Evolution and stability of 2-mercaptobenzimidazole inhibitor film upon Al alloy 6061

Journal of Applied Electrochemistry - Organic corrosion inhibitors have become competent alternatives to hazardous chrome conversion coatings due to their rapid adsorption over metal surfaces in...     

Corrosion resistance of Mg(OH)_2/Mg-Al-layered double hydroxide coatings on magnesium alloy AZ31:influence of hydrolysis degree of silane

Mg(OH)_2/Mg-Al-layered double hydroxide(LDH)coatings were modified with methyltrimethoxysilane(MTMS)on magnesium alloys.Effect of hydrolysis degree of silane solution on coating formation was investigated.Chemical compositions and surface morphologies of the coatings were examined using X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and field-emission scanning electronic microscopy(FESEM).Results indicated that the composite coatings consisted of polymethyltrimethoxysilane(PMTMS),LDH and Mg(OH)_2.Electrochemical and hydrogen evolution measurements revealed that the composite coatings possessed good corrosion resistance,especially the ones prepared in a high hydrolysis degree of silane.The optimum corrosion resistance of the composite coating was LDH/PMTMS-3 coating,which had the lowest value of corrosion current density(5.537 × 10~(-9) A·cm~(-2))and a dense surface.Plausible mechanism for coating formation and corrosion process of MTMS-modified Mg(OH)_2/Mg-Al-LDH coatings were discussed.     

Corrosion resistance of nanostructured magnesium hydroxide coating on magnesium alloy AZ31: influence of EDTA

A hexagonal nanosheet Mg(OH)_2 coating was prepared through a one-step hydrothermal method using LiOH solution as mineralizer and then modified by ethylenediaminetetraacetic acid(EDTA) to minimize the rapid corrosion of AZ31 Mg alloy.The performance of the coating was evaluated using electrochemical technique,hydrogen evolution measurements, nanoscratch test,Fourier-transform infrared spectroscopy(FTIR), X-ray diffraction(XRD) patterns and field-emission scanning electron microscopy(FESEM).The results suggested that the corrosion rate of bare AZ31 Mg alloys was significantly reduced by one and two orders of magnitude through the protection from Mg(OH)_2 coating and modification with EDTA(i.e., EDTA-Mg(OH)_2 coating), respectively.FESEM micrographs indicated that the modification in EDTA elicits to the formation of an EDTA-Mg(OH)_2 composite with a thickness as twice as that of as-prepared Mg(OH)_2 coating.Nanoscratch tests revealed strong adhesion between the composite or Mg(OH)_2 coating and the substrate.The study of formation and corrosion mechanisms of the coatings manifested that Mg(OH)_2 was first formed near the intermetallic compound AlMn particles and gradually covered the entire surface, wherein the AlMn particles played an important role in the coating growth process.And it also proved that EDTA accelerated the formation of Mg(OH)_2.     

A green-switch controller IC for cascade buck–boost converter with seamless transition over entire input and load range

To raise the utilization ratio of lithium-ion battery in portable devices, a novel green-switch controller IC is proposed to constitute a 4-switch cascade buck–boost prototype, which is capable of outputting non-inverting step down and step up voltages. According to the relations between the input and output voltages through duty ratio, a finite state machine automatically determines the work method of converter namely buck method, boost method or transition method by combining peak and valley current programmed mode so as to improve the line regulation over the entire input voltage range. A three-phase seamless transition method is introduced into the controller. Its additional advantage is to lower output ripples. Furthermore, a special burst mode is added to reduce the power consumption during light-load operation. An elaborately designed circuitry and rigorous stability analysis further improves the seamless performance. The controller IC is designed and fabricated in 1.5 μm BCD (Bipolar-CMOS-DMOS) technology with an area of 8.75 mm² and applied to a 2.7 V–4.2 V/3.3 V, maximum output power 1.65 W buck–boost converter. It features over 90% conversion efficiency during normal application and still remains over 80% under standby mode. The experimental results show that all functional and performance targets are successfully achieved as expected.     

Microstructures and Properties of Warm-Sprayed Carbonated Hydroxyapatite Coatings

Carbonated hydroxyapatite (CHA) coatings were deposited onto 316L stainless steel substrates using an in-house developed warm spraying system. Microstructures of the coatings were comprehensively investigated. Microhardness, tensile strength and wear resistance of the CHA coatings were examined. In addition, bioactivities of the coatings were studied after immersing in simulated body fluid (SBF). Results show that the as-sprayed coatings exhibited typical lamellar architectures consisting of partially melted and flattened splats, i.e., with molten shells and un-molten cores of original powders. The CHA coatings had nearly identical Ca/P ratios, crystalline structures and phase constitutions to those of the feedstock powders, indicating that undesired decompositions caused by overheating can be avoided by employing the warm spraying process. Microhardness and tensile strength of as-sprayed coatings were around 690 and 11.4-20.6 MPa, respectively. Moreover, the warm-sprayed CHA coating exhibited a high resistance against abrasion wear when sliding took place with polymers. After being immersed in Hank’s SBF for 28 and 60 days, new apatite was formed on the coating surface corroborating the good biocompatibility of the coating.     

Molecular composition of soluble fraction from depolymerized cornstalk powder in supercritical methanol and ethanol

Cornstalk was depolymerized in supercritical methanol and ethanol, respectively. The depolymerization products were analyzed with FTIR and GC/MS. The results show that the products can be classified into methyl esters and dimethyl diesters, ethyl esters and diethyl phthalate, hydroxybenzenes and dihydroxybenzenes, ketones, methoxybenzene to trimethyoxybenzenes, hydrocarbons, nitrogen-containing organic compounds and other compounds. Most of the products are oxygen-containing species. Palmitate and octadec-9-enoate are the two most abundant products both with supercritical methanol and with supercritical ethanol. The fact that the cornstalk depolymerization in different solvents afforded many different products suggests that the two solvents played different roles in the cornstalk depolymerization.     

基于正交试验的层压机架体结构分析及优化

在太阳能电池板的封装过程中,层压机的架体结构受到上下箱体的压力产生的变形,使电池板的破碎率增大,因此架体结构要具有足够的强度和刚度。论文利用有限元方法对层压机的架体进行了分析,并运用正交实验法,最终提出了相应的结构方案。与现有设备相比,架体结构更为简单,工作过程中架体受到的最大应力和变形都有所减少,并且节约了钢材。     

不同复水条件对香菇特征香味物质的影响

目的研究干香菇经不同复水条件处理后其特征香味物质含量的变化,实现干香菇的科学复水。方法新鲜香菇经热风干燥后进行复水处理,通过顶空固相微萃取-气相色谱-质谱联用(headspacesolid-phase microextraction-gaschromatography-massspectrometry,SPME-GC-MS)的方法对复水香菇中的挥发性含硫化合物和八碳化合物进行分析,以环己酮为内标物,采用内标法进行定量分析,分别考察不同复水时间、不同复水温度和不同复水pH值下香菇中特征香味物质的含量。结果经不同复水时间处理后,香菇中含硫化合物含量为38.30～79.84μg/g,八碳化合物含量为4.33～10.97μg/g;经不同复水温度处理后,香菇中含硫化合物含量为12.82～44.45μg/g,八碳化合物含量为2.50～9.84μg/g;不同pH值条件下复水处理后,香菇中含硫化合物含量为6.10～72.52μg/g,八碳化合物含量为0.86～7.61μg/g。结论结果表明,干香菇在温度为40℃、pH值为9时,复水处理40min,其挥发性含硫化合物的含量较高,复水香菇表现为浓郁的"香菇味";干香菇在温度为40℃、pH值为7时,复水处理20 min,其挥发性八碳化合物的含量较高,复水香菇表现为明显的"蘑菇味",应根据实际情况选择合适的复水条件。     

分光光度法测定乳粉中亚硝酸盐含量的不确定度评定

目的 研究分光光度法测定乳粉中亚硝酸盐的不确定度评定。方法 以乳粉为例, 参考JJF 1059.1-2012《测量不确定度评定与表示》, 对GB 5009.33-2016《食品安全国家标准 食品中亚硝酸盐与硝酸盐的测定》第二法分光光度法测定亚硝酸盐的不确定度进行评定。结果 乳粉中亚硝酸盐的含量为1.0 mg/kg 时, 测定结果的合成标准不确定度为0.042 mg/kg, 取k=2, 扩展不确定度为0.084 mg/kg, 其结果可表示为(1.0±0.1) mg/kg。结论 测量结果的不确定度主要是标准曲线拟合、标准工作液配制、试样检测重复性和测定用样液体积。前两者引入的不确定度分量贡献较大。