scholarly journals Reactive Sintering of Al2O3–Y3Al5O12 Ceramic Composites Obtained by Direct Ink Writing

Ceramics ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 1-12
Author(s):  
Joana Baltazar ◽  
Manuel Fellipe Rodrigues Pais Alves ◽  
Claudinei dos Santos ◽  
Susana Olhero
Keyword(s):  
Aqueous Media ◽  
Three Dimensional ◽  
Weight Ratio ◽  
Total Solid ◽  
Ceramic Composites ◽  
Solid Loading ◽  
Reactive Sintering ◽  
Direct Ink Writing ◽  
Percentage Weight ◽  
Diffraction Patterns

The main goal of this work was to obtain dense Al2O3–Y3Al5O12 ceramic composites by reactive sintering of three-dimensional samples, built by direct ink writing from a paste containing a mixture of Al2O3 and Y2O3 powders. To obtain a ceramic ink with proper rheological properties for extrusion-based printing, highly pure Al2O3 and Y2O3 powders in a percentage–weight ratio of 64:36 was mixed with 0.2 wt% MgO in a total solid loading of 42 vol% in aqueous media, adding carboxymethyl cellulose and polyethyleneimine solution as additives. The dried printed samples were sintered at final temperatures in the range of 1550 °C and 1650 °C; thus, relative densities of 83.7 ± 0.8%, 95.4 ± 0.4%, and 96.5 ± 0.5% were obtained for 1550 °C, 1600 °C, and 1650 °C, respectively. Rietveld refinement performed on the X-ray diffraction patterns indicated the presence of Al2O3 (42 to 47%) and Y3Al15O12 (58 to 61%) as crystalline phases, while micrographs showed the presence of equiaxial micrometric grains with average sizes of 1.8 ± 0.6 μm, for both phases and all sintering conditions. Samples sintered at 1600 °C and 1650 °C presented similar average Vickers hardness values of 14.2 ± 0.27 GPa and 14.5 ± 0.25 GPa, respectively. A slight increase in fracture toughness as sintering temperature increases was also stated, consistent with the densification.

Cryomicroscopy of crotoxin complex crystals at 400 KV

1989 ◽  
Vol 47 ◽  
pp. 826-827
Author(s):  
Jaap Brink ◽  
Wah Chiu
Keyword(s):  
Signal To Noise Ratio ◽  
3D Structure ◽  
Three Dimensional ◽  
Carbon Films ◽  
Depth Of Field ◽  
Basic Subunit ◽  
Ewald Sphere ◽  
Diffraction Patterns ◽  
Complex Crystals ◽  
Acidic Subunit

The crotoxin complex is a potent neurotoxin composed of a basic subunit (Mr = 12,000) and an acidic subunit (M = 10,000). The basic subunit possesses phospholipase activity whereas the acidic subunit shows no enzymatic activity at all. The complex's toxocity is expressed both pre- and post-synaptically. The crotoxin complex forms thin crystals suitable for electron crystallography. The crystals diffract up to 0.16 nm in the microscope, whereas images show reflections out to 0.39 nm2. Ultimate goal in this study is to obtain a three-dimensional (3D-) structure map of the protein around 0.3 nm resolution. Use of 100 keV electrons in this is limited; the unit cell's height c of 25.6 nm causes problems associated with multiple scattering, radiation damage, limited depth of field and a more pronounced Ewald sphere curvature. In general, they lead to projections of the unit cell, which at the desired resolution, cannot be interpreted following the weak-phase approximation. Circumventing this problem is possible through the use of 400 keV electrons. Although the overall contrast is lowered due to a smaller scattering cross-section, the signal-to-noise ratio of especially higher order reflections will improve due to a smaller contribution of inelastic scattering. We report here our preliminary results demonstrating the feasability of the data collection procedure at 400 kV.Crystals of crotoxin complex were prepared on carbon-covered holey-carbon films, quench frozen in liquid ethane, inserted into a Gatan 626 holder, transferred into a JEOL 4000EX electron microscope equipped with a pair of anticontaminators operating at −184°C and examined under low-dose conditions. Selected area electron diffraction patterns (EDP's) and images of the crystals were recorded at 400 kV and −167°C with dose levels of 5 and 9.5 electrons/Å, respectively.

scholarly journals Glucose/Graphene-Based Aerogels for Gas Adsorption and Electric Double Layer Capacitors

Polymers ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 40 ◽  
Author(s):  
Kang-Kai Liu ◽  
Biao Jin ◽  
Long-Yue Meng
Keyword(s):  
Gas Adsorption ◽  
High Surface ◽  
Aqueous Media ◽  
High Surface Area ◽  
Three Dimensional ◽  
High Specific Capacitance ◽  
Mesopore Size Distribution ◽  
Excellent Electrochemical Performance ◽  
Double Layer Capacitors ◽  
Hydrothermal Reduction

In this study, three-dimensional glucose/graphene-based aerogels (G/GAs) were synthesized using the hydrothermal reduction and CO2 activation method. Graphene oxide (GO) was used as a matrix, and glucose was used as a binder for the orientation of the GO morphology in an aqueous media. We determined that G/GAs exhibited narrow mesopore size distribution, a high surface area (763 m2 g−1), and hierarchical macroporous and mesoporous structures. These features contributed to G/GAs being promising adsorbents for the removal of CO2 (76.5 mg g−1 at 298 K), CH4 (16.8 mg g−1 at 298 K), and H2 (12.1 mg g−1 at 77 K). G/GAs presented excellent electrochemical performance, featuring a high specific capacitance of 305.5 F g−1 at 1 A g−1, and good cyclic stability of 98.5% retention after 10,000 consecutive charge-discharge cycles at 10 A g−1. This study provided an efficient approach for preparing graphene aerogels exhibiting hierarchical porosity for gas adsorption and supercapacitors.

scholarly journals Complex Aerogels Generated from Nano-Polysaccharides and Its Derivatives for Oil–Water Separation

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1593 ◽  
Author(s):  
Hajo Yagoub ◽  
Liping Zhu ◽  
Mahmoud H. M. A. Shibraen ◽  
Ali A. Altam ◽  
Dafaalla M. D. Babiker ◽  
...  
Keyword(s):  
Guar Gum ◽  
Corn Oil ◽  
Cellulose Nanofibers ◽  
Aqueous Media ◽  
Three Dimensional ◽  
Absorption Capacity ◽  
Water Contact ◽  
Water Separation ◽  
Oil Water Separation ◽  
Oil Water

The complex aerogel generated from nano-polysaccharides, chitin nanocrystals (ChiNC) and TEMPO-oxidized cellulose nanofibers (TCNF), and its derivative cationic guar gum (CGG) is successfully prepared via a facile freeze-drying method with glutaraldehyde (GA) as cross-linkers. The complexation of ChiNC, TCNF, and CGG is shown to be helpful in creating a porous structure in the three-dimensional aerogel, which creates within the aerogel with large pore volume and excellent compressive properties. The ChiNC/TCNF/CGG aerogel is then modified with methyltrichlorosilane (MTCS) to obtain superhydrophobicity/superoleophilicity and used for oil–water separation. The successful modification is demonstrated through FTIR, XPS, and surface wettability studies. A water contact angle of 155° on the aerogel surface and 150° on the surface of the inside part of aerogel are obtained for the MTCS-modified ChiNC/TCNF/CGG aerogel, resulting in its effective absorption of corn oil and organic solvents (toluene, n-hexane, and trichloromethane) from both beneath and at the surface of water with excellent absorption capacity (i.e., 21.9 g/g for trichloromethane). More importantly, the modified aerogel can be used to continuously separate oil from water with the assistance of a vacuum setup and maintains a high absorption capacity after being used for 10 cycles. The as-prepared superhydrophobic/superoleophilic ChiNC/TCNF/CGG aerogel can be used as a promising absorbent material for the removal of oil from aqueous media.

Effect of Boron and Carbon Addition on the Phase Transformations during High-Energy Ball Milling and Subsequent Sintering of Si3N4+B and Si3N4+C Powder Mixtures

2016 ◽  
Vol 869 ◽  
pp. 58-63
Author(s):  
Luiz Otávio Vicentin Maruya ◽  
Bruna Rage Baldone Lara ◽  
Belmira Benedita de Lima ◽  
Vanessa Motta Chad ◽  
Gilberto Carvalho Coelho ◽  
...  
Keyword(s):  
Phase Transformations ◽  
Ball Milling ◽  
Weight Ratio ◽  
High Energy ◽  
Ceramic Composites ◽  
Nitrogen Atmosphere ◽  
Carbon Addition ◽  
Powder Mixtures ◽  
X Ray ◽  
Milled Powders

This study reports on effect of boron and carbon addition on the phase transformations during ball milling and subsequent sintering of Si3N4+B and Si3N4+C powder mixtures. Ball milling at room temperature was conducted using stainless steel vials (225 mL) and balls (19mm diameter), 300 rpm and a bal-to-powder weight ratio of 10:1. The as-milled powders were uniaxially compacted in order to obtain cylinder samples with 10 mm diameter, which were subsequently sintered under nitrogen atmosphere at 1500°C for 1h. Characterization of the as-milled powders and sintered samples was performed by X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. Only peaks of Si3N4 were identified in X-ray diffractograms of as-milled Si3N4+B and Si3N4+C powders, suggesting that metastable structures were found during milling. After sintering at 1500°C for 1h, the Si3N4+BN and Si3N4+SiC ceramic composites were formed from the mechanically alloyed Si3N4+B and Si3N4+C powders.

2D X-ray diffraction and molecular modelling of the crystalline structure of polyesters under uniaxial stress

2021 ◽  
pp. 096739112199822
Author(s):  
Ahmed I Abou-Kandil ◽  
Gerhard Goldbeck
Keyword(s):  
Crystalline Structure ◽  
Molecular Modelling ◽  
Three Dimensional ◽  
Uniaxial Stress ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wide Range ◽  
Modelling Techniques ◽  
Diffraction Patterns

Studying the crystalline structure of uniaxially and biaxially drawn polyesters is of great importance due to their wide range of applications. In this study, we shed some light on the behaviour of PET and PEN under uniaxial stress using experimental and molecular modelling techniques. Comparing experiment with modelling provides insights into polymer crystallisation with extended chains. Experimental x-ray diffraction patterns are reproduced by means of models of chains sliding along the c-axis leading to some loss of three-dimensional order, i.e. moving away from the condition of perfect register of the fully extended chains in triclinic crystals of both PET and PEN. This will help us understand the mechanism of polymer crystallisation under uniaxial stress and the appearance of mesophases in some cases as discussed herein.

Heteroepitaxial Nucleation and Growth of Ge ON Si(100) Surfaces Using Remote Plasma Enhanced Chemical Vapor Deposition

1988 ◽  
Vol 116 ◽  
Author(s):  
R.A. Rudder ◽  
S.V. Hattangady ◽  
D.J. Vitkavage ◽  
R.J. Markunas
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Photoelectron Spectroscopy ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Layer By Layer ◽  
Heteroepitaxial Growth ◽  
Remote Plasma ◽  
Dimensional Growth ◽  
Diffraction Patterns

Heteroepitaxial growth of Ge on Si(100) has been accomplished using remote plasma enhanced chemical vapor deposition at 300*#x00B0;C. Reconstructed surfaces with diffraction patterns showing non-uniform intensity variations along the lengths of the integral order streaks are observed during the first 100 Å of deposit. This observation of an atomically rough surface during the initial stages of growth is an indication of three-dimensional growth. As the epitaxial growth proceeds, the diffraction patterns become uniform with extensive streaking on both the integral and fractional order streaks. Subsequent growth, therefore, takes place in a layer-by-layer, two-dimensional mode. X-ray photoelectron spectroscopy of the early nucleation stages, less than 80 Å, show that there is uniform coverage with no evidence of island formation.

scholarly journals Effect of Chemical Composition on Magnetic and Electrical Properties of Ferroelectromagnetic Ceramic Composites

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2488
Author(s):  
Dariusz Bochenek ◽  
Przemysław Niemiec ◽  
Artur Chrobak
Keyword(s):  
Magnetic Properties ◽  
Electrical Properties ◽  
Ferroelectric Properties ◽  
Ceramic Composites ◽  
Chemical Formula ◽  
Backscattered Electrons ◽  
Diffraction Patterns ◽  
And Performance ◽  
Composite Samples ◽  
Magnetic And Electrical Properties

In this paper, ferroelectric–ferrimagnetic ceramic composites based on multicomponent PZT-type (PbZr1-xTixO3-type) material and ferrite material with different percentages in composite compositions were obtained and studied. The ferroelectric component of the composite was a perovskite ceramic material with the chemical formula Pb0.97Bi0.02(Zr0.51Ti0.49)0.98(Nb2/3Mn1/3)0.02O3 (P), whereas the magnetic component was nickel-zinc ferrite with the chemical formula Ni0.5Zn0.5Fe2O4 (F). The process of sintering the composite compounds was carried out by the free sintering method. Six ferroelectric-ferrimagnetic ceramic P-F composite compounds were designed and obtained with different percentages of its components, i.e., 90/10 (P90-F10), 85/15 (P85-F15), 80/20 (P80-F20), 60/40 (P60-F40), 40/60 (P40-F60), and 20/80 (P20-F80). X-ray diffraction patterns, microstructural, ferroelectric, dielectric, magnetic properties, and DC electrical conductivity of the composite materials were investigated. In this study, two techniques were used to image the microstructure of P-F composite samples: SB (detection of the signals from the secondary and backscattered electron detectors) and BSE (detection of backscattered electrons), which allowed accurate visualization of the presence and distribution of the magnetic and ferroelectric component in the volume of the composite samples. The studies have shown that at room temperature, the ceramic composite samples exhibit good magnetic and electrical properties. The best set of physical properties and performance of composite compositions have ceramic samples with a dominant phase of ferroelectric component and a small amount of the ferrite component (P90-F10). Such a composition retains the high ferroelectric properties of the ferroelectric component in the composite while also acquiring magnetic properties. These properties can be prospectively used in new types of memory and electromagnetic converters.

Surface Modification of High Density Ceramic Powder for Increasing Suspension Capacity in Three-Dimensional Printing Application

2018 ◽  
Vol 936 ◽  
pp. 159-163 ◽  
Author(s):  
Huang Jan Hsu ◽  
Shyh Yuan Lee ◽  
Shinn Liang Chang ◽  
Cho Pei Jiang
Keyword(s):  
Surface Modification ◽  
Ball Milling ◽  
Ceramic Powder ◽  
Three Dimensional ◽  
Treatment Protocol ◽  
Weight Ratio ◽  
Average Diameter ◽  
Zirconia Powder ◽  
Three Dimensional Printing ◽  
Promising Tool

Three-dimensional slurry printing is a promising tool for making ceramic object but it limits in high dense ceramic powder because of poor suspension capacity. This study uses zirconia powder with an average diameter of 2 μm because its density is 5.67 g/cm3. A treatment protocol is proposed to improve the suspension capacity of zirconia powder including the ball milling, surface modification and resin blending. Experimental results show that adding 1% of isostearyl titanate, a coupling agent, for surface modification can enhance the lipophilicity of zirconia powder. Mixing surface modification powder in resin with a weight ratio of 7:3 and carrying on ball milling with 100 RPM for 6 hours can obtain the diameter of powder less than 400 nm. As a result, the zirconia slurry can obtain good suspension capacity which is over 48 hours.

scholarly journals Hard X-ray polarizer to enable simultaneous three-dimensional nanoscale imaging of magnetic structure and lattice strain

2016 ◽  
Vol 23 (5) ◽  
pp. 1210-1215 ◽  
Author(s):  
Jonathan Logan ◽  
Ross Harder ◽  
Luxi Li ◽  
Daniel Haskel ◽  
Pice Chen ◽  
...  
Keyword(s):  
Magnetic Circular Dichroism ◽  
Three Dimensional ◽  
Control Sample ◽  
Magnetic Ordering ◽  
X Rays ◽  
Diffractive Imaging ◽  
X Ray ◽  
Coherent Diffractive Imaging ◽  
Diffraction Patterns ◽  
A New Technique

Recent progress in the development of dichroic Bragg coherent diffractive imaging, a new technique for simultaneous three-dimensional imaging of strain and magnetization at the nanoscale, is reported. This progress includes the installation of a diamond X-ray phase retarder at beamline 34-ID-C of the Advanced Photon Source. The performance of the phase retarder for tuning X-ray polarization is demonstrated with temperature-dependent X-ray magnetic circular dichroism measurements on a gadolinium foil in transmission and on a Gd5Si2Ge2crystal in diffraction geometry with a partially coherent, focused X-ray beam. Feasibility tests for dichroic Bragg coherent diffractive imaging are presented. These tests include (1) using conventional Bragg coherent diffractive imaging to determine whether the phase retarder introduces aberrations using a nonmagnetic gold nanocrystal as a control sample, and (2) collecting coherent diffraction patterns of a magnetic Gd5Si2Ge2nanocrystal with left- and right-circularly polarized X-rays. Future applications of dichroic Bragg coherent diffractive imaging for the correlation of strain and lattice defects with magnetic ordering and inhomogeneities are considered.

scholarly journals Construction of Two Stable Co(II)-Based Hydrogen-Bonded Organic Frameworks as a Luminescent Probe for Recognition of Fe3+ and Cr2O72− in H2O

Molecules ◽  
2021 ◽  
Vol 26 (19) ◽  
pp. 5955
Author(s):  
Qi-Ying Weng ◽  
Ya-Li Zhao ◽  
Jia-Ming Li ◽  
Miao Ouyang
Keyword(s):  
Detection Limit ◽  
Aqueous Media ◽  
Three Dimensional ◽  
Cobalt Atom ◽  
High Sensitivity ◽  
X Ray Diffraction ◽  
Chlorobenzoic Acid ◽  
X Ray ◽  
Highly Sensitive ◽  
Hydrogen Bonded

A pair of cobalt(II)-based hydrogen-bonded organic frameworks (HOFs), [Co(pca)2(bmimb)]n (1) and [Co2(pca)4(bimb)2] (2), where Hpca = p-chlorobenzoic acid, bmimb = 1,3-bis((2-methylimidazol-1-yl)methyl)benzene, and bimb = 1,4-bis(imidazol-1-ylmethyl)benzene were hydrothermally synthesized and characterized through infrared spectroscopy (IR), elemental and thermal analysis (EA), power X-ray diffraction (PXRD), and single-crystal X-ray diffraction (SCXRD) analyses. X-ray diffraction structural analysis revealed that 1 has a one-dimensional (1D) infinite chain network through the deprotonated pca− monodentate chelation and with a μ2-bmimb bridge Co(II) atom, and 2 is a binuclear Co(II) complex construction with a pair of symmetry-related pca− and bimb ligands. For both 1 and 2, each cobalt atom has four coordinated twisted tetrahedral configurations with a N2O2 donor set. Then, 1 and 2 are further extended into three-dimensional (3D) or two-dimensional (2D) hydrogen-bonded organic frameworks through C–H···Cl interactions. Topologically, HOFs 1 and 2 can be simplified as a 4-connected qtz topology with a Schläfli symbol {64·82} and a 4-connected sql topology with a Schläfli symbol {44·62}, respectively. The fluorescent sensing application of 1 was investigated; 1 exhibits high sensitivity recognition for Fe3+ (Ksv: 10970 M−1 and detection limit: 19 μM) and Cr2O72− (Ksv: 12960 M−1 and detection limit: 20 μM). This work provides a feasible detection platform of HOFs for highly sensitive discrimination of Fe3+ and Cr2O72− in aqueous media.

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