Thermogravimetric Differential Scanning Calorimeter Research Articles

Synthesis of carbon nanotubes using Cu-Cr-O as catalyst by chemical vapor deposition

A novel powder catalyst Cu-Cr-O applied to the synthesis of carbon nanotubes (CNTs) was developed, which was prepared via ammonia precipitation method. Techniques of thermo-gravimetric/differential scanning calorimeter (TG-DSC), X-ray diffraction (XRD) as well as scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been employed to characterize the thermal decomposition procedure, crystal phase and micro structural morphologies of the as-synthesized materials, respectively. The results show that carbon nanotubes are successfully synthesized using Cu-Cr-O as catalyst when the precursors are calcined at 400, 500, 600, and 700 °C. The results indicate that the calcination of the Cu-Cr-O catalyst at 600 °C is an effective method to get MWCNT with few nano-tube defects or amorphous carbons.

Synthesis and self‐assembled mechanism of CuO peony‐flowers by a composite hydroxide‐mediated approach at low temperature

A composite‐hydroxide mediated (CHM) method was utilized for the synthesis of CuO peony‐flower nanostructures under temperatures ranging between 25 and 160 °C. The CHM mechanism was confirmed through X‐ray Powder Diffraction (XRD) and a Thermo‐Gravimetric Differential Scanning Calorimeter (TG‐DSC). Cu(NO3)2 was shown to transform into Cu(OH)2 in the mixed alkalis (NaOH/KOH); the reaction was facilitated by the solvent properties of the mixed alkalis. Cu(OH)2 subsequently consumed H2O in the adsorption of the mixed alkalis at 25∼65 °C. At higher reaction temperatures (>65 °C), the Cu(OH)2 was seen to decompose at an accelerated rate. Therefore, crystalline CuO could be obtained not only above 65 °C but also at 25 °C. The crystal morphology and structure of CuO were examined through Filed Emission Scanning Electron Microscopy (FE‐SEM) and Transmission Electron Microscopy (TEM). It was determined that the CuO peony‐flower had a polycrystalline structure composed of single crystalline CuO petals. Using the Selected Area Electron Diffraction (SAED) results, the rings were indexed as (002), (111), (112), (202) and (−113), which was in agreement with the XRD results. With increasing temperature, the CuO flower petals self‐assembled through random aggregation and gathered CuO nanorod parts, which led to incomplete CuO flower petals through orientated aggregation. Prolonged reaction time led to the growth of CuO flower petals in the direction of [001]. An ideal CuO flower structure was observed through TEM observation.

Preparation of layered potassium titanate whiskers with large length-diameter ratio by KDC method

Pure K2Ti4O9 whiskers were prepared by KDC (Kneading-Drying-Calcination) method with TiO2 and K2CO3 as raw materials. The influences of TiO2/K2CO3 molar ratio (RT/K), calcination temperature (TC) and cooling process on phase composition and morphology of the whiskers were investigated by TG-DSC (thermo gravimetric-differential scanning calorimeter), XRD (X-ray diffraction), and SEM (scanning electron microscope). Pure K2Ti4O9 potassium titanate whiskers with large length-diameter ratio (r) (over 250) can be obtained at RT/K = 2.9 and TC = 950 °C.

A novel resorbable strontium-containing α-calcium sulfate hemihydrate bone substitute: a preparation and preliminary study

Distraction osteogenesis after aggrieved bone segment resections is promising in the treatment of bone tumors and osteomyelitis. However, there is ambiguity with regard to the optimal choice of bone substitute, with biodegradability and excellent bone repair performance constituting key requirements. The purpose of this study was to develop a novel resorbable strontium-containing α-calcium sulfate hemihydrate (Sr-CaS) bone substitute to provide an alternative option for surgeons that better meets these requirements. The Sr-CaS was prepared using co-precipitation and hydrothermal methods and analyzed using x-ray diffraction (XRD), Fourier transform infrared (FTIR) scanning and thermogravimetric differential scanning calorimeter (TG–DSC) patterns. Cytotoxicity by tetrazolium bromide (MTT), sub-acute toxicity and hemolysis tests were performed to assess the initial biocompatibility of the new bone substitute. Radiographic analysis, micro-CT measurements and histological observation were used to evaluate the bone repair ability in rat tibia bone defects. The XRD and FTIR patterns of Sr-CaS were both very similar to CaS and the product had comparable characteristics similar to α-CaS as demonstrated by TG-DSC. Cytotoxicity of the substitute was class 1 (no cytotoxicity) and hemolysis was 4.3% (no hemolysis). Sub-acute toxicity was not seen after a 14 day evaluation. The substitute was radio-opaque. The empty group exhibited the lowest levels of both bone mineral densities (BMD) and bone volume/total volume (BV/TV) of the defects when compared to all other groups. The two Sr-CaS groups resulted in significantly greater BMDs and BV/TV of the defect compared to the CaS only group. However, there was no significant difference between the 5% and 10% Sr-CaS groups. The Sr-CaS was resorbable with satisfactory biocompatibility. The doped strontium ions enhanced the bone repair performance of CaS in a rat model and the new substitute demonstrated promising results for clinical use.

Performance of a Metal-Organic Framework MIL-53(Al)-Supported Cobalt Catalyst in the CO Catalytic Oxidation Reaction

采用溶剂法合成了热稳定性高的金属有机骨架材料MIL-53（AI）（MIL：Materials of Institut Lavoisier），用此材料为载体负载钴催化剂用于CO的催化氧化反应，并与Al2O3负载的钻催化剂进行了对比．采用热重．差热扫描量热（TG—DSC）、傅里叶变换红外（FTIR）光谱、X射线衍射（XRD）、N2物理吸附-脱附、透射电子显微镜（TEM）、氢气程序升温还原（H2-TPR）等方法对催化剂的结构性质进行了表征．TG和N2物理吸附．脱附结果表明，载体MIL-53（AI）有好的稳定性和高的比表面积：XRD以及TEM结果表明Co／MIL-53（AI）F负载的Co3O4颗粒粒径（平均约为5．03nm）明显小于Al2O3上Co3O4颗粒粒径（平均约为7．83nm）．MIL-53（AI）的三维多孔结构中分布均匀的位点能很好地分散固定Co3O4颗粒，高度分散的Co3O4颗粒有利于CO的催化氧化反应．H2-TPR实验发现Co／MIL（AI）催化剂的还原温度低于Co／Al2O3催化剂的还原温度，低的还原温度表现为高的催化氧化活性．CO催化氧化结果表明，MIL-53（AI）负载钴催化剂的催化活性明显高于Al3O3负载钴催化剂，MIL-53（AI）负载钴催化剂在160℃时使CO氧化的转化率达到98％，到180℃时CO则完全转化，催化剂的结构在催化反应过程中保持稳定．

PREPARATION OF NANO-TATB BY SEMIBATCH REACTION CRYSTALLIZATION

The 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) nanoparticles were prepared by using semibatch reaction crystallization method, and the influencing factors in close relationship with the grain size and crystal morphology control, such as the concentration of reaction system and categories of surfactants, were studied in this paper. The synthesized nano-TATB particles had been characterized by SEM, XRD, thermo gravimetric/differential scanning calorimetric (TG/DSC) and N 2 physisorption. The grain size of TATB particles using nonionic surfactant as the additive ranged from 30 nm to 65 nm with a shape of spheres or ellipsoids. The broadening of the peaks and the weakening of the strength for nano-TATB were observed by XRD analysis. The corrected average particle size of nano-TATB was calculated using the Debye–Scherrer equation and the range was from 18 nm to 50 nm. TG and DSC curves revealed that thermal decomposition of nano-TATB occurred in the range of 361.5°C–385.0°C and its peak temperature was 373.7°C with a decrease of approximately 7°C compared with original TATB. Furthermore, the specific surface area (21.54 m2/g) of nano-TATB was calculated by BET method using N 2 physisorption (at 77°C).

Solid-state Reaction Study on Physically and Tribochemically Prepared BaC2O4-SnC2O4 Mixtures

The synthesis of barium metastannate, BaSnO3, by heating mixtures of metal oxalates, either physically mixed or subjected to a phase of mechanical activation, up to temperatures in the range 750- 1200 °C has been studied. Simultaneous thermogravimetric-differential scanning calorimetric (TGDSC) analyses and powder X-ray diffractometry have been applied to check the advancement of the reactions. BaSnO3, though slightly contaminated by BaCO3, can be obtained by heating the activated mixture up to T ≥ 1000 °C while heating a sample of a physical mixture at temperature as high as 1200 °C resulted in a mixture of BaSnO3, SnO2 and Ba2SnO4. The heat capacities of BaSnO3 samples prepared at temperatures between 1000 and 1200 °C have been measured by modulated temperature differential scanning calorimetry (MTDSC) in the temperature range 50-400 °C.

Synthesis and Characterization of PVA/MMT Porous Nanocomposite Prepared by Directional Freeze-Drying Method

Porous PVA/MMT nanocomposites, which included a great deal of macroporous, mesoporous and a few micorporous were fabricated by directional freezing and freeze-drying. X-ray diffraction (XRD), Scan Electric Microscope (SEM), Fourier Transform Infrared (FT-IR) spectroscopy, and Thermo gravimetric-differential scanning calorimeter analysis (TG-DSC) were used characterize the samples. Results showed that the morphology and the interactions between MMT and PVA of the obtained porous nanocomposites were influenced by nanoparticle size, colloid concentration , aging time etc.O-H bond in PVA and Si-O bond in MMT, "acetate" in PVA and O-H bond in particle flat of MMT which occurred coupling constituted hydrogen bonding which enhanced the driving power to help PVA molecules insert into interlayer spaces of MMT.

Solid state studies on cobalt and copper tungstates nano materials

The cobalt and copper tungstates of the composition Co 1− x Cu x WO 4 (where x = 0.0, 0.3, 0.5, 0.7 and 1.0) were synthesized by co-precipitation method. The compounds were characterized by Thermogravimetric Differential Scanning Calorimeter, X-ray powder diffraction, Infrared spectroscopy, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. The Rietveld refinements of X-ray powder diffraction data for the composition Cu 0.5Co 0.5WO 4 reveal the triclinic structure with Pī symmetry. The SEM and TEM studies of the compounds show average particle size in the range of 30–50 nm. The XPS studies confirmed the 2+ oxidation state of the Co and Cu, whereas W exists in 6+ state. The Diffuse reflectance Ultraviolet–visible spectroscopy illustrates band gaps of the compounds ranging from 2.95 to 2.79 eV. The CoWO 4 shows promising photoluminescence result exhibiting strong emission intensity at 468 nm.

Effect of carbon nanotubes and their dispersion on thermal curing of polyimide precursors

The process of thermal imidization reaction is significant for temperature and time control in the polyimide industry. Here, we report the effect of carbon nanotubes and their states of dispersion on the thermal imidization of the precursor films of polyimide (poly(amic acid)) for the first time. The curing process was followed by measuring Fourier transform-infrared (FT-IR) spectra, fluorescence spectra, thermogravimetric-differential scanning calorimeter (TG-DSC) properties and the refractive indices of films. It was found that by evenly dispersing 1 wt% of carbon nanotubes assisted by a dispersant in the poly(amic acid),the full imidization temperature of the polyimide can be reduced from 300 °C to 250 °C. Different states of distribution of CNTs were observed by light microscopy and scanning electron microscopy, and proved that a better dispersion of carbon nanotubes dramatically enhanced the speed of imidization. Moreover, the DSC results showed that lower decomposition temperature of poly(amic acid) could be obtained with more uniform distribution of carbon nanotubes, which means the process of cyclodehydration of the poly(amic acid) was accelerated.

Microwave solvothermal synthesis of Eu 3+-doped (Y,Gd) 2O 3 microsheets

A microwave-assisted solvothermal process was employed to synthesize the sheet-like (Y,Gd)-oxalate precursors. (Y,Gd) 2O 3 was obtained by thermal decomposition of the precursors above 550 °C. The samples were analyzed by X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FT-IR), scanning electron microscopy (SEM), thermogravimetric/differential scanning calorimeters (TG/DSC), and transmission electron microscopy (TEM). It was found that the sheet-like (Y,Gd)-oxalate precursors (indicated as (Y,Gd) 2(C 2O 4) 3·nH 2O) were sensitive to the synthetic conditions such as microwave irradiation power and volume ratio of ethylene glycol (EG) to water (defined as R). When R = 1, the products presented sheet-like morphology, and higher R value could change the aspect ratio of precursor to micro/nano rod-like. The possible growth process was also proposed based on the results. The excitation spectrum of the (Y,Gd) 2O 3:Eu 3+ (5 mol% of Eu 3+) microsheets was observed with a maximum peak at 238 nm (λem = 611 nm). The emission spectrum was recorded under excitation wavelength of 238 nm and exhibited the strongest peak at 611 nm. In addition, (Y,Gd) 2O 3:Eu 3+ with sheet-like shape had the strongest emission peaks.

Ionic liquids in the selective recovery of fat from composite foodstuffs

AbstractBACKGROUND: Ionic liquids (ILs) are able to dissolve a wide range of organic and inorganic molecules and have potential application in the separation and recovery of valuable components from wastes. The potential for ILs to separate sugar and fat from food waste is demonstrated using chocolate as a model system.RESULTS: The ILs 1‐(2‐cyanoethyl)‐3‐methylimidazolium bromide (cyanoMIMBr), 1‐propyl‐3‐methylimidazolium bromide (propylMIMBr), 1‐hexylpyridinium bromide (hexylPyrBr) and 1‐butyl‐3‐methylimidazolium chloride (butylMIMCl) were synthesised by microwave technology and fully characterised by mass spectrometry, thermogravimetric differential scanning calorimetery, thin layer chromatography, nuclear magnetic resonance and Fourier transform infrared spectroscopy. The solubilities of the fat and carbohydrate components in the ILs are reported for the two main ingredients in chocolate. CyanoMIMBr and propylMIMBr selectively solubilise sugar leaving the fat insoluble. Both cyanoMIMBr and propylMIMBr have been used to successfully separate sugars and cocoa butter fat from white, milk and dark chocolate and the Fourier transform infrared spectra and thermogravimetric differential scanning calorimeter profiles of the extracted fat samples are in good agreement with reference material data.CONCLUSIONS: The ILs cyanoMIMBr and propylMIMBr are successful in the separation and recovery of fat from white, milk and dark chocolate, as confirmed by FTIR and TG‐DSC data. Copyright © 2009 Society of Chemical Industry

PREPARATION AND CHARACTERIZATION OF TITANIA-PILLARED MONTMORILLONITE

In this work, a Ti -pillared montmorillonite with high thermal stability has been prepared by using a Na -montmorillonite as the host clay and polyhydroxy-titania ions as the pillaring precursor. The formation of Ti -pillared montmorillonite has been confirmed from the characterizations through X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric–differential scanning calorimeter, and specific surface area analyses. In the preparation of Ti -pillared montmorillonite several parameters, such as the type of solvent in which the synthesis is realized, the ratio of polyhydroxy-titania ions and montmorillonite, the intercalation time, the calcining temperature, and calcining time, were tested to understand their effects on the basal spacing. It was shown that this method could produce a Ti -pillared montmorillonite with the basal spacing of 3.74 nm, specific surface area of 409 m2/g, and mean pore size of 2.94 nm, as well as a high thermal stability up to 900°C.