Synthesis of new thermosetting poly(2,6‐dimethyl‐1,4‐phenylene oxide)s containing epoxide pendant groups

A new class of thermosetting poly(2,6‐dimethyl‐1,4‐phenylene oxide)s containing pendant epoxide groups were synthesized and characterized. These new epoxy polymers were prepared through the bromination of poly(2,6‐dimethyl‐1,4‐phenylene oxide) in halogenated aromatic hydrocarbons followed by a Wittig reaction to yield vinyl‐substituted polymer derivatives. The treatment of the vinyl‐substituted polymers with m‐chloroperbenzoic acid led to the formation of epoxidized poly(2,6‐dimethyl‐1,4‐phenylene oxide) with variable pendant ratios, and the structures and properties were studied with nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. The ratios of pendant functional groups were tailored for the polymer properties, and the results showed that the glass‐transition temperatures increased as the benzylic protons were replaced by bromo‐, vinyl‐, or epoxide‐functional groups, whereas the thermal stability decreased in comparison with the original polymer. Within a molar fraction of 20–50%, the degree of functionalization had little effect on the glass‐transition temperature; however, it correlated inversely with the thermal stability of each functionalized polymer. The thermal curing behavior of the epoxide‐functionalized polymer was enhanced by the increment of the pendant functionality, which resulted in a significant increase in the glass‐transition temperature as well as the thermal stability after the curing reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5875–5886, 2006     

Synthesis of poly(ethylene oxide) with pending 2,2,6,6‐tetramethylpiperidine‐1‐oxyl groups and its further initiation of the grafting polymerization of styrene

A new stratagem for the synthesis of amphiphilic graft copolymers of hydrophilic poly(ethylene oxide) as the main chain and hydrophobic polystyrene as the side chains is suggested. A poly(ethylene oxide) with pending 2,2,6,6‐tetramethylpiperidine‐1‐oxyls [poly(4‐glycidyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐co‐ethylene oxide)] was first prepared by the anionic ring‐opening copolymerization of ethylene oxide and 4‐glycidyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl, and then the graft copolymerization of styrene was completed with benzoyl peroxide as the initiator in the presence of poly(4‐glycidyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐co‐ethylene oxide). The polymerization of styrene was under control, and comblike, amphiphilic poly(ethylene oxide)‐g‐polystyrene was obtained. The copolymer and its intermediates were characterized with size exclusion chromatography, ¹H NMR, and electron spin resonance in detail. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3836–3842, 2006     

具有HfN/HfO2栅结构的p型MOSFET中的负偏置-温度不稳定性研究

研究了HfN/HfO₂高K栅结构p型金属-氧化物-半导体(MOS)晶体管(MOSFET)中，负 偏置-温度应力引起的阈值电压不稳定性(NBTI)特征.HfN/HfO₂高K栅结构的等效 氧化层厚度(EOT)为1.3nm，内含原生缺陷密度较低.研究表明，由于所制备的HfN/HfO₂ 高K栅结构具有低的原生缺陷密度，因此在p-MOSFET器件中观察到的NBTI属HfN/HfO2高K栅结构的本征特征，而非工艺缺陷引起的；进一步研究表明，该HfN/HfO₂高K栅结构中观察到的NBTI与传统的SiO₂基栅介质p-MOSFET器件中观察 到的NBTI具有类似的特征，可以被所谓的反应-扩散(R-D)模型表征： HfN/HfO₂ 栅结构p-MOSFET器件的NBTI效应的起源可以归为衬底注入空穴诱导的界面反应机理，即在负 偏置和温度应力作用下，从Si衬底注入的空穴诱导了Si衬底界面Si-H键断裂这一化学反应的 发生，并由此产生了Si^＋陷阱在Si衬底界面的积累和H原子在介质层内部的扩散 ，这种Si^＋陷阱的界面积累和H原子的扩散导致了器件NBTI效应的发生. 关键词： 高K栅介质 负偏置-温度不稳定性(NBTI) 反应-扩散(R-D)模型     

Infrared combination and difference bands of the NO dimer

The mid-infrared (1500-3800 cm⁻¹) absorption spectrum of gaseous nitric oxide has been studied at low temperature (99 K) with a long absorption path (160 m) in order to observe weak combination, difference, and overtone bands of the NO dimer. About ten new bands were assigned with greater or lesser certainty. Combined with previous results, they lead to a set of 12 secure and 7 tentative vibrational term values for (NO)₂, essentially doubling our knowledge of NO dimer vibrational states. The strongest non-fundamental bands in this region, other than the ν₁ (symmetric N-O stretch) + ν₅ (asymmetric N-O stretch) overtone, involve combinations of ν₅ with ν₃ (intermolecular stretch). Excitation of ν₅ results in increased frequencies for the intermolecular modes ν₂, ν₃, and ν₄. A new value of 155.5 cm⁻¹ was obtained for ν₄, the elusive infrared-inactive out-of-plane fundamental vibration.     

Characterization of nonstoichiometric nickel manganite spinels NixMn3−x□3δ/4O4+δ by temperature programmed reduction

Cation deficient spinels Ni_xMn_3−x□_3δ/4O_4+δ (0≤x≤1) have been prepared by thermal decomposition of mixed oxalates Ni_x/3Mn_(3−x)/3(C₂O₄)·nH₂O in air at 623 K. They have been characterised by temperature programmed reduction (TPR) under H₂, the reaction being followed by gravimetric and powder X-ray diffraction measurements. It has been shown that TPR proceeds in several steps. The first steps correspond to the loss of nonstoichiometric oxygen leading to the formation of a stoichiometric oxide. During the following stages the manganese cations are reduced, causing the spinel structure to be destroyed, and the formation of solid solution of NiO in a cubic MnO. Subsequently, Ni²⁺ cations undergo a reduction to metallic nickel, and, finally, a mixture of nonstoichiometric MnO_1−δ and metallic nickel is formed. These oxides contain a high level of vacancies which vary with the nickel content with a maximum of δ≈1 near x=0.6. This nonstoichiometry is ascribed both to the presence of Ni³⁺ and excess of Mn⁴⁺.     

Nd2O3掺杂对SnO2气敏性质的影响

SnO_2是目前应用最广的一种气敏材料。我们曾经报道掺入La_2O_3,CeO_2,Pr_6O_(11),和Nd_2O_3后可使半导体元件的灵敏度提高,尤以对乙醇、乙醚、丙酮为显著。掺Nd_2O_3元件对乙炔的灵敏度也有提高。本文考察了SnO_2粒度和被测气氛的物化性质对掺Nd_2O_3元件灵敏度的影响。SnO_2采用水解SnCl_4法制备,纯度经光谱分析测定合格,试样用标准筛分目。在SnO_2中加1wt%Nd_2O_3(光谱纯)和适量水及甲基纤维素,混磨15分钟。将制成的悬浊液滴在一对铂     

K2NiF4型结构的A2－xSrxBO4(A＝La, Dy, B＝Mn, Fe, Co, Ni)希土复合氧化物的合成

以典型的轻希土镧和重希土镝及碱土金属锶作为Ａ位离子，以过渡金属锰、铁、钴、镍作为Ｂ位离子，合成了Ｋ２ＮｉＦ４型结构的Ａ２－ｘＳｒｘＢＯ４希土复合氧化物，采用粉末Ｘ射线衍射技术考察了反应条件等因素对生成Ｋ２ＮｉＦ４型四方（Ｔ）结构上析影响，实现结果表明，四方结构的形成不仅与几何因素有关，而且与各组分的物理化学性质有关。各个不同的组成，生成四方相的温度范围也有所不同。适当地提高反应温度以及延长灼烧时间     

THE RING OPENING REACTION OF AN EPOXY COMPOUND ON THE TOP OF CHEMISORBED CYSTAMINE STUDIED BY THE SERS TECHNIQUE

Metal foils for Raman scattering were prepared by HNO_3 etching method. These foils werefound to exhibit a strong SERS effect and excellent thermal stability. SERS spectra of cystaminehave been taken to illustrate the usefulness of this sample preparation method in the studies ofchemisorption. The ring opening reactions of an epoxy compound have been observed on the topof chemisorbed cystamine on silver foils.     

Effect of Oxalic Acid on Stabilization and Property of Sb-Doped Tin Oxide Sol

Zeta potential studies show that the ATO nanoparticle surface is positively charged in pH range from 2 to 5 without oxalic acid. The addition of oxalic acid brings a charge reversal on the surface of ATO particle in a wide pH range. The interaction of oxalic acid with surface of ATO nanoparticle was studied by FTIR and indicates that the most probable mechanism is the formation of Sn-O-C bonds via the condensation reaction between the oxalic acid and surface hydroxyl groups. TEM, X-ray diffraction and UV-Vis-Near IR spectra were used to characterize the nanocrystalline ATO sol and thin gel film.     

冲击波处理的结晶MgO的化学分析正电子谱研究

冲击波处理的结晶ＭｇＯ的化学分析正电子谱研究＊张菊郑小明（杭州大学催化研究所，杭州３１００２８）常志向（抚顺石油化工研究院，抚顺１１３００１）关键词冲击波，化学分析正电子谱，结晶氧化镁，丁烯，脱氢冲击波是在介质中以超音速传播的压力脉冲．气体中的冲击波...