Synthesis and characterization of maghemite nanosheets

Magnetic maghemite nanoparticles in the form of nanosheets were prepared by a topotactic transformation during the dehydroxylation of a γ-FeO(OH) precursor. The precursor was synthesized from tetrapyridin Fe(II) chloride (Fe(py)₄Cl₂). The nanosheets are several hundreds of nanometers wide, and less than 5 nm thick; they frequently bend and curl at the edges; they are nanocrystalline; and they are composed of smaller maghemite nanostructured domains, from a few nanometers up to several tens of nanometers wide.     

无机芯微胶囊相变储能材料制备、表征及其热物性研究

通过原位聚合法合成了Na2HPO4.12H2O@尿醛树脂微胶囊相变储能材料。考察了尿素和甲醛的物质的量比对所得微胶囊结构和形貌特征的影响。采用扫描电镜(SEM)观察微胶囊的表观形态,透射电镜(TEM)观察微胶囊的微观结构,傅里叶红外光谱(FT-IR)表征了微胶囊复合材料的成分,激光导热仪测量了微胶囊的导热系数,差示扫描量热仪(DSC)表征了微胶囊的相变特性,热重分析仪(TGA)测定了微胶囊质量与温度间的关系。结果表明,所制备出的微胶囊为球状壳/核结构,包封良好,球体粒径约为500nm,相变潜热约为121.2J/g,在30～84℃的温度范围内失重量<10%。该微胶囊相变储能材料具有一定的应用前景。     

CuO microflowers composed of nanosheets: Synthesis, characterization, and formation mechanism

CuO microflowers composed of nanosheets with tunable size have been fabricated through a simple reaction in ammonia solution at 90-180 °C, in which the nanosheets with zigzag edges were 20-40 nm in thickness and 500-800 nm in width. The high ammonia concentration, high ratio of CNH₃ to CCu2+ (R_ac) and elevated temperature were necessary for the formation of microflowers, and the ammonia concentration was critical for the morphology evolution of the particles. The fabrication mechanism of CuO microflowers based on the assembly of Cu(OH)₂ nanobelts was discussed. In addition, the CuO microflowers showed effective catalytic activity on the decomposition of ammonium perchlorate.     

Wearable yarn supercapacitors coated with twisted PPy@GO nanosheets and PPy@PAN-GO nanofibres

Journal of Materials Science - There is an urgent need to develop flexible yarn-type supercapacitors with excellent electrochemical and mechanical properties for flexible energy storage devices in...     

Synthesis and characterization of SnS nanosheets through simple chemical route

Tin Sulfide (SnS) nanosheets were synthesized by wet chemical route using ethylene glycol (EG) and without using any surfactant. Structural and phase purity were confirmed by powder X-ray diffraction pattern which shows the orthorhombic structure of SnS. The sheets like morphology and particle size of the synthesized product were identified by using analytical transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM). Agglomeration of SnS nanoparticles was found to lead to the formation of nanosheets. UV-VIS-NIR absorption spectrum of SnS nanosheets shows the direct transition at 1.88 eV. Compared to bulk band gap a blue shift of 0.58 eV has been observed for direct transition. This is due to the quantum confinement effect. Room temperature photoluminescence spectrum of SnS nanosheets shows two emission bands at 1.75 and 1.57 eV respectively which are assigned to band gap and defect level transitions.     

Synthesis, characterization, and thermal properties of biodegradable polyetheresteramide-based polyurethane

In this paper, a new kind of biodegradable polyetheresteramide-based polyurethane (PEEA-U) copolymers were prepared by melt polymerization from ε-caprolactone, 6-aminocaproic acid, poly(ethylene glycol), and toluene diisocyanate. The obtained polymers were characterized by ¹H NMR, FTIR, DSC, WAXD, and TGA/DTG. The water absorption, hydrolytic degradation, and alkaline degradation behavior of these copolymers were also studied in detail.     

Synthesis of high-performance graphene nanosheets by thermal reduction of graphene oxide

High-performance graphene nanosheets have been synthesized by thermal reduction of graphene oxide (GO) under ethanol atmosphere. The reduced GO nanosheets were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy and electrical transport measurements, respectively. The results indicated that the thermal reduction of GO under ethanol atmosphere can effectively remove the oxygen-containing functional groups and restore its graphic structure compared to the ones obtained using hydrazine or hydrogen. The electrical measurements indicated that the electrical mobility of single-layer graphene sheet reduced under ethanol atmosphere at 900 °C can reach 29.08 cm² V⁻¹ S⁻¹.     

Synthesis of nano-carbon (nanotubes,nanofibres, graphene) materials

In the present study, we report the synthesis of carbon nanotubes (CNTs) using a new natural precursor: castor oil. The CNTs were synthesized by spray pyrolysis of castor oil-ferrocene solution at 850°C under an Ar atmosphere. We also report the synthesis of carbon nitrogen (C-N) nanotubes using castor oil-ferrocene-ammonia precursor. The as-grown CNTs and C-N nanotubes were characterized through scanning and transmission electron microscopic techniques. Graphitic nanofibres (GNFs) were synthesized by thermal decomposition of acetylene (C₂H₂) gas using Ni catalyst at 600°C. As-grown GNFs reveal both planar and helical morphology. We have investigated the structural and electrical properties of multi-walled CNTs (MWNTs)-polymer (polyacrylamide (PAM)) composites. The MWNTs-PAM composites were prepared using as purified, with ball milling and functionalized MWNTs by solution cast technique and characterized through SEM. A comparative study has been made on the electrical property of these MWNTs-PAM composites with different MWNTs loadings. It is shown that the ball milling and functionalization of MWNTs improves the dispersion of MWNTs into the polymer matrix. Enhanced electrical conductivity was observed for the MWNTs-PAM composites. Graphene samples were prepared by thermal exfoliation of graphite oxide. XRD analysis confirms the formation of graphene.     

Synthesis, characterization, thermal and explosive properties of potassium salts of trinitrophloroglucinol

Three different substituted potassium salts of trinitrophloroglucinol (H(3)TNPG) were prepared and characterized. The salts are all hydrates, and thermogravimetric analysis (TG) and elemental analysis confirmed that these salts contain crystal H2O and that the amount crystal H2O in potassium salts of H3TNPG is 1.0 hydrate for mono-substituted potassium salts of H3TNPG [K(H2TNPG)] and di-substituted potassium salt of H3TNPG [K2(HTNPG)], and 2.0 hydrate for tri-substituted potassium salt of H3TNPG [K3(TNPG)]. Their thermal decomposition mechanisms and kinetic parameters from 50 to 500 degrees C were studied under a linear heating rate by differential scanning calorimetry (DSC). Their thermal decomposition mechanisms undergo dehydration stage and intensive exothermic decomposition stage. FT-IR and TG studies verify that their final residua of decomposition are potassium cyanide or potassium carbonate. According to the onset temperature of the first exothermic decomposition process of dehydrated salts, the order of the thermal stability from low to high is from K(H2TNPG) and K2(HTNPG) to K3(TNPG), which is conform to the results of apparent activation energy calculated by Kissinger's and Ozawa-Doyle's method. Sensitivity test results showed that potassium salts of H3TNPG demonstrated higher sensitivity properties and had greater explosive probabilities.     

Solvent thermal synthesis and gas-sensing properties of Fe-doped ZnO

In this study, pure ZnO microbullets, ZnO–ZnFe₂O₄ composite, and ZnO–Fe₂O₃–ZnFe₂O₄ composite with micron structured balloons, rods, and particles were prepared by a simple solvent thermal process using methanol or ethanol as solvents. The influence of solvents on the composition and morphology of the products was studied, and their gas-sensing properties were also investigated. The morphology of ZnO microbullets synthesized in ethanol is similar to but more uniform than that of ZnO microbullets synthesized in methanol. The Fe-doped ZnO synthesized in ethanol contains many micron particles homogeneously dispersing on the surface of the microbullets, which is composed of hexagonal wurtzite ZnO and franklinite ZnFe₂O₄, while Fe-doped ZnO prepared in methanol consists of micron structured balloons, rods, and particles, which is composed of hexagonal wurtzite ZnO, hematite Fe₂O₃, and franklinite ZnFe₂O₄. Compared with pure ZnO and ZnO–ZnFe₂O₄ composite, the ZnO–Fe₂O₃–ZnFe₂O₄ composite presented high response, rapid response/recovery characteristics, good selectivity, and excellent stability to acetone at relatively low operating temperature of 190 °C. This sensor could detect acetone in wide range of 1–1000 ppm, which was expected to be a promising gas sensor for detecting acetone.     

Synthesis,optical and thermal characterization of novel thiazolyl heterocyclic azo dye

Thiazolyl heterocyclic azo dye and its metal (Ni²⁺, Co²⁺)–azo complexes were synthesized. Their structures were confirmed by elemental analysis, UV–VIS absorption spectra, FT-IR, ¹H NMR and MALDI-MS. The thermal properties of metal complexes were studied by DSC–TGA. The optical constants (complex refractive index N = n + ik) and thickness of the complex thin films on polished single-crystal silicon substrates were investigated on a scanning ellipsometer. Results indicate that thiazolyl metal–azo complexes possess good optical and thermal properties. They would be a promising recording medium candidate for NVD with the Super-resolution near field structure (Super-RENS) technology.     

静电纺丝技术制备PAN/Eu(BA)3 phen复合发光纳米纤维与表征

采用静电纺丝技术制备出聚丙烯腈(PAN)/Eu(BA)3phen复合纳米纤维;采用扫描电子显微镜(SEM)对其结构进行了表征,复合纳米纤维表面光滑,平均直径在400～720nm.荧光光谱和荧光寿命分析表明,复合发光纳米纤维均能发出强的铕离子的特征荧光,具有较高发光效率和色纯度高,且荧光寿命高于稀土配合物.     

聚苯氧基磷酸对苯二酚酯的合成、表征及其热稳定性研究

以三氯氧磷、苯酚和对苯二酚为主要原料,通过两步合成法,采用本体聚合制备了含磷阻燃剂聚苯氧基磷酸对苯二酚酯。使用红外光谱、1 HNMR、13C NMR和31P NMR确定了阻燃剂的结构。用热重分析测试了阻燃剂的热稳定性。结果表明,聚磷酸酯的结构与预期结构相符;其初始分解温度为364℃,最快分解温度为547℃,700℃时的残炭量为36%,表现出良好的热稳定性。     

Synthesis, characterization and thermal studies on furazan- and tetrazine-based high energy materials

This paper reports the synthesis of high energy materials (HEMs) viz. 3,3'-diamino-4,4'-azoxyfurazan (DAAF), 3,3s'-azobis(6-amino-1,2,4,5-tetrazine) [DAAT] and 1,4-dihydrazino tetrazine (DHTz). The products obtained were characterized by IR, 1H NMR, 13C NMR and mass spectra. Thermolysis of these compounds carried out by applying TG-DTA and DSC techniques indicated that the thermal stability of DAAF and DAAT was in the temperature range of 230-250 degrees C, whereas that of DHTz was up to approximately 140 degrees C. TG-FTIR of gaseous products of these compounds suggests the evolution of NH2CN/NH3 and HCN as major decomposition products. The impact and friction sensitivity data revealed that DAAF is insensitive to mechanical stimuli whereas DAAT and DHTz are vulnerable to impact stimuli. The cyclic voltammetric studies brought out that, DAAF, DAAT and DHTz are electroactive compounds and thereby can be detected at even low concentration at pH 7 and 13. The theoretical predictions of explosive power of DAAF, DAAT and DHTz alone and their combinations with well-known insensitive high explosives using Becker-Kistiakowsky Wilson (BKW) code as well as that of propellants based on them by NASA-CEC-71 suggest their potential in specific systems.     

Synthesis,characterization and thermal studies of polyamide esters containing aryl-azo,azomethine and thianthrene units

New polyamide esters containing aryl-azo, azomethine and thianthrene tetraoxide units in the backbone and also having different aromatic moieties, were synthesized by reacting 4,4-ozodibenzoyl, 3,3-ozodibenzoyl, 4,4[1,4-phenylenebis(methylidynenitrilo)] dibenzoyl chlorides, 2,7-dichloroformyl-thianthrene-5-5,10,10-tetraoxide, 4,4-diphenic, isothaloyl and terephthaloyl dichlorides with ethanediamide-N,N-bis(2-hydroxyethyl) using the lowtemperature solution polycondensation technique. The yields and the values of reduced viscosity of the produced polyamide esters were found to be unaffected by the type of organic solvent used. In order to characterize the polymers, a model compound was prepared from ethanediamide-N,N-bis(2-hydroxyethyl) and benzoyl chloride and investigated by infrared, nuclear magnetic resonance and elemental analysis. The synthesized polymers were confirmed by infrared, ultraviolet, nuclear magnetic resonance spectroscopy, elemental analyses and viscosity measurements. The effect of the nature of different units on the thermal properties of polymers was evaluated by thermogravimetric analysis: the data showed that the thermal stabilities of the polymer were remarkably affected by the introduction of these groups.     

Synthesis,characterization, thermal and dielectric properties of pure and cadmium doped calcium hydrogen phosphate

The synthesis of pure and cadmium doped calcium hydrogen phosphate as single crystal has been accomplished by a room temperature solution growth technique viz., silica gel technique. Silica gel obtained from sodium metasilicate with a strongly acidic cation exchanger in the H-form, was used for crystal growth experiments. The nature of the grown material was established by powder X-ray diffraction (PXRD) studies, whereas from single crystal X-ray diffraction (SXRD) the crystal system comes out to be monoclinic. The stoichiometry of the grown composition was established by energy dispersive X-ray analysis (EDAX). Fourier transform infrared spectroscopic (FTIR) studies signifies the presence of phosphate (PO₄)²⁻ group and water of crystallization. Thermo gravimetrical analysis and investigations of dielectric properties were undertaken to study the thermal stability, dielectric constant and transition temperature of the grown material. Dielectric studies suggest that there is a shift in the value of transition temperature (T_c) thereby indicating relaxor behaviour of the material.     

高Tg含偶氮发色团侧链的聚酰亚胺的合成、表征及热稳定性

采用后重氮偶合法合成了6种含偶氮发色团侧链的聚酰亚胺非线性光学材料,用核磁共振、红外光谱和紫外光谱进行表征,采用示差扫描量热法研究了材料的热性能。研究表明这些聚合物具有较高的玻璃化温度(214～267℃)和热分解温度(315～384℃),侧基含芳香杂环的聚酰亚胺表现出良好的热稳定性和光学透明性。