (MWCNTs, BN, and ZnO) on flame retardant, thermal and mechanical properties of PA6/aluminum diisobutyl phosphinate composites

AbstractIn this paper, the effects of the synergistic flame retardation of aluminum diisobutyl phosphinate acid (APBA) with three inorganic fillers of different dimensions (multi‐walled carbon nanotubes [MWCNTs] [1‐dimensional], hexagonal boron nitride [BN] [2‐dimensional], and zinc oxide [ZnO] [3‐dimensional]), respectively, on the properties of nylon 6 (polyamide 6 [PA6]) materials were investigated. It was shown that under the same additive amount, with the increase of spatial dimension of inorganic fillers, the thermal stability and residual carbon capacity were improved. Which would catalyze the formation of more and denser carbon layers in the matrix material, effectively blocked the transfer of oxygen and heat, enhanced the cohesive‐phase flame retardancy of synergistic flame‐retardant PA6 composites, and exerted a better synergistic flame‐retardant effect with APBA. So that the flame‐retardant properties of PA6 composites were gradually improved, and the mechanical properties were also gradually increased. The comprehensive performance of three types of inorganic fillers gradually improves in the order of MWCNTs < BN < ZnO. When the addition amount of ZnO was 2 wt%, the vertical combustion grade (UL‐94) of PA6 composite was V‐0, and the limiting oxygen index (LOI) was as high as 36.5%. The tensile strain increased by 19.11% and impact strength increased by 20.26% compared with PA6, and PA6/APBA‐Zn can be used as a flame retardant PA6 composite material with balanced overall performance.Highlights Diisobutylaluminium hypophosphite and inorganic fillers have efficient synergistic flame retardant effects in PA6. With the increase of spatial dimension of inorganic fillers, the better the synergistic flame retardant effect in PA6. The flame retardant can degrade to release the phosphorous free radicals. Inorganic fillers can cross‐link with the PA6 substrate and promote the charring.

High-efficient separation of photoinduced charge carriers in CoFe2O4-ZnO magnetic heterostructures mediated by oxygen vacancies

In this work, magnetic heterostructures were obtained by the in-situ growth of various ZnO amounts on the preformed CoFe2O4 nanoparticles. The X-ray diffraction characterization shows the presence of both ZnO and CoFe2O4 crystalline phases, and the crystallite size is about 13–14 nm for both components. X-Ray Photoelectron Spectroscopy (XPS) analysis revealed a CoFe2O4 inversion degree of 0.7. The composite samples demonstrated an extended absorption edge into the visible range. The sample’s magnetic properties were investigated by vibrating-sample magnetometer (VSM) and correlated with Electron Paramagnetic Resonance (EPR) results. The magnetic behavior was attributed to the combination of CoFe2O4 and ferromagnetic ZnO. The emergence of a ferromagnetic phase within ZnO was elucidated to originate from charge/spin transfer of spin-up polarized states from the CoFe2O4 Fermi level into empty oxygen vacancies of ZnO. High efficiency in Rhodamine B (RhB) degradation under visible light was observed in the prepared composite materials, particularly with an optimal CoFe2O4-ZnO ratio of 1:5, achieving an 81 % degradation rate within 6 h. The proposed photodegradation mechanism, based on various spectroscopic and magnetic investigations, highlights the role of spin transfer and oxygen vacancies in facilitating reactive oxygen species (ROS) generation for pollutant degradation.

Ta2O5 coatings modified with CdS, ZnO, and Dy2O3 particles prepared by plasma electrolytic oxidation of tantalum for the photocatalytic degradation of methyl orange

Ta2O5/CdS, Ta2O5/ZnO and Ta2O5/Dy2O3 coatings for application in photocatalytic degradation of methyl orange were prepared by plasma electrolytic oxidation of tantalum in an alkaline electrolyte with different concentrations of CdS, ZnO, and Dy2O3 particles up to 2.0 g/L. The coatings were characterized by SEM/EDS, XRD, Raman spectroscopy, DRS and photoluminescence spectroscopy. The morphology, thickness, phase structure and absorption properties of all coatings are almost identical and independent of the content of CdS, ZnO, and Dy2O3 embedded in Ta2O5 coatings. The orthorhombic and monoclinic phases of Ta2O5 are the main constituents of the coatings. Due to the low content of embedded CdS, ZnO, and Dy2O3 in Ta2O5 coatings, they exhibit high absorption in the middle ultraviolet region, which is characteristic of Ta2O5. The photocatalytic activity (PA) of Ta2O5/CdS, Ta2O5/ZnO and Ta2O5/Dy2O3 is higher than that of pure Ta2O5 and depends on the amount of CdS, ZnO, and Dy2O3 in the electrolyte, respectively. The highest PA was observed for coatings formed in an electrolyte containing 0.5 g/L of CdS, ZnO, and Dy2O3. The improved PA of Ta2O5/CdS, Ta2O5/ZnO and Ta2O5/Dy2O3 compared to Ta2O5 is related to the reduction of photogenerated electron/hole recombination. The mechanism of the photogenerated electron/hole transfer process is presented and discussed.

Evaluation of acrylonitrile rubber containing zinc oxide as safety products

AbstractThe goal of this research is to find the ideal formulation with the best antimicrobial performance in terms of rheological, physicomechanical, and lowest toxic properties to produce safety rubber for the children toy's and other industrial products. In order to accomplish this, a number of formulations containing ZnO as activator for vulcanization process as well as an antimicrobial agent at concentrations ranging from 1.5 to 40 phr in the presence of 40 phr of different fillers were prepared. The rheological characteristics of prepared compounded rubber samples were assessed and the cure rate was calculated. The overall rheological test results indicate a raise in minimum and maximum torque along with a fall in scorch and optimum cure time. The compounded NBR was vulcanized as estimated curing time. The results illustrated that the NBR vulcanizates containing various amounts of ZnO and 40 phr talc have the best physicomechanical properties. Also, the scanning electron micrographs indicated surface homogeneity and good dispersion of the NBR components. The cytotoxicity test of the investigated vulcanizates on normal retina cell line gave no cytotoxic effect which assessed their safety. These findings offer useful information for antimicrobial NBR vulcanizates for kid's toys and other safety products.Highlights Synthesis of antimicrobial NBR rubber vulcanizates for safety applications. The antimicrobial agent used was ZnO. ZnO nanoparticles and other ingredients were incorporated with NBR on the ordinary rubber mixer. Rheological, physicomechanical properties and antimicrobial activity of NBR rubber were tested. The products have better mechanical and antimicrobial safety properties.

A comparative study on antibacterial properties of EuO, CuO, and ZnO dopped ZrO2 sol-gel coatings

ZnO, CuO, and EuO doped ZrO2 films were prepared using a sol-gel dip coating technique, and the effects of the doping on the film thickness, crystallite size, surface roughness, band gap energy, adhesion strength, and antibacterial properties of the coatings were investigated. It was found that the addition of small amounts of ZnO and EuO can significantly improve the uniforminty of the sol-gel coating, while the greater the difference in the coefficients of thermal expansion (CTEs) of the coating and the substrate, the higher the probability of developing surface microcracks. The XRD patterns of the coatings synthesized based on ZrO2 as well as EuO, ZnO, and CuO dopants showed that the ZrO2 structure was tetragonal for all of the compounds. In addition, it was revealed that with an increase in the calcination temperature, the crystallite sizes of the coatings containing ZrO2 and ZnO increased, and in contrast, the crystallite sizes of ZrO2:ZnO, ZrO2:ZnO,CuO and ZrO2:ZnO,EuO compounds decreased. The evaluation of the reflectance of visible light functions showed that adding 30 % ZnO led to a decrease in the band gap energy from 3.19 eV for ZnO2 to 3.01 eV for ZrO2 + 30 % ZnO. Moreover, the lowest band gap energy (2.81 eV) was achieved for the compound containing EuO. Finally, it was concluded that the ZrO2:ZnO,EuO sol-gel coating with the least band gap energy shows better antibacterial activity.

Enhancing 2.7 µm emission of Er3+ in bismuth glass by introducing ZnO

In recent years, 2.7 μm lasers have attracted the attention of many researchers due to their wide application in military, medical, aerospace and other fields. This study investigates the gain effect of ZnO on Er3+-doped bismuthate glasses by partially replacing GeO2 in the glass with ZnO. It is found that under 980 nm pump excitation, with the increase of ZnO, the emission of Er3+ at 1.5 μm and 2.7 μm was enhanced. This result is consistent with the changing trend of J-O parameter Ω2. All these results confirmed that the introduction of ZnO into bismuthate glasses is a reasonable and effective method to enhance the mid-infrared 2.7 μm emission in Er3+-doped bismuthate glasses. Therefore, the current research indicates that an appropriate amount of ZnO in Er3+-doped bismuthate glasses is a suitable materials for 2.7 um fiber lasers.

Preparation and characterization of ZnO modified solid state sintered 45S5 bioactive ceramics

In this research, the traditional 45S5 bioactive glass powder was modified using ZnO (<20 μm) by powder metallurgy route. Five different bioactive ceramics compositions (45BC, 45BC1, 45BC3, 45BC5 and 45BC7) were formulated containing varied amounts of ZnO in the step of 1, 3, 5 and 7 wt % respectively. Each body was thoroughly mixed in a porcelain-lined ball mill to ensure proper homogenization followed by an addition of prepared 2 % PVA (Polyvinyl alcohol) and then again thoroughly mixed. The batch material was uniaxially pressed at 70 MPa using a cylindrical mould of 40 × 20 mm. A total of 20 samples from each body composition were produced and allowed to dry in an ambient temperature followed by sintering at 1000 °C for 2h at the rate of 5 °C/min. The samples were then allowed to anneal within the furnace to room temperature. Selected samples were later immersed inside simulated body fluid. Physical, mechanical, microstructure and phase evaluation were conducted to examine the developed bioactive ceramics. The results showed that the bulk density increased from 1.6 to 2.64 g/cm3 while porosity decrease from 95 % to 58 % across the series, with increasing ZnO addition. Sample 45BC7 showed maximum hardness and compressive strength of 7.98 GPa and 83.54 MPa respectively. The carbonate-hydroxyapatite/hydroxyapatite (CHA/HA) deposits were found to also increased with ZnO addition showing good bioactivity, which affirms that the developed bioactive ceramics can bond well with living tissues, thus its suitability for bone regeneration.

Evaluating the impact of ZnO doping on electrical and thermal properties of calcium-aluminosilicate oxynitride glass-ceramics

This study aimed to investigate the impact of ZnO content on the structure, thermal, and electrical properties of oxynitride glass-ceramic(s) within the Ca–Al–Si–O–N (CASON) system. The base glass had the composition of Ca7Al14Si17O52N7, with ZnO additions ranging from 3 to 15 % by weight. A pristine Ca7Al14Si17O52N7 glass was successfully prepared by melt-quenching technique followed by converted into glass-ceramic by incorporating various amounts of ZnO using the field-assisted sintering technique. XRD and FESEM analysis confirmed that increasing the amount of Zn increases the crystallinity in the glass matrix. The observed crystalline phases were formed mostly from ZnO and showed higher conductivity than the remaining dielectric matrix. IR spectra confirmed the presence of bands correlated with the presence of Zn and suggested the progressive depolymerization of the silicate-aluminate network as a consequence of increasing Zn content. Density values varied between 2.75 and 2.94 gcm−3 and increased with increasing the Zn content in the glass-ceramic. The thermal expansion and thermal conductivity values increased and decreased, respectively, with the increase of Zn content in the matrix. The electrical properties of the samples were investigated using impedance spectroscopy over a wide range of frequencies (10 mHz to 1 MHz) and temperatures (153 K–623 K). The results showed that in the glass without ZnO and glass-ceramic(s) with a small addition of ZnO, the conductivity is mainly dominated by the transfer of oxygen ions and, to a small extent, by the presence of electronic conductivity. As the ZnO content increases, continuous conduction paths are formed between the ZnO crystallites, and the electrical conductivity increases rapidly and becomes dominated by electron transfer.

Xanthan gum and chitosan polyelectrolyte hydrogels with self-reinforcement of Zn+2 for wound dressing applications

A straightforward methodology was employed for the self-reinforcement of zinc ions (Zn+2) within the polyelectrolyte complexation of xanthan gum (XG) and chitosan (CS) using D (+)-glucuronic acid-δ-lactone (GDL) as an acidifying agent in aqueous environment. The self-reinforcement and polyelectrolyte complexation between XG and CS was primarily achieved by maintaining acidic conditions through the use of GDL. GDL produces H+ ions, not only in converting ZnO to Zn+2 ions but also in facilitating the polyelectrolyte complexation between XG and CS. The confirmation of Zn+2 self-reinforcement was evident through the disappearance of ZnO, as observed in Fourier transform infrared spectroscopy and X-ray diffraction patterns. The compressive properties of self-reinforced Zn+2 within XG-CS hydrogels were evaluated, and their compressive strength was found to depend significantly on the reinforcement of ZnO nanoparticles. Incorporating 1 wt% ZnO improved the compressive strength of the hydrogels, decreasing further with an increasing amount of ZnO (3 wt%), as confirmed by compressive analysis. Detailed SEM images conclusively demonstrated The hydrogels porous structure, and elemental analysis verified the presence of Zn+2 ions. The antibacterial activity of Zn+2 reinforced XG-CS hydrogel showed excellent antibacterial activity towards both positive and negative bacteria. Furthermore, the biocompatibility analysis was assessed through an in vitro study that confirmed good biocompatibility towards NIH3T3 fibroblast cells. Thus, a robust inhibitory effect of bacterial growth and biocompatibility of developed hydrogels hold promise in advanced wound dressings for infected wounds.

Efficient RhB dye degradation and E. coli inactivation using g-C3N4/CS/ZnO nanocatalyst: In silico molecular docking studies

2 and 4 wt% of g-C3N4 and a fixed amount of CS-doped ZnO have been prepared using co-precipitation techniques for catalytic dye degradation and antibacterial application. X-ray diffraction patterns and FTIR spectra have proven the confirmation of the development of g-C3N4/CS doped ZnO nanorods (NRs). The TEM study confirmed the formation of nanorods for ZnO, a sphere-like structure with the addition of CS and a layer over the carbon sphere, and nanorods were observed by doping g-C3N4. In the presence of NaBH4, 4 % g-C3N4/CS/ZnO nanostructures degraded 94.4 % RhB dye within 2 min, while 3.25 nm inhibitory zone was measured against Escherichia coli (E. coli) bacteria. These enhanced results were attributed to the increased surface area, which provided more active sites for the catalytic reduction and generated reactive oxygen species, contributing to enhanced antibacterial activity. The theoretical study of antibacterial activity for ZnO, CS-doped ZnO, and CS/g-C3N4-doped ZnO NRs was conducted through Molecular docking analysis against DNA gyrase in E. coli. The results of the docking studies show that these NRs may function as inhibitors of DNA gyrase. These findings provide valuable insights into the potential applications of NRs within the field of wastewater purification and biological sciences.

ZnO/TiO2 heterojunction nanorod array for efficient photoelectrochemical water splitting

This study presents a novel approach utilizing a simple, stable, reproducible CV (Cyclic Voltammetry) electrodeposition method to deposit varying amounts of ZnO onto ordered TiO2 (Rutile) nanorod arrays. Comprehensive investigations were conducted on the morphology, semiconductor band-gap structure of different ZnO/Rutile composites, and their performance in photocatalytic (PC) and photoelectrochemical (PEC) hydrogen production. Results demonstrate that the ZnO/TiO2 photoanodes fabricated in this manner exhibit outstanding PC/PEC hydrogen production capabilities. Particularly noteworthy is the Z/R-15 photoanode, showcasing superior PEC performance with a photocurrent density 3.5 times higher than that of the pristine TiO2 photoanode under equivalent conditions. Furthermore, it was observed that depositing ZnO onto highly crystalline, annealed TiO2 nanorods yields optimal photoelectrical properties. Incorporating oxygen-rich vacancies in ZnO significantly enhances the photoelectrocatalytic performance of TiO2 photoanodes. The CV electrodeposition method offers valuable insights for developing efficient photocatalytic hydrogen production catalysts.

Effect of ZnO on Luminescence Performance of Terbium-Activated Zinc Borosilicate Glasses.

In this study, terbium-doped ZnO-SiO2-B2O3-Na2O glasses were fabricated with the conventional melt-quenching method. The effect of altering the concentration of the host matrix on luminescence performance was investigated in terms of different ZnO/B2O3 and ZnO/SiO2 ratios. FT-IR results indicate that bridging oxygens (Bos) were converted to non-bridging oxygens (NBOs) with increments of ZnO. Furthermore, the emission intensity and luminescence lifetime of samples were influenced by the amount of ZnO; this was proven with photoluminescence spectra results. The maximum emission intensity was observed at a 1.1 ZnO/B2O3 ratio and a 0.8 ZnO/SiO2 ratio; however, the highest luminescence lifetime was observed at a 1.1 ZnO/SiO2 ratio. The emission intensity and luminescence lifetime of glass samples were improved by heat treatment as a result of the formation of willemite and zinc oxide phases. An increase in the ZnO/SiO2 ratio facilitated the formation of willemite and zinc oxide phases; therefore, crystallinity was directly related to the luminescence behavior of glass samples.

Use of ZIF‐8 as vulcanization additive to optimize natural rubber composites to lower the amount of ZnO

AbstractZinc oxide (ZnO) is widely used as an activator in the vulcanization process of natural rubber. However, due to its poor compatibility with natural rubber, a large amount of ZnO needs to use, and the unreacted ZnO can precipitate in various ways, posing significant harm to aquatic organisms and microorganisms. Therefore, it is necessary to reduce the dosage of ZnO in order to minimize its environmental impact. In this study, we applied ZIF‐8, a zinc‐based metal–organic framework, as a vulcanization additive in natural rubber. and it was found that ZIF‐8 could promote the rubber vulcanization reaction by adsorbing sulfur, promoting sulfur ring‐opening, and providing different ligand interactions of Zn2+. Moreover, even at low usage levels of ZIF‐8, it effectively reduces the amount of ZnO while simultaneously improving the mechanical properties of the samples. This work provides an effective method to reduce the amount of ZnO without sacrificing the rubber properties and provides a new idea for the application of ZIF‐8 in rubber materials.Highlights ZIF‐8 enhances properties of natural rubber composites with low ZnO dosages. Revealing the reason why ZIF‐8 promotes the vulcanization of natural rubber. Investigation of the effect of ZIF‐8 on the vulcanization properties of natural rubber.

Experimental evaluation of electrospun ZnO/WO3/PVA-coated glass nanocomposites for a potential radiation dosimetry application

This research aimed to fabricate a potential radiation dosimeter using electrospun ZnO/WO3/PVA-coated glass nanocomposites. Samples with varying ZnO molarities (2.46, 3.69, 4.91, 5, and 7 M) and 5 wt% of WO3 collected at different times were examined. Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray analysis (EDX) revealed favorable nanofiber morphology, although certain conditions produced larger nanofibers. The optical properties, analyzed via ultraviolet–visible (UV–Vis) spectroscopy, exhibited varying responses in different samples with changes in nanofiber collection time. The calculated optical energy band gap (Eg) for all samples is lower than Eg of pure ZnO. Moreover, the effective atomic number (Zeff), calculated based on EDX results, did not approach Zeff of human tissues, in all samples in general. Crucially, all samples demonstrated a strong linear response and low energy dependence when subjected to different X-ray exposure settings, closely resembling an Al2O3-based OSL dosimeter. Sample E3, consisting of 7.00 M ZnO and 5 wt% of WO3 collected over 4 h, emerged as the most promising candidate for a radiation dosimeter. Prior studies neglected to examine the influence of different amounts of ZnO on the radiation dosimetry properties of ZnO/WO3/PVA nanofibers. In contrast, this study specifically investigated the radiation dosimetry properties of ZnO/WO3/PVA nanofibers. The exceptional properties of ZnO in response to X-rays, combined with the desired X-ray attenuation capabilities of WO3, make them a distinct option as substitute materials in radiation dosimeters. This research paves the way for an alternative dosimeter solution with robust radiation detection capabilities.

Protein‐Mediated ZnO Synthesis for Self‐Healing in Natural Rubber

AbstractNatural rubber (NR) consists of mainly cis‐1,4‐polyisoprene with proteins as notable nonrubber components that significantly influence its properties. A relatively unexplored aspect is the role of these proteins in reducing and stabilizing metal ions to form metallic particles. Here, the NR/ZnO composite is successfully prepared by in situ generation of ZnO in the NR latex for the first time. With the aid of the proteins, the amount of ZnO is slightly higher than that formed in the saponified NR latex (SPNR), where some proteins are removed. Importantly, the noncovalent bonds between the proteins and/or amino acids with the ZnO formed in the NR latex can provide the self‐healing behavior of the NR/ZnO composite. However, heating at ≈40 °C is still necessary for reducing the healing time and increasing the self‐healing efficiency of the composite. Nevertheless, greater noncovalent bonds within NR/ZnO hinder rubber molecular chain interdiffusion and rearrangement essential for self‐healing behavior in uncross‐linked rubber, resulting in lower healing efficiency compared to SPNR/ZnO. This study underscores the significance of proteins and/or amino acids on NR's properties, despite their minor presence. Without sophisticated NR modification, this is a very simple and low‐cost technique to achieve the NR/ZnO composite with self‐healing behavior.

Surface ZnOx on zirconia is highly active for high temperature methanol synthesis

Zinc containing mixed metal oxides and supported zinc oxide are stable and selective methanol synthesis catalysts at temperatures where a subsequent methanol to hydrocarbons reaction can occur directly. This work provides fundamental insights into ZnO-based high temperature methanol synthesis catalysts. A pronounced support effect was observed, where ZrO2 provided a beneficial effect while SiO2 exerted a detrimental effect compared to bulk ZnO. Preparing co-precipitated ZnO-ZrO2 catalysts showed that the initial activity correlated with the amount of amorphous ZnO on the surface of the support and that the catalytic activity increased with time on stream as zinc oxide migrated out of a solid solution with ZrO2 and onto the support surface. Hence the active phase appeared to be ZnO surface species and not zinc oxide in a solid solution with ZrO2. Operando XAS coupled with modulation excitation spectroscopy unravelled that the surface ZnO was partly reduced under operating conditions, as surface ZnOx, with x approximately equal to 0.98. In-situ DRIFTS further uncovered that the surface ZnOx activated CO2 and formed methanol via carbonate, formate and methoxide species. XPS finally showed that ZrO2 withdrew electrons from ZnO, facilitating oxygen abstraction to form the partly reduced ZnOx, which in turn facilitated the activation of CO2.

Enhancing sintering behavior and conductivity of YSZ electrolyte by co-doping of ZnO and MnO2

This study aimed to enhance the sinterability and conductivity of yttria fully stabilized zirconia electrolyte through co-doping by 2 mol% of ZnO and different contents of MnO2 (0, 0.5, 1, 1.5 mol%) at two sintering temperatures of 1300 and 1400 °C. Phase composition identification, density, microstructure, and conductivity of the samples were evaluated using X-ray diffraction (XRD), Archimedes' method, field emission scanning electron microscopy (FESEM), and electrochemical impedance spectroscopy (EIS), respectively. The XRD results revealed that ZnO and MnO2 are successfully doped in the fluorite structure of YSZ sintered at 1400 °C, and the cubic structure is completely preserved. However, at a sintering temperature of 1300 °C, the (111) peaks of doped samples were slightly split, which implied a slight phase transformation of YSZ from cubic to a tetragonal structure. The co-doped samples, at both sintering temperatures, showed higher relative density and grain size compared with pure YSZ. The addition of 2 mol% of ZnO and 0.5 mol% of MnO2 at 1400 °C increased the relative density of YSZ from 81.6% to 95.1%. The increase in relative density and grain size, while maintaining the cubic structure, caused an increase in the conductivity of the mentioned sample. Compared with pure YSZ, the sample's total conductivity increased from 7.37 to 10.03 S m−1 at 800 °C. The proposed composition showed better sintering behavior, lower activation energy of grain conductivity, and higher conductivity than pure YSZ. This behavior is thought to be due to the facilitating rearrangement of atoms during sintering and an increase in oxygen ion vacancy concentration due to co-doping with the appropriate amount of ZnO and MnO2.

Mechanical and Antibacterial Properties of Bamboo Charcoal/ZnO-Modified Bamboo Fiber/Polylactic Acid Composites

In this study, biodegradable bamboo fiber/PLA composites (BPCs) modified using bamboo charcoal (BC)/ZnO were prepared. The effects of BC/ZnO addition on the mechanical properties and antibacterial properties of BPCs were investigated. The chemical structure, microscopic morphology, and crystallization of the composites were analyzed using FTIR, SEM, and XRD, respectively. The results showed that in terms of mechanical strength, when the addition of BC was 2%, the tensile impact and flexural strength of the BPCs were most obviously improved, with a tensile strength of 51.6 MPa. However, when the addition of BC was more than 2%, the uneven dispersion of too much BC in the BPCs resulted in a reduction in their mechanical strength. A certain amount of ZnO did not affect the crystallinity of the BPCs. In addition, the uneven distribution of ZnO and its poor compatibility with PLA resulted in a deterioration in the tensile properties of the BPCs. In terms of antibacterial properties, when 2% ZnO was added, the BPCs had better antibacterial properties against Escherichia coli and Staphylococcus aureus, with values of 58.9% and 52.5% against both, respectively. BPC biodegradable materials with both mechanical strength and antimicrobial properties have promising medical uses.

Transitioning from Methanol to Olefins (MTO) toward a Tandem CO2 Hydrogenation Process: On the Role and Fate of Heteroatoms (Mg, Si) in MAPO-18 Zeotypes.

The tandem CO2 hydrogenation to hydrocarbons over mixed metal oxide/zeolite catalysts (OXZEO) is an efficient way of producing value-added hydrocarbons (platform chemicals and fuels) directly from CO2via methanol intermediate in a single reactor. In this contribution, two MAPO-18 zeotypes (M = Mg, Si) were tested and their performance was compared under methanol-to-olefins (MTO) conditions (350 °C, PCH3OH = 0.04 bar, 6.5 gCH3OH h-1 g-1), methanol/CO/H2 cofeed conditions (350 °C, PCH3OH/PCO/PH2 = 1:7.3:21.7 bar, 2.5 gCH3OH h-1 g-1), and tandem CO2 hydrogenation-to-olefin conditions (350 °C, PCO2/PH2 = 7.5:22.5 bar, 1.4-12.0 gMAPO-18 h molCO2-1). In the latter case, the zeotypes were mixed with a fixed amount of ZnO:ZrO2 catalyst, well-known for the conversion of CO2/H2 to methanol. Focus was set on the methanol conversion activity, product selectivity, and performance stability with time-on-stream. In situ and ex situ Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), solid-state nuclear magnetic resonance (NMR), sorption experiments, and ab initio molecular dynamics (AIMD) calculations were performed to correlate material performance with material characteristics. The catalytic tests demonstrated the better performance of MgAPO-18 versus SAPO-18 at MTO conditions, the much superior performance of MgAPO-18 under methanol/CO/H2 cofeeds, and yet the increasingly similar performance of the two materials under tandem conditions upon increasing the zeotype-to-oxide ratio in the tandem catalyst bed. In situ FT-IR measurements coupled with AIMD calculations revealed differences in the MTO initiation mechanism between the two materials. SAPO-18 promoted initial CO2 formation, indicative of a formaldehyde-based decarboxylation mechanism, while CO and ketene were the main constituents of the initiation pool in MgAPO-18, suggesting a decarbonylation mechanism. Under tandem CO2 hydrogenation conditions, the presence of high water concentrations and low methanol partial pressure in the reaction medium led to lower, and increasingly similar, methanol turnover frequencies for the zeotypes. Despite both MAPO-18 zeotypes showing signs of activity loss upon storage due to the interaction of the sites with ambient humidity, they presented a remarkable stability after reaching steady state under tandem reaction conditions and after steaming and regeneration cycles at high temperatures. Water adsorption experiments at room temperature confirmed this observation. The faster activity loss observed in the Mg version is assigned to its harder Mg2+-ion character and the higher concentration of CHA defects in the AEI structure, identified by solid-state NMR and XRD. The low stability of a MgAPO-34 zeotype (CHA structure) upon storage corroborated the relationship between CHA defects and instability.

Influence of the content of stacked ZnO on the structural and optical properties of heterostructured ZnO/Ga2O3 films

The rising demand for heterojunction materials stimulated by the great achievements of modern nanotechnology has triggered enormous interests in the investigation of their materials properties. Heterostructured ZnO/Ga2O3 has been deployed for different device applications, but its several optical parameters have rarely been investigated. The present work attempts to investigate the influence of the thickness of stacked ZnO layer on the surface of Ga2O3 film. Optical parameters, such as absorption and extinction coefficient, Urbach energy, refractive index, dielectric constants, optical dispersion energy, single oscillator energy, static refractive index, oscillator strength, and oscillator wavelength of the ZnO/Ga2O3 films were studied. Morphological characterization showed microstructures of various shapes. Cross-section measurements showed that the thickness of the Ga2O3 layer remained approximately the same for all samples, while the thickness of the ZnO layer increased from 0 to 5.14 nm. Structural analysis revealed the coexistence of β-Ga2O3 and wurtzite ZnO crystal phases. UV–Vis absorption spectra demonstrated two distinct absorptions belonging to the β-Ga2O3 and ZnO. The bandgap of the composite ranged between 4.43 and 4.69 eV with an increase in the amount of ZnO at the surface. The absorption and extinction coefficient were in the order of 103 cm−1 and 10−5, respectively. The Urbach energy ranged between 0.688 and 1.125 eV. The refractive index was in the range 2.09–2.85, while the static refractive index ranged between 1.90 and 2.73. Also reported were other optical parameters, such as the real and imaginary dielectric constant, dispersive energy, single oscillator energy, oscillator strength, and oscillator wavelength.