Thermal Chemical Researches Of Bis-alkylammonium Tetrabromometallates(Ⅱ) Solid-solid Phase Change Materials And Metal Complexes Of Salicylic Acid

Phase change materials(PCMs) refer to the material which would change their forms responding to the temperature and would release or store a great amount of latent heat effectively. During the process of phase transition, PCMs would retain or release more heat from the surrounding and keep the temperature constantly. So it can be used for the energy storage, which would enhance considerably energy utilization and reduce pollution. According to the way of phase transition, PCMs can be divided into four categories: solid-solid phase, solid-gas phase, solid-liquid phase and liquid-gas phase.Solid-Solid PCMs, just as its name implies is to storage or release through solid-solid phase change. Compared with the solid phase change material, it has many great advantages. First, Solid-Solid PCMs has a good processability and it also has a fixed shape or form which would be held without the outer packaging. Second, small phase change expansion coefficient makes the volume change of phase transition also very small. Third, it will not lead to separate and in low temperature. Fourth, Solid-Solid PCMs has stable performance and long service life. Fifth, it has durable performance against corrosion, non-toxicity and no pollution. Last, the synthesis method equipment is very simple, and easy to popularize the promotion without any specific conditions. Above all, the developing trends for Solid-Solid PCMs in phase change thermal energy storage were brought great forward. Among them, Bis-alkylammonium tetrabromometallates(II)(1-CnH2n+1NH3)2MX4 is one kind of PCMs with excellent properties.Salicylic acid is an important raw material in fine chemical engineering. It is often used in the medical industry as disinfectants and antiseptics. As pharmaceutical intermediates, it can be used for synthetic nitrogen sulfanilamide, antipyretic analgesics suppression of aspirin, salicylic acid sodium and acetyl salicylic acid, B soft skin acidity, etc. It can also help reduce inflammation or redness induced by eczema, psoriasis, acne, dandruff. 3-6% of salicylic acid can be used in the striping of stratum corneum, at the concentration of below 40% is suitable for treatment of corns, thick cocoon, warts. Nowadays, many famous cosmetics also add salicylic acid ingredients for use. Otherwise, salicylic acids are very much in demand in bioengineering, such as induction of plant disease resistance. With the constant improvement of the technology and the reducing of production costs, salicylic acid will show promising prospects.With precision automatic adiabatic calorimeter, Low-temperature heat capacities of the Bis-alkylammonium tetrabromometallates(II) were measured in the temperature range from 78 to 400 K. Then the temperature, enthalpy and entropy of the phase change of the materials can be got. By using the simulation software through the server and the workstation equipment, molecular dynamics simulation provided a way to investigate the changing process of energy and density and obtained mechanism of phase transition. Molar enthalpy of dissolution, infinite dilution enthalpy and other important thermodynamic data were measured by isoperibol solution-reaction calorimeter at constant temperature. All these datum provide reliable basis for the wide use. This present thesis consists of three parts as follows: Synthesis of the samplesFour kinds of Bis-alkylammonium tetrabromometallates(II) and ten kinds of salicylic acid salt crystal complexes were synthesized. All this new compounds have been characterized by single-crystal X-ray diffraction, DSC/TG analysis, Chemical element analysis, powder X-ray diffraction. The lattice potential energies were calculated based on these crystals datum. Research of the properties of(1-CnH2n+1NH3)2MX41. The molar thermal capacities of these compounds have been measured by precision automatic adiabatic calorimeter within the temperature scope of 78 to 400 K. Test study indicated that two solid–solid phase changes were took place in the temperature interval. The mechanism of the solid-solid phase transition for each of the substances was speculated, by which need the way of DSC/TG analysis and melting point apparatus.2. Molar phase enthalpies and entropies derived by the analysis of the phase change zone. The polynomial equations of the thermal capacity along with the change of temperature were calculated by data fitting which based on the least square method. Using polynomial equations, smoothed Molar Heat Capacities, entropy, enthalpy, Gibbs free energy relative to 298.15 K were calculated.3. Molecular dynamics of four kinds of Bis-alkylammonium tetrabromometallates(II) in the temperature range from 78 to 400 K were computed by server in the means of Materials Studio. According to the calculated results and dectected results, the temperature range of phase transition would be ensured and the probable mechanism would be proposed. Research of the properties of salicylic acidDissolution enthalpy of reactant and products was measured by isoperibol dissolution calorimeter. According to Hess’ s Law, it states that the standard enthalpy of salicylate is the sum of the standard molar formation enthalpies of reactant and products in calorimetric solvent. The UV-vis spectroscopy and refractive index of reactants and products in solvent reflected the reasonability of thermochemical cycle. In addition, on the basis of Pitzer theory, some other thermodynamic functional value infinite could also be acquired, such as dilution dissolving enthalpies, Pitzer enthalpy parameters, partial relative molar enthalpies and apparent molar enthalpies.