原位聚合制备微胶囊相变材料及性能评价

研究了原位制备聚苯乙烯(PS)包覆石蜡微胶囊相变材料(MicroPCM)的方法,讨论了搅拌速率、石蜡和苯乙烯质量比对相变材料的潜热和粒径大小的影响。结果表明,在保证微球的形成条件下,所得储能材料包覆率可以达到67%,相变潜热达到114.76J/g;首次在聚合过程中加入的热塑性弹性体苯乙烯-乙烯-丁烯-苯乙烯共聚物(SEBS),不仅能有效地增加PS和石蜡的相容性,而且有效地降低了高温下MicroPCM中石蜡泄漏。     

EPDM和HDPE包覆石蜡相变储能材料的研究

用三元乙丙橡胶(EPDM)和高密度聚乙(烯HDPE)作为包覆材料,石蜡作为相变材料,通过热熔法制备了不同石蜡用量的定形相变储能材料。恒温热老化试验表明:当石蜡用量为60%时,EPDM基定形相变材料的石蜡质量损失率不超过1%,远低于HDPE基定形相变材料的9.44%。在恒温水浴试验中,随水浴时间延长,定形相变材料的质量损失率增加;而且当石蜡用量超过60%时,EPDM对石蜡的密封效果变差,质量损失率明显增加;相同条件下,EPDM基定形相变材料的密封效果优于HDPE基定形相变材料。     

石蜡的聚烯烃定形包覆研究

低熔点石蜡为芯材,聚苯乙烯、聚丙烯和聚乙烯3种高分子材料作支撑材料,以加热熔融的方法制备了3种定形复合相变材料,确定了3种高分子材料对潜热为222.01 kJ/kg的17℃石蜡的最大包裹量分别为w(石蜡)=46%、51%、73%。用差示扫描量热仪对3种定形复合相变材料进行了测定,分析了所制备的定形复合相变材料的相变温度、相变潜热、热稳定性等性能。结果表明,石蜡经过高分子材料包覆之后,其相变温度有所降低,相变焓值有所提高,而且该定形相变材料可以加工成粉体材料,进一步拓展了产品的应用领域。     

聚烯烃/石蜡复合相变储能材料的研究

分别以低密度聚乙烯(PE-LD)、高密度聚乙烯(PE-HD) .聚丙烯(PP).聚苯乙烯(PS)为支撑材料、石蜡为相变材料,采用加热熔融法制备聚烯烃石蜡复合相变储能材料。考察了不同种类的聚烯烃材料对复合材料储能的影响,通过DSC测出PE-LD/石蜡、PE-HD/石蜡、PP/石蜡、PS/石蜡复合相变材料的相变烩分别为68.44J/g、45.52J/g、40.06J/g、1.19J/g。结果表明,PE-LD是其中最好的基体材料,具有最大的相变烩。随着石蜡含量的增加,PE-LD/石蜡复合材料的相变烩逐渐增大。此外,硅藻土和活性炭填料的加人有利于提高相变烩,增强复合材料的稳定性。     

树脂基稻草吸附石蜡储能单元相变储能材料

利用稻草的天然空心结构,吸附包裹相变石蜡制作成储能单元,然后采用树脂将储能单元粘结成型,得到树脂基稻草吸附石蜡储能单元定形相变材料。显微分析表明,石蜡与稻草空腔结合紧密,材料在储热过程相变石蜡与稻草无界面脱离现象;热失重分析表明,该定形相变材料在多次相变过程中热失重率小于0.3%,具有很好的热稳定性。     

定形相变材料的制备及其稳定性能的研究

以石蜡为相变材料,膨胀珍珠岩为基体,采用真空吸附的方法,制备出膨胀珍珠岩——石蜡定形相变材料。为提高定形相变材料的稳定性,在制备的定形相变材料外包覆成膜乳液封装。采用扩散-渗出圈法对材料的稳定性能进行了测试。结果表明:石蜡与膨胀珍珠岩的最佳质量比为2∶1;最佳成膜封装乳液是苯丙乳液,最佳乳液用量是定形相变材料质量的20%;制备得到的成膜封装后的膨胀珍珠岩-石蜡定形相变材料的相变温度为25.05℃,相变潜热为128.93 J/g,稳定性能良好。     

聚烯烃包覆石蜡相变材料的结构和初步热性能

分别以低密度聚乙烯（LDPE）和乙烯-辛烯共聚物（POE）为包覆材料,以石蜡为相变材料,制备了定形相变材料,采用SEM、DSC和流变性能对其进行分析表征。SEM电镜显示了两种不同的表面形貌;DSC测试表明石蜡加入量越多,潜热越大,POE/石蜡体系的潜热高于LDPE/石蜡体系;流变性能研究表明,石蜡的加入在固态时提高了基体的储能模量,对于LDPE/石蜡体系,LDPE为连续相;对于POE/石蜡体系,由于POE和石蜡熔融温度非常接近,分辨不出谁是连续相谁是分散相。     

80#石蜡/膨胀石墨定形复合相变材料的特性表征与分析

以80^#石蜡为相变材料,利用不同粒径膨胀石墨的多孔隙结构,以多层吸附、模压法压制方式制备了80^#石蜡/膨胀石墨定形复合相变材料。通过循环融冻实验分析了80^#石蜡的热稳定性和循环稳定性,滴定滤纸渗漏实验确定了不同组分复合相变材料的渗漏率。采用差示扫描量热仪(DSC)、扫描电子显微镜（SEM）、Hot Disk热常数分析仪等仪器对所制备复合相变材料的相变潜热、多孔基吸附结构、热导率、渗漏率等特性进行了分析。结果表明：当膨胀石墨的添加质量分数达到整体组分的8%时,复合定形相变材料的相变温度为80.86℃（吸热）和76.08℃（放热）,相变潜热为130.12kJ/kg,且渗漏率小于0.3%。制备的复合定形相变材料具有形状稳定、渗漏率低、蓄热密度高的特点,且具有较长的使用寿命。     

聚乙二醇/二氧化硅复合定形相变储能材料的制备与研究

为拓宽相变储能材料在实际工程中的应用范围,以聚乙二醇(PEG)为相变储能材料,二氧化硅(SiO2)为载体基质,采用溶胶-凝胶法制备了一种有机-无机复合定形相变材料.通过DSC、TGA、SEM和相变循环试验对复合定形相变材料的结构与性能进行测试,试验结果表明:聚乙二醇的最佳质量分数为70％,相变温度为49.73℃,相变焓...     

石蜡定形相变材料的包裹及热性能

利用原位聚合法,提出了对定形相变材料进行无机高分子材料再包裹,制备了硅胶封装石蜡定形相变材料的微胶囊,其石蜡的含量最高达到w(石蜡)=69.12%。用差示扫描量热仪(DSC)测定了微胶囊的热性能,并将测定粉体材料润湿性能的W ashburn方程应用于相变材料的亲油亲水性测定,评价了定形相变材料在胶囊封装前后的亲水性变化。结果表明,经硅胶封装的相变材料其相变焓为153.46 J.g-1,相变焓降低较少,而亲水性能有很大提高,确定了微胶囊产品中石蜡最佳质量分数为w(石蜡)=50%~56%。     

The structures of VOx/MOx and alkali-VOx/MOx catalysts and their catalytic performances for soot combustion

Vanadium oxides supported on γ-Al₂O₃, SiO₂, TiO₂, and ZrO₂ were studied on their molecular structures and reactive performances for soot combustion. To investigate the effect of different alkali metals on the structures and reactivities of supported-vanadium oxide catalysts, they were doped into the V₄/TiO₂ catalyst which had the best intrinsic activity for soot combustion in the selected supported vanadium oxide catalysts. The experimental results demonstrated that the catalytic properties of these catalysts depended on the vanadium loading amount, support nature, and the presence or the absence of alkali metals. The spectroscopic analysis (FT-IR and UV–vis) and H₂-TPR results revealed that the higher activity of alkali-promoted vanadium oxide catalysts could be related to the ability of alkali metal promoting the redox cycle of the active vanadyl species. TG results showed that adding alkali to V_m/TiO₂ catalyst was beneficial to lowering their melting points. Low melting points could ensure the good surface atom migration ability, which would improve the contact between the catalyst and soot. Due to the alkali metal components promoting the redox ability and the mobility of the catalysts, alkali-modified vanadium oxide catalysts could remarkably improve their catalytic activities for soot combustion. The catalytic activity order for soot combustion followed Li > Na > K > Rb > Cs in the catalyst system of alkali-V₄/TiO₂, and the reason why it followed this sequence was discussed.     

Synthesis and characterization of MoOx-Pt/C and TiOx-Pt/C nano-catalysts for oxygen reduction

The oxygen reduction reaction (ORR) was studied at carbon supported MoO_x-Pt/C and TiO_x-Pt nanocatalysts in 0.5 mol dm⁻³ HClO₄ solution, at 25 °C. The MoO_x-Pt/C and TiO_x-Pt/C catalysts were prepared by the polyole method combined by MoO_x or TiO_x post-deposition. Home made catalysts were characterized by TEM and EDX techniques. It was found that catalyst nanoparticles were homogenously distributed over the carbon support with a mean particle size about 2.5 nm. Quite similar distribution and particle size was previously obtained for Pt/C catalyst. Results confirmed that MoO_x and TiO_x post-deposition did not lead to a significant growth of the Pt nanoparticles.The ORR kinetics was investigated by cyclic voltammetry and linear sweep voltammetry at the rotating disc electrode. These results showed the existence of two E − log j regions, usually observed with polycrystalline Pt in acid solution. It was proposed that the main path in the ORR mechanism on MoO_x-Pt/C and TiO_x-Pt/C catalysts was the direct four-electron process with the transfer of the first electron as the rate-determining step. The increase in catalytic activity for ORR on MoO_x-Pt/C and TiO_x-Pt/C catalysts, in comparison with Pt/C catalyst, was explained by synergetic effects due to the formation of the interface between the platinum and oxide materials and by spillover due to the surface diffusion of oxygen reaction intermediates.     

硅灰石、微囊化红磷/天然水镁石复配阻燃聚丙烯的制备与性能

将改性天然水镁石分别与改性硅灰石、微囊化红磷添加到聚丙烯中，制得两种复合材料，对这两种复合材料进行冲击试验、差热分析、氧指数和垂直燃烧性能测试分析，考察了两种复合材料的力学性能和阻燃性能。实验结果表明，天然水镁石微囊化红磷复配阻燃聚丙烯体系较天然水镁石硅灰石复配阻燃聚丙烯体系阻燃性能更好同时力学性能损失较小。     

Synthesis and Characterization of Ti0.33Ta0.33Nb0.33C and Ti0.33Ta0.33Nb0.33CxN1-x Whiskers

Ta_0.33Ti_0.33Nb_0.33C and Ta_0.33Ti_0.33Nb_0.33C _x N_{1− x} whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N₂. The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO₂, Ta₂O₅, Nb₂O₅, C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl₂( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature.     

Stable and Metastable Equilibria in the Systems Y2O2-Al2O3, and Gd2O3-Fe2O3

The phase equilibrium relations in the systems Y₂O₃-Al₂O₃ and Gd₂O₃-Fe₂O₃ were examined. Each system has two stable binary compounds. A 3:s molar ratio garnet-type compound exists in both systems. The 1:1 distorted perovskite structure is stable in the system Gd₂O₃-Fe₂O₃ but only metastable in the system Y₂O₃-AI₂O₃. This interesting example of metastable formation and persistence of a compound with ions of high Z/r values explains the discrepancies in the literature on the structure of the composition YA1O₃. A new 2:1 molar ratio cubic phase has been found in the system Y₂O₃-A1₂O₃. Since silicon can be completely substituted for aluminum in this compound, the aluminum ions are presumably in fourfold coordination.     

Reactor and in situ FTIR studies of Pt/BaO/Al2O3 and Pd/BaO/Al2O3 NOx storage and reduction (NSR) catalysts

The reduction of NO under cyclic “lean”/“rich” conditions was examined over two model 1 wt.% Pt/20 wt.% BaO/Al₂O₃ and 1 wt.% Pd/20 wt.% BaO/Al₂O₃ NO_x storage reduction (NSR) catalysts. At temperatures between 250 and 350 °C, the Pd/BaO/Al₂O₃ catalyst exhibits higher overall NO_x reduction activity. Limited amounts of N₂O were formed over both catalysts. Identical cyclic studies conducted with non-BaO-containing 1 wt.% Pt/Al₂O₃ and Pd/Al₂O₃ catalysts demonstrate that under these conditions Pd exhibits a higher activity for the oxidation of both propylene and NO. Furthermore, in situ FTIR studies conducted under identical conditions suggest the formation of higher amounts of surface nitrite species on Pd/BaO/Al₂O₃. The IR results indicate that this species is substantially more active towards reaction with propylene. Moreover, its formation and reduction appear to represent the main pathway for the storage and reduction of NO under the conditions examined. Consequently, the higher activity of Pd can be attributed to its higher oxidation activity, leading both to a higher storage capacity (i.e., higher concentration of surface nitrites under “lean” conditions) and a higher reduction activity (i.e., higher concentration of partially oxidized active propylene species under “rich” conditions). The performance of Pt and Pd is nearly identical at temperatures above 375 °C.     

Syntheses and Unit-Cell Determination of Ba3V4O13 and Low-and High-Temperature Ba3P4O13

The syntheses and the results of unit-cell determinations ofBa₃V₄O₁₃ and the two forms (low- and high-temperature) of Ba₃P₄O₁₃ are presented. Ba₃V₄O₁₃ crystallizes in the monoclinic system, space group Cc or C2/c with unit-cell dimensions a=16.087, b=8.948, c=10.159 (x10nm), β=114.52° Low-Ba₃P₄O₁₃ crystallizes in the triclinic system, space group P1 or P1 with unit-cell dimensions a=5.757, b=7.243, c=8.104 (x10 nm) α=82.75°, β=73.94°, γ=70.71°. Low-Ba₃P₄O₁₃ transforms at 870°C into high-Ba₃P₄O₁₃ which crystallizes in the orthorhombic system, space group Pbcm (No. 57) (or Pbc2, No. 29) with unit-cell dimensions a =7.107, b=13.883, c=19.219 (x10 nm). No relations have been found between the structures of the tribarium tetravanadate and the tribarium tetraphosphate.     

镁铝及镁锌铝水滑石的合成与表征

采用共沉淀法合成镁铝及镁锌铝水滑石,并通过X射线衍射（XRD）、红外光谱（FT-IR）、扫描电镜（SEM）、热分析（TG/DTG）、粒度分析等手段对合成的水滑石进行表征,研究不同镁、铝、锌的投料比例对合成的水滑石结构及热性能等的影响。XRD表征结果表明,合成产物均具有水滑石特征峰。合成的镁铝水滑石随着镁铝比的增加其层板间距增大,层板上原子密度降低;合成的镁锌铝水滑石随着锌含量的提高层板间距减小,层板上原子密度降低。镁铝水滑石热分解过程有两个明显阶段,层间结晶水先脱除,随后是层间阴离子脱除及层板上部分羟基脱水;镁锌铝水滑石热分解过程只有一个明显的阶段,层板间阴离子在层板间结晶水脱除的同时也在脱除。     

Activation and characterization of Fe---Mn---SO4/ZrO2 catalysts

Changes in Fe---Mn---SO₄²⁻/ZrO₂ catalyst formulations during activation have been observed. In air or an inert gas, the added salt, such as iron and/or manganese nitrate, decomposes over a temperature range of about 200–400°C to produce nitric oxide, oxygen and iron and/or manganese oxide. The crystallization of zirconia occurs at 450°C; when the sample contains sulfate the exothermic event occurs at a temperature that is about 200°C higher. Heating in the presence of hydrogen causes the evolution of nitric oxide to occur over a narrow temperature range and at a lower temperature than when the sample is heated in helium or air. It appears that the nitrate ions associated with Fe, Mn and Zr decompose to produce nitric oxide, and presumably water, at different temperatures when the sample is heated in the presence of hydrogen. Heating samples of sulfated zirconia containing iron and/or manganese in hydrogen causes sulfur evolution at a lower temperature, and a significant fraction of it in the form of H₂S.