生物质颗粒燃料的成型能耗试验研究

以陕西地区苹果树修剪枝为原料,采用自制的生物质成型燃料多参数调控试验系统,分析单颗粒成型过程中的压力-位移曲线,考察基质含水率(5%~20%)、成型温度(70~150℃)和压力(80~120 MPa)对颗粒燃料成型能耗的影响。结果表明:随着压具位移的增加,挤压过程的压力变化呈3个阶段:松散段、过渡段和压紧段;推出过程的压力变化总体呈波动下滑的趋势,且初期压力波动范围较大。试验范围内,随着温度的升高,挤压能耗降低、推出能耗升高;随着压力的增大,二者均升高;基质含水率影响趋势相同,15%均达到最低值(29.47、4.79 J/g)。     

Preparation of cellulose triacetate aerogel via non-solvent impacted thermally induced phase separation for oil absorption

The oil spill has caused significant attention on a global scale due to its damage to the environment and the economy. The development of economically and ecologically friendly oil sorbent materials has important meaning for the oil spill concern. In this work, we explored the non-solvent impacted thermally induced phase separation (NITIPS) method to prepare the cellulose triacetate aerogel (CA) with low density (6.4–40.5 mg/cm³), high porosity (96.9–99.5%), large water contact angle (>129°) and high specific surface area (193–573 m²/g) as the oil sorbent material. The oil absorption capacity of CA with vegetable oil and vacuum pump oil reached 80.8 g/g and 38.9 g/g, respectively, consistent with Fick's law of diffusion. Moreover, the NITIPS method provided simpler process and controlled the shape of CA compared with the traditional thermally induced phase separation method. This study proved that the CA prepared by NITIPS methods played an important role as a potential oil absorption solids in the field of oil spill and organic chemical leakage.     

Indoor fine particulate matter and demographic,household, and wood stove characteristics among rural US homes heated with wood fuel

Household heating using wood stoves is common practice in many rural areas of the United States (US) and can lead to elevated concentrations of indoor fine particulate matter (PM_2.5). We collected 6-day measures of indoor PM_2.5 during the winter and evaluated household and stove-use characteristics in homes at three rural and diverse study sites. The median indoor PM_2.5 concentration across all homes was 19 µg/m³, with higher concentrations in Alaska (median = 30, minimum = 4, maximum = 200, n = 10) and Navajo Nation homes (median = 29, minimum = 3, maximum = 105, n = 23) compared with Montana homes (median = 16, minimum = 2, maximum = 139, n = 59). Households that had not cleaned the chimney within the past year had 65% higher geometric mean PM_2.5 compared to those with chimney cleaned within 6 months (95% confidence interval [CI]: −1, 170). Based on a novel wood stove grading method, homes with low-quality and medium-quality stoves had substantially higher PM_2.5 compared to homes with higher-quality stoves (186% higher [95% CI: 32, 519] and 161% higher; [95% CI:27, 434], respectively). Our findings highlight the need for, and complex nature of, regionally appropriate interventions to reduce indoor air pollution in rural wood-burning regions. Higher-quality stoves and behavioral practices such as regular chimney cleaning may help improve indoor air quality in such homes.     

Esterified PVA-lignin resin by maleic acid applicable for natural fiber reinforced composites

This article reports an esterified polyvinyl alcohol (PVA)-lignin resin that is applicable for natural fiber reinforced polymer composites. To meet the requirement for the composites, a biopolymer-based resin is necessary, which should well interact with the natural fiber with good waterproof behavior. By mimicking the relationship between cellulose, lignin and hemicellulose in wood, the esterified PVA-lignin resin with maleic acid is provided. The preparation and characterization of the environment-friendly resin are illustrated in this article. 180 °C of esterification reaction temperature and 40% of maleic acid contents are shown to be an optimum condition for the preparation of the resin. The esterified PVA-lignin resin exhibits 13, 31, and 55% increase of its tensile strength, toughness, and failure strength, respectively. The water contact angle of the esterified PVA-lignin resin is improved from 0 to 57°. The prepared resin is originally thermoplastic composite and it turned to be a thermoset resin by the esterification reaction at 180 °C, which is beneficial for composite processing. The developed resin is applicable for environment-friendly and high strength-natural fiber reinforced polymer composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48836.     

云杉碳点的制备及其在甲醛检测中的应用

目的 为云杉木包装箱废弃物的二次利用提供新的途径。方法 将废弃的云杉木包装作为碳源，采用高温高压水热法，在180 ℃下反应10 h，制得云杉碳点(Spruce carbon dots，S?CDs)，并将其应用于甲醛检测。通过透射电镜(HRTEM)、原子力显微镜(AFM)、X射线衍射仪(XRD)等仪器对S?CDs的形貌、晶型结构、化学组成和光学性能进行表征。结果 S?CDs呈类球状，平均粒径为3.49 nm，量子产率为0.45%，其表面含有C—O、C=O、N—H等基团，水溶性较好，在365 nm紫外灯下会发出蓝色的荧光。采用比值荧光法将S?CDs应用于甲醛检测，S?CDs对甲醛表现出较好的响应性，在甲醛浓度为0~1 mmol/L内，其溶液的荧光强度F427/F490与甲醛浓度之间呈现良好的线性关系(R²=0.968)，检出极限值(LOD)达到0.045 mmol/L。结论 以云杉废弃木包装为单一碳源，成功地制备出可应用于甲醛检测的S?CDs，实现了废弃云杉木包装的二次利用和功能化。     

On the use of cellulose nanowhisker as reinforcement in all-cellulose composite membrane from corn stalk

All-cellulose composite (ACC) membranes were prepared with cellulose and cellulose nano whisker (CNW) extracted from corn stalk by using NaOH/thiourea as solvent. CNW was isolated via acid hydrolysis method and the yield, size distribution and morphology of CNW were investigated. ACC Membranes were characterized via SEM, XRD, TGA as well as water flux and were further plasticized with glycerol aqueous solution. The mechanical property and transparency of ACC membranes before and after plasticization were compared. CNW prepared with 63% sulfuric acid for 60 min of hydrolysis time had the biggest ratio of length to diameter and moderate yield. ACC membrane with 5% CNW content had the highest tensile strength and the structure of ACC membranes was observed clearly in SEM images. TGA testing indicated that the initial degradation temperature tended to lower after CNW was introduced into membrane. ACC membrane had good optical transmittance and good flexibility after plasticization.     

Flexible and sensitive piezoresistive electronic skin based on TOCN/PPy hydrogel films

In recent years, the wearable electronic skin (E-skin) has attracted more and more attention due to high sensitivity, good portability and flexibility. In this work, we used the 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TOCN) as the substrate, and used the in-situ polymerization method to introduce polypyrrole (PPy) into the TOCN substrate. Then, the nylon gauze was used as microstructure template to prepare a TOCN/PPy E-skin with a surface microstructure. This E-skin possessed excellent sensing and mechanical properties. In the pressure range of 0–600 Pa, the sensitivity of E-skin was 3.13 kPa⁻¹. In addition, the E-skin exhibited ultrafast response/recovery time (≤10 ms), ultralow detection limit of 0.3 Pa, good stability (>9000 cycles) and mechanical strength of up to 117 MPa. Therefore, the TOCN/PPy E-skin has broad development prospects in the fields of artificial intelligence and health monitoring.     

Forcespinning technique for the production of poly(d,l-lactic acid) submicrometer fibers: Process–morphology–properties relationship

This work addresses a systematic study for the process development and optimization of poly(d ,l -lactic acid) (PDLLA) submicrometer fibers utilizing the centrifugal spinning technique known as Forcespinning. This study analyzes the effect of polymer concentration (8, 10, and 12 wt %) and angular speed on the fiber morphology, diameter distribution, and fiber yield. The increase in polymer concentration and angular speed favored the formation of continuous and homogeneous submicrometer fibers with an absence of bead formation and higher output. The optimal conditions were established considering the morphological characteristics that exhibit a greater surface area (homogeneous and submicrometer fibers); and they were achieved at a polymer concentration of 10 wt % at an angular speed ranging from 8000 to 10 000 rpm. Optimization of PDLLA submicrometer fiber fabrication lays the groundwork for scaling up the process and serves as a platform to further develop promising applications of PDLLA nonwoven mats, particularly in the biomedical area such as in scaffolds for tissue engineering. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47643.     

木体系墙体混凝土质量问题分析及预防措施

介绍了墙体木模施工时，墙体混凝土常出现的表面平整度差、截面尺寸偏差大等质量问题，并针对这些质量问题逐一进行了原因分析，在原因分析的基础上制定了行之有效的预防措施。     

Estimating the Decay and Radiation Characteristics of 129I

New estimated values are given for the decay and radiation characteristics of ¹²⁹I derived from information published in the world literature up to 2003.