Synthesis and characterization of cellulose-g-polyoxyethylene (2) hexadecyl ether solid–solid phase change materials

A series of novel solid–solid phase change materials, namely, cellulose-g-polyoxyethylene (2) hexadecyl ether (Cellulose-g-E₂C₁₆) copolymers, were synthesized using toluene 2,4-diisocyanate (TDI) as a coupling reagent in the ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). The optimum prepolymerization conditions were determined to be 25 °C and 75 min without catalyst, and the optimum reaction conditions of the grafting step were 90 °C, 6 h and 0.1 wt% dibutyltin dilaurate (DBTDL, weight percent of TDI). The successful grafting was confirmed by FTIR and ¹H-NMR. The properties of the Cellulose-g-E₂C₁₆ copolymers were investigated by DSC, TG and XRD. It is shown that the heat storage ability and phase change temperature of Cellulose-g-E₂C₁₆ copolymers depended on the degree of substitution. The crystalline type of the grafted E₂C₁₆ was not affected by the cellulosic backbone. Compared with E₂C₁₆, Cellulose-g-E₂C₁₆ copolymers showed better thermal stability. They are expected to be widely applied in the area of thermal energy storage.     

Low-temperature heat capacity and thermodynamic parameters of γ-aminobutyric acid

Thermodynamic properties of γ-aminobutyric acid were studied in the temperature interval from 5.7 to 300 K using a vacuum adiabatic calorimeter. The curve C _p (T) in the mentioned temperature interval is S-shaped without any anomalies. Based on the smoothed values of heat capacity, the calorimetric entropy $ S_{m}^{0} (T) - S_{m}^{0} (0) $ and the difference in the enthalpies $ H_{m}^{0} (T) - H_{m}^{0} (0) $ were calculated and tabulated. At the standard temperature 298.15 K, these values are equal to 158.1 ± 0.3 J K^?1 mol^?1 and 23020 ± 50 J mol^?1, respectively. At temperatures from 5 to 10 K, the function C _p (T) was found to obey the Debye law C = AT ³. Contrary to what has been supposed previously, the empirical Parks–Huffman rule for estimating entropy in the homologous series was shown to be not valid for the series glycine–β-alanine–γ-aminobutyric acid.     

Synthesis and thermal properties of poly(styrene-co-acrylonitrile)-graft-polyethylene glycol copolymers as novel solid–solid phase change materials for thermal energy storage

A novel poly(styrene-co-acrylonitrile)-graft-polyethylene glycol(SAN-g-PEG) copolymer was synthesized as new solid–solid phase change materials(SSPCMs) by grafting PEG to the main chain of poly(styrene-co-acrylonitrile). The chemical structure of the SAN-g-PEG was confirmed by the Fourier transform infrared(FT-IR) and proton nuclear magnetic resonance(1H NMR) spectroscopy techniques. The thermal energy storage properties and the storage durability of the SAN-g-PEG were investigated by differential scanning calorimetry(DSC). The SAN-g-PEG was endowed with the solid–solid phase transition temperatures within the range of 23–36 8C and the latent heat enthalpy ranged from 66.8 k J/kg to 68.3 k J/kg. Thermal cycling tests revealed that the SAN-g-PEG kept great heat storage durability after 1000 thermal cycles. The thermal stability was evaluated by a thermal gravity analysis(TGA), and the initial decomposition temperature(Td) of SAN-g-PEG is 350 8C, which proves that the SAN-g-PEG possessed good thermal stability.     

An intrinsic antistatic polyethylene glycol-based solid–solid phase change material for thermal energy storage and thermal management

Polyethylene glycol (PEG) is an important and popular phase change material (PCM), but is not a good antistatic material, which would cause the accumulation of static electricity and electrostatic discharge when used for the thermal energy storage and thermal management of electrical devices. Herein, we prepared a PEG-based solid–solid PCM (SSPCM) with good antistatic property by introducing an ionic liquid onto the macromolecular chains. This SSPCM is in solid state even at 90°C, avoiding the leakage issue of pure PEG. Its latent heat values in the melting and solidifying processes are 56.2 and 30.6 J g⁻¹, respectively. Additionally, this SSPCM has good thermal stability and thermal reliability for thermal storage and thermal management according to thermogravimetric and thermal cycling tests. The volume- and surface resistivity of the SSPCM at ambient temperature are 10^8.87 Ω m and 10^8.92 Ω, respectively, showing good antistatic performance.     

Size-dependence of the heat capacity and thermodynamic properties of hematite (α-Fe2O3)

The heat capacity of a 13 nm hematite (α-Fe₂O₃) sample was measured from T = (1.5 to 350) K using a combination of semi-adiabatic and adiabatic calorimetry. The heat capacity was higher than that of the bulk which can be attributed to the presence of water on the surface of the nanoparticles. No anomaly was observed in the heat capacity due to the Morin transition and theoretical fits of the heat capacity below T = 15 K show a small T³ dependence (due to lattice contributions) with no T^3/2 dependence. This suggests that there are no magnetic spin-wave contributions to the heat capacity of 13 nm hematite. The use of a large linear term to fit the heat capacity below T = 15 K is most likely due to superparamagnetic contributions. A small anomaly within the temperature range (4 to 8) K was attributed to the presence of uncompensated surface spins.     

Low-temperature heat capacity of β-glycine and a phase transition at 252 K

Low-temperature heat capacity of unstable -glycine was measured in a temperature range 5.5 to 295 K, and thermodynamic functions were calculated. At very low temperatures, heat capacity fits a sum of cubic (Debye) and linear terms: C_p=aT+bT ³. The linear contribution increases with temperature and disappears at the second-order phase transition near 252 K which was observed for the first time.     

Thermal properties of chlorosulfonated polyethylene via gas–solid phase method

The thermal properties of chlorosulfonated polyethylene (CSM), which was prepared via gas–solid phase method, were studied in this article. The thermal curves were completely tested by differential thermal analysis, thermogravimetry, and differential thermogravimetry. The results showed that CSM 3550 and CSM 3570 prepared by gas–solid phase method had more excellent thermal properties (high initial/final temperature of degradation) than those via solution method, due to the uniform chlorine distribution of them in macromolecular chain. The differential scanning calorimetry curves showed that the transitions of CSM 3550 and CSM 3570 from glassy to the elastic state were also higher than those via solution method. Particularly, CSM 3570 was amorphous and no clear melting peak was observed during the melting process.     

Heat capacities and thermodynamic properties of M(HBTC)(4,4′-bipy)·3DMF (M?=?Ni and Co)

Two metal?Corganic frameworks (MOFs) of M(HBTC)(4,4??-bipy)·3DMF [M?=?Ni (for 1) and Co (for 2); H₃BTC?=?1,3,5-benzenetricarboxylic acid (1,3,5-BTC); 4,4??-bipy?=?4,4??-bipyridine; DMF?=?N,N??-dimethylformamide] were synthesized by a one-pot solution reaction and a solvothermal method, respectively, and characterized by powder X-ray diffraction and FT-IR spectra. The low-temperature molar heat capacities of M(HBTC)(4,4??-bipy)·3DMF were measured by temperature-modulated differential scanning calorimetry (TMDSC) for the first time. The thermodynamic parameters such as entropy and enthalpy relative to reference temperature 298.15?K were derived based on the above molar heat capacity data. Moreover, the thermal stability and the decomposition mechanism of M(HBTC)(4,4??-bipy)·3DMF were investigated by thermogravimetry analysis (TGA). The experimental results through TGA measurement demonstrate that both of the two compounds have a three-stage mass loss in air flow.     

Investigations of bis(methyltetrazolyl)triazenes as nitrogen-rich ingredients in solid rocket propellants – Synthesis,characterization and properties

The energetic nitrogen-rich compounds 1,3-bis(1-methyltetrazol-5-yl)triaz-1-ene (4) and 1,3-bis(2-methyltetrazol-5-yl)triaz-1-ene (5) were synthesized by diazotation of 1-methyl-5-aminotetrazole (2) and 2-methyl-5-aminotetrazole (3), respectively, by using half an equivalent of sodium nitrite. The reaction of 4 and 5 with diluted ammonia solution yields ammonium bis(1-methyltetrazol-5-yl)triazenate (6) and ammonium bis(2-methyl-tetrazol-5-yl)triazenate (7). Treating of 4 and 5 with aqueous sodium hydroxide solution yields sodium bis(1-methyltetrazol-5-yl)triazenate (8) and sodium bis(2-methyltetrazol-5-yl)triazenate (9) almost quantitative. Compounds 8 and 9 were methylated using methyl iodide and dimethyl sulfate, respectively, originating bis(1-methyltetrazol-5-yl)-3-methyltriaz-1-ene (10) and bis(2-methyltetrazol-5-yl)-3-methyltriaz-1-ene (11). The products 4–11 were characterized by Raman, IR, multinuclear NMR and UV–Vis spectroscopy, mass spectrometry, elemental analysis and differential scanning calorimetry. The structures of the crystalline state of 4 · H₂O, 5, 8 · MeOH, 10 and magnesium bis(2-methyltetrazol-5-yl)triazenate (12) were determined by low temperature single crystal X-ray diffraction. The heats of formation Δ_fH^° of 4–7, 10 and 11 were calculated using energies of combustion Δ_cU^° determined by bomb calorimetry, resulting in strongly endothermic values. With these data and by using calculated (4, 5, 10) as well as measured (6, 7, 11) crystal densities, several detonation parameter (heats of explosion, detonation pressure, detonation velocity, explosion temperature) were calculated by the explo5 software. In addition, the specific impulse of different propellant mixtures of the most promising compound 6 with ammonium dinitramide (ADN) were computed. Furthermore the n-octanol/water partition coefficients of 4, 5, 6 and 7 were determined and the long-term stability of 6 was tested by thermal safety calorimetry. Lastly the sensitivities toward impact and friction as well as electrical discharge were determined by the BAM drophammer, friction tester and a small scale electrical discharge tester.     

Structure and electronic properties and phase stabilities of the Cd(1-x)Zn(x)S solid solution in the range of 0≤x≤1

As an excellent bandgap-engineering material, the Cd(1-x)Zn(x)S solid solution, is found to be an efficient visible light response photocatalyst for water splitting, but few theoretical studies have been performed on it. A better characterization of the composition dependence of the physical and optical properties of this material and a thorough understanding of the bandgap-variation mechanism are necessary to optimize the design of high-efficience photocatalysts. In order to get an insight into these problems, we systematically investigated the crystal structure, the phase stability, and the electronic structures of the Cd(1-x)Zn(x)S solid solution by means of density functional theory calculations. The most energetically favorable arrangement of the Cd, Zn, S atoms and the structural disorder of the solid solution are revealed. The phase diagram of the Cd(1-x)Zn(x)S solid solution is calculated based on regular-solution model and compared with the experimental data. This is the first report on the calculated phase diagram of this solid solution, and can give guidance for the experimental synthesis of this material. Furthermore, the variation of the electronic structures versus x and its mechanism are elaborated in detail, and the experimental bandgap as a function of x is well predicted. Our findings provide important insights into the experimentally observed structural and electronic properties, and can give theoretical guidelines for the further design of the Cd(1-x)Zn(x)S solid solution.     

Experimental investigation and thermodynamic prediction of the Al–Ge–Zn phase diagram

The knowledge of the phase diagram of the Al?CGe?CZn ternary system is of importance in the development of high temperature soldering materials. In this study, the phase diagram of the Al?CGe?CZn ternary system was calculated by the calculation of phase diagrams method using binary thermodynamic parameters included in the COST MP0602 thermodynamic database. Chosen alloys with compositions along two vertical sections with molar ratio Al/Ge?=?3/1 and 1/3 were measured using DTA (differential thermal analysis). The experimentally determined phase transition temperatures from this work and phase equilibria data from literature were compared with calculation results and good mutual agreement was noticed.     

Synthesis and thermal properties of NiSbS–As doped phase

The substitution of Sb with As in the NiSbS intermetallic compound was studied in the framework of evaluating a possible increase of the thermoelectric properties. Different NiSb_1?xAs_xS samples were synthesized with increasing amounts of As (0 < x < 0.66) employing a simple synthetic route using a muffle furnace. Scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy was used to investigate the microstructure. X-ray powder diffraction techniques were employed in order to study the possible existence of a solid solution between NiSbS and NiAsS compounds, as well as to identify the crystal structure and determine the lattice parameters. All compounds were found to crystallise with the NiSbS prototype (cP12-P2₁3), with lattice parameters varying from a = 0.59341(7) nm (x = 0) to a = 0.56849(6) nm (x = 1). Good agreement with Vegard’s law was evidenced. Thermal measurements on NiSb_1?xAs_xS samples were carried out using DTA instruments to evaluate the thermal stability and the melting temperatures.     

Growth behavior and properties of (HF)1–16 clusters

Structural Chemistry - HF cluster is a typical hydrogen bond system. (HF)1–16 clusters have been studied by MP2/aug-cc-pvdz//B3LYP/6-311++G(d,p) method. The global minimum structures of them...     

Hybrid thermal management of lithium-ion batteries using nanofluid,metal foam,and phase change material: an integrated numerical–experimental approach

Safety issues of Li-ion batteries imposed by unfavorable thermal behavior accentuate the need for efficient thermal management systems to prevent the runaway conditions. To that end, a hybrid thermal management system is designed and further investigated numerically and experimentally in the present study. The passive cooling system is fabricated by saturating copper foam with paraffin as the phase change material (PCM) and integrated with an active cooling system with alumina nanofluid as the coolant fluid. Results for various Reynolds numbers and different heating powers indicate that the hybrid nanofluid cooling system can successfully fulfill safe operation of the battery during stressful operating conditions. The maximum time in which all PCM field is changed to the liquid phase is defined as the onset of the stressful conditions. Therefore, the start time of stressful conditions at 41 W and Re 420 is increased from 3700 s with nanofluid composed of 1% volume fraction nanoparticles (VF-1%) to 4600 s with nanofluid VF-2% during high current discharge rates. Nanofluid cooling extends the operating time of the battery in comparison with the water-based cooling system with 200-s (nanofluid with volume fraction of 1%) and 900-s (nanofluid with volume fraction of 2%) increases in operating time at Reynolds of 420. Using nanofluid, instead of water, postpones the onset of paraffin phase transition effectively and prolongs its melting time which consequently leads to a decrease in the rate of temperature rise.

     

Vapour pressure and thermodynamic properties of hexamethyldisilane at 305–387 K

The Swietoslawski's differential ebulliometer has been minimized to be usable for ca. 13 cm³ of liquid. After a performance test with acetone, the vapour pressure of hexamethyldisilane is determined over the temperature range 304.61–386.74 K. The Antoine equation obtained is log₁₀(P/kPa) = 5.97097 − 1319.85/{(T/K) − 52.96} and the normal boiling point is 385.81 K. The present results agree with literature values of Suga and Seki at 287–310 K and Brockway and Davidson at 293–334 K.     

Low-temperature heat capacities and thermodynamic properties of rare-earth triisothiocyanate hydrates (Ⅲ)——Sm(NCS)_3·6H_2O,Gd(NCS)_3·6H_2O,Yb(NCS)_3·6H_2O and Y(NCS)_3·6H_2O

The heat capacities of four RE isothiocyanate hydrates,Sm( NCS)3 6H2O,Gd( NCS)3 6H2O,Yb(NCS)3 6H2O and Y( NCS)3 6H2O,have been measured from 13 to 300 K with a fully-automated adiabatic calorimeter No obvious thermal anomaly was observed for the above-mentioned compounds in the experimental tem-peiatnre ranges.The polynomial equations for calculating the heat capacities of the four compounds in the range of 13-300K were obtained by the least-squares fitting based on the experimental Cp data.The Cp values below 13 K were estimated by using the Debye-Einstem heat capacity functions.The standard molar thermodynamic functions were calculated from 0 to 300 K.Gibbs energies of formation were also calculated.     

Chromogenic derivatives of new bis(phenylhydrazono-1H-tetrazol-5-yl-acetonitriles) – synthesis and properties

Derivatives of bis(phenylhydrazono-1H-tetrazol-5-yl-acetonitriles) with oxygen and sulphur atoms in the structure of aliphatic chains were successfully synthesised. The correlation between the ligand structure and its complexation properties was investigated by absorption spectroscopy. The formation of complexes of presented compounds with metal cations (Cu²⁺, Ni²⁺, Zn²⁺, Co²⁺, Fe²⁺ and Pb²⁺) was studied. Ligands 5–8 were additionally applied as ion carriers in ion-selective membrane electrodes. Membranes of ion-selective electrodes doped with these ligands are selective to Cu²⁺ and Pb²⁺ cations.