Liquid Precursor Infiltration Processing of Powder Compacts: II, Fracture Toughness and Strength

Si₃N₄ powder compacts were infiltrated with liquid precursors which produce either Zr(Y)O₂ (3 mol% Y₂O₃) solid solution or amorphous Si₃N₄ after pyrolysis at relative low temperatures and without shrinkage. Results show that cracks which occur within a thin, surface layer of the precursor during pyrolysis can extend into the powder compact. As suggested by theory, this cracking phenomenon could be avoided either by making the powder compact stronger before infiltration or by removing the thin precursor layer before pyrolysis. The mechanical properties of these materials were studied as a function of residual porosity. It was observed that crack extension occurred within the second phase produced by infiltration and pyrolysis. The second phase appeared to govern the critical stress intensity factor ( K_c ) of the material. K_c was found to be a linear function of the change in residual, relative porosity divided by the initial, relative porosity in the powder compact. Reasonable flexural strengths (∼300 MPa) could be achieved despite considerable residual porosity.     

400t／a苯基氯硅烷直接法合成工艺

本文介绍了４００ｔ／ａ苯基氯硅烷直接法合成工艺及其技术经济指标。     

高掺量粉煤灰碾压混凝土层面抗裂性能研究

针对碾压混凝土筑坝快速施工技术的筑坝材料采用高掺量粉煤灰与低胶凝材料用量的技术特点，本文结合高坝建设关键技术国家“九五”科技攻关课题，重点研究高掺量粉煤灰的碾压混凝土层面，在不同工况条件下的层面抗裂性能及其提高层面抗裂性能的措施。     

熔融法生物玻璃与溶胶-凝胶法生物玻璃的矿化特性研究

采用X射线衍射(XRD)、傅立叶转换红外光谱(FTIR)、扫描电镜(SEM)等方法对比分析了熔融法生物玻璃45S5与溶胶-凝胶法生物玻璃58S及77S的体外生物矿化性能,对它们表现出来的生物矿化性能差异进行初步的机理研究.结果表明,这3种生物玻璃中,58S具有最好的生物矿化性能,在37℃的模拟体液(simulated body fluid,SBF)中浸泡反应8 h即能在表面矿化形成结晶度较好的碳酸羟基磷灰石(HCA).     

An RFID-based enterprise application integration framework for real-time management of dynamic manufacturing processes

Enterprise application integration (EAI) is an important issue for a company trying to transform itself into a ubiquitous real-time organization. However, traditional techniques for EAI are only suitable for integrating the virtual information among different applications. The challenge of integrating physical objects with corresponding business processes and applications at the right time and location is a critical concern for companies building a real-time enterprise (RTE) information system. In this research, we proposed an EAI framework based on radio frequency identification (RFID) technology. On the basis of this framework, a prototype system is developed to demonstrate the applicability of the framework in a shop floor environment. This paper also presents a RFID-based standard operation procedure to configure a prototype system for a particular shop floor operation and an operator orientation for performing the corresponding tasks. The findings of this paper demonstrate that the proposed framework is more capable than most current industrial practices in both managing dynamic manufacturing processes and in providing real-time visibility of work-in-process information. Using this framework, an enterprise can easily integrate an RFID-based solution into its IT infrastructure and manufacturing environment to facilitate real-time management of dynamic production operations.     

地方本科院校环境工程专业实践教学的过程管理

地方本科院校运用过程管理方法可提高实践教学的管理水平和应用型本科人才的培养质量。文章以嘉应学院环境工程专业为例,分析其实践教学管理中存在的问题,探讨实践教学过程管理的方法,为地方本科院校工科专业的过程管理提供了参考。     

PEG分子量对PET—PEG共聚酯结晶性能的影响

通过ＰＥＴ和ＰＥＧ共缩聚，合成了ＰＥＴ—ＰＥＧ共聚酯，采用ＤＳＣ、等温结晶仪、Ｘ衍射分析仪和电子扫描电镜研究了ＰＥＧ分子量对该共聚酯结晶性能的影响。结果表明，在ＰＥＴ分子结构中引入ＰＥＧ链段，能有效提高结晶速度，共聚酯结晶结构与ＰＥＴ类似，但ＰＥＧ不进入晶格中，只起诱导结晶的作用。当ＰＥＧ分子量为４０００时，冷结晶温度Ｔｃｃ降得最低，但热结晶温度Ｔｃ反而比纯ＰＥＴ有所增加，１１０℃结晶速度ｔ１２＝１ｍｉｎ，而纯ＰＥＴ需１２ｍｉｎ。     

Synthesis and Electrical Characterization of Thin Films of PT and PZT Made from a Diol-Based Sol-Gel Route

Lead titanate (PT) sols were prepared using propanediol, butanediol, or pentanediol solutions of lead acetate trihydrate and titanium diisopropoxide bis(acetylacetonate). Precursor sols for PbZr_0.53Ti_0.47O₃ (PZT) films were prepared from propanediol solutions, with zirconium tetrapropoxide being used as the zirconium source. Films were formed by spin-coating the sols onto silicon and platinized silicon substrates; the resulting gel layers were converted to ceramic films by adopting a two-stage heating schedule with final firing temperatures of 600–700°C. Information on film crystallization, microstructure development, and electrical properties is presented for both compositions. The limiting thickness of surface-smooth crack-free single-layer films was ∼1 μm. The PT films exhibited a "linear" polarization-electric field ( P-E ) response, while the PZT films gave rise to characteristic ferroelectric P-E hysteresis loops. A 0.5 μm thick single-layer PZT film exhibited remanent polarization (P_r) values of ∼34 μC·Cm⁻², with a coercive field ( E _c) of ∼45 kV·Cm⁻²; the relative permittivity (ɛ_r) and the dissipation factor ( D ) were ∼1250 and 0.07. For a 1 μm single-layer PZT film, the respective values were P _r∼19 μC∼Cm⁻², E _c∼40 kV∼Cm⁻², ɛ_r∼750, and D = 0.03.     

Green electroluminescent polyfluorenes containing 1,8-naphthalimide moieties as color tuner

A series of copolymers (CNPFs) containing low-band-gap 1,8-naphthalimide moieties as color tuner was prepared by a Yamamoto coupling reaction of 2,7-dibromo-9,9-dioctylfluorene (DBF) and different amount of 4-(3,6-dibromocarbazol-9-yl)-N-(4′-tert-butyl-phenyl)-1,8-naphthalimide (Br-CN) (0.05-1 mol% feed ratio). The light emitting properties of the resulting copolymers showed a heavy dependence on the feed ratio. In photoluminescence (PL) studies, an efficient color tuning through the Förster energy transfer mechanism was revealed from blue to green as the increase of Br-CN content, while in electroluminescence (EL) studies, the color tuning was found to go through a charge trapping mechanism. It was found that by introduction of a very small amount of Br-CN (0.1-0.5 mol%) into polyfluorene, the emission color can be tuned from blue to pure green with Commission International de l'Echairage (CIE) coordinates being (0.21, 0.42) and (0.21, 0.48). A green emitting EL single-layer device based on CNPF containing 0.1 mol% of Br-CN showed good performances with a low turn-on voltage of 4.2 V, a brightness of 9104 cd/m², the maximum luminous efficiency of 2.74 cd/A and the maximum power efficiency of 1.51 lm/W. To further improve the EL performances through balancing the charge trapping process, a copolymer (BCNPF05) derived from 0.5 mol% of a triarylamine-containing 4-{3,6-bis-[4″-(4?-bromophenyl-p-tolyl-amino)-phenyl]-carbazol-9-yl}-N-(4′-tert-butyl-phenyl)-1,8-naphthalimide (Br-BCN) and 99.5 mol% of 2,7-dibromo-9,9-dioctylfluorene was also prepared. As expected, a single layer EL device based on BCNPF05 exhibited better performances with a brightness of 14228 cd/m², the maximum luminous efficiency of 4.53 cd/A and the maximum power efficiency of 1.57 lm/W.     

Study of electrical discharge grinding using metal matrix composite electrodes

An investigation was made into the combined technologies of electrical discharge machining and grinding (EDMG). A metal matrix (Cu/SiC_p) electrode with a rotating device was made and employed to study the EDMG technology. It was found that 3–7 times the normal electrical discharge machining (EDM) material removal rate (MRR) could be achieved in EDMG under suitable conditions of electrode rotating speed, SiC_p particle size and current. This novel achievement is attributed to the fact that, under appropriate conditions, the hump-shaped melted material created by the EDM mechanism is vulnerable to attack by the grinding mechanism during the EDMG operation, greatly increasing the removal rate. Conversely, under inappropriate conditions, in which hump-shaped material solidifies prior to the non-conductive ceramic particle grinding, the above function becomes negligible and results in much lower MRR.