scholarly journals Preparation of Silicon Hydroxyapatite Nanopowders under Microwave-Assisted Hydrothermal Method

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1548
Author(s):  
Zully Matamoros-Veloza ◽  
Juan Carlos Rendon-Angeles ◽  
Kazumichi Yanagisawa ◽  
Tadaharu Ueda ◽  
Kongjun Zhu ◽  
...  
Keyword(s):  
Microwave Heating ◽  
Self Assembly ◽  
Hydrothermal Process ◽  
Particle Growth ◽  
Hexagonal Structure ◽  
Crystal Habit ◽  
Molar Ratio ◽  
Hydrothermal Conditions ◽  
Processing Efficiency ◽  
Microwave Assisted

The synthesis of partially substituted silicon hydroxyapatite (Si-HAp) nanopowders was systematically investigated via the microwave-assisted hydrothermal process. The experiments were conducted at 150 °C for 1 h using TMAS (C4H13NO5Si2) as a Si4+ precursor. To improve the Si4+ uptake in the hexagonal structure, the Si precursor was supplied above the stoichiometric molar ratio (0.2 M). The concentration of the TMAS aqueous solutions used varied between 0.3 and 1.8 M, corresponding to saturation levels of 1.5–9.0-fold. Rietveld refinement analyses indicated that Si incorporation occurred in the HAp lattice by replacing phosphate groups (PO43−) with the silicate (SiO4−) group. FT-IR and XPS analyses also confirmed the gradual uptake of SiO4− units in the HAp, as the saturation of Si4+ reached 1.8 M. TEM observations confirmed that Si-HAp agglomerates had a high crystallinity and are constituted by tiny rod-shaped particles with single-crystal habit. Furthermore, a reduction in the particle growth process took place by increasing the Si4+ excess content up to 1.8 M, and the excess of Si4+ triggered the fine rod-shaped particles self-assembly to form agglomerates. The agglomerate size that occurred with intermediate (0.99 mol%) and large (12.16 mol%) Si contents varied between 233.1 and 315.1 nm, respectively. The excess of Si in the hydrothermal medium might trigger the formation of the Si-HAp agglomerates prepared under fast kinetic reaction conditions assisted by the microwave heating. Consequently, the use of microwave heating-assisted hydrothermal conditions has delivered high processing efficiency to crystallize Si-HAp with a broad content of Si4+.

scholarly journals Microwave Assisted Solvent-Free Synthesis of Some Imine Derivatives

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Yunus Bekdemir ◽  
Kürşat Efil
Keyword(s):  
Microwave Heating ◽  
Aromatic Amines ◽  
Environmentally Friendly ◽  
Aromatic Aldehydes ◽  
Solvent Free ◽  
Molar Ratio ◽  
Microwave Assisted ◽  
Solvent Free Conditions ◽  
Solvent Free Synthesis ◽  
Environmentally Friendly Method

Some imine derivatives (1a–7d) were synthesized using a rapid and an environmentally friendly method with reaction of aromatic aldehydes (a–d) and aromatic amines (1–7) (in 1 : 1 molar ratio) in the presence of β-ethoxyethanol as a wetting reagent (2 drops) under solvent-free conditions using microwave heating.

Microwave Assisted Fischer - Tropsch Synthesis at a Atmospheric Pressure

2017 ◽  
Vol 68 (5) ◽  
pp. 1040-1043
Author(s):  
Ioan Tudor Sibianu ◽  
Daniela Berger ◽  
Cristian Matei ◽  
Ioan Calinescu
Keyword(s):  
Microwave Heating ◽  
Atmospheric Pressure ◽  
Tropsch Synthesis ◽  
Molar Ratio ◽  
Microwave Activation ◽  
Fischer Tropsch ◽  
Fischer Tropsch Synthesis ◽  
Molar Ratios ◽  
Microwave Assisted ◽  
Co Conversion

The purpose of this study was to test the efficiency of the microwave activation of a Fischer-Tropsch used catalyst under atmospheric pressure. Experiments were carried out on a cobalt, manganese, calcium catalyst on a 10:1:1 molar ratio that was impregnated on a AlSBA-15 support. The amount of metal impregnated was equivalent to 20% of the supports mass. Experiments were carried out both with conventional as well as microwave heating. In order to compare the efficiency of both types of heating, the product compositions were determined at 110, 140, 170, 190, 200, 225, 250 oC. At each temperature 4:1, 2:1, 1.25:1 H2:CO molar ratios were tested. The microwave assisted Fischer-Tropsch reaction allows the use of lower temperatures, as well as larger CO conversion values with better yields especially in methane.

THE EFFECT OF CONVENTIONAL AND MICROWAVE HEATING TECHNIQUES ON TRANSESTERIFICATION OF WASTE COOKING OIL TO BIODIESEL

2016 ◽  
Vol 78 (8-3) ◽  
Author(s):  
Mohd Johari Kamaruddin ◽  
Nurulsurusiah Mohamad ◽  
Umi Aisah Asli ◽  
Muhammad Abbas Ahmad Zaini ◽  
Kamarizan Kidam ◽  
...  
Keyword(s):  
Microwave Heating ◽  
Processing Parameters ◽  
Waste Cooking Oil ◽  
Green Technology ◽  
Conventional Heating ◽  
Molar Ratio ◽  
Catalyst Loading ◽  
Thermal Heating ◽  
Microwave Assisted ◽  
Cooking Oil

This research is focused on the effect of processing parameters such as molar ratio of sample to solvent (1:3-1:15), catalyst loading (0.5-2.5 wt %), temperature (40-80 °C) and time of reaction (5-180 min) on the transesterification yield of waste cooking oil (WCO) in conventional thermal heating and microwave heating techniques. The analysis carried out revealed that the microwave assisted transesterification produced a comparable yield to conventional heating transesterification with ~5 times faster in heating up the reaction mixture to a reaction temperature and reduced ~90% of the reaction time required. This study concludes that microwave assisted transesterification, which is a green technology, may have great potential in reducing the processing time compared to conventional thermal heating transesterification.

Concomitance of octamolybdate isomers in metastable crystal structures isolated using homoleptic CoII/CoIII complexes as structure-directing templates

2021 ◽  
Vol 77 (1) ◽  
pp. 99-114
Author(s):  
Reinaldo Atencio ◽  
Alexander Briceño ◽  
Julia Bruno-Colmenarez ◽  
Pedro Silva ◽  
Laura Rodríguez ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Crystal Engineering ◽  
Self Assembly ◽  
Molar Ratio ◽  
Hydrothermal Conditions ◽  
Experimental Conditions ◽  
Spin Configuration ◽  
Cell Parameters ◽  
Intermolecular Contacts

Exploiting the kinetic domain provided by hydrothermal conditions, it was possible to isolate three transient metastable crystal structures, each bearing concomitant pairs of octamolybdate isomers, namely, α–β, γ–β or βcs–βgp stabilized by distinctive homoleptic [Co(bpy)3] n+ (bpy = 2,2′-bipyridine; n = 2 or 3) cations generated in situ: [Co(bpy)3]4[(α-Mo8O26)(β-Mo8O26)]·5H2O (1), [NH4][Co(bpy)3][(γ-Mo8O26)0.5(β-Mo8O26)0.5]·4H2O (2) and [Co(bpy)3]2[(βcs-Mo8O26)0.5(βgp-Mo8O26)]·12H2O (3). Solid 1 with the space group P21/n and unit-cell parameters a = 22.160 (6), b = 14.209 (3), c = 24.641 (4) Å, β = 99.10 (2)° and V = 7661 (3) Å3 resulted in the same crystal structure as that synthesized previously under different conditions by Sun et al. [J. Mol. Struct. (2005), 741, 149–153]. Factors directing the reaction, such as product composition and phase stability, were monitored by analysis of the PXRD patterns of the bulk solids obtained under different experimental conditions. The relative proportions of the mixed phases 1–3 or their stabilization are highly dependent on the initial Co:Mo molar ratio and the reaction temperature. In particular, an increase in temperature induces the transformation of 1–3 into more thermodynamically stable phases formed by one-dimensional coordination polymers [Co(bpy)2(β-Mo8O26)0.5] n (4) and [(MoO3)(bpy)] n (5). The crystal structures of 1–3 correspond to molecular salts self-assembled by C—H...O—Mo, C...H and H...H intermolecular contacts. A Hirshfeld surface analysis for 1 showed that the C...H and H...H interactions represent an average of 51.8% of the total cation–cation intermolecular contacts. In contrast, these interactions are vastly reduced in 2 (23.0%) and 3 (average 28.5% for both isomers). EPR experiments indicated that the crystal structures of 1 and 3 are paramagnetic, and that for 2 is diamagnetic. The paramagnetism of 3 stems from the in situ formation of [Co(bpy)3]3+ in a high-spin configuration. The structure-directing properties of the [Co(bpy)3] n+ cations in the isolation and self-assembly of concomitant octamolybdate isomers are also described from the viewpoint of crystal engineering.

scholarly journals Preparation and application of carbon and hollow TiO2 microspheres by microwave heating at a low temperature

e-Polymers ◽  
2021 ◽  
Vol 21 (1) ◽  
pp. 200-209
Author(s):  
Caiyun Zhang ◽  
Chunhong Li ◽  
Bolin Ji ◽  
Zhaohui Jiang
Keyword(s):  
Low Temperature ◽  
Microwave Heating ◽  
Raw Material ◽  
Carbon Microspheres ◽  
Microwave Assisted ◽  
The Core ◽  
Good Crystallinity ◽  
Carbon Core ◽  
Microwave Assisted Method ◽  
Uniform Particle Size

Abstract A fast, simple, and energy-saving microwave-assisted approach was successfully developed to prepare carbon microspheres. The carbon microspheres with a uniform particle size and good dispersity were prepared using glucose as the raw material and HCl as the dehydrating agent at low temperature (90°C) in an open system with the assistance of microwave heating. The carbon microspheres were characterized by elemental analysis, XRD, SEM, FTIR, TG, and Raman. The results showed that the carbon microspheres prepared under the condition of 18.5% (v/v) HCl and heating for 30 min by microwave had a narrow size distribution. The core–shell structure of the carbon core and TiO2 shell was prepared with (NH4)2TiF6, H3BO3 using the microwave-assisted method. The hollow TiO2 microspheres with good crystallinity and high photocatalytic properties were successfully prepared by sacrificing the carbon microspheres.

Microwave Assisted Synthesis of Schiff Bases: A Green Approach

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Mousumi Chakraborty ◽  
Sanjay Baweja ◽  
Sunita Bhagat ◽  
TejpalSingh Chundawat
Keyword(s):  
Microwave Irradiation ◽  
Microwave Power ◽  
Mass Spectra ◽  
Molar Ratio ◽  
Microwave Assisted Synthesis ◽  
Schiff’S Bases ◽  
Microwave Assisted ◽  
Green Approach ◽  
Schiff's Bases ◽  
Effects Of Temperature

Abstract In the present study Schiff’s bases are synthesized by the conventional as well as by microwave irradiation. Excellent yield within short reaction time is obtained using microwave irradiation along with other advantages like mild reaction condition, non-hazardous and safer environmental conditions. The effects of temperature, reactant molar ratio, and microwave power variation on yield are observed. Mathematical model has been developed using matlab software to obtain the yield as a function of microwave power. Kinetic study of the reaction has also been attempted. Schiff’s bases structures are confirmed by IR, 1HNMR, Mass Spectra and elemental analysis.

A novel additive-free oxides–hydrothermal approach for monazite-type LaPO4nanomaterials with controllable morphologies

2010 ◽  
Vol 43 (5) ◽  
pp. 990-997 ◽  
Author(s):  
Jie Ma ◽  
Qingsheng Wu
Keyword(s):  
Electron Microscopy ◽  
Treatment Time ◽  
Synthesis Temperature ◽  
Molar Ratio ◽  
Hydrothermal Conditions ◽  
Typical Sample ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
Hydrothermal Approach

A facile oxides–hydrothermal (O–HT) method is demonstrated to prepare high-purity monazite-type LaPO4nanomaterials. In this approach, La2O3and P2O5powder are first directly used as precursors under additive-free hydrothermal conditions. The as-prepared samples are characterized with X-ray diffraction, Fourier transform IR spectroscopy, thermogravimetry, scanning electron microscopy, transmission electron microscopy (high-resolution TEM, energy dispersive spectroscopy) and selected-area electron diffraction. The typical sample obtained at 433 K in 24 h comprises uniform single-crystal nanofibres with a diameter of ∼15–28 nm and an aspect ratio of 30–50. The influences of treatment time, synthesis temperature and P/La molar ratio are investigated. The phase transition from hexagonal hydrate to monoclinic anhydrous lanthanum phosphate and the growth process of nanofibres are revealed by the experimental results. The formation mechanism of the monoclinic LaPO4is discussed. The result indicates that the P/La ratio does not influence the composition and crystal phase but changes the morphology of the product in the O–HT system.

Efficient microwave-assisted hydrothermal synthesis of CuO sea urchin-like architectures via a mesoscale self-assembly

CrystEngComm ◽  
2010 ◽  
Vol 12 (6) ◽  
pp. 1696 ◽  
Author(s):  
Diogo P. Volanti ◽  
Marcelo O. Orlandi ◽  
Juan Andrés ◽  
Elson Longo
Keyword(s):  
Hydrothermal Synthesis ◽  
Sea Urchin ◽  
Self Assembly ◽  
Microwave Assisted

scholarly journals Deep Eutectic Solvent-Based Microwave-Assisted Extraction of Baicalin from Scutellaria baicalensis Georgi

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Hui Wang ◽  
Xiaodi Ma ◽  
Qibin Cheng ◽  
Xiaoli Xi ◽  
Liwei Zhang
Keyword(s):  
Maximum Yield ◽  
Deep Eutectic Solvent ◽  
Extraction Yield ◽  
Scutellaria Baicalensis ◽  
Molar Ratio ◽  
Extraction Temperature ◽  
Microwave Assisted Extraction ◽  
Scutellaria Baicalensis Georgi ◽  
Microwave Assisted ◽  
Assisted Extraction

Deep eutectic solvents (DESs) have attracted significant attention as green media for the extraction and separation of natural compounds from Chinese medicine. In this study, a hydrophobic DESs-based microwave-assisted extraction (MAE) was successfully used to efficiently extract baicalin from Scutellaria baicalensis Georgi. Firstly, DecA: N4444-Cl (DES-1 , molar ratio 1 : 2) was screened and selected as the most appropriate DES by comparing the extraction yield in different hydrophobic DESs. Based on the extraction yield of baicalin, response surface methodology (RSM) was employed to model and optimize the parameters (extraction temperature, liquid-solid ratio, and extraction time). Furthermore, the maximum yield of 106.96 mg·g−1 was achieved under optimum conditions in DES-containing aqueous solutions (33 vol% water content), which reached a similar level that was conducted using the pharmacopoeia procedure (104.94 mg·g−1). These results indicated that the proposed method is an excellent alternative for the extraction of baicalin.

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