石蜡/LDPE/OMMT/石墨复合相变储能材料的制备及性能

以石蜡为相变材料,低密度聚乙烯(LDPE)为支撑材料,有机蒙脱土(OMMT)为载体材料,石墨为填料,采用加热共熔法制备石蜡/LDPE/OMMT/石墨复合相变储能材料。采用扫描显微镜(SEM)、红外光谱仪(FTIR)、热重分析仪(TGA)、差示扫描量热仪(DSC)、广角X射线衍射仪(WAXD)、导热系数测定仪等对复合相变材料进行结构表征与性能测试。结果表明:当石蜡质量分数为50%,OMMT质量分数为15%,石墨质量分数为4%时,石蜡包覆良好,相变温度为57.45℃,相变潜热为92.95 J/g。该复合相变材料结构稳定、密封性能优异、热稳定性好和导热率高,应用前景广阔。     

HDPE/石蜡/活性炭三元相变储能材料的制备及热性能研究

以高密度聚乙烯(HDPE)、石蜡为相变主材料,活性炭为吸附载体材料,采用熔融共混法制备了HDPE/石蜡/活性炭三元相变储能材料,并分别利用真空烘箱和差示扫描量热仪(DSC)对该相变储能材料的宏观相变转换温度和热性能进行了表征。结果表明:随着HDPE/石蜡/活性炭相变储能材料中石蜡含量的增加(HDPE的含量相应减少),活性炭对石蜡的吸附能力相对降低;HDPE/石蜡/活性炭相变材料中,HDPE的实际焓值高于其理论焓值。     

交联聚乙烯／石蜡复合相变储能材料的研究

根据固-液相变材料石蜡在聚乙烯(PE)交联网络中的扩散溶胀特性,制备了一种以 PE 交联网络为支撑骨架和包覆层、以石蜡为储能材料的复合型高分子固-固相转变储能材料。通过测定不同温度下、不同交联程度 PE在石蜡中的溶胀速率、平衡溶胀比等,研究了交联 PE 在石蜡中的溶胀行为及溶胀动力学,为相变材料的制备工艺提供了依据;此外,还对复合相变材料中石蜡的扩散、渗透行为及扩散动力学进行了研究。结果表明制备的相变储能材料具有长期使用性能。     

复合相变储能材料的研究

以石蜡为相变材料,低密度聚乙烯、硅藻土为支撑材料,以加热熔融方法制备低密度聚乙烯/石蜡/硅藻土复合相变材料。随着石蜡含量的增加,复合材料的相变焓逐渐增大。在没有硅藻土的情况下,LDPE所能包覆的石蜡的最大含量为50%(ΔH(石蜡50%)=63.81 J/g);添加硅藻土(10%)后石蜡的最大含量为55%(ΔH(石蜡55%)=76.57 J/g)。     

化学交联PP/LDPE共混材料的熔体强度及发泡性能

通过化学交联提高聚丙烯/低密度聚乙烯(PP/LDPE)共混物的熔体强度,并对交联PP/LDPE共混物的发泡性能进行了研究.结果表明:交联PP/LDPE共混物熔体在拉伸过程中出现明显的应变硬化现象,熔体强度明显提高;采用交联PP/LDPE共混物可制得泡孔均匀、性能良好的闭孔泡沫材料;随着LDPE含量的增加,交联PP/LDPE共混物的凝胶含量逐渐增加,熔体流动速率(MFR)减小;随着发泡剂用量的增加,交联PP/LDPE共混物泡沫的密度逐渐减小,泡孔孔径略有增大;随着泡沫密度的减小,泡沫材料的拉伸强度、压缩强度及压缩永久变形逐渐减小,拉伸断裂伸长率基本不变.     

木粉/交联PE复合材料的制备及研究

文章以PE为塑料基体,以不同含量的KH570处理木粉,DCP为引发剂,采用双螺杆挤出造粒然后模压成型工艺制备一系列木粉/交联PE复合材料。研究PE基体交联前后、KH570含量对木粉/交联PE复合材料性能的影响;对比放在室温和模拟桑拿浴室复合材料力学性能变化。结果显示:PE基体交联后复合材料的力学性能得到提高;随着KH570含量的增加,木粉/交联PE复合材料力学性能不断增大,当KH570含量为5%时,材料的力学性能最大;经模拟桑拿浴室放置后,木粉/交联PE复合材料的力学性能有进一步的提高。     

相变微胶囊的制备及其在隔热保温涂料中的应用

采用无皂乳液聚合的方法,以二乙烯苯为交联单体,制备了以苯乙烯-甲基丙烯酸共聚物为外壳,相变材料石蜡为内核的相变微胶囊,研究了乳化剂含量、单体配比对相变微胶囊包覆率的影响。采用热重分析仪(TG)、扫描电子显微镜(SEM)分别考察了交联单体含量、可聚合乳化剂含量对相变微胶囊热稳定性能、形貌及分散性的影响。采用差示扫描量热仪(DSC)对相变微胶囊的储热性能进行表征,并将相变微胶囊应用到隔热保温涂料中,进行了隔热性能测试。     

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。     

化学交联PE-LD/SBS共混物的形状记忆效应研究

分别用3种不同苯乙烯含量的苯乙烯-丁二烯共聚物(SBS)与低密度聚乙烯(PE-LD)混合制成共混物,采用过氧化苯甲酰(BPO)为引发剂,使共混物发生化学交联形成网状结构,对交联共混物的交联度进行了分析,测试了交联共混物的拉伸强度与断裂伸长率,探讨了交联共混物的形状记忆效应。结果表明,在PE-LD/SBS共混物中,随着BPO含量的增加,共混物的交联度增大;BPO含量固定时,随着SBS中丁二烯含量的增大共混物的交联度增大;随着交联度的增加,共混物的拉伸强度与断裂伸长率均下降;当BPO含量为0.5 %～1.5 %时,交联共混物具有良好的形状记忆效应。     

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。     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

The System Si3N4-SiO2-Y2O3

Subsolidus phase relations were established in the system Si₃N₄-SiO₂-Y₂O₃. Four ternary compounds were confirmed, with compositions of Y₄Si₂O₇N₂, Y₂Si₃O₃N₄, YSiO₂N, and Y₁₀(SiO₄)₆N₂. The eutectic in the triangle Si₃N₄-Y₂Si₂O₇-Y₁₀(SiO₄)₆N₂ melts at 1500°C and that in the triangle Si₂N₂O-SiO₂-Y₂Si₂O₇ at 1550°C. The eutectic temperature of the Si₃N₄-Y₂Si₂O₇ join was ∼ 1520°C.     

Compact Swelling in Bi1.4Pb0.6Sr2Ca2Cu3.6Oy During the Formation of High-Tc Superconducting Phase

Compact swelling in Pb-doped Bi-Sr-Ca-Cu-O superconductor has been studied by observing the effects of the size of calcined powders, volatilization of materials, and sintering of high- T _c (2223) powders. The bulk density increases at the early stage of sintering, for about 20 h, and then decreases. Densification occurs when the low- T _c (2212) phase and a liquid phase exist, whereas dedensification occurs with the formation of the 2223 phase regardless of the presence of the liquid. Gas evolution from specimens does not appear to be responsible for compact swelling. Compact swelling is explained by anisotropic growth of thin, platelike 2223 grains in random orientation. When 2223 grains grow in a preferred direction, compact swelling is suppressed.