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Abstract
A non-ionic polymer (poly(vinyl alcohol) (PVA)) has been incorporated into the inorganic layers of calcium silicate hydrate (C–S–H) during precipitation of quasicrystalline C–S–H from aqueous solution. C–S–H and a C–S–H-polymer nanocomposite (C–S–HPN) material were synthesized and characterized by X-ray fluorescence (XRF), energy dispersive spectroscopy (EDS), 29Si magic angle spinning nuclear magnetic resonance (29Si MAS NMR) and 13C cross-polarization nuclear magnetic resonance (13C CP NMR) spectroscopy, atomic force microscopy (AFM), thermal conductivity, thermogravimetric analysis (TG) and differential thermal analysis (DTA). Thermal conductivity of PVA, C–S–H and C–S–HPN material was studied in the temperature range 25–50°C. C–S–HPN materials exhibited the highest thermal conductivity at 25 and 50°C. The thermal conductivity increases from 25 to 50°C are 7.03, 17.46 and 14.85% for PVA, C–S–H and C–S–HPN material, respectively. Three significant decomposition temperature ranges were observed on the TG curve of C–S–HPN material.
) + S E where SE denotes the energy equation's source term. Thermal conductivity, denoted by k , is computed as follows: (6) k = α l k l + α v k v The mass-averaged variables, i.e., the energy term ( E ), are given by the equation below. (7) E = α l ρ l
Abstract
As examples of studies on thermal characteristics of materials with a nanometer scale two topics are discussed. One is heat capacity and thermal conductivity of small materials at low temperatures. It based upon the recent findings that heat capacity depends on the limited number of the phonon modes in low angular frequency region and the distinct characteristic is the appearance of quantized thermal conductance in heat transfer through a narrow wire with hundreds nm. The other is the thermophysical properties at the ordinary interface. The disordered structure appearing in the interfacial region with a width of a few nm is discussed, which is comparable to the phonon mean free path, should be taken into account to reveal the characteristic thermal behavior at room temperature.
Thermal properties of 4,4′(2,2′-propylidene)-diphenol, referred to as bisphenol A, or BPA, are discussed. Parameters of thermal transitions were measured by DSC. The commercial product crystallizes in α-form crystals which melt at 157°C (onset) and 161°C (peak) with a heat of fusion 134.37 J g−1. Supercooled BPA shows a glass transition at about 40°C. Almost identical results were obtained for samples recovered by different methods: flakes, pastilles and prills. Two new polymorphs, the β and γ-forms were identified. The β-form melts at 131°C with a heat of fusion of 104.9 J g−1. The melting point of the γ-form was measured to be 138°C and its heat of fusion is 118.3 J g−1. Thermal conductivity of crystalline BPA was measured.
Abstract
Current work at Lawrence Livermore National Laboratory (LLNL) includes both understanding properties of old explosives and measuring properties of new ones. The necessity to know and understand the properties of energetic materials is driven by the need to improve performance and enhance stability to various stimuli, such as thermal, friction and impact insult. This paper will concentrate on the physical properties of RX-55-AE-5, which is formulated from heterocyclic explosive, 2,6-diamino-3,5-dinitropyrazine-1-oxide, LLM-105, and 2.5% Viton A. Differential scanning calorimetry (DSC) was used to measure a specific heat capacity, C p, of≈0.950 J g−1 �C−1, and a thermal conductivity, κ, of≈0.475 W m−1 �C−1. The LLNL kinetics modeling code Kinetics05 and the Advanced Kinetics and Technology Solutions (AKTS) code thermokinetics were both used to calculate Arrhenius kinetics for decomposition of LLM-105. Both obtained an activation energy barrier E≈180 kJ mol−1 for mass loss in an open pan. Thermal mechanical analysis, TMA, was used to measure the coefficient of thermal expansion (CTE). The CTE for this formulation was calculated to be ≈61 μm m−1 �C−1. Impact, spark, friction are also reported.
thermal conductivity K . The units clo and tog are measures of thermal resistance and include the insulation provided by any layer of trapped air between skin and clothing and insulation of clothing itself. One tog is equal to 0.1 m 2 K W −1 and clo is
conductivity of nanoscale thin films [ 1 ]. More recently, the thermal conductivity of nanostructured materials have been analyzed in order to improve efficiency of newer energy conversion device technologies [ 2 ]. While classical concepts of thermal
density and isothermal characteristics [ 1 , 2 ]. However, they have been reported to exhibit a rather slow thermal response especially for organic materials [ 3 ]. This is mainly due to the relatively low thermal conductivity of organic latent heat
