注塑成型工艺的探讨

本文研究了树脂拉伸试样在注塑成型过程中,锁模力、保压时间和机筒温度等重要影响因素对其表观状态的影响。即锁模力715KN,保压时间21S,料筒温度195℃等最优的参数设置,使得拉伸试样符合GB/T1040．2—2006中规定的1A型多用途聚乙烯拉伸实验试样的允许尺寸范围,提高了工作效率,延长了注塑机的使用寿命。     

聚乙烯/杨木粉基木塑复合材料的性能研究

目的 研究硅烷偶联剂(KH-550)处理木粉以及微胶囊红磷(HP)阻燃对木塑复合材料(WPC)的性能影响.方法 以杨木粉、低密度聚乙烯(LDPE)、线性低密度聚乙烯(LLDPE)和HP为原料,采用二次共混造粒及注射模塑法,制备WPC,通过熔体流动速率(MFR)试验、拉伸试验、TGA谱图分析、Kissinger动力学分析和SEM显微观察研究WPC的性能.结果 采用KH-550处理木粉后,体系的MFR提高了0.01 g/min,拉伸时的最大位移提高了2.59 mm,HP的添加使WPC在分解5％和50％时的温度分别提高了18℃和54℃,KH-550和HP共改性的WPC在420～500℃(主要分解阶段)的表观活化能为153 kJ/mol.结论 采用KH-550处理杨木粉后,使体系的拉伸性能得到有效改善,在添加质量分数为10％的HP后,WPC的阻燃效果得到显著提高.     

支座半固态压铸模具设计研究

根据支座产品及半固态浆料充型凝固特点,选用压射比压70MPa,压射速度为1．5m／s,浇注温度590℃,模具预热温度为220℃,进行计算机数值模拟,确定半固态压铸模具的设计方案。设计并制造出支座半固态铸模具。通过支座半固态压铸实验,压铸充型凝固过程非常平稳,得到了合格的支座产品,证实了数值模拟结果及模具设计的正确性。     

LDPE / LLDPE / APP / Sb2 O3 阻燃体系的成型工艺和阻燃性研究

以低密度聚乙烯和线性低密度聚乙烯为基础物质,添加阻燃剂聚磷酸铵和三氧化二锑,构成阻燃体系,研究了阻燃体系的成型加工工艺参数和阻燃性能。研究表明:随着阻燃剂添加量的增大,主螺杆转速需要逐步降低,牵引速度随之下降,主螺杆转速的较小变化,可引起机头压力的急剧增加,物料的实际挤出温度相应提高;当阻燃剂总添加量达到40%时,达到FV-0阻燃等级。     

铝合金端盖件压铸工艺的数值模拟

运用铸造模拟软件Procast对一模四腔的A356铝合金压铸零件进行数值模拟,分析铸件的充型凝固过程,预测缺陷。结果显示：在压射速度为2．5m／s,浇注温度为650℃,模具温度为240℃的条件下四腔同时充填,充型平稳,排气良好,得到充型完整、无缩松缩孔、气孔倾向小的铸件。     

微胶囊红磷阻燃木塑复合材料的性能研究

目的制备微胶囊红磷阻燃木塑复合材料,研究微胶囊红磷添加量对其力学性能、耐热性能和阻燃性能的影响,并扩大其应用范围。方法以微胶囊红磷为阻燃剂,将其添加到低密度聚乙烯、线性低密度聚乙烯和木粉三元复合体系中,采用二次挤出造粒和注射成型法制备阻燃试样。研究材料的力学性能、耐热性能、应力破坏行为,确定材料的阻燃级别。结果与未添加微胶囊红磷的木塑材料相比,当微胶囊红磷添加量(质量分数)达到10%时,材料的冲击强度由17.4 kJ/m2提高到19.0 kJ/m2,抗拉强度由19.53 MPa提高到21.7 MPa,断裂伸长率提高了58.7%,初始分解温度提高了73.17℃,阻燃达到V-0级,氧指数达到28.7%。结论随着微胶囊红磷含量的增加,木塑复合材料的冲击强度、抗拉强度和断裂伸长率变大,初始分解温度提高,阻燃耐热性能变好;材料阻燃剂的添加量低,综合性能优良,在包装、建筑、家具等领域具有广泛应用前景。     

利用金矿尾矿烧制陶粒的正交实验研究

采用正交实验方法研究金矿尾矿掺量、粉煤灰掺量、煤粉掺量、预热温度、预热时间、焙烧温度、焙烧时间7个因素对陶粒制品性能的影响;以陶粒的堆积密度、筒压强度和吸水率性能作为考查指标,得出烧制陶粒的最优方案。结果表明,金矿尾矿掺量为55 g,粉煤灰掺量为34 g,煤粉掺量为3 g,预热温度为450℃,预热时间为60 min,焙烧温度为1 150℃,焙烧时间为120 min时,制得的陶粒综合性能最好。     

铝合金壳体件压铸工艺的数值模拟

基于UG平台设计了铝合金壳体压铸件的浇注系统和排溢系统,并运用铸造模拟软件Anycasting进行了数值模拟。通过分析铸件的充型及凝固过程,判断设计的合理性。模拟结果表明,在压射速度为2m/s,浇注温度为670℃,模具预热温度为180℃的条件下,铸件充型平稳,无明显缺陷。     

航空座椅零部件等温锻造工艺及模具设计

利用DEFORM-3D有限元软件数模拟技术对航空座椅零部件工艺参数和等温锻造模具进行设计。建立有限元模型,采用DEFORM-3D有限元软件对其成形过程进行数值模拟,分析了锻造温度和锻造速度对锻造力的影响,并从模具寿命方面考虑设计了模具预热温度等成形工艺参数。结果表明,采用等温锻造模具在40MN液压机上能够生产出合格的航空座椅零部件工件;毛坯加热温度为370℃～390℃,模具预热温度为370℃～390℃,锻压速度为1.0 mm/s,锻造性能较好,符合设计要求。     

新型通用级苯酚-淀粉模塑料(PF2A1)的研制

研制的产品典型配方(质量份)是苯酚-淀粉树脂:六次甲基四胺:木粉:碳酸钙:氧化镁:硬脂酸锌:硬脂酸:油溶苯胺黑:群青=37.0:6.4:48.0:6.0:0.6:0.6:0.4:0.5:0.5;制备工艺参数是混合时间≥60min,工作辊温度85～95℃,空转辊温度145～155℃,辊距2.3～2.5mm,热炼时间4～5min,拼批时间≥45min;模塑工艺参数是预热温度100～110℃,预热时间10～15min,模塑压力≥25MPa,模塑温度175～180℃,模塑时间0.8～1.0min/mm,排气≥3次.产品性能达到酚醛模塑料(PF2A1)国家标准或优良,原料成本比苯酚-甲醛模塑料(PF2A1)低20.4%.     

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.     

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.     

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.     

Magnetic,electrical and thermal studies on the V1−xMox02

The monoclinic-to-tetragonal structure transition of oxides V_1?xMo_x0₂ with $\text{0≤}\text{x}\text{≤0.20}$ has been studied by means of DTA, X-ray diffraction, magnetic susceptibility (powder samples) and electrical conductivity (single crystals) measurements within the temperature region 80 K to 400 K. A linear decrease of the transition temperature of 11 K per atom % Mo was observed. The magnetic susceptibility of the low temperature phase was found to be temperature independent paramagnetic for all preparations. Electrical conductivity measurements on the same phase showed crystals with $\text{x}\text{? 0.04}$ to be semiconducting, while a metallic behavior was observed in the region $\text{0.10 ?}\text{x}\text{? 0.14}$.