Zirconium Loading Research Articles

Amplifying chlorinated phenol decomposition via Dual-Pathway O2 Activation: The impact of zirconium loading on BiOCl

The effectiveness of photocatalytic molecular oxygen (O2) activation in pollutant removal relies on the targeted production of reactive oxygen species (ROS). Herein, we demonstrate the dual-pathway activation of O2 on BiOCl through zirconium (Zr) loading. The incorporation of Zr onto the surface of BiOCl not only leads to an increased generation of oxygen vacancies (OV) but also fosters a coupling between the d electrons of Zr and OV, forming dual-active sites known as Zr-oxygen vacancies (Zr-OV). Generally, OV adsorbs O2 and transfers one electron directly to form superoxide radicals (•O2–). Contrary to the conventional single-electron direct activation of O2 to form •O2–, Zr-OV exhibits more flexible coordination and superior electron-donating capabilities. It facilitates O2 conversion to peroxide radicals (O22–) and enables the subsequent generation of •O2– from O22–, significantly promotes the dechlorination and mineralization efficiency of chlorophenol under visible light. This study presents a straightforward strategy to precisely regulate ROS production by expanding pathways, shedding light on the critical role of managing ROS generation for effective pollutant purification.

Sustainable synthesis of levulinic acid using waste derived silica-alumina-hydroxyapatite supported nano ZrO2 photo-acidic catalyst under synergistic UV-FIR irradiations

A novel nano-photocatalyst has been prepared using hydroxyapatite (HAp) derived from waste fish scale and fly ash-derived aluminosilicate (SiO2-Al2O3) grafted with zirconium oxide (ZrO2) active sites by innovative photo-hydrothermal protocol. The physiochemical properties of the prepared photocatalyst have been characterized by different analyses like TGA, XRD, FTIR, XPS, UV–VIS–NIR, BET, NH3-TPD, HRTEM, and DLS. The optimal catalyst has a zirconium loading of 20 wt% and has a low bandgap energy of 2.15 eV as confirmed by UV–VIS–NIR spectroscopy. The optimal catalyst also depicted a high acidity of 1.52 mmol NH3/g and a specific surface area of 62.872 m²/g. Owing to the high acidity, specific surface area, and low band gap energy the photocatalyst has led to achieving an elevated yield of 76.6% levulinic acid (LA) from glucose in hybrid irradiation reactor (HIR) deploying UV and FIR radiations at appreciably low temperature and reaction time of 115 ℃ and 2 h respectively. Under the same reaction conditions, the conventionally heated reactor (CHR) gave a very low yield of 23.7%. Individual radiation effects on LA yield evinced the synergistic advantageous effect of the hybrid irradiation technique. The catalyst reusability and regenerative study confirmed the high stability of the prepared catalyst. Also, a comparative LCA study has been conducted between HIR and CHR systems which revealed that HIR was more environmentally sustainable than CHR. HIR -based process demonstrated a reduction in 59% global warming potential, 70.66% forest resource scarcity, and 65% lower terrestrial ecotoxicity while being 120% more energy efficient than CHR-based reaction making HIR more environmentally sustainable as well as economically feasible.

Influence of the drying mode of support on the properties of Pd/Al2O3–ZrO2 materials used for methane combustion

This work constitutes a new trial to enhance the properties of palladium supported on alumina modified with zirconium used as catalysts for methane combustion. The effect of the support drying mode is studied. For this aim, Al2O3-ZrO2 binary oxides with zirconium loading of 2 and 5% in weight were prepared using sol–gel process then dried under ordinary or supercritical conditions. Palladium with a loading of 0.5% was deposited on the support by wet impregnation. Several techniques have been used to investigate differences between the two types of the derived catalysts.

Optimization of phosphate oxygen isotope pretreatment measurement method based on phosphate in situ enrichment blanket.

Phosphate oxygen isotope analysis is an effective tool for investigating phosphorus migration and transformation in water bodies. Unfortunately, current pretreatment methods for this technology are significantly limited due to their demanding sample amount requirements, complex operation, and limited scope of application. In order to enhance the efficiency of the pretreatment process, hydrated zirconia was synthesized through liquid-phase precipitation. Zeolite, D001 macroporous resin, activated carbon, and ceramsite were chosen as possible candidate materials for loading purposes. The optimal zirconium loading material was identified through a combination of field enrichment and laboratory elution experiments. The ideal in situ enrichment duration, material dosages, and elution time were ascertained using response surface methodology. The findings showed that D001 resin exhibited superior selective adsorption and elution capacity for phosphate. The response surface optimization yielded the optimal parameters for the in situ phosphate-enrichment blanket: a mass of 13 g for zirconium-loaded D001 resin, an enrichment period of 360 min, and an elution period of 853 min. The attainment of a bright yellow Ag3PO4 solid after purification served as proof of the reliability of the optimization method. The obtained results provide a fundamental basis for the preparation and application of phosphate oxygen isotope analysis in freshwater ecosystem.

Prediction of thermal and thermo‐mechanical behavior of nano‐zirconia reinforced aluminium matrix composites

AbstractAluminium bequeaths the same benefits to medical industry as it does to other industries: it is incredibly lightweight and possesses superior strength‐to‐weight ratio. This study‘s aim is to investigate the thermal and thermomechanical behaviour of aluminium 6061 alloy reinforced with nano zirconia (0 wt. % to 15 wt. %; in 5 % steps) for medical applications. The effect of nano zirconia loading on thermal conductivity and thermo‐mechanical (thermo‐gravimetric analysis and dynamic mechanical analysis) have been systematically investigated. The thermal conductivity (128 W/m⋅K to 79 W/m⋅K) decreases with the increasing of nano zirconia particles reinforcement. The storage modulus increases with the nano zirconia particles (64 GPa to 172 GPa), whereas loss modulus indicates an increasing trend concerning the increasing temperature. The thermogravimetric analysis and differential thermal analysis result shows that composites’ decomposition temperature improved with the weight percentage of nano zirconia particles. Furthermore, representative volume element analysis is conducted to evaluate the thermal conductivity and results indicates good agreement with the experimental results within a deviation of ∼5 %.

Lanthanum–Cerium-Modified Nickel Catalysts for Dry Reforming of Methane

The catalyst MNi0.9Zr0.1O3 (M = La, Ce, and Cs) was prepared using the sol–gel preparation technique investigated for the dry reforming of methane reaction to examine activity, stability, and H2/CO ratio. The lanthanum in the catalyst LaNi0.9Zr0.1O3 was partially substituted for cerium and zirconium for yttrium to give La0.6Ce0.4Ni0.9Zr0.1−xYxO3 (x = 0.05, 0.07, and 0.09). The La0.6Ce0.4Ni0.9Zr0.1−xYxO3 catalyst’s activity increases with an increase in yttrium loading. The activities of the yttrium-modified catalysts La0.6Ce0.4Ni0.9Zr0.03Y0.07O3 and La0.6Ce0.4Ni0.9Zr0.01Y0.09O3 are higher than the unmodified La0.6Ce0.4Ni0.9Zr0.1O3 catalyst, the latter having methane and carbon dioxide conversion values of 84% and 87%, respectively, and the former with methane and carbon dioxide conversion values of 86% and 90% for La0.6Ce0.4Ni0.9Zr0.03Y0.07O3 and 89% and 91% for La0.6Ce0.4Ni0.9Zr0.01Y0.09O3, respectively. The BET analysis depicted a low surface area of samples ranging from 2 to 9 m2/g. The XRD peaks confirmed the formation of a monoclinic phase of zirconium. The TPR showed that apparent reduction peaks occurred in moderate temperature regions. The TGA curve showed weight loss steps in the range 773 K–973 K, with CsNi0.9Zr0.1O3 carbon deposition being the most severe. The coke deposit on La0.6Ce0.4Ni0.9Zr0.1O3 after 7 h time on stream (TOS) was the lowest, with 20% weight loss. The amount of weight loss increases with a decrease in zirconium loading.

Modification of CeNi0.9Zr0.1O3 Perovskite Catalyst by Partially Substituting Yttrium with Zirconia in Dry Reforming of Methane.

Methane Dry Reforming is one of the means of producing syngas. CeNi0.9Zr0.1O3 catalyst and its modification with yttrium were investigated for CO2 reforming of methane. The experiment was performed at 800 °C to examine the effect of yttrium loading on catalyst activity, stability, and H2/CO ratio. The catalyst activity increased with an increase in yttrium loading with CeNi0.9Zr0.01Y0.09O3 catalyst demonstrating the best activity with CH4 conversion >85% and CO2 conversion >90% while the stability increased with increases in zirconium loading. The specific surface area of samples ranged from 1–9 m2/g with a pore size of 12–29 nm. The samples all showed type IV isotherms. The XRD peaks confirmed the formation of a monoclinic phase of zirconium and the well-crystallized structure of the perovskite catalyst. The Temperature Program Reduction analysis (TPR) showed a peak at low-temperature region for the yttrium doped catalyst while the un-modified perovskite catalyst (CeNi0.9Zr0.1O3) showed a slight shift to a moderate temperature region in the TPR profile. The Thermogravimetric analysis (TGA) curve showed a weight loss step in the range of 500–700 °C, with CeNi0.9Zr0.1O3 having the least carbon with a weight loss of 20%.

A novel antibacterial zirconia-containing PMMA bone cement

A non-leaching antibacterial bone cement has been developed and evaluated. Chlorine- and bromine-containing furanone derivatives were synthesized and covalently coated onto the surface of zirconia filler particles, followed by mixing into a conventional poly(methyl methacrylate) bone cement. Flexural strength and bacterial viability were used to evaluate the modified cements. Effects of coated antibacterial moiety content, coated zirconia loading and halogen on furanone were investigated. Results showed that the experimental cement showed significant enhanced antibacterial function against bone-associated Gram-positive Staphylococcus aureus as well as Gram-negative Pseudomonas aeruginosa, as compared to commercial PMMA cement. The cement also exhibited a comparable flexural strength to and 3–14% higher flexural modulus than commercial PMMA bone cement. Increasing antibacterial moiety content and filler loading significantly enhanced antibacterial activity. Increasing antibacterial moiety content slightly increased both flexural strength and modulus of the modified cement. Increasing filler loading slightly increased flexural strength up to 7% loading and then decreased. The bromine-containing furanone modified cement showed a higher antibacterial activity than its chlorine counterpart. Antibacterial agent leaching tests exhibited that the modified experimental cement showed no leachable antibacterial components to surroundings. Within the limitations of this study, this experimental poly(methyl methacrylate) cement may find potential applications in orthopedics for reducing in-surgical and post-surgical infection after further investigations are conducted.

Adsorption of tetracycline antibiotics using metal and clay embedded cross-linked chitosan

To enhance the adsorption capacity of chitosan (Cht), which is an plenty of biopolymer, zirconium loaded chitosan (Zr/Cht) and zirconium loaded chitosan modified by perlite (Zr/Cht/Pt) composites were synthesized and adsorption capacities were compared with raw chitosan using tetracycline (TC) as the adsorbate. These adsorbates were used to study the TC elimination from aqueous solution by examining the effect of zirconium loading amount, pH, contact time and temperature. Temkin, Freundlich and Langmuir isotherm models were studied to determine the most suitable isotherm model for adsorption process. Langmuir isotherm model has been found as the most appropriate model. The maximum adsorption capacities were found as 4.24 mg g−1, 49.019 mg g−1 and 104.17 mg g−1 for Cht, Zr/Cht and Zr/Cht/Pt, respectively. Pseudo-second order model has been found appropriate, considering the correlation coefficients, for the TC adsorption. The synthesized composites were found as the high adsorption capacity for TC adsorption.

Impact of changes in sintering temperatures on characteristics of 4YSZ and 5YSZ

ObjectivesThe aim of this study was to evaluate the effect of different sintering temperatures on biaxial flexural strength (BFS), dynamic loading, surface hardness, color reproduction, translucency, surface roughness and microstructure of zirconia with 4 mol% yttria (4YSZ) compared to zirconia with 5 mol% yttria (5YSZ). MethodsZirconia discs with 12 mm diameter and 1.2 mm thickness were prepared and divided into three groups (n = 53) according to different sintering temperatures (1400 °C, 1500 °C and 1600 °C). Each group was divided into five subgroups (n = 10) according to the dynamic loading procedure (none, 50%, 65%, 75% and 80%) conducted before the quasi-static BFS test and another subgroup (n = 3) used for X-ray-diffraction (XRD) microstructure analysis. BFS test and dynamic loading were performed with a piston-on-three-ball test. The surface hardness was evaluated according to Vickers. Color reproduction and translucency were measured with a spectrophotometer. A 3D laser scanning microscope was used to determine the surface roughness. Grain size measurements were performed using SEM. ResultsA significant increase in biaxial flexural strength was observed while the sintering temperature decreased. 4YSZ had significantly higher results in biaxial flexural strength than 5YSZ. A decrease in sintering temperature resulted in a significant increase in Vickers hardness. Furthermore, 4YSZ showed significantly better color reproduction with increasing sintering temperature. At higher temperatures (1500 °C and 1600 °C), 4YSZ showed better color reproduction than 5YSZ. Compared to 4YSZ, specimens of 5YSZ exhibited significant higher translucency. Using XRD, a distorted tetragonal phase was detected in addition to regular tetragonal and cubic phases in specimens without any stress and at a low sintering temperature. The grain sizes of both materials increased with an increase in sintering temperature. ConclusionThe sintering temperature has significant effects on the microstructure and thus on the mechanical and optical properties of the evaluated zirconia.

Selective glycerol esterification to monolaurate over ZrO2/MCM-41 catalysts prepared using impregnation and precipitation methods

In order to develop an active and selective catalyst for the selective esterification of glycerol with fatty acid to monoglycerides, zirconia was incorporated into mesoporous MCM-41 support using two methods, i.e., impregnation and precipitation. The zirconia loading was varied between 10 and 30 wt. % to demonstrate its effect on the properties and activity of the modified catalysts. The catalysts were then characterized by N2-adsorption surface analysis, SEM/EDX, FTIR, and TGA. The catalytic activity was then demonstrated in the selective esterification of glycerol with either lauric or palmitic acid at 160 °C for 6 h with glycerol/fatty acid molar ratios of 1:1, 4:1, and 6:1 and catalyst loadings up to 5 wt. %. Fatty acid conversion as well as monoglyceride selectivity and yield were monitored to measure the extent of reaction leading to the formation of the desired products. Correlations between the activity and the characteristics of the catalysts under various reaction conditions were successfully established. Relatively slower zirconia incorporation in the impregnation method caused more internal incorporation of the acidic component. MCM-41 catalyst with 30 wt. % zirconia loading that was prepared by impregnation method with a surface area of 589 m2/g and an acid site concentration of 6.83 µmol/g showed a lauric acid conversion of 98.6% and a monolaurin selectivity of 57.2%. An increase in the molar ratio exceeding 4:1 did not bring about the desired effect due to the dilution effect of the limiting reactant. Lower activity was demonstrated by stearic acid due to its higher molecular size and viscosity to mainly affect the mass transfer during the reaction.

Effect of solid loading on properties of zirconia ceramic by direct ink writing

High solid loading water-based zirconia slurries for direct ink writing had been successfully prepared in this paper. The water-soluble epoxy resin and sodium polyacrylate were used as the binder and dispersant, respectively. The effect of solid loading on the rheological properties of zirconia slurries was systematically investigated. The 54–58 vol.% zirconia slurries exhibited suitable printability for direct ink writing. After sintering at 1550 °C for 2 h, the properties of sintered zirconia ceramic specimens including linear shrinkage, relative density, flexural strength, tensile strength and microstructure were examined by a series of test methods. Further, the intrinsic relationships between the solid loading and physical and mechanical properties of zirconia ceramic specimens were explored. The experimental results showed that the densification and strength of sintered zirconia ceramic could be significantly improved by increasing the solid loading of zirconia due to the less content of organic matter and water. The maximum relative density, flexural strength and tensile strength of the sintered specimens were 98.8% ,676 ± 10 MPa and 92 ± 5 MPa, respectively, when the zirconia solid loading was 58 vol.%.

Synergy of Lewis and Brønsted acid sites for polyoxymethylene dimethyl ether synthesis from methanol and formaldehyde solution over Zr4+ modified sulfonated resin

Polyoxymethylene dimethyl ether (PODEn) is a clean, effective and promising diesel additive. In this work, acidic sulfonated resin modified by zirconium (Zr4+-SR), which possess both Lewis and Brønsted acid sites, was employed to catalyze the synthesis of PODEn from methanol (MeOH) and formaldehyde (FA) solution. The catalysts were investigated by various characterization methods including SEM, BET, XPS, FT-IR, NH3-TPD, Pyridine FT-IR, TG-MS and ICP-OES. It was found that the introduction of Zr4+ into cationic exchange resin formed the Lewis acid sites and improvement of the catalytic performance in PODEn synthesis from methanol and formaldehyde solution was attributed to the synergistic effect of Lewis and Brønsted acid sites. With the increase of zirconium loading, the amount of Lewis acid sites and weak acidity of the Zr4+-SR catalyst increased gradually, and the catalytic activity of the catalysts for the PODEn synthesis reaction exhibited a trend of increasing first and then decreasing. In the methanol and formaldehyde solution, Brønsted acid sites were active for the acetalization of hemiformal and methanol, while Lewis acid sites were conducive to the activation of the methylene glycol. A possible reaction route for the PODEn synthesis from methanol and formaldehyde solution was proposed. 61.1% methanol conversion, 98.7% PODE1–6 and 22.4% PODE3–6 selectivity were achieved under optimal reaction conditions. The reusability investigation of the Zr4+-SR catalyst showed a stable catalytic activity for the synthesis of PODEn from methanol and formaldehyde solution and revealed that the decrease of catalyst activity was attributed to the partial loss of the zirconium.

N-Hexane hydroisomerization over Zr-modified bicontinuous lamellar silica mordenite supported Pt as highly selective catalyst: Molecular hydrogen generated protonic acid sites and optimization

Zr-modified bicontinuous lamellar silica mordenite supported Pt catalysts were synthesized using the zirconyl chloride oxahydrate as the precursor for Zr species by the incipient wetness impregnation method. The influence of zirconium loading on the properties of Zr-modified HM@KCC-1 catalysts for n-hexane isomerization were studied. The results of XRD and lattice structure from IR study indicated that increasing zirconium loading did not change the properties of catalysts. The IR study with pre-adsorbed 2,6-dimethylpyridine as a probe molecule affirmed that increasing zirconium loading could increase the Lewis acid sites. The generation of protonic acid sites which were active in n-hexane hydroisomerization was mainly from molecular hydrogen through a hydrogen spill-over mechanism as established by in situ-IR study. The results for the catalytic testing indicated that PtZr/HM@KCC-1 catalyst was highly selective in n-hexane hydroisomerization due to abundant permanent Lewis acid sites for its promotive effect in the generation of protonic acid sites. However, the incorporation of excessive zirconium amount up to 10 wt percent loading led to a decline in the amount of protonic acid sites generated, thus reduced the hydroisomerization performance in the process. The optimum conditions for hydroisomerization of n-hexane over Pt5Zr/HM@KCC-1 were reaction temperature of 293 °C, treatment temperature of 474 °C and F/W of 502 mL/g.min with the predicted value for isomer yield of 83.9%.

Thermal, mechanical and morphological properties of polyurethane–zirconia loading

Abstract The polyurethane (PU) has been showing a dramatic increase in applications related to material science and technology. However, the mechanical, physical and thermal properties could be further improved by loading PU with zirconia (Zr) to create renewable materials known as polyurethane–zirconia (PUZ) composites. In this study, PU matrix was treated with wt.% Zr at 0.5, 1.0, 1.5 and 2.0. In this study, the thermo-mechanical properties and the morphology were investigated of PU and PUZ nano-samples. The images of the scanning electron microscope (SEM) were the prime tool in investigating PU and PUZ surfaces and fractured surfaces showing vanishing the cracks and formation of agglomeration on the sample PUZ-1.5%. In addition, the tensile strength, Young’s modulus and maximum loading were improved by 36.7, 31.8 and 39.1%, respectively, at Zr loading of 1.5 wt.%. The flexural stress and the load were improved by 94.3% and 93.6%, respectively, when Zr loading was 1.5 wt.%. The impact without and with a notch was improved by 110.7% and 62.6%, respectively, at Zr loading of 1.5 wt.%. The the morphologies of the PU surface and Zr surface supported by SEM images. Regarding the storage modulus ability of PU and PUZ composites, Zr loading has negatively influenced E. The E functioning temperature was observed to move from 142 to 183°C. Another effect was determined by adding a small amount of Zr. This small amount was enough to shift the crystallization temperature (${T}_c$) and the melting temperature (${T}_m$) of PU from 125 to 129°C and from 150 to 144°C, respectively.

Effects of Basalt Fiber and Zirconia Loading on Physico-Mechanical Behavior of PA66/HDPE Blend Composites

The polymer blend of polyamide 66 and high density polyethylene (PA66/HDPE) (70/30 wt. %) was selected for the study. The polymer blend was reinforced with 20 and 25 wt. % short basalt fibers (SBFs). Blend reinforced with 25wt. % SBFs was further loaded with 5 and 10wt. % zirconia (ZrO2) to study the positive hybrid effect. The physical properties such as density, void content and hardness of the composites were determined along with the mechanical properties such as tensile and impact as per the ASTM standards. Lastly, the fractured surfaces of specimens were examined using scanning electron microscope (SEM).

Hardness and Indentation Fracture Toughness of Slip Cast Alumina and Alumina-Zirconia Ceramics.

Alumina (Al2O3) and zirconia (ZrO2) have good overall properties and thus are widely used oxide technical ceramics. The biggest drawback of Al2O3 is its low fracture toughness. In contrast, ZrO2 is relatively tough, but is also much more expensive. In order to improve the alumina toughness, composite ceramics are being developed. Slip casting technology has economic advantages over the conventional hot isostatic pressure technology, but problems may arise when preparing stable highly-concentrated suspensions (slip) for filling the mold. The purpose of this study is to prepare aqueous suspensions using 70 wt. % α-Al2O3, with 0, 1, 5 and 10 wt. % of added t-ZrO2. Suspensions were electrosterically stabilized using the ammonium salt of polymethylacrylic acid, an alkali-free anionic polyelectrolyte dispersant. Also, magnesium oxide in form of magnesium aluminate spinel (MgAl2O4) was used to inhibit the abnormal alumina grain growth during the sintering process. Minimum viscosities were used as stability estimators, where an increase in ZrO2 content required adding more dispersant. After sintering, the Vickers indentation test was used to determine the hardness and the indentation fracture toughness from the measurement of the crack length. Also, the brittleness index (Bi, μm−1/2) was calculated from values of Vickers hardness and the Vickers indentation fracture toughness. It was found that with increasing ZrO2 content the fracture toughness increased, while the hardness as well as the brittleness index decreased. Zirconia loading reduces the crystallite sizes of alumina, as confirmed by the X-ray diffraction analysis. SEM/EDS analysis showed that ZrO2 grains are distributed in the Al2O3 matrix, forming some agglomerates of ZrO2 and some pores, with ZrO2 having a smaller grain size than Al2O3.

Cu and Zr surface sites in photocatalytic activity of TiO2 nanoparticles: The effect of Zr distribution

The present work is focused on the role of ZrO2 modification in the performance of CuO modified TiO2. Zirconia loading leads to formation of more resistant photocatalytic layers compared to samples modified with only copper containing species. Surface modification of mixed phase TiO2 with CuO/ZrO2 improves the degradation of Reactive blue 19 dye under simulated solar irradiation. An in-depth investigation of the catalysts showed that in case of CuO/ZrO2 modification, the covering of the TiO2 surface with zirconium containing species prevents morphological and harmful energetic changes induced by copper species formed on the rutile TiO2 phase at a higher copper loading.

Mechanical and Thermal Properties of Epoxy Composites Containing Zirconia-Impregnated Halloysite Nanotubes with Different Loadings.

Epoxy resins are widely used in various industrial fields due to their low cost, good workability, heat resistance, and good mechanical strength. However, they suffer from brittleness, an issue that must be addressed for further applications. To solve this problem, additional fillers are needed to improve the mechanical and thermal properties of the resins; zirconia is one such filler. However, it has been reported that aggregation may occur in the epoxy composites as the amount of zirconia increases, preventing enhancement of the mechanical strength of the epoxy composites. Herein, to reduce the aggregation, zirconia was well dispersed on halloysite nanotubes (HNTs), which have high thermal and mechanical strength, by a conventional wet impregnation method. The HNTs were impregnated with zirconia at different loadings using zirconyl chloride octahydrate as a precursor. The mechanical and thermal strengths of the epoxy composites with these fillers were investigated. The zirconia-impregnated HNTs (Zr/HNT) were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and tunneling electron microscopy (TEM). The hardening conditions of the epoxy composites were analyzed by differential scanning calorimetry (DSC). The thermal strength of the epoxy composites was studied by thermomechanical analysis (TMA) and micro-calorimetry and the mechanical strength of the epoxy composites (flexural strength and tensile strength) was studied by using a universal testing machine (UTM). The mechanical and thermal strengths of the epoxy composites with Zr/HNT were improved compared to those of the epoxy composite with HNT, and also increased as the zirconia loading on HNT increased.

Influence of calcination temperature on the activity of mesoporous CaO/TiO2\u2013ZrO2 catalyst in the esterification reaction

In the present study, the effect of calcination temperature on the structure and performance of mesoporous CaO/TiO2–ZrO2 catalyst fabricated by sol–gel method used in the esterification reaction was assessed. Then, CaO/TiO2 catalyst was also synthesized via the same method to evaluate the effect of zirconia cations on its properties and activity. The samples were characterized by X-ray Diffraction (XRD), Fourier transmittance infra-red (FT-IR), Brunauer–Emmett–Teller (BET)–Barrett-Joyner-Halenda (BJH), scanning electron microscope (SEM) and transmission electron microscopy (TEM) analyses. Moreover, Hammett indicator method was utilized to assess the acidity and basicity of the samples. It was found that zirconium was clearly incorporated in CaO/TiO2 lattice and transformed that from amorphous phase to crystalline structure. In addition, the basicity and acidity of CaO/TiO2 was clearly increased by zirconia loading. Evaluation of the samples’ activity presented that CaO/TiO2 catalyst exhibit no activity in the esterification reaction, while all CaO/TiO2–ZrO2 catalysts showed high ability to convert oleic acid to its ester. Moreover, the catalyst calcined at 400 °C showed the highest activity in the esterification reaction with desirable properties such as high crystallinity, acidity, basicity and surface area along with well-distribution of particle size and pore size. The best catalyst converted around 90% of oleic acid to ester at optimized conditions of 150 °C, 12:1 molar ratio of methanol/oleic acid, 3 wt% of catalyst for 4 h of reaction time. Moreover, the sample was successfully used for five runs without significant reduction in activity that makes it a suitable choice as a catalyst for industrial applications.Graphical abstract