聚羧酸盐SAS/MAA/APEG的制备与性能分析

以烯丙基聚乙二醇(APEG),甲基丙烯酸(MAA),烯丙基磺酸钠(SAS)为单体,在引发剂过硫酸钾(K2S2O8)、阻聚剂对苯二酚作用下直接聚合得到一系列具不同侧链长度的三元聚醚聚羧酸盐分散剂。通过红外光谱、热重分析、差示扫描量热分析和凝胶渗透色谱等手段对聚合物的结构、热力学性能和相对分子质量及其分布进行了表征和分析。将其作用于彬长煤制浆,考察了浆体的表观黏度、流变性、Zeta电位、最大成浆浓度和稳定性,并测定和煤的接触角。结果表明,侧链长度为SAS/MAA/APEG1000(n=23)的聚羧酸盐分散剂在最佳用量为0.4%时,水煤浆最高制浆浓度可达到72%,Zeta电位由-12.6 mV变化到-53.1 mV,具有良好的润湿效果,对彬长煤具有更好的降粘、分散和稳定作用。     

梳形聚羧酸盐AMPS/MAA/MAAMPEG的制备与性能研究

以甲氧基聚乙二醇(MPEG,氧乙烯单元数为11,23)和甲基丙烯酸(MAA)为原料制得甲氧基聚乙二醇甲基丙烯酸酯化单体(MAAMPEG);再以该酯化单体、甲基丙烯酸和2-丙烯酰胺-2-甲基丙磺酸(AMPS)为原料,制得具有不同长度侧链的梳形聚羧酸盐(PC)分散剂AMPS/MAA/MAAMPEG(AMAPEG)。利用核磁共振氢谱(~1 H-NMR)、红外光谱仪(FT-IR)、凝胶渗透色谱仪(GPC)对分散剂分子的结构、分子质量及分布进行了表征;并将其和工业分散剂萘磺酸盐(NSF)用于彬长煤制水煤浆,结果表明,所得目标聚合物的Mw为2×10~4~3×10~4,分子量分散系数D在约为1.3,煤质量浓度为65%时,最佳用量为0.4%,浆体粘度约为447mPa·s,zeta电位达到-56mV,比萘磺酸盐具有良好的润湿效果,更好的降粘分散和稳定作用。     

磺甲基化腐植酸缩聚物的合成及性能应用

以腐植酸、甲醛、对氨基苯磺酸钠、尿素等为原料,依次经过磺甲基化、缩聚反应合成了两种具有不同侧链结构的腐植酸分散剂,磺甲基化腐植酸缩聚物(简称HBF)和磺甲基化腐植酸脲醛缩聚物(简称HBUF)。通过对比考察了两种分散剂对陕西彬长煤的水煤浆的成浆性能、浆体稳定性能以及两种分散剂在煤颗粒表面的吸附性能,结果表明,具有较长侧链的HBUF分散剂具有较好的分散降粘效果,其用量为0.45%时,彬长煤的最高制浆浓度达68%,两种分散剂在煤颗粒表面均呈现单分子层吸附特征,其中HBUF吸附量大,吸附平衡常数高。     

羧基/磺酸基含量对聚羧酸盐水煤浆分散剂性能的影响

以甲基丙烯酸(MAA)、烯丙基磺酸钠(SAS)按一定比例合成了5种含有不同—COO~(-1)/—SO_3~(-1)比值的聚羧酸盐水煤浆分散剂PMAS系列。并通过红外光谱(FT-IR)、凝胶渗透色谱(GPC)进行了表征。并将其作用于彬长煤制浆,在用量0.4%(质量分数)时,水煤浆浆浓为65%时,考察了浆体的表观黏度与—COO~(-1)/—SO_3~(-1)比值的关系,在不同浓度下的zeta电位以及pH值对水煤浆应用的影响等。结果表明,当—COO~(-1)/—SO_3~(-1)比值为约3.238时,浆体的表观粘度最低,稳定性理想,此时浆体的zeta电位能达到-38mV,水煤浆粘度随着pH值的增大逐渐降低,当pH值大于10时水煤浆粘度趋于稳定。     

耐盐型吸水微球的反相悬浮法制备及表征

采用反相悬浮聚合法,以丙烯酸(AA)、丙烯酰胺(AM)、聚乙二醇甲基丙烯酸酯(PEGMA)为单体,合成了吸水膨胀微球聚(丙烯酸钠-丙烯酰胺-聚乙二醇甲基丙烯酸酯)(P(AA-AM-PEGMA))。研究了分散剂对反应体系稳定性和产品形态的影响以及搅拌速度、反应温度、单体配比、丙烯酸中和度、交联剂、引发剂用量对微球性能的影响。结果表明,最佳条件下(聚合温度为75℃,PEGMA用量为单体质量的35%,中和度为80%,引发剂和交联剂用量分别为单体质量的1.5%、0.1%)制备的吸水膨胀微球在去离子水中的吸水率为706 g/g,在0.9%NaCl溶液中的吸液率为85 g/g。     

IA/AA/AMPS水煤浆分散剂的制备与表征

以2-丙烯酰胺基-2-甲基丙磺酸(AMPS)-丙烯酸(AA)-衣康酸(IA)三元共聚物为水煤浆分散剂,通过对水煤浆液体流变性能的研究得到了分散剂的最佳合成条件:单体配比为m(AMPS)∶m(AA)∶m(IA)=3.8∶1∶1,反应温度为85℃,引发剂的添加量为单体总质量的5%,次亚磷酸钠的最佳添加量为单体总质量的10%;并通过FT-IR、XRD、GPC等对聚合物分散剂的结构、分子量进行测定。结果表明,共聚物中成功引入了磺酸基和羧酸基,重均相对分子质量约为1.6×104,多分散系数为3.41。     

疏水烷基酯侧链对聚羧酸系减水剂分散及保坍性能的影响

为了研究聚羧酸系减水剂(PCA)分子结构中疏水侧链对新拌混凝土坍落度及其损失的影响,以马来酸酐(MA)、异戊烯醇聚氧乙烯醚(TPEG)和丙烯酸烷基酯为原料,过硫酸铵为引发剂,通过自由基聚合合成了4种不同疏水侧链长度(疏水侧链含碳个数分别为4、8、12和18)的聚羧酸系减水剂。通过水泥净浆流动度、流动性损失等指标检验了聚羧酸系减水剂的分散性能及保坍性能,结果表明随着疏水侧链长度的增加,聚羧酸系减水剂的分散性能逐渐提高,保坍性能有所改善。吸附量和zeta电位测试结果解释了这种现象的原因,随着疏水侧链长度的增加,水泥颗粒表面zeta电位绝对值逐渐增加,水泥颗粒表面上的持续吸附能力逐渐增强。     

双亲性聚合物稠油降黏剂的合成及降黏性能

采用具有疏水结构的丁苯烯(PB)和具有亲水结构的丙烯酰胺(AM)、丙烯酸(AA)、2-丙烯酰胺-2甲基丙磺酸(AMPS)合成双亲性聚合物。聚合物链中的苯环结构可嵌进稠油沥青质的板结结构中,进入稠油内部聚合物链上的亲水基团可促进O/W乳状液的形成,进而降低稠油黏度。聚合物的红外光谱、热重分析、凝胶渗透色谱结果表明,单体AM,AA,AMPS和PB均参与了共聚,较高的热解温度(250℃)保证了降黏剂的热稳定性,较低的相对分子质量(8×10⁴～10×10⁴)之间有利于降黏剂进入到稠油的"内部"。以绥中36-1脱气稠油(SZ)和江汉油区八面河稠油(BMH)为降黏处理对象,降黏剂在一定条件下(70℃,质量分数为0.5%和0.6%),降黏率分别为86.14%和83.85%,表明双亲性聚合物具有优良的降黏效果,且在一定条件下(70℃,质量分数0.5%),降低油水体积比(低于6∶4)可有效提高降黏效果。     

三元共聚羧酸高效减水剂的聚合动力学

以过硫酸铵为引发剂,合成以马来酸酐、丙烯酸、烯丙基磺酸钠为主链的聚羧酸盐高效减水剂。考察了聚合温度、引发剂摩尔百分含量、各单体摩尔百分含量对聚合速率的影响。实验结果表明,共聚体系的表现活化能为37.604 kJ/mol,聚合速率同引发剂摩尔百分含量的0.361次方,马来酸酐摩尔百分含量1.1748次方,丙烯酸摩尔百分含量1.1952次方以及烯丙基磺酸钠摩尔百分含量1.4229次方分别成正比。烯丙基磺酸钠单体摩尔百分含量对聚合速率有较大的影响。     

耐盐型吸水膨胀微球的合成及性能研究

采用反相悬浮聚合法,以聚乙二醇二丙烯酸酯(PEGDA)为交联剂,过硫酸钾(KPS)-亚硫酸氢钠(NaHSO3)为引发剂合成了吸水膨胀微球聚(丙烯酸钠-丙烯酰胺)(P(AA-AM))。研究了分散剂对反应体系稳定性和产品形态的影响以及单体配比、丙烯酸中和度、交联剂及引发剂用量对微球吸水率的影响。最佳条件下制备的吸水膨胀微球在去离子水中的吸水率为880g/g,在0.9%NaCl溶液中的吸液率为82g/g。     

Structural and optical properties of AlxOy/Pt/AlxOy multilayer absorber

We report on the microstructure and optical properties of Al_xO_y–Pt–Al_xO_y interference-type multilayer films, deposited by electron beam (e-beam) deposition onto corning 1737 glass, silicon (1 1 1) and copper substrates. The structural properties were investigated by Rutherford backscattering spectrometry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The optical properties were extracted from specular reflection/transmission, diffuse reflectance and emissometer measurements. The stratification of the coatings consists of a semi-transparent middle Pt layer sandwiched between two layers of Al_xO_y. The top and bottom Al_xO_y layers were non-stoichiometric with no crystalline phases present. The Pt layer is in the fcc crystalline phase with a broad size distribution and spheroidal shape in and between the rims of Al_xO_y. The surface roughness of the stack was found to be comparable to the inter-particle distance. The optical calculations confirm a high solar absorptance of ∼0.94 and a low thermal emittance of ∼0.06 for the multilayer stack, which is attributed not only to the optimized nature of the multilayer interference stacks, but also to the specific surface morphology and texture of the coatings. These optical characteristics validate the spectral selectivity of the Al_xO_y–Pt–Al_xO_y interference-type multilayer stack for use in high temperature solar-thermal applications.     

Optimization of AlxOy/Pt/AlxOy multilayer spectrally selective coatings for solar-thermal applications

Spectrally selective Al_xO_y/Pt/Al_xO_y multilayer absorber coatings were deposited onto corning 1737 glass, Si (111) and copper substrates using electron beam (e-beam) vacuum evaporator at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit multilayer solar absorber coatings. The optical constants (n and k) measured using spectroscopic ellipsometry, showed that both Al_xO_y layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance α ∼ 0.94 ± 0.01 and low thermal emittance ? ∼ 0.06 ± 0.01 at 82 °C. The Rutherford backscattering spectroscopy (RBS) data of Al_xO_y/Pt/Al_xO_y multilayer absorber indicated the Al_xO_y layers present in the coating were nearly stoichiometry. The scanning electron microscope analysis (SEM) result indicated that the average diameter and inter-particles distance of Pt grains were statistically about 146 ± 0.17 nm and 6-10 ± 0.2 nm respectively.     

Interfacial microstructure of NiSix/HfO2/SiOx/Si gate stacks

Integration of NiSi_x based fully silicided metal gates with HfO₂ high-k gate dielectrics offers promise for further scaling of complementary metal-oxide- semiconductor devices. A combination of high resolution transmission electron microscopy and small probe electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis has been applied to study interfacial reactions in the undoped gate stack. NiSi was found to be polycrystalline with the grain size decreasing from top to bottom of NiSi_x film. Ni content varies near the NiSi/HfO_x interface whereby both Ni-rich and monosilicide phases were observed. Spatially non-uniform distribution of oxygen along NiSi_x/HfO₂ interface was observed by dark field Scanning Transmission Electron Microscopy and EELS. Interfacial roughness of NiSi_x/HfO_x was found higher than that of poly-Si/HfO₂, likely due to compositional non-uniformity of NiSi_x. No intermixing between Hf, Ni and Si beyond interfacial roughness was observed.     

Tc trend in high-Tc superconductors

In our previous works, we have shown that most existing ceramic superconductors can be considered to be built of superconductor-semiconductor composite and we have estimated the change in phonon spectrum of the intrinsic superconductor unit if a semiconductor unit is attached to it. Moreover, the proximity effect under the size quantization condition has been examined in the superconductor-semiconductor composite. Each of the stated effects by itself could causeT _c enhancement in general as more semiconductor blocks are added to the system. We extend our study in this paper to analyze the combined actions of phonon spectral change and proximity effect without size quantization condition onT _c variation in members of the Tl₁ series of high-T _c superconductors. Our results indicate that an optimumT _c is obtained if the stated effects are included in the idealized unit cells of the superconductors made up of a superconductor-semiconductor array.     

Anomalous Hall Effect in Sn1?x?yMnxEuyTe and Sn1?x?yMnxEryTe Mixed Crystals

The Anomalous Hall Effect (AHE) was investigated in IV–VI ferromagnetic semimagnetic semiconductors of Sn_1–x Mn _x Te codoped with either Eu or Er. The analysis of experimental data is as follows. Hall resistivity and magnetization showed that AHE coefficient R _s depends on temperature and its value decreases with thetemperature increase. We observe that above ferromagnet–paramagnet transition temperature R _s changes sign. We discuss the possible physical mechanisms responsible for observed temperature dependence of R _s , particularly change of the sign.     

Synthesis of a new perovskite Pb(Li14Nb34)O3

A high-pressure technique was adopted to obtain perovskite-type $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$. A new perovskite $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$ was characterized to have a cubic symmetry with $\text{a}{}_{\mathrm{<mtext>o</mtext>}}\text{= 4.069}\text{A}\text{?}$; Li and Nb ions in the B-site of perovskite lattice may be in a random arrangement.     

Bulk crystalline BaPb34Bi14O3: A ceramic superconductor

The preparation conditions of the high T_C ceramic superconductor Ba(Pb,Bi)O₃ is correlated with the superconducting transition. Transition onsets of all materials are similar, but transition widths and transition completeness is strongly dependent on firing temperature. Only materials prepared over a narrow temperature range, resulting in a nearly ideal weight loss, have a complete and narrow transition.     

Electrostriction in Pb (Zn13Nb23)O3

The electrostriction in $\text{Pb (Zn}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Nb}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{)}\text{O}{}_3$ crystals has been investigated using a strain gauge method. In the ferroelectric phase below 140 C, the strain vs the electric field shows a hysteresis, which is ascribed to the effect of ferroelectric domains. A quadratic relation holds between the strain x and the electric polarization P as x = QP² above about 170 C in the paraelectric phase. Values of the electrostrictive Q coefficients are determined from the measurements near 190 C, as Q₁₁ = 1.6·10^?2m⁴/C², Q₁₂ = ?0.86·10^?2m⁴/C², and Q₄₄ = 0.85·10^?2m⁴/C².     

Effect of pressure onTc in La2-xBaxCuO4 withx=0.125

The superconducting transition temperature,T _c , of La_2–x Ba _x CuO₄ has been measured under high pressure up to 8 GPa.T _c is found to change drastically at the pressure where the structural phase transition takes place. This finding clearly indicates that there exists an intimate relation between the crystal structure and superconductivity.