Temperature In Nitrogen Atmosphere Research Articles

Effect of annealing temperature in nitrogen atmosphere and under vacuum on structural, optical and electrical properties of sputtered ITO/Ni/ITO multilayer

Effect of annealing temperature in nitrogen atmosphere and under vacuum on structural, optical and electrical properties of sputtered ITO/Ni/ITO multilayer

Regulation of component transformation in MOF-derived vanadium oxide@C spindles for high-performance electromagnetic wave absorption

Metal-organic framework (MOF) derived carbon-based materials had drawn increasing research attention for developing advanced absorbers. In this work, vanadium (V)-MOF derived porous V oxide@C (vanadium oxide encapsulated carbon material) spindles had been successfully prepared by a two-step method. After sintering at different temperatures in nitrogen atmosphere, a series of phase transformation processes were generated in this V-MOF, where variant V oxide@C composite materials including V2O5, V2O3, VO are formed, respectively. Among these samples, V oxide@C with a sintering temperature of 500 ℃ exhibited the best EM wave absorption performance when the main form of vanadium oxide was V2O3. The minimum reflection loss of V oxide@C could reach − 19.5 dB, and the effective absorbing bandwidth is 5.2 GHz (from 12.8 GHz to 18 GHz) with the absorbent thickness of 1.7 mm, almost covering the whole Ku band. It is believed that the V oxide@C composite materials are expected to be novel absorbers in the electromagnetic wave absorption field.

Electron beam treatment of polylactide at elevated temperature in nitrogen atmosphere

Different irradiation temperatures (25, 80 and 170 °C) have been used to investigate the temperature dependence of electron beam (EB) induced cross-linking and degradation behavior of neat polylactide (PLA) without the use of any cross-linking agents. Free radicals were generated and the competing chain scission and cross-linking reactions were initiated when the PLA material was exposed by the EB treatment. The sol gel analysis showed that no gel occurred for an EB treatment at room temperature, whereas the maximum gel content (33%) appeared for the PLA modified at 80 °C with 200 kGy. The molar mass of control and EB modified PLA samples were studied by size exclusion chromatography (SEC). The results demonstrated that the weight average molar mass (Mw) decreased dramatically for EB treatments at 25 °C with increasing dose. In contrast, a significant enhancement of Mw was found for PLA after the EB treatment at 80 and 170 °C. In comparison to the EB treatment at 25 °C, the rheological analysis indicated a remarkably improved elasticity behavior of modified PLA, higher absolute values of complex viscosity and higher storage modulus at low frequencies for EB treatments at elevated temperature.

Synthesis and Evaluation of Olivine Material Coated with Carbon

Lithium iron phosphate, LiFePO 4 , was synthesized by hydrothermal process and subsequently coated with carbon by the thermal decomposition of acetylene gas. The products were characterized by XRD, SEM, and TG-DTA. As-synthesized LiFePO 4 was submicron sized plate-like particle. After heating at various temperature in nitrogen atmosphere, the particle size and the crystalline sizes were grown with increasing the heating temperature. Above 700°C, the grain growth was remarkably. Carbon coating temperature was set at 500-600°C because of fine particle and good crystallinity. As a carbon raw material, acetylene gas was flowing to the as-synthesized LiFePO 4 in nitrogen atmosphere, and the LiFePO 4 /C composite was obtained. TG curves showed weight loss above 500°C, which was thought to be associated with carbon layer composition.

Catalytic Etherification of Glycerol to Diglycerol Over Heterogeneous Calcium-Based Mixed-Oxide Catalyst: Reusability and Stability

The activities of different heterogeneous alkaline-earth metal oxide catalysts and mixed-metal oxide catalysts were investigated. Glycerol etherification was carried out at 250°C in a three-necked glass reactor vessel at atmospheric pressure. In a typical experiment, 50 g of anhydrous glycerol was loaded into the reactor. Then, 2 wt.% of catalyst was added to the reactor. The reactor was then heated to the appropriate reaction temperature in nitrogen atmosphere under continuous stirring. The heterogeneous CaO catalyst showed the highest catalytic conversion (72%) compared with other alkaline-earth metal oxides, with a diglycerol yield of 19%. The highest glycerol conversion of 96% and diglycerol yield of 52% were observed for the mixed-metal oxide catalyst (Ca1.6Al0.4La0.6O3). Reusability and stability of this catalyst were tested. The ICP-AES analysis was performed to confirm the leaching of the metal species in the liquid phase of the reaction mixture.

Poly(methylmethacrylate)-block-poly(N-hydroxyethylacrylamide) diblock copolymers: direct ATRP synthesis and characterization

Diblock copolymers consisting of methylmethacrylate (MMA) and N-hydroxyethylacrylamide (HEAAm) polymer were successfully synthesized via direct two steps atom transfer radical polymerization (ATRP). At first, poly(methylmethacrylate) (PMMA) macroinitiators were prepared using methyl 4-(bromo-methyl) benzoate initiator and were used for synthesizing PMMA-b-PHEAAm block copolymers. PMMA homopolymers were synthesized in N,N′-dimethylformamide (DMF) using CuBr/2, 2′bipyridine catalyst system at 110 °C temperature in nitrogen atmosphere. Block copolymers were synthesized in mixture of DMF/water (8/2 v/v%) and in pure DMF in the presence of CuBr/1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) catalyst system at 85 and 100 °C, respectively, while argon was used for deoxygenation and inert environment. Purification of block copolymers was conducted through dialysis against deionized water using a dialysis tubing (MWCO 3,500, cellulose membrane). Molecular weights of PMMA polymers (M n = 4,400, 6,200 and 8,400 Da) were determined by size exclusion chromatography using tetrahydrofuran (THF) as eluent. The chemical structure and actual copolymer compositions were determined using elemental analysis (EA), attenuated total reflectance infrared (ATR-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopic analysis. Phase separation of diblock copolymers resulting in two glass transition temperatures as detected by differential scanning calorimeter (DSC) proves their amphiphilic behavior. Thermogravimetric analysis (TGA) also showed that diblock copolymer, with two-step decomposition has higher thermal stability than PMMA.

Structural, Optical and Magnetic Properties of Mn-doped CdS Diluted Magnetic Semiconductor Nanoparticles

Diluted magnetic CdS:Mn nanoparticles were synthesized by the aqueous solution method with different manganese (Mn2+) concentrations (x=7–10 atom %) at room temperature in nitrogen atmosphere and capped with Thiogelycerol. The X-ray diffraction patterns of CdS nanoparticles with different Mn doping concentration indicated that samples have hexagonal structure at room temperature. Energy dispersive X-ray spectroscopy confirmed incorporative of Mn ions in CdS nanoparticles. UV-Visible spectroscopy is used to investigate optical absorption of Mn-doped CdS. From photoluminescence measurement it was found that the intensity of the luminescence spectra decreases by increasing Mn2+ dopant ions at high precursor concentration. Also, the room temperature ferromagnetic behavior of Mn-doped CdS nanoparticles is discussed by using hysteresis measurement results.

Terahertz spectroscopic investigation of magnetic materials

The absorption spectra of three kinds of magnetic materials in the frequency range of 0~2.0THz has been measured with terahertz time-domain spectroscopyat room temperature in nitrogen atmosphere. Simultaneously, the terahertz refraction, transmission and absorption spectrum of the three kinds of magnetic material are obtained through the experiment. Comparing the spectroscopic characteristics of the samples of the three kinds of magnetic materials, the difference can be obviously observed. The results provided in this paper will help us to study the terahertz application to magnetic materials quality evaluation and the development of rare earth resources.

Study on the THz spectra of four kinds of Nipagin esters

The transmission spectra of methylparaben, ethylparaben, propylparaben, and butylparaben in the range of 0.2–2.5 THz are measured using terahertz time-domain spectroscopy (THz-TDS). Their refractive index and absorption spectra are obtained at room temperature in nitrogen atmosphere. The results show that the four kinds of Nipagin esters have obvious absorption peaks at 1.54 and 1.83 THz for methylparaben, 1.98 THz for ethylparaben, 1.37 and 1.61 THz for propylparaben, and 0.76 and 1.68 THz for butylparaben. Their anomalous dispersion of the refractive index appears at the corresponding position. Based on the density functional theory (DFT), the vibration absorption spectra of their single molecule are simulated. The numerical simulation and experimental results generally agree with each other. Then the reasons for their minor differences are analyzed. Overall, the spectral properties of Nipagin esters are found to have great significance for the detection of preservatives and for food safety. OCIS codes: 300.1030, 300.6495. doi: 10.3788/COL201109.S10503. Food preservation is an enduring topic. With continuous scientific and technological progress, the preservatives in synthetic food have been found to threaten human health. With the improvement of living and consumption levels, people have thus proposed higher requirements on food safety and health. Therefore, food safety testing is very important. Food components can be analyzed by Terahertz Time-Domain Spectroscopy (THz-TDS). It has practical significance for the study of molecular structure and preservative functions. The molecular formula of methylparaben is C8H8O3. It is mainly used in organic synthesis, food, cosmetics, and preservatives. The molecular formula of ethylparaben is C9H10O3. It is mainly utilized in the production of soy sauce and beer and is also used in other aspects of corrosion. The molecular formula of propylparaben is C10H12O3. It is used in food, cosmetics, medicines, and biocides. The molecular formula of butylparaben is C11H14O3. It is used in medicines, food, and cosmetics preservatives. To date, the methods used for the analysis of Nipagin esters are high performance liquid chromatography (HPLC) [1] , capillary column gas chromatography [2] , gas chromatography [3] , infrared spectroscopy [4] , and liquid chromatography [5] , etc. The mechanism involved in Nipagin esters in food has been determined. The Fuzhou Product Quality Monitoring Bureau has examined the application of accelerating solvent extraction (ASE) and chromatograph of gel permeation (GPC) techniques for parabens assay [6] . However, there have been no studies to date which employed the terahertz (THz) spectroscopy of Nipagin esters. THz radiation is a kind of electromagnetic wave located between infrared ray and microwave with a frequency in the range of 0.1–10 THz and a wavelength in the range of 30 µm–3 mm [7] . It belongs to the far-infrared band and the transition region in electronics to photonics. It has important academic value and potential applications. Experimental results are obtained using THz spectrum technology in the domain of preservative food testing. Using fast Fourier transformation (FFT) of time-domain spectroscopy, frequency domain spectra such as amplitude and phase are obtained. A series of optical parameters can then be derived [8] such as refractive index, extinction coefficient, absorption coefficient, and so on. This is followed by the analysis of the THz optical characteristics of the materials. In a previous work, the components of vitamins have been analyzed using THz-TDS measurement [9] . In this letter, the THz transmission spectra of methylparaben, ethylparaben, propylparaben, and butylparaben in the range of 0.2– 2.5 THz were measured by THz-TDS. Their refractive index and absorption spectra were measured. Numerical simulations based on the Density Functional Theory (DFT) were also conducted using Gaussian 03 software package. By comparing the calculated results and the experimental measurements, their differences were analyzed. THz-TDS is expected to be used as a method for non-destructive spectral inspection. The experimental samples are commercially available, with their purity more than 99%. Four samples of methylparaben, ethylparaben, propylparaben, and butylparaben were pressed under the pressure of 4 tons after grinding by a tablet press machine. Their thicknesses are 0.754, 0.800, 0.724, and 0.806 mm, respectively, and their diameter is 13 mm. The surfaces of the samples are smooth and parallel. Using THz-TDS, the THz

Terahertz spectra of edible pigments

Terahertz time-domain spectroscopy (THz-TDS) is a new coherent spectral technique to measure transmission spectra and analyze the spectral characteristics of samples. In this letter, the transmission spectra of edible pigments in the THz frequency range are measured using THz-TDS technology at both room temperature and low temperature in nitrogen atmosphere. Their refractive index spectra and absorbance are obtained. The result shows that there is some obviously abnormal dispersion in the refractive index spectra as well as absorption peaks in absorbance at the corresponding frequencies. THz-TDS is expected to have a potential application in the identification of pigments.

Effects of thickness and annealing on the structural and optical properties of chemical bath deposited CdS thin films

Present work focuses on the preparation and characterization of IInVI thin film semiconductor compound Cadmium Sulfide (CdS), commonly used as window layer in polycrystalline thin-film photovoltaic cells. CdS thin films were prepared by chemical bath deposition (CBD) in six different thicknesses and subjected to heat treatment at five different temperatures in nitrogen atmosphere, in order to find the appropriate film for perfect window layer in copper indium diselenide (CIS)/CdS photovoltaic cells. Structural and optical characterizations were carried out by X-ray diffraction and UV-VIS-NIR spectrometer respectively. Both the Hawleyite (cubic) and Greenockite (hexagonal) phases were observed, the latter being most predominant. Films show good transmittance in visible region and the band gap was found to decrease with the increase in thickness and annealing temperature.

几种塑料的太赫兹光谱检测

Using Terahertz time-domain spectroscopy technology,the transmission spectra of polyethylene,polypropylene,polyvinyl chloride,polytetrafluoroethylene and acrylonitrile-butadiene-styrene are measured.Spectral characteristics of these five materials between 0.2~2.6 THz are studied.The absorbance and refractive index spectra of five plastic at room temperature in nitrogen atmosphere are obtained.The results show that refractive index and absorption coefficient of these five plastic are significant different,and the refractive indexes are in the ranges from 1.35 to 1.85.Compared to polyvinyl chloride and acrylonitrile-butadiene-styrene,the absorbance of polyethylene,polypropylene and polytetrafluoroethylene are much smaller.The research provides a method to identify plastic types and choose substrate of terahertz optical components using terahertz time-domain spectroscopy.

Synthesis and electroluminescent properties of polyfluorene‐based conjugated polymers containing bipolar groups

AbstractA bipolar dibromo monomer, bis‐(4‐bromophenyl)[4‐(3,5‐diphenyl‐1,2,4‐ triazole‐4‐yl)‐phenyl]amine (9), containing electro‐rich triphenylamine and electro‐deficient 1,2,4‐triazole moieties was newly synthesized and characterized. Two fluorescent fluorene‐based conjugated copolymers (TPAF, TPABTF) were prepared via facile Suzuki coupling from the dibromo bipolar monomer, 4,7‐dibromo‐2,1,3‐benzothiadiazole (BTDZ), and 9,9‐dioctylfluorene. They were characterized by molecular weight determination, IR, NMR, DSC, TGA, solubility, absorption and photoluminescence spectra, and cyclic voltammetry. The polymers showed good solubility in common organic solvents such as dichloromethane, chloroform, tetrahydrofuran, and dichlorobenzene at room temperature. They had glass transition temperatures (Tg) higher than 135 °C and 5% degradation temperatures in nitrogen atmosphere were higher than 428 °C. Single layer polymer light‐emitting diodes (PLED) of ITO/PEDOT:PSS/polymer/metal showed a blue emission at 444 nm and Commission Internationale de I'Eclairage (CIE) 1931 color coordinates of (0.16, 0.13) for TPAF. The device using TPABTF as emissive material showed electroluminescence at 542 nm with CIE1931 of (0.345, 0.625), low turn‐on voltage of 5 V, a maximum electroluminance of 696 cd/m2, and a peak efficiency of 2.02 cd/A. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6231–6245, 2009

Synthesis and Photosensitive Properties of Poly(aryl imino) Containing Azobenzene Group (PAI‐A)

AbstractUsing 4,4′‐dibromobenzophenone and 4,4′‐diaminoazobenzene as monomers, poly(aryl imino) containing azobenzene unit (PAI‐A) was synthesized via palladium‐catalyzed amination, and structurally characterized by means of FT‐IR, 1H NMR spectra and elemental analysis, the results of which show an agreement with the proposed structure. The UV absorption spectra were tested under different conditions. Additionally, differential scanning calorimetry (DSC) and thermogravimetric (TG) measurements show that PAI‐A possesses high glass transition temperature (Tg>176°C) and good thermal stability with high decomposition temperatures in nitrogen atmosphere (TD>410°C).

Synthesis of Soluble Fluorene‐polyimino Ketone

AbstractBased on the 9,9‐di(4‐anilinyl)fluorene, structurally different fluorene‐polyimino ketones have been obtained by the Buchwald‐Hartwig cross coupling reaction. Their structure and performance have been characterized by FT‐IR, 1H NMR, UV‐vis and thermal analysis. The results show an agreement with the proposed structure, which possesses high glass transition temperature (Tg>250 °C) and good thermal stability with high decomposition temperatures in nitrogen atmosphere (TD>520 °C). Additionally, the polymers synthesized showed good solubility, which can be dissolved in common organic solvent CHCl3 at room temperature.

SYNTHESIS AND PHOTOPHYSICAL PROPERTIES OF POLY(ARYL IMINO) CONTAINING ACRIDINE UNITS (PAIA)

1,4-Bis-(4-bromobenzoyl)benzene and proflavine, 3,6-diaminoacridine free base were synthesized first. Using 1,4-bis-(4-bromobenzoyl)benzene and proflavine, 3,6-diaminoacridine free base as the monomers, poly(aryl imino) containing acridine units (PAIA) was synthesized via palladium-catalyzed amination. The structure of PAIA was characterized by means of FTIR, 1H-NMR spectroscopy and elemental analysis, the results show an agreement with the proposed structure. The UV absorption and photoluminescence spectra were tested. The absorption spectrum of the PAIA was dependent on the acidity of the media. The emission and excitation spectra of the two different forms of PAIA were investigated by photoluminescence, the addition of the trifluoroacetic acid (TFA) to the solution of PAIA does not lead to a quenching effect in the photoluminescent spectra. Additionally, DSC and TG measurements show that PAIA possess high glass transition temperature (Tg > 230°C) and good thermal stability with high decomposition temperatures in nitrogen atmosphere (TD > 500°C).

Effects of high temperature drying in nitrogen atmosphere on mechanical and colour properties of Norway spruce

Heat treatment and drying processes of wood are always accompanied by material changes. These changes are partly caused by oxidative reactions. This study aims to compare high temperature drying in inert gas atmosphere with conventional kiln drying of spruce wood. The mechanical properties as well as colour changes were measured after drying. In general, higher compression strength was observed for samples dried at high temperatures in nitrogen atmosphere. However, tensile and bending strength proved no significant difference. Corresponding to the strength values increased stiffness values were also observed for the compression samples, whereas for tension and bending samples no significant effect was visible. Up to a temperature of approx. 125 °C discolouration is prevented by drying samples in nitrogen atmosphere.

A study of copper coatings electrodeposited in electrolyte with a metallic powder of chromium

Copper coatings modified with chromium and sulfur inclusions were electrodeposited in acidic copper sulfate electrolytes containing a metallic powder of chromium. It was found that a metallic powder of chromium is not suitable to obtain Cu–Cr composites in contrast to chemical inert particles of other non-metallic powders. Due to electrochemical reduction of partially dissolved chromium ions it is rather an “alloying precursor with chromium” of a fine-textured Cu–Cr matrix. The aim of this paper was to present the data on investigations of the morphology of formed new materials and functionality based on their mechanical properties (hardness, wear resistance), electrical resistivity and thermal stability of smooth-faced copper coatings with chromium and sulfur inclusions as compared with those of crystalline surface of pure copper matrix. With respect to increase in the smoothness of coating surface the hardness (HV 50) increases from 180 to 240 kgf mm − 2 , and shows a significantly higher wear resistance and more intensive phase transformations of Cu–Cr–S coating surface at higher temperatures in nitrogen atmosphere. Meta-stable phases of CuS were formed at temperatures higher than 200 °C and Cr 2N or CrN higher than 600 °C, which may be a stabilized matrix of copper coating in nitrogen atmosphere in contrast to an oxidative degradation of copper coatings in oxygen-containing atmosphere at higher temperatures. The electrical resistivity being the basic functional property of the formed Cu–Cr–S coating is similar to that of pure copper coating. The increase in temperature from − 150 to 100 °C results in increase in resistivity of copper materials from 1.2 to 2.8 × 10 − 8 Ω m for pure copper and from 0.8 and 0.6 to 2.6 and 2.1 × 10 − 8 Ω m for Cu–Cr–S coatings.

A new approach towards the growth of cadmium sulphide thin film by CBD method and its characterization

Cadmium sulphide thin films were deposited by the chemical bath deposition method using tartaric acid as a complexing agent and annealed at different temperature in nitrogen atmosphere and characterized. The crystallographic structure and the crystallite size were studied by the X-ray diffraction (XRD) pattern. Transmittance of the deposited film is significantly higher in the visible region. The optical band-gap of deposited film is 2.4 eV and it decreases with increase in annealing temperature. Temperature dependence of resistivity confirmed the semiconducting behaviour of the film. Scanning electron micrographs (SEM) showed the presence of grain particles of size < 1 μm. X-ray photoelectron spectroscopy (XPS) studies supported the composition of cadmium sulphide thin film determined by EMPA and also indicated the presence of carbon and oxygen as impurity in the film.

Preparation of Au2S3 and nanocrystalline gold by sonochemical method

We report a new synthesis of Au2S3 by a sonochemical reaction between Au(CH3COO)3 and S in decalin at room temperature in nitrogen atmosphere. When gold acetate is sonicated under similar conditions without the presence of sulfur, nanocrystalline gold is formed. The products were characterized by X-ray powder diffraction, transmission electron microscope and thermal analysis (TG and DSC). The synthesis procedure is substantially simpler than the previously reported methods.