Effect of pyrolysis temperature and hold time on the characteristic parameters of adsorbent derived from sewage sludge

According to the Doehlert's matrix method, the adsorbent derived from sewage sludge was prepared through chemical activation under controlling the pyrolysis temperature and hold time. The characteristic parameters including the total yield, adsorption of methylene blue, adsorption of iodine, BET surface area, micro-pore volume are 35%—49%, 16.5—38 mg/g, 285—362 mg/g, 185—359 m2/g, and 0.112—0.224 m3/g, respectively. According to the experimental data, the multi-linear regression method was adopted to fit the relations between the characteristic parameters and influential factors. At final, through optimization method, the optimal adsorbent is obtained when using 62 min as hold time and 1105K as pyrolysis temperature. Under the conditions, the adsorbent was produced and compared the characteristic parameters with model forecast value, the coherence is satisfied.

Effect of sintering temperature and holding time on structure and properties of Li_(1.5)Ga_(0.5)Ti_(1.5)(PO_4)_(3)electrolyte with fast ionic conductivity

Li_(1.5)Ga_(0.5)Ti_(1.5)PO_(4))_(3)(LGTP)is recognized as a promising solid electrolyte material for lithium ions.In this work,LGTP solid electrolyte materials were prepared under different process conditions to explore the effects of sintering temperature and holding time on relative density,phase composition,microstructure,bulk conductivity,and total conductivity.In the impedance test under frequency of 1-10^(6) Hz,the bulk conductivity of the samples increased with increasing sintering temperature,and the total conductivity first increased and then decreased.SEM results showed that the average grain size in the ceramics was controlled by the sintering temperature,which increased from(0.54±0.01)μm to(1.21±0.01)μm when the temperature changed from 750 to 950°C.The relative density of the ceramics increased and then decreased with increasing temperature as the porosity increased.The holding time had little effect on the grain size growth or sample density,but an extended holding time resulted in crack generation that served to reduce the conductivity of the solid electrolyte.

Characterization of Hydroxyapatite Extracted from Crab Shell Using the Hydrothermal Method with Varying Holding Times

Hydroxyapatite(HA)is a bio ceramic commonly utilized in bone tissue engineering due to its bioactive and osteoconductive properties.Crab shells are usually disregarded as waste material despite their significant CaCO_(3) content,and have not been widely utilized in the synthesis of HA.This study aims to synthesize and analyze HA derived from crab shells using the hydrothermal method with different durations of holding time.This study utilized precipitated calcium carbonate(PCC)derived from crab shells.With a hydrothermal reactor set at 160℃ and varying holding times of 14(HA_14),16(HA_16),and 18(HA_18)h,a PCC and(NH4)2HPO4 mixture was used to synthesize HA.The synthesis results were analyzed using scanning electron microscopy(SEM),fourier transform infrared spectroscopy(FTIR),and X-ray diffraction(XRD)tests.This study has accomplished the synthesis of HA from crab shells.Nonetheless,the final product of synthesis still contained CaCO_(3) as an impurity.The prolonged hydrothermal holding time of 14 to 18 h resulted in a reduction of impurities while increasing the percentage of crystal weight and crystallite size of HA.Specimen CH_18 is the best-quality product generated in this study.This specimen produced HA with the highest percentage of crystal weight and crystallite size compared to the other specimens.Furthermore,specimen CH_18 exhibited the lowest concentration of impurities.The Ca/P ratio in this specimen was also the closest to 1.67.The Ca/P ratio,crystallite size,and crystal weight percentage of this specimen are 1.54,19.06 nm,and 99.1%,respectively.

Application of a 2 Parameter Weibull Distribution in Modeling of State Holding Time in HIV/AIDS Transition Dynamics

This study investigates the application of the two-parameter Weibull distribution in modeling state holding times within HIV/AIDS progression dynamics. By comparing the performance of the Weibull-based Accelerated Failure Time (AFT) model, Cox Proportional Hazards model, and Survival model, we assess the effectiveness of these models in capturing survival rates across varying gender, age groups, and treatment categories. Simulated data was used to fit the models, with model identification criteria (AIC, BIC, and R2) applied for evaluation. Results indicate that the AFT model is particularly sensitive to interaction terms, showing significant effects for older age groups (50 - 60 years) and treatment interaction, while the Cox model provides a more stable fit across all age groups. The Survival model displayed variability, with its performance diminishing when interaction terms were introduced, particularly in older age groups. Overall, while the AFT model captures the complexities of interactions in the data, the Cox model’s stability suggests it may be better suited for general analyses without strong interaction effects. The findings highlight the importance of model selection in survival analysis, especially in complex disease progression scenarios like HIV/AIDS.

Effects of Calcining Temperature and Holding Time on the Synthesis of Aluminum Titanate

We aim in this research at synthesizing high-purity aluminium titanate with sludge from the aluminium profile factory by shock cooling method, and mainly discuss the effect of calcining reaction temperature and holding time on crystalline, microstructure and content of aluminum titanate materials to determine the preferred calcining temperature and holding time. XRD and SEM methods were utilized to characterize the crystalline and microstructure of each specimen, Rietveld Quantification software was used for the determination of different crystalline contents of specimens, and Philips plus software was applied to determine the cell parameters of aluminium titanate in different specimens. According to the experimental results, preferred calcining temperature is determined as 1400℃ and preferred holding time is 2 h, at which the grains of aluminum titanate grow completely and the purity of aluminum titanate is 97.2wt%.

Effect of Holding Time on the Microstructure and Mechanical Properties of Dual-Phase Steel during Intercritical Annealing

Continuous annealing simulation tests were conducted by using a continuous annealing thermomechanical simulator. Holding times of 5, 60, 180, and 480 seconds for an intercritical annealing temperature of 820℃ were adopted to investigate the evolution of the mierostructure and mechanical properties of ferrite-bainite dual-phase steel. The ferrite-bainite dual-phase steel was characterized by high strength and low yield ratio due to the presence of the constituents （polygonal ferrite, bainite, martensite and retained austenite） of the steel microstructure. Specimen 3 exhibits the highest value of A50 （7.67%） and a product of Rm × A50 （10453MPa%） after a 180s holding. This is likely attributed to the presence of a C-enriched retained anstenite in the microstructure. And the effect of martensite islands and carbide precipitate is thought to be able to contribute in strengthening the present steel. It is expected that equilibrium of anstenite fraction would be reached for reasonable intercritical holding period, regardless of the heating temperature. The results suggest that long increasing holding times may not be needed because the major phase of the microstructure does not change very significantly. It is favorable for industrial production of DP steels to shorten holding times. Key words： ferrite-bainite dual-phase steel; holding time; martensite islands; mechanical properties

Effect of holding time on microstructure and mechanical properties of Al-40 wt.%Si alloys fabricated by combination of gas atomization and spark plasma sintering

Hypereutectic Al-40 wt.%Si alloys were fabricated by the combination of gas atomization and spark plasma sintering(SPS) technology. The effects of holding time(15-60 min) on phase composition, microstructure, density,mechanical properties of Al-Si alloys were investigated by XRD, SEM, a hydrostatic balance, an automatic micro hardness tester and a universal tensile testing machine. The results showed that homogenous distribution of ultrafine primary Si and high density of alloys can be obtained at holding time of 30 min. Compared with primary Si(3.7 μm)fabricated by gas atomization, the average size increased from 5.17 to 7.72 μm with the increase of holding time during SPS process. Overall, the relative density, maximum tensile strength and Vickers hardness of 94.9%, 205 MPa and HV;196.86 were achieved at holding time of 30 min, respectively. In addition, all the diffraction peaks were corresponded to α-Al or β-Si and no other phase can be detected. Finally, the densification process of SPS was also discussed.

An Inventory Model for Deteriorating Items with Exponential Declining Demand and Time-Varying Holding Cost

In the present paper, a total optimal cost of an inventory model with exponential declining demand and constant deterioration is considered. The time-varying holding cost is a linear function of time. Shortages are not allowed. The items (like food grains, fashion apparels and electronic equipments) have fixed shelf-life which decreases with time during the end of the season. A numerical example is presented to demonstrate the model and the sensitivity analysis of various parameters is carried out.

Development of inclusions in 3104 alloy melt during heating and holding treatments

Developments in the contents of different typical inclusions in 3104 alloy melt were described during heating and holding processing. The settling process of inclusion particles was investigated by measuring the contents of inclusions in the surface, center, and bottom layers of the molten metal. In the results, main inclusions observed and determined by Prefil and PoD FA methods are MgO, Al2O3, spinel（MgAl2O4）, and TiB2 particles or thin films. It is found that some small particles of Al2O3 and MgO are transformed into spinel particles, and the formation rate increases as the temperature and the holding period of melt increase. The content of inclusions increases from 3.37 mm^2×kg^-1 to 7.54 mm^2×kg^-1 and then decreases to 3.08 mm^2×kg^-1 after holding for 90 min. This is attributed to a settling phenomenon and a significant increase in settling velocity after holding for 60 min. The content of inclusion particles decreases by means of settlement and flotation in liquid aluminum with an increase in holding time. The theoretical analysis and experiment results are in essential agreement with those from industrial production.

退火处理对热轧Al/Mg/Al复合板界面微观组织与性能的影响

采用1 mm Al+3 mm Mg+1 mm Al的组坯方式,轧制温度为400℃,压下率为35%,热轧得到6061/AZ31B/6061复合板。在退火温度为200℃的条件下,研究了不同退火时间对复合板拉伸性能、界面结合、微观组织以及表面残余应力的影响。在保温时间分别为0、0.5、1和1.5 h情况下,分别进行拉伸实验、能谱分析、微观组织观察和残余应力测试。结果表明,当轧制压下率为35%时,6061铝合金和AZ31B镁合金能够通过热轧方法得到很好的复合;随着退火时间的增加,6061/AZ31B/6061复合板的拉伸强度、伸长率和界面扩散厚度显著增加,且铝合金表面残余应力也增大。

重熔对Al-Ti-La中间合金中Ti_(2)Al_(20)La相的影响

通过扫描电镜、X射线衍射和电子探针等分析研究了重熔过程中不同保温时间和温度对Al-Ti-La中间合金中Ti_(2)Al_(20)La相的含量、形态尺寸和稳定性的影响。结果表明:在750℃下,随着保温时间的延长,Ti_(2)Al_(20)La相的溶解度逐渐增大,含量由未处理的20.776%下降至13.72%,形态由块状演变为圆整和细小的片状,长宽比由2.33下降至1.52;在1000℃下,保温15 min后溶解度较大,含量降低至4.5%,形态演变为尖锐的长条状,长宽比上升至2.55;溶解产生的La原子与Al在晶界处形成La-Al金属间化合物(IMC),Ti原子在基体中的分布密度随保温时间的延长和保温温度的升高而增高,以游离态均匀分布在基体中。

环形热管蓄冷保温箱空载均温性能研究

针对传统蓄冷箱箱内温度均匀性差的问题,提出环形热管结构蓄冷保温箱的设计,建立了空载均温性能的三维数值仿真模型,并进行了试验验证,对比分析了环形热管保温箱与常规结构蓄冷保温箱蓄冷板不同布置方式(四周布置、侧面+顶部+底部布置、中间布置)保温时间和温度均匀性的差异。结果发现,与常规结构蓄冷箱相比,环形热管结构的蓄冷保温箱的温度场、速度场均表现出较好的均匀性,其温度不均匀度为1.13,保冷时间为23 h。内部的环形热管在箱内形成环形流场,加强了对流换热,使整体温度均匀性更好。

煤矸石/黄土基陶瓷膜支撑体的制备及烧结特性

为了解决陶瓷膜成本过高的问题,以煤矸石和黄土为原料,CaCO 3为造孔剂,羧甲基纤维素(CMC)为黏结剂制备煤矸石/黄土基陶瓷膜支撑体,利用扫描电镜(SEM)、X射线衍射(XRD)及压汞法等方法对陶瓷膜支撑体的物化性质、表面微观形貌、物相组成等进行表征。结果表明:随着烧结温度的升高,支撑体内部形成新的晶相,导致支撑体的纯水通量和抗折强度增加。同时,随着保温时间的延长,颗粒熔融现象更加显著,进而降低支撑体的纯水通量但增加其抗折强度。在烧结温度为1125℃、保温时间为2 h条件下,制得的煤矸石/黄土基陶瓷膜支撑体综合性能较好。此时支撑体的纯水通量为9102.44 L/(m^(2)·h·MPa),抗折强度为12.317 MPa,酸/碱质量损失率分别为6.64%/0.35%,显气孔率为38.26%,孔隙率为49%。

钛元素对再生7050铝合金细化作用的研究

试验研究了Ti含量及加Ti后熔体在炉内停留时间对再生7050铝合金铸锭晶粒细化的影响。结果表明,以再生铝为原料配制的7050铝合金添加Ti的质量分数达到0.035%时,晶粒细化效果最佳,树枝晶基本消失。当Ti质量分数达到0.036%时,铝液在炉内停留不超过2 h时,晶粒有粗化倾向,但整体变化不大;当停留时间达到或超过3 h时,晶粒粗化明显。再生7050铝合金铝液添加Ti后,保温时间宜不超过2 h,宜快速冷却进行铸造。

一种新型高强韧弹簧钢的脱碳敏感性

以一种新研发的Si-Cr系高强韧弹簧钢为实验材料,对不同加热和保温条件下该弹簧钢表面脱碳层形貌特征、脱碳敏感性及其影响机理等进行了研究,并从理论上建立了弹簧钢脱碳层深度与保温条件的关系.结果表明:该弹簧钢的总脱碳层深度随加热温度的升高呈先增加后减小的趋势,当加热温度为1100℃时,总脱碳层深度达到最大,约为231.2μm,其脱碳敏感温度为(1100±50)℃;随着保温时间的延长,弹簧钢脱碳层深度增加,且脱碳层深度与保温时间的平方根存在线性关系.与其他Si-Mn系和Si-Cr系弹簧钢相比,该Si-Cr系弹簧钢中由于碳含量较低,硅含量也适当降低,并且添加了适量的Cr和V,有效降低了脱碳敏感性.

保温时长对DD5/FGH98扩散焊接头组织及力学性能的影响

目的为优化焊接工艺参数,探究不同保温时长对DD5/FGH98固相扩散焊接头组织和性能的影响。方法采用高熵合金和镍箔作为复合中间层,通过固相扩散焊方式连接DD5单晶高温合金和FGH98粉末高温合金。在1130℃、4 MPa的压力条件下,进行不同保温时长的焊接。焊接完成后,通过多种表征手段观察接头的微观组织,并通过剪切实验确定接头的性能。结果从微观组织上看,随着保温时间的延长,中间层中高熵合金晶粒长大,FGH98和DD5近焊缝处的γ′相溶解变小,DD5侧母材在高温高压下发生严重的筏化。母材与中间层的元素扩散更加充分。在力学性能方面,保温时间的延长导致中间层硬度降低,与基材硬度差距增加,接头剪切强度逐渐降低。在1130℃、4 MPa条件下,保温1 h的接头强度最高,达到650 MPa。保温1~4 h试样的剪切断裂位置在高熵中间层;保温6 h试样的断裂位置在镍箔区域。结论保温时长影响接头的微观结构和力学性能。在一定焊接温度下,实现完全键合的接头的剪切强度会随着保温时长的延长而降低。

2024年1月23日乌什7.1级地震强震动记录特征分析

新疆地震台网中心共获取乌什7.1级地震813条仪器烈度信息、496组强震动记录,其中PH002台站峰值加速度280.68 cm·s^(-2)为本次获得的最大峰值加速度。对获取的219个台站的峰值加速度与第五代中国地震动参数区划图衰减关系对比发现两者在100 km范围内比较符合。计算分析5个峰值加速度超过100 cm·s^(-2)的台站加速度反应谱,并与地震动设计反应谱进行比对分析,同时计算出5个台站地震动有效持时,显示200 km内地震能量释放较迅速,体现出地震破坏力较大。

增韧剂对环氧沥青性能的影响

文中通过比对研究不同增韧剂对国产环氧沥青的拉伸强度、断裂伸长率、杨氏模量与容留时间等指标参数,分析适合国产环氧沥青的增韧剂品牌.研究不同增韧剂掺量的环氧沥青力学性能指标与容留时间指标差异,分析适宜的增韧剂掺量区间.结果表明:增韧剂可显著改善环氧沥青的脆性属性,提高容留时间指标,降低施工难度.增韧剂指标控制在5.3%~6.1%区间时,国产环氧沥青与日本TAF环氧沥青力学指标相近,性能基本满足路面铺装需求,特别在容留时间指标得到了显著改善,大幅度降低环氧沥青铺装的施工难度.

烧成温度和保温时间对堇青石相的合成及其力学性能的影响

实验以高岭土、烧结镁砂和硅灰为主要原料,以稀土金属氧化物氧化镧为添加剂,采用半干压成型法将试样成型为直径30 mm的生坯,采用一次烧成法制备堇青石多孔陶瓷。主要研究氧化镧的引入量为1.5%时,烧成温度和保温时间对堇青石多孔陶瓷性能及显微结构的影响。结果表明:当试样的烧成温度为1300℃,保温时间为2 h时,试样的基本性能较优,即试样的线收缩率为4.43%,吸水率为20.35%,显气孔率为34.39%,体积密度为1.69 g/cm^(3),耐压强度为35.96 MPa;且从试样的XRD和SEM分析结果可知,在一定烧成温度下,适当提高保温时间有利于堇青石相的合成,为拓宽堇青石陶瓷的应用领域奠定了重要的理论基础。

温度制度对氧化铝陶瓷烧结性能影响的研究

氧化铝陶瓷因其原料来源广、成本较低、物理及机械性能较为优秀、化学性能十分稳定,因此在日常生产生活中应用十分广泛,在化工、军工、医疗、航空航天等领域发挥了重要作用。由于氧化铝的熔点较高,因此烧结氧化铝陶瓷的过程中能耗较高、对窑炉炉体的损伤大、烧结时间长。研究、制定合适的烧结制度,有利于降低氧化铝陶瓷的烧结温度、减少烧结时间、控制陶瓷的晶粒生长、提高陶瓷的烧结性能,并且响应国家节能减排的号召。本文以α-Al_(2)O_(3)含量为99.99%的造粒粉为原料,通过120 MPa的压力干压成型,并进行常压烧结。对烧结后的陶瓷进行性能表征,探究适合的温度和烧结制度。实验表明:从1000℃开始以8℃/min的速率升温至1500℃,保温1 h,试样相对密度达到97.43%,微观结构较为均匀,力学性能较好,晶粒平均粒径为1.31μm。