High Energy Planetary Ball Mill Research Articles

Synthesis of rGO-reinforced MgAl2O4 spinel composites by solid-state powder route mechanism: A comparative analysis between non-reinforced and rGO-reinforced spinel composites

Reduced Graphene Oxide (rGO)-reinforced MgAl2O4 spinel composite was successfully synthesized by a solid-state powder route mechanism via high-energy planetary ball milling of corresponding metal oxide precursors followed by a high-temperature single-stage sintering process. The effect of rGO on the homogeneity, phase development, morphology, chemical composition, rate of formation of spinel, and cation anti-site formation of the composites was methodically investigated. For comparison, a stoichiometric non-reinforced MgAl2O4 spinel was also synthesized. The addition of 0.2 wt% and 0.4 wt% of rGO as reinforcement increased the homogeneity of the ball-milled composite powder, with Polydispersity Index (PDI) values of 0.19 and 0.15 respectively, as compared to 0.24 obtained in non-reinforced spinel composite. The X-ray diffraction pattern and IR spectrum of 1650 °C sintered composites confirmed the formation of highly crystalline phases with spinel structure. The microstructural analysis revealed that the addition of rGO led to a reduction in porosity and improved the process of sintering. Calorimetric studies showed that spinelization started to occur at 858 °C and 880 °C for 0.2 wt% and 0.4 wt% rGO-reinforced composites respectively, which was faster than non-reinforced composite. 27Al solid-sate nuclear magnetic resonance (SS-NMR) analysis depicted that ceramic composite reinforced with rGO exhibited lesser inversion parameter of 0.09 (for 0.2 wt% rGO) and 0.055 (for 0.4 wt% rGO), as compared to 0.145 obtained in non-reinforced composite, indicating lesser cation anti-sites formation in rGO-reinforced spinel composite.

Effect of milling time on structural, mechanical and tribological behavior of a newly developed Ti-Ni alloy for biomedical applications

Ti-Ni alloy is the most attractive material in the medical field for orthopedic implants like total hip replacement due to its special properties. The purpose of this study was to examine the impact of grinding/milling times on the characteristics of the nanostructured Ti50-Ni50 alloys produced via the mechanical alloying process (MA), utilizing a planetary high-energy ball mill at different grinding times (2, 6, 12, and 18 h). The grinding time causes grain refinement and a decrease in the porosity of materials, which allows for the improvement of a material’s mechanical properties and wears resistance. The structural, physical and tribological behavior of Ti50-Ni50 alloy was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), nanoindentation test, and ball-on-disk tribometer operated under varying applied loads of 2, 10, and 20 N. The findings demonstrated that the crystallite size was reduced and the microstrain increased reaching values of 29 nm, and 0.99%, respectively, at higher grinding times. The percentage of porosity in the Ti50-Ni50 alloy was 11%, while the density attained was 89% after 18 h of grinding. Moreover, as the grinding duration increased up to 18 h, the hardness increased (341 HV) owing to the refinement of the grains. It was also noted that the Ti50-Ni50 alloy that was milled at 2 h exhibited the lowest elastic modulus (89 GPa). In addition, it was found that wear rates and the coefficient of friction were decreased reaching the values of 29.67 µm3/N.μm, and 0.31, respectively, for the samples milled at 18 h and examined under 2 N. Enhanced structural and mechanical qualities are responsible for this improvement in tribological properties. These properties make Ti50-Ni50 alloys clinically relevant for human biomedical implantation.

Enhancing RDX Thermal Decomposition in Al@RDX Composites with Co Transition Metal Interfacial Layer

In this study, an Al/Co@RDX composite was meticulously prepared through a combination of planetary high-energy ball-milling and a spray-drying technique. The thermal reactivity of these Al/Co@RDX composites was comprehensively investigated and compared using the TG/DSC technique. It is shown that the initial decomposition temperature of RDX in the DSC curve was decreased by 26.3 °C in the presence of Al/Co, which could be attributed to the nano-sized Co transition metal catalyzing the decomposition reaction of nitrogen oxides in RDX decomposition products. The decomposition peak temperature of RDX and the heat released by the thermal decomposition of RDX in the Al/Co@RDX composite were decreased by 26.3 °C and increased by 74.5 J·g−1, respectively, in comparison with those of pure RDX. The types of major gaseous products released from Al/Co@RDX were found to be identical to those of pure RDX, encompassing N2O, CH2O, CO2 and HCN. However, the concentrations of those gaseous products for Al/Co@RDX were higher than those observed for pure RDX, which may owe to the fact that the Al/Co composite can interact with the –CH2 and –NO2 within RDX molecules, which leads to the weakening of the C-N and N-N bonds. In addition, the decomposition of RDX in the Al/Co@RDX composite was observed as a one-step process with an apparent activation energy (Ea) of 115.6 kJ·cm−3. The decomposition mechanism of the RDX in the Al/Co@RDX composite was identified to follow the chain scission model (L2), whereas the two-step decomposition physical models observed for pure RDX were found to closely resemble the L2 and autocatalytic models.

All solid-state fabrication strategy of CdS@ZnS nanocomposites and their photocatalytic performance in water purification

Herein a systematic study of two-step solid-phase synthesis of CdS@ZnS nanocomposites and their photocatalytic activity is presented. First, CdS nanoparticles were synthesized in a planetary ball mill through a solid-state ion exchange reaction. In the second step, Cd2+ ions were partially replaced by Zn2+ ions at the surface of the nanoparticles using solvent free long-term activation in a high-energy planetary ball mill. The optimal activation time in a ball mill was determined to be 45 min. Spherical CdS nanoparticles with a diameter of 10 nm and modified CdS@ZnS (45 min) nanocomposites were characterized by X-ray diffraction analysis, Raman and UV-vis spectroscopy, and scanning electron microscopy. The ability of nanocomposites for photocatalytic water purification was tested on the degradation of the model organic dye Orange II in an aqueous solution under the visible light irradation. The modified CdS@ZnS nanocomposites showed higher photocatalytic activity compared to the original CdS nanoparticles.

NiO:Cu+2 mesoporous nanoparticles with enhanced oxidative sonophotocatalytic performance for visible-light driven organic pollutants remediation

Mesoporous nickel oxide nanostructures were synthesized using a solvothermal method. and then doped with Cu2+ via high energy planetary ball milling technique. crystallinity, morphology, porosity, size, and composition of the nanoparticles were evaluated using XRD, BET, TEM, and EDX techniques. The as-prepared doped nanoparticles were used for the first time in the oxidative sonophotocatalytic removing of organic pollutants in low-frequency and low-energy ultrasound waves at room temperature in the presence of visible light. After 60 min of double irradiation (ultrasound + Visible light) in the presence of doped nanoparticles, more than 86 % of the pollutants were removed; reaching a constant rate of 0.0363 min−1. integration ultrasonic and visible light in the oxidative sonophotocatalytic remediation process resulted in a synergistic effect of about 72 %. Above all, the results showed the high reusability and stability of the doped nanoparticles in consecutive runs with minor fading in their sonophotocatalytic performance. To investigate the mechanism, the performance of the oxidative sonophotocatalytic removing process was examined by the addition of different types of trapping and enhancer agents. Finally, the generality of the process was evaluated by the remediation of commercially available antibiotics from water.

Prediction of Wear Characteristics for Al-MnO2 Nanocomposites using Artificial Neural Network (ANN)

An Artificial Neural Network (ANN) model was developed to investigate the impact of various ball milling parameters on the wear characteristics of Al-MnO2 nanocomposites. The process involved the synthesis of nano-sized particles through a high-energy planetary ball milling process, followed by the fabrication of nanocomposites using the stir casting method. The synthesized nanoparticles are characterized using X-Ray diffraction (XRD), and the nanocomposites are examined through scanning electron microscopy. To evaluate the wear behavior of the nanocomposites, a pin-on-disc test is conducted, generating a data set used for training the ANN model. The primary objective was to predict the wear rate of the synthesized Al-MnO2 nanocomposites using the ANN. Upon comparing the ANN's predictions with actual experimental results, it became evident that a well-trained ANN model proved to be a highly effective tool for estimating the wear rate of Al-MnO2 nanocomposites.

Corrosion Resistance of Fe-Cr-Si Alloy Powders Prepared by Mechanical Alloying

Powders with nanometric crystallites of two ternary alloys Fe0.90Cr0.05Si0.05 and Fe0.85Cr0.10Si0.05 were prepared by mechanical alloying (MA) in a planetary high-energy ball mill at various milling times followed by annealing in a vacuum at 900 K to induce an oxygen-induced surface segregation of Cr and Si atoms. The prepared powders were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The obtained results show that all prepared powders crystallize in the body-centered cubic structure and are composed of micrometric particles, which are polycrystalline and consist of many nanometric crystallites. The mean size of the particles as well as the crystallites decreases progressively with milling time. In order to study the anti-corrosion properties of the obtained materials, the powders were exposed to atmospheric gases at 870 K. After each oxidation step, the formation of iron oxides was investigated using 57Fe transmission Mössbauer spectroscopy (TMS). It was found that the powders of Fe0.90Cr0.05Si0.05 and Fe0.85Cr0.10Si0.05 obtained after 10 and 20 h of MA are extremely resistant to oxidation. This result can be connected with the fact that XPS measurements reveal a high concentration of Cr and Si atoms on the surface of powder particles.

An investigation of microstructural basis for corrosion behavior of Al-CNT composites fabricated by SPS

In this research effect of the addition of multi-wall carbon nanotubes (MWCNTs) as additive powder on microstructure and corrosion behavior of fabricated Al-CNT composites was studied. The aluminum powder and CNTs were mixed with high energy planetary ball-mill. It is observed that by increasing milling time, the uniformity of CNTs on aluminum matrix and consequently corrosion resistance of Al-CNT composite is increased. On the other hand, by increasing the volume percentage of CNTs, the uniformity of CNTs on aluminum matrix and corrosion resistance of fabricated Al-CNT composite is reduced. The value of polarization resistance, Rp, for fabricated composites with 2 % CNT is improved from 1.28 to 3.60 Ω/cm2 by increasing milling time. Also, the value of Rp for fabricated composites with 4 h milling time, is reduced from 3.60 to 2.76 Ω/cm2 by increasing the percentage of CNTs from 2 % up to 5 %. Moreover, Cyclic Polarization results showed that the pitting corrosion resistance improves by increasing milling time and deteriorates by increasing the percentage of CNTs. The electrochemical impedance spectroscopy (EIS) results showed that the corrosion mechanism of Al-CNT composites is a combination of uniform and pitting corrosion. Indeed, the CNTs act as preferred cathode regions and cause to formation of micro galvanic couples. The Al-2%CNT-4 h showed better uniformity and the highest corrosion resistance. The Al-5%CNT-2 h presented non-uniform distribution of CNTs and the lowest corrosion resistance.

Particle size-dependent structural and magnetic properties of Pr0.6-xBixSr0.4MnO3 (x = 0.10 and 0.25)

Nanoparticles of Pr0.6-xBixSr0.4MnO3 (x = 0.10 and 0.25) have been prepared using the swift and cost-effective top-down approach in a high-energy planetary ball mill without any chemical processing and environmental impacts resulting due to pollutants arising from nanoparticle synthesis. The work investigates the role of particle size reduction on the structural and magnetic properties. An increase in milling time from 0 to 240 min results in the drastic reduction of particle size which drops significantly in the initial phase of ball milling i.e., 0–60 min while the microstrain and dislocation densities show nearly monotonic increase. Interestingly the magnetism and size reduction demonstrate a clear one to one correspondence. In both compositions, the paramagnetic (PM) to ferromagnetic (FM) transition, TC decreases and the magnetic transitions broaden both as function Bi and size reduction. The Curie–Weiss analysis of the inverse magnetic susceptibility ({chi }^{-1}) shows a deviation from linearity indicating the presence of the short-range FM interactions above TC which has been understood as Griffith’s phase like singularity. The size reduction can effectively reduce TC, enabling a significant control over tuning of transition temperature and net magnetization. The field dependent magnetization for x = 0.10 demonstrate dominant FM state whereas for x = 0.25, metamagnetic magnetization highlights competitive coexistence of FM and antiferromagnetic (AFM) interactions in the system. With ball milling, the net magnetization decreases, and the metamagnetic behaviour is suppressed. The M–H loops of ball milled nanoparticles are highly unsaturated indicating the enhanced surface disorder in the nanoparticles which can be understood using the core–shell structure.

Electrochemical Determination of Ascorbic Acid by Mechanically Alloyed Super Duplex Stainless Steel Powders

SAF-2507 super duplex stainless steel powders (SDSS) were prepared using a high-energy planetary ball milling process. The X-ray diffraction (XRD) shows peak broadening after 20 h of ball milling and revealed a phase transformation resulting in a two-phase alloy mixture containing nearly equal amounts of ferrite (α) and austenite (γ). After 20 h of ball milling the particle size was reduced to ~201 nm. Scanning electron microscope (SEM) micrographs showed small-size irregular grains with an average particle size ranging from 5–7 µm. The high-resolution transmission microscope (HRTEM) analysis confirmed the presence of nanocrystalline particles with sizes ranging from 10 to 50 nm. The presence of ferrite phase is visible in the corresponding diffraction pattern as well. In this paper, we have discussed the electrochemical sensor application of mechanically alloyed nano-structured duplex stainless steel powders. The fabricated 4 mg duplex stainless steel modified carbon paste electrode (SDSS-MCPE) has shown excellent current sensitivity in comparison with 2, 6, 8, and 10 mg SDSS-MCPEs during the detection of ascorbic acid (AA) in a phosphate buffer solution with a pH of 6.8. The calculated electrode active surface area of SDSS-MCPE was found to be almost two times larger than the surface area of the bare carbon paste electrode (BCPE). The limit of detection (LD) and limit of quantification (LQ) were found to be 0.206 × 10−8 M and 0.688 × 10−8 M, respectively, for the fabricated 4 mg SDSS-MCPE.

Nitrogen-Doped Titanium Carbide (Ti3 C2 Tx ) MXene Nanosheet Stack For Long-Term Stability and Efficacy in Au and Ag Recovery.

The development of efficient adsorbents for the practical recovery of precious metals from electronic waste is vital to advanced energy/environment industries. Ti3 C2 Tx MXene-based materials are promising adsorbents for aqueous environments; however, the highly defective and super hydrophilic nature of the MXene surface hinders its practical applications. Here,wereport that nitrogen-doped MXene (N-MXene) nanosheet stacks, prepared via high-energy planetary ball milling under N2 purging, exhibited a long-term stable and excellent recovery capability for Au and Ag ions via the nitrogenation of defective vacancies. Notably, these microscale nanosheets could facilitate the sustainable production of Au and Ag from secondary sources, exhibiting a high recovery rate and capability (1198 mg g-1 for Au and 1528 mg g-1 for Ag), long-term stable storability (21 d), and high selectivity (Kd of 1.67 × 106 for Au and 2.07 × 107 for Ag). Furthermore, the reversible redox chemistry of N-MXene facilitated its repeated use in adsorption/desorption cycles.

Crystallographic and magnetic analysis of ordered-disordered Ni51Mn34Sn15 Heusler alloy obtained by mechanical alloying and annealing

Ni51Mn34Sn15 Heusler alloy was prepared from elemental powders in a high energy planetary ball mill under argon atmosphere for milling times up to 10 h. Alloy formation was checked by X-ray diffraction, and by the means of the Rietveld method, the amount of phases was computed. It was found that by mechanosynthesis, B2 disordered structure was formed after 8 h of milling containing high lattice strains. By scanning electron microscopy, the morphology of the powders through the obtaining process was followed. The elemental powders degree of homogenization and distribution versus milling time was investigated by energy dispersive X-ray spectroscopy. The decrease of the magnetization with alloy formation was observed in connection with the disordered phase formation. Low and short temperature annealing was found to have an important influence on the alloy ordering to L21 structure and to enhance magnetic properties up to a value comparable with the arc-melted sample. The Curie temperature was found to be depended on the iron contamination occurred during milling and an ordering temperature of 60 °C was measured for the phase with L21 structure.

Non-doped phosphor for WLED with high CRI and R9

The effect of the ZnO/SnO2 ratio on phase formation and optical properties of the Zn-Sn-O compound was investigated by varying the ZnO/SnO2 molar ratio (ZnO/SnO2 = 1:2, 1:1, 2:1, 3:1, and 4:1). All samples were synthesised with high-energy planetary ball milling, followed by calcination at 1000 °C in the air. The result from X-Ray diffraction patterns (XRD) shows that the single-phase Zn2SnO4 is achieved at the ZnO/SnO2 ratio of 2:1. Whereas, the mixed phase of ZnO and Zn2SnO4 formed when ZnO is more than SnO2 (3:1 and 4:1). On the other hand, the XRD patterns of the products obtained at a ratio where SnO2 is more than ZnO present a mixture of SnO2 and Zn2SnO4. The photoluminescence of the two samples with the ratio of 2:1 and 1:3 gives full-visible range spectra from 400 to 800 nm, which are in the blue-far-red region centred at about 514, 580, and 690 nm. Temperature-dependent luminescence measurements were also carried out in this work, and the results indicate that the prepared phosphor Zn-Sn-O at the ZnO/SnO2 ratio of 1:2 has thermal stability. The obtained material was used to coat near UV LED chips, and the WLED possesses the highest CRI of 95. The SnO2-Zn2SnO4 powder can be used as a phosphor for WLED applications with high CRI and R9.

Study of the Mechanism of Dearsenification of Arsenopyrite Enhanced by Mechanically Modified Pyrite and Bacteria

This study investigated the impact of mechanically modified pyrite on the dearsenification of arsenopyrite through bacterial oxidation. Pyrite was mechanically modified using a planetary high-energy ball mill, and the resulting changes in the crystal structure were characterized using particle size analysis, specific surface area measurements, scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD). Pearson correlation analysis was employed to examine the relationship between the crystal structure of modified pyrite and the bacterial oxidation of arsenopyrite. The study also investigated the mechanism of arsenic removal using pyrite with varying degrees of mechanical modification during arsenopyrite bio-oxidation. The key findings are as follows: (1) The maximum extent of arsenopyrite dearsenification by bacteria was achieved at a pyrite modification degree of 400 r·min−1 and reached 96.01%, which was 14.49% higher than that for unmodified pyrite and 24.13% higher than that in the absence of pyrite. At this degree, the modified pyrite exhibited a median diameter of 1.33 μm (minimum) and a specific surface area of 3123 m2·kg−1 (maximum). (2) Pearson correlation analysis revealed a significant negative correlation between the extent of arsenopyrite dearsenification and the particle size and grain size of pyrite, and a significant positive correlation with the specific surface area and the amorphous degree of pyrite. A smaller particle size and grain size, larger specific surface area, and a higher amorphous degree were associated with a higher extent of dearsenification. (3) The mechanism of enhanced arsenopyrite dearsenification using mechanically modified pyrite was attributed to autocatalytic dissolution. The galvanic effect directly enhanced dearsenification, while the mechanical modification facilitated the direct oxidation of pyrite by bacteria, releasing a significant amount of Fe3+ and indirectly enhancing the dearsenification of arsenopyrite.

Size effect on magnetism and large magnetocaloric effect of Haldane chain antiferromagnet Er2BaNiO5

We investigated the size effect on magnetocaloric effect (MCE) of Haldane spin-chain antiferromagnet Er2BaNiO5. The bulk sample was prepared by solid state route and the nano-size samples (N-4 h, N-8 h) were produced by using the high-energy planetary ball mill machine. The crystal structure was obtained by the refinement of XRD results and the SEM images. The present magnetization results indicated that the decreasing of average crystallite size induced enhancement of magnetization and paramagnetic-like behavior. The zero-approaching of θp values for N-8 h revealed the suppression of the dominant antiferromagnetic (AFM) interactions in bulk sample. The fitting results of Haldane gap stated clearly its dramatical reduction which is consistent with the weaken of magnetic interactions. The size effect also presented great influence on MCE. The negative MCE in bulk sample disappeared and instead of monotonically increasing of MCE in N-4 h and N-8 h samples. The maximum entropy change (-ΔSmax) of N-8 h increased nearly 3.2 times compared to bulk sample. The increasing of PM ions in nano-samples were verified by the ESR results, in which the bulk sample showed unavailable ESR signals due to the complex competing 3D AFM interactions. While for the nano-samples, the ESR signals of Er3+ and Ni2+ ions were observed with the g value of gEr = 6.1 and gNi = 2.28. The size-effect on MCE in Er2BaNiO5 opened new approach of the research on magnetic refrigeration.

Manufacturing of Novel Nanostructured TiCrC Carbides Using Mechanical Alloying and Spark Plasma Sintering

Dense nanostructured carbides existing in ternary system Ti-Cr-C were elaborated thanks to a two-steps method. In the first step, nanostructured Ti0.9Cr0.1C carbides were prepared by high-energy planetary ball milling under various times (5, 10, and 20 h), starting from an elemental powder mixture of titanium, chromium, and graphite. In the second step, these nanostructured powders were used to produce densified carbides thanks to the spark plasma sintering (SPS) process under a pressure of 80 MPa. The temperature was fixed at 1800 °C and the holding time was fixed at 5 min. Microstructural characteristics of the samples were investigated using X-ray diffraction (XRD). Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX) was used to investigate the morphology and elemental composition of the samples obtained using SPS. The novelty of this work is to understand the effect of SPS on the microstructural and electrochemical properties of the nanostructured Ti0.9Cr0.1C carbides. The XRD results showed that, during sintering process, the (Ti,Cr)C carbide was decomposed into TiC, Cr7C3, and Cr3C2 phases. An amount of iron was detected as contamination during milling, especially in the case of a sample obtained from 20 h milled carbide. The bulk obtained from the milled powders for 5 and 20 h present similar relative densities of 98.43 and 98.51%, respectively. However, the 5 h milled sample shows slightly higher hardness (93.3 HRA compared to 91.5 HRA) because of the more homogeneous distribution of the (Ti,Cr)C phases and the low iron amount. According to the 0.0011 mm/year corrosion rate and 371.68 kΩ.cm2 charge transfer resistance obtained from the potentiodynamic polarization and EIS tests, the 20 h carbide was the specimen with the highest corrosion resistance.

Milling route for the synthesis of nano-aluminium hydroxide for the development of low-density polymer composites

Abstract High loadings of coarse alumina trihydrate (ATH), commercially used in polymers as a fire-retardant filler, cause uneven dispersion and reduce workability and affect physicomechanical properties. Better tensile properties can be achieved by uniform dispersion of nanosize ATH in polymers while maintaining its flame-retardant properties. Consequently, mechanical milling, being a sustainable approach towards the creation of nano-size materials, was carried out to reduce the particle size of coarse ATH in a high-energy planetary ball mill. Investigations were carried out to optimize the milling parameters such as time, rotational speed, milling media size and feed size. During milling, some of the physical properties of ATH change. The energy profile was studied to get the desired product properties. Nano-ATH within the PP matrix reduces the loadings with improvement in tensile and flexural strength. Hence, lightweight PP/nano-ATH composites for suitable use can be developed.

The effect of mechanical activation duration on the structure and physical properties of titanium slag

TiO2 is popular in modern industries, including dyestuffs, printing, and cosmetics. To convert titanium slag to TiO2 with maximum efficiency, mechanical activation is an important pretreatment step to control the particle size of the titanium slag and the subsequent leaching process. Our study used a planetary high-energy ball mill to wet the titanium slag by mechanical activation for 3, 9, and 15 h to obtain the optimized condition for particle size control of the pretreated titanium slag. The phase composition was characterized by XRD, FT-IR, and Raman spectroscopy. The main constituents of the titanium slag were determined to be rutile TiO2 and Fe3Ti3O10. Calculating the relative intensity showed that some encapsulated phases were opened because of mechanical activation. The weight and density of titanium slag in the same volume increased, resulting in significantly enhanced peaks. The results can greatly improve the efficiency of subsequent titanium dioxide production. A laser particle size analyzer and SEM characterized the mechanical activation product. The results showed that when the mechanical activation duration is 15 h, the titanium slag obtained has a small particle size and a uniform, smaller specific surface area, and narrow particle size distribution. The current report has not introduced wet grinding to pretreat titanium slag. This simple method can be effectively applied to pre-treat titanium slag raw materials.

Study of nanostructural and non-adiabatic small polaron hopping conduction in nanostructured Bi2O3 - Fe2O3 – BaTiO3

The nanostructured samples of BFBT were synthesized by mixing a stoichiometric ratio of the reactants (Bi2O3 - Fe2O3 – BaTiO3) in a high-energy planetary ball mill system. The mixture was mechanically milled for 1, 2, 5, and 10 h. Structural characterization of the mechanosynthesized powder for 5h followed by heat-treatment at 673, 873, and 1073K for 5 h has been investigated through the X-ray diffraction technique. After 5 h of mechanical milling and heat-treatment at 873K for 5 h, HRTEM confirmed the nanostructure of BFBT two samples with an average particle size of 14.79 and 49.77 nm, respectively. The effect of the heat-treatment temperature of nanostructured BFBT samples on their conductivity is studied in conformity with Mott’s theory. The measurements of electrical conductivity and thermoelectric power show the semiconductor behavior of the prepared samples. The increase in crystal size of the heat-treated nanostructured BFBT samples decreases the grain boundaries, leading to the conductivity enhancement. The conduction was predominantly caused by electronic transport between Fe ions, which revealed the non-adiabatic SPH. The hopping carrier mobility was found to be the primary factor for determining the conductivity in the nanostructured BFBT system. The Greaves model for variable range hopping (VRH) was investigated for the prepared samples.

Reducing the diffusion barriers of Pt/Beta catalyzed n-hexane isomerization by SBA-15 addition and high-energy milling

Aiming at improving reaction selectivity of zeolite Beta-catalyzed isomerization of normal alkane, we reported a facile but efficient route to prepare the Beta@SBA-15 composite supports with low surface diffusion barriers in isomers formation from normal alkane. Microporous Beta zeolite and mesoporous SBA-15 zeolite were physically mixed and milled by high-energy planetary ball-mill. The addition of SBA-15 and milling, which have little effect on the acid properties of Beta zeolites, disaggregate the Beta particles and anchor the Beta nanocrystals on the surface of SBA-15 mesostructure. The apparent diffusivities of 2-methyl pentane measured by zero-length column method increased by 50%. n-Hexane isomerization tests show that the Pt/Beta@SBA-15 catalysts exhibit much higher selectivity to isomers, especially the dibranched isomers and lower selectivity to cracking reaction, owning to the reduced transport limitation of composite supports.