氧化锆陶瓷磨球的滚制成型法制备技术与性能研究

研究了滚制成型法制备氧化锆陶瓷球坯工艺及烧结温度对陶瓷磨球体积密度、压碎强度和自磨损性能的影响.结果表明,凝胶固相合成法生产的亚微米级3mol% Y_2O_3-ZrO_2陶瓷粉体适用于滚制成型法制备体积密度高、圆度好、大小均匀的球坯.在1500 ℃保温2 h的烧结条件下得到的微晶氧化锆陶瓷磨球在快速研磨机中的自磨损率最低,其微观结构均匀,晶粒尺寸约0.5 μm,体积密度为5.97 g/cm~3,φ2.75 mm和φ6.36 mm陶瓷磨球的平均压碎强度分别达到326和1377 kg.     

Characterization of paramagnetic KHo(WO4)2 nanocrystals: Synthesized by polymeric mixed-metal precursor sol-gel method

Nanocrystalline KHo(WO₄)₂ (KHW) particles were successfully synthesized via conventional Pechini sol-gel method. Prepared precursor gel was calcined at 250, 550, 600, 650 and 700 °C, and the resulting samples were analyzed with TG-DTA, powder X-ray diffraction, FT-IR, Raman, FESEM, TEM, UV-Vis-NIR (diffuse reflectance spectrum (DRS)), fluorescence and vibrating sample magnetometer (VSM). Thermal degradation of derived gel was observed up to 400 °C and phase formation starts from 550 °C. The product phase formation at higher annealing temperature was investigated by means of powder XRD. Organic liberation in the samples with respect to temperature was analyzed using FT-IR spectrum. Raman spectrum reveals the formation of tungsten ribbons as well as the quality of the samples while increasing the calcination temperature. The nano size of the synthesized particles was confirmed with FESEM and TEM micrographs. Reflectance and emission studies reveal the corresponding absorption and emission properties of trivalent state holmium ion. Paramagnetic behavior of the derived KHW was confirmed with VSM results.     

Study on the synthesis of NiZnCu ferrite nanoparticles by PVA sol–gel method and their magnetic properties

Ni_0.65Zn_0.35Cu_0.1Fe_1.9O₄ nanoparticles fabricated by a polyvinyl alcohol (PVA) sol–gel process have been investigated by infrared spectra (IR), X-ray diffraction (XRD), transmission electron microscope (TEM) and Mössbauer spectroscopy measurements. The particles annealed at and above 250 °C are single phase NiZnCu ferrite with spinel structure. Particles annealed at and above 350 °C behave ferrimagnetically, while sample annealed at 250 °C is simultaneously paramagnetic and ferrimagnetic. In addition, the transition from the paramagnetic to the ferrimagnetic state can be observed in sample annealed at 250 °C as the measuring temperature decreases from 260 °C to liquid nitrogen temperature. The magnetic properties of NiZnCu ferrite nanoparticles are clearly size-dependent. The saturation magnetization increases with the annealing temperature. The coercivity of NiZnCu ferrite nanoparticles reaches a maximum when the annealing temperature is 550 °C.     

触变剂加入方式对银合金焊膏流变学性能的影响

采用不同的加入方式，使触变剂以分散态、溶胀凝胶态或溶解态存在于有机载体中，研究了由其制备所得不同银合金焊膏的流变学性能。结果表明，触变剂以分散态和溶胀凝胶态存在的焊膏，其触变性和结构恢复特性较好，且该状态下的触变剂与焊膏中的其他组分形成较强的内部网络结构，对提高焊膏的点胶性能和存储性能有利。     

Magnesium Octa[(4'-Benzo-15-Crown-5)-Oxy]Phthalocyaninate in Low-Molecular Hydrogels: Spectral Properties and Release under Stimulation

This work is dedicated to low-molecular hydrogels based on biodegradable sodium deoxycholate (SDC) and lysine hydrochloride (lys × HCl) with magnesium octa-[(4'-benzo-15-crown-5)-oxy]phthalocyaninate (Mgcr₈Pc) as the active component, namely, their synthesis, spectral properties of gel-solubilized Mgcr₈Pc, its release from the gel etc. Addition of Mgcr₈Pc occurs both via the mixing of the components and via its diffusion from the aqueous solution into the phase of the formed SDC/lys × HCl gel. Mgcr₈Pc-containing hydrogels are thermoreversible. The state of Mgcr₈Pc in the SDC/lys × HCl/NaCl gel at the room temperature and in the melt is studied using spectral methods. Gel melting releases Mgcr₈Pc in the form of a micelle-bound monomer. The presence of the Mgcr₈Pc monomer phase in the phthalocyanine-carrying supramolecular hydrogel causes fluorescent activity of the latter.     

Preparation of CeO_2 Nanoparticles and Its Application to Ion-selective Electrodes Based on Acetyl Cellulose

Recently, an increasing interest has beenfound in synthesizing nanoscale particles andclusters[l]' The physical and cheAncal proper-ties vary drastically with size and the use of ul-tTafine particles represents a potentially feftilefield fOr materials research[2]. In particular,the preparation and characterization of ceriumoxide nanopowders have attracted much atten-tion over the past few years due to their greatpotential in many fields. It is commonly used inglass, ceramics, fluorescent powd…     

溶胶-凝胶法制备氧化锆粉体

以正丙醇锆为锆源,采用溶胶-凝胶法制备了ZrO2粉体。研究了硝酸含量对凝胶时间及热处理温度对ZrO2晶型的影响规律。通过控制硝酸含量可以有效改变凝胶时间;通过锆醇盐水解缩聚制备的ZrO2干凝胶,在低温下热处理首先形成ZrO2四方相,在较高温度热处理后才转变为单斜相;锆醇盐水解缩聚制备的氧化锆粉体在1200℃以后烧结过程明显加快。     

Influence of cooling field on the magnetic properties of Ni/NiO nanostructure

Nanoparticles of Ni/NiO structure were prepared by sol–gel route followed by the annealing in presence of controlled oxygen and argon gas mixture. When the sample was cooled down to 5 K from room temperature in a static magnetic field, a systematic shift of the magnetic hysteresis loop was observed. The shift was absent when the sample was cooled in zero field. For cooling the sample in field-cooled mode a small horizontal shift was noticed along with a moderate vertical shift of the hysteresis loop at the saturation of magnetization, which indicates the typical manifestation of exchange bias effect. The horizontal shift increases with decreasing particle size retaining almost unchanged relative vertical shift, where vertical shift is found to be uncorrelated with the horizontal shift. The exchange bias like effect in the Ni/NiO nanostructure is suggested at the Ni/NiO interface, where Ni is ferromagnetic and NiO is in the disordered magnetic state.     

Synthesis and Modification of Ordered Silica Materials

Protection of Metals and Physical Chemistry of Surfaces - Ordered mesoporous silicates modified with d-metals were synthesized in situ under low temperature with a sol–gel method at a...     

聚丙烯酰胺凝胶法制备纳米BeO粉体前驱体的热分解过程及结晶机理

采用聚丙烯酰胺凝胶法制备纳米BeO粉体,通过TG-DSC、XRD和SEM等测试手段研究凝胶前驱体的热分解过程和所得粉体的性能,并借助负离子配位多面体生长基元理论分析热分解过程中纳米BeO的结晶机理。结果表明:随着温度的升高,凝胶前驱体内的有机凝胶逐渐分解,同时凝胶前驱体内的硫酸铍盐脱除结晶水;当温度达到600℃左右时,有机凝胶完全分解,得到纳米级的无水硫酸铍;继续升高温度,纳米级的无水硫酸铍分解得到纳米BeO;热分解过程中,纳米硫酸铍通过生长基元Be(SO4)6断键形成纳米BeO,成核过程为受迫状态下的非均匀成核。     

PVA/PF复合凝胶磨具精密磨削碳化硅陶瓷工艺实验研究

目的 针对传统粉末热压成形细粒度金刚石磨具存在颗粒团聚、磨削碳化硅陶瓷容易在表面产生较深划痕的问题,提出一种基于冷冻-解冻凝胶成形的细粒度金刚石磨具,用于精密磨削碳化硅陶瓷,并研究其加工工艺.方法 制备聚乙烯醇-酚醛树脂复合凝胶胶水,将金刚石和填料在凝胶胶水中剪切分散,得到的浆料浇筑在模具中,在–20℃低温条件下反复冷...     

双酚A型苯并恶嗪树脂软化-固化性质的研究

通过测试凝胶时间和软化点,优选了一种双酚A型苯并恶嗪树脂的合成工艺：95℃保温3h。测试了该树脂90℃的熔融粘度-时间曲线,熔融粘度稳定在0．5Pa·S。分别研究了该树脂加促进剂和不加促进剂两种情况下温度与凝胶时间的关系。测试了树脂的DSC曲线。试验结果说明：该树脂在200℃存在一个明显放热峰。200℃的树脂固化度大于90％,当温度高于200℃时,树脂凝胶时间的变化开始变缓。     

溶胶-凝胶法与金属表面改性

综述了玻璃或陶瓷低温合成新技术溶胶-凝胶涂层.其中特别介绍溶胶-凝胶涂层技术应用于金属材料上,以提高其耐蚀性、抗氧化性、耐磨性及拒水性能.     

304L不锈钢高温变形组织的演化

采用Gleeble-1500D热/力学模拟试验机对304 L不锈钢铸态及锻态试样进行了热压缩试验研究,工艺参数为：变形温度950℃～1 150℃、变形量0.7,变形速率0.1s-1。结果表明：铸态的峰值应力低于锻态的峰值应力,铸态组织的动态再结晶明显迟于锻态组织;铸态及锻态304L不锈钢流变应力随着温度的升高而降低;随着变形温度的升高,动态再结晶百分数增加,再结晶组织增多并趋于完全。     

钢的低温多元共渗——节能化学热处理工艺

在600℃以下钢的铁素体状态施行氮碳、硫氮碳、硫氮碳氧共渗可以显著提高钢件表面硬度,提高耐磨性、疲劳强度和抗腐蚀减摩能力,从而延长其服役寿命。由于温度低、时间短,与高温奥氏体状态下进行的渗碳、碳氮共渗相比较,具有明显的节约能源、显著减少零件畸变的效果。因此,对于中轻负荷条件下工作的机器零件,低温化学热处理工艺具有推广价值。在此,值得提出的是,在盐浴中施行的低温化学热处理工艺多少还存在含氰废水和盐渣的无害化处理后排放的问题,生产中应特别留意。     

Influence of Lanthanum Coatings on a Model 330 Alloy (Fe–35Ni–18Cr–2Si) Oxidation at High Temperatures

The influence of a lanthanum sol–gel coating on chromia scale adherence has been studied on the 330 alloy (Fe–35Ni–18Cr–2Si) oxidized at 900 °C, in air. Argon annealing of lanthanum sol–gel coatings were performed at various temperatures. Kinetic results show that lanthanum sol–gel coatings lead to a lower oxidation rate compared to blank specimens. On blank 330 specimens scale spallation is observed after cooling to room temperature. On the non-annealed sol–gel coated specimen and the argon annealed specimens at 600, 800 or 1,000 °C, the oxide scale formed at 900 °C is adherent after 48 h isothermal oxidation. The adherent oxide scales are convoluted, resulting from a mixed anionic + cationic diffusion process in the chromia scale. Thermal cycling tests on lanthanum the sol–gel coated specimen show that the oxide scale remains adherent after 250 cycles. It is concluded that argon annealing of the lanthanum sol gel coating is not necessary to improve the scale adherence.     

包晶合金定向凝固中的共生生长

对包晶合金定向生长特性进行分析，并与共晶系经典共生生长模型（Jackson-Hunt模型）所描述的共生生长特性进行对比，提出包晶稳态过热共生生长模型，同时以Fe-Ni合金系为对象，对其亚包晶和过包晶成分在不同温度梯度G和生长速度1，下进行定向凝固实验及组织分析。研究结果表明：在定向凝固条件下，包晶系两相严格的共生生长只有在进入稳态且温度高于包晶相变温度时才可能进行；包晶合金两相的共生生长尤其在G／v值高的平／胞界面形态，确实发生在Tp温度以上，与提出的模型所预测的一致。     

Spannungsrißkorrosion nichtrostender austenitischer Chrom-Nickel-Stähle bei Raumtemperatur

Stress corrosion cracking of austenitic chromium-nickel stainless steels at ambient temperature For the chloride-induced SCC with transgranular crack path in austenitic 18Cr10Ni stainless steel, a critical temperature between 45 and 50°C exists. This critical temperature, however, is valid only for the passive state of the steel in nearly neutral, chloride-containing aqueous environments. In the active state, SCC with transgranular crack mode can occur at temperatures down to ambient temperature. The active state is caused by highly acidic, high-chloride containing aqueous corrosive media. Adherent aqueous films with these properties can grow on the surface of structural components inside swimming-pools when the water is disinfected by addition of chlorine. Under these conditions, failure of austenitic CrNi and CrNiMo stainless steels by SCC with transgranular crack path at ambient temperature is possible and actually occurred. SCC with preferentially intergranular crack path can also occur at ambient temperature when austenitic stainless steels with a sensitized microstructure are used. Under these conditions, the corrosion attack is caused by non-specific aggressive environments, e.g., adherent aqueous films not containing chloride ions. The crack mode, intergranular or mixed, depends on the stress level.     

镀锌工艺对锌花状态的影响

针对实际生产中容易出现锌花轮廓模糊、均匀性差、大小不受控等问题,对镀锌大锌花产品的锌花控制进行了研究。分析了锌液中的Sb元素含量、带钢入锌锅温度及锌液温度、锌液冷却速率对锌花状态的影响,对锌花状态进行了评分定级。针对薄带钢(0.5 mm≤h≤0.8 mm),中厚带钢(0.9 mm≤h≤1.2 mm)、厚带钢(1.4 mm≤h≤2.0 mm)的锌花控制进行了工业试验研究。结果表明,随着Sb质量分数由0.07%增至0.09%,锌花状态逐步改善,Sb质量分数为0.09%时锌花状态最佳。随着Sb含量继续增加,锌花状态反而有一定下降。对于薄带钢,将带钢入锌锅温度设定为520 ℃,锌液温度设定为470 ℃,可得到较好锌花;对于中厚带钢,将带钢入锌锅温度设定为460 ℃,锌液温度设定为460 ℃,可得到较好锌花;对于厚带钢,将带钢入锌锅温度设定为435 ℃,将锌液温度设定为450 ℃,可得到较好锌花。     

SUPERPLASTICITY AND SOLID STATE BONDING OF TITANIUM ALLOYS

1.IntroductionItisknownthatsuperplasticity(SP)exertsafavourableeffectonthesolidstateweldabilityoftitaniumalloys[1--31.IthasbeenalsoestablishedthattheacceleratedsolidstatejointformationisdeterminedbytheinfluenceofthebasicmechanismofSPdeformationgrainboundarysliding(GBS).However,thecitedinvestigationswereconductedatrelativelyhightemperatures(~0.7Tin)whenthediffusivityoftitaniumalloysisconsiderable.Atthesametimeitisknown,thatthetemperaturerangeofsuperplasticitysubstantiallydependsonthemeangra…