Specific heat capacity The true specific heat capacity Cr and the average specific heat capacity CAr are calculated by the heat Q required for heating 1'C per unit glass mass: Cr=1dQ.CAT=1QCJ/(kg.'C)]mdTmT2-T1(4-49)

　　(1) The relationship between the specific heat capacity of glass and temperature

　　Like other substances, the specific heat capacity of glass is zero at absolute zero. As the temperature rises, the specific heat capacity gradually increases, and the specific heat capacity begins to increase particularly fast in the transition temperature region. In the molten state, the specific heat capacity increases with increasing temperature.

　　(2) The relationship between the specific heat capacity and composition of glass

　　Li2O, NazO, B2O3, Al2O3, SiO2, etc. increase the specific heat capacity. Especially for Li20, the glass containing a large amount of PbO and BaO has a lower specific heat capacity, and the other oxides have little effect.

　　Generally, the greater the density of the glass, the smaller the specific heat capacity, and the product of specific heat capacity and density is approximately constant. Calculation of specific heat capacity C-EP:C or Cm=at+Co(4-51)0.00146t 十1 In the formula, a=EPiai; Co=EP:Coi; Cm is the average specific heat capacity of 0~t'C. 4.9.3 Thermal conductivity of thermally conductive glass: When the temperature gradient is equal to 1, the heat per unit cross-sectional area of the sample passing through the unit time. Use the average thermal conductivity to measure: 入=Q8[W/(m·K)](4-52)sAT where Q is the heat passing through the thickness &, cross-sectional area s, temperature difference ム T material layer in time t . Into characterizes the difficulty of transferring heat of a substance, 1 in to is called thermal resistance. The thermal conductivity of a solid is the sum of the thermal conduction caused by the crystal lattice and electrons, that is, into ten into e. Since there are few electrons in the glass, it enters. Because of the disorder of the glass structure, the thermal resistance of the glass becomes larger.

　　(1) The relationship between the thermal conductivity of glass and temperature

　　The heat conduction inside the glass can be carried out through heat conduction and heat radiation, that is, input = input conduction and ten input radiation. At low temperature, heat conduction is the main component, and its size is mainly determined by the chemical composition; at high temperature, radiation is the main component, so the thermal conductivity increases with the increase of temperature.

　　(2) Relationship with composition

　　The introduction of alkali metal oxides in the glass will reduce the thermal conductivity, increase the content of SiO2, Al2O3, B2O3, and FezO3, and the thermal conductivity will increase accordingly. 4.9.4 Thermal stability The thermal stability of glass refers to the ability of glass to withstand drastic temperature changes without being damaged. It is measured by the temperature difference 스T that the sample will not be damaged under the shock of rapid cooling and rapid heating. It is a comprehensive performance of a series of physical properties of glass, and it has a certain relationship with the geometry and thickness of the glass sample. It can be expressed by the following formula: AT = AO strong (C) (4-53) aE where o is strong-the breaking strength limit of brittle materials; E-the modulus of elasticity. The thermal expansion coefficient is the main factor affecting the thermal stability of glass .