聚L-乳酸(PLLA)的热稳定性

聚L-乳酸（PLIA）是具有良好生物相容性和生物降解性的半结晶聚合物，其热稳定性较差，在加工中的热处理会造成材料严重降解，使其相对分子质量显著下降，机械性能明显降低。该文作者通过试验、分析，研究了加热时间和加热温度对提纯与未提纯PLLA降解的影响，并结合降解机理对其原因进行探讨。结果表明，当温度升高到180℃以上时，在aomin内PLLA的相对分子质量即减小一半；提纯后的PLLA模压最佳加热温度为185℃。     

Features of obtaining finely dispersed powders of molybdenum and tungsten diselenides by grinding in centrifugal planetary mills

The results of investigations into the dry grinding of tungsten and molybdenum diselenide powders in a planetary centrifugal mill are presented. It is shown that their efficient grinding occurs only for first 3 min of treatment. As the duration of the process increases, the equilibrium between dispersing the particles and their aggregation, which manifests itself in the absence of a rise of the specific surface of the powder, is attained. The best results of dispersion are attained at the mill filling coefficient of 0.7 and the mass ratio of the balls and material of 3 : 1.     

Sintering of dispersed tantalum powders

Translated from Poroshkovaya Metallurgiya, No. 12 (360), pp. 11–16, December, 1992.     

Obtaining of a finely dispersed powder of gadolinium hydroxide

Finely dispersed powders of gadolinium hydroxide are obtained by chemical deposition (dispersing). The influence of various factors on the powder characteristics such as dispersity, morphology, and chemical composition is investigated. The dependence that the mentioned characteristics have on the character of the anion of the gadolinium salt, the concentration and acidity of its solution, and the concentration of the precipitant and pH of precipitation, is established. The optimal results are observed with the use of diluted chloride solutions of gadolinium and a 5–10 wt % precipitant in the form of the NH₃ solution.     

Corrosion resistance of highly dispersed ferromagnetic materials

A study was made of the corrosion resistance of highly dispersed iron and composites of iron with silver, platinum, gold, copper, zinc, and the cobalt-nickel system. The composites were obtained by a thermochemical method. Corrosion resistance was studied in air and in reactions with hydrochloric acid (pH I-3) and sodium hydroxide (pH 10). It was determined that the highly dispersed ferromagnetic materials are corrosion-resistant and incombustible, and they do not require special storage conditions. The can be used in medicine, biology, and engineering. Translated from Poroshkovaya Metallurgiya, Nos. 3-4(412), pp. 1–3, March–April, 2000.     

某贫硫化物复杂含金矿石选冶技术研究与应用

吉林省临江市金银矿对现场生产工艺流程进行了改造。采用浮选-浮尾氰化炭浸工艺流程取代了原全泥氰化炭浸生产工艺流程,金的回收率由改造前的50．96％提高到82．54％,同时在不增加设备和投资的前提下,选厂处理能力由原来的100t／d左右提高到180t／d,生产成本由原来的222．76元／t,降低到177．31元／t,每年可为企业增加效益1157．40万元。     

Development of environmentally oriented processes for obtaining articles from aluminum powders by powder metallurgy: Report 2. Development of environmentally safe technology for compaction of finely dispersed aluminum powders

It is shown that the introduction of liquid film-forming lubricant into aluminum and the use of “warm” compaction make it possible to increase the environmental safety of powder metallurgy processes of aluminum via decreasing the dusting ability of finely dispersed powders, increasing the transportable properties of pressings, and excluding the operation of removing the grease lubricant from the pressing volume at the sintering stage.     

Thermal stability of amorphous alloys Mg65Cu25Y10, Mg63Ni30Y7 after electrochemical hydrogen absorption

Thin ribbons of the metallic glass Mg₆₅Cu₂₅Y₁₀ and Mg₆₃Ni₃₀Y₇ obtained by melt spinning were saturated with atomic hydrogen during electrochemical decomposition of water. The amount of absorbed hydrogen was as high as 4 mass% for the alloy Mg₆₅Cu₂₅Y₁₀H_x and 1.5 mass% for the alloy Mg₆₃Ni₃₀Y₇H_x. As the hydrogen content increases up to 3.6 mass%, the amorphous structure of the copper-containing alloy is transformed to a nanocrystalline structure with formation of magnesium and yttrium hydrides and also the intermetallic Cu₂Mg at room temperature. The appearance of crystalline compounds during saturation with hydrogen leads to a decrease in the thermal stability of the amorphous alloy and a shift of the differential scanning calorimetry curves toward lower temperatures. In the presence of nickel, the thermal stability of the amorphous alloy Mg₆₃Ni₃₀Y₇H_x increases with hydrogen saturation. After heating up to the crystallization temperature, the compounds Mg₂NiH_0.3 and YH₂ appear. __________ Translated from Poroshkovaya Metallurgiya, Nos. 3–4(448), pp. 105–111, March–April, 2006.     

Cu75Ni9Sn2P14非晶合金热稳定性的研究

研究了Ｃｕ７５Ｎｉ９Ｓｎ２Ｐ１４合金非晶态结构的形成及其热稳定性。在连续升温的条件下,观察各温度点的晶化情况,发现在１５０℃就有晶相出现,到４００Ｃ时结晶产物均为富铜相。     

High-chromium cast iron sintered of sprayed powders

The paper examines basic technological characteristics of high-chromium cast iron powders resulting from gas or water melt spraying. Sintering of billets made of these powders is investigated. It is shown that Fe-Cr-Mo-Cr powder alloys can combine high hardness and thermal stability. Therefore, they are candidate materials for operation in intensive wear and at high temperatures. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 111–115, 2007.     

Laws governing vibrating feeding of finely dispersed powder into a laser sintering zone

A vibrating powder feeder that makes it possible to deposit powder in a laser sintering zone in a continuous flow or in discrete portions has been developed. The dependence of the rate of flow of the powder on the rate of the vibrations, the parameters of the construction of the feeder, and the properties of the powder is investigated. The possibility of regulating the process of deposition of the powder is considered.     

Model systems for dissolution of finely divided (multisized) drug powders

Several reports have dealt with model systems for the dissolution of log-normally distributed powders. A numerical solution is presented for the previously published Higuchi-Hiestand equations for a log-normal particle-size distribution. This solution was realized via an application of the System 360 Continuous System Modeling Program (CSMP). The resulting computer-aided calculations were utilized in the comparisons between the Higuchi-Hiestand model and other existing models. These comparisons provided a basis for the development of an adaptation of the Nielsen moving sphere model for log-normally distributed powders. The adaptation of the Nielsen equation for multisized particle systems is suggested as being potentially useful for treating experimental data where hydrodynamic effects must be considered.