Densification and Mechanical Properties of Titanium Diboride with Silicon Nitride as a Sintering Aid

Titanium diboride (TiB₂) was hot-pressed at a temperature of 1800°C, and silicon nitride (Si₃N₄) was added as a sintering aid. The amount of Si₃N₄ that was added had a significant influence on the sinterability and mechanical properties of the TiB₂. When a small amount (2.5 wt%) of Si₃N₄ was added, the Si₃N₄ reacted with titania (TiO₂) that was present on the surface of the TiB₂ powder to form titanium nitride (TiN), boron nitride (BN), and amorphous silica (SiO₂). The elimination of TiO₂ suppressed the grain growth effectively, which led to an improvement in the densification of TiB₂. The formation of SiO₂ also was deemed beneficial for densification. The mechanical properties-especially, the flexural strength-were enhanced remarkably through these improvements in the sinterability and microstructure. On the other hand, when a large amount (greaterthan equal to5 wt%) of Si₃N₄ was added, the mechanical properties were not improved much, presumably because of the extensive formation of a glassy Si-Ti-O-N phase at the grain boundaries.     

Influence of calcination temperature on the piezoelectric properties of Ag2O doped 0.94(K0.5Na0.5)NbO3–0.06LiNbO3 ceramics

The effects of calcination temperature on the bulk density, piezoelectric, and ferroelectric properties were investigated for the Ag₂O doped 0.94(K_0.5Na_0.5)NbO₃–0.06LiNbO₃ ceramics. The calcination temperatures were varied from 750 to 950 °C by 50 °C differences. An tetragonal XRD pattern, consistent with single-phase 0.94(K_0.5Na_0.5)NbO₃–0.06LiNbO₃ was obtained after calcination at 850 °C for 2 h. And the experimental results showed that Ag₂O doped 0.94(K_0.5Na_0.5)NbO₃–0.06LiNbO₃ ceramics calcined at 850 °C had a remnant polarization P_r=24.5 μC/cm², bulk density=4.32 g/cm³, piezoelectric constant d₃₃=282 pC/N and electromechanical coefficient k_p=37.8%.     

Characterization of MoO3–V2O5/Al2O3 catalysts for selective catalytic reduction of NO by NH3

MoO₃–V₂O₅/Al₂O₃ catalysts were characterized by B.E.T., XRD, LRS, XPS and TPR and the effect of MoO₃ addition to alumina supported vanadia catalysts on the catalytic activity for the selective catalytic reduction of NO by ammonia was investigated. Upon the addition of MoO₃, catalytic activity was enhanced and the particle size of V₂O₅ which is shown by the results of B.E.T., XRD and Raman spectroscopy decreased. This was one reason for increased catalytic activity. The results obtained by XPS and TPR showed that MoO₃ addition to alumina supported vanadia catalysts increased the reducibility of vanadia and this was the another reason for synergy effect between MoO₃ and V₂O₅ in MoO₃–V₂O₅/Al₂O₃ catalysts.     

Methanation of carbon dioxide over mesoporous Ni–Fe–Al2O3 catalysts prepared by a coprecipitation method: Effect of precipitation agent

Mesoporous nickel (30 wt%)–iron (5 wt%)–alumina (denoted as NiFeAl–X) catalysts were prepared by a coprecipitation method with a variation of precipitation agent (X = (NH₄)₂CO₃, Na₂CO₃, NH₄OH, and NaOH), and they were applied to the methane production from CO₂ and H₂. Metal particle size of reduced NiFeAl–X catalysts decreased in the order of NiFeAl–NaOH > NiFeAl–NH₄OH > NiFeAl–Na₂CO₃ > NiFeAl–(NH₄)₂CO₃. In the methanation of CO₂, yield for CH₄ increased in the order of NiFeAl–NaOH < NiFeAl–NH₄OH < NiFeAl–Na₂CO₃ < NiFeAl–(NH₄)₂CO₃. This indicates that the catalytic performance in the methanation of CO₂ was strongly influenced by the identity of precipitation agent.     

Investigation of alkaline hydrolysis of phthalimide‐based azo dye and its application to after‐treatment optimisation for high‐fastness dyeing of polyesters

4‐Amino‐N‐methylphthalimide was prepared from phthalimide for use as a diazo component and was coupled with N,N‐Diethylaniline to produce a phthalimide‐derived monoazo disperse dye. The pseudo first‐order kinetics were confirmed by analyzing the dye hydrolysis under alkaline conditions using high performance liquid chromatography, and the optimal dyeing pH and alkali‐clearing conditions were proposed. The synthesised phthalimidyl disperse dyes exhibited excellent colour fastness with a mild alkaline after‐treatment instead of reduction clearing which results in a high biological oxygen demand and pH in conventional disperse dyeing wastewater.     

高精度封装工艺的基板输送技术

<正>踏入21世纪以来,商业半导体封装市场经历了重大发展;随着全球芯片生产厂商与业外的专家密切合作,使得新产品推出市场的时间和设计成本都得以降至最底。居全球市场领导地位的封装技术和服务供应商Amkor公司在2006年第一季便刷新销售记录,较去年同期增长了55%,证明了这个市场正稳步发展。而且服务于该市场的公司数量也在增加,加上封装性能现正影响着许多先进的设计方案。     

Kinetics analysis of the curing reaction of fast cure epoxy prepregs

In this article, the curing kinetics of two fast cure flip-chip epoxy encapsulants under both isothermal and nonisothermal conditions are investigated by differential scanning calorimetry. The method allows determination of the most suitable kinetic model and corresponding parameters. The kinetic analysis suggests that the two-parameter autocatalytic model is more appropriate to describe the kinetics of the curing reaction. There are certain differences between the kinetic data from isothermal and that from nonisothermal measurements. The apparent activation energy Ea and pre-exponential factor A of E-AB1 determined from nonisothermal experiments were higher than the isothermal values, whereas the Ea and A of E-RV2 determined from both methods are relatively close. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1501–1508, 1999     

Characterization and properties of polypropylene‐block‐poly(ethylene‐co‐propylene) synthesized by short‐period polymerization

The morphology and mechanical properties of novel block copolymers consisting of isotactic polypropylene (PP) and ethylene–propylene rubber (EPR) synthesized by a short‐period polymerization method were examined using differential scanning calorimetry, atomic force microscopy, dynamic mechanical analysis, and a rheooptical technique. It was found that the novel block copolymers show a single glass transition and EPR segments are trapped into the amorphous region of PP. Furthermore, the rheooptical analysis demonstrates that a drawing process of the EPR‐rich block copolymer induces orientation of the PP lamellae in the EPR matrix. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 958–964, 1999     

Tumor-Specific miRNA Signatures in Combination with CA19-9 for Liquid Biopsy-Based Detection of PDAC

Pancreatic ductal adenocarcinoma (PDAC) is considered one of the most aggressive malignancies and has high mortality and poor survival rates. Therefore, there is an urgent need to discover non-invasive biomarkers for early detection before PDAC reaches the incurable stage. We hypothesized that liquid biopsy of PDAC-derived extracellular vesicles (PDEs) containing abundant microRNAs (miRNAs) could be used for early diagnosis of PDAC because they can be selectively enriched and because they are biologically stable. We isolated PDEs by immunocapture using magnetic beads, and we identified 13 miRNA candidates in 20 pancreatic cancer patients and 20 normal controls. We found that expression of five miRNAs, including miR-10b, miR-16, miR-155, miR-429, and miR-1290, was markedly higher in PDEs. Furthermore, the miRNA signatures along with serum carbohydrate antigen 19-9 (CA19-9) were optimized by logistic regression, and the miRNA signature and CA19-9 combination markers (CMs) were effective at differentiating PDAC patients from normal controls. As a result, the CMs represented a high sensitivity (AUC, 0.964; sensitivity, 100%; specificity, 80%) and a high specificity (AUC, 0.962; sensitivity, 85.71%; specificity, 100%). These findings suggest that five miRNAs expressed in PDEs and CA19-9 are valuable biomarkers for screening and diagnosis of pancreatic cancer by liquid biopsy.