scholarly journals Ferromagnetic properties of ZnO:Mn nanocrystals obtained by the freeze-drying method

2020 ◽  
Vol 28 (1) ◽  
pp. 55-60
Author(s):  
O. V. Kovalenko ◽  
V. Yu. Vorovsky ◽  
O. V. Khmelenko ◽  
Ye. G. Plakhtii ◽  
O. I. Kushnerov
Keyword(s):  
Freeze Drying ◽  
Room Temperature ◽  
Hexagonal Lattice ◽  
Drying Method ◽  
Ferromagnetic Properties ◽  
Spintronic Devices ◽  
Broad Absorption Line ◽  
Destructive Action ◽  
Pure Phase ◽  
Impurity Defects

In the work, the nanocrystals ZnO and ZnO:Mn with a concentration of Mn 2 and 4 at.% were obtained by the low-temperature freeze-drying method. For this purpose, solutions of zinc acetate Zn(CH3COO)2∙2H2O and manganese one Mn(CH3COO)2∙4H2O were used. By means of XRD, it is established that nanocrystals (NC’s) have a pure phase and wurtzite-type hexagonal lattice, their size is d ~ 65 nm. The EPR spectra of the samples have a broad absorption line. It is due to the presence of a large number of intrinsic and impurity defects in the NC’s. These defects are the result of the destructive action of hydrogen, which is a product of the thermal decomposition of zinc and manganese acetates. It is shown that there is a relationship between the number of crystal lattice defects in the ZnO:Mn NC’s and their ferromagnetic properties at room temperature. Samples of ZnO:Mn with a concentration of Mn 2 and 4 at.%. have a specific magnetization value of Мs equal to 0.089 and 0.045 emu/g, respectively. The results can have great potential in spintronic devices and spin-based electronics.

Hydrothermal Synthesis and Ferromagnetic Properties of Mn-Doped Na0.5Bi0.5TiO3 Crystals

2011 ◽  
Vol 311-313 ◽  
pp. 2110-2113 ◽  
Author(s):  
Yong Gang Wang ◽  
Yu Jiang Wang
Keyword(s):  
Hydrothermal Synthesis ◽  
Hydrothermal Method ◽  
Room Temperature ◽  
Doping Concentration ◽  
Multiferroic Materials ◽  
Ferromagnetic Properties ◽  
Mn Doping ◽  
Pure Phase ◽  
Mn Doped

Pure phase Mn-doped Na0.5Bi0.5TiO3 crystals were successfully synthesized by a hydrothermal method. Magnetic loops measured at room temperature indicate that ferromagnetism can be obtained in Mn-doped Na0.5Bi0.5TiO3 crystals, and the magnetism of Na0.5Bi0.5TiO3 crystals can be controlled by adjusting Mn doping concentration. The magnetism of the Mn-doped Na0.5Bi0.5TiO3 crystals varied from diamagnetism, ferromagnetism, and paramagnetic on increasing Mn doping concentration from 0 to 30mol%. The results showed in this study may provide an approach to widely exploring more multiferroic materials.

scholarly journals Scientific Analysis and Conservation of Waterlogged Woods Excavated from Suyoeng-ri Site, Hwaseong, Korea

2021 ◽  
Vol 37 (5) ◽  
pp. 579-589
Author(s):  
Kwang-Hee Lee ◽  
Jeong-Eun Oh ◽  
Soo-Chul Kim
Keyword(s):  
Freeze Drying ◽  
Room Temperature ◽  
Manufacturing Processes ◽  
Drying Method ◽  
Manufacturing Method ◽  
Neolithic Age ◽  
Scientific Analysis ◽  
Morus Spp ◽  
The Neolithic Age ◽  
Shelf Temperature

Five waterlogged wood artefacts were excavated from Suyeong-ri site in Hwaseong, South Korea. The aim of the present study was to identify the species and estimate the date of manufacture and the manufacturing method of these artefacts. The study also aimed to conserve the original shapes of waterlogged wood artefacts by using the vacuum freeze drying method. The two large waterlogged woods were identified as Ulmus spp. and Morus spp., whereas one of the three small waterlogged woods was identified as Abies spp. and the other two as hard pine. Radiocarbon dating using wiggle match dated the manufacturing of these wooden artefacts between BCE 8520-8490 or BCE 8470-8290 in the Neolithic age, and a similar period was also confirmed for seed excavated from a place close to the location where the waterlogged wood artefacts were excavated. The surface of waterlogged wood artefacts had several traces of manufacturing processes - traces of tearing and chopping - were observed. Based on these observations, it was confirmed that stone adz was used to make these wooden artefacts. Thereafter, the waterlogged wood samples were conserved by immersing them into PEG#4,000 of concentration in water from 10% to 40% at room temperature(15~25℃) and subjecting them to vacuum freeze drying. However, the internal moisture was not completely removed in some thick parts of waterlogged woods by applying the general schedule such as raising the shelf temperature as the surface temperature rises. Therefore, additional study is required using the schedule-method for vacuum freeze drying of large waterlogged wood.

Scanning Electron Microscopy-cuticular Lesions on the Roundworm Ascaris Suum

1970 ◽  
Vol 28 ◽  
pp. 114-115
Author(s):  
P. A. Madden ◽  
W. R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Freeze Drying ◽  
Room Temperature ◽  
Secondary Electron ◽  
Distilled Water ◽  
Freeze Dried ◽  
Silver Paint ◽  
To Come ◽  
Scanning Electron

The intestinal roundworm of swine is pinkish in color and about the diameter of a lead pencil. Adult worms, taken from parasitized swine, frequently were observed with macroscopic lesions on their cuticule. Those possessing such lesions were rinsed in distilled water, and cylindrical segments of the affected areas were removed. Some of the segments were fixed in buffered formalin before freeze-drying; others were freeze-dried immediately. Initially, specimens were quenched in liquid freon followed by immersion in liquid nitrogen. They were then placed in ampuoles in a freezer at −45C and sublimated by vacuum until dry. After the specimens appeared dry, the freezer was allowed to come to room temperature slowly while the vacuum was maintained. The dried specimens were attached to metal pegs with conductive silver paint and placed in a vacuum evaporator on a rotating tilting stage. They were then coated by evaporating an alloy of 20% palladium and 80% gold to a thickness of approximately 300 A°. The specimens were examined by secondary electron emmission in a scanning electron microscope.

High-Resolution Scanning Electron Microscopy of Biological Specimens

1988 ◽  
Vol 46 ◽  
pp. 186-187
Author(s):  
M. Müller ◽  
R. Hermann
Keyword(s):  
High Resolution ◽  
Freeze Drying ◽  
Room Temperature ◽  
Structural Information ◽  
Freeze Substitution ◽  
Critical Point Drying ◽  
Sem Study ◽  
Major Factors ◽  
Structural Preservation ◽  
Preparation Techniques

Three major factors must be concomitantly assessed in order to extract relevant structural information from the surface of biological material at high resolution (2-3nm).Procedures based on chemical fixation and dehydration in graded solvent series seem inappropriate when aiming for TEM-like resolution. Cells inevitably shrink up to 30-70% of their initial volume during gehydration; important surface components e.g. glycoproteins may be lost. These problems may be circumvented by preparation techniques based on cryofixation. Freezedrying and freeze-substitution followed by critical point drying yields improved structural preservation in TEM. An appropriate preservation of dimensional integrity may be achieved by freeze-drying at - 85° C. The sample shrinks and may partially collapse as it is warmed to room temperature for subsequent SEM study. Observations at low temperatures are therefore a necessary prerequisite for high fidelity SEM. Compromises however have been unavoidable up until now. Aldehyde prefixation is frequently needed prior to freeze drying, rendering the sample resistant to treatment with distilled water.

Electron Microscope study of commensurate-incommensurate phase transition in BaZnGeO4

1990 ◽  
Vol 48 (4) ◽  
pp. 172-173
Author(s):  
Naoki Yamamoto ◽  
Makoto Kikuchi ◽  
Tooru Atake ◽  
Akihiro Hamano ◽  
Yasutoshi Saito
Keyword(s):  
Phase Transition ◽  
Electron Microscope Study ◽  
Room Temperature ◽  
Hexagonal Lattice ◽  
Ferroelectric Materials ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Periodic Arrays ◽  
Modulation Wave Vector

BaZnGeO4 undergoes many phase transitions from I to V phase. The highest temperature phase I has a BaAl2O4 type structure with a hexagonal lattice. Recent X-ray diffraction study showed that the incommensurate (IC) lattice modulation appears along the c axis in the III and IV phases with a period of about 4c, and a commensurate (C) phase with a modulated period of 4c exists between the III and IV phases in the narrow temperature region (—58°C to —47°C on cooling), called the III' phase. The modulations in the IC phases are considered displacive type, but the detailed structures have not been studied. It is also not clear whether the modulation changes into periodic arrays of discommensurations (DC’s) near the III-III' and IV-V phase transition temperature as found in the ferroelectric materials such as Rb2ZnCl4.At room temperature (III phase) satellite reflections were seen around the fundamental reflections in a diffraction pattern (Fig.1) and they aligned along a certain direction deviated from the c* direction, which indicates that the modulation wave vector q tilts from the c* axis. The tilt angle is about 2 degree at room temperature and depends on temperature.

Investigations on the Nature of Hemophilia A

1963 ◽  
Vol 09 (01) ◽  
pp. 030-052 ◽  
Author(s):  
Eberhard Mammen
Keyword(s):  
Factor Viii ◽  
Human Plasma ◽  
Barium Sulfate ◽  
Freeze Drying ◽  
Room Temperature ◽  
Hemophilia A ◽  
Normal Human Plasma ◽  
Normal Human ◽  
And Storage ◽  
Prothrombin Activation

SummaryIn this paper an inhibitor is described that is found in hemophilic plasma and serum different from any till now described inhibitor. The inhibitor only inhibits prothrombin activation in the “intrinsic clotting systems”. This inhibitor is probably not present in normal human plasma or serum. It is destroyed by ether and freeze drying, is labile to acid and storage at room temperature. It is stable upon dialysis and has not been adsorbed on barium sulfate, aluminum hydroxide or kaolin. It precipitates at 50% v/v saturation with alcohol. The nature of this inhibitor seems to be a protein or lipoprotein.Factor VIII was isolated from hemophilic plasma. The amount isolated was the same as from normal plasma and the activity properties were not different. Hemophiliacs have normal amounts of factor VIII.

scholarly journals Evaluation of Innovative Dried Purée from Jerusalem Artichoke—In Vitro Studies of Its Physicochemical and Health-Promoting Properties

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2644
Author(s):  
Jan Oszmiański ◽  
Sabina Lachowicz ◽  
Paulina Nowicka ◽  
Paweł Rubiński ◽  
Tomasz Cebulak
Keyword(s):  
Freeze Drying ◽  
Jerusalem Artichoke ◽  
Polyphenolic Compounds ◽  
Raw Material ◽  
Vacuum Drying ◽  
Drying Methods ◽  
Drying Method ◽  
Activity Inhibition ◽  
Health Promoting

The present study aimed to evaluate the effect of Jerusalem artichoke processing methods and drying methods (freeze drying, sublimation drying, vacuum drying) on the basic physicochemical parameters, profiles and contents of sugars and polyphenolic compounds, and health-promoting properties (antioxidant activity, inhibition of the activities of α-amylase, α-glucosidase, and pancreatic lipase) of the produced purée. A total of 25 polyphenolic compounds belonging to hydroxycinnamic phenolic acids (LC-PDA-MS-QTof) were detected in Jerusalem artichoke purée. Their average content in the raw material was at 820 mg/100 g dm (UPLC-PDA-FL) and was 2.7 times higher than in the cooked material. The chemical composition and the health-promoting value of the purées were affected by the drying method, with the most beneficial values of the evaluated parameters obtained upon freeze drying. Vacuum drying could offer an alternative to freeze drying, as both methods ensured relatively comparable values of the assessed parameters.

scholarly journals Environmentally Friendly and Multifunctional Shaddock Peel-Based Carbon Aerogel for Thermal-Insulation and Microwave Absorption

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Weihua Gu ◽  
Jiaqi Sheng ◽  
Qianqian Huang ◽  
Gehuan Wang ◽  
Jiabin Chen ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Thermal Insulation ◽  
Freeze Drying ◽  
Thermal Infrared ◽  
Carbon Aerogel ◽  
Carbon Aerogels ◽  
List Type ◽  
Drying Method ◽  
Cross Sectional ◽  
Compression Resistance

Highlights The eco-friendly shaddock peel-derived carbon aerogels were prepared by a freeze-drying method. Multiple functions such as thermal insulation, compression resistance and microwave absorption can be integrated into one material-carbon aerogel. Novel computer simulation technology strategy was selected to simulate significant radar cross-sectional reduction values under real far field condition. . Abstract Eco-friendly electromagnetic wave absorbing materials with excellent thermal infrared stealth property, heat-insulating ability and compression resistance are highly attractive in practical applications. Meeting the aforesaid requirements simultaneously is a formidable challenge. Herein, ultra-light carbon aerogels were fabricated via fresh shaddock peel by facile freeze-drying method and calcination process, forming porous network architecture. With the heating platform temperature of 70 °C, the upper surface temperatures of the as-prepared carbon aerogel present a slow upward trend. The color of the sample surface in thermal infrared images is similar to that of the surroundings. With the maximum compressive stress of 2.435 kPa, the carbon aerogels can provide favorable endurance. The shaddock peel-based carbon aerogels possess the minimum reflection loss value (RLmin) of − 29.50 dB in X band. Meanwhile, the effective absorption bandwidth covers 5.80 GHz at a relatively thin thickness of only 1.7 mm. With the detection theta of 0°, the maximum radar cross-sectional (RCS) reduction values of 16.28 dB m2 can be achieved. Theoretical simulations of RCS have aroused extensive interest owing to their ingenious design and time-saving feature. This work paves the way for preparing multi-functional microwave absorbers derived from biomass raw materials under the guidance of RCS simulations.

scholarly journals Anion ordering enables fast H− conduction at low temperatures

2021 ◽  
Vol 7 (23) ◽  
pp. eabf7883
Author(s):  
Hiroki Ubukata ◽  
Fumitaka Takeiri ◽  
Kazuki Shitara ◽  
Cédric Tassel ◽  
Takashi Saito ◽  
...  
Keyword(s):  
Ionic Conductivity ◽  
Room Temperature ◽  
Structural Transition ◽  
Hexagonal Lattice ◽  
Ionic Conductors ◽  
Activation Barriers ◽  
Energy Devices ◽  
Energy Applications ◽  
Chemical Disorder ◽  
New Energy

The introduction of chemical disorder by substitutional chemistry into ionic conductors is the most commonly used strategy to stabilize high-symmetric phases while maintaining ionic conductivity at lower temperatures. In recent years, hydride materials have received much attention owing to their potential for new energy applications, but there remains room for development in ionic conductivity below 300°C. Here, we show that layered anion-ordered Ba2−δH3−2δX (X = Cl, Br, and I) exhibit a remarkable conductivity, reaching 1 mS cm−1 at 200°C, with low activation barriers allowing H− conduction even at room temperature. In contrast to structurally related BaH2 (i.e., Ba2H4), the layered anion order in Ba2−δH3−2δX, along with Schottky defects, likely suppresses a structural transition, rather than the traditional chemical disorder, while retaining a highly symmetric hexagonal lattice. This discovery could open a new direction in electrochemical use of hydrogen in synthetic processes and energy devices.

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