Single-Grain Boundaries in PTC Resistors

Thin semiconducting barium titanate ceramic bars consisting of single grains joined together in series have been prepared, and the positive temperature coefficient of resistivity (PTCR) characteristics of strictly single-grain boundaries in the materials were investigated. The resistivity ( R )-temperature ( T ) characteristics obtained for the present samples can be classified into typically three categories: (1) normal type PTCR characteristics, similar to those observed in usual ceramic samples, (2) saw-tooth type PTCR characteristics, characterized by an abrupt increase in resistivity by more than three orders of magnitude at the Curie point, immediately follwoed by a monotonous decrease in it, and (3) flat type R–T characteristics, with substantially little or no resistivity jump. Of these R–T characteristics, normal type PTCR characteristics were the most frequently observed (about 60%; a total of 65 samples were examined). Flat type R–T characteristics were least frequently (about 10%) observed. Single boundaries with these three types of PTCR characteristics exhibited essentially the same ferroelectric capacitance–temperature characteristic; this demonstrates that the temperature dependence of the dielectric constant above the Curie point was not responsible for the PTCR anomalies. Single boundaries with normal and saw-tooth type PTCR characteristics showed significantly nonlinear current-voltage characteristics above the Curie point, which may be interpreted to be caused by a current strongly affected by traps (or surface acceptor states) present at the grain boundaries.     

Preparation and Photoelectrochemical Performance of Potassium Hexatitanate Nanofilm

Nanostructured K2Ti6O13 film photoelectrode produced in situ was prepared on indium-tin oxide (ITO) glass substrate by a sol-gel process and characterized by thermogravimetry (TG) and differential scanning calorimetry (DSC), X-ray diffraction (XRD), atomic force microscopy (AFM), UV-Visible diffuse reflectance and Raman spectrometry. The photoelectrochemical performance of K2Ti6O13 film was assessed by electrochemical method. The analytical results showed that the K2Ti6O13 film had a strong and wide absorption in the ultraviolet and visible light range. The band gap energy (Eg) of the film shifted from 3.45 eV (bulk) to 3.05 eV (film). The flat-band potential (Efb) of K2Ti6O13 film was -0.67 V [vs. saturated calomel electrode (SCE)]. The transport of photogenerated electrons and holes was better in K2Ti6O13 film electrode than that in TiO2 film electrode. The photoelectrochemical response of K2Ti6O13 photoelectrode was increased in electrolyte solution with KOH, compared with that in the solution without KOH. The adsorption of OH- on the nanofilm acted as the surface activity center. The mechanism of photolysis was analyzed in terms of photoelectrochemical behavior.     

歧化松香钾皂制备方法的改进与性能研究

以歧化松香为主要原料,在较低的温度(75~95℃)下,溶入KOH水溶液,并进行皂化反应,制备固体份质量分数45%的歧化松香钾皂。研究了反应温度、皂化时间、pH值、添加复合助剂TX-A对反应速度、去氢枞酸钾含量,以及黏度、结晶、胶凝等产品性能的影响。得出歧化松香钾皂化的较佳制备条件为:pH值为10.36,皂化时间分别为120 min(未加TX-A)、98 min(加TX-A),反应温度85℃,TX-A加入量为反应物质量的0.2%。制备出的歧化松香钾皂产品,在性能上完全符合行业标准ZBB 72003-84的要求,并且结晶、胶凝性质有所改善,加纳色号标准降低两个等级。     

新型缓凝剂的制备及其对混凝土性能的影响评价

为了延长混凝土的凝结时间,提高其使用效率,室内以亚甲基丁二酸、N,N-二甲基甲酰胺、三乙醇胺和对甲苯磺酸为原料制备了一种新型缓凝剂CHP-1,并评价了其对混凝土性能的影响。结果表明：新型缓凝剂CHP-1能够有效提高水泥净浆的流动度,当其加量为1.5%时,水泥净浆流动度由初始的75mm增大至150mm以上,增幅达到100%;缓凝剂CHP-1可以有效降低混凝土的泌水率,当其加量为1.5%时,混凝土的泌水率达到最低;缓凝剂CHP-1还能够有效提高混凝土的凝结时间和抗压强度,从而提高混凝土的使用效率;此外,新型缓凝剂CHP-1与粉煤灰之间的相容性较好,而与硅灰和矿渣之间的相容性则相对较差。     

Preparation and study of KNbO3 PTC ceramics

In KNbO₃ ceramics rendered semiconductive by additions of K₂O-GeO₂ glasses two PTC anomalies are observed: at the Curie point and in the vicinity of the orthorhombic-tetragonal phase transition. 'These results are explained on the basis of Heywang-Jonker model of the PTC effect modified to take account of intergranular layers of glassy phase and spontaneous polarization in grains.     

不同制备条件对镍基催化剂性能的影响研究

通过不同制备方法制取NiO-Ce0.75Zr0.25O2/Al2O3催化剂,考察制备条件对CH4/CO2重整反应催化性能的影响。催化性能尤其结构特性的研究,采用H2-TPR、BET手段进行表征。结果表明:沉淀-浸渍法与共沉淀法和溶胶凝胶法相比较,所制得催化剂活性组分NiO在载体表面分散度更高,此时催化剂抗积炭、抗烧结性能增强,催化剂稳定性提高,活性评价中CH4、CO2转化率和H2收率分别可达85.5%、86.4%和93.8%。     

高铁酸钾的制备及其氧化性的应用

综述了熔融法(干法)、次氯酸盐氧化法(湿法)和电解法制备高铁酸钾的研究进展,介绍了高铁酸钾的强氧化性在水处理、有机合成等方面的应用,展望了高铁酸钾的未来研究方向.     

PTC陶瓷材料制备与应用

描述了PTC效应及其原理，并从粉体制备、掺杂物的选择与加入和烧成制度各方面介绍了高性能PTC陶瓷研究方面的一些工艺新进展，进而从理论上探讨了获得高性能PTC陶瓷材料的途径。     

硫酸钙制取硫酸钾的实验研究

对硫酸钙和氯化钾制备硫酸钾的工艺进行了研究,得到了制备硫酸钾的工艺条件为：硫酸钙与氯化钾的配料比为1：1,NH3-H2O的浓度为35％。搅拌速度为300r／min,反应时间为1h。     

高吸水性树脂的制备及反应温度对性能影响

以N,N-亚甲基双丙烯酰胺及邻苯二甲酸二烯丙酯为交联剂,丙烯酸及丙烯酸钠为聚合单体,采用氧化还原引发剂和水溶液聚合制备高吸水性树脂(SAP)。研究了反应温度对聚合反应过程和SAP性能的影响。结果表明:当反应供热系统温度为65°C,反应物料温度为30°C的条件下,添加聚合引发剂,其聚合反应比较平稳,所制备的SAP产品性能较优。     

硫酸氢钾及硫酸钾铵的制备

论述了硫酸氢钾及硫酸钾铵的制备,硫酸和氯化钾反应得硫酸氢钾并释放ＨＣｌ气体;硫酸氢钾和碳酸氢铵反应得硫酸钾铵和ＣＯ２气体。ＨＣｌ气制盐酸,ＣＯ２气制液态二氧化碳。该工艺原料综合利用好,生产成本低,经济效益好。     

高铁酸钾的合成及性能研究

采用次氯酸盐氧化法及改进的提纯方法制备了可用于超级铁电池的高铁酸钾 ,其纯度在 94 %以上。紫外可见光谱、热重分析图谱表明 ,高铁酸钾的紫外可见光区的吸收峰在2 2 4、5 0 5nm处 ,在 2 30℃以上开始分解。研究了该物质在碱性条件下的循环伏安图 ,发现高铁酸钾的氧化还原过程是一不可逆过程 ,并计算出在 6mol/L的KOH溶液中 ,其扩散系数为6 0 4× 10 - 3 cm2 /s。     

铬酸钾电解-结晶制备重铬酸钾的工艺

利用阳离子膜,以K2CrO4电解结晶制备K2Cr2O7,考察了电流密度、温度、阴极液KOH浓度、阳极液K2CrO4浓度等因素对转化率、电流效率和直流能耗的影响;研究了K2Cr2O7不同浓度、不同转化率下的结晶纯度和收率及搅拌速率、降温速率和晶种加入量等对晶体粒度分布和形貌的影响. 结果表明,最佳电解工艺条件为：电流密度0.2 A/cm2,电解温度80℃,阴极液KOH浓度50 g/L,阳极液K2CrO4浓度400 g/L. K2Cr2O7转化率大于90%时,结晶纯度不低于99.8%. 优化的结晶条件为：溶液初始K2Cr2O7浓度500 g/L,搅拌速率300 r/min,降温速率0.5℃/min,不添加晶种. 所得产品符合GB 28657-2012要求.     

双施主掺杂对PTC陶瓷性能的影响

为了提高PTC陶瓷整体性能,本文用正交法对高温PTC进行了双施主Nb2O5和La2O3掺杂配比的实验,优选了配方,其中La2O3的摩尔分数应该控制在0.0006～0.0008之间,Nb2O5控制在0.0005～0.0007之间较好。同时研究了双施主掺杂与单施主掺杂分别对高居里点PTC陶瓷性能的影响。     

PTC用高纯碳酸锶的研制

论述了以硝酸锶和碳酸氢铵为原料,通过除钡、钙、镁、铁等杂质,利用自制专用化合器控制反应方式及反应条件,制得SrCO3产品含量大于99.5%,D50≤1.5μm,粒度分布均匀一致,可满足PTC用户要求。     

Influence of Process Variables on Microstructure and V-I Characteristics of Multicomponent ZnO-Based Nonlinear Resistors

Studies have been made of the effect of process variables such as calcination, initial particle size, and postsinterin on density, microstructure, V-I characteri stics, and energy -handling capability of a ZnO-based composite: 87.325 wt% ZuO + 0.1% Nb₂O₅+ 3.5% Sb₂O₅+ 6% Bi₂O₃+ 0.55% CoO + 0.7% MnO₂+ 0.9% Cr₂O₃+ 0.9% NiO + 0.025% Al(NO₃)₃. The nonlinear characteristics were found to be improved by the calcination of a ZnO + Nb₂O₅ mixture at 1200°C for 1h. The postsintering heat treatment was found to rejuvenate V-I characteristics of the degraded sample to a greater extent. Further, the postsintered sample containing Nb₂O₅, prepared by using a calcined charge of particle size around 1 μm, was found to possess better V-I characteristics and energy-handling capability compared to the samples prepared without the calcination step.     

晶界势垒和缺陷对PTC效应影响的研究

为了适应市场对低压集成电路过流保护作用的PTC热敏陶瓷的低阻化要求,采用还原-再氧化的烧结工艺来制备多层片式PTC热敏陶瓷.本文主要研究了(Ba1.022-xSmx)TiO3基陶瓷在还原气氛中1200℃烧结30 min并在800℃再氧化热处理后其室温电阻率随施主掺杂浓度的变化关系,以及冷却速率对该样品PyTC效应的影响.从氧化物半导体理论出发,阐述了在还原再氧化过程中该陶瓷的缺陷模型和晶界特性,讨论了施主掺杂BaTiO3基PTC陶瓷缺陷行为与晶界势垒及其导电机理,解释了冷却速率和再氧化时间对样品的电性能以及PTC效应的影响.     

由氯化钾制硫酸钾和聚氯化铝

提出以煤矸石在沸腾炉中焙烧,高温炉气加热氯化钾和硫酸的转化反应炉生产硫酸钾。副产盐酸用以浸取沸腾炉渣,生产聚合氯化铝。     

利用钾长石矿泥制钾钙肥

试验研究了钾长石在以硫酸钙、碳酸钙等为添加剂的体系中生产可溶性钾的工艺条件.采用单因素实验法对物料粒度、配比、焙烧温度、时间、助剂种类及用量进行研究.结果表明,在钾长石矿泥、硫酸钙、碳酸钙物质的量比为1∶1∶18、焙烧时间为3h、焙烧温度为1050℃时,制出的钾钙肥可溶性钾含量为4.89％.在焙烧时间2h、焙烧温度为1000℃时,添加助剂硫酸钠3.0％,制出的钾钙肥可溶性钾含量为5.76％.     

高性能阻裂抗渗外加剂的研制及其对混凝土性能影响的研究

采用将无机增强阻裂材料WJ和有机减水保塑憎水阻孔外加剂YJ进行分别研制并优化复合的技术路线研制了高性能阻裂抗渗外加剂KLFS.实验结果表明:以生明矾、硫铝酸盐水泥熟料、天然二水石膏和无机物质A作为主要成分的无机增强阻裂材料,膨胀性能稳定,膨胀率落差小,90d龄期仍有1.88×10-4的膨胀率,并有一定的增强作用;对高效减水剂引入憎水阻孔组分、保水组分进行改性研制成的有机减水保塑憎水阻孔外加剂YJ,可提高混凝土工作性,严格控制坍落度损失,并长期阻孔,同时降低混凝土早期水化温升,有效防止早期温度收缩裂缝的出现.混凝土中掺入KLFS后,2h后坍落度20cm,90d抗压强度比为128%,膨胀规律好,90d仍有1.12×10-4的限制膨胀率, 28d劈裂强度由基准混凝土的2.81MPa提高到3.28 MPa,碱含量低,无钢筋锈蚀,耐久性好.