金刚石颗粒表面形成氧化铝晶须的研究

采用Ti/Al/Graphite/Diamond粉体为原料,使用自蔓延高温烧结(SHS)技术,处于空气气氛下,在金刚石颗粒的表面形成了大量Al_2O_3晶须。采用XRD、SEM并结合EDS技术分析和研究试样。研究结果表明,原料经SHS反应后,生成了Ti_2AlC、TiC、TiN、TiO和Al_2O_3。此外,在金刚石表面可形成了大量Al_2O_3晶须。提出一种金刚石表面形成了Al_2O_3晶须的反应机制,即发生SHS反应后,首先在金刚石表面形成致密的Al-Ti层,然后Al与O_2反应,形成了大量Al_2O_3晶须。     

碳酸铝铵制备纳米氧化铝工艺的研究

本论文采用碳酸铝铵热解的工艺,以硫酸铝、硫酸铵和碳酸氢铵为原料,水为介质,运用正交试验法,采用共沉淀法制备出前驱体NH_4AlO(OH)HCO_3,将此前驱体洗涤,干燥,在一定温度下热解,制得具有特殊形貌和微观结构性能的氧化铝粉体。并用XRD、SEM等检测方法对粉体进行了表征。研究结果表明,反应体系的pH值、反应体系的温度、反应物的浓度以及加入的分散剂的量对前驱体AACH的生成以及粉体的性能都有很大影响。实验表明,在水溶液剂中控制反应体系的pH在9左右,温度控制在室温,加入适量分散剂(PEG),可制得颗粒细小,粒度分布均匀并且分散度优异的前驱体NH_4AlO(OH)HCO_3,其副产物(NH_4)_2SO_4又可循环利用。最后经过高温(1050℃)煅烧前驱体得到粒径约为10nm左右的超细α-Al_2O_3。     

基于铝热反应的金属结合剂金刚石工具初探

文章探索了一种基于铝热反应的新型金属结合剂金刚石工具的制备方法,分析了铝热反应制备结合剂过程的反应合成机理,研究了热压烧结温度对铝热反应结合剂的相组成、微观结构、力学性能的影响。制备了铝热反应结合剂金刚石磨具,并测试了干、湿磨两种条件下磨削建筑陶瓷砖的加工性能。研究表明, Fe_2O_3-Al复合粉体在1028.8℃开始发生铝热反应,反应产物主要为Fe、Fe_3Al相以及少量Al_2O_3及FeAl_2O_4(铁铝尖晶石)相,随着热压烧结温度的升高, FeAl_2O_4含量有所增加,结合剂的硬度、致密度和抗弯强度都随之升高。初步测试显示铝热反应结合剂金刚石磨具可以对建筑陶瓷砖进行加工,但工具耐磨性还存在不足。     

无机铝盐Sol—gel法制备超细氧化铝粉末

无机铝盐在一定的条件下水解形成均匀透明的凝胶,凝胶经干燥、热处理后可获得粒度在亚微米级且尺寸较均一的Al_2O_3超细粉末。本文着重探讨了溶胶—凝胶法制备Al_2O_3粉末的过程中,影响制得粉末颗粒大小、团聚状态和粒度分布的诸因素。结论认为,低的铝盐浓度和成胶温度、短的成胶保温时间有利于制备颗粒细小、粒度均一的Al_2O_3超细粉末。     

盐浴法合成Cr_2AlC陶瓷粉体工艺研究

Cr_2Al C陶瓷因其高电导和良好的高温抗氧化能力可应用于高温微波吸收领域而备受关注。本文以Cr_3C_2粉、Al粉、Cr粉为原料,在BaCl_2、KCl和NaCl混合盐浴中合成了Cr2AlC陶瓷粉体,并借助X射线衍射技术研究了原料组成、合成温度以及保温时间对合成粉体物相的影响。结果表明:铝含量的不足,会引起反应不充分,合成粉体中残留较多的Cr3C2;当铝过量达到30 wt%,原料中剩余的Al会氧化成Al_2O_3;随着合成温度的升高,合成粉体中Al_2O_3和Cr_3C_2相的量减少,但合成温度过高,合成粉体中会出现Cr7C3相;保温时间不足,合成粉体中有较多的Al_2O_3和Cr_3C_2相,保温时间过长,合成粉体中也会出现了Cr_7C_3相。当铝过量20 at%,合成温度为970℃,保温2 h时,可批次稳定地得到高纯度Cr_2AlC陶瓷粉体。     

水热法制取水合氧化铝系列产物

一、问题的提出不管是拜耳法或烧结法生产Al_2O_3,均先由铝土矿制出铝酸钠溶液,经水解析出平均粒径为40～60微米的晶体氢氧化铝(α～Al_2O_3·3H_2O),然后高温煅烧制得α-和r-Al_2O_3约各占一半的工业氧化铝。工业Al(OH)_3和Al_2O_3的技术指标均受电冶铝制约。由于Al_2O_3及其水合物的不同型态和性质,在石油化工、电子、环保、耐火和陶瓷等行业的用量与日俱增,已达几千吨,市场预测近年需万吨。这部分非炼铝用品,在欧美和日本发达国家,用量达230万吨/年,品种有一非多个之多。我厂是国内主要生产厂家。     

溶液浓度对共沉淀法制备ZnNb_2O_6粉体及陶瓷性能的影响

以Zn(NO_3)_2溶液和Nb_2O_5凝胶为原料,NH_3·H_2O为沉淀剂,采用共沉淀法制备了ZnNb_2O_6超细粉体。用XRD、TEM、SEM等对所制备的超细粉体进行了表征,并重点研究了不同反应溶液浓度对超细ZnNb_2O_6粉体结构和性能的影响。结果表明,本方法所制备的正交相ZnNb_2O_6粉体,其晶粒尺寸可控制在100~300 nm之间;随反应溶液浓度的提高,所合成粉体的晶型没有太大的变化,均为正交相,空间群Pnca[60],但是晶体结构的完整性略有不同;随着反应溶液浓度的增加,所合成粉体的晶粒尺寸先减少后增大,团聚现象加重;不同反应溶液浓度制备的粉体,所对应的ZnNb_2O_6陶瓷的致密度有所不同。当反应溶液浓度为0.5 mol/L时,烧结温度为1200℃下制备的陶瓷,晶体生长均匀,致密性可达到96.4%。,最佳微波介电性能为介电常数ε_r=24.4,谐振频率温度系数τ_f=-40×10~(-6)/℃,品质因数Q×f=78880 GHz。     

氧化铝/氧化石墨烯复合陶瓷的制备及性能

以Al_2O_3为原料,采用水热反应,通过基于静电引力的自组装机制,制备Al_2O_3/石墨烯e(GS)复合粉体。通过Fourier变换红外光谱、X射线衍射、扫描电子显微镜和透射电子显微镜等对Al_2O_3/GS复合粉体的物相组成和显微结构进行表征。采用热压烧结技术制备了Al_2O_3/GS复合陶瓷。研究了不同含量GS对复合材料性能的影响,测试了材料的室温力学性能。结果表明,当GS在Al_2O_3/GS复合粉体中的质量分数为0.75%时,复合陶瓷具有最高的抗弯强度和断裂韧性,其值分别为460.8 MPa和7.9 MPa·m~(1/2)。     

酸浸法制备硫酸铝时铝矾土矿的筛选

我国铝矾土矿属于高铝、高硅、低铁类矿,是酸浸法制备硫酸铝的良好原料。属于高铝、高硅的铝矾土矿主要有以下一些种类:蓝晶石Al_2O_3SiO_2、红栓石Al_2O_3SiO_2、硅线石Al_2O_3SiO_2、霞石(Na、K)_2OAl_2O_32SiO_2、长石(Na、K)_2OAl_2O_3·6SiO_2、白云母K_2O·Al_2O_3·6SiO_2·2H_2O、绢云母K_2O·3Al_2O_3·6SiO_2·2H_2O、白榴石K_2O·Al_2O_3·4SiO_2、高岭石Al_2O_3·SiO_2·2H_2O等。一水软铝石Al_2O_3H_2O、一水硬铝石Al_2O_3H_2O、三水铝石Al_2O_3·3H_2O等是属于高铝低硅的     

氧化铝粉体在水悬浮液中的分散特性研究

采用Zeta电位表征Al_2O_3粉在悬浮液中的分散特性,研究了超声波分散时间、不同粒度Al_2O_3粉以及分散剂六偏磷酸钠的浓度和Al_2O_3粉体悬浮液pH值对Al_2O_3粉体Zeta电位的影响.研究结果表明:Zeta电位绝对值随超声波作用时间发生明显变化,在一定条件下存在一个最佳分散时间为4～6 min;悬浮液中Al_2O_3粉体颗粒的粒度对悬浮液的Zeta电位有重要影响;在Al_2O_3粉体悬浮液中添加分散剂六偏磷酸钠,Zeta电位随其浓度发生变化,存在一个最佳浓度0.5%;在不同pH值下,Al_2O_3粉体悬浮液的Zeta电位不同,在碱性条件下,粉体的分散性较好,且碱性越强,分散性越好.     

浸取铝灰制取纳米氧化铝新工艺

介绍了一条回收铝灰中的铝制备纳米氧化铝的新工艺.用硫酸浸取电解铝工业中产生的铝灰,得到硫酸铝溶液,实验研究各参数对浸取过程的影响,得到适宜工艺条件;将硫酸铝溶液和碳酸氢铵反应生成碳酸铝铵沉淀,过滤、洗涤、焙烧碳酸铝铵得氧化铝粉体.实验研究了分散剂类型、分散剂用量、铝盐浓度对氧化铝粒径的影响,得出优化工艺条件.经X射线衍射分析和扫描电镜检测表明所得产品为粒径约70 nm的α-Al2O3.     

Synthesis of Ga2O3–Al2O3 Catalysts by a Coprecipitation Method for CH4-SCR of NO

Synthesis of the γ-Ga₂O₃–Al₂O₃ solid solutions by the coprecipitation method was examined. Precipitates were obtained by adding at once an aqueous solution of aluminum and gallium nitrates to an excess base solution (reverse strike precipitation). The precipitates were calcined at 700 °C to give γ-Ga₂O₃–Al₂O₃ solid solutions. When an ammonium carbonate solution was used as the precipitant, ammonium aluminum carbonate hydroxide (ammonium dawsonite, AACH)–ammonium gallium carbonate hydroxide (AGCH) solid solutions were obtained. Calcination of the AACH–AGCH solid solutions at 700 °C gave the γ-Ga₂O₃–Al₂O₃ solid solutions which exhibited high activity for selective catalytic reduction of NO with methane.     

Single step hydrothermal synthesis of 3D urchin like structures of AACH and aluminum oxide with thin nano-spikes

3D urchins like ammonium aluminum carbonate hydroxide (AACH) nanostructures with nano-spikes of dia. 20–30 nm were synthesized by a simple, single step hydrothermal technique by using aluminum nitrate and urea as precursor materials. It was found that morphology of the produced structure strongly depends upon the urea concentration. With increasing the amount of urea, the AACH particles having embedded rods like surface features transformed into 3D urchins. The added urea decomposed during hydrothermal treatment and increased the pH of the solution, which affected the morphology of the produced nanostructures. SEM, XRD, FTIR and TGA were employed to characterize the produced structures. On heating, the volatile ingredients of AACH were removed, leaving behind the alumina urchins.     

Synthesis of α-Al2O3 platelets and kinetics study for thermal decomposition of its precursor in molten salt

The precursor, ammonium aluminum carbonate hydroxide (AACH) was synthesized via solid-state reaction at 60 °C. The experimental results show that the AACH is orthorhombic NH₄Al(OH)₂CO₃, and the calcined powder products are hexagonal platelets of α-Al₂O₃ which can be obtained from calcining AACH in molten salt at 1000 °C. The linear and nonlinear methods were used to calculate the activation energies of the thermal process of AACH. The calculated results indicated the decomposition process involved two stages which were single-step kinetic processes. The most probable reaction mechanisms of the two stages were estimated by two comparative methods. The values of pre-exponential factor A of the two stages were obtained on the basis of E_α and the reaction mechanisms.     

Synthesis of Al2O3 whisker-reinforced yttria-stabilized-zirconia (YSZ) nanocomposites through in situ formation of alumina whiskers

Enhanced mechanical properties of yttria-stabilized zirconia based composites were obtained by introducing alumina whiskers as reinforcement. The alumina whiskers were formed in situ by decomposition of ammonium aluminum carbonate hydroxide (AACH) whiskers during calcination. The whiskers thus formed were amorphous and were converted to α-alumina during sintering at 1450 °C. The AACH whiskers were produced by hydrothermal treatment of an aqueous solution of urea and aluminum nitrate at 120 °C for 24 h. The Vickers hardness of the sintered composite sample increased with an increase in the alumina content up to 10 wt% and then decreased. The maximum hardness achieved at 10 wt% of alumina whiskers was 13.8 GPa, which further increased to 14.4 GPa with the addition of 1.0 wt% of cetyl-trimethyl-ammonium bromide (CTAB). The improved mechanical strength of the composites was attributed to the enhanced dispersion of alumina whiskers due to four times volume decrease during transformation of AACH to alumina and relatively lower aspect ratio of AACH whiskers as well as the deflocculating effect of CTAB.     

PREPARATION AND SEPARATING PROPERTIES OF MoS_2/γ-Al_2O_3 CERAMIC COMPOSITE MEMBRANE FOR H_2S-H_2 MIXTURE

MoS2/γ－Al2O3 ceramic composite membrane is successfully synthesized by the sol-gel method based on the inorganic salt route. The aluminum hydrate sol derived from the inorganic salt Al(NO3)3, whose transparence and viscosity are 97% and 1.2 × 10-3 Pa. s, respectively, can be formed through adjusting the ratio of the peptizing agent H+ to Al3+ to 0.3. The aluminum hydrate gel at 110℃ is amorphous in structure and is heat-treated in air at 800℃ to form γ－Al2O3. The precursor derived from the mixture solution of ammonium molybdate, thioacetamide and a reducing agent, can be transformed into crystal MoS2 under reducing condition at 800℃. MoS2/γ－Al2O3 composite membrane is an organic whole and bps no gradation from MoS2 layer to γ－Al2O3 Iayer. The separation factor a H2/H2S through the MoS2/γ－Al2O3 composite membrane increase with rising temperature and a H2/H2S at 600℃ is 4.45 higher than the theoretical separation factor produced by the ideal Knudsen diffusion.     

用煅烧-沥滤工艺从粉煤灰中提取高纯超细氧化铝

介绍了1种采用煅烧-沥滤工艺从粉煤灰中提取氧化铝(Al2O3)的新方法.以碳酸钠(NaCO3)为活化剂,在900 ℃下煅烧,使粉煤灰中惰性的Al2O3转变成活性的可以溶出的铝盐.选用硫酸(H2SO4)为活性铝盐的溶出剂,在一定温度下溶出铝盐,使活化后粉煤灰中的Al2O3以液相形式溶出.用乙二胺四乙酸为络合剂有效除去铝盐[Al2(SO4)3]中的杂质铁(Fe3 )等,用蒸馏水洗涤除去钠(Na )和其它可溶性杂质,有效提高Al2O3粉体的纯度.通过添加合适的分散剂、控制氢氧化铝[Al(OH)3]的结晶、干燥及煅烧的工艺条件,大大提高了Al2O3粉体的细度.通过X射线衍射、透射电子显微镜和N2吸附等技术分析获得的Al2O3粉体的组成与微观结构.通过以上工艺,获得Al2O3的提取率超过98%.将干燥后的Al(OH)3粉体在800 ℃下煅烧得到分散性好的纤维状γ-Al2O3,其纯度(质量分数)达99.6%.     

碳酸钠焙烧铝系钒铁炉渣共提取钒与铝

通过对铝系钒铁炉渣碳酸钠焙烧-水浸全过程的矿物分析、热力学计算及对比实验,研究了炉渣中钒、铝同步转化、溶出的机理与规律. 结果显示,焙烧进程中渣中镁铝尖晶石MgO×Al2O3相、CaO×2Al2O3相逐渐消失,MgO相生成,并生成碱熔相Na2O×Al2O3和钒酸盐. 随焙烧温度及时间增加,Na2O×Al2O3和钒酸盐相明显增多,钒、铝溶出率增加. 焙烧熟料经水浸后,液相呈碱性,钒、铝分别以可溶性钒酸钠和铝酸钠的形式进入水相,固相残留物为少量未反应的镁铝尖晶石及新生成的MgO和Ca(OH)2. 在磨矿粒度<75 mm、配碱系数1.0、焙烧温度1000℃及焙烧时间4 h的优化条件下,钒的溶出率可达90%,铝的溶出率可达75%.     

Yttrium-Aluminum Pomegranate Synthesis Based on Double Ammonium-Containing Carbonate Compounds of Yttrium and Aluminum

Glass and Ceramics - The mechanism of synthesis of yttrium-aluminum garnet Y3Al5O12 (YAG) from a mixture of yttrium and ammonium carbonates NH4Y(CO3)2?H2O with aluminum and ammonium...     

硫酸铝铵-氯化氢反应制备六水氯化铝过程中晶体形貌的研究

以十二水合硫酸铝铵为原料,采用氯化氢通气结晶法制备了六水氯化铝晶体,考察了通气速率、通气时间、反应温度、铝离子初始浓度对六水氯化铝晶体形貌的影响。结果表明,50 mL硫酸铝铵酸溶液中,当通气速率为60 mL/min、通气时间为2 h、反应温度为30 ℃、铝离子初始质量浓度为20 g/L时,可以得到形貌比较规整的棱柱形六水氯化铝晶体。该研究为提取、制备高品质六水氯化铝晶体提供了技术参考。