多壁碳纳米管改性热固性酚醛树脂的研究

本文研究了多壁碳纳米管(MWNTs)在热固性钡酚醛树脂中的分散效果以及碳纳米管对酚醛树脂固化和炭化的影响。酚醛树脂含有丰富的苯环结构和丰富的羟基基团,能吸附在碳纳米管上起到均匀分散碳纳米管的作用。同时,碳纳米管能吸附进而调整酚醛树脂在其周围的排列,使酚醛树脂固化时有更多的碰撞机会从而促进酚醛树脂的固化,也使酚醛树脂炭化时能形成更多更完整的石墨结构,提高它在高温下的耐热性能。     

典型煤碳燃烧特性研究和数值模拟

本文以三种典型煤的碳燃烧为研究对象，分别采用简单一维沉降燃烧方式和等温加热燃烧方式，实验研究了煤在快速加热条件下，其碳的初期和中，后期燃烧过程。以实验为基础，建立了煤的碳燃烧模型，变工况数值模拟了煤的碳燃烧过程，揭示了煤不同条件下的单颗粒碳燃烧特性。     

Combustion of single char particles in a turbulent fluidized bed

The combustion of single bituminous char particles (4-12 mm diameter) was studied in a turbulent fluidized bed operated at 1098 K using air as the fluidising medium. Results indicated that particles burn with constant density following a shrinking sphere model. Burning rates are much higher than those observed in a bubbling fluidized bed. The rate of transfer of oxygen to the particle surface is also higher than that observed in bubbling beds. A model is proposed to calculate the Sherwood numbers of the burning carbon particles. Experimental values of the Sherwood numbers agree well with those predicted from the model.     

Synthesis and characterization of liquid crystalline polymers containing aromatic ester mesogen and a nonmesogenic ferrocene unit in the spacer

A new series of liquid crystalline polymers containing aromatic triad ester mesogen and 1,1′‐disubstituted ferrocene as a nonmesogenic unit along with polymethylene spacer was synthesized. The polymer was synthesized by a room temperature polycondensation reaction between bis(4‐chloroformyl phenyloxy alkyl ferrocene dicarboxylate) and quinol. The alkyl groups have been varied by an even number of methylene groups with a range from two to ten groups. All the polymers were found to possess liquid crystalline properties. The identification of the mesophase is more transparent with an increase in the spacer. The thermal characteristics were studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results reveal that the thermal stability of the polymers was decreased with increasing spacer length. The T_g, T_m, and T_i of the polymers decreased with increasing methylene groups. The incorporation of the ferrocene moiety also has a considerable effect on the glass transition temperature. The char yield of the polymer decreases with an increasing methylene chain length. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3494–3501, 2002     

Maceral and rank influences on the morphology of coal char

Concentrates of vitrinite and inertinite macerals have been pyrolysed in a flame under conditions representative of the initial stages of pulverized coal combustion. Char was distinguished from soot by size analysis and the char yield correlated with the proximate analysis. The char morphology was studied by optical microscopy and quantitative measurements of porosity and pore size were made using image analysis. Vitrinite and inertinite produce chars of characteristic morphology. The softening behaviour of inertinite varies with coal rank and can be related to the optical reflectance. The porosity of vitrinite chars approaches that of inertinite chars at high rank.     

正交法选择COPNA树脂的最佳合成条件

COPNA树脂可作为炭／炭复合材料的基体前驱体。为提高以苯甲醛为交联荆，蔡为单体，浓硫酸为催化剂的缩合多核芳香烃（COPNA）树脂的残炭率，采用正交实验，研究了合成COPNA树脂的交联荆与单体的摩尔比、催化荆的用量、反应温度等因素对树脂的残炭率的影响。结果表明：影响因子强度大小依次为交联剂与单体的摩尔比、催化荆用量、反应温度。通过正交实验得到的最佳反应条件是交联剂与单体的摩尔比为2．5、催化剂的用量为5％、反应温度170℃，此条件下合成的COPNA树脂的残炭率达到76％。     

CO2 gasification of wood charcoals derived from vacuum and atmospheric pyrolysis

The gasification of biomass derived char obtained via vacuum and atmospheric pyrolysis of Populus tremuloides has been studied in the ranges of 725–960°C and 0.1 to 6 MPa. CO₂ was used as the oxidizing gas. The results show that char reactivity is influenced by the preheating rates and that pressure effects are significant between 850°C and 950°C. A correlation based on the expression: df/dt = k₀{exp(-E/RT)}(1 - f)^af^βP^yCO₂ was used to fit the experimental data. In general, vacuum pyrolysis derived char showed a higher reactivity than atmospheric pyrolysis chars. An explanation based on a higher oxygen content of the vacuum pyrolysis char is suggested.     

Acrylic-based fire-retardant coatings for steel protection: Employing the concept of in situ ceramization

Traditional intumescent coatings are widely used as passive fire-protective coatings for steel structures as they are capable of expanding in the range of 20–50 times the original thickness thereby providing excellent insulation. However, the fragile nature of such residue and susceptibility to thermo-oxidation given their carbonaceous nature are key problematic issues. The concept of in situ ceramization is explored in this work as a means to form inorganic cohesive char with improved rigidity and thermo-oxidative stability. Coating samples were prepared by incorporating ammonium polyphosphate, talc, Mg(OH)₂, and polydimethylsiloxane as additives into acrylic resin at different weight fractions. Thermal analysis and x-ray diffraction have confirmed the reactions between the additives to form various crystalline magnesium phosphate phases, and to a small extent, silicon phosphate, thereby ensuring the thermo-oxidative stability of the residue. This is reiterated by the fire performance tests (by exposing the coatings to a temperature profile in a furnace similar to ISO 834 fire curve). Despite the advantages of rigid char and its thermo-oxidative stability as a result of formation of inorganic phosphates, the lack of swelling has resulted in relatively poor insulation capabilities of the char, and subsequently, compromised the fire protection times (that are in the range of 45–55 min). However, pyrolysis flow combustion calorimeter results of the coatings are promising and have shown a significant drop of up to 70% in the peak of heat release rate values as compared to neat resin.     

金属催化剂在聚合物降解成炭阻燃中的研究进展

介绍了抗熔滴阻燃聚合物的研究现状,综述了金属催化剂在催化聚合物降解成炭方面的应用,主要包括铁系、钼系、镍系、锌系化合物及部分稀土材料等作为催化剂在聚合物阻燃中催化成炭抗熔滴的研究现状,尤其重点阐述了铁系催化剂的主要作用。最后,对金属催化剂在聚酯抗熔滴中的应用进行了展望。     

ZrSi_2/硼酚醛泡沫的制备及其裂解产物的增强机制

以ZrSi_2颗粒填充硼酚醛树脂制备了一种耐高温且裂解后结构较为完整的泡沫复合材料。研究了ZrSi_2颗粒质量分数对泡沫复合材料固化机制、高温裂解行为及裂解前后压缩性能的影响,并分析了ZrSi_2颗粒对泡沫复合材料裂解产物的增强机制。结果表明:添加的ZrSi_2颗粒虽未参与硼酚醛树脂的固化交联,但会和硼酚醛树脂裂解放出的气体挥发物发生化学反应,提高了裂解产物的残炭率和压缩比强度。当添加的ZrSi_2颗粒质量为硼酚醛树脂质量的10%时,裂解产物的残炭率和压缩比强度提高最为显著。ZrSi_2/硼酚醛泡沫经过裂解后,ZrSi_2颗粒作为第二相粒子钉扎在裂解产物的孔壁上,化学反应使得部分裂解气体挥发物被吸收并转化为固相产物,明显减少的缺陷提高了裂解产物的力学性能。