Aluminum and Activated Alumina Powder Additions on Microwave Synthesis of Al_(4)SiC_(4)

Aiming at improving the properties of magnesia carbon materials,silicon aluminum carbide(Al_(4)SiC_(4))containing materials were prepared using industrial aluminum powder,silicon carbide powder,and graphite as raw materials,and activated alumina powder as an additive,mixing thoroughly,pressing into cylinders and then firing at 1200℃for 30 min in a carbon embedded atmosphere by the microwave method.The effects of the aluminum powder addition(20%and 24%,by mass)and activated alumina powder addition(0,3%,5%and 7%,by mass)on the microwave synthesis of Al_(4)SiC_(4) as well as the effect of the obtained Al_(4)SiC_(4) containing material on the properties of magnesia carbon bricks were studied.The results show that:compared with the samples with 20%aluminum powder,those with 24%aluminum powder generate more Al_(4)SiC_(4).With the activated alumina powder addition increasing from 0 to 7%,the amount of Al_(4)SiC_(4) generated increases first and then decreases.Compared with the sample without activated alumina powder,the samples with activated alumina powder show lower bulk density and higher apparent porosity.With the activated alumina powder addition increasing from 3%to 7%,the bulk density of the samples increases first and then decreases,while the apparent porosity of the samples shows an opposite trend.The optimal additions are 24%aluminum powder and 5%activated alumina powder,and Al_(4)SiC_(4) synthesized in this sample has a hexagonal plate structure.With the synthesized Al_(4)SiC_(4) containing material added,the magnesia carbon brick has slightly increased cold modulus of rupture,basically the same modulus of elasticity and improved oxidation resistance.

Mass-Based Environmental Factor and Energy Assessment of Microwave-Assisted Synthesized Transition Metal Nanostructures

This paper describes mass-based energy phase-space projection of microwave-assisted synthesis of transition metals (zinc oxide, palladium, silver, platinum, and gold) nanostructures. The projection uses process energy budget (measured in kJ) on the horizontal axes and process density (measured in kJg−1) on the vertical axes. These two axes allow both mass usage efficiency (Environmental-Factor) and energy efficiency to be evaluated for a range of microwave applicator and metal synthesis. The metrics are allied to the: second, sixth and eleventh principle of the twelve principle of Green Chemistry. This analytical approach to microwave synthesis (widely considered as a useful Green Chemistry energy source) allows a quantified dynamic environmental quotient to be given to renewable plant-based biomass associated with the reduction of the metal precursors. Thus allowing a degree of quantification of claimed “eco-friendly” and “sustainable” synthesis with regard to waste production and energy usage.

Scalable solid-phase synthesis of defect-rich graphene for oxygen reduction electrocatalysis

Defect-engineered carbon materials have been emerged as promising electrocatalysts for oxygen reduction reaction(ORR)in metal-air batteries.Developing a facile strategy for the preparation of highly active nanocarbon electrocatalysts remains challenging.Herein,a low-cost and simple route is developed to synthesize defective graphene by pyrolyzing the mixture of glucose and carbon nitride.Molecular dynamics simulations reveal that the graphene formation is ascribed to two-dimensional layered feature of carbon nitride,and high compatibility of carbon nitride/glucose systems.Structural measurements suggest that the graphene possesses rich edge and topological defects.The graphene catalyst exhibits higher power density than commercial Pt/C catalyst in a primary Zn-air battery.Combining experimental results and theoretical thermodynamic analysis,it is identified that graphitic nitrogen-modified topological defects at carbon framework edges are responsible for the decent ORR performance.The strategy presented in this work can be can be scaled up readily to fabricate defective carbon materials.

Microwave-Assisted Au and Ag Nanoparticle Synthesis: An Energy Phase-Space Projection Analysis

Microwave-assisted synthesis of gold and silver nanoparticles, as a function of Green Chemistry, non Green Chemistry, and four applicator types are reported. The applicator types are Domestic microwave ovens, commercial temperature controlled microwave chemistry ovens (TCMC), digesters, and axial field helical antennae. For each of these microwave applicators the process energy budget where estimated (Watts multiplied by process time = kJ) and energy density (applied energy divided by suspension volume = kJ·ml-1) range between 180 ± 176.8 kJ, and 79.5 ± 79 kJ·ml-1, respectively. The axial field helical field an-tenna applicator is found to be the most energy efficient (0.253 kJ·m-1 per kJ, at 36 W). Followed by microwave ovens (4.47 ± 3.9 kJ·ml-1 per 76.83 ± 39 kJ), and TCMC ovens (2.86 ± 2.3 kJ·m-1 per 343 ± 321.5 kJ). The digester applicators have the least energy efficiency (36.2 ± 50.7 kJ·m-1 per 1010 ± 620 kJ). A comparison with reconstructed ‘non-thermal’ microwave oven inactivation microorganism experiments yields a power-law signature of n = 0.846 (R2 = 0.7923) four orders of magnitude. The paper provides a discussion on the Au and Ag nanoparticle chemistry and bio-chemistry synthesis aspects of the microwave applicator energy datasets and variation within each dataset. The visual and analytical approach within the energy phase-space projection enables a nanoparticle synthesis route to be systematically characterized, and where changes to the synthesis are to be mapped and compared directly with historical datasets. In order to help identify lower cost nanoparticle synthesis, in addition to potentially reduce synthesis energy to routes informed changes to potentially reduce synthesis energy budget, along with nanoparticle morphology and yield.

Green Chemistry Allometry Test of Microwave-Assisted Synthesis of Transition Metal Nanostructures

Microwave irradiation is considered an important approach to Green Chemistry, because of its ability to rapidly increase the internal temperature of polar-organic compounds that lead to synthesis times of minutes rather than hours when compared to conventional thermal heating. This works describes a dual allometry test for the discrimination between the solvents and reagents used in the microwave-assisted synthesis of transition metal (zinc oxide, palladium silver, platinum, and gold) nanostructures. The test is performed in log-log process energy phase-space projection, where the synthesis data (kJ against kJ·mol-1) has a power-law signature. The test is shown to discriminate between recommended Green Chemistry, problematic Green Chemistry, and Green Chemistry hazardous solvents. Typically, recommended Green chemistry exhibits a broad y-axes distribution within an upper exponent = 1 and lower exponent = 0.5. Problematic Green Chemistry exhibits a y-axes narrower distribution with an upper exponent = 0.94 and lower exponent = 0.64. Non-Green Chemistry hazardous data exhibits a further narrowing of the y-axes distribution within upper exponent = 0.87 and lower exponent = 0.66. In all three cases, the y-axes is aligned to original database power-law signature. It is also shown that in the x-axes direction (process energy budget) the grouped order of magnitude decreases from four orders for recommended Green Chemistry solvent and reagent data, through two orders for non-Green Chemistry hazardous material and down to one order for problematic Green Chemistry.

Microwave-Assisted Transition Metal Nanostructure Synthesis: Power-Law Signature Verification

A power-law (y = cxn) signature between process energy budget (kJ) and process energy density (kJ·ml-1) of microwave-assisted synthesis of silver and gold nanostructures has been recently described [Law and Denis. AJAC, 14(4), 149-174, (2023)]. This study explores this relation further for palladium, platinum, and zinc oxide nanostructures. Parametric cluster analysis and statistical analysis is used to test the power-law signature of over four orders of magnitude as a function of six microwave applicator-types metal precursor, non-Green Chemistry synthesis and claimed Green Chemistry. It is found that for the claimed Green Chemistry, process energy budget ranges from 0.291 to 900 kJ, with a residual error ranging between −33 to +25.9 kJ·ml-1. The non-Green Chemistry synthesis has a higher process energy budget range from 3.2 kJ to 3.3 MJ, with a residual error of −33.3 to +245.3 kJ·ml-1. It is also found that the energy profile over time produced by software controlled digestion applicators is poorly reported which leads to residual error problematic outliers that produce possible phase-transition in the power-law signature. The original Au and Ag database and new Pd, Pt and ZnO database (with and without problematic outliers) yield a global microwave-assisted synthesis power-law signature constants of c = 0.7172 ± 0.3214 kJ·ml-1 at x-axes = 0.001 kJ, and the exponent, n = 0.791 ± 0.055. The information in this study is aimed to understand variations in historical microwave-assisted synthesis processes, and develop new scale-out synthesis through process intensification.

Microwave direct synthesis and thermoelectric properties of Mg_(2)Si by solid-state reaction

In order to reduce the oxidation and volatilization caused by Mg element in the traditional methods for synthesizing Mg2Si compounds,Mg2Si thermoelectric materials were prepared by solid state reaction and microwave radiation techniques.Structure and phase composition of the materials were investigated by X-ray diffraction.The electrical conductivity,Seebeck coefficient and thermal conductivity were measured as a function of temperature from 300 to 700 K.It is found that high purity Mg2Si powders can be obtained with excessive content of 8% Mg from the stoichiometric Mg2Si at 853 K and 2.5 kW for 30 min.A maximum dimensionless figure of merit,ZT,of about 0.13 was obtained for Mg2Si at 600 K.

ResearchonS202一／Zr02solidsuperacidinsynthesisofn—amylacetateundermicrowaveradiation

采用沉淀一浸渍法制得S2O62 8-／ZrO2固体超强酸，在微波辐射下催化合成乙酸正戊酯。通过单因素实验和正交实验优化了合成的反应条件；采用Hammett指示剂法、BET法、红外光谱、电子透镜技术和x_射线衍射对其进行了表征。实验结果表明，采用最佳制备条件下得到的催化剂在微波辐射下催化合成乙酸正戊酯的最优合成条件为：醇酸摩尔比1．9：1，反应温度135℃，反应时间25min，催化剂用量1．2g，功率500W，收率为97．8％。该工艺具有绿色、安全、操作简单和收率高等优点。

Microwave synthesis of Li_2FeSiO_4 cathode materials for lithium-ion batteries

A novel synthetic method of microwave processing to prepare Li2FeSiO4 cathode materials is adopted. The Li2FeSiO4 cathode material is prepared by mechanical ball-milling and subsequent microwave processing. Olivin-type Li2FeSiO4 sample with uniform and fine particle sizes is successfully and fast synthesized by microwave heating at 700 ℃ in 12 rain. And the obtained Li2FeSiO4 materials show better electrochemical performance and microstructure than those of Li2FeSiO4 sample by the conventional solidstate reaction. ？2009 Yan Bing Cao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Preparation and characterization of Eu^(3+)-doped CaCO_3 phosphor by microwave synthesis

A Eu^3＋-doped CaCO3 phosphor with red emission was prepared by microwave synthesis. The scanning electron microscopy （SEM） image and laser particle size analysis show that the CaCO3：Eu^3＋ particles are needle-like in the length range of 5.0-10.0 μm. The results of X-ray diffraction （XRD） analysis, Fourier transform infrared spectroscopy （FT-IR）, and Raman spectroscopy indicate that pure aragonite CaCO3：Eu^3＋ is prepared using microwave irradiation and the Eu^3＋ ion as a luminescence center inhabits the site of Ca^2＋. The photoluminescence excitation （PLE） spectrum shows that the strong broad band at around 270 nm and weak sharp lines in 300-550 nm are assigned to the charge transfer band of Eu^3＋-O^2- and intra-configurational 4f-4f transitions of Eu^3＋, respectively. The photoluminescence （PL） spectrum implies that the red luminescence can be attributed to the transitions from the ^5D0 excited level to the ^7FJ （J = 0, 1, 2, 3, 4） levels of Eu^3＋ ions with the mainly electric dipole transition ^5D0 → ^7F2 （614 and 620 nm）, and the Eu^3＋ ions prefer to occupy the low symmetric site in the crystal lattice.

Microwave-assisted synthesis of asymmetric thiocarbonohydrazones under solvent-free conditions

Six new asymmetric thiocarbonohydrazones 3a-3f were synthesized from following steps： firstly hydrazine hydrate reacted with carbon disulfide to form thiocarbonohydrazide （1） under microwave irradiation. Then compound （1） reacted with ketone and different aldehydes step by step to give 3a-3f with excellent yields under solvent-free conditions using microwave irradiation. Their structures have been determined by elemental analysis, IR, MS and ^1H NMR data. 2009 Qing Han Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Synthesis Yttrium Aluminum Garnet Precursor via Homogeneous Precipitation under Microwave Irradiation

The lowly-agglomerated single-phase YAG nanopowders were synthesized for the first time by the microwave homogeneous precipitation in the presence of urea. The composition and transformations during calcination of YAG precursor were analyzed by IR, DTA/TG and XRD. The size and morphology of YAG powders were characterized by LD and TEM methods. Results show that amorphous precursor synthesized under [urea]/[metal ions] molar ratio of 15 crystallizes directly to single-phase YAG at 900degreesC. The size distribution and sinterability of YAG powders are obviously improved by adding (NH4)(2)SO4 into the reaction solution. YAG powders obtained from precursor with the (NH4)(2)SO4 content of 8% have good sinterability and are highly densified at a temperature of 1500degreesC

Fast, green microwave-assisted synthesis of single crystalline Sb_2Se_3 nanowires towards promising lithium storage

In this work, a fast(0.5 h), green microwave-assisted synthesis of single crystalline Sb_2Se_3 nanowires was developed. For the first time we demonstrated a facile solvent-mediated process, whereby intriguing nanostructures including antimony selenide(Sb_2Se_3) nanowires and selenium(Se) microrods can be achieved by merely varying the volume ratio of ethylene glycol(EG) and H_2O free from expensive chemical and additional surfactant. The achieved uniform Sb_2Se_3 nanowire is single crystalline along [001]growth direction with a diameter of 100 nm and a length up to tens of micrometers. When evaluated as an anode of lithium-ion battery, Sb_2Se_3 nanowire can deliver a high reversible capacity of 650.2 m Ah g^(-1) at 100 mA g^(-1) and a capacity retention of 63.8% after long-term 1000 cycles at 1000 mA g^(-1), as well as superior rate capability(389.5 m Ah g^(-1) at 2000 mA g^(-1)). This easy solvent-mediated microwave synthesis approach exhibits its great universe and importance towards the fabrication of high-performance metal chalcogenide electrode materials for future low-cost, large-scale energy storage systems.

Electrical Properties and Microwave Synthesis of Mixed Rare Earth Oxide Ln_(0.7)Sr_(0.3-x)Ca_xCo_(0.9)Fe_(0.1)O_(3-δ)

In order to lower the raw materials cost and develop a novel cathode materials for intermediate temperature solid oxide fuel cell(ITSOFC), using mixed rare earth replacing the expensive pure La2O3 as the raw materials, the powders of Ln0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(Ln = the mixed rare earth, x =0.05, 0. 10, 0. 15) for the applications as the cathode materials were prepared by microwave sintering process. The crystal structure and the particles morphology of the obtained powders were characterized by XRD and SEM, the electrical conductivity of all samples sintered at 1200℃for 3 h was also measured as the function of the temperature from 100 to 800℃by DC four-probe method in air. The experimental results show that due to the influence of mixed rare earth the powders of Ln0.7Sr0.3-xCaxCo0.9Fe0.1O3-δsynthesized at 1200℃for 0.5 h with the mean particle size of 1 ~ 20μm was of perovskite and cubic fluorite phase as well a little SrO phase, the electrical conductivity of the samples decreases with the adding Ca2+ content, and are all higher than 100 S·cm -1from 500 to 700℃when x≤0.10. Ln0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ. can meet the demand of the electrical properties for the cathode materials in ITSOFC.

Microwave Hydrothermal Synthesis PZT of Nanometer Crystal

It was focused on the applications and developments of microwave hydrothermal synthesis piezoelectric ceramic powder. The microwave hydrothermal vessel was designed and manufactured. The microwave hydrothermal synthesis system was established and the PZT piezoelectric ceramic powder was synthesized. XRD and TEM have been used to characterize the products in detail. The diameter of the PZT powder particle is from 40 to 60 nm.

Synthesis of a highly hydrophobic cyclic decapeptide by solid-phase synthesis of linear peptide and cyclization in solution

A general method was described to synthesize a highly hydrophobic cyclic peptide,cyclo[LWLWLWLWLQ]where underlines indicate D-configuration of the amino acid,by a two-step solid-phase/solution synthesis strategy.The linear decapeptide was assembled by standard Boc chemistry on solid-phase and subsequently cyclized in solution with high efficiency and reproducibility. In subsequent purification by semi-preparative HPLC,50%(v/v) DMF/H_2O was employed as the solvent to overcome the difficulty of solubilization...

Rapid Synthesis of Submicrometer-sized Red Phosphor CaS∶Cu^+,Eu^( 2+) in a Microwave Field

The red phosphor materials CaS∶Cu+,Eu 2+ were firstly synthesized in a microwave field, and characterized by XRD、SEM、fluorescent spectroscopy. The experimental results of XRD and SEM show that the phosphors of CaS∶Cu+,Eu 2+ possess a spherical crystallite structure, in the submicrometer(250～500 nm) size range. Compared to the conventional high temperature solid state reaction this new synthetic technique exhibits interesting features, such as rapid reactions without other protective atmosphere,phosphors with high purity, smaller particles,and higher efficient luminescence.

Solvent-Free Synthesis of Ultrafine Tungsten Carbide Nanoparticles-Decorated Carbon Nanosheets for Microwave Absorption

Carbides/carbon composites are emerging as a new kind of binary dielectric systems with good microwave absorption performance.Herein,we obtain a series of tungsten carbide/carbon composites through a simple solvent-free strategy,where the solid mixture of dicyandiamide(DCA)and ammonium metatungstate(AM)is employed as the precursor.Ultrafine cubic WC1-x nanoparticles(3-4 nm)are in situ generated and uniformly dispersed on carbon nanosheets.This configuration overcomes some disadvantages of conventional carbides/carbon composites and is greatly helpful for electromagnetic dissipation.It is found that the weight ratio of DCA to AM can regulate chemical composition of these composites,while less impact on the average size of WC1-x nanoparticles.With the increase in carbon nanosheets,the relative complex permittivity and dielectric loss ability are constantly enhanced through conductive loss and polarization relaxation.The different dielectric properties endow these composites with distinguishable attenuation ability and impedance matching.When DCA/AM weight ratio is 6.0,the optimized composite can produce good microwave absorption performance,whose strongest reflection loss intensity reaches up to-55.6 dB at 17.5 GHz and qualified absorption bandwidth covers 3.6-18.0 GHz by manipulating the thickness from 1.0 to 5.0 mm.Such a performance is superior to many conventional carbides/carbon composites.