CVD diamond coating for erosion protection at elevated temperatures

Small solid particles entrained in a gas-fluid turbomachinery flow can cause degradation of the component surfaces containing the flow by erosion and corrosion processes. As diamond is the hardest known material, much work has been done to use polycrystalline diamond (PCD) as a protective coating on parts operating in a hostile and abrasive environment. Little attention is given in the literature to the high-temperature erosion behavior of chemical vapor deposition (CVD) diamond on different substrates. The objectives of this research were to develop CVD diamond erosion barriers for surface protection of cemented tungsten carbide at high temperatures and to study the erosion behavior of the coatings. Microwave plasma chemical vapor deposition (MPCVD) was used to apply diamond films on WC-6%Co. The erosion behavior of the coated specimens was investigated experimentally by exposing them to abrasive particle-laden flow in a high-temperature wind tunnel. The obtained results show the effects of impingement angle, temperature, and particle dose on the erosion rate. The data demonstrate that uncoated substrates suffer 6–7 times higher wear compared to diamond-coated samples at elevated temperatures up to 538 °C when exposed to alumina particle flow. This study indicates that polycrystalline diamond is emerging as a promising erosion protective coating for high-temperature applications. Paper presented at Materials Solutions Conference & Exposition 2000, St. Louis, MO.     

硬质合金生产过程中回收料的使用

阐述了硬质合金生产过程中的一类回收料的特点 ,论述了用好这类物料 ,对硬质合金行业和企业都深具现实意义。作者针对本公司的一类回收料 ,通过低温煅烧与调整烧结工艺 ,最终获得了致密化与 C平衡良好的合金。     

CdTe单晶生长过程的分凝特性及其生长条件的选择

在Ｃｄ－Ｔｅ相图的基础出ＣｄＴｅ－Ｃｄ相图并定义其主要参数，讨论了高Ｃｄ的ＣｄＴｅ液体在结晶过程中的分凝特性及其生长条件对昌体中Ｔｅ固溶量的影响，进而维持平面生长界面所需的最小温度梯度。     

Multi-Functional and Stretchable Thermoelectric Bi2Te3 Fabric for Strain,Pressure, and Temperature-Sensing

Fiber-based electronics are essential components for human-friendly wearable devices due to their flexibility, stretchability, and wearing comfort. Many thermoelectric (TE) fabrics are investigated with diverse materials and manufacturing methods to meet these potential demands. Despite such advancements, applying inorganic TE materials to stretchable platforms remains challenging, constraining their broad adoption in wearable electronics. Herein, a multi-functional and stretchable bismuth telluride (Bi₂Te₃) TE fabric is fabricated by in situ reduction to optimize the formation of Bi₂Te₃ nanoparticles (NPs) inside and outside of cotton fabric. Due to the high durability of Bi₂Te₃ NP networks, the Bi₂Te₃ TE fabric exhibits excellent electrical reliability under 10,000 cycles of both stretching and compression. Interestingly, intrinsic negative piezoresistance of Bi₂Te₃ NPs under lateral strain is found, which is caused by the band gap change. Furthermore, the TE unit achieves a power factor of 25.77 µWm⁻¹K⁻² with electrical conductivity of 36.7 Scm⁻¹ and a Seebeck coefficient of −83.79 µVK⁻¹ at room temperature. The Bi₂Te₃ TE fabric is applied to a system that can detect both normal pressure and temperature difference. Balance weight and a finger put on top of the 3 × 3 Bi₂Te₃ fabric assembly are differentiated through the sensing system in real time.     

High-Efficiency Thermoelectric Module Based on High-Performance Bi0.42Sb1.58Te3 Materials

Bismuth-telluride-based alloy is the sole thermoelectric candidate for commercial thermoelectric application in low-grade waste heat harvest near room temperature, but the sharp drop of thermoelectric properties at higher temperature and weak mechanical strength in zone-melted material are the main obstacles to its wide development for power generation. Herein, an effective approach is reported to improve the thermoelectric performance of p-type Bi_0.42Sb_1.58Te₃ hot-pressed sample by incorporating Ag₅SbSe₄. A peak ZT of 1.40 at 375 K and a high average ZT of 1.25 between 300 and 500 K are achieved. Such outstanding thermoelectric performance originates from the synergistic effects of improved density-of-states effective mass, reduced bipolar thermal conductivity by the boosted carrier concentration, and suppressed lattice thermal conductivity by the induced phonon scattering centers including substitute point defects, dislocations, stress–strain clusters, and grain boundaries. Comprised of the p-type Bi_0.42Sb_1.58Te₃ + 0.10 wt% Ag₅SbSe₄ and zone-melted n-type Bi₂Te_2.7Se_0.3, the thermoelectric module exhibits a high conversion efficiency of 6.5% at a temperature gradient of 200 K, indicating promising applications for low-grade heat harvest near room temperature.     

碲镉汞量子点的离子交换能带调控及其近红外自吸收性质

通过软化学方法制备单分散的CdTe量子点,调节Hg²⁺的浓度离子交换实现从可见到近红外光谱准连续可调的碲镉汞(Hg_xCd_1-xTe)量子点制备。深入分析了近红外Hg_0.33Cd_0.67Te量子点的变温光致发光及其自吸收特性,研究结果表明：碲镉汞量子点的荧光强度随着温度的升高（0～100℃）呈线性降低趋势,谱线展宽,峰位发生红移（12nm）;量子点的吸收和发射光谱部分重叠导致自吸收效应随着量子点的浓度增加而增强,导致量子点荧光强度的降低。     

胶结充填体力学特性的加载速率效应试验

为探究胶结充填体在不同加载速率状态下的力学参数变化规律及其破坏模式,采用数显式压力机分别对2.0、4.0、6.0、8.0 mm/min这4种加载速率下的胶结充填体开展单轴压缩试验.试验结果表明:在2.0~8.0 mm/min加载速率范围内,加载速率对于胶结充填体的抗压强度值和割线模量均具有明显的强化效应,且峰值抗压强度值和割线模量随加载速率增大而增大.峰值抗压强度与加载速率呈多项式函数规律,而割线模量与加载速率则呈指数函数分布规律.且随着加载速率增大,胶结充填体试件破坏形式表现为拉剪混合破坏向单一剪切破坏形式逐渐转化.研究结果揭示了胶结充填体的力学特性加载速率效应,为研究充填体破坏机制提供一定的参考依据.     

基于强度试验的胶凝堆石材料破坏准则

基于胶凝堆石料的抗压、抗折和大三轴强度试验,对胶凝堆石料的基本力学特性进行了系统研究,得出试件破坏情况下的应力强度,通过拟合破坏强度和围压的关系式,推导出胶凝掺量为60 kg/m3的胶凝堆石料的破坏准则;进一步拟合破坏强度、围压和胶凝掺量的关系式,推导出胶凝掺量为变量的胶凝堆石料的破坏准则。验证结果表明,所推导的胶凝堆石料破坏准则合理可靠,具有良好的通用性。     

守口堡水库胶凝砂砾石坝 断面尺寸研究

胶凝砂砾石坝作为一种新坝型首次在我国永久工程守口堡水库中采用。本文对大坝断面形式、上下游坡比、稳定应力标准及胶凝砂砾石材料设计强度要求进行了初步研究,并提出了合理的设计断面,旨在为同类工程设计提供参考。     

The Cd–Te phase diagram

The properties of the liquid phase in the Cd–Te system are fit using thermodynamic properties of CdTe(c) recently optimized by the author. These include a high temperature heat capacity significantly lower than commonly used such that the enthalpy of formation of CdTe(c) at its melting point is about 10 kJ/mol less negative than previously thought. An associated solution model with Cd, CdTe, and Te species is used. Seven adjustable parameters are sufficient to quantitatively fit the liquidus and partial pressures of Te₂ and Cd. Additional partial pressures for Te rich CdTe(c) near its melting point are extracted from an earlier study and tabulated. The parameters giving good fits to the liquidus and partial pressures give only a fair fit to the enthalpy of mixing of the liquid phase. Moreover, the parameters giving a good fit to the enthalpy give poor fits to the other data. The sensitivity of the different data types to changes in the interaction parameters of the associated solution model is established. A variation of ±160 J/g atom in the enthalpy parameter determining the CdTe–Te interaction is sufficient to double the fractional standard deviation between experimental and calculated partial pressures of Te₂ over Te rich CdTe(c) from 0.034 to 0.07. Because the degree of association is near its maximum, the measures of fit to the data are insensitive to changes in the parameters determining the Cd–Te interaction.